Evolution of oxygen isotopic composition in the inner solar nebula

Changes in the chemical and isotopic composition of the solar nebula with time are reflected in the properties of different constituents that are preserved in chondritic meteorites. CR carbonaceous chondrites are among the most primitive of all chondrite types and must have preserved solar nebula records largely unchanged. We have analyzed the oxygen and magnesium isotopes in a range of the CR constituents of different formation temperatures and ages, including refractory inclusions and chondrules of various types. The results provide new constraints on the time variation of the oxygen isotopic composition of the inner (<5 AU) solar nebula - the region where refractory inclusions and chondrules most likely formed. A chronology based on the decay of short-lived 26Al (t1/2 ~ 0.73 Ma) indicates that the inner solar nebula gas was 16O-rich when refractory inclusions formed, but less than 0.8 Ma later, gas in the inner solar nebula became 16O-poor and this state persisted at least until CR chondrules formed ~1-2 Myr later. We suggest that the inner solar nebula became 16O-poor because meter-size icy bodies, which were enriched in 17,18O due to isotopic self-shielding during the ultraviolet photo dissociation of CO in the protosolar molecular cloud or protoplanetary disk, agglomerated outside the snowline, drifted rapidly towards the Sun, and evaporated at the snowline. This led to significant enrichment in 16O-depleted water, which then spread through the inner solar system. Astronomical studies of the spatial and/or temporal variations of water abundance in protoplanetary disks may clarify these processes.Comment: 27 pages, 5 figure

Reinvestigation of tris­odium dihydroxido­tetra­oxidoneptunate(VII) dihydrate

The title compound, Na3[NpO4(OH)2]·2H2O, contains distorted tetra­gonal–bipyramidal centrosymmetric [NpO4(OH)2]3− complex anions. The Np—O distances are 1.8975 (7) and 1.8891 (7) Å in the NpO4 group and 2.3451 (7) Å to the OH group. Both Na atoms (one in a general position, the second in a special position on an inversion centre) have a distorted octahedral oxygen environment

Thermal Processing of Silicate Dust in the Solar Nebula: Clues from Primitive Chondrite Matrices

The most abundant matrix minerals in chondritic meteorites, hydrated phyllosilicates and ferrous olivine crystals, formed predominantly in asteroids during fluid-assisted metamorphism. We infer that they formed from minerals present in three less altered carbonaceous chondrites that have silicate matrices composed largely of micrometer- and nanometer-sized grains of crystalline forsterite, Mg2SiO4, and enstatite MgSiO3, and amorphous, ferromagnesian silicate. Compositional and structural features of enstatite and forsterite suggest that they formed as condensates that cooled below 1300 K at \~1000 K/h. Most amorphous silicates are likely to be solar nebula condensates also, as matrix, which is approximately solar in composition, is unlikely to be a mixture of genetically unrelated materials with different compositions. Since chondrules cooled at 10-1000 K/h, and matrix and chondrules are chemically complementary, most matrix silicates probably formed close to chondrules in transient heating events. Shock heating is favored as nebular shocks capable of melting millimeter-sized aggregates vaporize dust. The crystalline and amorphous silicates in the primitive chondrite matrices share many characteristic features with silicates in chondritic interplanetary dust particles suggesting that most of the crystalline silicates and possibly some amorphous silicates in the interplanetary dust particles are also nebular condensates. Except for small amounts of refractory oxides that formed with Ca-Al-rich inclusions at the inner edge of the disk and presolar dust, most of the crystalline silicate dust that accreted into chondritic asteroids and long-period comets appears to have formed from shock heating at ~2-10 AU. Forsterite crystals around young stars may have a similar origin.Comment: 16 page

Budget impact of modern drugs for the treatment of schizophrenia: regional aspects

The article presents the results of comparative pharmacoeconomic analysis of treatment of schizophrenia with antipsychotics of the first and second generation in Khabarovsk territory. Regional «portrait» of the patient with schizophrenia is presented. Results of the analysis of experts’ preferences in prescription of psychotropic drugs in treatment of schizophrenia are given. Sociological, pharmacoeconomic and pharmacoepidemiologic methods of the analysis are chosen for carrying out present research. Analysis of «cost-effectiveness» and «budget impact» are used together for pharmacoeconomic method. The results of the conducted researches have allowed to develop the model of optimization of medicines’ provision for patients with schizophrenia taking into account the regional features

One of the earliest refractory inclusions and its implications for solar system history

