bluuebunny/crossref_metadata_2025 huggingface dataset:
The solid state
Authors: Slater John C.
Published: January 2009

The physics of the solid state is nothing new. In 1900 it was as well realized as now that mechanics, heat, electricity, magnetism, optics, all have their solid-state aspects. In mechanics we have elasticity, plasticity, elastic vibrations or sound. In heat we have specific heat, thermal expansion, heat conductivity. In electricity we have conductivity, dielectric constant. In magnetism we have paramagnetism, diamagnetism, ferromagnetism, the Hall effect. Optics involves the refractive index, optical absorption, double refraction, and so on. There are interrelations between different effects: Magnetostriction, the relation between magnetism and elasticity; pyroelectricity, the relation between heat and dielectric behavior; the Faraday effect, the relation between magnetism and optical double refraction; and a host of others. All these were known in 1900, there were tentative theories of many of them, and very elaborate studies of the interrelations of them with crystal symmetry, leading up to the proper mathematical description of many of the properties in terms of tensors, and such mathematical devices.
Physics of Ionic Crystals
Authors: Dexter D. L.
Published: January 2009

Summary of Illinois Conference
The atom
Authors: Condon E. U.
Published: January 2009

One can always tell which part of physics is advancing most rapidly by consulting a few numbers of The Physical Review. Judged by this criterion, the heroic period of the physics of the atom may be taken to be roughly the two decades from 1915 to 1935. (Such dates are never exact.) Prior to 1915 there had been much speculation about the electrical nature of the atom, and Rutherford's work on alpha particle scattering and Bohr's first work on a quantum theory of the atom came a little before 1915. By 1915, however, physicists had really caught the scent of an exciting new forward surge of discovery and were preparing to exploit it fully.
Physics in the Signal Corps
Authors: Zahl Harold A.
Published: January 2009

The signal corps engineering laboratories at Fort Monmouth, N.J., in staff, facilities, and annual budget, may be placed among the country's largest physical sciences laboratories. From a civilian staff of approximately 50 in 1930, a war-swollen peak of 14,800 was reached in 1943, largely resulting from the introduction of Army and Air Force radar as a combat weapon. The staff at present is slightly over 4000, of which approximately 1300 are professional scientists or engineers augmented by 75 highly trained officers and several hundred enlisted men. As the name implies, development of military gear under the purview of the Chief Signal Officer, Major General George I. Back, is the major responsibility of the organization. Most of this work is of an electronic type drawing heavily from all the physical sciences, and particularly physics. In addition to the major activity which is centered in the Fort Monmouth area, experimentation related to the prime tasks is spread throughout the U.S. and, in fact, to all the corners of the world through contract, field stations, and special task forces.
The Applied Physics Laboratory Research Center
Authors: Gray Dwight E.
Published: January 2009

The atomic bomb, the proximity fuze, and radar frequently have been cited as representing the three most outstanding advances in military science made by the U.S. during World War II. All, of course, are dramatic examples of so-called “practical” developments that would have been impossible without extensive prior fundamental scientific investigation carried out on an open-ended time scale in a research-for-its-own-sake environment. It is appropriate that the laboratory chiefly responsible for the wartime development of one member of the above triad should now be pioneering in the integration of applied and fundamental research within a single organization in a manner designed to produce optimum effectiveness for both. The establishment referred to is the Applied Physics Laboratory of The Johns Hopkins University, where the proximity fuze was developed. This laboratory, located in Silver Spring, Maryland, operates under a contract between the Bureau of Ordnance, U.S. Navy, and the University and for the past several years has been engaged principally in a guided-missile research and development program. An indication of its progress in this field is given by the fact that late in 1951 ground was broken in Pomona, California, for the construction for the Bureau of Ordnance of a multimillion dollar plant in which an APL-developed guided missile will be manufactured. The present discussion, however, is concerned only indirectly with the applied research and development to which most of APL's efforts are devoted. This article deals instead with the organization of and the thinking behind a particular division of the Laboratory called the Research Center.
Physics Teaching
Authors: Paton R. F.
Published: January 2009

The AAPT Meeting in Chicago
The founding of the American Institute of Physics
Authors: Compton Karl T.
Published: January 2009

First may I add my greeting to Senator McMahon, and add my appreciation of his willingness to meet with us tonight. He and we have a strong bond in common. We physicists have been largely responsible for creating the activity for whose wise handling in the national interest he has so great a responsibility. And may I say, on the basis of several opportunities to see him in the discharge of these responsibilities, that we are very fortunate in having this aspect of our common interest in the hands of a man who has shown such real understanding of the basic conditions for scientific development and for advantageous application of the great potentialities of atomic energy.
Physics in India
Authors: Curtiss L. F.
Published: January 2009

