Local inhomogeneities resolved by scanning probe techniques and their impact on local 2DEG formation in oxide heterostructures.

Lateral inhomogeneities in the formation of two-dimensional electron gases (2DEG) directly influence their electronic properties. Understanding their origin is an important factor for fundamental interpretations, as well as high quality devices. Here, we studied the local formation of the buried 2DEG at LaAlO3/SrTiO3 (LAO/STO) interfaces grown on STO (100) single crystals with partial TiO2 termination, utilizing in situ conductive atomic force microscopy (c-AFM) and scattering-type scanning near-field optical microscopy (s-SNOM). Using substrates with different degrees of chemical surface termination, we can link the resulting interface chemistry to an inhomogeneous 2DEG formation. In conductivity maps recorded by c-AFM, a significant lack of conductivity is observed at topographic features, indicative of a local SrO/AlO2 interface stacking order, while significant local conductivity can be probed in regions showing TiO2/LaO interface stacking order. These results could be corroborated by s-SNOM, showing a similar contrast distribution in the optical signal which can be linked to the local electronic properties of the material. The results are further complemented by low-temperature conductivity measurements, which show an increasing residual resistance at 5 K with increasing portion of insulating SrO-terminated areas. Therefore, we can correlate the macroscopic electrical behavior of our samples to their nanoscopic structure. Using proper parameters, 2DEG mapping can be carried out without any visible alteration of sample properties, proving c-AFM and s-SNOM to be viable and destruction-free techniques for the identification of local 2DEG formation. Furthermore, applying c-AFM and s-SNOM in this manner opens the exciting prospect to link macroscopic low-temperature transport to its nanoscopic origin.

Resistive switching in optoelectronic III-V materials based on deep traps.

Resistive switching random access memories (ReRAM) are promising candidates for energy efficient, fast, and non-volatile universal memories that unite the advantages of RAM and hard drives. Unfortunately, the current ReRAM materials are incompatible with optical interconnects and wires. Optical signal transmission is, however, inevitable for next generation memories in order to overcome the capacity-bandwidth trade-off. Thus, we present here a proof-of-concept of a new type of resistive switching realized in III-V semiconductors, which meet all requirements for the implementation of optoelectronic circuits. This resistive switching effect is based on controlling the spatial positions of vacancy-induced deep traps by stimulated migration, opening and closing a conduction channel through a semi-insulating compensated surface layer. The mechanism is widely applicable to opto-electronically usable III-V compound semiconductors.

Vulnerability and revictimization: Victim characteristics in a Dutch assault center.

Sexual and family violence are highly prevalent problems with numerous negative health consequences. Assault centres, such as the Centre for Sexual and Family Violence (CSFV) in the Netherlands, have been set up to provide optimal care to victims. We wanted to gain insight into characteristics of the population that presented to the Centre in order to customize care to their needs. File analysis was conducted of victims who attended the CSFV between 2013 and 2016. Data were analyzed in SPSS. A total of 121 victims entered the Centre, 93% of them being female. Forty-two per cent were adult victims of sexual violence, 28% minor victims of sexual violence and 30% adult victims of family violence. One-third of sexual and two-third of family violence victims had experienced prior abuse. Current use of psychosocial services and psychiatric medication was high, and a cognitive disability was present in 18% of the sexual violence victims. Half the victims reported, but when the perpetrator was a recent contact, e.g., someone met at a party, reporting rates went down. Sexual and family violence victims share characteristics that indicate vulnerability, suggesting that care for both groups might best be combined in one single assault centre. In this way, victims can make use of the same services and knowledge of gender-based violence. One of the major aims of assault centres is to provide psychosocial follow-up care and facilities for reporting. The victims' needs in these matters deserve further research.

Interface-driven formation of a two-dimensional dodecagonal fullerene quasicrystal.

