julilili42/papers huggingface dataset:
Canalization of auxin flow by Aux/IAA-ARF-dependent feedback regulation of PIN polarity
2006-10-15

Plant development is characterized by a profound ability to regenerate and form tissues with new axes of polarity. An unsolved question concerns how the position within a tissue and cues from neighboring cells are integrated to specify the polarity of individual cells. The canalization hypothesis proposes a feedback effect of the phytohormone auxin on the directionality of intercellular auxin flow as a means to polarize tissues. Here we identify a cellular and molecular mechanism for canalization. Local auxin application, wounding, or auxin accumulation during de novo organ formation lead to rearrangements in the subcellular polar localization of PIN auxin transport components. This auxin effect on PIN polarity is cell-specific, does not depend on PIN transcription, and involves the Aux/IAA-ARF (indole-3-acetic acid-auxin response factor) signaling pathway. Our data suggest that auxin acts as polarizing cue, which links individual cell polarity with tissue and organ polarity through control of PIN polar targeting. This feedback regulation provides a conceptual framework for polarization during multiple regenerative and patterning processes in plants.
Braucht niemanden zu scheren: A survey of NPI licensing in German
2006-10-15

In this contribution we will argue that negative polarity is a collocational phenomenon that does not follow from other properties of the respective lexical elements. With German data as evidence, we will follow a proposal by van der Wouden and treat Negative Polarity Items (NPIs) as collocates which must be licensed by abstract semantic properties of their contexts. Using a collocation module for HPSG, which has been independently motivated for bound words and idioms, we will show how to restrict the occurrence of NPIs to legitimate environments, starting from the negativity hierarchy of licensing environments by Zwarts. Besides a more fine-grained semantic licenser hierarchy, we will establish syntactic licensing domains and general collocational restrictions of NPIs.
Modeling typological markedness in semantics: The case of negative concord
2006-10-15

We will provide an analysis of negative concord in sentential negation in three languages, French, Polish and German. The focus of the paper is (1) the typological variation with respect to the realization of negative concord in the three languages under investigation and (2) the treatment of lexical exceptions within the different typological classes. We will propose a unified theory of negative concord which identifies a common core system and adds language-specific constraints which can handle typological variation between languages and lexical exceptions within a given language.
Cox rings and combinatorics
2006-10-16

Given a variety <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper X"> <mml:semantics> <mml:mi>X</mml:mi> <mml:annotation encoding="application/x-tex">X</mml:annotation> </mml:semantics> </mml:math> </inline-formula> with a finitely generated total coordinate ring, we describe basic geometric properties of <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper X"> <mml:semantics> <mml:mi>X</mml:mi> <mml:annotation encoding="application/x-tex">X</mml:annotation> </mml:semantics> </mml:math> </inline-formula> in terms of certain combinatorial structures living in the divisor class group of <inline-formula content-type="math/mathml"> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper X"> <mml:semantics> <mml:mi>X</mml:mi> <mml:annotation encoding="application/x-tex">X</mml:annotation> </mml:semantics> </mml:math> </inline-formula>. For example, we describe the singularities, we calculate the ample cone, and we give simple Fano criteria. As we show by means of several examples, the results allow explicit computations. As immediate applications we obtain an effective version of the Kleiman-Chevalley quasiprojectivity criterion, and the following observation on surfaces: a normal complete surface with finitely generated total coordinate ring is projective if and only if any two of its non-factorial singularities admit a common affine neighbourhood.
Asteroseismological constraints on the pulsating planetary nebula nucleus (PG 1159-type) RX J2117.1+3412
2006-10-16

