bluuebunny/crossref_metadata_2025 huggingface dataset:
Literature review of spatio-temporal database models
Authors: PELEKIS NIKOS , THEODOULIDIS BABIS , KOPANAKIS IOANNIS , THEODORIDIS YANNIS
Published: June 2005

Recent efforts in spatial and temporal data models and database systems have attempted to achieve an appropriate kind of interaction between the two areas. This paper reviews the different types of spatio-temporal data models that have been proposed in the literature as well as new theories and concepts that have emerged. It provides an overview of previous achievements within the domain and critically evaluates the various approaches through the use of a case study and the construction of a comparison framework. This comparative review is followed by a comprehensive description of the new lines of research that emanate from the latest efforts inside the spatio-temporal research community.
Representing and reasoning with situations for context-aware pervasive computing: a logic programming perspective
Authors: LOKE SENG W
Published: June 2005

Context-aware pervasive systems are emerging as an important class of applications. Such systems can respond intelligently to contextual information about the physical world acquired via sensors and information about the computational environment. A declarative approach to building context-aware pervasive systems is presented, and the notion of the situation program is introduced, which highlights the primacy of the situation abstraction for building context-aware pervasive systems. There is also a demonstration of how to manipulate situation programs using meta-programming within an extension of the Prolog logic programming language which is called LogicCAP. Such meta-reasoning enables complex situations to be described in terms of other situations. Furthermore, a discussion is given on how the design of situation programs can affect the properties of a context-aware system. The approach encourages a high-level of abstraction for representing and reasoning with situations, and supports building context-aware systems incrementally by providing modularity and separation of concerns.
User perceptions of conservation and participatory management of iGxalingenwa forest, South Africa
Authors: ROBERTSON JOHN , LAWES MICHAEL J.
Published: June 2005

New forest policies in South Africa seek to reconcile conservation and development objectives by devolving some responsibility for forest management from the state to local communities. Community participation in forest management aims to protect forest-based subsistence livelihoods by incorporating the interests of resource users, while simultaneously diffusing threats to biodiversity by managing resource use. To date, participatory forest management (PFM) has had mixed success in South Africa because the transfer of rights to users has not accompanied changes in policy. A questionnaire survey of 60 households (43%) revealed the attitudes of users toward current management and conservation options for iGxalingenwa forest. Users chose participatory forest management (52%) over community (25%) or state-dominated forest management (2%) structures. User choice was motivated by the desire to secure rights of access to, and ensure equitable benefit from, a dwindling resource base, rather than the conservation of these resources to sustain future yields. Users were unwilling to reduce resource use and compromise usufruct rights to achieve conservation goals, even to improve the availability of the resource stock. Current user needs compromise biodiversity conservation goals, and users regard state conservation practices as protectionist and obstructing their rights of access to resources. While the National Forests Act of 1998 seeks to conserve resources by limiting access to them and is based on principles of sustainable use, it is nevertheless perceived to offer few incentives to users to participate in forest management and conservation. Ideally, an institutional and legal framework that allocates user rights and managerial responsibilities to households is required, but clearly suitable alternatives to forest products are also vital for successful management. Greater trust between the provincial parks authority and users is needed, but is complicated by weak traditional leadership and poor community representation. Ultimately, users preferred PFM because, while recognizing that harvest rates are unsustainable, user dependence upon forest resources and weak traditional leadership means they can protect usufruct rights only by participation. Changes to any of these factors may create demands for a new management system. PFM allows the greatest flexibility for responding to changes in demands as well as the environment.
Self-organization of planar microlenses by periodic precipitation
Authors: Campbell Christopher J. , Baker Eric , Fialkowski Marcin , Bitner Agnieszka , Smoukov Stoyan K. , Grzybowski Bartosz A.
Published: June 2005

Arrays of planar, Fresnel-like microlenses are prepared by a spontaneous chemical process of periodic precipitation (PP) occurring in a thin layer of a dry gel, and initiated by wet stamping. The PP lenses focus white light more efficiently than the conventional Fresnel zone plates of similar dimensions. Nanoscale topographies of the micropatterned gels can be replicated into transparent elastomers, and used for focusing based on optical path differences. Experimental observations for both types of structures are in agreement with the Fresnel diffraction calculations.
Four-mode quantum calculations of resonance states in complex-forming bimolecular reactions: Cl−+CH3Br
Authors: Schmatz Stefan
Published: June 2005

The vibrational resonance states of the complexes formed in the nucleophilic bimolecular substitution (SN2) reaction Cl−+CH3Br→ClCH3+Br− were calculated by means of the filter diagonalization method employing a coupled-cluster potential-energy surface and a Hamiltonian that incorporates an optical potential and is formulated in Radau coordinates for the carbon-halogen stretching modes. The four-dimensional model also includes the totally symmetric vibrations of the methyl group (C–H stretch and umbrella bend). The vast majority of bound states and many resonance states up to the first overtone of the symmetric stretching vibration in the exit channel complex have been calculated, analyzed, and assigned four quantum numbers. The resonances are classified into entrance channel, exit channel, and delocalized states. The resonance widths fluctuate over six orders of magnitude. In addition to a majority of Feshbach-type resonances there are also exceedingly long-lived shape resonances, which are associated with the entrance channel and can only decay by tunneling. The state-selective decay of the resonances was studied in detail. The linewidths of the resonances, and thus the coupling to the energetic continuum, increase with excitation in any mode. Due to the strong mixing of the many progressions in the intermolecular stretching modes of the intermediate complexes, this increase as a function of the corresponding quantum numbers is not monotonic, but exhibits pronounced fluctuations.
Laser-induced-fluorescence characterization of velocity shear in a magnetized plasma column produced by a segmented, Q-machine source
Authors: Reynolds E. W. , Kaneko T. , Koepke M. E. , Hatakeyama R.
Published: June 2005

