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Chemical reduction of graphene oxide has emerged as one of the most suitable processes for low-cost and large-scale production of graphene for potential applications. Here we report a simple, efficient, scalable, room-temperature method for enhanced reduction of graphene oxide (GO). Nowadays, hydroiodic acid (HI) is being widely used as a reducing agent for synthesizing highly conductive reduced graphene oxide. Herein, aluminum (Al) powder was used in the second step to improve the extent of reduction using HI. Al3+, which is a strong lewis acid, helps further in the reduction and enhances the one-step reduction by HI. Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM), X-Ray Diffraction (XRD), Raman and X-Ray Photoelectron Spectroscopy (XPS) confirmed the formation of GO and assisted in understanding the potential of HI and Al–HI as reducing agents. The comparative analysis demonstrates the enhancement in the reduction properties of the novel Al supplemented reduced GO. Additionally, an electrically conductive dip-coated film with a sheet resistance of 4.56 × 104 Ω/sq was successfully fabricated using this Al-supplemented reduction technique. [ABSTRACT FROM AUTHOR]

The present work reveals the variation of nanomechanical properties (nanohardness-H and modulus-E) of black anodic coating on additively manufactured Al–10Si–Mg alloy. The plan-section of the coating has mud-crack-like morphology with various nano/micro-pores, micro-channels, and irregularities. In contrast, the cross-section possesses a compact morphology with minimum surface/sub-surface defects like micro-cracks or irregularities. The H and E are derived from nanoindentation experiments using Berkovich tip at loads 10–50 mN. The nanomechanical properties are higher across the cross-section than the plan section of the coating, attributing to the difference in morphology between the plan- and the cross-sections. Due to characteristic porosities, defects, and nano/micro-cracks in the anodic coating, Weibull statistical analysis has been employed to rationalize the scatter in nanoindentation-based data. For both plan and cross-sections, the H and E values decrease as the indentation load increases from 10 to 50 mN, confirming the indentation size effect (ISE). The well-established Meyer's law, Hays–Kendall approach, elastic recovery model, proportional specimen resistance (PSR) model and the modified PSR model have been used to thoroughly analyze the ISE characteristics. [ABSTRACT FROM AUTHOR]

Black anodic coating (BAC) is developed on 3D printed or additively manufactured (AM) Al–10Si–Mg alloy by sulphuric acid based anodization technique at low (∼9 °C) temperature. The microstructural and surface properties of the coating are investigated by optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and water contact angle (WCA) measurement techniques. The solar absorptance and infrared (IR) emittance of the coating have been evaluated in the range 200–2500 nm and 3–30 μm, respectively. Nanoindentation technique is employed with low load to evaluate the hardness and modulus of the coating at microstructural length scale. The anodic coating shows superior hardness (∼3.95 GPa) and modulus (∼96 GPa) as compared to reported literature values, possibly due to dense microstructure and the presence of harder ceramic phases, e.g., alumina and kyanite in anodic coating. Further, due to dense microstructure, corrosion resistance improves significantly after anodization of AM alloy. Finally, thermo-optical properties are not altered after the space environmental tests which ensures the usage of the present anodic coating on AM Al alloy for spacecraft thermal control application. The solar absorptance (0.87) and IR emittance (0.78) obtained for the present coating as flat absorber characteristics are higher than the coatings processed on conventional wrought alloys. The present anodic coating shows substantial improvement in mechanical, thermo-optical and corrosion properties due to higher silicon content unlike conventional wrought alloy and refinement in microstructure during additive manufacturing aiding continuous and uniform anodic oxide layer. [ABSTRACT FROM AUTHOR]

Numerical simulations with varying realism indicate an emergent principle−multiphase condensation and large cavity power occur when the ratio of the cooling time to the free-fall time (t cool/ t ff) falls below a threshold value close to 10. Observations indeed show cool-core signatures when this ratio falls below 20–30, but the prevalence of cores with t cool/ t ff  ratio below 10 is rare as compared to simulations. In X-ray observations, we obtain projected spectra from which we have to infer radial gas density and temperature profiles. Using idealized models of X-ray cavities and multiphase gas in the core and 3D hydro jet-ICM simulations, we quantify the biases introduced by deprojection based on the assumption of spherical symmetry in determining t cool/ t ff. We show that while the used methods are able to recover the t cool/ t ff ratio for relaxed clusters, they have an uncertainty of a factor of 2−3 in systems containing large cavities (≳ 20 kpc). We also show that the mass estimates from these methods, in the absence of X-ray spectra close to the virial radius, suffer from a degeneracy between the virial mass (M 200) and the concentration parameter (c) in the form of M 200 c 2 ≈ constant. Additionally, the lack of soft-X-ray (≲ 0.5 keV) coverage and poor spatial resolution makes us overestimate min(t cool/ t ff) by a factor of few in clusters with min(t cool/ t ff) ≲ 5. This bias can largely explain the lack of cool-core clusters with min(t cool/ t ff) ≲ 5. [ABSTRACT FROM AUTHOR]

The present work explores the adaptive behavior of well-known ureolytic bacterial strain namely Sporosarcina pasteurii for microbial-induced calcite precipitation (MICP) under saline environment. MICP activity was observed up to 10% NaCl supplementation and confirmed by several characterization techniques viz. scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The urease activity did not show appreciable decline till 5% NaCl supplementation but beyond that drastic reduction was observed though MICP process continued. These results indicated a shift in the biological pathway for MICP process at higher salt concentrations. This was confirmed by estimation of ammonium ion concentration which was approximately 4 µg/ml with 10% NaCl supplementation as compared to 8.5 µg/ml at 0% NaCl supplementation. To provide an insight on the nature of protein expressed, combination of liquid chromatography-mass spectrometry (nano-LC-MS) approaches along with an exponentially modified protein abundance index (emPAI) methodology were explored. The findings suggest the presence of significant number of osmoregulatory proteins substantiating halophilic adaptation of S. pasteurii and bicarbonate transport mediated precipitation at higher levels of salinity. Further, co-precipitation of CaCl2 and MgSO4 was also confirmed with SEM and energy dispersive spectroscopy (EDS) mapping under higher saline environment thus substantiating the efficacy of the strain. [ABSTRACT FROM AUTHOR]

