Reversible degradation of inverted organic solar cells by concentrated sunlight

Concentrated sunlight was used to study the performance response of inverted P3HT:PCBM organic solar cells after exposure to high intensity sunlight. Correlations of efficiency as a function of solar intensity were established in the range of 0.5-15 suns at three different stages: for a pristine cell, after 30 min exposure at 5 suns and after 30 min of rest in the dark. High intensity exposure introduced a major performance decrease for all solar intensities, followed by a partial recovery of the lost performance over time: at 1 sun only 6% of the initial performance was conserved after the high intensity exposure, while after rest the performance had recovered to 60% of the initial value. The timescale of the recovery effect was studied by monitoring the cell performance at 1 sun after high intensity exposure. This showed that cell performance was almost completely restored after 180 min. The transient state is believed to be a result of the breakdown of the diode behaviour of the ZnO electron transport layer by O(2) desorption, increasing the hole conductivity. These results imply that accelerated degradation of organic solar cells by concentrated sunlight is not a straightforward process, and care has to be taken to allow for a sound accelerated lifetime assessment based on concentrated sunlight.     

Heat dissipation in graphene foams

Graphene foam(GF)—a three-dimensional network of hollow graphene branches—is a highly attractive material for diverse applications.However,to date,the heat dissipation characteristics of GFs have not been characterized.To fill this gap,we synthesized GF devices,subjected them to high temperatures,and investigated their thermal behavior by using infrared microthermography.We find that while the convective area of GF devices is comparable to that of bulk materials(such as metals),the coefficient of convection of these devices is several orders of magnitude higher than that of metals.In addition,the GF devices showed a reproducible thermal behavior,which we attribute to negligible temperature-induced morphological changes(as confirmed by Raman analysis).Taken together,our findings suggest GF as a promising candidate material for advanced cooling applications where efficient heat dissipation is needed,e.g.,in electrical circuits.     

Endotoxemic-like shock induced by Loxosceles spider venoms: pathological changes and putative cytokine mediators

The systemic symptoms, tissue lesions and release of cytokines were analysed in four isogenic mouse strains with distinct haplotypes injected with various doses of Loxosceles intermedia spider venom. The estimated LD50 were 24.5 microg for C57Bl/6, 17.6 microg for BALB/c, 6.3 microg for C3H/HeJ and 4.6 microg for A/Sn mice. Prostration, acute cachexia, hypothermia, neurological disorders and hemoglobinuria were the signals preceding death. Accumulation of eosinophilic material inside the proximal and distal renal tubules and acute tubular necrosis were the most common histopathological findings. Death was prevented by previous treatment of venom with specific antivenom serum. The protein F35 purified from the whole venom retained the ability to induce the symptoms of the whole venom. The cytokines tumor necrosis factor (TNF), interleukins IL-6 and IL-10 and the radical nitric oxide were detected in serum at different levels after venom injection. These findings indicate that the state of shock produced in mice by whole endotoxin-free L. intermedia venom or by its purified fraction, protein F35, mimics the endotoxemic shock, that susceptibility to the systemic effects of the venom varies among mice of different haplotypes and that the pattern of in vivo cytokine release resembles that of endotoxemic shock.     

Tuning energetic levels in nanocrystal quantum dots through surface manipulations

We demonstrate tuning of the electronic level positions with respect to the vacuum level in colloidal InAs nanocrystals using surface ligand exchange. Electrochemical as well as scanning tunneling spectroscopy measurements reveal that the tuning is largely dependent on the nanocrystal size and the surface linking group, while the polarity of the ligand molecules has a lesser effect. The implications of affecting the electronic system of nanocrystal through its capping are illustrated through prototype devices.     

Large-scale unrestricted identification of post-translation modifications using tandem mass spectrometry

TwinPeaks, a close variant of the SEQUEST protein identification algorithm, is capable of unrestricted, large-scale, identification of post-translation modifications (PTMs). TwinPeaks is applied on a sample of 100441 tandem mass spectra from the HUPO Plasma Proteome Project data set, with full non-redundant human as a reference protein database. With a 3.5% error rate, TwinPeaks identifies a collection of 539 spectra that were not identified by the usual PTM-restricted identification algorithm. At this error rate, TwinPeaks increases the rate of spectra identifications by at least 17.6%, making unrestricted PTM identification an integral part of proteomics.     

