Collision of two identical hypersonic stellar winds in binary systems

We investigate the hydrodynamics of two identical hypersonic stellar winds in a binary system. The interaction of these winds manifests itself in the form of two shocks and a contact surface between them. We neglect the binary rotation and assume that the gas flow ahead of the shocks is spherically symmetrical. In this case the contact surface that separates the gas emanated from the different stars coincides with the midplane of the binary components. In the shock the gas is heated and flows away nearly along the contact surface. We find the shock shape and the hot gas parameters in the shock layer between the shock and the contact surface.Comment: 19 pages, 3 figures, accepted for publication in Ap

Fucans, but Not Fucomannoglucuronans, Determine the Biological Activities of Sulfated Polysaccharides from Laminaria saccharina Brown Seaweed

Sulfated polysaccharides from Laminaria saccharina (new name: Saccharina latissima) brown seaweed show promising activity for the treatment of inflammation, thrombosis, and cancer; yet the molecular mechanisms underlying these properties remain poorly understood. The aim of this work was to characterize, using in vitro and in vivo strategies, the anti-inflammatory, anti-coagulant, anti-angiogenic, and anti-tumor activities of two main sulfated polysaccharide fractions obtained from L. saccharina: a) L.s.-1.0 fraction mainly consisting of O-sulfated mannoglucuronofucans and b) L.s.-1.25 fraction mainly composed of sulfated fucans. Both fractions inhibited leukocyte recruitment in a model of inflammation in rats, although L.s.-1.25 appeared to be more active than L.s.-1.0. Also, these fractions inhibited neutrophil adhesion to platelets under flow. Only fraction L.s.-1.25, but not L.s.-1.0, displayed anticoagulant activity as measured by the activated partial thromboplastin time. Investigation of these fractions in angiogenesis settings revealed that only L.s.-1.25 strongly inhibited fetal bovine serum (FBS) induced in vitro tubulogenesis. This effect correlated with a reduction in plasminogen activator inhibitor-1 (PAI-1) levels in L.s.-1.25-treated endothelial cells. Furthermore, only parent sulfated polysaccharides from L. saccharina (L.s.-P) and its fraction L.s.-1.25 were powerful inhibitors of basic fibroblast growth factor (bFGF) induced pathways. Consistently, the L.s.-1.25 fraction as well as L.s.-P successfully interfered with fibroblast binding to human bFGF. The incorporation of L.s.-P or L.s.-1.25, but not L.s.-1.0 into Matrigel plugs containing melanoma cells induced a significant reduction in hemoglobin content as well in the frequency of tumor-associated blood vessels. Moreover, i.p. administrations of L.s.-1.25, as well as L.s.-P, but not L.s.-1.0, resulted in a significant reduction of tumor growth when inoculated into syngeneic mice. Finally, L.s.-1.25 markedly inhibited breast cancer cell adhesion to human platelet-coated surfaces. Thus, sulfated fucans are mainly responsible for the anti-inflammatory, anticoagulant, antiangiogenic, and antitumor activities of sulfated polysaccharides from L. saccharina brown seaweed

МР-томография миокарда с парамагнитным контрастным усилением Mn-етоксиизобутилизонитрилом (Mn-МИБИ) в эксперименте

