bluuebunny/crossref_metadata_2025 huggingface dataset:
A Precision Radiation Integrator
Authors: Müller Ralph H. , Shriver G. Edward
Published: February 2005

The condenser-photoelectric cell method of radiation integration has been investigated in detail and refined to the extent of yielding an instrument capable of precise integration over long periods of operation. A vacuum photoelectric cell charges an air-condenser placed in the input circuit of an FP-54 tube. The output of the latter operates two '58 tubes in parallel which actuate two relays, one operating a cyclometer counter, the other discharging the condenser. Automatic compensation is provided throughout to maintain stability. Suitable tests are reported indicating the sensitivity, reproducibility and overall reliability of the instrument. Over long periods the integration is reliable to 3 parts in 1000 and for a single photometric measurement to 1 part in 1000.
Construction and Test of an Alternating-Current Bolometer
Authors: Moon Parry , Mills W. R.
Published: February 2005

The purpose of the paper is to describe the construction and test of an alternating-current bolometer which was recently built at the Massachusetts Institute of Technology. Previous theoretical work had indicated that such an instrument would be of value in the measurement of radiation and would possess certain advantages over previous devices used for that purpose. Tests substantiate the predictions of the theory. The a.c. bolometer is found to be rugged, easily operated, not susceptible to vibration and unaffected by spurious thermal e.m.f.'s. The sensitivity obtained with an experimental cell using 0.0016-inch tungsten wire was 0.068 volt per watt/cm2 which was in good agreement with theory. There seems to be no reason why cells made with smaller wires should not give sensitivities of five or ten times this value. Experimental results are also given for bolometer response as a function of current and of time.
A New Apparatus for Studying the Elastic Properties of Filamentous Materials
Authors: Saxl Irving J.
Published: February 2005

A new apparatus is described with which it is possible to make load-extension diagrams for various filamentous materials. The principle of chainomatic weight application is used for the gradual application of reasonably heavy loads. An analogous construction can be used in a great many more instances where mercury or shot loading is used at the present. Load-extension diagrams have been taken with this instrument and the relations investigated with reference to the formation of hysteresis loops at various points of stress application and load removal. These hysteresis loops and stress-strain diagrams are characteristic for specific materials and are of assistance in their identification by physical methods. In addition to being of value from a physical and analytical viewpoint the investigation of the loading and deloading characteristics offers means of investigating the change of the physical characteristics of filamentous materials under conditions of controlled strain.
A Triple-Quartz-Plate Supersonic Generating and Receiving System
Authors: Yeagley Henry L.
Published: February 2005

This treatise is an exposition of the measurement of high frequency sound by means of an originally designed and constructed apparatus, together with results obtained and the interpretation thereof. The apparatus consists of a high precision, supersonic, sending and receiving system of a triple-quartz-plate type. Two of the piezo-quartz plates used act as supersonic transducers to transform electromagnetic energy into gas pressure waves and to retransform them. The third plate, of the same frequency, controls the oscillations of an external vacuum tube circuit, the output of which drives and controls the frequency of the first transducer plate in the gas chamber, within extremely narrow limits. An original interference method is used to eliminate troublesome standing waves along the supersonic path. The signal, amplified for observation, is the vector sum of the electromagnetic wave impressed on the receiver by the retransformed energy and a controlled direct pick-up through the capacity coupling of the high voltage leads to the gas chamber. The amplifier consists of two stages of radiofrequency amplification and a peak tube voltmeter. By this means absorption constant values are obtained to three significant figures. Velocity measurements may be made to include four significant figures.
The Measurement of Radium Emanation Implants
Authors: Macdonald P. A. , Campbell E. M.
Published: February 2005

A rapid method of measuring sources of ionization is described. The ionizing agent is moved relative to the ionization chamber and the change in the ionization current is treated as if it were half a wave of an alternating current. This wave is amplified by means of an a.c. thermionic amplifier. The sensitivity of the apparatus is of the order of 10−12 amp./mm and it is capable of measuring radon implants at the rate of three a minute.
A Method for Casting Molybdenum Buttons in Brass, for Water-Cooled Targets in X-Ray Tubes
Authors: Trimble F. H.
Published: February 2005

An electric arc furnace, for casting molybdenum buttons in brass, is described, which can be assembled from apparatus available in any laboratory. A water-cooled target, prepared by this method, has been used successfully by the writer in a demountable x-ray tube.
The Accurate Measurement of the Breakdown and Current Voltage Characteristics of Liquid Dielectrics with Direct Potentials
Authors: Baker Edward B. , Boltz Howard A.
Published: February 2005

An arrangement is described which permits unusually accurate measurement of high voltage current characteristics and breakdown potentials of liquid dielectrics with direct current. Currents from 10−16 ampere to 10−3 ampere may be measured up to 40 kv. Protective devices are incorporated which prevent damage to the sample measured and to the instruments when breakdown occurs.
Electromagnetic Control of High Rotational Speed
Authors: Davis Thomas
Published: February 2005

