1,103 research outputs found
p-Type semiconducting properties in lithium-doped MgO single crystals
The phenomenally large enhancement in conductivity observed when Li-doped MgO
crystals are oxidized at elevated temperatures was investigated by dc and ac
electrical measurements in the temperature interval 250-673 K. The
concentration of ([Li]^{0}) centers (Li^{+} ions each with a trapped hole)
resulting from oxidation was monitored by optical absorption measurements.
Both dc and ac experiments provide consistent values for the bulk resistance.
The electricalconductivity of oxidized MgO:Li crystals increases linearly with
the concentration of ([Li]^{0}) centers. The conductivity is thermally
activated with an activation energy of (0.70 +/- 0.01) eV, which is independent
of the ([Li]^{0}) content. The \textit{standard semiconducting} mechanism
satisfactorily explains these results. Free holes are the main contribution to
band conduction as they are trapped at or released from the ([Li]^{0})-acceptor
centers.
In as-grown MgO:Li crystals, electrical current increases dramatically with
time due to the formation of ([Li]^{0}) centers. The activation energy values
between 1.3 and 0.7 eV are likely a combination of the activation energy for
the creation of ([Li]^{0}) centers and the activation energy of ionization of
these centers. Destruction of ([Li]^{0}) centers can be induced in oxidized
crystals by application of an electric field due to Joule heating up to
temperatures at which ([Li]^{0}) centers are not stable.Comment: LaTeX, 20 pages, 9 Encapsulated Postscript Format Figures, use the
version 4.0 of REVTEX 4 macro packag
Specific heat and high-temperature series of lattice models: interpolation scheme and examples on quantum spin systems in one and two dimensions
We have developed a new method for evaluating the specific heat of lattice
spin systems. It is based on the knowledge of high-temperature series
expansions, the total entropy of the system and the low-temperature expected
behavior of the specific heat as well as the ground-state energy. By the choice
of an appropriate variable (entropy as a function of energy), a stable
interpolation scheme between low and high temperature is performed. Contrary to
previous methods, the constraint that the total entropy is log(2S+1) for a spin
S on each site is automatically satisfied. We present some applications to
quantum spin models on one- and two- dimensional lattices. Remarkably, in most
cases, a good accuracy is obtained down to zero temperature.Comment: 10 pages (RevTeX 4) including 11 eps figures. To appear in Phys. Rev.
Fission Hindrance in hot 216Th: Evaporation Residue Measurements
The fusion evaporation-residue cross section for 32S+184W has been measured
at beam energies of E_beam = 165, 174, 185, 196, 205, 215, 225, 236, 246,and
257 MeV using the ATLAS Fragment Mass Analyzer. The data are compared with
Statistical Model calculations and it is found that a nuclear dissipation
strength, which increases with excitation energy, is required to reproduce the
excitation function. A comparison with previously published data show that the
dissipation strength depends strongly on the shell structure of the nuclear
system.Comment: 15 pages 9 figure
Сутність адміністративного права за новою класифікацією юриспруденції
На основі новітніх підходів до розумінні завдань, об’єктів і класифікації юридичних наук запропонована перспектива розвитку адміністративного права і процесу, які повинні трансформуватися в нові юридичні науки: базисноантиделыктне «Адміністративне право України», процедурне «Админорегламентное право України» та у низку регулятивних юридичних наук, а також розробити Адміністративний кодекс України, Адміно-регламентній кодекс України, відповідні регулятивні кодекси.На основе новейших подходов к понимании задач, объектов и классификации юридических наук предложена перспектива развития административного права и процесса, которые должны трансформироваться в новые юридические науки: базисноантиделиктное «Административное право Украины», процедурное «Админорегламентное право Украины» и ряд регулятивных юридических наук, а также разработать Административный кодекс Украины, Админо-регламентный кодекс Украины, соответствующие регулятивные кодексы.On the basis of the newest fittings to for understanding of tasks, objects and classification of legal sciences the prospect of development of administrative law and process is offered, which must be transformed in new legal sciences: basisuntidelictical the «Administrative law of Ukraine», procedural «Administrative-reglamental law of Ukraine» and the row of regulative legal sciences, and also to develop the Administrative code of Ukraine, Administrative-reglamental code of Ukraine, proper regulative codes
Transient early wheeze and lung function in early childhood associated with chronic obstructive pulmonary disease genes
Background It has been hypothesized that a disturbed early lung development underlies the susceptibility to chronic obstructive pulmonary disease (COPD). Little is known about whether subjects genetically predisposed to COPD show their first symptoms or reduced lung function in c
Dynamic Ordering and Transverse Depinning of a Driven Elastic String in a Disordered Media
We examine the dynamics of an elastic string interacting with quenched
disorder driven perpendicular and parallel to the string. We show that the
string is the most disordered at the depinning transition but with increasing
drive partial ordering is regained. For low drives the noise power is high and
we observe a 1/f^2 noise signature crossing over to a white noise character
with low power at higher drives. For the parallel driven moving string there is
a finite transverse critical depinning force with the depinning transition
occuring by the formation of running kinks.Comment: 4 pages, 4 postscript figure
Production and Decay of D_1(2420)^0 and D_2^*(2460)^0
We have investigated and final states and
observed the two established charmed mesons, the with mass
MeV/c and width MeV/c and
the with mass MeV/c and width
MeV/c. Properties of these final states, including
their decay angular distributions and spin-parity assignments, have been
studied. We identify these two mesons as the doublet predicted
by HQET. We also obtain constraints on {\footnotesize } as a function of the cosine of the relative phase of the two
amplitudes in the decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by
sending mail to: [email protected]
Measurement of the branching fraction for
We have studied the leptonic decay of the resonance into tau
pairs using the CLEO II detector. A clean sample of tau pair events is
identified via events containing two charged particles where exactly one of the
particles is an identified electron. We find . The result is consistent with
expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS
94/1297, CLEO 94-20 (submitted to Physics Letters B
Measurement of the Decay Asymmetry Parameters in and
We have measured the weak decay asymmetry parameters (\aLC ) for two \LC\
decay modes. Our measurements are \aLC = -0.94^{+0.21+0.12}_{-0.06-0.06} for
the decay mode and \aLC = -0.45\pm 0.31 \pm
0.06 for the decay mode . By combining these
measurements with the previously measured decay rates, we have extracted the
parity-violating and parity-conserving amplitudes. These amplitudes are used to
test models of nonleptonic charmed baryon decay.Comment: 11 pages including the figures. Uses REVTEX and psfig macros. Figures
as uuencoded postscript. Also available as
http://w4.lns.cornell.edu/public/CLNS/1995/CLNS95-1319.p
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