Low-temperature high-frequency dynamic magnetic susceptibility of classical spin-ice Dy2Ti2O7.

Radio-frequency (14.6 MHz) AC magnetic susceptibility,χAC', of Dy2Ti2O7was measured using self-oscillating tunnel-diode resonator. Measurements were made with the excitation AC field parallel to the superimposed DC magnetic field up to 5 T in a wide temperature range from 50 mK to 100 K. At 14.6 MHz, a known broad peak ofχAC'(T)from kHz-range audio-frequency measurements around 15 K for both [111] and [110] directions shifts to 45 K, continuing the Arrhenius activated behavior with the same activation energy barrier ofEa≈ 230 K. Magnetic field dependence ofχAC'along [111] reproduces previously reported low-temperature two-in-two-out to three-in-one-out spin configuration transition at about 1 T, and an intermediate phase between 1 and 1.5 T. The boundaries of the intermediate phase show reasonable overlap with the literature data and connect at a critical endpoint of the first order transition line, suggesting that these features are frequency independent. An unusual upturn of the magnetic susceptibility atT→ 0 was observed in magnetic fields between 1.5 T and 2 T for both magnetic field directions, before fully polarized configuration sets in above 2 T.

µSR study of spin freezing and persistent spin dynamics in NaCaNi2F7.

A new pyrochlore compound, NaCaNi2F7, was recently synthesized and has a single magnetic site with spin-1 Ni2+ . We present zero field and longitudinal field muon spin rotation (µSR) measurements on this pyrochlore. Density functional theory calculations show that the most likely muon site is located between two fluorine ions, but off-centre. A characteristic F-µ-F muon spin polarization function is observed at high temperatures where Ni spin fluctuations are sufficiently rapid. The Ni2+ spins undergo spin freezing into a disordered ground state below 4 K, with a characteristic internal field strength of 140 G. Persistent Ni spin dynamics are present to our lowest temperatures (75 mK), a feature characteristic of many geometrically frustrated magnetic systems.

Continuum of quantum fluctuations in a three-dimensional S = 1 Heisenberg magnet.

Conventional crystalline magnets are characterized by symmetry breaking and normal modes of excitation called magnons, with quantized angular momentum ℏ. Neutron scattering correspondingly features extra magnetic Bragg diffraction at low temperatures and dispersive inelastic scattering associated with single magnon creation and annihilation. Exceptions are anticipated in so-called quantum spin liquids, as exemplified by the one-dimensional spin-1/2 chain, which has no magnetic order and where magnons accordingly fractionalize into spinons with angular momentum ℏ/2. This is spectacularly revealed by a continuum of inelastic neutron scattering associated with two-spinon processes. Here, we report evidence for these key features of a quantum spin liquid in the three-dimensional antiferromagnet NaCaNi2F7. We show that despite the complication of random Na1+-Ca2+ charge disorder, NaCaNi2F7 is an almost ideal realization of the spin-1 antiferromagnetic Heisenberg model on a pyrochlore lattice. Magnetic Bragg diffraction is absent and 90% of the neutron spectral weight forms a continuum of magnetic scattering with low-energy pinch points, indicating NaCaNi2F7 is in a Coulomb-like phase. Our results demonstrate that disorder can act to freeze only the lowest-energy magnetic degrees of freedom; at higher energies, a magnetic excitation continuum characteristic of fractionalized excitations persists.

NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7: novel single crystal pyrochlore antiferromagnets.

The crystal structures and magnetic properties of three previously unreported A2B2F7 pyrochlore materials, NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7 are presented. In these compounds, either S = 2Fe2+ or S = 5/2Mn2+ is on the B site, while nonmagnetic Na and Ca (Na and Sr) are disordered on the A site. The materials, which were grown as crystals via the floating zone method, display high effective magnetic moments and large Curie-Weiss thetas. Despite these characteristics, no ordering transition is detected. However, freezing of the magnetic spins, characterized by peaks in the susceptibility or specific heat, is observed at very low temperatures. The empirical frustration index, f = -θ CW/T f, for the materials are 36 (NaSrMn2F7), 27 (NaSrFe2F7), and 19 (NaCaFe2F7). AC susceptibility, DC susceptibility, and heat capacity measurements are used to characterize the observed spin glass behavior. The results suggest that the compounds are frustrated pyrochlore antiferromagnets with weak bond disorder. The magnetic phenomena that these fluoride pyrochlores exhibit, in addition to their availability as relatively large single crystals, make them promising candidates for the study of geometric magnetic frustration.

