julilili42/papers huggingface dataset:
Fetal MEG Redistribution by Projection Operators
2004-06-21

The fetal magnetoencephalogram (fMEG) is measured in the presence of large interference from the maternal and fetal magnetocardiograms. This interference can be efficiently attenuated by orthogonal projection of the corresponding spatial vectors. However, the projection operators redistribute the fMEG signal among sensors. Although redistribution can be readily accounted for in the forward solution, visual interpretation of the fMEG signal topography is made difficult. We have devised a general, model-independent method for correction of the redistribution effect that utilizes the assumption that we know in which channels the fMEG should be negligible (such channels are distant from the known fetal head position). In a simplified case where the fMEG can be explained by equivalent current dipoles, the correction can also be obtained from fitting the dipoles to the fMEG signal. The corrected fMEG signal topography then corresponds to the dipole forward solution, but without orthogonal projection. We illustrate the redistribution correction on an example of experimentally measured flash evoked fMEG.
Communication analysis for system-on-chip design
2004-06-21

In this paper we present an approach for analysis of systems of parallel, communicating processes for SoC design. We present a method to detect communications that synchronize the program flow of two or more processes. These synchronization points set the processes into relation and allow the determination of the global timing behavior of such a system. Using the results of our method for communication analysis, we present a new method to detect communications that might produce conflicts on shared communication resources. This information can be used for the assignment of communication resources.
Directional correlation in white matter tracks of the human brain
2004-06-21

Abstract Purpose To describe a technique for the detection of distinct brain fibers in sets of magnetic resonance (MR) diffusion tensor imaging (DTI) data. Materials and Methods MR‐DTI can be used for a tractography of brain fibers presuming a data set of high spatial resolution and high signal to noise. A less demanding technique for the visualization of discrete brain fiber bundles involves segmentation. By using a region‐growing algorithm, those voxels that have a direction similar to that of the major eigenvector in neighboring voxels of a data set can be marked. It has been shown recently by Mori et al ( 1 ) that this technique can be successfully applied to data from a single slice of a mouse brain. In this study, the segmentation technique was applied with modifications to multislice DTI data from the human brain. Results A distinct segmentation of various brain fiber bundles could be achieved by the use of a two‐step algorithm. In the first step, voxels within large fiber tracts‐such as corticofugal tracts (e.g., corticospinal tract) and the optic radiation‐were segmented by starting the region‐growing algorithm in the corpus callosum (CC) and erasing this major structure from the data set. In the second step, remaining voxels were segmented by the same algorithm; this revealed a good assignment of the similarly oriented fibers derived by segmentation to the anatomically given brain lobes. This two‐step procedure was successfully applied to DTI data of six healthy volunteers. Conclusion The segmentation technique for DTI data proposed by Mori et al ( 1 ) for data from mouse brains can be applied to multislice data from the human brain by using a two‐step algorithm including a masking of the major fiber tracts. J. Magn. Reson. Imaging 2004;20:25–30. © 2004 Wiley‐Liss, Inc.
The impact of example comparisons on schema acquisition: do learners really need multiple examples?
2004-06-22

Comparing multiple examples within problem categories is usually considered a necessary prerequisite for schema acquisition. However, there is an evident lack of conclusive empirical evidence supporting this claim. Moreover, there are findings indicating that carefully designed one-example conditions may allow for profitable processes of example comparison as well. In line with this reasoning, we present an experiment - that builds up on a series of studies conducted by Quilici and Mayer (1996) -- yielding that multiple examples are only helpful for schema acquisition if the examples are processed thoroughly and if additional instructional support is provided for learners. Moreover, our study gives first evidence that multiple examples may even impede performance under less optimal learning conditions.
Knowledge sharing in groups: experimental findings of how to overcome a social dilemma
2004-06-22

Shared databases are used for knowledge sharing in groups. The decision whether to contribute knowledge to such a database or to withhold it represents a public-goods dilemma. Each group member saves time and energy if s/he only uses the database to get information but does not contribute any information. But if all do so, the database is empty, and nobody has any benefit of it. An experimental environment enabling the study of this dilemma is described, and an overview of five experiments is given. They investigate the effect of the following factors: providing metaknowledge about the importance of the information, providing a bonus system to reward contributing, reducing costs for contribution, establishing prescriptive rules for the number of contributions, and providing feedback about the teammates' contribution behavior.
Learning from category-avoiding instructional examples reduces cognitive load and fosters cognitive skill acquisition
2004-06-22