India, as is well known, has a notable record in the A field of physics, the more remarkable in view of the differences between her cultural background and that of occidental countries. The major achievements in this record were made in the era preceding India's recently won independence. The people of India, having struggled so long for this independence, are making a determined effort to bring their country abreast those of other free peoples of the world. In this effort every phase of modern progress has come in for consideration. The impressions gained by an American physicist during several months in the spring and summer of 1951, while a Fulbright research scholar, may therefore be of interest to some of the readers of Physics Today. In presenting this discussion I should point out that I did not visit all the laboratories of this vast country, even though this statement might seem unnecessary to those familiar with India. Also this was my first visit so that I can make no firsthand comparisons with earlier conditions. My host institution was the Muslim University at Aligarh. During the six months spent in the country I visited the universities and research institutes located in Allahabad, Agra, Benares, Bombay, Delhi, Lucknow, and Madras. I also visited the University of Ceylon at Colombo and for about two months was in that part of the Himalayas situated in the province of Kashmir.
The Office of Ordnance Research
Authors: Gray Dwight E.
Published: January 2009

One of several sub-themes that have been considered from time to time in these Washington Reports is the support of basic research by agencies of the Department of Defense. Previous articles of this nature appearing in Physics Today have described the work of one particular Navy office (September, 1951) and of a major Navy contractor (February, 1952). The present discussion, which extends the story to another branch of the Armed Services, concerns the Army's Office of Ordnance Research (OOR). Let me first state very briefly the “what, why, where, and when” of OOR and then take up in greater detail the thinking behind its organization and the nature of its program. The Office of Ordnance Research is established under the command of the Chief of Ordnance, U.S. Army, to have responsibility for instituting and administering contracts for basic research in fields of Ordnance interest. It is located on the campus of Duke University, Durham, North Carolina, and officially began operation during June 1951. The Commanding Officer of OOR is Colonel Walker W. Holler and its Chief Scientist is Dr. T. J. Killian, until recently Deputy Assistant Chief for Research, Office of Naval Research.
Scientific Manpower
Authors: White Marsh W.
Published: January 2009

AAAS Conference in Philadelphia
Over and over again…
Authors: Smoluchowski R.
Published: January 2009

The drawn out, inconclusive, and fruitless debates and controversies on the distinction, if any, between the so-called “basic” and “applied” research, hopefully forgotten by scientists, seem to reappear as a horrible specter whenever the use of the almighty dollar for research has to be decided by laymen. Among scientists the problem is usually dragged out towards the end of a prolonged bull session when other more obvious ways of entertainment and gossip have been exhausted. And then with a big sigh “Not that again!” everyone staggers away.
The world's high altitude laboratories
Authors: Korff Serge A.
Published: January 2009

A recent survey article on high altitude laboratories has elicited so much correspondence that it was thought worth-while to present today's roster of such stations in tabular form. In the table below and on the map on p 30 several stations now in operation are listed in order of ascending geomagnetic latitude. In addition four stations at present under study are mentioned, one or more of which may be in operation in the near future. Omitted from this list are such well-known observatories as Mt. Wilson, Mt. Palomar and others, since their elevation is not particularly high. Also omitted are such cities which may happen to lie at high elevations, as for example La Paz, Bolivia, at which no formally organized high altitude laboratories are known to this writer. Finally, we do not list any observatories in countries behind the Iron Curtain, but only those which will welcome scientists of all nations. The majority of the stations have electric power available usually via transmission lines from generating stations located elsewhere. All these are marked, under the heading of “Power Available”, as 25. The asterisk indicates that while existing lines often carry 25 KW, if the observer should have requirements for larger amounts of power, such as for a large magnet, arrangements should be made for the installation of larger transformers if needed. The listing under access will at once convey to the prospective user of such a station the reasonable limits of weight of equipment which can be transported. Thus, for example, to carry a six-ton instrument to Morococha would present no insuperable difficulties, but if it were desired to take it to Pic du Midi, it would have to be disassembled. Under the heading “Housing, Persons”, is given the normal number which can comfortably sleep at the place mentioned. It goes without saying that this number is quite flexible, and it is only desired as an approximate guide to the housing situation. At many places, for example at the Jungfraujoch, Morococha, Echo Lake, Huancayo, and Climax, good hotels are available nearby. Further, if the experiment required 24-hour personnel presence, observers can usually make their own arrangements to sleep near the apparatus on cots they can bring with them. Under the heading “Officer in Charge” are listed the persons who at this writing are well qualified to provide information about the use of each station. The names will change from time to time, and it is the institutional connections which will be more permanent. The author of the present article, who has been fortunate in visiting almost all of the stations listed, will be glad to provide additional information, should other questions arise. Such correspondence should be addressed to: Prof. Serge A. Korff, New York University, University Heights, New York 53, N.Y.
American Institute of Physics: Director's report for 1951
Authors: Barton Henry A.
Published: January 2009

American physicists today find themselves in a national environment ever more complex. In this brief report, one can only note a few new components of this environment. One such is the National Science Foundation. It should be welcomed. It is civilian, it is an evidence of government conscience for the support of science in the face of declining private donations, it is staffed by men in whom physicists have confidence and it has already announced a farsighted program to strengthen the very foundation of science.
A survey of Alaskan peaks
Authors: Korff Serge A.
Published: January 2009

