*The Role of Silane Sol-Gel Coatings on the Corrosion Protection of Magnesium Alloys DOI: http://dx.doi.org/10.5772/intechopen.102085*

As observed, although sol-gel technology allows the preparation of different hybrid organic-inorganic sol-gel coating compositions, the obtention of effective coatings for Mg-based alloys still is a huge challenge. One of the main aspects, related to the synthesis of the sol-gel coatings on Mg alloys, is the pH of the hydrolyzed sol-gel solution. Indeed, magnesium is not stable and spontaneously degrades during sol-gel deposition step when using acidic conditions. Hernández-Barrios et al. [31] evaluated the corrosion behavior of AZ31 Mg alloy pretreated with a hybrid silica sol-gel coating prepared using acetic acid as acid-catalyst, and 3-glycidyloxypropyltrimethoxysilane (GPTMS) and TEOS as silica precursors. The results revealed that the sol synthesized with the highest acid concentration reached more stable gelation kinetics, but with the worst corrosion resistance performance (icorr: 1.3 × 10−6 A/cm2 ) compared with the sol synthesized with the slower acid concentration (icorr: 2.4 × 10−7 A/cm2 ). The decay of the corrosion resistance of the sample coated with the more acidic sol is attributed to defects on the coating's morphology and to the corrosion process advancing in the substrate. Indeed, during the sol-gel deposition, corrosion products are generated together with hydrogen evolution.

In this sense, pH of the sol is a critical parameter and should be considered to get a nondefective SiO2 coating not affecting the metallic substrate, and thus to provide a suitable corrosion resistance performance.

Another aspect to consider is related to the promotion of insulating coatings with high-density structures for blocking the penetration of electrolytes. In this case, complexing agents are added during the synthesis of the sol to react with the organic group of some organo-alkoxysilanes and therefore stimulate the organic polymerization. For instance, Qian et al. [32] prepared a hybrid sol-gel through hydrolysis and condensation reactions of TEOS and GPTMS. The opening of the epoxy group of GPTMS results in coatings with novel physical and chemical properties. The authors further incorporated triethylenetetramine (TETA) as an organic crosslinking agent to bond with the open epoxy groups. The corrosion behaviors of the coatings deposited on AZ31B magnesium alloy were evaluated by polarization curves measurements in the 3.5% NaCl solution. The results revealed that a compact and smooth silane film was formed on the substrate's surface, which provided good barrier protection, improving the corrosion resistance ability (icorr: 3.7 × 10−9 A/cm2 ) in comparison to untreated magnesium alloy substrate (icorr: 4.1 × 10−6 A/cm2 ) (**Figure 4**).

Furthermore, the corrosion resistance properties of silane films can be significantly improved by the incorporation of some nanoparticles into the sol-gel film. The beneficial effects of the addition of different nanoparticles on the corrosion resistance for Mg alloys have been reported by different researchers. For instance, the effect of incorporating SiO2 nanoparticles [33], graphene oxide [34, 35], carbon nanotubes [36], alumina, titania, zirconia [37], and Montmorillonite (MMT) [38] on the sol-gel synthesis has been evaluated.

For example, the addition of a colloidal silica nanoparticles suspension into the sol-gel coating is considered a good approach to increase the hardness, density, and wear resistance, and thus the corrosion resistance properties of hybrid silane coatings. Peres et al. [33] investigated the effect of adding different amounts of SiO2 nanoparticles into a hybrid silica sol based on TEOS and GPTMS on the corrosion resistance of AZ31 magnesium alloy. The results showed that the incorporation of nanoparticles improved the corrosion resistance of Mg alloy. However, the maximum amount of SiO2 recommended to obtain a coating with the best anticorrosive performance was between 100 and 300 mg l−1; coatings doped with a higher amount of SiO2 showed nanoparticles agglomeration and consequent defects and cracks. Thus, two critical issues should be

**Figure 4.**

*Potentiodynamic polarization curves of bare alloy and the hybrid coating in 3.5 wt.% NaCl (reprinted from Ref. [32], ESG).*

considered to avoid a detrimental effect on the anticorrosion behavior of the film: (i) the dispersion of nanoparticles into the film, and (ii) the amount of loaded nanoparticles.

On the other hand, graphene oxide (GO), which is a two-dimensional sp2 carbon material, with many inherent characteristics such as good mechanical strength, chemical inertness, and good thermal stability, has also been considered to reinforce organofunctional silane coatings for corrosion protection of Mg alloys [34]. However, the high specific surface area of graphene and the strong Van der Waals force (−stacking) between graphene layers made it to agglomerate easily, resulting in hybrid coatings with a decrease in corrosion performance and microhardness properties. As graphene-based compound [39], oxidized fullerene [40], and carbon nanotube [36] have also been considered as a novel promising reinforcement for hybrid composite silane coatings for Mg alloys due to their properties including high strength, lightweight, thermal and mechanical stability, hydrophobicity, corrosion resistance, and high specific surface area. The anticorrosion and protective action of a zeolite-filled silane sol-gel coating on AZ31 magnesium substrate was studied by Calabrese et al. [41]. The zeolite composite coating evidenced very high hydrophobicity behavior (contact angle up to 140° showed good adhesion and good barrier properties during immersion in 3.5 wt.% NaCl solution.

Although significant advances have been made regarding modified sol-gel coatings composition, there is still a large gap in this research since most of the studies only provide information about the instantaneous corrosion rate, but not about the kinetic of the sol-gel film degradation in standard aqueous solution of 3.5 wt*.*% NaCl, which is helpful for a comprehensive choice of anticorrosion strategies and a systematic control of the degradation of sol-gel films.

## *2.1.2 Active sol-gel coatings barrier*

Up to now, conventional physical barrier coatings with suitable composition designs have been considered to improve the corrosion resistance of Mg alloys; however, in very harsh environments when the aggressive agent and water reach the metal surface, the silane coatings are not capable to stop the corrosion process, reducing the lifetime of the coating protection. For this reason, smart self-healing protective coatings should be considered to provide long-term protection to the material. The smart


Introductory Chapter: Diabetic Foot

*Meriem Braiki, Mohamed Ali Khalifa, Bilel Faidi, Mosaab Ghannouchi and Fethi Derbel*

### **1. Introduction**

Diabetic foot disease is an important problem confronting the diabetologist, internists, and surgeons as it reduces patient's quality of life and affects social participation. It is including several chronic complications as infection, foot ulceration and even tissue destruction of the foot. These complications are considered as a significant cause of morbidity and mortality among diabetic patients. Consequently, chronic complications or diabetic foot disease are a growing concern worldwide and represent a major global medical, social, and economic problem.

Diabetic Foot Ulcer (DFU) is one of the most distressing complications and it is defined as the commonest major end-point of diabetic foot disease.

The main etiological factors for DFU are peripheral nerves damage and peripheral vascular disease. Series of mechanisms are documented such as decreased peripheral blood flow and decreased local angiogenesis.

Furthermore, biomechanical abnormalities and increased susceptibility for infection are associated factors exposing to DFU [1, 2].

