bluuebunny/crossref_metadata_2025 huggingface dataset:
Electroluminescence
Authors: Lowry Erwin F.
Published: January 2009

It is a curious thing, but the Dawn of Civilization coincides with the beginnings of Night Life. When our ancestors learned how to light their way to bed, they were able, for the first time, to come down out of the trees. The ability to build a fire was one of the early distinguishing marks of Homo sapiens. By reason of the light and heat from the fires he made, he was enabled to establish his career on the ground. The anthropoid ape remained in the trees.
Applied optics at NBS
Authors: Gardner Irvine C.
Published: January 2009

Applied optics, in a general sense, should have a very broad connotation, including all branches of optics that have been found useful to industry, and on this basis it should certainly embrace spectroscopy, interferometry, photometry, colorimetry, polarimetry, and, in fact, virtually all of optics. This wide use of optics is indicative of the manner in which the major portions of many branches of science have been attracted into industry and have become of commercial importance during the past half century. However, telescopes, microscopes, and photographic objectives were the principal optical instruments used by industry or constructed in quantity prior to 1900 or 1920 and, consequently, the term applied optics is generally restricted to the science of designing, building, and testing optical instruments.
Advantages and disadvantages of various interpretations of the quantum theory
Authors: Margenau Henry
Published: January 2009

Joseph Henry's genius was attracted primarily to the great experimental problems of his age. Although he was a professor of natural philosophy, a discipline which a century ago combined the various branches of physical science, he is not known to have indulged in the kind of formal considerations to which the title of this evening's discourse alludes. Yet I am confident that my subject is not wholly inappropriate to the occasion of a lecture in honor of Joseph Henry. For his eminent biographer, Charles Greeley Abbot, describes him as “a man of varied culture, of large breadth and liberality of views, of generous impulses and of great gentleness and courtesy of manner”. Hence, while the speculations on which I am about to embark can hardly aspire to honor his memory, we may take comfort in supposing that he would gracefully listen to them and accept them as a small token of respect.
Theoretical Physics in the Alps
Authors: Glauber R. J.
Published: January 2009

THIS past summer, as in the three preceding ones, the Ecole d'Eté de Physique Théorique has continued a program, now a tradition, uniquely its own. Thirty students, with widely assorted backgrounds but a common interest in research, spent the two-month session attending intensive courses on modern physical theory. While half of the participants were French, the remainder represented a list of nations, including Italy, Belgium, Sweden, Yugoslavia, Norway, India, Germany, Greece, Egypt, Argentina, and Japan. This variety of students lent great color to the School. All of the students had a substantial command of French and English, the languages between which the courses were about equally divided. The School location is hardly to be neglected as a source of color. Perched on a slope of the Valley of Chamonix, it faces the Massif du Mont Blanc, an awe-inspiring view at all times.
A physicist at Oxford and Cambridge
Authors: Hughes D. J.
Published: January 2009

A short time agoI finished a year spent as a Fulbright Professor, in a way very few Englishmen are privileged to spend their time, at both Oxford and Cambridge. This dual existence has been not only a privilege but a severe test of diplomatic skill, especially in conversation with the average alumnus of either university, who will hardly admit that the other exists. As my year was about equally divided I did have a unique, as well as leisurely, opportunity to observe both, and was led to the somewhat surprising conclusion that definite differences do exist. Along with their common features, I shall mention some of these differences—a dangerous procedure, I realize, that may well cost me some budding friendships.
Giauque- Kelvin Proposal
Authors: Brickwedde F. G.
Published: January 2009

IN 1939 Professor W. F. Giauque, of the University of California, proposed that we change the manner of defining the number scale of the absolute, thermodynamic (Kelvin) scale of temperatures by assigning a number to a single reproducible thermal state (e.g., triple point of H2O). At present the number scale is defined by assigning a number (100) to the interval between two fixed points (“ice” and normal boiling points of H2O). J. P. Joule and Lord Kelvin made the same proposal one hundred years ago but it was forgotten until it was made anew by Giauque. Joule and Thomson in 1854 said the proposed change in definition “must be adopted ultimately” because the definition based on a single fixed point is “preferable”.
Government support of basic research in university physics departments 1952–53
Authors: McMillen J. Howard
Published: January 2009

It has been said that there is no correspondence between the amount of money spent for research and the amount of “true” research being carried out in this country. Others use the terms “research funds” and “research activity” synonymously. It is not uncommon to hear it said that more funds tend to diminish the number of fundamental discoveries in basic research, and on the other hand, that more and more money is needed for the kind of research that we are doing today. Probably the true relationship between research funds and the prosecution of worthwhile research lies somewhere in between these extremes. But whatever the correct correlation factor between tangible funds and intangible research may be, good data on funds invested in research are needed in national thinking and in comprehending some of the problems met with in the administration of research programs.
Physics in Engineering Education
Authors: Watson W. W.
Published: January 2009

