Influences of e-retailer sponsored virtual community on consumer loyalty: an exploration of underlying mechanisms

An e-retailer sponsored virtual community (ESVC), as the backyard of an e-commerce website, provides consumers with an online platform to play with each other. Different from transactional e-commerce platform, ESVC assembles consumers together to fulfil their social needs. In recent years, with the popular of Web 2.0 information and communication technologies (ICTs), e-retailers also start to integrate social media within ESVC. This greatly increases consumers' online community participation, as social media facilitate information sharing and interactions among community members with a social flavour. Moreover, social media provide a variety of IT artefacts to visualize the interactions between consumers and e-retailer, which reshapes the relationship between e-retailer and customer as a triad model. However, in this new context, the influences of ESVC characteristics and IT artefacts on e-retailer- customer relationship were not well investigated. Some researchers have made effort to open the "black box" between ESVC with social media investment and customer loyalty, but still lack theoretical foundations. This research explores the underlying mechanisms from a new perspective, and proposes a theoretical framework based on reciprocal theory

Evolutionary Subnetworks in Complex Systems

Links in a practical network may have different functions, which makes the original network a combination of some functional subnetworks. Here, by a model of coupled oscillators, we investigate how such functional subnetworks are evolved and developed according to the network structure and dynamics. In particular, we study the case of evolutionary clustered networks in which the function of each link (either attractive or repulsive coupling) is updated by the local dynamics. It is found that, during the process of system evolution, the network is gradually stabilized into a particular form in which the attractive (repulsive) subnetwork consists only the intralinks (interlinks). Based on the properties of subnetwork evolution, we also propose a new algorithm for network partition which is distinguished by the convenient operation and fast computing speed.Comment: 4 pages, 4 figure

Small‐for‐size liver transplanted into larger recipient: A model of hepatic regeneration

Orthotopic liver transplantation was performed in 60 recipient rats weighing 200 to 250 gm. Sixty rats of the same strain were used as liver donors, 30 weighing 100 to 140 gm (small for size) and the other 30 weighing 200 to 250 gm (same size). After 1, 2, 3, 4, 7 and 14 days (n = 5 each) DNA synthesis, nuclear thymidine labeling and mitoses were increased in both the small‐for‐size and same‐size groups, but significantly more in the former. These changes were maximal after 48 to 72 hr, similar to but later than the well‐known regeneration response after partial hepatectomy, which peaks at 24 hr in rats. Indirect indexes of regeneration of the transplanted livers also were measured: plasma or serum ornithine decarboxylase; insulin and glucagon serum levels; estradiol and testosterone serum levels (and their nuclear and cytosolic receptors); and transforming growth factor‐ß, c‐Ha‐ras and c‐jun mRNA expressions. With the small‐for‐size transplantation, these followed the same delayed pattern as the direct regeneration parameters. The small livers gradually increased in size over the course of 1 to 2 wk and achieved a volume equal to that of the liver originally present in the recipient. In contrast, no significant liver weight gain occurred in the transplanted livers from same‐size donors despite the evidence of regeneration by direct indexes, but not by most of the surrogate parameters, including ornithine decarboxylase. (Hepatology 1993;19:210–216). Copyright © 1994 American Association for the Study of Liver Disease

Full calculation of clumpiness boost factors for antimatter cosmic rays in the light of Lambda-CDM N-body simulation results

Anti-proton and positron Galactic cosmic ray spectra are among the key targets for indirect detection of dark matter. The boost factors, corresponding to an enhancement of the signal and linked to the clumpiness properties of the dark matter distribution, have been taken as high as thousands in the past. The dramatic impact of these boost factors for indirect detection of antiparticles, for instance with the PAMELA satellite or the coming AMS-02 experiment, asks for their detailed calculation. We take into account the results of high resolution N-body dark matter simulations to calculate the most likely energy dependent boost factors linked to the cosmic ray propagation properties, for anti-protons and positrons. Starting from the mass and space distributions of sub-halos, the anti-proton and positron propagators are used to calculate the mean value and the variance of the boost factor for the primary fluxes. We take advantage of the statistical method introduced in Lavalle et al. (2007) and cross-check the results with Monte Carlo computations. By spanning some extreme configurations of sub-halo and propagation properties, we find that the average contribution of the clumps is negligible compared to that of the smooth dark matter component. Sub-halos do not lead to enhancement of the signals, unless they are taken with some extreme (unexpected) properties. This result is independent of the nature of the self-annihilating dark matter candidate considered, and provides precise estimates of the theoretical and the statistical uncertainties of the antimatter flux from dark matter substructures. Spectral distortions can still be expected in antimatter flux measurements, but scenarios invoking large and even mild clumpiness boost factors are strongly disfavoured by our analysis.Comment: Final version, matching the published one. 32 pages, 12 figure

