Mechanical properties of injection molded long fiber polypropylene composites,Part 2: Impact and fracture toughness

This study describes the effect of fiber length and compatibilizer content on notched izod impact and fracture toughness properties. Long fiber polypropylene (LFPP) pellets of different sizes were prepared by extrusion process using a new radial impregnation die, and subsequently, pellets were injection molded as described in previous publication 1 . The content of glass fiber reinforcement was maintained same for all compositions. Maleic‐anhydride grafted polypropylene (MA‐g‐PP) was chosen as a compatibilizer to increase the adhesion between glass fiber and PP matrix and its content was maintained at 2 wt%. Notched izod impact property was studied for LFPP composites prepared with and without compatibilizer for different pellet sizes. Failure mechanism due to sudden impact was analyzed with scanning electron micrographs and was correlated with impact property of LFPP composites. Fracture and failure behavior of injection molded LFPP composite were studied and relationship between fracture toughness and microstructure of LFPP composite was analyzed. The microstructure of the composites was characterized by the dimensionless reinforcing effectiveness parameter, which accounts for the influence of fiber layer structure, fiber alignment, fiber volume fraction, fiber length distribution, and aspect ratio. Matrix stress condition factor and energy absorption ratio were determined for LFPP composites prepared with and without compatibilizer. Failure mechanism of both the matrix and fiber, revealed with SEM images, were discussed. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Optical properties of Se1−x Sb x thin films (0<x<0.5)

The energy gap (E _g) of approximately 100 nm thick films of the Se_1–x Sb _x system has been investigated using an optical transmission method. E _g is found to decrease linearly with increasing Sb concentration in Se_1–x Sb _x films. No anomalous behaviour in E _g is observed at x = 0.4 as reported earlier by Wood et al.     

Nasal sill augmentation in adult incomplete cleft lip nose deformity using superiorly based turn over orbicularis oris muscle flap: an anatomic approach

Adult incomplete cleft lip nose deformity is not uncommon in India. Poverty, ignorance, and parental neglect account for its late presentation. Besides the classical features of cleft lip nose deformity, the constant findings observed in this patient population have been a widened and depressed nasal sill. This is attributable to the sparse, hypoplastic, and abnormally orientated orbicularis oris muscle in the region of the sill. Failure to restore the nasal sill symmetry by suitably augmenting the sill frequently leads to unsatisfactory and asymmetric results. However, in the literature, satisfactory restoration of the nasal sill has not been given the importance it deserves while performing cleft lip rhinoplasty. We present a method of augmenting the depressed nasal sill in cases of adult incomplete nose deformity using a superiorly based orbicularis oris muscle flap, which is harvested from the soft tissues between the apex of the cleft and the nostril sill. Following de-epithelialization of the overlying skin, the exposed muscle is raised as a superiorly based flap after dissecting it from the underlying mucosa. It is folded, turned over, and tucked into the nasal sill base and anchored to the anterior nasal spine to give the desired augmentation. Satisfactory results have been obtained in 18 cases of nasal deformity associated with incomplete cleft lip. In our opinion, this technique offers a simple and effective method of augmenting the depressed sill by utilizing locally available tissues and without the need for procuring autologous tissue from distant sites.     

Initial Empirical Testing of Potential Factors Contributing to Patient Use of Secure Medical Teleconferencing

Providing timely and cost-effective healthcare appears to be significantly desired. Factors such as computer skills and comprehension of instructions impact people’s perception of the accessibility of such alternatives, especially for medical professionals. There are limited studies examining the aforementioned factors in information systems (IS) literature in the context of medical teleconferencing (ehealth) from the patients’ perspective. Thus, the purpose of this research study was to examine the underlying structure of four factors, namely IS usage (ISU), computer self-efficacy (CSE), ethical severity of misusing IS (ESMIS), and the resistance to use IS (RESUIS). Based on data gathered from 140 participants, confirmatory factor analysis (CFA) was conducted, using the partial least squares (PLS) technique. Results indicated a very strong validity and reliability of the constructs, however, with a relatively low overall model predictability. Furthermore, the constructs of CSE and RESUIS appear to demonstrate significant contribution toward ISU.     

