Microstructural and optical properties of nanocrystalline ZnO deposited onto vertically aligned carbon nanotubes by physical vapor deposition

Nanocrystalline ZnO films with thicknesses of 5 nm, 10 nm, 20 nm, and 50 nm were deposited via magnetron sputtering onto the surface of vertically aligned multi-walled carbon nanotubes (MWCNTs). The ZnO/CNTs heterostructures were characterized by scanning electron microscopy, high resolution transmission electron microscopy, and X-ray diffraction studies. No structural degradation of the CNTs was observed and photoluminescence (PL) measurements of the nanostructured ZnO layers show that the optical properties of these films are typical of ZnO deposited at low temperatures. The results indicate that magnetron sputtering is a viable technique for growing heterostructures and depositing functional layers onto CNTs.     

Terminal functionalized hydroxyl‐terminated polybutadiene: An energetic binder for propellant

We report the functionalization of hydroxyl terminated polybutadiene (HTPB) backbone by covalently attaching 1‐chloro‐2, 4‐dinitrobenzene (DNCB) at the terminal carbon atoms of the HTPB. The modification of the HTPB by the DNCB does not alter the unique physico–chemical properties and the microstructure of the parent HTPB. IR, ¹H‐NMR, ¹³C‐NMR, size exclusion chromatography (SEC) and absorption spectroscopy studies prove that the DNCB molecules are covalently attached to the terminal carbon atoms of the HTPB. The π electron delocalization owing to long polymer chain, strong electron withdrawing effect of the DNCB molecule are the major driving forces for the covalent attachment of the DNCB at the terminal carbon atom of the HTPB. We are the first to observe the existence of intermolecular hydrogen bonding between the terminal hydroxyl groups of the HTPB. IR study shows that the attached DNCB molecules at the terminal carbon atoms of the HTPB breaks the intermolecular hydrogen bonding between the HTPB chains and forms a hydrogen bonding between the NO₂ groups of the DNCB and the OH groups of the HTPB. Absorption spectral study of the modified HTPB indicates the better delocalization of π electron of butadiene due to the strong electron withdrawing effect of the DNCB molecules. Theoretical calculation also supports the existence of hydrogen bonding between the OH and NO₂ groups. Theoretical calculation shows that the detonation performance of both the DNCB and the HTPB‐DNCB are promising. HTPB‐DNCB is the new generation energetic binder which has potential to replace the use of HTPB as binder for propellant.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Bioconversion of soysterols to androstenedione by Mycobacterium fortuitum subsp. fortuitum NCIM 5239, a mutant derived from total sterol degrader strain

BACKGROUND: The bioconversion of soysterols to androstenedione (AD) by microbial cleavage of C‐17 side chain is of practical interest since AD serves as the starting compound for the production of the majority of pharmaceutically active steroids. A total soysterols degrader strain was subjected to combined mitomycin C and UV treatments and a mutant designated Mycobacterium fortuitum subsp. fortuitum NCIM 5239 was isolated that accumulated AD as major bioconversion product. RESULTS: The maximum bioconversion of soysterols to AD (71.3 mol %) was obtained at 30 °C, pH 5, 15% inoculum grown for 48 h, glycerol (12.68 g L^?1) and urea (1.06 g L^?1) as carbon and nitrogen sources, respectively, at C:N ratio of 10, the use of 10% polypropylene glycol‐400 (PPG‐400) as soysterols carrier solvent and 3 mg mL^?1 concentration of soysterols after 240 h incubation period in shake flask culture. In a laboratory scale fermentor, a maximum of 64.8 mol % bioconversion of soysterols to AD was recorded after 99 h. CONCLUSION: The mutant Mycobacterium fortuitum subsp. fortuitum NCIM 5239 possesses high potential for industrial production of AD from soysterols. Copyright © 2010 Society of Chemical Industry     

Compactibility improvement of metformin hydrochloride by crystallization technique

The objectives of the present study were to address the issues of poor flow and inadequate compressibility of metformin HCl by adopting particle engineering technique. Metformin HCl was crystallized in the presence of polyvinylpyrrolidone (PVP K30). A 3² full factorial design (FFD) was employed for optimization of the processing parameters. Percentage PVP K30 in solution (X₁) and crystallization time (X₂) were chosen as the independent variables. Percentage yield (Y₁), Carr’s index (Y₂) and tensile strength of compacts (Y₃) were selected as dependent variables. Mathematical models were evolved and contour plots were drawn. Metformin HCl particles crystallized in the presence of 2% PVP K30 with crystallization time of four hours (CryMet), showed impressive improvement in flow property, compressibility as well as compactibility as compared to untreated metformin HCl (XMet). The derived compaction parameters ‘a’, ‘1/b’ and ‘P_y’, obtained using Kawakita and Heckel equations were 0.369, 15.34 and 198.54 MPa for XMet; and 0.249, 11.05 and 143.33 MPa for CryMet respectively. Compressibility evaluation of the samples revealed poor compressibility of XMet while CryMet was directly compressible. DSC and FTIR experiments showed that CryMet particles did not undergo chemical modifications during crystallization.     

