bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of plasma membrane calcium‐ATPase activity by local calcium microdomains near CRAC channels in human T cells
Authors: Bautista Diana M. , Lewis Richard S.
Published: February 2004

The spatial distribution of Ca2+ signalling molecules is critical for establishing specific interactions that control Ca2+ signal generation and transduction. In many cells, close physical coupling of Ca2+ channels and their targets enables precise and robust activation of effector molecules through local [Ca2+]i elevation in microdomains. In T cells, the plasma membrane Ca2+‐ATPase (PMCA) is a major target of Ca2+ influx through Ca2+ release‐activated Ca2+ (CRAC) channels. Elevation of [Ca2+]i slowly modulates pump activity to ensure the stability and enhance the dynamic nature of Ca2+ signals. In this study we probed the functional organization of PMCA and CRAC channels in T cells by manipulating Ca2+ microdomains near CRAC channels and measuring the resultant modulation of PMCAs. The amplitude and spatial extent of microdomains was increased by elevating the rate of Ca2+ entry, either by raising extracellular [Ca2+], by increasing the activity of CRAC channels with 2‐aminoethoxyborane (2‐APB), or by hyperpolarizing the plasma membrane. Surprisingly, doubling the rate of Ca2+ influx does not further increase global [Ca2+]i in a substantial fraction of cells, due to a compensatory increase in PMCA activity. The enhancement of PMCA activity without changes in global [Ca2+]i suggests that local [Ca2+]i microdomains near CRAC channels effectively promote PMCA modulation. These results reveal an intimate functional association between CRAC channels and Ca2+ pumps in the plasma membrane which may play an important role in governing the time course and magnitude of Ca2+ signals in T cells.
ATP participates in three excitatory postsynaptic potentials in the submucous plexus of the guinea pig ileum
Authors: Monro R. L. , Bertrand P. P. , Bornstein J. C.
Published: February 2004

Synaptic transmission between neurones intrinsic to the wall of the intestine involves multiple neurotransmitters. This study aimed to identify neurotransmitters responsible for non‐cholinergic excitatory synaptic transmission in the submucous plexus of the guinea pig ileum. Intracellular recordings were made from secretomotor and vasodilator neurones. A single electrical stimulus to a fibre tract evoked excitatory postsynaptic potentials (EPSPs) with three different time courses – fast, slow and an EPSP with an intermediate time course (latency 96 ms, duration 1.2 s). In all neurones, blocking nicotinic receptors reduced fast EPSPs, but they were abolished in only 57 of 78 neurones. Fast EPSPs were also reduced by P2 purinoceptor blockade (5 of 27 neurones) or 5‐HT3 receptor blockade (3 of 20 neurones). The intermediate EPSP was abolished by P2 receptor blockade (13 of 13 neurones) or by the specific P2Y1 receptor antagonist MRS 2179 (5 of 5 neurones) and was always preceded by a nicotinic or mixed nicotinic/purinergic fast EPSP. Intermediate EPSPs were observed in over half of all neurones including most non‐cholinergic secretomotor neurones identified by immunoreactivity for vasoactive intestinal peptide. The slow EPSP evoked by a single pulse stimulus was also abolished by P2 receptor blockade (5 of 5 neurones) or by MRS 2179 (3 of 3 neurones). We conclude that fast EPSPs in submucous neurones are mediated by acetylcholine acting at nicotinic receptors, ATP acting at P2X receptors and 5‐HT acting at 5‐HT3 receptors. Both the intermediate EPSP and the single stimulus slow EPSP are mediated by ATP acting at P2Y1 receptors.
Essential role of troponin I in the positive inotropic response to isoprenaline in mouse hearts contracting auxotonically
Authors: Layland Joanne , Grieve David J. , Cave Alison C. , Sparks Emma , Solaro R John , Shah Ajay M.
Published: February 2004

PKA‐dependent phosphorylation of cardiac troponin I (cTnI) contributes significantly to β‐adrenergic agonist‐induced acceleration of myocardial relaxation (lusitropy). However, the role of PKA‐dependent cTnI phosphorylation in the positive inotropic response to β‐adrenergic stimulation is unclear. We studied the contractile response to isoprenaline (10 nm) in isolated hearts and isolated cardiomyocytes from transgenic mice with cardiac‐specific expression of slow skeletal TnI (ssTnI, which lacks the N‐terminal protein extension containing PKA‐sensitive phosphorylation sites in cTnI) and matched wild‐type littermate controls. As expected, the lusitropic effect of isoprenaline was significantly blunted in ssTnI hearts. However, the positive inotropic response to isoprenaline was also blunted in ssTnI hearts. This effect was especially prominent for ejection‐phase indices in isolated auxotonically loaded ssTnI hearts whereas the positive inotropic response of isovolumic hearts or unloaded isolated myocytes was much less affected. Isoprenaline decreased left ventricular end‐systolic volume in wild‐type hearts (10.6 ± 1.6 to 6.2 ± 0.4 μl at a preload of 20 cmH2O; P < 0.05) but not transgenic hearts (11.4 ± 1.3 to 10.9 ± 1.3 μl; P= n.s.). Likewise, isoprenaline increased stroke work in control hearts (14.5 ± 1.0 to 22.5 ± 1.8 mmHg μl mg−1; P < 0.05) but not transgenic hearts (15.4 ± 1.3 to 18.3 ± 1.2 mmHg μl mg−1; P= n.s.). The end‐systolic pressure–volume relation was increased by isoprenaline to a greater extent in control than transgenic hearts. However, isoprenaline induced a similar rise in intracellular Ca2+ transients in transgenic and non‐transgenic cardiomyocytes. These results indicate that cTnI has a pivotal role in the positive inotropic response of the murine heart to β‐adrenergic stimulation, an effect that is highly dependent on loading conditions and is most evident in the auxotonically loaded ejecting heart.
Experimental Study of the Minto Engine—A Heat Engine for Converting Low Grade Heat to Mechanical Energy
Authors: Quickenden Terence I. , Hindmarsh Kathryn M. , Teoh Kean-Guan
Published: February 2004

