bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of Ordinary Sound in Liquid Helium near the λ Point
Authors: Chase C. E.
Published: December 2004

The velocity and attenuation of ordinary sound in liquid helium have been measured at a frequency of 1 Mc/sec in the neighborhood of the λ point. By using measuring techniques of high resolution, it was possible to observe the behavior in this region in considerable detail. The velocity passes through a minimum approximately 2 × 10−4 °K below the λ point; the maximum attenuation occurs about 8 × 10−5 °K below Tλ. Both velocity and attenuation behave in a manner characteristic of a relaxation process, with the relaxation time a rapid function of temperature near Tλ. The results below Tλ can be described with good quantitative accuracy if this relaxation time is given by τ = 8.8 × 10−12(Tλ − T)−1.

Excess attenuation is also observed above the λ point; this cannot be explained by the above relaxation process. The experimental uncertainties are so large in helium I that no reliable conclusions can be reached, but there is some indication that the quantity α/ω2 is not independent of frequency in this region.

The behavior of the velocity is considered with regard to the Ehrenfest relations, and it is shown that the discontinuity in isothermal compressibility which those relations predict must be almost entirely due to a discontinuity in γ. No contradiction of the Ehrenfest relations is implied, since present knowledge of γ suggests that a discontinuity of the required magnitude may indeed occur.
Nonlinear Oscillations of a Column of Gas
Authors: Betchov R.
Published: December 2004

Several authors studied experimentally the motion of a column of air in a long pipe, closed at one end and driven at the other by an oscillating piston. At resonance, they observed shock waves traveling in the tube. The paper presents a simple theoretical analysis of the motion, based on discontinuous linearized solutions and a secular equation. This equation guarantees that the motion remains periodic in spite of the cumulative effects of the nonlinear terms. For an inviscid gas, the amplitude at resonance is found to be finite and to be determined by nonlinear effects. This differs from previous results of Frederiksen. Friction can be taken into account and is included in the final results, which are presented in the form of a chart.
Kinetic Theory of Linear Shear Flow
Authors: Gross E. P. , Ziering S.
Published: December 2004

The flow of a monatomic gas between two parallel plates kept at the same temperature and moving in opposite directions is studied. The relative velocity of the plates is much smaller than the speed of sound. The deviation from the equilibrium distribution, φ(c, x), satisfies the linearized Boltzmann equation. The customary boundary conditions are adopted in which a fraction of the molecules is specularly reflected and the rest emitted with a Maxwellian distribution characteristic of the plate. The method consists of setting φ = φ+ for cx > 0 and φ = φ− for cx < 0 so that positive and negative velocities are distinguished. We take φ± = a0±(x)cz + a1±(x)czcx. The space functions are determined by taking half-range velocity moments of the Boltzmann equation. Explicit results for the distribution function, flow velocity and stress are given for a general law of force. Numerical results are worked out for hard sphere molecules. The method treats both microscopic boundary conditions and conservation laws exactly. Precise results are obtained both for the low-pressure region and for the high-pressure coefficient of viscosity. The region of slip flow is analyzed. Maxwell's slip condition is remarkably close to the condition obtained here from the kinetic theory. In this region of pressures, the deviations from the velocity profile of the hydrodynamic slip flow theory are everywhere very small, and are completely negligible at distances greater than ⅛ of a mean free path from a plate.
Shock-Front-Thickness Measurements by an Electron Beam Technique
Authors: Ballard H. N. , Venable Douglas
Published: December 2004

An electron beam densitometer is described for investigating the structure of a shock front in low-density gases. The parameters measured by this technique are directly related to those parameters used in the accepted definition of shock front thickness. Hence the interpretation of the data is direct; no model of the shock front structure must be assumed and no theoretical treatment of nonequilibrium flow conditions is needed. An approximate method of data reduction is used for treating preliminary results. The measured value of the thickness of a Mach 4 shock in argon is about three mean free paths, measured in terms of the undisturbed gas. This technique provides a new tool for investigating relaxation phenomena behind shock waves.
Nodal Expansions. II. The General Expansion of nth Order
Authors: Meeron Emmanuel , Rodemich Eugene R.
Published: December 2004

The first-order nodal expansion of potentials of average force and distribution functions, obtained in a previous publication, is summed over again and converted into a second-order expansion. The method is generalized, and recursion formulas are given for nth order expansions of potentials of average force in terms of ``sheaf potentials.'' These latter are seen to conform exactly to the Kirkwood superposition principle. The feasibility of actual calculations is briefly discussed. Possible applicability to quantum-mechanical problems (Feynman diagrams) is noted.
Criteria for Thermodynamic Equilibrium in Gas Flow
Authors: Rudin Morton
Published: December 2004

When gases flow at high velocity, the rates of internal processes may not be fast enough to maintain thermodynamic equilibrium. By defining quasi-equilibrium in flow as the condition in which the temperature, pressure, density, and velocity deviate by less than a fixed, small percentage from what they would be if the flowing gas could actually be in thermodynamic equilibrium, criteria are derived for determining whether quasi-equilibrium is a stable condition in the flow. By use of excitation of molecular vibration as an example, the general properties of criteria curves are discussed and interpreted. A discussion is given of how to use these results to determine definitely whether a flow is or is not in thermodynamic equilibrium. Applications to dissociating gases, to mixtures, and to the phenomenon of ``choking'' in a Laval nozzle are given special consideration. For cases when application of the criteria predict nonequilibrium, equations are provided in a form useful for numerical forward integration along streamlines.
The Free Molecule Probe and Its Use for the Study of Leading Edge Flows
Authors: Laurmann J. A.
Published: December 2004

