julilili42/papers huggingface dataset:
Neural correlates of duplex perception: A whole-head magnetencephalography study
2000-11-01

Simultaneous experience of the same stimulus events in two distinct phenomenological modes is referred to as duplex perception (DP). The most widely investigated DP paradigm decomposes the formant pattern of the stop consonant-vowel (CV) syllables /ga/ and /da/ into two complementary portions: the isolated transient of the third formant (‘‘chirp’’) and the remaining sound structure (‘‘base’’). Presentation of the two syllable components to opposite ears results in the perception, first, of the chirp and, second, the fused CV syllable. In order to further elucidate the mechanisms underlying DP, the present study recorded mismatch fields in response to a series of dichotically applied base and chirp components using whole-head magnetencephalography (MEG). This magnetic analog to mismatch negativity is considered a correlate of early cognitive stimulus representation. (a) Under a visual distraction task, the preattentive mismatch fields were stronger in response to contralateral deviants and lateralized to the left hemisphere. (b) Under attention toward the fused percept /da/, left ear deviant chirps yielded an ipsilateral enhanced and posteriorly shifted reaction. These data suggest representations of the phonetic percepts in secondary dominant auditory cortex. Perception tasks may activate these templates for syllable fusion.
Magnetic brain responses to second formant transitions in dependency of transition time, signal voicing, and attention
2000-11-01

Using an oddball paradigm, magnetoencephalographic (MEG) recordings were performed during perception of synthetic /i/-like signals (frequent stimuli) and interspersed /bi/ or /yi/-like deviants with an initial second formant (F2) transition of 20, 40, 60, or 80 ms. The experiment was run under two different signal conditions: formant-synthesized voiced stimuli or spectrally and loudness-matched unvoiced cognates generated by filtered white noise. Listeners’ attention was directed either to the infrequent stimuli or to a moving geometric pattern (visual distraction task). Left- and right-hemispheric M50, M100, and MMNm dipole strengths were derived from the MEG measurements. The results show a strong bilateral effect of signal voicing on the M50 and M100 responses, irrespective of F2 transition time, being enhanced with attention directed to the acoustic signal. The deviant stimuli evoked a significant mismatch reaction which under directed attention was lateralized to the left hemisphere. The strength of the MMNm increased across transition time, but exhibited a nonlinearity at 40 ms in terms of an interaction with signal voicing. In conclusion, these results suggest signal-related bilateral preprocessing during the M50 and M100 responses and attention-dependent lateralization of mismatch reactions to speech-relevant acoustic features.
X-Ray Crystal Structure Analysis of Substituted 5-(2,3-Dihydro-7-benzofuryl)- 2-methylpyrazolo[4,3-d]pyrimidin-7-one (iso-Biagra) [1]
2000-11-01

X-ray crystal structure data for the substituted 5-(2,3-dihydro-7-benzofuryl)-2-methylpyrazolo[ 4,3-d]pyrimidin-7-one (3) reveal that the two bicyclic heteroaryl systems show no coplanarity along their joint C (5) - C (11) axis with an interplanar angle of 9.6°. Nonetheless, the spatial interatomic distance for O(17)-N(6), determined as 2.73 A, allows the formation of a relatively weak intramolecular hydrogen bond between the pyrimidinone N(6)-H and the O(17) lone pair of the dihydrobenzofuryl moiety.
Noninteracting fermions in a one-dimensional harmonic atom trap: Exact one-particle properties at zero temperature
2000-11-03

One-particle properties of non-interacting Fermions in a one-dimensional harmonic trap and at zero temperature are studied. Exact expressions and asymptotic results for large Fermion number N are given for the particle density distribution n_0(z,N). For large N and near the classical boundary at the Fermi energy the density displays increasing fluctuations. A simple scaling of these tails of the density distribution with respect to N is established. The Fourier transform of the density distribution is calculated exactly. It displays a small but characteristic hump near 2 k_F with k_F being a properly defined Fermi wave number. This is due to Friedel oscillations which are identified and discussed. These quantum effects are missing in the semi-classical approximation. Momentum distributions are also evaluated and discussed. As an example of a time-dependent one-particle problem we calculate exactly the evolution of the particle density when the trap is suddenly switched off and find a simple scaling behaviour in agreement with recent general results.
Identification of a Novel Prostaglandin F2α Synthase in Trypanosoma brucei
2000-11-06

