*1.3.1 Alpha particles*

*DNA - Damages and Repair Mechanisms*

radiation safety [1–3].

nuclear weapon development etc., has increased the risk of exposure. Inadvertent accidents from nuclear power plant installations, nuclear weapon testing and illegal use of radioactive material in dirty bomb have raised an international concern for

Radiation therapy is the most common and deliberate exposure of high energy rays to living organisms. This exposure is mainly therapeutic for treatment of cancer but since there is no clear demarcation to protect the adjacent noncancerous cells leads to disastrous effect. The immediate exposure of high energy beam of radiation leads to destruction of cancerous cells. Whereas the adjacent normal cells are however exposed to these rays suffer adverse effects. It indirectly generates reactive oxygen species (ROS) inside the cellular system through hydrolysis of water. ROS directly targets cellular DNA and affect the cell survival by damaging macromolecules like lipid, proteins and carbohydrate. The damage induction in DNA molecules could be of various types like double strand break, single strand break, dimer formation, alteration of bases etc. Mammalian cells are equipped with very efficient DNA repair mechanism to handle these different damages [4]. Moreover among all, double strand breaks are known to be lethal damage for the cells. There are mainly two repair mechanisms that operate for repair of double strand breaks. These are 1) Homologous repair pathway (HR) 2) Non homologous end joining pathway (NHEJ). The basis on which cell decides to choose one of the two available pathways is simply on cell cycle phase, its type and damage threshold [5]. There are also exists third repair pathway i.e. Alternative non homologous end joining pathway (A-NHEJ) it is much slower than the above mentioned pathway. It comes into play when above mentioned pathway fail to repair the damage thus acting as a backup pathway. The presence of this alternative pathway has not been studied extensively but it has been speculated for its role in combinational cancer therapeutics. In this chapter, we have briefly described the various kind of DNA damage generated by radiation and role of DNA repair pathways specially NHEJ and A-NHEJ in handling the

repair and their applications in progression of disease [6].

and non-ionizing radiation [6, 7].

examples of non-ionizing radiation [5].

**1.1 Non-ionizing radiation**

**1.2 Ionizing radiation**

Radiation, which has particles with enough energy to rip electron from atoms or molecules is known as ionizing radiation. Radiation is the emission and propagation of energy in the form of rays or waves. The term radiation comes after the discovery of X-ray in 1895 by Wilhelm Conrad Roentgen. Henri Becquerel and Marie Curie have made significant contributions in studying the effect and application of radiation in various fields. Excitation and ionization properties are common responsible factor for radiation emitted by any radioisotopes. It has two major types: ionizing

It does not carry enough energy to remove electrons from an atom or molecule. Because of their low energy, non-ionizing radiation poses a lower risk than ionizing radiation. Visible light, near ultra violet, infrared, microwave and radio waves are

Ionizing radiation (IR), as the name indicates carry sufficient energy to remove

electrons from atoms or molecules. It can be in particulate or electromagnetic form. The particulate forms consist electrons, protons, neutrons, α-particles etc. and the electromagnetic form includes as cosmic rays, X-rays, gamma rays etc. [5]. Ionizing radiation exposure may cause tissue injuries to the biological system

**100**

An alpha ray consists of two protons and two neutrons. These rays have a strong nuclear force and have the ability to bind to the nucleus of any atom. Due to their charge and mass, alpha particles interact strongly with matter and only travel a few centimeters in air. Alpha particles are unable to penetrate the outer layer of dead skin cells but are capable of causing serious cell damage if an alpha emitting substance is ingested in food or air [5].


**Abstract**

The formation of defects and imperfections in the soldering process can have many causes, which primarily include a poorly setup technological process, inappropriate or inappropriately used materials and their combinations, the effect of the surroundings and design errors. This chapter lists some examples of errors that can occur in soldering, while review is devoted to selected defects: non-wettability of the solder pads, dewetting, wrong solder mask design, warpage, head-in-pillow, cracks in the joints, pad cratering, black pad, solder beading, tombstoning, dendrites, voids, flux spattering from the solder paste, popcorning and whiskers.

