543 research outputs found
One-Dimensional Extended States in Partially Disordered Planar Systems
We obtain analytically a continuum of one-dimensional ballistic extended
states in a two-dimensional disordered system, which consists of compactly
coupled random and pure square lattices. The extended states give a marginal
metallic phase with finite conductivity in a wide energy
range, whose boundaries define the mobility edges of a first-order
metal-insulator transition. We show current-voltage duality,
scaling of the conductivity in parallel magnetic field and
non-Fermi liquid properties when long-range electron-electron interactions are
included.Comment: 4 pages, revtex file, 3 postscript file
Antiferromagnetic resonance in ferroborate NdFe(BO)$_4
The AFMR spectra of the NdFe(BO) crystal are measured in a wide
range of frequencies and temperatures. It is found that by the type of magnetic
anisotropy the compound is an "easy-plane" antiferromagnet with a weak
anisotropy in the basal plane. The effective magnetic parameters are
determined: anisotropy fields =1.14 kOe and =60 kOe and
magnetic excitation gaps =101.9 GHz and =23.8 GHz.
It is shown that commensurate-incommensurate phase transition causes a shift in
resonance field and a considerable change in absorption line width.
At temperatures below 4.2 K nonlinear regimes of AFMR excitation at low
microwave power levels are observed
Diffusion and Localization of Cold Atoms in 3D Optical Speckle
In this work we re-formulate and solve the self-consistent theory for
localization to a Bose-Einstein condensate expanding in a 3D optical speckle.
The long-range nature of the fluctuations in the potential energy, treated in
the self-consistent Born approximation, make the scattering strongly velocity
dependent, and its consequences for mobility edge and fraction of localized
atoms have been investigated numerically.Comment: 8 pages, 11 figure
Noise Can Reduce Disorder in Chaotic Dynamics
We evoke the idea of representation of the chaotic attractor by the set of
unstable periodic orbits and disclose a novel noise-induced ordering
phenomenon. For long unstable periodic orbits forming the strange attractor the
weights (or natural measure) is generally highly inhomogeneous over the set,
either diminishing or enhancing the contribution of these orbits into system
dynamics. We show analytically and numerically a weak noise to reduce this
inhomogeneity and, additionally to obvious perturbing impact, make a
regularizing influence on the chaotic dynamics. This universal effect is rooted
into the nature of deterministic chaos.Comment: 11 pages, 5 figure
Universality of the critical conductance distribution in various dimensions
We study numerically the metal - insulator transition in the Anderson model
on various lattices with dimension (bifractals and Euclidian
lattices). The critical exponent and the critical conductance
distribution are calculated. We confirm that depends only on the {\it
spectral} dimension. The other parameters - critical disorder, critical
conductance distribution and conductance cummulants - depend also on lattice
topology. Thus only qualitative comparison with theoretical formulae for
dimension dependence of the cummulants is possible
The second International Symposium on Fungal Stress: ISFUS
The topic of ‘fungal stress’ is central to many important disciplines, including medical mycology, chronobiology, plant and insect pathology, industrial microbiology, material sciences, and astrobiology. The International Symposium on Fungal Stress (ISFUS) brought together researchers, who study fungal stress in a variety of fields. The second ISFUS was held in May 8-11 2017 in Goiania, Goiás, Brazil and hosted by the Instituto de Patologia Tropical e Saúde Pública at the Universidade Federal de Goiás. It was supported by grants from CAPES and FAPEG. Twenty-seven speakers from 15 countries presented their research related to fungal stress biology. The Symposium was divided into seven topics: 1. Fungal biology in extreme environments; 2. Stress mechanisms and responses in fungi: molecular biology, biochemistry, biophysics, and cellular biology; 3. Fungal photobiology in the context of stress; 4. Role of stress in fungal pathogenesis; 5. Fungal stress and bioremediation; 6. Fungal stress in agriculture and forestry; and 7. Fungal stress in industrial applications. This article provides an overview of the science presented and discussed at ISFUS-2017.Sao Paulo Research Foundation (FAPESP) 2010/06374-1, 2013/50518-6, 2014/01229-4Brazilian National Council for Scientific and Technological Development (CNPq) PQ2 302312/2011-0, PQ1D 308436/2014-8Coordenação de Aperfeiçoãmento de Pessoal de NÃvel Superior (CAPES) PAEP 88881.123209/2016-01Fundação de Amparo à Pesquisa do Estado de Goiás Brazil 20171026700011
Primakoff effect in eta-photoproduction off protons
We analyse data on forward eta-meson photoproduction off a proton target and
extract the eta to gamma gamma decay width utilizing the Primakoff effect. The
hadronic amplitude that enters into our analysis is strongly constrained
