julilili42/papers huggingface dataset:
Stereochemistry and Conformation of Skyllamycin, a Non‐Ribosomally Synthesized Peptide from Streptomyces sp. Acta 2897
2014-03-12

Abstract Skyllamycin is a non‐ribosomally synthesized cyclic depsipeptide from Streptomyces sp. Acta 2897 that inhibits PDGF‐signaling. The peptide scaffold contains an N‐terminal cinnamoyl moiety, a β‐methylation of aspartic acid, three β‐hydroxylated amino acids and one rarely occurring α‐hydroxy glycine. With the exception of α‐hydroxy glycine, the stereochemistry of the amino acids was assigned by comparison to synthetic reference amino acids applying chiral GC‐MS and Marfey‐HPLC analysis. The stereochemistry of α‐hydroxy glycine, which is unstable under basic and acidic conditions, was determined by conformational analysis, employing a combination of data from NOESY‐NMR spectroscopy, simulated annealing and free MD simulations. The simulation procedures were applied for both R ‐ and S ‐configured α‐hydroxy glycine of the skyllamycin structure and compared to the NOESY data. Both methods, simulated annealing and free MD simulations independently support S ‐configured α‐hydroxy glycine thus enabling the assignment of all stereocenters in the structure of skyllamycin and devising the role of two‐component flavin dependent monooxygenase (Sky39) as S ‐selective.
Topography-Correlated Confocal Raman Microscopy with Cylindrical Vector Beams for Probing Nanoscale Structural Order
2014-03-12

Cylindrical vector beams, such as radially or azimuthally polarized doughnut beams, are combined with topography studies of pentacene thin films, allowing us to correlate Raman spectroscopy with intermolecular interactions depending on the particular pentacene polymorph. Polarization-dependent Raman spectra of the C-H bending vibrations are resolved layer by layer within a thin film of ∼20 nm thickness. The variation of the Raman peak positions indicates changes in the molecular orientation and in the local environment at different heights of the pentacene film. With the assistance of a theoretical model based on harmonic oscillator and perturbation theory, our method reveals the local structural order and the polymorph at different locations within the same pentacene thin film, depending mainly on its thickness. In good agreement with the crystallographic structures reported in the literature, our observations demonstrate that the first few monolayers grown in a structure are closer to the thin-film phase, but for larger film thicknesses, the morphology evolves toward the crystal-bulk phase with a larger tilting angle of the pentacene molecules against the substrate normal.
High-Frequency Stimulation of the Subthalamic Nucleus Counteracts Cortical Expression of Major Histocompatibility Complex Genes in a Rat Model of Parkinson’s Disease
2014-03-12

High-frequency stimulation of the subthalamic nucleus (STN-HFS) is widely used as therapeutic intervention in patients suffering from advanced Parkinson's disease. STN-HFS exerts a powerful modulatory effect on cortical motor control by orthodromic modulation of basal ganglia outflow and via antidromic activation of corticofugal fibers. However, STN-HFS-induced changes of the sensorimotor cortex are hitherto unexplored. To address this question at a genomic level, we performed mRNA expression analyses using Affymetrix microarray gene chips and real-time RT-PCR in sensorimotor cortex of parkinsonian and control rats following STN-HFS. Experimental parkinsonism was induced in Brown Norway rats by bilateral nigral injections of 6-hydroxydopamine and was assessed histologically, behaviorally, and electrophysiologically. We applied prolonged (23h) unilateral STN-HFS in awake and freely moving animals, with the non-stimulated hemisphere serving as an internal control for gene expression analyses. Gene enrichment analysis revealed strongest regulation in major histocompatibility complex (MHC) related genes. STN-HFS led to a cortical downregulation of several MHC class II (RT1-Da, Db1, Ba, and Cd74) and MHC class I (RT1CE) encoding genes. The same set of genes showed increased expression levels in a comparison addressing the effect of 6-hydroxydopamine lesioning. Hence, our data suggest the possible association of altered microglial activity and synaptic transmission by STN-HFS within the sensorimotor cortex of 6-hydroxydopamine treated rats.
Impact of brain-derived neurotrophic factor (BDNF) gene polymorphism on cortical inhibition in schizophrenia
2014-03-12

