bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical value of anthropometric estimates of leg lean volume in nutritionally depleted and non-depleted patients with chronic obstructive pulmonary disease
Authors: Villaça Débora Strose , Lerario Maria Cristina , Corso Simone dal , Nápolis Lara , Albuquerque André Luiz Pereira de , Lazaretti-Castro Marize , Sachs Anita , Nery Luiz Eduardo , Neder Jose Alberto
Published: January 2008

This study aimed to investigate the clinical usefulness of an anthropometrically based method for estimating leg lean volume (LLV) in patients with chronic obstructive pulmonary disease (COPD) who presented or not with nutritional depletion. We prospectively evaluated a group of forty-eight patients (thirty-eight males) with moderate to severe COPD (Global Initiative for Chronic Obstructive Lung disease stages II–IV) who underwent a 6 min walking test and knee isokinetic dynamometry. Leg lean mass (muscle mass plus bone) was determined by dual-energy X-ray absorptiometry (DEXA) with derivation of its respective volume: these values were compared with those obtained by the truncated cones method first described by Jones and Pearson in 1969. As expected, depleted patients (n 19) had reduced exercise capacity and impaired muscle performance as compared to non-depleted subjects (P < 0·01). The mean bias of the LLV differences between anthropometry and DEXA were 0·40 litre (95 % CI − 0·59, 1·39) and 0·50 litre (95 % CI − 1·08, 2·08) for depleted and non-depleted patients, respectively. Anthropometrically and DEXA-based estimates correlated similarly with muscle functional attributes. A ROC curve analysis revealed that leg height-corrected LLV values had acceptable sensitivity and specificity to identify depleted patients (area under the curve 0·93 (range 0·86–1·00); P < 0·001). Moreover, patients with LLV ≤ 9·2 litres/m (the best cut-off value according to the ROC curve) had significantly lower exercise capacity and muscle performance than their counterparts (P < 0·05). In conclusion, an anthropometrically based method of estimating LLV (Jones and Pearson method) was shown to present with clinically acceptable accuracy and external validity in depleted and non-depleted patients with stable COPD.
The Nixon Administration and the Cienfuegos crisis of 1970: crisis-management of a non-crisis?
Authors: SINIVER ASAF
Published: January 2008

This article employs newly declassified documents from the National Archives in Washington and London to re-examine foreign policymaking of the Nixon Administration during the Cienfuegos crisis of 1970. The article seeks to answer two fundamental questions with regard to policy decision-making during the crisis: why did the Administration pursue a public policy of ‘business as usual’ while cloaking the crisis in extreme secrecy, and how was this achieved? Answers to these questions can be found in the unique situation the Administration found itself during the ‘Autumn of Crises’, and in Kissinger’s manipulation of NSC mechanisms and procedures, respectively.
Fluctuation history of the interior East Antarctic Ice Sheet since mid-Pliocene
Authors: Huang Feixin , Liu Xiaohan , Kong Ping , Fink David , Ju Yitai , Fang Aimin , Yu Liangjun , Li Xiaoli , Na Chunguang
Published: January 2008

Cosmogenic 10Be and 26Al measurements from bedrock exposures in East Antarctica provide indications of how long the rock surface has been free from glacial cover. Samples from the crests of Zakharoff Ridge and Mount Harding, two typical nunataks in the Grove Mountains, show minimum 10Be ages of 2.00 ± 0.22 and 2.30 ± 0.26 Ma, respectively. These ages suggest that the crests were above the ice sheet at least since the Plio–Pleistocene boundary. Adopting a ‘reasonable’ erosion rate of 5–10 cm Ma-1 increases the exposure ages of these two samples to extend into the mid-Pliocene. The bedrock exposure ages steadily decrease with decreasing elevation on the two nunataks, which indicates ~200 m decrease of the ice sheet in the Grove Mountains since mid-Pliocene time. Seven higher elevation samples exhibit a simple exposure history, which indicates that the ice sheet in the Grove Mountains decreased only ~100 m over a period as long as 1–2 Ma. This suggests that the East Antarctic Ice Sheet (EAIS) was relatively stable during the Pliocene warm interval. Five lower elevation samples suggest a complex exposure history, and indicate that the maximum subsequent increase of the EAIS was only 100 m higher than the present ice surface. Considering the uncertainties, their total initial exposure and subsequent burial time could be later than mid-Pliocene, which may not conflict with the stable mid-Pliocene scenario.
Edaphic and climatic effects on forest stand development, net primary production, and net ecosystem productivity simulated for Coastal Plain loblolly pine in Virginia
Authors: Sampson D. A. , Wynne R. H. , Seiler J. R.
Published: January 2008

