Showing papers by "University of Tsukuba published in 1998"
TL;DR: In this article, the temperature dependence of the Fermi surface in underdoped Bi2Sr2CaCu2O8+δ superconductors was investigated using angle-resolved photoemission spectroscopy.
Abstract: The Fermi surface—the set of points in momentum space describing gapless electronic excitations—is a central concept in the theory of metals. In this context, the normal ‘metallic’ state of the optimally doped high-temperature superconductors is not very unusual: above the superconducting transition temperature, Tc, there is evidence for a large Fermi surface1,2,3, despite the absence of well-defined elementary excitations. In contrast, the normal state of underdoped high-temperature superconductors differs in that there is evidence for a ‘pseudogap’ above Tc (4–7). Here we examine, using angle-resolved photoemission spectroscopy, the temperature dependence of the Fermi surface in underdoped Bi2Sr2CaCu2O8+δ. We find that, on cooling the sample, the pseudogap opens up at different temperatures for different points in momentum space. This leads to an initial breakup of the Fermi surface, at a temperature T*, into disconnected arcs, which then shrink with decreasing temperature before collapsing to the point nodes of the superconducting ground state below Tc. This unusual behaviour, where the Fermi surface does not form a continuous contour in momentum space as in conventional metals, is unprecedented in that it occurs in the absence of long-range order. Moreover, although the superconducting gap below Tc evolves smoothly into the pseudogap above Tc, the pseudogap differs in its unusual temperature-dependent anisotropy, implying an intimate but non-trivial relationship between the pseudogap and the superconducting gap.
820 citations
TL;DR: There is a retrotransposal insertion of tandemly repeated sequences within this candidate-gene interval in all FCMD chromosomes carrying the founder haplotype (87%).
Abstract: Fukuyama-type congenital muscular dystrophy (FCMD), one of the most common autosomal recessive disorders in Japan (incidence is 0.7-1.2 per 10,000 births), is characterized by congenital muscular dystrophy associated with brain malformation (micropolygria) due to a defect in the migration of neurons. We previously mapped the FCMD gene to a region of less than 100 kilobases which included the marker locus D9S2107 on chromosome 9q31. We have also described a haplotype that is shared by more than 80% of FCMD chromosomes, indicating that most chromosomes bearing the FCMD mutation could be derived from a single ancestor. Here we report that there is a retrotransposal insertion of tandemly repeated sequences within this candidate-gene interval in all FCMD chromosomes carrying the founder haplotype (87%). The inserted sequence is about 3 kilobases long and is located in the 3' untranslated region of a gene encoding a new 461-amino-acid protein. This gene is expressed in various tissues in normal individuals, but not in FCMD patients who carry the insertion. Two independent point mutations confirm that mutation of this gene is responsible for FCMD. The predicted protein, which we term fukutin, contains an amino-terminal signal sequence, which together with results from transfection experiments suggests that fukutin is a secreted protein. To our knowledge, FCMD is the first human disease to be caused by an ancient retrotransposal integration.
772 citations
TL;DR: In this paper, the authors present tunneling spectroscopy of single crystals as a function of oxygen doping and temperature, with a quasiparticle gap that is reduced with increasing oxygen concentration.
Abstract: We present tunneling spectroscopy of ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ single crystals as a function of oxygen doping and temperature. The doping dependence amounts essentially to an energy scaling of the tunneling spectra, with a quasiparticle gap that is reduced with increasing oxygen concentration. This superconducting gap is temperature independent up to the superconducting transition where the superconducting spectra merge continuously into another gaplike feature at the Fermi level. This pseudogap is found to be present both in underdoped and overdoped samples, and it scales with the superconducting gap.
683 citations
TL;DR: In this paper, the optimal geometries of carbon allotropes related to graphite, called graphyne, graphdiyne, graphyne-3, and Graphyne-4, as well as their electronic band structures were calculated using a full-potential linear combination of atomic orbitals method in the local density approximation.