#### **2. Etiopathogenesis**

The etipathogenesis of diabetic foot disease is multifactorial with major factors. Neuropathy, microvascular disease and infection are mainly included. These factors are leading to foot tissue necrosis and ulcer occurrence [2, 3].

#### **2.1 Neuropathy in diabetic foot**

About 50% of patients with diabetes mellitus develop symptomatic peripheral neuropathy within 25 years of disease onset. Distal polyneuropathy is commonly encountered. Whereas combined neuropathies with motor and autonomic fibers involvement can occur. Age, disease duration and poor glyceamic control quality over several years are strong predictors, leading to diabetic neuropathy [4].

Hyperglycemia, dyslipidemia, insulin resistance and oxidative stress can contribute to diabetic neuropathy [5].

According to Rochester Study [6], the severity of the neuropathy is related to the duration of hyperglycemia exposure. Other factors are studied in current researchs focusing on oxidative stress, advanced glycation-end products, protein kinase C and the polyol pathway [7].

#### **2.2 Vasculopathy**

Peripheral vascular disease is among the main etiological factors in foot ulceration. Chronic hyperglycemia causes peripheral arteries damage, smooth cell abnormalities and endothelial cell dysfunction.

Endothelial dysfunction, owing to changes in the proliferation of endothelial cells, thickening of the basement membrane, leads essentially to microvascular disease which is responsible for ischemia. Hyperglycemia is also associated with an increase in thromboxane A2 leading to plasma hypercoagulability [8].

#### **2.3 Immunopathy**

The immune system is compromised with hyperglycemia and research indicates the impairment of the immune system with serum glucose levels exceeding to 150 ml/dl. Thus, high blood glucose levels lead to inappropriate inflammatory response and disruption of cellular immunity (inhibition of fibroblast proliferation and impairment of the basal layer of keratinocytes, reducing epidermal cell migration) [8].

Consequently, diabetic patients are more exosed to the foot infection which is a limb-threatening and debilitating condition mainly seen in incontrolled diabetes. The soft tissue infection adversely affects diabetic control. This repetitive cycle leads to uncontrolled hyperglycemia, further affecting the immune response to infection [9]. The bone can be involved in case of infection resistance responsible for soft tissue infection dissemination making osteitis.

Bad glycemia control associated with an open wound creates a catabolic state and a metabolic dysfunction affecting the synthesis of proteins, collagen and fibroblasts. Furthermore, systemic deficiencies are propagated leading to nutritional compromise in diabetes [10].

## **3. Classification**

Many classifications of the diabetic foot are reported**.** The most commonly used is Wagner's classification, consisting of six simplistic wound grades used to assess ulcer depth (grades 0–5) [11]. This classification is limited as it is not able to recognize ischaemia and infection as independent risk factors in all classification grades [12]. A more recently proposed and popularized DFU classification is the University of Texas Wound Classification [13].

### **4. Clinical presentation**

Clinical foot examination at each follow-up is important to detect the disease early such as ulceration or gangrene. The clinical examination includes inspection of the skin integrity, foot deformities such as, Charcot's foot, hallux valgus, claw toe, hollow foot, skew or flat foot. The muscular condition and the bone structure should be evaluated as well [4].

Hyperkeratosis with dry and fissured skin are features of polyneuropathy. Lower extremity vascular insufficiency is made by one or more signs of claudication, night or rest pain, atrophic integument, absent peripheral pulses and loss of limb hair [8].

About 50% of patients with DFU present clinical signs of infection which is clinically featured by the presence of purulent secretions or at least two of the inflammatory classic signs (painful swelling, edema, hyperemia). The lack of the

**51**

*Introductory Chapter: Diabetic Foot*

make these signs masked [8].

**5. Investigations**

**6. Management**

foot function.

retinopathy [16].

*6.1.1 Glycemic control*

*6.1.2 Pharmacological therapy*

with a reduced amputation rate.

*DOI: http://dx.doi.org/10.5772/intechopen.94331*

flowmetry and television microscopy [2].

**6.1 Conservative therapeutic modalities**

with insulin-dependent diabetes mellitus [17, 18].

agent duloxetine and pregabalin for pain control [19].

sensitivity in patients with impaired immune response due to neuropathy can

Guideline development group selected recommendations from the National Institute of Clinical Excellence. In their most recent publishment, the annual assessment of the diabetic foot requires recommendations aiming essentially to

Peripheral vascular disease is diagnosed by angiography which studies the peripheral arterial tree. Non-invasive vascular screening is currently more used in

These investigations consist of Doppler ultrasound (for estimation of ankle brachial ratio), photo-plethysmography, transcutaneous oximetry, laser Doppler

Most guidelines recommend the use of Neurological foot testing with 10 g monofilament in order to assess diabetic neuropathy. An inability to sense a 10 g pressure is the current consensus definition of loss of protective sensation [15].

The management of the diabetic foot complications is multidisciplinary and requires the collaboration of a specialist team comprising a dialectologist, surgeons, podiatrist, microbiologist, tissue viability nurse with a thorough understanding of

The aim is to decrease the risk of the disease progression leading to feet deformities, ulcers and foot amputation. The prognosis is mainly highlighted by factors such as glycaemic and blood pressure control, diabetic nephropathy and diabetic

It is demonstrating that a good controlled glycaemia delays the onset and slows the progression of diabetic neuropathy, retinopathy and nephropathy in patients

Callaghan et al. [12] showed the decrease in the risk of developing clinical neuropathy with better glycaemic control, in diabetes requiring insulinotherapy.

The medication adherence to oral diabetic drugs is improved by the patient education. The pain resulting from the distal neuropathy requires the use of pain killers. The National Institute of Clinical Excellence recommends use of first-line

Various risk factors for atherosclerosis mainly smoking, should be completely stopped in diabetic patients in order to decrease the risk of distal vascular disease. Adding to that the use of statins and antiplatelet medications reduce the limb ischemia risk and the vascularisation, when it is improved, it is in turn associated

assess both of peripheral neuropathy and peripheral vascular status.

the diabetic foot to detect early the peripheral ischemia [14].

sensitivity in patients with impaired immune response due to neuropathy can make these signs masked [8].

## **5. Investigations**

*The Eye and Foot in Diabetes*

abnormalities and endothelial cell dysfunction.

for soft tissue infection dissemination making osteitis.

