bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiferroic magnetic recording read head technology for 1Tbit∕in.2 and beyond
Authors: Vopsaroiu Marian , Blackburn John , Muniz-Piniella A. , Cain Markys G.
Published: January 2008

Multiferroic (MF) materials are very promising candidates for new technologies and applications because they exhibit simultaneously multiple cooperative phenomena (i.e., magnetic, electric, and piezoeffects). The main feature of MF materials is the magnetoelectric (ME) effect, which can be used to engineer highly sensitive magnetic/electric sensors. In this paper, we discuss the requirements of a new kind of magnetic recording read head for 1Tbit∕in.2 recording densities, which is based on a MF structure. The MF sensor operates at room temperature via the strain mediated ME effect by producing a voltage signal in response to the magnetic field excitation from the recorded bits. We calculated the theoretical output from such a recording read head assuming a magnetic recording density of 1Tbit∕in.2. Our calculations demonstrate that the proposed read head technology could replace in the future the conventional magnetoresistive read heads bringing also a number of considerable advantages, as detailed in the paper.
Spin-dependent transport in quantum dots mediated by Mn2+ ions
Authors: Morais P. C. , Qu Fanyao , Neto O. O. Diniz. , Dantas N. O.
Published: January 2008

A quantum theory of single electron tunneling through single Mn2+ ion-doped II-VI quantum dot weakly coupled to ferromagnetic leads in Coulomb blockade regime is presented. It is found that spin injection from the ferromagnetic leads induces a finite magnetization of the quantum dot. Electron-Mn2+ ion exchange interaction dramatically enhances spin polarization of the current and tunneling magnetoresistance. It yields highly polarized current even when the ferromagnetic source is not completely polarized.
Order/disorder phase composite Fe–Pt exchange-spring thick film magnets
Authors: Nakano M. , Kuroda H. , Koga J. , Yanai T. , Tanaka Y. , Fukunaga H.
Published: January 2008

Fe–Pt exchange-spring film magnets composed of both order and disorder phases were fabricated by the sputtering method followed by an annealing process, and an increase in thickness was achieved up to 7μm. The remanence value for the films with the thickness ranging from 1.7to7μm showed approximately 0.9T which exceeded a theoretical value of 0.7T for an isotropic Fe–Pt film composed of only order phase. For example, the values of remanence, coercivity, and (BH)max for a 7-μm-thick film were 0.87T, 490kA∕m, and 118kJ∕m3, respectively. The film also had a superior recoil rate compared to that of a Fe–Pt film composed of only order phase. These results indicate that we can obtain Fe–Pt exchange-spring thick films with good magnetic properties and a recoil rate.
Exchange bias and the origin of room-temperature ferromagnetism in Fe-doped NiO bulk samples
Authors: He J. H. , Yuan S. L. , Yin Y. S. , Tian Z. M. , Li P. , Wang Y. Q. , Liu K. L. , Wang C. H.
Published: January 2008

A series of Ni(1−x)FexO (x=0, 0.015, 0.03, 0.05, and 0.1) bulk samples was synthesized by the chemical concentration-precipitation method. Phase composition analysis was carried out, which showed that trace amounts of ferromagnetic phase NiFe2O4 could not be detected by x-ray diffraction in these bulk samples with x≤0.03. When x>0.03, NiFe2O4 ferrite is detected easily. The magnetic properties of all the bulk samples were investigated by measuring their magnetization as a function of temperature and magnetic field. The results indicated that all the bulk samples sintered in air exhibited large room-temperature ferromagnetic behavior ascribed to a ferromagnetic impurity phase. Simultaneously, an exchange bias and training effect were also observed in all the bulk samples, suggesting the possibility of the existence of a strong ferromagnetic/antiferromagnetic exchange coupling in this kind of compound. Specifically, the exchange bias field could be tuned by changing the concentration of the Fe dopant.
Ab initio molecular dynamics simulations for thermal equation of state of B2-type NaCl
Authors: Ono Shigeaki , Brodholt John P. , Alfè Dario , Alfredsson Maria , Price G. David
Published: January 2008

The pressure as a function of volume and temperature has been investigated for B2-type NaCl over the pressure range of 20–360GPa and at temperatures between 300 and 3000K. The simulations were performed using ab initio molecular dynamics method within the density-functional theory framework. A Vinet equation of state fitted to the 300K data yielded a bulk modulus of BTa=128.66GPa and a pressure derivative of BTa′=4.374 at standard state pressure of 30GPa. The thermal pressure contribution was determined to be of the form ΔPth=[αBT(Va)+(∂BT∕∂T)Vln(Va∕V)]ΔT. When αBT(Va) is assumed to be constant, the fit to the data yielded αBT(Va)=0.0033GPa∕K at standard volume, corresponding to the pressure of 30GPa. In contrast, the volume dependence of the thermal pressure was very small, and fitting yielded (∂BT∕∂T)V=0.00087.
Measurement of d15 in Fe100−xGax (x=12.5,15,18.4,22), Fe50Co50, and Fe81Al19 highly textured polycrystalline rods
Authors: Restorff J. B. , Wun–Fogle M. , Clark A. E.
Published: January 2008