Abstract: The optimized geometries of carbon allotropes related to graphite, called graphyne, graphdiyne, graphyne-3, and graphyne-4, as well as their electronic band structures were calculated using a full-potential linear combination of atomic orbitals method in the local-density approximation. These carbon allotropes consist of hexagons connected by linear carbon chains. The bond length of a hexagon is a little longer than that of the bond that links a hexagon to the outside carbon. Furthermore, part of the linear carbon chain is composed of acetylenic linkages (---C\ensuremath{\equiv}C---) rather than cumulative linkages (=C=C=). The binding energies are 7.95 eV/atom for graphyne and 7.78 eV/atom for graphdiyne, and the optimized lattice lengths are 6.86 \AA{} for graphyne and 9.44 \AA{} for graphdiyne. These materials are semiconductors with moderate band gaps. The band gap occurs at the M point or \ensuremath{\Gamma} point depending on the number of acetylenic linkages that are contained between the nearest-neighboring hexagons. The effective masses are very small for both conduction and valence bands.
589 citations
TL;DR: A review of shape-memory materials can be found in this paper, where the basic phenomena in the materials, that is, the stimulus-induced phase transformations which result in the unique performance and govern the remarkable changes in properties of the materials are systematically lineated.
Abstract: A review is presented of the current research and development of shape-memory materials, including shape-memory alloys, shape-memory ceramics and shape-memory polymers. The shape-memory materials exhibit some novel performances, such as sensoring (thermal, stress or field), large-stroke actuation, high damping, adaptive responses, shape memory and superelasticity capability, which can be utilized in various engineering approaches to smart systems. Based on an extensive literature survey, the various shape-memory materials are outlined, with special attention to the recently developed or emerged materials. The basic phenomena in the materials, that is, the stimulus-induced phase transformations which result in the unique performance and govern the remarkable changes in properties of the materials, are systematically lineated. The remaining technical barriers, and the challenges to improve the present materials system and develop a new shape memory materials are discussed.
542 citations
TL;DR: A novel cadherin-related neuronal receptor (Cnr) gene family is found by studying Fyn-binding activity in mouse brain by finding the expression patterns of each member of this novel family were grossly similar to each other but restricted to subpopulations of neurons of the same type.
458 citations
TL;DR: In this paper, a theory for the resonant scattering mechanism has been developed by considering the splitting of the Mn $4p$ levels due to the orbital ordering, concomitant with a structural phase transition.
Abstract: Dipole resonant x-ray scattering from ordered Mn $3d$ orbitals in $\mathrm{LaMn}{\mathrm{O}}_{3}$ has been observed near the Mn $K$-absorption edge. The polarization of the scattered photons is rotated from $\ensuremath{\sigma}$ to ${\ensuremath{\pi}}^{\ensuremath{'}}$ and the azimuthal angle dependence shows a characteristic twofold symmetry. A theory for the resonant scattering mechanism has been developed by considering the splitting of the Mn $4p$ levels due to the Mn $3d$ orbital ordering. The order parameter of the orbital ordering decreases above the N\'eel temperature ( ${T}_{N}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}140\mathrm{K}$) and disappears at ${T}_{O}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}780\mathrm{K}$, concomitant with a structural phase transition.
407 citations
TL;DR: In this article, the authors show that recently innovated market positions are mimetically adopted by organizations that can easily observe previous adoptions and see them as relevant to their market situations, increasing the market differentiation.
Abstract: Managers planning to abandon a market position need to find a promising alternative, and face a choice of inventing a new market position or entering an existing one. The great uncertainty on the consequences of different actions leads them to rely on other organizations for information on how to compete, making adoption of existing market positions likely. Their wish to avoid direct rivalry and maximize growth leads them to seek out information on new market positions with few incumbents. As a result, recently innovated market positions are mimetically adopted by organizations that can easily observe previous adoptions and see them as relevant to their market situations, increasing the market differentiation. This theory is tested and supported by analysis of the spread of new radio formats in the United States. © 1998 John Wiley & Sons, Ltd.
373 citations
TL;DR: In this article, the alternating pattern of charge ordering and orbital ordering in real space was observed directly by making use of their anomalous dispersion using synchrotron x-ray diffraction.
Abstract: Charge ordering and orbital ordering in ${\mathrm{La}}_{0.5}{\mathrm{Sr}}_{1.5}{\mathrm{MnO}}_{4}$ have been investigated by using synchrotron x-ray diffraction. The alternating pattern of ${\mathrm{Mn}}^{3+}/{\mathrm{Mn}}^{4+}$ in real space is observed directly by making use of their anomalous dispersion. The first clear evidence of the orbital ordering of ${e}_{g}$ electrons on ${\mathrm{Mn}}^{3+}$ is also presented based on the measurements of ATS (anisotropy of the tensor of susceptibility) reflection near the Mn $K$-absorption edge. The present observations indicate that the charge ordering and orbital ordering occur simultaneously at a transition temperature higher than that of the spin ordering.
