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In this study, microelectrical discharge machining (μEDM) is used for drilling microholes on a thin sheet of Ti Grade 2 alloy of thickness 50 μm using a tungsten carbide (WC) microtool of diameter 470 μm. The main focus of the study is to understand the electrical and nonelectrical μEDM parameters on the accuracy, precision, and machining efficiency of drilled holes. The controllable process factors such as capacitance, voltage, tool rotation, and feed rate are considered when conducting the experiments based on a Taguchi L16 orthogonal array. The main effect and interaction contour plots have been prepared to investigate the influence of the process parameters on the response measures like material removal rate, overcut, circularity, and taper angle of the drilled holes. Analysis of variance (ANOVA) has been carried out to study the percentage contribution and significance of each process parameter on the performance measures. The micrographic images reveal the quality of the profiles and edges of the drilled holes. Further, the Overall Evaluation Criterion (OEC) is applied for multiparameter optimization. [ABSTRACT FROM AUTHOR]

In the current study, micro-electric discharge drilling (µEDD) is conducted on a titanium grade 2 alloy using a tungsten carbide (WC) tool electrode of 496 µm diameter. Capacitance, voltage, and feed rate are selected as machining variables to conduct the experiments based on the full factorial experimental design method. Overcut, material removal rate (MRR), circularity, and hole taper are considered as performance measures. Furthermore, overall evaluation criteria (OEC) is utilized for multiple-objective optimization by allotting varying and equal weight percentages to each response measure. The results of OECs are compared with a revolutionary heuristic multi-objective genetic algorithm (MOGA), resulting in a similar optimal parametric combination and close response measures are obtained. Micrographic investigation demonstrates that at lower capacitance and voltage levels, there is less burr formation, recast layer, and circularity error. Moreover, FESEM and EDS analyses are employed to investigate the machined surface topology and elemental composition respectively. [ABSTRACT FROM AUTHOR]

The current research aims at analyzing the machining performance measures of titanium diamond using electro-discharge machining (EDM) process. The selected control variables are peak current and pulse-on-time (Ton) while maintaining a 50% to 75% duty factor during experimental runs. The output responses considered for this operation are material removal rate (MRR), tool wear rate (TWR) and average surface roughness (Ra). A full factorial design (L16) has been employed to execute the current investigation. Analysis of variance along with overall evaluation criteria (OEC) is also carried out for determining the optimal input parametric combination. The work is further supported by mean effect plots and 3D performance plots for visual illustration of outputs. Analyzed results show that current has the most impact on MRR and Ra, while Ton has the most impact on TWR. The obtained results show MRR of 7.753 mg/min (highest), TWR of 0.02 mg/min (lowest) and Ra of 5.46 µm at the optimum parametric combination. Moreover, x-ray diffraction (XRD), scanning electron micrograph (SEM), and energy-dispersive x-ray (EDX) analysis also help in identifying different phases of material on machined work surface. [ABSTRACT FROM AUTHOR]

UnlabelledMultiple neural and peripheral cell types rapidly respond to tissue damage after spinal cord injury to form a structurally and chemically inhibitory scar that limits axon regeneration. Astrocytes form an astroglial scar and produce chondroitin sulfate proteoglycans (CSPGs), activate microglia, and recruit blood-derived immune cells to the lesion for debris removal. One beneficial therapy, olfactory ensheathing cell (OEC) transplantation, results in functional improvements and promotes axon regeneration after spinal cord injury. The lack of an OEC-specific marker, however, has limited the investigation of mechanisms underlying their proregenerative effects. We compared the effects of enhanced green fluorescent protein-labeled fibroblast (FB) and OEC transplants acutely after a complete low-thoracic spinal cord transection in adult rats. We assessed the preservation of neurons and serotonergic axons, the levels of inhibitory CSPGs and myelin debris, and the extent of immune cell activation between 1 and 8 weeks postinjury. Our findings indicate that OECs survive longer than FBs post-transplantation, preserve axons and neurons, and reduce inhibitory molecules in the lesion core. Additionally, we show that OECs limit immune-cell activation and infiltration, whereas FBs alter astroglial scar formation and increase immune-cell infiltration and concomitant secondary tissue damage. Administration of cyclosporine-A to enhance graft survival demonstrated that immune suppression can augment OEC contact-mediated protection of axons and neurons during the first 2 weeks postinjury. Collectively, these data suggest that OECs have neuroprotective and immunomodulatory mechanisms that create a supportive environment for neuronal survival and axon regeneration after spinal cord injury.Significance statementSpinal cord injury creates physical and chemical barriers to axon regeneration. We used a complete spinal cord transection model and olfactory ensheathing cell (OEC) or fibroblast (FB; control) transplantation as a repair strategy. OECs, but not FBs, intermingled with astrocytes, facilitated astroglial scar border formation and sequestered invading peripheral cells. OECs attenuated immune cell infiltration, reduced secondary tissue damage, protected neurons and axons in the lesion core, and helped clear myelin debris. Immunosuppression enhanced survival of OECs and FBs, but only OEC transplantation promoted scaffold formation in the lesion site that facilitated axon regeneration and neuron preservation.

