Development of a multiperspective optical measuring system for investigating decaying switching arcs at the nozzle exit of circuit breakers.

High-voltage gas circuit breakers, which play an important role in the operation and protection of the power grid, function by drawing an arc between two contacts and then extinguishing it by cooling it using a transonic gas flow. Improving the design of circuit breakers requires an understanding of the physical processes in the interruption of the arc, particularly during the zero crossing of the alternating current (the point in time when the arc can be interrupted). Most diagnostic techniques currently available focus on measurement of current, voltage, and gas pressure at defined locations. However, these integral properties do not give sufficient insight into the arc physics. To understand the current interruption process, spatially resolved information about the density, temperature, and conductivity of the arc and surrounding gas flow is needed. Owing to the three-dimensional, unstable nature of the arc in a circuit breaker, especially near current zero, a spatially resolved, tomographic diagnostic technique is required that is capable of freezing the rapid, transient behavior and that is insensitive to the vibrations and electromagnetic interference inherent in the interruption of short-circuit current arcs. Here a new measurement system, based on background-oriented schlieren (BOS) imaging, is presented and assessed. BOS imaging using four beams consisting of white light sources, a background pattern, imaging optics, and a camera permits measurement of the line-of-sight integrated refractive index. Tomographic reconstruction is used to determine the three-dimensional, spatially resolved index of refraction distribution that in turn is used to calculate the density. The quantitative accuracy of a single beam of the BOS setup is verified by using a calibration lens with a known focal length. The ability of the tomographic reconstruction to detect asymmetric features of the arc and surrounding gas flow is assessed semiquantitatively using a nozzle that generates two gas jets, as described in [Exp. Fluids43, 241 (2007)EXFLDU0723-486410.1007/s00348-007-0331-1]. Experiments using a simple model of a circuit breaker, which provides optical access to an ∼1 kA arc that burns between two contacts and is blown through a nozzle system by synthetic air from a high pressure reservoir, are also described. The density in the decaying arc and surrounding gas flow is reconstructed, and the limitations of the technique, which are related to the temporal and spatial resolution, are addressed.

Interaction driven subgap spin exciton in the Kondo insulator SmB6.

Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator SmB6 and describe its relation to the low energy insulating band structure. The resonant intensity is confined to the X and R high symmetry points, repeating outside the first Brillouin zone and dispersing less than 2 meV, with a 5d-like magnetic form factor. We present a slave-boson treatment of the Anderson Hamiltonian with a third neighbor dominated hybridized band structure. This approach produces a spin exciton below the charge gap with features that are consistent with the observed neutron scattering. We find that maxima in the wave vector dependence of the inelastic neutron scattering indicate band inversion.

Tunable zero-energy Dirac and Luttinger nodes in a two-dimensional topological superconductor.

Cooper pairing in ultrathin films of topological insulators, induced intrinsically or by proximity effect, can produce an energetically favorable spin-triplet superconducting state. The spin-orbit coupling acts as an SU(2) gauge field and stimulates the formation of a spin-current vortex lattice in this superconducting state. Here we study the Bogoliubov quasiparticles in such a state and find that the quasiparticle spectrum consists of a number of Dirac nodes pinned to zero energy by the particle-hole symmetry. Some nodes are 'accidental' and move through the first Brillouin zone along high-symmetry directions as the order parameter magnitude or the strength of the spin-orbit coupling are varied. At special parameter values, nodes forming neutral quadruplets merge and become gapped out, temporarily producing a quadratic band-touching spectrum. All these features are tunable by controlling the order parameter magnitude via a gate voltage in a heterostructure device. In addition to analyzing the spectrum at the mean-field level, we briefly discuss a few experimental signatures of this spectrum.

Global taxonomic, functional, and phylogenetic diversity of bees in apple orchards.

An essential prerequisite to safeguard pollinator species is characterisation of the multifaceted diversity of crop pollinators and identification of the drivers of pollinator community changes across biogeographical gradients. The extent to which intensive agriculture is associated with the homogenisation of biological communities at large spatial scales remains poorly understood. In this study, we investigated diversity drivers for 644 bee species/morphospecies in 177 commercial apple orchards across 33 countries and four global biogeographical biomes. Our findings reveal significant taxonomic dissimilarity among biogeographical zones. Interestingly, despite this dissimilarity, species from different zones share similar higher-level phylogenetic groups and similar ecological and behavioural traits (i.e. functional traits), likely due to habitat filtering caused by perennial monoculture systems managed intensively for crop production. Honey bee species dominated orchard communities, while other managed/manageable and wild species were collected in lower numbers. Moreover, the presence of herbaceous, uncultivated open areas and organic management practices were associated with increased wild bee diversity. Overall, our study sheds light on the importance of large-scale analyses contributing to the emerging fields of functional and phylogenetic diversity, which can be related to ecosystem function to promote biodiversity as a key asset in agroecosystems in the face of global change pressures.