Aim: to evaluate with MRI technique the uptake of paramagnetic complex Mn-methoxyisobutylisonitrile (MIBI) to myocardium in rats in normal control animals and in experimental infarction. Material and methods. Complex Mn-MOBI was obtained with one-stage synthesis from manganese (II) carbonate and methoxyisobutylisonitrile hydroxide (produced by the Laboratory of technology and control of radiopharmaceuticals of the A.I. Burnazyan Russian state federal medical and biophysics Center), obtaining finally the 0.5 M solution of Mn-MIBI at pH = 6.3. The Mn-MIBI was injected intravenously slowly to sleeping rats (Telazol, i/m), as 0.05 ml of 0,5 M solution per Kg of BW. For this study nine normal control Whistar rats were employed as well as ten animals with previously induced anterior myocardial infarction of the left ventricle (all males). MRI scanning in T1-weighted spin-echo has been carried out with TR = 500 ms and TE = 15 ms, in axial and frontal slices as thin as 2-2.5 mm, to the matrix 256 х 256, with the field of view as large as 200 х 200 mm. The uptake was scored visually as change in intensity of T1-weighted MRI frontal scans of the whole body of the animals, of axial scans of chest and heart; and also quantitatively, with calculating for the T1-weighted MRI the index of enhancement (IE) of intensity per voxel, as : IE = (MeanInt of T1-w.MRI)Mn-MIBI / (MeanInt of T1-w.MRI)initial Results. Visually on whole-body T1-weighted SE frontal scans the MN-MIBI induced increase of intensity of the heart image, essentially equal for all parts of the left ventricle and less intense over the right ventricle. The values of the IE were over 2.5 for all parts of the left ventricle, whereas only 1.8-1.9 in case of the septum. IE of the right ventricle did not differ significantly when compared to the LV values. When injected to animals with experimental myocardial infarction the Mn-MIBI did not induced any essential changes of intensity in non-perfused regiones, with IE = 1.19 ± 0. 08, but raised the intensity over intact lateral wall of the left ventricle, with IE = 2.65 ± 0.14, and also over intact anterior wall, with IE = 2.28 ± 0.17. Conclusion. Complexonate Mn-MIBI provides well enough intense enhancement of myocardium in T1-SE MRI and makes possible to image severe disorders of myocardial blood flow in experimental models. The Mn-MIBI complex can be suggested as basic molecule for nearest future design of paramagnetic contrast agents for myocarrdial perfusion imaging, as well as for other organs taking up the MIBI. Manganese also is conceivable to be employed for labelling of other complexones currently in use in nuclear medicine.Цель исследования: попытка оценки по данным МРТ накопления парамагнитного комплекса Mn-метоксиизобутилизонитрила (МИБИ) в миокарде у крыс в норме и при экспериментальном инфаркте. Материал и методы. Комплекс Mn с МИБИ был получен в один этап из карбоната марганца (II) и гидроксида метоксиизобутилизонитрила (синтезированного лабораторией технологий и методов контроля радиофармпрепаратов ГНЦ России - ФМБЦ им. А.И. Бурназяна) с выходом в итоге 0,5 М раствора Mn-МИБИ при pH 6,3. Препарат Mn-МИБИ вводился внутривенно медленно из расчета 0,05 мл 0,5 М раствора на 1 кг массы тела. В исследование включено 9 контрольных белых крыс и 10 (все самцы) с предварительно смоделированным инфарцированием передней стенки сердца. Сканирование в Т1-взвешенном спин-эхо выполнено до и спустя 8-10 мин после введения Mn-МИБИ при TR 500 мс и TE 15 мс в аксиальных и сагиттальных плоскостях при толщине среза 2-2,5 мм в матрицу 256 х 256 и при размерах поля сканирования 200 х 200 мм. Оценивалались визуальные изменения картины Т1-взвешенной МРТ всего тела и, в частности, сердца, а также количественно степень усиления интенсивности Т1-взвешенного спин-эхо МРТ, как: ИУ = (средн.инт. Т1-взв. МРТ)Mn-МИБИ/ (средн.инт. Т1-взв. МРТ)исходи. Результаты. Визуально отмечалось усиление интенсивности Т1- взвешенного спин-эхо-изображения МРТ в области миокарда левого желудочка в одинаковой степени по всем отделам левого желудочка и визуально меньше - в области правого желудочка. Интенсивность Т1-взвешенных изображений стенок левого желудочка усиливалась в 2,5 раза и более, тогда как в области перегородки - в 1,8-1,9 раза, т.е. достоверно меньше. Индекс усиления правого желудочка не отличался от значений для миокарда левого желудочка. При исследовании у животных с инфарктом миокарда усиление в области инфаркта визуально было незначительным; при количественной оценке индекса усиления для инфарцированных отделов составил 1,19 ± 0,08, в неповрежденной боковой стенке - 2,65 ± 0,14, в неповрежденной передней - 2,28 ± 0,17. Вывод. Комплекс Mn-МИБИ обеспечивает достаточно интенсивное усиление изображение миокарда при МРТ в Т1-взвешенном спин-эхо-режиме и позволяет визуализировать грубые нарушения кровоснабжения сердечной мышцы в эксперименте. Комплекс Mn-МИБИ может рассматриваться как основа для создания парамагнитных контрастных препаратов для визуализации миокарда и, вероятно, также других органов и структур, где было отмечено накопление метоксиизобутилизонитрила. Предполагается использовать комплексонаты99mTc как основу для аналогичных комплексонатов Mn, если их стабильность и R1-релаксивность окажутся достаточными для парамагнитного контрастирования в МР