We report the first measurements of d15, which relate torsion to an applied field, in the high magnetostriction Galfenol alloys Fe100−xGax (x=12.5,15,18.4,22), Fe50Co50, and Fe81Al19. Measurements were performed on highly textured polycrystalline 6.4×50.8mm2 rods by simultaneously applying a longitudinal magnetic field H∥ (−1200<H∥<1200Oe) along the rod axis and a circumferential magnetic field H⊥ generated by a current i (−60<i<+60A) through the sample. We obtained d15 from the twist ξ using du Trémolet de Lacheisserie’s [Magnetostriction (CRC, Boca Raton, 1993), 212] results for H⊥⪡H∥, modified for our nearly cubic samples: d15=2ξ∕j, where j is the current density in the sample. In the Fe100−xGax system, d15 (in nm/A) were 4.5±1, x=12.5 (sample 1); 7±2, x=12.5 (sample 2); 2.8±0.5, x=15; 16±3, x=22 (stress annealed); and 11.4±0.4, x=22. The Fe81.6Ga18.4 measurements did not yield a value. For Fe50Co50, d15=29±4 and for Fe81Al19, d15=8±1. Estimated values of λ111 were obtained by fitting ξ to 1∕H∥ and are compared to those obtained from single crystal measurements.
Patterned epitaxial vapor-liquid-solid growth of silicon nanowires on Si(111) using silane
Authors: Schmid H. , Björk M. T. , Knoch J. , Riel H. , Riess W. , Rice P. , Topuria T.
Published: January 2008

We have carried out a detailed study on the vapour-liquid-solid growth of silicon nanowires (SiNWs) on (111)-oriented Si substrates using Au as catalytic seed material. Arrays of individual seeds were patterned by electron-beam lithography, followed by Au evaporation and lift-off. SiNWs were grown using diluted silane as precursor gas in a low-pressure chemical vapor deposition system. The silane partial pressure, substrate temperature, and seed diameter were systematically varied to obtain the growth rate of the NWs and the rate of sidewall deposition. Activation energies of 19kcal∕mol for the axial SiNW growth and 29kcal∕mol for the radial deposition on the SiNW surface are derived from the data. SiNW growth at elevated temperatures is accompanied by significant Au surface diffusion, leading to a loss of Au from the tips of the SiNWs that depends on the layout and density of the Au seeds patterned. In contrast to NWs grown from a thin-film-nucleated substrate, the deterministic patterning of identical Au seeds of varying diameters allows accurate measurements of the nucleation yield of the SiNW, which is close to 100%, and analysis of the epitaxial relationship with the substrate. In addition to the vertical and the three 70.5°-inclined ⟨111⟩ epitaxial growth directions, we observe three additional 70.5°-inclined directions, which are rotated by 60°. The 60° rotation is explained by the occurrence of stacking faults in the SiNWs. The overall yield of vertically grown ⟨111⟩ NWs depends sensitively on the partial pressure of the silane and, to a lesser extent, on the growth temperature. At 80mTorr partial pressure and 470°C, up to 60% of the SiNWs grow in the vertical ⟨111⟩ direction. In situ doping of SiNWs using arsine resulted in a significant reduction of nucleation and wire growth, whereas doping with trimethylboron and phosphine exhibited no difference in growth and epitaxy compared with undoped samples.
The balance and noise properties of directly coupled high-Tc superconducting quantum interference device gradiometers with a serial array
Authors: Yang Hong-Chang , Chen J. C. , Wu C. H. , Chen K. L. , Horng Herng-Er , Tsai Yi-Shou , Yang S. Y.
Published: January 2008

We characterize the balance and noise properties of directly coupled high-Tc superconducting quantum interference device (SQUID) gradiometers with a series array. The gradiometer consisted of symmetrical pickup loops, in which a series of SQUID was symmetrically configured and directly coupled to pickup loops. We characterize the balance resolution B from the following formula: B=Aeff,uniformfield∕Aeff,gradientfield, where Aeff,uniformfield and Aeff,gradientfield are the parasitic effective area and the effective area of the gradiometer, respectively. We obtained B=1.25×10−2 which was comparable to the typical balance resolution of ∼10−2 for a gradiometer fabricated onto the 10×10mm2 substrate. This discrepancy was probably due to the many superconducting pads inside the pickup loops which deteriorated the uniformity of applied uniform magnetic fields. The gradient field sensitivity of ∼40fT∕Hz1∕2cm at 1kHz for two-SQUID gradiometers was demonstrated in a magnetically unshielded environment, which was comparable to the best gradient sensitivity of 30fT∕Hz1∕2cm, with gradiometric flip-chip flux transformer with a length of 24mm and a base line of 10mm in shielded environment.
Performance of bulk heterojunction photovoltaic devices prepared by airbrush spray deposition
Authors: Green R. , Morfa A. , Ferguson A. J. , Kopidakis N. , Rumbles G. , Shaheen S. E.
Published: January 2008

We have used airbrush spray deposition to fabricate organic photovoltaic devices with an active layer composed of a blend of poly(3-hexylthiophene) and [6,6]-phenyl-C61 butyric acid methyl ester. Working devices were prepared in ambient conditions from a variety of common organic solvents; active layers prepared from chlorobenzene exhibit improved homogeneity, resulting in narrower distributions of the relevant device parameters. Further studies on devices prepared from chlorobenzene showed that annealing at 120°C for 10min resulted in optimum performance, and that an active layer thickness of 150nm resulted in a maximum efficiency of 2.35% under AM1.5 illumination at 1sun.
James Dewar, His Flask and Other Achievements
Authors: Soulen Robert J.
Published: January 2008

