Search for Baryon-Number-Violating Processes in B

We report the results of the first search for B^{-} decays to the Ξ[over ¯]_{c}^{0}Λ[over ¯]_{c}^{-} final state using 711 fb^{-1} of data collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The results are interpreted in terms of both direct baryon-number-violating B^{-} decay and Ξ_{c}^{0}-Ξ[over ¯]_{c}^{0} oscillations which follow the standard model decay B^{-}→Ξ_{c}^{0}Λ[over ¯]_{c}^{-}. We observe no evidence for baryon number violation and set the 95% confidence-level upper limits on the ratio of baryon-number-violating and standard model branching fractions B(B^{-}→Ξ[over ¯]_{c}^{0}Λ[over ¯]_{c}^{-})/B(B^{-}→Ξ_{c}^{0}Λ[over ¯]_{c}^{-}) to be <2.7% and on the effective angular frequency of mixing ω in Ξ_{c}^{0}-Ξ[over ¯]_{c}^{0} oscillations to be <0.76 ps^{-1} (equivalent to τ_{mix}>1.3 ps).

Electromagnetic toroidal excitations in matter and free space.

The toroidal dipole is a localized electromagnetic excitation, distinct from the magnetic and electric dipoles. While the electric dipole can be understood as a pair of opposite charges and the magnetic dipole as a current loop, the toroidal dipole corresponds to currents flowing on the surface of a torus. Toroidal dipoles provide physically significant contributions to the basic characteristics of matter including absorption, dispersion and optical activity. Toroidal excitations also exist in free space as spatially and temporally localized electromagnetic pulses propagating at the speed of light and interacting with matter. We review recent experimental observations of resonant toroidal dipole excitations in metamaterials and the discovery of anapoles, non-radiating charge-current configurations involving toroidal dipoles. While certain fundamental and practical aspects of toroidal electrodynamics remain open for the moment, we envision that exploitation of toroidal excitations can have important implications for the fields of photonics, sensing, energy and information.

Modulating sub-THz radiation with current in superconducting metamaterial.

We show that subterahertz transmission of the superconducting metamaterial, an interlinked two-dimensional network of subwavelength resonators connected by a continuous superconducting wire loop, can be dynamically modulated by passing electrical current through it. We have identified the main mechanisms of modulation that correspond to the suppression of the superconductivity in the network by magnetic field and heat dissipation. Using the metamaterial fabricated from thin niobium film, we were able to demonstrate a transmission modulation depth of up to 45% and a bandwidth of at least 100 kHz. The demonstrated approach may be implemented with other superconducting materials at frequencies below the superconducting gap in the THz and subterahertz bands.

Infrared dielectric metamaterials from high refractive index chalcogenides.

High-index dielectric materials are in great demand for nanophotonic devices and applications, from ultrathin optical elements to metal-free sub-diffraction light confinement and waveguiding. Here we show that chalcogenide topological insulators are particularly apt candidates for dielectric nanophotonics architectures in the infrared spectral range, by reporting metamaterial resonances in chalcogenide crystals sustained well inside the mid-infrared, choosing Bi2Te3 as case study within this family of materials. Strong resonant modulation of the incident electromagnetic field is achieved thanks to the exceptionally high refractive index ranging between 7 and 8 throughout the 2-10 µm region. Analysis of the complex mode structure in the metamaterial allude to the excitation of circular surface currents which could open pathways for enhanced light-matter interaction and low-loss plasmonic configurations by coupling to the spin-polarized topological surface carriers, thereby providing new opportunities to combine dielectric, plasmonic and magnetic metamaterials in a single platform.

Note: Additionally refined new possibilities of plasma probe diagnostics.

