Critical aspects of sinter-hardening of prealloyed Cr–Mo steel

In recent years, growing demand for greater mechanical properties of PM steel components with competitive fabrication cost has led to significant innovations in different fields of powder metallurgy. Recent research has been focused on reaching higher performance with lower cost. To this end, the possibility of combining the conventional sintering and post-sintering processes for a particular powder composition has been introduced. Sinter-hardening is a result of the research conducted along this line. Elimination of any secondary operation such as quench-hardening by incorporating it in the sintering process (i.e. sinter-hardening) is of great interest, as it will lead to lower processing costs and equal, if not higher mechanical performance. However, to ensure the desired mechanical properties of the final component and robustness of the performance, critical aspects of the sinter-hardening process should be rigorously studied.Hence with specific attention to a Cr–Mo steel powder (FL-5305), this study deals with the influence of density on cooling rate, the effect of different sintering temperatures (e.g. 1120 °C and 1250 °C) on austenite grain size and consequently, hardenability. The microstructure development in sinter-hardened FL-5305 material has been analyzed and predicted by means of the available literature for solid steel and also using the commercial software (JMatPro 5.0) for materials assessment based on thermodynamic and kinetics modeling. Finally, inaccurate carbon control and its adverse impact on excessive formation of cementite have been addressed.     

Two-dimensional linear-combination model fitting of magnetic resonance spectra to define the macromolecule baseline using FiTAID,a Fitting Tool for Arrays of Interrelated Datasets

Object  

To propose the determination of the macromolecular baseline (MMBL) in clinical 1H MR spectra based on T₁ and T₂ differentiation using 2D fitting in FiTAID, a general Fitting Tool for Arrays of Interrelated Datasets.     

Solution‐Processed GaSe Nanoflake‐Based Films for Photoelectrochemical Water Splitting and Photoelectrochemical‐Type Photodetectors

Gallium selenide (GaSe) is a layered compound, which has been exploited in nonlinear optical applications and photodetectors due to its anisotropic structure and pseudodirect optical gap. Theoretical studies predict that its 2D form is a potential photocatalyst for water splitting reactions. Herein, the photoelectrochemical (PEC) characterization of GaSe nanoflakes (single‐/few‐layer flakes), produced via liquid phase exfoliation, for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both acidic and alkaline media is reported. In 0.5 m H₂SO₄, the GaSe photoelectrodes display the best PEC performance, corresponding to a ratiometric power‐saved metric for HER (Φ_saved,HER) of 0.09% and a ratiometric power‐saved metric for OER (Φ_saved,OER) of 0.25%. When used as PEC‐type photodetectors, GaSe photoelectrodes show a responsivity of ≈0.16 A W^?1 upon 455 nm illumination at a light intensity of 63.5 µW cm^?2 and applied potential of ?0.3 V versus reversible hydrogen electrode (RHE). Stability tests of GaSe photodetectors demonstrated a durable operation over tens of cathodic linear sweep voltammetry scans in 0.5 m H₂SO₄ for HER. In contrast, degradation of photoelectrodes occurred in both alkaline and anodic operation due to the highly oxidizing environment and O₂‐induced (photo)oxidation effects. The results provide new insight into the PEC properties of GaSe nanoflakes for their exploitation in photoelectrocatalysis, PEC‐type photodetectors, and (bio)sensors.     

Chemical natures and distributions of metal impurities in multicrystalline silicon materials

We present a comprehensive summary of our observations of metal‐rich particles in multicrystalline silicon (mc‐Si) solar cell materials from multiple vendors, including directionally‐solidified ingot‐grown, sheet, and ribbon, as well as multicrystalline float zone materials contaminated during growth. In each material, the elemental nature, chemical states, and distributions of metal‐rich particles are assessed by synchrotron‐based analytical x‐ray microprobe techniques. Certain universal physical principles appear to govern the behavior of metals in nearly all materials: (a) Two types of metal‐rich particles can be observed (metal silicide nanoprecipitates and metal‐rich inclusions up to tens of microns in size, frequently oxidized), (b) spatial distributions of individual elements strongly depend on their solubility and diffusivity, and (c) strong interactions exist between metals and certain types of structural defects. Differences in the distribution and elemental nature of metal contamination between different mc‐Si materials can largely be explained by variations in crystal growth parameters, structural defect types, and contamination sources. Copyright © 2006 John Wiley & Sons, Ltd.     