James Dewar is widely known today for his pioneering work in cryogenics. During his lifetime as well, he was amply recognized for that portion of his wide-ranging scientific work, receiving several international medals and the honor of being elevated to the British peerage as Sir James Dewar. Figure 1 is a photograph of Dewar taken in London at the height of his career, around 1900. The setting is the Royal Institution of Great Britain, where he carried out most of his cryogenics research. Dewar holds in his hands his most famous invention, the dewar flask. This double-walled container, constructed with reflective surfaces and insulated by an intervening vacuum, has been universally used to this day to store cryogenic fluids. So ubiquitous are these vessels in laboratories around the world and so frequently are they referred to by scientists in ordinary conversation that they are often simply called dewars. What is more, the general public has long made use of smaller versions of them as food and drink containers known as vacuum bottles or thermos flasks.
Power Applications of High-Temperature Superconductors
Authors: Lubkin Gloria B.
Published: January 2008

Ten years after Georg Bed-norz and Alex Müller discovered the first high-temperature superconductors, and nine years after superconductivity was found with a transition temperature higher than that of liquid nitrogen, considerable progress is being made in bulk applications of high-temperature superconductors. Electronics applications and thin-film technology are even more advanced. (See PHYSICS TODAY, March 1995, page 20.) Among the first bulk applications are: current leads, fault current limiters, and wire for power transmission cables.
Helium in Aerogel
Authors: Chan Moses , Mulders Norbert , Reppy John
Published: January 2008

An important theme that threads through many areas of current interest in condensed matter physics is the effect of randomness and disorder. Prior to the 1960s, disorder and impurities were often viewed as unavoidable nuisances that masked the true behavior of ideal systems. We have since learned that disorder itself can bring forth fascinating and often unexpected new phenomena in condensed phases of matter. (See the December 1988 special issue of PHYSICS TODAY, dedicated to disordered solids.)
Dynamics of Cardiac Arrhythmias
Authors: Glass Leon
Published: January 2008

An elderly gentleman with heart disease was admitted to hospital for treatment of an abnormal heart rhythm called ventricular tachycardia. This potentially fatal rhythm can occur days, or even years, after a heart attack. It is associated with an abnormally rapid heartbeat that arises from tissue in the heart attack-damaged portions of the ventricles—the two main pumping chambers of the heart. (See the box on page 41.)
Work on Atom Trapping and Cooling Gets a Warm Reception in Stockholm
Authors: Levi Barbara Goss
Published: January 2008

This month, Steven Chu, Claude Cohen-Tannoudji and William Phillips will doff their laboratory clothes and don white tie and tails to receive the 1997 Nobel Prize in Physics in Stockholm. The Royal Swedish Academy of Sciences selected these three “for the development of methods to cool and trap atoms with laser light.” Thanks to these methods, neutral atoms have now been slowed to speeds below a few centimeters per second, corresponding, for helium atoms, totemperatures of a few hundred nanokelvin. To bring atoms to such a crawl, the researchers broke not one but two barriers originally thought to limit the temperatures to which atoms could be cooled.
The Foundation of the Silicon Age
Authors: Ross Ian M.
Published: January 2008

If PHYSICS TODAY had been launched just one year earlier—in 1947 rather than 1948—it might have begun life by soliciting a number of articles to commemorate the 50th anniversary of the discovery of the electron by J. J. Thomson. That 1897 event could surely have qualified as the start of the electronics discipline and the industry that followed. It was the new understanding of the properties of the electron that created the field of electronics and that, combined with our developing capability in the electrical, magnetic and mechanical arts, made possible a rich array of new products and services.
Corona: The First Reconnaissance Satellites
Authors: Wheelon Albert D.
Published: January 2008

The first artificial satellite of Earth was placed in orbit almost 40 years ago. That event, in October 1957, had great political and technological significance. Almost overnight, thoughtful people began to discuss the possible uses of Earth satellites. Two great applications of space technology have emerged since then. Communication satellites in synchronous orbit now play a prominent role in our lives. They complement terrestrial links and offer communication services not previously available. Equally profound has been the development of a worldwide navigation service based on the constellation of Global Positioning System satellites.
Auger Project Seeks to Study Highest Energy Cosmic Rays
Authors: Schwarzschild Bertram
Published: January 2008

Fifty-nine years ago, Pierre Auger discovered the extensive air showers generated by high-energy cosmic rays when he saw that two Geiger counters several hundred meters apart in the Alps were recording coincident counts. Five years from now, if the funding is forthcoming, a pair of 3000 km2 air-shower detector arrays bearing his name will begin their concerted assault on the greatest remaining mystery posed by cosmic rays. The Pierre Auger Project, a collaboration of physicists and astronomers from 40 institutions in 19 countries, plans to have one array in Utah monitoring the northern sky while an identical array in the high desert of western Argentina keeps watch over the southern sky.
Securing Information with Optical Technologies
Authors: Javidi Bahram
Published: January 2008

