Evidence of second-order transition and critical scaling for the dynamical ordering transition in current-driven vortices.

Dynamical ordering from a disordered plastic flow to an anisotropically ordered smectic flow induced by a dc force has been studied in various many-particle systems, including vortices in type-II superconductors. However, it remains unclear whether the dynamical ordering is a true phase transition because of lack of suitable experimental methods. Here, we study the response of vortex flow to the transverse force using a cross-shaped amorphous Mo[Formula: see text]Ge[Formula: see text] film. From transverse current-voltage (force-velocity) characteristics under various longitudinal currents, we find a change of the transverse response in low voltage (velocity) regions from a nonlinear to linear behavior at a well-defined longitudinal current that marks the dynamical ordering transition. We also find the scaling collapse of the transverse current-voltage curves to a universal scaling function, providing evidence of the second-order transition for the dynamical ordering transition.

Kibble-Zurek Mechanism for Dynamical Ordering in a Driven Vortex System.

The Kibble-Zurek mechanism describes the formation of topological defects in systems crossing a continuous symmetry-breaking phase transition at a finite quench rate. While this mechanism has been extensively studied for equilibrium transitions, its applicability to nonequilibrium transitions has not yet been fully examined. Recent simulation has shown the applicability of the Kibble-Zurek mechanism to dynamical ordering transitions in particlelike assemblies, including superconducting vortices, driven over random disorder. Here, we experimentally study the configurational order of vortices in the course of dynamical ordering with various quench rates. We verify a power-law scaling of the defect density with the quench rate and an impulse-adiabatic crossover on the ordered side of the transition, which are key predictions of the Kibble-Zurek mechanism. Our results suggest the applicability of the Kibble-Zurek mechanism to other nonequilibrium phase transitions.

Critical behavior of nonequilibrium depinning transitions for vortices driven by current and vortex density.

We study the critical dynamics of vortices associated with dynamic disordering near the depinning transitions driven by dc force (dc current I) and vortex density (magnetic field B). Independent of the driving parameters, I and B, we observe the critical behavior of the depinning transitions, not only on the moving side, but also on the pinned side of the transition, which is the first convincing verification of the theoretical prediction. Relaxation times, [Formula: see text] and [Formula: see text], to reach either the moving or pinned state, plotted against I and B, respectively, exhibit a power-law divergence at the depinning thresholds. The critical exponents of both transitions are, within errors, identical to each other, which are in agreement with the values expected for an absorbing phase transition in the two-dimensional directed-percolation universality class. With an increase in B under constant I, the depinning transition at low B is replaced by the repinning transition at high B in the peak-effect regime. We find a trend that the critical exponents in the peak-effect regime are slightly smaller than those in the low-B regime and the theoretical one, which is attributed to the slight difference in the depinning mechanism in the peak-effect regime.

Critical behavior of density-driven and shear-driven reversible-irreversible transitions in cyclically sheared vortices.

Random assemblies of particles subjected to cyclic shear undergo a reversible-irreversible transition (RIT) with increasing a shear amplitude d or particle density n, while the latter type of RIT has not been verified experimentally. Here, we measure the time-dependent velocity of cyclically sheared vortices and observe the critical behavior of RIT driven by vortex density B as well as d. At the critical point of each RIT, [Formula: see text] and [Formula: see text], the relaxation time [Formula: see text] to reach the steady state shows a power-law divergence. The critical exponent for B-driven RIT is in agreement with that for d-driven RIT and both types of RIT fall into the same universality class as the absorbing transition in the two-dimensional directed-percolation universality class. As d is decreased to the average intervortex spacing in the reversible regime, [Formula: see text] shows a significant drop, indicating a transition or crossover from a loop-reversible state with vortex-vortex collisions to a collisionless point-reversible state. In either regime, [Formula: see text] exhibits a power-law divergence at the same [Formula: see text] with nearly the same exponent.

Quantum Criticality inside the Anomalous Metallic State of a Disordered Superconducting Thin Film.

