Cytoskeleton polarisation in Drosophila

Epithelial cells are polarised into distinct domains by the core apical and basolateral determinants. Cell polarity is critical for tissue integrity and also plays an important role in many morphogenetic processes. How polarity determinants act to polarise the cytoskeleton and orient cellular functions is unclear. The work presented in this thesis examines how the different components of the cytoskeleton – the actin filaments, Spectrins and microtubules – become polarised in response to polarity determinants and how this polarisation contributes to different cellular behaviours in development. Our results identify a novel role for Hippo signalling in linking cell polarity determinants to polarisation of the actin cytoskeleton during Drosophila border cell migration. We find that Hippo signalling acts independently of canonical Yorkie nuclear signalling. Instead, Warts phosphorylates and inhibits the actin regulator Enabled to activate F-actin Capping protein activity, thus polarising the actin cytoskeleton by restricting F-actin polymerisation to the outer rim of the migrating cluster. In addition to Hippo’s link with F-actin, our work also demonstrates a link between Hippo and the Spectrin cytoskeleton. We show that apical and basolateral Spectrins are upstream regulators of Hippo signalling and act as potential mechanosensors to regulate growth. Finally, we also show that polarity determinants are important for polarising microtubules in Drosophila follicle cells. We demonstrate that the Spectrin-associated proteins Patronin and Shortstop are required to polarise microtubules along the apical-basal axis of epithelial cells. These microtubules direct apical transport of Rab11-positive vesicles containing the microvilli determinant Cadherin99C via the Dynein motor and its adaptor protein Nuf. At the apical cortex, Rab11-positive vesicles switch to actin-based transport via the MyosinV motor and its adaptor protein dRip11 to direct apical delivery of Cadherin99C to drive biogenesis of apical microvilli. Taken together, our work demonstrates how determinants of apical-basal polarity can control polarisation of the cytoskeleton to direct diverse cellular processes

LTPP Data Analysis: Factors Affecting Pavement Roughness for the State of California

The contributions of pavement structure and features, rehabilitation techniques, climatic conditions, traffic levels, layer materials and properties, pavement distress, and other factors causing changes in pavement smoothness are not well documented. As a result, it becomes difficult to select the appropriate pavement structure, design features and rehabilitation strategies to ensure pavement smoothness. This study focuses on analysing the available LTPP data for asphalt pavements in California by investigating the correlation between the pavement roughness and the effect of pavement temperature, precipitation, fatigue, age of pavement, rutting, and the average annual daily truck traffic. IRI has been identified as the factor characterizing pavement smoothness. Results indicated that when diving pavement sections between three different groups according to the annual precipitation for pavement section in the State of California, the IRIchange can be predicted with 93.5% accuracy for sections with less than 200mm of annual precipitation, 85.9% accuracy for sections with annual precipitation between 200mm and 90mm, and 90.1% for sections with annual precipitation higher than 900mm

The dissimilar chemical composition of the planet-hosting stars of the XO-2 binary system

Using high-quality spectra of the twin stars in the XO-2 binary system, we have detected significant differences in the chemical composition of their photospheres. The differences correlate strongly with the elements' dust condensation temperature. In XO-2N, volatiles are enhanced by about 0.015 dex and refractories are overabundant by up to 0.090 dex. On average, our error bar in relative abundance is 0.012 dex. We present an early metal-depletion scenario in which the formation of the gas giant planets known to exist around these stars is responsible for a 0.015 dex offset in the abundances of all elements while 20 M_Earth of non-detected rocky objects that formed around XO-2S explain the additional refractory-element difference. An alternative explanation involves the late accretion of at least 20 M_Earth of planet-like material by XO-2N, allegedly as a result of the migration of the hot Jupiter detected around that star. Dust cleansing by a nearby hot star as well as age or Galactic birthplace effects can be ruled out as valid explanations for this phenomenon.Comment: ApJ, in press. Complete linelist (Table 3) available in the "Other formats -> Source" downloa

Wake-Tailplane Interaction of a Slingsby Firefly Aircraft

This paper presents in-flight measurements of the interaction of the wing wake of a stalled Slingsby T67 Firefly light aircraft with the aircraft tailplane. Tailplane data was recorded by a GoPro360 camera and analyzed using spatial correlation methods. The tailplane movement and corresponding spectra indicate that the aerodynamic wake shedding frequency closely matches the resonant frequency of the tailplane, resulting in a significant excitation of the structure during heavy stall. Large magnitude, lower frequency tailplane movement was also identified by analysis of the pitch attitude from the image data, with results consistent in post-stall behavior reported by previous modelling and measurements

Unsteady aerodynamics analysis and modelling of a Slingsby Firefly aircraft:Detached-Eddy Simulation model and flight test validation

