M Singh, S Sithanantham, 'A statistical procedure for testing the host plant perference under choice and no choice situation a statistical procedure for testing the host plant perference under choice and no choice situation', International Journal of Science and Engineering, vol. 1(3), pp.47-63, 2011

Introduction: Nanotechnology is the study and application of extremely small things and can be used across all the other science fields, such as chemistry, biology, physics, materials science, and engineering. An alternative method for considering the trend of research activities in countries is quantitative analysis of scientific output. The objective of current study is to analyze and visualize the trend of scientific output in the field of nanotechnology in MEDLINE during a period of 10 years 2001-2010. Method: The extraction of data was restricted to the data set that was indexed as a major main heading of “nanotechnology” in MEDLINE through 2001 – 2010. Data about patent applications was obtained from WIPO Statistics Database. Database of Science Citation Index Expanded (SCIE) was selected from Web of Science to obtain publications indexed under the topic of nanotechnology. Result: Analysis of data showed that the research activities in the field of nanotechnology have been increased steady through the period of study. The number of publications in 2010 was ~ 84 times greater than those in 2001. English language consisting of 98% of total publications was the most dominant language of publications. Based on Bradford’s scattering’s law the journal of “ Nanoscience and Nanotechnology“ distributing 12.8% of total publications was the most prolific journal. Conclusion: The USA contributing 39% of world’s publications in the field was the most productive country followed by China (10%), Germany (6%), Japan (6%), Korea (5%) and UK (4%). The most majority of world’s publications (70%) were produced by these six countries. The tremendous growth of publications was simultaneously with the rapid growth of patent application in the field of Micro-structural and nano-technology in WIPO.

The objective of this work was, first, to identify hydraulic engineering journals published throughout Latin America. To this end, the initial focus was to review the Science Citation Index-Expanded (SCI-E) database for journals associated with two categories-water resources and civil engineering. This resulted in a total of 20. Second, a bibliometric analysis was performed of papers published in those journals between 1997 and 2008 by Mexican research institutions. This analysis found 373 papers in the 20 journals, of which 298 were in Spanish, 73 in English and 2 in French. Mexico has become the second most published country in Latin American in terms of scientific articles and has the third greatest sum of mean impact for the journals in which they are published. Furthermore, the journal Ingeniería Hidráulica en México (Hydraulic Engineering in Mexico) represents 81% of all Mexican and 33.51% of all Latin American scientific production. International collaborations were also identified, mainly with the United States, France and Spain. | El objetivo del trabajo fue en primer lugar identificar las revistas de ingeniería hidráulica en las que se publica en toda Iberoamérica. Para ello, y como una primera aproximación, se han revisado, a través de la base de datos Science Citation Index-Expanded (SCI-E), las revistas que se encuentran asociadas con las categorías de Water Resources y Engineering, Civil, encontrándose un total de veinte. En segundo lugar, se han analizado bibliométricamente los trabajos publicados por instituciones mexicanas en dichas revistas entre los años 1997 y 2008, encontrándose 373 trabajos en las veinte revistas: 298 en español, 73 en inglés y dos en francés. México se consolida como el segundo país de Iberoamérica en número de artículos científicos y el tercero en la suma de impactos medios de las revistas donde se publica. Por otro lado, la revista Ingeniería hidráulica en México (hoy Tecnología y Ciencias del Agua) aglutina el 81% de toda la producción científica mexicana y representa el 33.51% de toda la de Iberoamérica. Asimismo, se constató una colaboración internacional centrada fundamentalmente en Estados Unidos, Francia y España.