The Minto engine is a liquid piston heat engine that converts heat energy into mechanical energy. Evaporation of the heated, volatile working fluid pushes it upwards against gravity. This causes the device to tip over and rotate. A 500 mm diameter Minto engine which used petroleum ether as the working fluid, was built and was operated between 344 K and 294 K. Thermal efficiencies of up to 0.25% (i.e. 1.7% of the Carnot maximum) were measured. This engine behaves as a power amplifier. It absorbs low grade heat over a long period of time and suddenly releases it as a pulse of mechanical energy over a short period of time.
Comparison of Two Sun Tracking Methods in the Application of a Heliostat Field
Authors: Chen Y. T. , Kribus A. , Lim B. H. , Lim C. S. , Chong K. K. , Karni J. , Buck R. , Pfahl A. , Bligh T. P.
Published: February 2004

The basic mathematics and structure of heliostat have remained unchanged for many decades. Following the challenge first made by Ries et al., the non-imaging focusing heliostat recently proposed by Chen et al. provides an alternative in the field of concentrated solar energy. This paper investigates the performance of a heliostat field composed of the newly proposed heliostats. In contrast to the dynamic curvature adjustment proposed in our previous work for a solar furnace, a fixed asymmetric curvature is used here with the spinning-elevation tracking method. This restriction is intended to equalize the manufacture cost of the new heliostat with that of traditional heliostats with azimuth-elevation tracking and spherical curvature. Fixing the curvature results in only partial aberration correction, compared to full correction using the dynamic adjustment of curvature. Nevertheless, the case studies presented in this paper show that the new heliostat design can reduce the receiver spillage loss by 10–30%, and provide a much more uniform performance without large variations with time of day.
Application of Suction Line Heat Exchanger on Adsorption Refrigeration System
Authors: Wang Wen , Qu Tianfei , Li Zhonghua , Wang Ruzhu
Published: February 2004

Quantitative thermodynamic analysis demonstrates that an adsorption refrigeration cycle could get higher cycle performance by employing a suction line heat exchanger (SLHX). Low temperature evaporated gas not only helps to cool down the adsorbent, it further increases the cooling output by recovering heat and cooling the condensed liquid. Experimental data also verifies that a SLHX recovers heat from the evaporated gas and helps the evaporator to provide higher cooling capacity.
Determination of Bearing Loads Due To Wind in Solar Tracking Systems
Authors: Sharan Anand M.
Published: February 2004

This paper deals with the calculation of the wind forces on the bearings of a solar tracking system. The forces involved are three dimensional-normal, and drag forces which act on the solar panel. These calculations are done in a rotating frame, and subsequently, they are transformed to a stationary frame. The effect of the weight forces of the solar panel is also included.
Analysis and Experimental Results of Solar-Blind Temperature Measurements in Solar Furnaces
Authors: Hernandez D. , Olalde G. , Gineste J. M. , Gueymard C.
Published: February 2004

Despite the existence of several possible pyrometric methodologies, temperature monitoring and control of samples heated at the focus of solar concentrators have still not received a universal and perfect solution. Here we present an analysis of solar-blind conditions and experimental measurements that have been carried out at the Odeillo Solar Furnace (IMP-CNRS). The aim here is to test different experimental configurations that can conceptually eliminate the reflected part of the concentrated solar flux. These configurations would allow near solar-blind measurements within the atmospheric absorption bands centered at 1.4 μm and 1.9 μm, and true solar-blind measurements within similar bands centered at 2.7 μm, 4.3 μm, and 6 μm. The parasitic reflected solar flux can be evaluated for each of these bands. In the case of alumina in particular, true solar-blind measurements can also be performed under blackbody conditions over the 8–12 μm band, and this is taken here as a convenient example of application. It is also demonstrated that solar-blind measurements are possible outside of these absorption bands, either by adding an appropriate radiation cutting filter (e.g., a quartz window) or by using an infrared narrow filter centered in a spectral region where the incident flux is negligible due to reflection losses (e.g., at 3.9 μm). The Solar Performance Factor is introduced to characterize the potential of any spectral region vis-a`-vis solar blindness.
Exergetic Efficiencies and the Exergy Content of Terrestrial Solar Radiation
Authors: Wright Sean E. , Rosen Marc A.
Published: February 2004