because it is fixed from a global fit to available gamma p to p eta data for
differential cross sections and polarizations. We compare our results with
present information on the two-photon eta-decay from the literature. We provide
predictions for future PrimEx experiments at Jefferson Laboratory in order to
motivate further studies.Comment: 5 pages, 6 figures, gamma-gamma*-eta form factor included, version to
appear in Eur. Phys. J. A
Eureka and beyond: mining's impact on African urbanisation
This collection brings separate literatures on mining and urbanisation together at a time when both artisanal and large-scale mining are expanding in many African economies. While much has been written about contestation over land and mineral rights, the impact of mining on settlement, notably its catalytic and fluctuating effects on migration and urban growth, has been largely ignored. African nation-states’ urbanisation trends have shown considerable variation over the past half century. The current surge in ‘new’ mining countries and the slow-down in ‘old’ mining countries are generating some remarkable settlement patterns and welfare outcomes. Presently, the African continent is a laboratory of national mining experiences. This special issue on African mining and urbanisation encompasses a wide cross-section of country case studies: beginning with the historical experiences of mining in Southern Africa (South Africa, Zambia, Zimbabwe), followed by more recent mineralizing trends in comparatively new mineral-producing countries (Tanzania) and an established West African gold producer (Ghana), before turning to the influence of conflict minerals (Angola, the Democratic Republic of Congo and Sierra Leone)
Stellar structure and compact objects before 1940: Towards relativistic astrophysics
Since the mid-1920s, different strands of research used stars as "physics
laboratories" for investigating the nature of matter under extreme densities
and pressures, impossible to realize on Earth. To trace this process this paper
is following the evolution of the concept of a dense core in stars, which was
important both for an understanding of stellar evolution and as a testing
ground for the fast-evolving field of nuclear physics. In spite of the divide
between physicists and astrophysicists, some key actors working in the
cross-fertilized soil of overlapping but different scientific cultures
formulated models and tentative theories that gradually evolved into more
realistic and structured astrophysical objects. These investigations culminated
in the first contact with general relativity in 1939, when J. Robert
Oppenheimer and his students George Volkoff and Hartland Snyder systematically
applied the theory to the dense core of a collapsing neutron star. This
pioneering application of Einstein's theory to an astrophysical compact object
can be regarded as a milestone in the path eventually leading to the emergence
of relativistic astrophysics in the early 1960s.Comment: 83 pages, 4 figures, submitted to the European Physical Journal
Association of interatrial septal abnormalities with cardiac impulse conduction disorders in adult patients: experience from a tertiary center in Kosovo
Interatrial septal disorders, which include: atrial septal defect, patent foramen ovale and atrial septal aneurysm, are frequent congenital anomalies found in adult patients. Early detection of these anomalies is important to prevent their hemodynamic and/or thromboembolic consequences. The aims of this study were: to assess the association between impulse conduction disorders and anomalies of interatrial septum; to determine the prevalence of different types of interatrial septum abnormalities; to assess anatomic, hemodynamic, and clinical consequences of interatrial septal pathologies. Fifty-three adult patients with impulse conduction disorders and patients without ECG changes but with signs of interatrial septal abnormalities, who were referred to our center for echocardiography, were included in a prospective transesophageal echocardiography study. Interatrial septal anomalies were detected in around 85% of the examined patients. Patent foramen ovale was encountered in 32% of the patients, and in combination with atrial septal aneurysm in an additional 11.3% of cases. Atrial septal aneurysm and atrial septal defect were diagnosed with equal frequency in 20.7% of our study population. Impulse conduction disorders were significantly more suggestive of interatrial septal anomalies than clinical signs and symptoms observed in our patients (84.91% vs 30.19%, P=0.002). Right bundle branch block was the most frequent impulse conduction disorder, found in 41 (77.36%) cases. We conclude that interatrial septal anomalies are highly associated with impulse conduction disorders, particularly with right bundle branch block. Impulse conduction disorders are more indicative of interatrial septal abnormalities in earlier stages than can be understood from the patient’s clinical condition
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