Problem-type schemata are often seen as an important prerequisite for skilled problem solving. These schemata represent problem categories together with category-specific solution procedures and can be best acquired by studying concrete instances of problem categories (i.e., examples). Usually instructional worked examples are designed in a molar way to convey knowledge on problem categories (that are defined by multiple structural problem features) and category-specific solution procedures (category-focusing examples). In contrast, we propose to design instructional examples in a modular way that focuses on the understanding of relations between individual structural problem features and individual solution steps, i.e. relations that hold below the category level (category-avoiding examples). We designed instructional examples (see Table 1) in the domain of calculating the probability of complex events (e.g., at the Olympics, 7 sprinters participate in the 100m-sprint - what is the probability of correctly guessing the winner of the gold, the silver, and the bronze medal?) Like many other topics, the calculation of complex-event probabilities is usually taught by means of a category-specific solution formula in which multiple steps are collapsed into a single formula that applies to all problems sharing a characteristic pattern of structural features. Studying category-focusing examples requires to consider multiple structural problem features in parallel in order to understand the problem's category membership. Therefore, a substantial cognitive load may result depending on the number of relevant structural problem features. Moreover, category-focusing examples typically result in a molar representation of solution procedures. For instance, one has to have knowledge on all defining structural features of a problem before being able to decide on a formula needed for its solution. Therefore, relations holding irrespective of category membership such as relations between structural problem features and individual solution steps might be poorly understood. As a result, learners may not learn to relate individual structural problem features to characteristics of the problem solution and thus may fail to adapt solution procedures to novel problems beyond the known problem categories. We developed a category-avoiding example format that does not require learners to consider multiple structural problem features simultaneously and that focuses on individual solution steps and their relation to individual structural features across the boundaries of problem categories. Two experiments showed a clear superiority of category-avoiding examples with regard to learning time, cognitive load, and problem-solving performance for isomorphic as well as novel problems compared to traditional category-focusing examples.
A conserved sequence in the mouse variable T cell receptor α recombination signal sequence 23‐bp spacer can affect recombination
2004-06-23

Abstract Although the V‐gene segments coding for the TCR α and δ chains are mixed together in the α δ locus and are recombined by the same processes, some gene segments (TRAV) are rearranged only with TCR Jα gene segments, some (TRDV) only with TCR Dδ gene segments and some (TRADV) with both. To date, no molecular signal is known that can characterize these three differenttypes of gene segments. Studying the recombination signal sequences (RSS) of all mouse TCR V‐gene segments we observed that 80% of the TRAV contain a palindrome sequence (CTGCAG) or its related variant CTGTAG in their 23‐bp spacer. Using gel‐shift assays we show that these sequences are specifically recognized by some nuclear proteins that are expressed by fresh thymocytes, fresh lymphocytes and tumor cells. Recombination assays on plasmid substrates in a pre‐B cell line showed that RSS containing the CTGCAG sequence can impair recombination. From the protein fractions containing the CTGCAG‐binding activity, three proteins were identified: G3BP1 (a nucleic‐acid‐binding protein with a proposed helicase activity) and two proteins from the high‐mobility group (HMG) family — HMGB2 and HMGB3. We hypothesize that these proteins can affect recombination at the TCR α δ locus.
A -catenin-dependent pathway regulates expression of cytochrome P450 isoforms in mouse liver tumors
2004-06-24