Peripheral vascular disease is among the main etiological factors in foot ulceration. Chronic hyperglycemia causes peripheral arteries damage, smooth cell

Endothelial dysfunction, owing to changes in the proliferation of endothelial cells, thickening of the basement membrane, leads essentially to microvascular disease which is responsible for ischemia. Hyperglycemia is also associated with an

The immune system is compromised with hyperglycemia and research indicates the impairment of the immune system with serum glucose levels exceeding to 150 ml/dl. Thus, high blood glucose levels lead to inappropriate inflammatory response and disruption of cellular immunity (inhibition of fibroblast proliferation and impairment of the basal layer of keratinocytes, reducing epidermal cell

Consequently, diabetic patients are more exosed to the foot infection which is a limb-threatening and debilitating condition mainly seen in incontrolled diabetes. The soft tissue infection adversely affects diabetic control. This repetitive cycle leads to uncontrolled hyperglycemia, further affecting the immune response to infection [9]. The bone can be involved in case of infection resistance responsible

Bad glycemia control associated with an open wound creates a catabolic state and a metabolic dysfunction affecting the synthesis of proteins, collagen and fibroblasts. Furthermore, systemic deficiencies are propagated leading to nutritional

Many classifications of the diabetic foot are reported**.** The most commonly used is Wagner's classification, consisting of six simplistic wound grades used to assess ulcer depth (grades 0–5) [11]. This classification is limited as it is not able to recognize ischaemia and infection as independent risk factors in all classification grades [12]. A more recently proposed and popularized DFU classification is the University

Clinical foot examination at each follow-up is important to detect the disease early such as ulceration or gangrene. The clinical examination includes inspection of the skin integrity, foot deformities such as, Charcot's foot, hallux valgus, claw toe, hollow foot, skew or flat foot. The muscular condition and the bone structure

Hyperkeratosis with dry and fissured skin are features of polyneuropathy. Lower extremity vascular insufficiency is made by one or more signs of claudication, night or rest pain, atrophic integument, absent peripheral pulses and loss of limb hair [8]. About 50% of patients with DFU present clinical signs of infection which is clinically featured by the presence of purulent secretions or at least two of the inflammatory classic signs (painful swelling, edema, hyperemia). The lack of the

increase in thromboxane A2 leading to plasma hypercoagulability [8].

**2.2 Vasculopathy**

**2.3 Immunopathy**

migration) [8].

compromise in diabetes [10].

of Texas Wound Classification [13].

**4. Clinical presentation**

should be evaluated as well [4].

**3. Classification**

**50**

Guideline development group selected recommendations from the National Institute of Clinical Excellence. In their most recent publishment, the annual assessment of the diabetic foot requires recommendations aiming essentially to assess both of peripheral neuropathy and peripheral vascular status.

Peripheral vascular disease is diagnosed by angiography which studies the peripheral arterial tree. Non-invasive vascular screening is currently more used in the diabetic foot to detect early the peripheral ischemia [14].

These investigations consist of Doppler ultrasound (for estimation of ankle brachial ratio), photo-plethysmography, transcutaneous oximetry, laser Doppler flowmetry and television microscopy [2].

Most guidelines recommend the use of Neurological foot testing with 10 g monofilament in order to assess diabetic neuropathy. An inability to sense a 10 g pressure is the current consensus definition of loss of protective sensation [15].

## **6. Management**

The management of the diabetic foot complications is multidisciplinary and requires the collaboration of a specialist team comprising a dialectologist, surgeons, podiatrist, microbiologist, tissue viability nurse with a thorough understanding of foot function.

The aim is to decrease the risk of the disease progression leading to feet deformities, ulcers and foot amputation. The prognosis is mainly highlighted by factors such as glycaemic and blood pressure control, diabetic nephropathy and diabetic retinopathy [16].

## **6.1 Conservative therapeutic modalities**

## *6.1.1 Glycemic control*

It is demonstrating that a good controlled glycaemia delays the onset and slows the progression of diabetic neuropathy, retinopathy and nephropathy in patients with insulin-dependent diabetes mellitus [17, 18].

Callaghan et al. [12] showed the decrease in the risk of developing clinical neuropathy with better glycaemic control, in diabetes requiring insulinotherapy.

## *6.1.2 Pharmacological therapy*

The medication adherence to oral diabetic drugs is improved by the patient education. The pain resulting from the distal neuropathy requires the use of pain killers. The National Institute of Clinical Excellence recommends use of first-line agent duloxetine and pregabalin for pain control [19].

Various risk factors for atherosclerosis mainly smoking, should be completely stopped in diabetic patients in order to decrease the risk of distal vascular disease. Adding to that the use of statins and antiplatelet medications reduce the limb ischemia risk and the vascularisation, when it is improved, it is in turn associated with a reduced amputation rate.

#### *The Eye and Foot in Diabetes*

A targeted antibiotherapy based on the wound culture results is needed in DFU with superadded infection. The duration of treatment depends on the underlying infection severity [20].

## *6.1.3 Debridement*

A 10-year review on standardized wound care protocol and integrated multidisciplinary team showed a reduction in amputation rate in diabetic foot patients as they had not delayed debridement [21].

Disease activity is measured by the degree of swelling, erythema and especially skin temperature. Superficial ulcer requires the removal of necrotic and hyperkeratotic tissue as it promotes better the wound healing. Whereas, Deep wounds with bone and soft tissue involvement need more aggressive debridement with some involving surgery [20].

## *6.1.4 Foot pressure relief*

The most important therapeutic principle is typically based on a quick and consistent pressure relief to promote wound healing as the weight bearing force is removed from the site of ulcer. The force redistribution is ensured by means of temporary immobilization, wearing of a protective cast or orthosis [22].

## *6.1.5 Wound dressings*

A variety of dressing modalities are available with the advancement in the promotion of wound healing.

Dressing materials can be of various categories including natural, modified and synthetic polymers, as well as their mixtures or combinations, processed in the

#### **Figure 1.**

*Wet gangrene of the toe with osteitis. Complete healing under antibiotic treatment and MMP's inhibitor (pharysor).*

**53**

**Figure 3.**

*Introductory Chapter: Diabetic Foot*

bioactive substances) [2].

dressings." [24].

in infected ulcers.

**Figure 2.**

*inhibitor (pharysor).*

*DOI: http://dx.doi.org/10.5772/intechopen.94331*

have not been shown to be more efficient in treating DFU.

form of films, foams, hydrogels and hydrocolloids. Furthermore, wound dressings can be used as medicated systems, through the delivery of healing enhancers and therapeutic substances (growth factors, peptides, drugs, stem cells and/or other

Randomized controlled trials [23], showed that Silver-impregnated dressings

Furthermore, "Moist dressings" are suggested to be more efficient than "dry

According to our experience in the "Olivier Private Clinic", Sousse, Tunisia. We noted the efficiency of Matrix Metalloproteinases (MMPs) inhibitors of natural or synthetic origin in the healing process of chronic diabetic wounds. We use mainly moist dressings with **Pharysor**\*, a MMPs inhibitor of natural origin, in diabetes with superficial and even with deep chronic ulcers. This agent has been

Adding to that, our standard non-surgical management for DFU requires negative pressure wound therapy, close glycemic control and nutritional support with enriched oral nutritional supplement. A targeted antibiotherapy is further delivered

*Wet gangrene of the second toe with osteo-arthritis. Complete healing under antibiotic treatment and MMP's*

*Wet gangrene of the forefoot complete healing under antibiotic treatment and MMP's inhibitor (pharysor).*

found to be beneficial in improving wound healing rates (**Figures 1**–**4**).

### *Introductory Chapter: Diabetic Foot DOI: http://dx.doi.org/10.5772/intechopen.94331*

*The Eye and Foot in Diabetes*

infection severity [20].

involving surgery [20].

