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Morphogens choreograph the generation of remarkable cellular diversity in the developing nervous system. Differentiation of stem cells toward particular neural cell fates in vitro often relies upon combinatorial modulation of these signaling pathways. However, the lack of a systematic approach to understand morphogen-directed differentiation has precluded the generation of many neural cell populations, and knowledge of the general principles of regional specification remain in-complete. Here, we developed an arrayed screen of 14 morphogen modulators in human neural organoids cultured for over 70 days. Leveraging advances in multiplexed RNA sequencing technology and annotated single cell references of the human fetal brain we discovered that this screening approach generated considerable regional and cell type diversity across the neural axis. By deconvoluting morphogen-cell type relationships, we extracted design principles of brain region specification, including critical morphogen timing windows and combinatorics yielding an array of neurons with distinct neuro-transmitter identities. Tuning GABAergic neural subtype diversity unexpectedly led to the derivation of primate-specific interneurons. Taken together, this serves as a platform towards an in vitro morphogen atlas of human neural cell differentiation that will bring insights into human development, evolution, and disease.

A procedure has been developed to determine the geometrical parameters of fuel assemblies (FA) by an ultrasonic pulse-echo technique used for all types of light-water reactor FAs. The measurement of geometrical parameters is achieved through the pairwise installation of ultrasonic transducers opposite the FA spacer grid faces at a distance of not more than a half of the transducer acoustic field near-region length such that the acoustic axes of the pairwise transducers are parallel to each other. The advantages of the presented technique is that it enables monitoring of any FA modifications, including the VVER reactor assemblies with a different number of spacer grids. The paper presents a mathematical model of the acoustic path developed in a geometrical acoustics approximation and its verification results. The model was used for computational and experimental studies of the ultrasonic test technique, and engineering formulas have been developed to calculate the errors of the transducer-measured distance to the FA surface. A code has been developed to simulate the FA form change monitoring and can be used to design new monitoring systems. The developed technique to determine the VVER-1000 FA geometrical parameters was introduced at units 1 and 2 of the Temelin NPP, the Czech Republic, for the TVSA-T FA form change monitoring. The successful use of the proposed technique makes it possible to recommend it for use in inspection benches at other NPPs.

The effects of many FDA-approved drugs on the development of the human brain are still poorly understood. Despite an extensive review process, verification of drug safety is often carried out in animal models, and later clinical trials tend to exclude pregnant women. For these reasons, new ways of evaluating the effects of drugs on early neurodevelopment in human cells are needed. Neural organoids derived from pluripotent stem cells present an excellent model system for studying brain development and dysfunction in human cells, but large-scale organoid culture has been difficult to maintain. In this study, I used a biocompatible polymer co-culture approach, which allows many organoids to be cultured simultaneously, to perform a screen investigating the effects of 298 drugs including FDA-approved compounds and teratogens on early cortical development in over 2,400 cortical organoids. Examining organoid growth over time, cytotoxicity, and distribution of a key neurodevelopmental marker allowed identification of a known teratogen affecting cortical organoid growth and development. I also found an intriguing result regarding the effect of a class of serotonin receptor agonists known as triptans on organoid growth. Taken together, the results of this study provide an evaluation of the effects of a wide variety of FDA-approved drugs on early cortical development and demonstrate the utility of cortical organoids for large-scale drug screens in the future.

