23 resultados para G-extremal processes
em BORIS: Bern Open Repository and Information System - Berna - Suiça
Resumo:
The aim of the present study was to measure transit patterns of nutrients and the absorptive ability in ruminal drinkers (RDs) compared with healthy unweaned calves. The acetaminophen (paracetamol) absorption test was used to characterize the oroduodenal transit rate. Clinical examination and the analysis of various blood parameters provided supplementary information on digestive processes. Three unweaned bucket-fed calves (one RD and two healthy controls) each from seven Swiss dairy farms were included in the study. Measurements (tests 1 and 2) were performed twice at an interval of 10 days. Between tests, the feeding technique of the RDs and one control calf per farm was changed to feeding with a nipple instead of by bucket (without nipple). Acetaminophen appearance in the blood was delayed and reduced in RDs compared with the controls. Acid-base metabolism and several haematological and metabolic parameters differed markedly between RDs and healthy controls. The characteristics of the oroduodenal transit rate, absorptive abilities and clinical status in RDs were nearly normalised within 10 days of reconditioning.
Resumo:
Through alternative splicing, multiple different transcripts can be generated from a single gene. Alternative splicing represents an important molecular mechanism of gene regulation in physiological processes such as developmental programming as well as in disease. In cancer, splicing is significantly altered. Tumors express a different collection of alternative spliceoforms than normal tissues. Many tumor-associated splice variants arise from genes with an established role in carcinogenesis or tumor progression, and their functions can be oncogenic. This raises the possibility that products of alternative splicing play a pathogenic role in cancer. Moreover, cancer-associated spliceoforms represent potential diagnostic biomarkers and therapeutic targets. G protein-coupled peptide hormone receptors provide a good illustration of alternative splicing in cancer. The wild-type forms of these receptors have long been known to be expressed in cancer and to modulate tumor cell functions. They are also recognized as attractive clinical targets. Recently, splice variants of these receptors have been increasingly identified in various types of cancer. In particular, alternative cholecystokinin type 2, secretin, and growth hormone-releasing hormone receptor spliceoforms are expressed in tumors. Peptide hormone receptor splice variants can fundamentally differ from their wild-type receptor counterparts in pharmacological and functional characteristics, in their distribution in normal and malignant tissues, and in their potential use for clinical applications.
Resumo:
This article reports on recent electrical and optical techniques for investigating cellular signaling reactions in artificial and native membranes immobilized on solid supports. The first part describes the formation of planar artificial lipid bilayers on gold electrodes, which reveal giga-ohm electrical resistance and the insertion and characterization of ionotropic receptors therein. These membranes are suited to record a few or even single ion channels by impedance spectroscopy. Such tethered membranes on planar arrays of microelectrodes offer mechanically robust, long-lasting measuring devices to probe the influence of different chemistries on biologically important ionotropic receptors and therefore will have a future impact to probe the function of channel proteins in basic science and in biosensor applications. In a second part, we present complementary approaches to form inside-out native membrane sheets that are immobilized on micrometer-sized beads or across submicrometer-sized holes machined in a planar support. Because the native membrane sheets are plasma membranes detached from live cells, these approaches offer a unique possibility to investigate cellular signaling processes, such as those mediated by ionotropic or G protein-coupled receptors, with original composition of lipids and proteins.
Resumo:
Our life is full of stories: some of them depict real-life events and were reported, e.g. in the daily news or in autobiographies, whereas other stories, as often presented to us in movies and novels, are fictional. However, we have only little insights in the neurocognitive processes underlying the reading of factual as compared to fictional contents. We investigated the neurocognitive effects of reading short narratives, labeled to be either factual or fictional. Reading in a factual mode engaged an activation pattern suggesting an action-based reconstruction of the events depicted in a story. This process seems to be past-oriented and leads to shorter reaction times at the behavioral level. In contrast, the brain activation patterns corresponding to reading fiction seem to reflect a constructive simulation of what might have happened. This is in line with studies on imagination of possible past or future events.