*6.1.4 Foot pressure relief*

*6.1.5 Wound dressings*

promotion of wound healing.

they had not delayed debridement [21].

*6.1.3 Debridement*

A targeted antibiotherapy based on the wound culture results is needed in DFU with superadded infection. The duration of treatment depends on the underlying

A 10-year review on standardized wound care protocol and integrated multidisciplinary team showed a reduction in amputation rate in diabetic foot patients as

Disease activity is measured by the degree of swelling, erythema and especially skin temperature. Superficial ulcer requires the removal of necrotic and hyperkeratotic tissue as it promotes better the wound healing. Whereas, Deep wounds with bone and soft tissue involvement need more aggressive debridement with some

The most important therapeutic principle is typically based on a quick and consistent pressure relief to promote wound healing as the weight bearing force is removed from the site of ulcer. The force redistribution is ensured by means of

A variety of dressing modalities are available with the advancement in the

*Wet gangrene of the toe with osteitis. Complete healing under antibiotic treatment and MMP's inhibitor*

Dressing materials can be of various categories including natural, modified and synthetic polymers, as well as their mixtures or combinations, processed in the

temporary immobilization, wearing of a protective cast or orthosis [22].

**52**

**Figure 1.**

*(pharysor).*

form of films, foams, hydrogels and hydrocolloids. Furthermore, wound dressings can be used as medicated systems, through the delivery of healing enhancers and therapeutic substances (growth factors, peptides, drugs, stem cells and/or other bioactive substances) [2].

Randomized controlled trials [23], showed that Silver-impregnated dressings have not been shown to be more efficient in treating DFU.

Furthermore, "Moist dressings" are suggested to be more efficient than "dry dressings." [24].

According to our experience in the "Olivier Private Clinic", Sousse, Tunisia. We noted the efficiency of Matrix Metalloproteinases (MMPs) inhibitors of natural or synthetic origin in the healing process of chronic diabetic wounds. We use mainly moist dressings with **Pharysor**\*, a MMPs inhibitor of natural origin, in diabetes with superficial and even with deep chronic ulcers. This agent has been found to be beneficial in improving wound healing rates (**Figures 1**–**4**).

Adding to that, our standard non-surgical management for DFU requires negative pressure wound therapy, close glycemic control and nutritional support with enriched oral nutritional supplement. A targeted antibiotherapy is further delivered in infected ulcers.

#### **Figure 2.**

*Wet gangrene of the second toe with osteo-arthritis. Complete healing under antibiotic treatment and MMP's inhibitor (pharysor).*

**Figure 4.** *Gangrene with osteitis of the calcaneus complete healing under antibiotic treatment, excision and MMP's inhibitor (pharysor).*

## **6.2 Surgical management of DFU**

Surgeons interfere in the second line and surgical approach becomes necessary when conservative and medical alternatives are not sufficient. All reconstructive surgery techniques, in particular local flaps and skin grafts, can be used depending on the location and size of the substance loss.

Furthermore, possibilities of revascularization of the lower limbs are needed to improve the chances of skin healing in case of limb ischemia.

The therapeutic decision of partial leg amputation is not systematic and should be taken as a last therapeutic option. Amputation is typically recommended for deep and chronic non healing ulcers with necrotic tissues.

### **7. Prevention**

Preventive strategies are important to decrease the risk of repeated ulcers and amputation. Measures are mainly based on patient education and foot assessements for peripheral vascular disease and neuropathy. Furthermore, foot pressure relief with individualized orthopedic shoe provision and insole treatment is necessary in order to adapt the pressure distribution to each foot. Consequently, lesions and chronic foot ulcers may be better prevented.

### **8. Conclusion**

Diabetic foot is a chronic complication which poses challenges in the early diagnosis and management. Paying attention to this complication is necessary during the follow-up of diabetes. The treatment is often conservative with a proper glycemic control. Management of risk factors including peripheral vascular disease, neuropathy and infection is essential to avoid serious complications leading to amputation.

**55**

**Author details**

Meriem Braiki1

and Fethi Derbel5

, Mohamed Ali Khalifa<sup>2</sup>

\*Address all correspondence to<EMAIL_ADDRESS>
provided the original work is properly cited.

, Bilel Faidi3

1 Department of Pediatric Surgery, Regional Hospital, Sidi Bouzid, Tunisia

2 Department of Orthopedic Surgery, Sahloul University Hospital, Sousse, Tunisia

3 Department of General Surgery, Kairouan University Hospital, Sousse, Tunisia

4 Department of General Surgery, Mahdia University Hospital, Mahdia, Tunisia

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

5 Department of General Surgery, Oliviers Private Clinic, Sousse, Tunisia

\*, Mosaab Ghannouchi4

*Introductory Chapter: Diabetic Foot*

*DOI: http://dx.doi.org/10.5772/intechopen.94331*

*Introductory Chapter: Diabetic Foot DOI: http://dx.doi.org/10.5772/intechopen.94331*

*The Eye and Foot in Diabetes*

**6.2 Surgical management of DFU**

**7. Prevention**

**Figure 4.**

*inhibitor (pharysor).*

**8. Conclusion**

amputation.

on the location and size of the substance loss.

chronic foot ulcers may be better prevented.

improve the chances of skin healing in case of limb ischemia.

deep and chronic non healing ulcers with necrotic tissues.

Surgeons interfere in the second line and surgical approach becomes necessary when conservative and medical alternatives are not sufficient. All reconstructive surgery techniques, in particular local flaps and skin grafts, can be used depending

*Gangrene with osteitis of the calcaneus complete healing under antibiotic treatment, excision and MMP's*

Furthermore, possibilities of revascularization of the lower limbs are needed to

The therapeutic decision of partial leg amputation is not systematic and should be taken as a last therapeutic option. Amputation is typically recommended for

Preventive strategies are important to decrease the risk of repeated ulcers and amputation. Measures are mainly based on patient education and foot assessements for peripheral vascular disease and neuropathy. Furthermore, foot pressure relief with individualized orthopedic shoe provision and insole treatment is necessary in order to adapt the pressure distribution to each foot. Consequently, lesions and

Diabetic foot is a chronic complication which poses challenges in the early diagnosis and management. Paying attention to this complication is necessary during the follow-up of diabetes. The treatment is often conservative with a proper glycemic control. Management of risk factors including peripheral vascular disease, neuropathy and infection is essential to avoid serious complications leading to

**54**

## **Author details**

Meriem Braiki1 , Mohamed Ali Khalifa<sup>2</sup> , Bilel Faidi3 \*, Mosaab Ghannouchi4 and Fethi Derbel5

1 Department of Pediatric Surgery, Regional Hospital, Sidi Bouzid, Tunisia

2 Department of Orthopedic Surgery, Sahloul University Hospital, Sousse, Tunisia

3 Department of General Surgery, Kairouan University Hospital, Sousse, Tunisia

4 Department of General Surgery, Mahdia University Hospital, Mahdia, Tunisia

5 Department of General Surgery, Oliviers Private Clinic, Sousse, Tunisia

\*Address all correspondence to<EMAIL_ADDRESS>
© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

## **References**

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[2] Prabhu Dayal Sinwar. The diabetic foot management – Recent advance. International Journal of Surgery.2015;15:27-30.

