Improved lifetimes of organic solar cells with solution‐processed molybdenum oxide anode‐modifying layers

We report on the use and stability of solution‐processed molybdenum oxide (sMoO_x) thin films as anode‐modifying layers to replace conventionally used poly(3,4‐ethyldioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) layers in poly(3‐hexylthiophene):[6,6]‐phenyl C₆₁ butyric acid methyl ester (P3HT/PC₆₁BM) bulk heterojunction organic solar cells. Our results show that while as prepared devices using the two anode‐modifying layers possess similar performances, the sMoO_x devices exhibit a staggering 20‐fold stability improvement in its performance half‐life compared with PEDOT/PSS devices, ~3400 h versus ~150 h, respectively. A further comparison of the stability between encapsulated and unencapsulated devices demonstrates the necessity for protection from atmospheric moisture and oxygen but again highlights the lucrative nature of sMoO_x as a protective anode‐modifying layer compared with PEDOT/PSS even under ambient conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Unified triaxiality at the crack tip subjected to plane strain condition under mixed‐mode (I + II) fracture

The new model of stress triaxiality, subjected to plane strain condition under mixed‐mode (I + II) loading, at the yield loci of the crack tip, has been formulated using unified strength theory. It evaluates critical values of triaxiality for various convex and non‐convex failure criteria, unlike the existing model. It shows the effects of Poisson's ratio and intermediate principal stress for materials whose strength in tension and compression is either equal or unequal. Further, on this basis, the crack initiation angles are predicted for various crack inclinations and compared with those obtained from other fracture criteria. The plastic zone shapes supplement the results. Critical yield stress factor, a significant parameter at the crack tip got lowered as the difference among the three principal stresses reduced to a minimum. The crack initiation angles obtained from the model showed good agreement with those obtained from G‐, S‐, and T‐criterion.     

An expert system for process planning of sheet metal parts produced on compound die for use in stamping industries

Process planning of sheet metal part is an important activity in the design of compound die. Traditional methods of carrying out this task are manual, tedious, time-consuming, error-prone and experience-based. This paper describes the research work involved in the development of an expert system for process planning of sheet metal parts produced on compound die. The proposed system is organized in six modules. For development of system modules, domain knowledge acquired from various sources of knowledge acquisition is refined and then framed in form of ‘IF-Then’ variety of production rules. System modules are coded in AutoLISP language and user interface is created using visual basic (VB). The system is capable to automate various activities of process planning including blank modeling, blank nesting, determining punch force required, selection of clearance between punch and die, identifying sheet metal operations, and determining proper sequence of operations for manufacturing the part. The proposed system can be implemented on a PC having VB and AutoCAD software, therefore its low cost of implementation makes it affordable even for small scale sheet metal industries.     

Determining double-K fracture parameters of concrete for compact tension and wedge splitting tests using weight function

The paper presents use of universal form of weight functions for determining the double-K fracture parameters and on compact test and wedge splitting test specimens. The proposed method enables to obtain a closed form expression of cohesion toughness of concrete specimens. A comparison with existing analytical method shows that the weight function method for determination of double-K fracture parameters yields results without any appreciable error. Significant influence of initial notch to depth (a₀/D) ratio on the double-K fracture parameters is not also observed. Finally, a possible definition of brittleness of concrete using double-K fracture parameters is proposed.     

Re-entrant auxetic structures fabricated by fused deposition modeling: An experimental study of influence of process parameters under compressive loading

The present article is focused on investigating the influence of process parameters under compressive loading in case of reentrant auxetic structures fabricated by fused deposition modeling (FDM). Auxetic structures of acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA) materials are fabricated. Three process parameters of FDM namely layer thickness, raster angle, and number of contours are considered to investigate their influence on compressive strength, stiffness, and specific energy absorption (SEA). Experiments are performed on the basis of central composite design and analysis is performed using ANOVA. It is found that compressive strength of auxetic structure improves with increase in layer thickness. But with increase in raster angle, it increases first and then decreases. Compressive stiffness of structures initially decreases and then increases with increase in raster angle, while it increases with increase in number of contours. SEA of structures increases with decrease in layer thickness. Based on the analysis of experimental results, regression models are developed to predict these responses. Also, multi-response optimization is performed to optimize strength, stiffness, and SEA. Auxetic structures failed under compressive loading are also examined using scanning electron microscope.     

