bluuebunny/crossref_metadata_2025 huggingface dataset:
Preventing Falls in Community‐Dwelling Frail Older People Using a Home Intervention Team (HIT): Results From the Randomized Falls‐HIT Trial
Authors: Nikolaus Thorsten , Bach Matthias
Published: December 2004

OBJECTIVES:  To evaluate the effect of an intervention by a multidisciplinary team to reduce falls in older people's homes.

DESIGN:   Randomized, controlled trial with follow‐up of subjects for 1 year.

SETTING:   University‐affiliated geriatric hospital and older patients' homes.

PARTICIPANTS:   Three hundred sixty subjects (mean age ± standard deviation = 81.5 ± 6.4) admitted from home to a geriatric hospital and showing functional decline, especially in mobility.

INTERVENTION:   The participants were randomly assigned to receive a comprehensive geriatric assessment followed by a diagnostic home visit and home intervention or a comprehensive geriatric assessment with recommendations and usual care at home. The home intervention included a diagnostic home visit, assessing the home for environmental hazards, advice about possible changes, offer of facilities for any necessary home modifications, and training in the use of technical and mobility aids. An additional home visit was made after 3 months to reinforce the recommendations. After 12 months of follow‐up, a home visit was made to all study participants.

MEASUREMENTS:   Number of falls, type of recommended home modifications, and compliance with recommendations.

RESULTS:   After 1 year, there were 163 falls in the intervention group and 204 falls in the control group. The intervention group had 31% fewer falls than the control group (incidence rate ratio (IRR) = 0.69, 95% confidence interval (CI) = 0.51–0.97). The intervention was most effective in a subgroup of participants who reported having had two or more falls during the year before recruitment into the study. In this subgroup, the proportion of frequent fallers and the rate of falls was significantly reduced for the intervention group compared with the control group (21 vs 36 subjects with recurrent falls, P = .009; IRR = 0.63, 95% CI = 0.43–0.94). The compliance rate varied with the type of change recommended from 83% to 33% after 12 months of follow‐up.

CONCLUSION:   Home intervention based on home visits to assess the home for environmental hazards, providing information about possible changes, facilitating any necessary modifications, and training in the use of technical and mobility aids was effective in a selected group of frail older subjects with a history of recurrent falling.
Predictors of Health Resource Use by Disabled Older Female Medicare Beneficiaries Living in the Community
Authors: Weiner Michael , Fan Ming‐Yu , Johnson Brent A. , Kasper Judith D. , Anderson Gerard F. , Fried Linda P.
Published: December 2004

OBJECTIVES: To identify specific clinical factors that could best predict resource use by disabled older women.

DESIGN:  Cross‐sectional.

SETTING:  Urban community in Baltimore, Maryland.

PARTICIPANTS:  One thousand two community‐dwelling, moderately to severely disabled, female Medicare beneficiaries aged 65 and older, from the Women's Health and Aging Study I (WHAS).

MEASUREMENTS:  WHAS data were merged with participants' 1992–1994 Medicare claims data for the year after baseline evaluation, reflecting inpatient, outpatient, home‐based, and skilled‐nursing services. The independent contributions of factors hypothesized to predict health expenditures were assessed, using chi‐square and regression analyses, with the logarithm of Medicare expenditures as the primary outcome.

RESULTS:  Demographic factors were not associated with Medicare expenditures. Factors associated with expenditures in bivariate analyses included heart disease (1.4x), chronic obstructive pulmonary disease (1.3x), diabetes mellitus (1.1x), smoking, comorbidity, and severity of disability, as well as low creatinine clearance, serum albumin, caloric expenditure, or skinfold thickness. Heart disease, diabetes mellitus, and low skinfold thickness remained significant after adjustment for other factors.

CONCLUSION:  Heart disease, diabetes mellitus, and low skinfold thickness are important independent predictors of 1‐year Medicare expenditures by disabled older women. Many other variables that reflect disease, disability, nutrition, or personal habits have less predictive ability. Most demographic factors are not predictors of expenditures in this population. Focusing on the best predictors may facilitate more‐effective risk adjustment and creation of related health policies.
Predictors of Alcohol‐Treatment Seeking in a Sample of Older Veterans in the GET SMART Program
Authors: Satre Derek D. , Knight Bob G. , Dickson‐Fuhrmann Elizabeth , Jarvik Lissy F.
Published: December 2004

OBJECTIVES:  To examine the predictive value of demographic characteristics and substance abuse indicators to explain treatment seeking for substance abuse problems by older male medical patients.

DESIGN:   Longitudinal analysis of screening data and treatment‐seeking behavior.

SETTING:   Inpatient medical and outpatient substance abuse treatment center.

PARTICIPANTS:   Participants in the study were 855 medically ill male veterans aged 55 and older, who were screened for alcohol problems during inpatient medical treatment after clinician referral.