In this work, we show that Microbial Induced Calcite Precipitation (MICP) can be used for making consolidated structures – space bricks – using lunar soil simulant (LSS). Sporosarcina pasteurii was used as a bacterial strain to initiate MICP process via ureolytic pathway. An admixture of a naturally occurring biopolymer (guar gum) and a structural reinforcement material (glass fibre) was used to enhance the mechanical properties of the bio-consolidated bricks. When supplemented with guar gum, the compressive strength of the resulting bricks was found to be significantly higher – by nearly six-fold – making them comparable to commercially used mud bricks. The addition of glass fibre reduced this strength a little, but had the benefit of making the space bricks machinable on a conventional lathe. This latter fact enabled the fabrication of precise and free-form shapes post-consolidation, without the need for specialized casting molds or dies. Details of the MICP process were investigated using field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses. The route demonstrated here holds great potential for making strong structures in extra-terrestrial habitats, while adhering to the principles of in situ resource utilization. [ABSTRACT FROM AUTHOR]

Aim: To investigate the relationship between changes in urine output during indomethacin treatment and ductal closure in preterm neonates.Methods: It is a retrospective study in neonates ≤32 weeks who had received two courses of indomethacin for PDA treatment over a 5-year period. Indomethacin courses with pre- and post-echocardiography confirmation of PDA status were included. Various urine output indices were collected and compared between successful versus unsuccessful indomethacin courses. Indomethacin treatment success was defined as: (i) where PDA closed or became haemodynamically insignificant (hisPDA) after treatment and (ii) only including neonates where PDA had complete closure after treatment. ROC analysis was performed to examine predictive ability of urine output during indomethacin for treatment success.Results: One hundred and eight indomethacin courses (first course: 52, second course: 56) in 80 neonates were included. The mean gestational age and birthweight were 25.4 ± 1.3 weeks and 762 ± 165 g, respectively. Irrespective of the definition used, there was no significant differences seen in any of urine output parameters between groups, except for a higher urine output during indomethacin associated with complete PDA closure (3.6 ± 1.3 vs. 3.0 ± 1.0 mL/kg/h, P = 0.02). The incidence of significant oliguria, hyponatraemia and need to withhold/delay indomethacin doses were also similar across groups.Conclusion: Urine output was not a useful predictor of ductal response to indomethacin treatment in preterm neonates. [ABSTRACT FROM AUTHOR]

Transparent super-hydrophobic monolithic silica aerogels are prepared by the cost-effective ambient pressure drying. The drying of aerogel is performed at various temperatures ranging from 25 to 200°C. Oxidation states of different silica aerogels are investigated by XPS which shows the presence of both SiO and SiO2 phases. Thermal stability of hydrophobic aerogel is found as ~320°C investigated by TGA and DSC. The chemical bonds (i.e., –CH3) responsible for the hydrophobic (WCA > 170°) nature of synthesized silica aerogels are identified by FTIR. Further, out-gassing properties of the silica aerogels have been investigated and they are found in limit for the space application. The highest hardness and Young’s modulus are measured by the nanoindentation technique for the aerogel dried at 120°C which has higher density, while density decreases for the aerogel dried at 200°C and the corresponding nanomechanical properties are found to be lowest as expected. [ABSTRACT FROM AUTHOR]

Doped and co-doped vanadium oxide (VO) thin films were deposited on quartz substrates with varying concentrations of doping elements by sol-gel spin coating technique. The VO thin films were characterized by the X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), cross-sectional FESEM and X-ray photoelectron spectroscopy (XPS) techniques. The optical properties, e.g., the average solar absorptance (α s), the average solar reflectance (ρ s) and the average solar transmittance (τ s) of the films deposited on quartz were evaluated by using a solar spectrum reflectometer. Based on the optical characterizations, an optimized doping concentration was identified. Further, a process optimized condition was utilized to grow both doped and co-doped vanadium oxide films on metallic Al6061 substrates; which are generally used in spacecraft. The phase transitions of all as grown vanadium oxide films on Al6061 were characterized by the differential scanning calorimetry (DSC) technique. The thin films showed reversible and repeatable phase transitions at sub-zero level of temperatures e.g., ∼ (̶ 23.3 °C). Thus, the VO thin films developed in the present work emerge out to be of paramount importance for the smart radiative device applications in spacecraft. [ABSTRACT FROM AUTHOR]

We investigate the spatial distribution of Ly α-emitting galaxies (LAEs) at z ≈ 2.67, selected from the NOAO Deep Wide-Field Survey, using two-point statistics and topological diagnostics adopted from network science. We measure the clustering length, r 0 ≈ 4  h −1 Mpc, and the bias,   |$b_{\mathrm{ LAE}} = 2.2^{+0.2}_{-0.1}$|⁠. Fitting the clustering with halo occupation distribution (HOD) models results in two disparate possibilities: (1) where the fraction of central galaxies is <1 per cent in haloes of mass >1012 M⊙ and (2) where the fraction is ≈20 per cent. We refer to these two scenarios as the 'Dusty Core Scenario' for Model#1, since most of the central galaxies in massive haloes are dead in Ly α emission, and the 'Pristine Core Scenario' for Model#2, since the central galaxies are bright in Ly α emission. Traditional two-point statistics cannot distinguish between these disparate models given the current data sets. To overcome this degeneracy, we generate mock catalogues for each HOD model using a high-resolution N -body simulation and adopt a network statistics approach, which provides excellent topological diagnostics for galaxy point distributions. We find three topological anomalies from the spatial distribution of observed LAEs, which are not reproduced by the HOD mocks. We find that Model#2 matches better all network statistics than Model#1, suggesting that the central galaxies in >1012  h −1 M⊙ haloes at z ≈ 2.67 need to be less dusty to be bright as LAEs, potentially implying some replenishing channels of pristine gas such as the cold mode accretion. [ABSTRACT FROM AUTHOR]

