Phase transitions and slow spin dynamics of slightly inverted A-site spinel CoAl2-xGaxO4.

We report the properties of an A-site spinel magnet, CoAl2-xGaxO4, and analyze its anomalous, low-temperature magnetic behavior, which is derived from inherent, magnetically frustrated interactions. Rietveld analysis of the x-ray diffraction profile for CoAl2-xGaxO4revealed that the metallic ions were randomly distributed in the tetrahedral (A-) and octahedral (B-) sites in the cubic spinel structure. The inversion parameterηcould be controlled by varying the gallium (Ga) composition in the range 0.055 ⩽η⩽ 0.664. The composition-induced Néel-to-spin-glass (NSG) transition occurred between 0.05 ⩽η⩽ 0.08 and was verified by measurements of DC-AC susceptibilitiesχand thermoremanent magnetization (TRM) below the Néel transition temperatureTN. The relaxation rate and derivative with respect to temperature of TRM increased at bothTNand the spin glass (SG) transition temperatureTSG. The TRM decayed rapidly above and below these transitions. TRM was highly sensitive to macroscopic magnetic transitions that occurred in both the Néel and SG phases of CoAl2-xGaxO4. In the vicinity of the NSG boundary, there was a maximum of the TRM relaxation rate atTmax

Unusually strong electronic correlation and field-induced ordered phase in YbCo2.

We report the first study of electrical resistivity, magnetization, and specific heat on YbCo2. The measurements on a single-phased sample of YbCo2bring no evidence of magnetic ordering down to 0.3 K in a zero magnetic field. The manifestations of low Kondo temperature are observed. The specific heat value divided by temperature,C/T, keeps increasing logarithmically beyond 7 J/mol K2with decreasing temperature down to 0.3 K without no sign of magnetic ordering, suggesting a very large electronic specific heat. Analysis of the magnetic specific heat indicates that the large portion of the low-temperature specific heat is not explained simply by the low Kondo temperature but is due to the strong intersite magnetic correlation in both the 3dand 4felectrons. Temperature-dependent measurements under static magnetic fields up to 7 T are carried out, which show the evolution of field-induced transition above 2 T. The transition temperature increases with increasing field, pointing to a ferromagnetic character. The extrapolation of the transition temperature to zero field suggests that YbCo2is in the very proximity of the quantum critical point. These results indicate that in the unique case of YbCo2, the itinerant electron magnetism of Co 3d-electrons and the Kondo effect within the vicinity of quantum criticality of Yb 4f-local moments can both play a role.

Impact of isoelectronic substitution and hydrostatic pressure on the quantum critical properties of CeRhSi3.

There is an ongoing dispute in the community about the absence of a magnetic quantum critical point (QCP) in the noncentrosymmetric heavy fermion compound CeRhSi3. In order to explore this question we prepared single crystals of CeRh(Si1-x Ge x )3 with x = 0.05 and 0.15 and determined the temperature-pressure (T-p) phase diagram by means of measurements of the electrical resistivity. The substitution of isoelectronic but large Ge enforces a lattice volume increase resulting in a weakening of the Kondo interaction. As a result, the x = 0.05 and x = 0.15 compound exhibit a transition into the antiferromagnetic (AFM) at higher temperatures being T N = 4.7 K and T N1 = 19.7 K, respectively. Application of pressure suppresses T N (T N1) monotonically and pressure induced superconductivity is observed in both Ge-substituted compounds above p ⩾ 2.16 GPa (x = 0.05) and p ⩾ 2.93 GPa (x = 0.15). Extrapolation of T N(p) → 0 of CeRh(Si0.95Ge0.05)3 yields a critical pressure of p c ≈ 3.4 GPa (in CeRh(Si0.85Ge0.15)3 p c ≈ 3.5 GPa) pointing to the presence of an AFM QCP located deep inside the superconducting state.

