3,382 research outputs found
Analysis of the interdependence between gross domestic product (GDP), steel production and iron production (10 states of European Union)
Given the intensification of the world economy globalization, the production represents one of the factors characterizing the development of a country and its performance. In this context, this paper aims to establish and analyze the influence of the crude steel production and blast furnace iron production on the gross domestic product, using the multiple linear regression model. Data subject to the study are related to the period 2004 – 2014, and the research refers to the first ten countries producing crude steel and blast furnace iron, members of the European Union
Heterocyst placement strategies to maximize growth of cyanobacterial filaments
Under conditions of limited fixed-nitrogen, some filamentous cyanobacteria
develop a regular pattern of heterocyst cells that fix nitrogen for the
remaining vegetative cells. We examine three different heterocyst placement
strategies by quantitatively modelling filament growth while varying both
external fixed-nitrogen and leakage from the filament. We find that there is an
optimum heterocyst frequency which maximizes the growth rate of the filament;
the optimum frequency decreases as the external fixed-nitrogen concentration
increases but increases as the leakage increases. In the presence of leakage,
filaments implementing a local heterocyst placement strategy grow significantly
faster than filaments implementing random heterocyst placement strategies. With
no extracellular fixed-nitrogen, consistent with recent experimental studies of
Anabaena sp. PCC 7120, the modelled heterocyst spacing distribution using our
local heterocyst placement strategy is qualitatively similar to experimentally
observed patterns. As external fixed-nitrogen is increased, the spacing
distribution for our local placement strategy retains the same shape while the
average spacing between heterocysts continuously increases.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in Physical Biology. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The definitive publisher-authenticated version
will be available onlin
High temperature ferromagnetism of Li-doped vanadium oxide nanotubes
The nature of a puzzling high temperature ferromagnetism of doped
mixed-valent vanadium oxide nanotubes reported earlier by Krusin-Elbaum et al.,
Nature 431 (2004) 672, has been addressed by static magnetization, muon spin
relaxation, nuclear magnetic and electron spin resonance spectroscopy
techniques. A precise control of the charge doping was achieved by
electrochemical Li intercalation. We find that it provides excess electrons,
thereby increasing the number of interacting magnetic vanadium sites, and, at a
certain doping level, yields a ferromagnetic-like response persisting up to
room temperature. Thus we confirm the surprising previous results on the
samples prepared by a completely different intercalation method. Moreover our
spectroscopic data provide first ample evidence for the bulk nature of the
effect. In particular, they enable a conclusion that the Li nucleates
superparamagnetic nanosize spin clusters around the intercalation site which
are responsible for the unusual high temperature ferromagnetism of vanadium
oxide nanotubes.Comment: with some amendments published in Europhysics Letters (EPL) 88 (2009)
57002; http://epljournal.edpsciences.or
Single spin measurement using spin-orbital entanglement
Single spin measurement represents a major challenge for spin-based quantum
computation. In this article we propose a new method for measuring the spin of
a single electron confined in a quantum dot (QD). Our strategy is based on
entangling (using unitary gates) the spin and orbital degrees of freedom. An
{\em orbital qubit}, defined by a second, empty QD, is used as an ancilla and
is prepared in a known initial state. Measuring the orbital qubit will reveal
the state of the (unknown) initial spin qubit, hence reducing the problem to
the easier task of single charge measurement. Since spin-charge conversion is
done with unit probability, single-shot measurement of an electronic spin can
be, in principle, achieved. We evaluate the robustness of our method against
various sources of error and discuss briefly possible implementations.Comment: RevTeX4, 4 pages, some figs; updated to the published versio
Search for Intermediate Mass Magnetic Monopoles and Nuclearites with the SLIM experiment
SLIM is a large area experiment (440 m2) installed at the Chacaltaya cosmic
ray laboratory since 2001, and about 100 m2 at Koksil, Himalaya, since 2003. It
is devoted to the search for intermediate mass magnetic monopoles (107-1013
GeV/c2) and nuclearites in the cosmic radiation using stacks of CR39 and
Makrofol nuclear track detectors. In four years of operation it will reach a
sensitivity to a flux of about 10-15 cm-2 s-1 sr-1. We present the results of
the calibration of CR39 and Makrofol and the analysis of a first sample of the
exposed detector.Comment: Presented at the 22nd ICNTS, Barcelona 200
The SPOrt Project: Cosmological and Astrophysical Goals
We present the cosmological and astrophysical objectives of the SPOrt
mission, which is scheduled for flying on the International Space Station (ISS)
in the year 2002 with the purpose of measuring the diffuse sky polarized
radiation in the microwave region. We discuss the problem of disentangling the
cosmic background polarized signal from the Galactic foregrounds.Comment: 10 pages; 5 PS figures; requires aipproc2.cls, aipproc2.sty,
epsfc.tex; to appear in Proc. of ``3K Cosmology'', Rome 5-10 Oct. 199
Lectures on BCOV holomorphic anomaly equations
The present article surveys some mathematical aspects of the BCOV holomorphic
anomaly equations introduced by Bershadsky, Cecotti, Ooguri and Vafa. It grew
from a series of lectures the authors gave at the Fields Institute in the
Thematic Program of Calabi-Yau Varieties in the fall of 2013.Comment: reference added, typos correcte
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