Smooth, uniform and crystalline vanadium oxide thin films were deposited on quartz by spin coating technique with four different rpm i.e., 1000, 2000, 3000 and 4000 and subsequently post annealed at 350, 450 and 550 °C in vacuum. Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were utilized for microstructural characterizations and phase analysis, respectively, for vanadium oxide powder and deposited film. Nanorods were observed to be grown after vacuum annealing. X-ray photoelectron spectroscopy (XPS) technique was utilized to study the elemental oxidation state of deposited vanadium oxide films. Thermo-optical and electrical properties such as solar transmittance (τ s ), reflectance (ρ s ), absorptance (α s ), infrared (IR) emittance (ε ir ) and sheet resistance (R s ) of different thin films were evaluated. Based on the optical characteristics the optimized condition of the film processing was identified to be spin coated at 3000 rpm. Subsequently, the nanoindentation technique was utilized to measure hardness and Young's modulus of the optimized film. The measured nanomechanical properties were found to be superior to those reported for sputtered vanadium oxide films. Finally, temperature dependent phase transition characteristics of optimized vanadium oxide films were studied by differential scanning calorimetry (DSC) technique. Reversible and repeatable phase transition was found to occur in the range of 44–48 °C which was significantly lower than the phase transition temperature (i.e., 68 °C) of bulk VO 2 . [ABSTRACT FROM AUTHOR]

Molybdenum doped vanadium oxide film on quartz and silicon substrates are grown by pulsed RF magnetron sputtering method. Surface morphology, phase analysis and oxide states are investigated by field emission scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy techniques, respectively. Crystalline nature of the film deposited on both quartz and silicon are depicted. The transmittance and reflectance spectra recorded for the entire solar region. Further, optical constants viz. optical band gap and refractive index of the deposited films are estimated. Wavelength dependent low reflectance characteristic is observed for the deposited film on silicon. IR emittance (εIR) and sheet resistance (Rs) of the film are also evaluated. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This work reports the loading rate effect on nanohardness of sapphire. The intrinsic nanoscale contact deformation resistance of sapphire increased with the loading rates following empirical power law dependence with a positive exponent. The results showed a significant enhancement (e.g., ~66%) of the nanohardness of sapphire with the increase in loading rates from 10 to 10,000 μN s −1 . These results were explained mainly in terms of the maximum shear stress generated underneath the nanoindenter, dislocation density and critical resolved shear stress of the sapphire. [ABSTRACT FROM AUTHOR]

Vanadium oxide thin films on silicon (Si) substrate are grown by pulsed radio frequency (RF) magnetron sputtering technique at RF power in the range of 100–700 W at room temperature. Deposited thin films are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques to investigate microstructural, phase, electronic structure and oxide state characteristics. The reflectance and transmittance spectra of the films and the Si substrate are recorded at the solar region (200–2300 nm) of the spectral window. Substantial reduction in reflectance and increase in transmittance is observed for the films grown beyond 200 W. Further, optical constants viz. absorption coefficient, refractive index and extinction coefficient of the deposited vanadium oxide films are evaluated. [ABSTRACT FROM AUTHOR]

Sunshield membranes made of germanium‐coated black polyimide (GBP) or Kapton are often used on the reflector/transmitter antenna of satellites for thermal control applications. However, the germanium top layer is prone to degrade during ground storage and implementation. Hence, vacuum/inert gas‐sealed packaging is required for storing the membranes, followed by a staggered fabrication schedule as the shelf‐life of the GBP is identified as only ~6 months. In the present study, microstructural, thermo‐optical, and electrical properties along with X‐ray photoelectron spectroscopy (XPS) studies for evaluating oxidation states of the as‐received and degraded GBP films have been investigated thoroughly. The radio frequency (RF) loss behavior of both the films has also been studied for S band (2.5–3.5 GHz), Ku band (10.5–14.5 GHz), and Ka band (30–35 GHz). Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Here, we present the results of nanoindentation experiments conducted at ultralow peak loads of, for example, 1000, 5000, and 10,000 μN on a dense (~99.5%), coarse grain (~10 μm) alumina ceramic. The results showed that the nanohardness values of alumina were sensitive to the applied loads as well as to the locations of measurements, for example, the center of the grain, away from the center of the grain and at the vicinity of the grain boundary. The location sensitivity of nanohardness was linked to compositional variations of the different locations and to the presence of an amorphous phase. [ABSTRACT FROM AUTHOR]

We apply simple analyses techniques developed for the study of complex networks to the study of the cosmic web, the large-scale galaxy distribution. In this paper, we measure three network centralities (ranks of topological importance): degree centrality (DC), closeness centrality (CL), and betweenness centrality (BC) from a network built from the Cosmological Evolution Survey (COSMOS) catalogue. We define eight galaxy populations according to the centrality measures: void, wall, and cluster by DC; main branch and dangling leaf by BC; and kernel, backbone, and fracture by CL. We also define three populations by Voronoi tessellation density to compare these with the DC selection. We apply the topological selections to galaxies in the (photometric) redshift range 0.91 < z < 0.94 from the COSMOS survey, and explore whether the red and blue galaxy populations show differences in colour, star formation rate, and stellar mass in the different topological regions. Despite the limitations and uncertainties associated with using photometric redshift and indirect measurements of galactic parameters, the preliminary results illustrate the potential of network analysis. Future surveys will provide better statistical samples to test and improve this 'network cosmology'. [ABSTRACT FROM AUTHOR]

