Photoluminescence study of SBA-15@ZnO/Au nanocomposite for potential use in Staphylococcus aureus detection

Journal of Porous Materials - Staphylococcus aureus is most common causes of hospital-acquired infections and food-associated disease. In the last years, sensing platform based on fluorescence-...     

Picosecond Capture of Photoexcited Electrons Improves Photovoltaic Conversion in MAPbI3:C70‐Doped Planar and Mesoporous Solar Cells

In this work, solar cells based on methylammonium lead iodide (MAPbI₃) doped in solution with C₇₀ fullerene in a mesoporous as well as planar electron‐transporting layer (ETL)‐free architecture are realized, showcasing in the latter case a record efficiency of 15.7% and an improved open‐circuit voltage (V_OC). Contrary to the bulk heterojunction previously reported, the C₇₀ molecules do not phase segregate and they are rather finely dispersed in the perovskite film, possibly infiltrating at the grain boundaries, while assisting the growth of a highly uniform perovskite layer. By means of time‐resolved femtosecond‐to‐nanosecond optical spectroscopy, with an extended spectral coverage, it is observed that electrons photogenerated in the perovskite are transferred to C₇₀ with a time constant of 20 ps. Despite being captured by C₇₀, electrons are not deeply trapped and can potentially bounce back into the perovskite, as suggested by the high fill factor and enhanced V_OC of the MAPbI₃:C₇₀ solar cells, especially in the case of the ETL‐free device configuration.     

Study of electrical conductivity changes and phase transitions in TiO2 doped ZrO2

The electrical conductivity in ZrO₂ doped with various molar ratios of TiO₂ has been measured at different temperatures. Phase transitions depending on the temperature for different molar compositions were investigated by doping of the samples. The conductivity is also found to increase with rise in temperature till 200 °C and thereafter decreases due to collapse of the fluorite framework. A second rise in conductivity in the doped samples around 462 °C is observed due to phase transition of ZrO₂. X-ray powder diffraction recorded at high temperature show the effect of doping and the phase relationships of doped materials. DTA was also carried out for confirming doping effect and phase transition in samples.     

Treatment of refractory and relapsed acute myelogenous leukemia with combination chemotherapy plus the multidrug resistance modulator PSC 833 (Valspodar)

A potential mechanism of chemotherapy resistance in acute myeloid leukemia (AML) is the multidrug resistance (MDR-1) gene product P-glycoprotein (P-gp), which is often overexpressed in myeloblasts from refractory or relapsed AML. In a multicenter phase II clinical trial, 37 patients with these poor risk forms of AML were treated with PSC 833 (Valspodar; Novartis Pharmaceutical Corporation, East Hanover, NJ), a potent inhibitor of the MDR-1 efflux pump, plus mitoxantrone, etoposide, and cytarabine (PSC-MEC). Pharmacokinetic (PK) interactions of etoposide and mitoxantrone with PSC were anticipated, measured in comparison with historical controls without PSC, and showed a 57% decrease in etoposide clearance (P =.001) and a 1.8-fold longer beta half-life for mitoxantrone in plasma (P <.05). The doses of mitoxantrone and etoposide were substantially reduced to compensate for these interactions and clinical toxicity and in Cohort II were well tolerated at dose levels of 4 mg/m2 mitoxantrone, 40 mg/m2 etoposide, and 1 g/m2 C daily for 5 days. Overall, postchemotherapy marrow hypoplasia was achieved in 33 patients. Twelve patients (32%) achieved complete remission, four achieved partial remission, and 21 failed therapy. The PK observations correlated with enhanced toxicity. The probability of an infectious early death was 36% (4 of 11) in patients with high PK parameters for either drug versus 5% (1 of 20) in those with lower PK parameters (P =.04). P-gp function was assessed in 19 patients using rhodamine-123 efflux and its inhibition by PSC. The median percentage of blasts expressing P-gp was increased (49%) for leukemic cells with PSC-inhibitable rhodamine efflux compared with 17% in cases lacking PSC-inhibitable efflux (P =.004). PSC-MEC was relatively well tolerated in these patients with poor-risk AML, and had encouraging antileukemic effects. The Eastern Cooperative Oncology Group is currently testing this regimen versus standard MEC chemotherapy in a phase III trial, E2995, in a similar patient population.     