357 citations
TL;DR: The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications.
Abstract: Helical polyacetylene was synthesized under an asymmetric reaction field consisting of chiral nematic (N*) liquid crystals (LCs). The chiral nematic LC was prepared by adding a chiroptical binaphthol derivative as a chiral dopant to a mixture of two nematic LCs. Acetylene polymerizations were carried out using the catalyst titanium tetra-n-butoxide-triethylaluminum dissolved in the chiral nematic LC solvent. The polyacetylene film was shown by scanning electron microscopy to consist of clockwise or counterclockwise helical structure of fibrils. A Cotton effect was observed in the region of the pi --> pi* transition of the polyacetylene chain in circular dichroism spectra. The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications.
350 citations
TL;DR: In this article, a thermoacoustic engine consisting of a differentially heated stack of plates in a looped tube and observed spontaneous gas oscillations of the traveling wave mode running around the loop was built.
Abstract: We have built a thermoacoustic engine consisting of a differentially heated stack of plates in a looped tube and observed spontaneous gas oscillations of the traveling wave mode running around the loop. Stability boundary and thermally produced acoustic power are compared with those for the engine tested in a resonator. The engine in a looped tube acts as a traveling wave power amplifier, whose onset temperature ratios are significantly smaller than those for the engine in a resonator.
TL;DR: Functional differences of p300 and CBP are reported in vivo, indicating that both co-activators are required for this process of retinoic-acid-induced differentiation and programmed cell death of embryonal carcinoma F9 cells.
Abstract: The related proteins p300 and CBP (cAMP-response-element-binding protein (CREB)-binding protein)) are transcriptional co-activators that act with other factors to regulate gene expression and play roles in many cell-differentiation and signal transduction pathways Both proteins have intrinsic histone-acetyltransferase activity and may act directly on chromatin, of which histone is a component, to facilitate transcription They are also involved in growth control pathways, as shown by their interaction with the tumour suppressor p53 and the viral oncogenes E1A and SV40 T antigen Here we report functional differences of p300 and CBP in vivo We examined their roles during retinoic-acid-induced differentiation, cell-cycle exit and programmed cell death (apoptosis) of embryonal carcinoma F9 cells, using hammerhead ribozymes capable of cleaving either p300 or CBP messenger RNAs F9 cells expressing a p300-specific ribozyme became resistant to retinoic-acid-induced differentiation, whereas cells expressing a CBP-specific ribozyme were unaffected Similarly, retinoic-acid-induced transcriptional upregulation of the cell-cycle inhibitor p21Cip1 required normal levels of p300, but not CBP, whereas the reverse was true for p27Kip1 In contrast, both ribozymes blocked retinoic-acid-induced apoptosis, indicating that both co-activators are required for this process Thus, despite their similarities, p300 and CBP have distinct functions during retinoic-acid-induced differentiation of F9 cells
TL;DR: In this article, a transition from fcc to hcp Co has been shown to occur at the Co/Pt interface and to cause the perpendicular magnetic anisotropy (PMA) enhancement.
Abstract: Magnetic circular x-ray dichroism (MCXD) measurements at the Co ${L}_{2,3}$ and ${M}_{2,3}$ core edges reveal a strongly enhanced perpendicular Co orbital moment ( ${m}_{\mathrm{orb}}$) in Co/Pt multilayers which show perpendicular magnetic anisotropy (PMA). MCXD signals at the Pt ${N}_{6,7}$ and ${O}_{2,3}$ edges, arising from Pt $5d\ensuremath{-}\mathrm{Co}3d$ hybridization, persist for the thinnest Co layer. The hybridization is shown to be localized at the Co/Pt interface and to cause the ${m}_{\mathrm{orb}}$ enhancement which drives PMA. Unambiguous evidence for a transition from fcc to hcp Co is presented and ${m}_{\mathrm{orb}}$ of bulk fcc Co has been determined to be $0.11{\ensuremath{\mu}}_{B}$ for the first time.
TL;DR: The crystal structure at 1.7 Å resolution and mass spectrometry revealed the structure of the non-heme iron catalytic center in the nitrosylated state, likely to enable the photo-regulation of NHase and will provide an excellent model for designing photo-controllable chelate complexes and, ultimately, proteins.
