16,070 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
The aromatic amino acid hydroxylase genes AAH1 and AAH2 in Toxoplasma gondii contribute to transmission in the cat
The Toxoplasma gondii genome contains two aromatic amino acid hydroxylase genes, AAH1 and AAH2 encode proteins that produce L-DOPA, which can serve as a precursor of catecholamine neurotransmitters. It has been suggested that this pathway elevates host dopamine levels thus making infected rodents less fearful of their definitive Felidae hosts. However, L-DOPA is also a structural precursor of melanins, secondary quinones, and dityrosine protein crosslinks, which are produced by many species. For example, dityrosine crosslinks are abundant in the oocyst walls of Eimeria and T. gondii, although their structural role has not been demonstrated, Here, we investigated the biology of AAH knockout parasites in the sexual reproductive cycle within cats. We found that ablation of the AAH genes resulted in reduced infection in the cat, lower oocyst yields, and decreased rates of sporulation. Our findings suggest that the AAH genes play a predominant role during infection in the gut of the definitive feline host
Study of Distribution and Asymmetry of Solar Active Prominences During Solar Cycle 23
In this paper we present the results of a study of the spatial distribution
and asymmetry of solar active prominences (SAP) for the period 1996-2007 (solar
cycle 23). For more meaningful statistical analysis we have analysed the
distribution and asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR,
DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The north-south
(N-S) latitudinal distribution shows that the SAP events are most prolific in
the 21-30degree slice in the northern and southern hemispheres and east-west
(E-W) longitudinal distribution study shows that the SAP events are most
prolific (best visible) in the 81-90degree slice in the eastern and western
hemispheres. It has been found that the SAP activity during this cycle is low
compared to previous solar cycles. The present study indicates that during the
rising phase of the cycle the number of SAP events were roughly equal on the
north and south hemispheres. However, activity on the southern hemisphere has
been dominant since 1999. Our statistical study shows that the N-S asymmetry is
more significant then the E-W asymmetry.Comment: 21 pages 5 figures; Published online; 02 October, 2009; Solar Physics
Journa
Neutrino Mass Matrices with a Texture Zero and a Vanishing Minor
We study the implications of the simultaneous existence of a texture zero and
a vanishing minor in the neutrino mass matrix. There are thirty six possible
texture structures of this type, twenty one of which reduce to two texture zero
cases which have, already, been extensively studied. Of the remaining fifteen
textures only six are allowed by the current data. We examine the
phenomenological implications of the allowed texture structures for Majorana
type CP-violating phases, 1-3 mixing angle and Dirac type CP-violating phase.
All these possible textures can be generated through the seesaw mechanism and
realized in the framework of discrete abelian flavor symmetry. We present the
symmetry realization of these texture structures.Comment: To appear in Phys. Rev.
Phytase production by the unconventional yeast Pichia anomala in fed batch and cyclic fed batch fermentations
A marked enhancement in the production of cell-bound phytase in Pichia anomala was achieved in cyclic fed batch fermentation (47333 UL-1) in comparison with that in batch (11569 UL-1) and fixed volume fed batch (36911 UL-1) fermentations in cane molasses medium. Phytase productivity was sustainable in cyclic fed batch fermentation over seven days, and therefore, this mode of fed batch fermentation appears to be a better approach for producing phytase in a cost-effective manner.Keywords: Fed-batch fermentation, cyclic fed batch fermentation, Pichia anomala, phytas
Similarity Measure Development for Case-Based Reasoning- A Data-driven Approach
In this paper, we demonstrate a data-driven methodology for modelling the
local similarity measures of various attributes in a dataset. We analyse the
spread in the numerical attributes and estimate their distribution using
polynomial function to showcase an approach for deriving strong initial value
ranges of numerical attributes and use a non-overlapping distribution for
categorical attributes such that the entire similarity range [0,1] is utilized.
We use an open source dataset for demonstrating modelling and development of
the similarity measures and will present a case-based reasoning (CBR) system
that can be used to search for the most relevant similar cases
Elemental Concentrations of Aerosols in the City of Gaborone
This paper presents aerosol studies carried out in Gaborone, the capital city of Botswana. The Gaborone aerosol is varied consisting of elements from Si to Au. Traffic contribution to the aerosol of Botswana is clearly visible as illustrated by strong positive bromine and lead correlation. The use of unleaded petrol could be the cause of the decrease of ambient lead (Pb) and bromine (Br) concentrations when the present measurements are compared to previous measurements. The elements present in the aerosol of Gaborone range from silicon to lead
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