bluuebunny/crossref_metadata_2025 huggingface dataset:
The meetings in Mexico
Authors: Korff S. A.
Published: January 2009

Mexico was the scene of three meetings during late August and early September 1955. The first of these was the joint meeting in Mexico City of the American Physical Society and the Sociedad Mexicana de Fisica. The second was the international cosmic-ray conference, the Congreso de Radiacion Cosmica, held at Guanajuato. The third, immediately following this and in the same place, was the meeting of the cosmicray component of CSAGI, the Comité Special pour l'Année Geophysique International.
G. Bernard Rossi
Authors: Seaborg Glenn T.
Published: January 2009

G. Bernard Rossi, supervisor of the Crocker Laboratory 60-inch cyclotron of the University of California at Berkeley, died very suddenly and unexpectedly of a heart attack on February 5th, at the age of 41.
Physics tonight
Authors: Oppenheimer J. Robert
Published: January 2009

Physicists are involved in a wonderfully diverse and varied set of enterprises, not simply and necessarily related. Your speaker is not distinguished by the development of his imagination; almost everything that happens amazes him. I shall not try to give a general landscape of all that physicists are up to. It ranges from the magnetohydrodynamics of interstellar matter to nuclear alignment at low temperatures; it ranges from the giant rocket to transistors, and to instruments for detecting valuable minerals in the ground; it ranges from automation to the coding problem of genetics; it ranges from teaching doctors and engineers and soldiers, and even ordinary men, to advising the heads of state.
Ionization Phenomena in Discharges
Authors: Brown Sanborn C.
Published: January 2009

Conference at Clarendon Laboratory.
Magnetic properties below 1 °K
Authors: de Klerk D.
Published: January 2009

Some substances , for example iron and nickel, show a rather complicated magnetic behavior at room temperature. When placed in a magnetic field they show a magnetic moment which not only is a function of field and temperature, but which also depends on the history of the specimen; that is, it depends on the fields and temperatures in which the substance has been before. These materials are called ferromagnetics. One characteristic property is the occurrence of remanent magnetism, i.e., if the material is taken out of the field the moment does not fall back to zero but it goes to a certain value also determined by the history.
Ferromagnetism
Authors: Batdorf S. B.
Published: January 2009

All substances react in some degree to a magnetic field, but only iron and those substances designated ferromagnetic by virtue of their similarity to iron become strongly enough magnetized in ordinary magnetic fields to be popularly regarded as magnetic. Ferromagnetic materials are generally characterized by (a) saturation in readily obtainable magnetic fields, (b) a magnetization curve exhibiting a hysteresis loop (see Fig. 1), and (c) a temperature, known as the Curie temperature, above which ferromagnetic effects disappear.
Luminous and dark formations of intergalactic matter
Authors: Zwicky Fritz
Published: January 2009

As astronomy pushed its limits from the solar system to the stars of the Milky Way and to the distant galaxies and clusters of galaxies, the following three problems suggested themselves automatically. Is there matter spread throughout interplanetary space? Is there matter in interstellar space? Are the enormous intergalactic spaces empty or not?
A new theory for the great ice ages
Authors: Zapffe Carl A.
Published: January 2009

With the exception of the Hiroshima bomb and Darwin's voyage on the Beagle, few developments of science have had as great an impact upon the human imagination as Agassiz's announcement in 1837 that currently habitable portions of the earth had been covered in geologically recent times by ice sheets thousands of feet in thickness and covering millions of square miles. At first hotly contested, the postulate finally gained universal acceptance because of such indisputable evidence as typically glacial till, drift, and boulders transported hundreds of miles from their bed-rock origins; deep abrasion markings on the surface of bed-rock recording the grinding flow; moraines and hills of glacial deposits along with typical lakes, rivers, and so forth.
“Mi casa es la suya”
Authors: Hanau Richard
Published: January 2009

It is Engineering Week at the College of Agriculture and Mechanic Arts in Mayagüez, Puerto Rico, February 22–27, 1954. Just as in stateside colleges of the United States, there are luncheons, lectures exhibits, and trips through local factories. I am in the main auditorium where we are about to hear a lecture by the head of a Puerto Rican research institute. Everyone is in shirtsleeves or sportshirts, for the weather is typical of the tropics. Through the open doors and louvered shutters I can see the royal palms, flowering African tulip trees, and the fern-leaved flamboyán. The breeze cools those of us who hurried over from a class the last hour.
A guidance device for the blind
Authors: Benham T. A.
Published: January 2009

In 1943 the Signal Corps began the development of a travel aid which was to be used to help the blinded of World War II in their rehabilitation program. The scope of the problem soon developed to include all blind people, civilians as well as veterans. The research on a suitable guidance device went through several stages and finally reached the point where RCA was contracted by the Signal Corps to manufacture 25 prototypes for test and evaluation. Subsequently, a contract was entered into between the Veterans Administration Research Division and Haverford College for the express purpose of giving the Signal Corps Sensory Aid a realistic series of field tests. Before describing the results of these tests let us say a few words about the instrument itself.
Much ado about nothing
Authors: Corben H. C.
Published: January 2009