An apparatus is described in which the principle of the synchronous motor was used to maintain constant speed of the air-driven rotors described by Beams and Pickels. The regulation was secured both with and without the use of an external driving circuit. The rotors have been driven in synchronism with an oscillator when the driving air jets were completely turned off.
Demodulation of Radio Broadcast Signals for Use as Sources of Electric Currents of High and Constant Frequency
Authors: Hector L. G. , Schultz H. L.
Published: February 2005

Many radio broadcasting transmitters are equipped with modern temperature controlled crystal controlled oscillators so that these sources of alternating current of constant high frequency would be readily available for use in laboratory measurements were it not for the presence of modulation by program material. Two methods for removing this modulation are described. The first employs an oscillator type circuit that is actuated by the incoming radio signal. It has the virtue of simplicity but is not stable in operation. The second method employs a demodulating amplifier that delivers to a low loss tuned circuit pulses of energy that are almost independent of the modulation. This circuit is stable and does not require adjustment after once having been put in operation on a signal of given frequency. Distorted wave forms appear only when the radio broadcast signal carries modulation approaching or exceeding 100 percent.
A New Receiver of Radiant Energy
Authors: Hayes Hammond Vinton
Published: February 2005

Describes a device to be actuated by impulses of radiant energy in the form of light or heat. The impulses may succeed each other with a frequency of one or more a second. Use is made of a finely divided gas occluding substance confined in a hermetically sealed chamber, one side of which is a thin metal diaphragm forming a portion of a condenser receiver. When light or heat falls upon this substance the gas within the chamber expands and changes the capacitance of the condenser receiver. When the device receives an impulse of radiation, it shows a sensitivity of more than 50 volts per watt per cm2.
Precision Apparatus for Measuring the Velocity of Sound in Solid Rods
Authors: Swigart J. Irvin
Published: February 2005

A method is described which yields exceptionally accurate values for the velocity of sound in solids as determined by measuring simultaneously the wave-length and frequency of stationary longitudinal waves in rods. The arrangement of apparatus permits the specimen to be subjected to various physical conditions whose effects are to be studied.
Note on Disk-Type Electrostatic Generators
Authors: Dahl Odd
Published: February 2005

Measurements using a rotating multiple-disk electrostatic generator of the classical Holz type show that a machine of this kind is entirely practical for producing currents up to 10 milliamperes at voltages as high as 200 kilovolts. For higher voltages a number of such units may be used in cascade, mounted on successive insulated platforms and making provision against corona and spark-over as in standard high voltage practice.
A Rotating Drum Camera for Photographing Transient Phenomena
Authors: Lambert Ray
Published: February 2005

A rotating drum camera suitable for photographing transient voltages or currents with a cathode-ray oscillograph is described. Film speeds up to 750 inches per second have been employed. The times of exposure are controlled and related transient phenomena are synchronized by means of rotating switches.
Regulator Systems for Electromagnets
Authors: Anderson H. L. , Dunning J. R. , Mitchell D. P.
Published: February 2005

A regulator for maintaining constant, to better than 0.1 percent over long periods, the magnetic field of large (100 kw) electromagnets is described. This consists of two basic components: (1) A vacuum tube voltage regulator which compensates for rapid changes in voltage and thus anticipates the change in current which would result. (2) A current actuated element arranged so as to alter the operating point of the voltage regulator in order to compensate for slow changes in current due to changes in the temperature of the windings. Very rapid regulator action is secured with no drift or hunting to the limit specified.
A Laboratory Frequency Standard
Authors: Harnwell G. P. , Kuper J. B. H.
Published: February 2005

An inexpensive laboratory frequency standard consisting of a crystal-controlled clock and auxiliaries has been constructed and thoroughly tested. Standardized by the signals from WWV, it permits the measurement of radio and audiofrequencies to one part in 105 or better and also furnishes second ticks for laboratory timing.
A Meter for Recording Slow Liquid Flow
Authors: Ivie J. O. , Richards L. A.
Published: February 2005

A description is given of a reversible flow meter designed to work as part of a soil moisture flow gauge. The flow is measured by forming drops of water in a less dense nonmiscible liquid and electrically recording the drops. The operating characteristics are discussed and an empirical equation giving the effect of temperature and flow rate on drop size is derived.
A Voltage Stabilizer Circuit
Authors: Ashworth J. A. , Mouzon J. C.
Published: February 2005

A new voltage stabilizer circuit is described. The circuit is of the bridge type wherein an essentially constant current is maintained in the output resistor. The particular feature of the circuit is the elimination of transients in the output voltage due to changes in emission of the cathode of the type 78 stabilizer tube. A precision method for the variation and measurement of the output voltage is also described.
A Vacuum Spectrograph for X-Rays
Authors: Olson C. M. , Pierce W. C.
Published: February 2005

The essential details of a small, readily constructed, vacuum spectrograph are described. Unique features of the instrument are in the method for rocking the crystal and in the use of a mercury seal instead of a taper joint for crystal mounting. The instrument may be used with or without evacuation.
A New Recording Microphotometer
Authors: Knorr H. V. , Albers V. M.
Published: February 2005

A recording microphotometer, which gives an inked record, has been constructed. It utilizes a photoelectric cell as the light sensitive device. The recording is done with a Leeds and Northrup Speedomax recorder.
A Measurement of the Velocity of Light
Authors: Anderson Wilmer C.
Published: February 2005