Ever since the cosmic-ray expedition of A. H. Compton's group in the early 1930's to Mt. McKinley, there has been a good deal of interest in the possibility of doing cosmic-ray work on Alaskan peaks. These mountains represent about the only means of obtaining observations over any protracted period at high altitudes and at far northern latitudes. Further stimulated by our own desire to obtain neutron measurements at such elevations and latitudes, it seemed worth while to make a comprehensive examination of the present situation with a view to finding out what peaks could be occupied as research stations, and what difficulties each peak presents. In the survey which is reported herein, the key feature making the entire operation possible was the Piper Super-Cub expertly piloted by Terris Moore, the energetic president of the University of Alaska
Fragmentation of subject matter
Authors: Osgood Thomas H.
Published: January 2009

There was a time, in the good old days, when a professor taught his students, no matter what their major interests, what he believed would be best for them. He chose carefully, from the field he knew well, the topics of fundamental or current value that he considered to be of the greatest importance. What he taught had a logical continuity. Today, a professor is more like a cog in a machine; he may be tossed about and buffeted by experts in curriculum construction, by planning and policy committees, by agencies of accreditation, and by financial, or even political pressures. It is small wonder that he finds difficulty in retaining his native enthusiasm for teaching a student what he thinks the student should know.
Physics in South America
Authors: Brownell G. L.
Published: January 2009

This report is based primarily on observations made during a three-month trip to South America during the summer of 1951. Obviously, the task of presenting a complete and comprehensive survey of physics in South America with the many ramifications in the economic, social, and political patterns of these countries cannot be undertaken with this experience and in this space. However, the evidences of vigorous development in physics and other basic sciences in South America have been sufficiently impressive to me to warrant recording my impressions of some of the leading laboratories in the hope that they will be of interest to other physicists. I am certain that in a relatively few years physics in South America will have developed to such an extent that physicists here will not only find it of interest, but will find it scientifically imperative, to maintain close contact with their colleagues on the opposite side of the equator.
Radiac and civil defense
Authors: Beiser Arthur
Published: January 2009

An essential element in any modern civil defense program is a radiological service, the principal function of which is the detection of radioactive contamination following the use of atomic weapons. As is the case with more conventional disaster emergencies, the medical, fire, and rescue units will have the greatest responsibilities in such an event, the radiological group being purely ancillary. The importance of the latter, while perhaps overemphasized in view of the properties of the “nominal” atomic bomb, still remains if for no other reason than the reassurance of the civilian population. Further, should radioactive warfare on a significant scale actually be employed, properly trained and equipped personnel could be very effective in minimizing casualties from that source. In this article the Bronx unit of the New York City Radiological Service (radiac) will be described, and it is hoped that this information may be of some assistance to physicists engaged in working with similar groups elsewhere.
AAPT Summer Meetings
Authors: Michels Walter C.
Published: January 2009

With Colloquium of College Physicists
Atomic physics…for physicists only?
Authors: Finkelnburg Wolfgang
Published: January 2009

Atomic physics in its wider sense, including nuclear, molecular, and solid-state physics, as well as quantum mechanics, seems to be taught at most schools either as separate fields of knowledge, or under the unwritten but nevertheless unmistakable label “For Physicists Only”. That means that it is taught with all the details and in particular with all the mathematics required for a thorough mastery of this difficult field. This custom was justified at a time when atomic physics was merely a small and restricted region of physics striving to establish its right of existence beside the older fields of mechanics, heat, acoustics, electricity, magnetism, and optics. This custom may have advantages for the graduate physicist who looks toward a career in atomic physics, though even here the predominance of mathematics makes many a student overlook the fact that the basic difficulties of a true understanding of atomic physics lie in its new concepts and ideas rather than in its mathematical formalism.
Theory and practice in engineering
Authors: Houston W. V.
Published: January 2009

During the past decade a great deal of thought has been given to the place of the sciences in an engineering curriculum and in engineering practice. There is often a difference in point of view between the traditional engineer who understands through experience how to build structures that will stand up, how to build rotating machinery that will not fail, how to build tools that will do the job, and the physicist or student of theoretical mechanics who feels he can treat any problem on a theoretical basis alone. But neither is solely correct. The problem each has before him is how these two aspects are to be combined. How is one going to make sure, in any particular case, that the best engineering experience is brought to bear and, at the same time, that the best theoretical knowledge is given appropriate consideration.
Voltage control of in-plane magnetic anisotropy in ultrathin Fe∕n-GaAs(001) Schottky junctions
Authors: Ohta K. , Maruyama T. , Nozaki T. , Shiraishi M. , Shinjo T. , Suzuki Y. , Ha S.-S. , You C.-Y. , Van Roy W.
Published: January 2009

We report on the realization of voltage control of in-plane magnetic anisotropy at room temperature in ultrathin Fe∕n-GaAs(001) Schottky junctions. Clear voltage-induced changes in magnetic anisotropy were observed in a Kerr ellipticity hysteresis loop using a lock-in modulation technique. The maximum change reached 4.5% of the saturation ellipticity under the application of a sinusoidal voltage signal of 1V peak-to-peak in an Fe layer with a thickness of 0.64nm. These results reveal the feasibility of controlling the in-plane magnetization process by the use of a perpendicular electric field. This can be a useful technique in ultralow power magnetization switching.
An optically induced cell lysis device using dielectrophoresis
Authors: Lin Yen-Heng , Lee Gwo-Bin
Published: January 2009