Control over the radial profile of one component of ion drift speed U, either perpendicular or parallel to the magnetic field, is demonstrated in the magnetized plasma column for two configurations of a double-ended Q machine in which one of the hot plates is segmented into a central disk and two concentric annuli. Each hot plate can be heated to ∼1800°C, and the segmented hot plate is bombarded with barium vapor, resulting in quasineutral, magnetized, barium-ion plasma. Since the electric potential in the plasma magnetically maps to the segments, the radial profile of plasma potential, and hence the E×B flow, can be made inhomogeneous. This configuration is referred to as the perpendicular configuration. A negatively biased, cross-sectional mesh, inserted between the two ends of the plasma column, reflects electrons from each source causing the radial profile of potential on the nonsegmented source side of the mesh to become uniform. In traversing the mesh sheath from the segmented source side, where the radial potential profile is inhomogeneous, to the nonsegmented source side, where the radial potential profile is homogeneous, the ions experience an axial acceleration that has an inhomogeneous radial profile. This configuration with the mesh is referred to as the parallel configuration. Laser-induced-fluorescence is used to measure the ion-velocity-distribution function on the nonsegmented-source side with and without the mesh inserted. Measurements show that the above configurations result in ion temperature anisotropy, 1<(T⊥∕T‖)<5, and radially nonuniform ion flows with a maximum in the shear profile (dU⊥∕dx)max as large as 0.6Ωi and (dU‖∕dx)max as large as 0.17Ωi where Ωi is the ion gyrofrequency.
Experimental measurement of Au M-band flux in indirectly driven double-shell implosions
Authors: Robey H. F. , Perry T. S. , Park H.-S. , Amendt P. , Sorce C. M. , Compton S. M. , Campbell K. M. , Knauer J. P.
Published: June 2005

Indirectly driven double-shell implosions are being investigated as a possible noncryogenic path to ignition on the National Ignition Facility [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)]. In recent double-shell experiments, the inner shell trajectory was shown to exhibit a strong sensitivity to the temporal history of the M-band (2–5keV) radiation emitted from the Au hohlraum wall. A large time-dependent discrepancy was observed between measurement and simulation of the x-ray flux in this range. In order to better characterize the radiation environment seen in these implosions, an experimental campaign was conducted on the Omega laser. A number of diagnostics were used to measure both the temporal and spectral nature of the M-band flux. Results were obtained from an absolutely calibrated 12-channel filtered x-ray diode array (Dante) as well as two streaked crystal spectrometers and an absolutely calibrated time-integrated spectrometer (Henway). X-ray backlighting was also used to directly measure the effect of M-band radiation on the trajectory of the inner shell. The data from all diagnostics are shown to be in excellent agreement and provide a consistent picture of the M-band flux. These results are being used to constrain and improve the simulation of hohlraum-generated M-band radiation that will be necessary for the design of future double-shell implosions employing higher-Z inner shells.
Resonant transmission of light waves in dielectric heterostructures
Authors: Lu Ye , Peng R. W. , Wang Z. , Tang Z. H. , Huang X. Q. , Wang Mu , Qiu Y. , Hu A. , Jiang S. S. , Feng D.
Published: June 2005

We investigate the propagation of electromagnetic wave through dielectric heterostructures with transfer-matrix method. It is shown that if a dimerlike positional correlation (DPC) is introduced to the heterostructure, resonant transmission of light waves will definitely take place. The resonant transmissions are characterized by perfect transmission peaks in the photonic band gap, which is demonstrated by the electric-field distribution at corresponding resonant modes. The numerical calculations are in good agreement with the analytical predictions. Furthermore, by applying the SiO2∕Si heterostructure with DPC, resonant modes can appear within the photonic band gap at the telecommunication wavelengths of 1.55 and 1.3μm. This finding is expected to have potential applications in wavelength division multiplexing system.
Charge-carrier transport and triplet exciton diffusion in a blue electrophosphorescent emitting layer
Authors: Matsusue Noriyuki , Ikame Satoshi , Suzuki Yuichiro , Naito Hiroyoshi
Published: June 2005

Charge-carrier transport and triplet exciton diffusion in iridium(III) bis[(4,6-di-fluoropheny)-pyridinato-N,C2′]picolinate (FIrpic) doped in 4,4′-N, N′-dicarbazole-biphenyl (CBP) thin films have been studied by time-of-flight (TOF) transient photocurrent and steady-state photocurrent measurements. With increasing FIrpic concentration, hole TOF transients become highly dispersive and the hole drift mobility is decreased. In contrast, the electron transit signals become unobservable. The TOF results are found to be consistent with those of steady-state photocurrent measurements of FIrpic-doped CBP thin films; the photocurrent spectra are symbatic and antibatic when the illuminated electrode is positively and negatively biased, respectively. The diffusion lengths of triplet excitons in FIrpic-doped CBP thin films are determined from the symbatic photocurrent spectra.
Spectroscopic measurement of radiation of high-pressure mercury discharge lamps
Authors: Fu Ling , Leutz Ralf , Ries Harald
Published: June 2005