Modern spectroscopic surveys produce large spectroscopic databases, generally with sizes well beyond the scope of manual investigation. The need arises, therefore, for an automated line detection method with objective indicators for detection significance. In this paper, we present an automated and objective method for emission line detection in spectroscopic surveys and apply this technique to observed spectra from a Lya emitter survey at z ~ 2.7, obtained with the Hectospec spectrograph on the MMT Observatory (MMTO). The basic idea is to generate on-source (signal plus noise) and off-source (noise only) mock observations using Monte Carlo simulations, and calculate completeness and reliability values, (C,R), for each simulated signal. By comparing the detections from real data with the Monte Carlo results, we assign the completeness and reliability values to each real detection. From 1574 spectra, we obtain 881 raw detections and, by removing low reliability detections, we finalize 652 detections from an automated pipeline. Most of high completeness and reliability detections, (C,R)≈(1.0,1.0), are robust detections when visually inspected, the low C and R detections are also marginal on visual inspection. This method of detecting faint sources is dependent on the accuracy of the sky subtraction. [ABSTRACT FROM AUTHOR]

We analyze several thousand archival images from the NOAO Science Archive obtained over a five year period (2006-2011) using the MOSAIC cameras on the Kitt Peak National Observatory 4 m Mayall and Cerro Tololo Inter-American Observatory 4 m Blanco telescopes in order to investigate the delivered image quality (DIQ). We fit the resulting point spread functions with Moffat functions and find that the profiles can be approximated by Moffat profiles with ß 3:5. We analyze the DIQ distributions and investigate their dependence on various observational, environmental, and temporal variables. We find that the DIQ of the MOSAIC cameras is similar at both sites. The Mayall data show no significant variation of DIQ with wavelength, but the Blanco data show a gradual rise of DIQ toward shorter wavelengths. The DIQ shows little variation with elevation for zenith distance <50° (airmass 1:6). The modal value of the DIQ distribution is larger for longer exposure time images, suggesting that improvements in the guiding, tracking, mirror support, and/or focus control may improve the DIQ. The DIQ also degrades when the mirror temperature deviates from the ambient temperature by more than 1°. Better thermal control of the mirror and focus will likely improve the DIQ. [ABSTRACT FROM AUTHOR]

Abstract: The evaluation of residual stress in bioactive hydroxyapatite (HAP) ceramic coating by nanoindentation technique has been attempted successfully for the very first time ever in the present work. The HAP coatings were deposited on surgical grade 316L austenitic stainless steel and Ti–6Al–4V substrates by microplasma spraying (MIPS) process. The coatings had Ca/P ratio of 1.67 and were ∼80–90% crystalline. The results showed a residual compressive stress of ∼22MPa for the MIPS-HAP coatings on the SS316L substrates. For the coatings deposited on the Ti–6Al–4V substrates, however, a residual tensile stress of ∼11MPa was estimated. These data matched well with those obtained by XRD based technique. Thus, favorable data comparison provides further support to the efficacy of the nanoindentation based technique utilized in the present work for residual stress estimations. [Copyright &y& Elsevier]

Highlights: [•] Three point bending test on SOFC single cell in pre- and post-reduced conditions. [•] Fractrography showed no signature of delamination in the SOFC layers. [•] In-depth nanoindentation study on SOFC single cell in pre- and post-reduced conditions. [•] Scatter of the nanoindentation data analyzed by well established Weibull statistics. [ABSTRACT FROM AUTHOR]

Hydroxyapatite coating was developed with high degree of crystallinity on SS316L substrate by the microplasma spraying technique. Systematic in vitro study of the coating was conducted after the immersion into the simulated body fluid for 1-14 days. Inductively coupled plasma-atomic emission spectroscopy, X-ray diffraction, Fourier transformed infrared spectroscopy, and scanning electron microscopy were utilized for physicochemical and microstructural characterizations. Nanoindentation technique employed to evaluate the nanohardness and Young's modulus of the coating at a constant load of 100 mN. Further, the tribological characteristic was also examined by microscratch testing at a ramping normal load of 10-10.6 N. [ABSTRACT FROM AUTHOR]

We present Keck DEIMOS spectroscopic observations of the most UV-luminous star-forming galaxies at redshifts 3.2 < z < 4.6. Our sample, selected in the Boötes field of the NOAO Deep Wide-Field Survey, contains galaxies with luminosities of L" ≲ LUV ≲ 7L " and is one of the largest samples to date of the most UV-luminous galaxies at these redshifts. Our spectroscopic data confirm 41 candidates as star-forming galaxies at 3.2 < z < 4.6 and validate the relatively clean selection of the photometric candidates with a contamination rate of 11%-28%. We find that the fraction of Lyα emitting galaxies increases with decreasing UV luminosity. None of the 12 galaxies with MUV < -22 (i.e., LUV > 3L") exhibit strong Lyα emission. We find strong evidence of large-scale outflows, transporting the neutral/ionized gas in the interstellar medium away from the galaxy. Galaxies exhibiting both interstellar absorption and Lyα emission lines show a significant offset between the two features, with a relative velocity of 200-1150 km s-1. We find tentative evidence that this measure of the outflow velocity increases with UV luminosity and/or stellar mass. The luminosity- and mass-dependent outflow strengths suggest that the efficiency of feedback and enrichment of the surrounding medium depend on these galaxy parameters. We also stack the individual spectra to construct composite spectra of the absorption-line-only and Lyα-emitting subsets of the UV luminous galaxies at z ≃ 3.7. The composite spectra are very similar to those of lower-redshift and lower-luminosity Lyman break galaxy (LBG) samples, but with some subtle differences. Analyses of the composite spectra suggest that the UV luminous LBGs at z ≃ 3.7 may have a higher covering fraction of absorbing gas, and may be older (or have had more prolonged star formation histories) than their lower-redshift and lower-luminosity counterparts. In addition, we have discovered that five galaxies in the sample belong to a massive overdensity at z = 3.78. Finally, two galaxies each show two distinct sets of interstellar absorption features. The latter may be a sign of a final stage of major merger, or clumpy disk formation. These systems are not expected in our sample: their presence implies that the frequency of such sources among our luminous z ≃ 3.7 LBGs may be an order of magnitude higher than in lower-redshift and lower-luminosity samples. [ABSTRACT FROM AUTHOR]

