Stopping power effects in the determination of14N by a resonance reaction

The applicability of the¹⁴N(p,p’ γ₁)¹⁴N nuclear reaction in the determination of the absolute abundance of¹⁴N, with a 2% uncertainty, was demonstrated at 4.3 MeV bombarding energy. The fact that almost all of the thick target γ-ray yield resulted from a resonance at Ep=4.0 MeV allowed to consider the necessary stopping-power corrections only at the energy of that resonance. Alternatively, the method was used to obtain the stopping power of 4.0 MeV protons in complex biological materials. Supported in part by the International Atomic Energy Agency, Vienna, Austria.     

Continuous nitrogen-doped carbon nanotube matrix for boosting oxygen electrocatalysis in rechargeable Zn-air batteries

Developing robust oxygen electrocatalyst with high-performance is very significant for practical rechargeable Zn-air battery.We report herein the preparation of three-dimensional continuous nanocarbon network composed of interconnected nitrogen-doped carbon nanotubes and its application as oxygen electrocatalysis in rechargeable Zn-air battery.Except the excellent electrochemical bifunctionality,this carbon nanotube matrix also delivers an impressive battery performance.Specifically,an opencircuit voltage of 1.50 V as well as a high power density of 220 m W cm^-2 with remarkable cycling stability for 1600 h is achieved in the rechargeable Zn-air battery.The study not only provides an efficient bifunctional oxygen electrocatalyst but more importantly may pave significant concepts in designing robust electrode for long-life rechargeable Zn-air battery and other energy technologies.     

An Overview on the Synthesis of Fused Pyridocoumarins with Biological Interest

Pyridocoumarins are a class of synthetic and naturally occurring organic compounds with interesting biological activities. This review focuses on the synthetic strategies for the synthesis of pyridocoumarins and presents the biological properties of those compounds. The synthesis involves the formation of the pyridine ring, at first, from a coumarin derivative, such as aminocoumarins, hydroxycoumarins, or other coumarins. The formation of a pyranone moiety follows from an existing pyridine or piperidine or phenol derivative. For the above syntheses, [4 + 2] cycloaddition reactions, multi-component reactions (MCR), as well as metal-catalyzed reactions, are useful. Pyridocoumarins present anti-cancer, anti-HIV, antimalarial, analgesic, antidiabetic, antibacterial, antifungal, anti-inflammatory, and antioxidant activities.     

A method for determining the location and depth of cracks in double-cracked beams

The influence of two transverse open cracks on the antiresonances of a double cracked cantilever beam is investigated both analytically and experimentally. It is shown that there is a shift in the antiresonances of the cracked beam depending on the location and size of the cracks. These antiresonance changes, complementary with natural frequency changes, can be used as additional information carrier for crack identification in double cracked beams. Experimental results from tests on plexiglas beams damaged at different locations and different magnitudes are found to be in good agreement with theoretical predictions. Based on the results of the present work, an efficient prediction scheme for crack localization and characterization in double cracked beams is proposed.     

The stability of biological specimens during charged particle bombardment

Consecutive short bombardment of thick biological specimens with proton beams demonstrated that the yield from oxygen decreases with increasing amounts of total deposited beam; those from carbon and sulfur appear not to be affected, while significant yield increases are observed with respect to the γ-ray yields of all the other investigated isotopic nuclear reactions. The yield alterations were investigated in freeze-dried plant and animal specimens as well as in targets prepared by air drying at several temperatures. Only in ashed specimens do the γ-ray yields remain constant as a function of increasing amounts of deposited beam. The yield alterations induced by the beam on non-ashed biological specimens depend on (I) the total dissipated beam charge, (II) energy of the beam, (III) chemical element, (IV) origin of the biological specimen, and (V) method of preparation of the target. The underlying mechanism and implications of the yield alterations in the elemental analysis of non-ashed biological specimens are investigated and discussed.     

