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On the evaluation of energy release rate and mode mixity for ductile asymmetric four point bend specimens
No full textA method for evaluating the contributions from mode I and II components of loading to the energy release rate J in ductile asymmetric four-point bend (4-PB) specimens is proposed. The validity of the method is established by conducting elastic-plastic finite element analysis of several asymmetric 4-PB specimens exhibiting a range of mode mixities from pure mode I to II and having different crack length to width (a/W) ratios. Further, a definition of plastic mode mixity is introduced based on the near-tip opening and sliding displacements. This definition and the proposed method to evaluate J are easy to apply since the required crack opening and sliding displacements can be determined from in-situ optical imaging coupled with Digital Image Correlation (DIC) technique. The application of the proposed methodology is demonstrated by analyzing mixed-mode fracture experiments being conducted with a magnesium alloy. It is found that the critical value of J at crack initiation reduces as loading changes from mode I to II
Let-7a-regulated translational readthrough of mammalian AGO1 generates a microRNA pathway inhibitor
No full textTranslational readthrough generates proteins with extended C-termini, which often possess distinct properties. Here, we have used various reporter assays to demonstrate translational readthrough of AGO1 mRNA. Analysis of ribosome profiling data and mass spectrometry data provided additional evidence for translational readthrough of AGO1. The endogenous readthrough product, Ago1x, could be detected by a specific antibody both in vitro and in vivo. This readthrough process is directed by a cis sequence downstream of the canonical AGO1 stop codon, which is sufficient to drive readthrough even in a heterologous context. This cis sequence has a let-7a miRNA-binding site, and readthrough is promoted by let-7a miRNA. Interestingly, Ago1x can load miRNAs on target mRNAs without causing post-transcriptional gene silencing, due to its inability to interact with GW182. Because of these properties, Ago1x can serve as a competitive inhibitor of miRNA pathway. In support of this, we observed increased global translation in cells overexpressing Ago1x. Overall, our results reveal a negative feedback loop in the miRNA pathway mediated by the translational readthrough product of AGO1
Challenges and opportunities in blood flow through porous substrate: A design and interface perspective of dried blood spot
No full textBlood microsampling is desired in clinical, pharmaceutical and biomedical fields to overcome the challenges of conventional whole blood sampling. One of the popular methods for blood microsampling is the dried blood spot (DBS) kit and the collected sample is subsequently used for bioanalysis. The current practice of DBS is simple to use, cheap and very well standardized from sample collection to analysis. However, DBS suffers from several well documented challenges related to blood spot formation such as varying hematocrit volume, thin layer chromatography effect and subsequent bio-analysis resulting in a variable and ocassionally high failure rate. A major source of these problems is our limited understanding of blood flow in porous media under different ambient and material conditions. Therefore, it is highly desirable to understand the parameters that affect blood flow in a porous medium to enable a more robust design of DBS and generally blood microsampling kits. In this review, we discuss some existing blood microsampling techniques while focusing on the challenges associated with blood flow dynamics. We also review existing studies on the potential factors that affect the permeation (imbibition or wicking) and spreading of blood in a thin, porous substrate as means to understand and overcome the challenges in designing new DBS kits and blood microsampling devices. Thereafter, we have discussed recent advances in the design of passive flow-based devices to overcome these challenges of current blood microsampling by DBS. Finally, we present a few applications of DBS in clinical and non-clinical studies. This review can benefit researchers working at the interface of complex fluid flow, surface chemistry, and material and device design for biomedical and biological applications
SN 2018hna: 1987A-like Supernova with a Signature of Shock Breakout
