bluuebunny/crossref_metadata_2025 huggingface dataset:
Compositions and Microstructures of the Primary Ceramic Materials in the Paleolithic Age Through XRD, SEM, and TEM Analyses
Authors: Yonekura Kaoru , Suzuki Tetsuya , Hashimoto Ayako , Hasegawa Hiroyuki
Published: September 2005

The mineral compositions and microstructures of Paleolithic materials were first investigated by X‐ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy in order to understand the primary ceramic material in human history. Shale and chalcedony artifacts excavated from upper Paleolithic sites were analyzed. As a result, from among various candidates with nonuniform mineral compositions, only limited materials containing polycrystals with approximately more than 95%α‐quartz content were selected as tool materials. Moreover, every Paleolithic material invariably exhibited densely packed and homogeneous micrograins approximately 0.1–0.5 μm in size and an equigranular structure with few porosities at the grain boundaries.
Human ATP‐dependent RNA/DNA helicase hSuv3p interacts with the cofactor of survivin HBXIP
Authors: Minczuk Michal , Mroczek Seweryn , Pawlak Sebastian D. , Stepien Piotr P.
Published: September 2005

The human SUV3gene encodes an NTP‐dependent DNA/RNA DExH box helicase predominantly localized in mitochondria. Its orthologue in yeast is a component of the mitochondrial degradosome complex involved in the mtRNA decay pathway. In contrast to this, the physiological function of human SUV3 remains to be elucidated. In this report we demonstrate that the hSuv3 protein interacts with HBXIP, previously identified as a cofactor of survivin in suppression of apoptosis and as a protein that binds the HBx protein encoded by the hepatitis B virus. Using deletion analysis we identified the region within the hSuv3 protein, which is responsible for binding to HBXIP. The HBXIP binding domain was found to be important for mitochondrial import and stability of the Suv3 protein in vivo. We discuss the possible involvement of the hSuv3p–HBXIP interaction in the survivin‐dependent antiapoptotic pathway.
A simulation model of mire patterning – revisited
Authors: Couwenberg John
Published: September 2005

The development of regular, oriented hummock‐hollow or string‐flark patterns in boreal peatlands can be explained by a simple spatially explicit model in which hummocks have a lower hydraulic conductivity than hollows and are more likely to occur at lower water levels. Revisiting a previously published model, the function used to simulate water flow is shown to be faulty. Nevertheless, the corrected model confirms the general conclusions of the original paper, showing the robustness of the approach.

Five phases can be discerned in the development of the pattern. Once the hummock strings reach from left to right across the grid, there is an increase in the volume of water stored in the system. The number of hummocks and hollows differs substantially from what would be expected based on the mean water level, showing that their arrangement is more important than the actual number of hummocks.

Parameter settings at which a pattern develops are sharply delineated, indicating there is a positive feedback mechanism that enhances initial patterning. Like in natural mire systems, the patterns anastomose and merge. In contrast to what is generally assumed for natural systems, the patterns show a distinct downward movement.
Computer Models for Concert Hall Acoustics
Authors: Schroeder M. R.
Published: September 2005

The design of a successful concert hall continues to be a difficult task. But recent applications of computer model studies combined with new methods of quantifying personal preference and subjective quality promise to make “the acoustics” of future halls more predictable and satisfactory.
The Brattsev-Epstein Theorem Applied to the Ground State Energy of a Molecule
Authors: Inagaki Takashi
Published: September 2005

A simple instructive demonstration of the Brattsev-Epstein theorem is presented. The theorem can be verified rigorously for the ground state energies of a coupled oscillator calculated exactly and in the adiabatic approximation.
Measurements of Reflected and Transmitted Energies Near the Critical Angle
Authors: Shaw D. E. , Hones M. J. , Wunderlich F. J.
Published: September 2005

We describe a quantitative experiment for an advanced laboratory in physical optics or electromagnetism. The experiment utilizes simple, readily available equipment and affords the student an opportunity to study the wellknown phenomenon of critical angle reflection. The percentage of reflected and transmitted radiation is measured as a function of the angle of incidence for plane polarized radiation. The results are then compared with the predictions of electromagnetic theory.
An Interdisciplinary Graduate Curriculum in Scientific Instrumentation
Authors: Elings V. , Phillips D.
Published: September 2005

An interdisciplinary master's degree program in scientific instrumentation has been developed in which students participate in the work of a variety of laboratories doing research in biology, chemistry, engineering, physiology, and physics. The program accepts students from all sciences. Training with contemporary electronic devices and methods has enabled the students to contribute effectively to laboratory research in areas quite different from their undergraduate training. Experience has shown that students have been highly motivated by instrumentation projects which contribute to real research work and much less interested informal lecture courses.
A Model for the Dielectric Aftereffect in Coaxial Geometry
Authors: Sevenich R. A.
Published: September 2005

A simple space charge polarization model for the dielectric aftereffect is developed. Expressions for the time dependence of the current density and resistivity are derived neglecting diffusion currents.
On the Theory of the Electromagnetic Field of a Moving Charged Particle in a Dielectric
Authors: Van Laak J. W.
Published: September 2005