Impact of Intracranial Artery Disease and Prior Cerebral Infarction on Central Nervous System Complications After Off-Pump Coronary Artery Bypass Grafting

We tried to determine whether postoperative CNS complications after off-pump coronary artery bypass grafting (OPCABG) are related to prior cerebral infarction or intracranial artery disease. Fifty-five patients (40 men, mean age 64.59 ± 8.86 years) subjected to OPCABG underwent neurological and neuropsychological examinations 24 h before surgery. MRI was used to identify old and/or new ischemic lesions before surgery, and MRA was used to determine the presence and severity of intracranial artery disease. The patients were examined eight days after surgery; possible development of stroke or cognitive dysfunction was evaluated. Associations between postoperative stroke and potential predictors, including prior cerebral infarction and intracranial artery disease, were analyzed using univariate methods. Two of 55 (3.64%) patients had postoperative stroke, and no patient showed cognitive decline. Univariate analysis found no significant association between postoperative stroke and prior cerebral infarction detected by MRI (P = 0.378) or intracranial artery disease detected by MRA (P = 0.103). Our results suggest that intracranial artery disease and prior cerebral infarction are not independent risk factors for stroke after OPCABG. Nonetheless, further investigation of these associations is necessary.Ми намагалися встановити, чи залежать післяопераційні ускладнення в ЦНС після шунтування коронарної артерії без застосування штучного кровообігу від наявності в попередній період церебрального геморагічного інсульту або стенозу краніальних артерій. 55 пацієнтів (40 чоловіків і 15 жінок, середній вік 64.59 ± 8.86 року), котрим була призначена вказана операція, були за добу перед нею піддані неврологічному та нейропсихологічному обстеженню. Магніторезонансне сканування (MRI) було використане для ідентифікації старих та/або нових ішемічних уражень, а магніторезонансна ангіографія (MRA) застосовувалася для встановлення наявності та ступеню стенозу краніальних артерій. Пацієнти були повторно обстежені через вісім діб після операції для виявлення можливих ускладнень (розвитку інсульту або когнітивної дисфункції). Зв’язки між розвитком постопераційного інсульту та можливими предикторами (попереднім інсультом та стенозом краніальних артерій) були проаналізовані із застосуванням методів варіаційної статистики. Післяопераційний інсульт розвився у двох із 55 пацієнтів (3.64 %); зниження рівня когнітивної активності не спостерігалося в жодному випадку. Аналіз не показав вірогідного зв’язку між розвитком післяопераційного інсульту та наявністю попереднього геморагічного інсульту (дані MRI; P = 0.378) або стенозу краніальних артерій (дані MRA; P= 0.103). Наші результати дозволяють вважати, що стеноз краніальних артерій та попередній інсульт не є незалежними факторами ризику щодо інсульту після шунтування коронарної артерії, але подальші дослідження можливості таких зв’язків є необхідними

Equilibrium Properties of Temporally Asymmetric Hebbian Plasticity

A theory of temporally asymmetric Hebb (TAH) rules which depress or potentiate synapses depending upon whether the postsynaptic cell fires before or after the presynaptic one is presented. Using the Fokker-Planck formalism, we show that the equilibrium synaptic distribution induced by such rules is highly sensitive to the manner in which bounds on the allowed range of synaptic values are imposed. In a biologically plausible multiplicative model, we find that the synapses in asynchronous networks reach a distribution that is invariant to the firing rates of either the pre- or post-synaptic cells. When these cells are temporally correlated, the synaptic strength varies smoothly with the degree and phase of synchrony between the cells.Comment: 3 figures, minor corrections of equations and tex