Abstract: The iron-containing nitrile hydratase (NHase) is a photoreactive enzyme that is inactivated in the dark because of persistent association with NO and activated by photo-dissociation of NO. The crystal structure at 1.7 A resolution and mass spectrometry revealed the structure of the non-heme iron catalytic center in the nitrosylated state. Two Cys residues coordinated to the iron were post-translationally modified to Cys-sulfenic and -sulfinic acids. Together with another oxygen atom of the Ser ligand, these modifications induced a claw setting of oxygen atoms capturing an NO molecule. This unprecedented structure is likely to enable the photo-regulation of NHase and will provide an excellent model for designing photo-controllable chelate complexes and, ultimately, proteins.
TL;DR: A new null mutation of vasa was generated, which deletes the entire coding region of the vasa gene and revealed roles for vasa in oocyte differentiation, anterior-posterior egg chamber patterning, and dorsal-ventral follicle patterned, in addition to its better-characterized functions in posterior embryonic patterning and pole cell specification.
Abstract: The Drosophila gene vasa is required for pole plasm assembly and function, and also for completion of oogenesis. To investigate the role of vasa in oocyte development, we generated a new null mutation of vasa, which deletes the entire coding region. Analysis of vasa-null ovaries revealed that the gene is involved in the growth of germline cysts. In vasa-null ovaries, germaria are atrophied, and contain far fewer developing cysts than do wild-type germaria; a phenotype similar to, but less severe than, that of a null nanos allele. The null mutant also revealed roles for vasa in oocyte differentiation, anterior-posterior egg chamber patterning, and dorsal-ventral follicle patterning, in addition to its better-characterized functions in posterior embryonic patterning and pole cell specification. The anterior-posterior and dorsal-ventral patterning phenotypes resemble those observed in gurken mutants. vasa-null oocytes fail to efficiently accumulate many localized RNAs, such as Bicaudal-D, orb, oskar, and nanos, but still accumulate gurken RNA. However, GRK accumulation in the oocyte is severely reduced in the absence of vasa function, suggesting a function for VASA in activating gurken translation in wild-type ovaries.
TL;DR: This core has a novel protein kinase structure, distinct from the serine/threonine/tyrosine kinase fold, with unanticipated similarities to both heat-shock protein 90 and DNA gyrase B.
Abstract: Bacteria live in capricious environments, in which they must continuously sense external conditions in order to adjust their shape, motility and physiology1. The histidine–aspartate phosphorelay signal-transduction system (also known as the two-component system) is important in cellular adaptation to environmental changes in both prokaryotes and lower eukaryotes2,3. In this system, protein histidine kinases function as sensors and signal transducers. The Escherichia coli osmosensor, EnvZ, is a transmembrane protein with histidine kinase activity in its cytoplasmic region2. The cytoplasmic region contains two functional domains4: domain A (residues 223–289) contains the conserved histidine residue (H243), a site of autophosphorylation as well as transphosphorylation to the conserved D55 residue of response regulator OmpR, whereas domain B (residues 290–450) encloses several highly conserved regions (G1, G2, F and N boxes) and is able to phosphorylate H243. Here we present the solution structure of domain B, the catalytic core of EnvZ. This core has a novel protein kinase structure, distinct from the serine/threonine/tyrosine kinase fold, with unanticipated similarities to both heat-shock protein 90 and DNA gyrase B.
TL;DR: A positive relationship was found between pleasantness and judgement of stimuli as edible, suggesting that culture-specific experiences-particularly of foods-may significantly influence odor perception.
Abstract: There is a growing appreciation that experience with odors may strongly influence their perception. To further investigate this, the responses of 40 Japanese and 44 age-matched German women to everyday odorants were compared. Subjects were presented with 18 stimuli in squeeze bottles and asked to rate them according to intensity, familiarity, pleasantness and edibility, to describe associations elicited by them and, if possible, to name them. One-third of the odorants were presumed to be familiar to the Japanese only, one-third to the Germans and one-third to both populations. Significant differences were found between the two populations on all measures. Better performance by the Japanese in providing appropriate descriptors for 'Japanese' odorants and by the Germans for 'European' odorants supported the pre-selection of stimuli as culture-typical. Particularly clear differences between the two populations were found in pleasantness ratings. In general, a positive relationship was found between pleasantness and judgement of stimuli as edible, suggesting that culture-specific experiences-particularly of foods-may significantly influence odor perception. Somewhat unexpectedly, significant differences were also found between the two populations in intensity ratings for some odorants. These differences did not seem simply to be artefacts of the test situation and raise the possibility that experience may even influence such basic aspects of odor perception as stimulus intensity.