The problem investigated is that of a charged particle traveling in the x, y plane in a dielectric. The electric field in the dielectric resulting from such a motion has been determined in the past using two methods, one employing Maxwell's equations for an electromagnetic field in the dielectric and another based on a molecular model in which the field in the dielectric is calculated from an interaction picture between the incident vacuum field and the molecular system. Recently, Lalor and Wolf (1971) derived on the basis of the molecular model some new laws relating to the field generated by a charge executing two-dimensional motion in a dielectric. In this paper it is shown that the same results can also be derived using Maxwell's equations.
Nerve Conduction in the Pre-Medical Physics Course
Authors: Hobbie Russell K.
Published: September 2005

The steady state electrical behavior of a nerve subjected to small signals provides an example of voltage attenuation in a resistance ladder. If capacitive effects are included, the nerve is similar to a cable with capacitance but without inductance. Discussion of the steady state problem is within the scope of a noncalculus general physics course, and students going into medicine or the life sciences would benefit from such a treatment. This paper introduces physics teachers to the basic properties of a nerve axon, the networks analogous to it, and the regenerative changes in the electrical properties of the nerve membrane which accompany the propagation of the action potential. These have been known to physiologists for over twenty years but are rarely discussed in physics courses.
Science and Society Test for Physicists: The Arms Race
Authors: Hafemeister David
Published: September 2005

A “Science and Society Test” which deals with questions (and the author's answers) of the arms race is presented. The test stresses historical facts and back-of-the-envelope questions which most academic physics professors should be able to answer. The results have been somewhat disappointing. It is suggested here that a question-answer format can be used to transmit science and society subject matter effectively.
General Physics Course for Pre-medical Students
Authors: Argos Patrick
Published: September 2005

A noncalculus, two-semester general physics course for pre-medical students is described. The biophysical examples used in the course are listed, lectures outlined, and comprehensive references given. The course emphasis is to convince the student of the relevance of his physical knowledge in biology and medicine and to take a clear, in-depth approach to a few biophysical topics utilizing physical concepts and equations discussed in recent lectures. No attempt is made to cover the wide spectrum of medical or biological physics.
An Experiment on Electronic Noise in the Freshman Laboratory
Authors: Livesey D. L. , McLeod D. L.
Published: September 2005

A simple method is described for investigating the shot-noise voltage developed across a resistor in series with a saturated thermionic diode. By measuring the ratio of the shot-noise voltage per unit current to the thermal noise in the same resistor, the effect of the amplifier bandwidth is eliminated and the ratio of the elementary charge to Boltzmann's constant is readily evaluated.
On the Propagation of a Pulse through a Dispersive Medium
Authors: Jones J.
Published: September 2005

The problem of the behavior of a pulse when propagating through a dispersive medium has been treated in terms of Fourier transforms. For a linearly dispersive medium the evaluation of the integrals is trivial, but when the dispersion relation contains a significant quadratic term the integrals can be evaluated using the properties of Fresnel integrals. The advantage of this treatment is that it shows that there is a very strong analogy between the pulse shape and the diffraction pattern produced when light passes through a small hole in an opaque screen.
Non-Colinearity of Angular Velocity and Angular Momentum
Authors: Burr A. F.
Published: September 2005

There is described the principle, construction, and operation of a simple apparatus to demonstrate the non-colinearity of the angular velocity vector and the angular momentum vector. Some details of the theory are given, as are complete details for the construction and operation of the apparatus. The apparatus is useful for individual or group demonstrations and helps students increase their understanding of angular velocity, angular momentum, and the inertial tensor.
Microwave Diffraction Techniques from Macroscopic Crystal Models
Authors: Murray William Henry
Published: September 2005

This project concerns itself with the diffraction of microwave radiation from the three dimensional planes of a macroscopic crystal model. A study of earlier activities indicates that microwave diffraction studies on ordered matrices have been done on model systems that do not represent crystals but only accurately spaced reflecting surfaces. In order to demonstrate diffraction techniques from macroscopic crystal structures, it was assumed that: (1) the reflecting surfaces of a working model could be embedded within a styrofoam ball model that represented the supposed shape of the atom or ion, and (2) microwave energy reflected from a surface is proportional to the surface area of that surface as is the x-ray energy reflected proportional to the atomic number of the atom or ion for small angles of incidence. The analysis of x-ray diffraction data concerns itself with Bragg angle measurements and the intensity of the Bragg reflections. Intensity results from macroscopic models have previously not been reported. In addition to the quantitative results obtained for the Bragg angles, qualitative results for intensity measurements could not be expected from a macroscopic model since: (1) The lack of collimators and filters for the microwave source permitted other than parallel monochromatic wavefronts; and (2) only a limited number of unit cells are possible if a reasonable sized model is to be preserved. The laboratory investigations, prepared to utilize the equipment developed in the classroom, serve also to introduce the computer as a teaching and problem-solving aid. The study indicates that crystal models can be built with structural alterations and doping that can be detected with microwave techniques. Additional laboratory investigations and the existing computer programs can be utilized to study the properties of imperfect crystals in the classroom.
Simple Method for Fitting Data when Both Variables Have Uncertainties
Authors: Barker David R. , Diana L. M.
Published: September 2005