Data security has become part of our everyday lives. For even the most banal transactions, a secure piece of identification—a passport, password, bank card, credit card, personal identification number or driver's permit—is often required. As those proofs of identity have become increasingly necessary in our complex world, they have also increased the opportunities for deception. Each year, US business spends many billions of dollars on information fraud, including forged credit cards. Many of those losses are passed onto the consumer. Each year, tens of millions of dollars in counterfeit US notes are seized worldwide. And counterfeit manufactured goods, such as computer chips and machine tools, are arriving on our shores in greater numbers than ever.
Patent Basics for Physicists
Authors: James Richardson A. , Wood Craig A.
Published: January 2008

The careers of many physicists, particularly those engaged in applied or industrial research, depend on the cerns grow, they are increasingly being asked to help expand their employers' sources of income. In many cases, the most direct link between an organization's scientific research, development and application efforts and its financial objectives is its portfolio of patents. And so it would not be unreasonable to say that the professional success of many physicists is greatly affected by the number and quality of the patents resulting from their efforts.
Trap Holds Condensates of Two Different Spin States at Once
Authors: Levi Barbara Goss
Published: January 2008

Everyone likes a bargain, and what could be better than two for the price of one? That's what researchers in Boulder, Colorado, must have figured when they snared not just one but two spin states of the rubidium atom in an ultracold trap and simultaneously formed overlapping Bose–Einstein condensates from them. The feat—accomplished by Eric Cornell, Carl Wieman and their colleagues at JILA, the University of Colorado and the National Institute of Standards and Technology in Boulder—gives a valuable tool to those interested in atomic collisions and their dependence on spin states, as well as to those interested in further exploration of interactions between and within condensates. As William Phillips of NIST in Gaithersburg, Maryland, points out, such a double condensate, of two different internal states of the same atom, is unlike anything seen in superfluid He4, a condensed-matter Bose–Einstein condensate.
Thermoelectric Materials: New Approaches to an Old Problem
Authors: Mahan Gerald , Sales Brian , Sharp Jeff
Published: January 2008

Thermoelectrics is an old field. In 1823, Thomas Seebeck discovered that a voltage drop appears across a sample that has a temperature gradient. This phenomenon provided the basis for thermocouples used for measuring temperature and for thermoelectric power generators. In 1838, Heinrich Lenz placed a drop of water on the junction of metal wires made of bismuth and antimony. Passing an electric current through the junction in one direction caused the water to freeze, and reversing the current caused the ice to quickly melt; thus thermoelectric refrigeration was demonstrated (figure 1).
HERA Groups Find Excess Deep Inelastic e+p Scattering Events
Authors: Lubkin Gloria B.
Published: January 2008

Over the last four years, the H1 and ZEUS detector groups at DESY in Hamburg have been studying the interaction of 27.5 GeV positrons colliding with 820 GeV protons in the Hadron-Electron Ring Accelerator (HERA). The events at the highest 4-momentum transfer explore a new kinematic regime, down to 10−16 cm. As early as 1994, some deep inelastic scattering events at very high momentum transfer were seen. Late last year, rumors became rampant in labs outside DESY that the H1 and ZEUS detectors were finding leptoquarks. Both groups independently analyzed their data sample of high-energy deep inelastic scattering collected from 1994 to 1996. The events they found have the signature of deep inelastic scattering—tne positron is scattered by a quark inside the proton through a large angle, almost completely back the way it came, and the struck quark generates a high-energy jet of hadrons.
Polar Orbiter Shows Evidence of Minicomet Bombardment
Authors: Schwarzschild Bertram
Published: January 2008

This multiple-exposure ultraviolet image, taken last September by the Visible Imaging System (VIS) aboard NASA's Polar orbiter, shows a 500-km-long trail of something roughly 10 000 km above the Atlantic, coming in toward Europe and shining brightly at 130.4 nm, a prominent UV emission line of atomic oxygen. The VIS has also recorded many such trails at 308.5 nm, a characteristic wavelength of hydroxyl-radical fluorescence.
Metal–Insulator Transition Unexpectedly Appears in a Two-Dimensional Electron System
Authors: Lubkin Gloria B.
Published: January 2008

For roughly the last two decades, it has generally been believed among those interested in two-dimensional disordered electron systems that, in zero magnetic field, such systems do not undergo a metal-insulator transition at 0 K. In an influential 1979 paper, Elihu Abrahams, Philip Anderson, Donald Licciardello and T. V. Ramakrishnan, who became known as the Gang of Four, had used scaling arguments, assumed there were no electron-electron interactions and found that an electron in a two-dimensional random potential at 0 K would not diffuse. So, if the temperature were lowered toward 0 K, no transition from insulator to metal would occur in a disordered system. Even if the twodimensional electron systems were conducting at high temperatures, the disorder and the two-dimensionality would be sufficient to localize the electrons, preventing metallic behavior at T = 0.
New Light on Quantum Transport
Authors: Raizen Mark , Salomon Christophe , Niu Qian
Published: January 2008

Cosider the following Experiment: Take a carton of eggs, open the lid and accelerate the carton with a sudden jerk. If you try this at home, you will find that the outcome strongly depends on the magnitude of the acceleration (the authors are not responsible for the results).
Accelerator Magnet with Brittle Superconductor Sets a Record
Authors: Schwarzschild Bertram
Published: January 2008