A method is described for measuring the velocity of light with a relatively short base line. A Kerr cell modulates a light beam at very high frequencies and a photoelectric cell is used for detection of the modulations. The modulated light beam is divided into two portions by means of a half-silvered mirror and the two parts sent over different optical paths. By noting the difference in path length required to produce a minimum of voltage in the tuned circuit of the photoelectric cell, and the frequency of modulation of the light, it is possible to measure the velocity of light with considerable precision. Modifications of this method are described and the theory developed. The mean result of a series of measurements involving 651 observations is given as 299,764 km/sec. ±15 km/sec. in vacuum.
Time-dependent density functional theory study on intramolecular charge transfer and solvent effect of dimethylaminobenzophenone
Authors: Duan Xiao-Hui , Li Xiang-Yuan , He Rong-Xing , Cheng Xue-Mei
Published: February 2005

The lower singlet excited states for dimethylaminobenzophenone have been investigated as a function of the twisting motion with inclusion of solvent effects. Theoretical calculations have been performed using time-dependent density functional theory. The B3LYP and MPW1PW91 functionals with a 6-311+G(2d,p) basis set have been used to compute transition energies. The solvent effects have been described within the polarizable continuum model. Ground-state geometries are optimized using density functional theory with both B3LYP and MPW1PW91 functionals combined with 6-31G(d) basis sets. Vertical absorption energy calculations characterize the lower singlet excited states both in vacuum and in different kinds of solvents. A large redshift of the absorption maximum in the polar solvent suggests an intramolecular charge transfer character of the excited state. We have constructed the potential energy curves of two possible twisting motions of the excited states both in vacuum and in the polar solvent of acetonitrile: the twisting of only the dimethylamino group and the twisting of the dimethylaminophenyl group with respect to the benzoyl group. Both twisting processes predict the formation of the twisted intramolecular charge transfer state associated with the crossing of a low barrier. The presence of the polar solvent significantly changes the shape of the energy curves. Calculated emission energies for both the isolated and the solvated systems show a large Stokes shift between the absorption and fluorescence maxima. Two possible twisting motions produce similar fluorescence spectroscopic consequences. Our results including solvent effects explain the weak “dual-fluorescence” feature of dimethylaminobenzophenone, and imply that the two possible twisting motions may occur in the excited-state relaxation dynamics, but the twisting of the dimethylamino group seems to take place easier.
On the stability of glycine-water clusters with excess electron: Implications for photoelectron spectroscopy
Authors: Ahn Doo-Sik , Kang Ae-Ri , Lee Sungyul , Kim Bongsoo , Kyu Kim Sang , Neuhauser Daniel
Published: February 2005

Calculations are presented for the glycine-(H2O)n− (n=0–2) anionic clusters with excess electron, with the glycine core in the canonical or zwitterion form. A variety of conformers are predicted, and their relative energy is examined to estimate thermodynamic stability. The dynamic (proton transfer) pathways between the anionic clusters with the canonical and the zwitterion glycine core are examined. Small barrier heights for isomerization from the zwitterion glycine-(H2O)2− anion to those with canonical glycine core suggest that the former conformers may be kinetically unstable and unfavorable for detection of neutral glycine zwitterion-(H2O)n (n=1,2) clusters by photodetachment, in accordance with the photoelectron spectroscopic experiments by Bowen and co-workers [Xu et al., J. Chem. Phys. 119, 10696 (2003)]. The calculated stability of the glycine-(H2O)n− anion clusters with canonical glycine core relative to those with zwitterion core indicates that the observation of the anionic conformers with the canonical glycine core would be much more feasible, as revealed by Johnson and co-workers [Diken et al. J. Chem. Phys. 120, 9902 (2004)].
Alchemical free energy calculations and multiple conformational substates
Authors: Leitgeb Martin , Schröder Christian , Boresch Stefan
Published: February 2005

Thermodynamic integration (TI) was combined with (adaptive) umbrella sampling to improve the convergence of alchemical free energy simulations in which multiple conformational substates are present. The approach, which we refer to as non-Boltzmann TI (NBTI), was tested by computing the free energy differences between three five-atomic model systems, as well as the free energy difference of solvation between leucine and asparagine. In both cases regular TI failed to give converged results, whereas the NBTI results were free from hysteresis and had standard deviations well below ±0.7kcal∕mole. We also present theoretical considerations that make it possible to compute free energy differences between simple molecules, such as the five-atomic model systems, by numerical integration of the partition functions at the respective end points.
The interpretation of molecular magnetic hyperfine interactions
Authors: Fitzpatrick James A. J. , Manby Frederick R. , Western Colin M.
Published: February 2005

Investigations of the hyperfine structure in the excited electronic states of several free radical species have revealed shortcomings in the currently accepted values used for the theoretical interpretation of such interactions. We introduce updated reference atomic values from a combination of experimental observations and ab initio calculations. The latter are at Hartree–Fock and multireference configuration interaction levels of theory and several atomic test cases are discussed. Furthermore, ground and excited electronic state hyperfine coupling constants are calculated using both levels of theory for a range of first- and second-row diatomic hydride and nonhydride radicals. These results, together with a selection of other experimental measurements are then compared with experimental data where available, and the implications of the revised interpretation are discussed.
Effects of triplet exciton confinement induced by reduced conjugation length in polyspirobifluorene copolymers
Authors: Rothe C. , Brunner K. , Bach I. , Heun S. , Monkman A. P.
Published: February 2005

