bluuebunny/crossref_metadata_2025 huggingface dataset:
Impacts of parasitic plants on natural communities
Authors: Press Malcolm C. , Phoenix Gareth K.
Published: May 2005

Parasitic plants have profound effects on the ecosystems in which they occur. They are represented by some 4000 species and can be found in most major biomes. They acquire some or all of their water, carbon and nutrients via the vascular tissue of the host's roots or shoots. Parasitism has major impacts on host growth, allometry and reproduction, which lead to changes in competitive balances between host and nonhost species and therefore affect community structure, vegetation zonation and population dynamics. Impacts on hosts may further affect herbivores, pollinators and seed vectors, and the behaviour and diversity of these is often closely linked to the presence and abundance of parasitic plants. Parasitic plants can therefore be considered as keystone species. Community impacts are mediated by the host range of the parasite (the diversity of species that can potentially act as hosts) and by their preference and selection of particular host species. Parasitic plants can also alter the physical environment around them – including soil water and nutrients, atmospheric CO2and temperature – and so may also be considered as ecosystem engineers. Such impacts can have further consequences in altering the resource supply to and behaviour of other organisms within parasitic plant communities.ContentsSummary737I.Introduction738II.Parasitism: direct consequences738III.Dynamics of parasite–host interactions: host range, preference and selection738IV.Impacts of parasitic plants on the plant community739V.Impacts of the plant community on parasite populations741VI.Impacts of the parasite on other trophic levels742VII.Impacts of the parasite on the abiotic environment747VIII.Concluding remarks748References748
Developmental Trends in Adolescent Suicidal Ideation
Authors: Rueter Martha A. , Kwon Hee‐Kyung
Published: May 2005

Research using retrospective or cross‐sectional data suggests that suicidal ideation rates peak during mid‐adolescence. This study used a longitudinal, community sample of adolescents who reported suicidal ideation repeatedly over 7 years to examine suicidal ideation trends. We hypothesized that a mid‐adolescence peak in ideation is limited to adolescents exposed to friends' or family members' suicidality. Ideation trends were compared across groups exposed and not exposed to others' suicidality and statistically assessed using growth curve analyses. Overall, ideation rates peaked at age 15 years. Group comparisons revealed that the peak was limited to adolescents whose parents reported suicidality.
Do Bank Relationships Affect the Firm's Underwriter Choice in the Corporate‐Bond Underwriting Market?
Authors: YASUDA AYAKO
Published: May 2005

This paper studies the effect of bank relationships on underwriter choice in the U.S. corporate‐bond underwriting market following the 1989 commercial‐bank entry. I find that bank relationships have positive and significant effects on a firm's underwriter choice,over and abovetheir effects on fees. This result is sharply stronger for junk‐bond issuers and first‐time issuers. I also find that there is a significant fee discount when there are relationships between firms and commercial banks. Finally, I find that serving as arranger of past loan transactions has the strongest effect on underwriter choice, whereas serving merely as participant has no effect.
Currency Returns, Intrinsic Value, and Institutional‐Investor Flows
Authors: FROOT KENNETH A. , RAMADORAI TARUN
Published: May 2005

We decompose currency returns into (permanent) intrinsic‐value shocks and (transitory) expected‐return shocks. We explore interactions between these shocks, currency returns, and institutional‐investor currency flows. Intrinsic‐value shocks are: dwarfed by expected‐return shocks (yet currency returns overreact to them); unrelated to flows (although expected‐return shocks correlate with flows); and related positively to forecasted cumulated‐interest differentials. These results suggest flows are related to short‐term currency returns, while fundamentals better explain long‐term returns and values. They also rationalize the long‐observed poor performance of exchange‐rate models: by ignoring the distinction between permanent and transitory exchange‐rate changes, prior tests obscure the connection between currencies and fundamentals.
What Determines the Domestic Bias and Foreign Bias? Evidence from Mutual Fund Equity Allocations Worldwide
Authors: CHAN KALOK , COVRIG VICENTIU , NG LILIAN
Published: May 2005

We examine how mutual funds from 26 developed and developing countries allocate their investment between domestic and foreign equity markets and what factors determine their asset allocations worldwide. We find robust evidence that these funds, in aggregate, allocate a disproportionately larger fraction of investment to domestic stocks. Results indicate that the stock market development and familiarity variables have significant, but asymmetric, effects on the domestic bias (domestic investors overweighting the local markets) and foreign bias (foreign investors under or overweighting the overseas markets), and that economic development, capital controls, and withholding tax variables have significant effects only on the foreign bias.
Predictive Value of Early Atrial Tachyarrhythmias Recurrence After Circumferential Anatomical Pulmonary Vein Ablation
Authors: BERTAGLIA EMANUELE , STABILE GIUSEPPE , SENATORE GAETANO , ZOPPO FRANCO , TURCO PIETRO , AMELLONE CLAUDIA , DE SIMONE ANTONIO , FAZZARI MASSIMO , PASCOTTO PIETRO
Published: May 2005

Objective: Radiofrequency (RF) ablation at the ostia of the pulmonary veins (PVs) to cure atrial fibrillation (AF) is often followed by early AF recurrence. The aims of this study were to determine the rate of early atrial tachyarrhythmia as recurrence after circumferential anatomical PV ablation; to evaluate whether the early recurrence of atrial tachyarrhythmias correlates with the long‐term outcome of ablation; and to identify the predictors of early atrial tachyarrhythmias relapse.