Introduction: Neuronal plasticity is a characteristic feature of the human central nervous system to dynamically respond to changes and demands inducing synaptical and neurochemical alterations. Using transcranial magnetic stimulation (TMS) in an intermittent theta-burst stimulation (iTBS) protocol, impaired cortical plasticity has been reported to be associated with a val/met gene-polymorphism in the brain-derived neurotrophic factor (BDNF) gene. Based on neuropathological findings and neuroimaging studies, impaired cortical plasticity has been described as a common, yet not fully understood phenomenon in patients with schizophrenia.
Development of a MEG compatible method to study the interaction of the sensory and motor cortex in humans
2014-03-12

The fine graded usage of the hand is a remarkable skill of humans. Even primates are not able to use their hands in a similar skilled fashion. The ability to use the fingers with high precision is thought to require close interaction between the motor and the sensory systems. In humans, unlike in other mammals, the layer V pyramidal cells of the primary motor cortex controlling hand muscles project monosynapticly onto the spinal motor neurons. However, it is still not fully understood, how sensory feedback modulates motor commands in demanding sensory-motor tasks. This is due to the fact, that there is no approach for investigating the sensory-motor cortical interaction in sufficient detail. The fast and precise communication between the sensory and motor systems which is reflected in the close topographic proximity of both cortical regions requires measurements of cortical activity with high temporal and spatial resolution. Magnetoencephalography (MEG) is capable of both, and is therefore the method of choice to validate or falsify network models. However, to take advantage of MEG an experimental paradigm capable of simultaneously recording functional responses and calculating response latencies in both cortices is necessary. Such a sensory-motor paradigm does not currently exist. In our previous studies, we showed that robust sensory responses can be generated by repetitive tactile stimulation. Further, robust responses of the motor cortex can be generated by active periodical increase and decrease of muscle tone. Utilizing both of these observations we have designed an MEG-compatible prototype of a stimulator. The stimulator consists of a rotating disk with an elevation on the otherwise flat surface such that subjects sense with his/her finger the speed of the disk. With the force applied by the finger onto the disk, the subject can control its speed. During the experiment the subject is asked to keep the speed of the disk constant while the driving torque of the motor is systematically manipulated. In a pilot study, we could show that a detailed analysis of the sensory motor network is principally possible when using this prototype in an MEG recording
Diffusion tensor imaging coefficients correlate with electrophysiological recordings in intramedullary neoplasms of the human cervical spinal cord
2014-03-12

Background: There is an increasing application of diffusion-weighted imaging (DTI) in the planning of neurosurgical treatment of brain tumors. During the last years, several MRI techniques have been proposed for the characterization of the water molecular diffusion in the spinal cord. However, due to technical challenges the validity of DTI in spinal cord disorders is still controversial. In the present study, DTI parameters were correlated to electrophysiological findings before and after microsurgical resection of intramedullary neoplasms of the human cervical spinal cord.
Psychopathic traits and neurophysiology of deception
2014-03-12

Background: Recent neuroimaging studies have suggested that prefrontal cortical regions are involved in the neural control of deception. However, to overcome the correlative restrictions of these studies Karim et al. (2010) have investigated the effects of modulating cortical excitability by transcranial direct current stimulation (tDCS) and have shown that inhibition of the frontopolar cortex (BA9/10) can facilitate skillful lying and decrease skin conductance response (SCR) and feelings of guilt while deceiving an interrogator of a mock crime. Whereas these findings support the hypotheses that a dysfunction of BA9/10 may underlie certain psychopathic symptoms characterized by the lack of feelings of guilt and the absence of sympathetic arousal during deception, the relationship between BA 9/10 and psychopathic personality traits remain elusive. We report here for the first time that psychopathic personality traits modulate the effects of frontopolar tDCS on deceptive behavior and SCR.
Enhancing Hebbian Learning to Control Brain Oscillatory Activity
2014-03-13