Комплексная МР-ангиографическая и МР-томографическая диагностика атеросклеротических поражений сонных артерий с парамагнитным контрастированием у больных с распространенным атеросклерозом

Aim. To evaluate the possibility of simultaneous magnetic resonance angiography of carotid arteries and contrast-enhanced magnetic resonance imaging of carotid atherosclerotic plaques. Material and methods. 24 persons entered in research: 16 (66.7%) patients with extensive atherosclerosis of aorta and large arteries and in 8 (33.3%) control persons. Using four-channel quadratur phase-array coil for head studies the brain MRI, MR-angiography of carotid arteries and MR-tomography of carotid atherosclerotic plaques were carried out using contrast enhancement with 0,5M cyclomang (Mn-diaminocyclohexanetetraacetate) solution. The angiography employed 3D GR FFE fast gradient echo protocol (TR/TE/FA/ST = 10 ms / 2.7ms / 20°/ 1.5 mm). MRI of carotid arteries used the T1-w.spin-echo scanning with TR = 500-700 ms, TE = 10 ms, with slices as thin as 1-3 mm, matrix 256 x 256, and voxel as small as 0.2 x x 0.2 x 2 mm. Results. The mean transit time for the paramagnetic contrast passage through brain haemispheres was in healthy control persons as short as MTT = 4.23 ± 0.14 s for the left and MTT = 4.27 ± 0.15 s for the right. The MTT in patients with single-side stenosis was on the involved side as long as 4.89 ± 0.23 s, whereas on the intact side 4.56 ± 0.19 s (p > 0.05). In bilateral stenosis the MTT was 4.98 ± 0.21 s and 5.01 ± 0.16 s (p > 0.05) for the left and right sides respectively. In all cases of aherosclerotic stenoses the contrast-enhanced MRA with cyclomang provided the correct diagnosis of both location and extent of the stenosis. The degree of stenosis calculated for the MR-angiography correlated significantly with the data of ultrasonic study calculated using ECST technique both for monolateral (r = 0.87, p 0,05). При двустороннем поражении эти показатели для левого и правого полушарий составляли 4,98 ± 0,21 с и 5,01 ± 0,16 с. (р > 0,05). МРА с цикломангом позволила во всех случаях визуализировать локализацию и характер стеноза. Величины степени стеноза, рассчитанные для МР-ангиограммы, высокодостоверно коррелировали с данными ультразвукового исследования, выполненного по методике ECSt, для случаев как одностороннего (r = 0,87, р < 0,05), так и двустороннего стенотического поражения (r = 0,85, р < 0,05). Неоднородные рыхлые бляшки с высоким содержанием липидов имели высокие показатели индекса усиления при контрастировании - 1,26 ± 0,07, тогда как плотные фиброзные аваскулярные бляшки - 1,09 ± 0,04 (р < 0,05). Полное время исследования составляло 41 ± 5 мин при выполнении времяпролетной МРА и 29 ± 5 мин без нее. Заключение. Одновременное проведение МРА и МРТ сонных артерий с парамагнитным контрастированием цикломангом возможно и целесообразно в рамках единого исследования с использованием квадратурной катушки для головы

Fucoidans of Brown Algae: Comparison of Sulfated Polysaccharides from Fucus vesiculosus and Ascophyllum nodosum

Preparations of sulfated polysaccharides obtained from brown algae are known as fucoidans. These biopolymers have attracted considerable attention due to many biological activities which may find practical applications. Two Atlantic representatives of Phaeophyceae, namely, Fucus vesiculosus and Ascophyllum nodosum, belonging to the same order Fucales, are popular sources of commercial fucoidans, which often regarded as very similar in chemical composition and biological actions. Nevertheless, these two fucoidan preparations are polysaccharide mixtures which differ considerably in amount and chemical nature of components, and hence, this circumstance should be taken into account in the investigation of their biological properties and structure&ndash;activity relationships. In spite of these differences, fractions with carefully characterized structures prepared from both fucoidans may have valuable applications in drug development

