Quenched lattice fluctuations in optically driven SrTiO3.

Crystal lattice fluctuations, which are known to influence phase transitions of quantum materials in equilibrium, are also expected to determine the dynamics of light-induced phase changes. However, they have only rarely been explored in these dynamical settings. Here we study the time evolution of lattice fluctuations in the quantum paraelectric SrTiO3, in which mid-infrared drives have been shown to induce a metastable ferroelectric state. Crucial in these physics is the competition between polar instabilities and antiferrodistortive rotations, which in equilibrium frustrate the formation of long-range ferroelectricity. We make use of high-intensity mid-infrared optical pulses to resonantly drive the Ti-O-stretching mode at 17 THz, and we measure the resulting change in lattice fluctuations using time-resolved X-ray diffuse scattering at a free-electron laser. After a prompt increase, we observe a long-lived quench in R-point antiferrodistortive lattice fluctuations. Their enhancement and reduction are theoretically explained by considering the fourth-order nonlinear phononic interactions to the driven optical phonon and third-order coupling to lattice strain, respectively. These observations provide a number of testable hypotheses for the physics of light-induced ferroelectricity.

Ultrafast Suppression of the Ferroelectric Instability in KTaO_{3}.

We use an x-ray free-electron laser to study the lattice dynamics following photoexcitation with ultrafast near-UV light (wavelength 266 nm, 50 fs pulse duration) of the incipient ferroelectric potassium tantalate, KTaO_{3}. By probing the lattice dynamics corresponding to multiple Brillouin zones through the x-ray diffuse scattering with pulses from the Linac Coherent Light Source (LCLS) (wavelength 1.3 Å and <10 fs pulse duration), we observe changes in the diffuse intensity associated with a hardening of the transverse acoustic phonon branches along Γ to X and Γ to M. Using force constants from density functional theory, we fit the quasiequilibrium intensity and obtain the instantaneous lattice temperature and density of photoexcited charge carriers. The density functional theory calculations demonstrate that photoexcitation transfers charge from oxygen 2p derived π-bonding orbitals to Ta 5d derived antibonding orbitals, further suppressing the ferroelectric instability and increasing the stability of the cubic, paraelectric structure.

Direct Observation of Coherent Longitudinal and Shear Acoustic Phonons in TaAs Using Ultrafast X-Ray Diffraction.

Using femtosecond time-resolved x-ray diffraction, we investigated optically excited coherent acoustic phonons in the Weyl semimetal TaAs. The low symmetry of the (112) surface probed in our experiment enables the simultaneous excitation of longitudinal and shear acoustic modes, whose dispersion closely matches our simulations. We observed an asymmetry in the spectral line shape of the longitudinal mode that is notably absent from the shear mode, suggesting a time-dependent frequency chirp that is likely driven by photoinduced carrier diffusion. We argue on the basis of symmetry that these acoustic deformations can transiently alter the electronic structure near the Weyl points and support this with model calculations. Our study underscores the benefit of using off-axis crystal orientations when optically exciting acoustic deformations in topological semimetals, allowing one to transiently change their crystal and electronic structures.

Beneficial changes on plasma apolipoproteins A and B, high density lipoproteins and oxidized low density lipoproteins in obese women after bariatric surgery: comparison between gastric bypass and sleeve gastrectomy.

BACKGROUND: The beneficial effects in lipid profiles after obesity surgery might be associated with the decrease in cardiovascular risk. However, direct comparison between different surgical techniques has not been extensively performed. METHODS: In the present study we compare 20 obese women submitted to laparoscopic Roux en Y gastric bypass (RYGB) with 20 women submitted to sleeve gastrectomy (SG). Twenty control women matched for age and baseline cardiovascular risk were also included. Both patients and controls were followed up for 1 year after surgery or conventional treatment with diet and exercise, respectively. Lipid profiles were measured at baseline, 6 and 12 months later. Carotid intima-media thickness was measured by ultrasonography at baseline and at the end of the study. RESULTS: Women submitted to bariatric surgery showed a decrease in total cholesterol, triglycerides, oxidized-LDL and ApoB, and an increase in HDL and ApoA concentrations that occurred regardless of the surgical procedure. LDL concentrations, however, decreased only after RYGB whereas Lp(a) showed no changes. We did not observe any correlation between the changes in serum lipid concentrations and those in carotid intima-media thickness. CONCLUSIONS: Sleeve gastrectomy and gastric bypass induce a similar beneficial effect on serum lipids in women with high cardiovascular risk 1 year after surgery.