This letter reports an optically induced cell lysis device that can selectively lyse a single cell within a group of cells, a function which cannot be performed using traditional tools. This chip-scale device was made of a photoconductive material, which can induce a nonuniform electric field at a specific position under illumination of a beam spot generating a transmembrane potential in the cell. With this approach, cell lysis can be performed using the optically induced electric field. Fibroblast cells and oral cancer cells were used to demonstrate the capability of the developed chip. In addition to lysing the whole cell, the developed method also allowed one to selectively disrupt the cell membrane without damaging the nucleus. Operating parameters such as illumination power density and beam spot diameter for cell lysis were systematically investigated.
The conserved NAD(H)-dependent corepressor CTBP-1 regulates
Caenorhabditis elegans
life span
Authors: Chen Shuzhen , Whetstine Johnathan R. , Ghosh Salil , Hanover John A. , Gali Reddy R. , Grosu Paul , Shi Yang
Published: January 2009

CtBP (C-terminal binding protein) is an evolutionarily conserved NAD(H)-dependent transcriptional corepressor, whose activity has been shown to be regulated by the NAD/NADH ratio. Although recent studies have provided significant new insights into mechanisms by which CtBP regulates transcription, the biological function of CtBP remains incompletely understood. Here, we report that genetic inactivation of the
Caenorhabditis elegans
homolog,
ctbp-1
, results in life span extension, which is suppressed by reintroduction of the
ctbp-1
genomic DNA encoding wild-type but not NAD(H)-binding defective CTBP-1 protein. We show that CTBP-1 possibly modulates aging through the insulin/IGF-1 signaling pathway, dependent on the forkhead transcription factor DAF-16, but independent of the NAD-dependent histone deacetylase SIR-2.1. Genome-wide microarray analysis identifies >200 potential CTBP-1 target genes. Importantly, RNAi inhibition of a putative triacylglycerol lipase gene
lips-7
(C09E8.2) but not another lipase suppresses the life span extension phenotype. Consistently, metabolic analysis shows that the triacylglycerol level is reduced in the
ctbp-1
deletion mutant, which is restored to the wild-type level by RNAi inhibition of
lips-7
. Taken together, our data suggest that CTBP-1 controls life span probably through the regulation of lipid metabolism.
A peroxide bridge between Fe and Cu ions in the O
2
reduction site of fully oxidized cytochrome
c
oxidase could suppress the proton pump
Authors: Aoyama Hiroshi , Muramoto Kazumasa , Shinzawa-Itoh Kyoko , Hirata Kunio , Yamashita Eiki , Tsukihara Tomitake , Ogura Takashi , Yoshikawa Shinya
Published: January 2009

The fully oxidized form of cytochrome
c
oxidase, immediately after complete oxidation of the fully reduced form, pumps protons upon each of the initial 2 single-electron reduction steps, whereas protons are not pumped during single-electron reduction of the fully oxidized “as-isolated” form (the fully oxidized form without any reduction/oxidation treatment) [Bloch D,
et al.
(2004) The catalytic cycle of cytochrome
c
oxidase is not the sum of its two halves.
Proc Natl Acad Sci USA
101:529–533]. For identification of structural differences causing the remarkable functional difference between these 2 distinct fully oxidized forms, the X-ray structure of the fully oxidized as-isolated bovine heart cytochrome
c
oxidase was determined at 1.95-Å resolution by limiting the X-ray dose for each shot and by using many (≈400) single crystals. This minimizes the effects of hydrated electrons induced by the X-ray irradiation. The X-ray structure showed a peroxide group bridging the 2 metal sites in the O
2
reduction site (Fe
3+
-O
−
-O
−
-Cu
2+
), in contrast to a ferric hydroxide (Fe
3+
-OH
−
) in the fully oxidized form immediately after complete oxidation from the fully reduced form, as has been revealed by resonance Raman analyses. The peroxide-bridged structure is consistent with the reductive titration results showing that 6 electron equivalents are required for complete reduction of the fully oxidized as-isolated form. The structural difference between the 2 fully oxidized forms suggests that the bound peroxide in the O
2
reduction site suppresses the proton pumping function.
Nonparametric entrainment of the in vitro circadian phosphorylation rhythm of cyanobacterial KaiC by temperature cycle
Authors: Yoshida Takuya , Murayama Yoriko , Ito Hiroshi , Kageyama Hakuto , Kondo Takao
Published: January 2009

The three cyanobacterial Kai proteins and ATP are capable of generating an autonomous rhythm of KaiC phosphorylation in a test tube. As the period is ≈24 hours and is stable in a wide temperature range, this rhythm is thought to function as the basic oscillator of the cyanobacterial circadian system. We have examined the rhythm under various temperature cycles and found that it was stably entrained by a temperature cycle of 20–28 hours. As the period length was not altered by temperature, entrainment by period change could be excluded from possible mechanisms. Instead, temperature steps between 30° and 45°C and
vice versa
shifted the phase of the rhythm in a phase-dependent manner. Based on the phase response curves of the step-up and step-down in temperature, phase shift by single temperature pulse was estimated using a nonparametric entrainment model (discontinuous phase jump by external stimuli). The predicted phase shift was consistent with the experimentally measured phase shift. Next, successive phase shifts caused by repeated temperature cycles were computed by two phase response curves and compared with actual entrainment of the rhythm. As the entrainment pattern observed after various combinations of temperature cycles matched the prediction, it is likely that nonparametric entrainment functions even in the simple three-protein system. We also analyzed entrainment of KaiC phosphorylation by temperature cycle in cyanobacterial cells and found both the parametric and the nonparametric models function in vivo.
Image-guided, noninvasive, spatiotemporal control of gene expression
Authors: Deckers Roel , Quesson Bruno , Arsaut Josette , Eimer Sandrine , Couillaud Franck , Moonen Chrit T. W.
Published: January 2009