THE Summer Institute conferences on Nuclear Physics in Engineering Education are being sponsored by the American Society for Engineering Education, the American Institute of Physics, and the National Science Foundation. A closed conference attended by over thirty engineers and physicists was held at Columbia University on April 22, 23, and 24, 1954, and a larger open conference will take place at Northwestern University September 7–10. This is a brief report of the closed conference, mostly abstracted from a more complete report, prepared by R. W. Houston, to be found in the June 1954 issue of the Journal of Engineering Education.
Physics society meetings yesterday and today
Authors: Lagemann Robert T.
Published: January 2009

Every physicist worthy of the name looks forward to attending one or more meetings of physical societies annually. Whatever his reasons for going—and they are many—he returns with some measure of inspiration as a reward. Often, as we say in the trade, he “gets an idea’’ from speaker or friend, or, as President Houston of the Rice Institute once put it, “He may get an idea of where to get a contract”, a very important consideration these days.
Transportation of matter and radioactivity by ionized air corrosion…
Authors: Primak W. , Fuchs L. H.
Published: January 2009

Several phenomena, essentially of chemical nature, which can cause a transportation of matter and radioactivity often occur in the handling of radioactive materials. The problem of confining radioactivity is a practical one and is of itself a concern. But in addition, the measurements of mass and radioactivity are basic data in many scientific experiments and a transportation of matter and radioactivity can give rise to baffling or spurious experimental results. It seems desirable to give wide notice to the phenomena for two reasons: first, since they occur most readily when large quantities of radioactivity are involved, close observation may be difficult or precluded; second, since many of the workers handling solid radioactive materials are engaged in physical experimentation rather than chemical, they might be led to an extensive and lengthy course of investigation before the proper explanation was discovered.
Karl Taylor Compton, 1887–1954
Authors: Harrison George R.
Published: January 2009

In the death of Karl Taylor Compton on June 22, 1954, American physicists lost one of their most stalwart colleagues, friends, and benefactors; the world of science lost one of its proudest examples of what a scientist should be and do; the nation lost a scientist-statesman of unusual insight and wisdom; and the world lost a human being of rare perception, integrity and charm.
Decibels of light and sound
Authors: Stevens S. S.
Published: January 2009

The usefulness of logarithms in the measurement of many of the stimuli to which human beings are sensitive is almost too obvious to need argument. Three reasons are commonly given to justify the practice:

1. The intensity ranges of the physical stimuli are enormous—energy ranges of trillions to one are involved in vision and hearing.

2. To a rough approximation, discrimination follows a law of relativity: the just detectable increment in a stimulus is proportional to the magnitude of the stimulus (Weber's law). Hence, to the extent that Weber's law holds, the logarithmic difference that is just detectable is constant.

3. According to Fechner's law, the subjective magnitude of a sensation is supposed to be proportional to the logarithm of the magnitude of the stimulus.
The role of physics in engineering education
Authors: Physics Committee of the American Institute of
Published: January 2009

The Report in Brief: The role of physics in engineering education is not a static one. It must respond and evolve with the momentous changes in both engineering and physics which are occurring continually. The predominent reliance of early engineering upon art is giving way to a modern technology based squarely upon the physical sciences. Since the beginning of this century we have seen as much progress in physics as had been obtained in the whole previous history of mankind. Yet the obvious and enormous increase in subject matter of modern physics is not the most significant factor relating to the aim of instruction in physics in the education of engineers. On the contrary, the cardinal aim should be that of imparting to the student a point of view, an attitude of mind, and a capacity to deal with the principles and methods of analysis of contemporary physics, for, without training and experience in these modes of thought, neither physicist nor engineer will prove competent to deal with the emerging problems of science and technology.
Letters to the Editor
Authors: Middleton W. E. K. , Salmon Vincent
Published: January 2009

As a photometrist I have read with much interest Dr. Stevens' article “Decibels of Light and Sound” in the October issue of Physics Today.
AIP Advisory Committee to NBS
Authors: Seitz F.
Published: January 2009

THE National Bureau of Standards faced a crisis in the spring of 1953 as a result of a controversy over the Bureau's position on certain types of battery additives. At the height of the tense situation, Secretary Weeks decided to attempt to resolve the controversy by seeking the advice of an Ad Hoc Committee composed of representatives of the professional scientific and engineering societies. L. A. DuBridge was appointed the American Institute of Physics representative of this group, which popularly came to be called the Kelly Committee since M. J. Kelly of the Bell Telephone Laboratories was its chairman. The committee was singularly effective in resolving the crisis through a series of actions and through recommendations contained in its final report of October 15, 1953. For example, its work in no small measure led to the reinstatement of A. V. Astin as Director of the Bureau.
Enrico Fermi 1901–1954
Authors: Allison S. K. , Segrè Emilio , Anderson Herbert L.
Published: January 2009