Since their discovery, quasicrystals have attracted continuous research interest due to their unique structural and physical properties. Recently, it was demonstrated that dodecagonal quasicrystals could be used as bandgap materials in next-generation photonic devices. However, a full understanding of the formation mechanism of quasicrystals is necessary to control their physical properties. Here we report the formation of a two-dimensional dodecagonal fullerene quasicrystal on a Pt3Ti(111) surface, which can be described in terms of a square-triangle tiling. Employing density functional theory calculations, we identify the complex adsorption energy landscape of the Pt-terminated Pt3Ti surface that is responsible for the quasicrystal formation. We demonstrate the presence of quasicrystal-specific phason strain, which provides the degree of freedom required to accommodate the quasicrystalline structure on the periodic substrate. Our results reveal detailed insight into an interface-driven formation mechanism and open the way to the creation of tailored fullerene quasicrystals with specific physical properties.

Tuning the surface electronic structure of a Pt3Ti(111) electro catalyst.

Increasing the efficiency and stability of bimetallic electro catalysts is particularly important for future clean energy technologies. However, the relationship between the surface termination of these alloys and their catalytic activity is poorly understood. Therefore, we report on fundamental UHV-SPM, LEED, and DFT calculations of the Pt3Ti(111) single crystal surface. Using voltage dependent imaging the surface termination of Pt3Ti(111) was studied with atomic resolution. Combining these images with simulated STM maps based on ab initio DFT calculations allowed us to identify the three upper layers of the Pt3Ti(111) single crystal and their influence upon the surface electronic structure. Our results show that small changes in the composition of the second and third atomic layer are of significant influence upon the surface electronic structure of the Pt3Ti electro catalyst. Furthermore, we provide relevant insights into the dependence of the surface termination on the preparation conditions.

Steroid Hormone Production in Patients with Aldosterone Producing Adenomas.

Primary aldosteronism encompasses 2 major underlying causes: (1) aldosterone producing adenoma and (2) bilateral adrenal hyperplasia. In addition to the aldosterone excess, increased production of other compounds of the steroidogenic pathways may be involved. Until recently, most studies examined the production of steroids other than aldosterone in tumor tissue, urine, or peripheral plasma samples, but several new studies have also addressed steroid levels in adrenal venous blood samples using liquid chromatography tandem mass spectrometry. Plasma and tissue levels of several precursors of aldosterone with mineralocorticoid activity are higher in patients with aldosterone producing adenomas than in those with bilateral hyperplasia. These include corticosterone, deoxycorticosterone, and their 18-hydroxylated metabolites. Similarly, urinary, peripheral, and adrenal venous concentrations of the hybrid steroids 18-oxocortisol and 18-hydroxycortisol are higher in patients with aldosterone producing adenomas than in bilateral hyperplasia. Differences in the pathophysiology and in clinical and biochemical phenotypes caused by aldosterone producing adenomas and bilateral adrenal hyperplasia may be related to the differential expression of steroidogenic enzymes, and associated to specific underlying somatic mutations. Correct appreciation of differences in steroid profiling between aldosterone producing adenomas and bilateral adrenal hyperplasia may not only contribute to a better understanding of the pathogenesis of primary aldosteronism but may also be helpful for future subtyping of primary aldosteronism.

[The fiscal position of medical specialists]. / De fiscale positie van medisch specialisten.

Independent medical specialists in the Netherlands are treated as entrepreneurs for tax purposes and therefore enjoy tax benefits. A change in the legal relationship between medical specialists and hospitals is foreseen in 2015. Independent medical specialists will then no longer be considered to be entrepreneurs. This could negatively affect their tax position. The Dutch government has adopted a policy aimed at controlling expenses arising from medical specialists' fees. According to this policy, the formation of regional practices or mega-practices of specialists will be discouraged. In contrast, the current fiscal legislation encourages medical specialists to incorporate their practice into regional practices or mega-practices or to become shareholders of their hospitals. It has been proposed that fiscal benefits be linked to certain aspects of entrepreneurship, such as investing in medical equipment or employing medical personnel.

Glucocorticoids induce long-lasting effects in neural stem cells resulting in senescence-related alterations.