The field-induced superconductor-insulator transition (SIT) in two-dimensional (2D) systems is a famous example of a quantum phase transition. However, an emergence of an anomalous metallic state induced by field has been a long-standing problem in 2D superconductors. While theories predicted that the emergence is attributed to strong phase fluctuations of the superconducting order parameter due to quantum fluctuations, usual resistance measurements have not probed them directly. Here, using Nernst effect measurements, we uncover superconducting fluctuations in the vicinity of the field-induced metallic state in an amorphous Mo_{x}Ge_{1-x} thin film. The field range where the vortex Nernst signals are detectable remains nonzero toward zero temperature, and it locates inside the metallic state defined by the magnetoresistance, indicating that the metallic state results from quantum vortex liquid (QVL) with phase fluctuations due to quantum fluctuations. Slow decay of transport entropy of vortices in the QVL with decreasing temperature suggests that the metallic state originates from broadening of a quantum critical point in SIT.

Critical behavior near the reversible-irreversible transition in periodically driven vortices under random local shear.

When many-particle (vortex) assemblies with disordered distribution are subjected to a periodic shear with a small amplitude [Formula: see text], the particles gradually self-organize to avoid next collisions and transform into an organized configuration. We can detect it from the time-dependent voltage [Formula: see text] (average velocity) that increases towards a steady-state value. For small [Formula: see text], the particles settle into a reversible state where all the particles return to their initial position after each shear cycle, while they reach an irreversible state for [Formula: see text] above a threshold [Formula: see text]. Here, we investigate the general phenomenon of a reversible-irreversible transition (RIT) using periodically driven vortices in a strip-shaped amorphous film with random pinning that causes local shear, as a function of [Formula: see text]. By measuring [Formula: see text], we observe a critical behavior of RIT, not only on the irreversible side, but also on the reversible side of the transition, which is the first under random local shear. The relaxation time [Formula: see text] to reach either the reversible or irreversible state shows a power-law divergence at [Formula: see text]. The critical exponent is determined with higher accuracy and is, within errors, in agreement with the value expected for an absorbing phase transition in the two-dimensional directed-percolation universality class. As [Formula: see text] is decreased down to the intervortex spacing in the reversible regime, [Formula: see text] deviates downward from the power-law relation, reflecting the suppression of intervortex collisions. We also suggest the possibility of a narrow smectic-flow regime, which is predicted to intervene between fully reversible and irreversible flow.

Vortex rectenna powered by environmental fluctuations.

A rectenna, standing for a rectifying antenna, is an apparatus which generates d.c. electricity from electric fluctuations. It is expected to realize wireless power transmission as well as energy harvesting from environmental radio waves. To realize such rectification, devices that are made up of internal atomic asymmetry such as an asymmetric junction have been necessary so far. Here we report a material that spontaneously generates electricity by rectifying environmental fluctuations without using atomic asymmetry. The sample is a common superconductor without lowered crystalline symmetry, but, just by putting it in an asymmetric magnetic environment, it turns into a rectifier and starts generating electricity. Superconducting vortex strings only annihilate and nucleate at surfaces, and this allows the bulk electrons to feel surface fluctuations in an asymmetric environment: a vortex rectenna. The rectification and generation can be switched on and off with only a slight change in temperature or external magnetic fields.

Anomalous vortex motion in the quantum-liquid phase of amorphous MoxSi1-x films.

We measure, in real time (t), the fluctuating component of the flux-flow voltage V(t), deltaV(t) identical withV(t)-V0, about the average V0 in the vortex-liquid phase of amorphous MoxSi1-x films. For the thick film, deltaV(t) originating from the vortex motion is clearly visible in the quantum-liquid phase, where the distribution of deltaV(t) is asymmetric, indicative of large velocity and/or number fluctuations of driven vortices. For the thin film the similar anomalous vortex motion is observed in nearly the same (reduced-)temperature regime. These results suggest that vortex dynamics in the low-temperature liquid phase of thick and thin films is dominated by common physical mechanisms, presumably related to quantum effects.

Enhancement of the quantum-liquid phase by increased resistivity in thick a-MoxSi1-x films.

Effects of normal-state resistivity rho(n) on the vortex phase diagram at low temperature T have been studied based on dc and ac complex resistivities for thick amorphous MoxSi(1-x) films. It is commonly observed irrespective of rho(n) that, in the limit T=0, the vortex-glass-transition line B(g)(T) is independent of T and extrapolates to a field below the T=0 upper critical field B(c2)(0), indicative of the quantum-vortex-liquid (QVL) phase in the regime B(g)(0)

Vortex glass transition and quantum vortex liquid at low temperature in a thick a- MoxSi1-x film.