Members of the genus Trypanosoma cause African trypanosomiasis in humans and animals in Africa. Infection of mammals by African trypanosomes is characterized by an upregulation of prostaglandin (PG) production in the plasma and cerebrospinal fluid. These metabolites of arachidonic acid (AA) may, in part, be responsible for symptoms such as fever, headache, immunosuppression, deep muscle hyperaesthesia, miscarriage, ovarian dysfunction, sleepiness, and other symptoms observed in patients with chronic African trypanosomiasis. Here, we show that the protozoan parasite T. brucei is involved in PG production and that it produces PGs enzymatically from AA and its metabolite, PGH2. Among all PGs synthesized, PGF2α was the major prostanoid produced by trypanosome lysates. We have purified a novel T. brucei PGF2α synthase (TbPGFS) and cloned its cDNA. Phylogenetic analysis and molecular properties revealed that TbPGFS is completely distinct from mammalian PGF synthases. We also found that TbPGFS mRNA expression and TbPGFS activity were high in the early logarithmic growth phase and low during the stationary phase. The characterization of TbPGFS and its gene in T. brucei provides a basis for the molecular analysis of the role of parasite-derived PGF2α in the physiology of the parasite and the pathogenesis of African trypanosomiasis.
ChemInform Abstract: The First Low Molecular Weight Antibiotic from Lactic Acid Bacteria: Reutericyclin (I), a New Tetramic Acid
2000-11-07

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform Abstract: Facile Synthesis of (2‐Nitrofluoren‐9‐yl)methyloxycarbonyl Amino Acids.
2000-11-07

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Identification and Quantification of Estrogenic Compounds in Recycled and Virgin Paper for Household Use As Determined by an in Vitro Yeast Estrogen Screen and Chemical Analysis
2000-11-10

The use of recycled paper for the manufacture of food contact materials is widespread, but very little is known about the presence of potential contaminants in the paper. The purpose of this study was to assess the worst-case migration of estrogenic active compounds using extracts of paper for household use. Twenty different brands of kitchen rolls, nine of which were made from recycled paper and the remainder from virgin paper, were obtained from retail shops. Paper extracts were subjected to (a) determination of the total estrogenic activity by using an in vitro estrogen screen based on yeast cells stably transfected with the human estrogen receptor alpha and (b) chemical analysis and quantification by GC/MS, GC/FTIR/MS, and GC/FID for detection of a variety of estrogenic compounds. A marked estrogenic response was observed in nine of the extracts, seven of which were made from recycled paper and two from virgin paper. The chemical analysis revealed that extracts made from recycled paper contained levels of bisphenol A ranging from 0.6 to 24 mg/kg of kitchen roll, whereas extracts from virgin paper contained no bisphenol A or only negligible amounts. In contrast, 4-tert-octylphenol, 4-nonylphenols, and di-n-butyl and diisobutyl phthalate were present to a varying degree in both recycled and virgin paper with no apparent preferable distribution between the two paper types. The estrogenic response of the two extracts made from virgin paper appeared to be due partly to the presence of the preservative propyl paraben. Diisopropylnaphthalene, which turned out to be weakly estrogenic active in vitro (EC(50) = 53 microM), was detected in minor amounts in most of the extracts with the major part, ranging from 0.3 to 4.7 mg/kg of paper, found in recycled paper. Our findings that recycled kitchen rolls contain bisphenol A and other xenoestrogens may apply to other types of recycled paper used for food packaging and emphasize the importance of identifying this and other contaminants in recycled paper in general. These data indicate that bisphenol A may be useful as a purity indicator for recycled paper.
The origin of contraversive pushing
2000-11-14

A separate pathway seems to be present in humans for sensing the orientation of gravity apart from the one for orientation perception of the visual world. This second graviceptive system decisively contributes to humans' control of upright body posture. Contraversive pushing occurring after stroke lesions may represent the behavioral correlate of a disturbed neural representation of this system.
The Optomotor Response and Spatial Resolution of the Visual System in Male Xenos Vesparum (Strepsiptera)
2000-11-15