Using gated optical spectroscopy at low temperatures, a polyspirobifluorene has been compared with an alternating carbazole-spirobifluorene copolymer in which the backbone conjugation is interrupted due to meta coupling of the carbazole moieties. In the copolymer both singlet and triplet energy levels are blueshifted by 130 meV with respect to the homopolymer, resulting in an unaltered singlet-to-triplet splitting. Though the barrier for triplet exciton migration increases from 4.4 to 6.0 meV for the copolymer compared to the homopolymer, it still remained low enough to ensure efficient triplet diffusion at ambient temperature.
Distribution patterns and controllable transport of water inside and outside charged single-walled carbon nanotubes
Authors: Huang Boda , Xia Yueyuan , Zhao Mingwen , Li Feng , Liu Xiangdong , Ji Yanju , Song Chen
Published: February 2005

The density distribution patterns of water inside and outside neutral and charged single-walled carbon nanotubes (SWNTs) soaked in water have been studied using molecular dynamics simulations based on TIP3P potential and Lennard-Jones parameters of CHARMM force field, in conjunction with ab intio calculations to provide the electron density distributions of the systems. Water molecules show different electropism near positively and negatively charged SWNTs. Different density distribution patterns of water, depending on the diameter and chirality of the SWNTs, are observed inside and outside the tube wall. These special distribution patterns formed can be explained in terms of the van der Waals and electrostatic interactions between the water molecules and the carbon atoms on the hexagonal network of carbon nanotubes. The electric field produced by the highly charged SWNTs leads to high filling speed of water molecules, while it prevents them from flowing out of the nanotube. Water molecules enter the neutral SWNTs slowly and can flow out of the nanotube in a fluctuating manner. It indicates that by adjusting the electric charge on the SWNTs, one can control the adsorption and transport behavior of polar molecules in SWNTs to be used as stable storage medium with template effect or transport channels. The transport rate can be tailored by changing the charge on the SWNTs.
Characterization of the interface dipole at the paraphenylenediamine-nickel interface: A joint theoretical and experimental study
Authors: Lindell L. , de Jong M. P. , Osikowicz W. , Lazzaroni R. , Berggren M. , Salaneck W. R. , Crispin X.
Published: February 2005

In organic-based (opto)electronic devices, charge injection into conjugated materials is governed to a large extent by the metal-organic interface dipole. Controlling the injection of charges requires a better understanding of the fundamental origin of the interface dipole. In this context, photoelectron spectroscopies and density functional theory calculations are used to investigate the interaction between para-phenylenediamine (PPDA), an electron donor, and a polycrystalline nickel surface. The interface dipole formed upon chemisorption of one PPDA monolayer strongly modifies the work function of the nickel surface from 5.10 to 3.55eV. The work function decrease of 1.55eV is explained by the electron-donor character of PPDA and the modification of the electronic density at the metal surface. PPDA monolayers are composed of tilted molecules interacting via the nitrogen lone-pair and PPDA molecules chemisorbed parallel to the surface via their π-electron density. Annealing the monolayer leads to dehydrogenation of PPDA activated by the nickel surface, as found for other amines.
Scalar relativistic all-electron density functional calculations on periodic systems
Authors: Peralta Juan E. , Uddin Jamal , Scuseria Gustavo E.
Published: February 2005

Scalar relativistic effects are included in periodic boundary conditions calculations with Gaussian orbitals. This approach is based on the third-order Douglas–Kroll–Hess approximation, allowing the treatment of all electrons on an equal footing. With this methodology, we are able to perform relativistic all-electron density functional calculations using the traditional local spin-density and generalized gradient approximations (GGA), as well as meta-GGA and hybrid density functionals. We present benchmark results for the bulk metals Pd, Ag, Pt, and Au, and the large band gap semiconductors AgF and AgCl.
Threading-unthreading equilibrium in solution of molecular nanotubes and linear flexible polymer chains
Authors: Yang Yuliang , Zhang Hongdong , Qiu Feng
Published: February 2005

Using the Flory–Huggins lattice model, we investigate the threading-unthreading equilibrium in a solution of linear flexible polymer chains and molecular nanotubes formed by covalently bonding the ringlike molecules, such as cyclodextrins (CDs). It is found that the threading-unthreading equilibrium depends on the temperature and the molar concentrations of the ringlike molecules and polymer chain segments but is independent of the polymer chain length, which agrees with the experimental observations. By fitting the experimental data of α-CD and poly(ethylene glycol) (PEG), the inclusion energy between α-CD and PEG, which includes the conformation energy loss of PEG resulted from the inclusion, is calculated to be ∼−20.45kJ∕mol per PEG unit.
Effect of boron doping on the electron-field-emission properties of nanodiamond films
Authors: Lee Yen-Chih , Lin Su-Jien , Lin I-Nan , Cheng Hsiu-Fung
Published: February 2005

