167 research outputs found
Collective excitations on a surface of topological insulator
We study collective excitations in a helical electron liquid on a surface of
three-dimensional topological insulator. Electron in helical liquid obeys
Dirac-like equation for massless particless and direction of its spin is
strictly determined by its momentum. Due to this spin-momentum locking,
collective excitations in the system manifest themselves as coupled charge- and
spin-density waves. We develop quantum field-theoretical description of
spin-plasmons in helical liquid and study their properties and internal
structure. Value of spin polarization arising in the system with excited
spin-plasmons is calculated. We also consider the scattering of spin-plasmons
on magnetic and nonmagnetic impurities and external potentials, and show that
the scattering occurs mainly into two side lobes. Analogies with Dirac electron
gas in graphene are discussed.Comment: 9 pages, 6 figure
P04-11. Prevalence of neutralizing antibody responses in chronic clades A and D human immunodeficiency virus type 1 (HIV-1) infections
The Northern Eurasia Earth Science Partnership: An Example of Science Applied to Societal Needs
Northern Eurasia, the largest landmass in the northern extratropics, accounts for ~20% of the global land area. However, little is known about how the biogeochemical cycles, energy and water cycles, and human activities specific to this carbon-rich, cold region interact with global climate. A major concern is that changes in the distribution of land-based life, as well as its interactions with the environment, may lead to a self-reinforcing cycle of accelerated regional and global warming. With this as its motivation, the Northern Eurasian Earth Science Partnership Initiative (NEESPI) was formed in 2004 to better understand and quantify feedbacks between northern Eurasian and global climates. The first group of NEESPI projects has mostly focused on assembling regional databases, organizing improved environmental monitoring of the region, and studying individual environmental processes. That was a starting point to addressing emerging challenges in the region related to rapidly and simultaneously changing climate, environmental, and societal systems. More recently, the NEESPI research focus has been moving toward integrative studies, including the development of modeling capabilities to project the future state of climate, environment, and societies in the NEESPI domain. This effort will require a high level of integration of observation programs, process studies, and modeling across disciplines
Extra Dirac Equations
This paper has rather a pedagogical meaning. Surprising symmetries in the
Lorentz group representation space are analyzed. The aim is
to draw reader's attention to the possibility of describing the particle world
on the ground of the Dirac "doubles". Several tune points of the variational
principle for this kind of equations are briefly discussed.Comment: REVTeX 3.0, 14p
ВЛИЯНИЕ ВЛАЖНОСТИ ПОЧВЫ НА СОДЕРЖАНИЕ КАДМИЯ, СВИНЦА И УРАНА В ПОДВИЖНЫХ ФОРМАХ
The content of Cd, Pb, U in the mobile form (Memob) in soil samples of the given moisture content after their keeping at the –18, +15 и +30 °С was established. An increase in the content of Memob after freezing of waterlogged soil was noted. The Pbmob content increased with raising the soil humidity in the range of 5.5–140 % of the total moisture capacity (TMC) at all temperature regimes, Cdmob – 5.5–60 % of the TMC at +30 °C, but Umob – 5.5–60 % of TMC at +15 and +30 °C.Установлено содержание Сd, Pb, U в подвижной форме (Меподв) в образцах почвы заданной влажности после их выдерживания при температуре –18, +15 и +30 °С. Отмечено повышение содержания Меподв после замораживания переувлажненной почвы. По мере увеличения почвенной влажности содержание Pbподв возрастало при влажности почвы в диапазоне 5,5–140 % от ее полной влагоемкости (ПВ) и всех температурных режимах, Cdподв – 5,5–60 % от ПВ при +30 °С, Uподв – 5,5–60 % от ПВ при +15 и +30 °С
Neutral Particles in Light of the Majorana-Ahluwalia Ideas
The first part of this article (Sections I and II) presents oneself an
overview of theory and phenomenology of truly neutral particles based on the
papers of Majorana, Racah, Furry, McLennan and Case. The recent development of
the construct, undertaken by Ahluwalia [{\it Mod. Phys. Lett. A}{\bf 9} (1994)
439; {\it Acta Phys. Polon. B}{\bf 25} (1994) 1267; Preprints LANL
LA-UR-94-1252, LA-UR-94-3118], could be relevant for explanation of the present
experimental situation in neutrino physics and astrophysics.
In Section III the new fundamental wave equations for self/anti-self
conjugate type-II spinors, proposed by Ahluwalia, are re-casted to covariant
form. The connection with the Foldy-Nigam-Bargmann-Wightman- Wigner (FNBWW)
type quantum field theory is found. The possible applications to the problem of
neutrino oscillations are discussed.Comment: REVTEX file. 21pp. No figure
Experimental system to displace radioisotopes from upper to deeper soil layers: chemical research
BACKGROUND: Radioisotopes are introduced into the environment following nuclear power plant accidents or nuclear weapons tests. The immobility of these radioactive elements in uppermost soil layers represents a problem for human health, since they can easily be incorporated in the food chain. Preventing their assimilation by plants may be a first step towards the total recovery of contaminated areas. METHODS: The possibility of displacing radionuclides from the most superficial soil layers and their subsequent stabilisation at lower levels were investigated in laboratory trials. An experimental system reproducing the environmental conditions of contaminated areas was designed in plastic columns. A radiopolluted soil sample was treated with solutions containing ions normally used in fertilisation (NO(3)(-), NH(4)(+), PO(4)(--- )and K(+)). RESULTS: Contaminated soils treated with an acid solution of ions NO(3)(-), PO(4)(--- )and K(+), undergo a reduction of radioactivity up to 35%, after a series of washes which simulate one year's rainfall. The capacity of the deepest soil layers to immobilize the radionuclides percolated from the superficial layers was also confirmed. CONCLUSION: The migration of radionuclides towards deeper soil layers, following chemical treatments, and their subsequent stabilization reduces bioavailability in the uppermost soil horizon, preventing at the same time their transfer into the water-bearing stratum
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