Fucoidan and Fucosylated Chondroitin Sulfate Stimulate Hematopoiesis in Cyclophosphamide-Induced Mice

Application of cytostatics in cancer patients’ chemotherapy results in a number of side effects, including the inhibition of various parts of hematopoiesis. Two sulfated polysaccharides, fucoidan from the seaweed Chordaria flagelliformis (PS-Fuc) and fucosylated chondroitin sulfate from the sea cucumber Massinium magnum (PS-FCS), were studied as stimulators of hematopoiesis after cyclophosphamide immunosuppression in mice. Recombinant granulocyte colony-stimulating factor (r G-CSF) was applied as a reference. Both tested polysaccharides PS-Fuc and PS-FCS have a similar activity to r G-CSF, causing pronounced neutropoiesis stimulation in animals with myelosuppression induced by cyclophosphamide (CPh). Moreover, these compounds are also capable to enhance thrombopoiesis and erythropoiesis. It should be noted that PS-FCS demonstrated a greater activity than r G-CSF. The results indicate the perspective of further studies of PS-Fuc and PS-FCS, since these compounds can be considered as potentially promising stimulators of hematopoiesis. Such drugs are in demand for the accompanying treatment of cancer patients who suffer from hematological toxicity during chemo and/or radiation therapy

InGaN/GaN heterostructures grown by submonolayer deposition

International audienceInGaN/(Al,Ga)N heterostructures containing ultrathin InGaN layers, grown by submonolayer deposition are studied. It is shown that significant phase separation with the formation of local In-enriched regions ∼3–4 nm in height and ∼5–8 nm in lateral size is observed in InGaN layers in the case of InGaN and GaN growth by cyclic deposition to effective thicknesses of less than one monolayer. The effect of growth interruption in a hydrogen-containing atmosphere during submonolayer growth on the structural and optical properties of InGaN/(Al,Ga)N heterostructures is studied. It is shown that these interruptions stimulate phase separation. It is also shown that the formation of In-enriched regions can be controlled by varying the effective InGaN and GaN thicknesses in the submonolayer deposition cycles

Marine Lake Mogilnoe (Kildin Island, the Barents Sea): one hundred years of solitude

Lake Mogilnoe (Kildin Island, the Barents Sea) is a marine stratified lake, a refuge for landlocked populations of marine organisms. Unlike other known marine lakes from polar areas, which communicate with the sea by water percolation at the surface, Mogilnoe has a subterranean connection with the sea like tropical and subtropical anchialine lakes. Similarly to some other marine lakes, Mogilnoe has traditionally been considered to be biologically isolated from the sea and subject to little change. We review the current status of the physical features, zooplankton and benthos of Mogilnoe and trace changes that have occurred in the lake since the start of observations in 1894. The anaerobic bottom water layer has expanded by 100 %, while the upper freshwater layer has diminished by 40 %. The species diversity of zooplankton and macrobenthos has halved. The occurrence of Atlantic cod likens Mogilnoe to some other Arctic marine lakes while the presence of large flocks of sea anemones, scyphomedusae and suberitid sponges makes it similar to tropical anchialine lakes. Lake Mogilnoe is not entirely biologically isolated; accidental introduction of species from the sea does occur. We argue that the idealised model of an isolated steady-state ecosystem can be applied to a marine lake with caution. A model of fluctuating abiotic environment and partial biological isolation portrays the real situation better

Effect of pressure in the growth reactor on the properties of the active region in the InGaN/GaN light-emitting diodes

International audienceEffect of pressure in the reactor in the case of growth of active regions in the InGaN/GaN light-emitting diodes by the method of vapor-phase epitaxy from metalorganic compounds on their electroluminescent and structural properties has been studied. It is shown that, as pressure is increased, the InGaN layers become transformed from being continuous in the lateral direction to the layers of separate InGaN islands. This transformation affects both the emission efficiency and the dependence of efficiency on current