TL;DR: In this article, a survey of shape-memory hybrid smart composites is presented, with a focus on the design, fabrication, characterization and performance of fiber-reinforced, particle reinforced, and multi-layered thin-film shape memory composites.
Abstract: By hybridizing or incorporating shape-memory materials with other functional materials or structural materials, smart composites can be fabricated which may utilize the unique functions or properties of the individual bulk materials to achieve multiple responses and optimal properties, or, to tune their properties to adapt to environmental changes. A variety of shape-memory hybrid composites have been designed and manufactured, with shape-memory elements being either the matrix or the reinforcement. The hybrid composites provide tremendous potential for creating new paradigms for material–structural interactions and demonstrate varying success in many engineering applications. This review, from the standpoint of materials science, will give a state-of-the-art survey on the various shape-memory hybrid smart composites developed during the last decade. Emphasis is placed on the design, fabrication, characterization and performance of fibre-reinforced, particle-reinforced and multi-layered thin-film shape-memory composites.
TL;DR: In this article, the decay mode B{sub c} mesons were observed in 1.8 TeV p{ovr p}collisions using the CDF detector at the Fermilab Tevatron.
Abstract: We have observed bottom-charm mesons via the decay mode B{sub c}{sup {+-}}{yields}J/{psi}{ell}{sup {+-}}v in 1.8 TeV p{ovr p}collisions using the CDF detector at the Fermilab Tevatron. A fit of background and signal contributions to the J/{psi}{ell} mass distribution yielded 20.4{sub -5.5}{sup +6.2} events from B{sub c} mesons. A fit to the same distribution with background alone was rejected at the level of 4.8 standard deviations. We measured the B{sub c}{sup +} mass to be 6.40{+-}0.39(stat){+-}0.13(syst) GeV/c{sup 2} and the B{sub c}{sup +} lifetime to be 0.46{sub -0.16}{sup +0.18}(stat){+-}0.03(syst) ps. Our measured yield (production cross section times branching ratio) for B{sub c}{sup +}{yields}J/{psi}{ell}{sup +}v relative to that for B{sup +}{yields}J/{psi} K{sup +} is 0.132{sub -0.037}{sup +0.041}(stat){+-}0.031(syst){sub -0.020}{sup +0.032}(lifetime).
01 Dec 1998
TL;DR: In this method, the self-localization of the robot is achieved by a model-based vision system, and nonstop navigation is realized by a retroactive position correction system.
Abstract: This paper describes a vision-based navigation method in an indoor environment for an autonomous mobile robot which can avoid obstacles. In this method, the self-localization of the robot is achieved by a model-based vision system, and nonstop navigation is realized by a retroactive position correction system. Stationary obstacles are avoided with single-camera vision and moving obstacles are detected with ultrasonic sensors. We report on experiments in a hallway using the YAMABICO robot.
TL;DR: The data indicate that genetic differences in transcriptional activity of the IL4 gene influence AD predisposition, particularly in Japanese, because of a high frequency of the T allele.
Abstract: We examined linkage between markers at and near the IL4 gene and atopic dermatitis (AD) in 88 Japanese nuclear families. Affected sib pair analysis suggested linkage between the IL4 gene and AD (SPLINK lod=2.28). Transmission disequilibrium testing showed a significantly preferential transmission to AD offspring of the T allele of the -590C/T polymorphism of the IL4 gene (p=0.001). A case-control comparison suggested a genotypic association of the TT genotype with AD (odds ratio=1.88, p=0.01). Since the T allele was reported to be associated with increased IL4 gene promoter activity compared with the C allele, our data indicate that genetic differences in transcriptional activity of the IL4 gene influence AD predisposition, particularly in Japanese, because of a high frequency of the T allele.
TL;DR: It is shown that MKK1 activation in developing T cells is sufficient for providing positive selection signals and that the MKK6-p38 signaling pathway is critically involved in inducingnegative selection of thymocytes, suggesting that intracellular signals through different MAP kinase cascades selectively guide positive and negative selection of T lymphocytes.