The problem of fitting data when both variables have uncertainties is discussed, and the insufficiency of the usual least-squares calculation which does not take into account uncertainties in both variables is demonstrated. An approximate least-squares method for fitting polynomials to data which contain uncertainties in both variables is presented. The excellent results of the approximate method are compared in three illustrative examples with the results of other methods.
Virial Theorem Generalized
Authors: McLellan A. G.
Published: September 2005

The quantum mechanical virial theorem as usually stated is correct only for a bound state of an unconfined system, because the proof depends on the vanishing not only of ψ but also of δψ/δxα at the bounding surface. The correct form is given and used to deduce the equation of state. A generalized form of the virial theorem is deduced for both quantum and classical mechanics, which may be used to obtain nonhydrostatic equations of state, i.e., expressions for the Cauchy stress tensor.
Evolution from Two Perspectives: An Interdisciplinary Course in Physics and Anthropology
Authors: Schwartz Joseph , Ragir Sonia
Published: September 2005

We describe an interdisciplinary course for senior students in the physical, biological, and social sciences. The unifying theme is evolution and evolutionary theories in physics and anthropology. Our experience from three years of teaching such a course is that this format is excellent for the purpose of introducing undergraduates to a more realistic view of scientific work than they would normally encounter and for exploring in an unusual way the scientific method and how it is expressed in our culture.
Singing Corrugated Pipes
Authors: Crawford Frank S.
Published: September 2005

A corrugated tube open at both ends, with air flowing through the tube, sings notes which depend on the flow velocity and the length of the tube. The notes it sings are the natural harmonics of the tube. A given note will sing when the flow velocity is such that the “bump frequency” (frequency at which the air bumps into the corrugations) equals the frequency of the note, provided also that the flow velocity is sufficiently high to induce turbulent flow. For some tube diameters and corrugation lengths the critical minimum Reynolds number that I observe for singing agrees with the classical result Rmin = 2000 observed by Reynolds for turbulent flow in smooth tubes. For other lubes I observe singing at much smaller values of R. Three new musical instruments are described: the Water Pipe, the Gas-Pipe Corrugahorn Bugle, and the Gas-Pipe Blues Corrugahorn.
Self-Excited, Alternating, High-Voltage Generation Using a Modified Electrostatic Influence Machine
Authors: Zahn Markus , Goslin Richard L. , Wicks Larry F.
Published: September 2005

The principles of the classic rotary Wimshurst machine, which produces dc high voltage by regenerative electrostatic induction, are used to develop a new alternating high-voltage machine. This device has no electrical inputs but can spontaneously produce either dc or three-phase ac high voltage, depending on external connections. The machine constructed by the authors produces voltages in excess of 18 kV with frequencies of operation up to 2 Hz. Improved design can extend the voltage and frequency operating ranges. Analysis is extended to include multiphase, multi-frequency operation by modeling the device with a distributed equivalent circuit representation. The natural frequencies of the system are calculated where it is found that many overstable modes are present.
Determination of Particle Size by Diffraction of Light
Authors: Rinard Phillip M.
Published: September 2005

In order to illustrate to high school students the relation of science to society, a simplified optical experiment was used in a workshop to determine an approximate size of cigarette smoke particles. The significance of particulate matter suspended in the atmosphere was discussed. The details of the apparatus and the experiment are given in this paper.
Orbits in the Solar Wind—a Mini-Research Problem
Authors: Luehrmann Arthur W.
Published: September 2005

A remarkable motion occurs when a classical inverse-square-law orbit is perturbed by a weak uniform force field in the orbital plane. The bizarre nature of the motion, together with the fact that most physicists and physics teachers have never seen or been aware of it, make it an ideal topic for independent research at the undergraduate level. Several modes of attack on the problem are suggested. They proceed from experimentation on a computer simulation, through analytic approximations, to closed-form solutions. A quantum mechanical treatment is also suggested.
A Light Flasher and Its Use in the Elementary Mechanics Laboratory
Authors: Wood G. Theodore
Published: September 2005

A light flasher has been developed for use with the open-shutter photography technique in elementary-mechanics experiments. The unit operates on two AAA-type batteries with a flash rate that can be made independent of battery potential. One to three lamps can be driven by a single flasher making it possible to determine, for example, the angular displacement of a puck as well as its position on an air table. One model of the flasher is integrally mounted on an air puck and provides space to mount ring magnets for experiments involving magnetic interaction. Several applications of the flasher circuit are discussed.
Musical Pitch Variations Caused by the Doppler Effect
Authors: Kelly Robert E.
Published: September 2005