The regenerative capacity of adult CNS neurons after injury is strongly inhibited by the spinal cord lesion site environment that is composed primarily of the reactive astroglial scar and invading meningeal fibroblasts. Olfactory ensheathing cell (OEC) transplantation facilitates neuronal survival and functional recovery after a complete spinal cord transection, yet the mechanisms by which this recovery occurs remain unclear. We used a unique multicellular scar-like culture model to test if OECs promote neurite outgrowth in growth-inhibitory areas. Astrocytes were mechanically injured and challenged by meningeal fibroblasts to produce key inhibitory elements of a spinal cord lesion. Neurite outgrowth of postnatal cerebral cortical neurons was assessed on three substrates: quiescent astrocyte control cultures, reactive astrocyte scar-like cultures, and scar-like cultures with OECs. Initial results showed that OECs enhanced total neurite outgrowth of cortical neurons in a scar-like environment by 60%. We then asked if the neurite growth-promoting properties of OECs depended on direct alignment between neuronal and OEC processes. Neurites that aligned with OECs were nearly three times longer when they grew on inhibitory meningeal fibroblast areas and twice as long on reactive astrocyte zones compared to neurites not associated with OECs. Our results show that OECs can independently enhance neurite elongation and that direct OEC-neurite cell contact can provide a permissive substrate that overcomes the inhibitory nature of the reactive astrocyte scar border and the fibroblast-rich spinal cord lesion core.

The microchannels are one of the most prominent components used in Lab on a chip device for mixing applications. For effective mixing, microchannels with obstacles are commonly used. Design and fabrication of a microchannel with obstacles (micro features) is a crucial one. By considering this motivation, a study on optimization of control parameters for fabrication of different microfeatures on copper and brass using photochemical machining (PCM) is carried out. The control parameters such as etchant concentration, etching temperature and time were considered to measure material removal rate (MRR), surface roughness (Ra) and the edge deviation (ED). In order to have better PCM performance, MRR desired to be higher, while Ra and ED are desired lesser. To obtain optimum conditions for attaining the higher MRR with lesser ED and Ra, Overall Evaluation Criteria (OEC) was articulated. Further, characterization has been carried out employing scanning electron microscopy. Finally, as an application of the study, different master molds of microchannels without and with triangular, semi-circular, and square obstacles were fabricated and using these molds, Polydimethylsiloxane (PDMS) microchannels were fabricated employing soft lithography technique. On the basis of fluid flow analysis, fabricated microchannels found to be suitable for the various microfluidic applications. [ABSTRACT FROM AUTHOR]

This paper introduces an experimental investigation of micro hole drilling on two different categories of material such as silicon and german silver using micro electrical discharge machining (μEDM) process. The conductivities of the two materials are of different levels; silicon being a semiconductor has relatively much lower electrical conductivity as compared to german silver which is an alloy of copper, nickel and zinc. The tool electrode used is tungsten rod of 518 μm diameter. Responses like material removal rate (MRR), taper angle (TA), circularity error (CE) and overcut (OC) have been calculated and their variation with respect to the process parameters such as capacitance and voltage are evaluated. In both the materials, the values of all the responses increases with an increase in both voltage and capacitance. German silver is observed to have a higher MRR and OC than that of silicon while silicon has a higher TA for the same values of process parameters. The CE of silicon is higher at lower capacitance while it is higher for german silver at higher capacitance. From the analysis of variance (ANOVA), it is observed that both the voltage and capacitance played a significant role in all the responses. An optimum condition of micro hole drilling of both the materials is achieved by formulating overall evaluation criteria (OEC), which combines all the response parameters into a single index. In most of the cases, OEC of german silver is found to be higher than silicon, thus justifying the superior machinability performance of german silver. From the ANOVA of OEC, the role of capacitance is found to be more significant as compared to the voltage. [ABSTRACT FROM AUTHOR]

Abstract Manganese plays multiple role in many biological redox reactions in which it exists in different oxidation states from Mn(II) to Mn(IV). Among them the high-valent manganese-oxo intermediate plays important role in the activity of certain enzymes and lessons from the natural system provide inspiration for new developments of artificial systems for a sustainable energy supply and various organic conversions. This review describes recent advances and key lessons learned from the nature on high-valent Mn-oxo intermediates. Also we focus on the elemental science developed from the natural system, how the novel strategies are realised in nano particles and molecular sites at heterogeneous and homogeneous reaction conditions respectively. Finally, perspectives on the utilisation of the high-valent manganese-oxo species towards other organic reactions are proposed.

Global warming has increased the frequency and duration of high temperature (HT) stress. Photosynthesis determines yield in maize and is extremely HT sensitive. The effects of HT on photosynthesis in maize leaves have been strongly examined under controlled conditions. Here, to explore the mechanism and primary inhibitory sites of HT to photosynthesis, the HT sensitivity of photosynthesis in XY335 and ZD958 maize hybrids was systematically studied in field by multiple methods. HT decreased leaf area and photosynthetic rate of unit leaf area and hence limited growth. HT disrupted chloroplast and mitochondrial membrane structure, possibly delaying photosynthetic recovery after HT. These changes were greater in XY335 than ZD958. Stomatal conductance decreased significantly under HT, and this did not restrict CO2 fixation but may weaken the heat dissipation through transpiration. HT caused photoinhibition of PSII but not PSI. HT damaged both the oxygen‐evolving complex, located at donor side of PSII, and electron transfer from QA to QB, located at acceptor side of PSII. Interference of electron transfer from QA to QB caused by degradation of QB‐binding (D1) protein was the primary site of PSII inhibition by HT in maize leaves. The different stomatal behaviour and photoinhibition sites under HT between maize and wheat were discussed. [ABSTRACT FROM AUTHOR]

In the present work, machining of boron carbide (B4C) has been performed using ultrasonic machining (USM) with the same material as abrasive particles. A comparative assessment of machining of B4C with that of glass and brass has also been carried out by drilling microholes using USM. The experimentation has been conducted according to Taguchi L9 orthogonal array. The effect of feed rate, slurry concentration, and grit size has been evaluated on the performance measures such as material removal rate, overcut, circularity error, taper angle and tool wear rate. Additionally, overall evaluation criteria (OEC) has been formulated to evaluate the combined performance measures. After ANOVA feed rate became the most significant parameters affecting OEC for all the materials. The machining of B4C has been found to be possible but lacks in the machining rate in comparison with that of glass and brass. Least tool wear rate has been found in case of glass whereas minimum overcut, circularity error and taper angle have been observed for brass. The quality of the drilled holes in B4C is better as minimal surface chipping and burr formation has been observed. [ABSTRACT FROM AUTHOR]