In two previous Notes published in this journal, a method of measuring probe sheath thickness and ion mass was described using Langmuir probe diagnostics in low pressure xenon plasma close to Maxwellian substance. According to the first Note, this method includes two stages: (i) in a special experiment with known ion mass, the Bohm and Child-Langmuir-Boguslavsky (CLB) equations for cylindrical Langmuir probes used in this xenon plasma were solved jointly to determine the probe sheath thicknesses and Bohm coefficient CBCyl ≈ 1.13; and (ii) in a general experiment, with known CBCyl, the same equations could be solved to obtain the probe sheath thicknesses and the mean ion mass. In the second Note, the (i) stage of this method was refined: the results of the CLB probe sheath model application, which were termed "evaluations," were corrected using the step-front probe sheath model, which was closer to reality in the special experiment with the xenon plasma. This process resulted in a Bohm coefficient of CBCyl ≈ 1.23 for the cylindrical probe. In the present Note, corrected xenon plasma parameters without the influence of the bare probe protective shield were used for the (i) stage of this diagnostic method. This action also refined the Bohm coefficient, lowering it to CBCyl ≈ 0.745 for cylindrical probes. This advance makes the new diagnostics method more objective and reliable.

Heavy metals in fish from the Barents Sea (summer 1994).

To assess the significance of metals in biota of the Barents Sea, preliminary information is presented for the concentrations of Cd, Pb, Hg, Ni, Cu and Zn in liver and muscle tissues of 15 marine fish species collected in the summer of 1994. Lead and Ni concentrations are below limits of detection (< 0.3 and 1.0 mg kg-1 dry wt.) in all tissues, as is Cd in muscle (< 0.10 mg kg-1). Generally, most of our results are within the reported literature range for various Arctic marine systems, especially regarding some commercially important species like cod and redfish, indicating that metal levels are not elevated. However, the interspecific variability is substantial and some remarkably high Cd levels (2.4 and 8.1 mg kg-1 dry wt.) in livers of Anarhichas species (catfish) and Raja fyllae (round skate) point to the problem of a general 'cadmium-anomaly' in polar marine waters, previously inferred from reported results for various pelagic and benthic invertebrates.

Heavy metals of inshore benthic invertebrates from the Barents Sea.

To assess metals in biota of the Barents Sea, information is presented on concentrations of Cu, Cd, Ni, Pb and Zn in the marine inshore benthic invertebrates Gammarus oceanicus, Littorina rudis, Nucella lapillus, Mytilus edulis and Arenicola marina collected in summer 1994. For geographical comparisons, the metal content to body size relationship was taken into account due to the different body sizes found at the localities investigated. In general, our data provide further evidence for the cadmium anomaly in invertebrates from polar waters which has been frequently discussed in the literature, with Cd concentrations reaching 1 mg x kg(-1) dry wt in G. oceanicus, 7 mg x kg(-1) in L. rudis and 24 mg x kg(-1) in N. lapillus. In contrast, our results obtained for Cd in M. edulis and A. marina are largely within a world-wide reported range (1-2 and 0.2-0.9 mg x kg(-1), respectively). Although some severe Ni emissions in the Kola region (Russia) mainly from nickel smelters have been reported, we do not find indications of an enhanced Ni availability in the marine biota studied compared to other areas

[alpha-Interferon indices in systemic lupus erythematosus and the effect of interferon therapy]. / Pokazateli al'fa-interferona pri sistemnoi krasnoi volchanke i vliianie na nikh interferonoterapii.

The effect of interferon inducers of viral and nonviral nature as well as of exogenous leukocyte interferon on interferon response of leukocytes (IRL) was studied in patients with different rheumatic diseases, mostly in patients with systemic lupus erythematosus (SLE). Studies in vitro showed that synthetic polyribonucleotide poly(1) X poly(C) induced in SLE patients on the average 3 times as high IRL indices as the viral interferon inducer Newcastle disease virus. A two-week course of treatment of some SLE patients with exogenous leukocyte interferon in various dosages (10(6), 3 X 10(5), and 10(4) units) resulted in a 2--16-fold increase of IRL values in the majority of the patients.

[Successful results in the interferon therapy of autoimmune disease in NZB/W strain mice]. / Uspeshnye rezul'taty interferonoterapii autoimmunnogo zabolevaniia myshei linii NZB/W.