An analysis is made of the change in pitch expected because of relative motion of a musical performance and a listener. The Doppler shift is combined with the cent as a measure of musical intervals, to result in an equation giving pitch changes as a function of velocity. The results show a typical pitch variation of 2.25 cents/mph; 3 cents is approximately the minimum detectable interval for the ear. Wind, temperature, and humidity have negligible effects. Brief discussions of reflections, arbitrary observation angles, and loudness effects are included, along with small asymmetries inherent in the Doppler shift.
Fluctuations in Particle Number in a Grand Canonical Ensemble of Small Systems
Authors: Stephenson John
Published: September 2005

The extraction of the basic equations of thermodynamics for a grand canonical ensemble of small systems is reviewed briefly. A modified formula for the fluctuation in the number of particles in a small system, for which the extensive property may not hold, is derived in terms of the isothermal compressibility.
Definitions of Electromagnetic Field Quantities
Authors: Page Chester H.
Published: September 2005

A logically consistent set of definitions of the electromagnetic field quantities is extremely difficult to find in the literature. Most textbooks either evade the problem, or present definitions that are applicable only to special cases. A philosophy of this problem is presented, and a consistent system developed.
Physicist+Geologist→Geophysics Course
Authors: Julian Glenn M. , Stueber Alan M.
Published: September 2005

A two-quarter introductory course in geophysics at the advanced undergraduate/beginning graduate level is described. Development and teaching of the course have been shared by a physicist and a geologist. The course aims primarily to provide a broad picture of the earth in terms of the physical processes which shape it. After a brief section on introductory geology, the topics covered are geochronology, origin and chronology of the solar system, gravity, seismology, heat, the earth's magnetic field and paleomagnetism, and geotectonics. Extensive use is made of students' previous background in mathematics and physics.
Molecular Dissociation Model
Authors: Falk H.
Published: September 2005

A two-particle model is discussed within the framework of classical, equilibrium statistical mechanics. The model is shown to exhibit behavior associated with the dissociation (or formation) of a diatomic molecule.
Reaction Rates and the T-Matrix
Authors: Opat Geoffrey I.
Published: September 2005

A fully covariant expression is given for the rate of an arbitrary reaction based on the theory of special relativity and the superposition principle of quantum mechanics. The expression gives all phase-space and flux factors explicitly from a unified viewpoint. A useful concept, covariant beam strength, is introduced. Application is made to decay rates, cross sections, and beam-beam collisions.
Car-Crash Experiment for the Undergraduate Laboratory
Authors: Ball Penny L. , Doolen Gary D. , Fry Edward S. , Wedin Marion D.
Published: September 2005

An interesting, inexpensive, and highly motivating experiment for the undergraduate laboratory has been developed. Uniform and accelerated motion is studied in this experiment by measuring the position of a car as a function of time as it crashes into a rigid wall. The data are obtained from a sequence of pictures made by high speed cameras which recorded the actual crash.
Simple Models of Injecting Metal-Insulator Contacts
Authors: Murgatroyd P. N.
Published: September 2005

This paper compares some elementary theories of the electron-injecting contact made by a metal to an insulator having larger work function. The subject is usually introduced with a one-band model including only electronic space charge. It is shown that a two-band model is preferable physically, and scarcely more complicated mathematically, and so provides a more satisfactory starting point.
Time Dependence of the Internal Excitation of an Oscillator in a Coulomb Field
Authors: Campo J. Gómez Del , Santibáñez F. García , Flores J.
Published: September 2005

In heavy-ion scattering only some of the internal degrees of freedom of the interacting nuclei are excited because of the long-range Coulomb interaction. In this note we discuss a very simple one-dimensional classical system which is useful in understanding some of the features of the above process. Both a qualitative and a numerical analysis of the classical system are given.
Larmor and the Prehistory of the Lorentz Transformations
Authors: Kittel C.
Published: September 2005

A historical analysis is given of the development by Larmor in 1900 of the Lorentz transformations of coordinates and time, and of electric and magnetic field components. The earlier work of Voigt is discussed.
Practice-Teaching Program in Physics for Future Elementary School Teachers
Authors: McDermott Lillian C.
Published: September 2005

A practice-teaching program directly related to a physics course for future elementary school teachers has been developed. Several student teaching experiences are described which demonstrate how this activity helps prepare future teachers to make effective use of the new inquiry-oriented science curricula. The contributions of the practice teaching program to the total effort in teacher education in the Physics Department are discussed.
Algebraic Description of Motion
Authors: Davidon William C.
Published: September 2005

An algebraic definition of time differentiation is presented and used to relate independent-measurements of position and velocity. With this, students can grasp certain essential physical, geometric, and algebraic properties of motion and differentiation before undertaking the study of limits.
An Experiment on Thermionic Emission Using a Nuvistor Triode
Authors: Luke Keung L.
Published: September 2005

A 6CW4 nuvistor triode is used in an experiment which deals with the following aspects of thermionic emission: verification of the assumption that thermionic electrons leave the cathode with velocity components distributed according to Maxwell distribution for an electron gas in temperature equilibrium with the hot cathode; illustration of temperature-limited emission; determination of cathode and anode work functions; illustration and determination of the contact difference in potential between the cathode and anode. Schottky's equation and its derivative for the log i-v characteristic of a cylindrical diode operating in the retarding-field region was computed for the 6CW4. The range of retarding potentials for which the planar diode approximation is valid is established.
Astronomical Photoelectric Photometry for Undergraduate Research
Authors: Grauer Albert D.
Published: September 2005

