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961.
P. Soffitta L. Barbanera E. Costa G. Di Persio M. Feroci B. Martino L. Piro A. Rubini E. Massaro G. Medici G. C. Perola A. Santangelo S. Giarrusso G. La Rosa G. Manzo G. Fazio P. Kaaret R. Novick I. Lapshov R. Sunyaev 《Il Nuovo Cimento C》1993,16(6):703-707
Summary The Stellar X-Ray Polarimeter SXRP will be flown at the focus of the SODART X-ray telescope aboard the Russian satellite SPECTRUM-X-Gamma
by the end of 1995. Four imaging proportional counters will detect photons diffracted by a graphite crystal (2.6 and 5.2 keV)
and scattered from a lithium rod enclosed in a beryllium case (from 5 to 20 KeV). The counters are position-sensitive by the
Wedge and Strip (WS) readout method. The gas mixture is 80% xenon, 10% argon and 10% methane. In this contribution we resume
the results of the measurements performed on the engineering models of the counters. Position resolution of about 1.5 mm is
attained with an energy resolution of about 25%. The pulse shape discrimination offers more than 98%60Co events rejection, with at least 90% X-ray acceptance. Some improvements are foreseen for the flight units in terms of sensitivity
and uniformity of response. 相似文献
962.
The kinetics of the gas phase pyrolyses of methyl 2-bromopropionate and 2-bromopropionic acid were studied in a seasoned, static reaction vessel and under maximum inhibition of the free radical suppressor toluene. The working temperature and pressure range was 310–430°C and 26.5–201.5 torr, respectively. The reactions proved to be homogeneous, unimolecular, and obeys a first-order rate law. The rate coefficients are expressible by the following equations: for methyl 2-bromopropionate, log k1(s?1) = (13.10 ± 0.34) ? (211.4 ± 4.4)kJ mol?1(2.303RT)?1; for 2-bromopropionic acid, log k1(s?1) = (12.41 ± 0.29) ? (180.3 ± 3.4)kJ mol?1(2.303RT)?1. The bromoacid yields acetaldehyde, CO and HBr. Because of this result, the mechanism is believed to proceed via a polar five-membered cyclic transition state. 相似文献
963.
964.
A. Di Pietro G. Cardella A. Musumarra M. Papa G. Pappalardo F. Rizzo A. De Rosa A. D'Onofrio G. Inglima V. Roca M. Romano M. Romoli M. Sandoli F. Terrasi E. Fioretto 《Zeitschrift für Physik A Hadrons and Nuclei》1994,350(3):199-205
The28Si+64Ni reaction at 163.8 MeV incident energy is studied by measuring in coincidenceγ-rays and charged particles identified from Z=2 to Z=16. The transition from quasi-elastic to more damped reactions is observed when the difference between the detected charge and the projectile one is increased. The strong influence of the particle decay on the measuredγ-ray multiplicity is evidenced with the help of the statistical model computer code CASCADE. Dissipative events are well described in the rolling limit with excitation energy equally shared between the fragments. The overall agreement is lost for the fragments with the projectile charge which show a small value of theγ-multiplicity even for dissipative events. This is probably connected with the previously observed non statistical behavior of gamma rays emitted in coincidence with projectile-like fragments. In the alpha-spectrum measured in coincidence with gamma-rays, the deexcitation of fused systems is clearly separated from in flight emission of deep inelastic fragments. The low measured gamma-ray multiplicity for fusion events is qualitatively explained taking into account the effect of alpha-emission in the statistical decay. 相似文献
965.
F. Rizzo G. Cardella A. De Rosa A. Di Pietro A. D'Onofrio E. Fioretto G. Inglima A. Musumarra M. Papa G. Pappalardo M. Romano M. Romoli F. Terrasi M. Sandoli G. S. Wang 《Zeitschrift für Physik A Hadrons and Nuclei》1994,349(2):169-175
It is shown that the Partially Overlapping Molecular Level Model (POMLM) accounts for the experimental results of the dissipative28Si +48Ti collision around 210 MeV incident energy. The general trend of the properties of the fluctuations as well as the average angular distributions are reproduced by the same set of main parameters. A general consistency is also found between the present data and the data obtained in previous work on the same colliding system performed at lower incident energy (around 123 MeV). 相似文献
966.
