PHYTOENE AS A PROTECTIVE AGENT AGAINST SUNBURN (>280nm) RADIATION IN GUINEA PIGS

Abstract— Phytoene, the colorless triene precursor of β-carotene (17 mg/g body weight) or a placebo was given to guinea pigs by daily intraperitoneal injection for 14 days, after which the animals were exposed to radiation (> 280 nm). It was found that the animals receiving phytoene developed significantly less erythema to the radiation than did the animals receiving placebo.     

EFFECT OF FLAME SUPPORT LAYER GEOMETRY AND MATERIALS ON THE RADIANT EFFICIENCY OF GAS RADIANT BURNERS

Parallel rods / tubes flame support layers were used to study variations in geometry and materials on radiant burner performance. An increased density of rods increased the efficiency, as more surface area was provided to extract the heat of combustion. This effect was attenuated far fraction closed areas above 0·33 because of increased interference of direct base-to-load radiation. Thinner rods (with fraction closed area constant), having a lower thermal conduction resistance, fostered higher efficiency. Greater distances between the base and rods decreased efficiency due to air entrainment. This functioned to cool the base, increasing the range of combustion intensities where a portion of combustion lifted from the burner base. Isolation of radiating materials from conducting to the burner housing resulted in a ～ 5% upward shift in efficiency. Low to high efficiency was measured for alumina, mullite, and oxidized stainless steel rods, respectively; this was related directly to the emittances of the materials used. SiC and MoSi₂ coatings on alumina rods resulted in burners which were as efficient as one with stainless steel rods. A burner designed as a restricted band spectral emitter was not as efficient in its high-emission range as a more graybody emitter under the same combustion intensity; the higher-temperature spectral emitter discouraged extraction of sensible heat from the combustion product stream.     

Probing surface plasmons by bare V-shaped tips: modeling by geometrical optics and rigorous diffraction theory

Optical Review - We consider probing inhomogeneous waves in the near fields of metallic nanostructures with the aid of a dielectric V-shaped wedge connected to a waveguide. A geometrical model...     

Dynamic crossover in hydration water of curing cement paste: the effect of superplasticizer

The influence of a new comb-shaped polycarboxylate-based superplasticizer (CSSP) on the hydration kinetics and transport properties of aged cement pastes has been investigated by high-resolution quasi-elastic neutron scattering (QENS) and low temperature differential scanning calorimetry (LT-DSC). A new method of analysis of QENS spectra is proposed. By applying the refined method we were able to access to four independent physical parameters including the self-diffusion coefficient of the hydration water confined in the cement paste. Mean squared displacement (MSD) of the hydrogen atom for mobile water molecules displays a dynamic crossover temperature in agreement with DSC data. The experimental results indicate that CSSP polymer added into cement paste moderates the hydration process and decreases the dynamic crossover temperature of the hydration water.     

Magnetic anisotropy and engineering of magnetic behavior of the edges in Co embedded graphene nanoribbons

Using first-principles calculations, we demonstrate the existence of anisotropic ferromagnetic interactions in Co embedded graphene nanoribbons (GNRs). Spin polarization of the edge states is found to alter significantly compared to the metal-free cases. Our findings can all be well-justified as the output of the interplay between the development of an induced spin polarization in the neighborhood of the Co atoms and the maintaining of the polarization picture of the Co-free GNR. Based on our results, we propose an efficient pathway for graphene-based spintronics applications.     

Magnetic properties of C60 polymers

Magnetic properties of various C60 polymers are calculated using tight-binding molecular-dynamics and ab initio methods. Our results suggest a mechanism involving an interplay between structural defects and sp(3) hybridization to be responsible for the origin of this magnetism. The onset of magnetism is found to occur much more readily for the Rh-C60 polymeric phase with defects than for any of the other polymers, in agreement with the recent experiment. Our estimate of the magnetic moment is also in very good agreement with the value observed in experiment.     

Carbon nanotube "T Junctions": formation pathways and conductivity

Using tight-binding molecular dynamics we simulate the formation of single wall carbon nanotube T junctions via the fusing of two nanotubes. We propose energetically efficient pathways for this process in which all atoms maintain their sp(2) arrangements throughout. Recent experimental advances have greatly increased the plausibility of synthesizing T junctions as proposed in the simulations. We further report I-V characteristics of the formed junctions.     

An analysis of phase-modulated heteronuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance

The design of variants of the swept-frequency two-pulse phase modulation sequence for heteronuclear dipolar decoupling in solid-state NMR is reported, their performance evaluated, and compared with other established sequences like TPPM and SPINAL. Simulations performed to probe the role of the homonuclear (1)H-(1)H bath show that the robustness of the decoupling schemes improves with the size of the bath. In addition, these simulations reveal that the homonuclear (1)H-(1)H bath also leads to broad baselines at high MAS rates. Results from a study of the SPINAL decoupling scheme indicate that optimisation of the starting phase and phase increment improves its performance and efficiency at high MAS rates. Additionally, experiments performed on a liquid crystal display the role of the initial phase in SPINAL-64 and sequences in the SW(f)-TPPM family.     

Essential Amino Acid–Enabled Lead Bromide Perovskite Nanocrystals with High Stability

This work reports the first synthesis of MAPbBr₃ perovskite nanocrystals (PNCs) using amino acids as the ligand with excellent optical properties. A variety of amino acids are used to optimize the luminescence properties. A mechanochemical approach has taken lead over conventional colloidal chemistry during synthesis. All morphological and optical studies are performed to characterize the synthesized perovskite nanoparticles. Later, stability studies are investigated through thermogravimetric analysis, temperature‐dependent photoluminescence, time‐dependent X‐ray diffraction, as well as X‐ray photoelectron spectroscopy. In an application, interestingly, these perovskites show high luminescence upon scratching on flexible conducting plates and on plain paper surface. These results suggest that the amino acid–ligated perovskite nanocrystals can be potential materials for optoelectronic application including light‐emitting diodes and imaging.     

High-resolution solid-state NMR spectroscopy of protons with homonuclear dipolar decoupling schemes under magic-angle spinning

High-resolution NMR spectroscopy of ¹H spins in the solid state is normally rendered difficult due to the strong homonuclear ¹H–¹H dipolar couplings. Even under very high-speed magic-angle spinning (MAS) at ca. 60–70 kHz, these couplings are not completely removed. An appropriate radiofrequency pulse scheme is required to average out the homonuclear dipolar interactions in combination with MAS to get high-resolution ¹H NMR spectrum in solid state. Several schemes have been introduced in the recent past with a variety of applications also envisaged. Development of some of these schemes has been made possible with a clear understanding of the underlying spin physics based on bimodal Floquet theory. The utility of these high-resolution pulse schemes in combination with MAS has been demonstrated for spinning speeds of 10–65 kHz in a range of ¹H Larmor frequencies from 300 to 800 MHz.