4,313 research outputs found
Network dynamics of ongoing social relationships
Many recent large-scale studies of interaction networks have focused on
networks of accumulated contacts. In this paper we explore social networks of
ongoing relationships with an emphasis on dynamical aspects. We find a
distribution of response times (times between consecutive contacts of different
direction between two actors) that has a power-law shape over a large range. We
also argue that the distribution of relationship duration (the time between the
first and last contacts between actors) is exponentially decaying. Methods to
reanalyze the data to compensate for the finite sampling time are proposed. We
find that the degree distribution for networks of ongoing contacts fits better
to a power-law than the degree distribution of the network of accumulated
contacts do. We see that the clustering and assortative mixing coefficients are
of the same order for networks of ongoing and accumulated contacts, and that
the structural fluctuations of the former are rather large.Comment: to appear in Europhys. Let
Growing Scale-Free Networks with Tunable Clustering
We extend the standard scale-free network model to include a ``triad
formation step''. We analyze the geometric properties of networks generated by
this algorithm both analytically and by numerical calculations, and find that
our model possesses the same characteristics as the standard scale-free
networks like the power-law degree distribution and the small average geodesic
length, but with the high-clustering at the same time. In our model, the
clustering coefficient is also shown to be tunable simply by changing a control
parameter - the average number of triad formation trials per time step.Comment: Accepted for publication in Phys. Rev.
Networking Effects on Cooperation in Evolutionary Snowdrift Game
The effects of networking on the extent of cooperation emerging in a
competitive setting are studied. The evolutionary snowdrift game, which
represents a realistic alternative to the well-known Prisoner's Dilemma, is
studied in the Watts-Strogatz network that spans the regular, small-world, and
random networks through random re-wiring. Over a wide range of payoffs, a
re-wired network is found to suppress cooperation when compared with a
well-mixed or fully connected system. Two extinction payoffs, that characterize
the emergence of a homogeneous steady state, are identified. It is found that,
unlike in the Prisoner's Dilemma, the standard deviation of the degree
distribution is the dominant network property that governs the extinction
payoffs.Comment: Changed conten
Interlayer Registry Determines the Sliding Potential of Layered Metal Dichalcogenides: The case of 2H-MoS2
We provide a simple and intuitive explanation for the interlayer sliding
energy landscape of metal dichalcogenides. Based on the recently introduced
registry index (RI) concept, we define a purely geometrical parameter which
quantifies the degree of interlayer commensurability in the layered phase of
molybdenum disulphide (2HMoS2). A direct relation between the sliding energy
landscape and the corresponding interlayer registry surface of 2H-MoS2 is
discovered thus marking the registry index as a computationally efficient means
for studying the tribology of complex nanoscale material interfaces in the
wearless friction regime.Comment: 13 pages, 7 figure
Increased Expression of Tissue Factor and Receptor for Advanced Glycation End Products in Peripheral Blood Mononuclear Cells of Patients With Type 2 Diabetes Mellitus with Vascular Complications
The aim of the study was to determine the correlation between
the expression of tissue factor (TF) and the receptor
for advanced glycation end products (RAGEs) and vascular
complications in patients with longstanding uncontrolled
type 2 diabetes (T2D). TF and RAGE mRNAs as well as
TF antigen and activity were investigated in 21 T2D patients
with and without vascular complications. mRNA expression
was assessed by reverse transcriptaseâpolymerase
chain reaction (RT-PCR) in nonstimulated and advanced
glycation end product (AGE) albuminâstimulated peripheral
blood mononuclear cells (PBMCs). TF antigen expression
