**Contents**

## **About the Editor**

#### **Antoaneta Ene**

Antoaneta Ene (Prof.dr.habil.eng.) obtained her Ph.D. in Particle Physics in 1997 at the University of Bucharest, Romania, studying the elemental composition of raw materials and finite products in iron and steel industry using atomic and nuclear methods. She has a MSc. in Environmental Sciences (2007) and obtained a Habilitation in Industrial Engineering (2015) at Dunarea de Jos University of Galati, Romania.

Her research interests include the determination of trace elements and radioisotopes in industrial, geological, food and environmental materials; heavy metal atmospheric deposition using mosses as biomonitors; identification of microplastics in personal care products; analysis of composition and structure of advanced materials using nuclear techniques and imaging microscopy; monitoring of toxic substances in the environment, including pharmaceutical residues and metabolites, and assessment of their impact upon ecosystems and human health.


**2. Model of go-kart energy usage**

In order to determine energy requirements, the model assumes that the energy stored in batteries EB must provide the possibility to finish a maximum duration race (based on the Rotax Max Challenge 2016 Cup) with the go-kart using maximum power, which was experimentally derived on different racetracks in Poland and Europe:

$$\mathbf{E}\_{\rm g} = \mathbf{W}\_{\rm gmax} \times \mathbf{n} \tag{1}$$

The model assumes that the energy used on one lap PO is equal to the sum of instantaneous

where PO—average power value used during lap (kW), Pch—instantaneous power (kW), NO—

In the presented approach, it was assumed that Pch—instantaneous power is calculated based on instantaneous engine rpm and the engine power/rpm specification curve presented in **Figure 4**. Due to the permanent coupling of the engine with the drive axle, in the course of the analysis, braking periods during the lap were identified and excluded from the calculation of average power. Based on observations and analysis, it was assumed that braking is a decrease in engine speed of at least 300 rpm with at least three measuring periods, that is, over 0.3 s and

is associated with a significant decrease in vehicle speed, that is, at least 2 km in 0.1 s.

**2.1. Analysis of race durations in the Rotax max challenge Poland championships in**

rounds of the Rotax Max Challenge Poland Championships in 2016.

**Figure 3.** Race durations in Rotax Max Challenge Poland Championships 2016 for given categories.

Championships in 2016 are shown separately.

Following Eq. (2), it was necessary to analyze the duration of races tRmax to calculate the work performed by the power train. This analysis is based on the duration of go-kart races in the 12

The analysis allowed us to determine maximum race times for the drivers who had completed full races in each of the age categories. **Figure 3** shows the time intervals in which the drivers finished the races of the given round of the Rotax Max Challenge Poland Championships in 2016. The data for wet races of the first round of the Rotax Max Challenge Poland

*NO P* \_\_\_\_\_\_\_*ch NO*

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power calculations in tenths of a second of the lap.

*PO* = ∑*i*=0

**2016**

number of measurements (measurement in 0.1-s intervals).

where EB—energy stored in batteries (kWh), WRmax—work done by running go-kart during the race with maximum energy consumption (kWh), n—coefficient of securing sufficient level of energy (%).

In simplified terms, it was assumed that WRmax is the work done by the combustion engine of a go-kart of average power POmax throughout the maximum duration of the race tRmax.

$$\mathcal{W}\_{\text{Rmax}} = \mathcal{P}\_{\text{Omax}} \times t\_{\text{Rmax}} \tag{2}$$

where tRmax—the maximum duration of the race based on an analysis of the Rotax Max Challenge 2016 Polish Championships (s), POmax—average power used by go-kart during a lap with the highest power usage (kW).

POmax was obtained by selecting the highest value from the calculated average power POs, for six different cases of go-kart racing in a given age category. We chose the shortest and longest run times on three racetracks with different characteristics.

The model assumes that the energy used on one lap PO is equal to the sum of instantaneous power calculations in tenths of a second of the lap.

$$P\_O = \frac{\sum\_{i=0}^{M\_b} P\_{ab}}{N\_0} \tag{3}$$

where PO—average power value used during lap (kW), Pch—instantaneous power (kW), NO number of measurements (measurement in 0.1-s intervals).