Alterations in intrauterine programming occurring during critical periods of development have adverse consequences for whole-organ systems or individual tissue functions in later life. In this paper, we show that rat embryonic neural stem cells (NSCs) exposed to the synthetic glucocorticoid dexamethasone (Dex) undergo heritable alterations, possibly through epigenetic mechanisms. Exposure to Dex results in decreased NSC proliferation, with no effects on survival or differentiation, and changes in the expression of genes associated with cellular senescence and mitochondrial functions. Dex upregulates cell cycle-related genes p16 and p21 in a glucocorticoid receptor(GR)-dependent manner. The senescence-associated markers high mobility group (Hmg) A1 and heterochromatin protein 1 (HP1) are also upregulated in Dex-exposed NSCs, whereas Bmi1 (polycomb ring finger oncogene) and mitochondrial genes Nd3 (NADH dehydrogenase 3) and Cytb (cytochrome b) are downregulated. The concomitant decrease in global DNA methylation and DNA methyltransferases (Dnmts) suggests the occurrence of epigenetic changes. All these features are retained in daughter NSCs (never directly exposed to Dex) and are associated with a higher susceptibility to oxidative stress, as shown by the increased occurrence of apoptotic cell death on exposure to the redox-cycling reactive oxygen species (ROS) generator 2,3-dimethoxy-1-naphthoquinone (DMNQ). Our study provides novel evidence for programming effects induced by glucocorticoids (GCs) on NSCs and supports the idea that fetal exposure to endogenous or exogenous GCs is likely to result in long-term consequences that may predispose to neurodevelopmental and/or neurodegenerative disorders.

Interleukin-7 (IL-7) and IL-7 splice variants affect differentiation of human neural progenitor cells.

Alternative splicing of pre-mRNA increases proteomic diversity, a crucial mechanism in defining tissue identity. We demonstrate differentially spliced interleukin (IL)-7 in distinct anatomic areas in the adult, in developing human brains and in normal human neuronal progenitor (NHNP) cells. IL-7c (c, the canonical form spanning all six exons) or its variants IL-7 delta 5, delta 4 or delta 4/5 were cloned and expressed as recombinant proteins. IL-7 and splice variants were able to shift the differentiation of NHNP cells as compared with the diluent control (P<0.01) defined by anti-beta (III)-tubulin and glial fibrillary acidic protein expression, with different degrees (IL-7c>delta 4/5>IL-7 delta 5); IL-7 delta 4 exhibited a significantly weaker potency. Differentiation was confirmed by transcriptome analysis of IL-7c-stimulated neural NHNP cells, resulting in 58 differentially expressed genes; some of these are involved in neural differentiation, for example, the developmentally regulated transcription factor krüppel-like factor 12, musashi 2, a translational regulator of cell fate or the sonic hedgehog receptor patch 1. This suggests that IL-7 influences neural development at a molecular level by participating in human brain architecture through glia cell formation: a paradigm that alternative splicing in cytokines, for example, for IL-7, has a physiological role in human organ development and progenitor cell differentiation.

Surface segregation of Au-Pd alloys in UHV and reactive environments: quantification by a catalytic atom probe.

The surface composition of an Au-62at%Pd alloy has been studied by means of a catalytic atom probe (CAP) before and after exposures to nitric oxide (NO) at temperatures ranging from 300 to 573K for 20min. Subsequent CAP analysis at 100K revealed a considerable surface enrichment in Pd (to approximately 80at%) after exposure at 573K. This is correlated with the occurrence of NO dissociation, and the formation of strong Pd-O bonds at the surface. Blank experiments in ultra-high vacuum reflect the surface composition of the bulk material, in excellent agreement with electron microprobe analysis. At 573K, no detectable surface segregation occurs in the absence of NO adsorption for the times and temperatures studied. However, classical Metropolis Monte-Carlo simulations performed with a semi-empirical potential on the Au(40)Pd(60) (111), (110) and (100) systems show surface enrichment of gold at equilibrium. This suggests that the temperatures of the clean surface segregation experiments are too low to reach equilibrium within times of the order of hours.

C2H2 interaction with Ni nanocrystals: towards a better understanding of carbon nanotubes nucleation in CVD synthesis.