We investigate ultrafast harmonic generation (HG) in Si:B, driven by intense pump pulses with fields reaching ~100 kV/cm and a carrier frequency of 300 GHz, at 4 K and 300 K, both experimentally and theoretically. We report several novel findings concerning the nonlinear charge carrier dynamics in intense sub-THz fields. (i) Harmonics of order up to n=9 are observed at room temperature, while at low temperature we can resolve harmonics reaching even n=13. The susceptibility per charge carrier at moderate field strength is as high as for charge carriers in graphene, considered to be one of the materials with the strongest sub-THz nonlinear response. (ii) For T=300 K, where the charge carriers bound to acceptors are fully thermally ionized into the valence subbands, the susceptibility values decrease with increasing field strength. Simulations incorporating multi-valence-band Monte-Carlo and finite-difference-time-domain (FDTD) propagation show that here, the HG process becomes increasingly dominated by energy-dependent scattering rates over the contribution from band non-parabolicity, due to the onset of optical-phonon emission, which ultimately leads to the saturation at high fields. (iii) At T=4 K, where the majority of charges are bound to acceptors, we observe a drastic rise of the HG yields for internal pump fields of 30 kV/cm, as one reaches the threshold for tunnel ionization. We disentangle the HG contributions in this case into contributions from the initial 'generational'- and subsequent band-nonlinearities, and show that scattering seriously degrades any coherent recollision during the subsequent oscillation of the holes.

The coronavirus pandemic has raised serious questions about the need to properly inform residents of large cities about the rules of hygiene, behavior in self-isolation, and maintaining health. This study aimed to identify in more detail the sources of information and to assess the levels of awareness and knowledge of the inhabitants of a typical metropolis about coronavirus infection to further search for ways to improve health information during pandemics. This research has a questionnaire survey design. Data from 478 adult Muscovites were collected on 20–25 March 2020 by the Institute of Social Sciences of Sechenov University. The aim of this study was to study the level of awareness in preventing the spread of infection and peculiarities in the perceptions of residents of the city of Moscow toward the large-scale social changes associated with the COVID-19 pandemic as well as their impact on the way of life, social relations, lifestyle, and ideas about the future of the population. This article presents the results of a medical and sociological survey of residents of Moscow implemented at the beginning of the spread of coronavirus infection in the country, which showed the awareness of residents of Moscow regarding the problem of the spread of coronavirus and the prevention of infection as well as a high level of anxiety and the pessimistic expectations of respondents regarding the consequences of the COVID-19 pandemic for the state, society, and people. At the same time, the fears of the survey participants involved both immediate risks of the disease and a wide range of socioeconomic problems from near and distant perspectives., publishedVersion

Elemental composition of two groups of 12 clay samples, at and above the Cretaceous/Paleogene(K/Pg) boundary at Byala (Black Sea shore, Eastern Bulgaria), is studied by Neutron Activation Analysis(NAA) in order to trace impact events. Iridium anomaly and a certain set of trace elements, together with biostratigraphicdata, point to two possible impact events recorded: the first one (at the K/Pg boundary), linkedto the giant Chicxulub impact in Mexico; and a second one (above the K/Pg boundary), possibly linked to thelater in age, smaller and closer in distance, Boltysh impact in Ukraine.

Contains fulltext : 284396.pdf (Publisher’s version ) (Closed access) IRMMW-THz 2022

Interstitial magnesium acts as a moderately deep double donor in silicon, and is relatively easily introduced by diffusion. Unlike the case of the chalcogen double donors, the binding energies of the even-parity valley-orbit excited states 1sT$_2$ and 1sE have remained elusive. Here we report on temperature dependence absorption measurements focusing on the neutral charge species. Our results demonstrate thermal activation from the ground state 1sA to the valley-orbit states, as observed by transitions from the thermally populated levels to the odd-parity states 2p$_0$ and 2p$_{\pm}$, 3 pages, 2 figures