Heat capacity peak at the quantum critical point of the transverse Ising magnet CoNb2O6.

The transverse Ising magnet Hamiltonian describing the Ising chain in a transverse magnetic field is the archetypal example of a system that undergoes a transition at a quantum critical point (QCP). The columbite CoNb2O6 is the closest realization of the transverse Ising magnet found to date. At low temperatures, neutron diffraction has observed a set of discrete collective spin modes near the QCP. Here, we ask if there are low-lying spin excitations distinct from these relatively high-energy modes. Using the heat capacity, we show that a significant band of gapless spin excitations exists. At the QCP, their spin entropy rises to a prominent peak that accounts for 30% of the total spin degrees of freedom. In a narrow field interval below the QCP, the gapless excitations display a fermion-like, temperature-linear heat capacity below 1 K. These novel gapless modes are the main spin excitations participating in, and affected by, the quantum transition.

NaSrCo2F7, a Co(2+) pyrochlore antiferromagnet.

We report the crystal growth, by the Bridgeman-Stockbarger method, and the basic magnetic properties of a new cobalt-based pyrochlore, NaSrCo2F7. Single-crystal structure determination shows that Na and Sr are completely disordered on the non-magnetic large atom A sites, while magnetic [Formula: see text] Co(2+) fully occupies the pyrochlore lattice B sites. NaSrCo2F7 displays strong antiferromagnetic interactions ([Formula: see text]), a large effective moment ([Formula: see text]), and no spin freezing until 3 K. Thus, NaSrCo2F7 is a geometrically frustrated antiferromagnet with a frustration index [Formula: see text]. Ac susceptibility, dc susceptibility, and heat capacity are utilized to characterize the spin freezing. We argue that NaSrCo2F7 and the related material NaCaCo2F7 are examples of frustrated pyrochlore antiferromagnets with weak bond disorder.

Crystal structure and electronic structure of CePt2In7.

We report a corrected crystal structure for the CePt(2)In(7) superconductor, refined from single crystal x-ray diffraction data. The corrected crystal structure shows a different Pt-In stacking along the c-direction in this layered material than was previously reported. In addition, all of the atomic sites are fully occupied with no evidence of atom site mixing, resolving a discrepancy between the observed high resistivity ratio of the material and the atomic disorder present in the previous structural model. The Ce-Pt distance and coordination is typical of that seen in all other reported Ce(n)M(m)In(3n+2 m) compounds. Our band structure calculations based on the correct structure reveal three bands at the Fermi level that are more 3D than those previously proposed, and density functional theory (DFT) calculations show that the new structure has a significantly lower energy.

Superconducting properties and electronic structure of NaBi.

Resistivity, dc magnetization, and heat capacity measurements are reported for superconducting NaBi. T(c), the electronic contribution to the specific heat γ, the ΔC(p)/γT(c) ratio, and the Debye temperature are found to be 2.15 K, 3.4 mJ mol(-1) K(-2), 0.78, and 140 K respectively. The calculated electron-phonon coupling constant (λ(ep) = 0.62) implies that NaBi is a moderately coupled superconductor. The upper critical field and coherence length are found to be 250 Oe and 115 nm, respectively. Electronic structure calculations show NaBi to be a good metal, in agreement with the experiments; the p(x) and p(y) orbitals of Bi dominate the electronic states at the Fermi Energy.

Ferromagnetism in Mn-doped Sb(2)Te.