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revascularisation investigation 2 Diabetes (BARI 2D) Cohort. Diabetes

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*DOI: http://dx.doi.org/10.5772/intechopen.94331*

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[21] Hsu CR, Chang CC, Chen YT, Lin WN and Chen MY. Organization of wound healing services: the impact on lowering the diabetes foot amputation rate in a ten-year review and the importance of early debridement. Division of Plastic Surgery, Chang Gung memorial hospital, Taiwan. Diabetes Res Clin Pract.2015;109:77-84.

[22] A.J.M. Boulton, C.I. Franks, R.P. Betts, T. Duckworth, J.D. Ward, Reduction of abnormal foot pressures in diabetic neuropathy using a new polymer insole material. Diabetes

[23] Jude EB, Apelqvist J, Spraul M and Martini J. Silver dressing study group. Prospective randomised controlled study of hydrofiber dressing containing ionic silver or calcium alginate dressing in nonischaemic diabetic foot ulcers.

Diabet Med.2007;24:280-288.

dressings for healing diabetic foot ulcers. Cochrane Database

Syst.2012;2:27.

[24] Dumville JC, Deschpande S, O'Meara S and Speak K. Hydrocolloid

Care.1984;7:42-46.

*Introductory Chapter: Diabetic Foot DOI: http://dx.doi.org/10.5772/intechopen.94331*

revascularisation investigation 2 Diabetes (BARI 2D) Cohort. Diabetes Care.2013;36:3208-3215.

[19] Tesfaye S, Boulton AJM and Dickenson A. Mechanisms and management of diabetic painful distal symmetrical polyneuropathy. Diabetes Care.2013;36:2456-2465.

[20] Jonathan Zhang Ming Lim, Natasha Su Lynn Ng, Cecil Thomas. Prevention and treatment of diabetic foot ulcers. Journal of the Royal Society of Medicine. 2017.110(3):104-109.

[21] Hsu CR, Chang CC, Chen YT, Lin WN and Chen MY. Organization of wound healing services: the impact on lowering the diabetes foot amputation rate in a ten-year review and the importance of early debridement. Division of Plastic Surgery, Chang Gung memorial hospital, Taiwan. Diabetes Res Clin Pract.2015;109:77-84.

[22] A.J.M. Boulton, C.I. Franks, R.P. Betts, T. Duckworth, J.D. Ward, Reduction of abnormal foot pressures in diabetic neuropathy using a new polymer insole material. Diabetes Care.1984;7:42-46.

[23] Jude EB, Apelqvist J, Spraul M and Martini J. Silver dressing study group. Prospective randomised controlled study of hydrofiber dressing containing ionic silver or calcium alginate dressing in nonischaemic diabetic foot ulcers. Diabet Med.2007;24:280-288.

[24] Dumville JC, Deschpande S, O'Meara S and Speak K. Hydrocolloid dressings for healing diabetic foot ulcers. Cochrane Database Syst.2012;2:27.

**56**

*The Eye and Foot in Diabetes*

**References**

[1] A.J.M. Boulton, H.Connor,

Sons Ltd, Chichester.2000:19-31.

[3] M.E. Edmonds. The diabetic foot: pathophysiology and treatment. Clinics in Endocrinology and Metabolism.1986;15(4):880-916.

[5] A.J.M.BoultonJ.D.Ward. Diabetic neuropathies and pain. Clinics in Endocrinology and Metabolism.

[6] P.J. Dyck, K.M. Kratz, J.L. Karnes, et al.The prevalence by staged severity of various types of diabetic neuropathy, retinopathy, and nephropathy in a population-based cohort: the Rochester Diabetic Neuropathy Study. Neurology.

[7] A.J.M. Boulton, R.A. Malik, J.C. Arezzo, J.M. Sosenko. Diabetic somatic neuropathies: technical review. Diabetes

[8] S Syafril. Pathophysiology diabetic foot ulcer. Earth and Environmental

[9] Clayton W, Elasy T A. A review of the pathophysiology, classification, and treatment of foot ulcers in diabetic patients. Clin. Diabetes.2009;27(2):52-8.

[10] Singh S, Pai R P, Yuhhui C. Diabetic foot ulcer-diagnosis and management. Clin. Res. Foot Ankle.2013;1(3):1-9.

[2] Prabhu Dayal Sinwar. The diabetic foot management – Recent advance. International Journal of

[4] Maren Volmer-Thole, Ralf Lobmann. Neuropathy and Diabetic Foot Syndrome. International Journal of Molecular Sciences. Int. J. Mol. Sci.

2016:17-917.

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1993;43: 817-824.

Science. 2018.

Care.2004;27:1458-1486.

Surgery.2015;15:27-30.

Peter R, P.R.Cavanagh. The Pathway to Ulceration: Aetiopathogenesis. The Foot in Diabetes, third edition. John Wiley &

[11] F.W. Wagner Jr. The dysvascular foot: a system for diagnosis and treatment. Foot Ankle.1981;2: 64-122.

[12] Callaghan BC, Little AA, Feldman EL and Hughes RA. Enhanced glucose control for preventing and treating diabetic neuropathy. Cochrane Database

[13] S.O. Oyibo, E.B. Jude, I. Tarawneh, H.C. Nguyen, L.B. Harkless, A.J. Boulton. A comparison of two diabetic foot ulcer classification systems: the Wagner and the University of Texas wound classification systems. Diabetes

[14] J.J. Hurley, F.B. Hershey, A.I. Auer, H.B. Binningtoni. Noninvasive evaluation of peripheral arterial status and the physiologic approach. The Diabetic Foot, C.V. Mosby Company,

[15] Satish Chandra Mishra, Kunal C Chhatbar, Aditi Kashikar, Abha Mehndiratta.Diabetic foot.

[16] Krishnan S, Nash F, Baker N, Fowler D and Rayman G. Reduction in diabetic amputations over eleven years in a defined UK population: benefits of multi-disciplinary team work and continuous prospective audit. Diabetes

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[17] The Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of longterm complications in insulin-dependent diabetes mellitus. N Engl J Med.1993; 329: 977-986.

[18] Pop-Busui R, Lu J, Brooks MM, Albert S, Althouse AD, Escobedo J, et al. Impact of glycaemic control strategies on the progression of diabetic peripheral neuropathy in the bypass angioplasty

**59**

**Chapter 5**

**Abstract**

healing, inflammation

**1. Introduction**

Matrix Metalloproteinases

(MMPs) and Diabetic Foot:

Pathophysiological Findings and

Management of diabetic foot remains a major challenge for healthcare system. Though wound healing is a multiphase process and involved multiple biomarkers that acts in stepwise manner, pathophysiology diabetic foot ulcers is still not much clear and need standardization. Matrix metalloproteinases (MMPs) are often linked with non-healing characteristic of diabetic foot ulcers. They play vital roles in various phases of healing process. Major functions are removal of damaged extracellular matrix in inflammatory phase, breakdown of capillary basement membrane prior to angiogenesis and facilitation in fibroblast migration during proliferation phase. For efficient healing, these enzymes are needed in certain amount only. Imbalance of these enzymes leads to excessive degradation which has been linked with the nonhealing nature of diabetic ulcers. This chapter will shed light on the role of MMP's in various phases of wound healing and the inhibitors of MMP's from natural as well as synthetic origin. It would help researchers and physicians to the understand nature of diabetic foot more clearly and design of strategies for diabetic foot management.

