Magnetic structures of RbCuCl_3 in a transverse field

A recent high-field magnetization experiment found a phase transition of unknown character in the layered, frustrated antiferromagnet RbCuCl_3, in a transverse field (in the layers). Motivated by these results, we have examined the magnetic structures predicted by a model of RbCuCl_3, using the classical approximation. At small fields, we obtain the structure already known to be optimal, an incommensurate (IC) spiral with wave vector q in the layers. At higher fields, we find a staircase of long-period commensurate (C) phases (separated initially by the low-field IC phase), then two narrow IC phases, then a fourth IC phase (also with intermediate C phases), and finally the ferromagnetically aligned phase at the saturation field H_S. The three-sublattice C states familiar from the theory of the triangular antiferromagnet are never optimal. The C phases and the two intermediate IC phases were previously unknown in this context. The magnetization is discontinuous at a field \approx 0.4H_S, in qualitative agreement with experiment, though we find much fine structure not reported.Comment: 9 pages, 8 figure

Oblique triangular antiferromagnetic phase in CsCu1−x_{1-x}Cox_xCl3_3

The spin-1/2 stacked triangular antiferromagnet CsCu$_{1-x}$Co$_x$Cl$_3$ with $0.015<x<0.032$ undergoes two phase transitions at zero field. The low-temperature phase is produced by the small amount of Co$^{2+}$ doping. In order to investigate the magnetic structures of the two ordered phases, the neutron elastic scattering experiments have been carried out for the sample with $x\approx 0.03$. It is found that the intermediate phase is identical to the ordered phase of CsCuCl$_3$, and that the low-temperature phase is an oblique triangular antiferromagnetic phase in which the spins form a triangular structure in a plane tilted from the basal plane. The tilting angle which is 42$^{\circ}$ at $T=1.6$ K decreases with increasing temperature, and becomes zero at $T_{\rm N2} =7.2$ K. An off-diagonal exchange term is proposed as the origin of the oblique phase.Comment: 6 pages, 7 figure

Fluctuation-induced phase in CsCuCl3 in transverse magnetic field: Theory

CsCuCl3 is a quantum triangular antiferromagnet, ferromagnetically stacked, with an incommensurate (IC) structure due to a Dzyaloshinskii-Moriya interaction. Because of the classical degeneracy caused by the frustration, fluctuations in CsCuCl3 have extraordinarily large effects, such as the phase transition in longitudinal magnetic field (normal to the planes, parallel to the IC wavenumber q) and the plateau in q in transverse field (perpendicular to q). We argue that fluctuations are responsible also for the new IC phase discovered in transverse field near the Neel temperature T_N, by T. Werner et al. [Solid State Commun. 102, p.609 (1997)]. We develop and analyse the corresponding minimal Landau theory; the effects of fluctuations on the frustration are included phenomenologically, by means of a biquadratic term. The Landau theory gives two IC phases, one familiar from previous studies; properties of the new IC phase, which occupies a pocket of the temperature-field phase diagram near T_N, agree qualitatively with those of the new phase found experimentally.Comment: 12 pages, revtex, 4 postscript figures, submitted to J. Phys: Condens. Matte

Polymerization of β-Propiolactone Initiated by Sodium Chloroaurate

Bulk polymerization of β-propiolactone (β-PL) initiated by sodium chloroautae (NaAuCl₄·2H₂O) at 30°C. was investigated. The polymerization initiated by NaAuCl₄·2H₂O is accelerated by photoirradiation similar to the polymerization of N-vinylcarbazole as mentioned in a previous paper. The time-conversion curve of the polymerization under photoirradiation reaches a dead end, particularly when the polymerization is carried out in a quartz vessel. The intial rate of polymerization is proportional to [Auᴵᴵᴵ]～1 in the light and [Auᴵᴵᴵ]～2 in the dark. From the effects of additives and solvents, and electronic spectroscopies, it is concluded that the polymerization is cationic initiated by charge transfer process from β-PL to the Auᴵᴵᴵ and/or the Auᴵᴵ species on other decomposition products of Auᴵᴵᴵ

IGF binding protein‐6 expression in vascular endothelial cells is induced by hypoxia and plays a negative role in tumor angiogenesis

Hypoxia stimulates tumor angiogenesis by inducing the expression of angiogenic molecules. The negative regulators of this process, however, are not well understood. Here, we report that hypoxia induced the expression of insulin‐like growth factor binding protein‐6 (IGFBP‐6), a tumor repressor, in human and rodent vascular endothelial cells (VECs) via a hypoxia‐inducible factor (HIF)‐mediated mechanism. Addition of human IGFBP‐6 to cultured human VECs inhibited angiogenesis in vitro . An IGFBP‐6 mutant with at least 10,000‐fold lower binding affinity for IGFs was an equally potent inhibitor of angiogenesis, suggesting that this action of IGFBP‐6 is IGF‐independent. The functional relationship between IGFBP‐6 and vascular endothelial growth factor (VEGF), a major hypoxia‐inducible angiogenic molecule, was examined. While VEGF alone increased angiogenesis in vitro , co‐incubation with IGFBP‐6 abolished VEGF‐stimulated angiogenesis. The in vivo role of IGFBP‐6 in angiogenesis was tested in flk1 :GFP zebrafish embryos, which exhibit green fluorescence protein in developing vascular endothelium, permitting visualization of developing blood vessels. Injection of human IGFBP‐6 mRNA reduced the number of embryonic inter‐segmental blood vessels by ∼40%. This anti‐angiogenic activity is conserved in zebrafish because expression of zebrafish IGFBP‐6b had similar effects. To determine the anti‐angiogenic effect of IGFBP‐6 in a tumor model, human Rh30 rhabdomyosarcoma cells stably transfected with IGFBP‐6 were inoculated into athymic BALB/c nude mice. Vessel density was 52% lower in IGFBP‐6‐transfected xenografts than in vector control xenografts. These results suggest that the expression of IGFBP‐6 in VECs is up‐regulated by hypoxia and IGFBP‐6 inhibits angiogenesis in vitro and in vivo .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90159/1/26201_ftp.pd