Unilateral Left Frontal Lobe Lesion in a Marburg's Variant of Multiple Sclerosis Patient with Impaired Swallowing and Speech: A 3-Year Clinical/Brain MRI Follow-up.

Although the importance of bilateral cortical innervation in the control of swallowing is well known, neurogenic dysphagia caused by unilateral hemispheric ischemic lesion has been also reported. Our patient is a 41-year-old male who developed difficulty swallowing liquids, oral apraxia, and motor dysphasia, followed by right-hand ataxia. Brain magnetic resonance imaging (MRI) showed subcortical tumefactive conglomerate of cystic lesions in the left frontal, precentral region, which were sharp edged, with perilesional edema, concordant with lesions in Marburg's variant of multiple sclerosis. Steroid treatment and plasma exchange therapy led to disappearance of neurological symptoms. Treatment with interferon ß-1a 40 mcg sc was initiated. During a 3-year follow-up, clinical/brain MRI scan showed no new neurological manifestations, a significant regression of lesion size, and no new brain lesions. To the best of our knowledge, this is a first case of dysphagia caused by unilateral hemispheric lesion in a multiple sclerosis patient.

Realistic time-reversal invariant topological insulators with neutral atoms.

We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. We introduce an original method to synthesize a gauge field in the near field of an atom chip, which effectively mimics the effects of spin-orbit coupling and produces quantum spin-Hall states. We also propose a feasible scheme to engineer sharp boundaries where the hallmark edge states are localized. Our multiband system has a large parameter space exhibiting a variety of quantum phase transitions between topological and normal insulating phases. Because of their remarkable versatility, cold-atom systems are ideally suited to realize topological states of matter and drive the development of topological quantum computing.

Combined FTIR and SEM-EDS study of Bi2O3 doped ZnO-SnO2 ceramics.

The effects of Bi(2)O(3) addition on the phase composition, microstructure and optical properties of ZnO-SnO(2) ceramics were investigated. Starting powders of ZnO and SnO(2) were mixed in the molar ratio 2:1. After adding Bi(2)O(3) (1.0 mol.%) this mixture was mechanically activated for 10 min in a planetary ball mill, uniaxially pressed and sintered at 1300 degrees C for 2 h. Far-infrared reflection spectra were measured (100-1000 cm(-1)). To investigate the occurred differences in FTIR spectra, the Bi(2)O(3)-doped sample was examined more carefully with a Perkin-Elmer FTIR spectrometer (Perkin Elmer, Waltham, MA, USA) connected with a Perkin-Elmer FTIR microscope and itemized points of interest were also studied with SEM-EDS.

Screened moments and extrinsic in-gap states in samarium hexaboride.

Samarium hexaboride (SmB6) is a Kondo insulator, with a narrow gap due to hybridization between localized and conduction electrons. Despite being an insulator, many samples show metal-like properties. Rare-earth purification is exceedingly difficult, and nominally pure samples may contain 2% or more of impurities. Here to determine the effects of rare-earth doping on SmB6, we synthesized and probed a series of gadolinium-doped samples. We found a relationship between specific heat and impurity moment screening which scales systematically. Consistent with this finding, our neutron scattering experiments of a high purity sample of doubly isotopic 154Sm11B6 show no intrinsic excitations below the well-established 13 meV spin-exciton. The result of introducing impurities into a Kondo insulator is incompletely understood, but it is clear from our measurements that there is a systematic relationship between rare-earth impurities and metal-like properties in SmB6.

LAMP assay and rapid sample preparation method for on-site detection of flavescence dorée phytoplasma in grapevine.

In Europe the most devastating phytoplasma associated with grapevine yellows (GY) diseases is a quarantine pest, flavescence dorée (FDp), from the 16SrV taxonomic group. The on-site detection of FDp with an affordable device would contribute to faster and more efficient decisions on the control measures for FDp. Therefore, a real-time isothermal LAMP assay for detection of FDp was validated according to the EPPO standards and MIQE guidelines. The LAMP assay was shown to be specific and extremely sensitive, because it detected FDp in all leaf samples that were determined to be FDp infected using quantitative real-time PCR. The whole procedure of sample preparation and testing was designed and optimized for on-site detection and can be completed in one hour. The homogenization procedure of the grapevine samples (leaf vein, flower or berry) was optimized to allow direct testing of crude homogenates with the LAMP assay, without the need for DNA extraction, and was shown to be extremely sensitive.

Apoptosis in the developing rat cochlea and its related structures.

