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371.
Strong transitions in the 58Ni(3He, α)57Ni reaction were analyzed using both the zero-range and exact finite-range DWBA. Data considered covered a range of bombarding energies from 15 to 205 MeV. The zero-range DWBA described all data well when finite-range and non-locality corrections were included in the local energy approximation. Comparison of zero-range and exact finite-range calculations showed the local energy approximation correction to be very accurate over the entire energy region. Empirically determined D0 values showed no energy dependence. A theoretical D0 value calculated using an α wave function which reproduced the measured α rms charge radius and the elastic electron scattering form factor agreed well with the empirical values. Comparison was made between these values and D0 values quoted previously in the literature. 相似文献
372.
L.K. Fifield T.J.M. Symons C.H. Zimmerman M.J. Hurst F. Watt K.W. Allen 《Physics letters. [Part B]》1977,68(2):125-128
Levels at 7.17, 8.29, 8.96 and 9.88 MeV in 19F have been assigned spin and parity , , and , respectively, from resonance strength and γ-ray angular distribution measurements employing the 15N(α,γ) 19F reaction. An earlier assignment of to the 8.96 MeV level is incorrect. The measured properties of the states are compared with the results of both SU (3) shell model and cluster model calculations. 相似文献
373.
Formaggio JA Zimmerman ED Adams T Alton A Avvakumov S de Barbaro L de Barbaro P Bernstein RH Bodek A Bolton T Brau J Buchholz D Budd H Bugel L Case S Conrad JM Drucker RB Fleming BT Frey R Goldman J Goncharov M Harris DA Johnson RA Kim JH Koutsoliotas S Lamm MJ 《Physical review letters》2000,84(18):4043-4046
The E815 (NuTeV) neutrino experiment has performed a search for a 33. 9 MeV/c(2) weakly interacting neutral particle produced in pion decay. Such a particle may be responsible for an anomaly in the timing distribution of neutrino interactions in the KARMEN experiment. E815 has searched for this particle's decays in an instrumented decay region; no evidence for this particle was found. The search is sensitive to pion branching ratios as low as 10(-13). 相似文献
374.
In continuing our investigations on rodlike molecules composed of bicyclo[2.2.2]octane units, we studied the effect of interposing a single aromatic ring in the rod. Thus, two [3]-rods were synthesized with the two outer units being bicyclooctyls, the central unit being benzenoid, and with one terminal unit bearing an alpha-naphthyl moiety and the other terminus bearing an acetyl or benzoyl group. Excitation of the alpha-naphthyl group led to fluorescence emission by both the naphthyl and the acetyl units. However, compared to the [1]- and [2]-rods previously studied, transmission of singlet excitation proved to be less efficient as determined by the fluorescence emission and also by the singlet lifetimes obtained from single photon counting measurement. Transmission to the benzoyl group proved more rapid than to the acetyl moiety. In assessing the factors controlling energy transmission, Delta-density determinations were employed to describe the distribution of electronic excitation in such systems. It was observed that despite most of the energy being located in the terminal chromophores, some is distributed in the bicyclooctyl units. The extent of this distribution provides a guide to the facility of through-bond energy transfer. Evidence is presented that energy transfer in the short rods is mainly through-bond while in the longer rods Forster through-space transfer is involved. 相似文献
375.
T. N. Mamedov D. G. Andrianov D. Gerlach K. I. Gritsai V. N. Gorelkin O. Cormann J. Major A. V. Stoikov M. Shevchik U. Zimmerman 《JETP Letters》2000,71(10):438-441
Temperature-dependent remanent polarization of negative muons in a silicon crystal doped with phosphorus (3.2 × 1012, 2.3 × 1015, and 4.5 × 1018 cm?3) and aluminum (2 × 1014 and 2.4 × 1018 cm?3) was examined. Measurements were made over the temperature range 4–300 K in a magnetic field of 2000 G perpendicular to the muon spin. Temperature dependence of the relaxation rate was determined for the magnetic moment of a shallow Al acceptor center in a nondeformed silicon sample, and the hyperfine interaction constant was estimated for the interaction between the magnetic moments of muon and electron shell of the muonic mAl atom in silicon. 相似文献
376.