Structural and kinetic determinants of aldehyde reduction by aldose reductase

Aldose reductase (AR) is a member of the aldo-keto reductase superfamily. Due to its ability to catalyze the formation of sorbitol from glucose during hyperglycemic and hypertonic stress, the aldose-reducing property of AR has been accepted as its main physiological and pathological function. Nonetheless, AR is a poor catalyst for glucose reduction and displays active-site properties unexpected of a carbohydrate-binding protein. We, therefore, examined the catalytic properties of AR with a series of naturally occurring aldehydes, compatible in their hydrophobicity to the large apolar active site of the enzyme. Our results show that recombinant human AR is an efficient catalyst for the reduction of medium- to long-chain unbranched saturated and unsaturated aldehydes. The enzyme displayed selective preference for saturated aldehydes, such as hexanal, and unsaturated aldehydes, such as trans-2-octenal and nonenal as well as their 4-hydroxy derivatives. Short-chain aldehydes such as propanal and acrolein were reduced less efficiently. Branched derivatives of acrolein or its glutathione conjugate (GS-propanal) were, however, reduced with high efficiency. In the absence of NADPH, the alpha, beta unsaturated aldehydes caused covalent modification of the enzyme. On the basis of electrospray mass spectrometric analysis of the wild-type and site-directed mutants of AR (in which the solvent exposed cysteines were individually replaced with serine), the site of modification was identified to be the active-site residue, Cys 298. The unsaturated aldehydes, however, did not modify the enzyme bound to NADPH and did not inactivate the enzyme during catalysis. Modeling studies indicate that the large hydrophobic active site of AR can accommodate a large number of aldehydes without changes in the structure of the binding site or movement of side chains. High hydrophobicity due to long alkyl chains or apolar substituents appears to stabilize the interaction of the aldehyde substrates with the enzyme. Apparently, such hydrophobic interactions provide substrate selectivity and catalytic efficiency of the order achievable by hydrogen bonding. Since several of the aldehydes reduced by AR are either environmental and pharmacological pollutants or products of lipid peroxidation, the present studies provide the basis of future investigations on the role of AR in regulating aldehyde metabolism particularly under pathological states associated with oxidative stress and/or aldehyde toxicity.     

38—THE EFFECT OF SPINNING CONDITIONS ON THE TENSILE PROPERTIES OF CORE-SPUN YARNS

A critical assessment of the merits of core-spinning by means of comparisons of the strength and extension of core-spun yarns with all-staple-fibre yarns forms the basis of this paper. Core-spinning was done by introducing the filament under tension into the drafted strand as the latter entered the front rollers of the ring-frame. A 20-den (2.2-tex) nylon monofilament was used as core, and three types of staple-fibre covering were investigated. The effects of twist, pre-tension, and feeding arrangements on the geometrical disposition and tensile properties of the yarns were examined. Improvements in strength are, in general, realized at low twists by the incorporation of the filament and by further constraining it to occupy the core. The contribution of the components to the yarn strength and the process of breaking were also subjected to a detailed study. The studies reported provide an interesting insight into the extent of cohesion developed between the fibres during the straining of the yarn and its influence on the process of breaking and ultimately on yarn extension.     

Dual gas sensing properties of graphene-Pd/SnO2 composites for H2 and ethanol: Role of nanoparticles-graphene interface

In the present work, role of palladium (Pd) and tin oxide (SnO₂) nanoparticles (NPs) deposited on graphene has been investigated in terms of dual gas sensing characteristics of ethanol and H₂ between two temperatures. The incorporation of nanoparticles into graphene has been observed which results a large change in the sensing response towards these gases. It is investigated that, incorporation of isolated Pd NPs on the graphene facilitates the room temperature sensing of H₂ gas with fast response and recovery time whereas, isolated SnO₂ NPs on graphene enables the detection of ethanol at 200 °C. However, combination of isolated Pd and SnO₂ NPs on graphene shows improved sensitivity and good selectivity towards H₂ and ethanol, usually not observed in chemiresistive gas sensors. Catalytic PdH interaction and corresponding change in work function of nanoparticles on hydrogenation resulting in modifications in electronic exchange between Pd, SnO₂ and graphene are responsible for the observed behavior. These results are important for developing a new class of chemiresistive type gas sensor based on change in the electronic properties of the graphene and NPs interfaces.     

Effects of Ti-based catalysts and synergistic effect of SWCNTs-TiF3 on hydrogen uptake and release from MgH2

The present investigations are focused on the effect of different Ti-based catalysts (Ti, TiO₂, TiCl₃ and TiF₃) on de/re-hydrogenation characteristics of nanocrystalline MgH₂. Desorption temperature of milled MgH₂ lowers from 380 to 350, 340, 310 and 260 °C with the addition of Ti, TiO_2, TiCl₃ and TiF₃ respectively. The rehydrogenation characteristics are also improved through the deployment of Ti-based catalysts. Among all Ti based additives, TiF₃ is found to be the most effective catalyst for hydrogen sorption from nano MgH₂. The better catalytic effect of TiF₃ over other Ti-based catalyst can be explained on the basis of temperature programmed reduction (TPR) studies. TPR experiments performed for different Ti additives, reveals that there is no oxidation/reduction reaction below 400 °C except for TiF₃. The TPR profile of TiF₃ shows some oxidation/reduction reaction exhibits at 200 °C. In order to further improve the sorption characteristics and cyclability of TiF₃ catalyzed nano MgH₂, we have investigated the effect of SWCNTs in MgH₂+TiF₃ sample. De/rehydrogenation characteristics reveal the synergistic effect of SWCNTs and TiF₃ in MgH₂+TiF₃ sample. The details of the improvement in sorption behavior of MgH₂–TiF₃ in presence of SWCNTs are described and discussed.