MEASUREMENTS:   The CAGE alcohol screen (Cut down on your drinking, Annoyed by criticism of your drinking, Guilty about your drinking, Eye‐opener), drug use, and demographic measures administered at time of screening. Predictors of treatment seeking in the sample were examined using structural equation modeling.

RESULTS:   Expressed interest in treatment and later attendance at a pretreatment evaluation were associated with younger age and a higher CAGE alcohol screening score. Being unmarried and using drugs in addition to alcohol were associated with treatment interest but not with evaluation attendance. In the path model tested, the effect of higher CAGE score partially explained the effect of younger age on treatment seeking.

CONCLUSION:   The model examined shows utility in predicting alcohol‐treatment seeking in this sample. Age‐related factors may deter treatment seeking by older male medical inpatients.
Cognitive Screening Using a Tape Recorder: A Pilot Study
Authors: Schofield Peter W. , Lee Stephen J. , Davies Graeme C.
Published: December 2004

OBJECTIVES:  To determine whether a tape recorder can be used to administer cognitive tests efficiently and yield valid results.

DESIGN:   Convenience sample. Administration of cognitive test materials by tape recorder and conventional technique.

SETTING:   Outpatient clinic.

PARTICIPANTS:   Subjects from memory disorder clinic, hostel accommodation, and community.

MEASUREMENTS:   Responses to Hopkins Verbal Learning Test–revised, verbal fluency items from the controlled oral word association test, 10‐item naming task, a construction task, and speed writing task.

RESULTS:   Performances on the tape‐ and clinician‐administered battery of tests were highly correlated. Memory impairment was accurately detected using the tape battery. Data from 30 minutes of testing via tape were obtained at the cost to the clinician of 2 to 3 minutes of scoring time.

CONCLUSION:   Tape‐administration of cognitive test material warrants further study as an efficient means of cognitive screening.
An Evaluation of a Low‐Intensity Intervention to Introduce Medical Students to Healthy Older People
Authors: Bernard Marie A. , McAuley William J. , Belzer John A. , Neal Karen S.
Published: December 2004

This is a report of a controlled, prospective, longitudinal trial of an intervention to affect medical students' attitudes toward aging. Members of the Class of 2002 at the University of Oklahoma College of Medicine were assigned a senior mentor (a community‐dwelling older person) upon matriculation into medical school. Students were required to perform a structured interview with the mentor once per semester for the first 2 preclinical years and to discuss these interviews in small groups mediated by geriatrics faculty. Members of the Class of 2001 were controls. Attitudes toward aging were determined using the Aging Semantic Differential (ASD) attitude scale in August 1998 and again at the end of the second year of medical school. Initial mean ASD scores were not significantly different for the two groups. Although both classes experienced improvements in their ASD scores from Time 0 to Time 1, the improvement for the class of 2002 was significantly greater than that for the class of 2001 (2001 class mean = 0.17, 2002 class mean = 0.40, t = −3.09, degrees of freedom (df) = 219, P = .002). This difference held up under controls for sex, age, prior visits to a nursing home, prior work/volunteering in an old‐age environment, and a prior course on aging (Model F = 3.00, df = 6/214, P = .008; class F = 9.70, df = 1, P = .002). It was concluded that a low‐intensity intervention to introduce entering medical students to healthy older people might have a positive effect on attitudes toward aging.
Depression Treatment in a Sample of 1,801 Depressed Older Adults in Primary Care
Authors: Unützer Jürgen , Katon Wayne , Callahan Christopher M. , Williams John W. , Hunkeler Enid , Harpole Linda , Hoffing Marc , Della Penna Richard D. , Noel Polly Hitchcock , Lin Elizabeth H. B. , Tang Lingqi , Oishi Sabine
Published: December 2004

OBJECTIVES: To examine rates and predictors of lifetime and recent depression treatment in a sample of 1,801 depressed older primary care patients

DESIGN: Cross sectional survey data collected from 1999 to 2001 as part of a treatment effectiveness trial.

SETTING: Eighteen primary care clinics belonging to eight organizations in five states.

PARTICIPANTS: One thousand eight hundred one clinic users aged 60 and older who met diagnostic criteria for major depression or dysthymia.

MEASUREMENTS: Lifetime depression treatment was defined as ever having received a prescription medication, counseling, or psychotherapy for depression. Potentially effective recent depression treatment was defined as 2 or more months of antidepressant medications or four or more sessions of counseling or psychotherapy for depression in the past 3 months.