The electron-field-emission (EFE) behavior of the nanodiamond films was observed to be pronouncedly superior to that of the diamond films with micrometer- or submicrometer-sized grains, which is ascribed to the presence of abundant grains boundaries with sp2 bonds. Incorporation of boron species into the nanodiamond films further improves the EFE properties for the films. The best EFE properties achieved are turn-on field E0=18V∕μm with EFE capacity J=0.7mA∕cm2 at around 30V∕μm applied field. However, boron doping into the nanodiamond films does not result in consistent boron-content dependence of the EFE properties for the films as those in conventional micrometer-sized diamonds. The complication is explained by the fact that the small size of the diamond grains (∼20nm) may not be able to accommodate the boron species into the lattices to effectively act as acceptor dopants. Moreover, the formation of aggregates of the nanosized diamond grains may alter the local field enhancement factor, which further complicates the correlation of the field-emission behavior with the boron-doping concentration for the nanodiamond films.
Local reaction rates and surface diffusion on nanolithographically prepared model catalysts: Experiments and simulations
Authors: Laurin M. , Johánek V. , Grant A. W. , Kasemo B. , Libuda J. , Freund H.-J.
Published: February 2005

Combining molecular beam methods and angular resolved mass spectrometry, we have studied the angular distribution of desorbing products during CO oxidation on a planar Pd/silica supported model catalyst. The model catalyst was prepared by means of electron beam lithography, allowing individual control of particle size, position, and aspect ratio, and was characterized by atomic force microscopy and scanning electron microscopy before and after reaction. In the experiment, both oxygen and CO rich regimes were investigated using separate molecular beams for the two reactants. This allows exploration of diffusion effects of reactants on the particles and of shadowing and backscattering phenomena. A reaction-diffusion model was developed in order to extract information about local reaction rates on the surface of the catalyst nanoparticles. The model takes into account the structural parameters of the catalyst as well as the backscattering of the reactants and products from the support. It allows a quantitative description of the experimental data and provides a detailed understanding of temperature and reactant flux dependent effects. Moreover, information on the surface mobility of oxygen under steady-state reaction conditions could be obtained by comparison with the experimental results.
Dynamics of glassy and liquid m-toluidine investigated by high-resolution dielectric spectroscopy
Authors: Mandanici Andrea , Cutroni Maria , Richert Ranko
Published: February 2005

The glass-former m-toluidine displays the characteristic properties of a fragile supercooled liquid, which suggest the existence of a slow secondary relaxation process. In view of the recently realized importance of such a secondary relaxation feature, we have conducted a dielectric search for the secondary process in viscous and glassy m-toluidine. Based on high-resolution experiments on the distilled liquid, a secondary process can be identified which has the properties typical of a Johari–Goldstein β relaxation. As a result, the previous hypothesis that the methyl group might be responsible for suppressing the secondary dynamics in glassy m-toluidine no longer holds.
Specular spectroscopic ellipsometry for the critical dimension monitoring of gratings fabricated on a thick transparent plate
Authors: Antos Roman , Pistora Jaromir , Ohlidal Ivan , Postava Kamil , Mistrik Jan , Yamaguchi Tomuo , Visnovsky Stefan , Horie Masahiro
Published: February 2005

Specular-mode spectroscopic ellipsometry is applied to analyze the optical response of gratings fabricated on a thick transparent plate substrate. The principles of the optical response of the gratings are described by employing incoherent contributions due to backreflections in the finite transparent substrate medium. A special function identifies a “diminution effect” caused by deflecting the secondary contributions from the primary beam axis. Two different methods are used to measure the ellipsometric response, a liquid solution method with the backreflections eliminated and a method including the incoherent backreflections. The grating parameters deduced by fitting from the measurement using the first method are applied to simulate the ellipsometric response using the second method. The spectral dependencies yielded by both methods are compared with remarkable agreement between the simulations and the measurements, which suggests the high usability of the backreflection method in the metrological characterization of gratings made on transparent plates.
Silent Raman modes in zinc oxide and related nitrides
Authors: Manjón F. J. , Marí B. , Serrano J. , Romero A. H.
Published: February 2005

Anomalous Raman modes have been reported in several recent papers dealing with doped- and undoped-ZnO layers grown by different methods. Most of these anomalous Raman modes have been attributed to local vibrational modes of impurities or defects. However, we will show that most of the observed modes correspond to wurtzite-ZnO silent modes allowed by the breakdown of the translational crystal symmetry induced by defects and impurities.
Plasma emission induced by an Nd-YAG laser at low pressure on solid organic sample, its mechanism, and analytical application
Authors: Suliyanti Maria Margaretha , Sardy Sar , Kusnowo Anung , Hedwig Rinda , Abdulmadjid Syahrun Nur , Kurniawan Koo Hendrik , Lie Tjung Jie , Pardede Marincan , Kagawa Kiichiro , Tjia May On
Published: February 2005