Nature abhors a vacuum, the ancient physicists told us. And judging from the modern quantum theory of the vacuum it is not very surprising. Indeed, since Dirac propounded his theory of the electron, there have appeared many papers in which the properties of the vacuum have been discussed in terms of very complicated (and sometimes divergent) integrals. Instead of being the simplest problem in the world, the motion of a free electron in a vacuum appears to be an extremely complicated phenomenon. Instead of being an elementary nothingness, like the antithesis of Hegel's “Being” or that which Torricelli would have produced with a perfect pump, the vacuum of quantum electrodynamics can “fluctuate”, can be “polarized”, and can contain “negative energy electrons”. What is worse, its fluctuations and polarization are infinite and the number of negative energy electrons is infinite also.
Stimulating physics research in colleges
Authors: Soller Theodore
Published: January 2009

Is there any point in trying to make a case for physics research in a small college? Isn't all of the really important research which needs to be done now being carried on in the universities and in the large government and industrial laboratories, where the extensive and costly facilities and necessary manpower are available? What role does the small college play in fulfilling the urgent need for increasing the national scientific potential? These are the basic questions which the recently held Conference on Physics Research in Colleges tried to answer.
Coherent systems of physical units
Authors: Williams Dudley
Published: January 2009

Most American physicists have great zest for the study of physical phenomena but complete apathy toward the problems involved in the development of a convenient system of units for general use in describing the phenomena. This attitude is understandable and even defensible, since the phenomena themselves and their interpretation are the subjects of prime importance, whereas the units used in quantitative description are of secondary importance. For example, if some nuclear physicist, for reasons of his own, chooses to publish his results in a table of nuclear properties with masses expressed in long tons, cross sections in acres, and spins in Btuṡhrs, these properties are stated definitely and can be expressed without serious difficulty in more conventional units for comparison with the results of other investigators; however, it is admittedly a matter of convenience for all nuclear physicists to employ certain standard units. We all recognize that the establishment of a convenient set of units for general use is desirable but most of us are so preoccupied with our own immediate research interests that we have little time or energy to devote to the matter.
Some thoughts on federal science
Authors: Piore E. R.
Published: January 2009

In reporting to my peers on my stewardship I shall be brief and cover only that portion of my duties that have direct impact on you. I shall not touch on the problems associated with the internal management of research and development within the Navy Department.
AEC research program and policy
Authors: Johnson T. H.
Published: January 2009

More than any other government agency, the AEC relies upon other people to do its work. The AEC has only 6000 employees, almost none of whom engage in technical work. Their function is to arrange for, and coordinate, the work of more than 80 000 employees of operating contractors, not to mention the construction. The atomic energy job is being done by American industry and American science—both operating in more or less their normal patterns.
Our common task
Authors: Decker Donald G.
Published: January 2009

The history of education has been a series of stormy, volcanic eruptions which have periodically changed the character of American Education. Educators have been hampered because they have been without one consistent aim. Education has been a public enterprise and therefore at the mercy of certain pressure groups, individual opinions, and community whims. Educators have also been hampered because the great philosophers of education have interpreted the values of education individually and personally. Each has been an educational missionary who gathers a group of followers, deviates from other groups, and eventually becomes powerful enough to break through a small fissure in the side of the volcano of education and start another little volcano.
Physics at Columbia University: The genesis of the nuclear energy project
Authors: Fermi Enrico
Published: January 2009

It seems fitting to remember, on this 200th anniversary of Columbia University, the key role that the University played in the early experimentation and the organization of the early work that led to the development of atomic energy.
Physics in Engineering Education
Authors: Novak Alfred
Published: January 2009

THE major points in the article by E. L. Woodside (“Physics Curriculum for Engineers”, Physics Today, November 1954, p. 4) are well made. First, given the premise that a fundamental knowledge of physical laws is desirable for engineering students, specialists do tend to emphasize the importance of their subject matter domain. Second, there is a need and a value in learning to think formally. Third, time is an important consideration in the development of the best curriculum possible for engineers. The issue is of real significance to the welfare of the nation and I would like to expand some of the points and take issue with another.
The new responsibilities of physicists
Authors: Smyth H. D.
Published: January 2009

Until the Second World War, physics belonged to the physicists. Discussions, disagreements, and debates about experiments or theories in physics were carried on within a small group of highly trained men. This happy situation ended in 1940. It has probably ended permanently. The developments of nuclear science and of electronics have brought physics and physicists into a new place in our society and in our Government. To understand clearly the complexities of our present position let me recall, by way of contrast, a scientific controversy of the 1920's.
Fluid dynamics
Authors: Emrich Raymond J.
Published: January 2009

On the three days preceding Thanksgiving 250 physicists and other scientists met at Lehigh University to talk over their work in fundamental fluid dynamics. The occasion was the Tenth Anniversary Meeting of the Division of Fluid Dynamics of the American Physical Society.
The ferromagnetic microwave amplifier
Authors: Suhl H.
Published: January 2009