The development of a free molecule probe for use as an instrument in the investigation of two dimensional rarefied gas flow fields is described. The probe consists of a cross-stream cylindrical wire of diameter small compared with the mean free path of the gas. Measurement of the probe temperature and heat transfer characteristics yields information that can be related theoretically to the state of the flowing gas. This paper describes the use of such information in the study of the qualitative nature of supersonic flow about sharp leading edges in regions where rarefaction, slip, and boundary layer-shock wave interaction effects are important. The results showed clearly the effect of increasing density. Thus, at the lowest densities and Mach numbers, a clearly defined shock wave and boundary layer emerged from a region of mixed compressive and viscous action at the leading edge, while at the higher densities and Mach numbers there was a large region of strong boundary layer-shock wave interaction and a considerable delay in the formation of clearly defined shock wave.
Comparison of High-Altitude Rocket and Satellite Density Measurements
Authors: LaGow H. E. , Horowitz R.
Published: December 2004

Atmospheric density measurements obtained with rocket-borne ionization gauges are compared with U. S. A. and U. S. S. R. satellite-drag density measurements. There is no significant disagreement between the results obtained by the two methods once atmospheric variations are taken into account.
Measurement of the Reflected Shock Hugoniot and Isentrope for Explosive Reaction Products
Authors: Deal W. E.
Published: December 2004

Measurement of the hydrodynamic state in an inert material adjacent to an interface with a detonating explosive yields a data point on the reflected shock Hugoniot of the explosive reaction products centered at the Chapman-Jouguet state or on the isentrope below this state. Such measurements have been made, using various inert materials, for a range of shock impedances which yields pressures in the explosive reaction products from 515 000 bars down to 571 bars. The data fit a polytropic equation of state (P/ργ = const. for the isentrope) with γ = 2.77.
Analysis of superoscillatory wave functions
Authors: Calder Matt S. , Kempf Achim
Published: December 2004

Surprisingly, differentiable functions are able to oscillate arbitrarily faster than their highest Fourier component would suggest. The phenomenon is called superoscillation. Recently, a practical method for calculating superoscillatory functions was presented and it was shown that superoscillatory quantum mechanical wave functions should exhibit a number of counter-intuitive physical effects. Following up on this work, we here present more general methods which allow the calculation of superoscillatory wave functions with custom-designed physical properties. We give concrete examples and we prove results about the limits to superoscillatory behavior. We also give a simple and intuitive new explanation for the exponential computational cost of superoscillations.
The generalized Stieltjes transform and its inverse
Authors: Schwarz John H.
Published: December 2004

The generalized Stieltjes transform (GST) is an integral transform that depends on a parameter ρ>0. In previous work a convenient form of the inverse transformation was derived for the case ρ=3∕2. This paper generalizes that result to all ρ>0. It is a well-known fact that the GST can be formulated as an iterated Laplace transform, and that therefore its inverse can be expressed as an iterated inverse Laplace transform. The form of the inverse transform derived here is a one-dimensional integral that is considerably simpler.
Calibrator for microflow delivery systems
Authors: Marinozzi Franco , Bini Fabiano , Cappa Paolo
Published: December 2004

An apparatus for calibrating the fluid flow rate down to 3×10−2ml∕h is proposed, based on the volumetric pump working principle. Constant flow rate is assured by means of the constant speed at which the plunger of a laboratory syringe is moved. To test effectiveness of the system, a flow sensor, composed by a differential pressure transducer and a needle was calibrated and afterward utilized for characterizing a clinical drug infusion device. The proposed apparatus showed a full scale (FS) uncertainty approximately equal to 3.5% over a range of 6 ml/h. The calibration range starts at 3×10−2ml∕h with a 1 ml syringe and at 3×10−3ml∕h with a 0.1 ml syringe. The minimum detectable signal (evaluated at 6 dB SNR) was equal to about 1.4×10−2ml∕h by using a syringe of 1 ml. The outcomes of the adopted procedure allowed a characterization of the performance of an infusion pump, without the need of the usual but somewhat cumbersome gravimetric calibration standard. Moreover, some issues about the expected resolution and uncertainty, depending on the characteristics of the system, is also reported.
Design of a delay-line position-sensitive detector with improved performance
Authors: Da Costa G. , Vurpillot F. , Bostel A. , Bouet M. , Deconihout B.
Published: December 2004

A delay-line position-sensitive detector with improved performance is presented. In this device, timing is carried out by means of fast digitizer boards. The use of dedicated signal processing procedures leads to a timing accuracy of 70 ps and a dead-time below 1.5 ns. As a result, the spatial resolving power of this detector is close to 1 mm leading to a high multihit capability. A temporary detector has been designed in which the delay-line anode is combined with a phosphor screen allowing additional positioning to be made via a charge-coupled device camera. This additional positioning is used to unambiguously quantify performances in terms of spatial resolution and multihit capabilities. A three-dimensional atom probe analysis of a material containing low evaporation field phases is used to demonstrate the capabilities of this detector.
Ray tracing study for a detuned nondispersed double crystal monochromator
Authors: Hou Zhengchi
Published: December 2004

