Novel Hybrids of Polystyrene Nanoparticles and Silica Nanoparticles-Grafted-Graphite Via Modified Technique

We have designed polystyrene nanoparticles through modified nanoprecipitation cosolvent evaporation technique and conventional nanoprecipitation and solvent evaporation. Polystyrene nanoparticles were embedded with silica nanoparticles and graphite to analyze scope of nanoprecipitation cosolvent evaporation. Ultraviolet–visible spectroscopic revealed decreased band gap of polystyrene nanoparticles obtained via nanoprecipitation cosolvent evaporation. Scanning electron microscopic showed uniform morphology of polystyrene nanoparticles and polystyrene nanoparticles-based nanocomposites engendered by nanoprecipitation cosolvent evaporation. X-ray diffraction disclosed presence of crystalline domains due to silica nanoparticles content in amorphous structure. Glass transition temperature was increased from 94 (polystyrene) to 124°C (PSNPs/SiNPs 0.6) and 137°C (PSNPs/SiNPs/G 0.6) with filler loading. Electrical conductivity of PSNPs/SiNPs/G 0.6 was also found to be higher (1.53 S/cm).     

Crystal Structure of HydG from Carboxydothermus hydrogenoformans: A Trifunctional [FeFe]‐Hydrogenase Maturase

The structure of the radical S‐adenosyl‐L ‐methionine (SAM) [FeFe]‐hydrogenase maturase HydG involved in CN^?/CO synthesis is characterized by two internal tunnels connecting its tyrosine‐binding pocket with the external medium and the C‐terminal Fe₄S₄ cluster‐containing region. A comparison with a tryptophan‐bound NosL structure suggests that substrate binding causes the closing of the first tunnel and, along with mutagenesis studies, that tyrosine binds to HydG with its amino group well positioned for H‐abstraction by SAM. In this orientation the dehydroglycine (DHG) fragment caused by tyrosine Cα?Cβ bond scission can readily migrate through the second tunnel towards the C‐terminal domain where both CN^? and CO are synthesized. Our HydG structure appears to be in a relaxed state with its C‐terminal cluster CysX₂CysX₂₂Cys motif exposed to solvent. A rotation of this domain coupled to Fe₄S₄ cluster assembly would bury its putatively reactive unique Fe ion thereby allowing it to interact with DHG.     

Experimental study of heat transfer by natural convection in a closed cavity: application in a domestic refrigerator

An experiment was carried out using a refrigerator model in which heat is transferred by natural convection between a cold vertical wall and the other walls, which are exposed to heat losses. The air temperature profile in the boundary layers and in the central zone of the empty refrigerator model was investigated. Temperature stratification in the vertical direction was observed with the cold zone at the bottom and warm zone at the top of the cavity. The effects of temperature and the surface area of the cold wall were studied.

In order to study the effect of obstacles on temperature profiles, the refrigerator model was filled with 4 blocks of hollow spheres. Temperature profiles in this case were compared with the results with no blocks. The air temperature is lower almost everywhere in the model containing blocks. The presence of the blocks seems to enhance heat transfer particularly near the cold wall.     

Effect of beam sizes on the amplitude and phase of photothermal deflection signals for both uniform and nonuniform heating

A detailed theoretical treatment of a one- (1D) and three-dimensional (3D) photothermal deflection (PTD) technique is presented. Important effects of the probe beam size occur in PTD experiments when the radius of this beam is of the order of magnitude of the thermal diffusion length. The calculation of this effect is checked by experiments in paraffin oil at low modulation frequency as well as for 1D and for 3D. In this last case, we have considered two kinds of deflection: normal and transverse, and we have studied their variation for different values of the pump beam radius. The coincidence between theoretical and experimental curves confirms the validity of our theoretical model.     

