julilili42/papers huggingface dataset:
Understanding the fundamental principles of metal oxide based gas sensors; the example of CO sensing with SnO2sensors in the presence of humidity
2003-05-09

This paper investigates the effect of water vapour in CO sensing by using Pd doped SnO2 sensors realized in thick film technology as an example of the basic understanding of sensing mechanisms applied to sensors. The results of phenomenological and spectroscopic measurement techniques, all of them obtained under working conditions for sensors, were combined with modelling in order to derive conclusions able to be generalized to the field of metal oxide based gas sensors. The techniques employed were: dc conductance, ac impedance spectroscopy, work function (by using the Kelvin probe method), catalytic conversion and diffuse reflectance infrared Fourier transform measurements. The most important conclusion is that the different parts of the sensor (sensing layer, electrodes, substrate) are all influencing the gas detection and their role has to be taken into consideration when one attempts to understand how a sensor works.
The Structure of a Functional Unit from the Wall of a Gastropod Hemocyanin Offers a Possible Mechanism for Cooperativity,
2003-05-09

Structure-function relationships in a molluscan hemocyanin have been investigated by determining the crystal structure of the Rapana thomasiana (gastropod) hemocyanin functional unit RtH2e in deoxygenated form at 3.38 A resolution. This is the first X-ray structure of an unit from the wall of the molluscan hemocyanin cylinder. The crystal structure of RtH2e demonstrates molecular self-assembly of six identical molecules forming a regular hexameric cylinder. This suggests how the functional units are ordered in the wall of the native molluscan hemocyanins. The molecular arrangement is stabilized by specific protomer-to-protomer interactions, which are probably typical for the functional units building the wall of the cylinders. A molecular mechanism for cooperative dioxygen binding in molluscan hemocyanins is proposed on the basis of the molecular interactions between the protomers. In particular, the deoxygenated RtH2e structure reveals a tunnel leading from two opposite sides of the molecule to the active site. The tunnel represents a possible entrance pathway for dioxygen molecules. No such tunnels have been observed in the crystal structure of the oxy-Odg, a functional unit from the Octopus dofleini (cephalopod) hemocyanin in oxygenated form.
Electrosurface Phenomena at Polymer Films for Biosensor Applications
2003-05-09

Electrosurface phenomena at thin polymer films utilized in the preparation of biosensors have been studied by use of the Microslit Electrokinetic set-up. For the investigated polymer layers (aminodextran, carboxylated dextran, diaminopoly(ethylene glycol), dicarboxypoly(ethylene glycol), biotinylated poly(ethylene glycol), and streptavidin on biotinylated poly(ethylene glycol), the charge formation in aqueous electrolyte solutions was found to depend on the pH value, that is, OH- and H3O+ are the charge determining ions. The isoelectric points obtained from zeta potential versus pH plots could be utilized to draw conclusions on the introduction of acidic or basic groups and on the degree of molecular surface coverage, respectively. The hydrodynamically mobile charge reflected by the magnitude of the zeta potential contributed to only about 6% or less of the total surface conductivity of the polymer layers. The experimental determination of the total surface conductivity was found to provide valuable information on structural features of biosensor interfaces in aqueous environments.
Cover Picture: Electrosurface Phenomena at Polymer Films for Biosensor Applications (ChemPhysChem 5/2003)
2003-05-09

Abstract The cover picture summarizes the principle of the Microslit Electrokinetic Set‐Up, which has been applied for the combined determination of zeta potential and surface conductivity of polymer films for biosensor applications. The method is based on streaming potential and streaming current measurements across rectangular channels formed by two planar sample carriers (20 mm×10 mm) at varied distances in the range of 1 to 60 μm. Combined determination of zeta potential and surface conductivity was advantageous for the analysis of interfacial charge distributions at swelling and reorganizing solid surfaces. The high sensitivity of the surface conductivity for structural variations of layered substrates may even allow the use of this parameter for detection in future biosensors. Find out more in the article by Zimmermann et al. on pages 509–514.
Hyper‐gravity effects on the Arabidopsis transcriptome
2003-05-12

