6112 research outputs found
Sort by
DNA barcodes reliably differentiate between nivicolous species of Diderma (Myxomycetes, Amoebozoa) and reveal regional differences within Eurasia
Get PDFThe nivicolous species of the genus Diderma are challenging to identify, and there are several competing views on their delimitation. We analyzed 102 accessions of nivicolous Diderma spp. that were sequenced for two or three unlinked genes to determine which of the current taxonomic treatments is better supported by molecular species delimitation methods. The results of a haplotype web analysis, Bayesian species delimitation under a multispecies coalescent model, and phylogenetic analyses on concatenated alignments support a splitting approach that distinguishes six taxa: Diderma alpinum, D. europaeum, D. kamchaticum, D. meyerae, D. microcarpum and D. niveum. The first two approaches also support the separation of Diderma alpinum into two species with allopatric distribution. An extended dataset of 800 specimens (mainly from Europe) that were barcoded with 18S rDNA revealed only barcode variants similar to those in the species characterized by the first data set, and showed an uneven distribution of these species in the Northern Hemisphere: Diderma microcarpum and D. alpinum were the only species found in all seven intensively sampled mountain regions. Partial 18S rDNA sequences serving as DNA barcodes provided clear signatures that allowed for unambiguous identification of the nivicolous Diderma spp., including two putative species in D. alpinum
The clockwork of spring: bud dormancy timing as a driver of spring leaf-out in temperate deciduous trees
Get PDFThe initiation of spring leaf-out is a critical determinant of the growing season in trees, affecting primary production and species interactions in forest ecosystems. Variations in the timing of leaf-out among tree species are linked to their differential progression of bud dormancy. However, identifying reliable markers for bud dormancy has been challenging, leaving the connection between the timing of autumn leaf senescence, bud dormancy and spring leaf-out unclear. To test whether species initiating dormancy release earlier also exhibit earlier leaf senescence in autumn and earlier leaf-out in spring, we estimated the dates of peak dormancy depth (PDD), senescence timing and spring leaf-out across various species, locations and experimental conditions in Central Europe. PDD was defined as the date when the maximum thermal sum was required for leaf-out, whereas leaf senescence was assessed through the decrease in leaf greenness. Our findings reveal that PDD timing is a more accurate predictor of species-level differences in spring leaf-out dates than the timing of leaf senescence, the latter being a poor proxy for PDD. The observed temporal asynchrony between PDD and senescence was linked to dormancy induction showing species-specific sensitivity to temperature variations. Conversely, the timing of leaf senescence showed a consistent reaction to temperature changes across all species. These findings suggest that the physiological processes within buds and leaves during autumn are governed by distinct environmental cues, with the bud dormancy process serving as a more reliable predictor of spring phenological differences among forest tree species than does autumn leaf senescence
The longitudinal relationship between internalizing and externalizing behavioral problems with academic achievement in elementary school
Get PDFBackground
Cascade models propose that behavioral difficulties and academic achievement are reciprocally intertwined. However, empirical evidence for this assumption is inconclusive.
Aims
The present study examines the relations between internalizing and externalizing behavioral difficulties and academic achievement in three achievement domains (i.e., reading, writing, mathematics) across four school years in primary school.
Sample
A sample of N = 461 primary school students was used to examine our research questions. Five waves of measurement were gathered to capture students’ educational development throughout elementary school.
Methods
A series of cross-lagged panel analyses was conducted controlling for potential confounders (i.e., attention, cognitive ability, gender).
Results
Contrary to our hypotheses, results point only to sporadic reciprocal effects between behavioral problems and achievement. Effects vary greatly both between achievement domain and between behavioral difficulties. On all longitudinal variable associations, there were consistently moderate to high stabilities across four years of primary education.
