242 research outputs found
Diffusion-limited reaction for the one-dimensional trap system
We have previously discussed the one-dimensional multitrap system of finite
range and found the somewhat unexpected result that the larger is the number of
imperfect traps the higher is the transmission through them. We discuss in this
work the effect of a small number of such traps arrayed along either a constant
or a variable finite spatial section. It is shown that under specific
conditions, to be described in the following, the remarked high transmission
may be obtained for this case also. Thus, compared to the theoretical large
number of traps case these results may be experimentally applied to real
phenomenaComment: 18 pages, 8 PS Figures; 3 former figures were removed, a new section
added and the representation is improve
Generalized Statistics and High Tc Superconductivity
Introducing the generalized, non-extensive statistics proposed by
Tsallis[1988], into the standard s-wave pairing BCS theory of superconductivity
in 2D yields a reasonable description of many of the main properties of high
temperature superconductors, provided some allowance is made for non-phonon
mediated interactions.Comment: 14 pages, 5 figure
Creating diamond color centers for quantum optical applications
Nitrogen vacancy (NV) centers in diamond have distinct promise as solid-state
qubits. This is because of their large dipole moment, convenient level
structure and very long room-temperature coherence times. In general, a
combination of ion irradiation and subsequent annealing is used to create the
centers, however for the rigorous demands of quantum computing all processes
need to be optimized, and decoherence due to the residual damage caused by the
implantation process itself must be mitigated. To that end we have studied
photoluminescence (PL) from NV, NV and GR1 centers formed by ion
implantation of 2MeV He ions over a wide range of fluences. The sample was
annealed at C to minimize residual vacancy diffusion, allowing for
the concurrent analysis of PL from NV centers and irradiation induced vacancies
(GR1). We find non-monotic PL intensities with increasing ion fluence,
monotonic increasing PL in NV/NV and GR1/(NV + NV) ratios, and
increasing inhomogeneous broadening of the zero-phonon lines with increasing
ion fluence. All these results shed important light on the optimal formation
conditions for NV qubits. We apply our findings to an off-resonant photonic
quantum memory scheme using vibronic sidebands
Associations of depression and anxiety symptoms with sexual behaviour in women and heterosexual men attending sexual health clinics: a cross-sectional study.
OBJECTIVE: To assess the association of symptoms of depression and anxiety with sexual risk behaviour and history, among women and heterosexual men attending genitourinary medicine (GUM) clinics. METHODS: Attitudes to and Understanding of Risk of Acquisition of HIV (AURAH) was a cross-sectional, self-administered questionnaire study recruited from 20 GUM clinics in England, 2013-2014. This analysis included women and heterosexual men. The prevalence of depression and anxiety symptoms was assessed. Modified Poisson regression was used to produce adjusted prevalence ratios (aPR) for the association of t demographic, socioeconomic and lifestyle factors with depression and anxiety, adjusted for gender, age, ethnicity, education level and study region. Among individuals reporting sex in the past 3âmonths, associations of depression and anxiety with sexual risk behaviour and history were assessed separately by gender, adjusted for age, ethnicity, study region, education and relationship status. RESULTS: Questionnaires were completed by 676 women and 470 heterosexual men. Depression symptoms were reported by 100 (14.8%) women and 33 men (7.0%). Anxiety symptoms were reported by 79 women (11.7%) and 21 men (4.5%). Among women reporting recent sex, those with depression symptoms were more likely to report condomless sex with a non-regular partner, aPR 1.38 (1.07-1.77) and recent condomless sex with two or more partners, 1.80 (1.25-2.59). Women with anxiety symptoms more likely to report recent condomless sex with two or more partners, 1.68 (1.13-2.50), low self-efficacy for condom use, 1.54 (1.02-2.31) and STI diagnosis in the last year 1.51 (1.04-2.20). Among heterosexual men reporting recent sex, depression and anxiety symptoms were associated with low self-efficacy with condom use, 2.32 (1.29-4.19) for depression and 2.23 (1.26-3.94) for anxiety, but not with measures of condomless sex. DISCUSSION: The associations between psychological symptoms and sexual risk behaviours highlight the importance of holistic assessment of need by both general and sexual health clinicians. We highlight the challenge in delivering holistic care associated with fragmentation of sexual health services
