bluuebunny/crossref_metadata_2025 huggingface dataset:
Students’ confidence and teachers’ styles: A binational comparison
Authors: Mallow Jeffry V.
Published: March 2005

A teaching-style inventory based on the American Association of Physics Teachers workshop, Developing Student Confidence in Physics was administered to Danish and American teachers. There are some national differences in responses; however, they do not appear to account for the much higher levels of confidence measured in Danish students. Explanations are proposed for the cause of these differences, as well as for the gender bifurcation among both Danish and American students. In addition, the Danish teachers in this study undertook a critique of the AAPT inventory, and proposed additional and alternate scenarios for assessment of relationship and content in the physics classroom.
Supercooling and the Mpemba effect: When hot water freezes quicker than cold
Authors: Auerbach David
Published: March 2005

Temperature measurements taken near vessel walls show that initially hot water may well begin to freeze quicker than cold. This is not, as previously surmised, due to the cooling history of the water (e.g., air expulsion during heating). Rather, supercooling virtually always takes place. On those occasions where the cold water supercools sufficiently more than the hot the Mpemba scenario is the following: The hot water supercools, but only slightly, before spontaneously freezing. Superficially it looks completely frozen. The cold water (in larger volume than that of the hot sample) supercools to a lower local temperature than the hot before it spontaneously freezes. This scenario can occur more often for ambient cooling temperatures between −6 °C and −12 °C.
Nonspreading wave packets
Authors: Wong Chun Wa
Published: March 2005

The spreading or nonspreading of wave packets in one-dimensional linear and quadratic potentials can readily be determined by solving Ehrenfest’s equations. The results for quadratic potentials can be understood in simple intuitive terms by using quantum distribution functions in phase space which, like classical distributions, rotate clocklike in time once per motional cycle. For more complicated situations, such as potentials with quantum energy spacings which are integral multiples of a basic unit, much can be learned instead by studying the quantum recurrence of their time-dependent wave functions or probability densities.
Nontrivial scaling laws for a block sliding down a rough plane
Authors: Brito V. P. , Gomes M. A. F.
Published: March 2005

The measured length distributions of slidings of solid cylinders of aluminum, brass, teflon, and polyvinyl chloride on an incline obey nontrivial scaling laws. No significant dependence of the scaling exponent on material is observed and the data obtained are in agreement with the Gutenberg–Richter law for the distribution of earthquakes and with numerical simulations exhibiting self-organized criticality made by Chen, Bak, and Obukhov [Phys. Rev. A 43, 625–630 (1991)].
Improving library research papers in undergraduate science classes
Authors: O’Connell Suzanne
Published: March 2005

After several years of trial and error, I have developed a method to generate consistently good library research papers in undergraduate science classes, papers that show thought and integrate information. It is based, in part, on treating the student papers as journal article submissions. There are five steps to the procedure which are spaced throughout the semester to ensure that the papers will not be done at the last minute. The steps are: (1) selecting a topic; (2) computerized on-line library reference search; (3) first draft of paper; (4) paper review by a classmate; and (5) submittal of revised paper. Each step requires a written document and has a class-discussion component. A side benefit of the discussion component is that it helps to set students at ease about participating in class discussions, which carries over to discussions about the scientific content of the class. The resulting well-written papers are usually a pleasure to read and grade.
An apparent paradox at the heart of quantum mechanics
Authors: Cereceda José L.
Published: March 2005

A simple conceptual experiment which seems to violate the general principles of quantum mechanics is reported. The reasoning leading to this contradiction contains a trick which makes the paradox possible. By discussing the failure of the argument the author wishes to draw attention to a fundamental feature of the wave function which is frequently overlooked. Finally, in light of this discussion, a kind of delayed-choice experiment is described, and an analysis of the related issue of complementarity is made.
A time-dependent study of resonant tunneling through a double barrier
Authors: Stamp A. P. , McIntosh G. C.
Published: March 2005

The resonant tunneling of a wave packet is studied, for a one-dimensional double barrier, by solving the time-dependent Schrödinger equation. The transmission is determined as a function of the spatial width of the incident wave packet. It is shown that if the double barrier acts as an energy filter, then the spatial width of the transmitted wave packet is increased, due to the trapping of the particle between the two barriers for a time, ℏ/Γ, where Γ is the width of the resonance. The reflected wave packet consists of two components: one corresponding to reflection from the first barrier and the other due to the particle being trapped between the barriers for a time ℏ/Γ.
Common misconceptions regarding quantum mechanics
Authors: Styer Daniel F.
Published: March 2005

This paper lists 15 commonly held misconceptions concerning quantum mechanics, such as ‘‘Energy eigenstates are the only allowed states’’ and ‘‘The wave function is dimensionless.’’ A few suggestions are offered to help combat these misconceptions in teaching.
Applications of the Mathieu equation
Authors: Ruby Lawrence
Published: March 2005

The properties of the Mathieu equation are reviewed in order to discuss some of the applications that have appeared in recent years. Those mentioned are: vibrations in an elliptic drum, the inverted pendulum, the radio frequency quadrupole, frequency modulation, stability of a floating body, alternating gradient focusing, the Paul trap for charged particles, and the mirror trap for neutral particles.
Microscopic approach to reflection, transmission, and the Ewald–Oseen extinction theorem
Authors: Fearn Heidi , James Daniel F. V. , Milonni Peter W.
Published: March 2005

