758 research outputs found
Large J expansion in ABJM theory revisited
Recently there has been progress in the computation of the anomalous
dimensions of gauge theory operators at strong coupling by making use of
AdS/CFT correspondence. On string theory side they are given by dispersion
relations in the semiclassical regime. We revisit the problem of large charges
expansion of the dispersion relations for simple semiclassical strings in
background. We present the calculation of the
corresponding anomalous dimensions of the gauge theory operators to an
arbitrary order using three different methods. Although the results of the
three methods look different, power series expansions show their consistency.Comment: 24 pages, 2 figure
Superconducting BSCCO Ceramics as Additive to the Zinc Electrode Mass in the Rechargeable Nickel-Zinc Batteries
The electronic conductivity of the main component of the zinc electrode in the rechargeable zinc-nickel battery â ZnO, is rather poor and this is the main reason for the electrochemical heterogeneity of the anode mass and the loss of active surface area during charge/discharge cycling with a corresponding negative effect on the electrode characteristics In the present work, the possibility of application of superconductive cuprate Bi-Pb-Sr-Ca-Cu-O (BSCCO) ceramic as a multifunctional conductive additive to the zinc electrode mass is studied. Powder samples of the BSCCO ceramic Bi1,7Pb0,3Sr2Ca2Cu3Ox are produced by two-stage solid-state synthesis and they are physicochemically characterized. The XRD patterns and SEM observation reveal a well crystallized single phase of superconducting 2212 BSCCO system with average crystallite size 5-10 ”m. The chemical stability of BSCCO ceramics in highly alkaline medium of the Ni-Zn battery is confirmed by structural and morphological analysis (XRD, SEM and EDX) of the samples before and after prolong exposure (96 h) to 7M KOH. The electrochemical tests are carried out by a specially designed prismatic alkaline Ni-Zn battery cell with conventional sintered type nickel electrodes and pasted zinc electrode with active electrode mass based on ZnO (88 wt.%) and addition of BSCCO powder or acetylene black as conductive additives. The study show that the zinc electrode with BSCCO superconducting ceramic additive exhibits very good cycleability, remarkable capacity stability and much higher discharge capacity at prolong charge/discharge cycling in comparison to the  zinc electrode with the âclassicâ carbon conductive additive. It is suggested that the addition of BSCCO ceramics improves not only conductivity of the electrode mass and reduces the gas evolution but also stabilizes porosity structure. The results obtained prove the possibility of application of superconducting BSCCO ceramics as a multifunctional additive to the active mass of the zinc electrodes for alkaline battery systems
Meat freshness revealed by visible to near-infrared spectroscopy and principal component analysis
Increasing concerns about adulterated meat encouraged industry looking for new non-invasive methods for rapid accurate meat quality assessment. Main meat chromophores (myoglobin, oxy-myoglobin, fat, water, collagen) are characterized by close comparable absorption in visible to near-infrared (NIR) spectral region. Therefore, structural and compositional variations in meat may lead to relative differences in the absorption of light. Utilizing typical fiber-optic probes and integrating sphere, a degradation of pork samples freshness was observed at room temperature referring to the relative changes in absorbance of main meat chromophores. The application of principal component analysis (PCA) used for examination of measured absorbance spectra revealed more detailed sub-stages of freshness, which are not observed by the conventional analysis of the reflectance spectra. The results show a great potential of the combined application of optical-NIR spectroscopy with complementary use of PCA approach for assessing meat quality and monitoring relative absorbance alternation of oxymyoglobin and myoglobin in visible, and fat, water, collagen in NIR spectral ranges
Vitamin D status in children with myopia
Introduction. A dramatic increase of myopia worldwide has been observed in recent years. New risk factors for the development of myopia have been the target of numerous investigations. The basis of our research is the correlation between serum levels of vitamin D [25(OH)D] and myopia itself.Purpose: To find out the relationship between serum levels of 25(OH) D and myopia. Patients and methods: The study included 222 children with different refraction status. Full ophthalmologic examination, cycloplegic refraction, echobiometry were performed. The serum levels of 25(OH)D were measured by liquid chromatographic mass spectrometry (level of insufficiency < 80 nmol/L).Results: The average patientsâ age (51% boys and 48,2% girls) was 11,7 y (SD ± 3,03). They were subdivided into two groups â children with myopia (84,7%) and those without myopia (15,3%). The mean serum 25(OH)D level of all tested was 61,48 nmol/L (16-140 nmol/L; SD ± 20,15); of myopia â 59,67 nmol/L (16-140 nmol/L; SD ± 19,30) and of the non-myopia group â 71,91 nmol/L (33-111 nmol/L; SD ± 21,79). There was a statistically significant difference in serum levels between the two groups (Đ = 0,001). The risk of myopia was higher with the decrease of 25(OH)D values (OR = 1,028 ; 95% CI 1,008-1,048). Conclusion. In our investigation group we established low serum levels of 25(OH)D which indicated the need for conducting a population study of its status among Bulgarian children. The correlation between the higher risk of myopia and the vitamin D scarcity has to be further studied, also considering the factor of outdoor/sun-exposure time.
Postsocialist disability matrix
This paper explores injustices experienced by disabled people in the postsocialist countries of Central and Eastern Europe. Drawing on Nancy Fraserâs theory of social justice, the analysis proposes a âmatrixâ that reveals the negative impact of two factors â state socialist legacy and postsocialist neoliberalization â on disabled peopleâs parity of participation in three dimensions of justice â economic redistribution, cultural recognition, and political representation. The legacy of state socialism has underpinned: segregated service provision; medical-productivist understanding of disability for assessment purposes; denial of disability on everyday level; and weak disability organizing. Neoliberal restructuring has resulted in: retrenchment of disability support through decentralization, austerity, and workfare; stigmatization of âdependencyâ through the discourse of âwelfare dependencyâ; responsibilization of disabled people; and depoliticization of disability organizations by restricting their activities to service provision and incorporating them in structures of tokenistic participation. The analysis is informed by reports and academic studies of disability in the postsocialist region
Purity-bounded uncertainty relations in multidimensional space -- generalized purity
Uncertainty relations for mixed quantum states (precisely, purity-bounded
position-momentum relations, developed by Bastiaans and then by Man'ko and
Dodonov) are studied in general multi-dimensional case. An expression for
family of mixed states at the lower bound of uncertainty relation is obtained.
It is shown, that in case of entropy-bounded uncertainty relations, lower-bound
state is thermal, and a transition from one-dimensional problem to
multi-dimensional one is trivial. Results of numerical calculation of the
relation lower bound for different types of generalized purity are presented.
Analytical expressions for general purity-bounded relations for highly mixed
states are obtained.Comment: 12 pages, 2 figures. draft version, to appear in J. Phys. A Partially
based on a poster "Multidimensional uncertainty relations for states with
given generalized purity" presented on X Intl. Conf. on Quantum Optics'2004
(Minsk, Belarus, May 30 -- June 3, 2004) More actual report is to be
presented on ICSSUR-2005, Besan\c{c}on, France and on EQEC'05, Munich. V. 5:
amended article after referees' remark
Photonic realization of the relativistic Kronig-Penney model and relativistic Tamm surface states
Photonic analogues of the relativistic Kronig-Penney model and of
relativistic surface Tamm states are proposed for light propagation in fibre
Bragg gratings (FBGs) with phase defects. A periodic sequence of phase slips in
the FBG realizes the relativistic Kronig-Penney model, the band structure of
which being mapped into the spectral response of the FBG. For the semi-infinite
FBG Tamm surface states can appear and can be visualized as narrow resonance
peaks in the transmission spectrum of the grating
- âŠ