Abstract: Microstructural, corrosion and nanomechanical behaviour of micro arc oxidised (MAO) coating grown on magnesium AZ31B alloy was evaluated. Microstructural characterization of the coating was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) followed by image analysis and energy dispersive spectroscopy (EDX). Linear polarization technique was used to evaluate the corrosion behaviour of the MAO coating. Further, nanoindentation was employed to evaluate nanohardness and Young’s modulus of the MAO coating. The characteristic values of both the nanohardness and the Young’s modulus were calculated through the application of the Weibull statistics. [Copyright &y& Elsevier]

Abstract: In spite of the wealth of literature, the role of the scratching speed in affecting the material removal mechanism in soda lime silica (SLS) glass is yet to be comprehensively understood. Here we report the surface and sub‐surface deformation mechanisms of SLS glass scratched under three different normal loads of 5, 10 and 15N at various speeds in the range of 100–1000μm/s with a diamond indenter of ~200μm tip radius. The results show that at any given applied normal load, the width, depth, wear volume of the scratch grooves and wear rate of the SLS glass decreased with an inverse power law dependence on the applied scratching speed. The surface damage also reduced with the increase in scratching speed. A new, simple model was developed to explain these observations. The significant contributions of the time of contact, the tensile stress behind the indenter and the shear stress active just underneath the indenter in governing the material removal mechanisms of the SLS glass were discussed. [Copyright &y& Elsevier]

Abstract: The motivation behind this study was the urge to understand how the high strain rate flyer plate impact affects the nanohardness of alumina ceramics. Therefore, the load controlled nanoindentation experiments were conducted with a Berkovich indenter on an as received coarse grain (~10μm), high density (~3.98g.cm3) alumina and the shock recovered tiny fragments of the same alumina. The shocked alumina fragments were obtained from an earlier flyer plate shock impact study in a two stage gas gun. The nanohardness of the as received alumina was much higher than that of the shocked alumina. The shocked alumina showed a relatively much stronger indentation size effect (ISE) while the as received alumina exhibited a mild ISE. A new explanation was given for the presence of the relatively strong ISE in the shock recovered alumina. Additional characterizations such as scanning electron microscopy, field emission scanning electron microscopy, transmission electron microscopy and analysis of the experimental load depth data were utilized for this purpose. Finally, a new, qualitative model was proposed to provide a rational picture of the nanoindentation responses of the as received and shocked alumina ceramics. [Copyright &y& Elsevier]

Understanding the mechanical response and failure of consolidated extra-terrestrial soils requires analyses of the interactions between propagating cracks and the material's inherent pore structure. In this work, we investigate the fracture behaviour of lunar soil simulant consolidated using microbially induced calcite precipitation (MICP). We develop a numerical lattice network model using local beam elements to simulate the nucleation, propagation, branching, and merging of multiple cracks within a space brick subject to uniaxial compression. Our simulations capture the effects of local pores on crack paths as well as provide a means to predict the behaviour of samples with varying global porosity and/or uncertainties in local material stiffness. We identify multiple statistical lattice parameters that encode signatures of single or multiple crack growth events. Our results reveal the complexities involved in the fracture process with porous brittle solids and may easily be adapted to understand failure mechanisms and micro/macro crack evolution in other consolidated structures. [ABSTRACT FROM AUTHOR]

Advanced applications of glass span the range from biomedical technology to special optical lenses to mobile phones and computers. Such advanced applications demand high-precision machining, which is like multiple single scratches occurring simultaneously on the glass surface. However, in spite of the wealth of literature on scratch deformation behavior of glass there is no significant information available on whether the nanomechanical properties are affected inside the scratch grooves. Therefore, nanoindentation experiments were deliberately conducted at a fixed load of 100 mN through the scratch grooves made at various applied normal loads (5-15 N) at a constant speed of 200 μm s on polished soda-lime-silica (SLS) glass slides. The results showed that depending upon the applied normal load used to generate the scratch grooves, the nanohardness and Young's modulus inside the scratch grooves decreased by about ∼30-60% from the corresponding data of the undamaged SLS glass due to the presence of sub-surface shear deformation and microcracking as observed by optical, scanning and field emission scanning electron microscopy. A model for microcracked brittle solids was utilized to explain these results. [ABSTRACT FROM AUTHOR]

The grinding and polishing of a fundamentally brittle material like glass to an utmost precision level for ultra-sophisticated applications ranging from mobile devices to aerospace as well as space shuttle components to biomedical appliances pose a big challenge today. Looking simplistically, the grinding and polishing processes are basically material removal by multiple scratching at a given speed. Unfortunately however, the role of the scratching speed in affecting the material removal mechanism in soda-lime-silica (SLS) glass is yet to be comprehensively understood. Therefore, the present work explores the surface and subsurface deformation mechanisms of SLS glass scratched under a normal load of 5 N at various speeds in the range of 100-1000 μm s with a diamond indenter of ∼200 μm tip radius. The results show important roles of the time of contact, the tensile stress behind the indenter and the shear stress just beneath the indenter in governing the material removal mechanisms of the SLS glass. [ABSTRACT FROM AUTHOR]