We report that Sb2Te, a natural superlattice phase consisting of two elemental Sb2 layers interleaved with single Sb2Te3 layers, becomes ferromagnetic at low temperatures on doping with small percentages of Mn. Ferromagnetism appears for Mn concentrations as low as Sb1.98Mn0.02Te, where a ferromagnetic Tc of ~8.6 K is observed. Tc decreases with increasing Mn content in the stoichiometric materials but increases with increasing Te excess in materials of the type Sb1.93-yMn0.07Te1+y, starting at ~3 K at y = 0 and reaching a Tc of ~8.9 K at y = 0.06.

Hierarchy of bound states in the one-dimensional ferromagnetic Ising chain CoNb2O6 investigated by high-resolution time-domain terahertz spectroscopy.

Kink bound states in the one-dimensional ferromagnetic Ising chain compound CoNb2O6 have been studied using high-resolution time-domain terahertz spectroscopy in zero applied magnetic field. When magnetic order develops at low temperature, nine bound states of kinks become visible. Their energies can be modeled exceedingly well by the Airy function solutions to a 1D Schrödinger equation with a linear confining potential. This sequence of bound states terminates at a threshold energy near 2 times the energy of the lowest bound state. Above this energy scale we observe a broad feature consistent with the onset of the two particle continuum. At energies just below this threshold we observe a prominent excitation that we interpret as a novel bound state of bound states--two pairs of kinks on neighboring chains.

[Primary aortoduodenal fistula (PADF)]. / Primární aortoduodenální pístel (PADF).

Primary aortoduodenal fistula is very rare acute abdomen with high mortality. Serious problem is often late diagnosis. Authors present case report from their University Hospital. Diagnosis and therapy options are discussed. Key words:primary aortoduodenal fistula - late diagnosis.

[Vascular system injuries]. / Poranení cévního systému.

PURPOSE OF THE STUDY: The aim of this retrospective study is to present our experience with the management of injuries to the vascular system at the Trauma Centre, University Hospital in Plzen. We show the most frequent mechanisms of injury, diagnostic pitfalls, therapeutic options and evaluate both the short-term and long-term results of surgical treatment and interventional radiology procedures. MATERIAL AND METHODS: We evaluated a group of patients with a serious vascular injury who were treated at the Traima Centre during the five-year period from January 2006 to December 2010. The group included 82 patients, 59 men and 23 women, with the average age of 34.5 years. We assessed the success rate of vascular reconstruction, primary and secondary graft patency and mortality and morbidity rates. Recovery of function in the injured extremities and return of the patient to normal daily activities were considered the most important parameters. In 28 patients (34%) vascular injury was due to polytrauma, in nine (11%) it was part of a combined injury, and 45 patients (55 %) sustained monotrauma. Most of the patients (68; 83%) were managed surgically. The most frequent procedures included direct suture of a lesion, resection and replacement of an injured artery or bypass grafting. In 13 patients we used interventional radiology procedures (in most cases it was for thoracic endovascular aortic repair). In one patient we were able to use a conservative treatment. RESULTS: The 30-day mortality rate was 8.5%, i.e., seven patients died of polytrauma. The morbidity rate was 35% (29 patients). The most frequent complications included respiratory failure in polytrauma (13%), transient leg/arm swelling (6%) and wound infection (4%). Primary and secondary graft patencies were 100% and 95.5%, respectively. Vascular reconstruction failed in three patients and, in two of them, we had to carry out limb amputation. CONCLUSIONS: From the viewpoint of vascular surgery, even very serious injuries of upper and lower extremities can be managed, if possible associated injuries of the skeletal and nerve structures allow for it. The key to success is good co-operation of the orthopaedic trauma surgeon, vascular surgeon and neurosurgeon.

[Procedures on internal carotid performed under locoregional anesthesia in the Plzen Surgical Clinic, over a seven-year period. A discussion on AHA and ESVS guidelines]. / Operace na vnitrrních karotidách v lokoregionální anestezii na chirurgické klinice v Plzni za uplynulých 7 let. Diskuse nad AHA a ESVS guidelines.