Resumo:
The Imager for Low Energetic Neutral Atoms test facility at the University of Bern was developed to investigate, characterize, and quantify physical processes on surfaces that are used to ionize neutral atoms before their analysis in neutral particle-sensing instruments designed for space research. The facility has contributed valuable knowledge of the interaction of ions with surfaces (e.g., fraction of ions scattered from surfaces and angular scattering distribution) and employs a novel measurement principle for the determination of secondary electron emission yields as a function of energy, angle of incidence, particle species, and sample surface for low particle energies. Only because of this test facility it was possible to successfully apply surface-science processes for the new detection technique for low-energetic neutral particles with energies below about 1 keV used in space applications. All successfully flown spectrometers for the detection of low-energetic neutrals based on the particle–surface interaction process use surfaces evaluated, tested, and calibrated in this facility. Many instruments placed on different spacecraft (e.g., Imager for Magnetopause-to-Aurora Global Exploration, Chandrayaan-1, Interstellar Boundary Explorer, etc.) have successfully used this technique.
Resumo:
We present SUSY_FLAVOR version 2 — a Fortran 77 program that calculates low-energy flavor observables in the general R-parity conserving MSSM. For a set of MSSM parameters as input, the code gives predictions for: 1. Electric dipole moments of the leptons and the neutron. 2. Anomalous magnetic moments (i.e. g − 2) of the leptons. 3. Radiative lepton decays (μ → eγ and τ → μγ , eγ ). 4. Rare Kaon decays (K0 L → π0 ¯νν and K+ → π+ ¯νν). 5. Leptonic B decays (Bs,d → l+l−, B → τ ν and B → Dτ ν). 6. Radiative B decays (B → ¯ Xsγ ). 7. ΔF = 2 processes ( ¯ K0–K0, ¯D–D, ¯Bd–Bd and ¯Bs–Bs mixing). Comparing to SUSY_FLAVOR v1, where the matching conditions were calculated strictly at one-loop level, SUSY_FLAVOR v2 performs the resummation of all chirally enhanced corrections, i.e. takes into account the enhanced effects from tan β and/or large trilinear soft mixing terms to all orders in perturbation theory. Also, in SUSY_FLAVOR v2 new routines calculation of B → (D)τ ν, g − 2, radiative lepton decays and Br(l → l′γ ) were added. All calculations are done using exact diagonalization of the sfermion mass matrices. The program can be obtained from http://www.fuw.edu.pl/susy_flavor.
Resumo:
Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels ("araneiform" terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.
Resumo:
Traditionally, critical swimming speed has been defined as the speed when a fish can no longer propel itself forward, and is exhausted. To gain a better understanding of the metabolic processes at work during a U(crit) swim test, and that lead to fatigue, we developed a method using in vivo (31)P-NMR spectroscopy in combination with a Brett-type swim tunnel. Our data showed that a metabolic transition point is reached when the fish change from using steady state aerobic metabolism to non-steady state anaerobic metabolism, as indicated by a significant increase in inorganic phosphate levels from 0.3+/-0.3 to 9.5+/-3.4 mol g(-1), and a drop in intracellular pH from 7.48+/-0.03 to 6.81+/-0.05 in muscle. This coincides with the point when the fish change gait from subcarangiform swimming to kick-and-glide bursts. As the number of kicks increased, so too did the Pi concentration, and the pH(i) dropped. Both changes were maximal at U(crit). A significant drop in Gibbs free energy change of ATP hydrolysis from -55.6+/-1.4 to -49.8+/-0.7 kJ mol(-1) is argued to have been involved in fatigue. This confirms earlier findings that the traditional definition of U(crit), unlike other critical points that are typically marked by a transition from aerobic to anaerobic metabolism, is the point of complete exhaustion of both aerobic and anaerobic resources.
Resumo:
The importance of long-term historical information derived from paleoecological studies has long been recognized as a fundamental aspect of effective conservation. However, there remains some uncertainty regarding the extent to which paleoecology can inform on specific issues of high conservation priority, at the scale for which conservation policy decisions often take place. Here we review to what extent the past occurrence of three fundamental aspects of forest conservation can be assessed using paleoecological data, with a focus on northern Europe. These aspects are (1) tree species composition, (2) old/large trees and coarse woody debris, and (3) natural disturbances. We begin by evaluating the types of relevant historical information available from contemporary forests, then evaluate common paleoecological techniques, namely dendrochronology, pollen, macrofossil, charcoal, and fossil insect and wood analyses. We conclude that whereas contemporary forests can be used to estimate historical, natural occurrences of several of the aspects addressed here (e.g. old/large trees), paleoecological techniques are capable of providing much greater temporal depth, as well as robust quantitative data for tree species composition and fire disturbance, qualitative insights regarding old/large trees and woody debris, but limited indications of past windstorms and insect outbreaks. We also find that studies of fossil wood and paleoentomology are perhaps the most underutilized sources of information. Not only can paleoentomology provide species specific information, but it also enables the reconstruction of former environmental conditions otherwise unavailable. Despite the potential, the majority of conservation-relevant paleoecological studies primarily focus on describing historical forest conditions in broad terms and for large spatial scales, addressing former climate, land-use, and landscape developments, often in the absence of a specific conservation context. In contrast, relatively few studies address the most pressing conservation issues in northern Europe, often requiring data on the presence or quantities of dead wood, large trees or specific tree species, at the scale of the stand or reserve. Furthermore, even fewer examples exist of detailed paleoecological data being used for conservation planning, or the setting of operative restorative baseline conditions at local scales. If ecologist and conservation biologists are going to benefit to the full extent possible from the ever-advancing techniques developed by the paleoecological sciences, further integration of these disciplines is desirable.