We present a study of the early stages of carbon nanotubes nucleation in CVD synthesis by combining field ion/electron emission microscopy (FIM/FEM) and atom-probe investigation (AP) of the nickel-carbon interaction. Acetylene decomposition on Ni tips at 873K is observed to induce additional step formation on an initially facetted (polyhedral) crystal. Carbon-enriched steps are then observed to act as preferential nucleation centers of graphene sheets formation. Atom-probe experiments reveal C(2) and C(3) species and frequency dependent studies demonstrate that the origin of these species is different from C(1). Experiments provide clear evidence for the crucial role of carbon-enriched steps as nucleation sites of graphene sheets on the Ni surface.

Activation of interleukin-1 receptor-associated kinase by gram-negative flagellin.

Flagellin from various species of gram-negative bacteria activates monocytes to produce proinflammatory cytokines. We have analyzed the pathway by which Salmonella enteritidis flagellin (FliC) activates murine and human monocyte/macrophage-like cell lines. Since lipopolysaccharide (LPS), the principal immune stimulatory component of gram-negative bacteria, is known to signal through Toll-like receptor 4 (TLR4), we tested the possibility that FliC also signals via TLR4. When murine HeNC2 cells were stimulated with LPS in the presence of a neutralizing anti-TLR4 monoclonal antibody, tumor necrosis factor alpha (TNF-alpha) and nitric oxide (NO) production were markedly reduced. In contrast, FliC-mediated TNF-alpha and NO production were minimally affected by the anti-TLR4 antibody. Furthermore, FliC, unlike LPS, stimulated TNF-alpha production in the TLR4 mutant cell line, GG2EE, indicating that TLR4 is not essential for FliC-mediated signaling. To test the possibility that FliC signals via another TLR, we measured FliC-mediated activation of interleukin-1 (IL-1) receptor-associated kinase (IRAK), a central component in IL-1R/TLR signaling. FliC induced IRAK activation in HeNC2 and GG2EE cells as well as in the human promonocytic cell line THP-1. IRAK activation was rapid in HeNC2 cells, with maximal activity observed after 5 min of treatment with FliC. In addition, FliC-mediated IRAK activation exhibited the same concentration dependence as was demonstrated for the induction of TNF-alpha. These results represent the first demonstration of IRAK activation by a purified bacterial protein and strongly suggest that a TLR distinct from TLR4 is involved in the macrophage inflammatory response to FliC.

Proteasome-mediated regulation of interleukin-1beta turnover and export in human monocytes.

Interleukin-1beta is a secreted protein that accumulates in the cytosol as an inactive precursor (pIL-1beta) before processing and release of biologically active protein. To understand the impact of this property on IL-1beta production, we examined the intracellular stability of pIL-1beta in lipopolysaccharide (LPS)-stimulated human monocytes. Precursor IL-1beta was degraded with a relatively short half-life of 2.5 h in the promonocytic cell line, THP-1, and in primary monocytes. MG132 (carbobenzoxyl-leucinyl-leucinyl-leucinal) stabilized pIL-1beta levels in THP-1 cells, suggesting that degradation was proteasome-mediated, but this inhibitor was toxic for primary monocytes, causing release of pIL-1beta as well as the cytoplasmic enzyme, lactate dehydrogenase (LDH) into supernatants. In contrast, clasto-lactacystin beta-lactone, a specific inhibitor of the proteasome, caused a dose-dependent stabilization of intracellular pIL-1beta, and this led to a corresponding increase in mIL-1beta and pIL-1beta but not LDH release into culture supernatants. Therefore, by regulating intracellular levels of precursor IL-1beta, the proteasome plays an important and previously unrecognized role in controlling the amount of biologically active IL-1beta that is exported by activated monocytes.

Stability of the Listeria monocytogenes ActA protein in mammalian cells is regulated by the N-end rule pathway.