At the Lawrence Berkeley National Laboratory, Ron Scanlan and colleagues are investigating the use of brittle superconducting cable to create accelerator bending magnets significantly stronger than those designed for the abandoned Superconducting Super Collider (SSC) and CERN's much-anticipated Large Hadron Collider (LHC). With the 1-meter-long prototype dipole magnet shown here end-on, the group recently achieved a record bending field of 13.5 tesla in the 5 cm beam aperture visible at the center.
Radio Telescope in Space Maps Quasar Jet
Authors: Day Charles
Published: January 2008

What's remarkable about this radio image of quasar 1156+295 (shown in false-color form) is how it was obtained—using a radio telescope in space.
Reading and Writing with Electron Beams
Authors: Murray Gibson J.
Published: January 2008

Cathode rays, accelerated by tens of thousands of volts or more, have had immense scientific and technological value in the hundred years since Joseph John Thomson used them to discover the electron. The most familiar use of these electron beams is in cathode-ray tubes—as used in television sets and computer displays, for example. Electron microscopy, a less familiar use, has been a keystone method for visualizing the structure of materials on the atomic level, and continues to offer exciting developments. Electron beams have also found an important role in patterning semiconductor chips, and they may even supplant optical beams as a basis for lithography in the 21st century. Before the discovery of electrons, photons dominated microscopy. Now it seems that in both microscopy and lithography, electrons will take over. More power to rest mass! In this article, I give a glimpse of the state of the art in electron microscopy and lithography, and point out where I believe these fields are going.
Amorphous Semiconductors Usher in Digital X-Ray Imaging
Authors: Rowlands John , Kasap Safa
Published: January 2008

Unlike other major medical imaging methods, such as computed tomography, ultrasound, nuclear medicine and magnetic resonance imaging—all of which are digital—conventional x-ray imaging remains a largely analog technology. Making the transition from analog to digital could bring several advantages to x-ray imaging: Contrast and other aspects of image quality could be improved by means of image processing; radiological images could be compared more easily with those obtained from other imaging modalities; the electronic distribution of images within hospitals would make remote access and archiving possible; highly qualified personnel could service remote or poorly populated regions from a central facility by means of “teleradiology”; and radiologists could use computers more effectively to help with diagnosis—work that has already been initiated at the University of Chicago by Kunio Doi and his coworkers.
The World Wide Web and High-Energy Physics
Authors: White Bebo
Published: January 2008

In his 1998 State of the Union address. President Bill Clinton told Congress: We should enable all the world's people to explore the far reaches of cyberspace. Think of this: The first time I made a State of the Union speech to you, only a handful of physicists used the World Wide Web—literally, just a handful of people. Now, in schools, in libraries, homes and businesses, millions and millions of Americans surf the Net every day.
Springtime Arctic Ozone Levels Fall Further in 1997
Authors: Collins Graham P.
Published: January 2008

Since the mid-1970s, an “ozone hole” has developed in the stratosphere over Antarctica each austral summer. The Arctic, by contrast, has been immune to such severe depletion because it is much less susceptible to developing a strong vortex, a pattern of winds that encircles the pole, isolating a continent-sized body of air in which all the conditions for ozone depletion can be established. In March 1997, however, the Arctic stratosphere behaved more like its southern counterpart than had ever been observed before, and Arctic ozone levels hit record lows for March. (See the figures on page 19.) The observations were reported in eight papers in the 15 November 1997 issue of Geophysical Research Letters.
Quantum Theory without Observers—Part One
Authors: Goldstein Sheldon
Published: January 2008

Since its inception some 70 years ago and despite its extraordinary predictive successes, quantum mechanics has been plagued by conceptual difficulties. Plainly put, the basic problem is this: It is not at all clear what quantum mechanics is about. What, in fact, does quantum mechanics describe?
Gamma-Ray Colliders and Muon Colliders
Authors: Sessler Andrew M.
Published: January 2008

The physics of beams is a discipline that has developed over the last 70 years, concerning itself with the manipulation and acceleration of beams of particles and light. Starting with electrostatic accelerators and advancing through cyclotrons and synchrotrons, this science has become ever more sophisticated. Nuclear physics exploits it nowadays in devices such as the continuous-beam superconducting electron accelerator at the Thomas Jefferson National Laboratory in Virginia, the ASTRID cooler ring at Aarhus University in Denmark and the Relativistic Heavy Ion Collider nearing completion at Brookhaven National Laboratory. The modern physics of beams has also made possible the dozens of synchrotron light sources that are currently making significant contributions to physics, chemistry and biology in many countries.
Gamma Rays Create Matter Just by Plowing into Laser Light
Authors: Schwarzschild Bertram
Published: January 2008

When a beam of 50-GeV electrons collides head on with a terawatt laser pulse focused down to a few microns, extraordinary things can happen: Almost every electron plowing through the very dense laser field at the focus kicks a low-energy photon up to multi-GeV gamma-ray energy, and lots of these “Compton-backscattered” gammas then create electron-positron pairs when they subsequently collide with laser photons coming toward them.
Ribosomal Robotics Approaches Critical Experiments; Government Agencies Watch with Mixed Interest
Authors: Watrous Jack
Published: January 2008