RESULTS: The mean age ± standard deviation was 71.2 ± 7.5; 65% of subjects were women. Twenty‐three percent of the sample came from ethnic minority groups (12% were African American, 8% were Latino, and 3% belonged to other ethnic minorities). The median household income was $23,000. Most study participants (83%) reported depressive symptoms for 2 or more years, and most (71%) reported two or more prior depressive episodes. About 65% reported any lifetime depression treatment, and 46% reported some depression treatment in the past 3 months, although only 29% reported potentially effective recent depression treatment. Most of the treatment provided consisted of antidepressant medications, with newer antidepressants such as selective serotonin reuptake inhibitors constituting the majority (78%) of antidepressants used. Most participants indicated a preference for counseling or psychotherapy over antidepressant medications, but only 8% had received such treatment in the past 3 months, and only 1% reported four or more sessions of counseling. Men, African Americans, Latinos, those without two or more prior episodes of depression, and those who preferred counseling to antidepressant medications reported significantly lower rates of depression care.

CONCLUSION: The findings suggest that there is considerable opportunity to improve care for older adults with depression. Particular efforts should be focused on improving access to depression care for older men, African Americans, Latinos, and patients who prefer treatments other than antidepressants.
Predictive Factors of In‐Hospital Mortality in Older Patients Admitted to a Medical Intensive Care Unit
Authors: Bo Mario , Massaia Massimiliano , Raspo Silvio , Bosco Francesca , Cena Paola , Molaschi Mario , Ap  , Fabris Fabrizio
Published: December 2004

OBJECTIVES: To identify prognostic factors that are independently predictive of in‐hospital mortality in older patients hospitalized in a medical intensive care unit (MICU).

DESIGN: Prospective cohort study.

SETTING: A MICU in an Italian university hospital.

PARTICIPANTS: Patients aged 65 and older consecutively admitted to the MICU directly from the first‐aid unit.

MEASUREMENTS: Upon admission, the following variables were examined: demographics, clinical history (diabetes mellitus, active neoplasm, cognitive impairment, immobilization, pressure ulcers, use of nutritional support, home oxygen therapy), physiopathology (Acute Physiology and Chronic Health Evaluation (APACHE) II), and cognition/function (activity of daily living (ADL), instrumental activity of daily living (IADL), Short Portable Mental Status Questionnaire (SPMSQ)). The vital status of the patient at the end of hospitalization was recorded.

RESULTS: Over a period of 10 months, 659 patients were recruited (mean age ± standard deviation = 76.6 ± 7.5; 352 men and 307 women). There were 97 deaths (14.71%). The following factors proved to be significantly associated with in‐hospital mortality: old age, low body mass index (BMI) values, low values of albumin, high scores on APACHE II, functional impairment (ADL, IADL), cognitive impairment (SPMSQ), history of cognitive deterioration, history of confinement to bed, and presence of pressure ulcers. Using multivariate analysis, the following variables were independently predictive of in‐hospital mortality: lack of independence in ADLs (P < .001), moderate‐to‐severe cognitive impairment on SPMSQ (P < .001), score on APACHE II (P = .002), and low BMI values (P = .031).

CONCLUSION: The prognosis of older patients hospitalized in medical intensive care units depends not only on the acute physiological impairments, but also on a series of preexisting conditions, such as loss of functional independence, severe and moderate cognitive impairment, and low BMI.
Effect of Radiation on Shock Wave Behavior
Authors: Marshak R. E.
Published: December 2004

The fundamental conservation equations governing fluid dynamics and including radiation are written down. The Rankine-Hugoniot conditions are derived for shock waves subjected to radiation flux. Similarity solutions are obtained for the constant density and constant pressure cases. Some results are stated for the combined radiation-fluid dynamics corresponding to a power law dependence of the temperature on the time.
Quantum Statistics of Interacting Particles; General Theory and Some Remarks on Properties of an Electron Gas
Authors: Montroll Elliott W. , Ward John C.
Published: December 2004

A systematic generalization of the Mayer cluster integral theory has been developed to deal with the quantum statistics of interacting particles. The grand partition function appears in a natural way and the cluster integrals are integrals over propagators which are derived from the Green's function solution of the Bloch equation (which follows from the Schroedinger equation by replacing it/ℏ by β = 1/kT). Every cluster integral can be represented by a hybrid of a Mayer graph and a Feynman diagram in (β, r) space.

The generalization of classical ring cluster integrals has been analyzed. It is shown that in the case of the electron gas the classical limit of the contribution of these integrals to the grand partition function yields the Debye-Huckel theory while the low temperature limit leads to the Gell-Mann—Brueckner equation for the correlation energy of the ground state.