Phenobarbital (PB) is a model tumor promoter in the rodent liver. In the mouse, the promotional effect of PB results from a selective stimulation of clonal outgrowth of hepatocytes harboring activating mutations in the beta-catenin (catnb) gene. Glutamine synthetase (GS), a downstream target in the Wnt/beta-catenin/T-cell factor (TCF) signaling pathway, is strongly up-regulated in catnb-mutated mouse liver tumors and may serve as a marker for their identification. Here we show that the levels of several cytochrome P450 (CYP) isoenzymes are also altered in GS-positive liver tumors. Immunohistochemical and western blotting analyses demonstrated that GS-positive, catnb-mutated tumors showed levels of CYP1A, CYP2B, CYP2C and CYP2E1, which were similar or slightly enhanced in comparison with non-tumoral liver tissue. This contrasts with tumors without catnb mutations, which exhibited decreased levels of these CYP isoforms. Real-time RT-PCR revealed that the differences in CYP levels in the tumors corresponded to changes in the respective mRNAs. Mouse hepatoma cells were transiently transfected with an expression vector encoding an S33Y-mutated beta-catenin protein, which was functional with regard to transactivation of a beta-catenin/TCF-responsive (topflash) reporter construct. Co-transfected with luciferase reporter vectors containing either the regulatory upstream sequence of the CYP2B1 gene or three dioxin-responsive core elements were activated by S33Y-beta-catenin. These results indicate that mutation of catnb leads to transcriptional activation of CYP isoenzymes in mouse liver tumors. As CYPs are involved in both the activation and the inactivation of several clinically important anticancer drugs, our findings may be relevant for chemotherapy of human cancers, where activation of beta-catenin-dependent signaling by mutation of the gene or alternative mechanisms is frequently observed.
Effects of Moxonidine vs. Metoprolol on Blood Pressure and Metabolic Control in Hypertensive Subjects with Type 2 Diabetes
2004-06-24

Subjects with type 2 diabetes experience an increased cardiovascular morbidity and mortality, related to a high prevalence of hypertension, dyslipidemia, and obesity. Antihypertensive treatment with beta-adrenergic receptor blockers may have deleterious metabolic consequences, including worsening of lipid profiles and insulin sensitivity. The centrally-acting sympatholytic agent moxonidine may improve these variables. In this randomised, double-blind multicenter study, the effects of two widely used antihypertensive agents--moxonidine (MOX) and the beta (1)-selective adrenergic receptor blocker metoprolol (MET)--on blood pressure and metabolic control were directly compared in hypertensive subjects with type 2 diabetes. Patients received either MOX (0.2 - 0.6 mg/d) or MET (50 - 150 mg/d) for 12 weeks, intending comparable blood pressure control. In total 200 patients were randomized. Here we report results from the per protocol population consisting of 127 patients (MOX 66, MET 61) but similar results were found in the ITT population. Reductions in systolic (SBP) and diastolic (DBP) blood pressures after 12 weeks were similar in both groups: In the MOX group, mean SBP (+/- SD) decreased from 154 +/- 12 to 142 +/- 17 mmHg and mean DBP from 91 +/- 9 to 83 +/- 9 mmHg. In the MET group, mean SBP decreased from 152 +/- 13 to 140 +/- 15 mmHg, and mean DBP from 90 +/- 8 to 84 +/- 10 mmHg. Mean HbA (1C) values did not differ between groups after 12 weeks (MOX 8.1 +/- 1.4 Hb%, MET 8.1 +/- 1.5 Hb%, intention-to-treat population). However, fasting plasma glucose decreased in the MOX group (median change - 5 mg/dl), but increased in the MET group (+ 16 mg/dl; p < 0.05). Median changes in the insulin resistance index (HOMA (IR)) were + 0.56 micro IU x mol/L (2) in the MET group, and - 0.27 micro IU x mol/L (2) in the MOX group. Correspondingly, fasting triglycerides increased with a median change of + 29.5 mg/dL in the MET group, but decreased in the MOX group (- 27.5 mg/dl; p < 0.05). These results indicate that MOX, unlike MET, may elicit beneficial adaptations in glucose and lipid metabolism in hypertensive subjects with type 2 diabetes, although mean HbA (1c) values did not differ. In long-term treatment in this high-risk population, MOX thus may decrease global vascular disease risk to a greater extent than MET.
Nucleon QCD sum rules in nuclear matter including four-quark condensates
2004-06-24