Spatiotemporal control of transgene expression is of paramount importance in gene therapy. Here, we demonstrate the use of magnetic resonance temperature imaging (MRI)-guided, high-intensity focused ultrasound (HIFU) in combination with a heat-inducible promoter [heat shock protein 70 (HSP70)] for the in vivo spatiotemporal control of transgene activation. Local gene activation induced by moderate hyperthermia in a transgenic mouse expressing luciferase under the control of the HSP70 promoter showed a high similarity between the local temperature distribution in vivo and the region emitting light. Modulation of gene expression is possible by changing temperature, duration, and location of regional heating. Mild heating protocols (2 min at 43°C) causing no tissue damage were sufficient for significant gene activation. The HSP70 promoter was shown to be induced by the local temperature increase and not by the mechanical effects of ultrasound. Therefore, the combination of MRI-guided HIFU heating and transgenes under control of heat-inducible HSP promoter provides a direct, noninvasive, spatial control of gene expression via local hyperthermia.
A critical role for IL-21 receptor signaling in the pathogenesis of systemic lupus erythematosus in BXSB-Yaamice
Authors: Bubier Jason A. , Sproule Thomas J. , Foreman Oded , Spolski Rosanne , Shaffer Daniel J. , Morse Herbert C. , Leonard Warren J. , Roopenian Derry C.
Published: January 2009

Interleukin 21 (IL-21) is a pleiotropic cytokine produced by CD4 T cells that affects the differentiation and function of T, B, and NK cells by binding to a receptor consisting of the common cytokine receptor γ chain and the IL-21 receptor (IL-21R). IL-21, a product associated with IL-17-producing CD4 T cells (TH17) and follicular CD4 T helper cells (TFH), has been implicated in autoimmune disorders including the severe systemic lupus erythematosus (SLE)-like disease characteristic of BXSB-Yaamice. To determine whether IL-21 plays a significant role in this disease, we compared IL-21R-deficient and -competent BXSB-Yaamice for multiple parameters of SLE. The deficient mice showed none of the abnormalities characteristic of SLE in IL-21R-competentYaamice, including hypergammaglobulinemia, autoantibody production, reduced frequencies of marginal zone B cells and monocytosis, renal disease, and premature morbidity. IL-21 production associated with this autoimmune disease was not a product of TH17 cells and was not limited to conventional CXCR5+TFHbut instead was produced broadly by ICOS+CD4+splenic T cells. IL-21 arising from an abnormal population of CD4 T cells is thus central to the development of this lethal disease, and, more generally, could play an important role in human SLE and related autoimmune disorders.
The near-infrared nitric oxide nightglow in the upper atmosphere of Venus
Authors: García Muñoz A. , Mills F. P. , Piccioni G. , Drossart P.
Published: January 2009

The
v′
= 0 progressions of the
C
→
X
and
A
→
X
band systems of nitric oxide dominate the middle-UV spectrum of the night-time upper atmospheres of the Earth, Mars, and Venus. The
C
(0) →
A
(0)+
h
ν radiative transition at 1.224 μm, the only channel effectively populating the
A
(0) level, must therefore occur also. There have been, however, no reported detections of the
C
(0) →
A
(0) band in the atmospheres of these or any other planets. We analyzed all available near-infrared limb observations of the dark-side atmosphere of Venus by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on the Venus Express spacecraft and found 2 unambiguous detections of this band at equatorial latitudes that seem to be associated with episodic events of highly enhanced nightglow emission. The discovery of the
C
(0) →
A
(0) band means observations in the 1.2–1.3 μm region, which also contains the
a
(0) →
X
(0) emission band of molecular oxygen, can provide a wealth of information on the high-altitude chemistry and dynamics of the Venusian atmosphere.
Capsule ofCryptococcus neoformansgrows by enlargement of polysaccharide molecules
Authors: Frases Susana , Pontes Bruno , Nimrichter Leonardo , Viana Nathan B. , Rodrigues Marcio L. , Casadevall Arturo
Published: January 2009

The human pathogenic fungusCryptococcus neoformanshas a distinctive polysaccharide (PS) capsule that enlarges during infection. The capsule is essential for virulence, but the mechanism for capsular growth is unknown. In the present study, we used dynamic light scattering (LS) analysis of capsular PS and optical tweezers (OT) to explore the architecture of the capsule. Analysis of capsular PS from cells with small and large capsules by dynamic LS revealed a linear correlation between PS effective diameter and microscopic capsular diameter. This result implied that capsule growth was achieved by the addition of molecules with larger effective diameter, such that some molecules can span the entire diameter of the capsule. Measurement of polystyrene bead penetration ofC. neoformanscapsules by using OT techniques revealed that the outer regions were penetrable, but not the inner regions. Our results provide a mechanism for capsular enlargement based on the axial lengthening of PS molecules and suggest a model for the architecture of a eukaryotic microbial capsule.
Self-assembled biomimetic [2Fe2S]-hydrogenase-based photocatalyst for molecular hydrogen evolution
Authors: Kluwer A. M. , Kapre R. , Hartl F. , Lutz M. , Spek A. L. , Brouwer A. M. , van Leeuwen P. W. N. M. , Reek J. N. H.
Published: January 2009

