Effective Field Theory for Bulk Properties of Nuclei

Recent progress in Lorentz-covariant quantum field theories of the nuclear many-body problem ({\em quantum hadrodynamics}, or QHD) is discussed. The importance of modern perspectives in effective field theory and density functional theory for understanding the successes of QHD is emphasized. The inclusion of hadronic electromagnetic structure and of nonanalytic terms in the energy functional is also considered.Comment: 11 pages, 0 figures, REVTeX 3.0; Invited talk at the 11th Conference on Recent Progress in Many-Body Theories (MB 11), Manchester, UK, July 9--13, 200

The Axial-Vector Current in Nuclear Many-Body Physics

Weak-interaction currents are studied in a recently proposed effective field theory of the nuclear many-body problem. The Lorentz-invariant effective field theory contains nucleons, pions, isoscalar scalar ($\sigma$) and vector ($\omega$) fields, and isovector vector ($\rho$) fields. The theory exhibits a nonlinear realization of $SU(2)_L \times SU(2)_R$ chiral symmetry and has three desirable features: it uses the same degrees of freedom to describe the axial-vector current and the strong-interaction dynamics, it satisfies the symmetries of the underlying theory of quantum chromodynamics, and its parameters can be calibrated using strong-interaction phenomena, like hadron scattering or the empirical properties of finite nuclei. Moreover, it has recently been verified that for normal nuclear systems, it is possible to systematically expand the effective lagrangian in powers of the meson fields (and their derivatives) and to reliably truncate the expansion after the first few orders. Here it is shown that the expressions for the axial-vector current, evaluated through the first few orders in the field expansion, satisfy both PCAC and the Goldberger--Treiman relation, and it is verified that the corresponding vector and axial-vector charges satisfy the familiar chiral charge algebra. Explicit results are derived for the Lorentz-covariant, axial-vector, two-nucleon amplitudes, from which axial-vector meson-exchange currents can be deduced.Comment: 32 pages, REVTeX 4.0 with 12pt.rtx, aps.rtx, revsymb.sty, revtex4.cls, plus 14 figures; two sentences added in Summary; two references adde

Partially conserved axial current constraints on pion production/absorption within nonrelativistic dynamics

We show the necessity of two-nucleon axial currents and associated pion emission/ absorption operators for the partial conservation of the axial current (PCAC) nuclear matrix elements with arbitrary nuclear dynamics described by a nonrelativistic Schroedinger equation. As examples we construct such nonrelativistic axial two-body currents in the linear- and heterotic (g_A = 1.26) sigma models, with an optional isoscalar vector (omega) meson exchange. The nuclear matrix elements obey PCAC only if the nuclear wave functions used in the calculation are solutions to the Schroedinger equation with the static one-meson-exchange potential constructed in the respective (sigma) model. The same holds true for the nucler pion production amplitude, since it is proportional to the divergence of the axial current matrix element, by virtue of PCAC. Thus we found a new consistency condition between the pion creation/absorption operator and the nuclear Hamiltonian. We present examples drawn from our models and discuss implications for one-pion-two-nucleon processes.Comment: 19 pages, 7 figures, submitted to Phys. Rev.

ПРОФИЛАКТИКА ХИРУРГИЧЕСКИХ ОСЛОЖНЕНИЙ, СВЯЗАННЫХ С МЕТОДИКОЙ АЛЬВЕОЛЯРНОЙ МЕЖКОМПАКТНОЙ ОСТЕОТОМИИ

The article examines possible medical errors during the interalveolar osteotomy that may negatively affect the effectiveness of the treatment. It also analyses the basic techniques that provide adequate vitality of the tissues in the place of surgery. It also demonstrates the necessity of the reconstruction of the full thickness of the gum in order to achieve long-term esthetic results in the area of dental implantation.Рассмотрены возможные врачебные ошибки при проведении альвеолярной межкомпактной остеотомии, отрицательно сказывающиеся на эффективности проводимого лечения. Помимо этого, проанализированы основные приемы, обеспечивающие адекватную жизнеспособность тканей в зоне хирургического вмешательства. Обоснована необходимость воссоздания полноценной толщины десны с целью достижения долгосрочных эстетических результатов в зоне дентальной имплантации

