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Second-order total freedom analysis of 3D objects in a single point contact
No full textThis paper studies the instantaneous second-order total freedom of two smooth objects initially in contact at a single point. The analytical determination of the set of physically allowed second-order motions is formulated in the Euclidean space using the screw theoretic concepts of twist and twist-derivative. Mathematical expression that characterizes the nature of second-order motion for an arbitrary contact geometry is derived in terms of twist coordinates, twist-derivative coordinates and the principle normal curvatures of the two surfaces at the point of contact. It is shown that the characteristic of this expression is equivalent to that of the derivative of reciprocal product of the instantaneous twist and contact normal line. The efficacy of the theory developed is demonstrated through two illustrative examples
Guidance law for mimicking short-range ballistic trajectories
No full textThis paper considers the problem of mimicking short-range ballistic trajectories and presents a feedback guidance law addressing that. Analysis of the ideal ballistic trajectory is carried out and closed-form expressions are derived for the heading error and its derivative. Satisfying the launch angle, the impact angle, and the initial heading error rate of the ballistic trajectory, a guidance law is proposed using bearings-only information of the impact point. Analysis of the proposed guidance law is carried out evaluating the variation in guidance gains, the maximum look-angle, and the capturability. Analyzing the time-varying effective navigation gain, boundedness of the lateral acceleration is also ascertained. Simulations are carried out mimicking the ideal and realistic ballistic trajectories. Robustness of the proposed guidance method is verified against wind disturbances and error in modeling drag coefficient
Using wavelet analysis to investigate synchronization
No full textWavelet analysis is shown to be a more robust technique than previously used methods in the investigation of synchronization. The highlight of the technique is that it encompasses most of the information obtained by conventional methods into a single picture, while giving a deeper insight into the dynamics of the system. Order parameters derived from continuous wavelet transform coefficients are proposed, which can be used in the quantification of measure synchronization in Hamiltonian systems and identical synchronization in dissipative systems, irrespective of the nature of coupling, the nature of synchronization (complete or partial, quasiperiodic or chaotic), and the number of coupled subsystems
MoS2-Modified Curcumin Nanostructures: The Novel Theranostic Hybrid Having Potent Antibacterial and Antibiofilm Activities against Multidrug-Resistant Hypervirulent Klebsiella pneumoniae
No full textThe recent emergence of hypervirulent clinical variants of Klebsiella pneumoniae (hvKP) causing community-acquired, invasive, metastatic, life-threatening infections of lungs, pleura, prostate, bones, joints, kidneys, spleen, muscles, soft-tissues, skin, eyes, central nervous system (CNS) including extrahepatic abscesses, and primary bacteremia even in healthy individuals has posed stern challenges before the existing treatment modalities. There is therefore an urgent need to look for specific and effective therapeutic alternatives against the said bacterial infection or recurrence. A new type of MoS2-modified curcumin nanostructure has been developed and evaluated as a potential alternative for the treatment of multidrug-resistant isolates. The curcumin quantum particles have been fabricated with MoS2 via a seed-mediated hydrothermal method, and the resulting MoS2-modified curcumin nanostructures (MQCs) have been subsequently tested for their antibacterial and antibiofilm properties against hypervirulent multidrug-resistant Klebsiella pneumoniae isolates. In the present study, we found MQCs inhibiting the bacterial growth at a minimal concentration of 0.0156 mu g/mL, while complete inhibition of bacterial growth was evinced at concentration 0.125 mu g/mL. Besides, we also investigated their biocompatibility both in vitro and in vivo. MQCs were found to be nontoxic to the SiHa cells at a dose as high as 1024 mu g/mL on the basis of the tested adhesion, spreading of the cells, and also on the various serological, biochemical, and histological investigations of the vital organs and blood of the Charles Foster Rat. These results suggest that MQCs have potent antimicrobial activities against hvKP and other drug resistant isolates and therefore may be used as broad spectrum antibacterial and antibiofilm agents