Many college physics departments would welcome the opportunity to initiate a modest research program which could involve their undergraduate students. Astronomical photoelectric photometry is a field in which it is possible to initiate a useful undergraduate oriented research program with relatively modest equipment, some of which can commonly be found in a college physics department. A sketch of the equipment necessary, opportunities, and challenges in this work are presented.
Behavorial Objectives in an Introductory Astronomy Laboratory
Authors: Ingerson T. E.
Published: September 2005

An astronomy laboratory course is described in which the distinctive features are strong student involvement in the process of astronomical measurement, specific definition of behavior which is to be expected from the student at the completion of each portion of his laboratory work, and a high degree of flexibility in the individual selection of goals by the student. Specific examples of the approach are given, and an exact outline of the entire course is presented.
Hyperfine Structure in Cesium—An Advanced Laboratory Experiment
Authors: Mulligan J. F.
Published: September 2005

An experiment to measure the ground-state hyperfine splitting in Cs133 is described. The four strong lines in the Cs spectrum, are photographed in higher orders with an Ebert spectrograph and the hyperfine splitting measured for each line. The experiment leads to a value for the ground-state hyperfine splitting of Cs133, the accepted standard of frequency, to 1% accuracy. Important features of the experiment are that the spectrum can be obtained with readily available equipment and the observed structure explained very simply.
Laboratory Exercise in Centripetal and Coriolis Accelerations
Authors: Johnson P. B. , Pipes P. B. , Johns M. W.
Published: September 2005

A simple apparatus used in an introductory physics course to quantitatively measure Coriolis and centripetal accelerations is discussed. Several strobe photographs of experimental situations are presented along with a quantitative analysis of each picture. In addition, students' response to the experiment is summarized.
Modification of the Becker Technique for Obtaining Distribution Functions in Statistical Mechanics
Authors: Sears Francis W.
Published: September 2005

The average values of the occupation numbers of the energy levels of a system in equilibrium are calculated by a modification of the Becker technique, in the Maxwell-Boltzmann, Bose-Einstein, and Fermi-Dirac statistics. No use is made of the Stirling approximation, or of Lagrange multipliers.
Repeatable Testing—A Tool for Learning Physics
Authors: Golden David E. , Fuller Robert G. , Jensen Donald D.
Published: September 2005

The performance of college students in introductory physics courses has been studied using conventional examination procedures as a measure of content mastery. Retesting over the same physics content using repeatable equivalent examinations results in a significant increase in the students mastery of physics. Students greatly preferred this type of examination procedure.
Two-Level Approximation in Atomic Systems
Authors: Berman Paul R.
Published: September 2005

In analyzing atomic systems undergoing interactions with external fields that are nearly resonant with two, and only two of the atom's energy levels, one commonly employs a two-level or resonance approximation in which all states of the atom are neglected except for the two in resonance with the field. In this paper, we examine the assumptions necessary to make the transition from a differential equation for the exact polarization of an atomic system to the corresponding equation in the two-level approximation. Only when one includes contributions from states outside the two-level subspace does he find the exact equation reduces to the two-level equation within correctional factors of an intuitive nature.
Electromagnetism Adapted for Life Science Students
Authors: Gurr F. M. , Moore R. B. , de Takacsy N. B. , Landry P. C.
Published: September 2005

The importance of including electronics in a single course in electromagnetism for life science students is discussed. A course in which this has been done is described, showing how the concepts traditionally taught in an electromagnetism course can be combined with a study of semiconductor devices to give a course with obvious relevance to the student's future career. We advocate a strong emphasis on practical experience and outline our laboratory program.
A Visual Demonstration of Two-Dimensional Electrostatic Fields
Authors: Chute F. S. , Vermeulen F. E.
Published: September 2005

Concurrently with the recently published work of Jones and Vacanti, the authors have developed a similar method for providing visual displays of electrostatic fields. However the preparation of the displays is somewhat different and leads, the authors believe, to higher quality reproductions. The purpose of the present note is to describe the method which utilizes the familiar field-mapping technique using resistive paper (teledeltos) and the thermal properties of cholesteric liquid crystals. As well some of the displays are presented here to demonstrate the effectiveness of this new electrostatics teaching aid.
A PSI Astronomy Course
Authors: Zeilik Michael
Published: September 2005

This report outlines the use of Keller's Personalized System of Instruction (PSI) format for some of the students enrolled in an astronomy course for non-science specialists at Harvard University. The students in the PSI section perceived the unit tests and their immediate correction by the instructor as the most important component in their learning, and they felt strongly positive about the structured student-teacher interaction. In comparison with the student in the traditionally taught sections, the PSI students did master the material somewhat better as measured by a common final exam. The students' perceptions of PSI's educational merits guided the instructor in isolating some of the potentials and problems with PSI.
Stoichiometry of Envelope Glycoprotein Trimers in the Entry of Human Immunodeficiency Virus Type 1
Authors: Yang Xinzhen , Kurteva Svetla , Ren Xinping , Lee Sandra , Sodroski Joseph
Published: September 2005

