Dynamically-Induced Frustration as a Route to a Quantum Spin Ice State in Tb2Ti2O7 via Virtual Crystal Field Excitations and Quantum Many-Body Effects

The Tb$_2$Ti$_2$O$_7$ pyrochlore magnetic material is attracting much attention for its {\em spin liquid} state, failing to develop long range order down to 50 mK despite a Curie-Weiss temperature $\theta_{\rm CW} \sim -14$ K. In this paper we reinvestigate the theoretical description of this material by considering a quantum model of independent tetrahedra to describe its low temperature properties. The naturally-tuned proximity of this system near a N\'eel to spin ice phase boundary allows for a resurgence of quantum fluctuation effects that lead to an important renormalization of its effective low energy spin Hamiltonian. As a result, Tb$_2$Ti$_2$O$_7$ is argued to be a {\em quantum spin ice}. We put forward an experimental test of this proposal using neutron scattering on a single crystal.Comment: 5 pages, 3 figures. Version 2 has a modified introduction. Figure 2b of version 1 (experimental neutron scattering has been removed. A proposal for an experimental test is now included accompanied by a new Figure (Fig. 3

Circulating Glycated Albumin and Glomerular Anionic Charges

Aiming to discern the mechanisms by which circulating glycated albumin alters the glomerular filtration properties that lead to glomerular dysfunction in diabetes, the authors studied the distribution and densities of anionic charges through the rat glomerular wall upon intravascular infusion of Amadori products, as well as in various conditions of increased glomerular permselectivity. Polylysine-gold was used as the probe to reveal the anionic charges. The study was carried on renal tissue sections of bovine serum albumin (BSA)- and glycated BSA–injected, normoglycemic animals. Results were generated through morphometrical evaluations of the gold labeling. Changes in glomerular anionic distribution were corroborated on renal tissue sections of short- and long-term diabetic rats and of normal newborn rats, situations known for abnormal glomerular filtration. Altered renal function in these conditions was clearly associated with changes in glomerular anionic charges. On the other hand, the infusion of glycated albumin in the circulation of normal rats, though altering glomerular filtration properties, did not modify the distribution and density of the polylysine-gold labeling through the glomerular basement membrane. Thus, anionic charges seem not to be the factor involved in the early changes of glomerular permeability induced by circulating glycated albumin

Financial Market Intermediaries and Information Asymmetry in Equity Markets

This dissertation examines the relationship between financial market intermediaries and information asymmetry. Chapters 5, 6, and 7 re-examines issues raised in the literature, but extends this research by using unique datasets not previously available to researchers. Overall, the results show that (i) market intermediaries help reduce information asymmetry in upstairs markets by filtering out information-motivated trades, (ii) market intermediaries produce information which is valuable to clients who are able to trade ahead of the market, and iii) market intermediaries are heterogeneously informed, and are therefore affected differently by a change in market structure

Analysis of protein complexes through model‐based biclustering of label‐free quantitative AP‐MS data

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102630/1/msb201041.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102630/2/msb201041-sup-0001.pd

Low temperature specific heat and possible gap to magnetic excitations in the Heisenberg pyrochlore antiferromagnet Gd2Sn207

The Gd2Sn2O7 pyrochlore Heisenberg antiferromagnet displays a phase transition to a four sublattice Neel ordered state at a temperature near 1 K. Despite the seemingly conventional nature of the ordered state, the specific heat has been found to be described in the temperature range 350-800 mK by an anomalous T-squared power law. A similar temperature dependence has also been reported for Gd2Ti2O7, another pyrochlore Heisenberg material. Such anomalous T-squared behavior in Cv has been argued to be correlated to an unusual energy-dependence of the density of states which also seemingly manifests itself in low-temperature spin fluctuations found in muon spin relaxation experiments. In this paper, we report calculations of Cv that consider spin wave like excitations out of the Neel order observed in Gd2Sn2O7 and argue that the parametric T-squared behavior does not reflect the true low-energy excitations of Gd2Sn2O7. Rather, we find that the low-energy excitations of this material are antiferromagnetic magnons gapped by single-ion and dipolar anisotropy effects, and that the lowest temperature of 350 mK considered in previous specific heat measurements accidentally happens to coincide with a crossover temperature below which magnons become thermally activated and Cv takes an exponential form. We argue that further specific heat measurements that extend down to at least 100 mK are required in order to ascribe an unconventional description of magnetic excitations out of the ground state of Gd2Sn2O7 or to invalidate the standard picture of gapped excitations proposed herein.Comment: 12 pages, 13 figures; shortened introduction and added 1 figur

Understanding Paramagnetic Spin Correlations in the Spin-Liquid Pyrochlore Tb2Ti2O7

Recent elastic and inelastic neutron scattering studies of the highly frustrated pyrochlore antiferromagnet Tb2Ti2O7 have shown some very intriguing features that cannot be modeled by the local classical Ising model, naively expected to describe this system at low temperatures. Using the random phase approximation to take into account fluctuations between the ground state doublet and the first excited doublet, we successfully describe the elastic neutron scattering pattern and dispersion relations in Tb2Ti2O7, semi-quantitatively consistent with experimental observations.Comment: revtex4, 4 pages, 1 Color+ 2 BW figure

PP4 is a γH2AX phosphatase required for recovery from the DNA damage checkpoint

Phosphorylation of histone H2AX on Ser 139 (γH2AX) is one of the earliest events in the response to DNA double-strand breaks; however, the subsequent removal of γH2AX from chromatin is less understood, despite being a process tightly coordinated with DNA repair. Previous studies in yeast have identified the Pph3 phosphatase (the PP4C orthologue) as important for the dephosphorylation of γH2AX. By contrast, work in human cells attributed this activity to PP2A. Here, we report that PP4 contributes to the dephosphorylation of γH2AX, both at the sites of DNA damage and in undamaged chromatin in human cells, independently of a role in DNA repair. Furthermore, depletion of PP4C results in a prolonged checkpoint arrest, most likely owing to the persistence of mediator of DNA damage checkpoint 1 (MDC1) at the sites of DNA lesions. Taken together, these results indicate that PP4 is an evolutionarily conserved γH2AX phosphatase