We used SECRETS‐3PG to simulate net primary production (NPP) and net ecosystem productivity (NEP) of loblolly pine (Pinus taeda L.) growing on the Virginia Coastal Plain, focusing on the effects of soils and climate, and stand age over a 30‐year rotation. Soil type was influential, with heavier soils having greater NEP earlier in the rotation than lighter, sandier soils, although these differences disappeared by the rotation end. Climate had only a small effect. Stand age had the largest effect, with simulated annual NEP strongly negative during the first 5 to 8 years of development but peaking at +600 g C m−2 a−1 by age 13. Modest declines in NEP after 13 years were associated with declines in LAI as stands aged. The 30‐year mean annual NEP was positive over most of the study area but in a few cases was indistinguishable from zero for northwestern portions of the study. Simulated annual NPP rose from zero to over 2300 g biomass m−2 a−1 by age 12, after which it declined to ∼1700 g biomass m−2 a−1 by rotation end. These results suggest that loblolly pine plantations on the Coastal Plain of Virginia may become net annual C sinks 5 to 9 years after planting but that when averaged over a whole rotation the net carbon accumulation during the baseline rotation simulated here is indistinguishable from zero. Our results also suggest, however, that this finding is sensitive to the length of the rotation, soil type (and thus fertility), and climate, implying that changes in management practices could significantly influence the carbon balance in managed loblolly pine plantations.
Performance‐based optimal design and rehabilitation of water distribution networks using life cycle costing
Authors: Jayaram Nirmal , Srinivasan K.
Published: January 2008

A new multiobjective formulation is proposed for the optimal design and rehabilitation of a water distribution network, with minimization of life cycle cost and maximization of performance as objectives. The life cycle cost is considered to comprise the initial cost of pipes, the cost of replacing old pipes with new ones, the cost of cleaning and lining existing pipes, the expected repair cost for pipe breaks, and the salvage value of the pipes that are replaced. The performance measure proposed in this study is a modification to the resilience index to suit application to water distribution networks with multiple sources. A new heuristic method is proposed to obtain the solution for the design and rehabilitation problem. This heuristic method involves selection of various design and rehabilitation alternatives in an iterative manner on the basis of the improvement in the network performance as compared to the change in the life cycle cost on implementation of the alternatives. The solutions obtained from the heuristic method are used as part of the initial population set of the multiobjective, nondominated sorting genetic algorithm (NSGA‐II) in order to improve the search process. Using a sample water distribution network, the modified resilience index proposed is shown to be a good indicator of the uncertainty handling ability of the network.
Polar stratospheric chlorine kinetics from a self‐match flight during SOLVE‐II/EUPLEX
Authors: Schofield R. , Frieler K. , Wohltmann I. , Rex M. , von Hobe M. , Stroh F. , Koch G. , Peter T. , Canty T. , Salawitch R. , Volk C. M.
Published: January 2008

In‐situ measurements of ClO made onboard the Geophysica aircraft on 30 January 2003 in the Arctic afford a novel approach to constrain the kinetic parameters governing polar stratospheric chlorine chemistry using atmospheric observations. The self‐match flight pattern, i.e. sampling individual air masses twice at different zenith angles, was utilized by simulating the evolution of ClO mixing ratios between two ‘matching’ points using a photochemical model and optimizing the model parameters to fit the observations within a retrieval framework. Our results suggest a ClO/ClOOCl thermal equilibrium constant Keq a factor of 5 smaller and a ratio J/kf a factor of 2 larger than the values based on the JPL recommendations. This concurs with other studies based on observed ClOx partitioning and corroborates that our understanding of stratospheric chlorine chemistry is incomplete, particularly in the light of the most recent laboratory experiments pointing to a J/kf ratio almost an order of magnitude below the JPL recommendation.
Widespread CO2 and other non‐ice compounds on the anti‐Jovian and trailing sides of Europa from Galileo/NIMS observations
Authors: Hansen Gary B. , McCord Thomas B.
Published: January 2008

An observation at wavelengths 0.7–5.3 μm of the anti‐Jovian and trailing sides of the moon Europa by the Near Infrared Mapping Spectrometer on the Galileo spacecraft has been reprocessed to reveal new details in the >3.0 μm infrared spectrum. The revealed features include strong absorption bands centered at 4.25 and 4.0 μm, attributed to CO2 and SO2, as well as weaker bands, such as near 3.5 μm attributed to H2O2. The calculated band depth distribution of both the CO2 and SO2 show that the CO2 is strongly associated with the (possibly endogenic) dark (typically hydrate) regions on the surface, while the SO2 is not strongly correlated with the CO2, but has a similar sparse distribution. The association of CO2 with the hydrates may indicate a CO2‐rich ocean that is a potential environment for autotrophic organisms that might thrive near the rock‐ocean interface, similar to the earliest life on Earth.
Profiles of volumetric water content in fault zones retrieved from hole B of the Taiwan Chelungpu‐fault Drilling Project (TCDP)
Authors: Lin Weiren , Matsubayashi Osamu , Yeh En‐Chao , Hirono Tetsuro , Tanikawa Wataru , Soh Wonn , Wang Chien‐Ying , Song Sheng‐Rong , Murayama Masafumi
Published: January 2008

To determine the distribution pattern of water content in the three major fault zones penetrated by the Taiwan Chelungpu‐fault Drilling Project (TCDP) hole B, and to assess a rapid, nondestructive water content measurement technique, time domain reflectometry (TDR), we determined the volumetric water content of sequential core samples and found that water content increased toward the center of each of the three fault zones, except in the disk‐shaped black material. We observed distinct anomalies in the water content and resistivity profiles, particularly in the shallowest major fault zone (FZB1136), supporting the hypothesis that FZB1136 ruptured during the 1999 Chi‐Chi earthquake. This study, the first successful application of the TDR technique to determine water content of core samples, including fault zone samples, collected by an active‐fault drilling project, showed that this technique is suitable for measuring water content of fault core samples.
Assessment of the non‐hydrostatic effect on the upper atmosphere using a general circulation model (GCM)
Authors: Deng Yue , Richmond Arthur D. , Ridley Aaron J. , Liu Han‐Li
Published: January 2008