The human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins (Envs) function as a trimer, mediating virus entry by promoting the fusion of the viral and target cell membranes. HIV-1 Env trimers induce membrane fusion through a pH-independent pathway driven by the interaction between an Env trimer and its cellular receptors, CD4 and CCR5/CXCR4. We studied viruses with mixed heterotrimers of wild-type and dominant-negative Envs to determine the number (
T
) of Env trimers required for HIV-1 entry. To our surprise, we found that a single Env trimer is capable of supporting HIV-1 entry; i.e.,
T
= 1. A similar approach was applied to investigate the entry stoichiometry of envelope glycoproteins from amphotropic murine leukemia virus (A-MLV), avian sarcoma/leukosis virus type A (ASLV-A), and influenza A virus. When pseudotyped on HIV-1 virions, the A-MLV and ASLV-A Envs also exhibit a
T
= 1 entry stoichiometry. In contrast, eight to nine influenza A virus hemagglutinin trimers function cooperatively to achieve membrane fusion and virus entry, using a pH-dependent pathway. The different entry requirements for cooperativity among Env trimers for retroviruses and influenza A virus may influence viral strategies for replication and evasion of the immune system.
Characterization of the Kaposi's Sarcoma-Associated Herpesvirus K1 Signalosome
Authors: Lee Bok-Soo , Lee Sun-Hwa , Feng Pinghui , Chang Heesoon , Cho Nam-Hyuk , Jung Jae U.
Published: September 2005

Kaposi's sarcoma (KS) is a multifocal angiogenic tumor and appears to be a hyperplastic disorder caused, in part, by local production of inflammatory cytokines. The K1 lymphocyte receptor-like protein of KS-associated herpesvirus (KSHV) efficiently transduces extracellular signals to elicit cellular activation events through its cytoplasmic immunoreceptor tyrosine-based activation motif (ITAM). To further delineate K1-mediated signal transduction, we purified K1 signaling complexes and identified its cellular components. Upon stimulation, the K1 ITAM was efficiently tyrosine phosphorylated and subsequently interacted with cellular Src homology 2 (SH2)-containing signaling proteins Lyn, Syk, p85, PLCγ2, RasGAP, Vav, SH2 domain-containing protein tyrosine phosphatase 1/2, and Grab2 through its phosphorylated tyrosine residues. Mutational analysis demonstrated that each tyrosine residue of K1 ITAM contributed to the interactions with cellular signaling proteins in distinctive ways. Consequently, these interactions led to the marked augmentation of cellular signal transduction activity, evidenced by the increase of cellular tyrosine phosphorylation and intracellular calcium mobilization, the activation of NF-AT and AP-1 transcription factor activities, and the production of inflammatory cytokines. These results demonstrate that KSHV K1 effectively recruits a set of cellular SH2-containing signaling molecules to form the K1 signalosome, which elicits downstream signal transduction and induces inflammatory cytokine production.
Patterns of Cytokine Production in Human Immunodeficiency Virus Type 1 (HIV-1)-Specific Human CD8
+
T Cells after Stimulation with HIV-1-Infected CD4
+
T Cells
Authors: Fujiwara Mamoru , Takata Hiroshi , Oka Shinichi , Tomiyama Hiroko , Takiguchi Masafumi
Published: September 2005

Although human immunodeficiency virus type 1 (HIV-1)-specific CD8
+
T cells can produce various cytokines that suppress HIV-1 replication or modulate anti-HIV-1 immunity, the extent to which HIV-1-specific CD8
+
T cells produce cytokines when they recognize HIV-1-infected CD4
+
T cells in vivo still remains unclear. We first analyzed the abilities of 10 cytotoxic T-lymphocyte (CTL) clones specific for three HIV-1 epitopes to produce gamma interferon, macrophage inflammatory protein 1β, and tumor necrosis factor alpha after stimulation with epitope peptide-pulsed cells. These CTL clones produced these cytokines in various combinations within the same specificity and among the different specificities, suggesting a functional heterogeneity of HIV-1-specific effector CD8
+
T cells in cytokine production. In contrast, the HIV-1-specific CTL clones for the most part produced a single cytokine, without heterogeneity of cytokine production among the clones, after stimulation with HIV-1-infected CD4
+
T cells. The loss of heterogeneity in cytokine production may be explained by low surface expression of HLA class I-epitope peptide complexes. Freshly isolated HIV-1-specific CD8
+
T cells with an effector/memory or memory phenotype produced much more of the cytokines than the same epitope-specific CTL clones when stimulated with HIV-1-infected CD4
+
T cells. Cytokine production from HIV-1-specific memory/effector and memory CD8
+
T cells might be a critical event in the eradication of HIV-1 in HIV-1-infected individuals.
Conversion of Mouse Mammary Tumor Virus to a Lymphomagenic Virus
Authors: Bhadra Sanchita , Lozano Mary M. , Dudley Jaquelin P.
Published: September 2005