Analysis of hemocoagulation tests for prediction of venom-induced consumption coagulopathy development after Viperidae bite.

OBJECTIVE: Viperidae snakes are responsible for 95 % of the bites caused by exotic-bred snakes in our country. Their envenoming may be associated with a severe acute coagulation disorder - venom-induced consumption coagulopathy (VICC). Thus, its early prediction is vital for an adequate therapy including antivenom delivery. MATERIAL AND METHODS: Laboratory coagulation tests of 14 patients suffering from VICC were processed and statistically analyzed to evaluate the importance of individual parameters in the time after the bite. RESULTS: The pathological values of D-dimer (D-dim) and fibrinogen (FBG) were found to be the first indicators of VICC development, with a median time of 4.55 hours since the bite, while median values for prothrombin time and international normalized ratio (PT/INR), activated partial thromboplastin time (APTT), and thrombin time (TT) were 5.9 h, 8.15 h, and 5.5 h, respectively. In the first samples, the values of D-dim were found to be pathologically increased in all 14 patients, while pathological levels of FBG were seen only in 11 cases. PT/INR and APTT were prolonged in 8 and 6 cases, respectively. CONCLUSION: An increase in D-dim values was found to be the first parameter signaling developing VICC in all analyzed cases (Tab. 2, Ref. 12).

Nearly perfect near-infrared luminescence efficiency of Si nanocrystals: A comprehensive quantum yield study employing the Purcell effect.

Thin layers of silicon nanocrystals (SiNC) in oxide matrix with optimized parameters are fabricated by the plasma-enhanced chemical vapor deposition. These materials with SiNC sizes of about 4.5 nm and the SiO2 barrier thickness of 3 nm reveal external quantum yield (QY) close to 50% which is near to the best chemically synthetized colloidal SiNC. Internal QY is determined using the Purcell effect, i.e. modifying radiative decay rate by the proximity of a high index medium in a special wedge-shape sample. For the first time we performed these experiments at variable temperatures. The complete optical characterization and knowledge of both internal and external QY allow to estimate the spectral distribution of the dark and bright NC populations within the SiNC ensemble. We show that SiNCs emitting at around 1.2-1.3 eV are mostly bright with internal QY reaching 80% at room temperature and being reduced by thermally activated non-radiative processes (below 100 K internal QY approaches 100%). The mechanisms of non-radiative decay are discussed based on their temperature dependence.

Silicon nanocrystal-based photonic crystal slabs with broadband and efficient directional light emission.

Light extraction from a thin planar layer can be increased by introducing a two-dimensional periodic pattern on its surface. This structure, the so-called photonic crystal (PhC) slab, then not only enhances the extraction efficiency of light but can direct the extracted emission into desired angles. Careful design of the structures is important in order to have a spectral overlap of the emission with extraction (leaky) modes. We show that by fabricating PhC slabs with optimized dimensions from silicon nanocrystals (SiNCs) active layers, the extraction efficiency of vertical light emission from SiNCs at a particular wavelength can be enhanced ∼ 11 times compared to that of uncorrugated SiNCs-rich layer. More importantly, increased light emission can be obtained in a broad spectral range and, simultaneously, the extracted light can stay confined within relatively narrow angle around the normal to the sample plane. We demonstrate experimentally and theoretically that the physical origin of the enhancement is such that light originating from SiNCs first couples to leaky modes of the PhCs and is then efficiently extracted into the surrounding.

Note: On the choice of the appropriate excitation-pulse-length for assessment of slow luminescence decays.

The decay-time distribution deduced from luminescence kinetics experiments is, in general, dependent on the excitation pulse length as a direct consequence of different onset dynamics. We demonstrate this effect for the case of square excitation pulses applied to study the luminescence kinetics in Si nanocrystals. The short- and long-pulse limits are defined as 0.1 times the shortest lifetime in the distribution and 3 times the longest time, respectively. Outside these limits the decay-time distribution is independent on the pulse duration. In addition, we describe experimental conditions required to obtain a correct depiction of slow luminescence decay in the µs to ms time range.