In the presented approach, it was assumed that Pch—instantaneous power is calculated based on instantaneous engine rpm and the engine power/rpm specification curve presented in **Figure 4**. Due to the permanent coupling of the engine with the drive axle, in the course of the analysis, braking periods during the lap were identified and excluded from the calculation of average power. Based on observations and analysis, it was assumed that braking is a decrease in engine speed of at least 300 rpm with at least three measuring periods, that is, over 0.3 s and is associated with a significant decrease in vehicle speed, that is, at least 2 km in 0.1 s.


**New Developments in Physical Education and Sport**

Editor

**Antonio Granero-Gallegos**

MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade • Manchester • Tokyo • Cluj • Tianjin

*Editor* Antonio Granero-Gallegos University of Almeria Spain

*Editorial Office* MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

This is a reprint of articles from the Special Issue published online in the open access journal *International Journal of Environmental Research and Public Health* (ISSN 1660-4601) (available at: https: //www.mdpi.com/journal/ijerph/special issues/new developments physical education sport).

For citation purposes, cite each article independently as indicated on the article page online and as indicated below:

LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. *Journal Name* **Year**, *Volume Number*, Page Range.

**ISBN 978-3-0365-0244-1 (Hbk) ISBN 978-3-0365-0245-8 (PDF)**

© 2021 by the authors. Articles in this book are Open Access and distributed under the Creative Commons Attribution (CC BY) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications.

The book as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND.


**4. Novel methods to discover and identify PAT/substrate specificity**

The chemistry supporting novel assays to study palmitoylation and the reagents that are be‐ ing incorporated into them have, for the most part, been known and available for years [88] . Most of the methods that are now being developed to study palmitoylation capitalize on many years of knowledge and development of cysteine-specific chemistries, developed mainly as methods to purify and/or specifically target proteins and peptides with various reagents. Many of the reagents that specifically label cysteines have been created as both af‐ finity and fluorescent tags, the former for purification and structure determinations [88]and the latter as cellular reporters of protein abundance, subcellular distribution, protein confor‐ mation changes, the formation of the Golgi, and even the concentration of cellular analytes in specific subcellular domains. The following references provide a short list of some of the most clever uses of thiol chemistry [113-119]. Given the wealth of information on the unique chemistry of the palmitoyl thioester bond and the tools for capturing and characterizing cys‐ teines in proteins, it is somewhat surprising that we are only now developing innovative as‐ says to increase our understanding of palmitoylation. This recent increase is most likely tied to the dramatic increase in the utility of mass spectrometry as a proteomic tool. To provide a general frame of reference for the recent shift in the types of assays that are being devel‐ oped, we will briefly discuss other assays that have been used successfully for a longer peri‐ od of time. These assays are by no means outdated and some continue to be the most appropriate way to answer specific questions.

versed in 0.1N HCl and reducing reagents like dithiothreitol (DTT) but apparently not by TCEP. Phenylmercury derivatives also react faster with thiols than do the commonly used

Compounds containing disulfide bonds are able to undergo disulfide exchange reactions with another thiol by the free thiol attacking the disulfide bond and subsequent formation of a new mixed thiol. Two examples of useful compounds in this category are Methylmethane‐ thiosulfonate (MMTS) and pyridyl disulfide derivitives like biotin HPDP ((*N*-(6-(Biotinami‐ do)hexyl)-3'-(2'-pyridyldithio)-propionamide). MMTS can be used in some cases to block free thiols more effectively than NEM, as it is uncharged and thus more likely to modify all free reactive cysteines. MMTS has been shown not to react with nitrosothiols or existing di‐

The most common method to identify palmitoyl proteins and to determine the residence half-life of palmitate on a specific protein or palmitate turnover (e.g. [122] for a particularly interesting example) is to metabolically label cells with radiolabled palmitate. 14C-, 3

tively inexpensive and widely available. However, using 125I -labeled palmitate provides some advantages. In practical terms, the time required for detection is considerably shorter -

patible with phosphorimaging technology which is much more rapid and quantitative than densitometric measurements from films generated by autofluorography (as is used with tri‐ tium). The principle downside of using 125I-labeled palmitate is that it is not commercially available, and the labeling must be done by the investigator. Reviews of the methods using radiolabeled palmitate and including technical details have been published recently