A prescription is given for the construction of the cluster integral associated with any given diagram.
The Electrical Conductivity of Glass Part III. Current-Voltage Relationships with Highly Resistant Layers
Authors: Kiehl H. R.
Published: December 2004

Some effects upon current-voltage and temperature relationships as caused by the formation of ``impregnated'' layers in the vicinity of the electrodes are described. For ``unimpregnated'' samples, Ohm's law appeared to be valid. Upon ``impregnation'' various current-voltage relationships from I=AVN to that of Poole were observed, the nature of the function apparently depending upon the characteristics of the layers produced. The Rasch and Hinrichson equation was found valid for fresh samples over the range of temperatures used, but the presence of these layers caused distinct changes in the characteristics of this relationship. The possible importance of such layers upon the electrical properties of glass and other insulating materials at the higher fields and temperatures and their possible effect in causing some of the apparent discrepancies in existing data is pointed out. The importance of much further detailed study of their properties is suggested.
Bending of a Centrally Loaded Rectangular Strip of Plywood
Authors: March H. W.
Published: December 2004

The deflection of a strip of plywood is calculated for the case in which the load is concentrated along a line through the center of the strip and perpendicular to its edges. This type of loading is commonly used in tests to determine the effective modulus of elasticity in bending. Use is made of the differential equation for a flat plate of plywood. Explicit expressions in terms of the elastic constants of the component plies are given for the coefficients that occur in this equation. For the smaller span-depth ratios the flat plate theory does not lead to exact results. A method is given for calculating the appropriate correction to the results obtained on the basis of this theory.
Spectral Emissivities, Resistivity, and Thermal Expansion of Tungsten-Molybdenum Alloys
Authors: Bossart P. N.
Published: December 2004

The spectral emissivities of three different W–Mo alloys were found by direct measurement with an optical pyrometer to be from about 120 percent at 1300°K to 110 percent at 2200°K of the values calculated as a simple mixture of the constituents. In the case of one alloy this result was compared with a similarly determined ratio of measured to calculated resistivities. According to Drude's law, the square root of this resistivity ratio should be the corresponding emissivity ratio. It was found at temperatures 1300°K to 2100°K that the square root of the resistivity ratio was practically constant at 1.215, which checked approximately the emissivity ratio 1.19 at 1300°K only. The emissivities of W and Mo were measured. The resistivity-temperature, and thermal expansion-temperature relations are given for the alloy 46.5 percent atoms of W. The resistivity relation is compared with those of its constituents and discussed with reference to the theory of Bragg and Williams.
The Application of Chain Weight Loading to the Determination of Jell Strength
Authors: Saxl Irving J.
Published: December 2004

In view of the importance of simple and precise methods for the determination of jelly strength, a new apparatus has been developed which permits the determination of jelly strength in terms of load versus compression. Chain weight loading is used for the gradual application or reduction of weight. The impression made in this manner within the gelatin specimen is compensated for by lifting it against the motion of a plunger with the aid of a calibrated micrometer screw. In this manner, it is possible to determine the load versus compression characteristics to better than three significant figures. The preparation of the sample has been standardized in such a manner that jelly strength determinations can be carried out at room temperature. Samples of load versus penetration diagrams are given. Also, the formation of hysteresis loops is described. The introduction of the term, jell factor, is suggested (A = ½·breaking load·penetration (gram centimeters).
The Theory of Acid Treatment of Oil Wells Producing from Limestone Reservoirs
Authors: Muskat M. , Wyckoff R. D.
Published: December 2004

A theory is given of the acid treatment of oil wells producing from limestone reservoirs, based upon the assumption of a potential flow of the liquid in the limestone. Calculations are presented for the increase in production capacity of a well resulting from an increase of the permeability in an annular ring surrounding the well bore, obtained by the reaction of the acid (HCl) with the limestone. It is found that the effects are maximal if this inner zone is initially of very low permeability, and is increased to a normal value, while if the permeability is normal originally, the effect of the acid treatment will be small. For limestones that are highly fractured, a representation is used wherein the fracture is replaced by a linear porous medium, of width equal to the fracture, bisecting the limestone proper and of a permeability that is equivalent to its fluid carrying capacity as given by the classical hydrodynamics for a free linear channel. The effect of the acid is then taken to be that of widening the fractures, thus increasing their effective permeability. The analysis here shows that increases in the production capacities as high as one hundred-fold can be obtained in such fractured limestone systems for increases in the fracture width no greater than 1 mm, the effects being greatest when the initial fracture widths are small.
The Seepage Flux Under Dams of Extended Base Width and Under Coffer Dams Resting on Permeable Strata of Finite Thickness. I
Authors: Muskat Morris
Published: December 2004

An exact theory is given of the seepage flux underneath dams of extended base width, with and without sheet piling, and under coffer dams with variable depths of excavation on the downstream side. The flux, per unit upstream-downstream potential drop, is expressed in all cases as 1/2 the ratio of two complete elliptic integrals of the first kind, the modulus of that in the numerator being the comodulus of that in the denominator, these moduli completely characterizing the detailed geometry of the various individual systems. In all cases the seepage becomes logarithmically infinite with increasing thickness of the underlying permeable stratum. The effectiveness of the sheet piling in cutting down the seepage flux is a maximum when it is set at the heel or toe of the dam, and increases as the ratio of the thickness of the permeable stratum to the dam width increases. Although the flux decreases with increasing piling depth, a large portion of the flux will in general persist until the piling penetrates to the very bottom of the permeable stratum. The same is true with regard to the penetration of coffer dams. The pressure distribution at the base of dams of finite width resting upon permeable strata is found to be only slightly different from that with infinitely thick underlying beds, except when the thickness of the permeable stratum is appreciably smaller than the width of the dam.
Design of Tuned Resistance-Capacity Coupled Amplifiers
Authors: Johnson E. A.
Published: December 2004