Despite government warnings to the contrary, and a Federal judge's finding that his research may violate the terms of his recent parole, Stephan Tiding has returned to his research at the Mesoscale Physics Institute. Imprisoned nearly ten years ago for violations of the critical self-organizational clause of the Cybernetics Restriction Treaty of 2022 (CRT-22), Tiding has returned with an obvious vengeance not only to his research, but also to his criticisms of government intervention in cybernetics research.
Experimental Evidence for More Dimensions Reported
Authors: Kane Gordon L.
Published: January 2008

The worldview of physicists working on unification theories has been changing rapidly recently. That change culminated in March, at the 46th annual Recontres de Moriond conference in Les Arcs. France, with the announcement of some startling data from CERN's Large Hadron Collider (LHC).
The Magic of Helium-3 in Two, or Nearly Two, Dimensions
Authors: Hallock Robert B.
Published: January 2008

Imagine a cork floating on a pond. the cork floats thanks to the buoyancy provided by the displaced water. With the upward buoyant force precisely equal to the weight of the cork, the balance is perfect.
Polymer Rheology
Authors: De Kee Daniel , Wissbrun Kurt F.
Published: January 2008

Polymers, foods, cosmetics, paints, Pharmaceuticals—these are just a few of the many industries in which rheoloev research finds application. Rheology addresses the relationship between the stress on materials and the resulting deformation, and is therefore a part of continuum mechanics. Two laws dating back to the 17th century are very important in rheology. Hooke's law describes the behavior of an elastic solid, relating the stress to the deformation via a constant elastic modulus. And Newton's law describes the behavior of a linear viscous fluid, relating the shear stress to the rate of deformation via a constant viscosity coefficient. The aim of rheology today is to describe the more complex behavior of most real materials when they are examined over a wide range of stresses and deformations.
The Physics of Ferroelectric Memories
Authors: Auciello Orlando , Scott James F. , Ramesh Ramamoorthy
Published: January 2008

Imagine you are in the last stages of typing your thesis, the year is 1980, and it's a hot, hazy summer afternoon, a thunderstorm brews on the horizon. Tense and tired, you have forgotten to save the document on your hard disk. Suddenly, lightning strikes! Your computer shuts down. Your final chapter is lost.
Trends in Electromechanical Transduction
Authors: Busch-Vishniac Ilene J.
Published: January 2008

In today's world, it is nearly impossible to avoid contact with electromechanical sensors and actuators over the course of the day, although we rarely recognize them. They drive the keyless entry systems, the light switches that respond to sound or motion, the detectors in cars that determine whether seat belts are fastened and the sound-receiving and sound-generating parts of the telephone, to name just a few examples.
The Revealing Role of Pressure in the Condensed Matter Sciences
Authors: Hemley Russell J. , Ashcroft Neil W.
Published: January 2008

Matter in bulk has both a microscopic and macroscopic description, with the latter going back to the very earliest days of thermodynamics. Of the common thermodynamic variables pressure (p) and temperature (T), it is temperature that has played by far the most prominent role in probing condensed matter and in our fundamental understanding of it. However, even as far back as 1660, Robert Boyle declared in his famous treatise commonly known as Touching the Spring of the Air that “perhaps the pressure of the air might have an interest in more phenomena than men have hitherto thought.” More than three centuries later, we can see how right he was, as systematic use of pressure has led to considerable insight into the properties of matter, especially its electronic properties. As A. Jayaraman noted when he was at AT&T Bell Laboratories, of all physical variables, pressure possesses one of the greatest ranges—over 60 orders of magnitude. At the high end, the pressures are those of the interiors of neutron stars; at the other, they gauge the conditions of the remotest vacua of outer space. And as Claude Berthelot demonstrated in early experiments on simple fluids, the pressure is not even obliged to be positive. (Negative pressure is created by, for example, pulling on the surface of a solid or on a wall of a sealed vessel full of fluid.)
Giant Air Shower Array Shows Cosmic-Ray Spectrum Violating Greisen Cutoff
Authors: Schwarzschild Bertram
Published: January 2008

For almost nine years, the Akeno Giant Air Shower Array in Japan has been accumulating data on the most energetic cosmic rays. AGASA, with its 111 scintillation detectors deployed over 100 km2, is by far the world's largest air shower array. (See PHYSICS TODAY, January 1998, page 31.) This collaboration of 14 Japanese institutions is led by Masahiro Teshima (University of Tokyo). The recent publication of its observations through October 1997 appears to confirm a provocative astrophysical paradox: How can it be that the cosmic-ray energy spectrum is extending beyond 1020electron volts without any clear sign of a cutoff?
Long-Pulse 60-Tesla Magnet Starts Routine Operation at Los Alamos
Authors: Lubkin Gloria B.
Published: January 2008

For experiments in very high magnetic fields, there are DC electromagnets that have operated continuously at fields as high as about 35 tesla and the National High Magnetic Field Laboratory (NHMFL) expects to generate fields close to 45 T early next year. Some high-field DC magnets are purely resistive, others are hybrids that also contain a superconducting magnet. For higher fields, pulsed technology has been employed. The highest magnetic fields for experiments are produced in self-destructing magnets, in which the pulse lasts a few microseconds before the magnet destroys itself.
The Global Electric Circuit
Authors: Bering III Edgar A. , Few Arthur A. , Benbrook James R.
Published: January 2008