Methods: We studied 143 consecutive patients who underwent circumferential anatomical PV ablation. We defined early atrial tachyarrhythmias relapse as the recurrence of atrial tachyarrhythmias during the first 3 months after RF ablation.

Results: After a mean follow‐up of 18.7 ± 7.2 months, 102/143 patients (71%) were deemed responders to ablation. Atrial tachyarrhythmias relapsed during the first 3 months of follow‐up in 65/143 (46%) patients. Patients without early atrial tachyarrhythmias relapse had a higher probability of long‐term clinical success than patients with early atrial tachyarrhythmias relapse (95% vs 43%, P < 0.0001). However, patients who relapsed within the first month had 45.5% probability of long‐term clinical success. On multivariate analysis, the presence of structural heart disease and the lack of a successful anatomical ablation of all targeted PV were significantly and independently correlated with early atrial tachyarrhythmias relapse.

Conclusion: A delayed cure may be expected in almost 50% of patients in whom atrial tachyarrhythmias relapses within the first month after circumferential anatomical PV ablation. The presence of structural heart disease and the lack of a successful anatomical ablation of all targeted PV predict early atrial tachyarrhythmias recurrence.
Feasibility of Using an Implantable System to Measure Thoracic Congestion in an Ambulatory Chronic Heart Failure Canine Model
Authors: WANG LI , LAHTINEN STUART , LENTZ LINNEA , RAKOW NANCY , KASZAS CAMERON , RUETZ LINDA , STYLOS LEE , OLSON WALTER H.
Published: May 2005

Background: Noninvasive measures of impedance reflect alterations in thoracic fluid and pulmonary edema in acute animal and human studies.

Materials and Methods: We evaluated the feasibility of using an implantable impedance measuring device and cardiac lead system to monitor intrathoracic congestion in a pacing‐induced heart failure canine model. Three devices were implanted in each of five dogs: a modified pacemaker to measure impedance from a defibrillation lead implanted in the right ventricle; an implantable hemodynamic monitoring device to measure left ventricular end diastolic pressure (LVEDP) and a second pacemaker to deliver rapid (240 pulses per minute) ventricular pacing to induce heart failure.

Results: All five dogs developed severe heart failure after 3–4 weeks of rapid pacing and recovered following pacing termination. The LVEDP increased and impedance decreased during pacing‐induced heart failure and recovered after pacing cessation. At the end of pacing, there was a mean impedance reduction of 10.6 ± 8.3% and a mean LVEDP increase of 18.1 ± 4.5 mmHg compared to baseline. The impedance and LVEDP were inversely correlated (r =−0.41 to −0.85, all P < 0.05).

Conclusions: In the canine model, measurement of chronic intrathoracic impedance with an implantable system effectively revealed changes in thoracic congestion due to heart failure reflected by LVEDP. These data suggest that implantable device‐based impedance measurement merits further investigation as a tool to monitor the fluid status of heart failure patients.
Kearns‐Sayre Syndrome: A Case Report and Review of Cardiovascular Complications
Authors: YOUNG TIMOTHY J. , SHAH AMIT K. , LEE MUN HENG , HAYES DAVID L.
Published: May 2005

Kearns‐Sayre syndrome (KSS) is a rare genetic abnormality. Classified as a mitochondrial cytopathy, the primary pathology of this syndrome is a disturbance of mitochondrial DNA, which codes for the proteins required for the respiratory chain reaction. Onset occurs before age 20, and is manifest as chronic progressive external ophthalmoplegia and retinal degeneration. Management issues of KSS include prophylactic cardiac pacing for conduction defects, which has been shown to improve survival. Other clinical considerations relate to dietary supplements to attempt to control the progressive effects of the disease.
A ‘Reveal’ing Diagnosis
Authors: OSMAN FAIZEL , AHMAD RAJAI A. , DAVIS RUSSELL C. , CONNOLLY DEREK L. , CADIGAN PATRICK J.
Published: May 2005

The present case report describes a 54‐year‐old woman with recurrent syncope of undetermined etiology. Despite several cardiological and neurological investigations, no firm diagnosis was established until an insertable loop recorder (REVEAL® Plus Model 9526, Medtronic Inc., Minneapolis, MN, USA) revealed muscle twitch artifact secondary to a seizure disorder.
Comparing Policy Networks: Marine Protected Areas in California
Authors: Weible Christopher M. , Sabatier Paul A.
Published: May 2005

While most of the network literature focuses on information and advice networks, there is increasing interest—particularly among Advocacy Coalition Framework (ACF) scholars—on ally networks and coordination networks. This article asks two basic questions: First, do information, ally, and coordination networks overlap with each other? Second, and drawing from the ACF, do policy core beliefs structure the interactions in ally, coordination, and advice/information networks? We pursue these research questions in the context of the California Marine Life Protection Act process. We find that ally and coordination networks overlap slightly more than information/advice networks and that policy core beliefs do a better job of predicting ally and coordination networks than advice/information networks. Thus, we show that ally networks can provide a useful proxy for coordination networks to identify advocacy coalitions.
Control Over Government: Institutional Isomorphism and Governance Dynamics in German Public Administration
Authors: Lodge Martin , Wegrich Kai
Published: May 2005