Актуальность исследования. Для контроля данных технических операций бурения скважин, различного вида ремонта скважин, геологоразведочного бурения в нефтяной и газовой промышленности на буровых и ремонтных установках всех типов используются технологические датчики (датчики нагрузки, давления, температуры жидкости, выхода раствора, плотности жидкости). Современные датчики имеют малые размеры и для повышения чувствительности изготавливаются на базе наноэлектромеханических систем, которые включают в себя составляющие элементы, нано балки и нанопластины. Эти элементы работают при высоких температурах и подвергаются механическим нагрузкам различного вида. Увеличение прочности этих элементов является несомненно актуальной задачей. Цель: построить математическую модель на базе кинематической гипотезы Тимошенко и модифицированной моментной теории чувствительного элемента в виде балки, нано электромеханического датчика под действием механических и тепловых полей; создать методологию получения оптимальной топологии нано балки для произвольной статической и динамической нагрузки и различных граничных условий с целью увеличения ее жесткости; провести сравнительный анализ статики и нелинейной динамики оптимальной и неоптимальной балок. Объекты: элемент наноэлектромеханических систем в виде балки с учетом оптимальной микроструктуры. Методы: методы топологической оптимизации, вариационные методы, метод конечных разностей второго порядка, методы типа Рунге-Кутта, Фурье и вейвлет анализ, фазовый портрет и сечение Пуанкаре. Результаты. Построена методология получения оптимальной микроструктуры нано балки на основе топологической оптимизации. На основе принципа Гамильтона-Остроградского построена математическая модель неоднородной в двух направлениях (по толщине и длине) нано балки Тимошенко на базе модифицированной моментной теории. Проведен сравнительный анализ статического изгиба и нелинейной динамики оптимальной и неоптимальной нано балок. The relevance of research. Technological sensors (sensors of load, pressure, liquid temperature, solution yield, liquid density) are used for monitoring data of technical operations of well drilling, various types repair of well, exploration drilling in the oil and gas industry on drilling and repair of all types of wells. Modern sensors are small in size and manufactured on the basis of nanoelectromechanical systems to increase sensitivity. They include constituent elements, nano beams and nano plates. These elements operate at high temperatures and are subjected to mechanical loads of various kinds. Increasing the strength of these elements is undoubtedly an urgent task. The main aim of the research is to build a mathematical model on the basis of Timoshenko kinematic hypothesis and the modified couple stress theory of a sensing element in the form of a beam, a nano-electro-mechanical sensor under the action of mechanical and thermal fields; to develop methodology for obtaining the optimal topology of nano beams for arbitrary static and dynamic loads and different boundary conditions in order to increase its rigidity; to conduct a comparative analysis of the statics and nonlinear dynamics of optimal and nonoptimal beams. Objects: element of nanoelectromechanical systems in the form of a beam taking into account the optimal microstructure. Methods: methods of topological optimization, variational methods, second order finite difference method, Runge-Kutta type methods, Fourier and wavelet analysis, phase portrait and Poincare section. Results. A methodology for obtaining the optimal microstructure of the nano beam based on topological optimization is developed. On the basis of the Hamilton-Ostrogradsky principle, a mathematical model of a Timoshenko nano beam inhomogeneous in two directions (in thickness and length) is constructed on the basis of a modified moment theory. A comparative analysis of static bending and nonlinear dynamics was performed for optimal and non-optimal nano beams.

Isotopic enrichment offers cutting-edge properties of materials opening exciting research and development opportunities. In semiconductors, reached progress of ultimate control in growth and doping techniques follows nowadays the high level isotopic purification. This requires deep understanding of isotopic disorder effects and techniques of their effective determination. Isotopic content of both crystal lattice and impurity centers cause the effects, which can be examined by different optical techniques. While disorder in the host lattice can be straight forward evaluated by inelastic light scattering or by SIMS measurements, determination of isotopic contributions of many orders less presented impurities remains challenging and usually observed in high-resolution photoluminescence or optical absorption spectra. Boron-doped diamonds exhibit complex infrared absorption spectra while boron-related luminescence remains unobserved. Boron, as a most light element acting as a hydrogen-like dopant in elemental semiconductors, has a largest relative difference in its isotope masses, and by this, cause the largest isotopic disorder in semiconductors, including diamond, an elemental semiconductor with the lightest atomic mass of a host lattice. This enables an access to the isotopic constitution of boron in diamond by infrared absorption spectroscopy. By comparison of low-temperature absorption spectra of a natural (20% of 10B and 80% of 11B isotopes) and 11B enriched (up to 99%) doped diamonds we differentiate the intracenter transitions related to 10B and to 11B isotopes. We have found that the isotopic spectral lines of the same boron intracenter transition are separated with the energy of about 0.7 meV. This is the largest impurity isotopic shift ever observed in semiconductors doped by hydrogen-like impurity centers.