The properties of a detuned nondispersive Si(111) double crystal monochromator were studied by using the ray tracing method. The program used was the PC version of shadow V2.3.3 with gui V1.2. This article concentrates on detuning of the second crystal since detuning of the first crystal causes a larger shift of the energy center of the transmitted beam than detuning of the second one does. The results indicate that for a large detuning angle of the second crystal, the transmitted spectrum splits into two bands with equal bandwidth, which is delayed at a large vertical divergence of the incident beam. With increasing detuning angle of the second crystal, both the fundamental bandwidth (for a well collimated beam) and the harmonic contamination decrease until they reach the minimum at a detuning angle of roughly half the full width at half maximum of the rocking curve, where the left fundamental flux is about 50%. The capability of harmonic suppression by detuning the second crystal is limited, with the harmonic contamination reduced by about two orders of magnitude at most, which implies that other methods, such as double mirror system, must be adopted when smaller harmonic contamination is required.
L
-band electron paramagnetic resonance spectrometer for use in vivo and in studies of aqueous biological samples
Authors: Walczak T. , Leśniewski P. , Salikhov I. , Sucheta A. , Szybiński K. , Swartz H. M.
Published: December 2004

The development of L-band (∼1.2GHz) frequency EPR spectrometers has made feasible many in vivo studies in laboratory animals and, recently, in human volunteers. The lower dielectric and eddy current losses that occur at L-band balance the lower Zeeman splitting so useful measurements can be made in conductive aqueous samples. We describe typical resonators used in such studies and provide details on the construction of the spectrometer, including the bridge, the automatic frequency control subsystem, the low-noise high-stability tunable L-band frequency source, as well as the low-frequency components—the signal receiver and the modulation unit. The application of EPR spectroscopy to larger subjects requires special care in the design of an appropriate magnet with sufficient homogeneity and stability, yet with dimensions that allow operation with a wide range of subject sizes. We describe our solution, which involves a permanent magnet, air-core scan coils to provide the field sweep and offset, and field stabilization by means of a field-frequency lock. We also describe the magnetic field modulation system, which operates at 25 kHz to avoid distortion in spectra from materials with narrow lines (such as lithium phthalocyanine). We refer to recent reviews to illustrate the range of in vivo studies and the clinical applications of the type of spectrometer described here.
Hall magnetic reconnection: Guide field dependence
Authors: Huba J. D.
Published: December 2004

Two-dimensional Hall magnetohydrodynamic simulations are used to study the dependence of a guide field on magnetic reconnection. The simulations are run until a steady state is achieved for Bgf∕B0=0, 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 where Bgf is the guide field and B0 is the reversed field. It is found that the reconnection rate and plasma energization are reduced for increasing guide field strength. This is caused by a J×B force associated with Hall currents and the guide field that reduce the inflow and outflow velocities. However, the reconnection rate and plasma energization are only reduced by a factor of 2 for Bgf=5B0. Additionally, the quadrupole field associated with Hall reconnection is eliminated for Bgf≃B0∕3. Applications to magnetospheric plasmas are discussed.
Time dependent 14MeV neutrons measurement using a polycrystalline chemical vapor deposited diamond detector at the JET tokamak
Authors: Angelone M. , Pillon M. , Bertalot L. , Orsitto F. , Marinelli M. , Milani E. , Pucella G. , Tucciarone A. , Verona-Rinati G. , Popovichev S. , Murari A. ,   JET EFDA contributors
Published: December 2004

A polycrystalline chemical vapor deposited (CVD) diamond detector was installed on a JET tokamak in order to monitor the time dependent 14MeV neutron emission produced by D–T plasma pulses during the Trace Tritium Experiment (TTE) performed in October 2003. This was the first tentative ever attempted to use a CVD diamond detector as neutron monitor in a tokamak environment. Despite its small active volume, the detector was able to detect the 14MeV neutron emission (>1.0×1015n∕shot) with good reliability and stability during the experimental campaign that lasted five weeks. The comparison with standard silicon detectors presently used at JET as 14MeV neutron monitors is reported, showing excellent correlation between the measurements. The results prove that CVD diamond detectors can be reliably used in a tokamak environment and therefore confirm the potential of this technology for next step machines like ITER.
Detection of magnetically enhanced cancer tumors using SQUID magnetometry: A feasibility study
Authors: Kenning G. G. , Rodriguez R. , Zotev V. S. , Moslemi A. , Wilson S. , Hawel L. , Byus C. , Kovach J. S.
Published: December 2004