The era of public management change is said to challenge traditional “command and control” modes of governance, encouraging a move toward either more informal forms of (co‐) governance or market‐type incentives and competition. Regardless of whether these claims are made by reform advocates or by more sceptical observers within the wider governance debate, less attention has been paid by either side on the mechanisms that are supposed to facilitate the spread of new forms of control. This article seeks to advance this state of affairs in two ways. First, it utilizes the notion of institutional isomorphism to explore the nature of change of modes of control. In particular, it assesses the mechanisms for change, whether control mechanisms are changing due to coercive, mimetic, or professional mechanisms. Second, it explores the impact of these mechanisms in the federal context of Germany in two policy domains, prison and local government supervision (in the field of building administration). Finally, this article suggests that cultural theory offers considerable insights for the study of institutional isomorphism by emphasizing conflicting worldviews and the diversity of related policy ideas as driving forces of change in modes of governance.
Effects of Autonomy, Performance Contracting, and Competition on the Performance of a Public Agency: A Case Study
Authors: Verhoest Koen
Published: May 2005

What effects do new control mechanisms have that governments use to monitor the performance of quasi‐autonomous public agencies? The control mechanisms under review are managerial autonomy, performance contracts, financial incentives, and competition. Using principal‐agent theory, a theoretical model is developed. In order to assess its value for further empirical research this model is then confronted with evidence of an in‐depth case study of a Flemish public agency, which encompasses two embedded cases. In this case, the four control mechanisms seem to induce the public agency to performance‐enhancing behavior through ways assumed in the theoretical model, but only under very specific conditions. The case study points to another and seemingly more fundamental motivation for such behavior, that is, the need of the public agency to strengthen or restore its legitimacy toward its customers and especially toward its political principals, when it is confronted with certain threats to legitimacy.
Governance and Performance: Theory‐Based Evidence from U.S. Coast Guard Inspections
Authors: Moffett Maurice , Bohara Alok K. , Gawande Kishore
Published: May 2005

Law enforcement by the U.S. Coast Guard (USCG) is characterized by soft penalties for safety violations, low incidence of penalties relative to the number of violations, and substantial resources devoted to inspections of vessels. Under what conditions can such an enforcement strategy be effective? And is it? This article seeks answers to these two questions. Harrington's (1988) model is motivated by such facts about U.S. regulation in general, and provides an answer to the first question via targeting of good and poor performers. The model generates hypotheses about optimal regulation in the context of pollution prevention activities of the USCG. In order to answer the second question, an organization‐level panel data set consisting of thousands of U.S. flag tank barges is constructed and those hypotheses tested. A count model that controls for vessel heterogeneity yields mixed evidence. If USCG inspections are considered exogenous variables (as the theory presumes), they appear to prevent pollution spills. But if inspections are endogenous and respond to previous spills, then correcting for endogeneity reverses the earlier result. In addition, violations are found to be good predictors of pollution occurrences, suggesting that inspections are not as effective as they could be. Targeting, as in Harrington's model, therefore appears to be incomplete, and the findings suggest that more complete targeting could increase performance. An interesting finding is that stronger penalties could increase performance.
COMMENTARY ON TIPPINS AND WITTMANN'S “EMPIRICAL AND ETHICAL PROBLEMS WITH CUSTODY RECOMMENDATIONS:
Authors: Kelly Joan B. , Johnston Janet R.
Published: May 2005

Although in substantial agreement with Tippins and Wittmann's analysis, their call for a moratorium on the practice of custody evaluators making recommendations to the court does not solve the many problems that they have raised, and may have unintended consequences which place families at even greater risk. This commentary reflects our agreement with some of the authors’ major points of contention, focuses on several points of disagreement, and suggests alternative remedies for the shortcomings and ethical problems described in child custody evaluations.
MEDITATION AND MEDIATION
Authors: Nobel Barry
Published: May 2005

Meditative disciplines, developed for millenia in wisdom traditions around the globe, may enrich a mediator's practice, bringing increased awareness and peace to practitioners and disputing parties alike. This article describes meditation generally, draws theoretical connections between meditation and mediation, and concludes by offering practical suggestions for integrating the two endeavors to increase a mediator's impartiality, humility, and compassion.
A Unified Approach to Analyze Vibration of Axisymmetric Rotating Structures with Flexible Stationary Parts
Authors: Tseng Chaw-Wu , Shen Jr-Yi , Kim Hyunchul , Shen I. Y.
Published: May 2005

This paper demonstrates a unified approach to analyze linear vibration of rotating machines with arbitrary geometry and complexity. In this formulation, the rotating machine consists of three components: a rotating part (rotor), a stationary part (stator or housing), and multiple bearings. The rotor is assumed axisymmetric and spinning at constant speed. Moreover, the rotor and the housing have arbitrary geometry and complexity. The bearings connecting the rotor and housing could be rolling-element bearings or hydrodynamic bearings. The paper consists of three major sections: mathematical modeling, integration with finite element analysis (FEA), and experimental verification. For the mathematical modeling, a stationary rotor with free boundary conditions is first discretized to obtain its normal vibration modes and modal parameters. In the meantime, the housing with its actual boundary conditions (but no bearings) is also discretized. The discretization can be achieved, for example, through FEA to accommodate arbitrary and complex geometry of the rotor and the housing. Because these vibration modes are complete, modal response of each mode can serve as a generalized coordinate to describe vibration of the actual spinning rotor and housing system. With these generalized coordinates, gyroscopic effects of the spinning rotor can be derived through material derivatives for a ground-based observer. As a result, application of Lagrange equation leads to a set of gyroscopic equations of motion with constant coefficients. These coefficients, however, contain complicated volume integrals of the mode shapes and their spatial derivatives. Therefore, algorithms are developed to calculate these coefficients explicitly from FEA. For the experimental verification, a ball-bearing spindle carrying a cylinder closed at one end is used to validate the mathematical model. Frequency response functions of the spindle/cylinder system are measured for spin speed ranging from 0 to 6000 rpm. Natural frequencies measured from the experiments agree very well with the theoretical predictions from the unified approach up to 2 kHz.
Wavelet Analysis of Stick-Slip Signals in Oscillators With Dry-Friction Contact
Authors: Liang Jin-Wei , Feeny Brian F.
Published: May 2005