\\n Aims.We present asteroseismological inferences on \\nRX J2117.1+3412, the hottest known pulsating PG 1159 star.\\nOur results are based on full PG 1159 evolutionary models recently\\npresented by Miller Bertolami &amp; Althaus (2006).\\n Methods.We performed\\nextensive computations of adiabatic g-mode pulsation periods on PG 1159 evolutionary models \\nwith stellar masses ranging from 0.530 to . PG 1159 stellar models are extracted from the\\ncomplete evolution of progenitor stars started from the ZAMS, through\\nthe thermally pulsing AGB and born-again phases to the domain of the\\nPG 1159 stars. We constrained the stellar mass of RX J2117.1+3412 by comparing\\nthe observed period spacing with the asymptotic period spacing and\\nwith the average of the computed period spacings. We also employed the\\nindividual observed periods to find a representative seismological\\nmodel for RX J2117.1+3412.\\n Results.We derive a stellar mass from the period \\nspacing data alone. In addition, we found a\\nbest-fit model representative for\\nRX J2117.1+3412 with an effective temperature K, \\na stellar mass , and a surface gravity . The derived stellar luminosity and radius are and , respectively,\\nand the He-rich envelope thickness is .\\nWe derive a seismic distance pc and a linear size of the\\nplanetary nebula pc. These inferences seem to\\nsolve the discrepancy between the RX J2117.1+3412 evolutionary timescale and the\\nsize of the nebula. All of the seismological tools we use concur to\\nthe conclusion that RX J2117.1+3412 must have a stellar mass , much in agreement \\nwith recent asteroseismology studies and\\nin clear conflict with the predictions of spectroscopy plus\\nevolutionary tracks.\\n
Chemically deposited La2Zr2O7buffer layers for YBCO-coated conductors: film growth and microstructure
2006-10-18

An adequate buffer layer architecture is of great importance for YBa2Cu3O7−δ (YBCO)-coated conductor fabrication. We present a transmission electron microscopy (TEM) analysis of La2Zr2O7 (LZO) buffer layers on biaxially textured Ni–5 at.%W substrates for YBCO-coated conductors prepared by chemical solution deposition (CSD). The LZO thin films were heat-treated at 900 and 1050 °C respectively. Electron diffraction patterns, and bright and dark-field images were used to determine the microstructure, texture and the nanoporosity of the films. By x-ray diffraction the films were found to be [100] oriented and strongly biaxially textured. Although x-ray diffraction suggests an epitaxial growth of LZO on Ni it was shown by TEM that this was not the case. The grain size of the films is between 100 and 300 nm and therefore much smaller than the Ni grain size of 40 μm. Appropriate acquisition conditions for scanning electron microscopy (SEM) and TEM imaging are given to identify the nanogranularity of the films. For the film annealed at 1050 °C high-resolution SEM images clearly show a polycrystalline LZO microstructure and the grain size can readily be determined. Electron diffraction rings are more pronounced than for the film annealed at 900 °C, indicating a higher level of polycrystallinity in the film. SEM images of the film annealed at 900 °C yield no evidence of a polycrystalline microstructure; only single misoriented LZO grains separated by 500 nm are observed. Nanovoids 10–40 nm in size were found in the LZO buffer layers with a high density. The voids had approximately cuboid shape, indicating an anisotropy of the surface energy in LZO. The surface planes of the voids were identified as {111} lattice planes. Despite the nanoporosity, which is a typical feature of CSD-grown buffer layers, the LZO buffer layers act as efficient Ni diffusion barriers. Energy dispersive x-ray microanalysis (EDX) in the transmission electron microscope yielded the composition of the films. In the LZO films no Ni-rich secondary phases were detected and significant C contamination occurred during spectrum acquisition.
Tip‐enhanced optical spectroscopy for surface analysis in biosciences
2006-10-18

Abstract Optical spectroscopy provides a wealth of information on the electronic and vibronic states of biological materials and surfaces, thus allowing for a detailed analysis of the sample constituents. Furthermore, information on photoprocesses such as excited‐state relaxation, charge transfer and coupling of individual quantum systems, as for example, in light‐harvesting complexes, can also be obtained. Advances in near‐field optics open up new means to overcome the diffraction limit and extend the range of optical measurements to the length scales of most nanosystems. In this paper, we describe a near‐field microscopic technique that relies on the enhanced electric field near a sharp, laser‐irradiated metal tip. This confined light source can be used for highly localized excitation of photoluminescence (PL) and Raman scattering. We study the properties of the enhanced fields and demonstrate PL and Raman imaging of single‐walled carbon nanotubes (SWCNTs) with sub‐15 nm resolution. The existing studies on biomaterials using tip‐enhanced techniques in the literature are reviewed and potential applications together with the requirements on sample materials are discussed. Copyright © 2006 John Wiley &amp; Sons, Ltd.
Reactivity of Dehydrometallophthalocyanines and ‐porphyrazines
2006-10-18