ABSTRACT The Strepsiptera are an enigmatic group of parasitic insects whose phylogenetic relationships are hotly debated. Male Strepsiptera have very unusual compound eyes, in which each of a small number of ommatidia possesses a retina of at least 60 retinula cells. We analysed the optomotor response of Xenos vesparum males to determine whether spatial resolution in these eyes is limited by the interommatidial angle or by the higher resolution potentially provided by the extended array of retinula cells within each ommatidium. We find that the optomotor response in Strepsiptera has a typical bandpass characteristic in the temporal domain, with a temporal frequency optimum at 1–3 Hz. As a function of spatial wavelength, the optomotor response is zero at grating periods below 12 ° and reaches its maximum strength at grating periods between 60 ° and 70 °. To identify the combination of interommatidial angles and angular sensitivity functions that would generate such a spatial characteristic, we used motion detection theory to model the spatial tuning function of the strepsipteran optomotor response. We found the best correspondence between the measured response profile and theoretical prediction for an irregular array of sampling distances spaced around 9 ° (half the estimated interommatidial angle) and an angular sensitivity function of approximately 50 °, which corresponds to the angular extent of the retina we estimated at the centre of curvature of the lens. Our behavioural data strongly suggest that, at least for the optomotor response, the resolution of the strepsipteran compound eye is limited by the ommatidial sampling array and not by the array of retinula cells within each ommatidium. We discuss the significance of these results in relation to the functional organisation of strepsipteran compound eyes, their evolution and the role of vision in these insects.
Cloning, Heterologous Expression and Kinetic Analysis of Glycerol Kinase (TbGLK1) from Trypanosoma brucei
2000-11-15

Abstract We have cloned and sequenced the gene for the glycerol kinase of Trypanosoma brucei (Tb GLK1 ), obtained by RT-PCR. The corresponding mRNA is 2.3 kb in size and contains an ORF encoding a protein with high homology to known glycerol kinases of other organisms. It is 512 amino acids in length with a PTS1-like targeting sequence (AKL) at its C-terminus, suggesting glycosomal compartmentalization of this enzyme. Although Northern blot analysis revealed higher mRNA levels in slender bloodstream forms than in the procyclic insect forms, specific glycerol kinase activities were found to be virtually identical in both life stages. Southern blot analysis suggested a single copy gene, but we were able to clone two alleles utmost similar to each other. Heterologous expression of the trypanosomal glycerol kinase in E. coli enabled us to perform a kinetic analysis of this enzyme. In particular, we have been able to monitor ATP production from glycerol-3-phosphate and ADP, a reaction which, although thermodynamically very unfavorable, is regarded essential for the survival of Trypanosoma brucei under anoxic conditions. Since the unique spatial separation of glycolysis in the kinetoplastida imposes important consequences for the regulation of the energy metabolism in these organisms, we discuss the observed differences between TbGLK1 and glycerol kinases from other organisms in view of its physiological relevance.
Local equilibrium in heavy-ion collisions: Microscopic analysis of a central cell versus infinite matter
2000-11-17

We study the local equilibrium in the central fm cell in heavy-ion collisions at energies from 10.7 AGeV (AGS) to 160 AGeV (SPS) calculated in the microscopic transport model. In the present paper the hadron yields and energy spectra in the cell are compared with those of infinite nuclear matter, as calculated within the same model. The agreement between the spectra in the two systems is established for times fm/ in the central cell. The cell results do not deviate noticeably from the infinite matter calculations with rising incident energy, in contrast to the apparent discrepancy with predictions of the statistical model (SM) of an ideal hadron gas. The entropy of this state is found to be very close to the maximum entropy, while hadron abundances and energy spectra differ significantly from those of the SM.
Plate tectonic evolution of the Cocos-Nazca spreading center
2000-11-20