Wavelet transforms were compared between various simulated friction models and real stick-slip data. While simulations of several models produced stick-slip transition oscillations seen in the real data, the wavelet features of the compliant contact model with light damping best captured the characteristics of the experimental signal. The wavelet contours were also used to estimate the contact stiffness.
Hydrostatic Gas Journal Bearings for Micro-Turbomachinery
Authors: Liu L. X. , Teo C. J. , Epstein A. H. , Spakovszky Z. S.
Published: May 2005

Several years ago an effort was undertaken at MIT to develop high-speed rotating MEMS (Micro Electro-Mechanical Systems) using computer chip fabrication technology. To enable high-power density the micro-turbomachinery must be run at tip speeds of order 500m∕s, comparable to conventional scale turbomachinery. The high rotating speeds (of order 2 million rpm), the relatively low bearing aspect ratios (L∕D<0.1) due to fabrication constraints, and the laminar flow regime in the bearing gap place the micro-bearing designs to an exotic spot in the design space for hydrostatic gas bearings. This paper presents a new analytical model for axially fed gas journal bearings and reports the experimental testing of micro gas bearings to characterize and to investigate their rotordynamic behavior. The analytical model is capable of dealing with all the elements of, (1) micro-devices, (2) dynamic response characteristics of hydrostatic gas bearings, (3) evaluation of stiffness, natural frequency and damping, (4) evaluation of instability boundaries, and (5) evaluation of effects of imbalance and bearing anisotropy. First, a newly developed analytical model for hydrostatic gas journal bearings is introduced. The model consists of two parts, a fluid dynamic model for axially fed gas journal bearings and a rotordynamic model for micro-devices. Next, the model is used to predict the natural frequency, damping ratio and the instability boundary for the test devices. Experiments are conducted using a high-resolution fiber optic sensor to measure rotor speed, and a data reduction scheme is implemented to obtain imbalance-driven whirl response curves. The model predictions are validated against experimental data and show good agreement with the measured natural frequencies and damping ratios. Last, the new model is successfully used to establish bearing operating protocols and guidelines for high-speed operation.
Investigation of the nanostructure and wear properties of physical vapor deposited CrCuN nanocomposite coatings
Authors: Baker M. A. , Kench P. J. , Tsotsos C. , Gibson P. N. , Leyland A. , Matthews A.
Published: May 2005

This article presents results on CrCuN nanocomposite coatings grown by physical vapor deposition. The immiscibility of Cr (containing a supersaturation of nitrogen) and Cu offers the potential of depositing a predominantly metallic (and therefore tough) nanocomposite, composed of small Cr(N) metallic and/or β-Cr2N ceramic grains interdispersed in a (minority) Cu matrix. A range of CrCuN compositions have been deposited using a hot-filament enhanced unbalanced magnetron sputtering system. The stoichiometry and nanostructure have been studied by x-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. Hardness, wear resistance, and impact resistance have been determined by nanoindentation, reciprocating-sliding, and ball-on-plate high-cycle impact. Evolution of the nanostructure as a function of composition and correlations of the nanostructure and mechanical properties of the CrCuN coatings are discussed. A nanostructure comprised of 1–3 nm α-Cr(N) and β-Cr2N grains separated by intergranular regions of Cu gives rise to a coating with significantly enhanced resistance to impact wear.
Discharge mode transitions in low-frequency inductively coupled plasmas with internal oscillating current sheets
Authors: Tsakadze Z. L. , Ostrikov K. , Tsakadze E. L. , Xu S.
Published: May 2005

Transitions between the two discharge modes in a low-frequency (∼460kHz) inductively coupled plasma sustained by an internal oscillating radio frequency (rf) current sheet are studied. The unidirectional rf current sheet is generated by an internal antenna comprising two orthogonal sets of synphased rf currents driven in alternately reconnected copper litz wires. It is shown that in the low-to-intermediate pressure range the plasma source can be operated in the electrostatic (E) and electromagnetic (H) discharge modes. The brightness of the E-mode argon plasma glow is found remarkably higher than in inductively coupled plasmas with external flat spiral “pancake” coils. The cyclic variations of the input rf power result in pronounced hysteretic variations of the optical emission intensity and main circuit parameters of the plasma source. Under certain conditions, it appears possible to achieve a spontaneous E→H transition (“self-transition”). The observed phenomenon can be attributed to the thermal drift of the plasma parameters due to the overheating of the working gas. The discharge destabilizing factors due to the gas heating and step-wise ionization are also discussed.
Using beam flux monitor as Langmuir probe for plasma-assisted molecular beam epitaxy
Authors: Wistey M. A. , Bank S. R. , Yuen H. B. , Harris J. S. , Oye M. M. , Holmes A. L.
Published: May 2005

