Physics of multi-GEM structures

We show that physics of multi-GEM structures is rather complex, regarding the number of phenomena affecting detector performance. The high-pressure operation in noble gases and the ion feedback are considered in more detail. It is proposed that the dominant avalanche mechanism in He and Ne, at high pressures, is the associative ionization. Ion feedback effects related to the dependence on gas, pressure and gain and to possible avalanche extension outside the GEM holes are discussed.Comment: Presented at the 8th International Conference on Instrumentation for Colliding Beam Physics, Novosibirsk, Febuary 28 - March 6, 2002. To be published in Nucl. Instr. and Meth.

Lichens of Callahan Mine, a copper and zinc-enriched Superfund site in Brooksville, Maine, U.S.A.

Metal-enriched habitats often harbor physiologically distinct biotas able to tolerate and accumulate toxic metals. Plants and lichens that accumulate metals have served as effective indicators of ecosystem pollution. Whereas the diversity of metal-tolerant lichens has been well documented globally, the literature of metal-tolerant lichen communities for eastern North America is limited. We examined the lichen flora of the Callahan Mine, a Cu-, Pb-, and Zn-enriched superfund site in Brooksville, Hancock County, Maine, U.S.A. Through collections along transects across metal-contaminated areas of the mine, we documented 76 species of lichens and related fungi. Fifty species were saxicolous, 26 were terricolous. Forty-three species were macrolichens, 31 were microlichens. Although no globally rare or declining species were encountered at the mine, two regionally rare or declining species, Stereocaulon tomentosum and Leptogium imbricatum, were found. The species found at the Callahan Mine were mostly ecological generalists frequenting disturbed habitats. Two extensively studied Cu-tolerant lichens, Acarospora smaragdula and Lecanora polytropa, and other known Cd-, Cu-, Pb-, and Zn-tolerant taxa, were found at the site

Development and applications of the Gas Electron Multiplier

The Gas Electron Multiplier (GEM) has been recently developed to cope with the severe requirements of high luminosity particle physics experimentation. With excellent position accuracy and very high rate capability, GEM devices are robust and easy to manufacture. The possibility of cascading two or more multipliers permits to achieve larger gains and more stable operation. We discuss major performances of the new detectors, particularly in view of possible use for high rate portal imaging and medical diagnostics

Regulation of the Cardiac Na+/K+ ATPase by Phospholemman

Hansraj Dhayan, Rajender Kumar, Andreas Kukol, ‘Regulation of the Cardiac Na+/K+ ATPase by Phospholemman’, in Sajal Chakraborti, Naranjan Dhalla, eds., Regulation of Membrane Na+-K+ ATPase, (Switzerland: Springer, 2016), ISBN 978-3-319-24748-9, eISBN 978-3-319-24750-2.Peer reviewe

Study of ion feedback in multi-GEM structures

We study the feedback of positive ions in triple and quadruple Gas Electron Multiplier (GEM) detectors. The effects of GEM hole diameter, detector gain, applied voltages, number of GEMs and other parameters on ion feedback are investigated in detail. In particular, it was found that the ion feedback is independent of the gas mixture and the pressure. In the optimized multi-GEM structure, the ion feedback current can be suppressed down to 0.5% of the anode current, at a drift field of 0.1 kV/cm and gain of 10^4. A simple model of ion feedback in multi-GEM structures is suggested. The results obtained are relevant to the performance of time projection chambers and gas photomultipliers.Comment: 9 pages, 11 figures. Submitted to Nucl. Instr. and Meth.

Quantitative assessment of atmospheric elements and their interaction with transplanted lichen Pyxine cocoes (Sw.) Nyl

A common foliose lichen Pyxine cocoes (Sw.) Nyl. was transplanted at 12 different sites of Dehradun City. The thalli of P. cocoes have been exposed for three months to monitor the accumulation of Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb and Zn along with C and N and their impact on photosynthetic pigments (Chl a, Chl b, Total Chl) were also estimated. The results showed that thalli transplanted close to the city centre (0 km) exhibit early stress as revealed by decreasing photosynthetic pigments as compared to the control site. The qualitative and quantitative results of elements showed negative correlations with distance from the city centre. Among the metals analysed, Fe (3396.71µg g-1 DW) at Haridwar road followed by Zn (279.52µg g-1 DW) at Rajpur road found in maximum concentration. Similarly, the maximum carbon (C) concentration (52.05%) was observed at Haridwar road whereas the nitrogen (N) concentration (1.73%) was observed maximum at Rajpur road. The lichen P. cocoes possess good accumulation capacity for most of the atmospheric elements. It is well evident from this study that selected lichen species could be used to detect low to higher atmospheric elemental emissions from vehicular activity in the ambient air and the biomonitoring procedure could be further standardized and used as part of an environmental monitoring programme