The problem of detecting feeble radio signals of short wavelengths, always important in obvious defense applications, has become crucial to the study of certain astrophysical questions by means of radio astronomy. Hitherto, the lower limit on the strength of a usefully detectable signal has been the background noise generated by the more or less “hot” electrons in the vacuum tube amplifiers or crystal detectors at the head of the receiver. This difficulty has led to suggestions for replacing these more conventional input stages by atomic resonant systems, which should be much less noisy. The most famous of these are the so-called “masers” (Microwave Amplification by Stimulated Emission of Radiation): the atomic beam maser of Townes, Gordon, and Zeiger, and the “Solid-State Maser” of N. Bloembergen which uses a paramagnetic impurity concentration in a solid as resonant system. For purposes of comparison as well as by way of introduction, we shall begin with a simple statement of their common operating principle.
Spin injection in silicon at zero magnetic field
Authors: Grenet L. , Jamet M. , Noé P. , Calvo V. , Hartmann J.-M. , Nistor L. E. , Rodmacq B. , Auffret S. , Warin P. , Samson Y.
Published: January 2009

In this letter, we show efficient electrical spin injection into a SiGe based p-i-n light emitting diode from the remanent state of a perpendicularly magnetized ferromagnetic contact. Electron spin injection is carried out through an alumina tunnel barrier from a Co/Pt thin film exhibiting a strong out-of-plane anisotropy. The electron spin polarization is then analyzed through the circular polarization of emitted light. All the light polarization measurements are performed without an external applied magnetic field, i.e., in remanent magnetic states. The light polarization as a function of the magnetic field closely traces the out-of-plane magnetization of the Co/Pt injector. We could achieve a circular polarization degree of the emitted light of 3% at 5 K. Moreover this light polarization remains almost constant at least up to 200 K.
Transmission electron microscopy and scanning tunneling microscopy investigations of graphene on 4H-SiC(0001)
Authors: Borysiuk J. , Bożek R. , Strupiński W. , Wysmołek A. , Grodecki K. , Stępniewski R. , Baranowski J. M.
Published: January 2009

Transmission electron microscopy (TEM), scanning tunneling microscopy (STM), and micro-Raman investigations of epitaxial graphene on 4H-SiC on-axis and 4° off-axis are presented. The STM images show that there is superimposed on 1×1 graphene pattern the carbon nanomesh of honeycomb 6×6 structure with the lattice vector of 17.5 Å. The TEM results give evidence that the first carbon layer is separated by 2 Å from the Si-terminated SiC surface and that subsequent carbon layers are spaced by 3.3 Å. It is also found in TEM that the graphene layers cover atomic steps, present on 4° off-axis SiC(0001) surface, indicating a carpetlike growth mode. However, a bending of graphene planes on atomic steps of SiC apparently leads to generation of stress which leads to creation of edge dislocations in the graphene layers.
Crystallography
Authors: Wyckoff Ralph W. G.
Published: January 2009

For many years I have been interested in why a science of crystallography came into being with the form and at the time it did, what its relation is to other physical sciences and what the future is liable to hold for it. When this lecture was first decided on I planned to make of it a more or less comprehensive lecture on the history of crystallography—one is needed. But I am not going to do this mainly because I have recently had to make certain unexpected major decisions that have consumed the time that would have been needed to document so serious a talk. There is, however, point to even some rambling comments on the growth of crystallography; we are already too inclined to take our subject for granted and to forget that little more than a generation ago the study of crystals was something carried out in very few universities and then usually in a bare attic room whose sole equipment consisted of a few pearwood models and some mineral specimens removed for the afternoon from the neighboring mineralogical museum. Crystallography was generally considered a useful adjunct to the blowpipe as a way of identifying minerals, but not much more. The discovery that practically all solids, rather than only a few curiosities of nature, are crystalline made this obscurity a thing of the past and demonstrated that a concern with crystalline order must provide the nucleus for an expanding science of solid bodies.
Physics Research Techniques
Authors: Gross B.
Published: January 2009

International Conference in Brazil
The National Academy of Science and the National Research Council
Authors: Gray Dwight E.
Published: January 2009

Finding myself unable to explain, in response to a colleague's query, just exactly how the National Academy of Sciences (NAS) and the National Research Council (NRC) are related, I recently conducted a small or garden variety survey among some of my scientific friends. Somewhat to my surprise—even though nourishing to my ego—I discovered their understanding on this point to be of about the same degree of preciseness as my own. They knew considerable, of course, about the work of the NAS and the NRC but, for the most part, were rather vague and uncertain regarding their interrelationships. The composite impression which the poll produced might be expressed mathematically, as NASCivil War = NRCWorld War I = OSRDWorld War II Obviously, however, this greatly over-simplified description of the situation leaves much to be desired as a sound, well-rounded description of the relations of NAS and NRC to each other and of the lines of demarcation between their respective responsibilities. Hence, this particular Washington Report.
Progress in heat pump engineering
Authors: Penrod E. B.
Published: January 2009