Fluorescently-labeled peptides that mimic PAT substrates have been used to characterize PAT activity and for the discovery of inhibitors of palmitoylation [123, 126, 127]. The use of these peptides over the last several years was reviewed recently [123]. Peptide substrates for palmitoylation have also been genetically fused to fluorescent proteins and expressed in cells. This strategy has been used to determine how palmitoylation affects subcellular traf‐ ficking both between and within membranes [124]. Monomeric GFP-based reporters and fluorescence resonance energy transfer proved to be helpful in the identification of lipid

Most of the novel assays for palmitoylation utilize the same basic foundation first described for a palmitoyl protein by Schmidt and colleagues [128] and now most commonly known as acyl-exchange. First, free cysteines are blocked on proteins that have been extracted from

rafts with an affinity for palmitate on the inner leaflet of the plasma membrane [5].

H- and

H-palmitate is most common because it is rela‐

Discovery of Selective and Potent Inhibitors of Palmitoylation

http://dx.doi.org/10.5772/52503

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H-palmitate. The *γ-*irradiation from the 125I is also com‐

thiol-reactive *N*-ethylmaleimide (NEM).

**4.2. Metabolic labeling with radiolabeled palmitate**

**4.3. Fluorescently-labeled peptide substrates for palmitoylation**

125I-labeled palmitate have all been used, but 3

hours instead of (often) weeks with 3

**4.4. Acyl-biotin exchange: ABE**

sulfides [121].

[123-125].

#### **4.1. Chemistry and physical properties of palmitoyl cysteines: Reactions and probes**

Working with palmitoylated proteins is inherently difficult due to the labile nature of the thioester bond and the increased hydrophobicity of the protein or peptide due to palmitate. On the other hand, the unique physical and chemical properties of thiols, palmitoylated thi‐ ols, and the thioester bond make them particularly amenable to modification by highly spe‐ cific chemistry and a wide variety of thiol reactive probes.

#### *Reactions of free thiols in the cytoplasm*

Thiol modification occurs most commonly in cells by one of two routes: disulfide exchange or alkylation. Many of the reactive groups that undergo these two reactions are relatively stable in aqueous environments; the reactions are rapid and provide high yields of thioether and disulfide bonds [88]. Thiols will also react with many amine reactive reagents including isothiocyanates and succinimidyl esters but lack a high degree of specificity, resulting in un‐ stable bonds that are much less useful for routine modification of thiols in proteins. Thiolspecific reagents and chemistry figure strongly into the design and development of novel assays for palmitoylation. Most investigators are limited somewhat to reagents that are available from a catalog but, fortunately, there are already many useful reagents available. Among the most useful are thio-reactive chemicals that are linked to another moiety (reac‐ tive or reporter) by a spacer arm of variable length and physical characteristics. Such heteroand homo-bifunctional crosslinking reagents have provided much of the foundation for recent developments in palmitoylation assays and provide a fairly rich toolbox for future as‐ say development.

#### *Chemical moieties that react with palmitoyl-cysteines*

Iodoacetamide conjugates are among the most commonly used tools for modifying cysteine thiols. These undergo nucleophilic substitution to form stable thioether bonds at physiologi‐ cal pH in aqueous environments. When using iodoacetamide and its conjugates, one should remember that depending on the pH of the solution, they can also react with histidine, ly‐ sine, and methionine (at pH >1.7) residues and N-terminal amines. However, when used at slightly alkaline pH in the dark and in the absence of reducing reagents, cysteine modifica‐ tion will be the exclusive reaction [88]. A good example of iodoacetamide-based probes are the isotope-coded affinity tags or ICAT [120]. These have proved particularly useful in de‐ termining the substrates of DHHC2 [37].

Maleimides are also common constituents of heterobifunctional crosslinking reagents and blocking reagents that target cysteines. They are ~1000 times more specific for cysteine sulf‐ hydryls at pH 6.5-7.5, but at higher pH some cross reactivity can occur with amines. Mal‐ eimides form stable thioether bonds by adding the sulfhydryl across the double bond of the maleimide.

Phenylmercury derivatives react with thiols, including nitrosothiols, under conditions simi‐ lar to iodoacetamides and maleimides to form stable mercury-thiol bonds that can be re‐ versed in 0.1N HCl and reducing reagents like dithiothreitol (DTT) but apparently not by TCEP. Phenylmercury derivatives also react faster with thiols than do the commonly used thiol-reactive *N*-ethylmaleimide (NEM).

