217 research outputs found
Progress in Developing Hybrid RPCs: GEM-like Detectors with Resistive Electrodes
We have recently developed an innovative detector of photons and charged
particles: a GEM-like gaseous amplification structure with resistive electrodes
instead of commonly used metallic ones. This novel detector combines the best
property of GEMs- the capability to operate in a cascaded mode and in poorly
quenched gases - and of RPC: the protection against sparks. In this paper will
shortly review our latest achievements in this direction, however the main
focus will be given on a new advanced design that allows to build large area
detectors manufactured by a screen printing technology. The proposed detector,
depending on the applications, can operate either in a GEM mode (electron
multiplications through holes only) or as a hybrid RPC with simultaneous
amplifications in the drift region and in the holes. The possible applications
of this new detector will be discussed
Advances in the Development of Micropattern Gaseous Detectors with Resistive Electrodes
We describe the most recent efforts made by various groups in implementing
resistive electrodes in micropattern gaseous detectors with the aim to combine
in the same design the best features of RPCs (for the example, their robustness
and spark protection property) with the high granularity and thus the good
position resolution offered by microelectronic technology. In the stream of
this activity, we have recently developed two novel detectors with resistive
electrodes: one was based on resistive micromeshes and the second one is a MSGC
with resistive electrodes. We have demonstrated that the resistive meshes are a
convenient construction element for various designs of spark protective
detectors: RPCs type, GEM type and MICROMEGAS type. These new detectors enable
to considerably enhance the RPC and micropattern detectors applications since
they feature not only a high position resolution but also a relatively good
energy resolution (25-30 persent FWHM at 6 keV) and, if necessary, they can
operate in cascaded mode allowing the achievement of a high overall gas gain.
The main conclusion from these studies is that the implementation of resistive
electrodes in micropattern detectors makes them fully spark protected; on this
basis we consider this direction very promising
Identifying the larva of the fan mussel, Atrina fragilis (Pennant, 1777) (Pinnidae)
This work was funded by the Scottish Government project SP004 and a MSS PhD studentship to DS. Many thanks are due to the Crews of the MV Alba na Mara (MSS), RV Sir John Murray (SEPA) and the MV Lochnevis (Caledonian Macbrayne) for facilitating sample collection, John Dunn for assistance with the manufacture and installation of the ferry sampler, Marian Thomson and other staff at the University of Edinburgh for laboratory assistance, Anastasia Imsiridou, Sofia Galinou-Mitsoudi and Vassilis Katsares of the Greek Department of Fisheries and Aquaculture Technology for supplying reference adult A. fragilis DNA, Pablo Diaz and staff at the University of Aberdeen microscopy department for assistance with SEM analysis, the National Museum of Wales for allowing reproduction of the juvenile A. fragilis image, Keith Hiscock and Eve Southward of Plymouth Marine Laboratory for historical information on the identification of A. fragilis larvae, Colin McAlister and the staff of the Fishery offices in Mallaig and Fraserburgh for assistance in the transport of zooplankton samples and materials, and the British Oceanographic Data Centre for supplying data on the UK Tidal Gauge Network. Comments from Associate Editor Simon Cragg and two anonymous reviewers were greatly appreciated for improving the manuscriptPeer reviewedPostprintPostprintPostprintPostprintPostprintPostprintPostprintPostprintPostprin
Inactivation of Ppp1r15a minimises weight gain and insulin resistance during caloric excess in female mice.