Characterization of pyrocarbon coated materials using laboratory based x-ray phase contrast imaging technique

In-line x-ray phase contrast is an emerging x-ray imaging technique that promises to improve the contrast in x-ray imaging process. This technique is most suited for x-ray imaging of soft materials, low atomic number elements such as carbon composite fibers, very thin coatings, etc. We have used this new emerging technique for visualization and characterization of the pyrocarbon coated materials using a combination of microfocus x-ray source and x-ray charge coupled device detector. These studies are important for characterization of coating and optimization of various process parameters during deposition. These experiments will help us to exploit the potential of this technique for studies in other areas of material science such as characterization of carbon fibered structures and detection of cracks and flaws in materials. The characterization of the imaging system and optimization of some process parameters for carbon deposition are also described in detail.     

Process Pathway Controlled Evolution of Phase and Van‐der‐Waals Epitaxy in In/In2O3 on Graphene Heterostructures

Many applications of 2D materials require deposition of non‐2D metals and metal‐oxides onto the 2D materials. Little is however known about the mechanisms of such non‐2D/2D interfacing, particularly at the atomic scale. Here, atomically resolved scanning transmission electron microscopy (STEM) is used to follow the entire physical vapor deposition (PVD) cycle of application‐relevant non‐2D In/In₂O₃ nanostructures on graphene. First, a “quasi‐in‐situ” approach with indium being in situ evaporated onto graphene in oxygen‐/water‐free ultra‐high‐vacuum (UHV) is employed, followed by STEM imaging without vacuum break and then repeated controlled ambient air exposures and reloading into STEM. This allows stepwise monitoring of the oxidation of specific In particles toward In₂O₃ on graphene. This is then compared with conventional, scalable ex situ In PVD onto graphene in high vacuum (HV) with significant residual oxygen/water traces. The data shows that the process pathway difference of oxygen/water feeding between UHV/ambient and HV fabrication drastically impacts not only non‐2D In/In₂O₃ phase evolution but also In₂O₃/graphene out‐of‐plane texture and in‐plane rotational van‐der‐Waals epitaxy. Since non‐2D/2D heterostructures' properties are intimately linked to their structure and since influences like oxygen/water traces are often hard to control in scalable fabrication, this is a key finding for non‐2D/2D integration process design.     

Inducing Personalities and Values from Language Use in Social Network Communities

A community in social networks is generally assumed to be composed of a group of individuals with similar characteristics. Although there has been a plethora of work on understanding network topologies (edge density, clustering coefficient, etc.) within an online community, the psycho-sociological compositions of social network communities have hardly been studied. The present paper aims to analyse the communities as composition of induced psycholinguistic and sociolinguistic variables (Personalities, Values and Ethics) across individuals in social media networks. The motivation behind this analysis is to understand the behavioural characteristics at individual as well as societal level in social networks. To this end, three studies were carried out on six different datasets: three Twitter corpora, two Facebook corpora, and an Essay corpus, annotated with Values and Ethics of the users. First, experiments on creating automatic models to determine the Personality and Values of individuals by analysing their language usage and social media behaviour. Second, experiments on understanding the characteristics or blend of characteristics of individuals within an online community. Finally, generation of a map of values and ethics for India, a multi-lingual and multi-cultural country. Striking similarities to general intuitive perception could be observed, i.e., the results obtained in the study resemble our general perception about the cities/towns of India.     

Evaluation of virtual reality interface for product shape designs

It is generally acknowledged that existing computer-aided design systems have inefficient user interfaces. Especially during the concept shape design stage, these systems prove to be cumbersome because of two reasons: (i) they require the usage of two-dimensional (2D) input devices, while the designs are typically three-dimensional (3D); and, (ii) CAD systems require the specification of dimensions, which may not be precisely known at the concept stage. To overcome these limitations, this research proposes the use of virtual reality (VR) devices to provide a physically intuitive interface for concept shape creation. The intuitiveness of the interface arises from the use of natural hand gestures and voice commands that emulate the way in which designers discuss concept shapes. In this scenario, the interface between the human and computer plays a central role with respect to usability, usefulness and accuracy. The focus of this research is on using two modalities: (i) hand input; and, (ii) voice driven commands, or a combination of these modalities to accomplish typical CAD tasks. Based on experience with a conventional CAD system, a set of typical CAD tasks are identified. A series of tests are then performed to determine the relative efficiency of the different modality combinations to achieve each task. The interface test results indicate that while voice commands are intuitive in initiating operations such as viewpoint zooming in/out and object creation/deletion, hand inputs are effective in performing spatial tasks such as interactive dimensioning and re-location of shapes. It was also found that a combination of voice and hand input can be used for accomplishing certain tasks more effectively such as, zooming in/out a particular direction (hand orientation indicates direction and voice is used for indicating zoom in/out operation). Based on the experience with the prototypical system developed it is concluded that voice and hand input are effective ways of building three-dimensional shapes in a virtual reality environment. To verify the efficiency of the VR-CAD interface, sample injection molded parts are built on the current VR-based CAD system and a traditional CAD system, and the times taken to build these parts are compared. The test results indicate that building geometry shapes containing canonical forms, such as block, cylinder, sphere, ⃛ etc, using a VR interface results in a speedup of five to ten times over traditional CAD systems.