Enhanced triplet superconductivity in next-generation ultraclean UTe2.

The unconventional superconductor UTe[Formula: see text] exhibits numerous signatures of spin-triplet superconductivity-a rare state of matter which could enable quantum computation protected against decoherence. UTe[Formula: see text] possesses a complex phase landscape comprising two magnetic field-induced superconducting phases, a metamagnetic transition to a field-polarized state, along with pair- and charge-density wave orders. However, contradictory reports between studies performed on UTe[Formula: see text] specimens of varying quality have severely impeded theoretical efforts to understand the microscopic origins of the exotic superconductivity. Here, we report a comprehensive suite of high magnetic field measurements on a generation of pristine quality UTe[Formula: see text] crystals. Our experiments reveal a significantly revised high magnetic field superconducting phase diagram in the ultraclean limit, showing a pronounced sensitivity of field-induced superconductivity to the presence of crystalline disorder. We employ a Ginzburg-Landau model that excellently captures this acute dependence on sample quality. Our results suggest that in close proximity to a field-induced metamagnetic transition the enhanced role of magnetic fluctuations-that are strongly suppressed by disorder-is likely responsible for tuning UTe[Formula: see text] between two distinct spin-triplet superconducting phases.

Quantum Interference between Quasi-2D Fermi Surface Sheets in UTe_{2}.

UTe_{2} is a spin-triplet superconductor candidate for which high quality samples with long mean free paths have recently become available, enabling quantum oscillation measurements to probe its Fermi surface and effective carrier masses. It has recently been reported that UTe_{2} possesses a 3D Fermi surface component [Phys. Rev. Lett. 131, 036501 (2023)PRLTAO0031-900710.1103/PhysRevLett.131.036501]. The distinction between 2D and 3D Fermi surface sections in triplet superconductors can have important implications regarding the topological properties of the superconductivity. Here we report the observation of oscillatory components in the magnetoconductance of UTe_{2} at high magnetic fields. We find that these oscillations are well described by quantum interference between quasiparticles traversing semiclassical trajectories spanning magnetic breakdown networks. Our observations are consistent with a quasi-2D model of this material's Fermi surface based on prior dHvA-effect measurements. Our results strongly indicate that UTe_{2}-which exhibits a multitude of complex physical phenomena-possesses a remarkably simple Fermi surface consisting exclusively of two quasi-2D cylindrical sections.

Quasi-2D Fermi surface in the anomalous superconductor UTe2.

The heavy fermion paramagnet UTe2 exhibits numerous characteristics of spin-triplet superconductivity. Efforts to understand the microscopic details of this exotic superconductivity have been impeded by uncertainty regarding the underlying electronic structure. Here we directly probe the Fermi surface of UTe2 by measuring magnetic quantum oscillations in pristine quality crystals. We find an angular profile of quantum oscillatory frequency and amplitude that is characteristic of a quasi-2D Fermi surface, which we find is well described by two cylindrical Fermi sheets of electron- and hole-type respectively. Additionally, we find that both cylindrical Fermi sheets possess considerable undulation but negligible small-scale corrugation, which may allow for their near-nesting and therefore promote magnetic fluctuations that enhance the triplet pairing mechanism. Importantly, we find no evidence for the presence of any 3D Fermi surface sections. Our results place strong constraints on the possible symmetry of the superconducting order parameter in UTe2.

Positron annihilation spectroscopy study of radiation-induced defects in W and Fe irradiated with neutrons with different spectra.

