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Understanding the modification of the graphene’s electronic structure upon doping is crucial for enlarging its potential applications. We present a study of nitrogen-doped graphene samples on SiC(000 ) combining angle-resolved photoelectron spectroscopy, scanning tunneling microscopy and spectroscopy and X-ray photoelectron spectroscopy (XPS). The comparison between tunneling and angle-resolved photoelectron spectra reveals the spatial inhomogeneity of the Dirac energy shift and that a phonon correction has to be applied to the tunneling measurements. XPS data demonstrate the dependence of the N 1s binding energy of graphitic nitrogen on the nitrogen concentration. The measure of the Dirac energy for different nitrogen concentrations reveals that the ratio usually computed between the excess charge brought by the dopants and the dopants’ concentration depends on the latter. This is supported by a tight-binding model considering different values for the potentials on the nitrogen site and on its first neighbors.

In this overview current insights in the regulation of presynaptic transmitter release, mainly acquired in studies using isolated CNS nerve terminals are highlighted. The following aspects are described. (i) The usefulness of pinched-off nerve terminals, so-called synaptosomes, for biochemical and ultrastructural studies of presynaptic stimulus-secretion coupling. (ii) The regulation of neurotransmitter release by multiple Ca2+ channels, with special emphasis on the specificity of different classes of these channels with respect to the release of distinct types of neurotransmitters, that are often co-localized, such as amino acids and neuropeptides. (iii) Possible molecular mechanisms involved in targeting synaptic vesicle (SV) traffic toward the active zone. (iv) The role of presynaptic receptors in regulating transmitter release, with special emphasis on different glutamate subtype receptors. Isolated nerve terminals are of great value as model system in order to obtain a better understanding of the regulation of the release of distinct classes of neurotransmitters in tiny CNS nerve endings.

Neuronal communication is tightly regulated by presynaptic signaling, thereby temporarily and locally secreting one or more transmitters in order to exert propagation or modulation of network activity. In the last 2 decades our insight into the molecular regulation of presynaptic transmitter vesicle traffic and fusion has exponentionally grown due to the identification of specific functional interactions between presynaptic proteins involved in these processes. In addition, a plethora of extracellular and intracellular messengers regulate neurotransmitter release, occasionally leading to short- or long-term adaptations of the synapse to altered environmental signals. Important in this respect is the ability of various nerve terminals to diverge their output by differentiation in secretion of co-localized transmitters. This divergence in presynaptic signaling may converge in the postsynaptic target neuron or spread to neighbouring cells. In this review differential presynaptic signaling mechanisms will be related to their potential divergent roles in transmitter release.

Retinol nanoparticles have been obtained by direct precipitation of retinol in the inner water cores of AOT/heptane/water microemulsions. The retinol dissolved in chloroform was injected into the microemulsion. The diameter of the so-obtained nanoparticles was measured using transmission electron microscope pictures where the revelation was made thanks to adsorbed iodine on the nanoparticles. The size is ca 6.0 nm, and it is not dependent either on the size of the water droplets or the concentration of the retinol molecules. This phenomenon is explained by the thermodynamic stabilization of the nanoparticles at a certain size. UV-visible spectra of the nanoparticles show a new band the maximum of which has a bathochromic shift with respect to the absorption band of the retinol monomers. If the bathochromic shift is plotted as a function of the line width, a linear correlation is obtained, the line width is decreasing with increasing shift. This behavior is interpreted as being due to an excitonic transition of a J-complex. Quantum chemical calculations have been carried out to confirm the presence of J-complexes. Taking into account the various possible geometries, the results confirm the presence of J-complexes composed of three head-to-tail molecules on the average.

Mastoparan induces Ca2+-dependent deflagellation of the unicellular green alga Chlamydomonas moewusii Gerloff, as well as the activation of phospholipase C and the production of inositol 1,4,5-trisphosphate (InsP3; T. Munnik et al., 1998, Planta 207: 133—145). Even in the absence of extracellular Ca2+, mastoparan still induces deflagellation (L.M. Quarmby and H.C. Hartzell, 1994, J Cell Biol 124: 807—815; J.A.J. van Himbergen et al., 1999, J Exp Bot, in press) suggesting that InsP3 mediates Ca2+ release from intracellular stores. To test this hypothesis, cells were pre-loaded with 45Ca2+ and their plasma membranes permeabilized by digitonin. Subsequent treatment of the cells with mastoparan (3.5 μM) induced release of intracellular 45Ca2+. Mastoparan also activated phospholipase C in permeabilized cells, as demonstrated by the breakdown of 32P-phosphatidylinositol 4,5-bisphosphate and the production of diacylglycerol. The mastoparan analogues mas7 and mas 17 were also effective and their efficacy was correlated with their biological activity. X-ray microanalysis showed that electron-dense bodies (EDBs) are a major Ca2+ store in C. moewusii. Analysis of digitonin-permeabilized cells showed that EDBs lost calcium at digitonin concentrations that released radioactivity from 45Ca2+-labelled cells, suggesting that 45Ca2+ monitored the content of EDBs. X-ray microanaysis of living cells treated with mastoparan also revealed that calcium was released from EDBs.