Compounds containing disulfide bonds are able to undergo disulfide exchange reactions with another thiol by the free thiol attacking the disulfide bond and subsequent formation of a new mixed thiol. Two examples of useful compounds in this category are Methylmethane‐ thiosulfonate (MMTS) and pyridyl disulfide derivitives like biotin HPDP ((*N*-(6-(Biotinami‐ do)hexyl)-3'-(2'-pyridyldithio)-propionamide). MMTS can be used in some cases to block free thiols more effectively than NEM, as it is uncharged and thus more likely to modify all free reactive cysteines. MMTS has been shown not to react with nitrosothiols or existing di‐ sulfides [121].


2.2.1. Conventional Space Vector Modulation

The current space vector diagram of conventional space vector modulation (C-SVM) for the AC–DC MC is illustrated in Figure 2. In order to synthesize the desired input current reference vector → *I re f* , C-SVM uses the two nearest active vectors and one zero vector among six active vectors → *I* 1 ∼ → *I* 6 and three zero vectors → *I* 7 ∼ → *I* 9, according to the sector location of the input current reference vector. Each sector is denoted as the area between two active vectors, for example, the area between two active vectors → *I* 1 and → *I* 2 is sector I, the area between two active vectors → *I* 2 and → *I* 3 is sector II, and so on. As it can be seen from Figure 2, the input current reference vector locates in sector I, thus two active vectors → *I* 1, → *I* 2 and one zero vector are used to synthesize the desired current reference vector. The selection of zero vector is based on the constraint to minimize the switching frequency of bidirectional switches so that the commutation between two switching states involves only two switches in two phase-legs of the converter, one switch is turned on, and one switch is turned off at the same time. Among three zero vectors, only zero vector → *I* 7 satisfies the requirements for switching devices. Therefore, zero vector → *I* 7 and two active vectors → *I* 1, → *I* 2 are selected.

**Figure 2.** Space vector diagram of conventional space vector modulation (C-SVM) for AC–DC matrix converter.

The duty cycles *d*1, *d*2, and *d*0 of the active and zero vectors, when the input current reference vector is in the sector I, are given by:

$$d\_1 = m\_l \sin\left(\frac{\pi}{3} - \delta\right) \tag{1}$$

$$d\varphi = m\_i \sin(\delta)\tag{2}$$

$$d\_0 = 1 - d\_1 - d\_2 \tag{3}$$

where *mi*: modulation index; *mi* = *ii*1/*idc mi* ∈ [0, 1]; *ii*1: the peak value of the fundamental-frequency component in *ii*; δ : input current reference vector angle, δ ∈ 0, π3 .

The durations *T*1, *T*2, and *T*0 of the active vectors → *I* 1, → *I* 2, and zero vector → *I* 0 are respectively expressed as:

$$T\_1 = d\_1 T\_s \tag{4}$$

$$T\_2 = d\_2 T\_s \tag{5}$$

$$T\_0 = T\_s - T\_1 - T\_2 \tag{6}$$

where *Ts*: switching period: *Ts* = 1*fs*; *fs*: switching frequency.

The calculation of the duty cycles and durations, when the input current reference vector passes through other sectors one by one, is obtained in a similar algorithm as sector I.


**4. Discussion**

#### *4.1. Opportunities in Virtual Stakeholder Engagement*

Overall, hosting the stakeholder meetings virtually using Zoom and GoogleDrive was successful. After participating in the workshop, stakeholders had the opportunity to complete an evaluation form to let us know about their experience, responses included:

• "I appreciate how difficult this was over Zoom, how difficult surveys are in general and how difficult trying to get consensus on the topic of microplastic can be. I found the discussion interesting and informative for our own work communicating about this problem. I look forward to seeing the results!"

#### *Societies* **2020**, *10*, 98

Conducting in-person social science research can be costly in terms of funding and time. Expenses include room reservations (multiple if breakout groups are necessary), mileage reimbursement for participants, hotel reservations for experts, video-recording equipment, food, and supplies. Given the limited funding in social sciences, these factors can be a major deterrent from being able to conduct stakeholder workshops. Additionally, Shelley-Egen emphasizes that there is a suite of technological alternatives already in existence [11]. However, most of those alternatives were created in conjunction with face-to-face meetings [11]. Thus, a challenge for this research was to utilize platforms that would eliminate the need for in-person interactions.

