bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of electron–phonon energy exchange on thermal wave propagation in semiconductors considering carrier diffusion and recombination
Authors: Villegas‐Lelovsky L. , Gonzalez de la Cruz G. , Volovichev I. N. 
Published: January 2005

AbstractThe electron, hole, and phonon temperatures are calculated in semiconductors by taking into account the finite carrier diffusion and nonradiative recombination time in the sample. We assume that the energy of the modulated excitation radiation is greater than the energy gap and absorbed at the surface of the semiconductor, therefore, a source of heat and carrier generation at the surface of the sample are time dependent and must be considered in the photothermal theory. Under this situation, the coupled one‐dimensional heat transport (for each quasiparticle system) and carrier diffusion equations in the strong hole–phonon energy interaction approximation and charge quasineutrality condition are solved. Since the nonequilibrium carrier concentration depends sensitively on the electron and phonon fluctuation temperature, the heat power density generated in the sample due to the recombination of the electron–hole pair will be greatly influenced by the inhomogeneous quasiparticle temperature distributions. This latter effect comes through the recombination rate of carriers and it will be considered in the photothermal signal. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Intraband relaxation time in InGaNAs quantum‐well lasers and comparison with experiment
Authors: Park Seoung‐Hwan 
Published: January 2005

AbstractThe intraband relaxation time is investigated theoretically for InGaNAs/InGaNAs/GaAs QW lasers. The result is compared with that obtained from comparison between the experimental gain spectra and theoretical gain. The InGaNAs/InGaNAs QW shows smaller intraband relaxation time than InGaAs/InGaAsP QW. This is due to the fact that the InGaNAs/InGaNAs structure has larger electron effective masses than the InGaAs/InGaAsP QW. The calculated gain spectra is in good agreement with the experiment. The intraband relaxation time τin obtained from fitting the experimental data is 60 fs. This value reasonably agrees well with the calculated value of 62 fs at the subband edge, considering that the electrons and the holes are mostly near the subband edge. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A teaching framework for cross‐cultural genetic counseling
Authors: Weil Jon , Mittman Ilana 
Published: January 2005

AbstractThe increasing diversity of American society has brought growing recognition of the need to bridge cultures in the delivery of genetic counseling services. New immigrants and members of diverse ethnic groups face multiple barriers to genetic counseling services. The need to train genetic counselors to deal with cultural diversity is especially crucial in the new genetic era, given the rapid expansion of available technology, with the resulting social and ethical ramifications. A framework for teaching cross‐cultural issues in genetic counseling training programs is presented that can be implemented in step‐wise fashion, consistent with available resources. Cross‐cultural issues can be incorporated into existing teaching and training modalities by expanding the orientation from monocultural to multicultural. Relevant clinical experience, exploration of students' preconceptions and biases, reading materials, and lectures by invited speakers can all enhance students' knowledge and sensitivity. It is critically important that training programs furnish students with the basic tools necessary for the ongoing process of learning about cultural diversity.
A survey of reimbursement for cystic fibrosis carrier testing
Authors: Bernhardt Barbara A. 
Published: January 2005

AbstractTo assess the current status of reimbursement for cystic fibrosis (CF) carrier testing, we surveyed individuals tested in the Mid‐Atlantic region. Results show that CF testing was covered by insurance in part or in full for greater than 50% of respondents. The test was nearly always covered when performed during pregnancy because of a positive family history, but it was also covered for more than 50% of pregnant respondents with a negative family history. There were no significant differences in coverage by type of insurance. Many respondents needed to supply additional information about the testing to their insurance company before a coverage decision could be made. Before population‐based CF screening programs are initiated, more data are needed on insurance reimbursement for testing, especially when performed pre‐conceptually.
Scientific aspects of early eugenics
Authors: Lubinsky Mark S. 
Published: January 2005