Phosphorylation of the translation initiation factor eIF2α within the mediobasal hypothalamus is known to suppress food intake, but the role of the eIF2α phosphatases in regulating body weight is poorly understood. Mice deficient in active PPP1R15A, a stress-inducible eIF2α phosphatase, are healthy and more resistant to endoplasmic reticulum stress than wild type controls. We report that when female Ppp1r15a mutant mice are fed a high fat diet they gain less weight than wild type littermates owing to reduced food intake. This results in healthy leaner Ppp1r15a mutant animals with reduced hepatic steatosis and improved insulin sensitivity, albeit with a possible modest defect in insulin secretion. By contrast, no weight differences are observed between wild type and Ppp1r15a deficient mice fed a standard diet. We conclude that female mice lacking the C-terminal PP1-binding domain of PPP1R15A show reduced dietary intake and preserved glucose tolerance. Our data indicate that this results in reduced weight gain and protection from diet-induced obesity.The work was also supported by Diabetes UK and the MRC [G1002610]. VP held an Arthur and Sadie Pethybridge PhD Studentship from Diabetes UK. The CIMR microscopy core facility is supported by a Wellcome Trust Strategic Award [100140] and a Wellcome Trust equipment grant [093026]
Development of innovative micropattern gaseous detectors with resistive electrodes and first results of their applications
The paper summarizes our latest progress in the development of newly
introduced micro pattern gaseous detectors with resistive electrodes. These
resistive electrodes protect the detector and the front-end electronics in case
of occasional discharges and thus make the detectors very robust and reliable
in operation. As an example, we describe in greater detail a new recently
developed GEM-like detector, fully spark-protected with electrodes made of
resistive kapton. We discovered that all resistive layers used in these studies
(including kapton), that are coated with photosensitive layers, such as CsI,
can be used as efficient photo cathodes for detectors operating in a pulse
counting mode. We describe the first applications of such detectors combined
with CsI or SbCs photo cathodes for the detection of UV photons at room and
cryogenic temperatures.Comment: Presented at the 11 Vienna Conference on Instrumentation, February,
200
Evolution of Linear Absorption and Nonlinear Optical Properties in V-Shaped Ruthenium(II)-Based Chromophores
In this article, we describe a series of complexes with electron-rich cis-{Ru^(II)(NH_3)_4}^(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845−4859). They have been isolated as their PF_6− salts and characterized by using various techniques including ^1H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru^(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities β have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d → π^* metal-to-ligand charge-transfer (MLCT) and π → π^* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant β_0 responses as high as ca. 600 × 10^(−30) esu. These pseudo-C_(2v) chromophores show two substantial components of the β tensor, β_(zzz) and β_(zyy), although the relative significance of these varies with the physical method applied. According to HRS, β_(zzz) dominates in all cases, whereas the Stark analyses indicate that β_(zyy) is dominant in the shorter chromophores, but β_(zzz) and β_(zyy) are similar for the extended species. In contrast, finite field calculations predict that β_(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand π-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al. J. Am. Chem. Soc. 2004, 126, 3880−3891)
Colossal dielectric constants in transition-metal oxides
Many transition-metal oxides show very large ("colossal") magnitudes of the
dielectric constant and thus have immense potential for applications in modern
microelectronics and for the development of new capacitance-based
energy-storage devices. In the present work, we thoroughly discuss the
mechanisms that can lead to colossal values of the dielectric constant,
especially emphasising effects generated by external and internal interfaces,
including electronic phase separation. In addition, we provide a detailed
overview and discussion of the dielectric properties of CaCu3Ti4O12 and related
systems, which is today's most investigated material with colossal dielectric
constant. Also a variety of further transition-metal oxides with large
dielectric constants are treated in detail, among them the system La2-xSrxNiO4
where electronic phase separation may play a role in the generation of a
colossal dielectric constant.Comment: 31 pages, 18 figures, submitted to Eur. Phys. J. for publication in
the Special Topics volume "Cooperative Phenomena in Solids: Metal-Insulator
Transitions and Ordering of Microscopic Degrees of Freedom
Shrinking-Hole Colloidal Lithography: Self-Aligned Nanofabrication of Complex Plasmonic Nanoantennas
Plasmonic nanoantennas create locally strongly enhanced electric fields in so-called hot spots. To place a relevant nanoobject with high accuracy in such a hot spot is crucial to fully capitalize on the potential of nanoantennas to control, detect, and enhance processes at the nanoscale. With state-of-the-art nanofabrication, in particular when several materials are to be used, small gaps between antenna elements are sought, and large surface areas are to be patterned, this is a grand challenge. Here we introduce self-aligned, bottom-up and self-assembly based Shrinking-Hole Colloidal Lithography, which provides (i) unique control of the size and position of subsequently deposited particles forming the nanoantenna itself, and (ii) allows delivery of nanoobjects consisting of a material of choice to the antenna hot spot, all in a single lithography step and, if desired, uniformly covering several square centimeters of surface. We illustrate the functionality of SHCL nanoantenna arrangements by (i) an optical hydrogen sensor exploiting the polarization dependent sensitivity of an Au-Pd nanoantenna ensemble; and (ii) single particle hydrogen sensing with an Au dimer nanoantenna with a small Pd nanoparticle in the hot spot
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