The Petaflops supercomputer "Zhores" recently launched in the "Center for Computational and Data-Intensive Science and Engineering" (CDISE) of Skolkovo Institute of Science and Technology (Skoltech) opens up new exciting opportunities for scientific discoveries in the institute especially in the areas of data-driven modeling, machine learning and artificial intelligence. This supercomputer utilizes the latest generation of Intel and NVidia processors to provide resources for the most compute intensive tasks of the Skoltech scientists working in digital pharma, predictive analytics, photonics, material science, image processing, plasma physics and many more. Currently it places 6th in the Russian and CIS TOP-50 (2018) supercomputer list. In this article we summarize the cluster properties and discuss the measured performance and usage modes of this scientific instrument in Skoltech.

We have devised a spatial­dynamic model that describes the structure of clusters of toxic cyanobacteria over large water areas. The application of the constructed model has been demonstrated in order to identify the structure of a cluster in digital photographs. The character of bioproductive processes that define the risk of accumulation of toxic microorganisms is determined by a series of parameters that can be measured remotely using aerospace methods (taking photographs). The proposed model, based on a digital image, makes it possible to restore the spatial­dynamic pattern of clusters by determining the state of bioproductive processes in different parts of the cluster. Information about such states is of great importance in order to optimize measures for eliminating the threat of toxicity.Development of a given spatially­dynamic model is related to the need to identify the structure of clusters of toxic cyanobacteria in water areas in order to eliminate the threats to biosecurity. Such clusters are extremely complex objects and are not reproduced by either theoretical or full­scale models.The constructed spatial­dynamic model makes it possible to discover a dynamic pattern of bioproductive processes in different parts of the accumulation of microorganisms. The applied significance of the results obtained is associated with increasing the effectiveness of measures for elimination of the threat of toxicity; in other words, given the model that we constructed, it becomes possible to detect the most effective plots in terms of eliminating the threat.The result of employing the model to the digital images of toxic cyanobacteria agrees well with the hydrobiological realization of this type of objects, Разработана пространственно-динамическая модель, описывающая структуру скоплений токсических цианобактерий на больших водных площадях. Продемонстрировано применение построенной модели для выявления структуры скопления на цифровых снимках. Характер биопродукционных процессов, определяющих опасность скопления токсичных микроорганизмов, определяется рядом параметров, которые могут быть измерены дистанционно аэрокосмическими методами (фотографированием). Предложенная модель на основании цифрового снимка позволяет восстановить пространственно-динамическую картину скоплений путем определения состояния биопродукционных процессов различных частей скопления. Информация о таких состояниях имеет большое значение для оптимизации мероприятий по элиминации угроз токсичности.Разработка данной пространственно-динамическая модели связана с необходимость выявления структуры скоплений токсических цианобактерий на водных площадях для целей устранения угроз биобезопасности. Такие скопления являются чрезвычайно сложными объектами и не воспроизводятся ни теоретическими, ни натурными моделями.Построенная пространственно-динамическая модель позволяет выявить динамическую картину биопродукционных процессов в разных частях скопления микроорганизмов. Прикладная важность полученных результатов связана с повышением эффективности мероприятий по элиминации угроз токсичности, т. е. благодаря построенной модели можно выявлять наиболее эффективные, с точки зрения устранения угрозы, участки.Результаты применения модели к цифровым снимкам скоплений токсических цианобактерий соответствуют гидробиологическим представлениям об объектах данного рода, Розроблено просторово-динамічну модель, що описує структуру скупчень токсичних ціанобактерій на великих водних площах. Продемонстровано застосування побудованої моделі до виявлення структури скупчення на цифрових знімках. Характер біопродукційних процесів, що визначають небезпеку скупчення токсичних мікроорганізмів, визначається рядом параметрів, які можуть бути виміряні дистанційно аерокосмічними методами (фотографуванням). Запропонована модель на підставі цифрового знімка дозволяє відновити просторово-динамічну картину скупчень шляхом визначення стану біопродукційних процесів різних частин скупчення. Інформація про такі стани має велике значення для оптимізації заходів по елімінації загроз токсичності.Розробка даної просторово-динамічна моделі пов'язана з необхідністю виявлення структури скупчень токсичних ціанобактерій на водних площах для цілей усунення загроз біобезпеки. Такі скупчення є надзвичайно складними об'єктами і не відтворюються ні теоретичними, ні натурними моделями.Побудована просторово-динамічна модель дозволяє виявити динамічну картину біопродукційних процесів в різних частинах скупчення мікроорганізмів. Прикладна важливість отриманих результатів пов'язана з підвищенням ефективності заходів по елімінації загроз токсичності, тобто завдяки побудованої моделі можна виявляти найбільш ефективні, з точки зору усунення загрози, ділянки.Результат застосування моделі до цифрових знімків токсичних ціанобактерій відповідають гідробіологичним уявлення про об'єкти даного роду