**Keywords:** electronic assembly, soldering, reflow soldering, soldering defects, reliability issues

## **1. Introduction**

A significant change in soldering technology was the transition to lead-free soldering. With this change and the increasing miniaturisation of electrical equipment comes the associated issue of developing suitable alloys, production technology, etc. Over time, soldering has become a very complex process, with many factors affecting the final quality of the solder joints, and thus the product.

The formation of defects and imperfections in the soldering process can have many causes, which primarily include a poorly setup technological process, inappropriate or inappropriately used materials and their combinations, the effect of the surroundings and design errors. This chapter lists some examples of errors that can occur in soldering.

## **2. Non-wettability**

One of the problems is the non-wettability of the soldering pads. During the soldering process, the soldering pads are not sufficiently wetted with the solder alloy (the solder does not create a connection with the entire surface of the soldered area). An example of this defect is shown in **Figure 1**.

This defect may be caused by the soldering pads being too oxidised, the flux not being active enough, insufficient PCB warming, soldering pad contamination as well as, for instance, a poor solder mask coating [1].

**Figure 1.** *Problems with the non-wettability of soldering pads.*


**3. Challenges of postharvest losses in vegetable crops**

Application of good postharvest management practices which are supported by good technologies and also improving postharvest systems will maintain the quality of vegetables and reduce quantitative losses. Losses in vegetables are the result of (i) poor knowledge about the right harvesting index; thus, a large proportion of the harvested beans are usually over-mature (ii) poor handling practices, such as the use of plastic sacks for bulk packaging and transportation

which results in mechanical damage that serves as entry points for disease-causing organisms leading to rotting of the pods (iii) poor transport practices such as the use of trucks that have no cover, thus exposing the produce to direct sunlight and high temperature (iv) the absence of low-temperature storage facilities and transport systems, and (v) rough handling practices during distribution in retail markets.


**2.1 Growth of nitride-based reflectors and micro-cavity**

The detail growth process and experiment parameters of the micro-cavity and nitride-based DBR on sapphire substrates by metal organic chemical vapor deposition (MOCVD) are described as follows:

First, the substrate was thermally cleaned in the hydrogen ambient for 5 min at 1100 °C. And then, a 30 nm-thick GaN nucleation layer was grown at 500°C. The growth temperature was raised up to 1100 °C for the growth of a 2 µm-thick GaN buffer layer. The subsequent epitaxial structure consisted of a 29-pair of quarter-wave AlN/GaN DBR grown at 1100 °C, a 7-lamda cavity ( = 410 nm) which includes a 860 nm-thick Si-doped n-GaN layer, 10 pairs In0.2Ga0.8N/GaN (2.5 nm/12.5 nm) MQWs, a 24 nm-thick AlGaN layer as the electron blocking layer, a 110 nm-thick Mg-doped p-GaN layer, and a 2 nm-thick p+ InGaN layer as the contact layer. The AlN/GaN super-lattices (SL) inserted in the stacks of 29-pair AlN/GaN layers are fabricated because they can release the strain during the growth of AlN/GaN DBR and further improve interface and raise reflectivity of the DBR. Besides, the AlN/GaN DBR can play the role of the low refractive index layer to confine the optical field in the active region in the whole structure. And then, the AlGaN electron blocking layer was served to reduce the electron overflow to the p-GaN layer. The reflectivity spectrum of the AlN/GaN DBR is shown in Fig. 1. It shows the highest reflectivity of the DBR is about 99% at 416 nm. The stop-band of the DBR is as wide as about 25 nm. Fig. 2. is (a) the OM and (b) cross-sectional TEM images of the as-grown micro-cavity sample.