Mammalian development involves proliferation and programmed cell death (apoptosis). This study was undertaken to analyse the spatial and temporal organisation of apoptosis in developing rat cochlear and associated tissues using in situ terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labelling of DNA fragments (TUNEL), and light and electron microscopy. Embryonic (E12-E19 days) and postnatal rats (P0-P21 days) were studied. Fixed tissues were stained for apoptosis using TUNEL technique and the cytomorphology of apoptosis was confirmed by light and electron microscopy. Apoptotic cells were detected predominantly during the embryonic and early postnatal development of the cochlea. Apoptosis occurred in embryonic precursors of the cochlear duct epithelium, mainly in the region of its outgrowth between E12 and E16. In the periotic mesenchyme, apoptosis occurred in areas committed to develop into the middle ear cavity (peaking at E16) and perilymphatic compartments (peaking around E18-E19). Apoptosis in the VIIIth nerve (statoacoustic) ganglion was detected throughout the embryonic and early postnatal periods, peaking at E18-E19, around the time when the cochlear neural connections are being established. At later postnatal days, apoptosis was seen only occasionally in cochlear tissues, predominantly in tissues lining the middle ear cavity and sporadically in cells of the otic capsule. Therefore, apoptosis appears to occur in areas of remodeling, in areas of cavitation and in areas of differentiation. These findings provide a template for studying the molecular mechanisms involved in the development of the rat inner ear.

Transient expression of P2X(1) receptor subunits of ATP-gated ion channels in the developing rat cochlea.

The expression pattern of the ATP-gated ion channel P2X(1) receptor subunit was studied in the developing rat cochlea by riboprobe in situ hybridisation and immunohistochemistry. Embryonic (E12, E14, E16 and E18) and postnatal (P0, P2, P4, P6, P10 and adult) rat cochleae were examined. Both mRNA and protein localisation techniques demonstrated comparable P2X(1) receptor expression from E16 until P6 but this expression was absent at later developmental stages. P2X(1) receptor mRNA expression was localised within the otic capsule and associated mesenchyme (from E16 to P6), spiral limbus (from P0 to P6) and within the spiral ligament adjacent to the insertion of Reissner's membrane (from P2 to P6). P2X(1) receptor protein had a similar distribution based upon immunoperoxidase localisation. P2X(1) receptor-like immunoreactivity was detected in the otic capsule and the surrounding mesenchyme (from E16 to P6), spiral limbus (from P0) and epithelial cells of Reissner's membrane (from P2 to P6). The spiral ganglion neurones showed the earliest P2X(1) receptor expression (from E16 to P6). This became associated with immunolabelling of their afferent neurite projections to the base of the developing inner and outer hair cells (observed from E18 and peaking at P2). Immunolabelling of the efferent nerve fibres of the intraganglionic spiral bundle (from E18 to P6) within the spiral ganglion was also observed. The results suggest that ATP-gated ion channels assembled from P2X(1) receptor subunits provide a signal transduction pathway for development of afferent and efferent innervation of the sensory hair cells and purinergic influence on cochlear morphogenesis.

Experimental study of the effects of known quantities of zearalenone on swine reproduction.

Experiments were carried out in order to study the effect of known quantities of zearalenone on reproductive performance of gilts. Zearalenone was produced on autoclaved corn using pure cultures of Fusarium graminearum Schwabe (local strain of Leskovac). The amount of 22.09 mg/kg of zearalenone in the ration of breeding gilts had an obvious harmful effect on their reproductive performance decreased number of corpora lutea, decreased weight of ovaries, decreased number of live embryos, increased number of dead-born piglets, and the occurrence of abortus. These effects were less pronounced in gilts fed mashes containing 2.2 mg/kg zearalenone. However, in both groups the uterotropic effect of zearalenone was obvious.

[Dissecting aortic aneurysm as the cause of a fever of unknown origin]. / Disekantna aneurizma aorte kao uzrok nejasnog febrilnog stanja.

Dissection of the aortic aneurysm is a clinical syndrome with the most dramatic course and bad prognosis. Fever is a frequent occurrence, but rarely a dominant symptom. The patient with a prolonged fever caused by dissecting aneurysm of the aorta in whom pleuropneumonia masked the real diseases has been presented.

Management of chronic active B hepatitis with alpha interferon.

Patients with chronic active B hepatitis entered into an open study of IFN maintenance therapy. They received 3 x 10(6) I.U. INTRON-A by subcutaneous injection three times a week for a 4-month period. Four patients out of ten became HBeAg negative and anti-HBe, which was accompanied by the return of serum liver function tests to normal. In a control group with eleven patients, given only vitamins, no changes were registered in serological and biochemical data. Fever, "flu-like illness", fatigue were the main side-effects observed during the course of IFN therapy, which had not to be discontinued.