We describe how the reflection and transmission of light at a dielectric interface can be understood starting from the fact that dielectrics are collections of molecules. More precisely, we consider from the microscopic perspective the interpretation and significance of the Ewald–Oseen extinction theorem of classical optics. The usual interpretation of the theorem is that an incident field is extinguished by the dipoles on the boundary and replaced by transmitted and reflected fields consistent with the Maxwell equations for the media. However, the extinction theorem is more appropriately regarded simply as a boundary condition effected by all the molecular scatterers, not just those at the boundary. To demonstrate this we take a microscopic approach to three familiar problems: (1) the electrostatic interaction of a point charge with a dielectric wall; (2) the reflection of a monochromatic plane wave at a dielectric interface; and (3) diffraction by an aperture. We show that the extinction of the incident field cannot be attributed to any finite dipole boundary layer, and in particular it does not involve any ‘‘extinction theorem distance.’’
Uniqueness of the Airy packet in quantum mechanics
Authors: Unnikrishnan K. , Rau A. R. P.
Published: March 2005

The general form of a nonspreading wave packet in one-dimensional free space is derived from first principles, employing a decomposition of the quantum mechanical evolution operator of the free particle. In agreement with the classical analysis of Berry and Balazs, the corresponding probability density is proportional to the square of an Airy function, and the packet propagates with constant acceleration.
Lagrangian field theories and energy-momentum tensors
Authors: Muñoz Gerardo
Published: March 2005

We discuss the implications of Poincaré invariance within the context of Lagrangian field theories. It is shown that the correct implementation of this invariance leads in a straightforward manner to a conserved energy-momentum tensor which is both symmetric and gauge invariant.
Teaching the theory of real lenses
Authors: Walther A.
Published: March 2005

Real lenses do not behave according to the laws of Gaussian optics to which the teaching of lens theory is often confined; Hamilton and Maxwell showed already that this would contradict Fermat’s principle. This paper shows that the rudiments of a correct treatment can be easily incorporated in an undergraduate course. This will help students to develop a clearer notion of what they can expect from the various lenses they will encounter in the laboratory. In addition, it will give them some insight into the value of variational principles.
A spherical electrostatic orrery
Authors: Smetana Carole , Alexander David , Robertson Scott , Vilkaitis Kim , Walch Bob
Published: March 2005

An electrostatic orrery for studying Keplerian orbits has been constructed in which one or more negatively charged hollow glass microparticles orbit a 9.5-mm-diam metal sphere at +8-kV potential in a vacuum. The device is similar to an earlier cylindrical orrery in which particles orbit a rod [Biewer et al., Am. J. Phys. 62(9), 821–827 (1994)]. Electrically biased cylinders covering the rod supporting the sphere give nearly spherical potential surfaces inside the trap. Additional electrodes at the boundary are used to reduce the perturbation of gravity and to prevent motion resulting in collisions with the supporting rod. Orbits last approximately 10 min or about 104 revolutions. The orbiters are illuminated with a slide projector and can be seen with the naked eye as well as videotaped. The trap has been used to observe orbital precession, interparticle collisions, and the effects of time-independent perturbations. This apparatus provides an opportunity for the study and demonstration of orbital motion in a laboratory.
A geometric approach to nonlocality in the Bohm model of quantum mechanics
Authors: Rice Dien A.
Published: March 2005

The nonlocality of Bohm’s model of quantum mechanics is demonstrated geometrically. This is done by using the properties that in the Bohm model the particle trajectories in configuration space do not cross, yet the predictions of quantum mechanics must be reproduced. This approach provides a simple demonstration of how a model of quantum mechanics that assumes “elements of reality” for unmeasured observables must be nonlocal. While it is tempting to try to use this type of nonlocality for superluminal signalling, we discuss the fact that any attempt to do this will result in failure.
A mechanical Duffing oscillator for the undergraduate laboratory
Authors: Berger J. E. , Nunes G.
Published: March 2005

The design and construction of a mechanical Duffing oscillator suitable for use in an undergraduate laboratory is described. The oscillator provides a straightforward introduction to nonlinear vibrations and chaotic behavior that is both pedagogically appealing and easily adapted to students at various levels of sophistication. Good agreement is observed between the motion of the oscillator and computer simulations, which provides students with an introduction to the power of mathematical modeling. Period-doubling routes to chaos can be observed both experimentally and numerically.
Modern optical signal processing experiments demonstrating intensity and pulse-width modulation using an acousto-optic modulator
Authors: Poon Ting-Chung , McNeill Mark D. , Moore Daniel J.
Published: March 2005

Two experiments are presented to introduce undergraduate students in electrical engineering or physics to modern optical signal processing. Both experiments use an acousto-optic (AO) Bragg cell together with additional electronics to modify the intensity of a laser beam. Specifically, we show how an AO feedback system operating in the Bragg regime can be configured to produce amplitude modulated (AM) and pulse-width modulated optical signals. The basic components of the AO feedback system include a laser, an AO Bragg cell, an electronic AM modulator, a photodetector, an amplifier, and an electronic adder. Except for the laser, the AM modulator, and the Bragg cell, each of these components can be constructed with low cost electronics. A tutorial outlining the principles of acousto-optics is included to provide sufficient understanding of the Bragg cell. The project described in the paper has been used as a demonstration for junior- and senior-level undergraduate students in electrical engineering communications and optics classes.
New eigenvalue equation for the Kronig–Penney problem
Authors: Szmulowicz Frank
Published: March 2005