Under hydrostatic equilibrium, a typical assumption used in global thermosphere ionosphere models, the pressure gradient in the vertical direction is exactly balanced by the gravity force. Using the non‐hydrostatic Global Ionosphere Thermosphere Model (GITM), which solves the complete vertical momentum equation, the primary characteristics of non‐hydrostatic effects on the upper atmosphere are investigated. Our results show that after a sudden intense enhancement of high‐latitude Joule heating, the vertical pressure gradient force can locally be 25% larger than the gravity force, resulting in a significant disturbance away from hydrostatic equilibrium. This disturbance is transported from the lower altitude source region to high altitudes through an acoustic wave, which has been simulated in a global circulation model for the first time. Due to the conservation of perturbation energy, the magnitude of the vertical wind perturbation increases with altitude and reaches 150 (250) m/s at 300 (430) km during the disturbance. The upward neutral wind lifts the atmosphere and raises the neutral density at high altitudes by more than 100%. These large vertical winds are not typically reproduced by hydrostatic models of the thermosphere and ionosphere. Our results give an explanation of the cause of such strong vertical winds reported in many observations.
Variability of the low‐level cross‐equatorial jet of the western Indian Ocean since 1660 as derived from coral proxies
Authors: Gong Dao‐Yi , Luterbacher Jürg
Published: January 2008

Using monthly‐seasonally resolved coral proxies from the Indian Ocean basin, we statistically reconstruct the June–July–August (JJA) low‐level jet in western Indian Ocean from 1660−1957 with skillful estimates for high‐ and low‐frequencies. The El Niño/Southern Oscillation (ENSO) signals are reasonably captured. The strength of the jet significantly increases from the late 17th century to late 19th century. The decreasing in reconstructed jet in 20th century disagrees with previous studies which indicated an enhancement of Southern Asian summer monsoon (SASM) in association with the rapid global warming. The jet reconstructions are useful for understanding of SASM variability and the validation of historical monsoon simulation.
Continuous positive airway pressure increases heart rate variability in heart failure patients with obstructive sleep apnoea
Authors: Gilman Matthew P. , Floras John S. , Usui Kengo , Kaneko Yasuyuki , Leung Richard S. T. , Bradley T. Douglas
Published: January 2008

Patients with heart failure or OSA (obstructive sleep apnoea) have reduced HF-HRV (high-frequency heart rate variability), indicating reduced cardiac vagal modulation, a marker of poor prognosis. CPAP (continuous positive airway pressure) abolishes OSA in patients with heart failure, but effects on daytime HF-HRV have not been determined. We hypothesized that, in patients with heart failure, treatment of coexisting OSA by CPAP would increase morning HF-HRV. In 19 patients with heart failure (left ventricular ejection fraction <45%) and OSA (≥20 apnoeas and hypopnoeas/h of sleep), HF-HRV was quantified before and 1 month after randomization to a control or CPAP-treated group. In the control group (n=7), there were no changes in HF-HRV over the 1 month study during wakefulness in the morning. In the CPAP-treated group (n=12) HF-HRV increased significantly during wakefulness in the morning [from 2.43±0.55 to 2.82±0.50 log(ms2/Hz); P=0.002] due to an increase in transfer function between changes in lung volume and changes in HF-HRV (92.37±96.03 to 219.07±177.14 ms/l; P=0.01). In conclusion, treatment of coexisting OSA by nocturnal CPAP in patients with heart failure increases HF-HRV during morning wakefulness, indicating improved vagal modulation of heart rate. This may contribute to improved prognosis.
Normal-sodium diet compared with low-sodium diet in compensated congestive heart failure: is sodium an old enemy or a new friend?
Authors: Paterna Salvatore , Gaspare Parrinello , Fasullo Sergio , Sarullo Filippo M. , Di Pasquale Pietro
Published: January 2008

The aim of the present study was to evaluate the effects of a normal-sodium (120 mmol sodium) diet compared with a low-sodium diet (80 mmol sodium) on readmissions for CHF (congestive heart failure) during 180 days of follow-up in compensated patients with CHF. A total of 232 compensated CHF patients (88 female and 144 male; New York Heart Association class II–IV; 55–83 years of age, ejection fraction <35% and serum creatinine <2 mg/dl) were randomized into two groups: group 1 contained 118 patients (45 females and 73 males) receiving a normal-sodium diet plus oral furosemide [250–500 mg, b.i.d. (twice a day)]; and group 2 contained 114 patients (43 females and 71 males) receiving a low-sodium diet plus oral furosemide (250–500 mg, b.i.d.). The treatment was given at 30 days after discharge and for 180 days, in association with a fluid intake of 1000 ml per day. Signs of CHF, body weight, blood pressure, heart rate, laboratory parameters, ECG, echocardiogram, levels of BNP (brain natriuretic peptide) and aldosterone levels, and PRA (plasma renin activity) were examined at baseline (30 days after discharge) and after 180 days. The normal-sodium group had a significant reduction (P<0.05) in readmissions. BNP values were lower in the normal-sodium group compared with the low sodium group (685±255 compared with 425±125 pg/ml respectively; P<0.0001). Significant (P<0.0001) increases in aldosterone and PRA were observed in the low-sodium group during follow-up, whereas the normal-sodium group had a small significant reduction (P=0.039) in aldosterone levels and no significant difference in PRA. After 180 days of follow-up, aldosterone levels and PRA were significantly (P<0.0001) higher in the low-sodium group. The normal-sodium group had a lower incidence of rehospitalization during follow-up and a significant decrease in plasma BNP and aldosterone levels, and PRA. The results of the present study show that a normal-sodium diet improves outcome, and sodium depletion has detrimental renal and neurohormonal effects with worse clinical outcome in compensated CHF patients. Further studies are required to determine if this is due to a high dose of diuretic or the low-sodium diet.
Pulsars Shed New Light on Evolution of Binary Stars
Authors: Andersen Per H.
Published: January 2008