The paper presents new knowledge on primary defect formation in tungsten (W) and iron (Fe) irradiated by fission and high-energy neutrons at near-room temperature. Using a well-established method of positron-annihilation lifetime-spectroscopy (PALS), it was found that irradiation of W in the fission reactor and by high-energy neutrons from the p(35 MeV)-Be generator leads to the formation of small radiation-induced vacancy clusters with comparable mean size. In the case of Fe, smaller mean size of primary radiation-induced vacancy clusters was measured after irradiation with fission neutrons compared to irradiation with high-energy neutrons from the p(35 MeV)-Be generator. It was found that one of the reasons of the formation of the larger size of the defects with lower density in Fe is lower flux in the case of irradiation with high-energy neutrons from the p(35 MeV)-Be source. The second reason is enhanced defect agglomeration and recombination within the energetic displacement cascade at high energy primary knock-on-atoms (PKAs). This is consistent with the concept of the athermal recombination corrected (arc-dpa) model, although the measured dpa cross-section of both fission neutrons and wide-spectrum high-energy neutrons in W is between the conventional Norgett-Robinson-Torrens (NRT-dpa) and arc-dpa predictions. This means that the physics of the primary radiation effects in materials is still not fully known and requires further study through a combination of modeling and experimental efforts. The present data serve as a basis for the development of an improved concept of the displacement process.

Pressure effect on the crystal lattice of unconventional superconductor UCoGe.

High-pressure techniques were used to determine the structural behaviour of the superconducting ferromagnet UCoGe up to 30 GPa enabling us to determine the link between the effect of pressure on the material magnetic properties and crystal structure. The TiNiSi type structure of UCoGe was preserved up to the highest pressure. The a direction, equivalent to the shortest U-U links, was identified as the critical soft direction. The data are compared with the structural variations in UCoGe α-hydride, which becomes non-magnetic and non-superconducting despite a volume expansion. We show that at least in this case, but probably more generally, the structure impact of hydrogenation is definitely not equivalent to negative pressure.

The effect of hydrogenation on magnetic interactions in CeNi.

The crystal structure and magnetic properties of CeNiH(3.7) were studied by means of powder x-ray diffraction, specific heat, and dc and ac magnetization techniques. It was established that hydrogenation stabilizes the 4f(1) state of Ce and turns CeNi-H into a dilute Kondo system with T(K) = 3.7 K. The Kondo screening in CeNiH(3.7) is suppressed by the applied magnetic field, although it still affects the properties of CeNiH(3.7) at 14 T, as indicated by the enhanced γ-coefficient of electronic specific heat, which remains more than twice as large as in the precursor compound CeNi. Its zero-field value is as high as 1890 mJ (mol K(2))(-1). Hydrogenation acts primarily as the negative pressure agent in CeNiH(3.7), while the role of H-metal bonding is secondary.

A comparison of measurements and CFD model predictions for pollutant dispersion in cities.

An accurate description of car movements in an urban area is required for accurate prediction of the air pollution concentration field. A 3-D Eulerian-Lagrangian approach to moving vehicles that takes into account the traffic-induced flow field and turbulence is presented. The approach is based on Computational Fluid Dynamics (CFD) calculations using Eulerian approach to the continuous phase and Lagrangian approach to the discrete phase of moving objects-vehicles. In the first part of the present contribution, the method is applied to pollutants dispersion in a city tunnel outlet in Brno and to a street structure in Hannover, Germany. In the second part, a model of traffic dynamics inside a street intersection in the centre of Brno is presented. This model accounts for the dynamics of traffic lights and a corresponding traffic-generated flow field and emissions in different time intervals during the traffic light sequence. All results of numerical modelling are compared with field measurements with very good agreement. A commercial CFD code StarCD was used into which the Lagrangian model and traffic dynamics model were integrated.

Catabolites of cholesterol synthesis pathways and forskolin as activators of the farnesoid X-activated nuclear receptor.

