Densely-connected Network Research Articles

Injection drug network characteristics as a predictor of injection behaviour

Social network characteristics of people who inject drugs (PWID) have previously been flagged as potential risk factors for HCV transmission such as increased injection frequency. To understand the role of the injecting network on injection frequency, we investigated how changes in an injecting network over time can modulate injecting risk behaviour. PWID were sourced from the Networks 2 Study, a longitudinal cohort study of PWID recruited from illicit drug street markets across Melbourne, Australia. Network-related correlates of injection frequency and the change in frequency over time were analysed using adjusted Cox Proportional Hazards and Generalised Estimating Equations modelling. Two-hundred and eighteen PWID followed up for a mean (s.d.) of 2.8 (1.7) years were included in the analysis. A greater number of injecting partners, network closeness centrality and eigenvector centrality over time were associated with an increased rate of infection frequency. Every additional injection drug partner was associated with an increase in monthly injection frequency. Similarly, increased network connectivity and centrality over time was also associated with an increase in injection frequency. This study observed that baseline network measures of connectivity and centrality may be associated with changes in injection frequency and, by extension, may predict subsequent HCV transmission risk. Longitudinal changes in network position were observed to correlate with changes in injection frequency, with PWID who migrate from the densely-connected network centre out to the less-connected periphery were associated with a decreased rate of injection frequency.

Procedencia del material pétreo de los molinos de los yacimientos Cogotas I (Bronce Medio y Tardío) de la Cuenca del Duero y modelos consecuentes de flujo

Se ha estudiado la procedencia del material pétreo de doce molinos de diferentes yacimientos cogotenses de la Cuenca del Duero. Utilizando una marcha metodológica previa, se alcanza una caracterización petrográfica, mineralógica y geoquímica del material, incluyendo el tratamiento de elementos traza mediante diagramas de normalización y comparación con datos disponibles de áreas fuente potenciales. Esto ha permitido, en muchos casos, la identificación de áreas fuente locales ya que la signatura geoquímica representa una huella arqueológica fidedigna de las facies o subtipos de rocas implicadas. La mayoría de las áreas fuente identificadas son graníticas, existiendo también granodioritas, gneises y areniscas, todas ellas pertenecientes al basamento varisco. Una de estas áreas incluye minerales de cobre, eventualmente aprovechables para metalurgia. Probablemente, ya desde la fase inicial de Cogotas I dejó de regir el principio del mínimo esfuerzo en el aprovisionamiento del material. El suministro de materias primas a los yacimientos arqueológicos es de carácter lejano y en direcciones cruzadas, de acuerdo con las áreas fuente establecidas, indicando una densa red de conexiones entre las comunidades de la región a escala hectokilométrica

Volume-Based Analysis of 6-Month-Old Infant Brain MRI for Autism Biomarker Identification and Early Diagnosis.

Autism spectrum disorder (ASD) is mainly diagnosed by the observation of core behavioral symptoms. Due to the absence of early biomarkers to detect infants either with or at-risk of ASD during the first postnatal year of life, diagnosis must rely on behavioral observations long after birth. As a result, the window of opportunity for effective intervention may have passed when the disorder is detected. Therefore, it is clinically urgent to identify imaging-based biomarkers for early diagnosis and intervention. In this paper, for the first time, we proposed a volume-based analysis of infant subjects with risk of ASD at very early age, i.e., as early as at 6 months of age. A critical part of volume-based analysis is to accurately segment 6-month-old infant brain MRI scans into different regions of interest, e.g., white matter, gray matter, and cerebrospinal fluid. This is actually very challenging since the tissue contrast at 6-month-old is extremely low, caused by inherent ongoing myelination and maturation. To address this challenge, we propose an anatomy-guided, densely-connected network for accurate tissue segmentation. Based on tissue segmentations, we further perform brain parcellation and statistical analysis to identify those significantly different regions between autistic and normal subjects. Experimental results on National Database for Autism Research (NDAR) show the advantages of our proposed method in terms of both segmentation accuracy and diagnosis accuracy over state-of-the-art results.

Рынки и рестораны Москвы: сетевые сообщества трудовых мигрантов из Азербайджана.


