Yes / Hair fibres show wide diversity across and within all human populations, suggesting that hair fibre form and colour have been subject to much adaptive pressure over thousands of years. All human hair fibres typically have the same basic structure. However, the three-dimensional shape of the entire fibre varies considerably depending on ethnicity and geography, with examples from very straight hair with no rotational turn about the long axis, to the tightly sprung coils of African races. The creation of the highly complex biomaterials in hair follicle and how these confer mechanical functions on the fibre so formed is a topic that remains relatively unexplained thus far. We review the current understanding on how hair fibres are formed into a nonlinear coiled form and which genetic and biological factors are thought to be responsible for hair shape. We report on a new GWAS comparing low and high curl individuals in South Africa, revealing strong links to polymorphic variation in trichohyalin, a copper transporter protein CUTC and the inner root sheath component keratin 74. This builds onto the growing knowledge base describing the control of curly hair formation. / Unilever R&D

This thesis treats two essentially different subjects: V-cycle schemes are considered in Chapters 2-4, whereas the aggregation-based coarsening is analysed in Chapters 5-6. As a matter of paradox, these two multigrid ingredients, when combined together, can hardly lead to an optimal algorithm. Indeed, a V-cycle needs more accurate prolongations than the simple piecewise-constant one, associated to aggregation-based coarsening. On the other hand, aggregation-based approaches use almost exclusively piecewise constant prolongations, and therefore need more involved cycling strategies, K-cycle <a href=http://www3.interscience.wiley.com/journal/114286660/abstract?CRETRY=1&SRETRY=0>[Num.Lin.Alg.Appl., vol.15(2008), pp.473-487]</a> being an attractive alternative in this respect. <br> <br> Chapter 2 considers more precisely the well-known V-cycle convergence theories: the approximation property based analyses by Hackbusch (see [Multi-Grid Methods and Applications, 1985, pp.164-167]) and by McCormick [SIAM J.Numer.Anal., vol.22(1985), pp.634-643] and the successive subspace correction theory, as presented in [SIAM Review, vol.34(1992), pp.581-613] by Xu and in [Acta Numerica, vol.2(1993), pp.285-326.] by Yserentant. Under the constraint that the resulting upper bound on the convergence rate must be expressed with respect to parameters involving two successive levels at a time, these theories are compared. Unlike [Acta Numerica, vol.2(1993), pp.285-326.], where the comparison is performed on the basis of underlying assumptions in a particular PDE context, we compare directly the upper bounds. We show that these analyses are equivalent from the qualitative point of view. From the quantitative point of view, we show that the bound due to McCormick is always the best one. <br> <br> When the upper bound on the V-cycle convergence factor involves only two successive levels at a time, it can further be compared with the two-level convergence factor. Such comparison is performed in Chapter 3, showing that a nice two-grid convergence (at every level) leads to an optimal McCormick's bound (the best bound from the previous chapter) if and only if a norm of a given projector is bounded on every level. <br> <br> In Chapter 4 we consider the Fourier analysis setting for scalar PDEs and extend the comparison between two-grid and V-cycle multigrid methods to the smoothing factor. In particular, a two-sided bound involving the smoothing factor is obtained that defines an interval containing both the two-grid and V-cycle convergence rates. This interval is narrow when an additional parameter α is small enough, this latter being a simple function of Fourier components. <br> <br> Chapter 5 provides a theoretical framework for coarsening by aggregation. An upper bound is presented that relates the two-grid convergence factor with local quantities, each being related to a particular aggregate. The bound is shown to be asymptotically sharp for a large class of elliptic boundary value problems, including problems with anisotropic and discontinuous coefficients. <br> <br> In Chapter 6 we consider problems resulting from the discretization with edge finite elements of 3D curl-curl equation. The variables in such discretization are associated with edges. We investigate the performance of the Reitzinger and Schöberl algorithm [Num.Lin.Alg.Appl., vol.9(2002), pp.223-238], which uses aggregation techniques to construct the edge prolongation matrix. More precisely, we perform a Fourier analysis of the method in two-grid setting, showing its optimality. The analysis is supplemented with some numerical investigations.