The low-temperature relaxation processes of non-equilibrium holes into gallium centers in moderately doped p-germanium (NA ≈ 2×10^15 cm-3) has been investigated by a degenerate pump-probe experiment using the free electron laser FELBE. The capture time decreases with increasing average photon flux density of the excitation pulse from about 10.9 ns (at ~1.2×10^24 cm-2 s-1) to ~1.2 ns (~2×10^26 cm-2 s-1). Relaxation inside the valence band is almost independent on pump light intensity and its characteristic time is about 200 ps. In Addition, the intracenter relaxation times of the lowest excited Ga states were measured. The lifetimes scale with the phonon density of states controlling a bound hole – acoustic phonon interaction. The lifetime of the lowest excited state, 1Γ_8^-, was measured to be ~275 ps; while the lifetimes of the higher excited states, 2Γ_8^-and 3Γ_8^-, were found to be ~157 ps and 162 ps, respectively.

Актуальность. При проведении горных работ и образовании горных выработок, происходит изменение естественного напряженно-деформированного состояния окружающего выработку массива. В результате изменяется деформированное и напряженное состояние массивов породы в окрестности выработки, что может привести к ее обрушению. Эти напряжения существенно зависят от формы поперечного сечения выработки и вида дополнительных укреплений свода штольни. Таким образом, возможность предсказывать эти процессы, а тем более управлять ими, создавая оптимальные формы и виды укрепления сводов, может снизить вероятность разрушения штольни и повысить их надежность. Цель работы: моделирование и оптимизация формы выработок в виде длинных тоннелей, которые можно считать находящимися в условиях плоского деформированного состояния; проектирование оптимальной топологии несущей конструкции вокруг выработки для оптимальных форм сводов, воспринимающей основные нагрузки как от собственного веса, так и от веса вышележащей породы. Методы. Для математического моделирования поведения выработки используются методы конечных и граничных элементов для задач механики твердого деформируемого тела и методы оптимизации формы упругих тел, разработанные авторами. Для задач укрепления свода штолен применяется метод топологической оптимизации. Результаты. Созданы алгоритмы и программы оптимизации формы и топологической оптимизации для плоской задачи теории упругости. На примере модельной задачи показаны возможности оптимизации формы свода выработки и ее оптимального внешнего укрепления стальной конструкцией с целью снижения максимального касательного напряжения (критерий Треска), что позволило снизить эти напряжения на порядок. Relevance. At mining and formation of excavation, the array natural stress-strain state, surrounding the extraction, changes. The result is the deformation of the rock and redistribution of stresses around the excavation, which could lead to its collapse. These stresses strongly depend on the shape of the cross section of the development and type of additional fortifications of the vault gallery. Thus, the ability to predict these processes, and especially to control them, developing optimal forms and types of arches strengthening, may reduce the probability of a tunnel destruction and increase their reliability. The aim of this work is modeling and shape optimization of excavations in the form of long tunnels that can be considered under plane strain state; design of optimal topology of the supporting structure around the excavation for optimal form of arches, perceiving the main load of its own weight and the weight of the overlying rocks. Methods. For mathematical modeling of the excavation behavior the authors have used the methods of finite and boundary elements for problems in mechanics of deformable body and the methods of elastic bodies forms optimization developed by the authors. For strengthening the arch of tunnels the method of topological optimization was used. Results. The authors developed the algorithms and programs of optimization of shape and topology optimization for a planar problem of elasticity theory. By the example of the model problem the authors demonstrate the possibility of optimizing the arch shape of the excavation and its optimal external strengthening with the steel structure for reducing the maximum shear stress (criterion Cod), thus decreasing these stresses.