Conclusions
Moderate to high stabilities of the variables under examination suggests that interventions beginning after school entrance might be too late to avoid adverse developmental trajectories adequately. Additionally, prevention and intervention programs are discussed which might avoid such educational developments
Is there a fast track (“Darmstrasse”) for fluids in the small intestine? Evidence from magnetic resonance imaging
Get PDFBackground
The transit and distribution pattern of fluids in the small intestine is a key parameter for the dissolution and absorption of drugs. Although some information is known about the small intestinal water content after administration of fluid volumes and meals, the intestinal transit of orally ingested fluids and solutions has been barely investigated. The aim of this three-arm, cross-over, 9-subject human study was to investigate the transit of orally ingested water in the small intestine under fasting and postprandial conditions using MRI. To identify the ingested water, manganese gluconate, which can be identified with T1-weighted MRI sequences, was added as a marker. Using Horos (DICOM software), quantification of the distribution of Mn2+ ions in the gastrointestinal tract in fasted versus fed state (standard meal by FDA guidance and a light meal) was possible. The distribution and approximate wetted intestinal length was very similar in the fasting and postprandial states, suggesting rapid transport of water ingested after a meal through the chyme-filled small intestine in continuation of the “Magenstrasse” (stomach road). In some subjects, manganese gluconate reached deeper parts of the small intestine even more quickly in the postprandial state than in the fasting arm of the study. A deeper understanding of the behaviour of solutes in the gastrointestinal tract is fundamental to a mechanistic explanation for the kinetic interaction between food and drug intake (food effects)
Terahertz Absorption Spectroscopy for Measuring Atomic Oxygen Densities - Development and Comparison with Established Techniques
Get PDFOxygen-containing plasmas are widely used in industry for a variety of applications, including thin-film deposition, etching, and other surface modification processes. Due to their high reactivity, oxygen atoms play a key role in most of these applications, and an accurate method for measuring their density is therefore of great importance, not only to gain a fundamental understanding of the chemistry in such plasmas, but also to improve industrial processes. However, existing techniques, such as two-photon absorption laser induced fluorescence (TALIF), vacuum ultraviolet (VUV) absorption spectroscopy, cavity ring-down spectroscopy (CRDS), and optical emission spectroscopy (OES), are all either bulky and expensive, experimentally challenging, or indirect and relying on a multitude of assumptions.
This work presents the first implementation of absorption spectroscopy in the terahertz (THz) spectral region as a novel diagnostic technique for measuring atomic oxygen densities in plasmas. It is based on the detection of the 3P1←3P2 fine structure transition at approximately 4.745 THz, using a newly developed tunable THz quantum cascade laser (QCL) as the radiation source. THz absorption spectroscopy allows for direct measurements (i.e. no calibration is required) of absolute ground-state atomic oxygen densities, and its accuracy depends almost exclusively on the accuracy to which the line strength of the transition is known. In addition, the narrow laser linewidth of just a few MHz makes it possible to determine the translational temperature from the detected absorption profiles as well. Furthermore, the experimental setup is relatively compact (especially compared to TALIF setups that typically involve bulky laser systems), vacuum conditions are not essential (as opposed to when working in the VUV), and the requirements for the optical alignment are not as strict as for CRDS. These features make THz absorption spectroscopy an attractive alternative to existing diagnostic techniques.