During the last two decades considerable effort has been made to introduce the heat pump for heating and cooling buildings. The capacity of the heat pumps, installed, ranges from three tons to five hundred and fifty tons of refrigeration. The heat sources and the heat sinks are atmospheric air, water, and the earth. In the commercial field the heat pump principle has proved to be practical and satisfactory wherever suitable heat sources and heat sinks were available.
Society of Rheology
Authors: Bondi A.
Published: January 2009

West Coast Section Meets at Berkeley
A Letter to the Editor
Authors: Golay Marcel J. E.
Published: January 2009

The broadplanners and program makers of many agencies have shown in the last few years a growing and disquieting tendency to use the words “development”, “applied research”, “basic research”, etc., in a context not conforming with time honored usage. A code can nearly be established to translate various documents into the physicist's language thus: For “basic research” read “applied research”, for “applied research” read “development”, for “development” read “engineering”, and so forth.
APS Spring Meeting
Authors: Darrow K. K.
Published: January 2009

To be Held in Washington Next Month
NSF one year later…
Authors: Gray Dwight E.
Published: January 2009

A year and a month ago one of these Washington Reports was devoted to an interview with Dr. Alan T. Waterman, Director of the then newly-established National Science Foundation. In that interview Dr. Waterman outlined the general long-range program of the Foundation as he and the National Science Board visualized it at that time and described in some detail the several specific areas of activity which he planned to emphasize in the initial phase of the work. It is appropriate at this time—the approximate close of the first complete fiscal year of NSF's operation—to summarize the very substantial accomplishments to date of this organization which can mean so much to the future of science in this country and, therefore, to the future of the nation itself.
IUPAP Executive Committee
Authors: Slater J. C.
Published: January 2009

June Meeting in Paris Reported
Effect of substrate roughness on c-oriented AlN thin films
Authors: Artieda Alvaro , Barbieri Michela , Sandu Cosmin Silviu , Muralt Paul
Published: January 2009

(001)-textured AlN thin films as needed for bulk acoustic wave devices exhibit large mechanical stress variations as a function of growth substrate properties. We studied the relationship between stress and the surface morphology of a thermally oxidized silicon substrate that was modified by a thin amorphous silicon layer. A rms roughness of 0.1–1.1 nm of the latter resulted in an increase in mechanical stress in the subsequently sputtered AlN thin film going from −700 to +200 MPa. At the same time, the x-ray rocking curve width of AlN increased from 1.3° to 2.3°. The roughness of the Si interlayer was controlled by the Ar sputter pressure. Interestingly, the maximal roughness is obtained at an intermediate pressure. This is explained by an interplay of nucleation and diffusion phenomena governed by the kinetics of impinging atoms and ions. The Si interlayer was essential to avoid cracking of membranes exhibiting mixed Pt and SiO2 surfaces below the AlN film.
Modeling phosphorus diffusion gettering of iron in single crystal silicon
Authors: Haarahiltunen A. , Savin H. , Yli-Koski M. , Talvitie H. , Sinkkonen J.
Published: January 2009

We propose a quantitative model for phosphorus diffusion gettering (PDG) of iron in silicon, which is based on a special fitting procedure to experimental data. We discuss the possibilities of the underlying physics of the segregation coefficient. Finally, we show that the proposed PDG model allows quantitative analysis of gettering efficiency of iron at various processing conditions.
Direct measurement of electric field screening in light emitting diodes with conjugated polyelectrolyte electron injecting/transport layers
Authors: Hoven Corey V. , Peet Jeffrey , Mikhailovsky Alexander , Nguyen Thuc-Quyen
Published: January 2009

Electroabsorption spectroscopy was used to directly probe the electric fields in a polymer light emitting diode that utilizes a conjugated polyelectrolyte electron transporting/injection layer. The electric field in the emitting layer was found to be negligible at applied biases greater than the built-in field of the device. Holes injected at these biases accumulate at the emitting layer/conjugated polyelectrolyte interface and screen the field from the emitting layer to the conjugated polyelectrolyte layer. In conjunction with mobile ions that redistribute the field in the conjugated polyelectrolyte layer, this leads to greatly improved electron injection from high work function cathodes.
An electrical microheater technique for high-pressure and high-temperature diamond anvil cell experiments
Authors: Weir S. T. , Jackson D. D. , Falabella S. , Samudrala G. , Vohra Y. K.
Published: January 2009

Small electrical heating elements have been lithographically fabricated onto the culets of “designer” diamond anvils for the purpose of performing high-pressure and high-temperature experiments on metals. The thin-film geometry of the heating elements makes them very resistant to plastic deformation during high-pressure loading, and their small cross-sectional area enables them to be electrically heated to very high temperatures with relatively modest currents (≈1 A). The technique also offers excellent control and temporal stability of the sample temperature. Test experiments on gold samples have been performed for pressures up to 21 GPa and temperatures of nearly 2000 K.
The plasmonic properties of elliptical metallic hole arrays
Authors: Li J. , Iu H. , Wan J. T. K. , Ong H. C.
Published: January 2009