**Keywords:** diabetic foot, matrix Metalloproteinases, MMP inhibitors, wound

Wound healing is a complex mechanism involves cascade of inter-related events, i.e., hemostasis, inflammation, proliferation and remodeling [1]. Various skin cells including epidermal, dermal, immune and endothelial cells are involved in initiating remodeling process. In wounded are, various signaling pathways and cellular mechanisms are observed to be active at same time which are responsible for ongoing the healing process. Moreover, various cellular events such as blood

Recent Developments in Their

Inhibitors of Natural as well as

*Kirandeep Kaur, Atamjit Singh, Shivani Attri,*

*Danish Malhotra, Aditi Verma, Neena Bedi*

Synthetic Origin

*and Preet Mohinder Singh Bedi*

## **Chapter 5**


**2. Conclusion**

It is known that GH acts directly through its receptor and indirectly stimulates the production of IGF-1. However, the mechanism through which physical exercise can be used to increase GH secretion is not completely understood. In this sense, this book aims to integrate scientific information about the relevance of exercises and/or GH to the management of individuals with obesity. Moreover, it is expected that this book might bring new insights into the role of growth hormone in the obesity.

*DOI: http://dx.doi.org/10.5772/intechopen.111402 Introductory Chapter: Growth Hormone – Obesity and Physical Exercise*


**1. Introduction**

Aluminum-based alloys are widely used in the automobile industry not only because they are easily castable in complex forms but also because of their excellent wear resistance, light weight, and good strength, which make them widely used in the manufacture of numerous automotive parts, such as engine blocks and wheels. Additionally, aluminumbased alloys alloy are used as a matrix for obtaining composites [1,2], which have an enhanced wear resistance, favorable mechanical properties, and higher strength, Young's modulus, and fatigue resistance [3,4] at room and elevated temperatures. Dispersionhardened alloys are characterized by isotropic mechanical properties, high plasticity, and high strength [5,6]. The physical theory of plasticity and strain hardening was developed by Orowan [7], Ashby [8], Hirsch, and Humphreys [9,10].

**Citation:** Matvienko, O.; Daneyko, O.; Kovalevskaya, T.; Khrustalyov, A.; Zhukov, I.; Vorozhtsov, A. Investigation of Stresses Induced Due to the Mismatch of the Coefficients of Thermal Expansion of the Matrix and the Strengthening Particle in Aluminum-Based Composites. *Metals* **2021**, *11*, 279. https://doi.org/ 10.3390/met11020279

Received: 9 December 2020 Accepted: 29 December 2020 Published: 5 February 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

According to continuum linear elastic dislocation theory, Orowan [7] proposed that the interaction between dislocation and hardening particles leads to the formation of shear loops around the particles. This dislocation interaction scenario leads to what is known as Orowan strain hardening. Humphreys and Hirsch [11] proposed an alternative mechanism in which, if all dislocations are edge-oriented, each dislocation/particle interaction leads to two pairs of prismatic loops, one on each side of the particle. This multi-dislocation interaction, which involves the cross-slip of screw components of dislocations, is known as Hirsch looping. The material hardening depends on the types of particles, their volume fraction and homogeneous distribution in the matrix, and the interaction between matrix and strengthening particles.

The stress–strain curves at room temperature and at 400 ◦C for various types of dispersion-hardened aluminum alloys were determined in [12]. The results of investigations demonstrated that the effect of particles on the flow stress is in agreement with Orowan's theory [7]. A model to describe the creep of FCC metals has been used [13] for alloys and composites strengthened by the dispersion of nanosized particles. According to investigation results, the volume fraction and size of the nanosized particulate assumes a key role in determining the creep response of these materials. The results of investigations of the mechanical properties of aluminum alloys indicate that the hardness, yield strength, and ultimate tensile strength of the Al–2 vol.% C60 nanocomposites are higher than those of the monolithic Al samples.

The investigation in [14] dealt with aspects of the deformation behavior of dispersionhardened aluminum materials during uniaxial creep in a broad temperature range. Results of the investigation demonstrated that the threshold stress decreases considerably with increasing temperature.

The authors of [15] focused on the examination of materials of submicron matrix grain size strengthened with nanosized particles. The results obtained within the scope of this work showed the possibility for significant improvement of the microcomposite properties.

The results of the studies of the effect of nanodiamond addition on the physicomechanical properties of the drilling tool metal matrix were discussed in [16]. The optimal concentration of nanodiamond powder additives in the composition of a hard alloy mixture was defined. The addition of 1–2 wt.% nanodispersed diamonds was shown to contribute to binding oxygen in the thermo-oxidation of diamond in the course of the tool manufacture, which makes it possible to reduce the number of pores in the matrix material structure and to increase its density by 1.7% and hardness by 24.3%.

In [17], the effect of the aspect ratio of carbon nanotubes (CNTs) on strengthening aluminum metal matrix composites (Al MMCs) was investigated. The tensile results showed that the CNTs exhibited a strong strengthening effect in the composites regardless of their aspect ratios. However, the post-loading examination and quantitative analysis indicated that there was a strengthening mechanism transition for CNTs, which was closely associated with the aspect ratio or length of CNTs. The origin of such a transition was explored from the viewpoint of the dislocation–CNT interaction under loading.

The effect of Al4C3 formation on the tensile properties of multiwalled carbon nanotubes which reinforce an Al metal matrix was investigated in [18]. It was concluded that the formation of Al4C3 could effectively enhance the load transfer in composites.

Mathematical modeling of composites hardened by nanoparticles with a metal matrix was considered in [19]. The authors covered in detail the effect of the bulk content, distribution, and morphology of nanoparticles per average path length of a dislocation in the alloy (L). The authors revealed that the uniform distribution of grains in the matrix gave the smallest value of L. An increase in the bulk content of nanoparticles from 1 to 7 vol.% decreased the average path length of the dislocation by 50%, and, if their fraction exceeded 7 vol.%, the value of L was almost invariable.

In [20–23], a physical model of plastic deformation was suggested. The modeling of plastic deformation and strain hardening is based on the concept that the plastic slip in FCC alloys with incoherent nanoparticles leads to the formation of a defect structure with shear-forming dislocations, prismatic dislocation loops of vacancy and interstitial types, dislocation dipoles of vacancy and interstitial types, and interstitial atoms, monovacancies, and bivacancies.

An approach which combines methods of plasticity physics and mechanics of deformable solid was used in [24–26] to explore the limits of elastic and plastic resistance of the tube from dispersion-hardened aluminum alloy subjected to internal and external pressure.