Effects of aminoperimidine on electrolyte transport across amphibian skin

The effect of aminoperimidine (AP)on transepithelial Na+ transport and Cl- conductance (G(Cl)) of isolated amphibian skin (Bufo viridis and Rana esculenta) was analyzed using transepithelial and intracellular electrophysiological techniques. AP, applied at concentrations between 30 and 100 mu M from the mucosal side, stimulated Na+ transport rapidly and reversibly by more than 30% of the control value due to an increase in apical membrane Na+ permeability. Influence of AP on basolateral membrane conductance and effective driving force for Na+ were negligible. Voltage-activated G(Cl) of toad skin, but not the resting, deactivated conductance, as well as spontaneously high G(Cl) in frog skin was rapidly inhibited by AP in a concentration-dependent manner. The half-maximal inhibitory concentration of 20 mu M is the highest hithero reported inhibitory power for G(Cl) in amphibian skin. The effect of AP on G(Cl) was slowly and incompletely reversible even after brief exposure to the agent. Serosal application of AP had similar, albeit delayed effects on both Nai and Cl- transport. AP did not interfere with the Cl- pathway after it was opened by 100-300 mu M CPT-cAMP, a membrane-permeable, nonhydrolyzed analogue of cAMP. Inhibition of the voltage-activated G(Cl) by AP was attenuated or missing when AP was applied during voltage perturbation to serosa-positive potentials. Since AP is positively charged at physiological pH, it suggests that the affected site is located inside the Cl- pathway at a certain distance from the external surface. AP affects then the Na+ and Cl- transport pathways independent of each other. The nature of chemical interference with AP, which is responsible for the influence on the transport of Na+ and Cl-, remains to be elucidated

Design of a novel flow-and-shoot microbeam

Presented here is a novel microbeam technology—the Flow-And-ShooT (FAST) microbeam—under development at RARAF. In this system, cells undergo controlled fluidic transport along a microfluidic channel intersecting the microbeam path. They are imaged and tracked in real-time, using a high-speed camera and dynamically targeted, using a magnetic Point and Shoot system. With the proposed FAST system, RARAF expects to reach a throughput of 100 000 cells per hour, which will allow increasing the throughput of experiments by at least one order of magnitude. The implementation of FAST will also allow the irradiation of non-adherent cells (e.g. lymphocytes), which is of great interest to many of the RARAF users. This study presents the design of a FAST microbeam and results of first tests of imaging and tracking as well as a discussion of the achievable throughput

Road-traffic pollution and asthma – using modelled exposure assessment for routine public health surveillance

Asthma is a common disease and appears to be increasing in prevalence. There is evidence linking air pollution, including that from road-traffic, with asthma. Road traffic is also on the increase. Routine surveillance of the impact of road-traffic pollution on asthma, and other diseases, would be useful in informing local and national government policy in terms of managing the environmental health risk. Several methods for exposure assessment have been used in studies examining the association between asthma and road traffic pollution. These include comparing asthma prevalence in areas designated as high and low pollution areas, using distance from main roads as a proxy for exposure to road traffic pollution, using traffic counts to estimate exposure, using vehicular miles travelled and using modelling techniques. Although there are limitations to all these methods, the modelling approach has the advantage of incorporating several variables and may be used for prospective health impact assessment. The modelling approach is already in routine use in the United Kingdom in support of the government's strategy for air quality management. Combining information from such models with routinely collected health data would form the basis of a routine public health surveillance system. Such a system would facilitate prospective health impact assessment, enabling policy decisions concerned with road-traffic to be made with knowledge of the potential implications. It would also allow systematic monitoring of the health impacts when the policy decisions and plans have been implemented

HUBUNGAN KANDUNGAN TIMBAL (Pb) DI UDARA DENGAN Pb DALAM TALUS LICHEN Xanthoparmelia xanthofarinosa

Penelitian ini bertujuan untuk mengetahui hubungan kandungan Pb di udara dengan Pb dalam talus lichen X. xanthofarinosa. Penelitian dilakukan di kota Malang. Hipotesis yang diajukan terdapat hubungan kandungan Pb di udara dengan Pb dalam X. xanthofarinosa. Lichen X. xanthofarinosa diambil dari 20 lokasi yang tersebar di kota Malang. Kandungan Pb dalam X. xanthofarinosa dianalisis dengan metode Atomic Absorption Spectrophotometer (ASS). Sedangkan kandungan Pb di udara diukur dengan menggunakan alat High Volume Air Sampler (HVAS). Data tentang hubungan kandungan Pb di udara dengan Pb dalam X. xanthofarinosa dianalisis dengan regresi. Hasil penelitian menyebutkan bahwa pada Standardized Coefisients (Beta) memiliki nilai 0,657, hal ini menunjukkan bentuk hubungan positif dan tingkat korelasi antara Pb di udara dengan Pb dalam X. Xanthofarinosa. Nilai t = 3,702 dengan tingkat signifikansi 0,002. Karena 0,002 < 0,05, maka hipotesis statistik (Ho) ditolak, dengan demikian hipotesis penelitian diterima. Sehingga dapat disimpulkan bahwa terdapat hubungan yang positif antara kandungan Pb di udara dengan Pb di dalam talus lichen X. Xanthofarinosa. Kata kunci : Pb, Udara, dan X. Xanthofarinos