The Kronig–Penney equation (KPE) has long been used as a pedagogic tool for explaining the formation of energy bands in a periodic potential in the form of a one-dimensional periodic array of square wells. However, the KPE does not readily reduce to the solution for an isolated square well in the limit of a large well-to-well separation. Moreover, the solutions at the center and the edge of the Brillouin zone are also not readily obtainable from the KPE. Computationally, the KPE can be inconvenient as it can vary over tens of orders of magnitude as the energy is increased from the bottom to the top of the well. In this paper, a new technique is developed for solving the Kronig–Penney problem and an alternative to the KPE is developed. The new eigenvalue equation has the conceptual advantage of immediately reducing to the equation for an isolated square well in the limit of infinite barrier width and of immediately providing the equation for the top and bottom of a band as well as the computational advantage of being on the order of unity.
Specific heats of model gas molecules: An oral exam teaching strategy
Authors: Styer Daniel F.
Published: March 2005

A teaching strategy is presented that investigates the specific heats of a simple harmonic oscillator, of a two-state system, and of an n-state system that interpolates between the two. One stage of the investigation provides a relation between the specific heats of two systems that differ by the addition of a single energy eigenstate. The strategy begins with a traditional analytic problem set whose results are investigated qualitatively in an oral exam. The oral exam raises questions that are then resolved in a second analytic problem set. As such, the strategy shows how conceptual understanding and rigorous analytic methods work together to solve problems. Although developed for a senior-level statistical mechanics course, the strategy is generally applicable to a wide range of course levels.
Coherent states composed of Stark eigenfunctions of the hydrogen atom
Authors: Baugh J. F. , Edmonds D. A. , Nellesen P. T. , Burkhardt C. E. , Leventhal J. J.
Published: March 2005

It is well known that for the nonrelativistic hydrogen atom it is possible to separate the Schrödinger equation in parabolic as well as spherical coordinates. The eigenfunctions obtained in these coordinate systems are each a suitable basis set in the absence of an electric field, but only the parabolic states, the Stark eigenfunctions, retain their character in the presence of a weak field. The properties of coherent superpositions of these Stark states are investigated and the motion of the resulting wave packet described. It is shown that a properly constituted superposition will mimic classical motion. It is also shown that the constant energy separation between adjacent Stark states of a given principal quantum number leads to periodic motion. In general, they split into distinct “clumps” of probability, but revive to form a single packet after each period. It is, however, possible to construct a packet that maintains its shape for all time.
Why is the propagation velocity of a photon in a transparent medium reduced?
Authors: de Grooth Bart G.
Published: March 2005

A path integral formalism is used to describe the propagation of photons through a transparent medium. It is shown that the reduced phase velocity of light can be understood quantitatively by taking into account the contribution of all the possible classical paths the photon could have taken in order to reach a detector. These paths include all the multiple scattering processes by the atoms in the medium.
Comment on “A simple, conservative understanding of many time-driven systems,” by Harvey Kaplan [Am. J. Phys. 62 (12), 1097–1099 (1994)]
Authors: Giordano C. M. , Plastino A. R. , Plastino A.
Published: March 2005

We show that Kaplan’s approach to time-driven systems provides interesting insights in regards to the problem of the motion of a particle in a uniformly rotating potential. Further, it allows for establishing a connection with the problem of a particle in a potential with cylindric helicoidal symmetry.
PDK1 Nucleates T Cell Receptor-Induced Signaling Complex for NF-κB Activation
Authors: Lee Ki-Young , D'Acquisto Fulvio , Hayden Matthew S. , Shim Jae-Hyuck , Ghosh Sankar
Published: March 2005

Activation of the transcription factor NF-κB after engagement of the T cell receptor (TCR) is important for T cell proliferation and activation during the adaptive immune response. Recent reports have elucidated a signaling pathway that involves the protein kinase C θ (PKCθ), the scaffold protein CARD11 (also called CARMA-1), the caspase recruitment domain (CARD)–containing protein Bcl10, and the paracaspase (protease related to caspases) MALT1 as critical intermediates linking the TCR to the IκB kinase (IKK) complex. However, the events proximal to the TCR that initiate the activation of this signaling pathway remain poorly defined. We demonstrate that 3-phosphoinositide-dependent kinase 1 (PDK1) has an essential role in this pathway by regulating the activation of PKCθ and through signal-dependent recruiting of both PKCθ and CARD11 to lipid rafts. PDK1-associated PKCθ recruits the IKK complex, whereas PDK1-associated CARD11 recruits the Bcl10-MALT1 complex, thereby allowing activation of the IKK complex through Bcl10-MALT1–dependent ubiquitination of the IKK complex subunit known as NEMO (NF-κB essential modifier). Hence, PDK1 plays a critical role by nucleating the TCR-induced NF-κB activation pathway in T cells.
Challenges in the provision of ICU services to HIV infected children in resource poor settings: a South African case study: Table 1
Authors: Jeena P M , McNally L M , Stobie M , Coovadia H M , Adhikari M A , Petros A J
Published: March 2005