We present measurements of ac complex resistivity, as well as dc resistivity, for a thick amorphous MoxSi1-x film at low temperatures ( T>0.04 K) in various constant fields B. We find that the vortex glass transition (VGT) persists down to T approximately 0.04Tc0 up to B approximately 0.9Bc2(0), where Tc0 and Bc2(0) are the mean-field transition temperature and upper critical field at T = 0, respectively. In the limit T-->0, the VGT line Bg(T) extrapolates to a field below Bc2(0), while the dc resistivity rho(T) tends to the finite nonzero value in fields just above Bg(0). These results indicate the presence of a metallic quantum vortex liquid at T = 0 in the regime Bg(0)

Irsogladine maleate may preserve gastric mucosal hydrophobicity against ethanol in phospholipids independent way in rats.

Irsogladine maleate (IM) has been used as a mucosal protective agent, whose action is partially explained as enhancement of mucosal blood flow, increase of cellular cyclic AMP and facilitation of gap-junctional intercellular communication. Effect of IM on rat gastric mucosal hydrophobicity, one of the mucosal barrier properties, was investigated, in comparison with that of 16,16-dimethyl prostaglandin E2 (dmPGE2). IM alone had no effect on mucosal hydrophobicity and mucosal phospholipids content. dmPGE2 alone did not change mucosal hydrophobicity significantly, but remarkably increased mucosal surface-active phospholipids. Intragastric administration of absolute ethanol significantly decreased gastric mucosal hydrophobicity and mucosal phospholipids content. IM could prevent the decrease in mucosal hydrophobicity by ethanol, maintaining the surface mucus gel layer and mucosal surface phospholipids almost as non-damaged control levels, whereas dmPGE2 also prevented the decrease in mucosal hydrophobicity by ethanol, with the surface epithelium being partially exfoliated and mucosal surface-active phospholipids showing remarkable enhancement. These results suggest that IM may preserve gastric mucosal hydrophobicity against ethanol, not through enhancement of mucosal phospholipids content like prostaglandin, but possibly through its reported stabilization action to the epithelial cell lining, which may preserve the surface epithelium with the mucous gel layer containing surface-active phospholipids, a possible origin of mucosal hydrophobicity.

[Sarcomatous malignant mesothelioma diagnosed after death].

A 77-year-old man with diabetes mellitus who was being treated as an outpatient had abnormal shadow in the right lower lobe on a chest roentgenogram in June 1993. In July 1994, a productive cough developed, and subsequent dyspnea obliged him to enter our hospital. Retention of pleural fluid led us to suspect tuberculosis pleurisy and to perform a pleural biopsy and a thoracentesis to remove pleural fluid but no final diagnosis was reached. About 14 months later he died of dyspnea with a rapidly growing tumor. An autopsy disclosed a giant tumor that occupied the right pleural cavity, excluding the lung. The tumor was well-defined between the lung and had infiltrated into the mediastinum. The histopathological diagnosis was primary malignant mesothelioma, sarcomatous type, of the visceral pleura.

Molecular mechanism of growth hormone (GH) deficiency in the spontaneous dwarf rat: detection of abnormal splicing of GH messenger ribonucleic acid by the polymerase chain reaction.

The spontaneous dwarf rat (SDR) is an experimental model for pituitary dwarfism with an autosomal recessive mode of inheritance. In the pituitary of the SDR, neither GH cells nor GH protein were detected by immunological methods, but SDR pituitary has a very small amount of GH mRNA. In the present study the effects of GH-releasing factor and an analog of its second messenger, (Bu)2cAMP, on the total accumulation and secretion of GH were studied in primary cultures from SDR pituitaries. GH-releasing factor and (Bu)2cAMP increased the amount of GH mRNA, but neither accumulation nor secretion of immunoreactive GH was detected. These results suggested that the mutation is not manifest during transcription, but at a later stage. The GH gene of SDR was cloned, and its sequence was determined. A point substitution was found in the consensus sequence of the 3' splice site of the third intron. Judging from this point mutation, one would predict an abnormal splicing and a 1-base deletion in the GH mRNA. Therefore, the fragment of SDR GH cDNA in which the deletion was predicted was amplified by the polymerase chain reaction. Its sequence analysis confirmed that the SDR GH mRNA had 1 base deletion which must cause a premature translational termination of GH mRNA. These results demonstrate that GH deficiency in SDR is caused by a point mutation in the GH gene producing an abnormal splicing of GH mRNA.