In the field of solar engineering the practical performance of solar energy conversion devices is generally evaluated strictly on an energy (first law) basis. However, the second law of thermodynamics determines the maximum work potential or exergy content of radiative fluxes independent of any conceptual device. The work in this paper quantifies the effect of directional and spectral distribution of terrestrial solar radiation (SR) on its exergy content. This is particularly important as the thermodynamic character of terrestrial SR is very different from that of blackbody radiation (BR). Exergetic (second law) efficiencies compare the work output of a device to the exergy content of the radiative source flux rather than its energy flux. As a result, exergetic efficiencies reveal that the performance of devices in practice is always better than what is indicated by the corresponding energy efficiency. The results presented in this paper introduce the benefits of using exergy analysis for solar cell design, performance evaluation and optimization.
Experimental Analysis on Chemical Dehumidification of Air by Liquid Desiccant and Desiccant Regeneration in a Packed Tower
Authors: Longo Giovanni A. , Gasparella Andrea
Published: February 2004

This paper presents the experimental tests on the chemical dehumidification of air by a liquid desiccant and desiccant regeneration carried out in an absorption/desorption tower with random packing. The experimental set-up is fully described together with measurements, procedures, data reduction, and accuracy. The experimental tests include 46 dehumidification runs and 38 desiccant regeneration runs carried out with the traditional hygroscopic solution H2O/LiBr and the new solution H2O/KCOOH in the typical operative ranges of air conditioning applications. The experimental results are reported in terms of humidity reduction, desiccant concentration change, and tower efficiency. The experimental tests show that chemical dehumidification of air by liquid desiccants ensures consistent reduction in humidity ratio, which is suitable for the application to air conditioning or drying processes. The experimental results are also compared to a one-dimensional simulation code of a packed tower: a fair agreement was found between experimental and calculated performance.
Flux Distribution Delivered by a Fresnel Lens Used for Concentrating Solar Energy
Authors: Ferriere A. , Rodriguez G. P. , Sobrino J. A.
Published: February 2004

The flux distribution delivered by a Fresnel lens when concentrating solar energy is characterized. The flux is measured with a Si photo-detector equipped with an integrating sphere. Flux mapping is performed by scanning lines at discrete positions on one plane. The peak concentration is determined as well as the distribution of the flux density in 3-D inside the focal area. Future utilization of this Fresnel lens for solar processing and surface modifications of materials is discussed. The analysis is made on the basis of the optical characteristics of the device and of the results of previous works in the same field. The size of the focus and the peak flux density are key parameters for examining the candidate processing and for discussing the dimensions of the treated components.
Revising and Validating Spectral Irradiance Reference Standards for Photovoltaic Performance Evaluation
Authors: Myers Daryl R. , Emery Keith , Gueymard C.
Published: February 2004

In 1982, the American Society for Testing and Materials (ASTM) adopted consensus standards for direct-normal and hemispherical (“global”) tilted solar terrestrial spectra (ASTM E891/E892/G159). These standard spectra were intended to evaluate photovoltaic (PV) device performance and other solar-related applications. The International Standards Organization (ISO) and International Electrotechnical Commission (IEC) adopted these spectra as spectral standards ISO 9845-1 and IEC 60904-3. Additional information and more accurately representative spectra are needed by today’s PV community. Modern terrestrial spectral radiation models, knowledge of atmospheric physics, and measured radiometric quantities are applied to develop new reference spectra under consideration by ASTM.
Polymers for Solar Domestic Hot Water: Long-Term Performance of PB and Nylon 6,6 Tubing in Hot Water
Authors: Wu Chunhui , Mantell Susan C. , Davidson Jane
Published: February 2004

Polymers offer a lightweight, low cost option for solar hot water system components. Key to the success of polymer heat exchanger components will be the long term mechanical performance of the polymer. This is particularly true for heat exchangers in which one of the fluids is pressurized hot water. For domestic hot water systems, polymer components must not fail after many years at a constant pressure (stress levels selected to correspond to 0.55 MPa in a tube) when immersed in 82°C potable water. In this paper, the long term performance of two potential heat exchanger materials, polybutylene and nylon 6,6, is presented. Two failure mechanisms are considered: failure caused by material rupture (as indicated by the hydrostatic burst strength) and failure caused by excessive deformation (as indicated by the creep modulus). Hydrostatic burst strength and creep modulus data are presented for each material. Master curves for the creep compliance as a function of time are derived from experimental data. These master curves provide a mechanism for predicting creep modulus as a function of time. A case study is presented in which tubing geometry is selected given the hydrostatic burst strength and creep compliance data. This approach can be used to evaluate properties of candidate polymers and to design polymer components for solar hot water applications.
Simplified Building and Air-handling Unit Model Calibration and Applications
Authors: Liu M. , Song L. , Wei G. , Claridge D. E.
Published: February 2004

Model calibration remains a significant topic for both researchers and practitioners in the HVAC field although calibrated building and air-handling unit (AHU) models have been used for “measuring” building energy retrofit/commissioning savings, identifying operational problems, and optimizing system operation and control schedules for decades. This paper discusses the modeling and simplification of building and AHU systems used in the simplified model calibration process. The paper presents a two-level calibration procedure integrated with energy signatures for simplified building and AHU heating and cooling energy consumption models. The procedures are demonstrated using a detailed example. This procedure can be implemented into computer simulation programs to allow automatic calibration and fault detection in many HVAC engineering processes.
Optical Design of an Infrared Non-Imaging Device for a Full-Spectrum Solar Energy System
Authors: Dye Dan , Wood Byard , Fraas Lewis , Muhs Jeff
Published: February 2004