Type B leukemogenic virus is a variant of mouse mammary tumor virus (MMTV) that causes thymic lymphomas rather than mammary tumors in mice. We demonstrate that conversion of a mammotropic MMTV to a T-cell-tropic virus requires two alterations in the long terminal repeat: (i) acquisition of a T-cell-specific enhancer and (ii) loss of transcriptional repression through deletion of negative regulatory elements (NREs) or by suppression of NRE activity after appropriate positioning of the enhancer.
The Bunyamwera Virus mRNA Transcription Signal Resides within both the 3′ and the 5′ Terminal Regions and Allows Ambisense Transcription from a Model RNA Segment
Authors: Barr John N. , Rodgers John W. , Wertz Gail W.
Published: September 2005

Bunyamwera virus
(BUNV) is the prototype of the
Bunyaviridae
family of RNA viruses. BUNV genomic strands are templates for both replication and transcription, whereas the antigenomic RNAs serve only as templates for replication. By mutagenesis of model templates, we showed that the BUNV transcription promoter comprises elements within both the 3′ and the 5′ nontranslated regions. Using this information, we designed a model ambisense BUNV segment that transcribed BUNV S mRNA from the genomic strand and green fluorescent protein (GFP) mRNA from the antigenome. Demonstration of GFP expression showed that this ambisense strategy represents a viable approach for generating BUNV segments able to express additional proteins.
Population genetic structure and postglacial colonization of Atlantic salmon (Salmo salar) in the Baltic Sea area based on microsatellite DNA variation
Authors: Säisä Marjatta , Koljonen Marja-Liisa , Gross Riho , Nilsson Jan , Tähtinen Jaana , Koskiniemi Jarmo , Vasemägi Anti
Published: September 2005

The genetic structure and phylogeography of Atlantic salmon (Salmo salar) across the Baltic Sea basin and neighbouring areas (eastern Atlantic Ocean, North Sea, Barents Sea, White Sea, and two Russian lakes, Onega and Ladoga) were studied to resolve the partly contradictory hypotheses of the species' postglacial colonization history. Thirty-eight populations (total of 2180 individuals) were studied for nine DNA microsatellite loci. Within the Baltic Sea, the anadromous populations formed three clear groups, corresponding to the northern (Gulf of Bothnia), eastern (Gulf of Finland and eastern Baltic Main Basin), and southern regions (western Baltic Main Basin). The genetic differences among these three groups were clearly greater (GGB5.6%; GGBbeing the proportion of diversity components between regions within basins) than were those among population groups in the eastern Atlantic Ocean (GGB2.2%) from Ireland to the White Sea. The isolation-by-distance model explained part of the differentiation within, but not between, the regions. The results strongly indicate colonization of the Baltic Sea by at least three glacial lineages. Potential refugium areas for each lineage are proposed.
Influence of physicochemical factors on the distribution and biomass of invasive mussels (Dreissena polymorpha and Dreissena bugensis) in the St. Lawrence River
Authors: Jones Lisa A , Ricciardi Anthony
Published: September 2005

Twenty sites along the St. Lawrence River were sampled to determine if the distribution and abundance of invasive mussels (zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena bugensis)) are explained by physicochemical variables. Calcium concentration, substrate size, and depth independently explained significant proportions of variation in biomass for both species. Zebra mussel populations occurred at calcium levels as low as 8 mg Ca·L1, but quagga mussels were absent below 12 mg Ca·L1, suggesting that they have higher calcium requirements. Both species increased in biomass with increasing substrate size but displayed contrasting patterns with depth. Using combinations of these environmental variables, we developed stepwise multiple regression models to predict zebra mussel biomass and quagga mussel biomass. The zebra mussel model included calcium concentration, substrate size, and depth (r2 = 0.36, P < 0.0001), while the quagga mussel model included only substrate size and depth (r2 = 0.32, P < 0.0001). These results suggest that dreissenid mussel abundance (and correlated impacts) will vary predictably across environmental gradients, but the same predictive model will not be accurate for both species.
Exploratory assessment of historical recruitment patterns using relative abundance and catch data
Authors: Walters Carl J , Hilborn Ray
Published: September 2005

Historical apparent recruitment rates can be estimated from time series of relative abundance and catch data using a simple difference equation in conjunction with assumed catchability coefficient and natural survival rate. Simple smoothing and optimal linear state estimation procedures can remove much of the variance in such estimates due to measurement error in relative abundance. The apparent patterns can be helpful to reveal important recruitment changes prior to availability of data for more complex stock assessments, provide checks on recruitments estimated by more complex assessment procedures, and provide warnings about biases in other assessment procedures that might result from using the relative abundance data for model tuning.
State-space likelihoods for nonlinear fisheries time-series
Authors: Valpine Perry de , Hilborn Ray
Published: September 2005

