Dynamical Order and Superconductivity in a Frustrated Many-Body System.

In triangular lattice structures, spatial anisotropy and frustration can lead to rich equilibrium phase diagrams with regions containing complex, highly entangled states of matter. In this work, we study the driven two-rung triangular Hubbard model and evolve these states out of equilibrium, observing how the interplay between the driving and the initial state unexpectedly shuts down the particle-hole excitation pathway. This restriction, which symmetry arguments fail to predict, dictates the transient dynamics of the system, causing the available particle-hole degrees of freedom to manifest uniform long-range order. We discuss implications of our results for a recent experiment on photoinduced superconductivity in κ-(BEDT-TTF)_{2}Cu[N(CN)_{2}]Br molecules.

Heating-Induced Long-Range η Pairing in the Hubbard Model.

We show how, upon heating the spin degrees of freedom of the Hubbard model to infinite temperature, the symmetries of the system allow the creation of steady states with long-range correlations between η pairs. We induce this heating with either dissipation or periodic driving and evolve the system towards a nonequilibrium steady state, a process which melts all spin order in the system. The steady state is identical in both cases and displays distance-invariant off-diagonal η correlations. These correlations were first recognized in the superconducting eigenstates described in Yang's seminal Letter [Phys. Rev. Lett. 63, 2144 (1989)PRLTAO0031-900710.1103/PhysRevLett.63.2144], which are a subset of our steady states. We show that our results are a consequence of symmetry properties and entirely independent of the microscopic details of the model and the heating mechanism.

Evidence for warmer interglacials in East Antarctic ice cores.

Stable isotope ratios of oxygen and hydrogen in the Antarctic ice core record have revolutionized our understanding of Pleistocene climate variations and have allowed reconstructions of Antarctic temperature over the past 800,000 years (800 kyr; refs 1, 2). The relationship between the D/H ratio of mean annual precipitation and mean annual surface air temperature is said to be uniform +/-10% over East Antarctica and constant with time +/-20% (refs 3-5). In the absence of strong independent temperature proxy evidence allowing us to calibrate individual ice cores, prior general circulation model (GCM) studies have supported the assumption of constant uniform conversion for climates cooler than that of the present day. Here we analyse the three available 340 kyr East Antarctic ice core records alongside input from GCM modelling. We show that for warmer interglacial periods the relationship between temperature and the isotopic signature varies among ice core sites, and that therefore the conversions must be nonlinear for at least some sites. Model results indicate that the isotopic composition of East Antarctic ice is less sensitive to temperature changes during warmer climates. We conclude that previous temperature estimates from interglacial climates are likely to be too low. The available evidence is consistent with a peak Antarctic interglacial temperature that was at least 6 K higher than that of the present day -approximately double the widely quoted 3 +/- 1.5 K (refs 5, 6).

Immortalization and characterization of a Sertoli cell line from the adult rat.

To facilitate investigations of the regulation of adult Sertoli cell function, we have established a Sertoli cell line from sexually mature Sprague-Dawley rats. The cells were immortalized with the temperature-sensitive mutant of the SV40 virus, tsA255. The tsA255 large T antigen is heat-labile and efficiently promotes propagation of cells at 33 degrees C (permissive temperature) but is inactive at 40 degrees C (nonpermissive temperature). The established clonal Sertoli cell line (ASC-17D) proliferates indefinitely at the permissive temperature. However, within 48 h at the nonpermissive temperature, cell proliferation ceases. ASC-17D cells show positive staining with antibodies to cytokeratin and vimentin, consistent with the Sertoli cell origin of these cells. Transferrin and sulfated glycoprotein (SGP)-2 mRNAs were nearly undetectable in ASC-17D cells cultured at the permissive temperature, but expression of both mRNAs was induced at the nonpermissive temperature. In contrast, SGP-1 was expressed equally at both the permissive and nonpermissive temperatures. There was no increase in either transferrin or SGP-2 with FSH or dibutyryl cAMP (db-cAMP) treatment at the permissive temperature or with FSH treatment at the nonpermissive temperature. However, the steady-state levels of both of these mRNAs were substantially increased in the presence of db-cAMP at the nonpermissive temperature. In contrast, SGP-1 mRNA was not affected by either FSH or db-cAMP. These results suggest that the ASC-17D cell line is derived from adult Sertoli cells and may be useful for the study of adult Sertoli cell function.