Some 20 years after pulsars were discovered in 1967, there has been a new burst of findings on these rapidly rotating neutron stars. The companion of a recently discovered millisecond pulsar may be literally evaporating into interstellar space.
Special Supplement: Physics News in 1987
Authors: Schewe Phillip F.
Published: January 2008

The American Institute of Physics is a not-for-profit membership corporation chartered in New York State in 1931 for the purpose of promoting the advancement and diffusion of the knowledge of physics and its application to human welfare. Leading societies in the field of physics and astronomy are its members. AIP's activities include providing services to its Member Societies in the publishing, fiscal, and educational areas, as well as other services which can best be performed by one operating agency rather than dispersed among the constituent societies.
The Tc to Beat is 125 K
Authors: Khurana Anil
Published: January 2008

After a long year the superconductivity community worldwide is confidentat last about the synthesis of stable superconducting materials with critical temperatures even higher than 90 K. There have been a series of reports since this January on the synthesis and studies of three, or perhaps four, new oxide superconductors with critical temperatures above 80 K. These discoveries strengthen the hope that the “revolution,” begun only two years ago by Georg Bednorz and Alex Müller (IBM Zurich Research Laboratory at Rüschlikon, Switzerland) with the discovery of superconductivity up to 30 K in La2−x(Ba)xCuO4−y, is still young and may engender many interesting surprises.
A Super Time to Renormalize
Authors: Levi Barbara Goss
Published: January 2008

What incredibly superlative times these are! Modern advances in physics are beyond description, or so their names imply: We have discovered superconducrors and superfluids, predicred supersymmetries and superstrings, observed supernovas, supergalaxies and superclusters; and we analyze them all on supercomputers. But where do we go from here? We avoided the dilemma for many years but technology has caught up with us at last. No words can describe our latest creations. The nextgeneration accelerator will have unprecedented size and efficiency, but we can only express its overwhelming capacity by repeating ourselves, as in on awestruck stutter: We call it the Superconducting Super Collider. The high-temperature superconductors discovered last year have been verbally elevated to their proper level only at the expense of the lower-temperature materials, which have been downgraded to “conventional superconductors.” (Do I detect a contradiction in terms?)
Very Small Tunnel Junctions Sense the Effect of Single Electrons
Authors: Levi Barbara Goss
Published: January 2008

In most capacitors the gain or loss of a single electron is hardly noticed. But in the very small tunnel junctions that can now be made, the capacitance is so small—on the order of 10−16 farads or less—that the addition of just one electron can change the electric potential across the barrier by several millivolts. In that case, a single electron certainly can make a difference. The change in potential when an electron tunnels across the junction is enough to impede the tunneling of the next electron. The resulting block of current flow—called the Coulomb blockade—should show up in the current-voltage characteristics of small-capacitance tunnel junctions at low temperatures.
First Echoes from SN1987a…87a…87a
Authors: Marynowski Margaret
Published: January 2008

The first visible-light echoes from supernova 1987a—in fact, the first ever observed from a supernova—have been detected. The echoes, visible in this photo as arcs of rings surrounding the central star, are the light of the exploding star reflected from dusty clouds in the Large Magellanic Cloud. Although the clouds lie almost directly in our line of sight to the supernova, they are quite distant from the star. Arlin Crotts (University of Texas, Austin) reported finding a double echo on 4 March using the 40-inch Swope telescope at the Carnegie Institution's Las Campanas Observatory in Chile. Confirmation of Crorrs's report came a week later from Michael Rosa (European Southern Observatory), who examined data he had taken in February with ESO's 3.6-meter relescope.
Now They're Even Trapping Antiprotons
Authors: Schwarzschild Bertram
Published: January 2008

The University of Washington group that made its reputation by doing measurements of exquisite precision on single protons, electrons and positrons held for astonishingly long times in a Penning trap (PHYSICS TODAY, May 1985, page 17) has finally succeeded in trapping antiprotons. They accomplished this feat in July at the LEAR low-energy antiproton ring at CERN, where they had been granted one day's running to do a feasibility test for precision antiproton measurements they hope to carry out next year.
Analysis of neutral active particle loss in afterglow in krypton at 2.6mbar pressure
Authors: Pejovic Momcilo M. , Karamarkovic Jugoslav P. , Ristic Goran S. , Pejovic Milic M.
Published: January 2008

