Hawking Radiation of Apparent Horizon in a FRW Universe

Hawking radiation is an important quantum phenomenon of black hole, which is closely related to the existence of event horizon of black hole. The cosmological event horizon of de Sitter space is also of the Hawking radiation with thermal spectrum. By use of the tunneling approach, we show that there is indeed a Hawking radiation with temperature, $T=1/2\pi \tilde r_A$, for locally defined apparent horizon of a Friedmann-Robertson-Walker universe with any spatial curvature, where $\tilde r_A$ is the apparent horizon radius. Thus we fill in the gap existing in the literature investigating the relation between the first law of thermodynamics and Friedmann equations, there the apparent horizon is assumed to have such a temperature without any proof. In addition, we stress the implication of the Hawking temperature associated with the apparent horizon.Comment: Latex, 9 paages; v2 published versio

The action of mimetic peptides on connexins protects fibroblasts from the negative effects of ischemia reperfusion

Connexins have been proposed as a target for therapeutic treatment of a variety of conditions. The main approaches have been by antisense or small peptides specific against connexins. Some of these peptides enhance communication while others interfere with connexin binding partners or bind to the intracellular and extracellular loops of connexins. Here, we explored the mechanism of action of a connexin mimetic peptide by evaluating its effect on gap junction channels, connexin protein levels and hemichannel activity in fibroblast cells under normal conditions and following ischemia reperfusion injury which elevates Cx43 levels, increases hemichannel activity and causes cell death. Our results showed that the effects of the mimetic peptide were concentration-dependent. High concentrations (100-300 μM) significantly reduced Cx43 protein levels and GJIC within 2 h, while these effects did not appear until 6 h when using lower concentrations (10-30 μM). Cell death can be reduced when hemichannel opening and GJIC were minimised

Observational study of the association of first insulin type in uncontrolled type 2 diabetes with macrovascular and microvascular disease

<p>Aims: To compare the risk of vascular disease, HbA1c and weight change, between first prescribed insulins in people with type 2 diabetes.</p> <p>Methods: People included in THIN United Kingdom primary care record database who began insulin (2000–2007) after poor control on oral glucose-lowering agents (OGLD) were grouped by the number of OGLDs in their treatment regimen immediately before starting insulin (n = 3,485). Within OGLD group, Cox regression compared macrovascular (all-cause mortality, myocardial infarction, acute coronary syndrome and stroke) and microvascular disease (peripheral neuropathy, nephropathy, and retinopathy) between insulin type (basal, pre-mix or Neutral Protamine Hagedorn, NPH) while ANCOVAs compared haemoglobin A1c (HbA1c) and weight change.</p> <p>Results: Mean follow-up was 3.6 years. Rates of incident macrovascular events were similar when basal insulin was compared to pre-mix or NPH, adjusted hazard ratio versus basal: pre-mix 1.08 (95% CI 0.73, 1.59); NPH 1.00 (0.63, 1.58) after two OGLDs, and pre-mix 0.97 (0.46, 2.02); NPH 0.77 (0.32, 1.86) after three OGLDs. An increased risk of microvascular disease in NPH versus basal after 3 OGLDs, adjusted hazard ratio1.87 (1.04, 3.36), was not seen after two agents or in comparisons of basal and pre-mix. At one year, after two OGLDs, weight increase was less with basal compared with pre-mix. After three OGLDs, mean HbA1c had reduced less in basal versus pre-mix or NPH at 6–8 and at 9–11 months, and versus pre-mix at 12–14 months.</p> <p>Conclusion: We found no difference in the risk of macrovascular events between first insulins in the medium term when started during poor glycaemia control. The increased risk of microvascular events with NPH warrants further study. In certain groups, first use of basal insulin was associated with less gain in weight and decrease in HbA1c compared to other insulins.</p&gt

Simulational study of anomalous tracer diffusion in hydrogels

In this article, we analyze different factors that affect the diffusion behavior of small tracer particles (as they are used e.g.in fluorescence correlation spectroscopy (FCS)) in the polymer network of a hydrogel and perform simulations of various simplified models. We observe, that under certain circumstances the attraction of a tracer particle to the polymer network strands might cause subdiffusive behavior on intermediate time scales. In theory, this behavior could be employed to examine the network structure and swelling behavior of weakly crosslinked hydrogels with the help of FCS.Comment: 11 pages, 11 figure

A companion to a quasar at redshift 4.7

There is a growing consensus that the emergence of quasars at high redshifts is related to the onset of galaxy formation, suggesting that the detection of concentrations of gas accompanying such quasars should provide clues about the early history of galaxies. Quasar companions have been recently identified at redshifts up to $z \approx 3$. Here we report observations of Lyman-$\alpha$ emission (a tracer of ionised hydrogen) from the companion to a quasar at $z$=4.702, corresponding to a time when the Universe was less than ten per cent of its present age. We argue that most of the emission arises in a gaseous nebula that has been photoionised by the quasar, but an additional component of continuum light -perhaps quasar light scattered from dust in the companion body, or emission from young stars within the nebula- appears necessary to explain the observations. These observations may be indicative of the first stages in the assembly of galaxy-sized structures.Comment: 8 pages, 4 figures, plain LaTeX. Accepted for publication in Natur

Biogenesis of the inner membrane complex is dependent on vesicular transport by the alveolate specific GTPase Rab11B