The dispersion relations of two-dimensional Au elliptical hole arrays have been studied by angle-dependent reflectivity. Other than the propagating surface plasmon polaritons (SPPs), both experiment and simulation show a strong local cavity mode emerges when the electric field of the incident light is parallel to the minor axis of the holes. In addition, the calculated field patterns show the field strength increases by five times when the hole shape changes from circular to elliptical. Finally, the interaction between the propagating SPPs and cavity mode has been found and it can be controlled systemically by changing the geometry of the arrays.
Bloch gain in quantum cascade lasers at high temperature
Authors: Gresch Tobias , Terazzi Romain , Faist Jérôme , Giovannini Marcella
Published: January 2009

We performed multisection cavity gain measurements at high temperature with quantum cascade lasers that are based on a single quantum well active region and work in a low-inversion regime. A modal gain coefficient g=3.7±0.9 cm kA−1 at 330 K is found for the sample with the lowest population inversion. We show that the weak dependence of the threshold current and the high values of the associated T0 parameter between 260 and 360 K are accompanied by a gain coefficient that depends weakly on temperature.
Highly efficient and stable organic light-emitting diode using 4,4′-bis(N-carbazolyl)-9,9′-spirobifluorene as a thermally stable host material
Authors: Tsuzuki Toshimitsu , Tokito Shizuo
Published: January 2009

We demonstrated efficient and stable organic light-emitting diodes (OLEDs) using 4,4′-bis(N-carbazolyl)-9,9′-spirobifluorene (CFL), which has spirobifluorene and two carbazole moieties, as a thermally stable host and tris(1-phenylisoquinolinolato-C2,N) iridium(III) [Ir(piq)3] or tris(2-phenylpyridinne)iridium(III) [Ir(ppy)3] as a guest. Glass transition temperature of CFL was 151 °C. The efficiency of OLEDs that use CFL as a host and Ir(piq)3 as a guest were higher than that of an OLED, which uses conventional 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) as a host. The external quantum efficiency of the OLED using CFL and Ir(piq)3 was 13%. The lifetime of the OLED using CFL as the host was longer than that of the OLED using CBP.
Nano-Ag:polymeric composite material for ultrafast photonic crystal all-optical switching
Authors: Hu Xiaoyong , Jiang Ping , Xin Cheng , Yang Hong , Gong Qihuang
Published: January 2009

We report a nanocomposite material possessing large nonlinear optical coefficients and fast response simultaneously, which is made of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] doped with Ag nanoparticles. Under resonant excitation of the polymer matrix and Ag nanoparticles, the value of the nonlinear susceptibility reaches the order of 10−6 esu. A nonlinear response time of 35 ps is achieved due to the energy transfer from organic molecules to Ag nanoparticles. An ultrafast photonic crystal all-optical switching with an ultralow pump intensity of 0.2 MW/cm2 is realized.
Selective targeting of perivascular macrophages for clearance of β-amyloid in cerebral amyloid angiopathy
Authors: Hawkes Cheryl A. , McLaurin JoAnne
Published: January 2009

Cerebral amyloid angiopathy (CAA), the deposition of β-amyloid (Aβ) peptides in leptomeningeal and cortical blood vessels, affects the majority of patients with Alzheimer's disease (AD). Evidence suggests that vascular amyloid deposits may result from impaired clearance of neuronal Aβ along perivascular spaces. We investigated the role of perivascular macrophages in regulating CAA severity in the TgCRND8 mouse model of AD. Depletion of perivascular macrophages significantly increased the number of thioflavin S-positive cortical blood vessels. ELISA confirmed that this increase was underscored by elevations in total vascular Aβ
42
levels. Conversely, stimulation of perivascular macrophage turnover reduced cerebral CAA load, an effect that was not mediated through clearance by microglia or astrocytes. These results highlight a function for the physiological role of perivascular macrophages in the regulation of CAA and suggest that selective targeting of perivascular macrophage activation might constitute a therapeutic strategy to clear vascular amyloid.
Evidence of gender differences in the ability to inhibit brain activation elicited by food stimulation
Authors: Wang Gene-Jack , Volkow Nora D. , Telang Frank , Jayne Millard , Ma Yeming , Pradhan Kith , Zhu Wei , Wong Christopher T. , Thanos Panayotis K. , Geliebter Allan , Biegon Anat , Fowler Joanna S.
Published: January 2009

Although impaired inhibitory control is linked to a broad spectrum of health problems, including obesity, the brain mechanism(s) underlying voluntary control of hunger are not well understood. We assessed the brain circuits involved in voluntary inhibition of hunger during food stimulation in 23 fasted men and women using PET and 2-deoxy-2[
18
F]fluoro-D-glucose (
18
FDG). In men, but not in women, food stimulation with inhibition significantly decreased activation in amygdala, hippocampus, insula, orbitofrontal cortex, and striatum, which are regions involved in emotional regulation, conditioning, and motivation. The suppressed activation of the orbitofrontal cortex with inhibition in men was associated with decreases in self-reports of hunger, which corroborates the involvement of this region in processing the conscious awareness of the drive to eat. This finding suggests a mechanism by which cognitive inhibition decreases the desire for food and implicates lower ability to suppress hunger in women as a contributing factor to gender differences in obesity.
Learning-related postburst afterhyperpolarization reduction in CA1 pyramidal neurons is mediated by protein kinase A
Authors: Oh M. Matthew , McKay Bridget M. , Power John M. , Disterhoft John F.
Published: January 2009