Sensorimotor rhythms (SMR, 8-15 Hz) are brain oscillations associated with successful motor performance, imagery, and imitation. Voluntary modulation of SMR can be used to control brain-machine interfaces (BMI) in the absence of any physical movements. The mechanisms underlying acquisition of such skill are unknown. Here, we provide evidence for a causal link between function of the primary motor cortex (M1), active during motor skill learning and retention, and successful acquisition of abstract skills such as control over SMR. Thirty healthy participants were trained on 5 consecutive days to control SMR oscillations. Each participant was randomly assigned to one of 3 groups that received either 20 min of anodal, cathodal, or sham transcranial direct current stimulation (tDCS) over M1. Learning SMR control across training days was superior in the anodal tDCS group relative to the other 2. Cathodal tDCS blocked the beneficial effects of training, as evidenced with sham tDCS. One month later, the newly acquired skill remained superior in the anodal tDCS group. Thus, application of weak electric currents of opposite polarities over M1 differentially modulates learning SMR control, pointing to this primary cortical region as a common substrate for acquisition of physical motor skills and learning to control brain oscillatory activity.
On equilibration of pore water in column leaching tests
2014-03-13

Column leaching tests are closer to natural conditions than batch shaking tests and in the last years have become more popular for assessing the release potential of pollutants from a variety of solids such as contaminated soils, waste, recycling and construction materials. Uncertainties still exist regarding equilibration of the percolating water with the solids, that might potentially lead to underestimation of contaminant concentrations in the effluent. The intention of this paper is to show that equilibration of pore water in a finite bath is fundamentally different from release of a certain fraction of the pollutant from a sample and that equilibrium is reached much faster at low liquid-to-solid ratios typical for column experiments (<0.25) than in batch tests with much higher liquid-to-solid ratios (e.g., 2-10). Two mass transfer mechanisms are elucidated: First-order type release (film diffusion) and intraparticle diffusion. For the latter, mass transfer slows down with time and sooner or later non-equilibrium conditions are observed at the column outlet after percolation has been started. Time scales of equilibrium leaching can be estimated based on a comparison of column length with the length of the mass transfer zone, which is equivalent to a Damköhler number approach. Mass transfer and diffusion coefficients used in this study apply to mass transfer mechanisms limited by diffusion in water, which is typical for release of organic compounds but also for dissolution of soluble minerals such as calcite, gypsum or similar. As a conclusion based on these theoretical considerations column tests (a) equilibrate much faster than batch leaching tests and (b) the equilibrium concentrations are maintained in the column effluent even for slow intraparticle diffusion limited desorption for extended periods of time (>days). Since for equilibration the specific surface area is crucial, the harmonic mean of the grain size is relevant (small grain sizes result in high concentrations even after short pre-equilibration of a column). The absolute time scales calculated with linear sorption and aqueous diffusion aim at organic compounds and are not valid for sparingly soluble mineral phases (e.g. metal oxides and silicates). However, the general findings on how different liquid-to-solid ratios and specific surface area influence equilibration time scales also apply to other mass transfer mechanisms.
When the polar bear encounters many polar bears: event-related potential context effects evoked by uniqueness failure
2014-03-13

When essential context information is not given in a discourse, understanding mostly fails. By means of event-related brain potentials we investigated what happens when the definite determiner does not find a unique referent in the context or when the appropriate use of the indefinite determiner is violated by the presence of an already introduced referent. The misuse of the determiners evoked an N400/P600 complex immediately upon reading the determiners. Since this result was the same for both determiners, we suggest that initial cognitive processes are similar and include the detection of a mismatch, triggering an N400, followed by a top-down monitoring process, indexed by a P600. This latter process presumably involves the evaluation of possible alternative sentence interpretations which might preserve the sentence's meaning. We hypothesise that theoretically assumed processing differences between the two determiners might occur at a later time point in processing.
A new strategy in the treatment of chemoresistant lung adenocarcinoma via specific siRNA transfection of SRF, E2F1, Survivin, HIF and STAT3†
2014-03-13