We are here to honor the memory of Enrico Fermi, Charles H. Swift Distinguished Service Professor of Physics at this University during the last decade. I shall try to express the sentiments of his associates here in the Institute for Nuclear Studies. Actually, the Institute is his Institute, for he was its outstanding source of intellectual stimulation. It was Enrico who attended every seminar and with incredible brilliance critically assayed every new idea or discovery. It was Enrico who arrived first in the morning and left last at night, filling each day with his outpouring of mental and physical energy. It was Enrico's presence and calm judgment, and the enormous respect we had for him, which made it impossible to magnify, or even mention, any small differences among us, such as can arise in any closely associated group. It was at Enrico's personal and urgent request that I took on the chore of directing the Institute in its routine affairs.
Physics south of the Sahara
Authors: Korff S. A.
Published: January 2009

We are sometimes inclined to think of Africa south of the Sahara as a country covered by tropical jungle and inhabited chiefly by elephants and pygmies. Any such oversimplification would lead us to conclude that this region had no interest for the world of physics. It is the purpose of this article to review (a) what is currently being done in physics and allied sciences and (b) the potentials for research and facilities which could be used by anyone having problems which could logically be undertaken there.
International Conference on Magnetism
Authors: Dreyfus B.
Published: January 2009

About two hundred participants, of whom three quarters came from abroad, were present at the International Conference on Magnetism that was held July 2–6, 1958, at Grenoble, France. The presence of delegates from 19 different countries, numerically well distributed, gave this meeting a truly international character. At Strasbourg (1939) and Grenoble (1950) the numbers of papers presented were 25 and 50, respectively; in 1958 there were 78 papers, taking in all 30 hours of meeting time. As purely technical papers were excluded, a high scientific level was ensured.
Frequency control symposium: Asbury Park, N.J., May 8, 1958
Authors: Plotkin H. H.
Published: January 2009

In the June 1956 issue of Physics Today we reported on the first meeting devoted to papers dealing with progress toward using atomic and molecular resonances as high-precision frequency standards. Since then, the Frequency Control Division of the US Army Signal Research and Development Laboratory has included papers in this field at its annual meetings. This year's meeting indicated the striking progress accomplished in all of the related phases of research and development, so that those present were again treated to an interesting and complete survey.
Unsolved problems in acoustics
Authors: Lindsay R. B.
Published: January 2009

The progress of science may be said to depend largely on our asking the most appropriate questions and hoping that the same kind of imagination that led to the questions will provide clues to the answers. There was a time, not so long ago, when it was felt that all possible appropriate fundamental questions about sound had been raised and that the answers indeed were all found in Lord Rayleigh's famous Theory of Sound. It was believed to be sure that there were hosts of engineering applications of acoustics to be explored, but that these would not turn up anything fundamentally new. This view is no longer held by those who have followed trends in acoustics during the past quarter century. Both as an active branch of physics and as a subject fundamental to modern engineering, acoustics poses many unsolved problems of fundamental character. Some of these indeed have been suggested by the very advances in instrumentation made possible through acoustical engineering. For it is only through such instrumentation that we can now work with sounds of the very high intensity and high frequency which produce curious and unexplained effects in matter under extreme conditions of temperature and pressure. At the same time it is also through experimental facilities of this kind that we can begin to study more effectively the influence of sound on human beings and other organisms, and this too immediately raises hosts of questions. Through the fertile interplay of theory and application, acoustics is in a particularly strategic position to suggest problems whose solution will cast new light on both the properties of matter and the interaction of sound and man.
Factors concerning education for science and engineering
Authors: Seitz Frederick
Published: January 2009

Our nation is now passing through one of the gravest periods in its history. The fate of many the most precious things in the heritage of modern man will depend upon our ability to surmount the present crisis. Apart from the physical well-being of those now living, many matters of profound cultural value which we have inherited through the intellectual enlightenment of the Greeks and the religious genius of the peoples of Asia Minor are at stake.
Basic research and defense developments
Authors: Frenkiel Francois N.
Published: January 2009

Planning defense developments ten or twenty years from now requires the prediction of the future progress in various fields of science. While such a prediction should be influenced by the experience gained from present and past progress it would be of little value to make a simple extrapolation from the present to the future. The future of scientific and technological developments will be what we make it. The best way to forecast them is to take into account the potentialities of rapidly advancing fundamental research. The best way to influence them is to increase those potentialities by close contacts between fundamental research, applied research, and engineering.
Max Planck: One hundredth birthday celebration
Authors: Weisskopf V. F.
Published: January 2009

On April 24–25, the German Academy of Sciences in Berlin and the German Physical Societies held memorial sessions in Berlin to commemorate the 100th birthday of Max Planck. This celebration was a remarkable event in many respects, but primarily in that it was the first time scientists from the two sectors of Germany had collaborated on a common project. Scientists from both sides of the Iron Curtain spoke at the meetings, which were held alternately in East and in West Berlin. In the true spirit of Max Planck, the celebration became a symbol of the fact that science represents values beyond the scope of politics.
Effect of neutral gas motion on the rotation of dust clusters in an axial magnetic field
Authors: Carstensen Jan , Greiner Franko , Hou Lu-Jing , Maurer Horst , Piel Alexander
Published: January 2009