Nanoparticles bound to various biological molecules and pharmacological agents can be administered systemically, to humans without apparent toxicity. This opens an era in the targeting of specific tissues and disease processes for noninvasive imaging and treatment. An important class of particles used predominantly for magnetic resonance imaging is based on iron-oxide ferrites. We performed computer simulations using experimentally determined values for concentrations of superparamagnetic particles achievable in specific tissues of the mouse in vivo and concentrations of particles linked to monoclonal antibodies specific to antigens of two human cancer cell lines in vitro. An instrument to target distance of 12cm, into the body, was selected as relevant to our goal of developing a rapid inexpensive method of scanning the body for occult disease. The simulations demonstrate the potential feasibility of superconducting quantum interference device magnetometry to detect induced magnetic fields in focal concentrations of superparamagnetic particles targeted, in vivo, to sites of disease.
A microchannel solution mixer for studying microsecond protein folding reactions
Authors: Bilsel Osman , Kayatekin Can , Wallace Louise A. , Matthews C. Robert
Published: December 2004

Many proteins fold through intermediates that are populated in the submillisecond time regime. To monitor directly the formation of these kinetic intermediates, we have developed a simple, robust, easy to assemble continuous flow mixer for studying folding reactions in the 35–1000μs time regime. The mixer is constructed by laser-machining 75-μm channels in a 127-μm-thick polyimide or polyetheretherketone polymer wafer. Mixing times of ∼25to∼50μs can be achieved for a 1∕10 dilution reaction of 8M urea with flow rates of 10–20mL∕min. CCD-based steady-state and time-correlated single-photon-counting-based fluorescence detection strategies are described. Preliminary results on the early events in the refolding of cytochrome c are presented.
Contribution of objective and subjective attributes to the variation in commercial value of Australian mohair: implications for mohair production, genetic improvement, and mohair marketing
Authors: McGregor B. A. , Butler K. L.
Published: December 2004

A database collected in the years 1998–01, from 2 mohair-selling agents in Australia, was analysed using multiple regression analysis to determine the effect on commercial sale prices of year, selling season within year, agent, mean fibre diameter (MFD), coefficient of variation of fibre diameter [CV(D)], vegetable matter base (VM), Schlumberger dry yield, visually assessed staple length, visually assessed fibre style, incidence of kemp, other faults, and interactions of these effects. The database consisted of 557 objectively measured lots. The weighted means ± s.d. of attributes analysed were: MFD, 30.9 ± 3.7 μm; CV(D), 29.1 ± 2.6%; VM, 1.0 ± 1.0%; Schlumberger dry yield, 84.0 ± 2.7%; lot weight, 1186 ± 938 kg. The final model for the price of greasy mohair had fixed terms involving a combination of selling agent, selling period, MFD, VM, and visual classing grades. This model accounted for 98% of the variation of the logarithm of greasy mohair price. Agent and selling period combinations accounted for 22% of the variation. Terms involving MFD accounted for 59% of the variation not accounted for by agent and period combinations. Although the response of greasy mohair price to MFD differed greatly with period, in the second quarter of 1999 the maximum relative price of greasy mohair was reached at a MFD of about 25 μm. The relative price typically declined to about 50% of the maximum at 30 μm and to a price of 10% of the maximum at 36 μm. The increase in relative value from poor to superior style mohair was about 43%. There were large discounts for length (up to 48%), kemp (up to 87%), and light stained mohair (70%). Deviations due to length differ with time and MFD. The discount for fault lines was proportionally higher when MFD was low, and proportionally less serious when the mohair MFD was high. The discount was proportionally greater the more serious the fault. There was a curvilinear response to the presence of VM in mohair and an interaction of VM with MFD, but these terms only accounted for the last 0.5% of the variation. After allowing for the effects of selling, agent, visual attributes, MFD, and VM, neither Schlumberger dry yield nor CV(D) was related to greasy mohair price. CV(D) was related to length, kemp, fault, and MFD. Apart from the current practice of price reporting on a greasy basis, the information supplied by agents provides transparency in mohair transactions as the current objective measurements and visual appraisal explain 97% of the variation not explained by agent and period of sale.
Effect of physical form of a lucerne hay on digestion and rate of passage in sheep
Authors: Faichney G. J. , Teleki E. , Brown G. H.
Published: December 2004

Six 2-year-old Corriedale wethers fitted with rumen and abomasal cannulas were given a lucerne hay to appetite then at restricted intakes, first as chopped hay (CH) then as ground and pelleted hay (GP). Voluntary feed consumption (VFC) was 43% greater on GP hay. Water intake increased as feed intake increased and was greater on GP. Organic matter digestibility (OMD) decreased as intake increased (P < 0.001) but was greater on GP hay at restricted intakes (P < 0.001). Potential OMD was marginally greater for GP hay. The digestibility of fibre constituents decreased as intake increased but was not significantly affected by grinding and pelleting. Rumen OM content and OM flow to the duodenum increased as intake increased on CH hay (P < 0.001), but only rumen OM content increased with grinding and pelleting (P < 0.001). Consequently, the mean retention times (MRT) of solutes, particles, and microbial protein decreased as intake increased (P < 0.001) and increased with grinding and pelleting (P < 0.001). However, at VFC, the MRT of each component was not affected by grinding and pelleting. Nitrogen digestibility decreased as intake increased but was greater on GP hay at restricted intakes. Non-ammonia nitrogen flow to and digestion in the intestines increased with intake but was not affected by grinding and pelleting. Ammonia synthesis in the rumen increased as feed intake increased (P < 0.001) but its 26–32% contribution to non-ammonia nitrogen flowing to the duodenum, which reflects microbial synthesis, was not affected by intake or grinding and pelleting. It was concluded that rate of passage cannot be accurately predicted because it is a derived parameter, determined by the differential responses of rumen digesta content and digesta outflow to the dietary, environmental, and physiological factors affecting the animal. These differential responses are involved in determining the effects of intake and grinding of hay on its digestibility.
Source - sink manipulation to increase melon (Cucumis melo L.) fruit biomass and soluble sugar content
Authors: Long Robert L. , Walsh Kerry B. , Rogers Gordon , Midmore David J.
Published: December 2004