In our study, we emphasized that siRNA interference might represent a productive platform for further research in order to investigate whether a new regimen in the treatment of multiresistant non-small-cell lung cancer could be established in vivo in the context of a multimodal cancer therapy.
Old challenges and new vistas for comparative education? Insights gained from improbable relations
2014-03-13

In this article I aim to initiate a more systematic dialogue between what is currently termed postfoundationalism and the mainstream of comparative education. I argue that comparative education, which is not only interdisciplinary by definition but also the one sub-discipline of education focusing most rigorously on relations, is the privileged locus for this debate. I offer my reflections on the issues in that decontextualization, characteristic of positivistic research, lacks the perspective of contextualization, and thus it is a deficiency by itself. The secularization of education, which forms the basis of empiricism, is self-contradictory when it conflates the founded with the foundation. The focus on the individual allows for possibilities but the social order of education shuts off individual possibilities, thus it might be viewed as self-contradictory in itself. I suggest that we ought to question the validity and the self-contradiction of empiricism and secularization in comparative education research, as its focus is on individuals, yet it claims universal and transnational terminologies.
Sleep benefits in parallel implicit and explicit measures of episodic memory
2014-03-14

Research in rats using preferences during exploration as a measure of memory has indicated that sleep is important for the consolidation of episodic-like memory, i.e., memory for an event bound into specific spatio-temporal context. How these findings relate to human episodic memory is unclear. We used spontaneous preferences during visual exploration and verbal recall as, respectively, implicit and explicit measures of memory, to study effects of sleep on episodic memory consolidation in humans. During encoding before 10-h retention intervals that covered nighttime sleep or daytime wakefulness, two groups of young adults were presented with two episodes that were 1-h apart. Each episode entailed a spatial configuration of four different faces in a 3 × 3 grid of locations. After the retention interval, implicit spatio-temporal recall performance was assessed by eye-tracking visual exploration of another configuration of four faces of which two were from the first and second episode, respectively; of the two faces one was presented at the same location as during encoding and the other at another location. Afterward explicit verbal recall was assessed. Measures of implicit and explicit episodic memory retention were positively correlated ( r = 0.57, P &lt; 0.01), and were both better after nighttime sleep than daytime wakefulness ( P &lt; 0.05). In the sleep group, implicit episodic memory recall was associated with increased fast spindles during nonrapid eye movement (NonREM) sleep ( r = 0.62, P &lt; 0.05). Together with concordant observations in rats our results indicate that consolidation of genuinely episodic memory benefits from sleep.
The monetary value of the demonstration effect of professional sports
2014-03-14

Research questionProfessional sports fulfil important societal functions. Previous studies have already attempted to quantify the intangible benefits of successful national athletes or hosting major sporting events. This study chooses an alternative channel of quantification. Based on the theoretical framework of sporting role models, it analyses whether the individual relevance of professional sports increases the frequency of sport participation. To quantify this effect, it subsequently analyses whether the increased sport participation increases sport-related expenditure.Research methodsA quantitative research design based on primary data of approximately 500 German amateur tennis players was chosen. Unfortunately, the econometric identification of the effect of the relevance of professional sports on sport participation behaviours is aggravated by a selection bias. To circumvent this issue, instrumental variables were constructed based on the starting year of the surveyed amateurs' sport participation, which is considered to be exogenous.Results and findingsThe results of the instrumental variable estimations show that amateurs with a higher relevance of professional tennis spend between 21.5% and 24.4% more time playing tennis. In addition, 1% more participation per week increases the yearly sport-related expenditure by approximately 0.45%. Consequently, approximately 200 million euros of the tennis-related expenditure of German amateur tennis participants could be attributed to professional tennis in Germany.ImplicationsThe results of this study provide evidence for positive external effects of professional sports in Germany. These external effects could act as an additional rationale for the use of public funds to promote professional sports.
Sulfur Species as Redox Partners and Electron Shuttles for Ferrihydrite Reduction by Sulfurospirillum deleyianum
2014-03-15