Upon infection of mammalian cells, Listeria monocytogenes lyses the phagosome and enters the cytosol, where it secretes proteins necessary for its intracellular growth cycle. Consequently, bacterial proteins exposed to the cytosol are potential targets for degradation by host cytosolic proteases. One pathway for degradation of host cytosolic proteins, the N-end rule pathway, involves recognition of the N-terminal amino acid and is mediated by the proteasome. However, very few natural N-end rule substrates have been identified. We have examined the L. monocytogenes ActA protein as a potential target for this pathway. ActA is an essential determinant of L. monocytogenes pathogenesis that is required to induce actin-based motility and cell-to-cell spread. We show that the half-life of a secreted form of ActA can be altered in the mammalian cytosol by changing the N-terminal amino acid. Moreover, the introduction of a destabilizing N-terminus into the functional, surface-bound form of ActA results in a small-plaque phenotype in L2 cells, which is partially reversible by an inhibitor of the proteasome. These results indicate that the L. monocytogenes ActA protein is a natural N-end rule substrate, and that optimal function of ActA in mediating cell-to-cell spread is dependent upon its intracellular turnover rate.

Expression of listeriolysin O and ActA by intracellular and extracellular Listeria monocytogenes.

Listeria monocytogenes requires listeriolysin O (LLO) and ActA, the products of hly and actA, respectively, to establish a productive intracellular infection. LLO is essential for vacuolar lysis and entry into the cytosol, while ActA is required for bacterial spread to adjacent cells. We have used a transcriptional reporter gene system to compare the expression of actA and hly during intracellular growth to that during growth in broth cultures. The hly and actA genes were transcriptionally fused to Escherichia coli lacZ and Bacillus pumilus cat-86 (cat), and the fusions were integrated in single copies into the L. monocytogenes chromosome. A chloramphenicol resistance assay indicated that the hly fusion but not the actA fusion was significantly activated in Luria-Bertani (LB) broth, and this finding correlated with LLO and ActA levels detectable in broth cultures. Quantitation of promoter activity on the basis of beta-galactosidase activity revealed up to 10-fold-higher level of expression of the hly fusion relative to the actA fusion in LB broth. In contrast, both fusions were active in the cytosol of J774 cells, and the activity of the actA fusion was approximately 3-fold higher than that of the hly fusion under these conditions. However, quantitative immunoprecipitation of ActA and LLO from infected J774 cells demonstrated approximately 70-fold more cytosolic ActA than cytosolic LLO. Finally, in comparison to induction in broth cultures, actA was highly induced (226-fold) and hly was moderately induced (20-fold) in J774 cells. Collectively, these results indicate that actA and hly are differentially regulated in response to the growth environment and that both genes are preferentially expressed during intracellular growth. Further, while the lower level of production of ActA than of LLO in broth can be accounted for by transcriptional regulation, the relative abundance of intracellular ActA compared to that of intracellular LLO is a function of additional, possibly host-mediated, factors.

Carbon-source regulation of virulence gene expression in Listeria monocytogenes.

All known virulence genes of Listeria monocytogenes are under positive regulation by the transcription factor PrfA. Previous work employing the L. monocytogenes strain NCTC7973 suggested that the disaccharide cellobiose might serve as a specific "signature molecule' which functions to prevent activation of the PrfA-controlled regulon in a soil environment. We have examined three other L. monocytogenes strains, 10403S, LO28 and EGD, all commonly regarded as wild-type isolates, and find that NCTC7973 is anomalous with respect to the effect of carbohydrates on the expression of PrfA-controlled gene expression. In the case of 10403S, LO28 and EGD, several other readily metabolized mono- and disaccharides are as effective as cellobiose in repressing expression of the PrfA-controlled gene hly, indicating that the cellobiose effect is not specific, and suggesting that NCTC7973 may be a partially deregulated variant. Moreover, concentrations of cellobiose and other sugars required for repression of hly expression (> 1 mM) were found to significantly enhance growth of L. monocytogenes cultures, suggesting that the repression phenomenon probably results from a metabolic effect of sugar utilization rather than a signal-sensing response. Thus the previously reported cellobiose effect may reflect an aspect of a more global mechanism of catabolite repression in L. monocytogenes. Although cellobiose represses expression of hly and plcA at the level of transcript accumulation, quantitative Western blot analysis indicates that cellobiose has no effect on PrfA levels. These results are consistent with a model in which PrfA activity is controlled by interaction with a hypothetical cofactor, the synthesis or depletion of which is responsive to the presence of readily metabolized carbohydrates.