Annual losses in grain production attributed to four major insect pests (shootfly, stem borers, midge and head bugs) are estimated at $1,098 million in Africa and Asia alone. Integrated pest management (IPM) strategies for these insects have been poorly focused. There is little scope for chemical insecticides in sorghum production in sub-Saharan Africa. Various cultural and biological methods, including recommended intercropping configurations and biocontrol have either not been adopted by farmers or have not shown lasting success. Although much effort has gone into the identification and development of insect resistant sorghums, apart from sorghum midge, conventional breeding techniques have not yielded agronomically desirable products. Several biotechnological approaches for achieving higher levels of resistance in sorghum are discussed. Marker-assisted selection can speed up the breeding process and lead to gene pyramiding from diverse sources. The transfer of resistance genes from wild relatives of sorghum is of particular relevance to shootfly. With recent advances in genetic engineering, the standardization of protocols for routine transformation is being pursued at ICRISAT. Three techniques are discussed. Biosafety concerns are briefly mentioned | K F Nwanze, N Seetharama, H C Sharma, J W Stenhouse, 'Biotechnology in Pest Management: Improving Resistance in Sorghum to Insect Pests', African Crop Science Journal, vol. 3(2), pp.209-215, African Crop Science Society, 2011

This paper focuses on developing methods for both potential and actual evapotranspiration (ET) models for the data scarce conditions of the Eastern Arc Mountains catchment of Tanzania. For reliable estimation of the components of the hydrological cycle and plant water uptake, potential ET estimates are required, and for catchment water balance actual ET estimates are needed. These potential and actual ET estimates, however, depend on reliable and good quality data records. The study catchments in this work are characterised by general lack of reliable meteorological (MET) data, though good records of rainfall, flow and pan evaporation data do exist in a few places. In the study reported here the Penman-Monteith (P-M) estimates were found to be closer to the pan evaporation model in areas where reliable records of pan data exist. By comparison, estimates derived solely from temperature (i.e. the Standard Thornthwaite method), were a lot lower. Assuming the P-M estimates to be reliable, new temperature based regional equations were developed using data obtained from six climate stations. The study also presents simpler methods for estimating actual ET from catchments | Zemadim et al., 'Evaporation modelling in data scarce tropical region of the eastern Arc Mountain Catchments of Tanzania', Nile Basin Water Science and Engineering Journal, vol. 4(1), pp.1-13, 2011

Inaugural lecture delivered on 2 February 2011. | Umezuruike Linus Opara was born on 1 July 1961 in a rural subsistence farming and hunting village, Umunam, in Imerienwe, Imo State, Nigeria, where he lived and obtained his primary and secondary education. He attended Upe/Umunam CMS (Anglican) Primary School, Upe Primary School and Umunam Central Primary School, receiving most of the first three years of classes in nearby rubber plantations, tree shades and other makeshift shelters during the Nigerian Civil War. At the end of his primary education in 1974, he baby-sat for one year before attending Owerri Grammar School, Imerienwe. He completed the West African Examination Council School Certificate examination in 1980 and won the annual Senior Essay Competition of the School for his essay entitled 1980 – The year of changes, in which he prematurely and naively predicted a sudden end of apartheid in South Africa. After high school, he travelled to northern Nigeria and joined his parents in Yola, the capital city of present day Adamawa State in Nigeria, where he worked for two years at UTC (Nig.) Ltd, rising from the position of Sales Assistant to First Sales/Storekeeper. During this period, he used his weekends for self-study and in 1982 sat as an external candidate and passed both the General Certificate of Education examination and the Joint Admissions and Matriculation Board examination, and gained admission to study Agricultural Engineering at the University of Nigeria, Nsukka, in the same year. Based on his first-year results, he was awarded the University of Nigeria Foundation Undergraduate Scholarship for Academic Merit in 1983, which he successfully retained throughout his undergraduate studies. He graduated with a bachelor’s degree in Agricultural Engineering in 1987 with first-class honours (cum laude) and received the Department Prize for Best Graduating Student. He was an elected member of the University of Nigeria Students Union Senate (Upper House) and president of the National Association of Ngor-Okpala Local Government Students. In December 1987, he was awarded the prestigious Prize for Academic Excellence by the Mezie Owerri national community development organisation in Nigeria. For his National Youth Service Corps assignment, he spent one year as agricultural engineer at the National Centre for Agricultural Mechanization, Ilorin. He returned to the University of Nigeria in 1988 with a Federal Government Postgraduate Scholarship and completed his master’s degree in Agricultural Engineering (cum laude) in record time in 1989. The results of his BEng honours thesis on Nomograph models for selective agricultural mechanization and his MEng thesis on Computer-aided model for selective agricultural mechanization (CAM-SAM) provided major inputs for the Agricultural Mechanization Study component of the 1989–2004 National Agricultural Development Strategy of Nigeria, of which he was co-leading author with the late Prof UGN Anazodo and Dr Taiwo Abimbola. In 1988 he was awarded a New Zealand University Grant’s Committee PhD Scholarship reserved for local students who made first class. He commenced his PhD studies in Agricultural Engineering 3 4 at Massey University 1990 and completed in 1993. His dissertation on Studies on stem-end splitting in apples under the supervision of Prof Cliff Studman and Prof Nigel