A full-spectrum solar energy system is being designed by a research team lead by Oak Ridge National Laboratory and the University of Nevada, Reno. [1,2] The benchmark collector/receiver and prototype thermophotovoltaic (TPV) array have been built [3], so the work performed here is to match the two systems together for optimal performance. It is shown that a hollow, rectangular-shaped non-imaging (NI) device only 23 cm long can effectively distribute the IR flux incident on the TPV array mounted behind the secondary mirror. Results of the ray-tracing analysis of the different systems tested are presented.
Feynman’s proof of Maxwell equations and Yang’s unification of electromagnetic and gravitational Aharonov–Bohm effects
Authors: Hokkyo Noboru
Published: February 2004

Feynman’s unpublished proof of the Maxwell and Lorentz equations, discovered in 1948, was published by Dyson in 1990, together with editorial comments to place the proof into historical context. The proof indicated that the only possible fields that can consistently act on a quantum mechanical particle were gauge fields. Yang’s proof of the Lorentz equation, given in 1983 on the occasion of Tonomura’s experimental confirmation of the Aharonov–Bohm effect, related the electromagnetic and gravitational Aharonov–Bohm effects with the gauge fields. Yang’s discussion, including a remark about Einstein’s objection to Weyl’s original idea of gauge (scale) fields, is given in the context of current research programs for the gauge unification of fundamental forces.
Numerov extension of transparent boundary conditions for the Schrödinger equation in one dimension
Authors: Moyer Curt A.
Published: February 2004

We describe an algorithm for animating time-dependent quantum wave functions in one dimension with very high accuracy. The algorithm employs the Crank–Nicholson approximation for the time dependence along with a Numerov extension of the discrete transparent boundary conditions described recently by Ehrhardt. We illustrate the power of this approach by simulating the decay of alpha particles from radioactive nuclei and the resonance scattering of electrons in a three-layer GaAs–GaAlAs sandwich.
An experimental method for studying two-dimensional percolation
Authors: Schwartz Gustavo Ariel , Ludueña Silvio J.
Published: February 2004

A simple experimental technique for analyzing a broad range of two-dimensional percolation problems is presented. The method is based on a combination of the use of a CAD program capable of dealing with a variety of site-bond combinations and an electrical measurement of conductance. The latter is achieved by printing the computer generated pattern using conducting ink. The metal-insulator transition is measured on the print out of the lattice, and the conductivity critical exponent and the percolation threshold are calculated from these measurements.
The Born–Oppenheimer approximation: A toy version
Authors: Gangopadhyay Gautam , Dutta-Roy Binayak
Published: February 2004

The Born–Oppenheimer approximation, which is central to the physics and chemistry of molecules and solids, is illustrated by a one-dimensional toy model that is easily solved.
The evolution of radiation toward thermal equilibrium: A soluble model that illustrates the foundations of statistical mechanics
Authors: Nauenberg Michael
Published: February 2004

In 1916 Einstein introduced the first rules for a quantum theory of electromagnetic radiation and applied them to a model of matter in thermal equilibrium with radiation to derive Planck’s black-body formula. Einstein’s treatment is extended here to time-dependent stochastic variables, which leads to a master equation for the probability distribution that describes the irreversible approach of his model to thermal equilibrium and elucidates aspects of the foundations of statistical mechanics. An analytic solution of the master equation is obtained in the Fokker–Planck approximation, which is in excellent agreement with numerical results. It is shown that the equilibrium probability distribution is proportional to the total number of microstates for a given configuration, in accordance with Boltzmann’s fundamental postulate of equal a priori probabilities. Although the counting of these configurations depends on the particle statistics, the corresponding probability is determined here by the dynamics which are embodied in Einstein’s quantum transition probabilities for the emission and absorption of radiation. In a special limit, it is shown that the photons in Einstein’s model can act as a thermal bath for the evolution of the atoms toward the canonical equilibrium distribution. In this limit, the present model is mathematically equivalent to an extended version of the Ehrenfests’s “dog-flea” model.
Physics of overarm throwing
Authors: Cross Rod
Published: February 2004

Measurements are presented of the speed at which objects of different mass can be projected by an overarm throw. Light objects can be thrown faster than heavy objects, although the difference in speed is not as large as one might expect. For a factor of 60 increase in the thrown mass, there was a decrease of only 2.4 in the throw speed. The relatively small change in throw speed is due to the fact that the force that can be applied to a thrown object increases with object mass. Estimates of the muscle forces involved indicate that the increase in force with mass is primarily an inertial rather than a physiological effect. The total kinetic energy of the mass, hand, and the forearm was found to be almost independent of the object mass, and the throw speed is almost independent of the mass of the upper arm.
What is a state in quantum mechanics?
Authors: Newton Roger G.
Published: February 2004

In quantum mechanics, states are supposed to be specified by vectors in Hilbert space. However, students become confused about the representation of states and the meaning of “state” itself. We discuss consequences of the fact that quantum mechanics is intrinsically a probabilistic theory, and the ubiquitous confusion over whether quantum states, when specified as well as nature permits, are described by state vectors or rays.
Electromagnetic waves in dissipative media revisited
Authors: Vitela Javier E.
Published: February 2004

