Mode-Selective Coupling of Coherent Phonons to the Bi2212 Electronic Band Structure.

Cuprate superconductors host a multitude of low-energy optical phonons. Using time- and angle-resolved photoemission spectroscopy, we study coherent phonons in Bi_{2}Sr_{2}Ca_{0.92}Y_{0.08}Cu_{2}O_{8+δ}. Sub-meV modulations of the electronic band structure are observed at frequencies of 3.94±0.01 and 5.59±0.06 THz. For the dominant mode at 3.94 THz, the amplitude of the band energy oscillation weakly increases as a function of momentum away from the node. Theoretical calculations allow identifying the observed modes as CuO_{2}-derived A_{1g} phonons. The Bi- and Sr-derived A_{1g} modes which dominate Raman spectra in the relevant frequency range are absent in our measurements. This highlights the mode selectivity for phonons coupled to the near-Fermi-level electrons, which originate from CuO_{2} planes and dictate thermodynamic properties.

Band-Resolved Imaging of Photocurrent in a Topological Insulator.

We study the microscopic origins of photocurrent generation in the topological insulator Bi_{2}Se_{3} via time- and angle-resolved photoemission spectroscopy. We image the unoccupied band structure as it evolves following a circularly polarized optical excitation and observe an asymmetric electron population in momentum space, which is the spectroscopic signature of a photocurrent. By analyzing the rise times of the population we identify which occupied and unoccupied electronic states are coupled by the optical excitation. We conclude that photocurrents can only be excited via resonant optical transitions coupling to spin-orbital textured states. Our work provides a microscopic understanding of how to control photocurrents in systems with spin-orbit coupling and broken inversion symmetry.

Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser.

The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a "coherent lock-in" measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.

Comb mode filtering silver mirror cavity for spectroscopic distance measurement.

In this work we present a design of an external optical cavity based on Fabry-Perot etalons applied to a 100 MHz Er-doped fiber optical frequency comb working at 1560 nm to increase its repetition frequency. A Fabry-Perot cavity is constructed based on a transportable cage system with two silver mirrors in plano-concave geometry including the mode-matching lenses, fiber coupled collimation package and detection unit. The system enables full 3D angle mirror tilting and x-y off axis movement as well as distance between the mirrors. We demonstrate the increase of repetition frequency by direct measurement of the beat frequency and spectrally by using the virtually imaged phased array images.

Inequivalence of Single-Particle and Population Lifetimes in a Cuprate Superconductor.

We study optimally doped Bi-2212 (T(c)=96 K) using femtosecond time- and angle-resolved photoelectron spectroscopy. Energy-resolved population lifetimes are extracted and compared with single-particle lifetimes measured by equilibrium photoemission. The population lifetimes deviate from the single-particle lifetimes in the low excitation limit by 1-2 orders of magnitude. Fundamental considerations of electron scattering unveil that these two lifetimes are in general distinct, yet for systems with only electron-phonon scattering they should converge in the low-temperature, low-fluence limit. The qualitative disparity in our data, even in this limit, suggests that scattering channels beyond electron-phonon interactions play a significant role in the electron dynamics of cuprate superconductors.

Distinguishing bulk and surface electron-phonon coupling in the topological insulator Bi(2)Se(3) using time-resolved photoemission spectroscopy.

We report time- and angle-resolved photoemission spectroscopy measurements on the topological insulator Bi(2)Se(3). We observe oscillatory modulations of the electronic structure of both the bulk and surface states at a frequency of 2.23 THz due to coherent excitation of an A(1g) phonon mode. A distinct, additional frequency of 2.05 THz is observed in the surface state only. The lower phonon frequency at the surface is attributed to the termination of the crystal and thus reduction of interlayer van der Waals forces, which serve as restorative forces for out-of-plane lattice distortions. Density functional theory calculations quantitatively reproduce the magnitude of the surface phonon softening. These results represent the first band-resolved evidence of the A(1g) phonon mode coupling to the surface state in a topological insulator.

Superconducting graphene sheets in CaC6 enabled by phonon-mediated interband interactions.

