Characterization of CuInTe2 thin films prepared by flash evaporation

peer reviewedThin films of CuInTe2 were grown by flash evaporation. The influence of the substrate temperature Ts during film deposition on the properties of the thin films was examined. CuInTe2 films were structurally characterized by the grazing incidence x-ray diffraction (GIXD) technique. Investigation by this technique demonstrates that the surface of thin films of CuInTe2 prepared by flash vaporation at Ts > 100 °C exhibits the chalcopyrite structure with additional binary compounds in the surface. However, in the volume the films exhibit the chalcopyrite structure only; no foreign phases were observed. X-ray reflectometry was utilized to evaluate the critical reflection angle bc of CuInTe2 (bCuInTe2 c 0.32°) which permitted us to calculate the density of the films to be 6 g cm−3. The evaporated films were p type and the films deposited at Ts = 100 °C had a resistivity in the range 0.3–2 cm. From optical measurements we have determined the optical energy gap Eg 0.94 eV and the effective reduced mass m*r 0.07me

The Casimir force at high temperature

The standard expression of the high-temperature Casimir force between perfect conductors is obtained by imposing macroscopic boundary conditions on the electromagnetic field at metallic interfaces. This force is twice larger than that computed in microscopic classical models allowing for charge fluctuations inside the conductors. We present a direct computation of the force between two quantum plasma slabs in the framework of non relativistic quantum electrodynamics including quantum and thermal fluctuations of both matter and field. In the semi-classical regime, the asymptotic force at large slab separation is identical to that found in the above purely classical models, which is therefore the right result. We conclude that when calculating the Casimir force at non-zero temperature, fluctuations inside the conductors can not be ignored.Comment: 7 pages, 0 figure

Simulation of networks of spiking neurons: A review of tools and strategies

We review different aspects of the simulation of spiking neural networks. We start by reviewing the different types of simulation strategies and algorithms that are currently implemented. We next review the precision of those simulation strategies, in particular in cases where plasticity depends on the exact timing of the spikes. We overview different simulators and simulation environments presently available (restricted to those freely available, open source and documented). For each simulation tool, its advantages and pitfalls are reviewed, with an aim to allow the reader to identify which simulator is appropriate for a given task. Finally, we provide a series of benchmark simulations of different types of networks of spiking neurons, including Hodgkin-Huxley type, integrate-and-fire models, interacting with current-based or conductance-based synapses, using clock-driven or event-driven integration strategies. The same set of models are implemented on the different simulators, and the codes are made available. The ultimate goal of this review is to provide a resource to facilitate identifying the appropriate integration strategy and simulation tool to use for a given modeling problem related to spiking neural networks.Comment: 49 pages, 24 figures, 1 table; review article, Journal of Computational Neuroscience, in press (2007

КЛИНИЧЕСКОЕ ЗНАЧЕНИЕ МАРКЕРА НЕОАРТЕРИОГЕНЕЗА – ПЛАЦЕНТАРНОГО ФАКТОРА РОСТА PLGF У РЕЦИПИЕНТОВ ТРАНСПЛАНТИРОВАННОГО СЕРДЦА

In transplanted hearts, peri- and postoperative ischemic and alloimmune stimuli may be interpreted as inadequate tissue perfusion leading to activation of angiogenic signaling. Placenta growth factor (PLGF) is a marker of neoangiogenesis, belonge to vascular endothelial growth factors (VEGF) family. It has been shown that PLGF serum levels are elevated during acute rejection and decrease after immunosuppressive therapy in pediatric heart transplant recipients. The study was aimed to investigate clinical and prognostic significance of PLGF in heart transplant recipients. 34 patients (pts) (42,5 ± 8,5 years, 29 men and 5 women, 21 patient with dilated cardiomyopathy, 13 – with ischemic heart disease) underwent heart transplantation (HTx) and were examined before and after HTx. Our results showed that pretransplant PLGF is a marker of posttransplant cardiovascular risk. Revealing PLGF plasma level in recipients during the first year after HTx also has prognostic value concerning development of cardiovascular complications. In the remote terms (1–16 years) after HTx PLGF plasma levels were significantly higher in recipients with TxCAD than in recipients without TxCAD. These findings confirm participation of PLGF in damage of the transplanted heart vessels. В последние годы активно изучается роль процессов неоангиогенеза при атеросклерозе и васкулопа- тии аллотрансплантата сердца. Плацентарный фактор роста (PLGF) – маркер неоангиогенеза – белок се- мейства эндотелиальных факторов роста (VEGF). Изучали связь уровня PLGF с развитием васкулопатии трансплантированного сердца и его значения для прогнозирования и оценки риска прогрессирования этой патологии. Обследовано 34 пациента до трансплантации сердца (ТС) и в различные сроки после нее (42,5 ± 8,5 года, 29 мужчин и 5 женщин, 21 пациент с дилатационной кардиомиопатией, 13 – с ишемиче- ской болезнью сердца). Результаты исследования показали, что уровень РLGF у пациентов до ТС яв- ляется независимым фактором риска развития сердечно-сосудистых осложнений после ТС. Выявление уровней РLGF > 12 пг/мл у реципиентов в первый год после ТС связано с высоким риском развития сер- дечно-сосудистых осложнений в более поздние сроки после ТС. Повышенный уровень РLGF (>12 пг/мл) у реципиентов с БКАПС в отдаленные сроки после ТС может служить индикатором риска прогрессиро- вания васкулопатии, развития рестенозов после ангиопластики.