A ∼175 µm refractory inclusion, A-COR-01 from one of the least altered carbonaceous chondrites, ALHA 77307 (CO3.0), has been found to bear unique characteristics that indicate that it is one of the first solids to have formed at the very birth of the solar system while isotopic reservoirs were still evolving rapidly. Its core is composed mainly of hibonite and corundum, the two phases predicted to condense first from a gas of solar composition, and like many common types of Calcium-, Aluminium-rich Inclusions (CAIs) is surrounded by a rim of diopside. Core minerals in A-COR-01 are very 16O-rich (Δ17OCore = -32.5 ± 3.3 (2SD) ‰) while those in the rim display an O isotopic composition (Δ17ORim = -24.8 ± 0.5 (2SD) ‰) indistinguishable from that found in the vast majority of the least altered CAIs. These observations indicate that this CAI formed in a very 16O-rich reservoir and either recorded the subsequent evolution of this reservoir or the transit to another reservoir. The origin of A-COR-01in a primitive reservoir is consistent with the very low content of excess of radiogenic 26Mg in its core minerals corresponding to the inferred initial 26Al/27Al ratio ((26Al/27Al)0 = (1.67 ± 0.31) × 10-7), supporting a very early formation before injection and/or homogenisation of 26Al in the protoplanetary disk. Possible reservoir evolution and short-lived radionuclide (SLRs) injection scenarios are discussed and it is suggested that the observed isotope composition resulted from mixing of a previously un-observed early reservoir with the rest of the disk

Моделирование и нелинейный анализ хаотических волновых процессов в электрохимически активных нейроновых средах на основе матричной декомпозиции

A general model of the origin and evolution of chaotic wave processes in electrochemically active neuronal media based on the proposed method of matrix decomposition of operators of nonlinear systems has been developed. The mathematical models of Hodgkin – Huxley and FitzHugh – Nagumo of an electrochemically active neuronal media are considered. The necessary conditions for self-organization of chaotic self-oscillations in the FitzHugh – Nagumo model are determined. Computer modeling based on the matrix decomposition of chaotic wave processes in electrochemically active neuronal media has shown the interaction of higher-order nonlinear processes leading to stabilization (to a finite value) of the amplitude of the chaotic wave process. Mathematically, this is expressed in the synchronous “counteraction” of nonlinear processes of even and odd orders in the general vector-matrix model of an electrochemically active neuronal media being in a chaotic mode. It is noted that the state of hard self-excitation of nonlinear oscillations in an electrochemically active neuronal media leads to the appearance of a chaotic attractor in the state space. At the same time, the  proposed vector-matrix model made it possible to find more general conditions for the appearance and evolution of chaotic wave  processes in  comparison with  the  initial  Landau  turbulence model  and,  as  a  result,  to  explain  the occurrence of consistent nonlinear phenomena in an electrochemically active neuronal media.Разработана общая модель возникновения и эволюции хаотических волновых процессов в электрохимически  активных  нейроновых  средах  на  основе  предложенного  метода  матричной  декомпозиции операторов нелинейных систем. Рассмотрены математические модели  Ходжкина –  Хаксли и ФитцХью – Нагумо электрохимически активной нейроновой среды. Определены необходимые условия самоорганизации хаотических автоколебаний в модели ФитцХью – Нагумо. Компьютерное моделирование на основе матричной декомпозиции хаотических волновых процессов в электрохимически активных нейроновых средах  показало  взаимодействие нелинейных процессов высших  порядков, приводящее к стабилизации (конечной величине) амплитуды хаотического волнового процесса. Математически это выражается  в  синхронном  «противодействии» нелинейных  процессов  четных  и  нечетных  порядков в общей векторно-матричной модели электрохимически активной нейроновой среды, находящейся в хаотическом режиме. Отмечено, что режим жесткого самовозбуждения нелинейных колебаний в электрохимически активной нейроновой среде приводит к появлению хаотического аттрактора в пространстве состояний. Вместе с тем предложенная векторно-матричная модель позволила найти более общие условия возникновения и эволюции хаотических волновых процессов по сравнению с моделью начальной турбулентности Ландау и, как следствие, объяснить возникновение согласованных нелинейных явлений в электрохимически активной нейроновой среде

An oxygen isotope study of Wark–Lovering rims on type A CAIs in primitive carbonaceous chondrites

Calcium–aluminium-rich Inclusions(CAIs) and the thin Wark–Lovering (WL) rims of minerals surrounding them offer a record of the nature of changing conditions during the earliest stages of Solar System formation. Considerable heterogeneity in the gas composition in the immediate vicinity of the proto-Sun had previously been inferred from oxygen isotopic variations in the WL rim of a CAI from Allende (Simon et al., 2011). However, high precision and high spatial resolution oxygen isotope measurements presented in this study show that WL rim and pristine core minerals of individual CAIs from meteorites that had experienced only low degrees of alteration or low grade metamorphism (one from Léoville (reduced CV3), two in QUE 99177 (CR3.0) and two in ALHA 77307 (CO3.0)) are uniformly 16O-rich. This indicates that the previously observed variations are the result of secondary processes, most likely on the asteroid parent body, and that there were no temporal or spatial variations in oxygen isotopic composition during CAI and WL rim formation. Such homogeneity across three groups of carbonaceous chondrites lends further support for a common origin for the CAIs in all chondrites. 16O-poor oxygen reservoirs such as those associated with chondrule formation, were probably generated by UV photo-dissociation involving self-shielding mechanisms and must have occurred elsewhere in outer regions of the solar accretion disk