Paleogeographic restorations for the oceanic crust formed by the Cocos-Nacza spreading center and its precursors were performed in steps of 0.5 m.y. The breakup of the Farallon plate into the Cocos and Nazca plates occurred at ~23 Ma and was followed by three subsequent spreading systems: CNS-1, ~23–19.5 Ma; CNS-2, 19.5–14.7 Ma; and CNS-3, 14.7 Ma–present. Based on the spreading history, we reconstructed the evolution and ages of submarine aseismic ridges in the Eastern Pacific Basin—the Carnegie, Coiba, Cocos, and Malpelo Ridges, which overprint oceanic crust formed at the subsequent Cocos-Nazca spreading system. The mophological bipartition of the Carnegie Ridge reflects the jump from CNS-2 to CNS-3 at 14.7 Ma and the later increasing distance of the CNS-3 spreading axis from the Galapagos hotspot. The Cocos Ridge is mainly composed of products from the Galapagos hotspot but also contains material from a suggested less productive second center of volcanic activity that is located ~600 km northeast of Galapagos. The Malpelo Ridge is a product of the second center of volcanic activity, whereas the Coiba Ridge probably formed directly at the Galapagos hotspot. The geometric relationship of the Cocos and Carnegie Ridges indicates symmetric spreading and a constant northward shift of the presently active CNS-3 system since its formation at 14.7 Ma.
Systematics of the low-energy pionic double charge exchange in nuclei
2000-11-20

The experimental results for the reaction on nuclei obtained in recent years reveal clear systematic features of this reaction. New data on and supplementing the existing data base are presented. The data on are partly at variance with previous results. The dependence of the cross sections on incident energy, scattering angle, and on the target mass is discussed for transitions leading to the ground state of the final nucleus or to the double isobaric analog state.
The neural representation of postural control in humans
2000-11-21

Lesion of the “vestibular cortex” in the human posterior insula leads to a tilted perception of visual vertical but not to tilted body posture and loss of lateral balance. However, some stroke patients show the reverse pattern. Although their processing of visual and vestibular inputs for orientation perception of the visual world is undisturbed, they push away actively from the ipsilesional side (the side of lesion location), leading to a contraversive tilt of the body (tilt toward the side opposite to the lesion) and falling to that side. Recently, the origin of contraversive pushing was identified as an altered perception of the body's orientation in relation to gravity. These patients experience their body as oriented “upright” when actually tilted enormously to the ipsilesional side (18° on average). The findings argued for a separate pathway in humans for sensing body orientation in relation to gravity apart from the one projecting to the vestibular cortex. The present study aimed at identifying this brain area. The infarcted brain regions of 23 consecutively admitted patients with severe contraversive pushing were projected onto a template MRI scan, which had been normalized to Talairach space. The overlapping area of these infarctions centered on the posterolateral thalamus. Our finding necessitates reinterpretation of this area as being only a “relay structure” of the vestibular pathway on its way from the brainstem to the vestibular cortex. The ventral posterior and lateral posterior nuclei of the posterolateral thalamus (and probably its cortical projections) rather seem to be fundamentally involved in the neural representation of a second graviceptive system in humans decisive for our control of upright body posture.
Function of the cytosolic N‐terminus of sucrose transporter AtSUT2 in substrate affinity
2000-11-21

AtSUT2 was found to be a low‐affinity sucrose transporter ( K M =11.7 mM at pH 4). Chimeric proteins between AtSUT2 and the high‐affinity StSUT1 were constructed in which the extended N‐terminus and central loop of AtSUT2 were exchanged with those domains of StSUT1 and vice versa. Chimeras containing the N‐terminus of AtSUT2 showed significantly lower affinity for sucrose compared to chimeras containing the N‐terminus of StSUT1. The results indicate a significant function of the N‐terminus but not the central cytoplasmic loop in determining substrate affinity. Expression of AtSUT2 in major veins of source leaves and in flowers is compatible with a role as a second low‐affinity sucrose transporter or as a sucrose sensor.
A Formal Total Synthesis of Dysidiolide
2000-11-22

