Surgical management of locally recurrent rectal cancer

The surgical management of locally recurrent rectal cancer may involve major procedures and is not for the faint-hearted. Nevertheless, such treatment is preferable to chemotherapy and radiotherapy; the latter will fail over a period of months during which the patient is likely to experience intractable pain. Radical surgery offers good palliation and a better quality of life. Survival is prolonged by such operations which may be curative in up to one-third of patients. Nevertheless, surgeons must be realistic in their assessment of and discussions with patients.     

Dielectric behavior of polystyrene foam at microwave frequency

Polystyrene foams have been generated and fabricated into differently shaped structures', by change of steaming period under constant impregnation time and solvent-nonsolvent composition. Optical photomicrographs of samples both plain and wax-copper-coated reveal uniform appearance, distinct grain-boundaries, and random cell size distribution. Dielectric measurements have been made on test specimens cut according to wave-guide size at 9.375 GHz X-band microwave frequency by short-circuited wave-guide method of Smith and Hippel modified by Dakin and Works. Dielectric constants are linear, on direct and semi-log scales in bulk-density and volume-fraction, obeying Weiner's inequalities. Formulae of Landau-Lifshitz, Beer, Maxwell-Wagner, Odelevsky, etc. have been tried. Data fit best with the logarithmic law of Lichtenecker and Rother. Specific polarization is also a true function of density. Dielectric constant vs bulk-density plots of foams resemble dielectric-constant vs fractional-density plots based on the theoretical derivation by Smith for polystyrene compacts, signifying that compacts containing closely-spaced oblong-spherical particles arc physically similar to foams having spherical gas inclusions in plastic structures. Tan δ lying in the range 0.002–0.0038 results from conformational polarization (β-relaxation at room-temperature for wide-angle torsional oscillations of side-groups with co-operative motion from wriggling chains). It is therefore possible for low-loss foam dielectrics suitable for micro-wave applications to be made by this method.     

Fabrication and testing of Al–SiCp composite poppet valve guides

Composite materials are replacing the materials used in various fields and are the candidate materials for future growth. Metal matrix composites are the class of composite materials finding vast applications in automotive, aircraft, defense, sports, and appliance industries. In the present work, Al–SiC_p composites with 5–30 wt.% of SiC particulates were fabricated using powder metallurgy as well as casting processes. Mechanical alloying of aluminum and SiC particles was done prior to compaction so as to enhance the properties of the fabricated powder metal components. A custom built sliding valve guide wear test rig was fabricated to simulate the valve stem/guide wear under cold start condition of an engine by reciprocation of a valve stem under different imposed loads, against a stationary poppet valve guide. The hardness and radial crushing load was measured for the Al–SiC_p composite poppet valve guides and were found better than the cast iron poppet valve guides presently used in engines. The wear test of the poppet valve guides was done using valve guide wear test rig, which revealed that the Al-20 wt.% SiC_p and Al-30 wt.% SiC_p composite poppet valve guides have higher wear resistance than the cast iron poppet valve guides. The hardness, radial crushing load, and wear resistance of Al–SiC_p composite poppet valve guides were found to increase with increase in weight percent of SiC_p. The microstructural analysis of the cast and PM Al–SiC_p composites was also done using scanning electron microscope. Finite element analysis of the Al–SiC_p composite poppet valve guide was also done using Ansys software, which supports the successful implementation of the Al–SiC_p composite poppet valve guides for automobiles.     

Ultrastructural analysis of cell wall of drug resistant and sensitive Mycobacterium tuberculosis isolated from cerebrospinal fluid by transmission electron microscope

Drug‐resistant tuberculosis is being increasingly recognized and is one among the leading cause of death worldwide. Remarkable impermeability of cell wall to antituberculous drugs protects the mycobacteria from drug action. The present study analyzed the cell wall thickness among first‐line drug resistant and sensitive Mycobacterium tuberculosis (Mtb) isolated from cerebrospinal fluid by transmission electron microscopy (TEM). The average thickness of the cell wall of sensitive isolates was 13.60 ± 0.98 nm. The maximum difference (26.48%) in the cell wall thickness was seen among multi‐drug resistant (18.50 ± 1.71 nm) isolates and the least difference (4.14%) was shown by streptomycin‐resistant (14.18 ± 1.38 nm) isolates. The ultrastructural study showed evident differences in the cell wall thickness among sensitive and resistant isolates. Preliminary TEM examination of cells indicates that morphological changes occur in the cell wall which might be attributed to the drug resistance. The thickened wall of Mtb appears to help the bacilli to overcome the action of antituberculous drugs.     

