Two-color interference stabilization of atoms

The effect of interference stabilization is shown to exist in a system of two atomic levels coupled by a strong two-color laser field, the two frequencies of which are close to a two-photon Raman-type resonance between the chosen levels, with open channels of one-photon ionization from both of them. We suggest an experiment, in which a rather significant (up to 90%) suppression of ionization can take place and which demonstrates explicitly the interference origin of stabilization. Specific calculations are made for H and He atoms and optimal parameters of a two-color field are found. The physics of the effect and its relation with such well-known phenomena as LICS and population trapping in a three-level system are discussed.Comment: the paper includes 1 TeX file and 16 picture

On details of the thermodynamical derivation of the Ginsburg--Landau equations

We examine the procedure of thermodynamical derivation of the Ginsburg--Landau equation for current, which is given unclear and contradictory interpretations in existing textbooks. We clarify all steps of this procedure and find as a consequence a limitation on the validity range of the thermodynamic Ginsburg--Landau theory, which does not seem to be explicitely stated up to now: we conclude that the thermodynamic theory is applicable only to a superconducting specimen that is not a part of an external current-carrying loop.Comment: 11 pages. Accepted for publication in 'Superconductor Science and Technology

Many-flavor electron gas approach to electron-hole drops

A many-flavor electron gas (MFEG) is analyzed, such as could be found in a multi-valley semiconductor or semimetal. Using the re-derived polarizability for the MFEG an exact expression for the total energy of a uniform MFEG in the many-flavor approximation is found; the interacting energy per particle is shown to be -0.574447E_h a_0^3/4 m*^3/4 n^1/4 with E_h being the Hartree energy, a_0 Bohr radius, and m^* particle effective mass. The short characteristic length-scale of the MFEG motivates a local density approximation, allowing a gradient expansion in the energy density, and the expansion scheme is applied to electron-hole drops, finding a new form for the density profile and its surface scaling properties.Comment: 11 pages, 5 figure

Features of systemic cytokine production in Behcet's disease associated with uveitis without ocular lesions

Behcet's disease (BD) is a systemic disease underlyed by chronic vasculitis. Hyperactivity of innate and adaptive immunity plays important role in its pathogenesis. Uveitis occurs in 30-70% of the patients, often recurring and reducing visual function. The objective of our work was to study the features of systemic production of immune mediators in BD patients, depending on presence and activity of uveitis. 116 BD patients were divided into 3 groups: (1) 41 patients with active uveitis (UA), (2) 64 subjects with uveitis remission (UR), (3) 11 uveitis-free BD patients (WU). Control group (CG) comprised 34 conditionally healthy people. Detection rate (%) and contents (pg/ml) were measured for IL-1β IL-2, IL-4, IL-5, IL-6, IL-12p70, IL-13, IL-18, IFNγ, CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, CCL5/RANTES, CCL11/Eotaxin, СXCL1/GRO-α, CXCL8/IL-8, CXCL10/IP-10, CXCL12/SDF-1α, GM-CSF, TNFα in blood serum by means of multiplex analysis using MAGPIX analyzer (Luminex Corp., USA), Procarta Plex “Human Th1/Th2&Chemokine Panel 20 plex” kits (Bioscience, Austria). TGF-P1, TGF-P2 levels were assayed by ELISA-test (“Vfector-Best”). All the BD patients showed high detection rates of CXCL1/GRO-α (but not its level) in comparison with CG. Detection rate and levels of IL-6, IL-8 were increased in 1st and 2nd BD groups, compared to CG. In UR, unlike UA and WU groups, IL-4 was detected more often than in CG. WU patients showed increased detection rate of only CXCL1/GRO -α. When compared with UA, WU patients had lower serum concentrations of IFNγ, MCP-1, IP-10, MIP-1a, SDF-1α, TGF-β1; UR patients also showed decreased serum levels of IL-18, Eotaxin, GRO-α, RANTES, TGF-β2. Our results indicate the importance of angiogenic and proinflammatory chemokines and cytokines in pathogenesis of BD uveitis, as well as imbalanced production of various immunomediators. Higher detection rates and levels of IL-6 and IL-8 in UA and UR patients may result from weak persistent intraocular inflammation, even upon relief of clinical symptoms, thus, probably, requiring therapeutic correction