We calculate the nucleon parameters in nuclear matter using the QCD sum rules\\napproach in Fermi gas approximation. Terms up to 1/q^2 in the operator product\\nexpansion (OPE) are taken into account. The higher moments of the nucleon\\nstructure functions are included. The complete set of the nucleon expectation\\nvalues of the four-quark operators is employed. Earlier the lack of information\\non these values has been the main obstacle for the further development of the\\napproach. We show that the four-quark condensates provide the corrections of\\nthe order 20% to the results obtained in the leading orders of the OPE. This is\\nconsistent with the assumption about the convergence of the OPE. The nucleon\\nvector self-energy \\\\Sigma_v and the nucleon effective mass m^* are expressed in\\nterms of the in-medium values of QCD condensates. The numerical results for\\nthese parameters at the saturation value of the density agree with those\\nobtained by the methods of nuclear physics.\\n
Methods to Investigate Mechanisms of Electroorganic Reactions
2004-06-24

Abstract The sections in this article are Introduction Scope: Methods of Molecular Electrochemistry Historical Development Why and How to Investigate Mechanisms of Electroorganic Reactions Steps of Electrode Reaction Mechanisms General Transport Electron Transfer Chemical Kinetic Steps Adsorption Organic Electrode Reaction Mechanisms Electron Transfer Initiates Chemistry Nomenclature of Electrode Reaction Mechanisms Formal Description of Events at an Electrode Current‐Potential‐Time Relationships Concentration Profiles Methods of Mechanistic Electroorganic Chemistry Classification Controlled‐Potential Techniques Controlled‐Current Techniques Hydrodynamic Voltammetry Exhaustive Electrolysis Techniques How to Gain Access to Kinetics, Thermodynamics, and Mechanisms of Electroorganic Reactions Qualitative and Quantitative Investigation of Electrode Reaction Mechanisms General Recommendations for Mechanistic Analysis Some Mechanistic Examples Pure ET Reactions Follow‐up Reactions Preequilibria to ETs Catalytic Reactions How to Gain Additional Information about Electroorganic Reaction Mechanisms Simulation Ultramicroelectrodes Electrogravimetry Spectroelectrochemistry Conclusion Acknowledgment
Desorption Kinetics of Phenanthrene in Aquifer Material Lacks Hysteresis
2004-06-25

Desorption experiments were carried out in flow through columns following long-term sorption batch experiments (up to 1010 days at 20 degrees C; Rügner, H.; Kleineidam, S.; Grathwohl, P. Long-term sorption kinetics of phenanthrene in aquifer materials. Environ. Sci. Technol. 1999, 33, 1645-1651) to elucidate sorption/desorption hysteresis phenomena of phenanthrene in aquifer materials. Most of the sorbents employed in this study (homogeneous lithocomponents separated from aquifer sediments or fresh rock fragments) showed highly nonlinear sorption isotherms because of coal particles embedded inside the grains. Because sorption capacities were high, sorption equilibrium was not reached in most of the sorbents during the initial sorptive uptake experiments lasting up to 1010 days. Desorption was studied up to 90 days at 20 degrees C. The temperature was raised after that stepwise from originally 20 to 30, 40, 50, and finally to 70 degrees C for selected samples to estimate activation energies of desorption. A numerical intraparticle pore diffusion model was used to fit sorptive uptake data and subsequently for pure forward prediction of the release rates in the desorption column experiments. Desorption was initially fast followed by extended tailing which in other studies is fitted by using multirate first-order models. Our results demonstrate that the retarded intraparticle pore diffusion model can predict the desorption rates with a single diffusion rate constant obtained independently from the long-term batch sorption experiment. No evidence for hysteresis was found, suggesting that many hysteresis phenomena reported earlier are experimental artifacts resulting from nonequilibrium effects and "nonphysical" models. The different temperature steps allowed one to additionally calculate activation energies of desorption (45-59 kJ mol(-1)), which were in reasonably good agreement with results from earlier studies for a retarded pore diffusion process. In addition, equilibrium sorption isotherms were determined at 20 and 40 degrees C to compare sorption and desorption enthalpies. Both were in good agreement, confirming that desorption was not significantly different from sorption.
Evidence for a narrow resonance at 1530MeV/c2 in the K0p-system of the reaction pp→Σ+K0p from the COSY-TOF experiment
2004-06-25