We present a simple method for measuring the ion flux from a molecular beam epitaxy (MBE) plasma cell in real time. A Langmuir probe was created by attaching the beam flux monitor to a picoammeter and measuring the current impinging upon the collector or filament wires. This provides a noninvasive, convenient, and direct measure of ion flux at the actual wafer position, yet requires no internal changes to the MBE machine. Quantitative measurements of maximum ion energies and relative ion fluxes are possible. Real-time feedback from this measurement allows rapid optimization of the plasma for the minimum ion flux. This method is applicable to GaN and related materials, but is particularly important for growth of dilute nitrides. This was one of the techniques which led to the longest wavelength GaInNAs(Sb) vertical cavity surface emitting lasers and continuous wave edge emitting lasers on GaAs to date.
Batch process for atomic layer deposition of hafnium silicate thin films on 300-mm-diameter silicon substrates
Authors: Okuyama Yoshi , Barelli Carl , Tousseau Christopher , Park Seung , Senzaki Yoshihide
Published: May 2005

Atomic layer deposition (ALD) of hafnium silicate HfxSi1−xO2 thin films from tetrakis(ethylmethylamino)hafnium, tetrakis(ethylmethylamino)silicon, and ozone was accomplished onto 300-mm-diam Si substrates using a hot-wall furnace system with a 50-wafer batch configuration. For 23-nm-thick hafnium silicate, excellent film thickness uniformity with a mean within-wafer uniformity of 0.84% (1σ∕mean) and a wafer-to-wafer thickness uniformity of 0.80% (1σ∕mean) was achieved over the top, middle, and bottom wafers in the full batch process. Over three times enhancement in wafer-per-hour throughput per chamber was observed as compared with a single-wafer ALD module.
X-ray photoelectron spectroscopic observation on B–C–N hybrids synthesized by ion beam deposition of borazine
Authors: Uddin Md. Nizam , Shimoyama Iwao , Baba Yuji , Sekiguchi Tetsuhiro , Nagano Masamitsu
Published: May 2005

B–C–N hybrid thin films were grown from ion beam plasma of borazine (B3N3H6) on graphite substrate at room temperature, 600 °C, and 850 °C. The films were characterized in situ by x-ray photoelectron spectroscopy (XPS). XPS study suggested that B and N atoms in the deposited films are in a wide variety of chemical bonds, e.g., B–C, B–N, N–C, and B–C–N. The substrate temperature and ion fluence were shown to have a significant effect on the coordination and elemental binding states on the B–C–N hybrids. It was found that B–C–N hybrid formation is enhanced at high temperature, and this component is dominantly synthesized at low fluence. The results imply that it is possible to control the composition of B–C–N hybrid by changing the ion fluence and the temperature during ion implantation.
Comprehensive analysis of chlorine-containing capacitively coupled plasmas
Authors: Franz Gerhard
Published: May 2005

Capacitively coupled discharges of strongly reactive atmospheres containing mixtures of boron trichloride (BCl3) and chlorine (Cl2) are investigated employing spatially resolved Langmuir probe measurements, and three probes that are spatially integrating methods: optical emission spectroscopy (OES), self-excited electron resonance spectroscopy (SEERS), and impedance characteristics of the discharge. The analysis covers the pure gases including some mixtures, discharge pressure, and rf power over nearly two orders of magnitude, and their impact on important plasma parameters of “first order,” such as plasma density, plasma potential, electron temperature, temperature of the plasma bulk, electron collision rate with neutrals, and actual rf power coupled into the discharge. From these, other properties (electrical conductivity, capacitance, plasma bulk resistance, sheath resistance, and its electrically defined thickness) can be derived. Since the methods are partially complementary, a mutual control of the obtained data is made possible, and we finally obtain a self-consistent model for capacitive coupling connecting data obtained with electrical and optical probes. Compared to electropositive discharges of inert atomic gases (Ar) and molecular gases (H2), which are used as calibration standard for BCl3 and Cl2, the electron plasma density ne is definitely lower, whereas the electron temperature Te is significantly higher, which would be expected by electron attachment to the electronegative molecules—at least at higher discharge pressures. Furthermore, we compared values for Te and ne obtained with OES and SEERS, respectively, and with the Langmuir-probe system. The agreement in electron plasma density and electron temperature for Ar is surprisingly good, despite the fact that the electron energy distribution would be described with two temperatures. For argon plasma, the variation of the calculated dc conductivity for nearly pure capacitive coupling either from impedance measurements or SEERS is within 30%. This is a result of uncertainties in current path rather than principal faults of the various methods. For the reactive, molecular gases, however, the results vary significantly. These data serve to determine several derived properties. Among these, are the sheath thickness, which is compared with optical and electrical data, and the conductivity of the plasma bulk. As they are derived from simultaneous, but independent measurements, they confirm the relative simple model of an electropositive discharge (argon and argon/krypton), and stress the difficulty to describe plasmas consisting of electronegative constituents (Cl2, BCl3, and their mixtures) which is due mainly to a pressure-dependent transition from stochastic to ohmic heating and from electropositive to electronegative behavior.
Rarefied gas flow through a long tube of variable radius
Authors: Sharipov Felix , Bertoldo Guilherme
Published: May 2005