Experiments are carried out to investigate the rotation of dust clusters in a radio-frequency plasma sheath with a vertical magnetic field. Our observations are in disagreement with the standard model, in which it was assumed that the neutral gas is at rest and that a steady rotation is attained when the ion-drag force is balanced by neutral friction. Here, we re-examine this basic assumption by carefully designed experiments. Our results suggest that the neutral gas is set into rotation by E×B induced ion flow through ion-neutral collisions and that the dust particles are advected by this flow. A hydrodynamic model is proposed to describe the rotation of the neutral gas and it can explain our observations.
The isotope effect in superconductivity
Authors: Maxwell E.
Published: January 2009

Ever since Kamerlingh-Onnes discovered in 1911 that the electrical resistance of mercury abruptly vanished at a temperature just a few degrees above the absolute zero, the phenomenon of superconductivity has presented an intriguing challenge to physicists. Subsequent experiments by Onnes and others definitely established that the resistivity of a superconductor, if at all finite, must be immeasurably small, and less than 10−20 ohm cm. Consequently the superconductor is assumed to have zero resistance. Onnes soon found that the superconducting property was not peculiar to mercury but was characteristic of a sizable group of metals. Twentyone of the metallic elements are known to be superconductors as are innumerable alloys and intermetallic compounds. The known superconductors are exhibited in Fig. 1 and are seen to fall into definite areas of the periodic table. None of the monovalent metals are observed to be superconducting, at least down to temperatures of the order of a few tenths of a degree absolute.
Radiation effects in solids
Authors: Seitz Frederick
Published: January 2009

As far as I am aware, this is the first invited session of the American Physical Society devoted to the topic of radiation effects in solids—a field that has been an active one for nearly a decade. I believe it is safe to say that it will not be the last such session. The long delay in this event arises, of course, from the fact that the field received its greatest stimulus from the wartime research in the field of atomic energy so that many aspects of it were classified at the start and will remain classified indefinitely in the future.
Dislocation mechanics of copper and iron in high rate deformation tests
Authors: Armstrong Ronald W. , Arnold Werner , Zerilli Frank J.
Published: January 2009

Different dislocation processes are shown to be operative under high rate loading by impact-induced shock tests as compared with shockless isentropic compression experiments (ICEs). Under shock loading, the plastic deformation rate dependence of the flow stress of copper is attributed to dislocation generation at the propagating shock front, while in shockless ICEs, the rate dependence is attributed to drag-controlled mobile dislocation movement from within the originally resident dislocation density. In contrast with shock loading, shockless isentropic compression can lead to flow stress levels approaching the theoretical yield stress and dislocation velocities approaching the speed of sound. In iron, extensive shock measurements reported for plate impact tests are explained in terms of plasticity-control via the nucleation of deformation twins at the propagating shock front.
The effect of ion irradiation and annealing on exchange spring magnets
Authors: Fassbender J. , Grenzer J. , Roshchupkina O. , Choi Y. , Jiang J. S. , Bader S. D.
Published: January 2009

It is demonstrated that both the nucleation field and the irreversible switching field of Sm2Co7/Fe exchange spring bilayers is decreased by means of 10 keV He ion irradiation. The reduction is attributed to interfacial mixing and irradiation induced softening of the hard magnetic layer. By lowering the energy to 0.8 keV the ions do not penetrate the hard magnetic layer and, consequently, no softening is observed. However, although irradiation induced interfacial mixing is still present it is not large enough to create a graded interface layer and the nucleation field decreases. In contrast, conventional annealing under appropriate conditions leads to an increase in the nucleation field. This distinct discrepancy can be explained by detailed investigation of the layer structure by x-ray reflectivity measurements.
Improvement of isentropic efficiency of a magnetohydrodynamic power generator by radio-frequency preionization
Authors: Murakami Tomoyuki , Okuno Yoshihiro
Published: January 2009

We describe the effect of a radio-frequency (rf) power application on the performance of a magnetohydrodynamic (MHD) electrical power generator, as determined through shock-tunnel-based experiments and quasi-three-dimensional numerical simulations. The temporal plasma-fluid behavior, the one-dimensional plasma-fluid structure, the enthalpy-entropy diagram, the quality of the energy conversion efficiency, and the energy flow in the power-generating system are investigated. Preionization assistance by a small amount of rf power drastically changes the entire MHD power-generating system; the MHD extraction length is considerably extended and the isentropic efficiency is significantly improved.
Efficient heterostructure doped-barrier varactor diodes
Authors: Reklaitis A.
Published: January 2009

Doped-barrier heterostructure varactor diodes are suggested for efficient frequency multiplication of the microwave radiation. It is shown that the efficiency of the heterostructure-barrier varactor is significantly enhanced if the undoped barrier is replaced by the doped one. The analysis is carried out using Boltzmann statistics. The analytical results are compared to the results of Monte Carlo simulations obtained by taking into account Fermi–Dirac statistics. The results of Monte Carlo calculations of the capacitance-voltage characteristics of the In0.53Ga0.47As/AlAs and InN/GaN doped-barrier varactor diodes are presented.
Microanode image porous dielectric detector
Authors: Lorikyan M. P.
Published: January 2009