The cell population of somatostatin and growth hormone-releasing factor using quantitative immunohistochemistry in the isolated GH deficient dwarf rat.

We examined the cell population of somatostatin (SS) in the periventricular nucleus (PN) and growth hormone-releasing factor (GRF) in the arcuate nucleus (ARC) between spontaneous dwarf rats (SDRs; gene symbol: dr), which show isolated GH deficiency, and normal rats using avidin-biotin complex (ABC) immunohistochemistry. The total number of SS perikarya per brain weight in the PN of SDRs was 824.8 +/- 49.6 (mean +/- S.E.M., n = 4), whereas that of controls was 1108.5 +/- 50.1 (n = 4). The GRF perikarya per brain weight in the ARC of SDRs numbered 1281.0 +/- 26.0 (n = 7), as compared to 685.4 +/- 64.6 (n = 7) in the controls. The SS perikarya in the PN of SDRs were significantly reduced (P less than 0.05), while the GRF perikarya in the SDRs were significantly increased (P less than 0.01). These results suggest that GH itself acts on SS to positively regulate its secretion and on GRF in a negative regulatory manner.

Studies on prolactin and growth hormone gene expression in the pituitary gland of spontaneous dwarf rats.

The spontaneous dwarf rat (SDR) is a newly established experimental model for pituitary dwarfism with an autosomal recessive mode of inheritance. GH and PRL gene expressions were studied in the pituitary gland of this animal. Immunocytochemistry failed to detect any immunoreactive GH cells in SDR pituitary gland, whereas numerous PRL cells were encountered throughout the anterior lobe. Similarly, GH was not detectable in the pituitary cytosol from SDR of 7, 20, and 80 days of age. PRL of the same mol wt as the authentic rat PRL was found in the pituitary glands in all SDRs examined. Since these results were thought to be due to the absence of GH mRNA in the SDR's pituitary gland, we attempted to detect GH mRNA by dot hybridization. Very small amounts of GH mRNA were found in the pituitary glands of both male (2.6% of normal) and female (6.0% of normal) SDRs. Reduced levels of PRL mRNA were also found in the pituitary glands of male (50%) and female (30%) SDRs. Northern blot analyses of total RNA extracts revealed that the GH mRNA of the SDR was similar in size to the mature GH mRNA found in the pituitary glands of control rats. PRL mRNA from the SDR also migrated to the same position as normal PRL mRNA. Nuclear DNA preparations were prepared from normal and SDR livers, and the genomic organizations of the GH and PRL genes were examined using restriction mapping. The DNA fragment length patterns obtained with the cDNA probes for GH or PRL using several restriction enzyme digestions were identical. The results suggest that the GH deficiency in SDR is not due to a gross deletion or rearrangement of the GH gene. It is proposed that SDR may be an excellent experimental model for the study of isolated GH deficiency in the human.

[Study of growth hormone in spontaneous dwarf rat].

In 1977, in the Research Laboratories, Morishita Pharmaceutical Co. Ltd., we were fortunate to discover that small mutant rats named Spontaneous Dwarf Rat (gene symbol dr), inherited an autosomal recessive. In previous papers, we reported that these rats might be characterized by a defect of growth hormone (GH). In this paper, we carried out the studies of the secretory cells and GH deficiency in the pituitary glands of +/dr and dr/dr rats using immunohistochemistry, electron microscopy and acrylamide gel electrophoresis. ACTH, PRL and GH secretory cells in the pituitary gland respectively identified with antiserum to porcine ACTH, rat PRL and ovine GH by indirect method of immunohistochemistry. In the pituitary of dr/dr rats, ACTH and PRL secretory cells were confirmed, but none of the cells were stained with ovine GH antiserum. Using electron microscopy, GH secretory cells could not be identified precisely although the other cells were identified in the pituitary gland of dr/dr rats. With the analysis of pituitary homogenate by acrylamide gel electrophoresis, PRL band appeared in dr/dr rats but GH did not. These results obviously indicated that the inhibition of body weight in dr/dr rats was caused by the absence of GH in the anterior pituitary. Therefore, the Spontaneous Dwarf Rat may be a useful animal model for human dwarfism caused by isolated GH deficiency.