Abstract The zinc dehydrophthalocyanine 2 and zinc dehydrobenzoporhyrazine 8 a were generated from the 1 N ‐aminobenzotriazole‐annulated zinc phtalocyanine 1 and zinc benzoporhyrazine 8 , respectively, by oxidation with Pb(OAc) 4 in different solvents, for example, diethyl ether, tetrahydrofuran, acetic acid, and benzene. The reactivity of 2 and 8 a was studied in detail. These species not only easily undergo Diels–Alder additions with dienes, but also the used solvents can be added. Among the addition products with solvents ethoxy‐, acetoxy‐, acetoxybutyloxy‐substituted and barrelen‐fused phthalocyanines and benzoporpyrazines were isolated. No products resulting from the dimerization of two dehydro species were observed either for 2 or 8 a . Analysis of the reaction products in comparison with those obtained by oxidation of 1‐aminobenzotriazole 15 under similar conditions proves a higher reactivity (electrophilicity) of the dehydro‐PcZn 2 and dehydro‐PzZn 8 a in comparison with unsubstituted benzyne towards the solvents used, such as diethyl ether and benzene.
Atom counting in ultracold gases using photoionization and ion detection
2006-10-18

We analyze photoionization and ion detection as a means of accurately counting ultracold atoms. We show that it is possible to count clouds containing many thousands of atoms with accuracies better than N^-1.2 with current technology. This allows the direct probing of sub-Poissonian number statistics of atomic samples. The scheme can also be used for efficient single-atom detection with high spatiotemporal resolution. All aspects of a realistic detection scheme are considered, and we discuss experimental situations in which such a scheme could be implemented.
Implications ofR-parity violating supersymmetry for atomic and hadronic electric dipole moments
2006-10-19

We calculate the electric dipole moments (EDM) of the neutral Hg(199) atom, deuteron, nucleons and neutral hyperons Lambda, Sigma(0) and Xi(0) in the framework of a generic SUSY model without R-parity conservation (RPV SUSY) on the basis of the SU(3) version of chiral perturbation theory (ChPT). We consider CP-violation in the hadronic sector induced by the chromoelectric quark dipole moments and CP-violating 4-quark effective interactions. From the null experimental results on the neutron and Hg(199) atom EDMs we derive limits on the imaginary parts of certain products Im(lambda' lambda'*) of the trilinear RPV-couplings and demonstrate that they are more stringent than those existing in the literature. Using these limits we give predictions for the EDMs of neutral hyperons. We also estimate the prospects of future storage ring experiments on the deuteron EDM and show that the expected improvement of the above limits in these experiments may reach several orders of magnitude.
Differential gene expression in periportal and perivenous mouse hepatocytes
2006-10-20

Hepatocytes located in the periportal and perivenous zones of the liver lobule show remarkable differences in the levels and activities of various enzymes and other proteins. To analyze global gene expression patterns of periportal and perivenous hepatocytes, enriched populations of the two cell types were isolated by combined collagenase/digitonin perfusion from mouse liver and used for microarray analysis. In total, 198 genes and expressed sequences were identified that demonstrated a ≥ 2‐fold difference in expression between hepatocytes from the two different zones of the liver. A subset of 20 genes was additionally analyzed by real‐time RT‐PCR, validating the results obtained by the microarray analysis. Several of the differentially expressed genes encoded key enzymes of intermediary metabolism, including those involved in glycolysis and gluconeogenesis, fatty acid degradation, cholesterol and bile acid metabolism, amino acid degradation and ammonia utilization. In addition, several enzymes of phase I and phase II of xenobiotic metabolism were differentially expressed in periportal and perivenous hepatocytes. Our results confirm previous findings on metabolic zonation in liver, and extend our knowledge of the regulatory mechanisms at the transcriptional level.
Risk Factors for Early Recurrent Cerebral Ischemia Before Treatment of Symptomatic Carotid Stenosis
2006-10-20