Structural stability,electronic structure,and novel transport properties with high thermoelectric performances of ZrIrX (X $$$$ As,Bi, and Sb)

We use the first-principles-based density functional theory with full potential linearized augmented plane wave method to investigate the structural, elastic, electronic, and thermoelectric properties of ZrIrAs, ZrIrBi, and ZrIrSb. The calculated structural and elastic constants with generalized gradient potential developed by Perdew–Burke–Ernzerhof (GGA-PBEsol) reveal that our compounds are stable in the cubic LiAlSi-type structure. The electronic structures are calculated with GGA-PBEsol and improved by Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. The thermoelectric properties were determined at temperatures of 300, 600, and 800 K with respect to the p-type and n-type doping levels. We find that the thermopower factors are larger for p-type doping, implying that the hole doping provides more enhancement of thermoelectric performances in ZrIrAs, ZrIrBi, and ZrIrSb. Among them, the best thermopower values were found for the ZrIrAs compound with optimal doping levels of 46.17, 133.05, and 185.92 \(\times 1014\,\upmu \hbox {W}\, \mathrm{cm}^{-1}\; \hbox {K}^{-2}\;\hbox {s}^{-1}\) at temperatures of 300, 600, and 800 K, respectively.     

A Review on Materials Derived from Polystyrene and Different Types of Nanoparticles

Nanoparticles are divided into different categories depending upon their significance in current research. The principle types of nanoparticles are inorganic, organic, and hybrid nanoparticles. Fabrication routes to nanoparticles play an important role to obtain the desired features. Therefore, methods and challenges in preparation of nanoparticles have been discussed. Taking polystyrene into consideration, materials derived from polystyrene and nanoparticles have also been overviewed. Nanoparticle-based nanostructures have been used in numerous technological areas, ranging from catalysis and coatings to biomedicine and optoelectronics, depending upon the final properties. Hence, recent trends and future outlook of nanoparticle-derived materials have been discussed at the end.     

The effects of volume and speed of injection in peribulbar anaesthesia

Therapy of detrusor hyperactivity with anticholinergic agents often is followed by adverse drug reactions. Intravesical application may be an interesting alternative. A randomised, single-blind, placebo-controlled, mono-centre clinical trial was carried out in 84 patients with urgency or urge incontinence. Due to intravesical administration of oxybutynin (CAS 5633-20-5) (n = 21) and trospium chloride (CAS 10405-02-4) (n = 21), respectively, a significant increase in maximum bladder capacity and decrease of detrusor pressure accompanied by an increase of residual urine were found in comparison to placebo in urodynamical investigations. Improvement of uninhibited bladder contractions occurred leading to higher filling volume. Under verapamil (CAS 152-11-4) (n = 21) no marked changes in the efficacy variables were found compared with placebo. All patients completed the study and were assessed with regard to efficacy and safety. No adverse events or marked changes in the vital signs were reported. The immediate onset of effect and the lack of adverse drug reactions suggest that treatment with topical oxybutynin or trospium chloride is an effective alternative in patients with intolerable side effects when orally treated. In addition, intravesical administration may be indicated in patients with bladder spasms due to indwelling catheter or in order to increase bladder capacity before percutaneous cystostomy.     

Optical amplification of diffraction-free beams by photorefractive two-wave mixing and its application to laser Doppler velocimetry

The Fraunhofer diffraction pattern of a narrow annular slit is recorded holographically to generate a beam that approximates a diffraction-free Bessel beam. The experimental limitations resulting from the annular-slit parameters such as the opening width and the transmission coefficient are discussed. The reconstructed Bessel beam is amplified by two-wave mixing in a photorefractive crystal. Thus the efficient conversion of a relatively large beam with a constant (or Gaussian) intensity distribution into a nondiffracting beam is achieved entirely by direct physical interference. We show that diffraction-free beams reproduced and amplified in this way can be applied to the measurement of the velocity of small objects by the use of the laser Doppler technique. In addition, the advantages of Bessel beams, especially in measuring the velocity of solids, are discussed.