14,451 research outputs found
Impact of Inter-Country Distances on International Tourism
Tourism is a worldwide practice with international tourism revenues
increasing from US\$495 billion in 2000 to US\$1340 billion in 2017. Its
relevance to the economy of many countries is obvious. Even though the World
Airline Network (WAN) is global and has a peculiar construction, the
International Tourism Network (ITN) is very similar to a random network and
barely global in its reach. To understand the impact of global distances on
local flows, we map the flow of tourists around the world onto a complex
network and study its topological and dynamical balance. We find that although
the WAN serves as infrastructural support for the ITN, the flow of tourism does
not correlate strongly with the extent of flight connections worldwide.
Instead, unidirectional flows appear locally forming communities that shed
light on global travelling behaviour inasmuch as there is only a 15%
probability of finding bidirectional tourism between a pair of countries. We
conjecture that this is a consequence of one-way cyclic tourism by analyzing
the triangles that are formed by the network of flows in the ITN. Finally, we
find that most tourists travel to neighbouring countries and mainly cover
larger distances when there is a direct flight, irrespective of the time it
takes
Incompressible Turbulence as Nonlocal Field Theory
It is well known that incompressible turbulence is nonlocal in real space
because sound speed is infinite in incompressible fluids. The equation in
Fourier space indicates that it is nonlocal in Fourier space as well. Contrast
this with Burgers equation which is local in real space. Note that the sound
speed in Burgers equation is zero. In our presentation we will contrast these
two equations using nonlocal field theory. Energy spectrum and renormalized
parameters will be discussed.Comment: 7 pages; Talk presented in Conference on "Perspectives in Nonlinear
Dynamics (PNLD 2004)" held in Chennai, 200
Hamster leukemia virus: lack of endogenous DNA synthesis and unique structure of its DNA polymerase
Infectious hamster leukemia virus (HaLV) contains a DNA polymerase different from those of murine and avian viruses. No endogenous reaction directed by the 60 to 70S RNA of HaLV could be demonstrated in detergenttreated HaLV virions, nor could the purified DNA polymerase copy added viral RNA. The virion RNA could, however, act as template for added avian myeloblastosis virus DNA polymerase and the HaLV DNA polymerase could efficiently utilize homopolymers as templates. The HaLV enzyme was like other reverse transcriptases in that certain ribohomopolymers were much better templates than the homologous deoxyribohomopolymers. No ribonuclease H activity could be shown in the HaLV enzyme, but neither could activity be found in the murine leukemia virus DNA polymerase. The hamster enzyme was unique in that poly(A) ·oligo(dT) was a poor template, and globin mRNA primed with oligo(dT) was totally inactive as a template. Its uniqueness was also indicated by its subunit composition; electrophoresis of the HaLV DNA polymerase in sodium dodecyl sulfate-containing polyacrylamide gels revealed equimolar amounts of two polypeptides of molecular weight 68,000 and 53,000. The sedimentation rate of the enzyme in glycerol gradients was consistent with a structure containing one each of the two polypeptides. The enzyme thus appears to be structurally distinct from other known virion DNA polymerases. Its inability to carry out an endogenous reaction in vitro might result from an inability to utilize certain primers
The Physical Properties of LBGs at z>5: Outflows and the "pre-enrichment problem"
We discuss the properties of Lyman Break galaxies (LBGs) at z>5 as determined
from disparate fields covering approximately 500 sq. arcmin. While the broad
characteristics of the LBG population has been discussed extensively in the
literature, such as luminosity functions and clustering amplitude, we focus on
the detailed physical properties of the sources in this large survey (>100 with
spectroscopic redshifts). Specifically, we discuss ensemble mass estimates,
stellar mass surface densities, core phase space densities, star-formation
intensities, characteristics of their stellar populations, etc as obtained from
multi-wavelength data (rest-frame UV through optical) for a subsample of these
galaxies. In particular, we focus on evidence that these galaxies drive
vigorous outflows and speculate that this population may solve the so-called
``pre-enrichment problem''. The general picture that emerges from these studies
is that these galaxies, observed about 1 Gyr after the Big Bang, have
properties consistent with being the progenitors of the densest stellar systems
in the local Universe -- the centers of old bulges and early type galaxies.Comment: 4 pages, to appear in "Pathways Through an Eclectic Universe", J. H.
Knappen, T. J. Mahoney, and A. Vazedekis (Eds.), ASP Conf. Ser., 200
Cohesion, Elastic Constants and Vibrational Mechanics of Fcc Platinum
A model in real space has been developed by extending the generalized form of the exponential potential known as extended generalized exponential potential (EGEP) to account for (a) the correct nature of repulsive and attractive components of forces for all the separations in general and that of small separations in particular, (b) the three-body forces such as volume forces in an indirect way in the framework of EGEP through the parameter n, (c) the dielectric screening functions in an alternative and simpler form through the parameter m. The model is employed to compute the cohesive energy, second-order elastic constants and phenon spectra for fcc platinum. The predictions show promising agreement with experimental findings.Author Affiliation: Divesh Verma
A. F. School of Engineering and Technology, Dhauj-121 004, Haryana, India
M L Verma* and A Verma
Department of Physics, GGDSD College, Palwal-121 102, Haryana, India
and
R P S Rathore
Department of Physics, B.M.A.S. Engineering College, Agra-282 002, Uttar Pradesh, India1.A. F. School of Engineering and Technology, Dhauj-121 004, Haryana, India 2.Department of Physics, GGDSD College, Palwal-121 102, Haryana, India 3.Department of Physics, B.M.A.S. Engineering College, Agra-282 002, Uttar Pradesh, Indi
Universal Scaling in Mixing Correlated Growth with Randomness
We study two-component growth that mixes random deposition (RD) with a
correlated growth process that occurs with probability p. We find that these
composite systems are in the universality class of the correlated growth
process. For RD blends with either Edwards-Wilkinson of Kardar-Parisi-Zhang
processes, we identify a nonuniversal parameter in the universal scaling in p.Comment: 4 pages, 6 figures, 11 references; under revie
Purification and characterization of a low molecular mass alkaliphilic lipase of Bacillus cereus MTCC 8372
A low molecular mass alkaliphilic extra-cellular lipase of Bacillus cereus MTCC 8372 was purified 35-fold by hydrophobic interaction (Octyl-Sepharose) chromatography. The purified enzyme was found to be electrophoretically pure by denaturing gel electrophoresis and possessed a molecular mass of approximately 8 kDa. It is a homopentamer of 40 kDa as revealed by native-PAGE. The lipase was optimally active at 55 °C and retained approximately half of its original activity after 40 min incubation at 55 °C. The enzyme was maximally active at pH 8.5. Mg 2+ , Cu 2+ , Ca 2+ , Hg 2+ , Al 3+ and Fe 3+ at 1 mM enhanced hydrolytic activity of the lipase. Interestingly, Hg 2+ ions synergized and Zn 2+ and Co 2+ ions antagonized the lipase activity. Among surfactants, Tween 80 promoted the lipase activity. Phenyl methyl sulfonyl fluoride (PMSF, 15 mM) decreased 98% of original activity of lipase. The lipase was highly specific towards p -nitrophenyl palmitate and showed a V max and K m of 0.70 mmol.mg −1 .min −1 and 32 mM for hydrolysis of p NPP.<br /
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