Many advanced applications of glass demand fabrication of engineering parts of utmost dimensional precision which require very accurate grinding and polishing that involves controlled removal of glass. Despite the wealth of literature, however; the mechanism of material removal in glass grinding and polishing is still far from well understood. For instance, it is not known at all to what extent the mechanical properties are compromised inside a scratch groove so as to optimize the machining parameters. Therefore, to develop better understanding about the mechanism of material removal, a series of combined nanoindentation and single pass scratch experiments were conducted on a commercially available soda-lime-silica glass as a function of various normal loads (2-20 N) and scratch speeds (0.1-1 mm/s). It was found that the nanohardness and Young's modulus at the local microstructural length scale inside the scratch groove could decrease quite dramatically (~30% to 70%) depending on the combination of load and scratching speed. Further, the tribological properties, the severity and the spatial density of damage evolution were sensitive to the normal loads, scratching speeds, and tensile stresses. Extensive scanning electron microscopy leads to interesting observations on material removal mechanisms. These observations were explained by the theoretical predictions of a model for a brittle, microcracked solid. [ABSTRACT FROM AUTHOR]

Abstract: Today the technological applications of glass span from everyday life to many advanced areas. These advanced applications require very accurate grinding and polishing that involve controlled removal of glass to achieve micron or even sub-micron surface finish. The major bottleneck in this connection is that the material removal mechanisms during such processes are yet to be fully understood. Since grinding involves many single pass scratch processes happening simultaneously, to develop better understanding about the effect of the normal load in affecting the material removal mechanisms; a number of single pass scratch experiments were conducted on a commercially available soda lime silica glass as a function of various normal loads (2–15N) at a constant scratch speed of 100μm.s−1. The results showed that the tribological properties, the severity and the spatial density of damage evolution were sensitive to the applied normal loads and the resultant tensile as well as shear stresses. Extensive optical and scanning electron photomicrography of the surface and sub-surface deformation zones proved the existence of three distinct deformation zones in the immediate vicinity of the scratch grooves and led to the development of a qualitative model of the material removal mechanisms. [Copyright &y& Elsevier]

Giant Lyα nebulae (or Lyα "blobs") are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Lyα nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Lyα nebulae at 2 ... ȥ ... 3 within deep broadband imaging and have carried out a survey of the 9.4 deg² NOAO Deep Wide-Field Survey Boötes field. With a total survey comoving volume of ≈ 108 h70-3 Mpc³, this is the largest volume survey for Lyα nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Lyα nebula. [ABSTRACT FROM AUTHOR]

Abstract: Bismuth ferrite (BiFeO3) is a unique magnetoelectric multiferroic that exhibits the coexistence of ferroelectricity and antiferromagnetism at room temperature. This unique combination of properties has pumped a huge surge in current research on BiFeO3 as a future material for very important technological applications such as magnetic detectors and as an active layer in magnetoelectric memories. For such applications involving miniaturized components and devices, it is essentially important to have an idea of the mechanical integrity of the system at the scale of the microstructure. In spite of the wealth of the literature, however, the attempt to evaluate the mechanical integrity of nano BiFeO3 at a scale comparable with the local microstructural length scale was almost non-existent. Here we report, possibly for the first time the nanoindentation behaviour of a sol–gel process derived nano BiFeO3 having particle size of 5–25nm. The nanoindentation studies were conducted at 100–1000μN loads on a green pellet annealed at a low temperature of only 300°C to avoid particle coarsening. The results showed interesting dependence of nanohardness and Young''s modulus on the nanoindentation load which could be explained in terms of elastic recovery and plastic deformation energy concepts. [Copyright &y& Elsevier]

The Spitzer Space Telescope has identified a population of ultraluminous infrared galaxies (ULIRGs) at z ~ 2 that may play an important role in the evolution of massive galaxies. We measure the stellar masses (M∗) of two populations of Spitzer-selected ULIRGs that have extremely red R - [24] colors (dust-obscured galaxies, or DOGs) and compare our results with submillimeter-selected galaxies (SMGs). One set of 39 DOGs has a local maximum in their mid-infrared (mid-IR) spectral energy distribution (SED) at rest frame 1.6 µm associated with stellar emission ("bump DOGs"), while the other set of 51 DOGs have power-law mid-IR SEDs that are typical of obscured active galactic nuclei ("power-law DOGs"). We measure M∗ by applying Charlot & Bruzual stellar population synthesis models to broadband photometry in the rest-frame ultraviolet, optical, and near-infrared of each of these populations. Assuming a simple stellar population and a Chabrier initial mass function, we find that power-law DOGs and bump DOGs are on average a factor of 2 and 1.5 more massive than SMGs, respectively (median and inter-quartile M∗ values for SMGs, bump DOGs, and power-law DOGs are log(M∗/M⊙) = Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed., and Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. respectively). More realistic star formation histories drawn from two competing theories for the nature of ULIRGs at z ~ 2 (major merger versus smooth accretion) can increase these mass estimates by up to 0.5 dex. A comparison of our stellar masses with the instantaneous star formation rate (SFR) in these z ~ 2 ULIRGs provides a preliminary indication supporting high SFRs for a given M∗, a situation that arises more naturally in major mergers than in smooth accretion-powered systems. [ABSTRACT FROM AUTHOR]

Abstract: For a thin commercial soda–lime–silica glass cover slip a significant increase in nanohardness (e.g. up to 74%) occurred with variations in the loading rate (10–20,000μN·s−1) along with presence of serrations in load–depth plots and deformation band formation inside the nanoindentation cavity. These results are explained in terms of shear stress acting at positions of structural weakness close to the tip of the nanoindenter and the time scale of interaction between the nanoindenter and the local microstructure of the glass. [Copyright &y& Elsevier]