The behavior of resistance-capacity coupled amplifiers is studied with regard to their behavior as resonant networks. Expressions are obtained for the optimum value of circuit constants and the design procedure developed. Tuning at one cycle per second has been successfully applied to low noise amplifiers.
Low Pressure Arc Characteristics
Authors: Cobine J. D.
Published: December 2004

The results of an oscillographic study of the short a.c. arc between pure graphite electrodes show that the reignition potential is a linear function of the gas pressure for air, N2, O2, and CO2. The relation is expressed by Vr=A+Bp. The constant A follows the minimum sparking potential of the gas, increases with the rate of rise of the impressed voltage, and is independent of the arc current, except for CO2. The constant B depends on the gas, arc current, and rate of rise of impressed voltage. The reignition potential is closely related to the glow discharge and is shown to approach the sparking potential of the gas as the r.m.s. value of the current approaches zero. The factors that affect reignition are indicated, and a reasonable mechanism of the phenomenon is stated.
The Thermal Stress in a Strip Due to Variation of Temperature Along the Length and Through the Thickness
Authors: Goodier J. N.
Published: December 2004

The thermal stress developed by unequal heating of a flat strip is investigated, the temperature varying along the length and through the thickness, but not across the width. The problem is reduced to one of edge tractions only, for which general solutions are already known. From the properties of these solutions it is shown that for heating local to a narrow transverse band across the width, as might occur in welding processes, there is a concentration of stress near the edge of the strip, at the hottest part, and a maximum tensile stress of magnitude EαTmax., when the temperature is constant through the thickness. The corresponding quantity is found also for temperatures varying through the thickness. For steel EαTmax,= lim ··350Tmax, pounds per in.2, the temperature being measured in centigrade degrees above that of the cool parts of the strip, and this approaches the yield point of mild steel for a maximum temperature (rise) of the order of 150°C. For a given maximum temperature, the maximum stress is reduced by about 40 percent by keeping one face cold.
Variations of the Rigidity Modulus with Changes in Applied Stress
Authors: Francis Gladys M.
Published: December 2004

An attempt to determine by an interferometer method whether or not any variations occurred in the rigidity modulus similar to those which occurred in Young's modulus in D. K. Froman's experiment. Any variations of more than 0.1 of a fringe could readily be detected. No such variations occurred.
The Synthesis of Gear Tooth Curves
Authors: Beggs J. Stiles
Published: December 2004

This paper sets forth a method of arriving analytically at a pair of gear tooth curves which will fulfill certain prescribed conditions. The method may also be used to find a curve which will mesh with a given curve and produce a constant angular velocity ratio, e.g., the mating curve for a circular pin tooth.
Cathode Sputtering in Arc Discharges
Authors: Koller Lewis R.
Published: December 2004

A method is described for measuring the number of atoms of thorium sputtered from tungsten by positive ions of various velocities in the positive column of an arc discharge. The threshold for mercury ions is 35 volts. The number of atoms sputtered per positive ion in mercury vapor increases with increase in filament temperature and with decrease in arc current. The effectiveness of ions in sputtering thorium from tungsten is in the order neon, argon, mercury. Measurements of emission from a probe permit observations of the rate of loss of barium from an oxide coated cathode. The threshold for sputtering from a cold oxide coated filament by neon ions is approximately 45 volts. The material sputtered is not electrically charged. There is a difference in nature between the material evaporated and sputtered from an oxide coated cathode. The threshold for sputtering of barium from tungsten is 14 volts for argon ions and approximately the same for neon. The arc current to a coated cathode reduces the rate of loss of coating material under certain conditions.
Comparison of CBS-QB3, CBS-APNO, G2, and G3 thermochemical predictions with experiment for formation of ionic clusters of hydronium and hydroxide ions complexed with water
Authors: Pickard Frank C. , Pokon Emma K. , Liptak Matthew D. , Shields George C.
Published: December 2004