TL;DR: The results showed that species-specific exclusion of sperm mtDNA in mammalian fertilized eggs is extremely stringent, ensuring strictly maternal inheritance of mtDNA.
Abstract: The transmission profiles of sperm mtDNA introduced into fertilized eggs were examined in detail in F1 hybrids of mouse interspecific crosses by addressing three aspects. The first is whether the leaked paternal mtDNA in fertilized eggs produced by interspecific crosses was distributed stably to all tissues after the eggs' development to adults. The second is whether the leaked paternal mtDNA was transmitted to the subsequent generations. The third is whether paternal mtDNA continuously leaks in subsequent backcrosses. For identification of the leaked paternal mtDNA, we prepared total DNA samples directly from tissues or embryos and used PCR techniques that can detect a few molecules of paternal mtDNA even in the presence of 10(8)-fold excess of maternal mtDNA. The results showed that the leaked paternal mtDNA was not distributed to all tissues in the F1 hybrids or transmitted to the following generations through the female germ line. Moreover, the paternal mtDNA leakage was limited to the first generation of an interspecific cross and did not occur in progeny from subsequent backcrosses. These observations suggest that species-specific exclusion of sperm mtDNA in mammalian fertilized eggs is extremely stringent, ensuring strictly maternal inheritance of mtDNA.
TL;DR: In this article, the authors compare light curves of two models to observations of quasar 0957+561 in terms of a structure function analysis, and conclude that the disk-instability model is favored over the starburst model in explaining the slopes of the observational structure function in the case of the quasar, though this object is a radio-loud object and thus is not really a fair test for the SB model.
Abstract: Aperiodic optical variability is a common property of active galactic nuclei (AGNs), though its physical origin is still open to question. To study the origin of the optical-ultraviolet variability in AGNs, we compare light curves of two models to observations of quasar 0957+561 in terms of a structure function analysis. In the starburst (SB) model, random superposition of supernovae in the nuclear starburst region produces aperiodic luminosity variations, while in the disk-instability (DI) model, variability is caused by instabilities in the accretion disk around a supermassive black hole. We calculate fluctuating light curves and structure functions, V(τ), by simple Monte Carlo simulations on the basis of the two models. Each resultant V(τ) possesses a power-law portion, [V(τ)]1/2 ∝ τβ, at short time lags (τ). The two models can be distinguished by the logarithmic slope β; β ~ 0.74-0.90 in the SB model and β ~ 0.41-0.49 in the DI model, while the observed light curves exhibit β ~ 0.35. Therefore, we conclude that the DI model is favored over the SB model in explaining the slopes of the observational structure function in the case of 0957+561, though this object is a radio-loud object and thus is not really a fair test for the SB model. In addition, we examine the time asymmetry of the light curves by calculating V(τ) separately for the brightening and the decaying phases. The two models exhibit opposite trends of time asymmetry to some extent, although the present observation is not long enough to test this prediction.
TL;DR: In this paper, the low-energy magnetic excitations of nanographite ribbons with zigzag edges were investigated by a random phase approximation of the corresponding Hubbard model, which was used to derive an effective Heisenberg model with ladder structure.
Abstract: We consider the low-energy magnetic excitations of nanographite ribbons with zigzag edges. The zigzag ribbons possess almost flat bands at the Fermi level which cause a ferrimagnetic spin polarization localized at the edge sites. The spin wave mode of this magnetic state is investigated by a random phase approximation of the corresponding Hubbard model. This result is used to derive an effective Heisenberg model with ladder structure. Although this system has a spin gap (Haldane type), our analysis shows that the gap is small and the tendency towards ferrimagnetic correlation at the edges is strong.
TL;DR: A study has demonstrated that the T allele of a polymorphism in the IL‐4 gene promoter region (C‐590T) is associated with elevated levels of total serum IgE.