Viruses are submicroscopic obligate parasites and depend on the host cell for their growth and reproduction. Plants are infected by diverse group of viruses that mostly possess RNA as their genome. As exception, viruses belonging to the family Geminiviridae are DNA viruses and infect both mono and dicotyledonous plants causing a large economic loss. These viruses are smaller in size encoding fewer proteins and employ the host cell machinery for successful infection and spread. Geminiviruses undergo frequent recombinations due to mixed infection resulting in vast diversity across the family and account for driving evolution in these viruses. Movement in these viruses is complex since they have to cross two important barriers, nuclear and cell wall barrier to establish systemic spread. All these factors play very important role while designing control measures against these viruses. Thus a detailed understanding of these processes at molecular level is essential. Cotton is the major cash crop in Indian subcontinent with huge export values. India has become the second largest producer of cotton in the world. However, the major constraint in cotton cultivation has been crop loss due to diseases caused by viruses, particularly the cotton leaf curl disease (CLCuD) caused by begomoviruses. Present thesis deals with the analysis of genetic variability of CLCuD in India and functional characterization of proteins involved in the movement of Cotton Leaf Curl Kokhran Virus-Dabawali (CLCuKV-Dab). CLCuKV-Dab belongs to family Geminiviridae and subgroup Begomovirus. A review of the literature on Geminiviridae classification, genome organization, virus entry, replication, transcription, translation, assembly and movement is presented in Chapter 1. This chapter also includes the review of host factors involved in replication, geminiviral proteins involved in gene silencing and a detailed report on CLCuD complexes and sub viral DNAs that are associated with CLCuD. The materials used in this study and the experimental protocols followed such as construction of recombinant clones, their overexpression in both bacterial and baculovirus expression systems, Protein purification techniques, site directed mutagenesis and all other biochemical, molecular biology and cell biology methods are described in detail in Chapter 2. Previous study has reported the complete genomic sequences of CLCuKV-Dab and Tomato leaf curl Bangalore virus-cotton [Fatehabad] (ToLCBV-Cotton [Fat]) and partial sequence of CLCuKV-Gang and the Cotton leaf curl Rajasthan virus (CLCuRV-Ban). Phylogenetic analysis of DNA-A sequences of these viruses with other CLCuD causing viruses is discussed in detail in Chapter 3. Chapter 4 deals with overexpression, purification and functional characterization of CLCuKV-Dab CP in terms of its interaction with DNA, the kinetics and its role in cell to cell movement. The proposed partners to CP in the cell to cell movement of monopartite begomoviruses are AV2 and AC4. Thus the Chapter 5 describes the functional characterization of recombinant AV2 of CLCuKV-Dab. Chapter 6 deals with expression of CP and AV2 as GFP fusion proteins in insect cells using baculovirus expression system to study the localization patterns of these proteins. Chapter 7 describes functional characterization of CLCuKV-Dab AC4. Bioinformatic analysis of AC4 showed that it belongs to the rare group of natively unfolded proteins that are functionally active In conclusion, there is a large genetic variability that exists among the begomoviruses and in particular, among the CLCuD causing begomoviruses in India. Functional characterization of the proteins involved in the cell to cell movement in CLCuKV-Dab led to a possible model for its movement; the CP translated in the cytoplasm is targeted the nucleus via its NLS and there binds to progeny ssDNA and exports the ssDNA out of nucleus through its export signals. AC4 or some other host proteins yet to be identified transports the ssDNA-CP complex from the nuclear periphery to AV2 present at the cell periphery. The complex is then transported from one cell to the neighboring cell via plasmodesmata. AC4 being an ATPase/NTPase could provide energy for the process.

Doctor of Philosophy / Department of Entomology / C. Michael Smith / The wheat curl mite, Aceria tosichella (Keifer), is an important global pest of bread wheat, Triticum aestivum L. Chronic and often severe reductions of winter wheat yield due to A. tosichella infestations have occurred in North America and all other wheat-production areas for over five decades. Moreover, A. tosichella is the only vector which transmits the three most important wheat viruses in the Great Plains, which are Wheat Streak Mosaic Virus (WSMV), the most economically important wheat virus in North America; Triticum Mosaic Virus (TriMV) and High Plains Wheat Mosaic Virus (HPWMoV). Mite infestation alone causes stunted, chlorotic plants in susceptible wheat varieties. To date, mite resistant wheat cultivars have been the only sufficient method to control A. tosichella. The discovery of new genes for A. tosichella resistance and their introgression into wheat cultivars are essential steps to combat the development of new and/or different A. tosichella biotypes which can develop to overcome resistance genes. Both A. tosichella biotype 1 and 2 exist in U. S. Great Plains wheat producing areas. Elucidating and predicting A. tosichella population composition changes based on climatic and geographic variables is a key to continued effective mite management. Experiments were conducted to: 1) assess A. tosichella virulence in mites collected from 25 sample sites in six states to wheat plants harboring the Cmc2, Cmc3 and Cmc4 mite resistance genes and the Wsm2 WSMV resistance gene in 2014 and 2015, and determine the