Compact size and high efficiency are important features for projection systems. As the most often used sources for projection optics, short arc lamps are characterized by their impressive economy and the ability to produce extremely bright light from small dimensional sources. In this contribution the old principle of back reflection towards the sources is applied to a high-pressure mercury discharge lamp with a reflector to improve the radiance of the source by 35% at a certain reduced solid angle. Increasing the optical thickness of sources is equivalent to reducing the total phase space (etendue) of emitted radiation by the same factor, which is very useful for compacting sources. In addition, by comparing the forward radiation and the back-reflected radiation obtained from spectroscopic measurements, we calculate the absorptivity, emissivity, absorption, and emission coefficients of the plasma of the arc lamp based on Kirchhoff’s Law and Planck’s equation which is necessary for determining its temperature and pressure.
Tunneling mechanism of the 1∕f noise in GaN∕AlGaN heterojunction field-effect transistors
Authors: Dmitriev A. P. , Levinshtein M. E. , Rumyantsev S. L. , Shur M. S.
Published: June 2005

We propose a model of the 1∕f noise in GaN∕AlGaN heterojunction field-effect transistors that links the 1∕f noise to the tunneling from the two-dimensional electron gas in the device channel into the tail states near the conduction band of the GaN layer. The model predicts a fairly weak temperature dependence of the 1∕f noise in the temperature interval from 50 to 600 K with the value of the Hooge parameter α within the range of 10−3–10−5. Both these predictions are in agreement with experimental data.
Complex ion-focusing effect by the sheath above the wafer in plasma immersion ion implantation
Authors: Stamate E. , Holtzer N. , Sugai H.
Published: June 2005

The ion flux on the wafer surface during plasma immersion ion implantation is investigated by three-dimensional simulations and experiments. Due to the finite size of the wafer and its stage, the evolving sheath acts as a lens that focuses the positive ions to distinct regions on the wafer surface. Depending on the sheath profile, two focusing effects are identified. Discrete focusing involves ions entering the sheath from its frontal side and leads to the formation of a passive surface near the wafer edge, while the modal focusing affects ions entering the sheath from the lateral side of the stage and are eventually directed to the wafer center.
Broadband spin dynamics of Permalloy rings in the circulation state
Authors: Zhu Xiaobin , Malac Marek , Liu Zhigang , Qian Hui , Metlushko Vitali , Freeman Mark R.
Published: June 2005

The spin dynamics of the remanent state of circulating magnetization in micrometer-scale Permalloy rings is studied by broadband ferromagnetic resonance. A number of resonance modes are observed, depending upon the geometries of coupling the transient excitation to the ring and of magneto-optically monitoring the response. The two dominant modes involve precession with uniform phase around the ring, or in a circularly antisymmetric standing wave pattern with two nodes. Other magnetic normal modes are also excited but with much smaller amplitude.
Absorption cross section and signal enhancement in Er-doped Si nanocluster rib-loaded waveguides
Authors: Daldosso N. , Navarro-Urrios D. , Melchiorri M. , Pavesi L. , Gourbilleau F. , Carrada M. , Rizk R. , García C. , Pellegrino P. , Garrido B. , Cognolato L.
Published: June 2005

Pump and probe experiments on Er3+ ions coupled to Si nanoclusters have been performed in rib-loaded waveguides to investigate optical amplification at 1.5μm. Rib-loaded waveguides were obtained by photolithographic and reactive ion etching of Er-doped silica layers containing Si nanoclusters grown by reactive sputtering. Insertion losses measurements in the infrared erbium absorption region allowed to gauge an Er3+ absorption cross section of about 5×10−21cm2 at 1534nm. Signal transmission under optical pumping at 1310nm shows confined carrier absorption of the Si nanoclusters. Amplification experiments at 1535nm evidence two pump power regimes: Losses due to confined carrier absorption in the Si nanoclusters at low pump powers and signal enhancement at high pump powers. For strong optical pumping, signal enhancement of about 1.2dB∕cm was obtained.
Theory and Application of Dipolar Ferrite Modes
Authors: Steier William H. , Coleman Paul D.
Published: June 2005

Experimental verification at X and K band of theoretical calculations on the magnetodynamic resonant modes of a ferrite rod between parallel conducting sheets is reported. Critically coupled mode Q's as high as 1100 have been measured.

The characteristic equation includes propagation effects and dipolar coupling between electron spins. Mode charts for the symmetric modes are displayed for biasing fields from 3 to 20 koe and for frequencies from 4 to 50 kMc for both Ferramic R-1 and polycrystalline YIG.

The modes have been experimentally observed in the ranges of 10 and 20 kMc. Comparison of theoretical and experimental data is made in these bands for both R-1 and YIG. The variation of the observed loaded Q with biasing magnetic field is described.