There is a great deal of fundamental and practical interest in the possibility of inducing superconductivity in a monolayer of graphene. But while bulk graphite can be made to superconduct when certain metal atoms are intercalated between its graphene sheets, the same has not been achieved in a single layer. Moreover, there is a considerable debate about the precise mechanism of superconductivity in intercalated graphite. Here we report angle-resolved photoelectron spectroscopy measurements of the superconducting graphite intercalation compound CaC6 that distinctly resolve both its intercalant-derived interlayer band and its graphene-derived π* band. Our results indicate the opening of a superconducting gap in the π* band and reveal a substantial contribution to the total electron-phonon-coupling strength from the π*-interlayer interband interaction. Combined with theoretical predictions, these results provide a complete account for the superconducting mechanism in graphite intercalation compounds and lend support to the idea of realizing superconducting graphene by creating an adatom superlattice.

Direct optical coupling to an unoccupied dirac surface state in the topological insulator Bi2Se3.

We characterize the occupied and unoccupied electronic structure of the topological insulator Bi2Se3 by one-photon and two-photon angle-resolved photoemission spectroscopy and slab band structure calculations. We reveal a second, unoccupied Dirac surface state with similar electronic structure and physical origin to the well-known topological surface state. This state is energetically located 1.5 eV above the conduction band, which permits it to be directly excited by the output of a Ti:sapphire laser. This discovery demonstrates the feasibility of direct ultrafast optical coupling to a topologically protected, spin-textured surface state.

Ultrafast optical excitation of a persistent surface-state population in the topological insulator Bi2Se3.

Using femtosecond time- and angle-resolved photoemission spectroscopy, we investigated the nonequilibrium dynamics of the topological insulator Bi2Se3. We studied p-type Bi2Se3, in which the metallic Dirac surface state and bulk conduction bands are unoccupied. Optical excitation leads to a metastable population at the bulk conduction band edge, which feeds a nonequilibrium population of the surface state persisting for >10 ps. This unusually long-lived population of a metallic Dirac surface state with spin texture may present a channel in which to drive transient spin-polarized currents.

Correlations of somatophysiological, biochemical, psychosocial and behavioral risk factors of cardiovascular diseases in a sample of employees of Prague enterprises and institutions.

The study is aimed at the detection and intervention of risk factors for cardiovascular diseases (CVD) and at the part played by stress in their development. The methods applied are designed to eliminate the risks and, simultaneously, to identify the function of the two main parts of stress reaction, i.e., in terms of the extent, level and type of the stressors experienced, and in terms of the level of mental resilience and related psychosocial factors which affect the experiencing of and coping with stress. The purpose of medical examination based on the patient's history, subjective complaints and objective tests, including a study of dietary habits and psychological methods was to establish the status praesens and identify the main risk factors and symptoms leading to ischemic heart disease (IHD). Intervention was performed in subjects with increased cardiovalscular risk factors.

Ribose supplementation in maximally exercising Thoroughbreds.

A diverse group of studies, which are equine exclusive, indicate that ribose administered to myocardial and skeletal muscle tissue stimulates ATP production and recovery. This study investigated the effects of ribose supplementation on blood and muscle metabolites and performance in Thoroughbred geldings performing a maximal treadmill standardised exercise test (SET). In Experiment 1, 6 conditioned Thoroughbred geldings performed a baseline SET and horses were assigned to one of 2 experimental treatment groups, placebo or ribose, based on VO2max. The placebo treatment group received 0.07 g glucose/kg bodyweight (bwt) and ribose treatment group received 0.07 g ribose/kg bwt top dressed on the feed twice daily. Following a 2 week treatment period, a second SET was performed. After a one-week washout period, the horses switched treatment groups. Following another 2 week treatment period, a third SET was performed. Blood ammonia-N was lower in the ribose treatment group at 15 min (P = 0.06) and 30 min (P = 0.02) postexercise. Plasma lactic acid was lower in the ribose treatment group at 30 min postexercise (P = 0.07). In Experiment 2, 1 h before a SET, 2 horses received 3 l water (control) and 3 horses 250 g of ribose dissolved in 3 l water (single ribose dose) via a nasogastric tube. Following a 2 week washout period, the horses switched treatment groups and another SET was performed. There were no differences in blood ammonia-N, plasma lactic acid or glucose between treatment groups. No differences in performance were detected between treatment groups in either experiment. In conclusion, the results from Experiment 1 show a trend that daily ribose supplementation may be beneficial during recovery from exercise. However, a single dose of ribose 1 h before exercise revealed no effect on the variables measured. Because moderate to intense daily exercise can cause a decrease in total adenine nucleotide (TAN) pool with no meaningful recovery even after 72 h rest, future experiments should be designed to futher elucidate the effects of ribose supplementation on TAN metabolism in horses exercising at high intensity.

A revised coil for the external cooling of the kidney.