Effect of temperature on tribological performance of a silicon nitride ball material with a linear perfluoropolyalkylether

The effect of temperature in rolling contact performance of a hot isostatically pressed (HIP) silicon nitride ball material with a linear perfluoropolyalkylether (PFPAE) was studied using a ball-on-rod type rolling contact fatigue tester. The test temperature ranged from ambient to 343°C for a period of 24 h at a stress of 5.5 GPa using thin dense chrome (TDC)-coated T-15 bearing races. The lubricant and its decomposition products, specifically acid fluoride and acids, attacked Si₃N₄ balls at all test temperatures resulting in corrosion pitting. The presence of metal fluoride on all the Si₃N₄, transferred from the races, was detected by X-ray photon spectroscopy (XPS). The thickness of the oxide layer formed on the balls, as determined by Auger electron spectroscopy (AES) increased with temperature. The changes in physical properties of post-test lubricant showed that the lubricant was stable at temperatures up to 288°C. The change in viscosity was constant up to 288°C and with a significant change above 288°C. The FTIR analysis of 316 and 343°C post-test lubricant showed the presence of carboxylic acid. The total acid number (TAN) increased linearly up to 288°C and accelerated at 316 and 343°C. The study indicates that the use of Si₃N₄ balls with a linear PFPAE results in an incompetent tribo system.     

Phonon dispersion and specific heat in <Emphasis Type=Italic>trans</Emphasis> 1,4, poly (2,3-dimethylbutadiene)

A comprehensive study of the normal modes and their dispersion for trans 1,4-poly (2,3 dimethylbutadiene) is described in the reduced zone scheme using Wilson’s GF matrix method as modified by Higg’s for an infinite polymeric chain. Urey Bradley force field is obtained by least square fitting of the observed IR and Raman bands. Optically active frequencies corresponding to the zone center and zone boundary are identified and discussed. Some of the characteristic features of dispersion curves are repulsion accompanied by exchange of character and Von Hove type singularities. The evaluation of normal modes and their dispersion has been taken to logical conclusion by calculating the heat capacity as a function of temperature. Specific heat has been obtained from dispersion curves via density of states in the range 10–400 K using Debye’s relation. The predictive values of specific heat show a typical variation for an one dimensional polymeric system.     

Polariton parametric amplification in semiconductor microcavities

Modifying the photonic environment of a semiconductor quantum well by embedding it in a high-reflectivity microcavity gives rise to new fundamental optical excitations, half-quantum well excitons, half-photons. These particles, called polaritons, have a light mass, as cavity photons, meaning that they have a large De Broglie wavelength. On the other hand, polaritons, like excitons, are subject to Coulomb interaction, a feature generating strong optical nonlinearities. Such properties favour quantum degeneracy and collective phenomena related to the bosonic statistics of polaritons. We review experiments on stimulated scattering of polaritons. In particular we concentrate on the resonant excitation of polaritons somewhere on the dispersion curve and the stimulation of their scattering into the fundamental state by means of an optical probe beam. The process is called polariton parametric amplification and results in very large and ultrafast optical amplification of the probe beam. The model, based on a Hamiltonian of interacting bosons, suggests that the amplification is related to the coherence between polaritons. We demonstrate that in clearly designed samples, this coherence can be preserved almost up to room temperature, so that intersting applications of this phenomenon can be conceived. At the same time we have been able to improve dramatically the efficiency of the parametric process, making the microcavity an unprecedented optical amplifier.     

Mechanical interaction between single-walled carbon nanotubes during the formation of a bundle

This paper investigates the intertubular van der Waals interactions that produce the initial cross sectional distortion of single-walled carbon nanotubes during a bundle formation. By combining the analysis of molecular dynamics with the continuum mechanics, the distributions of the van der Waals forces were determined. The dependence of the load parameters, deformation variables and the lattice constant on the nanotube radius, was also investigated. It was found that the van der Waals forces are attractive and vary circumferentially in a harmonic manner. For the considered zigzag nanotubes of radius 7–14 Å, the intensity of the van der Waals forces is radius-dependent and can be as large as 6–11 GPa in the channels of the bundle and 1–5 GPa at the closest points between the single-walled nanotubes.