The large-scale production of clean energy is one of the major challenges society is currently facing. Molecular hydrogen is envisaged as a key green fuel for the future, but it becomes a sustainable alternative for classical fuels only if it is also produced in a clean fashion. Here, we report a supramolecular biomimetic approach to form a catalyst that produces molecular hydrogen using light as the energy source. It is composed of an assembly of chromophores to a bis(thiolate)-bridged diiron ([2Fe2S]) based hydrogenase catalyst. The supramolecular building block approach introduced in this article enabled the easy formation of a series of complexes, which are all thoroughly characterized, revealing that the photoactivity of the catalyst assembly strongly depends on its nature. The active species, formed from different complexes, appears to be the [Fe
2
(μ-pdt)(CO)
4
{PPh
2
(4-py)}
2
] (
3
) with 2 different types of porphyrins (5a and 5b) coordinated to it. The modular supramolecular approach was important in this study as with a limited number of building blocks several different complexes were generated.
Adipokinetic hormone signaling through the gonadotropin-releasing hormone receptor modulates egg-laying in
Caenorhabditis elegans
Authors: Lindemans Marleen , Liu Feng , Janssen Tom , Husson Steven J. , Mertens Inge , Gäde Gerd , Schoofs Liliane
Published: January 2009

In mammals, hypothalamic gonadotropin-releasing hormone (GnRH) is a neuropeptide that stimulates the release of gonadotropins from the anterior pituitary. The existence of a putative functional equivalent of this reproduction axis in protostomian invertebrates has been a matter of debate. In this study, the ligand for the GnRH receptor in the nematode
Caenorhabditis elegan
s (
Ce
-GnRHR) was found using a bioinformatics approach. The peptide and its precursor are reminiscent of both insect adipokinetic hormones and GnRH-preprohormone precursors from tunicates and higher vertebrates. We cloned the AKH-GnRH-like preprohormone and the
Ce
-GnRHR and expressed the GPCR in HEK293T cells. The GnRHR was activated by the
C. elegans
AKH-GnRH-like peptide (EC
50
= 150 nM) and by
Drosophila
AKH and other nematode AKH-GnRHs that we found in EST databases. Analogous to both insect AKH receptor and vertebrate GnRH receptor signaling,
Ce
-AKH-GnRH activated its receptor through a Gα
q
protein with Ca
2+
as a second messenger. Gene silencing of
Ce
-GnRHR,
Ce
-AKH-GnRH, or both resulted in a delay in the egg-laying process, comparable to a delay in puberty in mammals lacking a normal dose of GnRH peptide or with a mutated GnRH precursor or receptor gene. The present data support the view that the AKH-GnRH signaling system probably arose very early in metazoan evolution and that its role in reproduction might have been developed before the divergence of protostomians and deuterostomians.
Chloroplast protein targeting involves localized translation in
Chlamydomonas
Authors: Uniacke James , Zerges William
Published: January 2009

The compartmentalization of eukaryotic cells requires that newly synthesized proteins be targeted to the compartments in which they function. In chloroplasts, a few thousand proteins function in photosynthesis, expression of the chloroplast genome, and other processes. Most chloroplast proteins are synthesized in the cytoplasm, imported, and then targeted to a specific chloroplast compartment. The remainder are encoded by the chloroplast genome, synthesized within the organelle, and targeted by mechanisms that are only beginning to be elucidated. We used fluorescence confocal microscopy to explore the targeting mechanisms used by several chloroplast proteins in the green alga
Chlamydomonas
. These include the small subunit of ribulose bisphosphate carboxylase (rubisco) and the light-harvesting complex II (LHCII) subunits, which are imported from the cytoplasm, and 2 proteins synthesized in the chloroplast: the D1 subunit of photosystem II and the rubisco large subunit. We determined whether the targeting of each protein involves localized translation of the mRNA that encodes it. When this was the case, we explored whether the targeting sequence was in the nascent polypeptide or in the mRNA, based on whether the localization was translation-dependent or -independent, respectively. The results reveal 2 novel examples of targeting by localized translation, in LHCII subunit import and the targeting of the rubisco large subunit to the pyrenoid. They also demonstrate examples of each of the three known mechanisms—posttranslational, cotranslational (signal recognition particle-mediated), and mRNA-based—in the targeting of specific chloroplast proteins. Our findings can help guide the exploration of these pathways at the biochemical level.
Targeted disruption of the Cl
−
/HCO
3
−
exchanger Ae2 results in osteopetrosis in mice
Authors: Josephsen Kaj , Praetorius Jeppe , Frische Sebastian , Gawenis Lara R. , Kwon Tae-Hwan , Agre Peter , Nielsen Søren , Fejerskov Ole
Published: January 2009