distribution of WSMV, TriMV and HPWMoV present in mites collected; 2) assess A. tosichella biotype composition using internal transcribed spacer 1 (ITS1) and cytochrome oxidase I (COI) polymorphisms; 3) use generalized additive modeling to capture the spatio-temporal factors contributing to the prevalence of A. tosichella biotypes 1 and 2; and 4) screen Kansas advanced breeding lines for resistance to A. tosichella biotypes 1 and 2. Results indicated that A. tosichella collected from 92% of the sample area were virulent to susceptible Jagger wheat plants with no Cmc resistance genes; that mites from 36% of the sample area were virulent to the Cmc2 gene, and that mites collected from 24% of sample area were virulent to Cmc3. Mite populations from only 8% of the sample sites exhibited virulence to plants containing Cmc4 + Wsm2 or Cmc4. The WSMV virus was predominant and present in 76% of all mites sampled. HPWMoV and TriMV were less apparent and present in 16% and 8% of all mites sampled, respectively. These results will enable breeders to increase the efficiency of wheat production by releasing wheat varieties containing A. tosichella resistance genes that contribute to reducing virus transmission. Results of spatio-temporal factor modeling provide new, more accurate information about the use of ground-cover and precipitation as key predictors of biotype prevalence and ratio. Experiments to determine if Kansas State University advanced breeding lines contain A. tosichella resistance found no resistance to biotype 1, resistance to biotype 2 in breeding lines AYN3-37 and AYN3-34; and moderate resistance to biotype 2 in breeding lines AYN2-28 and AYN2-36. The demonstrated correlation between reduced A. tosichella population size and avirulence; characterization and prediction of the A. tosichella biotype composition; and the identification of new sources of A. tosichella resistance in wheat can help entomologists and wheat breeders increase wheat production efficiency by releasing additional wheat cultivars containing A. tosichella resistance genes.

This study analyzed historical hydrographic data consist of 95 years of NODC data and 18 years of NCOR data. Variations of upper-layer current in Luzon Strait and its neighboring Northern South China Sea are investigated by the method of dynamical topography. On the other hand, higher salinity characteristic of the North Pacific Tropical Water (NPTW) is used to trace the water mass distribution and its seasonal variations in the studied area. The result shows that the maximum of x-component velocity (along 120.25˚E, relative to 400 m ) in the Luzon Strait occurs in the middle of the strait, the flow direction is westward and the speed increases toward the surface. At the north and south ends of the strait flows are eastward and the maximum speed core is at the depth of 0~50 m. Horizontal distribution of flow fields indicates that intrusion of the north Pacific waters into the South China Sea through the Luzon Strait in the whole year. Westward bifurcation of the intrusion flows occurs at 20~21˚N. A cyclonic eddy exists in the South China Sea all year-round, and its core is located at about 18˚N, 118˚E. This eddy strengthens as the monsoon prevails with its speed reached in January and February. Annual mean upper-layer transport (0~ 400 m) of the Luzon Strait is estimated to be about 3.5 Sv (positive value means westward) with a maximum value of about 6.5 Sv in December and a minimum value of 1.1 Sv in June. The Upper-layer current of the SCS is dominated by the monsoon. When the northeast monsoon prevails, the currents are affected by the Ekman effect to form high sea surface height in the north and low sea surface height in the south to produce a westward current. On the other hand, strong two coexistent wind stress curls with reversing signs during the northeast monsoon produce a westward current along the line of zero curl in the middle of the strait. The distribution of the NPTW(£m£c=23.5¡ã25.5 kg/m3,S >34.5 psu) is mostly at a depth of 120¡ã130 m in the South China Sea. NPTW were traced at 125 m depth, and the result indicates that this water mass enters the South China Sea through the Luzon strait all year-round. The intrusion path is along the continental slope of south China. The extent of intrusion reaches the maximum between December and February, and the water mass can spread into the South China Sea basin.

The issue of eddy currents induced by the rapid switching of magnetic field gradients is a long-standing problem in magnetic resonance imaging. A new method for dealing with this problem is presented whereby spatial harmonic components of the magnetic field are continuously sensed, through their temporal rates of change, and corrected. In this way, the effects of the eddy currents on multiple spatial harmonic components of the magnetic field can be detected and corrections applied during the rise time of the gradients. Sensing the temporal changes in each spatial harmonic is made possible with specially designed detection coils. However to make the design of these coils possible, general relationships between the spatial harmonics of the field, scalar potential, and vector potential are found within the quasi-static approximation. These relationships allow the vector potential to be found from the field – an inverse curl operation – and may be of use beyond the specific problem of detection coil design. Using the detection coils as sensors, methods are developed for designing a negative feedback system to control the eddy current effects and optimizing that system with respect to image noise and distortion. The design methods are successfully tested in a series of proof-of-principle experiments which lead to a discussion of how to incorporate similar designs into an operational MRI.