The nuclear receptors are a family of transcriptional mediators that, upon activation, bind DNA and regulate gene transcription. Among these receptors, the farnesoid X-activated receptor (FXR) has recently been identified as one activated by bile acids and farnesol. To investigate the potential of other sterols to activate FXR, as well as to examine relevant relationships among identified activators of FXR, the current study used a mammalian cell transcription assay to quantify and compare activation potential. In addition to the classical bile acids deoxycholate (DCA) and chenodeoxycholate (CDCA), FXR was shown to be transcriptionally active in the presence of the androgen catabolites 5alpha-androstan-3alpha-ol-17-one (androsterone) and 5beta-androstan-3alpha-ol-17-one (etiocholanolone), as well as the sterol bronchodilatory drug forskolin. Conversely, cholesterol and several other key precursors to the androgens and bile acids were either not active or only slightly active. Furthermore, it was observed that the bile acid ursodeoxycholate (UDCA) could inhibit DCA and CDCA activation of FXR in a manner parallel to its ability to antagonize DCA and CDCA induction of apoptosis. By far, the most efficacious activator of FXR was forskolin. Interestingly, although it is classically viewed as an initiator of the adenylate cyclase/protein kinase A (PKA) pathway, PKA inhibition did not inhibit forskolin's activation of FXR nor was cyclic AMP (cAMP) able to stimulate FXR-mediated transcription. These data would suggest that forskolin acts as a ligand for FXR rather than as a secondary activator of FXR and could have important implications with respect to its potential toxicity and pharmacological use.

Oxidative phenotype polymorphism (P450 2D6) and metabolism of toluene.

Oxidative phenotype P-450 2D6 was examined using sparteine test in 3 groups of persons to determine if there is a coincidence in the defect of the oxidative biotransformation of sparteine and impaired oxidation of toluene, which could explain interindividual differences in the amounts of hippuric acid in the urine in exposed persons. The following groups of persons were examined: 30 rotogravure printers exposed to toluene vapors at concentrations of 8-307 ppm; 20 workers, 2 months after the cessation of the long-term exposure to toluene at concentrations of 104-1,170 ppm; 48 healthy volunteers with no exposure to toluene. Among the 98 persons 5 poor metabolizers (PMs) of sparteine were found, none in the group of printers exposed to toluene. In the experimental exposure chamber 5 PMs and 6 extensive metabolizers (EMs) were exposed to toluene concentration of 245 ppm for 5 hours. Hippuric acid and o-cresol in the urine, and toluene both in blood and in alveolar air were measured. However, no significant differences were found in either of these parameters between the PM and EM groups. Thus, the sparteine test does not appear to be applicable in the identification of persons with higher risk arising from toluene exposure.

A graphical nomogram method for predicting toxic concentrations of unbound phenytoin.

The graphical nomogram method to estimate the phenytoin free concentration at any selected total serum phenytoin and/or albumin concentrations was applied using Scatchard binding equation. The binding parameters were calculated by the non-linear least-squares regression analysis of the binding data collected from 96 outpatients on common anticonvulsant therapy. Free phenytoin concentration was measured by the Amicon multi-micro ultrafiltration system. The mean values of N and Kapp were found to be: N = 1.03, and Kapp = 18,500 (M-1). Correlation coefficient for relationship between measured and predicted free phenytoin concentrations was very good (r = 0.94), but the results of prediction-error analysis (MPE = 0.153, and RMSE = 0.296) show that the nomogram method overpredicts the measured free phenytoin (PHT) concentration approximately about 10% higher (15-30 mg/l) than serum phenytoin levels.

[Use of diffusion methods in the determination of sensitivity of medically important micromycetes]. / Moznosti vyuzití difúzní metody pri stanovení citlivosti medicínsky významných mikromycetu.

The authors evaluated the sensitivity of 35 strains of mycotic agents to eight antifungal preparations, using two methods: the diffuse disc test and the method of assessment of the MIC in a liquid medium. On comparison of results obtained by the two methods they reached the conclusion that the diffuse disc method makes possible only orientation as regards sensitivity and does not fully correlate with the results of MIC. Some strains with MIC values at the sensitivity level seemed resistant according to the disc test. From a total of seven agar media used for the disc test only two were suitable: the medium with casitone and Sabouraud's glucose agar. In particular on the former there were inhibition zones round the discs which were easiest to evaluate and which were constant at different incubation temperatures.