State-space models are commonly used to incorporate process and observation errors in analysis of fisheries time series. A gap in analysis methods has been the lack of classical likelihood methods for nonlinear state-space models. We evaluate a method that uses weighted kernel density estimates of Bayesian posterior samples to estimate likelihoods (Monte Carlo Kernel Likelihoods, MCKL). Classical likelihoods require integration over the state-space, and we compare MCKL to the widely used errors-in-variables (EV) method, which estimates states jointly with parameters by maximizing a nonintegrated likelihood. For a simulated, linear, autoregressive model and a Schaefer model fit to cape hake (Merluccius capensis × M. paradoxus) data, classical likelihoods outperform EV likelihoods, which give asymptotically biased parameter estimates and inaccurate confidence regions. Our results on the importance of integrated state-space likelihoods also support the value of Bayesian analysis with Monte Carlo posterior integration. Both approaches provide valuable insights and can be used complementarily. Previously, Bayesian analysis was the only option for incorporating process and observation errors with complex nonlinear models. The MCKL method provides a classical approach for such models, so that choice of analysis approach need not depend on model complexity.
Empirical study of cyanobacterial toxicity along a trophic gradient of lakes
Authors: Giani A , Bird D F , Prairie Y T , Lawrence J F
Published: September 2005

A series of 22 lakes in southern Quebec spanning a wide trophic range were sampled to develop models of changes in cyanobacterial abundance and toxicity. All lakes contained toxic cyanobacteria, and epilimnetic toxin content, expressed as microcystin equivalents, was best predicted by total nitrogen concentration and total phosphorus concentration (TP). Although phytoplankton biomass increased linearly with increases in TP among lakes, toxigenic biomass increased as greater than the squared power of TP. The only potentially toxigenic genera whose biomass was correlated with microcystin concentration were Microcystis and Anabaena. Surprisingly, the best model for toxic-species biomass was based on epilimnetic nitrogen. The level of the hepatotoxin microcystin per unit biomass in these organisms did not vary markedly among lakes, supporting the idea that environmental factors control the occurrence, but have only a limited effect on the toxicity, of potentially toxic species.
Alkali atoms confined to a sphere and to a fullerene cage
Authors: Patil S H , Sen K D , Varshni Y P
Published: September 2005

A simple asymptotically correct model potential is considered for the valence electron in an alkali atom. Superposed with the confining infinite barrier potential, this potential yields the energies of various states and the dipole polarizability of the ground state of the confined alkali atom. Superposed with the fullerene shell potential, this potential yields the energies of the alkali atom inside a fullerene cage. Numerical results are presented for Li, Na, K, Rb, and Cs under such confinements. PACS Nos.: 03.65.Ge, 73.21.La, 78.67.Hc
Applications of data on the mobility of heavy metals in contaminated soil to the definition of site-specific remediation criteria
Authors: Dubé Jean-Sébastien , Galvez-Cloutier Rosa
Published: September 2005

More than a decade of research on the fractionation of heavy metals in soil has led scientists and engineers to the conclusion that the mobility of heavy metals can be defined by the relative sensitivity of their solid species to environmental stresses. The following paper presents a procedure to obtain the fractionation of heavy metals during the acidification of the soil and discusses the use such data. The procedure used combines an acid–base titration of the soil with the Tessier scheme of sequential chemical extractions (SCEs). The soil was strongly buffered against acidification by the dissolution of solid carbonates. Cadmium and zinc were nevertheless significantly dissolved by acidification from pH 8 to pH 5. All other heavy metals were dissolved once pH 5 was attained. The most soluble heavy metals were those that had formed less stable acid-soluble and reducible solid species. These results are used as an example to demonstrate the importance of knowing the buffering capacity of the soil and the fractionation of heavy metals to obtain a more rigorous assessment of the mobility of heavy metals and to determine site-specific remediation criteria. Key words: contaminated soil, heavy metals, mobility, sequential chemical extractions, buffering capacity, remediation criteria.
Effects of stress paths on the small-strain stiffness of completely decomposed granite
Authors: Wang Y. , Ng C WW
Published: September 2005

Research on the small-strain (0.001%1%) characteristics of sedimentary soils and sands has advanced to the stage where it has been utilized in engineering analysis and design for some time. Despite the progress, the stiffness characteristics of weathered materials such as completely decomposed granite (CDG) at small strains have still attracted relatively little research attention. This paper describes a systematic laboratory investigation of the small-strain characteristics of intact CDG subjected to various triaxial stress paths, including drained compression and extension tests. The small-strain stiffness was measured using bender elements and internal local transducers. Measurements from bender elements illustrate that the elastic shear modulus of CDG increases as the mean effective stress increases and the void ratio decreases. Significant nonlinear shear stiffness  shear strain and bulk modulus  volumetric strain relationships were observed. At 0.01% shear strain, the measured average shear stiffness obtained from the extension tests was about 60% higher than that from the compression tests. The average shear stiffness for the tests with a 90° rotation of the stress path was about 50%70% higher than that of tests without a change in the direction of the stress path after saturation.Key words: completely decomposed granite, nonlinearity, small strains, extension, compression, recent stress history.