Callus cultures of Arabidopsis thaliana (cv. Columbia) in Petri dishes were exposed to altered g ‐forces by centrifugation (1–10 g ). Using semi‐quantitative RT–PCR transcripts of genes coding for metabolic key enzymes (ADP‐glucose pyrophosphorylase, ADPG‐PP; β‐amylase, fructose‐1,6‐bisphosphatase, FBPase; glyceraldehyde‐P dehydrogenase, GAPDH; hydroxymethylglutaryl‐CoA reductase, HMG; phenylalanine‐ammonium‐lyase, PAL; PEP carboxylase, PEPC) were used to monitor threshold conditions for g‐number (all) and time of exposure (β‐amylase) which led to altered amounts of the gene product. Exposure to approximately 5 g and higher for 1 h resulted in altered transcript levels: transcripts of β‐amylase, PAL, and PEPC were increased, those of ADPG‐PP decreased, while those of FBPase, GAPDH, and HMG were not affected. This probably indicates a shift from starch synthesis to starch degradation and increased rates of anaplerosis (PEPC: supply of ketoacids for amino acid synthesis). In order to get more information about g ‐related effects on gene expression, we used a 1‐h exposure to 7 g for a microarray analysis, using a commercial A. thaliana chip with 4105 unique annotated clusters/genes (IncyteGenomics). Transcripts of more than 200 genes were significantly increased in amount (ratio 7 g /1 g control; 2 1.6 and larger). They fall into several categories. Transcripts coding for enzymes of major pathways form the largest group (25%), followed by gene products involved in cellular organization and cell wall formation/rearrangement (17%), signalling, phosphorylation/dephosphorylation (12%), proteolysis and transport (10% each), hormone synthesis plus related events (8%), defense (4%), stress‐response (2%), and gravi‐sensing (2%). Many of the alterations are part of a general stress response, but some changes related to the synthesis/rearrangement of cell wall components could be more hyper‐ g ‐specific. We only found few gene products, which were decreased in relation to 1 g controls, and these were less significant (ratio &lt; 2 1.6 ). We thus assume that g ‐forces above a threshold of about 5 g for 1 h are sensed by plant cells in general, causing distinct metabolic responses, which obviously in part, are regulated by gene expression.
Acquired Melanocytic Nevi as Risk Factor for Melanoma Development. A Comprehensive Review of Epidemiological Data
2003-05-13

Acquired melanocytic nevi (MN) in Caucasian populations are important markers for the risk of melanoma development. The total number of MN on the whole body is the most important independent risk factor for melanoma and the risk of melanoma development increases almost linearly with rising numbers of MN. Additionally, the presence of atypical MN and of actinic lentigines are likewise independent risk factors for melanoma. Atypical mole syndrome should be defined by the presence of many acquired MN and a threshold number of atypical MN. Acquired MN develops mainly during childhood and adolescence in the first two decades of life. The number of acquired nevi seems to be related to hereditary factors and nevus‐prone families exist. The amount of sun exposure is the most important environmental risk factor for nevus development, particularly in early childhood. Interestingly, sunburns may play a role in nevus development, but seem not to be required, and even moderate sun exposure promotes the process. Therefore, preventive measures for nevus and melanoma development should target young children and adolescents.
Adenoviral gene transfer of tumor necrosis factor-related apoptosis-inducing ligand overcomes an impaired response of hepatoma cells but causes severe apoptosis in primary human hepatocytes.
2003-05-15

Ligands of the tumor necrosis factor family play key roles in liver pathogenesis. The ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is unique, because it is thought to be nontoxic to normal cells while killing a broad range of tumor cells. However, hepatocellular carcinoma is considered resistant to soluble TRAIL treatment. Therefore, a direct gene transfer of TRAIL to malignant cells is part of an alternative delivery strategy. We show that an adenoviral gene transfer (Ad-TRAIL) overcomes an impaired response of hepatocellular carcinoma cell lines to soluble TRAIL, but the transduction of primary human hepatocytes revealed a high number of apoptotic cells. Our data imply that Ad-TRAIL administration in vivo must either be restricted to tumor tissue or controlled by a tumor-specific promoter to avoid severe liver damage in human trials.
Long‐term evaluation of retinal function in Prph2Rd2/Rd2 mice following AAV‐mediated gene replacement therapy
2003-05-15