A comparison of haemocoagulation tests in the experimental endotoxin model DIC and in rats whole-body irradiated by 250 Gy.

Based on comparing results of tests followed in the present work between the endotoxin model of the disseminated intravascular coagulation (DIC) and irradiated groups of rats we consider that after the whole-body irradiation by a high dose of 250 Gy, the DIC occurs, in spite of the fact that the first stage--hypercoagulation condition, can be hardly observed. In the experimental endotoxin model, an increase of activated partial thromboplastin test (APTT) values and prolongation of the thrombin time was observed up to 24 hours in both endotoxin doses. After both endotoxin doses, the fibrinogen level was transiently decreased with its subsequent increase. The fibrin monomers correspond to decreasing the fibrinogen level. After the first dose, they were positive between the 3rd and 12th hours and after the second dose, the positivity was observed 6 hours after the application. The antithrombin III level was decreased after 12 hours in both endotoxin doses. The thrombocyte count was considerably reduced already from the 6th hour after administering endotoxin to the end of the experiment. Considerable changes of the thrombocyte aggregation were observed only 3 hours after administering the second dose. When comparing the resulting values of these tests with values observed in irradiated animals, then we can see a certain agreement in the nature of the changes after the exposure to 250 Gy. The fibrinogen level was transiently decreased 3 hours after irradiation, when considerable changes in the thrombocyte aggregation also occurred.

[Relation between lipid-bound sialic acid in blood serum and plasma andin human tumors]. / Vztah lipidicky vázané kyseliny sialové v krevním séru a plazme k lidským nádorum.

Athymic mice with transplanted osteosarcoma and carcinoma of the rectum were found to have increased blood plasma levels of lipid-bound sialic acid (LSA). To verify the applicability of the method of LSA determination, patients with cancer of the mammary gland, rectum, and colon were examined for their LSA level. The serum LSA level was significantly increased in patients with cancer of the mammary gland and rectum, compared to levels determined in the serum of healthy volunteers. The serum LSA level elevation was even more pronounced in patients with carcinoma of the colon. In patients with carcinoma of the colon who were in remission at the time of blood collection the serum LSA level was found to be reduced to control values.

Determination of ethyl biscoumacetate and its metabolite 7-hydroxyethyl biscoumacetate in human serum by high-performance liquid chromatography and mass spectrometry.

An efficient reversed-phase high-performance liquid chromatographic method has been developed for the determination of ethyl biscoumacetate (EBA) and its metabolite in human serum, using the mu Bondapak C18 column and methanol-water-phosphoric acid (56:46.8:0.2, v/v/v) as the mobile phase. This method permitted the determination of both EBA and a metabolite in human serum. The latter has been mentioned by other authors only in urine samples, where significant concentrations were found. Identification of the metabolite as 7-hydroxyethyl biscoumacetate was based on its chromatographic separation, followed by isolation from the eluate and direct mass spectrometric identification. It has been found that the higher EBA concentrations in human serum described by Brodie et al. [J. Pharmacol. Exp. Ther., 106 (1952) 453] were caused by the insufficient resolving power of the spectrophotometric method used, leading to overlapping of the UV spectra of the parent drug and its metabolite.

Binding parameters of phenytoin during monotherapy and polytherapy.

The present in vivo study elucidated the effect of other commonly comedicated drugs on the phenytoin (PHT) Scatchard binding parameters. Specimens of 150 epileptic patients chronically treated with anticonvulsant drugs were analyzed. The results of covariance analysis suggest that phenobarbitone, ethosuximide, diazepam and folic acid do not alter binding of PHT to serum albumin. The contribution of carbamazepine and medazepam to the free fraction of PHT (decrease of about 0.4%) and/or Scatchard binding capacity (increase of about 1/3) is ambiguous and not statistically significant at the p less than 0.05 level. On the contrary, we found a statistically significant decrease of PHT binding in patients comedicated with valproic acid (VPA) and primidone (PRM). The decrease of about 25% in binding capacity evoked an increase of about 1% (VPA), and 1.5% (PRM), respectively in PHT free fraction.