The hadronic reaction pp --&gt; Sigma(+)K(0)p was measured exclusively at a beam momentum of 2.95 GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K(0)p-subsystem at 1530 +/- 5 MeV/c(2) with a significance of 4-6 standard deviations, depending on background assumptions. The upper limit of 18 +/- 4 MeV/c(2) (FWHM) for its width is given by the experimental resolution. The corresponding total cross section is estimated to be about 0.4 +/- 0.1 (stat) 0.1 (syst) mub. Since a resonance in this subsystem must have strangeness S = + I we claim it to be the Theta(+) state for which very recently evidence was found in various experiments. (C) 2004 Elsevier B.V. All rights reserved.
Structure of D-63 from Sulfolobus Spindle-Shaped Virus 1: Surface Properties of the Dimeric Four-Helix Bundle Suggest an Adaptor Protein Function
2004-06-25

ABSTRACT Sulfolobus spindle-shaped virus 1 (SSV1) and its fusellovirus homologues can be found in many acidic (pH ≤ 4.0) hot springs (≥70°C) around the world. SSV1 contains a 15.5-kb double-stranded DNA genome that encodes 34 proteins with greater than 50 amino acids. A site-specific integrase and a DnaA-like protein have been previously identified by sequence homology, and three structural proteins have been isolated from purified virus and identified by N-terminal sequencing (VP1, VP2, and VP3). The functions of the remaining 29 proteins are currently unknown. To assign functions to these proteins, we have initiated biochemical and structural studies on the SSV1 proteome. Here we report the structure of SSV1 D-63. The structure reveals a helix-turn-helix motif that dimerizes to form an antiparallel four-helix bundle. Mapping residues conserved among three fusellovirus isolates onto the structure shows that one face of the rod-shaped molecule is highly conserved. This conserved surface spans the dimer axis and thus exhibits 2-fold symmetry. Two smaller conserved patches, also related by 2-fold symmetry, are found on the opposite face of the molecule. All of these conserved surfaces are devoid of clefts or pockets typically used to bind small molecules, suggesting that D-63 may function as an adaptor protein in macromolecular assembly.
Number and position of wounds on honey bee (Apis mellifera) pupae infested with a single Varroa mite
2004-06-25

The wounds inflicted on pupae in capped brood cells of the honey bee, Apis mellifera, infested with a single female of the ectoparasitic mite, Varroa destructor, were investigated after visualisation by vital staining with trypan blue. On average the mites made two integumental perforations for feeding on prepupae and one on pupae. Most of the punctures were on particular ventral sites on the abdomen. Possible reasons for this pronounced preference and the evolutionary aspects of this highly specialised parasite-host relationship are discussed.
Comprehensive analysis of thiopurine S-methyltransferase phenotype–genotype correlation in a large population of German-Caucasians and identification of novel TPMT variants
2004-06-28

The thiopurine S-methyltransferase (TPMT) genetic polymorphism has a significant clinical impact on the toxicity of thiopurine drugs. It has been proposed that the identification of patients who are at high risk for developing toxicity on the basis of genotyping could be used to individualize drug treatment. In the present study, phenotype-genotype correlation of 1214 healthy blood donors was investigated to determine the accuracy of genotyping for correct prediction of different TPMT phenotypes. In addition, the influence of gender, age, nicotine and caffeine intake was examined. TPMT red blood cell activity was measured in all samples and genotype was determined for the TPMT alleles *2 and *3. Discordant cases between phenotype and genotype were systematically sequenced. A clearly defined trimodal frequency distribution of TPMT activity was found with 0.6% deficient, 9.9% intermediate and 89.5% normal to high methylators. The frequencies of the mutant alleles were 4.4% (*3A), 0.4% (*3C) and 0.2% (*2). All seven TPMT deficient subjects were homozygous or compound heterozygous carriers for these alleles. In 17 individuals with intermediate TPMT activity discordant to TPMT genotype, four novel variants were identified leading to amino acid changes (K119T, Q42E, R163H, G71R). Taking these new variants into consideration, the overall concordance rate between TPMT genetics and phenotypes was 98.4%. Specificity, sensitivity and the positive and negative predictive power of the genotyping test were estimated to be higher than 90%. Thus, the results of this study provide a solid basis to predict TPMT phenotype in a Northern European Caucasian population by molecular diagnostics.