Observation of a Charge Density Wave Incommensuration Near the Superconducting Dome in Cu_{x}TiSe_{2}.

X-ray diffraction was employed to study the evolution of the charge density wave (CDW) in Cu_{x}TiSe_{2} as a function of copper intercalation in order to clarify the relationship between the CDW and superconductivity. The results show a CDW incommensuration arising at an intercalation value coincident with the onset of superconductivity at around x=0.055(5). Additionally, it was found that the charge density wave persists to higher intercalant concentrations than previously assumed, demonstrating that the CDW does not terminate inside the superconducting dome. A charge density wave peak was observed in samples up to x=0.091(6), the highest copper concentration examined in this study. The phase diagram established in this work suggests that charge density wave incommensuration may play a role in the formation of the superconducting state.

Differential effects of clozapine and haloperidol on dopamine receptor mRNA expression in rat striatum and cortex.

The regulation of the dopamine (DA) receptors is of considerable interest, in part because treatment with antipsychotic drugs is known to upregulate striatal D2-like receptors. While previous studies have focused on the regulation of striatal DA receptors, less is known about the pharmacological regulation of cortical DA receptors. The purpose of this study was to examine the regulation of DA mRNA receptor expression in the cortex compared to the striatum following treatment with antipsychotic agents. Adult male Sprague-Dawley rats were injected daily with haloperidol (2 mg/kg/day), clozapine (20 mg/kg/day) or a control vehicle for a period of 14 days. Following treatment, brains were subjected to in situ hybridization for the mRNAs encoding the five dopamine receptors; only D1, D2, and D3 receptor mRNAs were detected in these regions. Haloperidol tended to either modestly upregulate or have no effect on dopamine receptor mRNAs detected in striatal structures, while clozapine generally downregulated these mRNAs. On the other hand, in the cortex, both drugs had striking effects on D1 and D2 mRNA levels. Cortical D1 mRNA was upregulated by haloperidol, but this effect was primarily restricted to cingulate cortex; clozapine also upregulated D1 mRNA, but primarily in parietal regions. Haloperidol downregulated D2 mRNA in the majority of cortical regions, but most dramatically in frontal and cingulate regions; clozapine typically upregulated this mRNA, but primarily in regions other than frontal and cingulate cortex. These results indicate that clozapine and haloperidol each have regionally-specific effects, and differentially regulate dopamine receptor mRNA expression in striatal and cortical regions of the rat brain.

Haloperidol disrupts lipid rafts and impairs insulin signaling in SH-SY5Y cells.

Haloperidol exerts its therapeutic effects basically by acting on dopamine receptors. We previously reported that haloperidol inhibits cholesterol biosynthesis in cultured cells. In the present work we investigated its effects on lipid-raft composition and functionality. In both neuroblastoma SH-SY5Y and promyelocytic HL-60 human cell lines, haloperidol inhibited cholesterol biosynthesis resulting in a decrease of the cell cholesterol content and the accumulation of different sterol intermediates (7-dehydrocholesterol, zymostenol and cholesta-8,14-dien-3beta-ol) depending on the dose of the drug. As a consequence, the cholesterol content in lipid rafts was greatly reduced, and several pre-cholesterol sterols, particularly cholesta-8,14-dien-3beta-ol, were incorporated into the cell membrane. This was accompanied by the disruption of lipid rafts, with redistribution of flotillin-1 and Fyn and the impairment of insulin-Akt signaling. Supplementing the medium with free cholesterol abrogated the effects of haloperidol on lipid-raft composition and functionality. LDL (low-density lipoprotein), a physiological vehicle of cholesterol in plasma, was much less effective in preventing the effects of haloperidol, which is attributed to the drug's inhibition of intracellular vesicular trafficking. These effects on cellular cholesterol homeostasis that ultimately result in the alteration of lipid-raft-dependent insulin signaling action may underlie some of the metabolic effects of this widely used antipsychotic.

Comportamiento de la infeccion hospitalaria en los hospitales de Ciudad de La Habana. Ano 1980. / Behavior of hospital infection in the hospitals of Habana city. Year 1980

Se realiza una revision de la informacion obtenida, de los diferentes Comites de prevencion y control de la infeccion intrahospitalaria de Ciudad de La Habana correspondiente al ano 1980, a fin de conocer cual ha sido la incidencia reportada por los diferentes servicios hospitalarios Estas cifras se comparan con las del ano 1979 y se constata que la infeccion intrahospitalaria constituye un problema de salud que despierta el interes y obliga al conocimiento y uso de la misma por parte del internista