The experiment used 50 female NZB/W mice divided into 2 groups of 25 animals each. Beginning at the age of 3 weeks and up to 1 year the animals of the experimental group were given once in 2 weeks 104 U/injection of mouse interferon intraperitoneally; the animals of the control group received physiological saline according to the same schedule. At the age of 3 months and subsequently at 6-week intervals up to 1 year mice of the two groups were examined for blood serum antibodies to native DNA and double-stranded RNA. The presence of p30 antigen of mouse leukemia virus in the spleen and blood serum was determined by the competitive radioimmunoassay in mice of both groups at the age of 3 months but not later because immune complexes with virus-specific antibodies appeared to be formed. The difference in the average longevity of the animals between the experimental (425 +/- 25.6 days) and control (315 +/- 15.1 days) groups is statistically highly significant. At the age of 3 months mice of the experimental group had significantly lower mean tires of antibody to DNA than in the control group (12.3 +/- 8.1 and 56.1 +/- 9.7, respectively), subsequently no significant differences in the titres were observed. Similar data were obtained with regard to antibodies to double-stranded RNA in the animals under 6 months of age. Morphological signs of development of lupus-nephritis in control mice appeared in histological studies earlier and were more marked than in the treated mice. It is concluded that the autoimmune disease in NZB/W mice was successfully treated with interferon.

[Results of the combined treatment of cancer of the cardial region of the stomach (a cooperative, randomized study)]. / Rezul'taty kombinirovannogo lecheniia raka kardial'nogo otdela zheludka (kooperirovannoe, randomizirovannoe issledovanie).

Immediate and long-term results of treatment of cancer of the proximal part of the stomach were compared in two groups of patients: (1) surgery and (2) combined treatment (preoperative Co-60 teletherapy + radical surgery). The patients were randomly assigned to the treatment schedules. The study was cooperative. Study group 1 included 128 patients, group 2-106. Radiotherapy was accompanied by mild complications; it neither adversely affected the terms of surgery nor resulted in an increased postoperative complication rate. Combination treatment was followed by a significant increase in 3-year survival matched by a decrease in relapse rate as well as metastasis development at a later stage, as compared with surgery alone. Application of standard preoperative irradiation procedures (NSD-20 Gy) led to degree 1-2 radiation pathomorphosis of tumor. Further search for higher effectiveness of the radiation component in causing injury to tumor should be continued.

Resonant transparency and non-trivial non-radiating excitations in toroidal metamaterials.

Engaging strongly resonant interactions allows dramatic enhancement of functionalities of many electromagnetic devices. However, resonances can be dampened by Joule and radiation losses. While in many cases Joule losses may be minimized by the choice of constituting materials, controlling radiation losses is often a bigger problem. Recent solutions include the use of coupled radiant and sub-radiant modes yielding narrow asymmetric Fano resonances in a wide range of systems, from defect states in photonic crystals and optical waveguides with mesoscopic ring resonators to nanoscale plasmonic and metamaterial systems exhibiting interference effects akin to electromagnetically-induced transparency. Here we demonstrate theoretically and confirm experimentally a new mechanism of resonant electromagnetic transparency, which yields very narrow isolated symmetric Lorentzian transmission lines in toroidal metamaterials. It exploits the long sought non-trivial non-radiating charge-current excitation based on interfering electric and toroidal dipoles that was first proposed by Afanasiev and Stepanovsky in [J. Phys. A Math. Gen. 28, 4565 (1995)].

Flux exclusion superconducting quantum metamaterial: towards quantum-level switching.

Nonlinear and switchable metamaterials achieved by artificial structuring on the subwavelength scale have become a central topic in photonics research. Switching with only a few quanta of excitation per metamolecule, metamaterial's elementary building block, is the ultimate goal, achieving which will open new opportunities for energy efficient signal handling and quantum information processing. Recently, arrays of Josephson junction devices have been proposed as a possible solution. However, they require extremely high levels of nanofabrication. Here we introduce a new quantum superconducting metamaterial which exploits the magnetic flux quantization for switching. It does not contain Josephson junctions, making it simple to fabricate and scale into large arrays. The metamaterial was manufactured from a high-temperature superconductor and characterized in the low intensity regime, providing the first observation of the quantum phenomenon of flux exclusion affecting the far-field electromagnetic properties of the metamaterial.