The HIV/AIDS epidemic has placed increasing demands on limited paediatric intensive care services in developing countries. The decision to admit HIV infected children withPneumocystis cariniipneumonia (PCP) into the paediatric intensive care unit (PICU) has to be made on the best available evidence of outcome and the ethical principles guiding appropriate use of scarce resources. The difficulty in confirming the diagnosis of HIV infection and PCP in infancy, issues around HIV counselling, and the variance in the outcome of HIV infected children with PCP admitted to the PICU in African studies compound this process. Pragmatic decision making will require evaluation of at least three ethical questions: are there clinical and moral reasons for admitting HIV positive children with PCP to the PICU, should more resources be committed to caring for HIV children who require the PICU, and how can we morally choose candidates for the PICU? Those working in the PICU in HIV endemic regions need to make difficult personal decisions on effective triage of admissions of HIV infected children with PCP based on individual case presentation, availability of resources, and applicable ethical principles.
The case for physician assisted suicide: not (yet) proven
Authors: Steinbock B
Published: March 2005

The legalisation of physician assisted suicide (PAS) in Oregon and physician assisted death (PAD) in the Netherlands has revitalised the debate over whether and under what conditions individuals should be able to determine the time and manner of their deaths, and whether they should be able to enlist the help of physicians in doing so. Although the change in the law is both dramatic and recent, the basic arguments for and against have not really changed since the issue was debated by Glanville Williams and Yale Kamisar nearly 50 years ago. In this paper, the author argues in favour of Kamisar’s consequentialist framework. Any change in law and social policy should not be based solely on individual cases, heart wrenching though these may be. Instead, we need to assess theneedfor PAS, and weigh this against therisksof mistake and abuse.
Laboratory animals and the art of empathy
Authors: Thomas D
Published: March 2005

Consistency is the hallmark of a coherent ethical philosophy. When considering the morality of particular behaviour, one should look to identify comparable situations and test one’s approach to the former against one’s approach to the latter. The obvious comparator for animal experiments is non-consensual experiments on people. In both cases, suffering and perhaps death is knowingly caused to the victim, the intended beneficiary is someone else, and the victim does not consent. Animals suffer just as people do. As we condemn non-consensual experiments on people, we should, if we are to be consistent, condemn non-consensual experiments on animals. The alleged differences between the two practices often put forward do not stand up to scrutiny. The best guide to ethical behaviour is empathy—putting oneself in the potential victim’s shoes. Again to be consistent, we should empathise with all who may be adversely affected by our behaviour. By this yardstick, too, animal experiments fail the ethical test.
In the world of Dolly, when does a human embryo acquire respect?
Authors: Cameron C , Williamson R
Published: March 2005

For most of the 20th century, it was possible to regard fertilisation astheidentifiable point when life begins, because this moment could be defined unequivocally and was thought to be the single most essential biological step in the establishment of a new human entity. Since the successful reproductive cloning of Dolly and other mammals, it is clear that any human cell has the potential to supply the full genome of an embryo, and hence a person, without going through fertilisation. At what point in time do such embryos acquire the respect accorded to human beings? The authors argue that the time of implantation is the most useful point at which the potential and the intention to create a new person are translated into reality, because from that point a new life develops. Implantation differentiates a somatic cell in culture (which is not due respect) from a human entity that has acquired its own identity and developmental potential. The authors examine the value of quickening or viability as alternative developmental stages in the process of acquiring respect for the Dolly embryo.
Legitimate requests and indecent proposals: matters of justice in the ethical assessment of phase I trials involving competent patients
Authors: Kong W M
Published: March 2005

The death of Jesse Gelsinger in 1999 during a gene therapy trial raised many questions about the ethical review of medical research. Here, the author argues that the principle of justice is interpreted too narrowly and receives insufficient emphasis and that what we permit in terms of bodily invasion affects the value we place on individuals. Medical research is a societally supported activity. As such, the author contends that justice requires that invasive medical research demonstrates sufficiently compelling societal benefit. Many consider this societal benefit to be self evident. However, medical research is a complex activity; it yields new treatments but also creates financial rewards and affects health resource allocation. As research evolves into a multibillion pound, multinational enterprise, justice requires a much broader analysis of societal benefit. Without such evaluation we risk undermining the value of bodily integrity and of research participants.
The moral status of the embryo post-Dolly
Authors: Stanton Catherine , Harris John
Published: March 2005

Cameron and Williamson have provided a provocative and timely review of the ethical questions prompted by the birth of Dolly. The question Cameron and Williamson seek to address is “In the world of Dolly, when does a human embryo acquire respect?”. Their initial discussion sets the scene by providing a valuable overview of attitudes towards the embryo, summarising various religious, scientific, and philosophical viewpoints. They then ask, “What has Dolly changed?” and identify five changes, the first being that fertilisation is no longer required to create an embryo. Following this analysis they then ask when an embryo created other than by fertilisation begins to acquire respect. This paper explores the ethical and legal issues highlighted by Cameron and Williamson’s paper.
Anti-inflammatory Activity of CML-1: An Herbal Formulation
Authors: Eum Hyun-Ae , Lee Woo-Yong , Kim Sung-Ho , Kim Joo-Young , Park Sang-Won , Lee Jun-Seok , Choi Sun-Mi , Pyo Suhkneung , Kang Myung-Ja , Min Yong-Deuk , Shim Sang-Ho , Shin Dae-Hee , Lee Sun-Mee
Published: March 2005