An Nd-YAG laser (1064 nm, 120 mJ, 8 ns) was focused on various types of solid organic samples such as a black acrylic plate, a black polyvinyl chloride plastic sheet, and a methoxy polyaniline film coated on the surface of a glass substrate, under a surrounding air pressure of 2 Torr. A modulated plasma technique was used to study the mechanism of excitation of the emission of the organic material. As a result, we conclude that ablated atoms and molecules are excited by a shock-wave mechanism, similar to the case of hard samples such as metal. The ablation speed of hydrogen emission (H I 656.2 nm) was examined and the results show that the release speed of the ablated atoms is relatively low (less than Mach 10) and persists for a longer period of time (around 1 μs); this phenomenon can be understood by assuming that the soft target absorbs recoil energy, causing a low release speed of ablated atoms which would form the shock wave. This was overcome by placing a subtarget on the back of the soft sample so as to enhance the repelling force, thus increasing the release speed of the atoms. A possible application of the low-pressure plasma on an organic solid was demonstrated in the detection of chlorine in a black polyvinyl chloride plastic sheet.
Current bursts in lipid bilayers initiated by colloidal quantum dots
Authors: Ramachandran Sujatha , Kumar George L. , Blick Robert H. , van der Weide Daniel W.
Published: February 2005

Inorganic semiconductor nanocrystals, also called quantum dots, have recently attracted considerable interest as fluorescent labels. We report that CdSe QDs initiate current bursts in lipid bilayer membranes upon application of a bias voltage. The current bursts observed resemble those produced by the peptaibol class of antibiotics such as alamethicin and trichorzins. The current fluctuations are dependent on the bias voltage and on the concentration of the quantum dots applied to the membrane. Our data suggest that quantum dots with dipole moments similar to alamethicin are influenced by an external electric field, which creates a torque resulting in the insertion into the lipid membrane. We predict that at least three quantum dots are required to form a pore due to aggregation that leads to a macroscopic conductance.
Photoconductive switching of a high-voltage spark gap
Authors: Brussaard G. J. H. , Hendriks J.
Published: February 2005

We have demonstrated photoconductive switching of a gas-filled spark gap. A femtosecond Ti:sapphire laser was focused in a 1 mm spark gap biased at 4.5 kV. There is a clear transition between triggered operation, when only part of the path between the electrodes is ionized, and photoconductive switching, when the entire length of the gap is ionized directly by the laser. The measured standard deviation of the time fluctuations between the rising edge of the transmitted electrical pulse and the laser was less than 15 ps.
Self-assembly of aligned ZnO nanoscrews: Growth, configuration, and field emission
Authors: Liao L. , Li J. C. , Liu D. H. , Liu C. , Wang D. F. , Song W. Z. , Fu Q.
Published: February 2005

We report the syntheses of self-catalyst-grown and self-assembled ZnO nanoscrews (ZNS). The morphology and microstructures were characterized by using scanning electron microscopy, transmission electron microscopy and x-ray diffraction. The results reveal that the aligned ZNS are single crystalline grown along the c axis, with 18 sides on their tops but six sides on their stems, while the whole exhibits sixfold symmetry. The formation of such a special-shaped ZNS that may have potential applications in fabrication of nanodevices, is related to the increase of the oxygen supply during the growth followed by a rapidly cooling down process. The growth kinetics of the ZNS is discussed. The field-emission studies show a good stability of the emission current and a low turn-on electrical field.
Strongly electric-field-dependent spatial properties of fanning beam in polymeric medium
Authors: Sassa Takafumi , Muto Tsuyoshi , Wada Tatsuo , Takeda Yosuke , Fujihara Takashi , Umegaki Shinsuke
Published: February 2005

The emission angle and output profile of a fanning beam were evaluated in a high-gain polymeric medium utilizing a conventional sandwich cell structure. An abrupt change of the emission angle and a spread of the beam profile were found with an applied electric field. These beam properties were explained in terms of the electric-field-induced Pockels coefficient of the medium.
Direct observation of a photon spin-induced constant acceleration in macroscopic systems
Authors: Delannoy G. , Emile O. , Le Floch A.
Published: February 2005

The use of a spider silk allows the direct observation of the dynamics induced by the transfer of angular momentum of laser light in a Beth-type experiment. In the optical domain, a uniform angular acceleration of a macroscopic object is demonstrated in agreement with the expected equation of motion. The intrinsic angular momentum exerts a stable torque thats modulus can be continuously adjusted from 0to10−12Nm by changing the optical power. Moreover, a macroscopic no-node mirror is proposed to improve the optical angular momentum transfer in micro-manipulation in the context of optical tweezers.
Codirectional couplers in GaAs-based planar photonic crystals
Authors: Leuenberger David , Ferrini Rolando , Dunbar L. Andrea , Houdré Romuald , Kamp Martin , Forchel Alfred
Published: February 2005

Several designs for codirectional couplers in planar photonic crystals etched into GaAs-based heterostructures were investigated both theoretically and experimentally. Two different numerical techniques, i.e., plane wave expansion and finite difference time domain, were used to calculate the coupling lengths. Both methods are shown to be in good agreement with the experimental results. The measured coupling lengths are in the order of 350 periods, leading to a physical length of the order of 80μm, much smaller than what is achieved in classical integrated optics couplers.
Agrammatic but numerate
Authors: Varley Rosemary A. , Klessinger Nicolai J. C. , Romanowski Charles A. J. , Siegal Michael
Published: February 2005