Repeated oral dose toxicity of iron oxide nanoparticles: biochemical and histopathological alterations in different tissues of rats

Iron oxide (Fe2O3) nanoparticles are widely used in different fields of nanotechnology. However, studies on its toxicological effects in humans and the environment are scarce. Therefore in this investigation 28 days repeated dose oral toxicity studies were conducted on Fe2O3-30 nanoparticles and its counterpart Fe2O3-Bulk with special reference to target biochemical enzymes and histopathological changes in different tissues of female albino Wistar rats. The alterations observed after Fe2O3-30 treatment in various tissues of exposed rats were dose dependent. Low dose was less effective than medium and high doses with low dose demonstrating "no observed adverse effect" (NOAEL). Further, high dose treated rats showed toxic sign and symptoms but no mortality. Due to the repeated doses of Fe2O3-30 nanoparticles, significant inhibition was observed in total, Na(+)-K+, Mg2+ and Ca(2+)-ATPases in brain of exposed rats. Similarly, significant inhibition was recorded in RBC and brain acetylcholinesterase indicating that both synaptic transmission and nerve conduction were affected by this compound. Fe2O3-30 significantly increased aspartate amino transferase, alanine amino transferase and lactate dehydrogenase in serum and liver, whereas, these enzymes were significantly decreased in kidney indicating tissue necrosis and possible leakage of these enzymes into the blood stream. Increased levels of these enzymes in liver as well as in serum might be an adaptive mechanism due to the stress of iron nanoparticles. High dose treated rats of Fe2O3-30 showed dilated central vein, perivascular round cell collections in liver along with focal areas of necrosis, whereas kidney showed focal tubular damage and red pulp congestion, whereas prominent white pulp indices were observed in spleen. However, histopathological analysis of heart and brain tissues failed to show any adverse changes in their architecture exposed to repeated doses of Fe2O3-30 when compared with controls. Fe2O3-Bulk did not induce any adverse effects in either biochemical parameters or histopathology in the treated rats and the changes observed were near to controls and mostly insignificant, indicating that the counter part of nanoparticles i.e., bulk material is less potent than the nanoparticles in causing toxicity in the exposed animals. These results suggested that as particle size decreases, this iron nanoparticle showed increased toxicity, even though the same material is relatively inert in bulk form. The changes observed in these target enzyme activities could be useful as biomarkers of exposure to nanoparticles.     

Recent developments in spectroscopy of quantum structures

Two spectroscopic techniques, modulated reflectance spectroscopy and surface photovoltage spectroscopy, are being used increasingly to probe the electronic structure of low-dimensional semiconductors. We have found improved versions of these techniques: soft contact electroreflectance and soft contact surface photovoltage which offer operational advantages as well as extend the range of these spectroscopies. We also provide analytic formulation for extracting the transition parameters from the measured surface photovoltage spectrum of a quantum structure.     

Current and Future Biomarkers in Multiple Sclerosis

Multiple sclerosis (MS) is a debilitating autoimmune disorder. Currently, there is a lack of effective treatment for the progressive form of MS, partly due to insensitive readout for neurodegeneration. The recent development of sensitive assays for neurofilament light chain (NfL) has made it a potential new biomarker in predicting MS disease activity and progression, providing an additional readout in clinical trials. However, NfL is elevated in other neurodegenerative disorders besides MS, and, furthermore, it is also confounded by age, body mass index (BMI), and blood volume. Additionally, there is considerable overlap in the range of serum NfL (sNfL) levels compared to healthy controls. These confounders demonstrate the limitations of using solely NfL as a marker to monitor disease activity in MS patients. Other blood and cerebrospinal fluid (CSF) biomarkers of axonal damage, neuronal damage, glial dysfunction, demyelination, and inflammation have been studied as actionable biomarkers for MS and have provided insight into the pathology underlying the disease process of MS. However, these other biomarkers may be plagued with similar issues as NfL. Using biomarkers of a bioinformatic approach that includes cellular studies, micro-RNAs (miRNAs), extracellular vesicles (EVs), metabolomics, metabolites and the microbiome may prove to be useful in developing a more comprehensive panel that addresses the limitations of using a single biomarker. Therefore, more research with recent technological and statistical approaches is needed to identify novel and useful diagnostic and prognostic biomarker tools in MS.