From the Big Bang Theory to the Theory of a Stationary Universe
We consider chaotic inflation in the theories with the effective potentials
phi^n and e^{\alpha\phi}. In such theories inflationary domains containing
sufficiently large and homogeneous scalar field \phi permanently produce new
inflationary domains of a similar type. We show that under certain conditions
this process of the self-reproduction of the Universe can be described by a
stationary distribution of probability, which means that the fraction of the
physical volume of the Universe in a state with given properties (with given
values of fields, with a given density of matter, etc.) does not depend on
time, both at the stage of inflation and after it. This represents a strong
deviation of inflationary cosmology from the standard Big Bang paradigm. We
compare our approach with other approaches to quantum cosmology, and illustrate
some of the general conclusions mentioned above with the results of a computer
simulation of stochastic processes in the inflationary Universe.Comment: No changes to the file, but original figures are included. They
substantially help to understand this paper, as well as eternal inflation in
general, and what is now called the "multiverse" and the "string theory
landscape." High quality figures can be found at
http://www.stanford.edu/~alinde/LLMbigfigs
The antiferromagnetic phi4 Model, I. The Mean-field Solution
Certain higher dimensional operators of the lagrangian may render the vacuum
inhomogeneous. A rather rich phase structure of the phi4 scalar model in four
dimensions is presented by means of the mean-field approximation. One finds
para- ferro- ferri- and antiferromagnetic phases and
commensurate-incommensurate transitions. There are several particles described
by the same quantum field in a manner similar to the species doubling of the
lattice fermions. It is pointed out that chiral bosons can be introduced in the
lattice regularized theory.Comment: To appear in Phys. Rev.
An enhanced gas ionization sensor from Y-doped vertically aligned conductive ZnO nanorods
A stable and highly sensitive gas ionization sensor (GIS) constructed from vertically aligned, conductive yttriumâdoped ZnO nanorod (YZO NR) arrays is demonstrated. The conductive YZO NRs are synthesized using a facile one-pot hydrothermal method. At higher Y/Zn molar ratio, the aspect ratio of the YZO NRs is increased from 11 to 25. Doping with yttrium atoms decreases the electrical resistivity of ZnO NRs more than 100 fold. GIS measurements reveal a 6-fold enhancement in the sensitivity accompanied with a significant reduction in breakdown voltage from the highly conductive YZO NRs. Direct correlations between the resistivity of the NRs and GIS characteristics are established
Canonical moments and random spectral measures
We study some connections between the random moment problem and the random
matrix theory. A uniform draw in a space of moments can be lifted into the
spectral probability measure of the pair (A,e) where A is a random matrix from
a classical ensemble and e is a fixed unit vector. This random measure is a
weighted sampling among the eigenvalues of A. We also study the large
deviations properties of this random measure when the dimension of the matrix
grows. The rate function for these large deviations involves the reversed
Kullback information.Comment: 32 pages. Revised version accepted for publication in Journal of
Theoretical Probabilit
Monopolium: the key to monopoles
Dirac showed that the existence of one magnetic pole in the universe could offer an explanation for the discrete nature of the electric charge. Magnetic poles appear naturally in most Grand Unified Theories. Their discovery would be of greatest importance for particle physics and cosmology. The intense experimental search carried thus far has not met with success. Moreover, if the monopoles are very massive their production is outside the range of present day facilities. A way out of this impasse would be if the monopoles bind to form monopolium, a monopole- antimonopole bound state, which is so strongly bound, that it has a relatively small mass. Under these circumstances it could be produced with present day facilities and the existence of monopoles could be indirectly proven. We study the feasibility of detecting monopolium in present and future accelerators
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