A central question in cognitive neuroscience concerns the extent to which language enables other higher cognitive functions. In the case of mathematics, the resources of the language faculty, both lexical and syntactic, have been claimed to be important for exact calculation, and some functional brain imaging studies have shown that calculation is associated with activation of a network of left-hemisphere language regions, such as the angular gyrus and the banks of the intraparietal sulcus. We investigate the integrity of mathematical calculations in three men with large left-hemisphere perisylvian lesions. Despite severe grammatical impairment and some difficulty in processing phonological and orthographic number words, all basic computational procedures were intact across patients. All three patients solved mathematical problems involving recursiveness and structure-dependent operations (for example, in generating solutions to bracket equations). To our knowledge, these results demonstrate for the first time the remarkable independence of mathematical calculations from language grammar in the mature cognitive system.
Structure of a mitochondrial supercomplex formed by respiratory-chain complexes I and III
Authors: Dudkina Natalia V. , Eubel Holger , Keegstra Wilko , Boekema Egbert J. , Braun Hans-Peter
Published: February 2005

Mitochondria are central to the efficient provision of energy for eukaryotic cells. The oxidative-phosphorylation system of mitochondria consists of a series of five major membrane complexes: NADH–ubiquinone oxidoreductase (commonly known as complex I), succinate–ubiquinone oxidoreductase (complex II), ubiquinol–cytochrome
c
oxidoreductase (cytochrome bc
1
complex or complex III), cytochrome
c
–O
2
oxidoreductase (complex IV), and F
1
F
0
–ATP synthase (complex V). Several lines of evidence have recently suggested that complexes I and III–V might interact to form supercomplexes. However, because of their fragility, the structures of these supercomplexes are still unknown. A stable supercomplex consisting of complex I and dimeric complex III was purified from plant mitochondria. Structural characterization by single-particle EM indicates a specific type of interaction between monomeric complex I and dimeric complex III in a 1:1 ratio. We present a model for how complexes I and III are spatially organized within the I+III
2
supercomplex.
Designed Performance of High Resolution Chopper Spectrometer at J-PARC
Authors: Itoh S. , Ohoyama K. , Otomo T. , Nakajima K. , Kuwahara K. , Kajimoto R. , Kamiyama T. , Yamamuro O.
Published: February 2005

A designed performance of the high resolution chopper spectrometer of which construction has been proposed at J-PARC to study dynamical properties of materials showing a wide spatial and temporal correlations is summarized.
Single Crystal Neutron Diffraction Studies on Proteins
Authors: Bau Robert
Published: February 2005

This article is a short review of the results of single crystal neutron diffraction studies on proteins, and is meant to serve two purposes: firstly, as a brief update of new results which appeared since our last review in 2002, [Tsyba, I. and Bau, R. (2002) “Neutron Diffraction Studies on Proteins”, Chemtracts 15, 233] and secondly to focus on one particular area: cases in which neutron diffraction studies have helped in the understanding of the catalytic activity of enzymes.
Pulsed Neutron Diffraction of Phosphorous Acid and its Aqueous Solution with Inactivation Capability of Activated Oxygen
Authors: Iwadate Y. , Tani Y. , Fukushima K. , Misawa M. , Fukunaga T. , Itoh K. , Nakazawa T.
Published: February 2005

Pulsed neutron diffraction was carried out to analyze an intramolecular structure of D3PO3 and an orientational characteristic of adjacent molecules in D3PO3–n D2O(n = 0, 1 and 20) solutions by using the high intensity total scattering spectrometer in High Energy Accelerator Research Organization (KEK) at Tsukuba, Japan. The radial distribution method and the correlation method were employed for the analysis of structural parameters such as interatomic distances, coordination numbers and temperature factors, being consulted with those by simulations. The intramolecular structure of the phosphorous acid in the liquid state did not differ much from that in the crystalline state. In the liquid phosphorous acid, two intramolecular P–O bonds were recognized, the shorter P–O bond being assigned to the P–O double bond and the longer P–O to the single bond. On addition of heavy water, the coordination numbers of the intramolecular P–O correlations, i.e. both the shorter P–O double bond and the longer P–O single bond, increased a little.
Occurrence of violence and violence-related injuries among 12—18 year-old Finns
Authors: Mattila Ville M. , Parkkari Jari , Lintonen Tomi , Kannus Pekka , Rimpelä Arja
Published: February 2005

Aims: The aim of this study was to investigate the occurrence, nature, and severity of violence and violence-related injuries, and the occurrence of alcohol-related violence among Finnish adolescents. Methods: A 12-page questionnaire was mailed to a nationwide representative sample of 12-, 14-, 16-, and 18-year-olds (n=10,883). The response rate was 75%. Results: Of the 8,135 respondents, 7.9% (646) reported violence occurrence and 1.7% violence-related injury during the past month. The male—female ratio for violence occurrence was 1.9 (95% CI 1.6—2.2) and for violence-related injury occurrence 0.8 (95% CI 0.6—1.2). Sixteen-year-old girls reported the highest injury rate (23/1,000). Most typically, the violent persons were individuals known by the victim before the incident. Girls were significantly ( p<0.001) more often (43%) in a fight with, or assailed by, a family member than boys (8%). Although boys' violent actions were related to leisure-time activities (64%), violence rarely took place during sports activities. Alcohol-related violence increased with age. Some 13% of 14-year-olds reported being under the influence of alcohol at the time of violence. The corresponding figures for 16- and 18-year-olds were 41% and 62%, respectively. Moreover, alcohol was closely associated with violence-related injuries. Conclusions: Violence is common among Finnish adolescents. While violence does not always lead to injury, related injuries are an important cause of adolescent morbidity. Alcohol seems to be strongly associated with adolescent violence and related injuries.
Cell migration without a lamellipodium
Authors: Gupton Stephanie L. , Anderson Karen L. , Kole Thomas P. , Fischer Robert S. , Ponti Aaron , Hitchcock-DeGregori Sarah E. , Danuser Gaudenz , Fowler Velia M. , Wirtz Denis , Hanein Dorit , Waterman-Storer Clare M.
Published: February 2005