Network-State Modulation of Power-Law Frequency-Scaling in Visual Cortical Neurons

Various types of neural-based signals, such as EEG, local field potentials and intracellular synaptic potentials, integrate multiple sources of activity distributed across large assemblies. They have in common a power-law frequency-scaling structure at high frequencies, but it is still unclear whether this scaling property is dominated by intrinsic neuronal properties or by network activity. The latter case is particularly interesting because if frequency-scaling reflects the network state it could be used to characterize the functional impact of the connectivity. In intracellularly recorded neurons of cat primary visual cortex in vivo, the power spectral density of Vm activity displays a power-law structure at high frequencies with a fractional scaling exponent. We show that this exponent is not constant, but depends on the visual statistics used to drive the network. To investigate the determinants of this frequency-scaling, we considered a generic recurrent model of cortex receiving a retinotopically organized external input. Similarly to the in vivo case, our in computo simulations show that the scaling exponent reflects the correlation level imposed in the input. This systematic dependence was also replicated at the single cell level, by controlling independently, in a parametric way, the strength and the temporal decay of the pairwise correlation between presynaptic inputs. This last model was implemented in vitro by imposing the correlation control in artificial presynaptic spike trains through dynamic-clamp techniques. These in vitro manipulations induced a modulation of the scaling exponent, similar to that observed in vivo and predicted in computo. We conclude that the frequency-scaling exponent of the Vm reflects stimulus-driven correlations in the cortical network activity. Therefore, we propose that the scaling exponent could be used to read-out the “effective” connectivity responsible for the dynamical signature of the population signals measured at different integration levels, from Vm to LFP, EEG and fMRI

Context Matters: The Illusive Simplicity of Macaque V1 Receptive Fields

Even in V1, where neurons have well characterized classical receptive fields (CRFs), it has been difficult to deduce which features of natural scenes stimuli they actually respond to. Forward models based upon CRF stimuli have had limited success in predicting the response of V1 neurons to natural scenes. As natural scenes exhibit complex spatial and temporal correlations, this could be due to surround effects that modulate the sensitivity of the CRF. Here, instead of attempting a forward model, we quantify the importance of the natural scenes surround for awake macaque monkeys by modeling it non-parametrically. We also quantify the influence of two forms of trial to trial variability. The first is related to the neuron’s own spike history. The second is related to ongoing mean field population activity reflected by the local field potential (LFP). We find that the surround produces strong temporal modulations in the firing rate that can be both suppressive and facilitative. Further, the LFP is found to induce a precise timing in spikes, which tend to be temporally localized on sharp LFP transients in the gamma frequency range. Using the pseudo R[superscript 2] as a measure of model fit, we find that during natural scene viewing the CRF dominates, accounting for 60% of the fit, but that taken collectively the surround, spike history and LFP are almost as important, accounting for 40%. However, overall only a small proportion of V1 spiking statistics could be explained (R[superscript 2]~5%), even when the full stimulus, spike history and LFP were taken into account. This suggests that under natural scene conditions, the dominant influence on V1 neurons is not the stimulus, nor the mean field dynamics of the LFP, but the complex, incoherent dynamics of the network in which neurons are embedded.National Institutes of Health (U.S.) (K25 NS052422-02)National Institutes of Health (U.S.) (DP1 ODOO3646

EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial

More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369

Ce que les vibrisses disent au cerveau tactile

Le système des vibrisses des rongeurs est devenu un des modèles principaux pour l’étude des propriétés fonctionnelles des neurones sensoriels. Ceci est dû, d’une part, à la structure très bien connue des voies afférentes qui relient les mécanorécepteurs à la base des vibrisses au cortex somatosensoriel primaire et, d’autre part, à l’accessibilité des senseurs tactiles permettant de contrôler l’entrée sensorielle à l’échelle du micron et de la milliseconde. L’observation de l’utilisation des vibrisses par le rongeur indique que les contacts avec des objets et des textures se font avec des dizaines de vibrisses simultanément. Nous avons exploré le codage neuronal dans le cortex à tonneaux, le cortex qui reçoit les informations depuis les vibrisses. En combinant enregistrements multi-électrodes et stimulation tactile multivibrissales avec une analyse théorique, nous avons mis en évidence que plusieurs types de réponses neuronales, semblables à celles décrites dans des aires différentes du système visuel, coexistent dans le même volume cortical. Ceci indique que des schémas de codage variés peuvent être implémentés dans le même réseau cortical et seraient mis en jeu pour analyser au mieux les stimulations tactiles diverses et changeantes auxquelles sont confrontés les rongeurs dans leur environnement naturel