Learning-related reductions of the postburst afterhyperpolarization (AHP) in hippocampal pyramidal neurons have been shown ex vivo, after trace eyeblink conditioning. The AHP is also reduced by many neuromodulators, such as norepinephrine, via activation of protein kinases. Trace eyeblink conditioning, like other hippocampus-dependent tasks, relies on protein synthesis for consolidating the learned memory. Protein kinase A (PKA) has been shown to be a key contributor for protein synthesis via the cAMP-response element-binding pathway. Here, we have explored a potential involvement of PKA and protein kinase C (PKC) in maintaining the learning-related postburst AHP reduction observed in CA1 pyramidal neurons. Bath application of isoproterenol (1 μM), a β-adrenergic agonist that activates PKA, significantly reduced the AHP in CA1 neurons from control animals, but not from rats that learned. This occlusion suggests that PKA activity is involved in maintaining the AHP reduction measured ex vivo after successful learning. In contrast, bath application of the PKC activator, (–) indolactam V (0.2 μM), significantly reduced the AHP in CA1 neurons from both control and trained rats, indicating that PKC activity is not involved in maintaining the AHP reduction at this point after learning.
Probing deeper into first American studies
Authors: Dillehay Tom D.
Published: January 2009

The initial peopling of the Americas has proved one of the most challenging episodes in reconstructing global prehistory, challenging because researchers struggle with the vagaries of early archaeological site preservation, and debates continue over the date and place of human entry, the rapidity and direction of dispersion, and the variety of cultural responses to climatic change during the terminal Pleistocene period. Despite many recent advances in our understanding of these issues, especially in the areas of genetics and new archaeological discoveries, the field continues facing limitations in the sampling and quality of data, the research problems defined, and the epistemologies and theories applied. Theoretical development of first American studies has been uneven, and its contribution to global issues of early human migration has been restricted. This essay discusses what is known and not known about the process of the first peopling of the Americas from the perspective of archaeology, genetics, and bioanthropology. Some approaches to fill voids in data, methods, and the broader conceptualization of the process also are considered.
Infectious bursal disease virus is an icosahedral polyploid dsRNA virus
Authors: Luque Daniel , Rivas Germán , Alfonso Carlos , Carrascosa José L. , Rodríguez José F. , Castón José R.
Published: January 2009

Viruses are a paradigm of the economy of genome resources, reflected in their multiplication strategy and for their own structure. Although there is enormous structural diversity, the viral genome is always enclosed within a proteinaceous coat, and most virus species are haploid; the only exception to this rule are the highly pleomorphic enveloped viruses. We performed an in-depth characterization of infectious bursal disease virus (IBDV), a non-enveloped icosahedral dsRNA virus with a bisegmented genome. Up to 6 natural populations can be purified, which share a similar protein composition but show higher sedimentation coefficients as particle density increases. Stoichiometry analysis of their genome indicated that these biophysical differences correlate with the copy number of dsRNA segments inside the viral capsid. This is a demonstration of a functional polyploid icosahedral dsRNA virus. We show that IBDV particles with greater genome copy number have higher infectivity rates. Our results show an unprecedented replicative strategy for dsRNA viruses and suggest that birnaviruses are living viral entities encompassing numerous functional and structural characteristics of positive and negative ssRNA viruses.
A synthesized pheromone induces upstream movement in female sea lamprey and summons them into traps
Authors: Johnson Nicholas S. , Yun Sang-Seon , Thompson Henry T. , Brant Cory O. , Li Weiming
Published: January 2009

Female insect pheromone blends induce robust tracking responses in males and direct them into traps. In vertebrates, pheromones that induce strong and precise tracking responses in natural habitats have rarely been described. Here, we show in the sea lamprey (
Petromyzon marinus
), a vertebrate invader of the Laurential Great Lakes, that a synthesized component of the male mating pheromone, 7α, 12α, 24-trihydroxy-5α-cholan-3-one 24-sulfate (3kPZS), when released into a stream to reach concentrations of 10
−14
, 10
−13
, 10
−12
, 10
−11
, or 10
−10
M, triggers robust upstream movement in ovulated females drawing ≈50% into baited traps. Experiments conducted in diverse stream segments demonstrate the level of behavioral response was not affected by habitat conditions and is effective over hundreds of meters. 3kPZS is equally effective at luring ovulated females as the whole pheromone blend released by males between 10
−14
and 10
−11
M. 3kPZS diverts ovulated females away from and disrupts orientation to male washings when applied at concentrations higher than washings. Indeed, a single pheromone compound is able to redirect female sea lampreys away from a natural pheromone source and lure them into traps, which should be more effective than targeting males when applied in population control. Our findings may spur the discovery of other potent and environmentally benign agents to combat biological invasion, a process accelerated by globalization, exacerbated by climate change, and costing the global economy US$ 1.4 trillion of damage annually.
A signal-anchor sequence stimulates signal recognition particle binding to ribosomes from inside the exit tunnel
Authors: Berndt Uta , Oellerer Stefan , Zhang Ying , Johnson Arthur E. , Rospert Sabine
Published: January 2009