The advantages that these modes possess over the magnetostatic modes for microwave engineering applications are pointed out. These include: (a) relatively high Q, (b) ability to critically couple, and (c) sample size is comparable to the wavelength.
Ferrimagnetic Resonance at High Power
Authors: Weiss M. T.
Published: June 2005

Ferrimagnetic resonance experiments have been performed on single-crystal manganese ferrite at high microwave powers. The variation of susceptibility with power level is in good agreement with Suhl's recent theoretical treatment of the saturation process in which scattering of the uniform precession at impurities and imperfections is taken into account. Our results show that the ratio of intrinsic to scattering decay constants is close to zero, so that χ′′ decreases gradually at power levels substantially below the theoretical critical signal level. At very high power levels various anomalous effects appear such as bistabilities, line asymmetries, and flat topped absorption lines.
Finite Amplitude Electromagnetic Waves in Gyromagnetic Media
Authors: Auld B. A.
Published: June 2005

A perturbation method is developed for obtaining forced steady-state solutions to Maxwell's equations and the torque equation subject to the usual boundary condition. This procedure is applied to the scattering of a normally incident plane wave from a semi-infinite gyromagnetic slab and numerical results are presented.
Fast Switching by Domain Walls in Ferrites
Authors: Wiechec Walter , Kelley Clinton M.
Published: June 2005

Experimental evidence indicates that small grain size is associated with faster domain wall switching in ferrite cores. It has been shown by H. Amar that small grain size contributed an additional energy to the wall energy density σω. Incorporation of this energy into the power equation H · (dM/dt) = λHe2 reveals that the loss coefficient decreases more than σω increases, and, therefore, faster switching results.

A qualitative explanation is given for faster switching by domain walls in magnetic materials. The significant variables in the switching coefficient equation are “d,” Tc, K, and α. Experimental data show that the switching coefficient is lowered by decreasing values of the first three variables. Considerably faster switching is predicted when similar cores with grain sizes less than 1 μ are made.
Temperature Dependence of the Saturation Magnetization of Nickel Films of Thickness Less Than 100A
Authors: Neugebauer C. A.
Published: June 2005

Nickel films varying in thickness from 300 to 15A were prepared by evaporation on glass substrates in a vacuum sufficiently high to prevent gas adsorption on the film during preparation and measurement. Their magnetization was measured as a function of field up to 10000 oe using a vacuum torsion magnetometer. The saturation magnetization of these films was determined as a function of their thickness at various temperatures. No decrease in saturation magnetization from that of bulk nickel has been observed for films of thickness down to 20A, at room temperature. The Curie temperature of a 30A film was found to coincide with that of bulk nickel.
Double Pump Degenerate Ferrite Amplifier
Authors: Gottlieb Peter
Published: June 2005

A theoretical discussion of the possibilities for the design of a parametric amplifier using a pump frequency lower than the signal frequency (but higher than one half the signal frequency) is given. In particular, a detailed mechanism for the operation of a ferrite amplifier with such properties is described. The amplifieroperation is similar to that used by Bloom and Chang for a diode amplifier with cubic nonlinearity. Hogan,Jepsen, and Vartanian have proposed a ferrite device to serve the same purpose as the present amplifier;however, their scheme is quite different, and a detailed comparison is given in this paper.

The main feature of the present amplifier is a doubling of the pump frequency to obtain an effective pump frequency which is larger than the signal frequency. The whole amplifier requires four resonances:the pump frequency, twice the pump frequency, the signal frequency, and twice pump minus signal (idle). The most efficient assignment of the modes uses cavity resonances for the signal and pump, and then uses either cavity or ferrite resonances for the other frequencies.

Since the pump doubling is a result of nonlinear mixing, the efficiency of doubling will be greater for larger pump fields. This is limited in practice by the onset of saturation in the ferrite. For pump fields close to saturation the required pump field is calculated to be five to ten times larger than that required to produce the same gain in an ordinary three resonance amplifier.
A Necessary Factor for Heat Treatment of the Permalloys in a Magnetic Field
Authors: Nesbitt E. A. , Heidenreich R. D. , Williams A. J.
Published: June 2005

Recently, we have been able to show that Perminvar (Ni-Fe-Co alloy) has an inhomogeneous structure and that this inhomogeneity is due to an impurity fault. Evidence was obtained that small amounts of oxygen as an impurity in Perminvar caused both the faulting and the heat treatment in a magnetic field. It was exceedingly difficult, however, to remove sufficient oxygen from this material to prevent heat treatment in a magnetic field. More conclusive experiments have now been done to demonstrate the effect of oxygen on the response to magnetic annealing in the nickel-iron alloys without cobalt (Permalloys). Magnetic torque curves on a single crystal of 63% Ni-35% Fe-2% Mo for two different heat treatments illustrate this point. When the crystal was purified in hydrogen and then was heat treated in a magnetic field, it did not respond. However, after a slightly oxidizing heat treatment (pot annealing at 1000°C for 16 hrs), it did respond to the field heat treatment by developing a uniaxial anisotropy of approximately 2000 ergs per cm3.

