Chiral Cooperativity in Helical Polymers

Human experience informs us of the two extreme consequences of crowding: random behavior of the individuals, in which each takes a singular path; and cooperative behavior, in which the individuals in the crowd act in a predictable uniform manner, such as in a military organization These extremes find parallels in the crowded situations encountered at the molecular level, exemplified for the former by glassy states, such as often encountered in polymeric materials, 1 or for the latter, in the uniform archetypal arrangements of crystals or liquid crystals. Here we review the cooperative characteristics of uniform arrangements that take a chiral form and explore how these characteristics lead to left- and right-handedness. These studies lead us to understand the basis of amplification of chirality in regular arrays, in which small influences have large consequences, and how chiral cooperativity acts in the resolution of conflict between influences favoring left- and right-handedness. 2     

Ultrasound‐induced nucleation in microcellular polymers

In this study, microcellular Acrylonitrile–Butadiene–Styrene foams with high cell density and expansion ratio has been manufactured using ultrasound‐induced nucleation technique in solid‐state batch foaming process. Influence of sonication time, sonication frequency, and ultrasound power were found very crucial in designing of cellular morphology. The initial 10 s of ultrasound exposure was found to influence the foam morphology critically. Longer periods of ultrasound exposure developed foams with lower average cell size as compared to foams developed with lesser ultrasound exposure time. Higher sonication power resulted in foams with uniform morphology and higher cell densities as compared to foams developed with lower sonication intensities. Finally, the ultrasonic frequency was also found to influence the morphology intensely. Low frequency sonication resulted in foams with uniform cell distribution, whereas high frequency sonication developed bimodal microcellular type of microstructure. The results coherently demonstrate that with the advent of ultrasonic waves, the energy barrier for cell nucleation swiftly decreases which enhances the cell density in the final foamed product. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40742.     

Catalytic effect of carbon nanostructures on the hydrogen storage properties of MgH2–NaAlH4 composite

The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH₂–NaAlH₄ composite. De/rehydrogenation study reveals that MgH₂–NaAlH₄ composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH₄ and MgH₂. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH₂–NaAlH₄ composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH₂–NaAlH₄ catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH₂–NaAlH₄ is diminished to 0.45 wt.%.     

A new facet in robust digital watermarking framework

Generally, in watermarking techniques the size of the watermark is very small when compared to the host image. On the contrary, this is an attempt in which a new facet in watermarking framework is presented where the size of host image is very small when compared to the watermark image. The core idea of the proposed technique is to first scale up the size of host image equal to the size of watermark using chaotic map and Hessenberg decomposition followed by the redundant wavelet transform. A meaningful gray scale watermark is embedded in the low frequency sub-band at the finest level using singular value decomposition. To prevent ambiguity and enhance the security, a binary watermark is also embedded in loss-less manner which ensures the authenticity of the watermarked image. Finally, a reliable watermark extraction scheme is developed for extracting both the watermarks. The experimental results demonstrate better visual imperceptibility and resiliency of the proposed scheme against intentional or un-intentional variety of attacks.     

Evaluation of compressive behaviour of porous structures under large deformation using micro-CT,DVC and micro-FE

Compressive behaviour of open and closed cell polyurethane foam samples under large deformation is studied using micro-Computed Tomography (micro-CT), Digital Volume Correlation (DVC) technique and micro-Finite Element (micro-FE) modelling. The micro-CT images of the foam samples at different compression strains are used to determine anisotropy in the foams, to obtain qualitative information on deformation mechanisms, to quantify the deformation and strains using a local DVC approach and to generate images for micro-FE modelling of the foam samples. Micro-FE modelling predicts the deformation using an elastoplastic material model coupled with continuum damage mechanics. Two different types of boundary conditions, experimentally derived (ExBC) and interpolated from DVC (IPBC), were implemented to evaluate the displacements in the micro-FE models. A reduced integration scheme in micro-FE analysis resulted in high artificial energy and was discarded in favour of full integration. The displacement predicted by IPBC matched with DVC displacement contours for closed cell foam. The ExBC-predicted axial displacement (W) showed a better agreement with DVC than transverse displacements (U, V) contours. However, a significant statistical comparison (R² > 0.70) of all displacements was obtained for both IPBC and ExBC. For open cell foam, both boundary conditions predicted a significant difference in the displacement contours with respect to DVC measurements. Still, the axial displacements of ExBC and IPBC showed a better statistical significance (R² > 0.70).     