To confirm the accuracy of THz absorption spectroscopy, the obtained atomic oxygen densities were compared to those yielded by more established techniques. Therefore, TALIF and CRDS measurements of atomic oxygen densities were carried
out as well. All measurements were performed in the same capacitively coupled radio frequency (RF) oxygen discharge for a variation of the applied RF power (20 W to 100 W) and the gas pressure (0.7 mbar and 1.3 mbar). The atomic oxygen densities obtained with the three different diagnostic techniques (all of the order of 1*10^14 cm^-3) were found to be in excellent agreement, both qualitatively and quantitatively. This demonstrated that these techniques all allow for accurate measurements and can be used interchangeably as long as no spatial resolution is required. The novel technique of THz absorption spectroscopy is thus well suited for measuring atomic oxygen densities. It has the potential to turn into a standard diagnostic technique once tunable THz QCLs become commercially available and is of particular interest for industrial applications due to the simplicity and compactness of the experimental setup.Sauerstoffhaltige Plasmen werden in der Industrie für eine Vielzahl von Anwendungen eingesetzt, darunter Dünnschichtabscheidung, Ätzen und andere Oberflächenmodifizierungsprozesse. Aufgrund ihrer hohen Reaktivität spielen Sauerstoffatome in den meisten dieser Anwendungen eine Schlüsselrolle, und eine genaue Methode zur Messung ihrer Dichte ist daher von großer Bedeutung, nicht nur um ein grundlegendes Verständnis der Chemie in solchen Plasmen zu erlangen, sondern auch um industrielle Prozesse zu verbessern. Bestehende Messtechniken wie die Zwei-Photonen Absorptions-Laser-induzierte Fluoreszenz (TALIF), die Vakuum-Ultraviolett (VUV)-Absorptionsspektroskopie, die Cavity-Ring-Down-Spektroskopie (CRDS) und die optische Emissionsspektroskopie (OES) sind jedoch alle entweder umständlich und teuer, experimentell anspruchsvoll, oder indirekt und basiert auf einer Vielzahl von Annahmen.
Diese Arbeit präsentiert die erste Anwendung der Absorptionsspektroskopie im Terahertz (THz)-Spektralbereich als neuartige Methode zur Messung von atomaren Sauerstoffdichten in Plasmen. Die Methode beruht auf der Detektion des 3P1←3P2 Feinstrukturübergangs bei ungefähr 4,745 THz unter Verwendung eines kontinuierlich durchstimmbaren THz-Quantenkaskadenlasers (QCLs), der zu diesem Zweck neu entwickelt wurde. Die THz-Absorptionsspektroskopie ermöglicht direkte Messungen (d. h. es ist kein Kalibrierungsverfahren erforderlich) und liefert absolute Grundzustandsdichten, und die Messgenauigkeit hängt fast ausschließlich von der Genauigkeit ab, mit der die Übergangswahrscheinlichkeit bekannt ist. Aufgrund der schmalen Laserlinienbreite von nur wenigen MHz ist es möglich, aus den erfassten Absorptionsspektren nicht nur die Dichte, sondern auch die Translationstemperatur zu bestimmen. Darüber hinaus ist der Versuchsaufbau relativ kompakt (insbesondere im Vergleich zu TALIF-Aufbauten, die typischerweise sperrige Lasersysteme beinhalten), Vakuumbedingungen sind nicht notwendig (im Gegensatz zur VUV-Spektroskopie) und die Anforderungen an die optische Ausrichtung sind nicht so streng wie bei CRDS. Diese Eigenschaften machen die THz-Absorptionsspektroskopie zu einer attraktiven Alternative zu bereits bestehenden Messmethoden.
Um die Genauigkeit der THz-Absorptionsspektroskopie zu bestätigen, wurden die gemessenen atomaren Sauerstoffdichten mit denen verglichen, die durch etabliertere Methoden gewonnen wurden. Daher wurden sowohl TALIF- als auch CRDS-Messungen an derselben kapazitiv gekoppelten Radiofrequenz (RF)-Sauerstoffentladung durchgeführt, für eine Variation der angelegten RF-Leistung (20 W bis 100 W) und bei unterschiedlichem Gasdruck (0,7 mbar und 1,3 mbar). Es wurde festgestellt, dass die mit den drei verschiedenen Messmethoden erhaltenen atomaren Sauerstoffdichten (alle in der Größenordnung von 1*10^14 cm^-3) sowohl qualitativ als auch quantitativ hervorragend übereinstimmen. Dies zeigt, dass die Methoden in Bezug auf die Messergebnisse gleichwertig sind und austauschbar verwendet werden können, solange keine räumliche Auflösung erforderlich ist. Die in dieser Arbeit vorgestellte Methode der THz-Absorptionsspektroskopie eignet sich daher gut zur Messung von atomaren Sauerstoffdichten. Sie hat das Potenzial, sich zu einer Standardmethode zu entwickeln, sobald durchstimmbare THz-QCLs kommerziell verfügbar werden, und ist aufgrund der Einfachheit und Kompaktheit des Versuchsaufbaus für industrielle Anwendungen von besonderem Interesse
Streptokinase reduces Streptococcus dysgalactiae subsp. equisimilis biofilm formation
Get PDFBackground
Streptococcus dysgalactiae subspecies equisimilis (SDSE) is increasingly recognized as an emerging cause of invasive diseases including necrotizing soft tissue infections (NSTIs). In contrast to the closely related Streptococcus pyogenes , SDSE infections mainly affect older and comorbid patients. Biofilm formation has been demonstrated in soft tissue biopsies of S. pyogenes NSTI cases.