Evidence for E-selectin complement regulatory domain mRNA splice variants in the rat.

The adhesion protein E-selectin is one mediator of endothelial cell-leukocyte interaction during acute inflammation. To investigate the molecular regulation of E-selectin function, we have examined the expression of E-selectin mRNA in target rat tissues after administration of lipopolysaccharide, a potent inducer of acute inflammation. In the course of these studies we isolated two unique rat E-selectin cDNA fragments. Both cDNA fragments show extensive nucleotide sequence homology to previously isolated mouse and human E-selectin cDNAs. However, they differ for the presence of sequences that encode complement regulatory domain-5 (CR5). Previous studies have shown that different animal species express E-selectin mRNAs that encode different numbers of CR domains. The isolation of these two rat E-selectin cDNA fragments, which differ only for the presence of CR5, represents the first direct evidence for the existence of E-selectin CR-variant mRNAs in the same species. Moreover, the sequence of the CR5(-) cDNA is consistent with its origin from an mRNA splice variant of a CR5(+) mRNA. We have demonstrated the presence of the two predicted mRNA species in rat heart tissue and have investigated their expression in response to lipopolysaccharide. Although both mRNA variants were greatly induced by lipopolysaccharide, the CR5(-) form was more abundant in both treated and control tissues. This difference in mRNA abundance may indicate different levels of CR5 variant proteins that perform functionally distinct tasks in E-selectin dependent inflammatory processes.

Chloracne and chloracnegens.

Chloracne, an acneform eruption resulting from poisoning by halogenated aromatic compounds, has been a considerable problem over the last 40 years. The condition is always a symptom of systemic poisoning and should be familiar to all practitioners, particularly dermatologists. It is difficult to treat and can last for long periods without known additional exposure to chloracnegens. Some chloracnegens are capable of causing a variety of systemic signs and symptoms and may be oncogenic. Although there are probably fewer than 4,000 persons with chloracne worldwide, those found with the disorder should be evaluated medically on a regular basis and followed, if possible, throughout their lives.

Aseptic (avascular) necrosis of the femoral head in psoriasis.

Aseptic (avascular) necrosis of the femoral head associated with psoriasis is reported. The clinical histories of nine patients with avascular necrosis of the femoral head and one patient with bilateral humeral head osteonecrosis are summarized. Psoriasis was the only associated condition found in three of the patients. Only two patients had received systemic corticosteroids in significant amounts (greater than 1 gm of prednisone). Four patients had received methotrexate therapy for psoriasis. Other possible contributing factors including serum uric acid levels are discussed. Psoriasis should be added to the list of systemic diseases associated with aseptic (avascular) necrosis. Avascular necrosis of the femoral head should be considered in any patient with psoriasis and pain in the hip or thigh.

Skin changes and lesions in our senior citizens: incidences.

One hundred and sixty-three community volunteers were interviewed and examined. After a decade, the 69 survivors were again interviewed and examined. The incidences of their skin changes and lesions were recorded and interrelationships sought relative to internal and external signs of aging. Asteatosis of moderate or severe degree, large numbers of scrotal angiomas in men, and retention of nevi appeared to be associated with a relatively shortened life expectancy and may be signs of decline and approaching death in older individuals.

Is methotrexate therapy for psoriasis carcinogenic? A modified retrospective-prospective analysis.

The use of methotrexate in psoriasis has recently been questioned because of possible carcinogenic potential. Two hundred twenty-four patients began methotrexate therapy during 1960 to 1965 at the Cleveland Clinic and at Duke University Medical Center. The incidence of malignant neoplasms and mortality has been studied in 205 of these 224 patients. Mortality increased with hepatic disease. No increased incidence of total internal malignancy was found, nor did any one type of neoplasm appear predominant.