Although UV-C radiation has been in use for killing unwanted cyanobacteria, experiments with lower doses of UV-C radiation instead showed induction of growth related parameters and enhanced biomass production in the cyanobacterium Nostoc muscorum Meg1. When the cyanobacterial cultures were exposed to UV-C radiation of varying doses (6, 12 and 18 mJ/cm2), concentrations of various photo-absorbing pigments, RuBisCO and D1 protein of PSII; activities of oxygen evolving complex, nitrogenase and glutamine synthetase were significantly increased upon 6 and 12 mJ/cm2 UV-C radiation exposures. Resulting higher photosynthetic performance was evident from the augmentation in carbohydrate content by ∼49% under single exposure to 6 mJ/cm2 UV-C by fifteenth day. The increased performances of both RuBisCO and D1 proteins were in part also due to induction at the genetic level as seen from the increase in their mRNA and protein levels under treatment. Similar increase was also observed in protein (16%) and in lipid contents (43%) that reflected an upsurge in the total biomass. Highest biomass (463 mg/L/d) was noted in culture exposed to 6 mJ/cm2 UV-C radiation, representing a ∼25% increase. Furthermore the possibility of this organism using part of the incident UV-C radiation as an additional source of energy was deduced from an experiment where the thylakoid membranes excited within UV (226–400 nm) range showed emission at longer wavelengths with an emission maximum at ∼640 nm. Thus this work provides evidence that lower UV-C doses can potentially augment cyanobacterial growth and use of unstandardized UV-C doses for restricting cyanobacterial growth may in fact produce contrary result. • Lower doses of UV-C radiation induced CO 2 and N 2 -fixation in cyanobacteria. • This in turn led to increase in biomass production. • The organism could use UV radiation as auxiliary energy for photosynthesis. • This indicated not all UV-C radiation doses are detrimental to cyanobacteria. • Hence caution is required while using UV-C in controlling cyanobacterial bloom. [ABSTRACT FROM AUTHOR]

QM(UB3LYP)/MM(AMBER) calculations were performed for the locations of the transition structure (TS) of the oxygen–oxygen (O–O) bond formation in the S4 state of the oxygen-evolving complex (OEC) of photosystem II (PSII). The natural orbital (NO) analysis of the broken-symmetry (BS) solutions was also performed to elucidate the nature of the chemical bonds at TS on the basis of several chemical indices defined by the occupation numbers of NO. The computational results revealed a concerted bond switching (CBS) mechanism for the oxygen–oxygen bond formation coupled with the one-electron transfer (OET) for water oxidation in OEC of PSII. The orbital interaction between the σ-HOMO of the Mn(IV)4–O(5) bond and the π*-LUMO of the Mn(V)1=O(6) bond plays an important role for the concerted O–O bond formation for water oxidation in the CaMn4O6 cluster of OEC of PSII. One electron transfer (OET) from the π-HOMO of the Mn(V)1=O(6) bond to the σ*-LUMO of the Mn(IV)4–O(5) bond occurs for the formation of electron transfer diradical, where the generated anion radical [Mn(IV)4–O(5)]-• part is relaxed to the •Mn(III)4 ... O(5)- structure and the cation radical [O(6)=Mn(V)1]+ • part is relaxed to the +O(6)–Mn(IV)1• structure because of the charge-spin separation for the electron-and hole-doped Mn–oxo bonds. Therefore, the local spins are responsible for the one-electron reductions of Mn(IV)4->Mn(III)4 and Mn(V)1->Mn(IV)1. On the other hand, the O(5)- and O(6)+ sites generated undergo the O–O bond formation in the CaMn4O6 cluster. The Ca(II) ion in the cubane- skeleton of the CaMn4O6 cluster assists the above orbital interactions by the lowering of the orbital energy levels of π*-LUMO of Mn(V)1=O(6) and σ*-LUMO of Mn(IV)4–O(5), indicating an important role of its Lewis acidity. Present CBS mechanism for the O–O bond formation coupled with one electron reductions of the high-valent Mn ions is different from the conventional radical coupling (RC) and acid-base (AB) mechanisms for water oxidation in artificial and native photosynthesis systems. The proton-coupled electron transfer (PC-OET) mechanism for the O–O bond formation is also touched in relation to the CBS-OET mechanism. [ABSTRACT FROM AUTHOR]

Little is known regarding the detailed mechanism of CuO NPs' toxicity to microalgal primary metabolism pathway. Photosynthesis and respiration are the most important primary metabolism and the main sources of production of reactive oxygen species (ROS), but the effect of CuO NPs on both of them has not been systematically studied to date. Our research demonstrated that long-term treatment with CuO NPs significantly inhibited activities of photosynthesis and respiration in microalgae, and the photosynthesis was more sensitive to the toxicity of CuO NPs than respiration. CuO NPs could be absorbed by microalgae and be converted into Cu2O NPs concentrated in chloroplast. The internalized Cu, regardless of whether the exposure was Cu2+ or CuO NPs had the same capacity to damage chloroplast structure. The result also shows that the oxygen-evolving complex (OEC) in the photosynthetic electron transport chain was the most sensitive site to CuO NPs and Cu2+-treated microalgae had the same damage site as that of CuO NPs, which may be related to the Mn cluster that is dissociated by Cu ions released from CuO NPs. The damage of OEC inhibited photosynthetic electron transport to increase excess excited energy, which caused the accumulation of ROS in chloroplast. The accumulation of ROS damaged the structure of cell membrane and aggravated the PSII photoinhibition, further decreasing the efficiency of light energy utilization. In conclusion, the Cu ionic toxicity of photosynthetic apparatus by CuO NPs resulted in the carbon starvation and the accumulation of ROS to inhibit the growth of microalgae. [ABSTRACT FROM AUTHOR]