Banks provided the first scientific evidence linking the development of stem-end splitting with a precursor internal ring-cracking. Through the combination of engineering knowledge of the physico-chemical properties of fruit and horticultural science, industry guidelines were developed and disseminated on practical measures to predict and reduce the incidence of fruit-splitting damage. He subsequently held the position of postdoctoral researcher in the Department of Agricultural Engineering from 1993 to 1994. He joined Lincoln Technology in Hamilton briefly as Postharvest Research Engineer but returned to Massey in 1995 as lecturer in Postharvest Engineering, was promoted to senior lecturer in 1999 and to program director for Engineering Technology in 2001, and was a founding member of the Centre for Postharvest and Refrigeration Research. He held several management and administrative positions, including that of coordinator of the Agricultural Engineering programme and coordinator of the BApplSc (General) programme. In 1993 he was awarded the inaugural Dean’s Prize for Meritorious Contributions to the Affairs of the Faculty of Agricultural and Horticultural Sciences. He was an elected member of the Massey University Governing Council (1993–1997), representing all internal and extramural students, and served on several council committees, panels and other university-wide committees, including the University Disciplinary Appeals Committee, chaired by the chancellor, and the panel for the appointment of a new vice-chancellor (1994– 1995). He was also the residential community coordinator (1995–2001) responsible for mentoring and overseeing the welfare of students living in on-campus university accommodation. He was executive committee member of the Africa Association of New Zealand, president of the African Students Association, elected member of the Massey University Students’ Association Executive, and president of International Students. He is a chartered engineer (UK), currently chair of Section VI: Postharvest Technology and Process Engineering and executive committee member of the International Commission of Agricultural and Biosystems Engineering (CIGR), vice-chair of the Roots and Tuber section of the International Society for Horticultural Science, section chair for Engineering and Information Technology of the International Society for Food, Agriculture and Environment, and former vicepresident (Postharvest Technology and Biotechnology) of the Asian Association for Agricultural Engineering (AAAE). He is a life member of the AAAE and the American Society of Agricultural and Biological Engineers, and member of several international and national scientific societies. At the 80th anniversary of the CIGR and the World Congress in Quebec in 2010, he received the CIGR Presidential Citation for significant contributions to the advancement of agricultural engineering in Africa. He is founding editor-in-chief of the International Journal of Postharvest Technology and Innovation and member of the editorial board and regular reviewer for several international peer-reviewed journals. He has published over 60 articles in peer-reviewed journals and book chapters, co-edited three special issues of the International Journal of Engineering Education documenting recent advances in agricultural and biological engineering education, was the editor of two conference proceedings and made over 150 oral presentations at international conferences, including keynotes and invited lectures. Prior to joining Stellenbosch University, he worked at Sultan Qaboos University in Oman (2002– 2008), where he held the positions of associate professor of Agricultural Engineering, director of the Agricultural Experiment Station, assistant dean for Postgraduate Studies and Research, and acting dean during summer periods. During this period, he also developed a new research programme and courses in postharvest technology and received the university’s Distinguished Researcher Award in 2006. He also served in many university and national policy and advisory committees, including the university’s Academic Council (Senate), he was a member of the University Quality Audit Committee, which prepared the first quality audit report, and is a certified quality auditor of the Oman Accreditation Council. He is active in the international development arena, serving as visiting expert on postharvest technology at the headquarters of the Food and Agriculture Organization (FAO) of the United Nations (UN) in Rome (2000–2001), agricultural mechanisation expert in Iraq for the FAO/UN (2001–2002), FAO expert panel on microbial safety of green leafy vegetables (2008), FAO expert on postharvest and marketing systems and member of the technical panel that developed an agricultural development strategy for Timor-Leste (2009) as well as a member of the International Advisory Board of the USAID Horticulture Collaborative Research Support Program (Hort CRSP). Prof Opara holds the South African Research Chair in Postharvest Technology at Stellenbosch University, and his current research programmes focus on cold chain technologies, non-destructive technologies for quality measurement and mapping and reducing postharvest food losses. He is married to Gina and has two daughters, Ijeoma (15) and Okaraonyemma (13), who both enjoy playing the piano and watching their dad play football.