The intimate connection between the presence of impurity faults and the ability to respond to heat treatment in a magnetic field is shown by observations on single crystals of 68% Ni-31.9% Fe-0.1%Mg, which were grown for this purpose. The (100) surfaces of these crystals showed heavily and lightly faulted regions. The work on the Perminvars has shown that the heavily faulted areas contain more oxygen than the lightly faulted areas. The magnetic torque measurements on the 68% Ni alloy confirm this idea. The heavily faulted crystal had a uniaxial anisotropy of approximately 3000 ergs per cm3 while the lightly faulted crystal had a value of only 1000 ergs per cm3.
Strong Field Magnetization at Low Temperatures and Approach to Absolute Saturation of Thulium Metal
Authors: Henry Warren E.
Published: June 2005

Magnetization studies of metallic thulium have been carried out at low temperatures and in magnetic fields up to 70 000 gauss. Near 100°K, the magnetization (M) is linear in field and reaches 0.8 Bohr magnetons per atom of thulium at 70 000 gauss. At 4.2°K, a magnetization curve is traced in which the direction of concavity changes twice. In the high field range, (∂M/∂H) is decreasing and between 60 000 and 70 000 gauss, it is very small. At 70 000 gauss, the magnetization reaches 3.4 Bohr magnetons per atom of thulium,suggesting the validity of the F7/22 ground state assignment for metallic thulium. At 1.3°K, the magnetization is slightly lower at equivalent fields, but approaches the same 70 000 gauss value as at 4.2°K. The remanence is 0.3 Bohr magneton per atom at 4.2°K and 0.4 Bohr magneton per atom at 1.3°K. A pronounced hysteresis is observed in the liquid helium range. A sample motion technique is used in the measurements and the calibration carried out with pure nickel.
Magnetic Susceptibilities of Single Crystal NiCl2·6H2O and CoCl2·6H2O at Low Temperatures
Authors: Flippen R. B. , Friedberg S. A.
Published: June 2005

The magnetic susceptibilities of single crystal NiCl2·6H2O and CoCl2·6H2O have been measured down to 1.3°K for various orientations. The occurrence of antiferromagnetism in CoCl2·6H2O below ∼2.3°K is confirmed as is the anisotropy of the g-factor of the Co++ ion over the whole range. It is concluded that NiCl2·6H2O is antiferromagnetic in the helium region and that the temperature-independence of the powder susceptibility here is caused by the fact that χ⊥ rises as T falls below TN.
Direct Cation-Cation Interactions in Primarily Ionic Solids
Authors: Goodenough John B.
Published: June 2005

It is pointed out that there is considerable experimental evidence for direct cation-cation interactions in several primarily ionic solids containing transition-element cations with outer-electron configuration ndm,where m≤5. Competitive indirect (cation-anion-cation) interactions are dominant if m = 5. Nevertheless, if cation-occupied octahedra share a common face, as in the corundum and NiAs-type structures, the direct(cation-cation) interactions may also significantly influence the physical properties of the material. If octahedral-site cations have m≤3, the cation-anion-cation interactions are weak and cation- -cation interactionsmay be dominant. The consequences of cation- -cation interactions are described and shown to be quite distinct from those of cation-anion-cation interactions so that the dominant mechanism can usually be distinguished. Data for several illustrative materials are presented.
Promotion of Cubic Grain Growth in 3% Silicon Iron by Control of Annealing Atmosphere Composition
Authors: Kohler Dale
Published: June 2005

Under certain special conditions of processing and annealing,silicon iron can be made to have cubic orientation. This phenomenon was first reported by Assmus et al.

The driving force for the growth of the cubic grains has been determined by several investigators to be surface energy. We have found that by controlling the concentration of impurities in the annealing atmosphere the growth of grains having the (100) plane parallel to the sheet surface can be greatly improved. Calculations of the surface energies in the body-centered system show that the surface energy of atomic planes are (110), (100) and (111) in order of ascending values. From this orientation dependency of the surface energy, there results a discrepancy between theory and the observed fact of (100) surface energy growth.

It is proposed that adsorption by the metal surface of atmosphere constituents in a very special manner can accomplish a change in relative surface energy so that the (100) plane becomes the lowest energy crystal plane.

Data on some atmosphere composition effects on transformation to cube texture of silicon iron 2 to 14 mils thick were obtained.

The degree of transformation was found to be closely related to the concentration of certain compounds that are added to the atmosphere. The degree of cube growth reaches a maximum at a certain small concentration of impurity.

These effects were studied in both metal and ceramic annealing tubes. With proper additives excellent cube growth can be obtained in either type annealing tube.
Ink4a and Arf differentially affect cell proliferation and neural stem cell self-renewal in Bmi1-deficient mice
Authors: Bruggeman Sophia W.M. , Valk-Lingbeek Merel E. , van der Stoop Petra P.M. , Jacobs Jacqueline J.L. , Kieboom Karin , Tanger Ellen , Hulsman Danielle , Leung Carly , Arsenijevic Yvan , Marino Silvia , van Lohuizen Maarten
Published: June 2005

The Polycomb group (PcG) gene Bmi1 promotes cell proliferation and stem cell self-renewal by repressing the Ink4a/Arf locus. We used a genetic approach to investigate whether Ink4a or Arf is more critical for relaying Bmi1 function in lymphoid cells, neural progenitors, and neural stem cells. We show that Arf is a general target of Bmi1, however particularly in neural stem cells, derepression of Ink4a contributes to Bmi1-/- phenotypes. Additionally, we demonstrate haploinsufficient effects for the Ink4a/Arf locus downstream of Bmi1 in vivo. This suggests differential, cell type-specific roles for Ink4a versus Arf in PcG-mediated (stem) cell cycle control.
A structural perspective of CTD function
Authors: Meinhart Anton , Kamenski Tomislav , Hoeppner Sabine , Baumli Sonja , Cramer Patrick
Published: June 2005