Survival of Methanogenic Archaea from Siberian Permafrost under Simulated Martian Thermal Conditions

Since ESA mission Mars Express determined water on Mars, a fundamental requirement for life, as well as the presence of CH4 in the Martian atmosphere, which could only have originated from active volcanism or from biological sources, it is obviously that microbial life could still exist on Mars, for example in the form of subsurface lithoautotrophic ecosystems, which are also exist in permafrost regions on Earth. Present work deals with the resistance investigation of methanogenic archaea from Siberian permafrost complementary to the already well-studied methanogens from non-permafrost habitats under simulated Martian conditions. The methanogenic archaea in pure cultures as well as in permafrost samples represent higher survival potential (up to 90 percent) than the referent organisms (0.3-5.8 percent) after 22 days of exposure to thermo-physical Martian conditions at low- and mid-latitudes. It is suggested that methanogens from terrestrial permafrost seem to be more resistant against Martian conditions and could be used as a prime candidates for the search for extraterrestrial life

Microbial communities and processes in Arctic permafrost environments

In polar regions, huge layers of frozen ground, termed permafrost, are formed. Permafrost covers more than 25 % of the land surface and significant parts of the coastal sea shelfs. Its habitats are controlled by extreme climate and terrain conditions. Particularly, the seasonal freezing and thawing in the upper active layer of permafrost leads to distinct gradients in temperature and geochemistry. Microorganisms in permafrost environments have to survive extremely cold temperatures, freeze-thaw cycles, desiccation and starvation under long-lasting background radiation over geological time scales. Although the biology of permafrost microorganisms remains relatively unexplored, recent findings show that microbial communities in this extreme environment are composed by members of all three domains of life (Archaea, Bacteria, Eukarya), with a total biomass comparable to temperate soil ecosystems. This chapter describes the environmental conditions of permafrost and reviews recent studies on microbial processes and diversity in permafrost-affected soils as well as the role and significance of microbial communities with respect to global biogeochemical cycles

Diversity of Isomerization Patterns and Protolytic Forms in Aminocarbene Pd^II and Pt^II Complexes Formed upon Addition of <i>N</i>,<i>N</i>′‑Diphenylguanidine to Metal-Activated Isocyanides

Reaction of the palladium­(II) and platinum­(II) isocyanide complexes <i>cis</i>-[MCl₂(CNR)₂] [M = Pd, R = C₆H₃(2,6-Me₂) (Xyl), 2-Cl-6-MeC₆H₃, cyclohexyl (Cy), <i>t</i>-Bu, C­(Me)₂CH₂(Me)₃ (1,1,3,3-tetramethylbuth-1-yl abbreviated as tmbu); M = Pt, R = Xyl, 2-Cl-6-MeC₆H₃, Cy, <i>t</i>-Bu, and tmbu] with <i>N</i>,<i>N</i>′-diphenylguanidine (DPG) leads to DPG-derived metal-bound deprotonated acyclic diaminocarbene (ADC) species. This reaction occurs via a two-step process, involving the initial coupling of the guanidine with one of the isocyanides and leading to deprotonated monocarbene monochelated species, while the next addition grants the deprotonated bis-carbene bis-chelated metal compounds. DPG behaves as nucleophile, deprotonating base, and chelator. The addition of DPG proceeded with different regioselectivity depending on the metal center and, in a larger extent, on the substituent R in RNCs. The X-ray diffraction studies for the deprotonated mono- and bis-carbene complexes confirmed the regioisomerism of these species and allowed the identification of ADC protolytic forms stabilized in the solid-state. 1D (¹H and ¹³C­{¹H}) and 2D (¹H,¹H-NOESY; ¹H,¹⁵N-HSQC; ¹H,¹⁵N-HMBC) solution NMR of the obtained systems demonstrated their configuration isomerism accompanied by prototropic tautomerism. Together, the solid-state and solution data provide an insight into the flexible character of ADC species