The rapid increase of the quality of life together with the progress of medical science asks for the development of new, tuneable and controllable materials. For the same reason, materials used for biomedical applications have to be increasingly biocompatible, biodegradable and biofunctional. Most of the available systems, however, lack one property or the other. For example, conventional animal-derived gelatin that is often used in biomedicine, is susceptible to a risk of contamination with prions or viruses and has a risk of bringing out allergic reactions, particularly against the non helix-forming domains of collagen [1]. Furthermore, gelatin is composed of a variety of molecules and structures with different thermal stabilities and molecular sizes. This, in combination with the impossibility to change the molecular structure at will, limits the chances to elucidate the relation between the structure and function. On the other hand, synthetic materials that have a rather well-controlled size distribution often lack biocompatibility, biofunctionality or biodegradability. In addition to that, as their synthesis often requires toxic solvents, their application in the human body is restricted. All the drawbacks of the presently used materials have brought scientists towards a new approach in designing materials viz. genetic engineering. Rapid progress in recombinant techniques has led to new ways of producing molecules with well-defined composition and structure and with full control over the length and sequence of the biopolymer and its constituent blocks. These methods thus combine the advantages of natural and synthetic polymers. Using molecular biology tools, unique molecules can be created by merging in a desired manner naturally occurring self-assembling motifs such as elastin, silk or collagen [2-4], or entirely artificial fragments. As we show in this thesis, the precise control over the molecular design of these biotechnologically produced block polypeptides is extremely valuable as it also leads to control over their physicochemical properties. In this thesis we present a new class of monodisperse, biodegradable and biocompatible network-forming block polymers that are produced by genetically modified strain of yeast, Pichia pastoris (Chapter 2). Trimer-forming end blocks, abbreviated as T, consisting of nine Pro-Gly-Pro amino acid triplets, are symmetrically flanking a random coil-like middle block composed of four or eight repeats of highly hydrophilic R or P sequences (Figure 8.1). R and P are identical with respect to length (99 amino acids) and composition but have different amino acid sequences. The P block has a glycine in every third position (as in collagen) but does not form any supramolecular structures and maintains a random coil-like conformation at any temperature [5]. The R block is a shuffled version of the P block. Four recombinant gelatins are reported in this thesis, denoted as TR4T, TR8T, TP4T and TP8T (Figure 8.1). All of these were successfully produced with high yields (1-3 g/l of fermentation broth) by the Pichia pastoris GS115 strain transformed with a pPIC9 vector with the gene of interest in its expression cassette. Figure 8.1 Schematic representation of collagen-inspired telechelic polypeptides: TR4T, TR8T, TP4T and TP8T. In Chapter 3 we described the linear rheological properties of hydrogels formed by TR4T polypeptides. At a temperature of 50 °C, the solution does not show any viscoelastic response. However, upon cooling, the collagen-like trimer-forming domains (T) start to assemble into triple helical nodes and a well-defined network, with a node multiplicity of three, is formed. In the beginning of the gelation process, viscous properties are predominant, but as the network formation progresses, the elastic properties prevail. A plateau storage modulus is reached within a few hours. At this point the triple helices are in equilibrium with the free T blocks. An equilibrium or near-equilibrium state is reached, contrary to natural gelatin, because the collagen-like (T) assembling domains are relatively short and well-defined. The T blocks are solely responsible for the network formation. We have shown that a solution of the middle blocks only (i.e. R4) does not demonstrate any elastic response at any time and temperature. In addition, differential scanning calorimetry (DSC) (Chapter 5) proved that the collagen-like side blocks are near-quantitatively responsible for trimerization, as the observed melting enthalpies are in good agreement with values obtained by Frank et al. [6] for free (Pro-Gly-Pro)10 peptides. The equilibrium fraction of T blocks involved in triple helices shifts with temperature. By lowering the temperature, the fraction of triple helices increases, while the fraction of free ends decreases. There are two possibilities to form a triple helix. It can be formed either by three T blocks from three different chains, or by three T blocks from two different chains, so that two side blocks come from the same polypeptide. As a consequence, the network is composed of dangling ends, elastically active bridges and inactive loops (Figure 8.2). Because of the precisely-known junction multiplicity of three, we could develop an analytical model that links the internal structure of the gel, with dangling ends, loops, and bridges, to the physicochemical properties. This model uses a limited set of input parameters that can all be measured independently. It describes the experimental data quantitatively without further adjustable parameters. Using this model, we could show that the observed strong dependency of the storage modulus, the relaxation time and the viscosity on concentration and temperature is related to the changes in the number of loops, active bridges, and dangling ends in the gel matrix. Figure 8.2 Network formation by collagen-inspired telechelic biopolymers. In Chapter 4 we show that the number of intermolecular junctions and intramolecular loops depends not only on protein concentration and temperature but also on the length and the stiffness of the middle block. We synthesised new triblock copolymers with middle blocks, of different lengths and amino acid sequences, named TP4T, TR8T and TP8T (Figure 8.1). For all new proteins, there is a strong dependency of the storage modulus, the relaxation time and the viscosity on concentration and temperature (as for TR4T). However at comparable molar concentrations, the longer versions of polypeptides i.e. TR8T and TP8T show a significantly higher storage modulus and relaxation time than their counterparts TR4T and TP4T. This is because a longer middle block leads to a larger radius of gyration (Rg), which decreases the probability that two end blocks from the same molecule associate with each other, and form a loop. The consequence of fewer loops in the system is a higher storage modulus and a higher overall relaxation time. TR8T TP8T Besides the effect of polymer length, we also observed that the R series, i.e. TR4T and TR8T, show a higher storage modulus than their P