Results
Here, we show that bacterial aggregations indicative of biofilms are also present in SDSE NSTI. Although streptokinase (Ska) activity and biofilm formation did not correlate in a diverse set of clinical SDSE isolates, addition of exogenous Ska at an early time point prevented biofilm formation for selected strains. Deletion of ska in SDSE S118 strain resulted in increased biofilm forming capacity. Ska-deficient mutant strain was characterized by a higher metabolic activity and consequent metabolome profiling of biofilms identified higher deposition of a wide range of metabolites as compared to the wild-type.
Conclusions
Our results argue that Ska suppresses biofilm formation in SDSE independent of its original plasminogen converting activity. However, the impact of biofilms and its consequences for patient outcomes in streptococcal NSTIs remain to be elucidated
Optimal control of a dengue model with cross-immunity
Get PDFMathematical modelling of a dengue epidemic with two serotypes including a temporary cross-immunity yields a nonlinear system consisting of ordinary differential equations (ODEs). We investigate an optimal control problem, where the integral of the infected humans is minimised within a time interval. The controls represent human actions to decrease the number of mosquitos in the model. An integral constraint is added, which takes a limitation on the sum of the human actions into account. On the one hand, we derive and apply a direct approach to solve the optimal control problem. Therein, a discretisation of the controls is constructed using spline interpolation in time. Consequently, a finite-dimensional constrained minimisation problem can be solved. On the other hand, we employ an indirect approach, where necessary conditions for an optimal solution are considered. This technique yields a multipoint boundary value problem of a larger system of ODEs including adjoint equations. We present results of numerical computations, where the two methods are compared
Prevalence and risk factors of self-reported hearing loss, tinnitus, and dizziness in a population-based sample from rural northeastern Germany
Get PDFA close anatomical and physiological relationship is known between the senses of hearing and balance, while an additional pathophysiological interaction is supposed. The mechanisms underlying this association are not yet fully understood, especially in individuals without a known specific otologic disorder. In particular, only scarce information on the combined occurrence of audiovestibular sensory impairment is available so far. Therefore, this study aims to provide further insight into the prevalence and co-prevalence of the audiovestibular symptoms hearing loss, tinnitus and dizziness. Additionally, the influence of potential risk factors from lifestyle habits as well as cardiovascular and metabolic conditions on the development of those symptoms is studied. Data was analyzed from 8134 individuals from the population-based Study of Health in Pomerania (SHIP). SHIP pursues a broad and comprehensive examination program in chronologically separated cohorts with longitudinal follow-up. Cohorts are sampled from Western Pomerania, a rural region of north-eastern Germany. The study population represents a cross-sectional analysis from the cohorts SHIP-START (recruited 1997–2001) and SHIP-TREND (recruited 2008–2012), sampled for baseline investigations (SHIP-START-0 and SHIP-TREND-0) at the age of 20–79 years. Audiovestibular symptoms as outcome variables were assessed by structured questionnaires. Additionally, individuals were comprehensively characterized regarding modifiable lifestyle factors as well as cardiovascular and metabolic disorders, allowing the assessment of their role as exposure variables. We calculated a weighted prevalence of 14.2% for hearing loss, 9.7% for tinnitus, and 13.5% for dizziness in the population. Prevalence increased with age and differed among the sexes. A considerable share of 28.0% of the investigated individuals reported more than one symptom at once. The prevalence of hearing loss as well as tinnitus increased between the two cohorts. A moderate positive correlation was found between the occurrence of hearing loss and tinnitus (phi-coefficient 0.318). In multivariable