Fig. 1. The reflectivity spectrum of the AlN/GaN

Here, the fabrication processes are composed of two parts. One is the epitaxial growth on sapphire substrates by metal organic chemical vapour deposition (MOCVD), including a 29 pair distributed Bragg reflectors (DBR), a p-GaN layer, multi-quantum wells, a n-GaN, and a un-doped GaN layer, etc. Another one is to fabricate the PhC nanostructure on the epitaxial wafers by the E-beam lithography system and inductive coupled plasma reactive ion etching (ICP-RIE) system. Finally, the GaN-based photonic crystal surface emitting laser

The detail growth process and experiment parameters of the micro-cavity and nitride-based DBR on sapphire substrates by metal organic chemical vapor deposition (MOCVD) are

First, the substrate was thermally cleaned in the hydrogen ambient for 5 min at 1100 °C. And then, a 30 nm-thick GaN nucleation layer was grown at 500°C. The growth temperature was raised up to 1100 °C for the growth of a 2 µm-thick GaN buffer layer. The subsequent epitaxial structure consisted of a 29-pair of quarter-wave AlN/GaN DBR grown at 1100 °C, a 7-lamda cavity ( = 410 nm) which includes a 860 nm-thick Si-doped n-GaN layer, 10 pairs In0.2Ga0.8N/GaN (2.5 nm/12.5 nm) MQWs, a 24 nm-thick AlGaN layer as the electron blocking layer, a 110 nm-thick Mg-doped p-GaN layer, and a 2 nm-thick p+ InGaN layer as the contact layer. The AlN/GaN super-lattices (SL) inserted in the stacks of 29-pair AlN/GaN layers are fabricated because they can release the strain during the growth of AlN/GaN DBR and further improve interface and raise reflectivity of the DBR. Besides, the AlN/GaN DBR can play the role of the low refractive index layer to confine the optical field in the active region in the whole structure. And then, the AlGaN electron blocking layer was served to reduce the electron overflow to the p-GaN layer. The reflectivity spectrum of the AlN/GaN DBR is shown in Fig. 1. It shows the highest reflectivity of the DBR is about 99% at 416 nm. The stop-band of the DBR is as wide as about 25 nm. Fig. 2. is (a) the OM and (b)

**2. Fabrication processes**

described as follows:

(PCSEL) devices with AlN/GaN DBR are performed.

**2.1 Growth of nitride-based reflectors and micro-cavity**

cross-sectional TEM images of the as-grown micro-cavity sample.

Fig. 1. The reflectivity spectrum of the AlN/GaN

**99% at 416nm**


*3.5. Plantlets Adaptation to Ex Vitro Conditions*

After being acclimatized to changes in temperature, humidity, and water loss, the invitro-propagated plantlets (4.0–5.0 cm in length, with 3–4 leaves (Figure 7a)) were directly planted on two soil types. The results presented in Table 4 show that the mean survival rate of in vitro plantlets on the two soil types reached 75.6–83.3% after a month of planting and 41.1–48.9% after 3 months of planting (Figure 7b,d). Among the two soil types studied, "Fasco" bio-soil produced a higher survival rate of 83.3% after a month of planting and 48.9% after 3 months of planting. The plantlets grew on this soil type better (mean length of 23.3 cm and a mean number of leaves of 5.7). The corresponding results when planting on "Garden Star" soil were all lower (Figure 7c,e).

**Figure 7.** Effect of acclimatization of in-vitro-propagated black cardamom plantlets after transfer in the greenhouse conditions: (**a**) in-vitro-propagated plantlets; plantlets after 1 (**b**) and 3 (**d**) months of planting on "Fasco" bio-soil; plantlets after 1 (**c**) and 3 (**e**) months of planting on "Garden Star" soil. Scale bar = 2 cm.

**Table 4.** Effect of different soil types on efficiency of black cardamom plantlet adaptation and their morphometric characteristics.

1 Mean ± standard error.


**Author details**

Adil M. Allahverdiyev, Malahat Bagirova, Olga Nehir Oztel, Serkan Yaman, Emrah Sefik Abamor, Rabia Cakir Koc, Sezen Canim Ates and Serap Yesilkir Baydar *Department of Bioengineering, Yildiz Technical University, Istanbul, Turkey*

Serhat Elcicek

*Department of Bioengineering, Yildiz Technical University, Istanbul, Turkey Department of Bioengineering, Firat University, Elazig, Turkey*