Various source–sink perturbations were employed to alter partitioning to orange flesh melon (Cucumis melo L. reticulatus group) and thus to influence fruit biomass and soluble sugar content (indexed as total soluble solids of fruit juice, % TSS), with attention given to the timing of treatment application. A strong relationship existed between harvest index and fruit mass (r2 = 0.88) in control plants, whereas the correlation with fruit TSS was poor (r2 = 0.11). Augmentation of assimilate supply to fruit early in fruit development (before approx. 21 days before harvest, DBH) resulted in more fruit set and increased fruit biomass, whereas augmentation after 21 DBH resulted in increased fruit TSS. Thus, fruit biomass was increased (1644 cf. 1442 g FW per fruit for control, P = 0.02), but not TSS, on plants in which fruit set was delayed (source biomass increased, harvest index decreased from 59% for control to 38%). Treatment of plants with a cytokinin-based vegetative growth inhibitor at 14 DBH produced fruit with higher TSS (11.3 cf. 10.7% for control). Thinning fruit to leave 1 fruit per plant 1 week before harvest increased the proportion of fruit in a population that exceeded a quality control standard of 10% TSS from 20 to 80%. Variations in plant response with timing of treatment application are interpreted in terms of fruit development (cell division, cell expansion, and sugar accumulation phases). Although a detriment to yield (15 cf. 31 t/ha for control), the fruit thinning treatment was recommended for commercial use and a simple model was developed to calculate the required farm-gate price of fruit to make thinning economically viable.
Chemical Bonding in Octahedral XeF6 and SF6
Authors: Lein Matthias , Frenking Gernot
Published: December 2004

Quantum chemical density functional theory calculations have been carried out for octahedral XeF6 and SF6 at the BP86/TZ2P level with relativistic effects included by the ZORA approximation. The energy decomposition analysis of XeF6 and SF6 using neutral and charged fragments EF5 + F and EF5+ + F− as well as E + F6 and E6+ + F66− indicates that the dominant E–F orbital interactions take place between σ-orbitals which have t1u symmetry in the octahedral point group. The contribution of the a1g orbitals is negligible in the 16 valence electron compound XeF6. The a1g contribution becomes larger in the 14 valence electron species SF6 but it is less important than the t1u term. The bonding between the neutral species comes mainly from covalent (orbital) interactions but the quasiclassical electrostatic attraction significantly contributes to the attractive interactions. The bonding which comes from the ΔEorb term is compensated by the Pauli repulsion ΔEPauli. The sum of ΔEorb and ΔEPauli is repulsive for XeF6 and SF6, which would not be stable molecules without quasiclassical electrostatic attraction.
Single Photon Emission from a Dendrimer Containing Eight Perylene Diimide Chromophores
Authors: Bell Toby D. M. , Habuchi Satoshi , Masuo Sadahiro , Österling Ingo , Müllen Klaus , Tinnefeld Phillip , Sauer Markus , van der Auweraer Mark , Hofkens Johan , De Schryver Frans C.
Published: December 2004

A novel dendrimer containing eight perylene diimide chromophores has been synthesized and studied by ensemble and single-molecule spectroscopic techniques. Photon anti-bunching (coincidence) measurements on single molecules embedded in zeonex polymer films show that the dendrimer behaves as a deterministic (triggered) single photon source with only one fluorescence photon being emitted following pulsed laser excitation, even when more than one chromophore is excited. This behaviour is due to efficient singlet–singlet annihilation being operative in this dendrimer. Preliminary results indicate that the triplet lifetime and yield for this molecule are similar to the values for a molecule containing a single perylene diimide chromophore.
Hydrogen peroxide is a common signal for darkness- and ABA-induced stomatal closure in Pisum sativum
Authors: Desikan Radhika , Cheung Man-Kim , Clarke Andrew , Golding Sarah , Sagi Moshe , Fluhr Robert , Rock Christopher , Hancock John , Neill Steven
Published: December 2004

The requirement for hydrogen peroxide (H2O2) generation and action during stomatal closure induced by darkness and abscisic acid (ABA) was investigated in pea (Pisum sativum L.). Stomatal closure induced by darkness or ABA was inhibited by the H2O2-scavenging enzyme catalase or the antioxidant N-acetyl cysteine (NAC), or by diphenylene iodonium (DPI), an inhibitor of the H2O2-generating enzyme NADPH oxidase. Exogenous H2O2 induced stomatal closure in a dose- and time-dependent manner, and H2O2 was also required for ABA-inhibition of stomatal opening in the light. H2O2 accumulation in guard cells was increased by darkness or ABA, as assessed with the fluorescent dye dichlorodihydrofluorescein diacetate (H2-DCFDA) and confocal microscopy. Such increases were inhibited by catalase, NAC or DPI, consistent with the effects of these compounds on stomatal apertures. Employing polymerase chain reaction (PCR) with degenerate oligonucleotide primers, several NADPH oxidase homologues were identified from pea genomic DNA that had substantial identity to the Arabidopsis thaliana (L.) Heynh. rboh (respiratory burst oxidase homologue) genes. Furthermore, an antibody raised against the tomato rboh identified immunoreactive proteins in epidermal, mesophyll and guard cells.
Theoretical considerations about carbon isotope distribution in glucose of C3 plants
Authors: Tcherkez Guillaume , Farquhar Graham , Badeck Franz , Ghashghaie Jaleh
Published: December 2004