[Dissecting aortic aneurysm as a cause of fever of unknown origin]. / Disekantna aneurizma aorte kao uzrok nejasnog febrilnog stanja.

Dissecting aortic aneurysm is a clinical syndrome commonly with a dramatic course and a fatal prognosis. The disease often has a fatal ending at the very beginning, a few hours after the onset. High temperature happens sometimes, but is rarely a dominant symptom. We presented a case of a patient with a long term febrile state caused by dissecting aortic aneurysm, where pleuropneumenia covered the real nature of the disease. It has been pointed out that dissecting of aorta should be thought of in patients with unclear febrile states, especially if they have difficulties in the area of thorax.

[The status of the respiratory organs in students in Sabac exposed to increased air pollution]. / Stanje kisajnih organa kod ucenika iz Sapca izlozenih povecanjom aerozagadjenju.

The authors followed up the health of 322 elementary-school pupils at Sabac who were exposed to increased air pollution with chemical agents (ammonia, fluor hydrogen, chloracetic acid, sulfur dioxide, soot). The mean annual concentration of these gases were above or insignificantly under maximally permitted values. The results of the examination were as follows: recurrent cough in 12.4 per cent of cases and clinical signs of chronic or obstructive bronchitis in 8.4 per cent of children. Values of vital capacity were under normal in 27.6 per cent of cases and almost in the half of children vital capacity was at the lower normal limit. FEV1/FVC was under normal in 15 per cent of cases and at the lower normal limit in about 18.6 per cent of children. In spite of a great number of children with positive cutaneous tests to inhalation allergens with Prick's method IgE was within normal limits in these children. Thus, a significant noxious effect of allergic components on respiratory organs should be excluded. This was also confirmed by spirometric measurements of the two subsequent maximal expiriums when differences of +/- 3% were registered. However, in children with allergic bronchitis the value dispersion was by 2-3 times greater. Consequently, the authors concluded that damaged respiratory organs in children at Sabac appeared in a greater number of cases than in other places and that these damages were due to increased concentrations of different chemical air pollution agents.

A virologically studied epidemic of type A hepatitis in a school for the mentally retarded.

The occurrence of hepatitis A virus (HAV) infection in a small boarding school for mildly to moderately mentally retarded children in Umka, Yugoslavia, in the spring of 1979, six years after the last recognized occurrence, provided an opportunity to study the spread of the agent among 79 classroom and dormitory contacts. Only 51% of those who had entered subsequent to the prior outbreak had detectable antibody (anti-HAV) with immunoglobulin G predominance, and the proportion within the first six years of training did not vary. Both findings suggest a lack of endemicity during the interval. The outbreak ended spontaneously just before the summer vacation with an anti-HAV prevalence of 90%. The ratio of silent to overt cases was approximately 2:1. HAV was found in fecal samples from susceptible residents with inapparent infection as well as those with hepatitis. Among those with prior experience, there were no significant anti-HAV increases to suggest HAV reinfection in this group. Overall, 32% were seropositive for markers of past or chronic hepatitis B virus (HBV) infection, but this status did not correlate with sex, year of training, or HAV experience. Only one instance of HBV transmission was observed in the same interval as the 26 HAV infections.

Brain-applied magnetic fields and immune response: role of the pineal gland.

In an attempt to clarify the mechanisms underlying immunopotentiation induced by prolonged exposure of the rat brain to static magnetic fields, and to evaluate the role of the pineal gland in that phenomenon, experiments were carried out on the following groups of adult rats (maintained under a 12 hr light/12 hr dark photoperiod): pinealectomized rats (Px); rats with micromagnets implanted to the occipito-parietal region of the skull (M); rats pinealectomized and implanted with micromagnets to the skull (PxM); sham-pinealectomized rats with non-magnetic beads implanted to the occipito-parietal area of the skull (ShPxMx); and intact controls (IC). Twenty-one days after surgery, animals of all groups were immunized with sheep red blood cells and tested for plaque forming cell (PFC) response and serum hemagglutinin level. Humoral immune reactions decreased significantly in Px rats, while increased markedly in M rats in comparison to the ShPxMx and IC controls. Compromised immune function induced by pinealectomy was restored by prolonged exposure of the brain to magnetic fields (PxM rats). Thus reconstituted immune responsiveness in PxM rats reached the level observed in controls, but was lower than that in M rats. The results imply that magnetic fields applied to the rat brain may exert their immunoenhancing activity in the absence of the pineal gland. However, this activity of magnetic fields is more pronounced in the presence of the pineal organ. The latter finding suggests the involvement of the pineal in the immunopotentiation induced by magnetic fields, but does not imply that magnetic fields operate solely via the pineal gland.(ABSTRACT TRUNCATED AT 250 WORDS)