We chose technology platforms that were not only familiar to participants but also at a low cost to us (GoogleDrive services were free and the upgraded Zoom account was already provided to professors from the University). There were no costs associated with on-boarding participants to these platforms since Zoom is free and GoogleDrive allows the host to send materials for review and manipulation by non-Gmail users. There were also no expenses associated with travel by hosts, experts, or participants. Oftentimes, the funding constrains the number of people who can participate given the associated costs per person. With this virtual workshop, we were able to invite as many stakeholders as appropriate. Additionally, over the three days, only 10 percent of participants recruited did not show up, whereas 30 percent of participants recruited for previous work did not show up [16]. Altogether, using virtual platforms to conduct social science research removes the constraints detailed above and may provide an opportunity for the direction of future social science research.

We acknowledge that the success of this methodology is constrained by internet connectivity and quality and users comfort with technology and remote meetings. Belzunegui-Eraso and Erro-Garces emphasize the important role technology plays in the successful development of telework [27]. According to Belzunegui-Eraso and Erro-Garces, the ideal teleworker is a "Millenial woman holding a higher education degree, with 4–10 years of professional experience, and working from home two days a week in the management and administration field" whereas the least ideal person is a "man of the baby boomers' generation, holding a university degree, with 20 years or more of professional experience, and who started working remotely only during quarantine" [27]. However, conducting human-centric research does not always allow for the ideal teleworker. Thus, this [meaning, technology literacy] is an important indicator of successful research during these COVID-19 times; future work should keep in mind socioeconomic status and geographic location of participants to assure that data is irrespective of technological challenges. For our research, we assumed that the participants were technologically literate, given their professions and backgrounds, but we also provided an opportunity prior to the workshop to confirm and adjust based on their technological literacy as needed.

Participants were required to view presentations ahead of their participation date. The presentations were from experts in the field of microplastics and oysters as well as one from the host explaining the general agenda of the workshop as well as the indicators that were to be evaluated by participants day-of. Typically, these presentations would have been done at the beginning of the workshops; however, in the initial discussions with participants about changing the format of the workshops from in-person to online, participants expressed that their time availability had become truncated, in essence due to other work obligations and childcare. Taking that into account, we shortened the time of the workshop from 5 h to 3 h and moved certain agenda items (e.g., expert presentations) prior to the workshop to be sure that participants had enough time for group deliberation. As a result of this, we may have encouraged more folks to participate given that they did not have to travel to Boston in order to participate (as was the plan during initial outreach). As of March 2020, we had 20 stakeholders agree to participate in the in-person workshop (30% from the Academic sector, 30% from Government, 25% from NGO, and 15% from Industry). At the completion of the virtual workshops, 30 stakeholders had participated (21% from the Academic sector, 41% from government, 24% from NGO, and 14% from Industry). This increase in stakeholders could be attributed to increased outreach and the virtual nature of the workshops. However, given childcare constraints, as discussed in the previous section, some may have still been discouraged to participate.

The change from in-person to virtual was communicated via email through the description of the three participation phases:

The expert presentations were uploaded to a shared GoogleFolder and shared with participants 5 days prior to their participation date. One participant said "I liked participating, it was very interesting and the format was fine, nice job! I am happy to have been part of this. I liked being able to listen to the information ahead of time and to hear a range of comments from such a group of stakeholders ... " When asked if participants were able to successfully view the presentations, 83 percent of participants indicated 'yes,' 10 percent indicated 'partially' and 7 percent indicated 'no' (Figure 4A). All participants found the instructional material provided was helpful either in totality (67 percent) or partially (33 percent) (Figure 4B). Additionally, participants were exposed to the key points of each experts' pre-workshop presentation at the start of Phase II; participants were o ffered the opportunity to ask questions and/or clarify points made by the experts at this time. For future work, one participant suggested that the videos be placed on a secure Youtube Channel rather than GoogleDrive. Furthermore, click rates could be monitored to assure that the videos were actually viewed ahead of the workshops and an additional question could be added to the post-workshop evaluation form asking participants if they viewed the material undistracted or while doing other work.