The authors describe a coil they have developed for contact peroperative hypothermia of the kidney. This new type of coil eliminates the disadvantages of existing cooling coils, namely slow thermal transfer from kidney to cooling agent due to imperfect contact between the coil and the concave surface of the kidney, use of an inadequately conductive material and thermal losses from the outer surface of the coil. Special features of the coil described here include its construction to match the contours of the kidney, isolation of external shell to reduce thermal losses and continuous monitoring of renal tissue to reduce the danger of overcooling.

Comparative pharmacokinetics and pharmacodynamics of epoetin alfa and epoetin beta.

Different recombinant human erythropoietin products have been developed. Although they appear to have similar pharmacokinetics and function, these have not been directly compared. This randomized, double-blind, four-period crossover study compared the pharmacokinetics and pharmacodynamics of intravenous and subcutaneous epoetin alfa and epoetin beta in 18 normal male volunteers. As a control, three subjects received placebo treatment. After intravenous administration, the steady-state volume of distribution and beta-phase volume of distribution of epoetin beta were 7.7% and 16.9% larger than for epoetin alfa (p less than 0.05). The terminal elimination half-life after intravenous administration of epoetin beta was 20% longer than the terminal elimination half-life of epoetin alfa. After subcutaneous administration there was a delayed drug absorption with epoetin beta compared with epoetin alfa (p less than 0.05). There was a small but significantly greater absolute reticulocyte response after subcutaneous epoetin beta compared with subcutaneous epoetin alfa. The findings support differences in the pharmacokinetics and function of epoetin alfa and beta that are possibly caused by differences in their glycosylation.

[Computer tomography in the diagnosis of hyperparathyroidism]. / Výpocetní tomografie v diagnostice hyperparathyreoidismu.

The paper presents long-term experience in the diagnosis of hyperparathyroidism by means of computer tomography. A large number of examinations (164) of parathyroid glands, the possibility of verification and comparison with sonography or with other diagnostic methods of visualization make it possible to define the role of computer tomography in hyperparathyroidism and to show advantages and limitations of the method. For the high diagnostic precision the CT examination may be considered to be the reliable method in the demonstration of enlarged parathyroid glands.

[Reconstructive procedures in war injuries of the larynx and trachea]. / Rekonstrukcní výkony po válecných poraneních hrtanu a prudusnice.

In recent years the authors operated three casualties from non-European battlefields with severe laryngotracheal stenoses due to war injuries. Median laryngotomy (thyrocricotracheotomy) made a revision and modification of the internal injury possible. An implanted tube from a vascular prosthesis, packed in Hydron kept the replaced cartilaginous cross bar and possibly mucous grafts from a gingivobuccal fold in the correct position. A cross bar made from a cartilaginous or bony portion of a rib also dilated the lumen. It was kept in position by the perichondrium of the cartilaginous cross bar sutured to the margin of the mucosal remnants. All three patients were decannulated.

[Ultrasonography in the diagnosis of hyperparathyroidism]. / Ultrasonografie v diagnostice hyperparathyreoidismu.

Ultrasonography is a direct method of representation, giving various advantages over other methods in the examination of parathyroid glands: it is rapid, non-radiation and economically undemanding. Dynamic examination by means of the linear electronic transducer of 3.5 MHz and the use of water path was used in 37 patients. In 7 patients with primary hyperparathyroidism was the examination rapid and the pictures of the adenomas were persuasive. In 30 patients with secondary hyperparathyroidism were found characteristic pictures, if the glands were enlarged to 8 mm or more. For the diagnosis of smaller glands a high resolution transducer will be necessary. Histological finding was available in 21 patients undergoing operation, and easily available method and it is therefore the procedure of the first choice.

Review of cardiovascular findings in humans treated with minoxidil.

Minoxidil is an antihypertensive vasodilator with no known capability of inducing human cardiovascular pathology; however, the compound does cause a late, canine-specific lesion of the right atrium and acute right atrial and ventricular papillary muscle changes. In all the autopsy cases of minoxidil-treated humans to date, 9 cases were reported with significant right atrial or other cardiac pathology and were carefully reviewed for similarity to either the early or late canine lesion. Three new cases (G, H, and I) were added in this update to 6 cases already described. None of the 3 cases newly analyzed in this paper, as well as the previously reported 6 cases, had gross or histologic constellations which could be diagnosed as associated with minoxidil treatment. Further, the examination of autopsy cases of minoxidil-treated hypertensive right atrial histology findings appear no different than those found in the baseline non-minoxidil treated hypertensive and non-hypertensive cases.