Sorting of eukaryotic membrane and secretory proteins depends on recognition of ribosome-bound nascent chain signal sequences by the signal recognition particle (SRP). The current model suggests that the SRP cycle is initiated when a signal sequence emerges from the ribosomal tunnel and binds to SRP. Then elongation is slowed until the SRP-bound ribosome–nascent chain complex (RNC) is targeted to the SRP receptor in the endoplasmic reticulum (ER) membrane. The RNC is then transferred to the translocon, SRP is released, and translation resumes. Because RNCs do not target to the translocon efficiently if nascent chains become too long, the window for SRP to identify its substrates is short. We now show that a transmembrane signal–anchor sequence (SA) significantly enhances binding of SRP to RNCs even before the SA emerges from the ribosomal tunnel. In this mode, SRP does not contact the SA directly but is in close proximity to the portion of the nascent polypeptide that has already left the ribosomal tunnel. Early recruitment of SRP provides a mechanism to expand the window for substrate identification. We suggest that the dynamics of the SRP–ribosome interaction is affected not only by the direct binding of SRP to an exposed signal sequence but also by properties of the translating ribosome that are triggered from within the tunnel.
Functional organization of the yeast proteome by a yeast interactome map
Authors: Valente André X. C. N. , Roberts Seth B. , Buck Gregory A. , Gao Yuan
Published: January 2009

It is hoped that comprehensive mapping of protein physical interactions will facilitate insights regarding both fundamental cell biology processes and the pathology of diseases. To fulfill this hope, good solutions to 2 issues will be essential: (
i
) how to obtain reliable interaction data in a high-throughput setting and (
ii
) how to structure interaction data in a meaningful form, amenable to and valuable for further biological research. In this article, we structure an interactome in terms of predicted permanent protein complexes and predicted transient, nongeneric interactions between these complexes. The interactome is generated by means of an associated computational algorithm, from raw high-throughput affinity purification/mass spectrometric interaction data. We apply our technique to the construction of an interactome for
Saccharomyces cerevisiae
, showing that it yields reliability typical of low-throughput experiments from high-throughput data. We discuss biological insights raised by this interactome including, via homology, a few related to human disease.
The coactivator CRTC1 promotes cell proliferation and transformation via AP-1
Authors: Canettieri Gianluca , Coni Sonia , Della Guardia Michele , Nocerino Valentina , Antonucci Laura , Di Magno Laura , Screaton Robert , Screpanti Isabella , Giannini Giuseppe , Gulino Alberto
Published: January 2009

Regulation of gene expression in response to mitogenic stimuli is a critical aspect underlying many forms of human cancers. The AP-1 complex mediates the transcriptional response to mitogens, and its deregulation causes developmental defects and tumors. We report that the coactivator CRTC1 cyclic AMP response element-binding protein (CREB)-regulated transcription coactivator 1 is a potent and indispensable modulator of AP-1 function. After exposure of cells to the AP-1 agonist 12-O-tetradecanoylphorbol-13-acetate (TPA), CRTC1 is recruited to AP-1 target gene promoters and associates with c-Jun and c-Fos to activate transcription. CRTC1 consistently synergizes with the proto-oncogene c-Jun to promote cellular growth, whereas AP-1–dependent proliferation is abrogated in CRTC1-deficient cells. Remarkably, we demonstrate that CRTC1-Maml2 oncoprotein, which causes mucoepidermoid carcinomas, binds and activates both c-Jun and c-Fos. Consequently, ablation of AP-1 function disrupts the cellular transformation and proliferation mediated by this oncogene. Together, these data illustrate a novel mechanism required to couple mitogenic signals to the AP-1 gene regulatory program.
Hyperactivity and hyperconnectivity of the default network in schizophrenia and in first-degree relatives of persons with schizophrenia
Authors: Whitfield-Gabrieli Susan , Thermenos Heidi W. , Milanovic Snezana , Tsuang Ming T. , Faraone Stephen V. , McCarley Robert W. , Shenton Martha E. , Green Alan I. , Nieto-Castanon Alfonso , LaViolette Peter , Wojcik Joanne , Gabrieli John D. E. , Seidman Larry J.
Published: January 2009

