285 research outputs found
AC Conductance in Dense Array of the GeSi Quantum Dots in Si
Complex AC-conductance, , in the systems with dense
GeSi quantum dot (QD) arrays in Si has been determined from
simultaneous measurements of attenuation, ,
and velocity, , of surface acoustic waves (SAW)
with frequencies = 30-300 MHz as functions of transverse magnetic field 18 T in the temperature range = 1-20 K. It has been shown that in the
sample with dopant (B) concentration 8.2 cm at
temperatures 4 K the AC conductivity is dominated by hopping between
states localized in different QDs. The observed power-law temperature
dependence, , and weak frequency dependence,
, of the AC conductivity are consistent with
predictions of the two-site model for AC hopping conductivity for the case of
1, where is the SAW angular frequency and
is the typical population relaxation time. At 7 K the AC
conductivity is due to thermal activation of the carriers (holes) to the
mobility edge. In intermediate temperature region 4 7 K, where AC
conductivity is due to a combination of hops between QDs and diffusion on the
mobility edge, one succeeded to separate both contributions. Temperature
dependence of hopping contribution to the conductivity above 4.5 K
saturates, evidencing crossover to the regime where 1. From
crossover condition, = 1, the typical value, , of
the relaxation time has been determined.Comment: revtex, 3 pages, 6 figure
Density of States and Conductivity of Granular Metal or Array of Quantum Dots
The conductivity of a granular metal or an array of quantum dots usually has
the temperature dependence associated with variable range hopping within the
soft Coulomb gap of density of states. This is difficult to explain because
neutral dots have a hard charging gap at the Fermi level. We show that
uncontrolled or intentional doping of the insulator around dots by donors leads
to random charging of dots and finite bare density of states at the Fermi
level. Then Coulomb interactions between electrons of distant dots results in
the a soft Coulomb gap. We show that in a sparse array of dots the bare density
of states oscillates as a function of concentration of donors and causes
periodic changes in the temperature dependence of conductivity. In a dense
array of dots the bare density of states is totally smeared if there are
several donors per dot in the insulator.Comment: 13 pages, 15 figures. Some misprints are fixed. Some figures are
dropped. Some small changes are given to improve the organizatio
Correlated electron states and transport in triangular arrays
We study correlated electron states in frustrated geometry of a triangular
lattice. The interplay of long range interactions and finite residual entropy
of a classical system gives rise to unusual effects in equilibrium ordering as
well as in transport. A novel correlated fluid phase is identified in a wide
range of densities and temperatures above freezing into commensurate solid
phases. The charge dynamics in the correlated phase is described in terms of a
height field, its fluctuations, and topological defects. We demonstrate that