Porous dielectric detectors (PDDs) can expand the methods of image registration of charged particles, neutrons, and x rays to a great extent; however they are not sufficiently studied yet. Recently it was revealed that multiwire and microstrip PDDs operate stably in dc mode. This paper presents a new two-dimensional microanode image PDD (MAIPDD). Also, preliminary results of investigation of MAIPDD for 5.9 keV x rays and two types of microstrip PDDs are presented.
Measurements of accurate x-ray scattering data of protein solutions using small stationary sample cells
Authors: Hong Xinguo , Hao Quan
Published: January 2009

In this paper, we report a method of precise in situ x-ray scattering measurements on protein solutions using small stationary sample cells. Although reduction in the radiation damage induced by intense synchrotron radiation sources is indispensable for the correct interpretation of scattering data, there is still a lack of effective methods to overcome radiation-induced aggregation and extract scattering profiles free from chemical or structural damage. It is found that radiation-induced aggregation mainly begins on the surface of the sample cell and grows along the beam path; the diameter of the damaged region is comparable to the x-ray beam size. Radiation-induced aggregation can be effectively avoided by using a two-dimensional scan (2D mode), with an interval as small as 1.5 times the beam size, at low temperature (e.g., 4 °C). A radiation sensitive protein, bovine hemoglobin, was used to test the method. A standard deviation of less than 5% in the small angle region was observed from a series of nine spectra recorded in 2D mode, in contrast to the intensity variation seen using the conventional stationary technique, which can exceed 100%. Wide-angle x-ray scattering data were collected at a standard macromolecular diffraction station using the same data collection protocol and showed a good signal/noise ratio (better than the reported data on the same protein using a flow cell). The results indicate that this method is an effective approach for obtaining precise measurements of protein solution scattering.
Electronic structure and band-gap modulation of graphene via substrate surface chemistry
Authors: Shemella Philip , Nayak Saroj K.
Published: January 2009

We have studied the electronic structure of graphene deposited on a SiO2 surface using density functional methods. The band structure of the graphene monolayer strongly depends on surface characteristics of the underlying SiO2 surface; for an oxygen-terminated surface, the monolayer exhibits a finite energy band gap while the band gap is closed when the oxygen atoms on the substrate are passivated with hydrogen atoms. We find that at least a graphene bilayer is required for a near zero energy gap when deposited on a substrate without H-passivation. Our results are discussed in the light of recent experiments.
Design considerations for refractive solid immersion lens: Application to subsurface integrated circuit fault localization using laser induced techniques
Authors: Goh S. H. , Sheppard C. J. R. , Quah A. C. T. , Chua C. M. , Koh L. S. , Phang J. C. H.
Published: January 2009

With fast scaling and advancement of integrated circuit (IC) technology, circuitries have become smaller and denser. New materials and more sophisticated designs have evolved. These changes reduced the effectiveness of conventional laser induced fault localization techniques. Since IC fault localization is the most critical step in failure analysis, there are strong motivations to improve both spatial resolution and sensitivity of such systems to meet the new challenges from advanced technology. Refractive solid immersion lens (RSIL) is well known to enhance the laser spot size which directly affects resolution and sensitivity in back side fault localizations. In practice, it is difficult to operate RSIL at the ideal configurations to obtain the smallest spot resolution. It is necessary to understand the resolution performance at the other design focal planes. Besides resolution, there are also other factors that affect sensitivity in a RSIL enhanced system. This paper identifies and characterizes key RSIL design parameters to optimize RSIL performance on laser induced techniques. We report that the most efficient conditions are achieved close to aplanatic RSIL design to within 20–25 μm (for a 1 mm diameter lens), and the backing objective should be the minimum numerical aperture required for optimum resolution performance. The size of the mechanical clear aperture opening should be large enough (>80%) to exploit the advantage of aplanatic RSIL. RSIL is developed on a laser scanning optical microscope in this work, and a resolution of 0.3 μm (for a wavelength of 1340 nm) was achieved over a range of operating conditions. A quantitative resolution of 0.25 μm is achieved and a pitch structure of 0.4 μm is easily resolvable. Close to 15 times enhancement in laser induced signal is obtained.
Optical constants of graphene layers in the visible range
Authors: Bruna M. , Borini S.
Published: January 2009

We show that the optical constants of graphene in the visible range can be estimated by means of a very simple procedure involving their consistence with universal optical conductivity and experimentally measured optical spectra, within the framework of Fresnel coefficients calculation. The obtained complex refractive index allows for accurate prediction of the optical behavior of graphene in the visible range, from the two-dimensional limit (single atomically thick graphene layer) to the bulk limit (graphite). Therefore, it may result very useful for quantitative optical analysis of graphene layers and graphitic structures in general.
Integrin αvβ1 promotes infection by human metapneumovirus
Authors: Cseke Gabriella , Maginnis Melissa S. , Cox Reagan G. , Tollefson Sharon J. , Podsiad Amy B. , Wright David W. , Dermody Terence S. , Williams John V.
Published: January 2009