Elimination of the listeriolysin O-directed immune response by conservative alteration of the immunodominant listeriolysin O amino acid 91 to 99 epitope.

A major H2-Kd-presented epitope for antilisterial cytotoxic T lymphocytes (CTLs) is the nanomer peptide which corresponds to the amino acid 91 to 99 (aa91-99) sequence from listeriolysin O (LLO). Although the LLO sequence contains at least five additional nanomer peptides which also satisfy the H2-Kd binding motif, aa91-99 is the only LLO-derived target peptide that is recognized by antilisterial CTLs following infection of BALB/c mice with Listeria monocytogenes. In order to investigate further the immunodominance of the LLO aa91-99 epitope following endogenous processing of LLO, we introduced a point mutation in hly (the gene for LLO) which results in a conservative Y-to-F substitution for the anchor residue at position 2 within the aa91-99 sequence. This "92F" L. monocytogenes mutant produces biologically active LLO and is phenotypically indistinct from wild-type L. monocytogenes in terms of intracellular growth in vitro and virulence in vivo. BALB/c mice actively immunized with the 92F L. monocytogenes mutant are protected against challenge with wild-type L. monocytogenes. Antilisterial CTLs from mice immunized with the 92F mutant lyse targets infected with L. monocytogenes; however, these CTLs do not lyse target cells pulsed with either the LLO aa91-99 peptide, other LLO-derived peptides which satisfy the H2-Kd binding motif, or a peptide corresponding to the LLO aa91-92F-99 sequence. Target cells pulsed with the LLO aa91-92F-99 peptide are, however, lysed by wild-type LLO aa91-99-specific cytotoxic cells. Thus, a conservative amino acid change in the first anchor residue of the immunodominant aa91-99 sequence of LLO eliminates the induction of the cytotoxic cell response to this epitope as well as to any of the other candidate LLO-derived peptides which fit the H2-Kd binding motif. The lack of anti-LLO-specific CTLs following immunization with the 92F mutant does not appear, however, to influence the protective antilisterial immune response.

Comparative shear bond strength of some orthodontic bonding resins to enamel.

The aim of this study was to compare the in vitro bond strength, to bovine enamel measured in shear, of the orthodontic adhesives Lee Insta-bond (LiB), Rely-a-Bond (RaB), Right-on (Ro), Concise precoating method (Cc), Concise mixed method (CaB), Super-C (Sc), and Orthon (Or), and of the glass ionomer cement Ketac-Cem (KC). The fracture surfaces after debonding were also examined in order to determine the sites of failure. The results indicate that there is a significant difference between the shear bond strength obtained with the different adhesives so that the mean shear bond strength decreases in the order [Ro approximately Cab approximately Sc] > [LiB approximately RaB approximately Cc] > Or > KC. Moreover, for Cab and Sc it was found that the shear bond strength varies depending on the location on the bovine tooth. The failure site was essentially at the resin-bracket interface, except for Concise, where only 50 per cent of the cases failed at the resin-bracket interface.

Solid-phase extraction of small drugs on apolar and ion-exchanging silica bonded phases: towards the development of a general strategy.

In connection with the development of a general strategy for solid-phase extraction (SPE) of drugs, the use of the apolar octadecyl silica bonded phase and ion-exchanging phases with a benzene sulphonic acid or quaternary amine bonded functionality is investigated for the SPE of small polar drugs. This investigation was performed on a set of 15 drugs, belonging to varying pharmacological groups and with varying structures. For each analyte, its adsorption on the C18 and the ion-exchanging phase was controlled for an aqueous solution and for a spiked plasma sample. For those analytes retained on the sorbent, different elution solvents were compared. Although SPE methods could successfully be developed for some drugs, no general solution can be proposed and no solution was found for a few drugs. The main problems are that for these few drugs no sufficient retention is obtained on any SPE phase investigated or the selectivity is too low.