We present a systematic and self-consistent analysis of the polarization characteristics of monochromatic electromagnetic waves in linear, isotropic, and homogeneous dissipative media. It is shown that in general the transversality property of the waves no longer holds when they propagate in dissipative media. The same is true for electromagnetic waves traveling parallel to the boundary interface if total internal reflection occurs, even in a strictly nondissipative medium. A systematic characterization of elliptically polarized fields for incident s and p waves is presented. Examples in which the time averaged Poynting vector is not parallel to the direction of propagation of the electromagnetic waves are presented. A general expression for the Poynting vector is derived and is interpreted as the power per unit area developed by the electric stress tensor along the direction of propagation of the wave. An equivalent expression is obtained in terms of the magnetic stress tensor with, in general, a different direction of propagation.
Faraday’s law, Lenz’s law, and conservation of energy
Authors: Wood Lowell T. , Rottmann Ray M. , Barrera Regina
Published: February 2004

We describe an experiment in which the induced electromotive force in a coil caused by an accelerating magnet and the position of the moving magnet are measured as a function of the time. When the circuit is completed by adding an appropriate load resistor, a current that opposes the flux change is generated in the coil. This current causes a magnetic field in the coil which decreases the acceleration of the rising magnet, as is evident from the position versus time data. The circuit provides a direct observation of effects that are a consequence of Lenz’s law. The energy dissipated by the resistance in the circuit is shown to equal the loss in mechanical energy of the system to within experimental error, thus demonstrating conservation of energy. Students in introductory physics courses have performed this experiment successfully.
Nota Bene: Moving Mountains
Authors: Smith Orla
Published: February 2004

A Short History of Nearly Everything
. by Bill Bryson. Broadway Books, New York, 2003. 559 pp. $27.50. ISBN 0-7679-0817-1. Doubleday, London, 2003. 527 pp. £20. ISBN 0-385-40818-8.

In this accessible survey of the whole of science, Bryson sketches both what we know and how we have come to know it.
Anterior Cingulate Conflict Monitoring and Adjustments in Control
Authors: Kerns John G. , Cohen Jonathan D. , MacDonald Angus W. , Cho Raymond Y. , Stenger V. Andrew , Carter Cameron S.
Published: February 2004

Conflict monitoring by the anterior cingulate cortex (ACC) has been posited to signal a need for greater cognitive control, producing neural and behavioral adjustments. However, the very occurrence of behavioral adjustments after conflict has been questioned, along with suggestions that there is no direct evidence of ACC conflict-related activity predicting subsequent neural or behavioral adjustments in control. Using the Stroop color-naming task and controlling for repetition effects, we demonstrate that ACC conflict-related activity predicts both greater prefrontal cortex activity and adjustments in behavior, supporting a role of ACC conflict monitoring in the engagement of cognitive control.
Structural Basis of Transcription: Separation of RNA from DNA by RNA Polymerase II
Authors: Westover Kenneth D. , Bushnell David A. , Kornberg Roger D.
Published: February 2004

The structure of an RNA polymerase II–transcribing complex has been determined in the posttranslocation state, with a vacancy at the growing end of the RNA-DNA hybrid helix. At the opposite end of the hybrid helix, the RNA separates from the template DNA. This separation of nucleic acid strands is brought about by interaction with a set of proteins loops in a strand/loop network. Formation of the network must occur in the transition from abortive initiation to promoter escape.
Lowland Forest Loss in Protected Areas of Indonesian Borneo
Authors: Curran L. M. , Trigg S. N. , McDonald A. K. , Astiani D. , Hardiono Y. M. , Siregar P. , Caniago I. , Kasischke E.
Published: February 2004

The ecology of Bornean rainforests is driven by El Niño–induced droughts that trigger synchronous fruiting among trees and bursts of faunal reproduction that sustain vertebrate populations. However, many of these species- and carbon-rich ecosystems have been destroyed by logging and conversion, which increasingly threaten protected areas. Our satellite, Geographic Information System, and field-based analyses show that from 1985 to 2001, Kalimantan's protected lowland forests declined by more than 56% (>29,000 square kilometers). Even uninhabited frontier parks are logged to supply international markets. “Protected” forests have become increasingly isolated and deforested and their buffer zones degraded. Preserving the ecological integrity of Kalimantan's rainforests requires immediate transnational management.
Photoreceptor Regulation of CONSTANS Protein in Photoperiodic Flowering
Authors: Valverde Federico , Mouradov Aidyn , Soppe Wim , Ravenscroft Dean , Samach Alon , Coupland George
Published: February 2004

Many plants flower in response to seasonal fluctuations in day length. The
CONSTANS
(
CO
) gene of
Arabidopsis
promotes flowering in long days. Flowering is induced when
CO
messenger RNA expression coincides with the exposure of plants to light. However, how this promotes CO activity is unknown. We show that light stabilizes nuclear CO protein in the evening, whereas in the morning or in darkness the protein is degraded by the proteasome. Photoreceptors regulate CO stability and act antagonistically to generate daily rhythms in CO abundance. This layer of regulation refines the circadian rhythm in
CO
messenger RNA and is central to the mechanism by which day length controls flowering.
Evolutionary Ecology of the Prezygotic Stage
Authors: Bernasconi G. , Ashman T.-L. , Birkhead T. R. , Bishop J. D. D. , Grossniklaus U. , Kubli E. , Marshall D. L. , Schmid B. , Skogsmyr I. , Snook R. R. , Taylor D. , Till-Bottraud I. , Ward P. I. , Zeh D. W. , Hellriegel B.
Published: February 2004