Osteoclasts are multinucleated bone-resorbing cells responsible for constant remodeling of bone tissue and for maintaining calcium homeostasis. The osteoclast creates an enclosed space, a lacuna, between their ruffled border membrane and the mineralized bone. They extrude H
+
and Cl
−
into these lacunae by the combined action of vesicular H
+
-ATPases and ClC-7 exchangers to dissolve the hydroxyapatite of bone matrix. Along with intracellular production of H
+
and HCO
3
−
by carbonic anhydrase II, the H
+
-ATPases and ClC-7 exchangers seems prerequisite for bone resorption, because genetic disruption of either of these proteins leads to osteopetrosis. We aimed to complete the molecular model for lacunar acidification, hypothesizing that a HCO
3
−
extruding and Cl
−
loading anion exchange protein (Ae) would be necessary to sustain bone resorption. The Ae proteins can provide both intracellular pH neutrality and serve as cellular entry mechanism for Cl
−
during bone resorption. Immunohistochemistry revealed that Ae2 is exclusively expressed at the contra-lacunar plasma membrane domain of mouse osteoclast. Severe osteopetrosis was encountered in Ae2 knockout (Ae2−/−) mice where the skeletal development was impaired with a higher diffuse radio-density on x-ray examination and the bone marrow cavity was occupied by irregular bone speculae. Furthermore, osteoclasts in Ae2−/− mice were dramatically enlarged and fail to form the normal ruffled border facing the lacunae. Thus, Ae2 is likely to be an essential component of the bone resorption mechanism in osteoclasts.
Conformational disturbance in Abl kinase upon mutation and deregulation
Authors: Iacob Roxana E. , Pene-Dumitrescu Teodora , Zhang Jianming , Gray Nathanael S. , Smithgall Thomas E. , Engen John R.
Published: January 2009

Protein dynamics are inextricably linked to protein function but there are few techniques that allow protein dynamics to be conveniently interrogated. For example, mutations and translocations give rise to aberrant proteins such as Bcr-Abl where changes in protein conformation and dynamics are believed to result in deregulated kinase activity that provides the oncogenic signal in chronic myelogeous leukemia. Although crystal structures of the down-regulated c-Abl kinase core have been reported, the conformational impact of mutations that render Abl resistant to small-molecule kinase inhibitors are largely unknown as is the allosteric interplay of the various regulatory elements of the protein. Hydrogen exchange mass spectrometry (HX MS) was used to compare the conformations of wild-type Abl with a nonmyristoylated form and with 3 clinically relevant imatinib resistance mutants (T315I, Y253H and E255V). A HX-resistant core localized to the interface between the SH2 and kinase domains, a region known to be important for maintaining the down-regulated state. Conformational differences upon demyristoylation were consistent with the SH2 domain moving to the top of the small lobe of the kinase domain as a function of activation. There were conformational changes in the T315I mutant but, surprisingly, no major changes in conformation were detected in either the Y253H or the E255V mutants. Taken together, these results provide evidence that allosteric interactions and conformational changes play a major role in Abl kinase regulation in solution. Similar analyses could be performed on any protein to provide mechanistic details about conformational changes and protein function.
Clathrin adaptor AP-1 complex excludes multiple postsynaptic receptors from axons in
C. elegans
Authors: Margeta Milica A. , Wang George J. , Shen Kang
Published: January 2009

Neurons are highly polarized cells with morphologically and molecularly distinct axonal and dendritic compartments. It is not well understood how postsynaptic receptors are selectively enriched in dendrites in vivo. We investigated the molecular mechanisms of dendritically polarized localization of a glutamate receptor, an acetylcholine receptor, and a ROR-type receptor tyrosine kinase in the interneuron RIA in
C. elegans
. We found that the clathrin adaptor AP-1 complex μ1 subunit UNC-101 functions cell autonomously to maintain the correct localization of these receptors in a dynamin-dependent manner. In
unc-101
mutants, instead of being dendritically enriched, all 3 receptors are evenly distributed in the axonal and dendritic compartments. Surprisingly, UNC-101 predominantly localizes to the axonal compartment, suggesting a possible transcytosis model for the dendritic targeting of neurotransmitter receptors.
Long-lived
Indy
induces reduced mitochondrial reactive oxygen species production and oxidative damage
Authors: Neretti Nicola , Wang Pei-Yu , Brodsky Alexander S. , Nyguyen Hieu H. , White Kevin P. , Rogina Blanka , Helfand Stephen L.
Published: January 2009

Decreased
Indy
activity extends lifespan in
D. melanogaster
without significant reduction in fecundity, metabolic rate, or locomotion. To understand the underlying mechanisms leading to lifespan extension in this mutant strain, we compared the genome-wide gene expression changes in the head and thorax of adult
Indy
mutant with control flies over the course of their lifespan. A signature enrichment analysis of metabolic and signaling pathways revealed that expression levels of genes in the oxidative phosphorylation pathway are significantly lower in
Indy
starting at day 20. We confirmed experimentally that complexes I and III of the electron transport chain have lower enzyme activity in
Indy
long-lived flies by Day 20 and predicted that reactive oxygen species (ROS) production in mitochondria could be reduced. Consistently, we found that both ROS production and protein damage are reduced in
Indy
with respect to control. However, we did not detect significant differences in total ATP, a phenotype that could be explained by our finding of a higher mitochondrial density in
Indy
mutants. Thus, one potential mechanism by which
Indy
mutants extend life span could be through an alteration in mitochondrial physiology leading to an increased efficiency in the ATP/ROS ratio.
Circadian oscillation of nucleotide excision repair in mammalian brain
Authors: Kang Tae-Hong , Reardon Joyce T. , Kemp Michael , Sancar Aziz
Published: January 2009

