Poikilodermatous mycosis fungoides: clinical and histopathological analysis of a case and literature review.

Poikilodermatous mycosis fungoides is a rare distinct clinical variant of cutaneous T-cell lymphoma (CTCL), formerly referred to as poikiloderma vasculare atrophicans or parapsoriasis variegata. Mycosis fungoides (MF) is a malignant neoplasm of T-lymphocyte origin, most commonly memory CD4+ T-cells.We report here a patient with generalized poikilodermatous skin lesions whose diagnosis of mycosis fungoides was made only a few years after the onset of his disease due to its bizarre clinical behavior and a natural reluctance to diagnose this disease in children and adolescents.The variability of atypical clinical presentations of MF and its similarity to benign inflammatory and noninflammatory skin disorders may become a source of considerable confusion and controversy, challenging a dermatologist to make a precise diagnosis. Therefore, scrupulous clinicopathological correlation is an absolute necessity.

Exact-exchange spin-density functional theory of Wigner localization and phase transitions in quantum rings.

We apply exact-exchange spin-density functional theory in the Krieger-Li-Iafrate approximation to interacting electrons in quantum rings of different widths. The rings are threaded by a magnetic flux that induces a persistent current. A weak space and spin symmetry breaking potential is introduced to allow for localized solutions. As the electron-electron interaction strength described by the dimensionless parameter r(S) is increased, we observe-at a fixed spin magnetic moment-the subsequent transition of both spin sub-systems from the Fermi liquid to the Wigner crystal state. A dramatic signature of Wigner crystallization is that the persistent current drops sharply with increasing r(S). We observe simultaneously the emergence of pronounced oscillations in the spin-resolved densities and in the electron localization functions indicating a spatial electron localization showing ferrimagnetic order after both spin sub-systems have undergone the Wigner crystallization. The critical r(S)(c) at the transition point is substantially smaller than in a fully spin-polarized system and decreases further with decreasing ring width. Relaxing the constraint of a fixed spin magnetic moment, we find that on increasing r(S) the stable phase changes from an unpolarized Fermi liquid to an antiferromagnetic Wigner crystal and finally to a fully polarized Fermi liquid.

Evaluation of three serological tests manufactured in Belarus for the diagnosis of syphilis.

The performance of three serological tests manufactured in Belarus for the diagnosis of syphilis, i.e. a microprecipitation reaction (MPR) and two enzyme-linked immunosorbent assays (ELISAs) were compared with internationally recognized assays, namely the rapid plasma reagin test and the Treponema pallidum passive particle agglutination assay (TPPA). Sera from 392 consecutive patients attending Brest (Belarus) regional dermatovenereological dispensaries were tested. The sensitivity of the MPR test was low (77.3%) compared with the rapid plasma reagin test, while the specificity was high (100%). In contrast, both Belarusian ELISAs performed well when compared with the TPPA (sensitivities of 99.2% and 100%, specificities of 98.7% and 99.0%, respectively). There is a clear need to improve the sensitivity of the existing Belarusian MPR test or to use a more sensitive screening test in order to improve diagnosis of the disease in Belarus.

Many-body effects in the excitation spectrum of a defect in SiC.

We show that electron correlations control the photophysics of defects in SiC through both renormalization of the quasiparticle band structure and excitonic effects. We consider the carbon vacancy with two possible excitation channels that involve conduction and valence bands. Corrections to the Kohn-Sham ionization levels strongly depend on the defect charge state. Excitonic effects introduce a redshift of 0.23 eV. The analysis reassigns excitation mechanism at the thresholds in photoinduced paramagnetic resonance measurements [J. Dashdorj, J. Appl. Phys. 104, 113707 (2008)].

Density functional study of collective electron localization: detection by persistent current.

We apply the optimized effective potential (OEP) implementation of density functional theory (DFT) to the model system of interacting spinless electrons on a quantum ring. The ring encircles a magnetic flux that induces a persistent current. In a perfect rotationally invariant system the current does not depend on the electron-electron interaction (the latter is characterized by a standard dimensionless parameter r(S)) and hence is not sensitive to the microscopic structure of the electron correlated state. This changes, however, if a symmetry-breaking external potential is introduced or, in a realistic system, due to the crystal lattice potential (Hamer et al 1987 J. Phys. A: Math. Gen. 20 5677-93). In our model, we calculate the persistent current as a function of r(S) in the presence of a weak Gaussian-shaped 'impurity' potential. We find that while below a threshold value r(S)r(S)(c). This signals the formation of an electron Wigner crystal pinned by the impurity potential. The electron density, homogeneous below r(S)(c), indeed shows a periodic modulation at r(S)>r(S)(c). The modulation amplitude follows a (r(S)-r(S)(c))((1)/(2)) behaviour which is characteristic for a second-order phase transition, as expected in the mean-field-type DFT-OEP approach. Our calculation shows that the macroscopic current, which is a quantity directly accessible in DFT, can serve as an indicator of the formation of a correlated electron state.

Ab initio study of graphene on SiC.

Employing density-functional calculations we study single and double graphene layers on Si- and C-terminated 1x1-6H-SiC surfaces. We show that, in contrast with earlier assumptions, the first carbon layer is covalently bonded to the substrate and cannot be responsible for the graphene-type electronic spectrum observed experimentally. The characteristic spectrum of freestanding graphene appears with the second carbon layer, which exhibits a weak van der Waals bonding to the underlying structure. For Si-terminated substrate, the interface is metallic, whereas on C face it is semiconducting or semimetallic for single or double graphene coverage, respectively.

Epidemiology of syphilis in pregnant women and congenital syphilis in Belarus.

In Belarus the spread of syphilis has been on the increase since 1988, and the incidence reached its peak in 1996 with 209.7 cases per 100 000 inhabitants. During the following years the incidence has reduced, but still remains high with 41 cases in 2004. In the years 1996-2004 all together 4239 pregnant women infected with syphilis were registered in Dermatovenereological Dispensaries in Belarus, giving birth to 116 children with congenital syphilis. The social end economic background of these events is reviewed.