During a seven-year period (2002-2008), 830 patients underwent internal carotid surgery in the Plzen Surgical Clinic. The mean age of the patients was 68 y.o.a. (range 48-86 years). A total of 916 internal carotid procedures were performed, the male/female ratio was 667/249. 639 procedures were performed for asymptomatic and 277 for symptomatic conditions. 677 patients suffered from unilateral carotid disorders and 153 subjects from bilateral carotid disorders. All the procedures were performed under locoregional anesthesia. The 30-day mortality rate was 1% (9 subjects) of all the procedures.

Altered distribution of NK and NKT cells in follicular fluid is associated with IVF outcome.

The aim of this study was to investigate differences in the relative distributions of subsets of natural killer (NK) cells, including immunoregulatory NK cells (CD56(+)CD16(-)), cytotoxic NK cells (CD56(+)CD16(+)), as well as total NK cells (CD56(+)CD3(-)), and NKT cells (CD56(+)CD3(+)) in peripheral blood and follicular fluid in subjects with successful or unsuccessful IVF treatment. The immunoregulatory NK cell population in follicular fluid of women who failed to achieve pregnancy after IVF treatment was significantly decreased compared to women who became pregnant after IVF. Conversely, the NKT cell population in the follicular fluid of women with unsuccessful treatment was significantly elevated compared with those with successful IVF. Understanding the changes in the distribution of NK and NKT cell populations in follicular fluid might serve as the basis for a more detailed study to determine whether NK cell parameters have prognostic value in guiding the selection of individual ova for use in IVF procedures.

Leukaemia inhibitory factor (LIF) gene mutations in women diagnosed with unexplained infertility and endometriosis have a negative impact on the IVF outcome. A pilot study.

The frequency of functionally relevant mutations of the leukaemia inhibitory factor (LIF) gene in infertile women is significantly enhanced in comparison with fertile controls. The objective of this retrospective cohort study was to evaluate the impact of LIF gene mutations on the outcome of the treatment in women with various causes of infertility. Fifteen infertile women with the G to A transition at position 3400 leading to the valine to methionine exchange at codon 64 were analysed. Group A was made up of women with diagnoses that are frequently accompanied by changes in humoral as well as cell-mediated immunity - idiopathic infertility and endometriosis (N = 7). Group B consisted of patients with polycystic ovary syndrome (PCOS), andrological factor, tubal factor and hyperprolactinaemia (N = 8). The control group comprised 136 infertile women with no LIF gene mutation diagnosed with idiopathic infertility and endometriosis (N = 37) (group C) and patients with PCOS, tubal and andrological factor (N = 99) (group D). Seven of the mutation-positive patients were successfully treated by in vitro fertilization (IVF), but nobody in this group was diagnosed with idiopathic infertility and only one with endometriosis, which means that there is a statistically significant difference in the pregnancy rates between groups A and B (P = 0.01, Fisher's 2 by 2 exact test) but no statistically significant difference when comparing patients with the LIF gene mutation (group A+B) to no LIF gene mutation (group C+D). The results suggest that in mutation-positive women the idiopathic infertility and endometriosis have a negative impact on the outcome of IVF treatment.

Hybrid procedures in the treatment of pseudoaneurysms of the aortic arch--case report.

Classical surgical therapy of dilatation disorders of the aortic arch require extracorporeal circulation, selective brain perfusion and/or deep hypothermia and it is still associated with very high mortality and morbidity. Endovascular therapy has until recently indicated only been in cases when the disease did not affect the area of the origins of the main branches within the aortic arch. We are presenting a case report of a 68 year female patient with a vascular anomaly (arteria lusoria) and 2 pseudoaneurysms of the aortic arch between the origins of arteria carotis communis on the right and arteria carotis communis on the left, respectively between a. carotis communis on the left and arteria subclavia on the left, when we took advantage of a hybrid procedure in the therapy. The patient was treated by creating a new branching of the aortal arch using a prosthesis from the ascendant aorta and subsequently by an introduction of 2 stent-grafts to the aortic arch using femoral arteries.

[Management of the lienal artery aneurysms in the Plzen Surgical Clinic during 2002-2007]. / Resení aneuryzmat lienálni tepny na Chirurgické klinice v Plzni v letech 2002-2007.