On a clear day, there is a downward electric field of 100 to 300 volts/meter at Earth's surface, although this field is not noticeable in daily life. That is, one does not encounter a 1 kV potential difference when getting into a car on an upper floor in a parking garage, and electrocution is not the major hazard associated with jumping out of trees. The major reason why we don't notice the fair-weather field is that virtually everything is a good conductor compared to air. Objects such as tree trunks and our bodies are excellent ionic conductors that short out the field and keep us from noticing it. But the field is there.
Small-World Networks Can Provide a New Tool to Study Diverse Systems
Authors: Lubkin Gloria B.
Published: January 2008

The concept of six degrees of separation, as studied over three decades ago by the social psychologist Stanley Milgram, grew from an experiment in which two target persons were identified in the Boston area, and then individuals in Kansas and Nebraska were each sent a letter describing some parameters of the two targets. Each individual was given a folder with the rule for reaching the target: If the individual didn't know the target, he was asked to send the folder to a friend he knew on a first-name basis who was likely to know the target person. Mil-gram's surprising result was that the number of links needed to reach the target person had a median value of six. This concept is also known as the small-world phenomenon.
A Different Approach to Cosmology
Authors: Burbidge Geoffrey , Hoyle Fred , Narlikar Jayant V.
Published: January 2008

Modern cosmology began with the solutions to Einstein's theory of gravity discovered by Aleksandr Friedmann and Georges Lemaitre in the 1920s. When combined with the Hubble redshift-distance relation, these solutions could be interpreted as showing that we live in an expanding universe. By 1930, the scientific establishment and much of the lay public believed in this expanding cosmos. It then requires only time reversal and elementary logic to conclude that the universe must originally have been so compact that we can talk of a beginning. Lemaitre tried to describe this state as the “primeval atom.”
Correlated-Photon Metrology Without Absolute Standards
Authors: Migdall Alan
Published: January 2008

Just like human twins who evoke amazement and a ense of mystery by reporting empathetic experiences across great distances, photons born in pairs also astonish us by their quantum-correlated behavior.
Archaeology of a Bookstack: Some Major Introductory Physics Texts of the Last 150 Years
Authors: Holbrow Charles H.
Published: January 2008

Beyond its teaching purpose, a textbook of introductory physics is also a historical document. It contains the physics and the pedagogy of its authors and their times, and reflects the era in which it was written. This article—paralleling an exhibit prepared by the American Physical Society's forum on education for display at the APS centennial celebration in Atlanta this month—examines historical aspects of introductory physics texts. It begins with a 19th-century text, Ganot's Physics, and then works up to the present, examining various editions of popular introductory college-level texts by Millikan, Franklin, Duff, Sears and Zemansky, and Halliday and Resnick (figure 1). It is interesting to see what has changed in the teaching of introductory physics over the last 150 years and what has remained the same.
Reply to “A Different Approach to Cosmology”
Authors: Albrecht Andreas
Published: January 2008

As physicists confront the unknown, a crucial part of the job is choosing a set of assumptions that will guide their efforts in productive directions. The only certainty is that only a small fraction of the many conceivable outcomes of the inquiry process will remain viable as the field continues to progress—assuming it does indeed progress. Along the way, choices must be made: Which results should be taken as important hints to be used as the foundations of future work, and which results should be viewed with skepticism, needing further confirmation before being allowed to influence the field significantly? Those who wind up making good choices (either through wisdom or good luck) will eventually be recognized as pioneers.
Plutonium May Be Hitching a Ride on Colloids
Authors: Levi Barbara Goss
Published: January 2008

If nuclear waste leaks out of its underground containers, how far is it likely to migrate? That's a critical question to answer, with hundreds of thousands of cubic meters of waste from nuclear power and nuclear weapons operations now awaiting permanent burial. It has long been thought that at least one of the more toxic contaminants—plutonium—would stay put. Because of its low solubility in water and its tenacious capacity to cling to mineral surfaces, some argued, plutonium would remain adsorbed on local rocks. That viewpoint has been challenged in the last 15 years by suggestions that plutonium can adhere to submicrometer-sized colloids and thereby be transported considerable distances by groundwater. This suggestion, however, has not been strongly supported by field studies. A recent study by researchers from Lawrence Livermore National Laboratory and Los Alamos National Laboratory now provides the firmest evidence to date that, at least in one case, the plutonium has migrated 1.3 km from its source in 30 years—a speed that is consistent with the flow: of groundwater in the area.
Battling Decoherence: The Fault-Tolerant Quantum Computer
Authors: Preskill John
Published: January 2008

Information carried by a quantum system has notoriously weird properties. Physicists and engineers are now learning how to put that weirdness to work. Quantum computers, which manipulate quantum states rather than classical bits, may someday be able to perform tasks that would be inconceivable with conventional digital technology. (See the article by Charles H. Bennett, PHYSICS Today, October 1995, page 24, and the “Search and Discovery” report in PHYSICS Today, March 1996, page 21.)b
Electron Spin and Optical Coherence in Semiconductors
Authors: Awschalom David D. , Kikkawa James M.
Published: January 2008

