Low-energy optical conductivity of TaP : comparison of theory and experiment

The ab-plane optical conductivity of the Weyl semimetal TaP is calculated from the band structure and compared to the experimental data. The overall agreement between theory and experiment is found to be best when the Fermi level is slightly (20 to 60 meV) shifted upwards in the calculations. This confirms a small unintentional doping of TaP, reported earlier, and allows a natural explanation of the strong low-energy (50 meV) peak seen in the experimental ab-plane optical conductivity: this peak originates from transitions between the almost parallel non-degenerate electronic bands split by spin-orbit coupling. The temperature evolution of the peak can be reasonably well reproduce by calculations using an analog of the Mott formula.Deutsche Forschungsgemeinschaf

Fractional power-law intraband optical conductivity in the low-dimensional Dirac material CaMnBi2

We studied the broadband optical conductivity of CaMnBi2, a material with two-dimensional Dirac electronic bands, and found that both components of the intraband conductivity follow a universal power law as a function of frequency at low temperatures. This conductivity scaling differs from the Drude(-like) behavior, generally expected for free carriers, but matches the predictions for the intraband response of an electronic system in a quantum critical region. Since no other indications of quantum criticality are reported for CaMnBi2 so far, the cause of the observed unusual scaling remains an open question.Deutsche Forschungsgemeinschaf

Boxnep - модульный подводный робот перспективных технологий

The article discusses the relevance of the underwater vehicles are able to solve a wide range of problems. The decision puts in a basis of the research is designing a modular underwater robot. It allows to make a mounting of various equipment and testing it in the water medium. The paper deals with the concept of the robot and its characteristics

Возможности позитронной эмиссионной томографии, совмещенной с компьютерной томографией, с 18F-ФДГ в диагностике почечно-клеточного рака

Positron emission tomography combined with computed tomography (PET/CT) is a method, capable of evaluation of not only structural, but also metabolic alterations in organs and tissues. 18F-fluorodeoxyglucose (18F-PDG) PET/CT is widely used in diagnostics of various malignant tumors, but its role in renal cell carcinoma (RCC) remains obscure.Despite its limited effectiveness in primary and differential diagnosis of RCC, PET/CT can be used to determine the grade of malignancy and the histological type of tumor. According to various authors, 18F-FDG standardized uptake value (SUV) of a renal neoplasm can serve as an independent prognostic factor of overall survival.18F-FDG PET/CT is widely used to detect local recurrence and metastatic lesions in various neoplastic processes. Numerous studies confirm the high efficiency of PET/CT in detection of metastases and recurrence discernment for RCC.The ability to assess the metabolic activity of neoplastic foci using PET/CT may allow for evaluation of RCC therapy effectiveness, which is confirmed by clinical studies of various targeted therapy agents, such as tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors, and monoclonal antibodies.Thus, there is growing evidence that 18F-FDG PET/CT is a useful tool in diagnostics of RCC.Позитронная эмиссионная томография, совмещенная с компьютерной томографией (ПЭТ/КТ), является методом оценки не только структурных, но и метаболических изменений в органах и тканях. ПЭТ/КТ с 18F-фтордезоксиглюкозой (18F-ФДГ) широко применяется в диагностике различных злокачественных опухолей, однако роль данного метода при почечно-клеточном раке (ПКР) остается неясной.Несмотря на ограниченную эффективность в первичной и дифференциальной диагностике ПКР, ПЭТ/КТ может быть использована для определения степени злокачественности и гистологического типа опухоли. Кроме этого, по данным различных авторов, показатель стандартизированной величины поглощения (standardized uptake value, SUV) 18F-ФДГ неопластического очага при ПКР может служить независимым прогностическим фактором общей выживаемости.ПЭТ/КТ с 18F-ФДГ широко применяется для выявления местного рецидива и метастатической диссеминации при различных неопластических процессах. Результаты многочисленных исследований подтверждают высокую эффективность ПЭТ/КТ в оценке распространенности и диагностике рецидива ПКР.Возможность определения метаболической активности неопластических очагов с помощью ПЭТ/КТ позволяет использовать этот метод для оценки эффективности терапии ПКР, что подтверждается данными клинических исследований различных таргетных препаратов, таких как ингибиторы тирозинкиназы, ингибиторы мишени рапамицина млекопитающих и моноклональные антитела.Таким образом, все больше данных свидетельствует в пользу того, что ПЭТ/КТ с 18F-ФДГ является полезным инструментом в диагностике ПКР.

Rotational coherence of encapsulated ortho and para water in fullerene-C60 revealed by time-domain terahertz spectroscopy

We resolve the real-time coherent rotational motion of isolated water molecules encapsulated in fullerene-C60 cages by time-domain terahertz (THz) spectroscopy. We employ single-cycle THz pulses to excite the low-frequency rotational motion of water and measure the subsequent coherent emission of electromagnetic waves by water molecules. At temperatures below ~ 100 K, C60 lattice vibrational damping is mitigated and the quantum dynamics of confined water are resolved with a markedly long rotational coherence, extended beyond 10 ps. The observed rotational transitions agree well with low-frequency rotational dynamics of single water molecules in the gas phase. However, some additional spectral features with their major contribution at ~2.26 THz are also observed which may indicate interaction between water rotation and the C60 lattice phonons. We also resolve the real-time change of the emission pattern of water after a sudden cooling to 4 K, signifying the conversion of ortho-water to para-water over the course of 10s hours. The observed long coherent rotational dynamics of isolated water molecules confined in C60 makes this system an attractive candidate for future quantum technology.Deutsche ForschungsgemeinschaftEPSRC-UKProjekt DEA

Advances in Topological Materials

Materials with electronic bands that possess nontrivial topology have remained a focal point of condensed matter physics since 2005, when topological insulators were theoretically discovered by Kane and Mele [...

Low-Energy Optical Conductivity of TaP: Comparison of Theory and Experiment

The ab-plane optical conductivity of the Weyl semimetal TaP is calculated from the band structure and compared to the experimental data. The overall agreement between theory and experiment is found to be best when the Fermi level is slightly (20 to 60 meV) shifted upwards in the calculations. This confirms a small unintentional doping of TaP, reported earlier, and allows a natural explanation of the strong low-energy (50 meV) peak seen in the experimental ab-plane optical conductivity: this peak originates from transitions between the almost parallel non-degenerate electronic bands split by spin-orbit coupling. The temperature evolution of the peak can be reasonably well reproduce by calculations using an analog of the Mott formula