The issue of eddy currents induced by the rapid switching of magnetic field gradients is a long-standing problem in magnetic resonance imaging. A new method for dealing with this problem is presented whereby spatial harmonic components of the magnetic field are continuously sensed, through their temporal rates of change, and corrected. In this way, the effects of the eddy currents on multiple spatial harmonic components of the magnetic field can be detected and corrections applied during the rise time of the gradients. Sensing the temporal changes in each spatial harmonic is made possible with specially designed detection coils. However to make the design of these coils possible, general relationships between the spatial harmonics of the field, scalar potential, and vector potential are found within the quasi-static approximation. These relationships allow the vector potential to be found from the field – an inverse curl operation – and may be of use beyond the specific problem of detection coil design. Using the detection coils as sensors, methods are developed for designing a negative feedback system to control the eddy current effects and optimizing that system with respect to image noise and distortion. The design methods are successfully tested in a series of proof-of-principle experiments which lead to a discussion of how to incorporate similar designs into an operational MRI.

Pathogen-derived resistance (PDR) strategies, particularly those based on post-transcriptional gene silencing, have been used with great success for the generation of transgenic plants with resistance to RNA viruses. In contrast, a suitable strategy for transgenic resistance to ssDNA plant viruses, including those viruses belonging to the Geminiviridae, has remained elusive. Further, there is no convincing evidence that either post-transcriptional gene silencing, or pathogen-derived resistance in general, would be broadly applicable to ssDNA plant viruses. Researchers at QUT have been developing a novel resistance strategy against ssDNA viruses based on virus-activated expression of a stably integrated suicide gene. The strategy, based on InPAct (In Plant Activation) technology, relies on a &quotsplit" suicide gene cassette being arranged in such a way that expression of a lethal ribonuclease (barnase) is dependent on the virus-encoded replication-associated protein (Rep). Upon infection, Rep mediates the release of the construct resulting in the reconstitution of a transcribable and translatable episomal suicide gene expression cassette. The research for this PhD describes the development of an InPAct vector designed to confer resistance to Tomato leaf curl begomovirus (ToLCV), a major cause of disease in Solanaceous crops in the tropics and subtropics. ToLCV-based InPAct vectors were constructed based upon two ToLCV isolates from Australia and North Vietnam. Prior to the generation of InPAct cassettes, the entire ToLCV-[Au] and ToLCV-Vie intergenic regions (IRs) were embedded within the castorbean catalase intron of a β-glucuronidase expression vector to determine the effect of the IR upon transcript processing. Using transient reporter gene assays in tobacco NT-1 cells, it was demonstrated that the ToLCV IRs both contained cryptic intron splice sites which interfered with efficient transcript processing and GUS expression. A series of truncations to the IRs were subsequently made to identify the potential cryptic intron splice sites and/or interfering sequences in both the ToLCV-[Au] and ToLCV-Vie IRs. The final truncated IRs, which were used in the construction the InPAct cassettes, comprised approximately 100 bp and appeared to contain all the necessary cis-acting elements required for efficient rolling circle replication (RCR). Using histochemical GUS assays and Southern analyses, the InPAct cassettes were shown to be activated and replicated only in the presence of the cognate viral Rep. GUS expression levels were shown to be further enhanced in the presence of the ToLCV replication-enhancer protein (REn) and by the addition of the Tobacco yellow dwarf mastrevirus origin of second strand synthesis into the cassette. Under these conditions, Rep-activated GUS expression from the InPAct vectors was found to reach levels similar to that of the benchmark CaMV 35S promoter. Fifteen independent transgenic lines containing the ToLCV-[Au] and -Vie InPAct-GUS cassettes were generated by Agrobacterium-mediated transformation of tobacco leaf discs. Using agroinfiltration and histochemical assays, Rep-mediated activation of the InPAct cassettes and subsequent GUS expression was demonstrated in 11 out of the 15 lines tested; six of which showed expression levels equivalent to, or higher than, that obtained using a CaMV 35S promoter control. Evidence for activation of the integrated InPAct cassettes at the molecular level was provided by Southern analyses, with showed both linear and open circular forms of the replicating InPAct episome in genomic DNA extracted from infiltrated leaf tissue. Following the demonstration of Rep-activatable reporter gene expression and episomal replication of the ToLCV-based InPAct-GUS vectors using transient and stable tobacco transformation assays, new ToLCV-based InPAct vectors were designed to express the lethal RNase, barnase, in an attempt to generate virus resistant plants. Although transient assays in NT-1 cells demonstrated