The actin cytoskeleton is locally regulated for functional specializations for cell motility. Using quantitative fluorescent speckle microscopy (qFSM) of migrating epithelial cells, we previously defined two distinct F-actin networks based on their F-actin–binding proteins and distinct patterns of F-actin turnover and movement. The lamellipodium consists of a treadmilling F-actin array with rapid polymerization-dependent retrograde flow and contains high concentrations of Arp2/3 and ADF/cofilin, whereas the lamella exhibits spatially random punctae of F-actin assembly and disassembly with slow myosin-mediated retrograde flow and contains myosin II and tropomyosin (TM). In this paper, we microinjected skeletal muscle αTM into epithelial cells, and using qFSM, electron microscopy, and immunolocalization show that this inhibits functional lamellipodium formation. Cells with inhibited lamellipodia exhibit persistent leading edge protrusion and rapid cell migration. Inhibition of endogenous long TM isoforms alters protrusion persistence. Thus, cells can migrate with inhibited lamellipodia, and we suggest that TM is a major regulator of F-actin functional specialization in migrating cells.
L1, a novel target of β-catenin signaling, transforms cells and is expressed at the invasive front of colon cancers
Authors: Gavert Nancy , Conacci-Sorrell Maralice , Gast Daniela , Schneider Annette , Altevogt Peter , Brabletz Thomas , Ben-Ze'ev Avri
Published: February 2005

Aberrant β-catenin-TCF target gene activation plays a key role in colorectal cancer, both in the initiation stage and during invasion and metastasis. We identified the neuronal cell adhesion molecule L1, as a target gene of β-catenin-TCF signaling in colorectal cancer cells. L1 expression was high in sparse cultures and coregulated with ADAM10, a metalloprotease involved in cleaving and shedding L1's extracellular domain. L1 expression conferred increased cell motility, growth in low serum, transformation and tumorigenesis, whereas its suppression in colon cancer cells decreased motility. L1 was exclusively localized in the invasive front of human colorectal tumors together with ADAM10. The transmembrane localization and shedding of L1 by metalloproteases could be useful for detection and as target for colon cancer therapy.
Reduction of total E2F/DP activity induces senescence-like cell cycle arrest in cancer cells lacking functional pRB and p53
Authors: Maehara Kayoko , Yamakoshi Kimi , Ohtani Naoko , Kubo Yoshiaki , Takahashi Akiko , Arase Seiji , Jones Nic , Hara Eiji
Published: February 2005

E2F/DP complexes were originally identified as potent transcriptional activators required for cell proliferation. However, recent studies revised this notion by showing that inactivation of total E2F/DP activity by dominant-negative forms of E2F or DP does not prevent cellular proliferation, but rather abolishes tumor suppression pathways, such as cellular senescence. These observations suggest that blockage of total E2F/DP activity may increase the risk of cancer. Here, we provide evidence that depletion of DP by RNA interference, but not overexpression of dominant-negative form of E2F, efficiently reduces endogenous E2F/DP activity in human primary cells. Reduction of total E2F/DP activity results in a dramatic decrease in expression of many E2F target genes and causes a senescence-like cell cycle arrest. Importantly, similar results were observed in human cancer cells lacking functional p53 and pRB family proteins. These findings reveal that E2F/DP activity is indeed essential for cell proliferation and its reduction immediately provokes a senescence-like cell cycle arrest.
The Surly Bonds: American Cold War Constraints on British Aviation
Authors: Engel Jeffrey A.
Published: February 2005

The battle for dominance of the global aviation marketplace after 1945 was largely an Anglo-American competition, yet to date historians have overlooked the important role diplomacy played in shaping its outcome. Divisions over the proper regulation of strategically vital aircraft and aviation technology seriously impeded aircraft manufacturers, British producers especially. This article traces the impact of Anglo-American diplomacy upon British aviation manufacturers during the first half of the Cold War, from 1946 until the Sino-American rapprochement of the early 1970s. It explores three periods in particular: the initial postwar years, highlighted by disputed British jet engine sales to the Soviet Union; the early 1950s, when British jetliner exports seemed a genuine strategic threat in Washington; and the early 1960s, when Whitehall authorized covert transfers of American-licensed aviation equipment to complete the first British aircraft sales to the People’s Republic of China. These examples demonstrate not only the effect of strategic balancing by governments on the marketplace, but also diplomacy’s impact on business.