the height field fluctuations give rise to a ``free'' charge flow and finite dc
conductivity. We show that freezing into the solid phase, controlled by the
long range interactions, manifests itself in singularities of transport
properties.Comment: 19 pages, 10 figure
Absorption of Terahertz Radiation in Ge/Si(001) Heterostructures with Quantum Dots
The terahertz spectra of the dynamic conductivity and radiation absorption
coefficient in germanium-silicon heterostructures with arrays of Ge hut
clusters (quantum dots) have been measured for the first time in the frequency
range of 0.3-1.2 THz at room temperature. It has been found that the effective
dynamic conductivity and effective radiation absorption coefficient in the
heterostructure due to the presence of germanium quantum dots in it are much
larger than the respective quantities of both the bulk Ge single crystal and
Ge/Si(001) without arrays of quantum dots. The possible microscopic mechanisms
of the detected increase in the absorption in arrays of quantum dots have been
discussed.Comment: 9 pages, 4 figures; typos correcte
High representation of archaea across all depths in oxic and low-pH sediment layers underlying an acidic stream
Parys Mountain or Mynydd Parys (Isle of Anglesey, United Kingdom) is a mine-impacted environment, which accommodates a variety of acidophilic organisms. Our previous research of water and sediments from one of the surface acidic streams showed a high proportion of archaea in the total microbial community. To understand the spatial distribution of archaea, we sampled cores (0β20 cm) of sediment and conducted chemical analyses and taxonomic profiling of microbiomes using 16S rRNA gene amplicon sequencing in different core layers. The taxonomic affiliation of sequencing reads indicated that archaea represented between 6.2 and 54% of the microbial community at all sediment depths. Majority of archaea were associated with the order Thermoplasmatales, with the most abundant group of sequences being clustered closely with the phylotype B_DKE, followed by βE-plasma,β βA-plasma,β other yet uncultured Thermoplasmatales with Ferroplasma and Cuniculiplasma spp. represented in minor proportions. Thermoplasmatales were found at all depths and in the whole range of chemical conditions with their abundance correlating with sediment Fe, As, Cr, and Mn contents. The bacterial microbiome component was largely composed in all layers of sediment by members of the phyla Proteobacteria, Actinobacteria, Nitrospirae, Firmicutes, uncultured Chloroflexi (AD3 group), and Acidobacteria. This study has revealed a high abundance of Thermoplasmatales in acid mine drainage-affected sediment layers and pointed at these organisms being the main contributors to carbon, and probably to iron and sulfur cycles in this ecosystem
1/f Noise and Extreme Value Statistics
We study the finite-size scaling of the roughness of signals in systems
displaying Gaussian 1/f power spectra. It is found that one of the extreme
value distributions (Gumbel distribution) emerges as the scaling function when
the boundary conditions are periodic. We provide a realistic example of