The C-terminal domain (CTD) of RNA polymerase II (Pol II) integrates nuclear events by binding proteins involved in mRNA biogenesis. CTD-binding proteins recognize a specific CTD phosphorylation pattern, which changes during the transcription cycle, due to the action of CTD-modifying enzymes. Structural and functional studies of CTD-binding and -modifying proteins now reveal some of the mechanisms underlying CTD function. Proteins recognize CTD phosphorylation patterns either directly, by contacting phosphorylated residues, or indirectly, without contact to the phosphate. The catalytic mechanisms of CTD kinases and phosphatases are known, but the basis for CTD specificity of these enzymes remains to be understood.
Defining the impact of β-catenin/Tcf transactivation on epithelial stem cells
Authors: Lowry William E. , Blanpain Cedric , Nowak Jonathan A. , Guasch Geraldine , Lewis Lisa , Fuchs Elaine
Published: June 2005

Wnt signaling has been implicated in stem cell (SC) biology, but little is known about how stabilized β-catenin functions within native SC niches. We address this by defining the impact of β-catenin stabilization on maintenance, proliferation, and lineage commitment of multipotent follicle SCs when in their native niche and in culture. We employ gain of function mutations and inducible loss of function mutations to demonstrate that β-catenin stabilization is essential for promoting the transition between SC quiescence and conversion to proliferating transit amplifying (TA) progeny. We transcriptionally profile purified SCs isolated directly from wild-type and elevated β-catenin follicles in both resting and activated states to uncover the discrete set of genes whose expression in native SCs is dependent upon β-catenin stabilization. Finally, we address the underlying mechanism and show that in the SC niche, Wnt signaling and β-catenin stabilization transiently activate Lef1/Tcf complexes and promote their binding to target genes that promote TA cell conversion and proliferation to form the activated cells of the newly developing hair follicle. We also show that these changes precede subsequent Wnt signals that impact on the TA progeny to specify the differentiation lineages of the follicle.
An Examination of Biodata Theory‐Based Constructs in a Field Context
Authors: Dean Michelle A. , Russell Craig J.
Published: June 2005

This study examined whether items from a biodata inventory were consistent with theory‐based constructs as suggested by the ecology model. The model posits five constructs explain biodata predictive ability. Items were sorted using the theory‐based construct domains. The resulting scale scores were assessed for evidence of content, criterion‐related, and construct validity in a sample of 6032 automated systems controllers. Results suggested moderate support for the theory‐based constructs. A notable finding was that items capturing a theoretical construct were impacted by the life stage in which they were anchored. Results further suggest the need to examine if certain life stages are more predictive than others or perhaps if certain constructs are more predictive when related to a particular life stage.
Community nurses’ talk of equality and the discursive constitution of selves
Authors: Aranda Kay
Published: June 2005

Aim.  The aim of this paper is to explore how stories revealed the discursive constitution of particular selves and to consider the implications for future understandings of equality and practice.

Background.  Equality has long been an objective of most Western healthcare systems, as enshrined in the principles of equal rights to access, treatment and care. Service users, however, continue to experience inequities, oppression and discrimination. These continuing inequalities have resulted in demands for nurses to tackle discrimination and oppression and promote equality in their practice.

Methods.  Semi‐structured interviews were conducted with 14 community nurse students and 14 practice teachers from two universities in England in 1998. Discourse analysis was used to interpret the narratives.

Findings.  Community nurses were actively positioning themselves and were being positioned through dominant and competing discourses. Their narratives revealed stories of equality in health care that were contingent upon complex discursively constituted selves. They were found to take up, rework and in some cases subvert and reject dominant subject positions. The implications of these selves are considered in relation to the development of equality and practice.

Conclusions.  Educationalists and practitioners need to engage with these discourses and diverse selves and begin to develop approaches which remain open to scrutiny and challenge so that specific and localized understandings of equality and practice can evolve.
Using concept maps to optimize the composition of collaborative student groups: a pilot study
Authors: Kinchin Ian , Hay David
Published: June 2005

Aim.  The aim of this paper is to stimulate interest in the practical classroom application of concept mapping strategies as an approach that teachers can easily use to enhance collaborative learning.

Background.  Concept mapping has been developed as a tool to support meaningful learning. However, much of the research literature fails to explain how concept maps might be most gainfully employed within the classroom. As a result, concept mapping is a tool that is under‐used.

Methods.  Students on a postgraduate teacher preparation programme for nurses were arranged in triads on the basis of the morphology of individually‐produced concept maps for the topics of ‘genetics’ and ‘pathogenic microbes’. They were arranged in heterogeneous triads to produce a consensus map for ‘pathogenic microbes’, and then in homogeneous triads to produce a consensus map for ‘genetics’. The number of acceptable propositions found in their individual maps was compared with the number found in the consensus group maps, and gain scores were calculated for each participant.

Findings.  Participants arranged in triads of individuals having very different knowledge structures were found to make a greater improvement than those arranged in triads composed of individuals with qualitatively similar knowledge structures.