A method to calculate a mass flow rate of rarefied gas through a long tube of variable radius subject to arbitrary drops of pressure and temperature is proposed. The method is based on the results obtained previously on the basis of the kinetic equation and it requires very modest computational efforts. As a demonstration of its application some examples of isothermal and nonisothermal flows are given. The thermomolecular pressure difference for a variable radius tube is also considered.
Method and setup for photodesorption measurements for a nonevaporable-getter-coated vacuum chamber
Authors: Malyshev Oleg B. , Anashin Vadim V. , Dostovalov Rodion V. , Fedorov Nikita V. , Krasnov Alexander A. , Collins Ian R. , Ruzinov Vladimir L.
Published: May 2005

This article describes a method for measurement of the photodesorption yield and sticking probability for a vacuum chamber coated with nonevaporable getter (NEG). This method is based on a three-gauge method of measurement which was developed and used on a specially designed and assembled setup for the photodesorption yield measurements of test chambers. It has been modified for photodesorption measurements of a vacuum chamber with sorbing walls. Although a short description of the installation and the results of the photodesorption measurements with the NEG-coated vacuum chamber have been published [V. V. Anashin, I. R. Collins, R. V. Dostovalov, N. V. Fedorov, A. A. Krasnov, O. B. Malyshev, and V. L. Ruzinov, The 8th European Particle Accelerator Conference, Paris, France, 2002, p. 2550; Vacuum 75, 155 (2004)], the details of the method, the analysis, and the experimental setup are also described in this article. Special attention is paid to define the sensitivity limit of the method and the setup and to reduce electron- and photon-stimulated desorption in the measurement port.
Axial-symmetric transmission gauge: Extension of its pressure measuring range and reduction of the electron stimulated desorption ion effect in ultrahigh vacuum
Authors: Takahashi N. , Yuyama J. , Tuzi Y. , Akimichi H. , Arakawa I.
Published: May 2005

The basic characteristics of the axial-symmetric transmission gauge (AT gauge), that were modified for measurement over a wide pressure range, are reported. A Faraday cup ion collector is used instead of a secondary electron multiplier to extend the measurable pressure range to 10−3Pa. The sensitivity of the gauge was determined by a conductance modulation method, and by direct comparison against an extractor gauge and a spinning rotor gauge as well. When operating in O2, there was systematic disagreement between pressure readings with the AT gauge and the extractor gauge. This is due to the difference in the elimination efficiency of the electron stimulated desorption ion.
Relationship between pH and Medium Dissolved Solids in Terms of Growth and Metabolism of Lactobacilli andSaccharomyces cerevisiaeduring Ethanol Production
Authors: Narendranath Neelakantam V. , Power Ronan
Published: May 2005

The specific growth rates of four species of lactobacilli decreased linearly with increases in the concentration of dissolved solids (sugars) in liquid growth medium. This was most likely due to the osmotic stress exerted by the sugars on the bacteria. The reduction in growth rates corresponded to decreased lactic acid production. Medium pH was another factor studied. As the medium pH decreased from 5.5 to 4.0, there was a reduction in the specific growth rate of lactobacilli and a corresponding decrease in the lactic acid produced. In contrast, medium pH did not have any significant effect on the specific growth rate of yeast at any particular concentration of dissolved solids in the medium. However, medium pH had a significant (P< 0.001) effect on ethanol production. A medium pH of 5.5 resulted in maximal ethanol production in all media with different concentrations of dissolved solids. When the data were analyzed as a 4 (pH levels) by 4 (concentrations of dissolved solids) factorial experiment, there was no synergistic effect (P> 0.2923) observed between pH of the medium and concentration of dissolved solids of the medium in reducing bacterial growth and metabolism. The data suggest that reduction of initial medium pH to 4.0 for the control of lactobacilli during ethanol production is not a good practice as there is a reduction (P< 0.001) in the ethanol produced by the yeast at pH 4.0. Setting the mash (medium) with ≥30% (wt/vol) dissolved solids at a pH of 5.0 to 5.5 will minimize the effects of bacterial contamination and maximize ethanol production by yeast.
Quantification of Enterococci and Human Adenoviruses in Environmental Samples by Real-Time PCR
Authors: He Jian-Wen , Jiang Sunny
Published: May 2005

Pathogenic bacteria and enteric viruses can be introduced into the environment via human waste discharge. Methods for rapid detection and quantification of human viruses and fecal indicator bacteria in water are urgently needed to prevent human exposure to pathogens through drinking and recreational waters. Here we describe the development of two real-time PCR methods to detect and quantify human adenoviruses and enterococci in environmental waters. For real-time quantification of enterococci, a set of primers and a probe targeting the 23S rRNA gene were used. The standard curve generated using
Enterococcus faecalis
genomic DNA was linear over a 7-log-dilution series. Serial dilutions of
E. faecalis
suspensions resulted in a lower limit of detection (LLD) of 5 CFU/reaction. To develop real-time PCR for adenoviruses, degenerate primers and a Taqman probe targeting a 163-bp region of the adenovirus hexon gene were designed to specifically amplify 14 different serotypes of human adenoviruses, including enteric adenovirus serotype 40 and 41. The standard curve generated was linear over a 5-log-dilution series, and the LLD was 100 PFU/reaction using serial dilutions of purified adenoviral particles of serotype 40. Both methods were optimized to be applicable to environmental samples. The real-time PCR methods showed a greater sensitivity in detection of adenoviruses in sewage samples than the viral plaque assay and in detection of enterococci in coastal waters than the bacterial culture method. However, enterococcus real-time PCR overestimated the number of bacteria in chlorinated sewage in comparison with the bacterial culture method. Overall, the ability via real-time PCR to detect enterococci and adenoviruses rapidly and quantitatively in the various environmental samples represents a considerable advancement and a great potential for environmental applications.
Deuterium-Resistant Algal Cell Line for D Labeling of Heterotrophs Expresses Enhanced Level of Hsp60 in D2O Medium
Authors: Unno Keiko , Hagima Naoko , Kishido Takahiro , Okada Shoji , Oku Naoto
Published: May 2005