counterparts, i.e. TP4T and TP8T, at the same concentration and temperature. This can be explained by differences in coil flexibility. Although the P and R blocks have exactly the same amino acid composition, their amino acid sequence is different. Fitzkee et al. [7] have shown that even a polypeptide chain that assumes a random coil conformation still has locally folded conformations that contribute to the overall flexibility of the chain. This apparently leads to a smaller radius of gyration for the P middle block than for the R middle block and thus to a higher probability of loop formation. Even though the melting behaviour obtained with DSC is the same for all four polypeptides (as the end blocks stay the same), the temperature at which the G0 value approaches zero and the gel completely loses its elastic properties varies with the length of the middle block. Shorter molecules, i.e. TP4T and TR4T, melt at lower temperatures. A solution of 1.2 mM TP4T melts at 298 K, while TP8T at a comparable molar concentration melts at a temperature which is 15 degrees higher. Furthermore, the R versions show slightly higher melting temperatures than the P versions. These differences in melting behaviour are related to the gel structure and the relative probabilities of forming intramolecular and intermolecular assemblies. We could account for these findings with the help of the analytical model presented in Chapter 3. The only parameter that had to be varied in the model was the coil size of the polymer, since the enthalpy and the melting temperatures of the triple helices did not change with the length of the middle block. The theoretical calculations clearly show that the molecules with smaller Rg form up to 30 % more loops than their bigger counterparts. Loops that act as gel stoppers do not contribute to the network elasticity and significantly lower the melting temperatures detected with rheology. The network junctions in our gels are solely formed by triple helices. The mechanism of junction formation by the T blocks can be well-described by a two-step kinetic model (Chapter 5). Prior to triple helix propagation, a trimeric nucleus has to be formed. For dilute systems, nucleation is the limiting step, giving an apparent reaction order of three. These results indicate that only triple helices are stable. For more concentrated solutions, when nucleation is relatively fast, propagation of triple helices becomes rate-limiting and the apparent reaction order is close to unity. The propagation of triple helices is probably limited by cis-trans isomerization of peptide bonds, in which proline residues are involved. Above overlap concentration (C*) the measured enthalpy for stable gels (~15 hours) indicates that almost 100 % of the T blocks are involved in triple helices. Values obtained by us are in good agreement with values obtained by Frank et al. [6] for single (Gly-Pro-Gly)10 peptides. Conversely, at concentrations below C*, the enthalpy per mole of protein is becoming less, suggesting that the fraction of free ends or mismatched helices becomes more pronounced. The apparent melting temperature increases slightly with increasing concentration. This can be explained on the basis of the reaction stoichiometry under equilibrium conditions [8, 9]. Except for the highest measured concentration (2.4 mM), the apparent melting temperature revealed a dependence on the scan rate, indicating that it was not possible to maintain equilibrium during the heating step. At a concentration of 2.4 mM concentration there is no scan rate dependence, since the melting occurs at a higher temperature, where the dissociation kinetics is faster [4, 10]. The kinetics of triple helix formation determines the rate of gel formation. The gelation starts when the first triple helical node is formed. At that time viscous properties (loss modulus) predominate, but as the network formation evolves the elastic response (storage modulus) becomes more pronounced. The storage modulus (G’) reaches a plateau value within a few hours. Changes in network structure and mechanical properties of the gel in time can be predicted from the kinetics of triple helix formation, using the model presented in Chapter 3. By comparing the kinetics obtained with rheology and with DSC we could see that for our system, the helix content is not simply proportional to the network progress and that the relation between the elastic properties (G’) and the helix content (pH) depends on the protein concentration. The reason for this concentration dependence is the formation of loops, which is more likely at low concentrations. The investigated hydrogels undergo time-dependent macroscopic fracturing when a constant shear rate or shear stress is applied (start-up and creep experiments, respectively) (Chapter 6). Observations with particle image velocimetry (PIV) showed that in the beginning of a start-up (or creep) experiment the sample flows homogenously. After some time, the gel fractures, and is separated into two fractions. The inner region moves at the same velocity as the moving bob, while the outer fraction does not move at all. From the rate-dependence of the fracture strength we can conclude that gel fracture is due to stress-activated rupture of the triple helical nodes in the network.When the deformation is taken away, the gel can heal (Chapter 6). The capacity of self-healing is due to the transient character of the network nodes with a finite relaxation time. Such behaviour, impossible for most permanent gels, is highly desired in many applications, as hydrogels are often subjected to deformations, which easily go beyond the linear regime. As we present in Figure 8.3, TR4T gels cut into small pieces (grey and transparent), can heal within 2 hours. As measured with rheology the broken gel can recover up to 100 % of its initial elastic properties, even after several fracturing cycles. Interestingly, the kinetics of healing differs from the kinetics of fresh gel formation (Chapter 5). The latter is characterized by a lag-phase before elastic properties start to appear. This lag-phase occurs because at low degrees of crosslinking there is not yet a percolated network, so that the storage modulus is undetectable. By