Influence of gas dynamics on arc dynamics and the discharge power of a rotating gliding arc
No full textThis work reports the design and characterization of a rotating gliding arc (RGA) reactor developed with novel electrode configuration. This RGA uses gas swirl discs having ` tangential gas entry ports/holes' (NH) to achieve arc rotation and does not employ any external magnets. This work investigates the effect of gas dynamics on (1) arc dynamics such as the arc's rotation and shape; (2) voltage fluctuation pattern; and (3) plasma discharge power for the designed RGA. Experiments were conducted using argon as the plasma forming gas with (a) two gas swirl discs (NH = 3 and 12) and (b) three different gas flow rates (Q = 5, 25 and 50 LPM) as control parameters. Cold flow simulation (CFS) studies using a multidimensional solver were used to understand gas dynamics. The arc rotational frequency (farc) measured from (1) a high-speed camera (HSC) and (2) fast Fourier transform (FFT) analysis of voltage, shows linear dependency on the Reynolds number (Re) calculated from CFS, with an R-2 = 0.98. The agreement improves (R-2 = 0.99) by applying linear fit only for the cases having turbulent Re. A close match between gas rotational frequency (f(gas)) calculated from CFS and experimentally measured f(arc) is seen. The turbulent regime of the gas flow causes: (1) twisting and bending of the arc; (2) sawtooth-like voltage fluctuations with irregular and non-sinusoidal waveform; and (3) arc blow off. The high-frequency voltage fluctuations were reduced/absent when the flow Re reduced from approximate to 6.0 x 10(4) to approximate to 1.0 x 10(4). These findings establish that the gas dynamics, in particular, the bulk flow phenomenon of the gas, has an explicit influence on arc dynamics of the RGA reactor. This novel RGA design has the potential to replace magnetically driven rotating gliding arc systems
Assessing predictions on fitness effects of missense variants in calmodulin
No full textThis paper reports the evaluation of predictions for the ``CALM1'' challenge in the fifth round of the Critical Assessment of Genome Interpretation held in 2018. In the challenge, the participants were asked to predict effects on yeast growth caused by missense variants of human calmodulin, a highly conserved protein in eukaryotic cells sensing calcium concentration. The performance of predictors implementing different algorithms and methods is similar. Most predictors are able to identify the deleterious or tolerated variants with modest accuracy, with a baseline predictor based purely on sequence conservation slightly outperforming the submitted predictions. Nevertheless, we think that the accuracy of predictions remains far from satisfactory, and the field awaits substantial improvements. The most poorly predicted variants in this round surround functional CALM1 sites that bind calcium or peptide, which suggests that better incorporation of structural analysis may help improve predictions
Role of stress state on dynamic recrystallization behaviour of Ni during hot deformation: Analysis of uniaxial compression and plane strain compression
No full textIn the present work, the role of deformation stress state (uniaxial compression (UC) and plane strain compression (PSC)) on work hardening, softening and dynamic recrystallization (DRX) behaviour of Ni during hot deformation is investigated. Hot deformation was performed through UC and PSC to a von Mises equivalent true strain of 0.7 at 973 K, 1023 K and 1073 K at strain rates of 0.01 s(-1), 0.1 s(-1) and 1 s(-1) in a thermomechanical simulator. Analysis of flow curves revealed rapid work hardening followed by softening in PSC samples, In UC samples, continuous work hardening at a slower rate was observed and at 1123 K, steady state was achieved. Analysis of the work hardening parameter `h' and dynamic recovery parameter `r' from the flow curve data showed that the h and r values of PSC deformed samples are higher than UC deformed samples. The DRX behaviour is dependent on temperature and strain rate and significant difference in DRX fraction was observed between UC and PSC samples deformed at strain rate of 0.1 s(-1). Evaluation of microstructure from electron back scatter diffraction maps showed that DRX fraction is significantly higher in PSC deformed samples. Samples deformed through PSC have higher annealing twin density and number of twins per grain. It is reasoned that annealing twin formation is activated by the presence of shear stress component during PSC mode of deformation. Annealing twin formation and growth in turn facilitate DRX and explain the observed differences between UC and PSC modes of deformation
Recent advances in MXenes: From fundamentals to applications