Strain mediated enhancement in magnetoelectric properties of sonochemically synthesized piezoelectric and piezomagnetic composites

Materials with magneto-electric (ME) properties are of great importance because of their demand in electronic industries. Three dimensional nano-particles of the ME-composites having the general formula (1-x)CoCr_0.3Fe_1.7O₄(CCFO)+(x)BaTiO₃(BTO) (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were obtained by comprising the piezoelectric-BTO and piezomagnetic-CCFO phases. The individual phases of CCFO and BTO were synthesized separately by ultrasonic irradiation assisted sonochemical and sol-gel routs. X-ray diffraction patterns (XRD) confirmed the well-crystalline nature of both the phases. BTO and CCFO phases were under tensile strain as confirmed by the variation in lattice constants with varying proportion of BTO and CCFO. An energy-dispersive X-ray spectroscopy spectrum confirmed the phase purity of the samples and stoichiometric concentration of elements. Magnetic properties were investigated by M ? H loop measurements and dielectric properties by using RF impedance analyzer. Dielectric constant increased with the increasing percentage of BTO. The maximum value of ME coefficient (24.7 mV/cm?Oe) is observed for the 60%CCFO+40%BTO sample. The obtained results were discussed in the light of grain size, strain and the basic properties of the individual phases. The prepared materials can be applicable in electronic devices where high magneto-electric coefficient is desirable.     

Two-Dimensional Silicene–Stanene Heterostructures by Epitaxy

The synthesis of new Xenes and their potential applications prototypes have achieved significant milestones so far. However, to date the realization of Xene heterostructures in analogy with the well known van der Waals heterostructures remains an unresolved issue. Here, a Xene heterostructure concept based on the epitaxial combination of silicene and stanene on Ag(111) is introduced, and how one Xene layer enables another Xene layer of a different nature to grow on top is demonstrated. Single-phase (4 × 4) silicene is synthesized using stanene as a template, and stanene is grown on top of silicene on the other way around. In both heterostructures, in situ and ex situ probes confirm layer-by-layer growth without intercalations and intermixing. Modeling via density functional theory shows that the atomic layers in the heterostructures are strongly interacting, and hexagonal symmetry conservation in each individual layer is sequence selective. The results provide a substantial step toward currently missing Xene heterostructures and may inspire new paths for atomic-scale materials engineering.     

Microneedles for transdermal drug delivery: a systematic review

Transdermal route has been explored for various agents due to its advantage of bypassing the first pass effect and sustained release of drug. Due to strong barrier properties of the skin, mainly stratum corneum (SC), the delivery of many therapeutic agents across the skin has become challenging. Few drugs with specific physicochemical properties (molecular weight <500?Da, adequate lipophilicity, and low melting point) can be effectively administered via transdermal route. However, delivery of hydrophilic drugs and macromolecular agents including peptides, DNA and small interfering RNA is challenging. Drug penetration through the SC may involve bypass or reversible disruption of SC layer by various means. Recently, the use of micron-scale needles has been proposed in increasing skin permeability and shown to dramatically increase permeation, especially for macromolecules. Microneedles (MNs) can penetrate through the SC layer of the skin into the viable epidermis, avoiding contact with nerve fibers and blood vessels that reside primarily in the dermal layer. This review summarizes the types of MNs and fabrication techniques of different types of MNs. The safety aspects of the materials used for fabrication have been discussed in detail. Biological applications and relevant phase III clinical trials are also highlighted.     

Difference expansion based reversible data embedding and edge detection

Multimedia Tools and Applications - Difference Expansion (DE) based techniques are evolving in the last decade. The DE based techniques aims at reversibly embedding the data into cover content....     

Anisotropic photoresponse investigation of chemical vapor transport (CVT) grown quaternary Cu2ZnSnS4 single crystals

The single crystals of quaternary transition metal chalcogenide Cu₂ZnSnS₄ (CZTS) are grown by a closed system chemical vapor transport technique. The high purity individual elemental precursors are employed in the growth of the crystals. These crystals are found to be single-phase by X-ray diffraction and Raman analysis. The near stoichiometry of the grown crystals is confirmed by spectroscopy analysis of the photoelectron generated by X-rays and analysis of the energy of the dispersive X-rays generated by electrons. The surface study by scanning electron microscopy showed the growth to happen by sheet spread mean and the electron diffraction showed fringe width match with (112) plane spacing. The study of the CZTS/Ag-paste/Cu-wire system for incident white light and three wavelengths of laser lights in two configuration modes of top-contact (II to the plane) and bottom-top-contact (⊥ to the plane) showed anisotropic behavior. The incident white light illumination intensity of 120 mW/cm² showed utmost photoresponse. The top-contact mode configuration showed maximum responsivity and detectivity of 0.72 mA/W and 0.33 × 10⁹ Jones, respectively, while bottom-top-contact showed 0.18 mA/W and 0.13 × 10⁹ Jones, respectively. The anisotropic photoresponse by the CZTS crystals insinuates the potential for future applications.