Human metapneumovirus (hMPV) is a recently described paramyxovirus that causes lower respiratory infections in children and adults worldwide. The hMPV fusion (F) protein is a membrane-anchored glycoprotein and major protective antigen. All hMPV F protein sequences determined to date contain an Arg-Gly-Asp (RGD) sequence, suggesting that F engages RGD-binding integrins to mediate cell entry. The divalent cation chelator EDTA, which disrupts heterodimeric integrin interactions, inhibits infectivity of hMPV but not the closely related respiratory syncytial virus (RSV), which lacks an RGD motif. Function-blocking antibodies specific for αvβ1 integrin inhibit infectivity of hMPV but not RSV. Transfection of nonpermissive cells with αv or β1 cDNAs confers hMPV infectivity, whereas reduction of αv and β1 integrin expression by siRNA inhibits hMPV infection. Recombinant hMPV F protein binds to cells, whereas Arg-Gly-Glu (RGE)-mutant F protein does not. These data suggest that αvβ1 integrin is a functional receptor for hMPV.
Congenitally altered motor experience alters somatotopic organization of human primary motor cortex
Authors: Stoeckel M. Cornelia , Seitz Rüdiger J. , Buetefisch Cathrin M.
Published: January 2009

Human motor development is thought to result from a complex interaction between genes and experience. The well-known somatotopic organization of the primate primary motor cortex (M1) emerges postnatally. Although adaptive changes in response to learning and use occur throughout life, somatotopy is maintained as reorganization is restricted to modifications within major body part representations. We report of a unique opportunity to evaluate the influence of experience on the genetically determined somatotopic organization of motor cortex in humans. We examined the motor “foot” representation in subjects with congenitally compromised hand function and compensatory skillful foot use. Functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) of M1 revealed that the foot was represented in the classical medial foot area of M1 and was several centimetres away in nonadjacent cortex in the vicinity of the lateral “hand” area. Both areas had direct output to the spinal motor neurons innervating foot muscles and were behaviorally relevant because experimental disruption of either area by TMS altered reaction times. We demonstrate a unique, nonsomatotopically organized M1 in humans, which emerged as a function of grossly altered motor behavior from the earliest stages of development. Our results imply that during early motor development experience may play a more critical role in the shaping of genetically determined neural networks than previously assumed.
Src-dependent repression of ARF6 is required to maintain podosome-rich sealing zones in bone-digesting osteoclasts
Authors: Heckel Tobias , Czupalla Cornelia , Expirto Santo Ana Isabel , Anitei Mihaela , Arantzazu Sanchez-Fernandez Maria , Mosch Kerstin , Krause Eberhard , Hoflack Bernard
Published: January 2009

Bone digestion occurs when osteoclasts adhere onto bone surfaces and polarize to form acidic, hydrolase-rich resorption lacunae. For this process, they condense their actin-rich podosomes in tight belts to establish sealing zones, which segregate their basal membranes from those facing resorption lacunae. This polarization process remains poorly understood. Here, we combined quantitative proteomics and gene silencing to identify new substrates of the Src tyrosine kinase, a key regulator of osteoclast function. We now report that a depletion of the ARF GTPase-activating protein GIT2, which localizes to sealing zones upon Src phosphorylation, or a lack of GTP hydrolysis on ARF6 impairs sealing zone formation and polarized membrane traffic. Surprisingly, the Rho guanine nucleotide exchange factors α and β PIX, which usually coordinate ARF and Rho signaling, were found to be dispensable. We conclude that the Src-dependent localization of GIT2 is essential for down-regulating ARF6 activity at sealing zones, and thus for maintaining osteoclast polarity.
GLP-1 receptor stimulation preserves primary cortical and dopaminergic neurons in cellular and rodent models of stroke and Parkinsonism
Authors: Li Yazhou , Perry TracyAnn , Kindy Mark S. , Harvey Brandon K. , Tweedie David , Holloway Harold W. , Powers Kathleen , Shen Hui , Egan Josephine M. , Sambamurti Kumar , Brossi Arnold , Lahiri Debomoy K. , Mattson Mark P. , Hoffer Barry J. , Wang Yun , Greig Nigel H.
Published: January 2009

Glucagon-like peptide-1 (GLP-1) is an endogenous insulinotropic peptide secreted from the gastrointestinal tract in response to food intake. It enhances pancreatic islet β-cell proliferation and glucose-dependent insulin secretion, and lowers blood glucose and food intake in patients with type 2 diabetes mellitus (T2DM). A long-acting GLP-1 receptor (GLP-1R) agonist, exendin-4 (Ex-4), is the first of this new class of antihyperglycemia drugs approved to treat T2DM. GLP-1Rs are coupled to the cAMP second messenger pathway and, along with pancreatic cells, are expressed within the nervous system of rodents and humans, where receptor activation elicits neurotrophic actions. We detected GLP-1R mRNA expression in both cultured embryonic primary cerebral cortical and ventral mesencephalic (dopaminergic) neurons. These cells are vulnerable to hypoxia- and 6-hydroxydopamine–induced cell death, respectively. We found that GLP-1 and Ex-4 conferred protection in these cells, but not in cells from
Glp1r
knockout (-/-) mice. Administration of Ex-4 reduced brain damage and improved functional outcome in a transient middle cerebral artery occlusion stroke model. Ex-4 treatment also protected dopaminergic neurons against degeneration, preserved dopamine levels, and improved motor function in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson's disease (PD). Our findings demonstrate that Ex-4 can protect neurons against metabolic and oxidative insults, and they provide preclinical support for the therapeutic potential for Ex-4 in the treatment of stroke and PD.
Sensory transmission in cerebellar granule cells relies on similarly coded mossy fiber inputs
Authors: Bengtsson Fredrik , Jörntell Henrik
Published: January 2009