contrast, the recovery of the gel after rupturing is much faster and does not show a lag-phase. The elastic modulus, depending on the rupturing history, comes back to its initial value within 1-5 hours. These findings indicate that outside the fracture zone, the network nodes have not dissociated significantly, so that healing only requires the reformation of junctions that connect the undamaged pieces of the network (gel clusters). Figure 8.3 Self-healing of TR4T hydrogels. (A) Pieces of broken gel. (B) Two gel pieces healed after 2 hours. In Chapter 7 we demonstrated the shape-memory effects in hydrogels formed by permanently crosslinked TR4T molecules. The programmed shape of these hydrogels was achieved by chemical crosslinking of lysine residues present in the random coil. The chemical network could be stretched up to 200 % and “pinned” in a temporary shape by lowering the temperature and allowing the collagen-like end blocks to assemble into the physical nodes. The deformed shape of hydrogel can be maintained, at room temperature, for several days, or relaxed within few minutes upon heating to 50 ºC or higher. The presented hydrogels could return to their programmed shape even after several thermo-mechanical cycles, hence indicating that they remember the programmed shape. We have studied in more detail the shape recovery process by describing our hydrogels by a mechanical model composed of two springs and a dashpot. With the help of this model we showed that above the melting temperature of the triple helices, the recovery is exponential and that the decay time is roughly ten times slower than the relaxation of the physical network. 1.Biomedical applications - perspectives and considerations The class of collagen-inspired self-assembling materials, which we present in this thesis are nice model systems for a systematic study of physical networks, but they also have a lot of potential for biomedical applications. In this section we discuss the possibilities for these self- assembling hydrogels in biomedicine. Drug delivery systems One of the major goals of modern medicine is to ensure that the required amount of an active substance is available at the desired time at the desired location in the body. Consequently, a lot of effort is put into designing delivery systems with precisely adapted release profiles, sensitive to external stimuli such as temperature or pH. A frequently used group of materials in this field are hydrogels, both chemically and physically crosslinked. In the case of covalently crosslinked networks the release of the drug is mostly via diffusion of the drug out of the gel particle after it swells. The rate of drug release is governed by the resistance of the network to volume increase [11]. Although permanent networks are widely used as drug carriers they have some disadvantages such as incomplete release of active substances and poor biodegradability in the body. The problem can be partially solved by introducing enzymatic cleavage or hydrolysis sites into the main chain, but still the hydrogel erosion cannot be precisely controlled and complete material degradation can not be guaranteed. These obstacles can be overcome by using physical hydrogels that are formed by weak interactions. These can dissociate in a controlled manner and completely release the active component. In contrast to chemical gels, erosion of physical gels occurs spontaneously. The erosion rate is determined by the life time of the junctions, but it depends also on the relative amount of intramolecular loops and intermolecular junctions, as demonstrated by Shen et al. [12]. These authors showed that, by using triblock polymers with dissimilar coiled-coil side domains rather than identical ones, loop formation could be suppressed, leading to a lower erosion rate [12]. The potential of our gels for drug delivery applications was tested by Teles et al. [13]. It was shown that trapped proteins (BSA) can be completely released from TR4T and TR8T gels, both at 37 ºC and 20 ºC. The release at 37 ºC from 20 % gels was completed within 48 hours while at 20 ºC it took about 5 times longer. At body temperature the release was mostly driven by dissociation of trimeric junction and dissolution of the separate polymer chains (gel erosion). At 20 ºC the junction life time was long so that erosion was slower and swelling and diffusion played a more important role. The observations of Teles are in agreement with studies of several groups that demonstrated the importance of hydrogel erosion for controlled release [12, 14]. The erosion rate of physical hydrogels is governed by the junction relaxation time. The mean relaxation time of transient networks can be manipulated either by varying the gel architecture (Chapter 3 and 4) or by changing the relaxation time of a single triple helix. The gel architecture (i.e. the number of loops and bridges) can be altered either as we show in Chapter 3 by changing the protein concentration or as we demonstrate in Chapter 4 by manipulating the design of the middle block. The number of loops becomes lower as the spacer length and stiffness increase (Chapter 4). The lifetime of a single node can be changed by enzymatic hydroxylation of proline to hydroxyproline, [15] which leads to more hydrogen bonds among adjacent T blocks, or by changing the length of the collagen-like T domains. Preliminary results showed that average relaxation time of the network is roughly hounded times higher for molecules with collagen-like domains composed of sixteen Pro-Gly-Pro repeats instead of nine (unpublished data). For these biotechnologically produced collagen-inspired polymers, the length or the composition of the blocks can be changed simply by changing the DNA template. This, in combination with the model elaborated in Chapter 3 and 4 that links the internal gel architecture with the physicochemical gel behaviour, gives ample possibilities to design materials with custom-desired release profiles of active components. Tissue engineering Materials for tissue engineering scaffolds have to mimic the in vivo extracellular matrix environment. They provide physical support, but also have to guarantee proper adhesion of cells and controlled release of growth