No full textHigh-cadence ultraviolet, optical, and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early-phase multiband light curves (LCs) exhibit the adiabatic cooling envelope emission following the shock breakout up to similar to 14 days from the explosion. SN. 2018hna has a rise time of similar to 88 days in the V band, similar to SN 1987A. A Ni-56 mass of similar to 0.087 +/- 0.004 M-circle dot is inferred for SN 2018hna from its bolometric LC. Hydrodynamical modeling of the cooling phase suggests a progenitor with a radius similar to 50 R-circle dot, a mass of similar to 14-20 M-circle dot, and an explosion energy of similar to 1.7-2.9 x 10(51) erg. The smaller inferred radius of the progenitor than a standard red supergiant is indicative of a blue supergiant progenitor of SN 2018hna. A subsolar metallicity (similar to 0.3 Z(circle dot)) is inferred for the host galaxy UGC 07534, concurrent with the low-metallicity environments of 1987A-like events
Light management through up-conversion and scattering mechanism of rare earth nanoparticle in polymer photovoltaics
No full textPrimary loss mechanisms in a single junction solar cell are below E-g loss and thermalization loss which limits the maximum achievable cell efficiency. In order to overcome the fundamental loss mechanisms called transmission loss due to the mismatch of the solar spectrum with the photoactive layer absorption spectrum, the up-conversion mechanism was adopted to improve the performance of organic photovoltaics. This mechanism was adopted using rare-earth nanoparticle beta-NaYF4:Yb3+/Er3+ in P3HT and PTB7 conducting polymer-based n-i-p organic photovoltaic device. beta-NaYF4:Yb3+/Er3+ nanoparticles absorb infrared (IR) photons whose wavelength approximately 980 nm and emit photons in the green wavelength region with the emission intensity maximum occurs at 520 nm and 541 nm. This non-linear optical process (up-conversion mechanism) was used in the polymer solar cell. The polymers used in this study exhibits the absorption range from similar to 300 nm to 680 nm and 300 nm-800 nm respectively for P3HT and PTB7. Using beta-NaYF4:Yb3+/Er3+ in polymer solar cell can reduce the transmission loss through harvesting IR photons. In this study, up-conversion nanoparticles (UCNPs) were embedded between the photoactive layer and anode interface to harvest IR light. Presence of these UCNPs assists in visible photons generation process in the vicinity of the photoactive layer which leads to the increased photo collection. Optimum loading of beta-NaYF4:Yb3+/Er3+ nanoparticles in the device interface for improvement in the photocurrent and efficiency were investigated and correlated with the device optical and electrical processes. The optical process suggests that improvement in photocurrent is a synergistic effect of the up-conversion process and light scattering by beta-NaYF4:Yb3+/Er3+. The device with UCNPs showed absorbance improvement which suggests that backscattered light at the anode/active layer interface improve the active layer absorption. Detailed investigation of the device properties allows interpreting that the photocurrent improvement is an up conversion process as well as the scattering. In the optimized up-conversion based device, the photo-current due to up-conversion process and light scattering are of the same order. However, this can vary with respect to photoactive layer absorption properties
Low-cost novel synthesis route to prepare cobalt ferrite based nanocrystals
No full textMagnetic nanoparticles of cobalt ferrite are synthesized via a simple reduction route. These synthesized nanoparticles were characterized using x-ray diffraction (XRD), Scanning Electron Microscopy, Raman Spectroscopy, Fourier Transform Infrared studies and their magnetic properties were measured using Vibrating-sample magnetometer. The XRD analysis confirms the formation of single phase CoFe2O4 nanoparticles, with cubic spinel structure, having crystalline size of 5-10 nm, depending on the annealing temperature. Raman spectra analysis confirmed that all the synthesized powders are phase pure. The maximum magnetic saturation of 268 A m(-1) has been observed for the sample calcined at 600 degrees C and correspondingly the magnetic anisotropic constant values are reported. The proposed hydrazine reduction synthesis route is simple in execution and cost effective, which makes it economically adaptable for large scale production of CoFe2O4 nanoparticles
Identification of Indian monsoon predictors using climate network and density-based spatial clustering