This paper presents the analysis of the surface recombination and/or de-excitation of neutral active particles in two different volume krypton-filled tubes at pressure of 2.6mbar with 1ppm oxygen impurities. The analysis was performed on the basis of secondary electron emission from the cathode induced by positive ions and neutral active particles using the experimental data of electrical breakdown time delay mean value td¯ as a function of afterglow period τ (“memory curve”). It was shown that the main channel of neutral active particles' loss in afterglow is their recombination and/or de-excitation on the bulb walls. The loss rate increases with the increase of available wall surface per unit of gas volume. It was also shown that in early afterglow (15ms for the tube with smaller bulb volume and 30ms for the tube with bigger bulb volume) positive ions are formed in the mutual collisions of neutral active particles, and these ions dominantly influence the secondary electron emission from the cathode. In late afterglow (to 30s for the tube with smaller bulb volume and to 150s for the tube with bigger bulb volume) neutral active particles have dominant role in secondary electron emission from the cathode. The probability for this process decreases with the increase of afterglow period as a consequence of the decrease of the concentration of neutral active particles in gas, and this probability is smaller for the tube with smaller bulb volume. The influence of additional electron yield in the electrode gap caused by gamma radiation on breakdown initiation is also analyzed. It is shown that the influence of the neutral active particles in the process of secondary electron emission in the case of gamma radiation is also significant in both early and late afterglow.
Transient absorption of vibrationally excited ice Ih
Authors: Dokter Adriaan M. , Bakker Huib J.
Published: January 2008

The ultrafast dynamics of HDO:D2O ice Ih at 180K is studied by midinfrared ultrafast pump-probe spectroscopy. The vibrational relaxation of HDO:D2O ice is observed to proceed via an intermediate state, which has a blueshifted absorption spectrum. Polarization resolved measurements reveal that the intermediate state is part of the intramolecular relaxation pathway of the HDO molecule. In addition, slow dynamics on a time scale of the order of 10–100ps is observed, related to thermally induced collective reorganizations of the ice lattice. The transient absorption line shape is analyzed within a Lippincott-Schroeder model for the OH-stretch potential. This analysis identifies the main mechanism behind the strong spectral broadening of the vOH=1→2 transition.
Growth of InP on GaAs (001) by hydrogen-assisted low-temperature solid-source molecular beam epitaxy
Authors: Postigo P. A. , Suárez F. , Sanz-Hervás A. , Sangrador J. , Fonstad C. G.
Published: January 2008

Direct heteroepitaxial growth of InP layers on GaAs (001) wafers has been performed by solid-source molecular beam epitaxy assisted by monoatomic hydrogen (H∗). The epitaxial growth has been carried out using a two-step method: for the initial stage of growth the temperature was as low as 200 °C and different doses of H∗ were used; after this, the growth proceeded without H∗ while the temperature was increased slowly with time. The incorporation of H∗ drastically increased the critical layer thickness observed by reflection high-energy electron diffraction; it also caused a slight increase in the luminescence at room temperature, while it also drastically changed the low-temperature luminescence related to the presence of stoichiometric defects. The samples were processed by rapid thermal annealing. The annealing improved the crystalline quality of the InP layers measured by high-resolution x-ray diffraction, but did not affect their luminescent behavior significantly.
Etching of nanopatterns in silicon using nanopantography
Authors: Xu Lin , Nasrullah Azeem , Chen Zhiying , Jain Manish , Ruchhoeft Paul , Economou Demetre J. , Donnelly Vincent M.
Published: January 2008

Nanopantography is a technique for parallel writing of nanopatterns over large areas. A broad ion beam impinges on a substrate containing many microfabricated electrostatic lenses that focus ions to spots at the substrate surface. Here, etching of nanopatterns is demonstrated. The substrate was continuously titled about x and y axes with 0.11° precision, corresponding to a translation of the ion foci of 1.5nm on the substrate. With tilting in one direction, 15nm full width at half maximum trenches 45nm deep were etched into a Si wafer using an Ar+ beam in a Cl2 ambient. T-shaped patterns were etched by tilting the substrates in two directions.
Fiber-focused diode bar optical trapping for microfluidic flow manipulation
Authors: Applegate Robert W. , Squier Jeff , Vestad Tor , Oakey John , Marr David W. M.
Published: January 2008

The direct integration of light and optical control into microfluidic systems presents a significant hurdle to the development of portable optical trapping-based devices. We present a simple, inexpensive fiber-based approach that allows for easy implementation of diode bars for optical particle separations within flowing microfluidic systems. We also develop models that demonstrate the advantages of manipulating particles within flow using linear geometries as opposed to individually focused point traps as traditionally employed in optical trapping micromanipulation.
Langmuir-Blodgett Films
Authors: Agarwal Vijendra K.
Published: January 2008

