The crystallographic analysis of the structure of a new compound with the metal-organic framework (MOF) Li
2
Zn
2
(bpy)(ndc)
3
(bpy = 4,4′-bipyridine, ndc
2–
= naphthalene-1,4-dicarboxylate) shows ...that its stability is provided by a body-centered quasi-cubic lattice of nodes, one sixth of which is occupied by ZnO
3
N tetrahedra. The local concentration of vacant nodes forms bulk channels and cavities in the structure.
Protons and helium nuclei are the most abundant components of the cosmic radiation. Precise measurements of their fluxes are needed to understand the acceleration and subsequent propagation of cosmic ...rays in our Galaxy. We report precision measurements of the proton and helium spectra in the rigidity range 1 gigavolt to 1.2 teravolts performed by the satellite-borne experiment PAMELA (payload for antimatter matter exploration and light-nuclei astrophysics). We find that the spectral shapes of these two species are different and cannot be described well by a single power law. These data challenge the current paradigm of cosmic-ray acceleration in supernova remnants followed by diffusive propagation in the Galaxy. More complex processes of acceleration and propagation of cosmic rays are required to explain the spectral structures observed in our data.
DDO 68 (UGC 5340) is an unusual dwarf galaxy with extremely low gas metallicity 12 + log (O/H) = 7.14 residing in the nearby Lynx-Cancer void. Despite its apparent isolation, it shows both optical ...and H i morphological evidence for strong tidal disturbance. Here, we study the resolved stellar populations of DDO 68 using deep images from the HST archive. We determined a distance of 12.75 plus or minus 0.41 Mpc using the tip of the red giant branch (TRGB). The star formation history reconstruction reveals that about 60 per cent of stars formed during the initial period of star formation, about 12-14 Gyr ago. During the next 10 Gyr, DDO 68 was in the quenched state, with only slight traces of star formation. The onset of the most recent burst of star formation occurred about 300 Myr ago. We find that young populations with ages of several million to a few hundred million years are widely spread across various parts of DDO 68, indicating an intense star formation episode with a high mean rate of ... A major fraction of the visible stars in the whole system (~80 per cent) have low metallicities: ... The properties of the northern periphery of DDO 68 can be explained by an ongoing burst of star formation induced by the minor merger of a small, gas-rich, extremely metal-poor galaxy with a more typical dwarf galaxy. The current TRGB-based distance of DDO 68 implies a total negative peculiar velocity of ... (ProQuest: ... denotes formulae/symbols omitted.)
Collaboration in TB and COVID-19 control in Moscow Bogorodckaya, E; Sinitsyn, M; Borisov, S
The international journal of tuberculosis and lung disease,
06/2020, Letnik:
24, Številka:
6
Journal Article
The crystallographic analysis of the structures of Yb
3
(BO
3
(OH)
6
)·2H
2
O (
I
), Ba
8
Ni
4
BP
3
O
11
(OH)
2
4
(
II
), and Pb
4
(O(OH)
2
)SiO
4
(
III
) shows that they are based on sublattices of ...heavy Yb, Ba, Pb cations with similar parameters and a significant fraction of vacant nodes, which provides the formation of bulk voids. The key role of these cations also manifests itself in the fact that they occupy special positions with fixed coordinates and a high local symmetry. The crystallization process is a coherent assembly of chemically stable cation groups formed in the precrystallization phase of a substance.
This review is devoted to the consideration of mass spectrometric platforms as applied to omics sciences. The most significant attention is paid to omics related to life sciences (genomics, ...proteomics, meta-bolomics, lipidomics, glycomics, plantomics, etc.). Mass spectrometric approaches to solving the problems of petroleomics, polymeromics, foodomics, humeomics, and exosomics, related to inorganic sciences, are also discussed. The review comparatively presents the advantages of various principles of separation and mass spectral techniques, complementary derivatization, used to obtain large arrays of various structural and quantitative information in the mentioned omics sciences.
The energy spectra of galactic cosmic rays carry fundamental information regarding their origin and propagation. These spectra, when measured near Earth, are significantly affected by the solar ...magnetic field. A comprehensive description of the cosmic radiation must therefore include the transport and modulation of cosmic rays inside the heliosphere. During the end of the last decade, the Sun underwent a peculiarly long quiet phase well suited to study modulation processes. In this paper we present proton spectra measured from 2006 July to 2009 December by PAMEFA. The large collected statistics of protons allowed the time variation to be followed on a nearly monthly basis down to 400 MV. Data are compared with a state-of-the-art three-dimensional model of solar modulation.
The crystallographic analysis of three modifications of CaCO
3
– rhombohedral calcite (
), orthorhombic aragonite (
Pmcn
), and monoclinic vaterite (
C
2/
c
) – reveals different mechanisms of atomic ...ordering in the structures. An important role in the formation of a specific structure is played by the point symmetry of energetically stable atomic groups (templates) in the precrystallization phase, which depends on the crystallization conditions, impurities, and local heterogeneities. Then the template symmetry forms the structure symmetry by placing heavy atoms and mass centers of stable CO
3
atomic groups mainly in special positions with fixed coordinates. The details of this
crystal dynamics
(the ordering of atomic positions by translational and point symmetries) are shown.
Monomeric and dimeric mono-BHT magnesium complexes BuMg(μ-BHT)2 (2), BuMg(BHT)(THF)2 (3), and (μ-EtO)Mg(BHT)(THF)2 (4) were synthesized starting from 2,6-di-tert-butyl-4-methylphenol (butylated ...hydroxytoluene, BHT-H) and Bu2Mg. The molecular structures of compounds 2–4 were established using X-ray diffraction. Being activated by alcohol (monomeric 3) or thermally (dimeric 4), mono-BHT complexes demonstrate high catalytic activity in the ring-opening polymerization of ε-caprolactone (ε-CL), ω-pentadecalactone (ω-PDL) and (dl)-lactide. In the latter case, a heterotactic polymer with a Pr of up to 87% is formed. Analysis of the terminal groups of poly(ε-CL), which was obtained using 3/BnOH, indicated that the ROP initiator possesses an alkoxy-magnesium nature.
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•Dimeric and monomeric 1:1 BHT-magnesium complexes have been synthesized.•The first example of fully characterized (Aryloxide)Mg(Alkoxide) is reported.•(BHT)Mg(Alkoxide) catalyses ROP of ε-CL, ω-PDL and (dl)-lactide.•ROP initiated by (BHT)Mg(Alkoxide) goes by coordination-insertion mechanism.•BHT-magnesium complexes catalyse heterotactic (dl)-lactide ROP with Pr up to 87%.
Results of the crystallographic analysis of monoclinic Lu
5
Ba
6
B
9
O
27
= Lu
5
Ba
6
(BO
3
)
9
(
I
) and orthorhombic Sr
3
Bi
2
(BO
3
)
4
(
II
) orthoborate structures are discussed in terms of ...crystal dynamics (mechanical and energetic processes underlying the formation of translational and point symmetries). The templates in both cases are massive and crystallochemically active cations (Lu, Bi) localized, together with their anionic environments, at fixed symmetry-determined sites. The centers of BO
3
groups are partially included in the sublattice of heavy cations, and their relative orientation complies with the local symmetry of the templates.
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