Semiconductors are ubiquitous in device electronics because their charge distributions are easily shaped and controlled to make logic gates. Since gate switching and intercommunication rates limit device speed, efforts to improve computational power have led the semiconductor industry to push devices to ever-shrinking sizes. Yet, as advances in this area have improved the function of today's chip architectures, miniaturization may soon bring additional complications in the form of quantum mechanical effects. Because quantum systems tend to behave statistically, these effects will introduce unpredictable fluctuations in essential; design parameters, such as charge distribution, that will affect performance as device sizes shrink.
Revisiting the Black Hole
Authors: Blandford Roger , Gehrels Neil
Published: January 2008

Twenty-eight years ago, in a celebrated article in PHYSICS TODAY entitled “Introducing the Black Hole,” Remo Ruffini and John Wheeler filed a dispatch from the campaign to understand gravity. With hindsight, we now see that they wrote in the middle of a golden age—spanning the mid-1960s and the late 1970s—when remarkable discoveries in the theory of general relativity were made to confront equally stunning developments in observational astronomy.
Special Issue: Everyday Physics
Authors: Benka Stephen G. , Day Charles
Published: January 2008

We've all been there. Too often, what happens next is an awkward silence. As scientists, we should all be concerned about how the general public perceives us and our profession. Most people are not scientists and really don't understand how science is done. To the laity, modern physics in particular seems remote. Huge particle accelerators lie in underground tunnels; nuclear-powered space probes speed toward their planetary destinations; individual atoms are prodded and probed; the bizarreness of quantum mechanics is confirmed in the lab. But the laws of physics apply to matter and energy everywhere—in our living rooms, gardens, and motor vehicles, as well as on the surface of a neutron star. To imbue our nonphysicist friends, families, and neighbors with the excitement and importance of our field, we should perhaps engage them first where the physical world is most immediate—in their everyday lives.
Progress Made in Near-Field Imaging with Light from a Sharp Tip
Authors: Levi Barbara Goss
Published: January 2008

R esearchers are striving to image objects optically at smaller and smaller scales. For example, they'd like to determine the chemical identity of individual molecules and examine the optical properties of semiconductor nanostructures. The required resolution is finer than that allowed by diffraction, which sets a lower limit of half the wavelength of light (hundreds of nanometers for visible light). But much higher resolution can be achieved by viewing objects at distances closer than the wavelength of light. Such near-field imaging has been hotly pursued since the early 1990s, when researchers demonstrated its promise for imaging single molecules (see PHYSICS Today. May 1994, page 17 and November 1997, page 67). As Dieter Pohl (University of Basel) puts it, “Imagine the potential of microscopy that combines the resolving power of an electron microscope with the enormous spectral resolving power of light.”
Lecture in Lyons: Science and Freedom
Authors: Sakharov Andrei , Bonner Elena , Yankelevich Matvei E.
Published: January 2008

Upon receiving an honorary degree from Claude Bernard University, Andrei Sakharov delivered the following Lyons lecture at a joint session of the university and the Société Française de Physique on 27 September 1989.
Berkeley Lab Leapfrogs to Elements 116 and 118
Authors: Levi Barbara Goss
Published: January 2008

If nuclear physicists were surprised last January by a reported sighting of element 114, they were utterly floored by a recent report of elements 116 and 118. No one had thought that these two were worth looking for with today's accelerators. No one, that is, except theorist Robert Smolańczuk of Warsaw's Andrej Soltan Institute for Nuclear Studies, who had calculated that certain reactions can generate isotopes of elements 116 through 119 with cross sections orders of magnitude greater than expected. Researchers at Lawrence Berkeley National Laboratory, where Smolańczuk is currently a Fulbright scholar, took a chance that he was right and set up the prescribed experiment for producing the new element 118293 (and its daughter 116289). They found three candidates in 11 days.
Space Telescope Key Project Completes Task of Measuring the Hubble Constant Within 10%
Authors: Schwarzschild Bertram
Published: January 2008

Five years before the Hubble Space Telescope was launched in 1990, NASA designated a “Key Project” for the orbiting telescope. The project's goal was to pin down the Hubble constant H0 to within 10% At the time, H0, a fundamental cosmological parameter that measures the universe's present rate of expansion, was uncertain to within a factor of two. Estimates ranged from 50 to 100 km/s per megaparsec. (Hubble's law of universal expansion asserts that, at cosmological distances, recessional velocity is proportional to distance; 1 Mpc is about 3 million light-years.)
Single Microwave Photons Can Be Measured Nondestructively
Authors: Fitzgerald Richard
Published: January 2008

A deeply held tenet of quantum mechanics, dating back to its infancy, is that one can't measure a system without disturbing it. That doesn't mean, however, that one can't influence the form such a disturbance takes. Over the past 25 years, researchers have been developing schemes for controlling the effects of measurements so that the properties of interest emerge unscathed. Now a group led by Serge Haroche at the Ecole Normale Supérieure (ENS) in Paris has demonstrated such techniques at the most fundamental level—detecting the presence of a single photon in a nondestructive way.
Jordan, Pauli, Politics, Brecht, and a Variable Gravitational Constant
Authors: Schucking Engelbert L.
Published: January 2008

November 1952: “Eisenhower Elected President” proclaimed the headline in Die Welt. Why did they do that, those crazy Americans? This will mean the Dulles brothers in power and Adenauer's rearmament of Germany. But I put politics out of my mind and rang the doorbell of the apartment on Hamburg's Bundesstrasse. A maid with a little white cap opened the door.