It is known that, in composites, there is a large difference in the coefficients of thermal expansion between the matrix and the strengthening particles [27–29]. Thermally induced stresses could be generated as the result of a global heating and cooling of constructions, as well as local heating and cooling effects when a temperature gradient develops.

Therefore, the problem of thermally induced stresses due to a mismatch of the coefficients of thermal expansion between the matrix and strengthening particles has implications for the determination of mechanical properties of composite materials. The stress–strain state in plastic area around an oversized spherical particle which was introduced into a spherical hole in the matrix was analyzed in [30]. The analysis of stress–strain state must consider the contribution of thermally induced stresses in addition to the mechanically induced stresses [31]. These thermal stresses may be higher than the yield strength of the matrix and induce either debonding between particles and matrix or crack propagation leading to damage accumulation in the matrix [32,33].

The thermal stresses may be sufficient to generate new dislocations at the interfaces between the matrix and the reinforcement. In [29,34], the authors proposed that the increased strength observed in Al–SiC composites could be accounted for by a high dislocation density in the aluminum matrix, as observed in transmission electron microscopy (TEM). An increase in the density of newly created dislocations near reinforcement fibers was calculated in [24,35]. According to [36], when the composite is heated or cooled, misfit strains which are sufficient to generate dislocations occur because of differential thermal contraction at the Al–SiC interface. The investigations of the elastic and plastic stresses and strains generated about an inclusion, which has a coefficient of thermal expansion different from that of the matrix as a result of heating or cooling, was carried out in [34]. Furthermore, an in situ transmission electron microscopy investigation was undertaken into dislocation generation at the composite due to the differential thermal contraction. A simple model based on results of experimental investigation was developed to account for the relative dislocation density due to the differential thermal contraction.

Thus, it is very important to analyze the thermal stresses on the particle–matrix interface in order to predict a possible modification of the composite properties [37].

The purpose of this work was to experimentally and theoretically investigate the strength properties of aluminum alloys strengthened by nanoparticles, as well as to determine the significance of various mechanisms responsible for strengthening the material. Particular attention is paid to the development of a physicomathematical model of the occurrence of thermal stresses caused by a mismatch between the coefficients of thermal expansion (CTEs) of the matrix and strengthening particles, according to the fundamental principles of solid mechanics and taking into account, in contrast to previously existing models, the elastic properties of not only the matrix, but also the particle.


*3.1. Shortcake Biscuits Manufacturing*

*3.1. Shortcake Biscuits Manufacturing*  The recipe for reference biscuits (denoted as R in the text) was as follows: 200 g wheat flour (type 500) (GoodMills Polska sp. z o.o., Grodzisk Wielkopolski, Poland), 64 g white sugar (Pfeifer & Langen Polska S.A., Środa Wielkopolska, Poland), 20 g brown sugar (Pfeifer & Langen Polska S.A., Środa Wielkopolska, Poland), 2 g milk powder (SM Mlekovita, Wysokie Mazowieckie, Poland), 2.5 g salt (Kopalnia Soli 'Kłodawa' S.A., Kłodawa, Poland), 2 g baking powder (Dr. Oetker Polska Sp. z o.o., Gdańsk, Poland), 80 g baking margarine (Upfield Polska sp. z o.o., Warsaw, Poland), and 44 g water. In the test The recipe for reference biscuits (denoted as R in the text) was as follows: 200 g wheat flour (type 500) (GoodMills Polska sp. z o.o., Grodzisk Wielkopolski, Poland), 64 g white sugar (Pfeifer & Langen Polska S.A., Sroda Wielkopolska, Poland), 20 g brown ´ sugar (Pfeifer & Langen Polska S.A., Sroda Wielkopolska, Poland), 2 g milk powder ´ (SM Mlekovita, Wysokie Mazowieckie, Poland), 2.5 g salt (Kopalnia Soli 'Kłodawa' S.A., Kłodawa, Poland), 2 g baking powder (Dr. Oetker Polska Sp. z o.o., Gda´nsk, Poland), 80 g baking margarine (Upfield Polska sp. z o.o., Warsaw, Poland), and 44 g water. In the test samples, wheat flour was replaced with cricket powder (Crunchy Critters, Derby, UK) in three different quantities of 2%, 6%, and 10% (*w*/*w*) and denoted as CP2, CP6, and CP10, respectively. The amounts of other components were unchanged. The composition of CP (determined in a previously published study [16]) is: protein 42.0 ± 0.4 [%]; fat 29.1 ± 0.6 [%]; 3.6 ± 0.3 [%]; fiber 3.5 ± 0.02; and carbohydrate 21.8 ± 0.8 [%]. All the dry compounds were mixed together with the KitchenAid mixer (5KPM5EWH, KitchenAid, Greenville, OH, USA) for 3 min. Water was then added and mixing continued for another 1 min. The dough was rolled into 2 mm thick sheets, rounded shapes were cut with a Ø60 mm cookie cutter and placed in an aluminum tray. The position of biscuits on baking trays was the same for all variations. Biscuits were baked at 205 ◦C (MIWE Condo, MIWE Michael Wenz GmbH, Amstein, Germany) for 11 min, and then allowed to cool at room temperature for 15 min. The cool biscuits were packed in polypropylene pouches and stored at room temperature in darkness until analysis.


1. Introduction

The conduct of practical studies to optimize basic parameters in engineering systems of buildings is urged by power-saving requirements.

The given practical problem of improving engineering systems is to optimize the design of the heat exchanger in air heating systems of buildings.

Air heating systems of buildings are resource-consuming systems, for this reason, improving their resource efficiency appears to be of great significance.

Heating of air is provided by heat exchangers, which have been studied quite thoroughly. The studies involved different authors to deal with particular aspects of improving heat exchange elements [1].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The main properties of heat exchangers, such as amount of heat exchange, area of heat exchange, metal capacity and cost of an apparatus depend largely on the size of ribbing, so the efficiency of the design is determined by the optimal height of the rib [2, 3].

2. Materials/methods

puting complex IOZO NM 3.0b [9].

criteria are constrained [10].

mation function.

3. Results and discussion

In order to set optimal parameters for the heat exchanger and balance its design with technological elements the author conducted actual studies with the help of the complex method. It comprises optimization of parameters for heat exchanging process based on multicriterion multiparameter mathematical models and experiments with thermal field visualization.

The Solution of Private Problems of Optimization for Engineering Systems

http://dx.doi.org/10.5772/intechopen.80520

91

The optimization problems are solved using the method of non-linear optimization in com-

Besides, the solution of such problems is also possible with the help of non-linear optimization program Generalized Reduced Gradient (GRG2), designed by Leon Lasdon, University of Texas at Austin and Allan Waren, Cleveland State University, and based on the method of conjugate gradients—iterative method for unconstrained optimization in multidimensional space. The main advantage of this software package is that it is able to solve the quadric optimization problem within finite number of moves. So, first the author describes the method of conjugate gradients to optimize the quadric functional, then he derives iterative formulas and estimates convergence rate. Next, the author demonstrates how the method of conjugate gradients is generalized to optimize arbitrary functional, looks at different variations of the method, and assesses convergence. The shortcoming is that controllable and non-controllable parameters and

It is possible to use as a mathematical model a two-criterion problem of clusterization with fuzzy constraints. The fuzzy constraints can be set by specific preference functions. The solution is made in Boolean variables with the help of stochastic search, improved by heuristics.