Abdul-Majeed WS Parada JH Zimmerman WB 《Analytical and bioanalytical chemistry》2011,401(9):2713-2722
In this work, an optimization study was conducted to investigate the performance of a custom-designed miniaturized dielectric
barrier discharge (DBD) microplasma chip to be utilized as a radiation source for mercury determination in water samples.
The experimental work was implemented by using experimental design, and the results were assessed by applying statistical
techniques. The proposed DBD chip was designed and fabricated in a simple way by using a few microscope glass slides aligned
together and held by a Perspex chip holder, which proved useful for miniaturization purposes. Argon gas at 75–180 mL/min was
used in the experiments as a discharge gas, while AC power in the range 75–175 W at 38 kHz was supplied to the load from a
custom-made power source. A UV-visible spectrometer was used, and the spectroscopic parameters were optimized thoroughly and
applied in the later analysis. Plasma characteristics were determined theoretically by analysing the recorded spectroscopic
data. The estimated electron temperature (T
e = 0.849 eV) was found to be higher than the excitation temperature (T
exc = 0.55 eV) and the rotational temperature (T
rot
= 0.064 eV), which indicates non-thermal plasma is generated in the proposed chip. Mercury cold vapour generation experiments
were conducted according to experimental plan by examining four parameters (HCl and SnCl2 concentrations, argon flow rate, and the applied power) and considering the recorded intensity for the mercury line (253.65 nm)
as the objective function. Furthermore, an optimization technique and statistical approaches were applied to investigate the
individual and interaction effects of the tested parameters on the system performance. The calculated analytical figures of
merit (LOD = 2.8 μg/L and RSD = 3.5%) indicates a reasonable precision system to be adopted as a basis for a miniaturized
portable device for mercury detection in water samples. 相似文献
377.
Total Reflection X-ray Fluorescence (TXRF) is a well-established technique for chemical analysis, but it is mainly employed for quality control in the electronics semiconductor industry. The capability to analyze liquid and uniformly thin solid samples makes this technique suitable for other applications, and especially in the very critical field of environmental analysis. Comparison with standard methods like inductively coupled plasma (ICP) and atomic absorption spectroscopy (AAS) shows that TXRF is a practical, accurate, and reliable technique in occupational settings. Due to the greater sensitivity necessary in trace heavy metal detection, TXRF is also suitable for environmental chemical analysis. In this paper we show that based on appropriate standards, TXRF can be considered for non-destructive routine quantitative analysis of environmental matrices such as air filters. This work has been developed in the frame of the EU-FP6 PHIME (Public Health Impact of long-term, low-level Mixed element Exposure in susceptible population strata) Integrated Project (www.phime.org). The aim of this work was to investigate Mn air pollution in the area of Vallecamonica (Italy). 相似文献
378.
Yang SK Shi X Park S Doganay S Ha T Zimmerman SC 《Journal of the American Chemical Society》2011,133(26):9964-9967
Herein we report the synthesis of water-soluble polyglycerol-dendronized perylenediimides with a single reactive group that undergoes high-yielding click reactions. Single-molecule studies and target-specific biolabeling are reported, including the highly specific labeling of proteins on the surface of living bacterial and mammalian cells. 相似文献
379.
380.
Density functional theory has been used to elucidate the mechanistic underpinnings of the regeneration of ammonia-borane (H3B−NH3, AB ) from polyborazylene (BxNxHx, PBz ) in the presence of hydrazine (H2N−NH2, Hz ). Herein, borazine (B3N3H6, Bz ) is used as the simplest relevant model of PBz for the regeneration process. Digestion of Bz using Hz was found to occur by a string of Lewis acid base adduct (between B atoms of Bz and Hz molecule) formation and Hz assisted proton transfer processes. Later, B−H bonds of HB(NHNH2)2, the Bz digested product, are redistributed to form hydrazine-borane (H3B−NH2NH2, HzB ) and B(NHNH2)3. Redistribution of B−H bonds occurs through hydroboration and concerted proton-hydride transfer. Another B−H redistributed product, B(NHNH2)3, produces HzB as a result of proton and hydride transfer from cis-diazene ( Dz ), the oxidized product of Hz in presence of O2. 相似文献