The life cycles of sexually reproducing animals and flowering plants begin with male and female gametes and their fusion to form a zygote. Selection at this earliest stage is crucial for offspring quality and raises similar evolutionary issues, yet zoology and botany use dissimilar approaches. There are striking parallels in the role of prezygotic competition for sexual selection on males, cryptic female choice, sexual conflict, and against selfish genetic elements and genetic incompatibility. In both groups, understanding the evolution of sex-specific and reproductive traits will require an appreciation of the effects of prezygotic competition on fitness.
Direct Activation of Bax by p53 Mediates Mitochondrial Membrane Permeabilization and Apoptosis
Authors: Chipuk Jerry E. , Kuwana Tomomi , Bouchier-Hayes Lisa , Droin Nathalie M. , Newmeyer Donald D. , Schuler Martin , Green Douglas R.
Published: February 2004

The tumor suppressor p53 exerts its anti-neoplastic activity primarily through the induction of apoptosis. We found that cytosolic localization of endogenous wild-type or trans-activation–deficient p53 was necessary and sufficient for apoptosis. p53 directly activated the proapoptotic Bcl-2protein Bax in the absence of other proteins to permeabilize mitochondria and engage the apoptotic program. p53 also released both proapoptotic multidomain proteins and BH3-only proteins [Proapoptotic Bcl-2family proteins that share only the third Bcl-2homology domain (BH3)] that were sequestered by Bcl-xL. The transcription-independent activation of Bax by p53 occurred with similar kinetics and concentrations to those produced by activated Bid. We propose that when p53 accumulates in the cytosol, it can function analogously to the BH3-only subset of proapoptotic Bcl-2proteins to activate Bax and trigger apoptosis.
Chondrules with Peculiar REE Patterns: Implications for Solar Nebular Condensation at High C/O
Authors: Pack Andreas , Shelley J. Michael G. , Palme Herbert
Published: February 2004

Rare earth element (REE) data from two ordinary chondrite chondrules show distinct negative chondrite-normalized concentration anomalies of samarium, europium, and ytterbium. The peculiar patterns may be the result of REE gas/solid fractionation at an oxygen fugacity lower than has been assumed for the canonical solar nebula. We suggest that the two ordinary chondrite chondrules acquired the fractionated REE patterns by incorporation of highly reduced, ultrarefractory condensates in their precursors. This interpretation implies that high-temperature condensation processes occurred in nebular environments with a strong deficit in oxygen, such as regions with an enhanced carbon/oxygen ratio.
Medicago truncatula DMI1
Required for Bacterial and Fungal Symbioses in Legumes
Authors: Ané Jean-Michel , Kiss György B. , Riely Brendan K. , Penmetsa R. Varma , Oldroyd Giles E. D. , Ayax Céline , Lévy Julien , Debellé Frédéric , Baek Jong-Min , Kalo Peter , Rosenberg Charles , Roe Bruce A. , Long Sharon R. , Dénarié Jean , Cook Douglas R.
Published: February 2004

Legumes form symbiotic associations with both mycorrhizal fungi and nitrogen-fixing soil bacteria called rhizobia. Several of the plant genes required for transduction of rhizobial signals, the Nod factors, are also necessary for mycorrhizal symbiosis. Here, we describe the cloning and characterization of one such gene from the legume
Medicago truncatula
. The
DMI1
(does not make infections) gene encodes a novel protein with low global similarity to a ligand-gated cation channel domain of archaea. The protein is highly conserved in angiosperms and ancestral to land plants. We suggest that DMI1 represents an ancient plant-specific innovation, potentially enabling mycorrhizal associations.
Nanotubular Highways for Intercellular Organelle Transport
Authors: Rustom Amin , Saffrich Rainer , Markovic Ivanka , Walther Paul , Gerdes Hans-Hermann
Published: February 2004

Cell-to-cell communication is a crucial prerequisite for the development and maintenance of multicellular organisms. To date, diverse mechanisms of intercellular exchange of information have been documented, including chemical synapses, gap junctions, and plasmodesmata. Here, we describe highly sensitive nanotubular structures formed de novo between cells that create complex networks. These structures facilitate the selective transfer of membrane vesicles and organelles but seem to impede the flow of small molecules. Accordingly, we propose a novel biological principle of cell-to-cell interaction based on membrane continuity and intercellular transfer of organelles.
Ultra-Low Thermal Conductivity in W/Al
2
O
3
Nanolaminates
Authors: Costescu R. M. , Cahill D. G. , Fabreguette F. H. , Sechrist Z. A. , George S. M.
Published: February 2004

Atomic layer deposition and magnetron sputter deposition were used to synthesize thin-film multilayers of W/Al
2
O
3
. With individual layers only a few nanometers thick, the high interface density produced a strong impediment to heat transfer, giving rise to a thermal conductivity of ∼0.6 watts per meter per kelvin. This result suggests that high densities of interfaces between dissimilar materials may provide a route for the production of thermal barriers with ultra-low thermal conductivity.
A Most Productive Passion for Natural History
Authors: Baldwin Ian T.
Published: February 2004

For Love of Insects
. by Thomas Eisner. Belknap (Harvard University Press), Cambridge, MA, 2003. 462 pp. $29.95, £19.95, €27.70. ISBN 0-674-01181-3.