was determined by enzyme-linked immunosorbent assay
(ELISA) and TF activity by a modified prothrombin
time assay. Basal RAGE mRNA expression was 0.2 ± 0.06
in patients with complications and 0.05 ± 0.06 patients without
complications (P = .004). Stimulation did not cause any
further increase in either group. TF mRNA was 0.58 ± 0.29
in patients with complications and 0.21 ± 0.18 in patients
without complications (P = .003). Stimulation resulted in
a nonsignificant increase in both groups. Basal TF activity
(U/106 PBMCs) was 18.4 ± 13.2 in patients with complications
and 6.96 ± 5.2 in patients without complications (P =
.003). It increased 3-fold in both groups after stimulation
(P = .001). TF antigen (pg/106 PBMCs) was 33.7 ± 28.6 in
patients with complications, 10.4 ± 7.8 in patients without complications (P = .02). Stimulation tripled TF antigen in
both groups of patients (P = .001). The RAGE/TF axis is
up-regulated inT2Dpatients with vascular complications as
compared to patients without complications. This suggests
a role for this axis in the pathogenesis of vascular complications
in T2D
Novas opçÔes para o tratamento preventivo da migrùnea: revisão com consideraçÔes fisiopatológicas
BACKGROUND: The pharmacological treatment of migraine may be acute or preventive. Frequent, severe and long-lasting migraine attacks require prophylaxis. Multiple threads of research over the last 15 years have led to the concept that migraine is generated from a hyperexcitable brain. A variety of causes for hyperexcitability of the brain in migraine have been suggested. These causes include low cerebral magnesium levels, mitochondrial abnormalities, dysfunctions related to increased nitric oxide or the existence of a P/Q type calcium channelopathy. The better knowledge about migraine pathophisiology led us to discuss new treatment options. OBJECTIVES: The aim of the present study is to present an evidence-based review of some new drugs or some agents that even though available for a long time, are not frequently used. METHODS/RESULTS: We present a review of anticonvulsants with various mechanisms of action such as lamotrigine, gabapentin, topiramate, tiagabine, levetiracetam and zonisamide. We also review natural products, like riboflavin and magnesium, botulinum toxin A, a specific CGRP antagonist and the anti-asthma medication montelukast, with pathophysiological discussion. CONCLUSIONS: We aimed to present an update of newer or less frequently used preventive migraine therapies, drugs that might reduce the burden and the costs of a disease that should be considered as a public health problem all around the world.INTRODUĂĂO: O tratamento farmacolĂłgico da migrĂąnea pode ser dividido em agudo e preventivo. Crises de migrĂąnea severas, de longa duração e incapacitante requerem profilaxia. MĂșltiplas linhas de pesquisa ao longo dos Ășltimos 15 anos sedimentaram o conceito de que a migrĂąnea Ă© gerada a partir de um cĂ©rebro hiperexcitĂĄvel. Variadas causas para essa hiperexcitabilidade tĂȘm sido sugeridas e incluem baixo nĂvel de magnĂ©sio cerebral, anormalidades mitocondriais, disfunçÔes relacionadas ao Ăłxido nĂtrico e a existĂȘncia de distĂșrbios nos canais de cĂĄlcio do tipo P/Q. O melhor conhecimento sobre a fisiopatologia da migrĂąnea nos permite discutir novas opçÔes terapĂȘuticas. OBJETIVOS: O objetivo do presente estudo Ă© apresentar revisĂŁo baseada em evidĂȘncias de novos agentes e outros que, embora disponĂveis hĂĄ mais tempo, nĂŁo sĂŁo freqĂŒentemente utilizados, com consideraçÔes fisiopatolĂłgicas. MĂTODOS/RESULTADOS: SerĂŁo revistos anticonvulsivantes com vĂĄrios mecanismos de ação, como gabapentina, lamotrigina, topiramato, tiagabina, levetiracetam e zonisamida. SerĂŁo revistos tambĂ©m produtos naturais, como riboflavina e magnĂ©sio, toxina botulĂnica do tipo A, um antagonista CGRP especĂfico e uma nova opção para o tratamento da asma, o montelukast. CONCLUSĂES: Objetivamos apresentar artigo de atualização em opçÔes novas ou nĂŁo freqĂŒentemente utilizadas no tratamento preventivo da migrĂąnea, drogas que podem reduzir o fardo e os custos de uma doença que deve ser considerada um problema de saĂșde pĂșblica em todo o mundo
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