The authors present their experience with the management of the lienal artery aneurysms. Individual types of aneurysms are presented according to their pathogenesis. Furthermore, the diagnostic options, indication criteria and treatment options are discussed.

Internal carotid artery surgery in regional anesthesia at the Clinic of Surgery in Pilsen during the past 5 years.

A low percentage of perioperative complications and excellent long-term outcome following carotid artery surgery in Vascular Centers demonstrate the priority of surgical solutions in patients with significant findings on carotid arteries, in the prevention and treatment of ischemic cerebrovascular accidents. The group of patients from the Clinic of Surgery in Pilsen demonstrates the benefits of regional anesthesia during internal carotid artery surgery, both in terms of the patients' health and the financial costs incurred by the hospital.

[The leukemia inhibitory factor gene mutations in the population of infertile women: the heterozygote transition G to A on the position 3400 does not affect the outcome of the infertility treatment]. / Mutace v genu pro leukemický inhibicní faktor v populaci neplodných zen: heterozygotní bodová zámena G za A na pozici 3400 neovlivnuje úspesnost lécby.

OBJECTIVE: The leukemia inhibitory factor (LIF) is one of the most important signaling factors in the embryo-maternal cross talk during the embryo implantation. We investigated the prevalence of the LIF gene mutations in the population of infertile women and their impact on infertility treatment. DESIGN: A cohort study. SETTING: Department of Obstetrics and Gynecology, Faculty of Medicine and University Hospital of Charles University, Pilsen. SUBJECTS AND METHODS: The population to screen consisted of 399 infertile women. The control population was comprised of 202 healthy fertile subjects. For the mutational analysis, the temperature gradient gel electrophoresis (TGGE) followed by subsequent sequencing of the positive samples, had been used. The groups of fertile controls and infertile patients were compared for statistically significant difference using the Fisher's 2 by 2 Exact test. RESULTS: Twelve potentially functional LIF gene mutations, the G to A transversion at the position 3400 leading to the valin to methionin exchange at codon 64 (V64M) were detected in the group of infertile women. No mutations were identified in the control group, which means that the frequency of functionally relevant mutations of the LIF gene in infertile women is significantly enhanced in comparison with controls (P = 0.01, Fisher's 2 by 2 Exact test ). Seven of these patients were successfully treated by in vitro fertilization (IVF). CONCLUSION: The results suggest that the LIF gene mutation, the heterozygote G to A transition on the position 3400, affects fertility but the infertility treatment can succeed. Even though LIF gene mutations occur infrequently and can be overcome by infertility treatment, their impact on molecular events during early phases of pregnancy should be further elucidated.

Historical and ecological determinants of genetic structure in arctic canids.

Wolves (Canis lupus) and arctic foxes (Alopex lagopus) are the only canid species found throughout the mainland tundra and arctic islands of North America. Contrasting evolutionary histories, and the contemporary ecology of each species, have combined to produce their divergent population genetic characteristics. Arctic foxes are more variable than wolves, and both island and mainland fox populations possess similarly high microsatellite variation. These differences result from larger effective population sizes in arctic foxes, and the fact that, unlike wolves, foxes were not isolated in discrete refugia during the Pleistocene. Despite the large physical distances and distinct ecotypes represented, a single, panmictic population of arctic foxes was found which spans the Svalbard Archipelago and the North American range of the species. This pattern likely reflects both the absence of historical population bottlenecks and current, high levels of gene flow following frequent long-distance foraging movements. In contrast, genetic structure in wolves correlates strongly to transitions in habitat type, and is probably determined by natal habitat-biased dispersal. Nonrandom dispersal may be cued by relative levels of vegetation cover between tundra and forest habitats, but especially by wolf prey specialization on ungulate species of familiar type and behaviour (sedentary or migratory). Results presented here suggest that, through its influence on sea ice, vegetation, prey dynamics and distribution, continued arctic climate change may have effects as dramatic as those of the Pleistocene on the genetic structure of arctic canid species.