Abstract Background Prph2 Rd2/Rd2 mice have a retinal degeneration due to a null mutation for the Prph2 gene which encodes a photoreceptor‐specific glycoprotein, peripherin2, essential for outer‐segment formation. We have previously shown improvement of photoreceptor function at a single time point following AAV‐mediated gene replacement therapy. Here we quantify the functional rescue over a 15‐week time course and present a detailed analysis of the improvement in retinal function. Methods An AAV2 vector, AAV.rho.rds, carrying a peripherin2 c‐DNA, was in injected subretinally into 10‐day‐old Prph2 Rd2/Rd2 mice. One group was injected at a single time point while in a second group the injections were repeated after 5 days. The effect of treatment was analysed histologically using electron microscopy and electroretinography (ERG) was used to assess functional changes. Treated mice were recorded at regular intervals over 15 weeks. Untreated contralateral eyes served as internal control. Results A significant increase in b‐wave amplitude was first noted 3 weeks after treatment of 10‐day‐old Prph2 Rd2/Rd2 mice and persisted for up to 14 weeks. An increase in the area of retina exposed to vector resulted in a significant increase in both b‐wave amplitude and persistence. Conclusions In this study AAV‐mediated gene replacement in Prph2 Rd2/Rd2 mice resulted in a significant functional improvement over a period of 14 weeks. These results support the utility of gene therapy approaches as treatment for photoreceptor dystrophies. Copyright © 2003 John Wiley &amp; Sons, Ltd.
Extending the 3ω method for thin-film analysis to high frequencies
2003-05-15

Although the 3ω method was originally introduced to measure the thermal conductivity of bulk material and was later developed further to include thin-film materials, many thermal and geometrical parameters influence the 3ω signal. We show that several of these parameters can be determined simultaneously from a single 3ω measurement. With the commonly used frequency range, however, some parameter combinations cannot be determined uniquely. To overcome this problem we have developed an electronic setup for measurements from 5 Hz up to 200 kHz. We show numerically and experimentally that we can determine four physical parameters from a single measurement in this frequency range. This makes the 3ω method very suitable for microelectronics and microsensor testing, where physical parameters should ideally be determined by purely electrical measurements.
Magnetic two-dimensional short-range order in hexagonal manganites
2003-05-15

Hexagonal manganites REMnO3 consist of layers of two-dimensional connected distorted MnO5 bipyramids separated by distorted layers of RE, leading to frustrated Mn3+–O2−–Mn3+ in-plane exchange paths (superexchange) and Mn3+–O2−–O2−–Mn3+ interplane exchange paths (super-superexchange). We report single-crystal diffraction experiments (RE=Ho,Er,Y) indicating magnetic 2D short-range order up to temperatures of T=150 K (TN∼74 K), and SQUID magnetization data (RE=Y) indicating short-range order up to at least 250 K. Fits of a model based on an extended mean-field theory to the single-crystal data show in-plane exchange about 3 orders of magnitude stronger than the interplane exchange, explaining the unusual strong deviation from the Curie–Weiss law of the SQUID magnetization data.
Limited Diversity of Measles Field Isolates after a National Immunization Day in Burkina Faso: Progress from Endemic to Epidemic Transmission?
2003-05-15

Despite recent National Immunization Days in Burkina Faso, the rural province of Houët reported >400 measles cases in 2001 (82% not vaccinated). Phylogenetic analysis of 58 measles virus field isolates plus the first sequences from the Democratic Republic of the Congo and the Republic of Congo are reported. All viruses were genotype B3, which is common in the region. In Houët, there were two geographically confined genetic variants, suggesting two independent importation events. Strain diversity in Houët (1.5%) and the Congos was limited in comparison with Ibadan, Nigeria (4.6%), where measles is endemic. Strain variability, assessed by heteroduplex mobility assay, confirmed these findings. Despite large local pools of susceptible persons even after several rounds of vaccination, the limited strain diversity suggests that parts of rural Burkina Faso may be moving from an endemic to an epidemic transmission pattern of measles virus.
A Binuclear Phthalocyanine Containing Two Different Metals
2003-05-16

Abstract The unsymmetrical binuclear phthalocyanine 4a and the symmetrical binuclear phthalocyanine 4b with two different metals (Ni and Cu), as well as the correspondent binuclear phthalocyanines with two Ni atoms ( 4c and 4d ) were synthesized from the benzoannulated dicyano‐substituted Ni phthalocyanine 2 . Atomic absorption spectroscopy verified unambiguously the presence of Ni and Cu in the binuclear phthalocyanines. The proposed synthetic route demonstrates great versatility towards substitution at the peripheral positions of the ring and the variation of the chelating central metal. Complexes 4a − 4d are soluble in common organic solvents of medium polarity. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)
Identification and functional characterization of a novel R621C mutation in the synphilin-1 gene in Parkinson's disease
2003-05-21