 Ольга Владимировна Пинчук – аспирант кафедры теоретической и специальной социологии Института социально-гуманитарного образования Московского педагогического государственного университета (МПГУ), Москва, Россия. Электронная почта: Pinchuk_olya@list.ru
 Тимур Рифатович Миняжев – к. с. н., доцент кафедры теоретической и специальной социологии Института социально-гуманитарного образования Московского педагогического государственного университета (МПГУ), Москва, Россия. Электронная почта: Minyazhev@gmail.com
 В статье рассматривается участие трудовых мигрантов из Азербайджана в двух сферах занятости в Москве: рыночная инфраструктура и общественное питание. Проверяя гипотезу о присутствии азербайджанских предпринимателей в столичных «этнических кафе», исследователи обнаружили два сообщества трудовых мигрантов: «сообщество работников ресторанов» и «сообщество работников рыночной инфраструктуры». Рассматривая сообщества мигрантов из Азербайджана через призму сетевого подхода и концепцию социального капитала, пространство возможностей для каждого мигранта задается на основе уже имеющегося набора связей с другими мигрантами. Сообщество характеризуется плотностью социальных связей, оно не всегда локализовано в пространстве. Включенность в сетевое пространство обеспечивает мигранту доступ к социальному капиталу сообщества, что помогает не только начать свой «миграционный путь», но и успешно его продолжить. Чем плотнее социальные связи, тем больше у мигранта шансов добиться лучшего социально-экономического положения. Два сообщества трудовых мигрантов из Азербайджана в Москве функционируют по-разному. Члены «рыночного сообщества» имеют плотные связи в рамках одного рынка, и слабые «межрыночные» связи, что, однако, не мешает мигрантам при желании легко находить работу на другом рынке столицы. «Ресторанное сообщество» не имеет конкретной локации, его члены рассредоточены по удаленным друг от друга ресторанам, но поддерживают активную связь «по телефону». Авторы делают вывод о том, что сообщества связаны слабо и однонаправленно: зафиксирована лишь возможность перехода из «рыночного сообщества» в «ресторанное». При этом, как правило, мигранты, совершившие этот условный переход, обратно на рынок уже не возвращаются.

New Technologies as a Tool for Changing Academic Communities in the Global Context

Abstract It has been defined that knowledge society emerges at the end of the twentieth century as the socio-economic structure characteristic for developed societies in which unlike in industrial societies, the dominant sector of economy is services and the largest social group is the “men of knowledge”. It has been indicated that the development of the knowledge society is considered in connection with scientific and technological development and the expansion of new technologies as they determined is that we live in a globalized world, connected by a dense network of connections and intensive contacts both between the individuals and the authorities at local, regional, national and transnational or institutions level or between the institutions of various types, among which, of course, there are also educational institutions, including universities. It has been concluded that the accentuated thought should be read as a contemporary call for the implementation of the classic academic ideas in the conditions of the use of new technologies. Paraphrasing a metaphor of J. Morbitzer, modern university institutions should become intellectual arcs that will save humanity from the information deluge, the flood of endless, murky waves to safely bring it to the port of the society in which knowledge will be a resource for creative and innovative activities. A very important task is in the situation of current unprecedented acceleration of technical and technological progress not to lose the deep humanistic character of the educational process in which the modern technology should well serve a man and not contribute to its enslavement.

Comparative properties of excitatory and inhibitory inter-laminar neocortical axons

In recent years it has become increasingly clear that variations in voltage-gated channels, as well as highly diverse geometrical properties, shape the way axons conduct action potentials to their terminals. Numerous cell types in the mammalian neocortex form a dense network of connections, and the properties of their axons may have an effect on the processing performed by this network. We studied the conduction properties of local, inter-laminar axons emanating from regular-spiking (RS) pyramidal neurons and Martinotti type inhibitory neurons (MCs) in layer 5 of the mouse barrel neocortex by comparing the patterns of their antidromic activation from layer 1.Both types of axons had similarly slow conduction velocities (∼0.3 m/s), compatible with thin unmyelinated fibers. In addition, in both types of neurons, subthreshold changes of the somatic membrane potential affected the stimulus threshold for evoking an antidromic spike in layer 1, a distance of 600–800 μm. However, the axons differed considerably in their antidromic activation profiles. 1) The antidromic latency in RS neurons was highly consistent while some MCs display considerable activation-latency jitter; 2) RS neurons displayed a steeper increase in excitability to repeated 40 Hz stimulation; 3) RS neurons displayed a sharp, step-like antidromic activation threshold to both somatic voltage and stimulus intensity, while MCs displayed a gradual recruitment pattern. Morphological differences in the branching pattern of the two types of neurons may account for some of these distinctions. These results suggest differences among excitatory and inhibitory neocortical neurons in the computational tasks of their local axons.

Cortical feedback improves discrimination between figure and background by V1, V2 and V3 neurons.

A single visual stimulus activates neurons in many different cortical areas. A major challenge in cortical physiology is to understand how the neural activity in these numerous active zones leads to a unified percept of the visual scene. The anatomical basis for these interactions is the dense network of connections that link the visual areas. Within this network, feedforward connections transmit signals from lower-order areas such as V1 or V2 to higher-order areas. In addition, there is a dense web of feedback connections which, despite their anatomical prominence, remain functionally mysterious. Here we show, using reversible inactivation of a higher-order area (monkey area V5/MT), that feedback connections serve to amplify and focus activity of neurons in lower-order areas, and that they are important in the differentiation of figure from ground, particularly in the case of stimuli of low visibility. More specifically, we show that feedback connections facilitate responses to objects moving within the classical receptive field; enhance suppression evoked by background stimuli in the surrounding region; and have the strongest effects for stimuli of low salience.