The computational principles underlying the processing of sensory-evoked synaptic inputs are understood only rudimentarily. A critical missing factor is knowledge of the activation patterns of the synaptic inputs to the processing neurons. Here we use well-defined, reproducible skin stimulation to describe the specific signal transformations that occur in different parallel mossy fiber pathways and analyze their representation in the synaptic inputs to cerebellar granule cells. We find that mossy fiber input codes are preserved in the synaptic responses of granule cells, suggesting a coding-specific innervation. The computational consequences of this are that it becomes possible for granule cells to also transmit weak sensory inputs in a graded fashion and to preserve the specific activity patterns of the mossy fibers.
Elevation increases in moth assemblages over 42 years on a tropical mountain
Authors: Chen I-Ching , Shiu Hau-Jie , Benedick Suzan , Holloway Jeremy D. , Chey Vun Khen , Barlow Henry S. , Hill Jane K. , Thomas Chris D.
Published: January 2009

Physiological research suggests that tropical insects are particularly sensitive to temperature, but information on their responses to climate change has been lacking—even though the majority of all terrestrial species are insects and their diversity is concentrated in the tropics. Here, we provide evidence that tropical insect species have already undertaken altitude increases, confirming the global reach of climate change impacts on biodiversity. In 2007, we repeated a historical altitudinal transect, originally carried out in 1965 on Mount Kinabalu in Borneo, sampling 6 moth assemblages between 1,885 and 3,675 m elevation. We estimate that the average altitudes of individuals of 102 montane moth species, in the family Geometridae, increased by a mean of 67 m over the 42 years. Our findings indicate that tropical species are likely to be as sensitive as temperate species to climate warming, and we urge ecologists to seek other historic tropical samples to carry out similar repeat surveys. These observed changes, in combination with the high diversity and thermal sensitivity of insects, suggest that large numbers of tropical insect species could be affected by climate warming. As the highest mountain in one of the most biodiverse regions of the world, Mount Kinabalu is a globally important refuge for terrestrial species that become restricted to high altitudes by climate warming.
Market forces affect patterns of polygyny in Uganda
Authors: Pollet Thomas V. , Nettle Daniel
Published: January 2009

Polygynous marriage is generally more beneficial for men than it is for women, although women may choose to marry an already-married man if he is the best alternative available. We use the theory of biological markets to predict that the likelihood of a man marrying polygynously will be a function of the level of resources that he has, the local sex ratio, and the resources that other men in the local population have. Using records of more than 1 million men in 56 districts from the 2002 Ugandan census, we show that polygynously married men are more likely to own land than monogamously married men, that polygynous marriages become more common as the district sex ratio becomes more female biased, that owning land is particularly important when men are abundant in the district, and that a man's owning land most increases the odds of polygyny in districts where few other men own land. Results are discussed with reference to models of the evolution of polygyny.
Inhibition of RIG-I and MDA5-dependent antiviral response by gC1qR at mitochondria
Authors: Xu Lijuan , Xiao Nengming , Liu Feng , Ren Hongwei , Gu Jun
Published: January 2009

gC1qR is one of the C1q receptors implicated in the regulation of innate and adaptive immunity. We found that gC1qR inhibits RIG-I and MDA5-dependent antiviral signaling. Double stranded RNA and virus trigger the translocation of gC1qR to the mitochondrial outer membrane leading to the interaction of gC1qR with the RIG-I and MDA5 adaptor, VISA/MAVS/IPS-1/Cardif. The interaction of gC1qR with VISA/MAVS/IPS-1/Cardif at mitochondria results in the disruption of RIG-I and MDA5 signaling and the promotion of virus replication. Knockdown of endogenous gC1qR enhances RIG-I-dependent antiviral signaling, and augments the inhibition of virus proliferation. Therefore, gC1qR is a physiological inhibitor of the RIG-I and MDA5-mediated antiviral signaling pathway. These data uncover a new viral mechanism used to negatively control antiviral signaling in host cells.
Periodic reversal of direction allows Myxobacteria to swarm
Authors: Wu Yilin , Kaiser A. Dale , Jiang Yi , Alber Mark S.
Published: January 2009