Synphilin-1 is linked to the pathogenesis of Parkinson's disease (PD) based on its identification as an alpha-synuclein (PARK1) and parkin (PARK2) interacting protein. Moreover, synphilin-1 is a component of Lewy bodies (LB) in brains of sporadic PD patients. Therefore, we performed a detailed mutation analysis of the synphilin-1 gene in 328 German familial and sporadic PD patients. In two apparently sporadic PD patients we deciphered a novel C to T transition in position 1861 of the coding sequence leading to an amino acid substitution from arginine to cysteine in position 621 (R621C). This mutation was absent in a total of 702 chromosomes of healthy German controls. To define a possible role of mutant synphilin-1 in the pathogenesis of PD we performed functional analyses in SH-SY5Y cells. We found synphilin-1 capable of producing cytoplasmic inclusions in transfected cells. Moreover we observed a significantly reduced number of inclusions in cells expressing C621 synphilin-1 compared with cells expressing wild-type (wt) synphilin-1, when subjected to proteasomal inhibition. C621 synphilin-1 transfected cells were more susceptible to staurosporine-induced cell death than cells expressing wt synphilin-1. Our findings argue in favour of a causative role of the R621C mutation in the synphilin-1 gene in PD and suggest that the formation of intracellular inclusions may be beneficial to cells and that a mutation in synphilin-1 that reduces this ability may sensitize neurons to cellular stress.
Theoretical directional and modulated rates for direct supersymmetric dark matter detection
2003-05-21

Exotic dark matter together with the vacuum energy (cosmological constant)\\nseem to dominate in the flat Universe. Thus direct dark matter detection is\\ncentral to particle physics and cosmology. Supersymmetry provides a natural\\ndark matter candidate, the lightest supersymmetric particle (LSP). It is\\npossible to obtain detectable rates, but realystically they are expected to be\\nmuch lower than the present experimental goals. So one should exploit two\\ncharacteristic signatures of the reaction, namely the modulation effect and the\\ncorrelation with the sun's motion in directional experiments. In standard non\\ndirectional experiments the modulation is small, less than two per cent. In the\\ncase of the directional experiments, the main subject of this paper, we find\\ntwo novel features, which are essentially independent of the SUSY model\\nemployed, namely: 1) The forward-backward asymmetry, with respect to the sun's\\ndirection of motion, is very large and 2) The modulation observed in a plane\\nperpendicular to the sun's motion can be higher than 20 per cent and is\\ndirection dependent.\\n
Ribavirin and Alpha Interferon Enhance Death Receptor-Mediated Apoptosis and Caspase Activation in Human Hepatoma Cells
2003-05-21

ABSTRACT The molecular mechanisms underlying the clinical effects of alpha interferon (IFN) and ribavirin are not understood. Elimination of infected cells occurs in part by cytotoxic T lymphocytes (CTLs) expressing CD95 ligand and thereby attacking target cells which are positive for the death receptor CD95. Since many viruses have evolved mechanisms to inhibit apoptosis, the opposite, namely, promotion of apoptosis, could be a strategy to strengthen the host antiviral response. In the present study, we have asked whether the antiviral substances IFN and ribavirin could support CD95-mediated apoptosis by interfering with the activation of caspases, a family of proteases known for their essential role in apoptosis. HepG2 cells, stimulated with the agonistic anti-CD95 antibody, served as a minimal model to mimic the CD95 stimulation ocurring during a CTL attack of target cells in vivo. Apoptosis was quantitated by flow cytometric detection of hypodiploid nuclei. Caspase activity was measured by cytofluorometry, immunocytochemistry, and immunoblot analysis. IFN and ribavirin sensitized HepG2 cells for CD95-mediated apoptosis. This effect was correlated with an increase in CD95-mediated caspase activation and enhanced cleavage of the caspase substrate poly(ADP-ribose) polymerase. Furthermore, the positive effect on CD95-mediated caspase activation by IFN and ribavirin was confirmed by immunocytochemistry for activated caspase-3 and by immunoblot detection of activated caspase-3, caspase-7, and caspase-8. Our data demonstrate that the antiviral substances IFN and ribavirin are able to sensitize for CD95-mediated apoptosis. IFN and ribavirin also enhance CD95-mediated caspase activation, which might in part be responsible for the apoptosis-promoting effect of these antiviral compounds.
Detecting dynamic occlusion in front of static backgrounds for AR scenes
2003-05-22