We examined the status of the neural network mediating the default mode of brain function, which typically exhibits greater activation during rest than during task, in patients in the early phase of schizophrenia and in young first-degree relatives of persons with schizophrenia. During functional MRI, patients, relatives, and controls alternated between rest and performance of working memory (WM) tasks. As expected, controls exhibited task-related suppression of activation in the default network, including medial prefrontal cortex (MPFC) and posterior cingulate cortex/precuneus. Patients and relatives exhibited significantly reduced task-related suppression in MPFC, and these reductions remained after controlling for performance. Increased task-related MPFC suppression correlated with better WM performance in patients and relatives and with less psychopathology in all 3 groups. For WM task performance, patients and relatives had greater activation in right dorsolateral prefrontal cortex (DLPFC) than controls. During rest and task, patients and relatives exhibited abnormally high functional connectivity within the default network. The magnitudes of default network connectivity during rest and task correlated with psychopathology in the patients. Further, during both rest and task, patients exhibited reduced anticorrelations between MPFC and DLPFC, a region that was hyperactivated by patients and relatives during WM performance. Among patients, the magnitude of MPFC task suppression negatively correlated with default connectivity, suggesting an association between the hyperactivation and hyperconnectivity in schizophrenia. Hyperactivation (reduced task-related suppression) of default regions and hyperconnectivity of the default network may contribute to disturbances of thought in schizophrenia and risk for the illness.
Intersubunit allosteric communication mediated by a conserved loop in the MCM helicase
Authors: Barry Elizabeth R. , Lovett Janet E. , Costa Alessandro , Lea Susan M. , Bell Stephen D.
Published: January 2009

The minichromosome maintenance (MCM) helicase is the presumptive replicative helicase in archaea and eukaryotes. The archaeal homomultimeric MCM has a two-tier structure. One tier contains the AAA+ motor domains of the proteins, and these are the minimal functional helicase domains. The second tier is formed by the N-terminal domains. These domains are not essential for MCM helicase activity but act to enhance the processivity of the helicase. We reveal that a conserved loop facilitates communication between processivity and motor tiers. Interestingly, this allostery seems to be mediated by interactions between, rather than within, individual protomers in the MCM ring.
Negative regulation of
Caenorhabditis elegans
epidermal damage responses by death-associated protein kinase
Authors: Tong Amy , Lynn Grace , Ngo Vy , Wong Daniel , Moseley Sarah L. , Ewbank Jonathan J. , Goncharov Alexandr , Wu Yi-Chun , Pujol Nathalie , Chisholm Andrew D.
Published: January 2009

Wounding of epidermal layers triggers multiple coordinated responses to damage. We show here that the
Caenorhabditis elegans
ortholog of the tumor suppressor death-associated protein kinase,
dapk-1
, acts as a previously undescribed negative regulator of barrier repair and innate immune responses to wounding. Loss of DAPK-1 function results in constitutive formation of scar-like structures in the cuticle, and up-regulation of innate immune responses to damage. Overexpression of DAPK-1 represses innate immune responses to needle wounding. Up-regulation of innate immune responses in
dapk-1
requires the TIR-1/p38 signal transduction pathway; loss of function in this pathway synergizes with
dapk-1
to drastically reduce adult lifespan. Our results reveal a previously undescribed function for the DAPK tumor suppressor family in regulation of epithelial damage responses.
Somatosensory function in speech perception
Authors: Ito Takayuki , Tiede Mark , Ostry David J.
Published: January 2009

Somatosensory signals from the facial skin and muscles of the vocal tract provide a rich source of sensory input in speech production. We show here that the somatosensory system is also involved in the perception of speech. We use a robotic device to create patterns of facial skin deformation that would normally accompany speech production. We find that when we stretch the facial skin while people listen to words, it alters the sounds they hear. The systematic perceptual variation we observe in conjunction with speech-like patterns of skin stretch indicates that somatosensory inputs affect the neural processing of speech sounds and shows the involvement of the somatosensory system in the perceptual processing in speech.
Role of calcium-independent phospholipase A
2
in the pathogenesis of Barth syndrome
Authors: Malhotra Ashim , Edelman-Novemsky Irit , Xu Yang , Plesken Heide , Ma Jinping , Schlame Michael , Ren Mindong
Published: January 2009

Quantitative and qualitative alterations of mitochondrial cardiolipin have been implicated in the pathogenesis of Barth syndrome, an X-linked cardioskeletal myopathy caused by a deficiency in tafazzin, an enzyme in the cardiolipin remodeling pathway. We have generated and previously reported a tafazzin-deficient
Drosophila
model of Barth syndrome that is characterized by low cardiolipin concentration, abnormal cardiolipin fatty acyl composition, abnormal mitochondria, and poor motor function. Here, we first show that tafazzin deficiency in
Drosophila
disrupts the final stage of spermatogenesis, spermatid individualization, and causes male sterility. This phenotype can be genetically suppressed by inactivation of the gene encoding a calcium-independent phospholipase A
2
, iPLA2-VIA, which also prevents cardiolipin depletion/monolysocardiolipin accumulation, although in wild-type flies inactivation of the iPLA2-VIA does not affect the molecular composition of cardiolipin. Furthermore, we show that treatment of Barth syndrome patients' lymphoblasts in tissue culture with the iPLA
2
inhibitor, bromoenol lactone, partially restores their cardiolipin homeostasis. Taken together, these findings establish a causal role of cardiolipin deficiency in the pathogenesis of Barth syndrome and identify iPLA2-VIA as an important enzyme in cardiolipin deacylation, and as a potential target for therapeutic intervention.