AbstractThe eugenics movement supported applications of scientific breeding principles to humans, ultimately to encourage a better society, but actually with often disastrous social consequences. Although mostly viewed as quackery today, legitimate scientific considerations of fact and theory had an important role in determining the course of eugenics. A school of eugenics arose formally from attempts to apply Darwinian principles to humans in the context of biometry, a school that used statistical approaches to biology. Biometry emphasized blending inheritance and continuous traits, in marked contrast to the particulate inheritance of unit traits in Mendelism. Genetics was therefore a scientific challenge to eugenics, which was rooted in biometry. A Mendelian eugenics arose in the United States primarily under the influence of Charles Davenport. This paper reviews some of the technical issues involved in the development of this new paradigm, as well as Davenport's role as a scientist in this process.
Vibrational Interactions in Pariser—Parr—Pople Theory. II. Ground- and Excited-State Force Fields
Authors: Donath Wilm E. 
Published: January 2005

Expressions are derived for the interaction between ground and excited states to give resonance contributions to the vibrational force field. Two contributions are found: The dominating term reflects largely the change in the bond resonance integral due to bond length variation with some contribution of the electrostatic terms; the other, a relatively small term, is generated by the polarization due to the field generated by a vibrational distortion. Calculations are made for the ground states of a number of aromatics; adequate agreement with experiment is found for benzene and naphthalene.
The possible distortion of molecules and the Born—Oppenheimer approximation are investigated when the resonance interactions become strong. Application is made to the 1B1u and 3B1u states of benzene. Distortion and violation of the Born—Oppenheimer approximation is predicted to occur for the two B1u states of benzene.
Spectroscopic Constants and Vibrational Assignment for the B 3Πu + State of Iodine
Authors: Steinfeld J. I. , Zare R. N. , Jones L. , Lesk M. , Klemperer W. 
Published: January 2005

Portions of the iodine B 3Π0u+←X 1Σg+ absorption spectrum have been remeasured under high resolution. A new analysis of 719 lines in the 3–6, 4–7, 5–4, 7–5, 11–1, 12–2, 13–2, 25–0, and 29–0 bands, combined with previous measurements by Mecke, Loomis, and Brown, gives the following revised constants: ωe′=125.273 cm−1Te′=15770.59γe′=−4.0×10−7ωexe′=0.7016Be′=0.028969δe′=−3.5×10−8ωeye′=−0.00567re′=3.0276 ÅDe′=3.5×10−9ωeze′=+0.000032αe′=0.0001562βe′=3.9×10−10De′=4391.0Constants for ground state rotational levels were found to be in good agreement with Rank's latest determinations.
Using these new constants for the B state, Franck—Condon factors for this system were computed. The vibrational numbering originally assigned by Mecke and Loomis to the B state was decreased by one unit to bring calculated intensity distribution into complete agreement with all observed fluorescence data, including new photoelectric measurements on a number of bands. No systematic variation of the electronic transition moment could be derived from these data. These revised Franck—Condon factors were also used to recalculate radiative lifetimes from absolute absorption data which are in fair agreement with the phase-shift determination of Brewer, Berg, and Rosenblatt.
Slow-Neutron Inelastic Scattering from Low-Temperature Gaseous Methane, Liquid Methane, and Solid Methane
Authors: Harker Y. D. , Brugger R. M. 
Published: January 2005

The partial differential cross sections for inelastic scattering of neutrons from samples of cold gaseous methane (T=125°K), liquid methane (T=99°K), and solid methane (T=83°K) were measured with the materials testing reactor (MTR) phased chopper velocity selector. These results are compared to the theory reported by Griffing for methane gas, which fits the cold-gas data very well over the entire range of the experiment and also fits the liquid and solid data at the large momentum transfers. The results of these comparisons indicate that the rotations are free in all three phases and that, in the liquid and solid phases, there are oscillations of the center of mass of the molecule with dominant transitions having an energy change near 0.017 eV. The range of agreement of the gas theory with the liquid and solid data indicates that the liquid and solid act according to the gas model out to a time of roughly 5×10−13 sec. The similarity of the liquid and solid data over the range of the experiment suggest further that they act similarly out to even longer times.
The zeroth and first moments of energy transfer were calculated and for the gas compare favorably with a molecular theory which treats the rotations classically. For the liquid and solid data, the moments give further indications of the molecular oscillations.
Spin Diffusion Measurements: Spin Echoes in the Presence of a Time-Dependent Field Gradient
Authors: Stejskal E. O. , Tanner J. E. 
Published: January 2005