We investigate the average physical properties and star formation histories (SFHs) of the most UV-luminous star- forming galaxies at z ~ 3.7. Our results are based on the average spectral energy distributions (SEDs), constructed from stacked optical-to-infrared photometry, of a sample of the 1913 most UV-luminous star-forming galaxies found in 5.3 deg2 of the NOAO Deep Wide-Field Survey. We find that the shape of the average SED in the rest optical and infrared is fairly constant with UV luminosity, i.e., more UV-luminous galaxies are, on average, also more luminous at longer wavelengths. In the rest UV, however, the spectral slope β (≅dlogFλ/dlogλ; measured at 0.13 μm <λrest < 0.28μm) rises steeply with the median UV luminosity from -1.8 at L ≈ L* to -1.2 (L ~ 4-5L*). We use population synthesis analyses to derive their average physical properties and find that (I) LUV and thus star formation rates (SFRs) scale closely with stellar mass such that more UV-luminous galaxies are also more massive, (2) the median ages indicate that the stellar populations are relatively young (200-400 Myr) and show little correlation with UV luminosity, and (3) more UV-luminous galaxies are dustier than their less- luminous counterparts, such that L ≈ 4-5L* galaxies are extincted up to A(1600) = 2 mag while L ≈ L* galaxies have A(1600) = 0.7-1.5 mag. We argue that the average SFHs of UV-luminous galaxies are better described by models in which SFR increases with time in order to simultaneously reproduce the tight correlation between the UV-derived SFR and stellar mass and their universally young ages. We demonstrate the potential of measurements of the SFR-M* relation at multiple redshifts to discriminate between simple models of SFHs. Finally, we discuss the fate of these UV-brightest galaxies in the next 1-2 Gyr and their possible connection to the most massive galaxies at z ~ 2. [ABSTRACT FROM AUTHOR]

Structural and mechanical reliability of glass for both conventional and advanced applications is determined by the rate at which it can deform and sustain externally applied static or dynamic strain at the microstructural length scale. Hence, a large number of nanoindentation experiments were conducted on a thin (∼300 μm) commercial soda lime-silica glass with a 150 nm radius Berkovich tip at a constant load of 10,000 μN as a function of variations in the loading rates in the range of 10-20,000 μN/s. The results showed that the nanohardness of the soda lime-silica glass increased by as much as 74% as the loading rate was increased from 10 to 20,000 μN/s. Further, the presence of serrations in load-depth plots and deformation band formations inside the nanoindentaion cavities were more vividly observed in the nanoindentation experiments conducted at lower loading rates rather than those conducted at higher loading rates. These results are explained in terms of shear stress acting underneath the indenter as well as the time scale of interaction between the nanoindenter and the weak links at local microstructural length scale, which owe their origin to the subtle variations in the composition of the given glass. [ABSTRACT FROM AUTHOR]

Abstract: Here we report a comparative study of the healing kinetics of surgically created artificial defects in the tibia of New Zealand white rabbits. Comparison of the healing kinetics was made for uncoated conventional SS316L intramedullary pins, and the same pins with microplasma sprayed (MIPS) pure hydroxyapatite (HAp) and beta-tri calcium phosphate (β-TCP) coatings. After thorough material characterizations including XRD, FTIR, SEM, etc., MIPS coated pins were implanted to such animals. Serum biochemistry, radiology and fluorochrome labelling were used to evaluate the comparative healing kinetics of these implants in vivo. In comparison to those of the uncoated pins, the pins coated with both MIPS HAp and β-TCP showed significant increment of alkaline phosphatase up to 15th postoperative day, insignificant changes in serum phosphorus and calcium with uneventful healing of bone defect. There was development of Havarsian canals and well-defined peripherally placed osteoblasts along with evidence of angiogenesis and comparatively more new bone formation in the defect site. On a comparative scale, the performance of the β-TCP coated intramedullary pins was much better than that of the pure HAp coated pins than the uncoated intramedullary pins. [Copyright &y& Elsevier]

We report the fracture toughness ( K) measured by nanoindentation technique at five different loads in the range of 100-1000 mN on the cross section of a highly porous microplasma-sprayed hydroxyapatite (MIPS-HAP) coating. The unique advantage of this technique was that it could evaluate K at a scale comparable with that of the local microstructure of the coating. In spite of high porosity (∼11 vol%), the coating showed a toughness (∼0.6 MPa m) comparable to typical literature data (∼0.5 MPa m) on dense HAP coating. Scanning electron microscopy of nanoindents suggested some plausible reasons for achieving a relatively higher toughness in the coating. [ABSTRACT FROM AUTHOR]

2D carbon fiber (C-fiber)-reinforced carbon/carbon (C/C) composites were prepared by vacuum infiltration with coal-tar pitch followed by carbonization and graphitization in inert atmosphere. Liquid silicon infiltration was done in controlled atmosphere at 1600°C to convert the matrix carbon of the C/C composites into silicon carbide. The 2D C/C and carbon/carbon-silicon carbide (C/C-SiC) composites had density of ∼1.65 and ∼2.32 g/cm, respectively with corresponding flexural strength of ∼70 and ∼169 MPa, respectively. The local mechanical properties like hardness, Young's modulus, contact pressure, relative stiffness, relative spring back, and indentation energies of the two composites under different loading conditions were measured at an ultra low load of 10 mN using a nanoindentation instrument with a Berkovich indenter. The scatter in the data was treated in terms of the two-parameter Weibull statistical analysis. The maximum characteristic Young's modulus (∼16 GPa) and hardness (1.20 GPa) was obtained for the C/C-SiC composites in parallel direction of fabric stacking. The elastic rebounce was also the maximum (0.77) for the C/C-SiC composites when loaded in parallel direction of fabric stacking. The extent of structural anisotropy was higher in the C/C-SiC composite than that of the C/C composite. [ABSTRACT FROM AUTHOR]