The surface and electronic structure of MOCVD-grown layers of Ga(0.92)In(0.08)N have been investigated by means of photoemission. An additional feature at the valence band edge, which can be ascribed to the presence of In in the layer, has been revealed. A clean (0001)-(1x1) surface was prepared by argon ion sputtering and annealing. Stability of chemical composition of the investigated surface subjected to similar ion etching was proven by means of X-ray photoemission spectroscopy.

PurposeThe conceptualization of flexibility in organizations historically emerged from three views which relate to economic, to organizational and to manufacturing perspectives. Despite the growing number of publications about supply chain flexibility in the area of supply chain management, there is a lack of consensus on how to define and to conceptualize supply chain flexibility from a management point of view. The purpose of this paper is to present a comprehensive overview of the literature on the supply chain flexibility perspective and contributes to our understanding of the current state of research and its future development.Design/methodology/approachThe research methodology used is the systematic literature review. In total 92 articles were selected from databases of well-known journal publishers in the field of economics, business studies and management sciences as well as grey literature to cover the topic of supply chain flexibility.FindingsA limited number of studies in the field of supply chain flexibility apply theories and define the term supply chain flexibility. Instead they focus on a particular part or dimension of the supply chain. Based on the analysis, a distinction is made between flexibility in the supply chain and supply chain flexibility. Based on the function and characteristics of the supply chain, the authors selected 30 flexibility dimensions that cover supply chain flexibility by concentrating on the different business areas involved.Research limitations/implicationsThe results support researchers and practitioners by identifying relevant trends and gaps in the field of supply chain flexibility.Originality/valueThe authors review the dimensions and aspects of supply chain flexibility that are currently taken into account in the literature. In this way, the authors provide an overarching perspective on the flexibility literature relating to supply chains.

Purpose - The purpose of this paper is to make a contribution to categorising explanations of non-compliance of EU tendering directives and to report on a survey study to the impact of these reasons on compliance with the directives.Design methodology approach - A literature review resulted in a conceptual model and related hypotheses, pointing at four potential reasons for (non-)compliance: the purchaser's familiarity with the rules, the perceived inefficiency, organisational incentives to comply, and the expected resistance and readiness of suppliers to take action in case of non-compliance. The paper uses data from a survey among 147 responding purchasing professionals of the Dutch Ministry of Defence.Findings - The empirical findings indicate that both purchaser's familiarity with the rules and organisational incentives have a positive, statistically significant impact on compliance. Nor the alleged inefficiency of the directives, nor the expected supplier resistance seem to influence the compliance with the directives.Research limitations implications - The study is limited in its setting: measuring perceptions of purchasing professionals within the Dutch Ministry of Defence. Future research could combine perceptual data and objective, measurable data on compliance. Future research might include other samples from other public agencies, questioning other respondents than purchasers, measuring factors from other fields and disciplines such as criminology (risk of detection and sanction risks), economy (costs and benefits), public choice theory (legitimacy), sociology (peer pressure), and social psychology (personal values).Practical implications - A managerial implication of the findings of this study would be that educating and training public purchasers will be an effective tool for increasing the compliance with the directives. In addition, public agencies could try to establish incentives in order to stimulate compliance.Originality value - Although many studies have reported on the (limited) effectiveness of the EU tendering directives, little work has been undertaken on the compliance as such, while no empirical studies have been carried out to explain the (lack of) compliance with EU directives. This paper reports on a quantitative study, explaining the (non-) compliance with the directives. The study could be of value to public policy makers, to public agencies, and to researchers in the academic world.

Ivacaftor has been shown to restore the functionality of the S1251N (also known as c.3752G>A) mutated CFTR, which may cause alterations in both airway and gut physiology and micro-environment, resulting in a change of microbiota in these organs. The aim of the present study was to analyze the effects of ivacaftor on the microbial community composition of both airway and gut in subjects with CF carrying one S1251N mutation, using a 16S rRNA gene-based sequencing approach. In 16 subjects with CF, repetitive samples from airways and gut were collected just before, and 2 months after, and, for 8 patients, also 9 and 12 months after, start of ivacaftor. 16S rRNA based sequencing identified 344 operational taxonomical units (OTUs) in a total of 139 samples (35 nasopharyngeal, 39 oropharyngeal, 29 sputum, and 36 fecal samples). Ivacaftor significantly enhanced bacterial diversity and overall microbiota composition in the gut (p < 0.01). There were no significant changes in the overall microbial composition and alpha diversity in upper and lower airways of these patients after ivacaftor treatment. Treatment with ivacaftor induces changes in gut microbiota whereas airway microbiota do not change significantly over time.