When these workshops are video-recorded in-person, it is evident to participants that a camera is recording their conversations and movements. This may become a hindrance to 'camera shy' individuals. With this new virtual format, participants were read a consent form pertaining to the use of video-recording at the start of the workshop. The camera was not as apparent throughout the virtual workshop (as it would have been in-person) which may have allowed those individuals to participate more comfortably.

We also decided to keep the daily groupings smaller in number compared to doing it in-person. Acknowledging that free-flowing conversation is not as easy in a virtual workshop, we wanted to make sure that all voices could be heard. Aided by a facilitator, participants were called on to help move the conversation forward when needed. One participant mentioned that they "appreciated the moderator calling on people to speak up. Often one person dominates the conversations, especially during remote meetings ... Getting more people to speak can only improve the discussion ... ". Even with the virtual format, however, participants were generally satisfied with the outcome of the group deliberation (Figure 4C).

**Figure 4.** Responses from the evaluation form that participants were asked to complete post-workshop.

#### *4.2. Challenges in Virtual Stakeholder Engagement*

At the crux of stakeholder engagement, and specifically the DMCE methodology, is the ability to interact with fellow participants. This interaction is important for both the researchers and the participants. For the researchers, the qualitative data (e.g., the discussions between participants) are just as, if not more important, than the quantitative data (e.g., the ranking values given to the scenarios). We wanted to understand the reasoning behind choices (why did participants preferences change during the group deliberation when compared to pre-deliberation preferences?). For the participants, being able to learn from other participants during the group deliberation is essential to the learning process that takes place while implementing the DMCE methodology. While using Zoom was a decent substitute for in-person relations (one participant said "We are all becoming more comfortable and competent with Zoom. It will be a most valuable tool in the future."), not all participants were able to use Zoom as a result of work-related mandates (one participant, who had initially agreed to participate, had to cancel because of the use of Zoom). Since participant and data security is integral to working with human subjects, using platforms that provide that is essential. Based on this experience, we can identify how we need to improve technological tools that we used in this process.

Lacking these in-person relations was one of the major challenges of this research. Previous work done using this methodology emphasized the need for the in-person relations [16]. Typically, participants would have been provided with a printout of the scenario cards in addition to the scale bar so that individuals could move the cards based on their preferences in real-time and others could evaluate and suggest changes, thus prompting conversation among participants. In hopes of providing some of that tactile learning, we provided images of the cards on a GoogleSlide (that all participants had access to) so that they could move the cards in real-time. What we found, however, is that most participants did not utilize that function during the group deliberation section of the workshop and thus we required a graduate student to help move the cards based on the discussion.

One of the unique aspects of this methodology is being able to evaluate participant preferences before, during, and after knowledge consumption in order to see if preferences change or stagnate with the gaining of more knowledge. Typically, all of the information would have been provided day-of so that we were able to record initial preferences in real-time, rather than allow the participants to contemplate the information for days prior. However, as mentioned above, we had to adapt to current times by shortening the day-of workshop and providing materials ahead of time. Given that materials

were provided 5 days in advance, participants technically had the opportunity to reflect on the content, specifically the indicators, prior to completing the initial, individual survey day-of. For future work, participants could be asked to complete the initial, individual survey when they received the materials in advance.

Providing opportunities for participants to gain knowledge throughout the workshop is integral to successfully implementing this methodology. Knowledge building can happen during structured expert presentations, conversations with other participants, as well as candid conversations with experts throughout the day. For the latter, participants are told that experts are available throughout the workshop to clarify any points/questions. While experts were present during each virtual workshop for its entirety, participants oftentimes forgot they were there since they (the experts) are not meant to interject unless called upon, which may have led to the discrepancies in how influential the scientists ('experts') were on the outcome of the group deliberation (Figure 4D).


**4. Toward heavy-payload multirotor UAV prototype**

This chapter will present the results of individual design phases of a multirotor aircraft that is planned to be used as an integral part of the presented concept of an air robotic system for applications in precision agriculture. Experimental measurements of the considered propulsion units were conducted, on the basis of which payload analysis was performed for several configurations. Based on obtained physical parameters, a model was set up and preliminary simulations were performed, with the help of which it is possible to estimate the energy consumption of a real system.