The circadian clock regulates the daily rhythms in the physiology and behavior of many organisms, including mice and humans. These cyclical changes at molecular and macroscopic levels affect the organism's response to environmental stimuli such as light and food intake and the toxicity and efficacy of chemo- and radiotherapeutic agents. In this work, we investigated the circadian behavior of the nucleotide excision repair capacity in the mouse cerebrum to gain some insight into the optimal circadian time for favorable therapeutic response with minimal side effects in cancer treatment with chemotherapeutic drugs that produce bulky adducts in DNA. We find that nucleotide excision repair activity in the mouse cortex is highest in the afternoon/evening hours and is at its lowest in the night/early morning hours. The circadian oscillation of the repair capacity is caused at least in part by the circadian oscillation of the xeroderma pigmentosum A DNA damage recognition protein.
Semantico-syntactic environments of the verbs show and demonstrate and Spanish mostrar and demostrar in a bilingual corpus of medical research articles
Authors: Williams Ian A.
Published: January 2009

The verbs show and demonstrate, and their potential Spanish counterparts mostrar and demostrar, are frequent lexical verbs appearing in various settings in medical research articles (RAs). This study analyses the contextual environments of these verbs in an extensive corpus of medical RAs, composed of three subcorpora: English source texts, their Spanish translations, and comparable Spanish native language texts. The verbs are analysed in terms of syntax (active and passive) and the semantics of the main associated noun: ‘Characteristics’, ‘Authors’, ‘Evidence’, ‘Techniques’, and ‘Metatextual’. The study uses quantitative and qualitative methods in a three-way analysis: intralinguistic analysis compares the environments for the verb pairs in English and Spanish; interlinguistic analysis assesses similarities and differences in the environments between the two native language subcorpora; and comparison of source and target texts provides insight into translation behaviour. The implications for translation are discussed in terms of context, collocation and appropriateness of discourse style.
A reconsideration of the motivations for preferred argument structure
Authors: Everett Caleb
Published: January 2009

Previous studies on Preferred Argument Structure have suggested (Du Bois 1987, 2002) and accepted (e.g. Goldberg 2004) specific cognitive motivations for PAS, namely that the general restriction of lexical arguments and new referents to the S and O roles facilitates the conceptually onerous task of referent introduction. In this paper, conversation data from English and Portuguese are analyzed. The data are generally inconsistent with the putative cognitive motivations for PAS presented in the literature. They suggest instead that PAS is most likely epiphenomenal and due to basic semantic and pragmatic factors, for example the correlation between human referents and given/non-lexical arguments, and the correlation between human referents and the A role.
A unified account of causal clause sequences in Mandarin Chinese and its implications
Authors: Song Zuoyan , Tao Hongyin
Published: January 2009

Causal clauses introduced by yīnwèi in Chinese can have either an initial position or a final position with regard to the main clause. While traditional grammars have treated the initial sequence as the default form, numerous discourse-based studies have shown just the opposite. However, few have attempted to explain why both sequence orders exist and why they have skewed distribution patterns across discourse registers. In this paper we use a telephone conversation corpus and a written Chinese corpus as data and provide a comprehensive analysis of the usage patterns. Our main findings are that final and initial causal clause sequences are ostensibly two different linguistic constructions, functioning as an interactional device and an information-sharing device, respectively. Quantitative distributional disparities are seen as a function of the discourse utilities of the linguistic devices in question and the communicative demands of different registers. From a cross-linguistic perspective, our findings raise questions about the ways in which universal and language-specific properties of clause sequencing can be better understood.
“Reciprocity”
Authors: Wierzbicka Anna
Published: January 2009

This paper develops a semantic approach to the study of “reciprocity” — an area increasingly seen as central to linguistic typology. “Reciprocal” and “reflexive-reciprocal” constructions from five languages — English, Russian, Polish, French and Japanese — are analyzed in considerable detail. The different, though interrelated, meanings of these constructions are explicated, and the proposed explications are supported with linguistic evidence. The paper challenges current approaches which tend to lump formally and semantically distinct constructions under one arbitrary label such as “RECIP”, and it seeks to show how linguistic typology can be transformed by joining forces with rigorous cross-linguistic semantics. It also challenges the Nijmegen School approach, which privileges extensionalist “video-clipping” over conceptual analysis. The analysis presented in the paper demonstrates the descriptive and explanatory power of the NSM methodology. The results achieved through semantic analysis are shown to be convergent with hypotheses about “shared intentionality” put forward by Michael Tomasello and colleagues in the context of evolutionary psychology, and to throw new light on social universals (“human sociality”).