Using examples and spectacular photographs from his long and productive career in chemical ecology, Eisner provides a captivating account of the biology and behavior of insects and their relatives.
Assembly Properties of the Human Immunodeficiency Virus Type 1 CA Protein
Authors: Ganser-Pornillos Barbie K. , von Schwedler Uta K. , Stray Kirsten M. , Aiken Christopher , Sundquist Wesley I.
Published: February 2004

During retroviral maturation, the CA protein oligomerizes to form a closed capsid that surrounds the viral genome. We have previously identified a series of deleterious surface mutations within human immunodeficiency virus type 1 (HIV-1) CA that alter infectivity, replication, and assembly in vivo. For this study, 27 recombinant CA proteins harboring 34 different mutations were tested for the ability to assemble into helical cylinders in vitro. These cylinders are composed of CA hexamers and are structural models for the mature viral capsid. Mutations that diminished CA assembly clustered within helices 1 and 2 in the N-terminal domain of CA and within the crystallographically defined dimer interface in the CA C-terminal domain. These mutations demonstrate the importance of these regions for CA cylinder production and, by analogy, mature capsid assembly. One CA mutant (R18A) assembled into cylinders, cones, and spheres. We suggest that these capsid shapes occur because the R18A mutation alters the frequency at which pentamers are incorporated into the hexagonal lattice. The fact that a single CA protein can simultaneously form all three known retroviral capsid morphologies supports the idea that these structures are organized on similar lattices and differ only in the distribution of 12 pentamers that allow them to close. In further support of this model, we demonstrate that the considerable morphological variation seen for conical HIV-1 capsids can be recapitulated in idealized capsid models by altering the distribution of pentamers.
Salmonella osteomyelitis of the thoracic spine: an unusual presentation
Authors: Gupta S K , Pandit A , White D G , Evans P D
Published: February 2004

A case of thoracic vertebral osteomyelitis due to Salmonella enteritidis phage type 2 in an immunocompetent patient is reported. The patient initially presented with abdominal, urinary and chest symptoms, which were followed by a large pleural effusion. The infection was successfully treated with ciprofloxacin. This is the only case of salmonella thoracic vertebral osteomyelitis in an immunocompetent patient reported in the English literature.
Assessing clinical competency in medical senior house officers: how and why should we do it?
Authors: Carr S J
Published: February 2004

Most consultants are involved in the training and assessment of several grades of doctors in training especially senior house officers (SHOs) and specialist registrars. In the medical and other specialties there is an increasing trend towards assessing junior doctors’ competency using the record of in-training assessment process for specialist registrars and using the Royal College of Physicians folder to record competences of medical SHOs. It is necessary to consider why there is a need to assess competency, how it may be done practically, and the advantages and disadvantages of this system of assessment. There are considerable hurdles to the implementation of this system in the medical specialties within today’s NHS and the organisation may need to undergo fairly radical change to facilitate this system.
History of asbestos related disease
Authors: Bartrip P W J
Published: February 2004

The first medical article on the hazards of asbestos dust appeared in the British Medical Journal in 1924. Following inquiries by Edward Merewether and Charles Price, the British government introduced regulations to control dangerous dust emissions in UK asbestos factories. Until the 1960s these appeared to have addressed the problem effectively. Only then, with the discoveries that mesothelioma was an asbestos related disease and that workers other than those employed in the dustiest parts of asbestos factories were at risk, were the nature and scale of the hazard reassessed. In Britain, America, and elsewhere new and increasingly strict regulations were enacted.
PROPERTIES OF ARRANGEMENT GRAPHS
Authors: BOSE PROSENJIT , EVERETT HAZEL , WISMATH STEPHEN
Published: February 2004

An arrangement graph G is the abstract graph obtained from an arrangement of lines L, in general position by associating vertices of G with the intersection points of L, and the edges of G with the line segments joining the intersection points of L. A simple polygon (respectively path) of n sides in general position, induces a set of n lines by extension of the line segments into lines. The main results of this paper are:

• Given a graph G, it is NP-Hard to determine if G is the arrangement graph of some set of lines.

• There are non-Hamiltonian arrangement graphs for arrangements of six lines and for odd values of n>6 lines.

• All arrangements of n lines contain a subarrangement of size [Formula: see text] with an inducing polygon.

• All arrangements on n lines contain an inducing path consisting of n line segments. A Java applet implementing the algorithm for determining such a path is also provided.

• All arrangements on n hyperplanes in Rd contain a simple inducing polygonal cycle of size n.
AN EXPERIMENTAL STUDY OF ON-LINE METHODS FOR ZONE CONSTRUCTION IN ARRANGEMENTS OF LINES IN THE PLANE
Authors: LINHART CHAIM , HALPERIN DAN , HANNIEL IDDO , HAR-PELED SARIEL
Published: February 2004

Given a finite set ℒ of lines in the plane we wish to compute the zone of an additional curve γ in the arrangement [Formula: see text], namely the set of faces of the planar subdivision induced by the lines in ℒ that are crossed by γ, where γ is not given in advance but rather provided on-line portion by portion. This problem is motivated by the computation of the area bisectors of a polygonal set in the plane. We present four algorithms which solve this problem efficiently and exactly (giving precise results even on degenerate input). Our main algorithm is a novel approach based on the binary space partition technique. We implemented all four algorithms. We present implementation details, comparison of performance, and a discussion of the advantages and shortcomings of each of the proposed algorithms.
AREA-EFFICIENT ORDER-PRESERVING PLANAR STRAIGHT-LINE DRAWINGS OF ORDERED TREES
Authors: GARG ASHIM , RUSU ADRIAN
Published: February 2004

Ordered trees are generally drawn using order-preserving planar straight-line grid drawings. We investigate the area-requirements of such drawings and present several results. Let T be an ordered tree with n nodes. We show that:

• T admits an order-preserving planar straight-line grid drawing with O(n log n) area.