Conclusions.  The study was undertaken with a very small sample and only looked at two topic areas. However, the findings support the idea that collaborative groups work most effectively when individuals within the group bring different perspectives to a problem, and that this perspective can be usefully identified within the classroom environment as variations in concept map morphology.
Installation of telerobotic surgery and initial experience with telerobotic radical prostatectomy
Authors: Costello Anthony J. , Haxhimolla Hodo , Crowe Helen , Peters Justin S.
Published: June 2005

OBJECTIVE

To assess the ability of untrained laparoscopic surgeons to learn and implement laparoscopic telerobotic radical prostatectomy (TRP) using the daVinci Surgical System (Intuitive Surgical, CA), and assess the education, safety and efficacy issues when instituting this system.

PATIENTS AND METHODS

Between December 2003 and October 2004, 122 consecutive TRPs were performed by two surgeons for clinically localized prostate cancer. The individual robotic surgeon was assisted at the bedside by another surgeon. The TRP was performed robotically by the surgeon at the remote console unit. Perioperative data and pathological results were recorded. The two surgeons spent 1 week in a skills laboratory using a porcine model of laparoscopic TRP, and then cadaveric robotic prostatectomy. The first six cases were mentored by an experienced telerobotic surgeon.

RESULTS

The TRP was conducted by two surgeons with no previous laparoscopic experience. There were no conversions to open surgery. Assessing the complications, postoperative continence, operating time and transfusion rates showed equivalent efficacy and safety to open and pure laparoscopic methods.

CONCLUSION

TRP represents a novel computer‐based surgical approach to prostate cancer, which offers the benefits of minimally invasive surgery without the extensive experience associated with the laparoscopic method. It remains to be seen whether the robotic approach can deliver better outcomes in continence and potency over time.
Radical prostatectomy versus high‐dose rate brachytherapy for prostate cancer: effects on health‐related quality of life
Authors: Jo Yoshimasa , Junichi Hiratsuka , Tomohiro Fujii , Yoshinari Imajo , Masato Fujisawa
Published: June 2005

OBJECTIVE

To examine the effects of different treatments on the health‐related quality of life (HRQoL) of men with localized prostate cancer.

PATIENTS AND METHODS

Between October 1997 and August 2002, 182 men diagnosed with prostate cancer (T1c to T3bN0M0) had radical prostatectomy (RP, 89) or 192iridium high‐dose rate brachytherapy (HDR‐BT, 93) with external beam radiotherapy, and were followed for ≥ 6 months. A postal survey was sent in which HRQoL was assessed using the 36‐item Short‐Form Health Survey (SF‐36) QoL questionnaire, and disease‐specific QoL using the University of California Los Angeles Prostate Cancer Index (UCLA‐PCI).

RESULTS

Questionnaire responses were obtained from 151 of 182 patients; there was no significant difference in SF‐36 scale scores between men treated with RP or HDR‐BT. In the UCLA‐PCI, the HDR‐BT group had better urinary function (P < 0.001) and sexual function scores (P= 0.043). Men treated with RP had better bowel bother scores (P = 0.027). In patients with ≥ 2 years of follow‐up, urinary function (P < 0.001) and sexual bother (P = 0.029) were better for men treated with HDR‐BT than for men treated with RP. Men treated with HDR‐BT had significantly better urinary function (P = 0.009) and sexual bother (P = 0.013) even than 30 men treated with unilateral nerve‐sparing RP.

CONCLUSIONS

In terms of HRQoL, RP and HDR‐BT did not differ, but HDR‐BT resulted in better urinary and sexual function than RP. When planning treatment, QoL concerns, including mental health issues associated with prostate cancer, need to be addressed with the patients, as do the potential side‐effects.
Myogenic bladder decompensation in boys with a history of posterior urethral valves is caused by secondary bladder neck obstruction?
Authors: Androulakakis Philippos A. , Karamanolakis Dimitrios K. , Tsahouridis Georgios , Stefanidis Antonios A. , Palaeodimos Ilias
Published: June 2005

OBJECTIVE

To investigate whether myogenic bladder decompensation in patients treated for congenital posterior urethral valves (PUV, the most serious cause of infravesical obstruction in male neonates and infants) may be secondary to bladder neck obstruction, as despite prompt ablation of PUV these patients can have dysfunctional voiding during later childhood or adolescence, the so‐called ‘valve bladder syndrome’.

PATIENTS AND METHODS

The study comprised 18 boys (mean age 14 years, range 6.2–18.5) who had had successful transurethral ablation of PUV between 1982 and 1996, and had completed a follow‐up which included serial assessment of serum creatinine, completion of a standard voiding diary, ultrasonography with measurement of urine before and after voiding, a urodynamic examination with simultaneous multichannel recording of pressure, volume and flow relationships during the filling and voiding phases, coupled with video‐cystoscopy at least twice. The mean (range) follow‐up was 9.3 (6–17) years.

RESULTS

Urodynamic investigation showed myogenic failure with inadequate bladder emptying in 10 patients; five with myogenic failure also had unstable bladder contractions. On video‐cystoscopy the posterior bladder neck lip appeared elevated in all patients but in those with myogenic failure it was strongly suggestive of hypertrophy, with evidence of obstruction. At the last follow‐up one patient with myogenic failure who had had bladder neck incision and four others who were being treated with α‐adrenergic antagonists had a significant reduction of their postvoid residual urine.