[A study of the morphology of the descending branch of the lateral circumflex femoral artery (DBLCFA) as a possible vascular graft for the reconstruction of coronary arteries using angio CT]. / Studie morfologie r. descendens a. circumflexae femoris lateralis jako mozné cévní náhrady pro rekonstrukci koronárního reciste pomocí angio CT vysetrení

INTRODUCTION: Due to the need for alternative arterial grafts suitable for the reconstruction of the coronary bloodstream, we conducted a morphological analysis of the descending branch of the lateral circumflex femoral artery (DBLCFA) using an AGCT scan. MATERIAL AND METHODS: Not only anatomical variations and the quantitative representation of sclerotic changes, but also the presence of a collateral system in the event of significant stenosis of the pelvic and femoral artery system were analysed. RESULTS: The results revealed favorable findings in the sense of the studied arteries length (9.3 cm on average), a relatively low anatomical variability and a very small percentage of the studied blood vessels participating in collateral blood flow, despite that 72% of tests revealed significant stenotic disease (stenosis of more than 50%) of the upper branch of lower limb arteries. CONCLUSION: According to the defined criteria, 68% of vessels were found to be suitable for grafting. We suppose that this number would be considerably higher in patients with only insignificant or no ischemic disease of the lower extremities.

[Peripartal life-threatening hemorrhage - interdisciplinary consensus opinion]. / Peripartální zivot ohrozující krvácení - mezioborové konsenzuální stanovisko.

22 experts from the fields of gynecology and obstetrics, anesthesiology and resuscitation, intensive care, hematology and transfusion medicine has developed recommendations for diagnosis and procedure for life-threatening peripartum haemorrhage, which is still one of the most common causes of maternal mortality in childbirth. This guidelines, which is valid for the Czech Republic, supported by a total of 10 professional medical societies. There are based on new knowledge applicable at this time and is focused mainly on eliminating the most common causes of bleeding during delivery and prevention of haemorrhagic shock.

Black mamba dendroaspis polylepis bite: a case report.

Although very rare in a European context, a bite from the black mamba Dendroaspis polylepis is an event that poses an immediate threat to life. Given the content of neurotoxins in the snake's venom, the mortality of envenomation reaches 100% in almost every case if ventilation is not provided in a timely manner and adequate therapy initiated. The report describes a case of a snake breeder being envenomed. This 31-year-old man was bitten by a black mamba on his finger, and who subsequently developed clinical symptoms of envenoming typical for the species. Thanks to mechanical ventilation being employed promptly, with myorelaxation during generalized muscle fasciculations, and particularly owing to the eventual antivenin therapy, the patient's condition settled without consequences. In addition to describing the given case in detail, the paper discusses the composition and mechanisms of action of black mamba venom, while providing guidelines for adequate therapy.

Envenoming after a snakebite from the Northeast African saw-scaled viper Echis pyramidum: prolonged therapy upon failed treatment by antivenom.

A reptile holder based in the Czech Republic was bitten into his hand and foot by the Northeast saw-scaled viper (Echis pyramidum). The person arrived at the health institution after twenty hours for anuria. Despite the antivenom against the Asian Echis carinatum - the Echis pyramidum's close relative - was readily available and administered repeatedly, the envenoming continued to develop with subsequent coagulopathy, hepatopathy and respiratory failure. The effects of plasmapheresis and symptomatic therapy were positive, but only temporary. Continual renal replacement therapy and plasmapheresis were complicated by thrombotic occlusions of the device tubing set. A turning point arrived following repeated application of imported antivenom containing antigens against venom components of another African saw-scaled viper species, Echis leucogaster (the antivenom containing E. pyramidum antigens was not available). The clinical status, including complications, resolved following 30 days of hospitalization. The case further validates the geographical specifics of immunogenicity of venom components with similar clinical action in snakes of the same genus.