CML-1 is a purified extract from a mixture of 13 Oriental herbs (Achyranthis Radix, Angelicae Gigantis Radix, Cinnamomi Cortex Spissus, Eucommiae Cortex, Glycyrrhizae Radix, Hoelen, Lycii Fructus, Paeoniae Radix, Rehmanniae Radix Preparata and Atractylodis Rhizoma, Zingiberis Rhizoma, Zizyphi Semen, Acori Graminei Rhizoma) that have been widely used for the treatment of inflammatory diseases in Asia. The aim of this study was to investigate the anti-inflammatory and analgesic potential of CML-1. The animals used in this study were administered either vehicle or CML-1 (30, 100, 300 and 600 mg/kg) orally. The vascular permeability induced by acetic acid was significantly reduced by CML-1 in all doses. The swelling of the rat's hind paw induced by carrageenan was significantly inhibited by CML-1 in doses of 100, 300 and 600 mg/kg. In the case of rheumatoid arthritis induced by complete Freund's adjuvant in rats, the treatment with CML-1 at a dose level of 300 mg/kg inhibited edema. CML-1 at a dose level of 600 mg/kg inhibited acetic acid-induced writhing syndrome, however it did not have any anti-nociceptive action in the Randall-Selitto assay or the hot plate test. Our findings suggest that CML-1 has a potent anti-inflammatory activity.
CONFORMAL SCALING GAUGE SYMMETRY AND INFLATIONARY UNIVERSE
Authors: WU YUE-LIANG
Published: March 2005

Considering the conformal scaling gauge symmetry as a fundamental symmetry of nature in the presence of gravity, a scalar field is required and used to describe the scale behavior of the universe. In order for the scalar field to be a physical field, a gauge field is necessary to be introduced. A gauge invariant potential action is constructed by adopting the scalar field and a real Wilson-like line element of the gauge field. Of particular, the conformal scaling gauge symmetry can be broken down explicitly via fixing gauge to match the Einstein–Hilbert action of gravity. As a nontrivial background field solution of pure gauge has a minimal energy in gauge interactions, the evolution of the universe is then dominated at earlier time by the potential energy of background field characterized by a scalar field. Since the background field of pure gauge leads to an exponential potential model of a scalar field, the universe is driven by a power-law inflation with the scale factor a(t)~tp. The power-law index p is determined by a basic gauge fixing parameter gF via [Formula: see text]. For the gauge fixing scale being the Planck mass, we are led to a predictive model with gF=1 and p≃62.
ELECTRON GENERATION OF LEPTONS AND HADRONS WITH CONJUGATE α-QUANTIZED LIFETIMES AND MASSES
Authors: MAC GREGOR MALCOLM H.
Published: March 2005

In elementary particle theories the fine structure constant α = e2/ℏc serves as the coupling constant for lepton interactions (QED), but is assumed to play no role in hadron interactions (QCD). However, experiments have long indicated an α spacing in the lifetimes of the long-lived threshold-state hadrons, and they also suggest an α-related mass structure. Lifetimes and masses are conjugate quantum mechanical variables, so the α-dependence of these two variables is a mutual property. The relevance of α to hadron interactions is an experimental question, independent of theory. In the present paper we first make a detailed analysis of the experimental lifetime data. This analysis demonstrates that out of 156 particles with well-determined lifetimes τ, the 120 short excited-state lifetimes τ<10-21 sec have a continuum of values, but the 36 long threshold-state lifetimes τ>10-21 sec occur in α-spaced groups that cleanly sort out the s, c, b quark flavors. These 36 metastable lifetimes also exhibit a factor-of-3 c-to-b "flavor structure" and a pervasive factor-of-2 "hyperfine structure." We then invoke the conjugate relationship between lifetimes and masses to trace out an α-defined set of mass quanta that tie together leptons and hadrons. Mass generation occurs via an initial "α-leap" from an electron pair to a "platform state" M, and then subsequent excitations by a dominant quantum X. The low-mass "MX octet" of particles — μ, p, τ, π, η, η′, K, ϕ — is reproduced to an average accuracy of 0.4%, with no adjustable parameters except a small binding energy for hadronic pairs. Without the inclusion of lepton masses, the spectrum of hadron masses is difficult to understand. These conjugate α-quantized results reinforce the reality of the spin 1/2 u, d, s, c, b quarks, and they also lead to the identification of a closely-related set of spinless mass quanta for the pseudoscalar mesons.
ON THE Cλ-EXTENDED w∞-SYMMETRY
Authors: DOUARI J. , EL KINANI E. H.
Published: March 2005

Starting from the Cλ-extended oscillator algebras, we obtain a new deformed w∞-algebra. More precisely, we show that the Cλ-extended w∞-algebra generators may be expressed via the annihilation and creation operators of the Cλ-extended oscillator algebras a and a† as an infinite-dimensional extension of the realization of sp(2) algebra.
EFFECTIVELY CLOSED INFINITE-GENUS SURFACES AND THE STRING COUPLING
Authors: DAVIS SIMON
Published: March 2005