ABSTRACT Iron(III) (oxyhydr)oxides can represent the dominant microbial electron acceptors under anoxic conditions in many aquatic environments, which makes understanding the mechanisms and processes regulating their dissolution and transformation particularly important. In a previous laboratory-based study, it has been shown that 0.05 mM thiosulfate can reduce 6 mM ferrihydrite indirectly via enzymatic reduction of thiosulfate to sulfide by the sulfur-reducing bacterium Sulfurospirillum deleyianum , followed by abiotic reduction of ferrihydrite coupled to reoxidation of sulfide. Thiosulfate, elemental sulfur, and polysulfides were proposed as reoxidized sulfur species functioning as electron shuttles. However, the exact electron transfer pathway remained unknown. Here, we present a detailed analysis of the sulfur species involved. Apart from thiosulfate, substoichiometric amounts of sulfite, tetrathionate, sulfide, or polysulfides also initiated ferrihydrite reduction. The portion of thiosulfate produced during abiotic ferrihydrite-dependent reoxidation of sulfide was about 10% of the total sulfur at maximum. The main abiotic oxidation product was elemental sulfur attached to the iron mineral surface, which indicates that direct contact between microorganisms and ferrihydrite is necessary to maintain the iron reduction process. Polysulfides were not detected in the liquid phase. Minor amounts were found associated either with microorganisms or the mineral phase. The abiotic oxidation of sulfide in the reaction with ferrihydrite was identified as rate determining. Cysteine, added as a sulfur source and a reducing agent, also led to abiotic ferrihydrite reduction and therefore should be eliminated when sulfur redox reactions are investigated. Overall, we could demonstrate the large impact of intermediate sulfur species on biogeochemical iron transformations.
New examples of conformally constrained Willmore minimizers of explicit type
2014-03-15

Abstract We develop a convergence procedure to improve weak convergence of conformally constrained Willmore immersions to smooth convergence and apply this to get new examples of conformally constrained Willmore minimizers of explicit type. In fact by estimates of Li–Yau in [Inventiones Mathematicae 69 (1982), 269–291] and Montiel–Ros in [Inventiones Mathematicae 83 (1986), 153–166], the Clifford torus <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:msub> <m:mi>T</m:mi> <m:mi> Cliff </m:mi> </m:msub> <m:mo>=</m:mo> <m:mrow> <m:mo>(</m:mo> <m:mn>1</m:mn> <m:mo>/</m:mo> <m:msqrt> <m:mn>2</m:mn> </m:msqrt> <m:mo>)</m:mo> </m:mrow> <m:mrow> <m:mo>(</m:mo> <m:msup> <m:mi>S</m:mi> <m:mn>1</m:mn> </m:msup> <m:mo>×</m:mo> <m:msup> <m:mi>S</m:mi> <m:mn>1</m:mn> </m:msup> <m:mo>)</m:mo> </m:mrow> <m:mo>⊆</m:mo> <m:msup> <m:mi>S</m:mi> <m:mn>3</m:mn> </m:msup> </m:mrow> </m:math> minimizes the Willmore energy in its conformal class. We extend this using our convergence procedure to the flat constant mean curvature tori <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:msub> <m:mi>T</m:mi> <m:mi>r</m:mi> </m:msub> <m:mo>=</m:mo> <m:mi>r</m:mi> <m:msup> <m:mi>S</m:mi> <m:mn>1</m:mn> </m:msup> <m:mo>×</m:mo> <m:msqrt> <m:mrow> <m:mn>1</m:mn> <m:mo>-</m:mo> <m:msup> <m:mi>r</m:mi> <m:mn>2</m:mn> </m:msup> </m:mrow> </m:msqrt> <m:msup> <m:mi>S</m:mi> <m:mn>1</m:mn> </m:msup> <m:mo>⊆</m:mo> <m:msup> <m:mi>S</m:mi> <m:mn>3</m:mn> </m:msup> </m:mrow> </m:math> for <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:mi>r</m:mi> <m:mo>≈</m:mo> <m:mn>1</m:mn> <m:mo>/</m:mo> <m:msqrt> <m:mn>2</m:mn> </m:msqrt> </m:mrow> </m:math> .