Resumo:
After 5 years of conceptualizing, investigating, and writing about corrective experiences (CEs), we (the authors of this chapter) met to talk about what we learned. In this chapter, we summarize our joint understanding of (a) the definition of CEs; (b) the contexts in which CEs occur; (c) client, therapist, and external factors that facilitate CEs; (d) the consequences of CEs; and (e) ideas for future theoretical, clinical, empirical, and training directions. As will become evident, the authors of this chapter, who represent a range of theoretical orientations, reached consensus on some CE-related topics but encountered controversy and lively debate about other topics. (PsycINFO Database Record (c) 2013 APA, all rights reserved)
Resumo:
Due to the ongoing trend towards increased product variety, fast-moving consumer goods such as food and beverages, pharmaceuticals, and chemicals are typically manufactured through so-called make-and-pack processes. These processes consist of a make stage, a pack stage, and intermediate storage facilities that decouple these two stages. In operations scheduling, complex technological constraints must be considered, e.g., non-identical parallel processing units, sequence-dependent changeovers, batch splitting, no-wait restrictions, material transfer times, minimum storage times, and finite storage capacity. The short-term scheduling problem is to compute a production schedule such that a given demand for products is fulfilled, all technological constraints are met, and the production makespan is minimised. A production schedule typically comprises 500–1500 operations. Due to the problem size and complexity of the technological constraints, the performance of known mixed-integer linear programming (MILP) formulations and heuristic approaches is often insufficient. We present a hybrid method consisting of three phases. First, the set of operations is divided into several subsets. Second, these subsets are iteratively scheduled using a generic and flexible MILP formulation. Third, a novel critical path-based improvement procedure is applied to the resulting schedule. We develop several strategies for the integration of the MILP model into this heuristic framework. Using these strategies, high-quality feasible solutions to large-scale instances can be obtained within reasonable CPU times using standard optimisation software. We have applied the proposed hybrid method to a set of industrial problem instances and found that the method outperforms state-of-the-art methods.
Resumo:
Climate models predict more frequent and more severe extreme events (e.g., heat waves, extended drought periods, flooding) in many regions for the next decades. The impact of adverse environmental conditions on crop plants is ecologically and economically relevant. This review is focused on drought and heat effects on physiological status and productivity of agronomically important plants. Stomatal opening represents an important regulatory mechanism during drought and heat stress since it influences simultaneously water loss via transpiration and CO2 diffusion into the leaf apoplast which further is utilized in photosynthesis. Along with the reversible short-term control of stomatal opening, stomata and leaf epidermis may produce waxy deposits and irreversibly down-regulate the stomatal conductance and non-stomatal transpiration. As a consequence photosynthesis will be negatively affected. Rubisco activase—a key enzyme in keeping the Calvin cycle functional—is heat-sensitive and may become a limiting factor at elevated temperature. The accumulated reactive oxygen species (ROS) during stress represent an additional challenge under unfavorable conditions. Drought and heat cause accumulation of free amino acids which are partially converted into compatible solutes such as proline. This is accompanied by lower rates of both nitrate reduction and de novo amino acid biosynthesis. Protective proteins (e.g., dehydrins, chaperones, antioxidant enzymes or the key enzyme for proline biosynthesis) play an important role in leaves and may be present at higher levels under water deprivation or high temperatures. On the whole plant level, effects on long-distance translocation of solutes via xylem and phloem and on leaf senescence (e.g., anticipated, accelerated or delayed senescence) are important. The factors mentioned above are relevant for the overall performance of crops under drought and heat and must be considered for genotype selection and breeding programs.