regression analyses, education was identified as a significant protective factor while only smoking was significantly associated with all three symptoms. Furthermore, several cardiovascular risk factors contributed to both hearing loss and dizziness. In conclusion, audiovestibular symptoms are highly prevalent in the investigated population. A considerable but complex influence of risk factors points towards a relation with neuronal as well as cardiovascular disease processes. To clarify the underlying mechanisms, the interaction between the senses of hearing and balance as well as the mode of action of the risk factors should be evaluated in more detail in the future
The understanding of the agriculturally shaped environment: from the theoretical construct to an applied indicator of sustainable development
Get PDFSustainable development of the resource ‘land’ is increasingly being discussed with a focus on rural areas. Understanding is key to solving land use conflicts. It can lead to joint solutions and can thus enable sustainable development at a practical level. It goes beyond environmental consciousness, which is related to general issues, and instead aims to address concrete challenges in the context of sustainable development at an applicable level. ‘Understanding’ with regard to land use conflicts has not yet been defined in the literature. Based on this motivation, it is the aim of this study to create the construct of ‘understanding’ conceptually, to validate it empirically with structural equation modelling, and to demonstrate that understanding might be an important prerequisite for sustainable development. In this case, the focus is not on a general kind of understanding, but rather on specific aspects of understanding in relation to the agriculturally shaped environment in rural areas. The empirical data for the paper were collected by means of a large-scale population survey in Western Pomerania, Germany, a rural peripheral region characterized by typical land-use conflicts in predominantly rural areas. A tripartite division of the construct into cognitive, emotional, and opinion levels was derived theoretically. The construct is supported empirically and that it can be applied as an SDG indicator. Thus, the refined construct of understanding the agriculturally shaped environment can make a substantial contribution towards closing the knowledge/attitude-behavior gap
Molecular and structural basis of oligopeptide recognition by the Ami transporter system in pneumococci
Get PDFATP-binding cassette (ABC) transport systems are crucial for bacteria to ensure sufficient uptake of nutrients that are not produced de novo or improve the energy balance. The cell surface of the pathobiont Streptococcus pneumoniae (pneumococcus) is decorated with a substantial array of ABC transporters, critically influencing nasopharyngeal colonization and invasive infections. Given the auxotrophic nature of pneumococci for certain amino acids, the Ami ABC transporter system, orchestrating oligopeptide uptake, becomes indispensable in host compartments lacking amino acids. The system comprises five exposed Oligopeptide Binding Proteins (OBPs) and four proteins building the ABC transporter channel. Here, we present a structural analysis of all the OBPs in this system. Multiple crystallographic structures, capturing both open and closed conformations along with complexes involving chemically synthesized peptides, have been solved at high resolution providing insights into the molecular basis of their diverse peptide specificities. Mass spectrometry analysis of oligopeptides demonstrates the unexpected remarkable promiscuity of some of these proteins when expressed in Escherichia coli, displaying affinity for a wide range of peptides. Finally, a model is proposed for the complete Ami transport system in complex with its various OBPs. We further disclosed, through in silico modelling, some essential structural changes facilitating oligopeptide transport into the cellular cytoplasm. Thus, the structural analysis of the Ami system provides valuable insights into the mechanism and specificity of oligopeptide binding by the different OBPs, shedding light on the intricacies of the uptake mechanism and the in vivo implications for this human pathogen