No full textThe Indian summer monsoon is a complex climatic phenomenon with a large variability over the years. The climatic predictors affecting the phenomenon evolve with time, and consequently new predictors have gained importance. Several statistical approaches are being explored in the literature to identify the potential predictors influencing the Indian summer monsoon. A complex network paradigm involving climatic variables at the grids over the globe has been proposed for predictor identification and monsoon prediction. The approach initiates with the identification of communities in the climate network considering mutual similarity and the influence of climate variables of grids on the Indian summer monsoon. Spatial clustering is performed over the communities to identify the geographical regions of significance. The climatic predictors extracted from variables of these regions are evaluated in terms of their correlation with the monsoon as well as their forecasting skills in predicting the summer monsoon of the country. The newly identified predictors forecast monsoon with an error of 4.2%, which is significant for the prediction of the complex phenomenon of monsoon
Effect of Different Crosslinking Strategies on Physical Properties and Biocompatibility of Freestanding Multilayer Films Made of Alginate and Chitosan
No full textFreestanding multilayer films prepared by layer-by-layer technique have attracted interest as promising materials for wound dressings. The goal is to fabricate freestanding films using chitosan (CHI) and alginate (ALG) including subsequent crosslinking to improve the mechanical properties of films while maintaining their biocompatibility. Three crosslinking strategies are investigated, namely use of calcium ions for crosslinking ALG, 1-ethyl-3-(-3-dimethylaminopropyl) carbodiimide combined with N-hydroxysuccinimide for crosslinking ALG with CHI, and Genipin for crosslinking chitosan inside the films. Different characteristics, such as surface morphology, wettability, swelling, roughness, and mechanical properties are investigated showing that films became thinner, exhibited rougher surfaces, had lower water uptake, and increased mechanical strength after crosslinking. Changes of wettability are moderate and dependent on the crosslinking method. In vitro cytotoxicity and cell attachment studies with human dermal fibroblasts show that freestanding CHI-ALG films represent a poorly adhesive substratum for fibroblasts, while studies using incubation of plastic-adherent fibroblast beneath floating films show no signs of cytotoxicity in a time frame of 7 days. Results from cell experiments combined with film characteristics after crosslinking, indicate that crosslinked freestanding films made of ALG and CHI may be interesting candidates for wound dressings
Enhanced stability of an intrinsically disordered protein against proteolytic cleavage through interactions with silver nanoparticles
No full textIntrinsically disordered proteins (IDPs), being sensitive to proteolytic degradation both in vitro and in vivo, can be stabilized by the interactions with various binding partners. Here, we show for the first time that silver nanoparticles (AgNPs) have the ability to enhance the half-life of an IDP, thereby rendering it stable for a month against proteolytic degradation. The conjugate of the unstructured linker domain of human insulin-like growth factor binding protein-2 (L-hIGFBP2) with 10 nm citrate-capped AgNPs was studied using two-dimensional NMR spectroscopy and other biophysical techniques. Our studies reveal the extent and nature of residue-specific interactions of the IDP with AgNPs. These interactions mask proteolysis-prone sites of the IDP and stabilize it. This study opens new avenues for the design of appropriate nanoparticles targeting IDPs and for storage, stabilization and delivery of IDPs into cells in a stable form
1,4-Diazacubane crystal structure rectified as piperazinium
No full textAll 21 n]-azacubanes are proposed by theoreticians to be stable, however, to-date only the synthesis of 1,4-diazacubane has been reported - as a Ni2+ templated Kagome metal organic framework (MOF). Described herein is the structural reassignment of this Kagome MOF on the basis of deducing the precise experimental procedure, and demonstrating that rather than the formation of 1,4-diazacubane, charge is balanced by disordered piperazinium cations across a twelve-fold symmetry site. Furthermore, quantum chemical calculations reveal that 1,4-diazacubane is unlikely to form under the reported conditions due to unfavorable enthalpies for select hypothetical reactions leading to such a product. This significant structure correction upholds the unconquered synthesis status quo of azacubane