Background and Purpose— In patients with a recently symptomatic carotid stenosis, surgical or interventional treatment is often delayed for weeks to months. Because therapy should be instituted as early as possible in patients at highest risk for recurrent ischemia, the aim of this study was to identify these individuals using clinical data and serial diffusion-weighted imaging (DWI). Methods— One hundred thirty-one patients (98 male; mean age 68±9 years) who had been referred to our department within 14 days (median; interquartile range, 4 to 36 days) after experiencing an ischemic event caused by a carotid stenosis were followed-up until carotid angioplasty and stenting. Risk factors predicting recurrent transient ischemic attack, stroke, or new DWI lesions were examined. Results— During a median follow-up period of 7 days (interquartile range, 5 to 13 days) no patient experienced a stroke, 4 patients (3.1%) developed a hemispherical transient ischemic attack, and in 15 patients (12%) new asymptomatic DWI lesions were present in the territory of the treated artery. Multivariable regression analysis revealed that motor symptoms (odds ratio, 5.6; 95% CI, 1.2 to 26.3; P &lt;0.05) or the presence of a contralateral carotid occlusion (odds ratio, 4.6; 95% CI, 1.0 to 20.4; P &lt;0.05) were significant independent predictors of further cerebral ischemic events before carotid angioplasty and stenting. Conclusions— In patients with a recently symptomatic carotid stenosis, the risk of early recurrent ischemia is highest in those with motor symptoms and in those with a contralateral carotid occlusion. In these high-risk patients urgent preventive treatment might be warranted.
Crystallization and preliminary X-ray analysis of the aromatic prenyltransferase CloQ from the clorobiocin biosynthetic cluster ofStreptomyces roseochromogenes
2006-10-20

Crystals of recombinant CloQ (subunit MW = 35 626 Da; 324 amino acids), an aromatic prenyltransferase from Streptomyces roseochromogenes, were grown by vapour diffusion. The protein crystallizes in space group I4(1)22, with unit-cell parameters a = b = 135.19, c = 98.13 A. Native data from a single crystal were recorded to a resolution of 2.2 A in-house. Preliminary analysis of these data indicated that the asymmetric unit corresponds to a monomer, giving an estimated solvent content of 60.6%. CloQ is involved in the biosynthesis of the aminocoumarin antibiotic clorobiocin, which targets the essential bacterial enzyme DNA gyrase.
Three‐dimensional MRI perfusion maps: a step beyond volumetric analysis in mental disorders
2006-10-20

Abstract A new type of magnetic resonance imaging analysis, based on fusion of three‐dimensional reconstructions of time‐to‐peak parametric maps and high‐resolution T1‐weighted images, is proposed in order to evaluate the perfusion of selected volumes of interest. Because in recent years a wealth of data have suggested the crucial involvement of vascular alterations in mental diseases, we tested our new method on a restricted sample of schizophrenic patients and matched healthy controls. The perfusion of the whole brain was compared with that of the caudate nucleus by means of intrasubject analysis. As expected, owing to the encephalic vascular pattern, a significantly lower time‐to‐peak was observed in the caudate nucleus than in the whole brain in all healthy controls, indicating that the suggested method has enough sensitivity to detect subtle perfusion changes even in small volumes of interest. Interestingly, a less uniform pattern was observed in the schizophrenic patients. The latter finding needs to be replicated in an adequate number of subjects. In summary, the three‐dimensional analysis method we propose has been shown to be a feasible tool for revealing subtle vascular changes both in normal subjects and in pathological conditions.
High-resolution ultraviolet spectroscopy of PG 1159-035  with HST andFUSE
2006-10-24