[Binding of phenytoin to serum albumin in vitro and in vivo]. / Studium vazby fenytoinu na sérový albumin v podmínkách in vitro a in vivo.

The present paper describes an ultrafiltration method of determination of the concentration of free phenytoin (DPH) in serum and its use for the study of the binding equilibrium phenytoin--albumin. The procedure was employed to determine the binding affinity of serum albumin (a) in a group of healthy volunteers (n = 8) in in vitro conditions, (b) in a group of healthy volunteers (a mixed serum, n = 6) and (c) in a group of patients suffering from epilepsy with fits of the generalized type grand mal (n = 15) in in vivo conditions. The calculation of binding parameters was carried out by the method of nonlinear regression analysis with the use of the one-parameter Scatchard's model of the bond. Binding activity of serum albumin in the volunteers of group (a) was N.Ka = 17,500 l/mol, group (b) N.Ka = 18,700 l/mol, and in patients with epilepsy n.Ka = 19,200 l/mol. The results of covariational analysis demonstrated good agreement in the binding parameters of all three groups under study. The paper also discusses the suitability of the binding model used and the mathematical processing and possible use of the binding parameters measured in in vitro conditions for the estimation of the value of the free fraction of the drug in patients with epilepsy.

[Changes in platelet aggregation and cAMP levels in isolated blood platelets in rats after 5.0 Gy and 10.0 Gy whole-body irradiation doses]. / Zmeny agregace krevních desticek a hladiny cAMP v izolovaných krevních destickách u celotelove ozárených potkanu dávkami 5.0 Gy a 10.0 Gy.

Rats were subjected to whole-body irradiation with doses of 5.0 Gy and 10.0 Gy. After intervals of 1.5 hours, 3, 6, 12 and 24 hours following irradiation the authors tested the aggregation capacity of thrombocytes after induction with adenosine--5--diphosphate and the cAMP level in isolated thrombocytes. Statistically significant differences between experimental and control groups were found particularly at some time intervals in rats irradiated with 10.0 Gy. The authors found a significant acceleration of the time of maximal aggregation at time intervals of 3.6 and 24 hours following irradiation with 10.0 Gy. Only at the time interval of 3 hours after irradiation with 10 Gy a statistically significant reduction of the maximum aggregation, as compared with the control group, occurred, and similarly the tang alpha value indicates that also the initial rate of aggregation was lower. The cAMP level in isolated thrombocytes was markedly reduced in particular after 5.0 Gy already during the early intervals after irradiation. A temporary increase of the cAMP levels was recorded 3 hours after irradiation with 10.0 Gy which may explain the reduced aggregation capacity of thrombocytes found during the same time interval. The results of both tests are not sufficient evidence of a hypercoagulation state after irradiation with the mentioned doses within 24 hours after irradiation.

[Torulopsis glabrata. Morphologic characteristics, biotyping and sensitivity to isolates of antifungal agents in vitro]. / Torulopsis glabrata. Morfologické vlastnosti, biotypizace a citlivost izolátu k antifungálním preparátum in vitro.

The authors described morphological and biochemical properties of twenty strains of Torulopsis glabrata and two strains of T. candida and T. sphaerica, mostly of human origin. By means of eight biotyping tests based on the evaluation of so-called resistograms the isolates of T. glabrata were divided into eight biotypes. The authors discussed the problem of possible use of biotyping of T. glabrata in investigations of the epidemiology and pathogenesis of mycoses caused by this microorganism. In investigations of the sensitivity of strains of Torulopsis spp. to nine antimycotic agents in vitro it was revealed that the isolates were sensitive to all polyene antibiotics (amphotericin B, nystatin and pimaricin) and to 5-fluorocytosine. The sensitivity to azole chemotherapeutic agents (clotrimazole, econazole, miconazole, ketoconazole and itraconazole) was more varied: some strains were resistant to clotrimazole and econazole.