The origin of the non-statistical intramolecular distribution of 13C in glucose of C3 plants is examined, including the role of the aldolisation of triose phosphates as proposed by Gleixner and Schmidt (1997). A modelling approach is taken in order to investigate the relationships between the intramolecular distribution of 13C in hexoses and the reactions of primary carbon metabolism. The model takes into account C–C bond-breaking reactions of the Calvin cycle and leads to a mathematical expression for the isotope ratios in hexoses in the steady state. In order to best fit the experimentally-observed intramolecular distribution, the values given by the model indicate that (i), the transketolase reaction fractionates against 13C by 4–7‰ and (ii), depending on the photorespiration rate used for estimations, the aldolase reaction discriminates in favour of 13C by 6‰ during fructose-1,6-bisphosphate production; an isotope discrimination by 2‰ against 13C is obtained when the photorespiration rate is high. Additionally, the estimated fractionations are sensitive to the flux of starch synthesis. Fructose produced from starch breakdown is suggested to be isotopically heavier than sucrose produced in the light, and so the balance between these two sources affects the average intramolecular distribution of glucose derived from stored carbohydrates. The model is also used to estimate photorespiratory and day respiratory fractionations that appear to both depend only weakly on the rate of ribulose-1,5-bisphosphate oxygenation.
23Na NMR microimaging: a tool for non-invasive monitoring of sodium distribution in living plants
Authors: Rokitta Markus , Medek Danielle , Pope James M. , Critchley Christa
Published: December 2004

Detailed knowledge of the sodium (Na) distribution within the tissues of highly salt-tolerant Australian native species could help in understanding the physiological adaptations of salt-tolerance or salt-sensitive plants. 23Na nuclear magnetic resonance (NMR) microimaging is presented as a tool to achieve this goal. Maps of the Na distribution in stem tissue were obtained with an in-plane resolution of approximately125 µm and a slice thickness of 4 mm. Simultaneously recorded high resolution 1H NMR images showing water distribution in the same slice with 31 µm in-plane resolution and 1 mm slice thickness, were used as an anatomical reference together with optical micrographs that were taken immediately after the NMR experiments were completed. To quantify the Na concentration, reference capillaries with known NaCl concentrations were located in the NMR probe together with the plant sample. Average concentration values calculated from signal intensities in the tissue and the capillaries were compared with concentration values obtained from atomic emission photometry and optical microscopy performed on digested stem sections harvested immediately after NMR experiments. Results showed that 23Na NMR microimaging has great potential for physiological studies of salt stress at the macroscopic level, and may become a unique tool for diagnosing salt tolerance and sensitivity.
The terrestrial vertebrate fauna of Litchfield National Park, Northern Territory: monitoring over a 6-year period and response to fire history
Authors: Woinarski J. C. Z. , Armstrong M. , Price O. , McCartney J. , Griffiths A. D. , Fisher A.
Published: December 2004

Forty-seven 50 m × 50 m quadrats were sampled systematically for vertebrates at Litchfield National Park, northern Australia, in both 1995–96 and 2001–02. A total of 184 vertebrate species was recorded from this sampling, of which 92 species were recorded from five or more quadrats. There was substantial change in the reported species composition of these quadrats between these two periods: the mean Bray–Curtis index for similarity in species composition from the baseline to subsequent sampling of a quadrat was only 22.1 (for an index that varies from 0 for complete turnover in species to 100 for unchanged composition). For individual species, correlations across quadrats in the abundance scores from baseline to resampling varied from –0.12 to 0.85. Matched-pairs testing showed that there was significant change in abundance for 18 species from the baseline to repeat sampling, and significant increase in total bird species richness and total native mammal abundance, but significant decrease in reptile species richness.
Fire history was recorded biannually for 40 of the 47 quadrats. Fire was very frequent, with quadrats being burnt in an average of 3.65 years of the six years between fauna samples. Three aspects of this fire history (total number of years of fires, number of fires in the late dry season, and interval from the last fire to the date of resampling) were related to change in the fauna composition of quadrats. Neither the similarity in species composition, nor change in richness or total abundance of all vertebrates or of the four taxonomic classes considered (frogs, reptiles, birds and mammals) were significantly correlated with these components of the fire history of sampled quadrats. This lack of association was possibly because the monitoring period was too short to show pronounced directional change, because the system was responding to many factors other than fire, because the variations in abundance were too large and the number of samples too small to detect true associations, or because fire histories preceding baseline sampling were not considered.
The apparent instability of fauna species and communities in this system provides a considerable challenge for broad-brush (that is, vertebrate community–wide) monitoring. Power analysis demonstrated that, for most species, more than 1000 sample sites are needed to be 90% certain of detecting a 20% change in abundance, and with a 10% chance of accepting a Type I error. This level of sampling effort is commensurate with the current level of vertebrate sampling in this region. Broad-brush monitoring approaches such as described here are valuable, but need also to be complemented by more targetted monitoring for individual threatened species or species of particular management interest.
Direct experimental observation of the low ionization potentials of guanine in free oligonucleotides by using photoelectron spectroscopy
Authors: Yang Xin , Wang Xue-Bin , Vorpagel Erich R. , Wang Lai-Sheng
Published: December 2004