PG1159-035 is the prototype of the PG1159 spectral class which consists of extremely hot hydrogen-deficient (pre-) white dwarfs. It is also the prototype of the GW Vir variables, which are non-radial g-mode pulsators. The study of PG1159 stars reveals insight into stellar evolution and nucleosynthesis during AGB and post-AGB phases. We perform a quantitative spectral analysis of PG1159-035 focusing on the abundance determination of trace elements. We have taken high-resolution ultraviolet spectra of PG1159-035 with the Hubble Space Telescope and the Far Ultraviolet Spectroscopic Explorer. They are analysed with non-LTE line blanketed model atmospheres. We confirm the high effective temperature with high precision (Teff=140,000+/-5000 K) and the surface gravity of logg=7. For the first time we assess the abundances of silicon, phosphorus, sulfur, and iron. Silicon is about solar. For phosphorus we find an upper limit of solar abundance. A surprisingly strong depletion of sulfur (2% solar) is discovered. Iron is not detected, suggesting an upper limit of 30% solar. This coincides with the Fe deficiency found in other PG1159 stars. We redetermine the nitrogen abundance and find it to be lower by one dex compared to previous analyses. The sulfur depletion is in contradiction with current models of AGB star intershell nucleosynthesis. The iron deficiency confirms similar results for other PG1159 stars and is explained by the conversion of iron into heavier elements by n-capture in the s-processing environment of the precursor AGB star. However, the extent of the iron depletion is stronger than predicted by evolutionary models. The relatively low nitrogen abundance compared to other pulsating PG1159 stars weakens the role of nitrogen as a distinctive feature of pulsators and non-pulsators in the GW Vir instability strip.
High-resolution ultraviolet spectroscopy of PG 1159-035  with HST and\\nFUSE
2006-10-24

\\n Context.PG 1159-035 is the prototype of the PG 1159 spectral class which consists\\nof extremely hot hydrogen-deficient (pre-) white dwarfs. It is also the prototype of\\nthe GW Vir variables, which are non-radial g-mode pulsators. The study of PG 1159\\nstars reveals insight into stellar evolution and nucleosynthesis during AGB and\\npost-AGB phases.\\n Aims.We perform a quantitative spectral analysis of PG 1159-035 focusing on the abundance\\n determination of trace elements.\\n Methods.We have taken high-resolution ultraviolet spectra of PG 1159-035 with the\\n Hubble Space Telescope and the Far Ultraviolet Spectroscopic\\n Explorer. They are analysed with non-LTE line blanketed model atmospheres.\\n Results.We confirm the high effective temperature with high precision\\n ( K) and the surface gravity of log 7. For the first\\n time we assess the abundances of silicon, phosphorus, sulfur,\\n and iron. Silicon is about solar. For phosphorus we find an upper limit of\\n solar abundance. A surprisingly strong depletion of sulfur (2% solar) is discovered. Iron\\n is not detected, suggesting an upper limit of 30% solar. This coincides\\n with the Fe deficiency found in other PG 1159 stars. We redetermine the\\n nitrogen abundance and find it to be lower by one dex compared to previous\\n analyses.\\n Conclusions.The sulfur depletion is in contradiction with current models of AGB star\\n intershell nucleosynthesis. The iron deficiency confirms similar results for\\n other PG 1159 stars and is explained by the conversion of iron into heavier\\n elements by n-capture in the s-processing environment of the precursor AGB\\n star. However, the extent of the iron depletion is stronger than predicted by\\n evolutionary models. The relatively low nitrogen abundance compared to other\\n pulsating PG 1159 stars weakens the role of \\nnitrogen as a distinctive feature of pulsators and non-pulsators in the GW Vir instability strip.\\n
Rare‐Earth Nickel Nitridoborates with (BN) Anions: Characterized LnNi(BN) and Anticipated LnM(BN) Compounds.
2006-10-24

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Synthesis and Crystal Structure of Na3[W3Cl13].
2006-10-24

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Total Synthesis of (.+‐.)‐Symbioimine (I).
2006-10-24

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.