In this work we compare the effectiveness of photodynamic therapy with the use of conventional continuous laser irradiation of tumors and newly developed selective laser-scanning method. The proposed method consists in tumor irradiation with a beam of low power and small cross section, which moves through the selected area with a certain delay at each point. The scanning is performed only in the tumor zones with detected fluorescence. To register tumor fluorescence we use CCD-camera, connected to a PC on Windows 7. We have developed a program «ControLS» for our complex of diagnostic and treatment. Comparison of the developed PDT version with the traditional method in experiments on photodynamic treatment of mice with lung carcinomas showed that the proposed method is capable to produce an equal tumor-inhibiting effect under much lower doses of laser irradiation. This diagnostic system can permit more efficient use of laser radiation and consider fluctuations in the concentration of photosensitizer in the tumor, depending on the availability of fluorescence in the tumor tissue., В работе показан новый метод фотодинамической терапии с выборочным сканированием в зоне флуоресценции опухоли. Предложенный метод заключается в определении границ флуоресценции с последующим «точечным» облучением лазерным лучом малого поперечного сечения с фиксированной временной задержкой в каждой локальной области, при этом терапия проводится только в той зоне, в которой имеется флуоресценция. Для реализации данного метода была разработана новая лечебно-диагностическую установку на основе сканирующего лазера. Для регистрации флюоресценции ФС опухоли использовалась цветная видеокамера SD на базе ПЗС-матрицы, подключенная к ПК на основе Windows 7. Программное обеспечение лечебно-диагностического комплекса реализовано в виде авторского программного пакета «ControLS». Данная диагностическая система может позволить более эффективно использовать лазерное излучение и учитывать колебания концентрации ФС в опухоли, в зависимости от наличия флюоресценции в конкретный момент времени, Розглянуто метод фотодинамічної терапії із вибірковим лазерним опроміненням в області флуоресценції пухлини. Запропонований метод полягає у визначенні границь флуоресценції із подальшим «поточковим» опроміненням сфокусованим лазерним пучком із фіксованою часовою затримкою в кожній локальній ділянці тканини, терапія пухлини відбувається лише у тій зоні, в якій наявна флуоресценція. Для реалізації даного методу використано нову лікувально-діагностичну установку на основі скануючого лазерного пристрою. Для реєстрації флюоресценції ФС пухлини використано кольорову відеокамеру SD на базі ПЗЗ-матриці, підключену до ПК. Програмне забезпечення лікувально-діагностичного комплексу реалізовано у вигляді авторського програмного пакету «ControLS». Дана діагностична система може дозволити ефективніше використовувати лазерне випромінювання та враховувати коливання концентрації ФС в пухлині, залежно від наявності флюоресценції в конкретний момент часу.