The GAUSSIAN 2, GAUSSIAN 3, complete basis set-QB3, and complete basis set-APNO methods have been used to calculate ΔH∘ and ΔG∘ values for ionic clusters of hydronium and hydroxide ions complexed with water. Results for the clusters H3O+(H2O)n and OH−(H2O)n, where n=1–4 are reported in this paper, and compared against experimental values contained in the National Institutes of Standards and Technology (NIST) database. Agreement with experiment is excellent for the three ab initio methods for formation of these clusters. The high accuracy of these methods makes them reliable for calculating energetics for the formation of ionic clusters containing water. In addition this allows them to serve as a valuable check on the accuracy of experimental data reported in the NIST database, and makes them useful tools for addressing unresolved issues in atmospheric chemistry.
Dynamics of unidirectional exciton migration to the molecular periphery in a photoexcited compact dendrimer
Authors: Nishioka Keita , Suzuki Masato
Published: December 2004

We have studied dynamical natures of electronic excited states in a compact series of phenylacetylene dendrimers. So as to clarify the mechanism of unidirectional migration of a photogenerated exciton in a compact dendrimer, we theoretically investigated the temporal behavior of the photogenerated exciton in the molecule by numerically solving the time-dependent Schrödinger equation for the electronic excited states. The structure of the dendrimers is optimized in the ground state, and it is fixed during the calculation of the exciton dynamics. The calculated results show that the exciton generated in the dendrimeric framework tends to migrate toward the outside of the molecule rather than the inside, and to itinerate around the periphery via the through-space interaction between the outer crowding benzene units. This is one of the intrinsic properties that originates from a highly branched treelike structure of the compact dendrimers.
Simulation studies of pore and domain formation in a phospholipid monolayer
Authors: Knecht Volker , Müller Michiel , Bonn Mischa , Marrink Siewert-Jan , Mark Alan E.
Published: December 2004

Despite extensive study the phase behavior of phospholipid monolayers at an air–water interface is still not fully understood. In particular recent vibrational sum-frequency generation (VSFG) spectra of DPPC monolayers as a function of area density show a sharp transition in the order of the lipid chains at 1.10 nm2/molecule. This is in a region where the lateral pressure as a function of area is effectively constant. We have investigated the nature of this transition by studying the phase behavior of DPPC monolayers as a function of area density using molecular-dynamics simulations. The changes in order within the monolayer as a function of area density correlate well with the experimental signal. At 0.58 nm2/molecule we observe the onset of lateral separation of highly ordered and disordered lipids, indicating the coexistence of a gel-like liquid condensed and a fluidlike liquid expanded phase. At 0.97 nm2/molecule the monolayer ruptures, marking the onset of the liquid–gas (G) coexistence region. This is much earlier than suggested by fluorescence microscopy results and implies that at the point of rupture, the initial pores have an equilibrium size smaller than ∼500 nm in diameter. The rupture of the monolayer leads to a sharp increase in the overall lipid order that explains the sharp transition observed in the VSFG measurements. VSFG measurements thus may represent a sensitive means to determine the onset of the liquid–gas (G) coexistence region for such systems.
Nondivergent classical response functions from uncertainty principle: Quasiperiodic systems
Authors: Kryvohuz Maksym , Cao Jianshu
Published: December 2004

Time-divergence in linear and nonlinear classical response functions can be removed by taking a phase-space average within the quantized uncertainty volume O(ℏn) around the microcanonical energy surface. For a quasiperiodic system, the replacement of the microcanonical distribution density in the classical response function with the quantized uniform distribution density results in agreement of quantum and classical expressions through Heisenberg’s correspondence principle: each matrix element 〈u|α(t)|v〉 corresponds to the (u−v)th Fourier component of α(t) evaluated along the classical trajectory with mean action (Ju+Jv)/2. Numerical calculations for one- and two-dimensional systems show good agreement between quantum and classical results. The generalization to the case of N degrees of freedom is made. Thus, phase-space averaging within the quantized uncertainty volume provides a useful way to establish the classical-quantum correspondence for the linear and nonlinear response functions of a quasiperiodic system.
Nonadiabatic photodissociation process using an optical near field
Authors: Kawazoe Tadashi , Kobayashi Kiyoshi , Takubo Satoru , Ohtsu Motoichi
Published: December 2004

We demonstrated the deposition of nanometric Zn dots using photodissociation with gas-phase diethylzinc and an optical near field under nonresonant conditions. To explain the experimental results, we proposed an exciton-phonon polariton model, and discuss the quantitative experimental dependence of the deposition rate on the optical power and photon energy based on photodissociation involving multiple-step excitation via molecular vibration modes. The physical basis of this process, which seems to violate the Franck-Condon principle, is the optically nonadiabatic excitation of the molecular vibration mode due to the steep spatial gradient of the optical near-field energy.
A Liouville equation for systems which exchange particles with reservoirs: Transport through a nanodevice
Authors: Ovchinnikov Igor V. , Neuhauser Daniel
Published: December 2004