Tropospheric ozone is currently regarded as one of the most important air pollutants, since it causes more damage to vegetation world-wide than all the other pollutants combined (Ashmore and Bell 1991). Due to its oxidative nature ozone causes leaf damage and a decrease in photosynthesis. Ozone tolerance varies widely between species and genotypes. The aim of this study was to identify and quantify the physiological and biochemical constraints imposed by chronic ozone exposure of two bush bean (Phaseolus vulgaris L.) genotypes with known difference in sensitivity, namely S156 (sensitive) and R123 (resistant), to charcoal-filtered air and 80 nmol.mol-1 O3. The study was conducted in open-top growth chambers (OTCs) over the entire growth period by measuring chlorophyll a fluorescence (JIP-test) and photosynthetic gas exchange of the test plants weekly. The status of the photosynthetic apparatus was assessed by analysis of chlorophyll a fluorescence kinetics (JIP test) and CO2 response curves (A:Ci). O3-induced physiological effects were detected in S156 long before appearance of necrotic spots on the trifoliate leaves. Photosynthesis was substantially inhibited in S156, mainly due to disengagement of the oxygen evolving complex (OEC), in hibition of intersystem electron transport and the reduction of end-electron acceptors of PSI (ferredoxin, NADP+), causing the concomitant decrease in the carboxylation and regeneration of ribulose-1,5-bisphosphate. Seed and pod yield closely reflected the photosynthetic response of the test plants. Although leaves of both the genotypes were affected visually, it was S156 that displayed severe necrotic ozone injury on the trifoliate leaves. Our data contribute to and complement the existing knowledge on the processes underlying the phytotoxicity of O3 needed for development of tolerant genotypes. [ABSTRACT FROM AUTHOR]

This article focuses on parametric optimization for photochemical machining (PCM) of brass and german silver. The aim of the study is to analyze the effect of control parameters on response measures, that is, surface roughness, material removal rate, and edge deviation and optimization of parameters considering different weight percentage for each performance measure. The control parameters have been selected as etchant concentration, etching temperature, and etching time. Using full factorial method of design of experiments, PCM has been carried out using ferric chloride as etchant. Surface roughness and edge deviation should be less, while material removal rate is desired high. For satisfying this multi-objective condition, overall evaluation criteria (OEC) have been formulated by assigning different and equal weight percentage to response measures. The optimized condition for particular OEC is obtained, and analysis of variance (ANOVA) has been performed for observing effect of control parameters on response measures. Surface topography study has been performed using scanning electron microscopy, and material composition analysis has been carried out using energy dispersive spectroscopy. The surface roughness is observed lower for brass, while the edge deviation is found lesser for german silver. The material removal rate is observed higher for brass compared to german silver. [ABSTRACT FROM PUBLISHER]

The in situ immunocytochemical properties of olfactory ensheathing cells (OECs) have been well studied in several small to medium sized animal models including rats, mice, guinea pigs, cats and canines. However, we know very little about the antigenic characteristics of OECs in situ within the adult and developing human olfactory bulb and nerve roots. To address this gap in knowledge we undertook an immunocytochemical analysis of the 11-19 pcw human foetal olfactory system. Human foetal OECs in situ possessed important differences compared to rodents in the expression of key surface markers. P75 was not observed in OECs but was strongly expressed by human foetal Schwann cells and perineurial olfactory nerve fibroblasts surrounding OECs. We define OECs throughout the 11-19 pcw human olfactory system as S100/vimentin/SOX10+ with low expression of GFAP. Our results suggest that P75 is a robust marker that could be utilised with cell sorting techniques to generate enriched OEC cultures by first removing P75 expressing Schwann cells and fibroblasts, and subsequently to isolate OECs after P75 upregulation in vitro. O4 and PSA-NCAM were not found to be suitable surface antigens for OEC purification owing to their ambiguous and heterogeneous expression. Our results highlight the importance of corroborating cell markers when translating cell therapies from animal models to the clinic. [ABSTRACT FROM AUTHOR]

Nowadays, billions of people use the Web in connection with their daily needs. A significant part of these needs are constituted by search tasks that are usually addressed by search engines. Thus, daily search needs result in regular user engagement with a search engine. User engagement with web services was studied in various aspects, but there appears to be little work devoted to its regularity and periodicity. In this article, we study periodicity of user engagement with a popular search engine through applying spectrum analysis to temporal sequences of different engagement metrics. First, we found periodicity patterns of user engagement and revealed classes of users whose periodicity patterns do not change over a long period of time. In addition, we give an exhaustive analysis of the stability and quality of identified clusters. Second, we used the spectrum series as key metrics to evaluate search quality. We found that the novel periodicity metrics outperform the state-of-the-art quality metrics both in terms of significance level (p-value) and sensitivity to a large set of larges-scale A/B experiments conducted on real search engine users. [ABSTRACT FROM AUTHOR]

Olfactory ensheathing cells ( OECs) are a unique glial population found in both the peripheral and central nervous system: they ensheath bundles of unmyelinated olfactory axons from their peripheral origin in the olfactory epithelium to their central synaptic targets in the glomerular layer of the olfactory bulb. Like all other peripheral glia (Schwann cells, satellite glia, enteric glia), OECs are derived from the embryonic neural crest. However, in contrast to Schwann cells, whose development has been extensively characterised, relatively little is known about their normal development in vivo. In the Schwann cell lineage, the transition from multipotent Schwann cell precursor to immature Schwann cell is promoted by canonical Notch signalling. Here, in situ hybridisation and immunohistochemistry data from chicken, mouse and human embryos are presented that suggest a canonical Notch-mediated transition also occurs during OEC development. [ABSTRACT FROM AUTHOR]