We present a physical model for the origin of dust-obscured galaxies (DOGs), a class of high-redshift ultraluminous infrared galaxies (ULIRGs) selected at 24 μm which are particularly optically faint . By combining N-body/smoothed particle hydrodynamic simulations of high-redshift galaxy evolution with 3D polychromatic dust radiative transfer models, we find that luminous DOGs (with mJy at ) are well modelled as extreme gas-rich mergers in massive haloes, with elevated star formation rates (SFR; ) and/or significant active galactic nuclei (AGN) growth , whereas less luminous DOGs are more diverse in nature. At final coalescence, merger-driven DOGs transition from being starburst dominated to AGN dominated, evolving from a ‘bump’ to a power-law (PL) shaped mid-IR (Infrared Array Camera, IRAC) spectral energy distribution (SED). After the DOG phase, the galaxy settles back to exhibiting a ‘bump’ SED with bluer colours and lower SFRs. While canonically PL galaxies are associated with being AGN dominated, we find that the PL mid-IR SED can owe both to direct AGN contribution and to a heavily dust obscured stellar bump at times that the galaxy is starburst dominated. Thus, PL galaxies can be either starburst or AGN dominated. Less luminous DOGs can be well-represented either by mergers or by massive secularly evolving gas-rich disc galaxies (with ). By utilizing similar models as those employed in the submillimetre galaxy (SMG) formation study of Narayanan et al., we investigate the connection between DOGs and SMGs. We find that the most heavily star-forming merger-driven DOGs can be selected as submillimetre galaxies, while both merger-driven and secularly evolving DOGs typically satisfy the BzK selection criteria. The model SEDs from the simulated galaxies match observed data reasonably well, though Mrk 231 and Arp 220 templates provide worse matches. Our models provide testable predictions of the physical masses, dust temperatures, CO linewidths and location on the relation of DOGs. Finally, we provide public SED templates derived from these simulations. [ABSTRACT FROM AUTHOR]

Microplasma sprayed (MIPS) HAP coatings on SS316L substrates were characterized by x-ray diffraction, Fourier transformed infrared spectroscopy, optical microscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy and image analysis. The coating showed a high degree of crystallinity ~92%, a high porosity level of 20 vol.% and a moderate bonding strength of about 13 MPa. The displacement controlled three-point bend tests and associated results of optical microscopy indicated that crack deflection, crack branching, and also local crack bridging occurred during crack propagation in the coating. The nano-hardness ( H) and Young’s modulus ( E) of the MIPS-HAP coatings as measured by nanoindentation technique were about 6 and 92 GPa, respectively. The fracture toughness ( Kic) of the coating was ~0.6 MPa·m0.5. From the nano-scratch experiments, the critical normal load at which localized microcracking led to delamination was measured to be ~400 mN. [ABSTRACT FROM AUTHOR]

Here we report the microstructural dependence of nano-hardness ( H) and elastic modulus ( E) of microplasma sprayed (MIPS) 230 μm thick highly porous, heterogeneous hydroxyapatite (HAP) coating on SS316L. The nano-hardness and Young’s modulus data were measured on polished plan section (PS) of the coating by the nanoindentation technique with a Berkovich indenter. The characteristic values of nano-hardness and Young’s modulus were calculated through the application of Weibull statistics. Both nano-hardness and the Young’s modulus data showed an apparent indentation size effect. In addition, there was an increasing trend of Weibull moduli values for both the nano-hardness and the Young’s modulus data of the MIPS-HAP coating as the indentation load was enhanced from 10 to 1,000 mN. An attempt was made in the present work, to provide a qualitative model that can explain such behavior. [ABSTRACT FROM AUTHOR]

There is an overwhelming evidence that white dwarfs host planetary systems; revealed by the presence, disruption, and accretion of planetary bodies. A lower limit on the frequency of white dwarfs that host planetary material has been estimated to be ≃ 25–50 per cent; inferred from the ongoing or recent accretion of metals on to both hydrogen-atmosphere and warm helium-atmosphere white dwarfs. Now with the unbiased sample of white dwarfs observed by the Dark Energy Spectroscopic Instrument (DESI) survey in their Early Data Release (EDR), we have determined the frequency of metal enrichment around cool-helium atmosphere white dwarfs as 21 ± 3 per cent using a sample of 234 systems. This value is in good agreement with values determined from previous studies. With the current samples we cannot distinguish whether the frequency of planetary accretion varies with system age or host-star mass, but the DESI data release 1 will contain roughly an order of magnitude more white dwarfs than DESI EDR and will allow these parameters to be investigated. [ABSTRACT FROM AUTHOR]

Background: Gastric pneumatosis is a rare condition characterized by the presence of intramural gas in the stomach wall. It is uncommon in infants and is usually caused by proximal intestinal obstruction or necrotizing enterocolitis, a serious condition typically seen in preterm babies. Case Presentation: An extremely preterm baby born at 23 weeks of gestation weighing 640 grams, with bronchopulmonary dysplasia and other comorbidities like patent ductus arteriosus, staph aureus sepsis, developed abdominal distension and non-bilious vomiting at 4 months of age. X-ray abdomen revealed gastric pneumatosis. The condition was managed with conservative measures. Conclusion: Gastric pneumatosis secondary to necrotizing enterocolitis is uncommon in infants and needs prompt evaluation and management to prevent further deterioration. [ABSTRACT FROM AUTHOR]

We demonstrate that Microbial Induced Calcite Precipitation (MICP) can be utilized for creation of consolidates of Martian Simulant Soil (MSS) and Lunar Simulant Soil (LSS) in the form of a 'brick'. A urease producer bacterium, Sporosarcina pasteurii, was used to induce the MICP process for the both simulant soils. An admixture of guar gum as an organic polymer and NiCl2, as bio- catalyst to enhance urease activity, was introduced to increase the compressive strength of the biologically grown bricks. A casting method was utilized for a slurry consisting of the appropriate simulant soil and microbe; the slurry over a few days consolidated in the form of a 'brick' of the desired shape. In case of MSS, maximum strength of 3.3 MPa was obtained with 10mM NiCl2 and 1% guar gum supplementation whereas in case of LSS maximum strength of 5.65 Mpa was obtained with 1% guar gum supplementation and 10mM NiCl2. MICP mediated consolidation of the simulant soil was confirmed with field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and thermogravimetry (TG). Our work demonstrates a biological approach with an explicit casting method towards manufacturing of consolidated structures using extra-terrestrial regolith simulant; this is a promising route for in situ development of structural elements on the extra-terrestrial habitats. [ABSTRACT FROM AUTHOR]