[structure] A formal total synthesis of the natural product dysidiolide is described. Starting from a Diels-Alder reaction between an enoate and a Rawal diene, the cyclohexenone 4 was synthesized. A subsequent stereospecific methyl cuprate addition established the desired trans configuration in the cyclohexane 3. Wacker oxidation of the pentenyl side chain to the diketone 17 followed by an intramolecular aldol condensation led to the bicyclic enone 2, a key intermediate in a recently reported synthesis of dysidiolide.
Contrasting effects of alloxan on islets and single mouse pancreatic β-cells
2000-11-24

Alloxan is used to induce diabetes in animals; however, the underlying mechanisms are still a matter of debate. Alloxan evoked a rapid hyperpolarization of the plasma membrane potential and suppressed electrical activity elicited by 15mM glucose, thus terminating voltage-dependent Ca2+ influx. Accordingly, glucose-induced oscillations in intracellular free Ca2+ concentration were abolished. The effect of alloxan on membrane potential could not be reversed by glucose but was reversed by tolbutamide. However, the sensitivity to tolbutamide was decreased after treatment of the cells with alloxan. These effects closely resemble those described earlier for H2O2. H2O2 and alloxan decreased the mitochondrial membrane potential, indicating a decrease in ATP production and thus interference with cell metabolism. A decrease in ATP synthesis would explain the plasma membrane hyperpolarization observed in intact islets, reflecting the activation of ATP-dependent K+ channels. Surprisingly, alloxan inhibited the whole-cell K+ATP current measured in single cells and the single-channel K+ATP current registered in excised patches. This inhibitory effect of alloxan is not mediated by changes in cell metabolism but seems to be due to direct interactions with the K+ATP channels via thiol-group oxidation. We have monitored the appearance of reactive oxygen species in single cells and islets treated with alloxan and H2O2 for comparison. In contrast to H2O2, alloxan induced the appearance of measurable reactive oxygen species only in islets but not in single cells. The results show that alloxan evokes different effects in islets and single cells, giving a possible explanation for inconsistent results reported in the past. It is concluded that alloxan exerts its diabetogenic effect by the production of H2O2 in intact islets.
ChemInform Abstract: Homonuclear and Heteronuclear Cluster Compounds of Gold
2000-11-28

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Zur Differenziertheit des Phänomens „Fabrikverkauf”
2000-11-30

&#x0D; &#x0D; &#x0D; The current debate on the spatial effects of factory shops has focused predominantly on factory outlet centres (FOCs) as the channel of supply. This orientation tends to ignore the long history of factory shops in some parts of Germany, a tradition which lies behind the broad range of shopping facilities of this type available today. This heterogeneity is clearly revealed in the studies on supply and demand at two representative outlets: thesBoss andSamtfabrikshops at the “Mecca of factory shops” situated in Metzingen, near Reutlingen (Baden-Württemberg). In addition to forms of supply which are of questionable value to regional economies, there are — as these studies show — also other types of outlet which appear to be less problematic from the spatial planning perspective. Outlets of the latter type offer high-quality products and pull purchasing power into the region. As these outlets are themselves homegrown within the region, the retail sector in the region has been able to adapt to face the challenge they pose. Businesses of this type may even provide a boost for city-centre development if they are located relatively close to city centres.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D;
Impact of theagrQuorum‐Sensing System on Adherence to Polystyrene inStaphylococcus aureus
2000-12-01

Biofilm formation by Staphylococcus aureus is a serious problem in nosocomial infections. There are great differences in the capacity of S. aureus to express biofilms, but the reasons are unknown. In all, 105 S. aureus strains were tested for a correlation between the agr quorum-sensing system phenotype and the ability of S. aureus to adhere to polystyrene. Some 78% of agr-negative, but only 6% of agr-positive, strains formed a biofilm, demonstrating a profound impact of agr on biofilm formation. This result was confirmed with defined agr mutants and by inhibition of agr with quorum-sensing blockers. The observed effect was not due to differential expression of the autolysin Atl or of the exopolysaccharide polysaccharide intercellular adhesin but seemed to be caused, at least in part, by the surfactant properties of delta-toxin. The detected biofilm-enhancing effect of S. aureus quorum-sensing blockers call into question the proposed therapeutic use of such substances.