The regenerative capacity of adult CNS neurons after injury is strongly inhibited by the spinal cord lesion site environment that is composed primarily of the reactive astroglial scar and invading meningeal fibroblasts. Olfactory ensheathing cell (OEC) transplantation facilitates neuronal survival and functional recovery after a complete spinal cord transection, yet the mechanisms by which this recovery occurs remain unclear. We used a unique multicellular scar-like culture model to test if OECs promote neurite outgrowth in growth-inhibitory areas. Astrocytes were mechanically injured and challenged by meningeal fibroblasts to produce key inhibitory elements of a spinal cord lesion. Neurite outgrowth of postnatal cerebral cortical neurons was assessed on three substrates: quiescent astrocyte control cultures, reactive astrocyte scar-like cultures, and scar-like cultures with OECs. Initial results showed that OECs enhanced total neurite outgrowth of cortical neurons in a scar-like environment by 60%. We then asked if the neurite growth-promoting properties of OECs depended on direct alignment between neuronal and OEC processes. Neurites that aligned with OECs were nearly three times longer when they grew on inhibitory meningeal fibroblast areas and twice as long on reactive astrocyte zones compared to neurites not associated with OECs. Our results show that OECs can independently enhance neurite elongation and that direct OEC–neurite cell contact can provide a permissive substrate that overcomes the inhibitory nature of the reactive astrocyte scar border and the fibroblast-rich spinal cord lesion core. [ABSTRACT FROM AUTHOR]

[Display omitted] • The huge different redox potential in OEC model complex Mn 3 CaO 4 and Mn 4 CaO 4 arises from the different ligand environments, net charge, and the oxygen bridge induced by the fourth Mn atom. • The redox potential of Mn 3 CaO 4 complex can be modulated to that in OEC and Mn 4 CaO 4 complexes by changing the ligand and charge, together with the functionalization on oxygen bridges. • Our results show that the fourth Mn atom may not be obligatory in maintaining the redox potential of OEC model complex. In recent years, major breakthroughs have been achieved in the synthesis and mimicking of oxygen evolution center (OEC) in photosystem II. Mn 3 CaO 4 and Mn 4 CaO 4 complexes, which are very similar to the core structure of Mn 4 CaO 5 in OEC, were synthesized successively. Interestingly, the Mn 4 CaO 4 complexes have similar redox potential as OEC and show the reactivity of water oxidation. While the Mn 3 CaO 4 complex has much lower redox potential and does not have water oxidation reactivity. In this work, with carefully designed theoretical models, we found the net charge, ligand environments and oxygen bridges are mutually important for the different potential in the two model complexes. The fourth Mn in Mn 4 CaO 4 modulates the potential by changing the oxygen bridges of the [Mn 3 O 4 ] core, and the modulating effect can also be accomplished by functionalization on the bridging oxygen atoms together with certain ligand modifications, suggesting the fourth Mn may not be obligatory in maintaining the redox potential of OEC and Mn 4 CaO 4 complex. [ABSTRACT FROM AUTHOR]

The use of oxygen evolution co-catalysts (OECs) with hematite photoanodes has received much attention because of the potential to reduce surface charge recombination. However, the low surface charge transfer and bulk charge separation rate of hematite are not improved by decorating with OECs, and the intrinsic drawbacks of hematite still limit efficient photoelectrochemical (PEC) water splitting. Here, we successfully overcame the sluggish oxygen evolution reaction performance of hematite for water splitting by inserting zero-dimensional (0D) nanofragmented MXene (NFMX) as a hole transport material between the hematite and the OEC. The 0D NFMX was fabricated from two-dimensional (2D) MXene sheets and deposited onto the surface of a three-dimensional (3D) hematite photoanode via a centrifuge-assisted method without altering the inherent performance of the 2D MXene sheets. Among many OECs, NiFe(OH) x was selected as the OEC to improve hematite PEC performance in our system because of its efficient charge transport behavior and high stability. Because of the great synergy between NFMX and NiFe(OH) x , NiFe(OH) x /NFMX/Fe 2 O 3 achieved a maximum photocurrent density of 3.09 mA cm -2 at 1.23 V RHE , which is 2.78-fold higher than that of α-Fe 2 O 3 (1.11 mA cm -2 ). Furthermore, the poor stability of MXene in an aqueous solution for water splitting was resolved by uniformly coating it with NiFe(OH) x , after which it showed outstanding stability for 60 h at 1.23 V RHE . This study demonstrates the successful use of NFMX as a hole transport material combined with an OEC for highly efficient water splitting.

Background Skiers and snowboarders incur a variety of injuries and medical emergencies each year at ski resorts. The ski patrol is primarily responsible for initial triage, assessment and stabilization of these problems. Objective The purpose of this study was to subjectively evaluate the type of training, resources, and equipment available to local ski patrols within Utah. Methods Ski patrol directors at ski resorts in Utah were asked to complete a voluntary computerized survey. Results Of the 14 ski areas in Utah, ski patrol directors representing 8 resorts responded. The majority of patrols in Utah use Outdoor Emergency Care (OEC) as their primary education and certification source. Most programs also include site-specific training in addition to basic certification. All responding resorts had basic first responder equipment, including splinting devices, basic airway management, and hemorrhage control. Six of 8 responding resorts had affiliated clinics, and all had access to aeromedical transport. All of the responding ski patrol directors believed the current training level was adequate. Conclusions Utah area ski patrollers frequently see trauma-related injuries and have the resources to assess and provide initial immobilization techniques. Many resorts have affiliated clinics with advanced providers, and all have access to aeromedical support to rapidly transfer patients to trauma centers. Medical directors may be of use for training as well as developing extended scope of practice protocols for advanced airway use or medication administration. Patrols may benefit from additional resort-specific training that addresses other frequently seen injuries or illnesses. [ABSTRACT FROM AUTHOR]