#### **4.1 Electric propulsion unit characterization**

In order to adequately select aircraft components to ensure the performance of aircraft required for certain tasks (maximum cargo weight, flight speed, flight time, others), it is important to determine the thrust generated by a specific combination of motor and propeller and to determine power consumption. Based on a certain thrust, the maximum load capacity of the aircraft is determined with regard to the defined thrust-to-weight ratio. Based on electricity consumption, more specifically through the relationship between electric current and thrust, it is possible to estimate the maximum flight time depending on the mission. Manufacturers of propulsion elements generally also provide specifications, as previously shown in **Figure 6**; however, these data are not in all cases consistent with actual characteristics. Therefore, for a more precise analysis of the propulsion, it is necessary to perform characterization, and in this paper, the method described in the previous research was used [45] utilizing the experimental test stand RCbenchmark 1780 [46]. **Figure 10** shows the thrust force as a function of the angular velocity of the rotor for the considered propulsion units where the measured experimental characteristics and the characteristics according

**Figure 10.** *Thrust force with respect to rotor angular velocity.*

**Figure 11.** *Electric current with respect to the thrust force.*

to the manufacturer's specifications are shown. Furthermore, **Figure 11** shows the electric current as a function of the thrust force for the purpose of estimating the flight time.


*3.1. In Physiology*

HS are loaded with biological roles, as illustrated in Figure 2A. Acting as mediators in a multitude of regulatory mechanisms, ranging from embryonic development to ECM assembly and regulation of cell signalling [6,47,48]. HS interact with a plethora of molecular partners, including soluble proteins (growth factors, morphogens and chemokines), ECM proteins, bioactive fragments and membrane receptors, such as integrins and receptor tyrosine kinase (RTKs). HS chains also promote pathogen attachment and invasion of specific tissues by binding to numerous microorganisms, including viruses, bacteria, parasites and fungi [2,5,49–51]. Moreover, HSPGs are expressed in all main organ systems having essential roles in several biological activities like metabolism regulation, transcellular transport, cellular communication, ECM support and modulation. The classical role attributed to cell surface HSPGs was to assist as signalling co-receptor for growth factors activity, allowing a correct presentation to their cognate receptors and helping to stabilise gradients, to control the range of signalling and to protect the proteins against degradation [1]. However, it has been increasingly accepted that besides these co-receptor functions, HSPGs stand alone as key regulators of cell behaviour [52].

During embryonic development, HSPGs modulate the morphogen gradients distribution and other extracellular ligands signalling involved in the formation of the different tissue architectures [53]. In this light, the particular interaction of HS with the Hedgehog signalling pathway is very important to a proper embryonic development [54]. Similarly, HSPGs, being the most abundant PGs in basal lamina and cell surface of skeletal muscle, have been shown to regulate fibroblast growth factor (FGF)**,** Wnt and bone morphogenetic protein pathways, fundamental for the development of skeletal structures [55].

More recently, it was revealed that SDCs can regulate calcium channels of the TRPC (transient receptor potential canonical) family, with functional consequences on the actin cytoskeleton, cell adhesion, junctions and migration. Moreover, this interaction was suggested to be evolutionary conserved and relevant for the progression of some diseases [48,56].

HSPGs are also important modulators of metabolism, as illustrated by their role in the liver mediated clearance of triglyceride-rich lipoproteins [57]. Additionally, several SDCs and GPCs have been implicated in the uptake of different forms of lipoproteins [58–60].

Given the many essential cellular and developmental processes in which HS and HSPGs are involved, it is expected that modifications in HSPG expression and structure contribute to a dysregulation in function and lead to pathological scenarios, such as cancer [12,17]. In Section 4, we address several cancer cellular features that are regulated by changes in expression, glycosylation and sulfation profiles of HSPGs, which in turn translate into cancer progression.

**Figure 2.** Overview of heparan sulfate proteoglycans functions. (**A**) HSPGs roles in cellular activities, (**B**) HSPGs aberrant expression and functional implications in cancer and (**C**) HSPGs biomedical potential as a biomarker and as a therapeutic target regarding cancer improved diagnosis and prognosis.