periodic 1/f noise, and demonstrate by simulations that the Gumbel distribution
is a good approximation for the case of nonperiodic boundary conditions as
well. Experiments on voltage fluctuations in GaAs films are analyzed and
excellent agreement is found with the theory.Comment: 4 pages, 4 postscript figures, RevTe
Granular Electronic Systems
A granular metal is an array of metallic nano-particles imbedded into an
insulating matrix. Tuning the intergranular coupling strength a granular system
can be transformed into either a good metal or an insulator and, in case of
superconducting particles, experience superconductor-insulator transition. The
ease of adjusting electronic properties of granular metals makes them most
suitable for fundamental studies of disordered solids and assures them a
fundamental role for nanotechnological applications. This Review discusses
recent important theoretical advances in the study of granular metals,
emphasizing on the interplay of disorder, quantum effects, fluctuations and
effects of confinement in formation of electronic transport and thermodynamic
properties of granular materials.Comment: 51 pages, 23 figures, submitted to Reviews of Modern Physic
Influence of delta-doping on the hole capture probability in Ge/Si quantum dot mid-infrared photodetectors
Clinical and Epidemiological Features of Hepatitis C in Adults and Children in the City of Tomsk and Tomsk Area for 1994-2009
Epidemiological features of acute HCV infection were studied in adults and children in Tomsk and Tomsk area for the period 1994-2009. The statistics of the Office of Rospotrebnadzor (Federal service on customers' rights protection and human well-being surveillance) for Tomsk area as well as our own research data such as analysis of the epidemiological anamnesis of medical history and epidemiological survey questionnaires, retrospective, dynamic (longitudinal) analysis were used at carrying out of this epidemiological study. The following conclusions are drawn by the team of authors as a result of the study: the severe forms of HCV infection werenβt found in adults and children; hepatomegaly, jaundice, and intoxication were the main clinical symptoms, and splenomagaly was met rarely regardless of age. Intensive morbidity with HCV often exceeds the average for Russia; the incidence in senior age groups with predominance of males among those infected has increased; the proportion of women has increased too; HCV infection in children was more frequently detected in the school-age children of 7-14 years; the predominance of non-working population including socially maladjusted and students at the beginning of the study period; an increase of the proportion of working population, a decrease of infection through intravenous drug use, the increase of nosocomial infection, as well as household and sexual ways of transmission in recent years. HCV infection in children was detected more frequently in school-age children of 7-14 years. The rise of HCV infection both in adults and children was marked at the initial stage of the study.ΠΠ·ΡΡΠ΅Π½Ρ ΡΠΏΠΈΠ΄Π΅ΠΌΠΈΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΎΡΠΎΠ±Π΅Π½Π½ΠΎΡΡΠΈ ΠΎΡΡΡΠΎΠΉ ΠΈ Ρ