Step-like enhancement of luminescence quantum yield of silicon nanocrystals.

Carrier multiplication by generation of two or more electron-hole pairs following the absorption of a single photon may lead to improved photovoltaic efficiencies and has been observed in nanocrystals made from a variety of semiconductors, including silicon. However, with few exceptions, these reports have been based on indirect ultrafast techniques. Here, we present evidence of carrier multiplication in closely spaced silicon nanocrystals contained in a silicon dioxide matrix by measuring enhanced photoluminescence quantum yield. As the photon energy increases, the quantum yield is expected to remain constant, or to decrease as a result of new trapping and recombination channels being activated. Instead, we observe a step-like increase in quantum yield for larger photon energies that is characteristic of carrier multiplication. Modelling suggests that carrier multiplication is occurring with high efficiency and close to the energy conservation limit.

[Alternative autologous arterial graft in cardiovascular surgery]. / Alternativní autologní tepenný step v kardiovaskulární chirurgii.

Arterial revascularization of myocardium is a method of choice for surgical treatment of ischemic heart disease. The descending branch of lateral femoral circumflex artery (DBLFCA) is one of possible alternative autologous arterial grafts. Up to now, since 2003, 12 of these grafts have been harvested and used for revascularization of myocardium at our department. All grafts have been used as a Y-graft to the left internal mammary artery for revascularization of target vessels on lateral and inferior heart wall. Graft patency was controlled by the angio-CT procedure after three months. One of the grafts was occluded at the control. It means patency rate after three months was more than 91%. No other complications (such as problematic wound healing, paraesthaesia of lower leg, bleeding, spasm of the graft, infection etc.) were observed with graft harvesting. DBLCFA is a high-quality and safe alternative arterial graft, available for arterial revascularization of myocardium.

Acute pancreatitis after viperid snake cerastes cerastes envenoming: a case report.

Snakebites by the viper snake Cerastes cerastes are quite common across the world but rarely published with regard to their mostly benign course. The reported case study depicts the envenoming of a 36-year-old Czech man, a private herpetologist, who suffered snakebite to his finger. He developed a painful local reaction with hemorrhagic oedema. Subsequently, consumption coagulopathy with thrombocytopenia and haemolysis, colicky pain in the epigastrium and acute renal failure developed. Acute exudative pancreatitis was diagnosed on the third day after envenoming. Hemorrhagic oedema of the arm was complicated by a phlegmon. Symptomatic treatment including haemodialysis, fresh frozen plasma and thrombocytes was administered. Antivenom was not administered due to the delay in referral to the specialized unit. The patient recovered within one month, only postnecrotic defects of the finger persisted.

Effects of the adenosine A 2A antagonist KW 6002 (istradefylline) on pimozide-induced oral tremor and striatal c-Fos expression: comparisons with the muscarinic antagonist tropicamide.

Typical antipsychotic drugs, including haloperidol and pimozide, have been shown to produce parkinsonian motor effects such as akinesia and tremor. Furthermore, there is an antagonistic interaction between adenosine A(2A) and dopamine D(2) receptors in the basal ganglia, which is important for motor functions related to the production of parkinsonian symptoms. Several experiments were conducted to assess the effects of the selective adenosine A(2A) antagonist KW 6002 on both the motor and cellular effects of subchronic administration of pimozide. The motor test employed was tremulous jaw movements, which is used as a model of parkinsonian tremor. In addition, c-Fos expression in the ventrolateral neostriatum, which is the striatal area most associated with tremulous jaw movements, was used as a marker of striatal cell activity in animals that were tested in the behavioral experiments. Repeated administration of 1.0 mg/kg pimozide induced tremulous jaw movements and increased ventrolateral striatal c-Fos expression, while administration of 20.0 mg/kg of the atypical antipsychotic quetiapine did not. The tremulous jaw movements induced by pimozide were significantly reduced by co-administration of either the adenosine A(2A) antagonist KW 6002 or the muscarinic antagonist tropicamide. Pimozide-induced increases in ventrolateral striatal c-Fos expression were reduced by a behaviorally effective dose of KW 6002, but c-Fos expression in pimozide-treated rats was actually increased by tropicamide. These results indicate that two different drug manipulations that act to reduce tremulous jaw movements can have different effects on DA antagonist-induced c-Fos expression, suggesting that adenosine A(2A) antagonism and muscarinic receptor antagonism exert their motor effects by acting on different striatal circuits.