The science and technology of thin films have advanced so rapidly in recent years that investigators are now specializing, responding to the growing need to understand the properties of films of various compositions and thicknesses. Of particular scientific and technological promise are organic thin films grown by the classical dipping technique developed during the period 1917–35 by Irving Langmuir and Katharine Blodgett. By building multiplayer films on solid surfaces from monolayer films on water, investigators are now developing and studying innovative materials with a wide range of potential technological applications, including molecular electronics, microelectronics, integrated optics and microlithography. Inorganic thin films of materials such as silicon dioxide have made possible the very-large-scale integration of electronic circuits. If the device geometries in these circuits shrink to nanometer dimensions over the next several decades, as some expect, Langmuir-Blodgett films with nanometer dimensions and a high degree of structural order will be of special importance.
The Statistical Physics of Sedimentary Rock
Authors: Wong Po-Zen
Published: January 2008

Sedimentary rock makes up much of the Earth's surface and contains two of the most vital fluids for our lives—water and hydrocarbons. Yet physicists have paid little attention to rock, mainly because we are discouraged by its apparent complexity. We are well trained in working with idealized models, but when faced with a piece of rock, not only do we not know where to begin, but we also may question whether it is even possible to find interesting physics in such a “dirty” and uncontrolled system. With further thought, however, we should realize that these are but the usual mental barriers that we have to overcome every time we study something new.
Flavor SU(3) Symmetries in Particle Physics
Authors: Georgi Howard
Published: January 2008

The development of the so-called standard model of the strong and electroweak interactions of particle physics is one of the most remarkable accomplishments of 20th century science. The standard model is based on the idea of gauge symmetry, in which the mathematical idea of symmetry determines the dynamics. According to the model, the strong, weak and electromagnetic forces are mediated by an exchange of particles: The strong force is mediated by the gluons, the weak force by the W+, W− and Z bosons, and the electromagnetic force by the photon. In turn the gluons, the bosons and the photon are associated with the SU(3), SU(2) and U(1) symmetries of the standard model. In this article I shall discuss a different kind of symmetry, the so-called flavor symmetry, which turns out to be only approximate. Flavor symmetry is not associated with the forces of the standard model; instead it pertains to the particles, especially the quarks, between which the forces act.
100 Years of Photoemission
Authors: Margaritondo Giorgio
Published: January 2008

With these words, Heinrich Hertz announced in 1887 the discovery of the photoelectric effect. Although he realized that the phenomenon was important, he certainly could not have imagined how fundamental its role in physics was to be over the next 100 years. Even now, many physicists do not completely understand that role. For example, the effect is often, but incorrectly, credited with leading Albert Einstein to the quantization of the electromagnetic field. Photoemission experiments actually made their most important contributions to field quantization after Einstein had formulated the theory, by demonstrating its validity.
Special Issue: Lasers Then and Now
Authors: Lubkin Gloria B.
Published: January 2008

With this special issue on lasers, we celebrate the completion of the Laser History Project, an effort begun in 1982. The project was founded by four societies—The American Physical Society, the IEEE Lasers and Electro-Optics Society, the Laser Institute of America and the Optical Society of America.
Superconductivity Research: A Different View
Authors: Rowell John M.
Published: January 2008

Much has been written about superconductivity in the past 18 months. Some of it is technical, and usually it is accurate. Some of it promises applications on time scales that I find difficult to believe. But in a good fraction of this writing the technological challenge posed by the discovery of the new high-temperature superconductors is used to justify sweeping generalizations about US research, development and manufacturing capabilities. The theme underlying this sort of writing is that “superconductivity is our last chance to prove our technological prowess,” or, more simply, “we will lose out to Japan—again.” It is this aspect of the superconductivity news that I will discuss. I find that there is some underlying cause for concern but that many positive aspects of US commercialization of conventional, low-temperature superconductors are being ignored. Furthermore, suggestions that US industry is not contributing at the forefront of research in high-Tc superconductivity are demonstrably incorrect.
Special Issue: International Space Science
Authors: Donahue Thomas M.
Published: January 2008

The articles in this special issue of PHYSICS TODAY, together with Minoru Oda's article on the space science program in Japan (December, page 26), portray a research field beset by contradictions. The space research programs of the USSR, Europe and Japan are flourishing. Their scientists are busy analyzing the results of recent successes in Solar System exploration and in astrophysics. They are also busy constructing new projects, some of which are joint international ventures involving a substantial pooling of resources. International cooperation is the mot d'ordre in Europe and the USSR, where enthusiasm and optimism are pervasive.
Macromolecular Structure from Anomalous Dispersion
Authors: Karle Jerome
Published: January 2008

Knowledge of the structures of macromolecules is of major importance both to basic science and to new, burgeoning industries. The determination of these structures is improving our understanding of fundamental biological processes, and so it sets the stage for the broad explanation of diseases on the molecular level and for the rational design of drugs. It promises to give insight into such topics as the mechanisms of enzyme action, the implications of protein structure for evolutionary development, the relation of amino acid sequences to three-dimensional structure and the relation between structure and function in complicated systems such as viruses, muscle, ribosomes and chromatin.
Physical Limits to the Performance of Imaging Systems
Authors: Rose Albert , Weimer Paul K.
Published: January 2008

Our visual system provides our principal contact with the world around us. This system, thanks to millions of years of natural development, achieved a high degree of perfection long before humans arrived on the scene. To attain such perfection, these evolutionary processes had to recognize the quantum nature of light—a remarkable accomplishment.
Color Science for Imaging Systems
Authors: DeMarsh LeRoy E. , Giorgianni Edward J.
Published: January 2008