Role of alkyl moieties in the antiwear and antioxidant performance of alkyl phosphorodithioates

Phosphorodithioate derivatives having different alkyl substitu‐ents have been synthesised, while keeping the core phosphorus‐sulphur moiety intact. The change in antiwear, extreme‐pressure, and antioxidant properties with the variation in sub‐stituents at oxygen and at sulphur linkages in the phosphorodithioates has been studied. The role of the heteroatoms with regard to the alkyl substituents has been examined. The experimental data show that the chemical structure of an additive influences its physicochemical and tribological properties.     

Additive‐additive interactions: The search for synergistic antioxidant—antiwear phosphorodithioate compositions

Additive‐additive interactions between zinc dialkylphosphorodithioates and ashless alkylaminophosphorodithioates have been studied with the object of reducing the zinc level in the lubricant formulations. Various combinations of these components were evaluated for their antiwear and antioxidant properties using four‐ball and differential scanning calorimetry techniques.     

Hot oil oxidation test (HOOT) — a laboratory simulation of ASTM Sequence IIID/IIIE engine tests

Reliable laboratory screening tests are an important stage in the development of automotive oils, because these oils are required to pass expensive engine tests to establish their performance credentials. The oxidation stability of crankcase lubricants is a vital parameter which defines the longevity of these oils in service. ASTM Sequence IIID and IIIE tests are used in the industry to evaluate this parameter. The present paper describes the development of a simple, bubbling oxygen, glassware, catalyst inhibited, type oxidation test. The test conditions have been optimised to get better discretion in the results, and the test results, when statistically correlated with the corresponding ASTM Sequence IIID and IIIE data, indicate that a 50–375% viscosity rise in HOOT will ensure a comfortable IIID pass with 98% confidence. However, in the case of IIIE, a viscosity rise of HOOT below 50% may indicate a IIID+ or IIIE performance with only 50% confidence. Improvement of the correlation between HOOT and IIIE can only be achieved by increasing the severity of the test conditions.     

Soluble molybdenum compound and sulphur ep additive combinations: Synergistic and adverse effects on antifriction and antiwear characteristics

Antifriction and antiwear performance of three soluble molybdenum (Mo) compounds (Mo dithiophosphate, Mo dithiocarbamate and Mo amine complex) and four sulphur-containing EP additives (sulphurised isobutylene, dibenzyl disulphide, sulphurised fat and synthesised ethylene sulphur derivative) have been studied, alone and in combination, using an SRV test rig. The additive behaviour in combination has been found to be selective, and dependent on the chemistry and ratio of the additive components. Certain sulphur EP additives in combination with Mo compounds have exhibited a synergistic effect. The antifriction performance of additives, in general, has been found to be further enhanced at higher test temperatures. However, a reduction in antiwear property has been noticed.     

Breathable,Flexible, Transparent,Hydrophobic, and Biotic Sustainable Electrodes for Heating and Biopotential Signal Measurement Applications

Pressure to reduce the global amount of e-waste has increased in recent years. The optimal use of natural resources is a demanding area especially due to the overabundance of the use of resources and challenges with after-life disposal. Herein, an easy method is developed to fabricate an improved version of leaf skeleton-based biodegradable, transparent, flexible, and hydrophobic electrodes. A fractal-like rubber leaf skeleton is used as the substrate, physical vapor deposited Au interlayer to promote adhesion, and uniform deposition of overlayer silver nanowires. The fabricated surfaces present a high level of electrical stability, optical transparency, hydrophobicity, and robust mechanical properties. The prepared electrodes demonstrate a comparable level of optical transmittance to the virgin leaf skeleton. The mechanical sturdiness of the electrodes is verified by 1k bending cycles. To demonstrate the functionality of these hybrid biotic conductive network (HBCN) electrodes, their performance is evaluated as flexible transparent heating elements and as biosignal measurement electrodes. The heater can reach a temperature of 140 °C with only 2.5 V in ≈5 s and Ag nanowire loading of ≈160 μg cm⁻². Likewise, electrocardiogram (ECG) and electromyogram (EMG) signals are successfully obtained from the electrodes without using any electrode gel or other electrolytes.