Boc-protected tyrosine-attached corrole ligand on the ' ortho' position compound 3, its corresponding copper (III) 4a, manganese (IV) 4b, and manganese (III) 4c complexes have been designed and synthesized based on the structures of active-centers of related biological systems. H NMR and electronic absorption spectra of these metal complexes are investigated. The crystal structure of 4a displays the relative position of TyrOH unit to the high valent metal center. Electrochemistry investigations display the possibilities of intramolecular electron or energy transfer between TyrOH group and metal corrole group. [ABSTRACT FROM AUTHOR]

The assignment of the two substrate water sites of the tetra-manganese penta-oxygen calcium (Mn4O5Ca) cluster of photosys tem II is essential for the elucidation of the mechanism of biological O-O bond formation and the subsequent design of bio-inspired water-splitting catalysts. We recently demonstrated using pulsed EPR spectroscopy that one of the five oxygen bridges (μ-oxo) exchanges unusually rapidly with bulk water and is thus a likely candidate for one of the substrates. Ammonia, a water analog, was previously shown to bind to the Mn40.,Ca cluster, potentially dis placing a water/substrate ligand [Britt RD, et al. (1989) J Am Chem Soc 111(10):3522-3532]. Here we show by a combination of EPR and time-resolved membrane inlet mass spectrometry that the binding of ammonia perturbs the exchangeable u-oxo bridge without dras tically altering the binding/exchange kinetics of the two substrates. In combination with broken-symmetry density functional theory, our results show that (i) the exchangable μ-oxo bridge is 05 {using the labeling of the current crystal structure [Umena Y, et al. (2011) Nature 473(7345):55-60]}; (ii) ammonia displaces a water ligand to the outer manganese (MnA4-W1); and (iii) as W1 is trans to 05, ammonia binding elongates the MnA4-05 bond, leading to the per turbation of the u-oxo bridge resonance and to a small change in the water exchange rates. These experimental results support O-O bond formation between 05 and possibly an oxyl radical as proposed by Siegbahn and exclude W1 as the second substrate water. [ABSTRACT FROM AUTHOR]

Olfactory ensheathing cells (OECs) and Schwann cells (SCs) are closely-related cell types with regeneration-promoting properties. Comparative gene expression analysis is particularly relevant since it may explain cell type-specific effects and guide the use of each cell type into special clinical applications. In the present study, we focused on β-tubulin isotype expression in primary adult canine glia as a translational large animal model. β-tubulins so far have been studied mainly in non-neuronal tumors and implied in tumorigenic growth. We show here that primary OECs and SCs expressed βII-V isotype mRNA. Interestingly, βIII-tubulin mRNA and protein expression was high in OECs and low in SCs, while fibroblast growth factor-2 (FGF-2) induced its down-regulation in both cell types to the same extent. This was in contrast to βV-tubulin mRNA which was similarly expressed in both cell types and unaltered by FGF-2. Immunocytochemical analysis revealed that OEC cultures contained a higher percentage of βIII-tubulin-positive cells compared to SC cultures. Addition of FGF-2 reduced the number of βIII-tubulin-positive cells in both cultures and significantly increased the percentage of cells with a multipolar morphology. Taken together, we demonstrate cell type-specific expression (βIII) and isotype-specific regulation (βIII, βV) of β-tubulin isotypes in OECs and SCs. While differential expression of βIII-tubulin in primary glial cell types with identical proliferative behaviour argues for novel functions unrelated to tumorigenic growth, strong βIII-tubulin expression in OECs may help to explain the specific properties of this glial cell type. [ABSTRACT FROM AUTHOR]

Clonal in vitro analysis represents a powerful tool for studying cellular differentiation. In the present study, microscope-assisted single cell transfer was combined with immunofluorescence to establish clonal cultures of identified primary rat olfactory ensheathing cells (OECs). During development, OECs originate from the neural crest, a transient population of multipotent cells. Since only neural crest cells have been analyzed at clonal density, it remained unclear whether OECs may retain multipotent features. Neurotrophin receptor p75 (p75)-immunolabelled rat OECs were seeded at clonal density under visual control using a semiautomated cell selection and transfer device (Quixell™) and emerging clones were analyzed with regard to proliferation and antigenic expression. We demonstrate that OECs from neonatal (P1) and 7 day-old (P7) but not from adult rats formed clones in the presence of OEC- and astrocyte-conditioned media (OEC-CM, A-CM). Cloning efficiency but not in vitro growth of OECs was independent of age but increased upon treatment with OEC-CM. Interestingly, about 75 % of P1 compared to 27 % of P7 OEC clones lost p75 expression during 2 weeks in vitro and acquired immunoreactivity for Thy-1. The observation that primary OECs from P1 lost expression of p75 at clonal density and initiated expression of the fibroblast marker Thy-1 may suggest that their developmental potential is greater than previously anticipated. Since microscope-assisted selection of immunofluorescent cells combined with semiautomated transfer guarantees monoclonality in a single step and affords selection of cells according to fluorescent label and/or morphological criteria it may be relevant for a variety of other cell types. [ABSTRACT FROM AUTHOR]

Abstract: The effect of OEC on soot formation and thermal radiation was studied in confined acetylene diffusion flames. Confined flames are widely used in industrial settings. The flames were produced in a combustion chamber with a burner operating with a parallel annular coaxial flow of the oxidizer. The soot concentration was calculated by the laser-induced light extinction method. The thermal radiation was measured with a radiometer in the narrow band of influence of soot radiation. The oxygen content in the combustion air was less than 30% – 21 to 25% – which does not require significant retrofitting of existing equipment when combustion conditions are varied. The results suggest that the use of OEC enables soot formation and thermal radiation in confined acetylene flames to be managed and controlled. [Copyright &y& Elsevier]