Electronic structure of Co_xTiSe_2 and Cr_xTiSe_2

The results of investigations of intercalated compounds Cr_xTiSe_2 and Co_xTiSe_2 by X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) are presented. The data obtained are compared with theoretical results of spin-polarized band structure calculations. A good agreement between theoretical and experimental data for the electronic structure of the investigated materials has been observed. The interplay between the M3d--Ti3d hybridization (M=Cr, Co) and the magnetic moment at the M site is discussed. A 0.9 eV large splitting of the core Cr2p{3/2} level was observed, which reveals a strong exchange magnetic interaction of 3d-2p electrons of Cr. In the case of a strong localization of the Cr3d electrons (for x<0.25), the broadening of the CrL spectra into the region of the states above the nominal Fermi level was observed and attributed to X-ray re-emission. The measured kinetic properties are in good accordance with spectral investigations and band calculation results.Comment: 14 pages, 11 figures, submitted to Phys.Rev.

Electrochemical anionic polymerization of 4‐vinylpyridine in pyridine

The preparation of poly‐4‐vinylpyridine (poly‐4VP) by electrochemical polymerization of 4‐vinylpyridine (4VP) in pyridine containing sodium tetraphenylboron (NaBPh 4 ) is described. Information on the influence of monomer concentration, current density, polymerization rate, molecular weight, and electrochemical efficiency is presented. The polymerizations were performed under conditions of constant electrolysis current. Polymer formed in the cathodic compartment only, where a red‐orange solution developed after about 15 min of electrolysis time. The optical absorption spectra of these colored solutions were studied. Cyclic voltammograms of 4VP in pyridine and NaBPh 4 are also reported, and the influence of the scan rate upon peak current is described. The results indicate that the polymerization was anionic and nonterminating. The characteristics of the electrochemical polymerization of 4VP in pyridine are compared with those of the same monomer in liquid NH 3 . In the former case, the catholyte was homogeneous, and polymer growth occurred in the liquid phase, while in the latter growth took place in a heterogeneous environment. Kinetic consequences of these physical differences are pointed out. Suggestions for the mechanism of this electrochemical initiation are advanced.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/100167/1/150080121_ftp.pd

Parenteral Nutrition Administration Leads to Specific Alterations in the Expression of Adipocytokines and Peroxisome Proliferator‐Activated Receptors in a Rat Model

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141876/1/jpen0329-sup-0001.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141876/2/jpen0329.pd

Laparoscopic ligation of a congenital extrahepatic portosystemic shunt for children with hyperammonemia: a single-institution experience

This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1007/s00595-018-1731-y.Purpose: A congenital extrahepatic portosystemic shunt (CEPS) associated with hyperammonemia requires occlusion of the shunt vessels. We evaluated the effectiveness and safety of laparoscopic ligation of a CEPS in children with hyperammonemia. Methods: The subjects of this retrospective study were seven children with hyperammonemia who underwent laparoscopic ligation of a CEPS. Their median age was 5.2 years (range 1–16 years). Before the laparoscopic procedure, a catheter was inserted through the femoral vein and placed in the portal vein via the shunt vessel. The shunt vessel was dissected and taped laparoscopically. After measuring the portal vein pressure under temporal occlusion, the shunt vessels were ligated. Results: The types of shunts according to location were patent ductus venosus (n = 2), splenorenal shunt (n = 2), gastrorenal shunt (n = 2), and superior mesenteric vein–inferior vena cava shunt (n = 1). Laparoscopic ligation of the shunt vessel was completed uneventfully in all patients. The median portal vein pressure was 19 mmHg after ligation. The median preoperative blood ammonia level was 94 µg/dL (range 71–259 µg/dL), which decreased after ligation in all patients. There was no incidence of postoperative liver failure. Conclusion: Laparoscopic ligation of a CEPS is safe and effective for children with hyperammonemia

Expression of candidate marker genes of sugar starvation is upregulated in growth-suppressed parthenocarpic cucumber fruit. Novel gene markers for sugar starvation in growth-suppressed cucumber fruit

To examine the physiological change in the growth suppression and abortion of parthenocarpic cucumber fruit, the expression of candidate marker genes of sugar starvation in relation to growth activity was examined. Fruits that failed to start exponential growth seemed to eventually abort. Hexose concentration of fruits was low in growth-suppressed fruit and increased in normally growing fruit consistent with the vacuolization. The correlation matrix indicated that the transcript levels of the genes, except CsaV3_6G046050 and CsaV3_5G032930, had a highly significant negative correlation with the relative growth rate in fruit length and had highly significant mutual positive correlations, suggesting that the asparagine synthetase gene, Cucumis sativus putative CCCH-type zinc finger protein CsSEF1, C. sativus BTB/POZ domain-containing protein At1g63850-like, CsaV3_3G000800, CsaV3_3G041280, and CsaV3_7G032930 are good markers of sugar starvation in cucumber fruit. The expression of candidate marker genes together with the hexose analysis strongly suggests that severe sugar starvation is occurring in growth-suppressed fruit