Many bacteria can rapidly traverse surfaces from which they are extracting nutrient for growth. They generate flat, spreading colonies, called swarms because they resemble swarms of insects. We seek to understand how members of any dense swarm spread efficiently while being able to perceive and interfere minimally with the motion of others. To this end, we investigate swarms of the myxobacterium,
Myxococcus xanthus
. Individual
M. xanthus
cells are elongated; they always move in the direction of their long axis; and they are in constant motion, repeatedly touching each other. Remarkably, they regularly reverse their gliding directions. We have constructed a detailed cell- and behavior-based computational model of
M. xanthus
swarming that allows the organization of cells to be computed. By using the model, we are able to show that reversals of gliding direction are essential for swarming and that reversals increase the outflow of cells across the edge of the swarm. Cells at the swarm edge gain maximum exposure to nutrient and oxygen. We also find that the reversal period predicted to maximize the outflow of cells is the same (within the errors of measurement) as the period observed in experiments with normal
M. xanthus
cells. This coincidence suggests that the circuit regulating reversals evolved to its current sensitivity under selection for growth achieved by swarming. Finally, we observe that, with time, reversals increase the cell alignment, and generate clusters of parallel cells.
X chromosome inactivation in the absence of Dicer
Authors: Kanellopoulou Chryssa , Muljo Stefan A. , Dimitrov Stoil D. , Chen Xi , Colin Christian , Plath Kathrin , Livingston David M.
Published: January 2009

Dicer is central to the RNA interference (RNAi) pathway, because it is required for processing of double-stranded RNA (dsRNA) precursors into small RNA effector molecules. In principle, any long dsRNA could serve as a substrate for Dicer. The X inactive specific transcript (
Xist
) is an untranslated RNA that is required for dosage compensation in mammals. It coats and silences 1 of the 2 X chromosomes in female cells and initiates a chromosomewide change in chromatin structure that includes the recruitment of Polycomb proteins, but it is largely unknown how
Xist
RNA mediates these processes. To investigate a potential link between the RNAi pathway and X inactivation, we generated and analyzed Dicer-deficient embryonic stem (ES) cells. In the absence of Dicer, coating by
Xist
RNA, initiation of silencing, and recruitment of Polycomb proteins occur normally. Dicer ablation had modest effects on the steady-state levels of spliced
Xist
RNA. Together our data indicate that the RNAi machinery is not essential for the initiation of X inactivation.
Two proteolytic pathways regulate DNA repair by cotargeting the Mgt1 alkylguanine transferase
Authors: Hwang Cheol-Sang , Shemorry Anna , Varshavsky Alexander
Published: January 2009

O
6
-methylguanine (O
6
meG) and related modifications of guanine in double-stranded DNA are functionally severe lesions that can be produced by many alkylating agents, including
N
-methyl-
N′
-nitro-
N
-nitrosoguanidine (MNNG), a potent carcinogen. O
6
meG is repaired through its demethylation by the O
6
-alkylguanine-DNA alkyltransferase (AGT). This protein is called Mgmt (or MGMT) in mammals and Mgt1 in the yeast
Saccharomyces cerevisiae
. AGT proteins remove methyl and other alkyl groups from an alkylated O
6
in guanine by transferring the adduct to an active-site cysteine residue. The resulting S-alkyl-Cys of AGT is not restored back to Cys, so repair proteins of this kind can act only once. We report here that
S. cerevisiae
Mgt1 is cotargeted for degradation, through a degron near its N terminus, by 2 ubiquitin-mediated proteolytic systems, the Ubr1/Rad6-dependent N-end rule pathway and the Ufd4/Ubc4-dependent ubiquitin fusion degradation (UFD) pathway. The cotargeting of Mgt1 by these pathways is synergistic, in that it increases not only the yield of polyubiquitylated Mgt1, but also the processivity of polyubiquitylation. The N-end rule and UFD pathways comediate both the constitutive and MNNG-accelerated degradation of Mgt1. Yeast cells lacking the Ubr1 and Ufd4 ubiquitin ligases were hyperresistant to MNNG but hypersensitive to the toxicity of overexpressed Mgt1. We consider ramifications of this discovery for the control of DNA repair and mechanisms of substrate targeting by the ubiquitin system.
RNA repair restores hemoglobin expression in IVS2–654 thalassemic mice
Authors: Svasti Saovaros , Suwanmanee Thipparat , Fucharoen Suthat , Moulton Hong M. , Nelson Michelle H. , Maeda Nobuyo , Smithies Oliver , Kole Ryszard
Published: January 2009

Repair of β-globin pre-mRNA rendered defective by a thalassemia-causing splicing mutation, IVS2–654, in intron 2 of the human β-globin gene was accomplished in vivo in a mouse model of IVS2–654 thalassemia. This was effected by a systemically delivered splice-switching oligonucleotide (SSO), a morpholino oligomer conjugated to an arginine-rich peptide. The SSO blocked the aberrant splice site in the targeted pre-mRNA and forced the splicing machinery to reselect existing correct splice sites. Repaired β-globin mRNA restored significant amounts of hemoglobin in the peripheral blood of the IVS2–654 mouse, improving the number and quality of erythroid cells.