• If T is a binary tree, then T admits an order-preserving planar straight-line grid drawing with O(n log log n) area.

• If T is a binary tree, then T admits an order-preserving upward planar straight-line grid drawing with optimalO(n log n) area.

We also study the problem of drawing binary trees with user-specified aspect ratios. We show that an ordered binary tree T with n nodes admits an order-preserving planar straight-line grid drawing with area O(n log n), and any user-specified aspect ratio in the range [1,n/ log n]. All the drawings mentioned above can be constructed in O(n) time.
A NEW APPROACH OF BIVARIATE FUZZY TIME SERIES ANALYSIS TO THE FORECASTING OF A STOCK INDEX
Authors: HSU YU-YUN , TSE SZE-MAN , WU BERLIN
Published: February 2004

In recent years, the innovation and improvement of forecasting techniques have caught more and more attention. Especially, in the fields of financial economics, management planning and control, forecasting provides indispensable information in decision-making process. If we merely use the time series with the closing price array to build a forecasting model, a question that arises is: Can the model exhibit the real case honestly? Since, the daily closing price of a stock index is uncertain and indistinct. A decision for biased future trend may result in the danger of huge lost. Moreover, there are many factors that influence daily closing price, such as trading volume and exchange rate, and so on. In this research, we propose a new approach for a bivariate fuzzy time series analysis and forecasting through fuzzy relation equations. An empirical study on closing price and trading volume of a bivariate fuzzy time series model for Taiwan Weighted Stock Index is constructed. The performance of linguistic forecasting and the comparison with the bivariate ARMA model are also illustrated.
CLASSES OF INTUITIONISTIC FUZZY T-NORMS SATISFYING THE RESIDUATION PRINCIPLE
Authors: DESCHRIJVER GLAD , KERRE ETIENNE E.
Published: February 2004

Intuitionistic fuzzy sets constitute an extension of fuzzy sets: while fuzzy sets give a degree to which an element belongs to a set, intuitionistic fuzzy sets give both a membership degree and a non-membership degree. The only constraint on those two degrees is that the sum must be smaller than or equal to 1. In fuzzy set theory, an important class of triangular norms is the class of those that satisfy the residuation principle. In the fuzzy case a t-norm satisfies the residuation principle if and only if it is left-continuous. Deschrijver, Cornelis and Kerre proved that for intuitionistic fuzzy t-norms the equivalence between the residuation principle and intuitionistic fuzzy left-continuity only holds for t-representable t-norms.1 In this paper we construct particular subclasses of intuitionistic fuzzy t-norms that satisfy the residuation principle but that are not t-representable and we show that a continuous intuitionistic fuzzy t-norm [Formula: see text] satisfying the residuation principle is t-representable if and only if [Formula: see text].
THE EXTENDED TRANSFORMATION METHOD FOR THE SIMULATION AND ANALYSIS OF FUZZY-PARAMETERIZED MODELS
Authors: HANSS MICHAEL
Published: February 2004

The transformation method has been proposed as a practical tool for the simulation and the analysis of systems with uncertain, fuzzy-valued model parameters using fuzzy arithmetic. Up to now, this method has been available in two forms: in a general form, which can be used for the simulation and the analysis of arbitrarily non-monotonic problems, and in a reduced form, which reduces the computational costs of the method to a large extent, but requires, instead, an additional condition to be fulfilled. In this paper, the extended transformation method will be introduced as an advanced version of the previously presented formulations of the transformation method. This extended version includes the former versions as marginal cases and allows a pre-adjustment of the method subject to the number of model parameters that are expected to cause non-monotonic behavior of the model output. Furthermore, to set up the method properly, a novel approach, again based on the transformation method, is presented to practically detect those parameters that are responsible for a non-monotonic behavior of the model output. Finally, to show its effectiveness, the method is applied to a static and a dynamic model with uncertain parameters.
PRODUCTS AND MARGINALS OF POSET-VALUED FUZZY AND POSSIBILISTIC MEASURES
Authors: KRAMOSIL IVAN
Published: February 2004

Fuzzy measures and possibilistic measures taking their values in partially ordered sets, in particular, in semilattices and lattices, are introduced. Suggested and investigated in more detail are Cartesian products and marginals of poset-valued fuzzy and possibilistic measures. The conditions under which the resulting set functions possess the properties of poset-valued fuzzy and possibilistic measures are analyzed and some relevant assertions are stated and proved.
APPROXIMATION OF BELIEF FUNCTIONS
Authors: WEILER THOMAS
Published: February 2004

This paper addresses the approximation of belief functions by probability functions where the approximation is based on minimizing the Euclidean distance. First of all, we simplify this optimization problem so it becomes equivalent to a standard problem in linear algebra. For the simplified optimization problem, we provide the analytic solution. Furthermore, we show that for Dempster-Shafer belief the simplified optimization problem is equivalent to the original one.

In terms of semantics, we compare the approximation of belief functions to various alternative approaches, e.g. pignistic transformation for Dempster-Shafer belief and Shapley value for fuzzy belief functions. For the later one, we give an example where the approximation method has some obvious statistical advantages.

Additionally, for the approximation of additive belief functions, we can provide a semantical justification.