Random Walks for Spike-Timing Dependent Plasticity

Random walk methods are used to calculate the moments of negative image equilibrium distributions in synaptic weight dynamics governed by spike-timing dependent plasticity (STDP). The neural architecture of the model is based on the electrosensory lateral line lobe (ELL) of mormyrid electric fish, which forms a negative image of the reafferent signal from the fish's own electric discharge to optimize detection of sensory electric fields. Of particular behavioral importance to the fish is the variance of the equilibrium postsynaptic potential in the presence of noise, which is determined by the variance of the equilibrium weight distribution. Recurrence relations are derived for the moments of the equilibrium weight distribution, for arbitrary postsynaptic potential functions and arbitrary learning rules. For the case of homogeneous network parameters, explicit closed form solutions are developed for the covariances of the synaptic weight and postsynaptic potential distributions.Comment: 18 pages, 8 figures, 15 subfigures; uses revtex4, subfigure, amsmat

Induced magnetization in La0.7_{0.7}Sr0.3_{0.3}MnO3_3/BiFeO3_3 superlattices

Using polarized neutron reflectometry (PNR), we observe an induced magnetization of 75$\pm$ 25 kA/m at 10 K in a La$_{0.7}$Sr$_{0.3}$MnO$_3$ (LSMO)/BiFeO$_3$ superlattice extending from the interface through several atomic layers of the BiFeO$_3$ (BFO). The induced magnetization in BFO is explained by density functional theory, where the size of bandgap of BFO plays an important role. Considering a classical exchange field between the LSMO and BFO layers, we further show that magnetization is expected to extend throughout the BFO, which provides a theoretical explanation for the results of the neutron scattering experiment.Comment: 5 pages, 4 figures, with Supplemental Materials. To appear in Physical Review Letter

Delayed blood transfusion is associated with mortality following radical cystectomy

Objectives: To examine the temporal association between blood transfusion and 90-day mortality in patients with bladder cancer treated with radical cystectomy. / Methods: This represents a retrospective cohort study of patients treated with radical cystectomy within the Premier Hospital network between 2003 and 2015. Patients outcomes were stratified those who received early blood transfusion (day of surgery) vs delayed blood transfusion (postoperative day ≥1) during the index admission. Primary end point was 90-day mortality following surgery. / Results: The median age of 12,056 patients identified was 70 years. A total of 7,201 (59.7%) patients received blood transfusion. Within 90 days following surgery, 57 (2.2%), 162 (5.9%) and 123 (6.7%) patients in the early, delayed and both early and delayed transfused patients died respectively. Following multivariate logistic regression to account for patient (age and Charlson Comorbidity Index [CCI]) and hospital (surgeon volume, surgical approach and academic status) factors, delayed blood transfusion was independently associated with 90-day mortality (Odds ratio [OR], 2.64; 95% Confidence Interval [CI], 1.98–3.53; p < 0.001). A sensitivity analysis defining early blood transfusion as <2 days postoperatively, increased 90-day mortality persisted in patients receiving delayed transfusion (OR, 2.20; 95% CI, 1.63-3.00; p < 0.001). Older patients (≥77 years) with the highest CCI (≥2) had a 7% absolute increase in the predicted probability of 90-day mortality if they were transfused late compared to patients transfused early. / Conclusion: Patient undergoing cystectomy may benefit from expedited transfusion to prevent subsequent clinical deterioration which may lead to patient mortality. Future work is needed to elucidate the optimal timing of blood transfusion

Spatial representation of temporal information through spike timing dependent plasticity

We suggest a mechanism based on spike time dependent plasticity (STDP) of synapses to store, retrieve and predict temporal sequences. The mechanism is demonstrated in a model system of simplified integrate-and-fire type neurons densely connected by STDP synapses. All synapses are modified according to the so-called normal STDP rule observed in various real biological synapses. After conditioning through repeated input of a limited number of of temporal sequences the system is able to complete the temporal sequence upon receiving the input of a fraction of them. This is an example of effective unsupervised learning in an biologically realistic system. We investigate the dependence of learning success on entrainment time, system size and presence of noise. Possible applications include learning of motor sequences, recognition and prediction of temporal sensory information in the visual as well as the auditory system and late processing in the olfactory system of insects.Comment: 13 pages, 14 figures, completely revised and augmented versio