A derivation is given of the effect of a time-dependent magnetic field gradient on the spin-echo experiment, particularly in the presence of spin diffusion. There are several reasons for preferring certain kinds of time-dependent magnetic field gradients to the more usual steady gradient. If the gradient is reduced during the rf pulses, H1 need not be particularly large; if the gradient is small at the time of the echo, the echo will be broad and its amplitude easy to measure. Both of these relaxations of restrictions on the measurement of diffusion coefficients by the spin-echo technique serve to extend its range of applicability. Furthermore, a pulsed gradient can be recommended when it is critical to define the precise time period over which diffusion is being measured.
The theoretical expression derived has been verified experimentally for several choices of time dependent magnetic field gradient. An apparatus is described suitable for the production of pulsed gradients with amplitudes as large as 100 G cm−1. The diffusion coefficient of dry glycerol at 26°±1°C has been found to be (2.5±0.2)×10−8 cm2 sec−1, a value smaller than can ordinarily be measured by the steady gradient method.
Triplet Excitons in Crystals of Aromatic Molecules
Authors: Jortner Joshua , Rice Stuart A. , Katz Joseph L. , Choi Sang-Il 
Published: January 2005

In the present paper we consider the band structure and the Davydov splitting of the first triplet exciton states in crystalline naphthalene, anthracene, and biphenyl. It is found that: (a) An important contribution to the triplet exciton bandwidth arises from intermolecular exchange interaction. These interactions are calculated in the molecular orbital π-electron approximation. (b) Excitation exchange effects due to spin—orbit coupling are negligible. (c) Nonorthogonality corrections, considered within the framework of the symmetric orthogonalization procedure, have been found to be small. (d) Crystal-field mixing of triplet states arising from π→π* excitations has no effect on the triplet bands. (e) An important contribution to the triplet exciton bandwidth may arise from configuration interaction with charge-transfer states.
The dynamics of triplet excitons in aromatic crystals was studied in the two limiting cases of strong and weak scattering. The band model, with the constant mean-free-path approximation, leads to a mean free path of the order of one to two lattice distances and seems to be inappropriate. Triplet—triplet annihilation leading to delayed blue fluorescence in crystalline anthracene can be adequately described in terms of a random-walk diffusion model when the effects of charge-transfer interactions are included.
Infrared and Raman Spectra of α,α,α-Trichlorotoluene, C6H5CCl3
Authors: Stephenson C. V. , Coburn W. C. 
Published: January 2005

The Raman spectrum between 3500 and 100 cm−1, including polarization measurements, and the infrared spectrum between 4000 and 265 cm−1 of liquid α,α,α-trichlorotoluene, C6H5CCl3, have been recorded. Wavenumber assignments of the phenyl vibrations have been made on the basis of C2v symmetry, although the molecule is undoubtably of lower symmetry.
The 24-substituent-insensitive ring modes were assigned without much difficulty. The nine substituent modes and the six substituent-sensitive ring modes were assigned with less certainty, but the Raman polarization data helped in the assignment of some of these. The phenyl-substituent torsional mode was assigned to the strong, broad Raman line observed at 118 cm−1. The six phenyl vibrations whose wavenumbers are sensitive to the nature of the substituent were assigned, in our previous notation [C. V. Stephenson, W. C. Coburn, Jr., and W. S. Wilcox, Spectrochim. Acta 17, 933 (1961)], as follows: ν20′(δCC)b2, 176 cm−1;ν14′(βCX)b1, 246 cm−1;ν18′(αCCC)a1, 308 cm−1;ν19′(γCX)b2, 507 cm−1;ν2(νCX)a1  629 cm−1;and ν2(νCX)a1; 1185 cm−1.
Raman Spectra of Polycrystalline Methylene Halides
Authors: Ito Mitsuo 
Published: January 2005

The Raman spectra of CH2Cl2, CH2Br2, and CH2I2 have been observed at 77° and 195°K. Band splitting due to the crystal field has been found for the Raman bands ν3, ν4, and ν9 of CH2Cl2 and for the band ν1 of CH2Br2. No apparent splitting has been observed for the Raman bands of CH2I2. The band splittings and frequency shifts of the intramolecular vibrations are discussed.
The Raman bands due to the lattice vibrations have been obtained and tentative assignments are presented for some of the bands. Much temperature effect has been found on the Raman frequencies of the lattice vibrations.
Unrestricted Hartree—Fock Calculations. II. Spin Properties of Pi-Electron Radicals
Authors: Snyder Lawrence C. , Amos Terry 
Published: January 2005