Molecular Recognition of Two 2,4‐syn‐Functionalized (S)‐Glutamate Analogues by the Kainate Receptor GluK3 Ligand Binding Domain

The kainate receptors are the least studied subfamily of ionotropic glutamate receptors. These receptors are thought to have a neuromodulatory role and have been associated with a variety of disorders in the central nervous system. This makes kainate receptors interesting potential drug targets. Today, structures of the ligand binding domain (LBD) of the kainate receptor GluK3 are only known in complex with the endogenous agonist glutamate, the natural product kainate, and two synthetic agonists. Herein we report structures of GluK3 LBD in complex with two 2,4‐syn‐functionalized (S)‐glutamate analogues to investigate their structural potential as chemical scaffolds. Similar binding affinities at GluK3 were determined for the 2‐(methylcarbamoyl)ethyl analogue (K_i=4.0 μM ) and the 2‐(methoxycarbonyl)ethyl analogue (K_i=1.7 μM ), in agreement with the similar positioning of the compounds within the binding pocket. As the binding affinity is similar to that of glutamate, this type of Cγ substituent could be used as a scaffold for introduction of even larger substituents reaching into unexplored binding site regions to achieve subtype selectivity.     

Adaptive sampling for detecting a change point in the past

Consider the problem of estimating a change point in the drift of Brownian motion which is known to have occurred at some time during the time interval [0,1], Rather than observing the process, we use "adaptive (dynamic) sampling" which allows us to continuously select the time points at which increments of the motion may be observed. Our main results are that the steepest descent method will continuosly select the current Bayes estimator of the change point as the next time point to observe. The method results in a very convergence rate.

In addition, a discrete formulation is given. In this case, a slightly different method based on the mean and the standard deviation is suggested, and is proved to result in an exponential rate of convergence.     

Effect of CaO addition on acid properties of Ni–Ca/Al2O3 catalysts applied to ethanol steam reforming

Ni/Al₂O₃ catalysts containing 5 wt% of Ni and modified by addition of CaO (0–5 wt%) were tested in ethanol steam reforming reaction in order to reduce the dehydration ethanol reaction, which produces ethylene that may polymerize and produce coke. The catalysts were prepared by impregnation (I) and co-precipitation (C) methods. All catalysts were investigated for ethanol steam reforming and the catalytic performance was compared in terms of additive addition. The catalysts 5Ni–5Ca/Al (I) and 5Ni–5Ca/Al (C) were less selective to ethylene production and therefore were characterized by the following techniques: energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), temperature programmed reduction (TPR), X-ray absorption near edge structure (XANES), specific surface area by the BET method, scanning electron microcopy (SEM) and isopropanol decomposition reaction. By comparing the catalysts, the 5Ni–5Ca/Al (I) catalyst presented the lowest acidity and carbon deposition, and also presented no deactivation in 24 h of catalytic test.     

Thermal Modeling of Hybrid Storage Clusters

There is a lack of thermal models for storage clusters; most existing thermal models do not take into account the utilization of hard drives (HDDs) and solid state disks (SSDs). To address this problem, we build a thermal model for hybrid storage clusters that are comprised of HDDs and SSDs. We start this study by generating the thermal profiles of hard drives and solid state disks. The profiling results show that both HDDs and SSDs have profound impacts on temperatures of storage nodes in a cluster. Next, we build two types of hybrid storage clusters, namely, inter-node and intra-node hybrid storage clusters. We develop a model to estimate the cooling cost of a storage cluster equipped with hybrid storage nodes. The thermal model is validated against data acquired by temperature sensors. Experimental results show that, compared to the HDD-first strategy, the SSD-first strategy is an efficient approach to minimize negative thermal impacts of hybrid storage clusters.