Emergency Dose Estimation Using Optically Stimulated Luminescence from Human Tooth Enamel

Human teeth were studied for potential use as emergency Optically Stimulated Luminescence (OSL) dosimeters. By using multiple-teeth samples in combination with a custom-built sensitive OSL reader, (60)Co-equivalent doses below 0.64 Gy were measured immediately after exposure with the lowest value being 27 mGy for the most sensitive sample. The variability of OSL sensitivity, from individual to individual using multiple-teeth samples, was determined to be 53%. X-ray and beta exposure were found to produce OSL curves with the same shape that differed from those due to ultraviolet (UV) exposure; as a result, correlation was observed between OSL signals after X-ray and beta exposure and was absent if compared to OSL signals after UV exposure. Fading of the OSL signal was "typical" for most teeth with just a few of incisors showing atypical behavior. Typical fading dependences were described by a bi-exponential decay function with "fast" (decay time around of 12 min) and "slow" (decay time about 14 h) components. OSL detection limits, based on the techniques developed to-date, were found to be satisfactory from the point-of-view of medical triage requirements if conducted within 24 hours of the exposure.     

State-insensitive cooling and trapping of single atoms in an optical cavity

Single cesium atoms are cooled and trapped inside a small optical cavity by way of a novel far-off-resonance dipole-force trap, with observed lifetimes of 2-3 s. Trapped atoms are observed continuously via transmission of a strongly coupled probe beam, with individual events lasting approximately 1 s. The loss of successive atoms from the trap N>/=3-->2-->1-->0 is thereby monitored in real time. Trapping, cooling, and interactions with strong coupling are enabled by the trap potential, for which the center-of-mass motion is only weakly dependent on the atom's internal state.     

Observation of the vacuum Rabi spectrum for one trapped atom

The transmission spectrum for one atom strongly coupled to the field of a high finesse optical resonator is observed to exhibit a clearly resolved vacuum Rabi splitting characteristic of the normal modes in the eigenvalue spectrum of the atom-cavity system. A new Raman scheme for cooling atomic motion along the cavity axis enables a complete spectrum to be recorded for an individual atom trapped within the cavity mode, in contrast to all previous measurements in cavity QED that have required averaging over 10(3)-10(5) atoms.     

UV LASER INDUCED RNA-PROTEIN CROSSLINKS AND RNA CHAIN BREAKS IN TOBACCO MOSAIC VIRUS RNA in situ

The efficiency of RNA-protein crosslink and RNA chain break formation under nanosecond or picosecond UV-laser pulse irradiation of tobacco mosaic virus was determined. It was found that on high-intensity UV-laser irradiation the quantum yields of both reactions increase considerably as compared to the usual (low-intensity) UV-irradiation. The RNA-protein crosslink quantum yield was found to be 1.8 x 10(-5) and 1.2 x 10(-4) and that of RNA chain breaks 1.7 x 10(-4) and 8.9 x 10(-4) for nanosecond and picosecond irradiation, respectively.     

Application of Precipitation-based and Nanoparticle-based Techniques for Fabrication of Potentiometric Sensors for Nano Molar Determination of Chitosan and Polyvinyl Pyrrolidone in Pharmaceutical Formulations and Biological Fluids

Chitosan (CH) is one of the most abundant biopolymers with multiple applications. Polyvinyl pyrrolidone (PVP) has specific binding and detoxification properties that are of great interest in health care. Hence, it arises a crucial urge to develop economic sensors to analyze CH and PVP in pharmaceutical formulations and biological samples. Two portable sensors were fabricated using precipitation-based technique, and nanoparticles-based technique, for determination of CH and PVP in sensor 1 and 2; respectively. Linear responses of 10⁻⁵ to10⁻⁷ M and 10⁻² to10⁻⁷ M at pH 3.6–4.8 and 7.2–8.4, with ideal Nernstian slopes of 60.00 and 59.83 mV /decade, and nanomolar LODs of 94.90 and 81.20 nM were observed for CH and PVP; respectively. The percentage recoveries were 100.40±1.03 and 100.19±0.64 for sensors 1 and 2; respectively. Both sensors were successfully applied in biological fluids without pre-treatment. Accurate results were obtained using sensor 1, in pure form, pharmaceutical formulations, human plasma, rat liver and rat brain, as well as sensor 2, in pure form, pharmaceutical formulations and urine samples. The results were statistically compared with the reported methods and no significant difference was observed.     

Characteristics of LM-OSL from several different types of quartz

We present Linear-Modulation OSL (LM-OSL) curves from several different types of quartz, including sedimentary quartz, bulk rock crystal and synthetic quartz. The LM-OSL method consists of linearly increasing the intensity of the stimulation light while continuously monitoring the OSL emission from the sample. With this technique, one obtains peaks of luminescence intensity versus time (Bulur, 1996) in which the position of the peak is inversely related to the photoionization cross-section of the trap. The shape of the LM-OSL curve is directly related to the shape of the conventional OSL decay curve in which the stimulating light source is maintained at constant intensity (so-called Continuous-Wave OSL, or CW-OSL). In the latter, the OSL from the traps with the highest photoionization cross-section decays most rapidly with stimulation time, while OSL from those traps with smaller photoionization cross-sections is characterized by longer decay times. In this paper, data are presented comparing the CW-OSL and LM-OSL curves for several different quartz types with particular focus on the changes in the shapes of each of these curves with sample type pre-heat temperature, and measurement temperature. Several different LM-OSL components are found for each sample, each with different photoionization cross-sections, but a universal behavior for quartz is not observed; each sample is different. From the dependence upon pre-heat temperature, features associated with shallow traps can be identified. Traps which empty very rapidly can be observed more easily in the LM-OSL curves than in the conventional CW-OSL curves, and the temperature dependence of the photoionization cross-section for the various components can be clearly discerned.     

Stereoselective Synthesis of Tetrahydroindolizines through the Catalytic Formation of Pyridinium Ylides from Diazo Compounds

Commercially available iron(III) and copper(I) complexes catalyzed multicomponent cycloaddition reactions between diazo compounds, pyridines, and electrophilic alkenes to give alkaloid‐inspired tetrahydroindolizidines in high yield with high diastereoselectivity. Hitherto, the catalytic formation of versatile pyridinium ylides from metal carbenes has been poorly developed; the broad utility demonstrated herein sets the stage for the invention of further multicomponent reactions in future.     

Total synthesis of mollamide, a reverse prenyl substituted cytotoxic cyclic peptide from Didemnum molle

A total synthesis of the novel reverse prenyl substituted cyclic peptide mollamide, isolated from the ascidian Didemnum molle, is described.