some &quotleaky" expression of barnase from the InPAct vectors, the level of barnase-mediated cell death from the InPAct vectors was found to be significantly increased in the presence of the cognate Rep and REn. Thirteen independently transformed tobacco lines containing the ToLCV-[Au] InPAct-barnase cassette were generated by Agrobacterium-mediated transformation of tobacco leaf discs. However, agroinfiltration of these plants with ToLCV Rep and REn failed to activate a barnase response. Subsequent molecular analyses on two transgenic lines revealed that both contained mutations in the barnase-coding gene in a region known to encode the active site. These mutations were presumed to result from the leaky barnase expression during initial stages of the Agrobacterium transformation which would favour the selection of barnase mutant InPAct plants. To overcome the problems associated with leaky expression of barnase, a barstar-expression cassette was included in the ToLCV-[Au] InPAct-barnase cassette. Transient assays in non-transgenic tobacco leaves demonstrated that the basal levels of barstar expressed from the modified InPAct vector were sufficient to negate the effects of leaky barnase expression. Importantly, however, the level of barnase expression in the presence of Rep and REn was shown to be sufficient to overcome the basal levels of barstar. Seventeen independently transformed lines were generated with the ToLCV-[Au] InPAct-barnase/barstar cassette, and analysis of one line revealed the presence of an uncorrupted barnase-coding region. Using transient agroinfiltration assays, seven of the transgenic lines showed varying levels of cognate Rep and REn-activated, barnase-induced cell death. Fifteen transgenic lines were challenged with ToLCV-[Au] by injection of recombinant Agrobacteria containing an infectious ToLCV clone. Unfortunately, all lines displayed typical ToLCV symptoms and tested positive for virus by PCR at 28 days post-inoculation. The inability of the InPAct cassette to confer resistance to ToLCV may have been due to one or a combination of factors, including (i) a delay in barnase-induced cell death, (ii) homology-dependent silencing of the integrated cassette, (iii) generally low-level, Rep-activated barnase expression or (iv) excessive virus load due to the artifical method of inoculation. This study details the first report of a ToLCV-based InPAct system for Rep-induced transgene expression in planta. Despite failing to generate ToLCV-resistant plants, the research findings will provide a solid foundation to develop a more effective InPAct vector and ultimately assist in the generation of transgenic plants with resistance to ToLCV and potentially other ssDNA plant viruses, particularly the begomoviruses.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed May 23, 2007). PDF text: iv, 165 p. : ill. (some col.) ; 1.95Mb UMI publication number: AAT 3237062. Includes bibliographical references. Also available in microfilm and microfiche formats.

Master of Science / Department of Plant Pathology / Erick D. DeWolf / Wheat streak mosaic (WSM) is a devastating disease of winter wheat (Triticum aestivum L.) in Kansas. Although WSM can cause heavy crop losses, the severity of regional and statewide losses varies by year and location. Wheat streak mosaic is caused primarily by the Wheat streak mosaic virus (WSMV) and is spread by the wheat curl mite, Aceria tosichella Keifer. To infect fall planted wheat, both the virus and mite require a living, grass host to survive the summer months. The first research objective was to determine the risk of different grass species to serve as a source of WSM. Published experiments and surveys were reviewed to determine the suitability of each host based on a set of criteria. An analysis of the reports from the reviewed literature found 39 species to host both pests. Categorical analysis of these observations suggested that well-studied grass species could be placed in four risk groupings with ten species at high risk of carrying both pests. Furthermore, results from controlled experimentation generally agrees with results from field survey results for both pests. The second objective was to determine the weather and cropping factors that are associated with regional epidemics of WSM in Kansas. Historic disease observations, weather summaries, soil moisture indices, and cropping statistics were collected from Kansas crop reporting districts from 1995-2013. Binary response variables (non-epidemic case vs epidemic cases) were developed from different thresholds of district losses attributed to WSM. Variables associated with WSM epidemics were identified by a combination of non-parametric correlation, classification trees, and logistic regression. This analysis indicates that the total acres of wheat planted per season was associated with the low frequency of epidemics in Eastern Kansas. Temperature during September appears to influence the yield losses caused by WSM. Wheat planting generally begins during September and continues through October in the state. Temperature during the winter months (December-February) was also identified as important with warm conditions favoring outbreaks of disease. Dry soil conditions in February was also associated with epidemics of WSM. Models combining these variables correctly classified 60 to 74% of the cases considered in this analysis.