Very recently Umena et al. have determined the X-ray diffraction (XRD) structure of the CaMn4O5 cluster in the oxygen evolution complex (OEC) of photosystem II (PSII) refined to 1.9 Å resolution. We have performed theoretical attempts to elucidate possible electronic and spin states of their new XRD structure of the CaMn4O5 cluster. For the purpose, hybrid density functional theory (UB3LYP and UBHandHLYP) calculations have been performed for the mixed-valence (MV) CaMn(III)4-ω(IV)ωO5(H2O)4 ( 1) and CaMn(III)4-ω(IV)ωO4(OH)(H2O)4 ( 2) clusters as active catalytic site for water splitting reaction in OEC of PSII. Full geometry optimizations of 1a (ω = 2) and 2a (ω = 2) have been performed to elucidate scope and limitation of the cluster models. Both charge and spin fluctuated structures (48 UB3LYP solutions) have been considered for the MV 1a (ω = 2). Total energies obtained by these calculations have elucidated quasi-degenerated electronic and spin states that are characterized by charge and spin density populations. The energy levels revealed by hybrid DFT are analyzed on the basis of the Heisenberg spin Hamiltonian model, providing the effective exchange integrals between manganese ions at a uniform or MV structure. The spin projections for hybrid DFT solutions are performed using the effective exchange integrals. The charge fluctuation model is introduced to analyze relative stabilities among MV structures of 1a and 2a. These computational results for 1a and 2a have explored several characteristic electronic properties of the species that are used for theoretical elucidation of possible mechanisms of water splitting reaction. Orbital and spin correlation diagrams are derived for the OO bond formation and oxygen evolution in the reaction. Implications of the computational results are also discussed in relation to available experiments and theoretical results by other groups. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012 [ABSTRACT FROM AUTHOR]

Axons of primary olfactory neurons are intimately associated with olfactory ensheathing cells (OECs) from the olfactory epithelium until the final targeting of axons within the olfactory bulb. However, little is understood about the nature and role of interactions between OECs and axons during development of the olfactory nerve pathway. We have used high resolution time-lapse microscopy to examine the growth and interactions of olfactory axons and OECs in vitro. Transgenic mice expressing fluorescent reporters in primary olfactory axons (OMP-ZsGreen) and ensheathing cells (S100ß-DsRed) enabled us to selectively analyse these cell types in explants of olfactory epithelium. We reveal here that rather than providing only a permissive substrate for axon growth, OECs play an active role in modulating the growth of pioneer olfactory axons. We show that the interactions between OECs and axons were dependent on lamellipodial waves on the shaft of OEC processes. The motility of OECs was mediated by GDNF, which stimulated cell migration and increased the apparent motility of the axons, whereas loss of OECs via laser ablation of the cells inhibited olfactory axon outgrowth. These results demonstrate that the migration of OECs strongly regulates the motility of axons and that stimulation of OEC motility enhances axon extension and growth cone activity. [ABSTRACT FROM AUTHOR]

Abstract: The electronic properties of the Mn4O x Ca cluster in the S 2 state of the oxygen-evolving complex (OEC) were studied using X- and Q-band EPR and Q-band 55Mn-ENDOR using photosystem II preparations isolated from the thermophilic cyanobacterium T. elongatus and higher plants (spinach). The data presented here show that there is very little difference between the two species. Specifically it is shown that: (i) only small changes are seen in the fitted isotropic hyperfine values, suggesting that there is no significant difference in the overall spin distribution (electronic coupling scheme) between the two species; (ii) the inferred fine-structure tensor of the only MnIII ion in the cluster is of the same magnitude and geometry for both species types, suggesting that the MnIII ion has the same coordination sphere in both sample preparations; and (iii) the data from both species are consistent with only one structural model available in the literature, namely the Siegbahn structure [Siegbahn, P. E. M. Accounts Chem. Res. 2009, 42, 1871–1880, Pantazis, D. A. et al., Phys. Chem. Chem. Phys. 2009, 11, 6788–6798]. These measurements were made in the presence of methanol because it confers favorable magnetic relaxation properties to the cluster that facilitate pulse-EPR techniques. In the absence of methanol the separation of the ground state and the first excited state of the spin system is smaller. For cyanobacteria this effect is minor but in plant PS II it leads to a break-down of the S T =½ spin model of the S 2 state. This suggests that the methanol–OEC interaction is species dependent. It is proposed that the effect of small organic solvents on the electronic structure of the cluster is to change the coupling between the outer Mn (MnA) and the other three Mn ions that form the trimeric part of the cluster (MnB, MnC, MnD), by perturbing the linking bis-μ-oxo bridge. The flexibility of this bridging unit is discussed with regard to the mechanism of O-O bond formation. [Copyright &y& Elsevier]

Olfactory ensheathing cells (OECs) are the non-myelinating glial cells of the olfactory nerves and bulb. The fragmentary characterization of OECs in situ during normal development may be due to their small size requiring intricate ultrastructural analysis and to the fact that available markers for in situ detection are either expressed only by OEC subpopulations or lost during development. In the present study, we searched for markers with stable expression in OECs and investigated the spatiotemporal distribution of CNPase, an early oligodendrocyte/Schwann cell marker, in comparison with the prototype marker p75. Anti-CNPase antibodies labeled canine but not rat OECs in situ, while Schwann cells and oligodendrocytes were positive in both species. CNPase immunoreactivity in the dog was confined to all OECs throughout the postnatal development and associated with the entire cell body, including its finest processes, while p75 was mainly detected in perineural cells and only in some neonatal OECs. Adult olfactory bulb slices displayed CNPase expression after 4 and 10 days, while p75 was detectable only after 10 days in vitro. Finally, treatment of purified adult canine OECs with fibroblast growth factor-2 significantly reduced CNPase expression at the protein and mRNA level. Taken together, we conclude that CNPase but not p75 is a stable marker suitable for in situ visualization of OECs that will facilitate their light-microscopic characterization and challenge our general view of OEC marker expression in situ. The fact that canine but not rat OECs expressed CNPase supports the idea that glia from large animals differs substantially from rodents. [ABSTRACT FROM AUTHOR]