The class of effectively closed infinite-genus surfaces, defining the completion of the domain of string perturbation theory, can be included in the category OG, which is characterized by the vanishing capacity of the ideal boundary. The cardinality of the maximal set of end points is shown to be 2N. The product of the coefficient of the genus-g superstring amplitude in four dimensions by 2g in the g→∞ limit is an exponential function of the genus with a base comparable in magnitude to the unified gauge coupling. The value of the string coupling is consistent with the characteristics of configurations which provide a dominant contribution to a finite vacuum amplitude.
ON THE TRANSFORMATIONS OF HAMILTONIAN GAUGE ALGEBRA UNDER ROTATIONS OF CONSTRAINTS
Authors: BATALIN IGOR , TYUTIN IGOR
Published: March 2005

By explicit calculation of the effect of a ghost-dependent canonical transformation of BRST-charge, we derive the corresponding transformation law for structure coefficients of Hamiltonian gauge algebra under rotation of constraints. We show the transformation law to deviate from the behavior (expected naively) characteristic to a genuine connection.
Inequality of Opportunity in Comparative Perspective: Recent Research on Educational Attainment and Social Mobility
Authors: Breen Richard , Jonsson Jan O.
Published: March 2005

Studies of how characteristics of the family of origin are associated with educational and labor market outcomes indicate the degree of openness of societies and have a long tradition in sociology. We review research published since 1990 into educational stratification and social (occupational or class) mobility, focusing on the importance of parental socioeconomic circumstances, and with particular emphasis on comparative studies. Large-scale data now available from many countries and several time points have led to more and better descriptions of inequality of opportunity across countries and over time. However, partly owing to problems of comparability of measurement, unambiguous conclusions about trends and ranking of countries have proven elusive. In addition, no strong evidence exists that explains intercountry differences. We conclude that the 1990s witnessed a resurgence of microlevel models, mostly of a rational choice type, that signals an increased interest in moving beyond description in stratification research.
Endogenous effectors of human liver glycogen phosphorylase modulate effects of indole-site inhibitors
Authors: Ercan-Fang Nacide , Taylor Miriam R. , Treadway Judith L. , Levy Carolyn B. , Genereux Paul E. , Gibbs E. Michael , Rath Virginia L. , Kwon Younggil , Gannon Mary C. , Nuttall Frank Q.
Published: March 2005

Phosphorylase is regulated by a number of small-molecular-weight effectors that bind to three sites on the enzyme. Recently, a fourth site referred to as the indole-inhibitor site has been identified. Synthetic compounds bind to the site and inhibit activity. However, the effects of these compounds in the presence of other endogenous effectors are unknown. We have determined the effects of four indole derivative glycogen phosphorylase inhibitors (GPI) on recombinant human liver glycogen phosphorylase a activity. The GPIs tested were all potent inhibitors. However, the endogenous inhibitors (glucose, ADP, ATP, fructose 1-phosphate, glucose 6-phosphate, UDP-glucose) and the activator (AMP) markedly reduced the inhibitory effect of GPIs. Consistent with these in vitro findings, the IC50for the inhibition of glycogenolysis in cells and the liver drug concentration associated with glucose-lowering activity in diabetic ob/ ob mice in vivo were also significantly higher than those determined in in vitro enzyme assays. The inhibitory effect of indole-site effectors is modulated by endogenous small-molecular-weight effectors of phosphorylase a activity. However, at higher concentrations (10–30 μM), the GPI effect was dominant and resulted in inhibition of phosphorylase a activity irrespective of the presence or absence of the other modulators of the enzyme.
Effect of murine strain on metabolic pathways of glucose production after brief or prolonged fasting
Authors: Burgess Shawn C. , Jeffrey F. Mark H. , Storey Charles , Milde Angela , Hausler Natasha , Merritt Matthew E. , Mulder Hindrik , Holm Cecilia , Sherry A. Dean , Malloy Craig R.
Published: March 2005

Background strain is known to influence the way a genetic manipulation affects mouse phenotypes. Despite data that demonstrate variations in the primary phenotype of basic inbred strains of mice, there is limited data available about specific metabolic fluxes in vivo that may be responsible for the differences in strain phenotypes. In this study, a simple stable isotope tracer/NMR spectroscopic protocol has been used to compare metabolic fluxes in ICR, FVB/N (FVB), C57BL/6J (B6), and 129S1/SvImJ (129) mouse strains. After a short-term fast in these mice, there were no detectable differences in the pathway fluxes that contribute to glucose synthesis. However, after a 24-h fast, B6 mice retain some residual glycogenolysis compared with other strains. FVB mice also had a 30% higher in vivo phospho enolpyruvate carboxykinase flux and total glucose production from the level of the TCA cycle compared with B6 and 129 strains, while total body glucose production in the 129 strain was ∼30% lower than in either FVB or B6 mice. These data indicate that there are inherent differences in several pathways involving glucose metabolism of inbred strains of mice that may contribute to a phenotype after genetic manipulation in these animals. The techniques used here are amenable to use as a secondary or tertiary tool for studying mouse models with disruptions of intermediary metabolism.
Ischemic proximal tubular injury primes mice to endotoxin-induced TNF-α generation and systemic release
Authors: Zager R. A. , Johnson Ali C. M. , Hanson Sherry Y. , Lund Steve
Published: March 2005