CONCLUSION

Despite early valve ablation, a large proportion of boys treated for PUV have gradual detrusor decompensation, which may be caused by secondary bladder neck obstruction leading to obstructive voiding and finally detrusor failure. Surgical or pharmacological intervention to improve bladder neck obstruction may possibly avert this course, but further studies are needed to validate this hypothesis.
COMMINUTED FRACTURE OF THE DISTAL SESAMOID BONE AND DISTAL RUPTURE OF THE DEEP DIGITAL FLEXOR TENDON
Authors: Hoegaerts Michel , Pille Frederik , De Clercq Tom , Fulton Ian C. , Saunders Jimmy H.
Published: June 2005

A 10‐year‐old show jumper was evaluated for an acute severe lameness (grade 4 of 5) of the right foreleg. During weight bearing, the toe of the affected limb rotated dorsally suggesting rupture of the deep digital flexor tendon (DDFT). Upon radiographic examination of the hoof, a severe erosion at the flexor surface and a parasagittal fracture of the distal sesamoid bone were found. Ultrasonographic examination confirmed rupture of the DDFT. These findings were confirmed on post‐mortem examination. Prior to the acute lameness, the horse was treated with corticosteroid injections into the podotrochlear bursa. Repeated intra‐bursal injections of corticosteroids as a possible cause for DDFT rupture are discussed as well as the possible association between a degenerative distal sesamoid bone, a distal sesamoid bone fracture and a DDFT rupture.
AGE‐RELATED CHANGES IN THE ULTRASOUND APPEARANCE OF THE NORMAL FELINE PANCREAS
Authors: Larson Martha Moon , Panciera David L. , Ward Daniel L. , Steiner Jörg M. , Williams David A.
Published: June 2005

In humans, pancreatic hyperechogenicity and duct dilation are reported as normal aging changes. Similar changes have been reported with pancreatitis in the cat. We attempted to determine if aging changes occur in the ultrasound appearance of the normal feline pancreas. The pancreas of 84 normal (based on history, physical exam, biochemical profile, and feline trypsin‐like immunoreactivity and pancreatic lipase immunoreactivity concentrations) cats of varying ages was scanned. Pancreatic width at the left limb and body, pancreatic duct diameter at left limb and body, and pancreatic echogenicity compared with liver and surrounding fat were noted and compared with age and body weight. Lower and upper limits of the 95% reference intervals for pancreatic left limb width were 2.6 and 9.5 mm, and 3.5 and 8.5 mm for the pancreatic body width. There was no significant difference in pancreatic width between the left limb and body. Lower and upper limits of the 95% reference interval for the diameter of the pancreatic duct at the left limb and body were similar, and were 0.65 and 2.5 mm. There was a weak but significant linear correlation between pancreatic duct diameter and age, with increasing pancreatic duct diameter with increasing age. There was no correlation of pancreatic width with age, and no correlation of pancreatic echogenicity with age or body weight. Based on this study, feline pancreatic size and echogenicity do not change with age. Pancreatic duct diameter increases slightly with age and should not be used as a sole indicator of pancreatitis in the geriatric cat.
TRPV4 plays an evolutionary conserved role in the transduction of osmotic and mechanical stimuli in live animals
Authors: Liedtke Wolfgang
Published: June 2005

The TRPV4 ion channel, previously named vanilloid receptor‐related osmotically activated channel (VR‐OAC), functionsin vivoin the transduction of osmotic and mechanical stimuli. Intrpv4null mice, TRPV4 was found to be necessary for the maintenance of systemic osmotic equilibrium, and for normal thresholds in response to noxious mechanical stimuli. In aCaenorhabditis elegansTRPV mutant transgenic for mammalian TRPV4, the mammalian transgene was directing the osmotic and mechanical avoidance response in the context of the ASH ‘nociceptive’ neurone. Molecular mechanisms of gating of TRPV4in vivoare not known at this point and have to be determined.
The structural basis of the increase in isometric force production with temperature in frog skeletal muscle
Authors: Linari M. , Brunello E. , Reconditi M. , Sun Y.‐B. , Panine P. , Narayanan T. , Piazzesi G. , Lombardi V. , Irving M.
Published: June 2005

X‐ray diffraction patterns were recorded from isolated single fibres of frog skeletal muscle during isometric contraction at temperatures between 0 and 17°C. Isometric force was 43 ± 2% (mean ±s.e.m., n= 10) higher at 17°C than 0°C. The intensity of the first actin layer line increased by 57 ± 18% (n= 5), and the ratio of the intensities of the equatorial 1,1 and 1,0 reflections by 20 ± 7% (n= 10), signalling radial or azimuthal motions of the myosin head domains. The M3 X‐ray reflection from the axial repeat of the heads along the filaments was 27 ± 4% more intense at 17°C, suggesting that the heads became more perpendicular to the filaments. The ratio of the intensities of the higher and lower angle peaks of the M3 reflection (RM3) was 0.93 ± 0.02 (n= 5) at 0°C and 0.77 ± 0.02 at 17°C. These peaks are due to interference between the two halves of each myosin filament, and the RM3 decrease shows that heads move towards the midpoint of the myosin filament at the higher temperature. Calculations based on a crystallographic model of the heads indicated that the observed RM3 change corresponds to tilting of their light‐chain domains by 9 deg, producing an axial displacement of 1.4 nm, which is equal to that required to strain the actin and myosin filaments under the increased force. We conclude that the higher force generated by skeletal muscle at higher temperature can be accounted for by axial tilting of the myosin heads.