Artists and artisans in all eras and civilizations have produced color images for aesthetic and informational purposes. The desire to produce images that record visual experiences and to share those images with others seems intrinsic to human nature. Color is an important aspect of the visual experience. It is only natural that we attempt to understand it so that we may have control over the way we use it in drawings, paintings, photographs and electronic images.
George Uhlenbeck and the Discovery of Electron Spin
Authors: Pais Abraham
Published: January 2008

The owl depicted on the signet ring George Uhlenbeck used to wear—“Uhlenbeck” in German means “owl's brook”—derives from his family's coat of arms. The shield reads, in the language of heraldry: Azure, on a tree trunk proper rising from water argent, an owl contourne, head affronty. In plain language, it depicts an owl with its head turned toward you, sitting on a tree trunk in natural color, which rises up out of a silvery brook. (I owe the transcription of the Dutch blazon into English heraldry to Michael Maclagan, the Richmond Herald in the College of Arms, in London.)
An APS President Reflects on His Two-Year Term
Authors: Fitch Val L.
Published: January 2008

When Robert Oppenheimer was president of the APS, just 40 years ago, he observed that, fortunately for the society, it was impossible for a president to do any great damage in a one-year term. We now have to reassess this observation. Because of the untimely death of my intended successor, George Vineyard, I have had two years to inflict havoc and chaos. Happily, the more permanent staff of the society—Bill Havens, Harry Lustig, Miriam Forman and Bob Park—are all deft at damage-limiting techniques, and the society has survived, rather well I think, even two years of a transient president.
The Young Feynman
Authors: Wheeler John Archibald
Published: January 2008

“This chap from MIT: Look at his aptitude test ratings in mathematics and physics. Fantastic! Nobody else who's applying here at Princeton comes anywhere near so close to the absolute peak.” Someone else on the Graduate Admissions Committee broke in, “He must be a diamond in the rough. We've never let in anyone with scores so low in history and English. But look at the practical experience he's had in chemistry and in working with friction.”
A Path to Quantum Electrodynamics
Authors: Schwinger Julian
Published: January 2008

On 10 December 1965 three people shared a Nobel Prize “for their fundamental work in quantum electrodynamics.” I am the sole survivor of that trio. Almost a decade ago I delivered a memorial lecture for Sin-itiro Tomonaga. Now I join with others in a tribute to Richard P. Feynman.
Richard P. Feynman, Teacher
Authors: Goodstein David L.
Published: January 2008

One of the principal purposes of this article is to consider Dick Feynman in his role as teacher. Let me not keep you in suspense about my conclusion. I think Dick was a truly great teacher, perhaps the greatest of his era and ours. That's not to say he was always completely successful, as he himself emphasized in his preface to The Feynman Lectures on Physics. I would contend that these lectures often failed at the level of their superficial intent: If his purpose in giving them was to prepare classes of adolescent boys to solve examination problems in physics, he may not have succeeded particularly well; if his purpose in creating those three red volumes was to provide effective introductory college textbooks, he may not have succeeded, either. If, however, his purpose was to illustrate, by example, how to think and reason about physics, then, by all indications, he was brilliantly successful. Perhaps this is why the books are genuine and lasting classics of the scientific literature and why his lectures left an enduring trace on those fortunate enough to have heard or read them.
Richard Feynman and the Connection Machine
Authors: Hillis W. Daniel
Published: January 2008

One day in the spring of 1983, when I was having lunch with Richard Feynman, I mentioned to him that I was planning to start a company to build a parallel computer with a million processors. (I was at the time a graduate student at the MIT Artificial Intelligence Lab). His reaction was unequivocal: “That is positively the dopiest idea I ever heard.” For Richard a crazy idea was an opportunity to prove it wrong—or prove it right. Either way, he was interested. By the end of lunch he had agreed to spend the summer working at the company.
A Lowbrow's View of Feynman
Authors: Telegdi Valentine L.
Published: January 2008

I learned by accident that PHYSICS TODAY was preparing a special issue in memory of Richard Feynman, whose death about a year ago shocked his fellow physicists worldwide so deeply. In looking at the tentative list of contributors to the memorial issue, I noticed with surprise that it consisted almost entirely of theoretical physicists. While eminent theorists obviously were best qualified to eulogize Feynman's extraordinary contributions to their own specialty, something essential might have been lost to the readers by this restricted choice. Feynman was not a theorist's theorist, but a physicist's physicist and a teacher's teacher.
Cosmic Strings: Topological Fossils of the Hot Big Bang
Authors: Press William H. , Spergel David N.
Published: January 2008

Was the physics of the early universe like the physics of a rotating bucket of superfluid helium? Condensed matter physicists know that phase transitions can form exotic topological objects, such as quantized vortices in superfluid helium or vortex lines of magnetic field in superconductors. In recent years cosmologists have been exploring whether analogous phenomena occurred in the early universe. Cosmic strings, remnants of an ultrahightemperature phase transition at 1029 K, may have seeded galaxy formation and could have given rise to other effects observable in the universe today.
The Phase Problem of X-Ray Crystallography
Authors: Hauptman Herbert A.
Published: January 2008