A Redfield-like Liouville equation for an open system that couples to one or more leads and exchanges particles with them is derived. The equation is presented for a general case. A case study of time-dependent transport through a single quantum level for varying electrostatic and chemical potentials in the leads is presented. For the case of varying electrostatic potentials the proposed equation yields, for the model study, the results of an exact solution.
The isomers of HF–HCN formed in helium nanodroplets: Infrared spectroscopy and ab initio calculations
Authors: Douberly G. E. , Miller R. E.
Published: December 2004

Binary complexes containing hydrogen cyanide and hydrogen fluoride are formed in helium nanodroplets, and studied using high-resolution infrared laser spectroscopy. Rotationally resolved spectra are reported for the H–F and C–H stretches of the linear HCN–HF complex, a system that has been thoroughly studied in the gas phase. We report the high-resolution spectra of the higher energy, bent HF–HCN isomer, which is also formed in helium. Stark spectra are reported for both isomers, providing dipole moments of these complexes. The experimental results are compared with ab initio calculations, also reported here. Spectra are reported for several ternary complexes, including (HCN)2–HF, HCN–(HF)2, HF–(HCN)2, and HF–HCN–HF.
Distance measurements between paramagnetic centers and a planar object by matrix Mims electron nuclear double resonance
Authors: Zänker Paul-Philipp , Jeschke Gunnar , Goldfarb Daniella
Published: December 2004

Frequency-domain electron nuclear double resonance (ENDOR), two time-domain electron nuclear double resonance techniques, and electron spin echo envelope modulation spectroscopy are compared with respect to their merit in measurements of small hyperfine couplings to nuclei with intermediate gyromagnetic ratio such as P31. The frequency-domain Mims ENDOR experiment is found to provide the most faithful line shapes. In the limit of long electron-nuclear distances of more than 0.5 nm, sensitivity of this experiment is optimized by matching the first interpulse delay to the transverse relaxation time of the electron spins. In the same limit, Mims ENDOR efficiency scales inversely with the sixth power of distance. Hyperfine splittings as small as 33 kHz can be detected, corresponding to an electron-31P distance of 1 nm. In systems, where a certain kind of nuclei is distributed in a plane, measurements of intermolecular hyperfine couplings can be analyzed in terms of a distance of closest approach of a paramagnetic center to that plane. By applying this technique to spin-labeled lipids in a fully hydrated lipid bilayer it is found that for a fraction of lipids, chain tilt angles can be 25° larger than the mean tilt angle of the lipid chains. This model of all-trans hydrocarbon chains with a broad distribution of tilt angles is also consistent with orientation selection effects in high-field ENDOR spectra.
Influence of hydrodynamic coupling on the density dependence of quasi-one-dimensional diffusion
Authors: Xu Xinliang , Rice Stuart A.
Published: December 2004

The effect on the short time one particle diffusion coefficient of hydrodynamic interaction between pairs of colloid particles, and between colloid particles and the walls of a quasi-one-dimensional cylindrical channel, are calculated using the method of reflections. The nonzero size of the colloid particle is accounted for in the analysis, and the theoretical predictions are compared with the experimental data of Lin, Cui, Lee, and Yu for the short time one particle diffusion coefficient of colloids in a square open channel [Europhys. Lett. 57, 724 (2002)].
Improved implementation and application of the individually selecting configuration interaction method
Authors: Stampfuß P. , Wenzel W.
Published: December 2004

We report on the progress of our implementation of the configuration-selecting multireference configuration interaction method on massively parallel architectures with distributed memory, which now permits the treatment of Hilbert spaces of dimension O(1012). Of these about 50 000 000 can be selected in the variational subspace. We provide scaling data for the running time of the code for the IBM/SP3 and the CRAY-T3E. We present benchmark results for two selected applications: the energetics of the isomers of dinitrosoethylene and the benchmark results for the ring closure reaction of enediyene.
Polarizable continuum model study of solvent effects on electronic circular dichroism parameters
Authors: Pecul Magdalena , Marchesan Domenico , Ruud Kenneth , Coriani Sonia
Published: December 2004

We present an implementation of the polarizable continuum model for the calculation of solvent effects on electronic circular dichroism spectra. The computational model used is density functional theory in the length-gauge formulation, and gauge-origin independence is ensured through the use of London atomic orbitals. Results of calculations carried out for methyloxirane and bicyclic ketones, camphor, norcamphor, norbornenone, and fenchone are presented, and the theoretically obtained solvent effects are compared with experimental observations.
The determination of absolute anion formation cross sections from electron beam scattering data
Authors: Ziesel J.-P. , Jones N. C. , Field D. , Madsen L. B.
Published: December 2004