Duarte-Mermoud Manuel A.; La Rosa Patricio S. 《IMA Journal of Mathematical Control and Information》2003,20(4):387-391
In this paper we investigate the observer design for Single-InputSingle-Output (SISO) systems with unknown input. We find thatthe design conditions proposed by several authors in the pastlead to unity relative degree of the plant and zeros of theplant in the open left half of the complex plane, for SISO systems.In other words an observer for a SISO plant with unknown inputcan be designed if and only if the plant is of unity relativedegree and the numerator of the transfer function is Hurwitz.These conditions have an interesting consequence in the contextof model reference adaptive control (MRAC) for the case of relativedegree one, in the sense that strictly real positive (SPR) conditionfor the model reference is not needed. 相似文献
967.
Joaquin F. Prez-benito Rosa M. Rodriguez Jaime De Andrs Enrique Brillas Jos A. Garrido 《国际化学动力学杂志》1989,21(2):71-81
The permanganate oxidation of L-valine has been studied by visible spectrophotometry in neutral aqueous solutions. Under these conditions, both the zwitterionic and anionic forms of the amino acid are oxidized, the reaction being autocatalyzed by soluble colloidal manganese dioxide. Kinetic data for both the uncatalyzed and autocatalytic reaction pathways have been obtained, and reaction sequences consistent with the experimental findings are proposed. 相似文献
968.
E. Costa L. Piro P. Soffitta E. Massaro G. Matt G. C. Perola S. Giarrusso G. La Rosa G. Manzo A. Santangelo T. Hamilton P. Kaaret C. Martin R. Novick P. Shaw E. Silver R. Elsner M. Weisskopf G. Chanan G. Fraser I. Lapshov R. Sunyaev 《Il Nuovo Cimento C》1992,15(5):791-799
Summary TheStellar X-ray Polarimeter (SXRP) is a focal plane instrument which will be flown on the SPECTRUM-X-Gamma mission in 1993. The polarimeter is composed
of two separate instruments: the first exploits the dependence on the polarization of the Bragg reflection from a graphite
crystal, and of the Thomson scattering from a metallic lithium target. The second instrument makes use of the recently discovered
polarization dependence of X-ray photoemission from CsI. The SXRP will permit sensitive measurements of several hundreds of
known X-ray sources. X-ray polarization measurements will allow us to constrain the physical mechanisms and the geometries
of several classes of galactic X-ray sources, such as X-ray pulsars, black-hole candidates and supernova remnants. Moreover,
and for the first time, SXRP will be able to perform highly sensitive measurements of the brightest extragalactic sources.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
969.
Newton L Dias Filho Devaney R do Carmo Laércio Caetano André H Rosa 《Analytical sciences》2005,21(11):1359-1363
A mercury-sensitive chemically modified graphite paste electrode was constructed by incorporating modified silica gel into a conventional graphite paste electrode. The functional group attached to the (3-chloropropyl) silica gel surface was 2-mercaptoimidazole, giving a new product denoted by 3-(2-thioimidazolyl)propyl silica gel, which is able to complex mercury ions. Mercury was chemically adsorbed on the modified graphite paste electrode containing 3-(2-thioimidazolyl)propyl silica (TIPSG GPE) by immersion in a Hg(II) solution, and the resultant surface was characterized by cyclic and differential pulse anodic stripping voltammetry. One cathodic peak at 0.1 V and other anodic peak at 0.34 V were observed on scanning the potential from -0.1 to 0.8 V (0.01 M KNO3; v = 2.0 mV s(-1) vs. Ag/AgCl). The anodic peak at 0.34 V show an excellent sensitivity for Hg(II) ions in the presence of several foreign ions. A calibration graph covering the concentration range from 0.02 to 2 mg L(-1) was obtained. The detection limit was estimated to be 5 microg L(-1). The precision for six determinations of 0.05 and 0.26 mg L(-1) Hg(II) was 3.0 and 2.5% (relative standard deviation), respectively. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal. 相似文献
970.
EPR spectra of the Er3+, Nd3+, and Ce3+ ions substituting for the Y3+ ion in the YAlO3 yttrium orthoaluminate lattice are studied. The EPR spectra of these rare-earth ions are described by a spin Hamiltonian of rhombic symmetry with an effective spin S=1/2. The principal values of the g tensors were determined from an analysis of the angular dependences of the EPR spectra. The orientation of the local magnetic axes of paramagnetic centers relative to the YAlO3 crystallographic directions are shown to depend on the actual rare-earth species. The EPR spectra exhibit a hyperfine structure due to the 167Er, 143Nd, and 145Nd odd isotopes, which permitted unambiguous identification of these spectra. The hyperfine coupling constants for the odd erbium and neodymium isotopes are determined. 相似文献