No full textThe family of MAX phases and their derivative MXenes are continuously growing in terms of both crystalline and composition varieties. In the last couple of years, several breakthroughs have been achieved that boosted the synthesis of novel MAX phases with ordered double transition metals and, consequently, the synthesis of novel MXenes with a higher chemical diversity and structural complexity, rarely seen in other families of two-dimensional (2D) materials. Considering the various elemental composition possibilities, surface functional tun ability, various magnetic orders, and large spin orbit coupling, MXenes can truly be considered as multifunctional materials that can be used to realize highly correlated phenomena. In addition, owing to their large surface area, hydrophilicity, adsorption ability, and high surface reactivity, MXenes have attracted attention for many applications, e.g., catalysts, ion batteries, gas storage media, and sensors. Given the fast progress of MXene-based science and technology, it is timely to update our current knowledge on various properties and possible applications. Since many theoretical predictions remain to be experimentally proven, here we mainly emphasize the physics and chemistry that can be observed in MXenes and discuss how these properties can be tuned or used for different applications
Comparative study of keratin extraction from human hair
No full textKeratin has been attracting interest due to its stability against enzymatic degradation thereby allowing more predictable degradation profile for tissue regeneration applications. While the efficacy of keratin has been demonstrated in different tissue models, there has been no systematic study to investigate and compare the different routes of keratin extraction from human hair. Here, we compared the four commonly used extraction methods and highlighted both physical and chemical differences in the extracted keratin. Keratin was extracted from human hair using one of four common agents, namely, sodium sulfide, peracetic acid, urea and thioglycolic add. Whereas no specific trend was observed, the keratin extracted through peracetic acid method had significantly different properties. It resulted in lowest yield of 52 mu g/mL and low crystallinity but the protein formed aggregates with highest hydrodynamic average size of around 283 nm compared to the other three methods. However, despite greater aggregation, keratin extracted from peracetic acid method exhibited secondary structural conformation similar to thioglycolic acid method. All the four extracted keratin promoted cellular proliferation of osteoblasts compared to the uncoated surface. These results provide new insight into the extraction of keratin from human hair with implications for its use as a biomaterial
Role of Large-Scale Tectonic Forces in Intraplate Earthquakes of Central and Eastern North America
No full textCentral and eastern United States (CEUS) have experienced large intraplate earthquakes. Yet, at present there is no comprehensive model to explain stresses, strain, and seismicity in this intraplate setting. Models to explain the intraplate stresses in CEUS include glacio-isostatic adjustment, ridge push effects, local stresses along preexisting fracture zones, and large-scale convection. In this paper, we present a self-consistent model of the dynamics of CEUS that explains the stress field responsible for these intraplate earthquakes. The earthquakes represent slow, ongoing deformation associated with forces arising from a combination of lithosphere topography and structure, together with the effects of density-driven mantle flow. Using GPS data, we calculate strain rates that are likely to arise from tectonic effects and conclude that intraplate strain rates associated with tectonic effects are unlikely to exceed 1 x 10(-9) year(-1). We test several models of lateral viscosity variations by comparing model stress orientation output with earthquake moment tensors, SHmax directions from stress inversion, and P axes of earthquakes. A model that satisfies stress and earthquake constraints and also strain rate magnitude constraints requires high viscosity (1025 Pa.s) craton and old oceanic lithosphere of the western Atlantic block and weaker (5 x 1024 Pa.s) accreted Appalachian terrane. Other strength contrasts within the lithosphere are likely present. Incorporation of these into future models using constraints from seismology, along with refined geodetic measurements and improved estimates of crust and upper mantle densities, is needed to further refine long-term dynamic models and better evaluate the hazards associated with this very slow, ongoing permanent deformation within the eastern and central United States