Apicomplexan parasites belong to a recently recognised group of protozoa referred to as Alveolata. These protists contain membranous sacs (alveoli) beneath the plasma membrane, termed the Inner Membrane Complex (IMC) in the case of Apicomplexa. During parasite replication the IMC is formed de novo within the mother cell in a process described as internal budding. We hypothesized that an alveolate specific factor is involved in the specific transport of vesicles from the Golgi to the IMC and identified the small GTPase Rab11B as an alveolate specific Rab-GTPase that localises to the growing end of the IMC during replication of Toxoplasma gondii. Conditional interference with Rab11B function leads to a profound defect in IMC biogenesis, indicating that Rab11B is required for the transport of Golgi derived vesicles to the nascent IMC of the daughter cell. Curiously, a block in IMC biogenesis did not affect formation of sub-pellicular microtubules, indicating that IMC biogenesis and formation of sub-pellicular microtubules is not mechanistically linked. We propose a model where Rab11B specifically transports vesicles derived from the Golgi to the immature IMC of the growing daughter parasites

Expression of a diverse array of Ca²⁺-activated K⁺ channels (SK1/3, IK1, BK) that functionally couple to the mechanosensitive TRPV4 channel in the collecting duct system of kidney

The voltage- and Ca2+-activated, large conductance K+ channel (BK, maxi-K) is expressed in the collecting duct system of kidney where it underlies flow- and Ca2+-dependent K+ excretion. To determine if other Ca2+-activated K+ channels (KCa) may participate in this process, mouse kidney and the K+-secreting mouse cortical collecting duct (CCD) cell line, mCCDcl1, were assessed for TRPV4 and KCa channel expression and cross-talk. qPCR mRNA analysis and immunocytochemical staining demonstrated TRPV4 and KCa expression in mCCDcl1 cells and kidney connecting tubule (CNT) and CCD. Three subfamilies of KCa channels were revealed: the high Ca2+-binding affinity small-conductance SK channels, SK1and SK3, the intermediate conductance channel, IK1, and the low Ca2+-binding affinity, BK channel (BKα subunit). Apparent expression levels varied in CNT/CCD where analysis of CCD principal cells (PC) and intercalated cells (IC) demonstrated differential staining: SK1:PCIC, IK1:PC>IC, BKα:PC = IC, and TRPV4:PC>IC. Patch clamp analysis and fluorescence Ca2+ imaging of mCCDcl1 cells demonstrated potent TRPV4-mediated Ca2+ entry and strong functional cross-talk between TRPV4 and KCa channels. TRPV4-mediated Ca2+ influx activated each KCa channel, as evidenced by selective inhibition of KCa channels, with each active KCa channel enhancing Ca2+ entry (due to membrane hyperpolarization). Transepithelial electrical resistance (TEER) analysis of confluent mCCDcl1 cells grown on permeable supports further demonstrated this cross-talk where TRPV4 activation induce a decrease in TEER which was partially restored upon selective inhibition of each KCa channel. It is concluded that SK1/SK3 and IK1 are highly expressed along with BKα in CNT and CCD and are closely coupled to TRPV4 activation as observed in mCCDcl1 cells. The data support a model in CNT/CCD segments where strong cross talk between TRPV4-mediated Ca2+ influx and each KCa channel leads to enhance Ca2+ entry which will support activation of the low Ca2+-binding affinity BK channel to promote BK-mediated K+ secretion

Avoiding catastrophic failure in correlated networks of networks

Networks in nature do not act in isolation but instead exchange information, and depend on each other to function properly. An incipient theory of Networks of Networks have shown that connected random networks may very easily result in abrupt failures. This theoretical finding bares an intrinsic paradox: If natural systems organize in interconnected networks, how can they be so stable? Here we provide a solution to this conundrum, showing that the stability of a system of networks relies on the relation between the internal structure of a network and its pattern of connections to other networks. Specifically, we demonstrate that if network inter-connections are provided by hubs of the network and if there is a moderate degree of convergence of inter-network connection the systems of network are stable and robust to failure. We test this theoretical prediction in two independent experiments of functional brain networks (in task- and resting states) which show that brain networks are connected with a topology that maximizes stability according to the theory.Comment: 40 pages, 7 figure

Seek Help from Teachers or Fight Back? Student Perceptions of Teachers’ Actions during Conflicts and Responses to Peer Victimization

Previous research has shown that teachers’ actions when addressing conflict on school grounds can shape adolescent perceptions regarding how well the school manages victimization. Our objective in this study was to determine how these perceptions influenced the likelihood that adolescent students would react to victimization scenarios by either seeking help from school authority or physically fighting back. Vignettes describing two events of victimization were administered to 148 ethnic minority adolescents (Latino, African American, and Asian backgrounds; 49% female) attending an urban high school with high rates of conflict. Positive perceptions of teachers’ actions during conflicts—assessed via a questionnaire tapping how teachers manage student conflicts both generally and in a specific instance of strife—predicted a greater willingness to seek help from school authority, which in turn negatively predicted self-reported aggressive responses to the victimization scenarios. Path analysis established the viability of this indirect effect model, even when we controlled for sex, beliefs about the acceptability of aggression, and previous levels of reactive aggression. Adolescents’ perceptions of teachers’ actions during conflicts are discussed in relation to social information processing models, improving student–teacher relations, and decreasing aggression at schools