Mechanism of oxidation of 1-benzyl-1,4-dihydronicotinamide by the biologically active p-benzoquinone derivative, avarone, in a cationic micellar medium: An electrochemical approach

The electrochemical reduction of avarone (Q), an antitumor sesquiterpenoid quinone, was investigated at various pH in aqueous ethanol containing a cationic surfactant, cetyltrimethylammonium bromide (CTAB) by cyclic and rotating disc electrode voltammetry, using a glassy carbon electrode. Comparison of the electrochemical reduction of Q in presence of CTAB with the same process in a homogeneous water + ethanol solution shows an anodic shift of the reduction potential in the presence of CTAB; at pH > 9.5 and in presence of CTAB, two well-defined reduction peaks are observed, thus confirming one-electron reduction of Q, whereby the intermediate radical-anion is stabilized by the cationic micellar medium. The electrochemical oxidation of BNAH was investigated by cyclic voltammetry, and the anodic shift of the peak potential in presence of CTAB was observed. From the electrochemical behaviour of Q and BNAH, and the kinetics of the oxidation of BNAH with Q, it is suggested that the reaction takes place in two successive one-electron transfer steps. The application of the Marcus theory gives additional proof that, in this case, the first electron transfer is the rate determining step.     

Long term radioactive uptake by two pasture plants in a field contaminated by the Chernobyl fallout

The radioactive content of alfalfa and rye grass was measured in five consecutive harvests covering a period of one and a half years after the contamination of a field caused by the Chernobyl fallout. The measured long-lived isotopes were¹⁰⁶Ru,¹³⁴Cs and¹³⁷Cs. In the first four harvests alfalfa contained significantly less radioactivity than rye grass, while in the last harvest both plants contained comparable levels of radioactivity. The results from the first harvest, demonstrating the radioactivity obtained in the direct fallout, indicate that the fraction of total initial deposition retained on rye grass is by 55% and 70% greater than alfalfa for Cs and Ru isotopes, respectively. The second, third and fourth harvests demonstrate values of plant to soil concentration ratios /CR/ considerably larger than those observed in the fifth harvest. Only the CR values obtained in the last harvest overlap with commensurate values previously reported in the literature.     

A Ninhydrin‐Type Urea Sorbent for the Development of a Wearable Artificial Kidney

The aim of this study is to develop polymeric chemisorbents with a high density of ninhydrin groups, able to covalently bind urea under physiological conditions and thus potentially suitable for use in a wearable artificial kidney. Macroporous beads are prepared by suspension polymerization of 5‐vinyl‐1‐indanone (vinylindanone) using a 90:10 (v/v) mixture of toluene and nitrobenzene as a porogen. The indanone groups are subsequently oxidized in a one‐step procedure into ninhydrin groups. Their urea absorption kinetics are evaluated under both static and dynamic conditions at 37 °C in simulated dialysate (urea in phosphate buffered saline). Under static conditions and at a 1:1 molar ratio of ninhydrin: urea the sorbent beads remove ≈0.6–0.7 mmol g^?1 and under dynamic conditions and at a 2:1 molar excess of ninhydrin ≈0.6 mmol urea g^?1 sorbent in 8 h at 37 °C, which is a step toward a wearable artificial kidney.     

Suppression of charge-induced yield increases in PIGE analysis of biological specimens

A simple target-moving system, in which the movement of the target is achieved by externally moving the whole miniature scattering chamber, was developed and tested as a means for suppressing -ray yield increase induced by proton beams in biological specimens. Although there is a limit in the total beam charge which may be safely deposited on a moving biological target, the duration of the safe bombardment is sufficiently prolonged by the motion to allow the accumulation of meaningful statistics.     

Electrochemical reduction of p-nitrosodiphenylamine in, a cationic micellar system

The electroreduction of p-nitrosodiphenylamine (p-NDPA) in an alkaline aqueous solution containing cetyltrimethylammonium bromide (CTAB) as a cationic surfactant was investigated by polarography, cyclic and rotating disc voltammetry. It was found that the reduction of p-NDPA in cationic micellar systems takes place by the ECE mechanism, and, compared to the reduction of the same compound in a homogeneous water solution, has a somewhat lower rate of the overall electrode reaction. The lower reaction rate of p-NDPA reduction in micellar medium is probably due to three main factors: solubilization of p-NDPA in CTAB micelles, adsorption of monomeric surfactant species at the electrode surface and a lower rate of the base catalyzed dehydration reaction (C-step) in the micellar system.