Abstract: Background Susceptibility to the development of asthma and other atopic diseases is known to be associated with genetic components. Several investigator have linked the interleukin-4 (IL-4) gene and nearby markers located on chromosome 5 to atopy and asthma. Recent study has demonstrated that the T allele of a polymorphism in the IL-4 gene promoter region (C-590T) is associated with elevated levels of total serum IgE. Objective The objective of this study was to evaluate the possible role of this IL-4 polymorphism (C-590T) in modulating the allergic response and asthma in Japanese children. Methods and results The study was conducted in two different populations: families ascertained through asthmatic children (asthmatic group, 306 members) in whom linkage of asthma and atopy to chromosome 5q31-33 is suggested and a random general population (control group, 215 members). The IL-4 C-590T polymorphism was genotyped by PCR-restriction fragment length polymorphism analysis. Frequency of the T allele was 0.73 in the asthmatic group and 0.70 in the control group. No significant difference in the levels of total serum IgE and specific IgE to house dust mite was observed between subjects with homozygote for the C allele, a heterozygote and a homozygote for the T allele by intrafamilial and interfamilial comparisons. Using the transmission disequilibrium test, however, we found a significantly frequent transmission of the T allele to asthmatic children (chi2=5.72, P=0.023). Conclusion Our data suggest that the IL-4 promoter C-590T polymorphism may be associated with the development of asthma in Japanese children, but not through modulating total serum IgE levels.
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10 Aug 1998TL;DR: Findings suggest that Zic1 may determine the cerebellar folial pattern principally via regulation of cell proliferation in the EGL.
Abstract: Zic genes encode zinc finger proteins, the expression of which is highly restricted to cerebellar granule cells and their precursors. These genes are homologs of the Drosophila pair-rule gene odd-paired . To clarify the role of the Zic1 gene, we have generated mice deficient in Zic1 . Homozygous mice showed remarkable ataxia during postnatal development. Nearly all of the mice died within 1 month. Their cerebella were hypoplastic and missing a lobule in the anterior lobe. A bromodeoxyuridine labeling study indicated a reduction both in the proliferating cell fraction in the external germinal layer (EGL), from 14 d postcoitum, and in forward movement of the EGL. These findings suggest that Zic1 may determine the cerebellar folial pattern principally via regulation of cell proliferation in the EGL.
TL;DR: Results indicate that Spm accumulates outside of cells after lesion formation and induces both acidic PR proteins and resistance against TMV via a SA-independent signaling pathway.
Abstract: Intercellular spaces are often the first sites invaded by pathogens. In the spaces of tobacco mosaic virus (TMV)-infected and necrotic lesion-forming tobacco (Nicotiana tabacum L.) leaves, we found that an inducer for acidic pathogenesis-related (PR) proteins was accumulated. The induction activity was recovered in gel-filtrated fractions of low molecular mass with a basic nature, into which authentic spermine (Spm) was eluted. We quantified polyamines in the intercellular spaces of the necrotic lesion-forming leaves and found 20-fold higher levels of free Spm than in healthy leaves. Among several polyamines tested, exogenously supplied Spm induced acidic PR-1 gene expression. Immunoblot analysis showed that Spm treatment increased not only acidic PR-1 but also acidic PR-2, PR-3, and PR-5 protein accumulation. Treatment of healthy tobacco leaves with salicylic acid (SA) caused no significant increase in the level of endogenous Spm, and Spm did not increase the level of endogenous SA, suggesting that induction of acidic PR proteins by Spm is independent of SA. The size of TMV-induced local lesions was reduced by Spm treatment. These results indicate that Spm accumulates outside of cells after lesion formation and induces both acidic PR proteins and resistance against TMV via a SA-independent signaling pathway.
TL;DR: The Bach2–small‐Maf heterodimer may represent the first example of a B‐cell lineage, and of a developmental stage‐restricted negative effector of the MARE in the IgH 3′ enhancer region.
Abstract: Maf family transcription factors are important regulators in various differentiation systems. Putative Maf recognition elements (MAREs) are found in the 3' enhancer region of the immunoglobulin heavy chain (IgH) gene. These elements are bound in B-cell extracts by a heterodimeric protein complex containing both Bach2 and a small Maf protein. Analysis of normal hematopoietic cells revealed that Bach2 is specifically expressed in B cells. Bach2 is abundantly expressed in the early stages of B-cell differentiation and turned off in terminally differentiated cells. Bach2 acts together with MafK as a negative effector of the IgH 3' enhancer and binds to the co-repressor SMRT (silencing mediator of retinoid and thyroid receptor). Hence the Bach2-small-Maf heterodimer may represent the first example of a B-cell lineage, and of a developmental stage-restricted negative effector of the MARE in the IgH 3' enhancer region.