Unrestricted Hartree—Fock wavefunctions have been computed for a large number of conjugated-hydrocarbon pi-electron radicals. Pi-electron spin-density and charge-density functions have been computed with and without annihilation of the major contaminating spin multiplet in the wavefunction.
Three different empirical relations have been used to relate our results to proton isotropic hyperfine splittings measured in ESR experiments. These are the simple McConnell expression; the Colpa and Bolton relation which includes a term depending on the excess charge density at the carbon atom; and that due to Giacometti, Nordia, and Pavan which introduces a contribution from the spin densities in the bonds between the carbon and its nearest neighbors. When the Pariser—Parr method with semiempirical electron-repulsion integrals is employed in the unrestricted Hartree—Fock calculation, then the experimental splittings are almost always bounded by those computed with spin densities before and after the annihilation of the major contaminating spin state, but spin densities after annihilation are closer to the experimental values derived with the empirical relations. This was found to be true for all the three relations used, but the simplest one gave slightly less satisfactory results.
The general problem of the interpretation of spin densities obtained from an unrestricted Hartree—Fock wavefunction which is not an eigenstate of spin is discussed. It is found, however, that unrestricted computations with semiempirical integrals give small splittings of the underlying ``closed''shell orbitals, so that a single annihilation is a good approximation to projection and the spin densities after annihilation should be satisfactory from a theoretical point of view.
Electron Paramagnetic Resonance Spectra of Zinc-Doped Copper Acetate Monohydrate
Authors: Kokoszka Gerald F. , Allen Harry C. , Gordon Gilbert 
Published: January 2005

The electron paramagnetic resonance of the copper—zinc pairs in zinc-doped copper acetate monohydrate has been observed at 77°K by using an X-band EPR spectrometer. Single crystals containing less than 1% zinc ions were grown from a slightly acidic aqueous solution containing about 75% copper acetate and 25% zinc acetate.
The experimental results could be fit to the spin Hamiltonian: H=gzβHzSz+gxβHxSx+gyβHySy+AzSzIz+AxSxIx+AySyIy.The values Az=0.0147±0.006 cm−1, Ax&lt;0.0018 cm−1, and Ay&lt;0.0023 cm−1 were measured for the doublet-state cupric ions. The g values were found to be: gz=2.344±0.005, gx=2.052±0.007, and gy=2.082±0.007.
These results are consistent with the model proposed by Slichter, in which he has shown that the components of the hyperfine tensor should be twice as large for a doublet species as compared to the corresponding triplet species when the exchange integral J is much larger than the components of the hyperfine tensor.
Since the microsymmetry at the cupric ion site is no higher than C2v, the EPR results were interpreted by using the theory of Bleaney, Bowers, and Pryce for lower than axial symmetry. The optical data have been interpreted on the basis of weakly interacting cupric ions. A consistent explanation for the magnetic resonance data and optical data is discussed.
Enthalpies of Mixing in Silver Bromide—Alkali Bromide and Thallium Chloride—Alkali Chloride Liquid Mixtures
Authors: Hersh L. S. , Navrotsky A. , Kleppa O. J. 
Published: January 2005

The enthalpies of mixing in silver bromide—alkali bromide and thallium chloride—alkali chloride liquid mixtures have been determined by high-temperature reaction calorimetry.
The following semiempirical relations represent the molar enthalpies of mixing to a good approximation: AgBr–AlkBr:  HM=N1N2(U0+++52δ12−340δ122) kcal/mole,TlCl–AlkCl:  HM=N1N2(U0+++21δ12−340δ122) kcal/mole.In these expressions N1 and N2 are the mole fractions of the two components, while δ12 = (d1 — d2)/d1d2, when d1 and d2 are the sums of the ionic radii in the two component salts. The positive term U0+ + differs from system to system. It represents a theoretical estimate of the contribution to the mixing enthalpy which arises from the dispersion interaction between next-nearest-neighbor cations, calculated by an adaptation of the method of Mayer.
These expressions are similar to the ones previously determined for the silver chloride—alkali chloride and silver nitrate—alkali nitrate systems, except for the coefficient of the term linear in δ12. This term is absent in the corresponding expression for the binary alkali halides and nitrates. For the considered silver systems, it increases in the sequence NO3—&lt;Cl—&lt;Br—. The term is attributed to the partly covalent bonding between cations and anions in the silver and thallium salts.
Collective-Coordinate Treatment of Electrolytes
Authors: Eisenthal K. B. , McMillan W. G. 
Published: January 2005

