Optoelectronic properties comparison of 10 and 20 multi quantum wells Ga0.952In0.048N0.016As0.984/GaAs p-i-n photodetector for 1.0 µm wavelength

This study proves the addition of quantum wells to the intrinsic regions of p-i-n GaInNAs/GaAs has improved the performance of optoelectronic devices. The optoelectronic properties that contribute to the device's dark current and photocurrent need to be well understood to develop photo-response at longer wavelengths. This study reports an optoelectronic properties comparison of different quantum well number for Ga0.952In0.048N0.016As0.984/GaAs-based dilute nitride multi-quantum wells (MQWs) p-i-n photodetector devices. From photoluminescence (PL) analysis, 20 MQWs shows a higher PL peak than 10 MQWs. The maximum quantum efficiency (QE) is found to be 80.3% for 20 MQWs and 46% for 10 MQWs, where 20 MQWs being the highest QE value ever reported for GaInNAs-based MQWs photodetector. Current versus voltage (I–V) measurement shows that 20 MQWs produces lower dark current than 10 MQWs. Besides, 20 QWs sample produces a higher current density (−12.43 μAcm−2) than 10 MQWs (−7.52 μAcm−2) under illumination. Impedance spectroscopy analysis shows that a lower dark current of 20 MQWs is due to a high intrinsic resistivity and low dielectric loss peak compared to 10 MQWs. SimWindows simulation shows good correlation with responsivity analysis and impedance analysis where at −5 V, 20 MQWs produces higher responsivity (0.65AW-1) due to wider depletion region (deduce from conduction band profile) and lower intrinsic capacitance and dielectric loss (deduces from impedance analysis) than 10 MQWs (0.37AW-1). At room temperature, the detectivity (D*) of the 20 MQWs photodetector (7.12 × 1010 cmHz0.5W−1) is higher than 10 MQWS photodetector (4.89 × 1010 cmHz0.5W−1). Finally, the 20 MQWs's (4.02 × 10−11 WHz−0.5) has produces lower noise-equivalent power (NEP) than 10 MQWs (5.85 × 10−11 WHz−0.5). This study has successfully presenting an understanding of optoelectronic properties and simultaneously producing a sensitive photodetector with high quality, low-noise which is comparable with ∼1010 cmHz0.5W−1 of commercial III-V alloy based near-infrared GaAs-based photodetectors

Species Used for Drug Testing Reveal Different Inhibition Susceptibility for 17beta-Hydroxysteroid Dehydrogenase Type 1

Steroid-related cancers can be treated by inhibitors of steroid metabolism. In searching for new inhibitors of human 17beta-hydroxysteroid dehydrogenase type 1 (17β-HSD 1) for the treatment of breast cancer or endometriosis, novel substances based on 15-substituted estrone were validated. We checked the specificity for different 17β-HSD types and species. Compounds were tested for specificity in vitro not only towards recombinant human 17β-HSD types 1, 2, 4, 5 and 7 but also against 17β-HSD 1 of several other species including marmoset, pig, mouse, and rat. The latter are used in the processes of pharmacophore screening. We present the quantification of inhibitor preferences between human and animal models. Profound differences in the susceptibility to inhibition of steroid conversion among all 17β-HSDs analyzed were observed. Especially, the rodent 17β-HSDs 1 were significantly less sensitive to inhibition compared to the human ortholog, while the most similar inhibition pattern to the human 17β-HSD 1 was obtained with the marmoset enzyme. Molecular docking experiments predicted estrone as the most potent inhibitor. The best performing compound in enzymatic assays was also highly ranked by docking scoring for the human enzyme. However, species-specific prediction of inhibitor performance by molecular docking was not possible. We show that experiments with good candidate compounds would out-select them in the rodent model during preclinical optimization steps. Potentially active human-relevant drugs, therefore, would no longer be further developed. Activity and efficacy screens in heterologous species systems must be evaluated with caution

Ordered Patterns of Cell Shape and Orientational Correlation during Spontaneous Cell Migration