ΡΠΎΠ½ΠΈΡΠ΅ΡΠΊΠΎΠΉ HCV ΠΈΠ½ΡΠ΅ΠΊΡΠΈΠΈ Π½Π° ΡΠ΅ΡΡΠΈΡΠΎΡΠΈΠΈ Π³. Π’ΠΎΠΌΡΠΊΠ° ΠΈ Π’ΠΎΠΌΡΠΊΠΎΠΉ ΠΎΠ±Π»Π°ΡΡΠΈ Ρ Π²Π·ΡΠΎΡΠ»ΠΎΠ³ΠΎ Π½Π°ΡΠ΅Π»Π΅Π½ΠΈΡ ΠΈ Π΄Π΅ΡΠ΅ΠΉ Π·Π° ΠΏΠ΅ΡΠΈΠΎΠ΄ 1994-2009 Π³Π³.. ΠΡΠΈ ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½ΠΈΠΈ Π΄Π°Π½Π½ΠΎΠ³ΠΎ ΡΠΏΠΈΠ΄Π΅ΠΌΠΈΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π»ΠΈΡΡ ΡΡΠ°ΡΠΈΡΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ Π΄Π°Π½Π½ΡΠ΅ Π£ΠΏΡΠ°Π²Π»Π΅Π½ΠΈΡ Π ΠΎΡΠΏΠΎΡΡΠ΅Π±Π½Π°Π΄Π·ΠΎΡΠ° ΠΏΠΎ Π’ΠΎΠΌΡΠΊΠΎΠΉ ΠΎΠ±Π»Π°ΡΡΠΈ, Π΄Π°Π½Π½ΡΠ΅ ΡΠΎΠ±ΡΡΠ²Π΅Π½Π½ΡΡ
ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΉ: Π°Π½Π°Π»ΠΈΠ· ΡΠΏΠΈΠ΄Π΅ΠΌΠΈΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ Π°Π½Π°ΠΌΠ½Π΅Π·Π° ΠΏΠΎ ΠΈΡΡΠΎΡΠΈΡΠΌ Π±ΠΎΠ»Π΅Π·Π½Π΅ΠΉ ΠΈ Π°Π½ΠΊΠ΅ΡΠ°ΠΌ ΡΠΏΠΈΠ΄Π΅ΠΌΠΈΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΎΠ±ΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ: ΡΠ΅ΡΡΠΎΡΠΏΠ΅ΠΊΡΠΈΠ²Π½ΡΠΉ, Π΄ΠΈΠ½Π°ΠΌΠΈΡΠ΅ΡΠΊΠΈΠΉ (ΠΏΡΠΎΠ΄ΠΎΠ»ΡΠ½ΡΠΉ) Π°Π½Π°Π»ΠΈΠ·. Π ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ΅ ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½Π½ΠΎΠ³ΠΎ Π°Π½Π°Π»ΠΈΠ·Π° ΠΊΠΎΠ»Π»Π΅ΠΊΡΠΈΠ²ΠΎΠΌ Π°Π²ΡΠΎΡΠΎΠ² Π±ΡΠ»ΠΈ ΡΠ΄Π΅Π»Π°Π½Ρ ΡΠ»Π΅Π΄ΡΡΡΠΈΠ΅ Π²ΡΠ²ΠΎΠ΄Ρ: ΠΏΡΠΈ 0ΠΠΠ‘ Ρ Π²Π·ΡΠΎΡΠ»ΡΡ
ΠΈ Π΄Π΅ΡΠ΅ΠΉ Π½Π΅ Π²ΡΡΡΠ΅ΡΠ°Π»ΠΈΡΡ ΡΡΠΆΠ΅Π»ΡΠ΅ ΡΠΎΡΠΌΡ; ΠΎΡΠ½ΠΎΠ²Π½ΡΠΌΠΈ ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΠΌΠΈ ΡΠΈΠΌΠΏΡΠΎΠΌΠ°ΠΌΠΈ Π±ΡΠ»ΠΈ Π³Π΅ΠΏΠ°ΡΠΎΠΌΠ΅Π³Π°Π»ΠΈΡ, ΠΆΠ΅Π»ΡΡΡ
Π° ΠΈ ΠΈΠ½ΡΠΎΠΊΡΠΈΠΊΠ°ΡΠΈΡ, Π° ΡΠΏΠ»Π΅Π½ΠΎΠΌΠ΅Π³Π°Π»ΠΈΡ Π²ΡΡΡΠ΅ΡΠ°Π»Π°ΡΡ ΡΠ΅Π΄ΠΊΠΎ Π½Π΅Π·Π°Π²ΠΈΡΠΈΠΌΠΎ ΠΎΡ Π²ΠΎΠ·ΡΠ°ΡΡΠ°. ΠΠ½ΡΠ΅Π½ΡΠΈΠ²Π½ΡΠ΅ ΠΏΠΎΠΊΠ°Π·Π°ΡΠ΅Π»ΠΈ Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π΅ΠΌΠΎΡΡΠΈ ΠΠΠΠ‘ ΡΠ°ΡΡΠΎ ΠΏΡΠ΅Π²ΡΡΠ°ΡΡ ΡΡΠ΅Π΄Π½Π΅ΡΠΎΡΡΠΈΠΉΡΠΊΠΈΠ΅; ΡΠ²Π΅Π»ΠΈΡΠΈΠ»Π°ΡΡ Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π΅ΠΌΠΎΡΡΡ Π² ΡΡΠ°ΡΡΠΈΡ
Π²ΠΎΠ·ΡΠ°ΡΡΠ½ΡΡ
Π³ΡΡΠΏΠΏΠ°Ρ
, Ρ ΠΏΡΠ΅ΠΎΠ±Π»Π°Π΄Π°Π½ΠΈΠ΅ΠΌ Π»ΠΈΡ ΠΌΡΠΆΡΠΊΠΎΠ³ΠΎ ΠΏΠΎΠ»Π° ΡΡΠ΅Π΄ΠΈ ΠΈΠ½ΡΠΈΡΠΈΡΠΎΠ²Π°Π½Π½ΡΡ
, Π½ΠΎ Π²ΠΎΠ·ΡΠΎΡΠ»Π° ΠΈ Π΄ΠΎΠ»Ρ ΠΆΠ΅Π½ΡΠΈΠ½; Ρ Π΄Π΅ΡΠ΅ΠΉ ΡΠ°ΡΠ΅ HCV ΠΈΠ½ΡΠ΅ΠΊΡΠΈΡ ΡΠ΅Π³ΠΈΡΡΡΠΈΡΠΎΠ²Π°Π»Π°ΡΡ Π² ΡΠΊΠΎΠ»ΡΠ½ΠΎΠΌ Π²ΠΎΠ·ΡΠ°ΡΡΠ΅ 7-14 Π»Π΅Ρ. ΠΏΡΠ΅ΠΎΠ±Π»Π°Π΄Π°Π½ΠΈΠ΅ Π² Π½Π°ΡΠ°Π»Π΅ ΠΈΡΡΠ»Π΅Π΄ΡΠ΅ΠΌΠΎΠ³ΠΎ ΠΏΠ΅ΡΠΈΠΎΠ΄Π° Π½Π΅ΡΠ°Π±ΠΎΡΠ°ΡΡΠ΅Π³ΠΎ Π½Π°ΡΠ΅Π»Π΅Π½ΠΈΡ, Π² ΡΠΎΠΌ ΡΠΈΡΠ»Π΅ ΡΠΎΡΠΈΠ°Π»ΡΠ½ΠΎ Π½Π΅ Π°Π΄Π°ΠΏΡΠΈΡΠΎΠ²Π°Π½Π½ΡΡ
ΠΈ ΡΡΡΠ΄Π΅Π½ΡΠΎΠ² Ρ ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΠ΅ΠΌ Π΄ΠΎΠ»ΠΈ ΡΠ°Π±ΠΎΡΠ°ΡΡΠΈΡ
Π² ΠΏΠΎΡΠ»Π΅Π΄Π½ΠΈΠ΅ Π³ΠΎΠ΄Ρ ΡΠΎ ΡΠ½ΠΈΠΆΠ΅Π½ΠΈΠ΅ΠΌ Π·Π°ΡΠ°ΠΆΠ΅Π½ΠΈΡ ΠΏΡΠΈ Π²Π½ΡΡΡΠΈΠ²Π΅Π½Π½ΠΎΠΌ Π²Π²Π΅Π΄Π΅Π½ΠΈΠΈ Π½Π°ΡΠΊΠΎΡΠΈΠΊΠΎΠ² ΠΈ ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΠ΅ΠΌ ΡΠΈΡΠ»Π° Π²Π½ΡΡΡΠΈΠ±ΠΎΠ»ΡΠ½ΠΈΡΠ½ΠΎΠ³ΠΎ ΠΈΠ½ΡΠΈΡΠΈΡΠΎΠ²Π°Π½ΠΈΡ, ΠΊΠΎΠ½ΡΠ°ΠΊΡΠ½ΠΎ-Π±ΡΡΠΎΠ²ΠΎΠ³ΠΎ ΠΈ ΡΠ΅ΠΊΡΡΠ°Π»ΡΠ½ΡΡ
ΠΏΡΡΠ΅ΠΉ ΠΏΠ΅ΡΠ΅Π΄Π°ΡΠΈ. Π£ Π΄Π΅ΡΠ΅ΠΉ ΡΠ°ΡΠ΅ HCV ΠΈΠ½ΡΠ΅ΠΊΡΠΈΡ ΡΠ΅Π³ΠΈΡΡΡΠΈΡΠΎΠ²Π°Π»Π°ΡΡ Π² ΡΠΊΠΎΠ»ΡΠ½ΠΎΠΌ Π²ΠΎΠ·ΡΠ°ΡΡΠ΅ 7-14 Π»Π΅Ρ. ΠΠ°ΠΊ Ρ Π²Π·ΡΠΎΡΠ»ΡΡ
, ΡΠ°ΠΊ ΠΈ Ρ Π΄Π΅ΡΠ΅ΠΉ ΠΏΠΎΠ΄ΡΠ΅ΠΌ Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π΅ΠΌΠΎΡΡΠΈ ΠΠΠΠ‘ Π±ΡΠ» ΠΎΡΠΌΠ΅ΡΠ΅Π½ Π² Π½Π°ΡΠ°Π»ΡΠ½ΠΎΠΌ ΠΏΠ΅ΡΠΈΠΎΠ΄Π΅ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ
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