EFFECT OF HUMAN HERPES VIRUS REACTIVATION ON SYSTEMIC CYTOKINE PRODUCTION IN PATIENTS WITH BEHCET’S DISEASE AND UVEITIS

Behcet’s disease (BD) is a systemic autoinflammatory-autoimmune disease (chronic systemic vasculitis) of unknown etiology, almost 70% of patients develop uveitis. BD pathogenesis is complex, human herpesviruses (HHV) play an important role among infectious trigger factors. Ability of herpesviruses to modulate cytokine production and evade host’s immune response is known.Aim of the study was to assess the effect of Herpes simplex virus type 1, Herpes simplex virus type 2, Cytomegalovirus, Epstein-Barr virus on systemic levels of chemokines, pro- and anti-inflammatory cytokines in BD with and without uveitis. Serum samples were collected from 116 BD patients chronically infected with HHV and examined in ELISA-test for markers of HHV reactivation (IgG-antibodies to immediate early HSV antigens 1, 2 and CMV, early EBV antigen). Concentration of IL-1β, IFNγ, MCP-1, IL-2, IL-4, IL-5, IL-6, IL-8, IL-12p70, IL-13, IL-18, TNFα, GMCSF, Eotaxin, GRO-α, IP-10, MIP-1α, MIP-1β, SDF-1α, RANTES detected in multiplex analysis. TGF-β1, TGF-β2 were measured in ELISA-test. Depending on presence and activity of uveitis 3 groups of patients with BD were identified: group 1 – active uveitis, group 2 – remission of uveitis, group 3 – BD without ocular manifestations. After serological study 2 subgroups were highlighted in each group: a) patients with antibody markers of reactivation of at least one HHV, b) patients chronically infected with HHV, without serological signs of reactivation. Mean level and detection rate of cytokines and chemokines in patients with active uveitis (1a, 1b) and in remission (2a, 2b) were compared with patients without eye damage (3a, 3b). Chronic HHV infection (subgroup “b”) was compared with reactivation (subgroup “a”). A significant increase of MCP-1/ CCL2, MIP-1α/CCL3, MIP-1β/CCL4, RANTES/CCL5, IP-10, SDF-1α chemokines in serum, as well as IFNγ, TGF-β1, and TGF-β2 was observed in patients with uveitis (regardless of their activity) and HHV reactivation compared to patients without uveitis. Our data indicate that systemic production of cytokines and chemokines in BD patients and uveitis could be affected by the activity of chronic herpesvirus infections, and the greatest changes are related to chemokines

Quantum Well Based on Graphene and Narrow-Gap Semiconductors

We consider the energy spectrum of the planar quantum well which consisted of two ribbons of narrow-gap semiconductors and a graphene ribbon between ones. It is shown that the gapless mode appears only in case of inverted narrow-gap semiconductors. Spin splitting of the energy spectrum for a nonsymmetric quantum well is calculated taking into account a specificity of graphene. We investigate interface states and optical transitions. It is shown that the optical transitions are possible only with a conservation of a parity.Comment: 13 pages, 2 figures, 1 tabl

Size Quantization in Planar Graphene-Based Heterostructures: Pseudospin Splitting, Interface States, and Excitons

A planar quantum-well device made of a gapless graphene nanoribbon with edges in contact with gapped graphene sheets is examined. The size-quantization spectrum of charge carriers in an asymmetric quantum well is shown to exhibit a pseudospin splitting. Interface states of a new type arise from the crossing of dispersion curves of gapless and gapped graphene materials. The exciton spectrum is calculated for a planar graphene quantum well. The effect of an external electric field on the exciton spectrum is analyzed.Comment: 15 pages, 14 figure

Diffusion Monte Carlo study of a valley degenerate electron gas and application to quantum dots

A many-flavor electron gas (MFEG) in a semiconductor with a valley degeneracy ranging between 6 and 24 was analyzed using diffusion Monte Carlo (DMC) calculations. The DMC results compare well with an analytic expression derived by one of us [Phys. Rev. B 78, 035111 (2008)] for the total energy to within 1% over an order of magnitude range of density, which increases with valley degeneracy. For Bi2Te3 (six-fold valley degeneracy) the applicable charge carrier densities are between 7*10^19cm^{-3} and 2*10^20cm^{-3}. DMC calculations distinguished between an exact and a useful approximate expression for the 24-fold degenerate MFEG polarizability for wave numbers 2p_F<q<7p_F. The analytical result for the MFEG is generalized to inhomogeneous systems by means of a gradient correction, the validity range of this approach is obtained. Employed within a density functional theory calculation this approximation compares well with DMC results for a quantum dot.Comment: 15 pages, 7 figures, PRB (to appear