Solution of multicriterion multiparameter nonlinear optimization problem of engineering systems in buildings suggested applying software package IOSO NM version 3.0b, where the author entered empirical data from thermal imaging. A special feature of this software is its compatibility with Microsoft Excel and other programs. IOSO package allows setting controllable and noncontrollable parameters, optimal criteria, and constraints for the process. Further,

Preliminary IOSO procedure is forming the initial experiment plan, which can be passive (using the previously obtained information about variable parameters, optimization criteria and constraints), as well as active, when the set is generated in the initial search field in accordance with the preset partition law. Each vector of variable parameters for optimization and constraints implies direct use of mathematical model of the object studied. The number of points in the initial experiment plan depends on the problem dimension and the chosen variant of approxi-

To find the minimum mass of the ribs of the heat-exchange apparatus with the maximum of its heat productivity developed mathematical model of multi-criteria optimization problem

The algorithm is implemented in the form of a universal software module [11].

IOSO program establishes optimal process parameters by using the data from Excel.

One of the authors of this paper, Khrustalev, looked into the criterion to assess the efficiency of heat exchanger design. The paper also suggests theoretical dependencies to calculate technical characteristics of heat exchangers. However, these dependencies do not allow optimization on several parameters [4–6].

A.A. Melekhin in his previous papers studied the multicriterion optimization of the rib in heat exchangers based on two criteria; however, other parameters were not considered [7].

In the given paper the author makes a thermodynamic analysis and optimizes heat exchangers of air-cooling, at the same time these improvements are not based on the complex approach [8].

The occurrence of new methods, namely a complex method, allows combining mathematical modeling with visualization of heat fields, and as a result, obtaining optimal parameters of heat exchangers for the given systems.

The purpose of the given study is improving the efficiency of heat exchangers by optimizing their parameters and design.

To achieve this goal we set and solved the following tasks:

The novelty of the given paper lies in the following:

The practical value of the paper is in the following:


*2.2.2. Antioxidants determination*

Soybean samples approximately (1 g) were powdered and homogenized in 10 ml 80% methanol. The mixture was shaken at 300 rpm at room temperature for 3 h. Then the extract was centrifuged for 10 min at 3000 rpm and upper aqueous phase were transferred to new Eppndorf tubes. Moreover, the residues were again extracted with 5 ml 80% methanol overnight. The extraction was performed in three replicates, later on extracts combined and stored in dark at 4°C. The Folin-Ciocalteu reagent was used to determine the total phenolic compounds from the extracts using gallic acid calibration curve as standard. The total phenolics were expressed as mg/g gallic acid equivalents (GAE). An extract was aliquot (50 μl) and mixed with Folin-Ciocalteu reagent of 250 μl and 7.5% sodium carbonate of 750 μl. The volume was increased to 5 ml with water and sample was incubated for 2 h. The absorbance was measured at 765 nm against distilled water as blank. The flavonoid determination was measure by aluminum chloride method with the help of Quercetin equivalent as standard. An aliquot of extract (250 μl) was mixed with ddH2O and 5% NaNO2 (15:1, v/v). After 6 min, 150 μl of 10% AlCl3 was added to the mixture. A 500 μl of 1 M NaOH was added to the mixture at the 5th min, and volume made up to 2.5 ml with distills water and the absorbance was measured spectrophotometrically at 410 nm.

among genotypes were recorded and that might observed due to differences in genetic background and/or origin. The higher protein content in the genotypes is also reported previously which ranged from 43 to 45% [18]. These results are also in line with Zarkadas et al. [19, 20] who reported crude protein contents in soybean ranging from 33.67 to 42.11%. The minimum moisture contents were recorded in Giza 83 (3.08%) while maximum was recorded for Indo-1 (5.88%) with an average (4.90%) mean value showing non-significant difference. Ash contents ranged from 4.55 to 6.28% with an average of 5.44%. The maximum was recorded for Giza 111 (6.28%) genotype while Romal-1 genotype had the lowest (4.55%) of ash contents. The moisture and ash contents values were recorded lower than that reported by [21]. Total fat ranged from 16.92 to 22.94% with a mean value of 21.16%. The genotype Indo-black contained the lowest while the genotype 3803 recorded the highest content. Soybean is considered about 47% of its energy value in fat content [22, 23] which is compared to other legumes.  The minimum carbohydrate content in Clark (26.11%) while maximum in Argentinian (33.18%), with an average (29.48%) was recorded

Phytochemical Profiling of Soybean (*Glycine max* (L.) Merr.) Genotypes Using GC-MS Analysis

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143

Flavonoid and phenolic compounds are the important phytochemicals and natural antioxidants founds in fruits, vegetable and cereals grains. It serves as multiple biological functions, i.e., defense against cardiovascular disease, cancer and aging [25]. The results regarding total phenolic and flavonoids contents for 24 soybean genotypes are presented in **Table S1**, and significant differences were recorded for all soybean genotypes. The seed extracted results indicated that the maximum phenolic contents was recorded in Romal-1 (1.7 mg/g) while minimum in Giza 111 (1.15 mg/g) with an average 1.45 GAE/g mg/g (**Table 2**). However, total flavonoid content ranged 0.68 to 2.13 mg QE/g (**Table 2**). Phenolic content is strongly linked with antioxidant capacity [26, 27] and can contribute towards antioxidants activities [28]. The use and demands of phenolic are

increasing rapidly in food industry to enhance nutritional value and quality of food [29].

**Crude protein (g/100 g)**

Stand. dev.

Coeff. Var.

**Moisture (g/100 g)**

**Ash (g/100 g)**

**Table 2.** Descriptive statistics of chemical composition in 24 soybean genotypes.

**3.2. Flavonoid and phenolic contents**

#### *2.2.3. Gas chromatography-mass spectroscopy*

The GC-MS analysis of fractions were performed using a TSQTM 8000 Evo Triple Quadrupole GC-MS/MS (Thermo Fisher Scientific) equipped with an Elite-5 capillary column (length 30 nm and inner diameter 0.25 mm and film thickness 0.25 μm) and mass detector was operated in electron impact (EI) mode with full scan (50–550 amu). Helium was used as the carrier gas at constant flow rate 1 mL/min and an injection volume of 1 μL. The oven injector temperature was programmed from 50°C with an increase of 8°C/min to 200°C, then 7°C/min to 290°C/min. The results were compared using the database of National Institute Standard and Technology (NIST).

## **2.3. Data analysis**

The data were subjected to descriptive statistics (mean, standard deviation, coefficient of variability, minimum and maximum values) and principal component analysis (PCA) using statistical software Past3 program [17].