Endotoxemia (LPS) can exacerbate ischemic tubular injury and acute renal failure (ARF). The present study tested the following hypothesis: that acute ischemic damage sensitizes the kidney to LPS-mediated TNF-α generation, a process that can worsen inflammation and cytotoxicity. CD-1 mice underwent 15 min of unilateral renal ischemia. LPS (10 mg/kg iv), or its vehicle, was injected either 45 min before, or 18 h after, the ischemic event. TNF-α responses were gauged 2 h post-LPS injection by measuring plasma/renal cortical TNF-α and renal cortical TNF-α mRNA. Values were contrasted to those obtained in sham-operated mice or in contralateral, nonischemic kidneys. TNF-α generation by isolated mouse proximal tubules (PTs), and by cultured proximal tubule (HK-2) cells, in response to hypoxia-reoxygenation (H/R), oxidant stress, antimycin A (AA), or LPS was also assessed. Ischemia-reperfusion (I/R), by itself, did not raise plasma or renal cortical TNF-α or its mRNA. However, this same ischemic insult dramatically sensitized mice to LPS-mediated TNF-α increases in both plasma and kidney (∼2-fold). During late reperfusion, increased TNF-α mRNA levels also resulted. PTs generated TNF-α in response to injury. Neither AA nor LPS alone induced an HK-2 cell TNF-α response. However, when present together, AA+LPS induced approximately two- to fivefold increases in TNF-α/TNF-α mRNA. We conclude that modest I/R injury, and in vitro HK-2 cell mitochondrial inhibition (AA), can dramatically sensitize the kidney/PTs to LPS-mediated TNF-α generation and increases in TNF-α mRNA. That ischemia can “prime” tubules to LPS response(s) could have potentially important implications for sepsis syndrome, concomitant renal ischemia, and for the induction of ARF.
Apical ammonia transport by the mouse inner medullary collecting duct cell (mIMCD-3)
Authors: Handlogten Mary E. , Hong Seong-Pyo , Westhoff Connie M. , Weiner I. David
Published: March 2005

The collecting duct is the primary site of urinary ammonia secretion; the current study determines whether apical ammonia transport in the mouse inner medullary collecting duct cell (mIMCD-3) occurs via nonionic diffusion or a transporter-mediated process and, if the latter, presents the characteristics of this apical ammonia transport. We used confluent cells on permeable support membranes and examined apical uptake of the ammonia analog [14C]methylammonia ([14C]MA). mIMCD-3 cells exhibited both diffusive and saturable, transporter-mediated, nondiffusive apical [14C]MA transport. Transporter-mediated [14C]MA uptake had a Kmof 7.0 ± 1.5 mM and was competitively inhibited by ammonia with a Kiof 4.3 ± 2.0 mM. Transport activity was stimulated by both intracellular acidification and extracellular alkalinization, and it was unaltered by changes in membrane voltage, thereby functionally identifying an apical, electroneutral NH4+/H+exchange activity. Transport was bidirectional, consistent with a role in ammonia secretion. In addition, transport was not altered by Na+or K+removal, not inhibited by luminal K+, and not mediated by apical H+-K+-ATPase, Na+-K+-ATPase, or Na+/H+exchange. Finally, mIMCD-3 cells express the recently identified ammonia transporter family member Rh C glycoprotein (RhCG) at its apical membrane. These studies indicate that the renal collecting duct cell mIMCD-3 has a novel apical, electroneutral Na+- and K+-independent NH4+/H+exchange activity, possibly mediated by RhCG, that is likely to mediate important components of collecting duct ammonia secretion.
Differential renal gene expression in prehypertensive and hypertensive spontaneously hypertensive rats
Authors: Seubert J. M. , Xu F. , Graves J. P. , Collins J. B. , Sieber S. O. , Paules R. S. , Kroetz D. L. , Zeldin D. C.
Published: March 2005

Development of hypertension stems from both environmental and genetic factors wherein the kidney plays a central role. Spontaneously hypertensive rats (SHR) and the nonhypertensive Wistar-Kyoto (WKY) controls are widely used as a model for studying hypertension. The present study examined the renal gene expression profiles between SHR and WKY at a prehypertensive stage (3 wk of age) and hypertensive stage (9 wk of age). Additionally, age-related changes in gene expression patterns were examined from 3 to 9 wk in both WKY and SHR. Five to six individual kidney samples of the same experimental group were pooled together, and quadruplicate hybridizations were performed using the National Institute of Environmental Health Sciences Rat version 2.0 Chip, which contains ∼6,700 genes. Twenty two genes were found to be differentially expressed between SHR and WKY at 3 wk of age, and 104 genes were differentially expressed at 9 wk of age. Soluble epoxide hydrolase ( Ephx2) was found to be significantly upregulated in SHR at both time points and was the predominant outlier. Conversely, elastase 1 ( Ela1) was found to be the predominant gene downregulated in SHR at both time points. Analysis of profiles at 3 vs. 9 wk of age identified 508 differentially expressed genes in WKY rats. In contrast, only 211 genes were found to be differentially expressed during this time period in SHR. The altered gene expression patterns observed in the age-related analysis suggested significant differences in the vascular extracellular matrix system between SHR and WKY kidney. Together, our data highlight the complexity of hypertension and the numerous genes involved in and affected by this condition.
Rosiglitazone restores renal D1A receptor-Gs protein coupling by reducing receptor hyperphosphorylation in obese rats
Authors: Trivedi Meghna , Lokhandwala Mustafa F.
Published: March 2005