Photodetachment photoelectron spectroscopy is used to probe the electronic structure of mono-, di-, and trinucleotide anions in the gas phase. A weak and well defined threshold band was observed in the photoelectron spectrum of 2′-deoxyguanosine 5′-monophosphate at a much lower ionization energy than the other three mononucleotides. Density function theory calculations revealed that this unique spectral feature is caused by electron-detachment from a π orbital of the guanine base on 2′-deoxyguanosine 5′-monophosphate, whereas the lowest ionization channel for the other three mononucleotides takes place from the phosphate group. This low-energy feature was shown to be a “fingerprint” in all the spectra of dinucleotides and trinucleotides that contain the guanine base. The current experiment provides direct spectroscopic evidence that the guanine base is the site with the lowest ionization potential in oligonucleotides and DNA and is consistent with the fact that guanine is most susceptible to oxidation to give the guanine cation in DNA damage.
Actin-destabilizing factors disrupt filaments by means of a time reversal of polymerization
Authors: Orlova Albina , Shvetsov Alexander , Galkin Vitold E. , Kudryashov Dmitry S. , Rubenstein Peter A. , Egelman Edward H. , Reisler Emil
Published: December 2004

Actin, one of the most highly conserved and abundant eukaryotic proteins, is constantly being polymerized and depolymerized within cells as part of cellular motility, tissue formation and repair, and embryonic development. Many proteins exist that bind to monomeric or filamentous (F) forms of actin to regulate the polymerization state. It has become increasingly apparent that the ability of different proteins to bind to and regulate actin filament dynamics depends on the ability of the filament to exist in altered conformations. Yet, little is known about how these conformational changes occur at the molecular level. We have destabilized F-actin filaments by forming a disulfide that locks the “hydrophobic plug” to the body of the actin subunit or by altering the C terminus of actin with a tetramethylrhodamine label. We also examined F-actin filaments at short times after the initiation of polymerization. In all three cases, a substantial fraction of protomers can be found in a “tilted” state that also is induced by actin depolymerizing factor/cofilin proteins. These observations suggest that F-actin filaments are annealed over time into a stable filament and that actin-depolymerizing proteins can effect a time reversal of polymerization.
Per-Arnt-Sim domain-dependent association of cAMP-phosphodiesterase 8A1 with IκB proteins
Authors: Wu Ping , Wang Peng
Published: December 2004

Phosphodiesterase (PDE) 8A1 is a cAMP-specific PDE isozyme characterized by the presence of a Per-Arnt-Sim (PAS) domain. However, the function(s) of the PAS domain has remained unknown. In this study, using a lysate of HEK293 cells overexpressing recombinant human PDE8A1, we detected a physical association between PDE8A1 and endogenous IκBβ by an antibody array technique. The association was specific for PDE8A1 and depended on the presence of the PAS domain. Subsequent coimmunoprecipitation experiments revealed that, in addition to IκBβ, other IκB family members examined (p105, p100, and IκBα) also associated with PDE8A1. Furthermore, it was found that PDE8A1 competed with the p65/p50 NF-κB for IκBβ binding. Taken together, these data indicate that PDE8A1, through its PAS domain, may bind with IκB proteins in a region containing their ankyrin repeats. Functionally,
in vitro
and
in vivo
experiments demonstrated that the association with IκB greatly enhanced the enzyme activity of PDE8A1. However, the PDE8A1–IκB association did not affect NF-κB activation. The biological role of the PDE8A1–IκB association remains to be elucidated.
Speed-up of Monte Carlo simulations by sampling of rejected states
Authors: Frenkel Daan
Published: December 2004

The Markov chain Monte Carlo method is an important tool to estimate the average properties of systems with a very large number of accessible states. This technique is used extensively in fields ranging from physics to genetics and economics. The rejection of trial configurations is a central ingredient in existing Markov chain Monte Carlo simulations. I argue that the efficiency of Monte Carlo simulations can be enhanced, sometimes dramatically, by properly sampling configurations that are normally rejected. This “waste-recycling” of microstates is useful in sampling schemes in which only one of a large set of trial configurations is accepted. It differs fundamentally from schemes that extract information about the density of macrostates from virtual Monte Carlo moves. As a simple illustration, I show that the method greatly improves the calculation of the order-parameter distribution of a two-dimensional Ising model. This method should enhance the efficiency of parallel Monte Carlo simulations significantly.
DNA replication-timing analysis of human chromosome 22 at high resolution and different developmental states
Authors: White Eric J. , Emanuelsson Olof , Scalzo David , Royce Thomas , Kosak Steven , Oakeley Edward J. , Weissman Sherman , Gerstein Mark , Groudine Mark , Snyder Michael , Schübeler Dirk
Published: December 2004