With the invention some 200 years ago of the goniometer, an instrument for measuring the angles between the faces of a crystal, the science of crystallography was born. The goniometer made possible the discovery of the fundamental laws of descriptive crystallography: that the angles between the facial planes are determined by the chemical composition of the crystal and that the relative orientations of the facial planes follow a simple rule, the law of rational positions.
Introducing the Physics of Technology into the High School Curriculum
Authors: Eisenstein Barbara , Millman Sidney , Pallrand George
Published: January 2008

Only about 20% of American high school graduates have studied physics, and this percentage has not changed much the last couple of decades. The situation is distressing when one considers that our way of life has become increasingly tied to technology, with physics playing a critical role. In many other developed countries, including Japan, England and Korea, all high school students study physics, and they start much earlier than the 11th or 12th grade.
Difficulties in tracking the long-term global trend in tropical forest area
Authors: Grainger Alan
Published: January 2008

The long-term trend in tropical forest area receives less scrutiny than the tropical deforestation rate. We show that constructing a reliable trend is difficult and evidence for decline is unclear, within the limits of errors involved in making global estimates. A time series for all tropical forest area, using data from Forest Resources Assessments (FRAs) of the United Nations Food and Agriculture Organization, is dominated by three successively corrected declining trends. Inconsistencies between these trends raise questions about their reliability, especially because differences seem to result as much from errors as from changes in statistical design and use of new data. A second time series for tropical moist forest area shows no apparent decline. The latter may be masked by the errors involved, but a “forest return” effect may also be operating, in which forest regeneration in some areas offsets deforestation (but not biodiversity loss) elsewhere. A better monitoring program is needed to give a more reliable trend. Scientists who use FRA data should check how the accuracy of their findings depends on errors in the data.
Cooperative binding of ATP and RNA induces a closed conformation in a DEAD box RNA helicase
Authors: Theissen Bettina , Karow Anne R. , Köhler Jürgen , Gubaev Airat , Klostermeier Dagmar
Published: January 2008

RNA helicases couple the energy from ATP hydrolysis with structural changes of their RNA substrates. DEAD box helicases form the largest class of RNA helicases and share a helicase core comprising two RecA-like domains. An opening and closing of the interdomain cleft during RNA unwinding has been postulated but not shown experimentally. Single-molecule FRET experiments with the
Bacillus subtilis
DEAD box helicase YxiN carrying donor and acceptor fluorophores on different sides of the interdomain cleft reveal an open helicase conformation in the absence of nucleotides, or in the presence of ATP, or ADP, or RNA. In the presence of ADP and RNA, the open conformation is retained. By contrast, cooperative binding of ATP and RNA leads to a compact helicase structure, proving that the ATP- and ADP-bound states of RNA helicases display substantially different structures only when the RNA substrate is bound. These results establish a closure of the interdomain cleft in the helicase core at the beginning of the unwinding reaction, and suggest a conserved mechanism of energy conversion among DEAD box helicases across kingdoms.
The A2b adenosine receptor protects against vascular injury
Authors: Yang Dan , Koupenova Milka , McCrann Donald J. , Kopeikina Katherine J. , Kagan Herbert M. , Schreiber Barbara M. , Ravid Katya
Published: January 2008

The A2b adenosine receptor (A2bAR) is highly abundant in bone marrow macrophages and vascular smooth muscle cells (VSMC). To examine the functional significance of this receptor expression, we applied a femoral artery injury model to A2bAR knockout (KO) mice and showed that the A2bAR prevents vascular lesion formation in an injury model that resembles human restenosis after angioplasty. While considering related mechanisms, we noted higher levels of TNF-α, an up-regulator of CXCR4, and of VSMC proliferation in the injured KO mice. In accordance, CXCR4, which is known to attract progenitor cells during tissue regeneration, is up-regulated in lesions of the KO mice. In addition, aortic smooth muscle cells derived from A2bAR KO mice display greater proliferation in comparison with controls. Bone marrow transplantation experiments indicated that the majority of the signal for lesion formation in the null mice originates from bone marrow cells. Thus, this study highlights the significance of the A2bAR in regulating CXCR4 expression
in vivo
and in protecting against vascular lesion formation.
Specific expression of long noncoding RNAs in the mouse brain
Authors: Mercer Tim R. , Dinger Marcel E. , Sunkin Susan M. , Mehler Mark F. , Mattick John S.
Published: January 2008

A major proportion of the mammalian transcriptome comprises long RNAs that have little or no protein-coding capacity (ncRNAs). Only a handful of such transcripts have been examined in detail, and it is unknown whether this class of transcript is generally functional or merely artifact. Using
in situ
hybridization data from the Allen Brain Atlas, we identified 849 ncRNAs (of 1,328 examined) that are expressed in the adult mouse brain and found that the majority were associated with specific neuroanatomical regions, cell types, or subcellular compartments. Examination of their genomic context revealed that the ncRNAs were expressed from diverse places including intergenic, intronic, and imprinted loci and that many overlap with, or are transcribed antisense to, protein-coding genes of neurological importance. Comparisons between the expression profiles of ncRNAs and their associated protein-coding genes revealed complex relationships that, in combination with the specific expression profiles exhibited at both regional and subcellular levels, are inconsistent with the notion that they are transcriptional noise or artifacts of chromatin remodeling. Our results show that the majority of ncRNAs are expressed in the brain and provide strong evidence that the majority of processed transcripts with no protein-coding capacity function intrinsically as RNAs.