Fully deuterated components from autotrophic cell lysate are useful materials for labeling of heterotrophs with deuterium. To facilitate the faster production of deuterated algal lysate, we selected a mutantChlorellastrain that grows faster in heavy water than the wild type. The mutant DR-17 was found to have a higher level of Hsp60 and an elevated level of protein synthesis. We previously isolated a deuterium-resistant yeast cell line that was also found to express elevated level of Hsp70 (K. Unno, T. Kishido, M. Morioka, S. Okada, and N. Oku, Biol. Pharm. Bull.26:799-802, 2003). This suggests that the overexpression of heat shock proteins is required to compensate for the deuterium isotope effect.
Seasonal Response of Stream Biofilm Communities to Dissolved Organic Matter and Nutrient Enrichments
Authors: Olapade Ola A. , Leff Laura G.
Published: May 2005

Dissolved organic matter (DOM) and inorganic nutrients may affect microbial communities in streams, but little is known about the impact of these factors on specific taxa within bacterial assemblages in biofilms. In this study, nutrient diffusing artificial substrates were used to examine bacterial responses to DOM (i.e., glucose, leaf leachate, and algal exudates) and inorganic nutrients (nitrate and phosphate singly and in combination). Artificial substrates were deployed for five seasons, from summer 2002 to summer 2003, in a northeastern Ohio stream. Differences were observed in the responses of bacterial taxa examined to various DOM and inorganic nutrient treatments, and the response patterns varied seasonally, indicating that resources that limit the bacterial communities change over time. Overall, the greatest responses were to labile, low-molecular-weight DOM (i.e., glucose) at times when chlorophyll
a
concentrations were low due to scouring during significant storm events. Different types of DOM and inorganic nutrients induced various responses among bacterial taxa in the biofilms examined, and these responses would not have been apparent if they were examined at the community level or if seasonal changes were not taken into account.
Production of Rhamnolipids by
Pseudomonas chlororaphis
, a Nonpathogenic Bacterium
Authors: Gunther Nereus W. , Nuñez Alberto , Fett William , Solaiman Daniel K. Y.
Published: May 2005

Rhamnolipids, naturally occurring biosurfactants constructed of rhamnose sugar molecules and β-hydroxyalkanoic acids, have a wide range of potential commercial applications. In the course of a survey of 33 different bacterial isolates, we have identified, using a phenotypic assay for rhamnolipid production, a strain of the nonpathogenic bacterial species
Pseudomonas chlororaphis
that is capable of producing rhamnolipids. Rhamnolipid production by
P. chlororaphis
was achieved by growth at room temperature in static cultures of a mineral salts medium containing 2% glucose. We obtained yields of roughly 1 g/liter of rhamnolipids, an amount comparable to the production levels reported in
Pseudomonas aeruginosa
grown with glucose as the carbon source. The rhamnolipids produced by
P. chlororaphis
appear to be exclusively the mono-rhamnolipid form. The most prevalent molecular species had one monounsaturated hydroxy fatty acid of 12 carbons and one saturated hydroxy fatty acid of 10 carbons.
P. chlororaphis
, a nonpathogenic saprophyte of the soil, is currently employed as a biocontrol agent against certain types of plant fungal diseases. The pathogenic nature of all bacteria previously known to produce rhamnolipids has been a major obstacle to commercial production of rhamnolipids. The use of
P. chlororaphis
therefore greatly simplifies this matter by removing the need for containment systems and stringent separation processes in the production of rhamnolipids.
Nested PCR-Denaturing Gradient Gel Electrophoresis Approach To Determine the Diversity of Sulfate-Reducing Bacteria in Complex Microbial Communities
Authors: Dar Shabir A. , Kuenen J. Gijs , Muyzer Gerard
Published: May 2005

Here, we describe a three-step nested-PCR-denaturing gradient gel electrophoresis (DGGE) strategy to detect sulfate-reducing bacteria (SRB) in complex microbial communities from industrial bioreactors. In the first step, the nearly complete 16S rRNA gene was amplified using bacterial primers. Subsequently, this product was used as a template in a second PCR with group-specific SRB primers. A third round of amplification was conducted to obtain fragments suitable for DGGE. The largest number of bands was observed in DGGE patterns of products obtained with primers specific for the
Desulfovibrio-Desulfomicrobium
group, indicating a large diversity of these SRBs. In addition, members of other phylogenetic SRB groups, i.e.,
Desulfotomaculum
,
Desulfobulbus
, and
Desulfococcus-Desulfonema-Desulfosarcina
, were detected. Bands corresponding to
Desulfobacterium
and
Desulfobacter
were not detected in the bioreactor samples. Comparative sequence analysis of excised DGGE bands revealed the identity of the community members. The developed three-step PCR-DGGE strategy is a welcome tool for studying the diversity of sulfate-reducing bacteria.
Chemical Forms of Selenium in the Metal-Resistant Bacterium
Ralstonia metallidurans
CH34 Exposed to Selenite andSelenate
Authors: Sarret Géraldine , Avoscan Laure , Carrière Marie , Collins Richard , Geoffroy Nicolas , Carrot Francine , Covès Jacques , Gouget Barbara
Published: May 2005