This paper presents unsteady stall characteristics of a Slingsby T67M260 Fire y light aircraft from both a computational uid dynamics (CFD) half model and ight tests. Initial results from the steady CFD, based on a RANS k . ! SST turbulence model, established the critical angle of attack of the stall to be stall = 16 , with a maximum lift coe cient of CLmax = 1.2. Comparisons with straight and level ight test data were comparable up to = 12 { 14 , with the increasing deviation at higher attributed to the e ect of the propeller slipstream under these ight conditions. The RANS CFD model was then extended to an unsteady Detached-Eddy Simulation (DES) model for three angles of attack at pre-stall and stall condition ( = 14 , 16 , 18 ), with analysis of the vortex shedding frequency. Further comparisons were then made with ight test data taken using on-board accelerometers and wing tuft surface ow visualization, at a stalled condition at equivalent . These unsteady CFD data established a dominant shedding frequency ranging from 11.7 Hz { 8.74 Hz with increasing and a Strouhal number based on wing chord of St = 0.11, which when compared to flight test accelerometer spectra matched within 2.9% of the measured frequenc

Biospectroscopy of Nanodiamond-Induced Alterations in Conformation of Intra- and Extracellular Proteins: A Nanoscale IR Study

The toxicity of nanomaterials raises major concerns because of the impact that nanomaterials may have on health, which remains poorly understood. We need to explore the fate of individual nanoparticles in cells at nano and molecular levels to establish their safety. Conformational changes in secondary protein structures are one of the main indicators of impaired biological function and hence, the ability to identify these changes at a nanoscale level offers unique insights into the nanotoxicity of materials. Here, we used nanoscale infrared spectroscopy and demonstrated for the first time that nanodiamonds induced alterations in both extra- and intracellular secondary protein structures, leading to the formation of antiparallel β-sheet, β-turns, intermolecular β- sheet and aggregation of proteins. These conformational changes of the protein structure may result in the loss of functionality of proteins and in turn lead to adverse effects

Associations of combined genetic and epigenetic scores with muscle size and muscle strength: a pilot study in older women

Background: Inter-individual variance in skeletal muscle is closely related to genetic architecture and epigenetic regulation. Studies have examined genetic and epigenetic relationships with characteristics of ageing muscle separately, while no study has combined both genetic and epigenetic profiles in ageing muscle research. The aim of this study was to evaluate the association between combined genetic and methylation scores and skeletal muscle in older women. Methods: 48 older Caucasian women (aged 65–79 yr) were included in this study. Biceps brachii thickness and vastus lateralis anatomical cross-sectional area (ACSAVL) were measured by ultrasonography. Maximum isometric elbow flexion (MVCEF) and knee extension (MVCKE) torques were measured by a customized dynamometer. The muscle-driven genetic predisposition score (GPSSNP) was calculated based on seven muscle-related single nucleotide polymorphisms (SNPs). DNA methylation levels of whole blood samples were analysed using Infinium MethylationEPIC BeadChip arrays. The DNA methylation score was calculated as a weighted sum of methylation levels of sarcopenia-driven CpG sites (MSSAR) or an overall gene-wise methylation score (MSSNP, the mean methylation level of CpG sites located in muscle-related genes). Linear regression models were built to study genetic and epigenetic associations with muscle size and strength. Three models were built with both genetic and methylation scores: (1) MSSAR + GPSSNP, (2) MSSNP + GPSSNP, (3) gene-wise combined scores which were calculated as the ratio of the SNP score to the mean methylation level of promoters in the corresponding gene. Additional models with only a genetic or methylation score were also built. All models were adjusted for age and BMI. Results: MSSAR was negatively associated with ACSAVL, MVCEF and MVCKE, and explained 10.1%, 35.5% and 40.1% of the variance, respectively. MSSAR explained more variance in these muscular phenotypes than GPSSNP, MSSNP and models including both genetic and methylation scores. MSSNP and GPSSNP accounted for less than 8% and 5% of the variance in all muscular phenotypes, respectively. The genotype and methylation level of MSTN was positively related to MVCKE (p < 0.03) and explained 12.2% of the variance. The adjusted R2 and Akaike information criterion showed that models with only a MSSAR performed the best in explaining inter-individual variance in muscular phenotypes. Conclusion: Our results improve the understanding of inter-individual variance in muscular characteristics of older women and suggest a possible application of a sarcopenia-driven methylation score to muscle strength estimation in older women while the combination with a genetic score still needs to be further studied

Perturbation of FRW Spacetime in NP Formalism

Perturbation of FRW spacetime is carried out in NP formalism. The equation governing the scalar, vector and tensor modes take on a very simple and transparent form. All of them can be combined in one master equation for all helicities. The solutions for the closed, flat and open FRW are analytic continuation of the same functions, so only the solutions in the closed model are described. The scalar equation is the same as that of the conformally coupled massless Klein-Gordon field, the vectorial ones are the same as Maxwell equations, and the tensorial ones are for spin-2 fields. The corresponding eigen-functions are all determined, and in particular, the Green's function and the Lienard-Wiechert type potential also solved. These solutions reduce to the familiar form in flat space.Comment: 11 pages including 3 figure

Quasi-normal modes of Schwarzschild-de Sitter black holes

The low-laying frequencies of characteristic quasi-normal modes (QNM) of Schwarzschild-de Sitter (SdS) black holes have been calculated for fields of different spin using the 6th-order WKB approximation and the approximation by the P\"{o}shl-Teller potential. The well-known asymptotic formula for large $l$ is generalized here on a case of the Schwarzchild-de Sitter black hole. In the limit of the near extreme $\Lambda$ term the results given by both methods are in a very good agreement, and in this limit fields of different spin decay with the same rate.Comment: 9 pages, 1 ancillary Mathematica(R) noteboo