factors. A very important role in scaffolds design is played by the mechanical properties of the matrix [16-18]. As shown by Engler et al. [17], the elasticity of the matrix directs stem cell development to different lineages. Soft networks (0.1-1 kPa), which mimic brain tissue, promote neuron development, stiffer scaffolds (8-17 kPa) are myogenic, while gels with an elastic modulus of 24-40 kPa promote growth of bone cells. The stiffness of the matrix affects focal-adhesions and the organization of the cytoskeleton structure, and thus contractility, motility and spreading [16, 18]. Another significant factor, which plays a role in tissue growth is the degradation rate of the scaffold. The degradation should be synchronized with cellular repair in such a way, that tissue replaces the material within the desired time interval. The scaffold disintegration also controls the release of growth factors. For naturally derived materials such as alginate, the degradation rate could be influenced by partial oxidation of the polymer chain or via a bimodal molecular weight distribution [19]. For synthetic polymers different degradation profiles can be realized by incorporating in the polymer backbone groups with different susceptibility to hydrolysis [19]. Presently the most widely used scaffolds for tissue engineering are natural polymers such as collagen, gelatin, and polysaccharides [20] or synthetic, biodegradable polymers such as poly (L-lactic acid) (PLLA), poly(glycolic acid) (PGA), and poly(ethylene glycol) (PEG). [21-23]. Although these materials show promising properties, their use is limited as they suffer from batch to batch variations, polydispersity, viral contamination, allergic reactions or toxic byproducts after degradation. Also their mechanical properties are poorly-controlled and it is difficult to relate the molecular structure to the resulting properties. Furthermore, in the case of synthetic polymers, there is no intrinsic mechanism to interact with cells and to propagate cell adhesion proliferation or migration. This problem can be partially solved by functionalizing synthetic materials with bioactive molecules, such as collagen [24] or short peptides (for example arginine-glycine-aspartic (RGD) or tyrosine-isoleucine-glycine-serine-arginine (YIGSR) [25]). It remains difficult, however, to precisely control the spatial distribution, of these biofunctional domains [25]. A very promising alternative for the currently used scaffolds are hydrogels formed by self-assembling protein polymers [2, 26-28], including the collagen-inspired polypeptides presented in this thesis. Our block polymers form physical gels with precisely controlled elastic properties. As discussed in Chapter 3 and 4, the gel structure and the resulting mechanical properties strongly depend on concentration, temperature and on the molecular design of the polymer. Within the investigated range of conditions our gels have an elastic modulus between 0.03 and 5 kPa. Thus they seem most appropriate for neuron cell growth [17]. Moreover, it is also possible to incorporate specific short adhesive peptide sequences (such as RGD) in the middle block to improve attachment and cell propagation. The presently investigated proteins, with T domains composed of nine Pro-Gly-Pro repeats, still need some enhancement in terms of stability. As shown by Teles et al. the currently available molecules erode within 2 days [13]. For tissue engineering applications, this is too fast. We therefore propose some strategies to stabilize our hydrogels. A first possibility alternative is to introduce amino acids which can form chemical bonds such as cysteines that can form disulfide bridges under oxidizing conditions [29], or lysines, which can be functionalized with acrylate and then photo-crosslinked with UV radiation [30-32]. However, one has to be aware that this additional procedure may have negative side effects such as toxic byproducts, incomplete polymer degradation in the body, or loss of responsiveness to external stimuli. Alternatively, the erosion can be moderately slowed down by increasing the relaxation time of the network (as discussed in section on drug delivery systems). Wound dressing materials Under normal circumstances wound healing is a very long process. In order to speed it up, so that bacterial infections or wound dehydration can be avoided, wound dressing materials are used [33-37]. These materials should fulfil several general requirements such as biocompability, ease of application and removal, proper adherence (to avoid fluid pockets, in which bacteria could proliferate), ease in gas exchange between tissue and environment, and controlled release of active components such as antimicrobial agents or wound repair agents (for example Epidermal Growth Factor (EGF)) [37]. All above-mentioned requirements can be fulfilled by the collagen-inspired hydrogels presented in this thesis. The advantage of our materials is that they can follow the contour of the wound and entirely fill it, thus forming an efficient barrier for microbes, but at the same time being permeable for water vapour and oxygen. Furthermore they can entrap active components and release them in a controlled way during the healing process, as discussed above. Depending on the circumstances, the release profile can be synchronised with the wound healing process. An additional advantage of our genetically engineered molecules is that adhesion domains can be introduced along the middle block, assuring better integration of the gel with the damaged tissue. 