Identification of Photosystem I and Photosystem II enriched regions of thylakoid membrane by optical microimaging of cryo-fluorescence emission spectra and of variable fluorescence.

Oxygenic photosynthesis of higher plants requires linear electron transport that is driven by serially operating Photosystem II and Photosystem I reaction centers. It is widely accepted that distribution of these two types of reaction centers in the thylakoid membrane is heterogeneous. Here, we describe two optical microscopic techniques that can be combined to reveal the heterogeneity. By imaging micro-spectroscopy at liquid nitrogen temperature, we resolved the heterogeneity of the chloroplast thylakoid membrane by distinct spectral signatures of fluorescence emitted by the two photosystems. With another microscope, we measured changes in the fluorescence emission yield that are induced by actinic light at room temperature. Fluorescence yield of Photosystem II reaction centers varies strongly with light-induced changes of its photochemical yield. Consequently, application of moderate background irradiance induces changes in the Photosystem II fluorescence yield whereas no such modulation occurs in Photosystem I. This contrasting feature was used to identify regions in thylakoid membranes that are enriched in active Photosystem II.

[Role of morphology in medical education, clinical practice and research]. / Postavení morfologie ve výuce medicíny a v klinické praxi a výzkumu.

Rapid development of molecular biology, biochemistry, physiology and other sciences has diminished the previously dominant role of morphology in the theoretical part of medical studies. Morphology, closely related to various disciplines, should, however, be included in clinical lectures. Changes in the curricula would require concise and well-structured textbooks, based on recent clinico-morphological studies, for the theoretical parts of both medical and allied health care study programmes. Comprehensive textbooks are still necessary for the specific needs of clinicians and researches.

[Present possibilities in vascular surgery]. / Soucasné moznosti cévní chirurgie.

Contemporary vascular surgery relies on the progress in imaging techniques and on modern materials for vascular substitutes. The collaboration with radiodiagnosticians enabled the treatment of arterial thromboses by means of fibrinolysis. Radiodiagnostics plays an important role also in the field of endovascular operations, namely percutanous transluminal angioplasty, insertion of stents, and recently in the abdominal aorta aneurysms treatment by means of stents. Long-lasting effects of such operations, namely those in the aorta, have not been fully established and the classical reconstructive surgery has not lost its importance.

Aleukemic granulocytic sarcoma with AML1/ETO fusion gene expression and clonal T cell populations.

We report a unique case of aleukemic granulocytic sarcoma of the neck, originally misdiagnosed as non-Hodgkin's lymphoma (NHL), though chloroma was also suspected due to a greenish macroscopic appearance and the presence of myeloid chloroacetate esterase (CAE)+ cells. The proof of clonal T cell receptor gamma chain (TcRgamma) gene rearrangements in the recurring tumor was deemed to confirm the initial diagnosis of T cell NHL. Altogether five distinct types of clonal TcRgamma gene rearrangements were found in the tumor, bone marrow and peripheral blood. Only retrospectively, using RT-PCR, did we detect the acute myeloid leukemia subset-specific fusion gene AML1/ETO in the frozen samples of the relapsed tumor, as well as in the otherwise unaffected bone marrow and peripheral blood (representing 'minimal initial disease' in the latter two samples). Simultaneous staining verified that the neoplastic CAE+ cells and CD45RO+ T cells were different populations.