The configuration integral for an electrolyte in a continuous dielectric medium is calculated using the method of collective coordinates. The pair potential energy is taken to be Coulombic (with fixed dielectric constant) for all interionic distances outside some separation a and zero inside. This form permits handling the potential energy completely within the collective-coordinate framework, but has the disadvantage of limiting the concentration to which the treatment is applicable.
For low concentrations, the configurational partition function can be approximated to yield an analytic expression for the activity coefficient. For higher concentrations a numerical integration is used to calculate the mean molal activity coefficients for univalent salts in water at 25°C. The theoretical values obtained from the numerical integrations are within experimental error of the observed values up to molalities of 0.30 to 1.0, depending on the salt considered. As the concentration of the electrolyte goes to zero, the activity coefficient correctly tends to the Debye—Hückel limiting law.
Effect of Chemical Combination on the X-Ray K Emission Spectra of Oxygen and Fluorine
Authors: Fischer David W. 
Published: January 2005

Band shapes, wavelengths, and intensities are presented and discussed for the K emission spectra of oxygen and fluorine from some simple oxides and fluorides. It is shown that band shapes and peak positions are dependent upon the target material from which they are emitted. Evidence is presented illustrating that this dependence is in part due to such solid-state properties as crystal structure, valence, and coordination.
Results were obtained from a flat-crystal vacuum spectrometer with a thin window flow proportional counter using electron excitation.
Polarization Effects in the Two-Photon Excitation of Anthracene Fluorescence
Authors: Peticolas Warner L. , Norris Robert , Rieckhoff Klaus E. 
Published: January 2005

The polarization of the fluorescence of anthracene has been measured after two-photon excitation with ruby laser light. The anthracene molecules were rigidly held in a 2×10−3M solution in EPA glass at liquid-nitrogen temperatures. For comparison, the polarization of the fluorescence was measured from one-photon excitation at approximately twice the laser frequency. The measured polarization of the two-photon excited light is in satisfactory agreement with the polarization as calculated from the Goeppert-Mayer process involving a transition through an intermediate state. It is in disagreement with the polarization calculated in terms of the process recently suggested involving the A2 term in the Hamiltonian. Thus the measurement of the polarization of the two-photon fluorescent light appears to be one way of experimentally estimating the relative contribution of these two second-order processes.
The concentration and intensity independent quantity δ, which is the ratio of the cross section to the laser flux, was found experimentally to be 0.9×10−51 cm4·sec/atom·photon for anthracene molecules in a dilute glass.
Reaction of Atomic Hydrogen with Propylene at 77°K as Studied by Electron Spin Resonance
Authors: Hill Charles G. , Reid Robert C. , Strandberg Malcolm W. P. 
Published: January 2005

Hydrogen-atom reaction rates with thin solid propylene films were studied at 77°K. Propylene was deposited on the walls of a quartz resonance cavity of an ESR spectrometer and hydrogen-atom concentrations were monitored during reaction. The hydrogen atoms were produced in a 2450 Mc/sec microwave discharge external to the cavity and either diffused into or were pumped through the reaction zone.
The products of the reaction were found to be propane and 2,3-dimethylbutane. The ratio of propane to 2,3-dimethylbutane in the products increased as the average hydrogen-atom concentration in the reactor increased. The product distribution and the variation of this distribution with hydrogen-atom concentration may be explained by the following sequence of reactions: CH3–CH=CH2+H→ lim k1CH3–ĊH–CH3,2 CH3–ĊH–CH3→ lim k2CH3–CH2–CH3+CH3–CH=CH2,[Complex chemical formula]CH3–ĊH–CH3+H→ lim k4CH3–CH2–CH3.
The rate constant k1 was found to be 1.8×106 cc/mole·sec at 77°K assuming that the monitored hydrogen-atom concentration was equal to that in the reaction zone.