83 research outputs found
Non equilibrium anisotropic excitons in atomically thin ReS
We present a systematic investigation of the electronic properties of bulk
and few layer ReS van der Waals crystals using low temperature optical
spectroscopy. Weak photoluminescence emission is observed from two
non-degenerate band edge excitonic transitions separated by 20 meV. The
comparable emission intensity of both excitonic transitions is incompatible
with a fully thermalized (Boltzmann) distribution of excitons, indicating the
hot nature of the emission. While DFT calculations predict bilayer ReS to
have a direct fundamental band gap, our optical data suggests that the
fundamental gap is indirect in all cases
Lentinula edodes as a source of bioelements released into artificial digestive juices and potential anti-inflammatory material
Lentinula edodes (shiitake), an edible and medicinal mushroom, was chosen for this study with the aim of evaluating the possibility of release of bioelements into artificial digestive juices and analyzing the anti-inflammatory properties. The extracts were prepared from fruiting bodies and biomass enriched with copper (Cu), zinc (Zn), and selenium (Se). The content of bioelements was analyzed by total reflection X-ray fluorescence method. Relatively low content of elements was observed in the fruiting bodies: Cu–1.6, Zn–7.6, and Se–0.12 mg/100 g d.w. compared tomycelial cultures. The anti-inflammatory properties were evaluated in RAW264.7 cells. Based on the levels of cyclooxygenase 2 protein, nuclear factor erythroid 2-related factor 2, and peroxisome proliferator-activated receptor γ determined using Western blot technique, it was found that the addition of bioelements enhanced the anti-inflammatory properties ofmycelium. This indicates that L. edodes cultured on a suitablemedium may be used as a potential component of anti-inflammatory products
Determination of the parameters of semiconducting CdF2:In with Schottky barriers from radio-frequency measurements
Physical properties of semiconducting CdF_2 crystals doped with In are
determined from measurements of the radio-frequency response of a sample with
Schottky barriers at frequencies 10 - 10^6 Hz. The dc conductivity, the
activation energy of the amphoteric impurity, and the total concentration of
the active In ions in CdF_2 are found through an equivalent-circuit analysis of
the frequency dependencies of the sample complex impedance at temperatures from
20 K to 300 K. Kinetic coefficients determining the thermally induced
transitions between the deep and the shallow states of the In impurity and the
barrier height between these states are obtained from the time-dependent
radio-frequency response after illumination of the material. The results on the
low-frequency conductivity in CdF_2:In are compared with submillimeter (10^{11}
- 10^{12} Hz) measurements and with room-temperature infrared measurements of
undoped CdF_2. The low-frequency impedance measurements of semiconductor
samples with Schottky barriers are shown to be a good tool for investigation of
the physical properties of semiconductors.Comment: 9 pages, 7 figure
Non equilibrium anisotropic excitons in atomically thin ReS2
We present a systematic investigation of the electronic properties of bulk and few layer ReS2 van der Waals crystals using low temperature optical spectroscopy. Weak photoluminescence emission is observed from two non-degenerate band edge excitonic transitions separated by similar to 20 meV. The comparable emission intensity of both excitonic transitions is incompatible with a fully thermalized (Boltzmann) distribution of excitons, indicating the hot nature of the emission. While DFT calculations predict bilayer ReS2 to have a direct fundamental band gap, our optical data suggests that the fundamental gap is indirect in all cases
Luminescent and scintillation properties of Ce3+ doped Ca2RMgScSi3O12 (R = Y, Lu) single crystalline films
The work is dedicated to the growth and investigation of the luminescent and scintillation properties of single crystalline films (SCFs) of Ca2-xR1+xMg1+xSc1-xSi3O12:Ce (R = Y, Lu) mixed garnets with x = 0-0.25, grown using the liquid phase epitaxy method onto Y3Al5O12 substrates from PbO-B2O3 based flux. The absorption, luminescent and scintillation properties of Ca2-xY1+xMg1+xSc1-xSi3O12:Ce and Ca2-xLu1+xMg1+xSc1-xSi3O12:Ce SCFs with x = 0 and 0.25 were investigated and compared with the reference YAG:Ce and LuAG:Ce SCFs. Using the Ca2+, Mg2+ and Si4+ alloying, the Ce3+ emission spectra in Ca2-xR1+xMg1+xSc1-xSi3O12:Ce (R = Y, Lu; x = 0-0.25) SCFs can be notably extended in the red range in comparison with YAG: Ce and LuAG: Ce SCFs due to the increase of crystal field strength and Ce3+ multicenter creation in the dodecahedral positions of the lattices of these mixed garnet compounds. Due to the formation of Ce4+ ions, the as-grown Ca2-xR1+xMg1+xSc1-xSi3O12:Ce (R = Y, Lu) SCFs at x = 0 and 0.25 show relatively low light yield. However, after annealing in reducing atmosphere (95% N-2 + 5% H-2) at T > 1000 degrees C, a recharging Ce4+ -> Ce3+ takes place. After that, these SCFs possess the light yield about of 30% and 31% in comparison with the reference YAG: Ce and LuAG: Ce SCFs, respectively, and a fast scintillation response with the decay times in the ns range under a-particles excitation by Pu-239 (5.15 MeV) source
Stromal myofibroblasts in breast cancer: relations between their occurrence, tumor grade and expression of some tumour markers
It is suggested that tumour stromal myofibroblasts exert an
unfavourable effect on the biology of breast cancer. We are
aware of only a single study which examined relationships
between manifestation of myofibroblasts in the stroma of breast
cancer and clinicopathological data of the patients. The present
study was aimed at estimation of the effect exerted by
myofibroblasts present in the tumour stroma on principal
pathological parameters and on expression of Ki67, P53 and HER-2
proteins in the group of the most frequent breast cancers, the
ductal cancers. In paraffin sections of 60 ductal breast cancers
(20 cases in G1, 20 in G2 and 20 in G3), immunohistochemical
reactions were performed to detect expression of smooth muscle
actin (SMA) in order to visualize myofibroblasts, Ki67, P53 and
HER-2. The studies demonstrated that the most numerous
myofibroblasts were present in G3 cases and they were the least
frequent in G1 cases (P = 0.02). Positive correlations were
observed between the presence of myofibroblasts in tumour stroma
and expression of Ki67 and HER-2 in breast cancer cells in the
entire group (P < 0.001 and P = 0.001, respectively), in G2
cases (P = 0.003 and P = 0.03) and in G3 cases (P = 0.01 and P =
0.03). Considering that the higher grade, Ki67 and HER-2 are
thought to represent unfavourable prognostic factors, the
elevated content of myofibroblasts in tumour stroma is probably
typical for cases with worse prognosis
Numerical and experimental investigation of a small gas turbine combustor
Workshop byl částečně podpořen projektem CZ.1.07/2.3.00/20.0139. Tento projekt je spolufinancován
Evropským sociálním fondem a státním rozpočtem České republiky
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