8.3 Final conclusions and outlook In this final chapter we have discussed the potential of our collagen-inspired materials in biomedical applications. They are biocompatible and biodegradable, whilst offering numerous possibilities to change the molecular design in order to meet the desired mechanical or biological properties. Furthermore, the well-defined nature of the triple helical junctions allows us to predict the mechanical properties of the gel from the molecular design of polypeptides. This exclusive feature of our system makes it unique and offers great flexibility to design custom biomedical materials. Biomedical needs, however, are very variable and often require an individual approach. That is why in our group we have created a family of genetically engineered block copolypeptides. Besides collagen we use other motifs present in nature, such as silk or elastin. We can combine these motifs in various ways in order to create unique stimuli-responsive (often multi-responsive) molecules that can meet individual application needs. The silk-like domains consist of (Gly-Ala-Gly-Ala-Gly-Ala-Gly-Xxx)n repeats. Position Xxx is occupied by charged amino acids such as histidine, lysine or glutamic acid. When the charge is screened, the molecules assemble, forming first β sheet-like secondary structures, and then long fibres. As shown by Martens et al. [38], block polymers comprising silk-like domains with glutamic acid or histidine in the Xxx position form fibre-like gels at a pH of 2 or 12, respectively. They also assemble when mixed with oppositely charged (coordination) polymers [3, 38]. Probably, the assembling conditions can be tuned even more precisely by adjusting the isoelectric point of the assembling domain. This will allow the production of hydrogels that are formed after being injected into the body, while they disassemble (releasing the drug) when exposed to the acidic or the alkaline conditions. The nanofibre gels are also stable enough to serve as scaffolds for tissue engineering [39-41]. Another motif that has been used is elastin. It consists of (Val-Pro-Gly-Xxx-Gly)n repeats and it self-assembles above a lower critical solution temperature (LCST). The transition temperature can be tuned by introducing more or less polar amino acid residues in position Xxx. By combining elastin-like or collagen-like blocks with silk-like blocks, thermo and pH responsive networks can be obtained. This may allow us toswitch from fibre-like gels to associative networks. Block polypeptides, produced using recombinant techniques, besides biocompability and biodegradability offer many possibilities to adjust the molecular design in will, to realize the desired mechanical or biological properties. 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Mechanized construction of micro-catchments for water harvesting (WH) was successfully tested in the Badia (dry rangeland) areas in Syria and Jordan, using the “Vallerani” plow, model Delfino (50 MI/CM), manufactured by Nardi, Italy. The plow was able to construct intermittent and continuous contour ridges, and could potentially be used to rehabilitate degraded rangelands. However, one major issue for large-scale implementation is the high cost and time required to manually identify contours for the plow to follow. Most existing auto-guiding systems, as usually used in road construction and agricultural land leveling, were expensive or impractical. The objective, therefore, was to add, adapt, and evaluate an auto-guiding system to enable a tractor to follow contours without demarcation through conventional surveying. A low-cost Contour Laser Guiding (CLG) system, with specifications that suit the contour ridging in undulating topographic conditions of dry rangelands, was chosen, adapted, mounted, and tested, under actual field conditions. The system consisted mainly of a portable laser transmitter and a tractor-mounted receiver, connected to a guidance display panel. The system was field-tested on 95 ha of land where the system capacity was determined under different terrains, slopes (1-8%), and ridge spacings (4-12 m). The easy adaptation and implementation of the CLG to the “Vallerani” unit tripled the system capacity, improved efficiency and precision, and substantially reduced the cost of constructing micro-catchments for WH. The system is recommended for large-scale rangeland rehabilitation projects in the dry areas, not only in West Asia, but worldwide.

Drought research requires data on precipitation and actual soil moisture of fields because precipitation is variable among years and the soil textures differ with crop fields. Measurement of soil water content in the field is simple but labor-intensive. A prototype of an automatic field data monitoring system has been recently developed to collect data more efficiently. Using this system, data of soil water contents was successfully transmitted onto the personal computer approximately 700 m away from wheat field plots, for the period from March to May which was critical for soil drying and wheat growth. In addition, sample data of soil water content and grain yield was obtained from field plots of three bread wheat genotypes.

Rainwater harvesting in micro-catchments such as contour ridges and semicircular bunds is an option for utilizing the limited rainfall, improving productivity and combating land degradation in dry rangeland areas (Badia). However, implementation of this practice using manual labor or traditional machinery is slow, tedious and costly, and often impractical on a large scale. These limitations can be overcome using the ‘Vallerani’ plow for quickly constructing continuous and intermittent ridges. The plow (model Delfino (50 MI/CM), manufactured by Nardi, Italy) was tested and adapted to dry steppe (Badia) conditions in Jordan. The performance of the machine, its weaknesses and potential improvements were assessed in the 2006/07 season at three sites on 165 hectares of various terrain, slope and soil conditions. The performance parameters included effective field capacity (EFC), machine efficiency (ME) and fuel consumption (FC). Field tests were carried out at different tractor (134 HP) traveling speeds, pit sizes and contour spacings. Overall mean performance indicators gave an EFC of 1.2 ha/h, 51% ME and an average FC of 5.15 liter/ha. Increasing ridge spacing had a small effect on ME where, increasing traveling speed had a greater effect. A guide table was developed, relating performance parameters with ridge spacing, speed, and bund size setting. This could be a useful reference for the implementation and management of mechanized microcatchment construction in the Badia. The system performed well in the construction of continuous ridges. However, it was unable to construct intermittent ridges at speeds over 4 km/h; problems were encountered in properly staggering the bunds at successive contours.