Abstract: Olfactory ensheathing cells (OEC), which normally associate closely with but do not myelinate axons in situ, myelinate axons in the adult mammalian spinal cord. They are of clinical interest as candidate cells for autologous transplantation but the ability of OEC to myelinate axons in vitro has been controversial. To clarify this issue, we isolated OEC from olfactory bulbs (OB) of juvenile and adult rats expressing GFP and analyzed their ability to myelinate axons. Using a well-defined assay for myelination of dorsal root ganglia (DRG) axons in culture, we found that OEC from juvenile pups associated with and then myelinated DRG axons. OEC assembled into bundles with the axons by 1week and required more than a week before myelination on axons was detected. In contrast, rat Schwann cells did not bundle axons and they formed P0+ and MBP+ myelin segments after as little as 1week. Most of the OEC in culture exhibited staining for calponin, a marker that was not found on Schwann cells in culture, whereas in both OEC and Schwann cell populations nearly all cells were positive for p75NTR and GFAP. These results confirm previous reports showing only subtle immunological differences between Schwann cells and OEC. Besides differences in the rate of myelination, we detected two additional functional differences in the interactions of OEC and Schwann cells with DRG axons. First, the diameter of OEC generated myelin was greater than for Schwann cell myelin on DRG axons. Second, OEC but not Schwann cells myelinated DRG axons in the absence of vitamin C. OEC isolated from adult OB were also found to bundle and myelinate DRG axons but the latter occurred only after incubation times of at least 3weeks. The results indicate that adult OEC require longer incubation times than juvenile OEC to myelinate axons and suggest that patterns of myelination by OEC and Schwann cells are distinguishable at least on axons in vitro. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair. [Copyright &y& Elsevier]

Abstract: Engraftment of nasal olfactory ensheathing cells (OEC) is considered as a promising therapeutic strategy for spinal cord repair and one clinical trial has already been initiated. However, while the vast majority of fundamental studies were focused on the recovery of locomotor function, the efficiency of this cellular tool for repairing respiratory motor dysfunction, which affects more than half of paraplegic/tetraplegic patients, remains unknown. Using a rat model that mimics the mechanisms encountered after a cervical contusion that induces a persistent hemi-diaphragmatic paralysis, we assessed the therapeutic efficiency of a delayed transplantation (2weeks post-contusion) of nasal OECs within the injured spinal cord. Functional recovery was quantified with respiratory behavior tests, diaphragmatic electromyography and neuro-electrophysiological recording of the phrenic motoneurons while axogenesis was evaluated using immunohistochemistry. We show that 3months post-transplantation, nasal OECs improve i) breathing movements, ii) activities of the ipsilateral diaphragm and corresponding phrenic nerve, and iii) axonal sprouting in the injury site. We also demonstrate that this functional partial recovery is mediated by the restoration of ipsilateral supraspinal command. Our study brings further evidence that olfactory ensheathing cells could have clinical application especially in tetraplegic patients with impaired breathing movements. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair. [Copyright &y& Elsevier]

Olfactory ensheathing cells (OECs) are Schwann cell-like glial cells of the olfactory system that promote neural regeneration after transplantation into the injured central nervous system. Compared to the closely related Schwann cells, however, the biological characterization of OECs has remained fragmentary. This is due to the fact that the expression of OEC-specific markers is subject to complex regulation and that intricate ultrastructural analysis is essential to determine their localization. The p75 neurotrophin receptor (p75) as the prototype OEC marker, for example, is only expressed by a minor population of neonatal rat OECs in situ. The major population carries O4-positive axonal fragments on their surface after dissociation and up-regulates p75 during culturing (Wewetzer et al. in Glia 49:577-587, ). In the present study, we investigated whether the cell surface determinant 27C7, defined by a monoclonal antibody to Schwann cells, is also expressed by neonatal rat OECs in situ and in vitro. Primary cell suspensions of the olfactory bulb displayed 27C7 expression of both p75-negative and p75-positive OECs, while immature oligodendrocytes and astrocytes were devoid of any 27C7 labeling. This together with the finding that the intrafascicular OECs of the olfactory nerves in the mucosa expressed 27C7 but not p75, suggests that 27C7 was expressed by the entire OEC population in situ. Maintenance of OECs in the absence of olfactory neurons in organotypic slice culture up-regulated p75 but did not alter 27C7 expression. It is concluded that 27C7 unlike p75 is constitutively expressed by OECs and may, therefore, be a useful marker for characterization of neonatal OECs in situ and in vitro. [ABSTRACT FROM AUTHOR]

Abstract: The concept of environmental efficiency in equipment is increasing with the unfolding of global warming. In terms of industrial equipment, it is the burners which have a major impact in this discussion because of industrial combustion. Demand for environmentally more efficient burners with a reduction in emissions is essential for the proper use of fossil fuels during the transition between this energy and alternative energy sources for the next fifty years or more. This study experimentally evaluates the technique of oxygen-enhanced combustion – OEC – and its interaction with soot formation and thermal radiation in natural gas confined flames. The literature shows that the OEC technique – an important technique for improving the thermal efficiency of combustion – causes under certain conditions an increase in soot formation. Soot, as an important participant in radiant heat transfer, can increase the thermal efficiency of burners, implementing heat transfer from the flame to the heating areas, thereby reducing fuel consumption, the temperature of the flame, and consequently a reduction in the emission of NOx. In the experiment was used low enriched with oxygen, which does not require significant existing equipment changes. This technology can play an important role in preparing particularly the oil and gas industry for the technological challenge of reducing global warming. [Copyright &y& Elsevier]