Correctly finding and handling occlusion between virtual and real objects in an Augmented Reality scene is essential for achieving visual realism. Here, we present an approach for detecting occlusion of virtual parts of the scene by natural occluders. Our algorithm is based on a graphical model of static backgrounds in the natural surroundings, which has to be acquired beforehand. The design of the approach aims at providing real-time performance and an easy integration into existing AR systems. No assumptions about the shape or color of occluding objects are required. The algorithm has been tested with several graphical models.
Silver Complexes with Cyanoguanidine: Preparation and Crystal Structures of [Ag(cgn)2]F and [Ag(cgn)2][BF4]
2003-05-23

Abstract The silver cyanoguanidine complexes [Ag(cgn) 2 ]F ( 1 ), [Ag(cgn) 2 ][BF 4 ] ( 2 ), [Ag(cgn) 2 ][ClO 4 ] ( 3 ) and [Ag(cgn)][NO 3 ] ( 4 ) were obtained from aqueous solutions of the corresponding silver salts and cyanoguanidine. The crystal structures of 1 and 2 have been determined by single crystal X‐ray diffraction. 1 : Space group P1 ̄, Z = 2, cell constants at —65 °C: a =618.18(3), b = 761.49(8), c = 971.2(1) pm; α = 93.56(1), β = 97.439(8), γ = 97.376(9)β; R 1 = 0.0218 2 : Space group P1 ̄, Z = 2, cell constants at —65 °C: a = 549.79(9), b = 958.17(17), c = 1121.04(12) pm; α = 90.026(13), β = 102.520(11), γ = 95.937(14)°; R 1 = 0.0283.
Synthese und Kristallstruktur von [(n‐Bu)4N][W6Cl18]
2003-05-23

Abstract Synthesis and Crystal Structure of [(n‐Bu) 4 N][W 6 Cl 18 ] Single‐crystals of [(n‐Bu) 4 N][W 6 Cl 18 ] were obtained as thin needles by adding methanol to a solution of W 6 Cl 18 and [(n‐Bu) 4 N]Cl in tetrahydrofuran. The structure was determined by single‐crystal X‐ray diffraction at 210 K. [(n‐Bu) 4 N][W 6 Cl 18 ] crystallizes in the monoclinic space group C 2/c with Z = 8 and the lattice parameters a = 2175.6(1) pm, b = 1738.0(1) pm, c = 2160.36(9) pm, and β = 91.680(5) °. The crystal structure contains isolated [(W 6 Cl 12 i )Cl 6 a ] — clusters and [(n‐Bu) 4 N] + ions.
Smart hardware-accelerated volume rendering
2003-05-26

For volume rendering of regular grids the display of view-plane aligned slices has proven to yield both good quality and performance. In this paper we demonstrate how to merge the most important extensions of the original 3D slicing approach, namely the pre-integration technique, volumetric clipping, and advanced lighting. Our approach allows the suppression of clipping artifacts and achieves high quality while offering the fiexibility to explore volume data sets interactively with arbitrary clip objects. We also outline how to utilize the proposed volumetric clipping approach for the display of segmented data sets. Moreover, we increase the rendering quality by implementing efficient over-sampling with the pixel shader of consumer graphics accelerators. We give prove that at least 4-times over-sampling is needed to reconstruct the ray integral with sufficient accuracy even with pre-integration. As an alternative to this brute-force over-sampling approach we propose a hardware-accelerated ray caster which is able to perform over-sampling only where needed and which is able to gain additional speed by early ray termination and space leaping.
Nonperturbative propagators, running coupling, and the dynamical quark mass of Landau gauge QCD
2003-05-27

The coupled system of renormalized Dyson-Schwinger equations for the quark, gluon and ghost propagators of Landau gauge QCD is solved within truncation schemes. These employ bare as well as non-perturbative ansaetze for the vertices such that the running coupling as well as the quark mass function are independent of the renormalization point. The one-loop anomalous dimensions of all propagators are reproduced. Dynamical chiral symmetry breaking is found, the dynamically generated quark mass agrees well with phenomenological values and corresponding results from lattice calculations. The effects of unquenching the system are small. In particular the infrared behavior of the ghost and gluon dressing functions found in previous studies is almost unchanged as long as the number of light flavors is smaller than four.
Cold atoms in a high-Qring cavity
2003-05-27

We report the confinement of large clouds of ultra-cold 85-Rb atoms in a standing-wave dipole trap formed by the two counter-propagating modes of a high-Q ring-cavity. Studying the properties of this trap we demonstrate loading of higher-order transverse cavity modes and excite recoil-induced resonances.