Automatic quantification of changes in bone in serial MR images of joints

Recent innovations in drug therapies have made it highly desirable to obtain sensitive biomarkers of disease progression that can be used to quantify the performance of candidate disease modifying drugs. In order to measure potential image-based biomarkers of disease progression in an experimental model of rheumatoid arthritis (RA), we present two different methods to automatically quantify changes in a bone in in-vivo serial magnetic resonance (MR) images from the model. Both methods are based on rigid and nonrigid image registration to perform the analysis. The first method uses segmentation propagation to delineate a bone from the serial MR images giving a global measure of temporal changes in bone volume. The second method uses rigid body registration to determine intensity change within a bone, and then maps these into a reference coordinate system using nonrigid registration. This gives a local measure of temporal changes in bone lesion volume. We detected significant temporal changes in local bone lesion volume in five out of eight identified candidate bone lesion regions, and significant difference in local bone lesion volume between male and female subjects in three out of eight candidate bone lesion regions. But the global bone volume was found to be fluctuating over time. Finally, we compare our findings with histology of the subjects and the manual segmentation of bone lesions.     

B-spline explicit active surfaces: an efficient framework for real-time 3-D region-based segmentation

A new formulation of active contours based on explicit functions has been recently suggested. This novel framework allows real-time 3-D segmentation since it reduces the dimensionality of the segmentation problem. In this paper, we propose a B-spline formulation of this approach, which further improves the computational efficiency of the algorithm. We also show that this framework allows evolving the active contour using local region-based terms, thereby overcoming the limitations of the original method while preserving computational speed. The feasibility of real-time 3-D segmentation is demonstrated using simulated and medical data such as liver computer tomography and cardiac ultrasound images.     

Monomolecular and Bimolecular Recombination of Electron–Hole Pairs at the Interface of a Bilayer Organic Solar Cell

While it has been argued that field‐dependent geminate pair recombination (GR) is important, this process is often disregarded when analyzing the recombination kinetics in bulk heterojunction organic solar cells (OSCs). To differentiate between the contributions of GR and nongeminate recombination (NGR) the authors study bilayer OSCs using either a PCDTBT‐type polymer layer with a thickness from 14 to 66 nm or a 60 nm thick p‐DTS(FBTTh₂)₂ layer as donor material and C₆₀ as acceptor. The authors measure JV‐characteristics as a function of intensity and charge‐extraction‐by‐linearly‐increasing‐voltage‐type hole mobilities. The experiments have been complemented by Monte Carlo simulations. The authors find that fill factor (FF) decreases with increasing donor layer thickness (L_p) even at the lowest light intensities where geminate recombination dominates. The authors interpret this in terms of thickness dependent back diffusion of holes toward their siblings at the donor–acceptor interface that are already beyond the Langevin capture sphere rather than to charge accumulation at the donor–acceptor interface. This effect is absent in the p‐DTS(FBTTh₂)₂ diode in which the hole mobility is by two orders of magnitude higher. At higher light intensities, NGR occurs as evidenced by the evolution of s‐shape of the JV‐curves and the concomitant additional decrease of the FF with increasing layer thickness.     

Functionalized Graphene as Extracellular Matrix Mimics: Toward Well‐Defined 2D Nanomaterials for Multivalent Virus Interactions

Polysulfated nanomaterials that mimic the extracellular cell matrix are of great interest for their potential to modulate cellular responses and to bind and neutralize pathogens. However, control over the density of active functional groups on such biomimetics is essential for efficient interactions, and this remains a challenge. In this regard, producing polysulfated graphene derivatives with control over their functionality is an intriguing accomplishment in order to obtain highly effective 2D platforms for pathogen interactions. Here, a facile and efficient method for the controlled attachment of a heparin sulfate mimic on the surface of graphene is reported. Dichlorotriazine groups are conjugated to the surface of graphene by a one‐pot [2+1] nitrene cycloaddition reaction at ambient conditions, providing derivatives with defined functionality. Consecutive step by step conjugation of hyperbranched polyglycerol to the dichlorotriazine groups and eventual conversion to the polyglycerol sulfate result in the graphene based heparin biomimetics. Scanning force microscopy, cryo‐transmission electron microscopy, and in vitro bioassays reveal strong interactions between the functionalized graphene (thoroughly covered by a sulfated polymer) and vesicular stomatitis virus. Infection experiments with highly sulfated versions of graphene drastically promote the infection process, leading to higher viral titers compared to nonsulfated analogues.     

A 3–10 GHz Ultra Wideband Receiver LNA in 0.13 \mu m CMOS

A fully integrated low-power, low-complexity ultra wideband (UWB) 3–10 GHz receiver front-end in standard 130 nm CMOS technology is proposed for UWB radar sensing applications. The receiver front-end consists of a full UWB band low-noise amplifier and an on-chip diplexer. The on-chip diplexer has a 1 dB insertion loss and provides a \(-\) 30 dB isolation. The diplexer switch was co-designed with the receiver input matching network to optimize the power matching while simultaneously achieving good noise matching performance. The receiver low-noise amplifier provides a 3–10 GHz bandwidth input matching and a power gain of 17 dB. The overall receiver front-end consumes an average power of 13 mW. The core area of the transceiver circuit is 500 \(\mu \) m by 700 \(\mu \) m.