Ralstonia
metallidurans
CH34, a soil bacterium resistant to a
variety of metals, is known to reduce selenite to
intracellular granules of elemental selenium (Se
0
). We have
studied the kinetics of selenite (Se
IV
) and selenate
(Se
VI
) accumulation and used X-ray absorption spectroscopy
to identify the accumulated form of selenate, as well as possible
chemical intermediates during the transformation of these two
oxyanions. When introduced during the lag phase, the presence of
selenite increased the duration of this phase, as previously
observed. Selenite introduction was followed by a
period of slow uptake, during which the bacteria contained
Se
0
and alkyl selenide in equivalent proportions. This
suggests that two reactions with similar kinetics take place:
an assimilatory pathway leading to alkyl selenide and a slow
detoxification pathway leading to Se
0
. Subsequently,
selenite uptake strongly increased (up to 340 mg Se per g of proteins)
and Se
0
was the predominant transformation product,
suggesting an activation of selenite transport and reduction systems
after several hours of contact. Exposure to selenate did not induce an
increase in the lag phase duration, and the bacteria accumulated
approximately 25-fold less Se than when exposed to selenite.
Se
IV
was detected as a transient species in the first
12 h after selenate introduction, Se
0
also
occurred as a minor species, and the major accumulated form was alkyl
selenide. Thus, in the present experimental conditions, selenate mostly
follows an assimilatory pathway and the reduction
pathway is not activated upon selenate exposure. These results show
that
R. metallidurans
CH34 may be suitable for the
remediation of selenite-, but not selenate-, contaminated
environments.
LuxS-Based Signaling Affects
Streptococcus mutans
Biofilm Formation
Authors: Yoshida Akihiro , Ansai Toshihiro , Takehara Tadamichi , Kuramitsu Howard K.
Published: May 2005

Streptococcus mutans
is implicated as a major etiological agent in human dental caries, and one of the important virulence properties of this organism is its ability to form biofilms (dental plaque) on tooth surfaces. We examined the role of autoinducer-2 (AI-2) on
S. mutans
biofilm formation by constructing a GS-5
luxS
-null mutant. Biofilm formation by the
luxS
mutant in 0.5% sucrose defined medium was found to be markedly attenuated compared to the wild type. Scanning electron microscopy also revealed that biofilms of the
luxS
mutant formed larger clumps in sucrose medium compared to the parental strain. Therefore, the expression of glucosyltransferase genes was examined and the
gtfB
and
gtfC
genes, but not the
gtfD
gene, in the
luxS
mutant were upregulated in the mid-log growth phase. Furthermore, we developed a novel two-compartment system to monitor AI-2 production by oral streptococci and periodontopathic bacteria. The biofilm defect of the
luxS
mutant was complemented by strains of
S. gordonii
,
S. sobrinus
, and
S. anginosus
; however, it was not complemented by
S. oralis
,
S. salivarius
, or
S. sanguinis
. Biofilm formation by the
luxS
mutant was also complemented by
Porphyromonas gingivalis
381 and
Actinobacillus actinomycetemcomitans
Y4 but not by a
P. gingivalis luxS
mutant. These results suggest that the regulation of the glucosyltransferase genes required for sucrose-dependent biofilm formation is regulated by AI-2. Furthermore, these results provide further confirmation of previous proposals that quorum sensing via AI-2 may play a significant role in oral biofilm formation.
Reduced Genetic Variation Occurs among Genes of the Highly Clonal Plant Pathogen
Xanthomonas axonopodis
pv. vesicatoria, Including the Effector Gene
avrBs2
Authors: Wichmann Gale , Ritchie David , Kousik C. S. , Bergelson Joy
Published: May 2005

The bacterial plant pathogen
Xanthomonas axonopodis
pv. vesicatoria, also known as
Xanthomonas campestris
pv. vesicatoria group A, is the causal agent of bacterial spot in pepper and tomato. In order to test different models that may explain the coevolution of
avrBs2
with its host plants, we sequenced
avrBs2
and six chromosomal loci (total of 5.5 kb per strain) from a global sample of 55
X. axonopodis
pv. vesicatoria strains collected from diseased peppers. We found an extreme lack of genetic variation among all
X. axonopodis
pv. vesicatoria genomic loci (average nucleotide diversity, π = 9.1 × 10
−5
), including
avrBs2
. This lack of diversity is consistent with
X. axonopodis
pv. vesicatoria having undergone a recent population bottleneck and/or selective sweep followed by population expansion. Coalescent analysis determined that approximately 1.4 × 10
4
to 7.16 × 10
4
bacterial generations have passed since the most recent common ancestor (MRCA) of the current
X. axonopodis
pv. vesicatoria population. Assuming a range of 50 to 500 bacterial generations per year, only 28 to 1,432 years have passed since the MRCA. This time frame coincides with human intervention with the pathogen's host plants, from domestication to modern agricultural practices. Examination of 19 mutated (loss-of-function)
avrBs2
alleles detected nine classes of mutations. All mutations affected protein coding, while no synonymous changes were found. The nature of at least one of the
avrBs2
mutations suggests that it may be possible to observe one stage of an evolutionary arms race as
X. axonopodis
pv. vesicatoria responds to selection pressure to alter
avrBs2
to escape host plant resistance.