High-resolution molecular spectroscopy is a powerful tool for investigations of the structure and energy levels of molecules and atoms. In addition to the scientific interest, terahertz (THz) spectroscopy is also of interest for the detection and identification of gases in safety and security applications. While for frequencies below 2 THz many different methods have been developed, spectroscopy above 2 THz is hampered by the lack of frequency-tunable, continuous-wave, powerful, and narrow-linewidth radiation sources. For this frequency range, THz quantum-cascade lasers (QCLs) are promising radiation sources. We report on a THz absorption spectrometer, which combines a grating monochromator, a QCL, and a microbolometer camera. The QCL used in these experiments contains a single-plasmon waveguide and a Fabry-Pérot cavity with both facets uncoated. It is optimized for low electrical pumping powers an emits several modes centered around 3.4 THz. The laser is mounted in a compact air-cooled cryocooler (model K535 from Ricor). The emitted beam is focused with a TPX lens and guided through a 27 cm long absorption cell onto the monochromator, which spectrally resolves the laser modes. The modes are imaged onto the microbolometer camera. The absorption spectrum of methanol around 3.4 THz is measured by detecting simultaneously the signal of each of the laser modes as a function of the laser driving current. By this means, frequency multiplexing is achieved.

High-resolution molecular spectroscopy is a powerful tool for investigations of the structure and energy levels of molecules and atoms. In addition to scientific utilization, terahertz (THz) spectroscopy is of interest for detection and identification of gases in safety and security applications. While for frequencies below 2 THz many different methods have been developed, spectroscopy above 2 THz is hampered by the lack of frequency-tunable, continuous-wave, powerful, and narrow-linewidth radiation sources. For this frequency range, THz quantum-cascade lasers (QCLs) are promising radiation sources. We report on a THz absorption spectrometer, which combines a grating monochromator, a QCL, and a microbolometer camera. The QCL used for these experiments is based on a single-plasmon waveguide and a Fabry-Pérot cavity with both facets uncoated and is optimized for a low electrical pump power. It operates on several modes centered around 3.4 THz. The laser is mounted in a compact air-cooled cryocooler (model K535 from Ricor). The emitted beam is focused with a TPX lens and guided through a 27 cm long absorption cell onto the monochromator, which spectrally resolves the laser modes. The modes are imaged onto the microbolometer camera. The absorption spectrum of methanol around 3.4 THz is measured by detecting simultaneously the signal of each of the laser modes as a function of the laser driving current.

We report on the development of a compact local oscillator (LO) for operation on board of SOFIA, namely for GREAT, the German Receiver for Astronomy at Terahertz Frequencies. The LO combines a quantum-cascade laser (QCL) with a compact, low-input-power Stirling cooler. The output power is sufficient for pumping a hot-electron bolometer mixer. Frequency stabilization is achieved by locking to a molecular absorption line. Detectors operating at room temperature can be used for the stabilization as well. High-resolution molecular spectroscopic experiments demonstrate the usability as LO for SOFIA.

We report on the development of a compact, easy-to-use terahertz radiation source, which combines a quantum cascade laser (QCL) with a compact, low-input-power Stirling cooler.

We report on the development of a compact, easy-to-use terahertz radiation source, which combines a quantum-cascade laser (QCL) with a compact, low-input-power Stirling cooler. The QCL, which is based on a two-miniband design, has been developed for high output and low electrical pump power. Special care has been taken to achieve a good thermal coupling between the QCL and the cold finger of the cooler. The whole system weighs less than 15 kg including the cooler and power supplies. The maximum output power is 8 mW at 3.1 THz. With an appropriate optical beam shaping, the emission profile of the laser is fundamental Gaussian. The applicability of the system is demonstrated by imaging and molecular-spectroscopy experiments.