Dopamine D1A receptor function is impaired in obesity-induced insulin resistance, contributing to sodium retention. We showed previously that uncoupling of D1A receptors from G proteins is responsible for diminished natriuretic response to dopamine in obese Zucker rats (OZRs). We hypothesized that overexpression of G protein-coupled receptor kinases (GRKs) leads to increased phosphorylation of D1A receptors, which in turn causes uncoupling of the receptors from Gs proteins in proximal tubules of OZRs. We also examined effects of an insulin sensitizer, rosiglitazone, in correcting these defects. We found that basal and agonist (fenoldopam)-induced coupling of D1A receptors to Gs proteins was impaired in proximal tubules of OZRs compared with lean Zucker rats (LZRs). Moreover, basal serine phosphorylation of D1A receptors was elevated two- to threefold in proximal tubules of OZRs compared with LZRs. Fenoldopam increased D1A receptor phosphorylation in proximal tubules of LZRs but not OZRs. Compared with that in LZRs, GRK4 expression in OZRs was elevated 200–300% in proximal tubule cell lysates and GRK2 expression was ∼30% higher in plasma membranes isolated from proximal tubules of OZRs. Rosiglitazone treatment restored basal and agonist-induced coupling of D1A receptors to Gs proteins and reduced basal serine phosphorylation of D1A receptors, GRK4 expression, and translocation of GRK2 to the plasma membrane in proximal tubules of OZRs. Furthermore, rosiglitazone significantly reduced fasting blood glucose and plasma insulin in OZRs. Collectively, these results suggest that insulin resistance is responsible for GRK4 overexpression and GRK2 translocation leading to hyperphosphorylation of D1A receptors and their uncoupling from Gs proteins as rosiglitazone treatment corrects these defects in OZRs.
Epidermal growth factor activates nuclear factor-κB in human proximal tubule cells
Authors: Häussler Ulla , von Wichert Götz , Schmid Roland M. , Keller Frieder , Schneider Günter
Published: March 2005

The promotion of cell survival and regeneration in acute renal failure (ARF) is important for the restitution of renal function. Epidermal growth factor (EGF) has been implicated in the regulation of cell proliferation. We provide evidence for a direct link between EGF, nuclear factor-κB (NF-κB), and cell cycle regulation (cyclin D1). EGF was found to stimulate NF-κB-dependent gene transcription and DNA binding. In addition, EGF stimulated cyclin D1 promoter activity as well as cyclin D1 expression. Moreover, inhibition of NF-κB caused a pronounced reduction of EGF-induced cyclin D1 promoter activity. Furthermore, both EGF-mediated NF-κB activation and cyclin D1 expression were inhibited by coexpression of super IκB. Taken together, these data identify NF-κB and cyclin D1 as downstream targets of EGF and establish a molecular link between stimulation of EGF via activation of NF-κB and cyclin D1 expression in human proximal tubular cells.
Temperature Affects Voltage-Sensitive Conductances Differentially in Octopus Cells of the Mammalian Cochlear Nucleus
Authors: Cao Xiao-Jie , Oertel Donata
Published: March 2005

Temperature is an important physiological variable the influence of which on macroscopic electrophysiological measurements in slices is not well documented. We show that each of three voltage-sensitive conductances of octopus cells of the mammalian ventral cochlear nucleus (VCN) is affected differently by changes in temperature. As expected, the kinetics of the currents were faster at higher than at lower temperature. Where they could be measured, time constants of activation, deactivation, and inactivation had Q10 values between 1.8 and 4.6. The magnitude of the peak conductances was differentially affected by temperature. While the peak magnitude of the high-voltage-activated K+ conductance, gKH, was unaffected by changes in temperature, the peak of the low-voltage-activated K+ conductance, gKL, was reduced by half when the temperature was lowered from 33 to 23°C ( Q10 = 2). Changing the temperature changed the kinetics and the magnitude of the hyperpolarization-activated mixed cation conductance, gh, but the changes in magnitude were transient. The voltage sensitivity of the three conductances was unaffected by temperature. The action of temperature on these conductances is reflected in the resting potentials and in the shapes of action potentials.
Gene expression profiling of cerebellar development with high-throughput functional analysis
Authors: Saito Sakae , Honma Kimi , Kita-Matsuo Hiroko , Ochiya Takahiro , Kato Kikuya
Published: March 2005

We measured the expression levels of 450 genes during mouse postnatal cerebellar development by quantitative PCR using RNA purified from layers of the cerebellar cortex. Principal component analysis of the data matrix demonstrated that the first and second components corresponded to general levels of gene expression and gene expression patterns, respectively. We introduced 288 of the 450 genes into PC12 cells using a high-throughput transfection assay based on atelocollagen and determined the ability of each gene to promote neurite outgrowth or cell proliferation. Five genes induced neurite outgrowth, and seven genes enhanced proliferation. Evaluation of the functional data and gene expression patterns showed that none of these genes exhibited elevated expression at maturation, suggesting that genes characteristic of mature neurons are not likely to participate in neuronal development. These results demonstrate that functional data can facilitate interpretation of expression profiles and identification of new molecules that participate in biological processes.