Duplication of the genome during the S phase of the cell cycle does not occur simultaneously; rather, different sequences are replicated at different times. The replication timing of specific sequences can change during development; however, the determinants of this dynamic process are poorly understood. To gain insights into the contribution of developmental state, genomic sequence, and transcriptional activity to replication timing, we investigated the timing of DNA replication at high resolution along an entire human chromosome (chromosome 22) in two different cell types. The pattern of replication timing was correlated with respect to annotated genes, gene expression, novel transcribed regions of unknown function, sequence composition, and cytological features. We observed that chromosome 22 contains regions of early- and late-replicating domains of 100 kb to 2 Mb, many (but not all) of which are associated with previously described chromosomal bands. In both cell types, expressed sequences are replicated earlier than nontranscribed regions. However, several highly transcribed regions replicate late. Overall, the DNA replication-timing profiles of the two different cell types are remarkably similar, with only nine regions of difference observed. In one case, this difference reflects the differential expression of an annotated gene that resides in this region. Novel transcribed regions with low coding potential exhibit a strong propensity for early DNA replication. Although the cellular function of such transcripts is poorly understood, our results suggest that their activity is linked to the replication-timing program.
On the use of Social Relations and Actor–Partner Interdependence Models in developmental research
Authors: Little Todd D. , Card Noel A.
Published: December 2004

We offer comments on the eight works contained in the Special Issue, all of which use advanced methods for analysing interdependencies using variants of the Social Relations Model (SRM) or the Actor–Partner Interdependence Model (APIM). After critically discussing the SRM and APIM as used in these works, we describe similarities and differences between these two approaches. We also discuss the substantive contributions of this collection and then offer our suggestions for future development of the two models.
Rapid Detection of Group B Streptococcus and Escherichia coli in Amniotic Fluid Using Real‐Time Fluorescent PCR
Authors: Straka Michele , Cruz Wifred Dela , Blackmon Camille , Johnson Oswald , Stassen Sara , Streitman David , Golden Stephen , Stamilio David
Published: December 2004

Objective: To establish reliability and validity of real‐time fluorescent PCR for early detection of bacterial
invasion of the amniotic cavity.

Methods: Amniotic fluid samples from 40 patients undergoing mid‐trimester genetic amniocentesis were
incubated for 6 h at 37℃ and were cultured on media specific for group B streptococcus (GBS) and E. coli.
Concurrently, samples were analyzed with real‐time fluorescent PCR (Roche LightCycler) using DNA primers
and probes designed to detect the CAMP factor encoding cfb gene and uidA gene of GBS and E. coli,
respectively. For positive control and to simulate amniotic fluid colonization, 104 cfu/ml of GBS and E. coli were
inoculated on sterile amniotic fluid and incubated for 6 h. Bacterial genomic DNA for the two organisms was
extracted and purified via the two‐step precipitation method using a commercial kit. The real‐time PCR assays
were also tested against 25 non‐GBS and non‐E. coli bacterial species. The lower limit of detection for each
pathogen was established using serial dilution of bacterial genomic DNA.

Results: All patient samples were negative for evidence of GBS and E. coli with both culture and real‐time PCR
methods. Amniotic fluid samples inoculated with GBS and E. coli were positive with real‐time PCR whereas the
25 bacterial species other than GBS or E. coli tested negative with the assay. Average total sample processing
time including the pre‐enrichment step was 7 h 40 min. The average cost for DNA extraction and PCR testing
was $8.50 per test.

Conclusion: Real‐time fluorescent PCR is a valid and reliable method for detection of specific pathogens in
amniotic fluid. This technique is sensitive for low inoculation levels. Real‐time fluorescent PCR has potential to
impact clinical management as a rapid, reliable detection method for GBS and E. coli in chorioamnionitis.
The Unity of the Common Law and the Ending of Appeals to the Privy Council
Authors: Keith KJ
Published: December 2004

In 1769, by a nice coincidence, Captain James Cook made landfall in New Zealand, the first British mariner to do so, and William Blackstone published the final volume of hisCommentaries on the Law of England. Blackstoněs discussion of the application of the law of Englandto newly acquired colonies is not completely coherent, but it does give a strong sense that much, if not all, of the common law did come to apply to many, if not all, of them.1The Privy Council was reminded of this, with express reference to Blackstone, in November 2003 when it was asked to determine whether the rule inSmith v Selwyn,2a decision of the English Court of Appeal given in 1914, was part of the law of Jamaica.3
Storms, Foxes, and Nebulous Legal Arguments: Twelve Years of Force against Iraq, 1991–2003
Authors: Åkermark Sia Spiliopoulou
Published: December 2004

Vaughan Lowe has recently argued that the most important task of international lawyers at times of flux is to identify claims with precision.1 In order to accomplish this task with regard to the issue of use of force in Iraq, it seems necessary to review the main American and British arguments, including the formal legal arguments presented, as well as the relevant reactions of other States over a longer period of time. This will allow us to reveal patterns of argumentation, similarities, and differences in the American and British justifications as well as in the responses of the international community.