BACKGROUND: In the absence of stimuli, most motile eukaryotic cells move by spontaneously coordinating cell deformation with cell movement in the absence of stimuli. Yet little is known about how cells change their own shape and how cells coordinate the deformation and movement. Here, we investigated the mechanism of spontaneous cell migration by using computational analyses. METHODOLOGY: We observed spontaneously migrating Dictyostelium cells in both a vegetative state (round cell shape and slow motion) and starved one (elongated cell shape and fast motion). We then extracted regular patterns of morphological dynamics and the pattern-dependent systematic coordination with filamentous actin (F-actin) and cell movement by statistical dynamic analyses. CONCLUSIONS/SIGNIFICANCE: We found that Dictyostelium cells in both vegetative and starved states commonly organize their own shape into three ordered patterns, elongation, rotation, and oscillation, in the absence of external stimuli. Further, cells inactivated for PI3-kinase (PI3K) and/or PTEN did not show ordered patterns due to the lack of spatial control in pseudopodial formation in both the vegetative and starved states. We also found that spontaneous polarization was achieved in starved cells by asymmetric localization of PTEN and F-actin. This breaking of the symmetry of protein localization maintained the leading edge and considerably enhanced the persistence of directed migration, and overall random exploration was ensured by switching among the different ordered patterns. Our findings suggest that Dictyostelium cells spontaneously create the ordered patterns of cell shape mediated by PI3K/PTEN/F-actin and control the direction of cell movement by coordination with these patterns even in the absence of external stimuli

An Excitable Cortex and Memory Model Successfully Predicts New Pseudopod Dynamics

Motile eukaryotic cells migrate with directional persistence by alternating left and right turns, even in the absence of external cues. For example, Dictyostelium discoideum cells crawl by extending distinct pseudopods in an alternating right-left pattern. The mechanisms underlying this zig-zag behavior, however, remain unknown. Here we propose a new Excitable Cortex and Memory (EC&M) model for understanding the alternating, zig-zag extension of pseudopods. Incorporating elements of previous models, we consider the cell cortex as an excitable system and include global inhibition of new pseudopods while a pseudopod is active. With the novel hypothesis that pseudopod activity makes the local cortex temporarily more excitable – thus creating a memory of previous pseudopod locations – the model reproduces experimentally observed zig-zag behavior. Furthermore, the EC&M model makes four new predictions concerning pseudopod dynamics. To test these predictions we develop an algorithm that detects pseudopods via hierarchical clustering of individual membrane extensions. Data from cell-tracking experiments agrees with all four predictions of the model, revealing that pseudopod placement is a non-Markovian process affected by the dynamics of previous pseudopods. The model is also compatible with known limits of chemotactic sensitivity. In addition to providing a predictive approach to studying eukaryotic cell motion, the EC&M model provides a general framework for future models, and suggests directions for new research regarding the molecular mechanisms underlying directional persistence

Rapid and efficient microwave-assisted Friedländer quinoline synthesis

A microwave‐based methodology facilitates reaction of 2‐aminophenylketones with cyclic ketones to form a quinoline scaffold. Syntheses of amido‐ and amino‐linked 17β‐hydroxysteroid dehydrogenase type 3 inhibitors with a benzophenone‐linked motif were pursued using 2‐aminobenzophenone as building block. Two amido‐linked targets were achieved in modest yield, but when using microwave‐assisted reductive amination for the amino‐linked counterparts an unexpected product was observed. X‐ray crystallography revealed it as a quinoline derivative, leading to optimisation of a simple and efficient modification of Friedländer methodology. Using reagents and acetic acid catalyst in organic solvent the unassisted reaction proceeds only over several days and in very poor yield. However, by employing neat acetic acid as both solvent and acid catalyst with microwave irradiation at 160 °C quinoline synthesis is achieved in 5 minutes in excellent yield. This has advantages over the previously reported high temperatures or strong acids required, not least given the green credentials of acetic acid, and examples using diverse ketones illustrate applicability. Additionally, he unassisted reaction proceeds effectively at room temperature, albeit much more slowly

The effects of thermal annealing on the obliquely deposited Ag–Ge–S thin films

Obliquely deposited thin films of ternary Ag–Ge–S glasses are characterized in this work. Thin films are fabricated in a vacuum thermal evaporator at different evaporation angles and examined by Raman spectroscopy. The Raman mode frequency of GeS4 corner-sharing (CS) structure of the as-deposited films display a red-shift as a function of Ag content due to reduced global connectivity, and therefore decreased network stress. Film thickness of normally deposited thin films is significantly less when compared against obliquely deposited ones. Sulfur-ring (S8) modes are observed in thin films but not in corresponding bulk material. Thermal annealing of thin films results in the disappearance of Sulfur-ring (S8) modes, while the temperature required for this phenomenon is deposition angle dependent. Thickness of the obliquely deposited films shrinks significantly after thermal annealing, which indicates a collapse of the micro-column structure introduced by oblique depositio