Using recent low energy electron scattering data for CCl4 and SF6, and accompanying theory illustrating the coupling of attachment and elastic scattering, absolute cross sections are derived for electron attachment to CCl4 and SF6 between impact energies, respectively, of 8–52 meV and 7–42 meV. Values of attachment cross sections are compared with those obtained by laser and threshold photoionization techniques, which include normalization to rate coefficient data. Excellent agreement with the latest CCl4 data is obtained, with less precise agreement for SF6, but still lying within experimental uncertainties.
Spectroscopic study of mutual solubilities of water and benzene at high temperatures and pressures
Authors: Jin Yusuke , Ikawa Shun-ichi
Published: December 2004

Near-infrared and ultraviolet absorption of water–benzene mixtures has been measured at temperatures and pressures in the ranges of 323–673 K and 50–400 bar, respectively. Concentrations of water and benzene in both the water-rich phase and the benzene-rich phase of the mixtures were obtained from absorption intensities of near-infrared bands of water and benzene and ultraviolet bands of benzene. Mutual solubilities in molar fractions increase remarkably with increasing temperature at pressures in the two-liquid-phase coexistence region, and are consistent with previously reported values. It proves that the solubility of benzene in water is an order of magnitude smaller than that of water in benzene throughout the two-phase region. In addition, it is found that effect of pressure on the solubilities is opposite between water in benzene and benzene in water. These solubility properties are discussed on the basis of a cavity-based solvation model. It is suggested that the asymmetry in the mutual solubility and the opposite direction of the pressure effect are caused by difference in molecular size and difference in thermal compressibility, respectively, between water and benzene.
High-resolution pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopic study of the two lowest electronic states of the ozone cation O3+
Authors: Willitsch S. , Innocenti F. , Dyke J. M. , Merkt F.
Published: December 2004

The pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectrum of jet-cooled O3 has been recorded in the range 101 000–104 000 cm−1. The origins of the X̃ 1A1→X̃+ 2A1 and X̃ 1A1→Ã+ 2B2 transitions could be determined from the rotational structure of the bands, the photoionization selection rules, the photoionization efficiency curve, and comparison with ab initio calculations. The first adiabatic ionization energy of O3 was measured to be 101 020.5(5) cm−1 [12.524 95(6) eV] and the energy difference between the X̃+ 2A1 (0,0,0) and Ã+ 2B2 (0,0,0) states was determined to be ΔT0=1089.7(4) cm−1. Whereas the X̃→X̃+ band consists of an intense and regular progression in the bending (ν2) mode observed up to v2+=4, only the origin of the X̃→Ã+ band was observed. The analysis of the rotational structure in each band led to the derivation of the r0 structure of O3+ in the X̃+ [C2v,r0=1.25(2) Å,α0=131.5(9)°] and Ã+[C2v,r0=1.37(5) Å,α0=111.3(38)°] states. The appearance of the spectrum, which is regular up to 102 300 cm−1, changes abruptly at ≈102 500 cm−1, a position above which the spectral density increases markedly and the rotational structure of the bands collapses. On the basis of ab initio calculations, this behavior is attributed to the onset of large-amplitude motions spreading through several local minima all the way to large internuclear distances. The ab initio calculations are consistent with earlier results in predicting a seam of conical intersections between the X̃+ and Ã+ states ≈2600 cm−1 above the cationic ground state and demonstrate the existence of potential minima at large internuclear distances that are connected to the main minima of the X̃+ and Ã+ states through low-lying barriers.
Towards the realization of the quantum chemistry approach to tunneling photoionization processes in strong laser fields
Authors: Mishima K. , Nagaya K. , Hayashi M. , Lin S. H.
Published: December 2004

Based on Keldysh’s theory, we investigate the possibility to use the molecular orbital theoretic approach for calculating the tunneling photoionization rates of molecules. As a demonstration, we concentrate on the 1s state of the hydrogen atom as the initial state.
Phase transformation of methane hydrate under high pressure
Authors: Sun Qiang , Duan Ti-Yu , Zheng Hai-Fei , Ji Jian-Qing , Wu Xiang-Yang
Published: December 2004

In situ Raman spectroscopy is employed to study the phase behavior of methane hydrate at high pressure. The structure 1 of methane hydrate can be maintained up to 950 MPa at 299 K. The transformation of structure I↔structure H+water+CH4 occurs at 880 MPa and 323 K. The structure H of methane hydrate, however, decomposes to methane and water at 960 MPa and 348 K. The initiation mechanism of methane hydrate sI is also discussed.
A novel orientation-dependent potential model for prolate mesogens
Authors: Martı́nez-Haya B. , Cuetos A. , Lago S. , Rull L. F.
Published: December 2004

An intermolecular potential is introduced for the study of molecular mesogenic fluids. The model combines distinct features of the well-known Gay-Berne and Kihara potentials by incorporating dispersive interactions dependent on the relative pair orientation to a spherocylinder molecular core. Results of a Monte Carlo simulation study focused on the liquid crystal phases exhibited by the model fluid are presented. For the chosen potential parameters, molecular aspect ratio L*=5 and temperatures T*=2, 3, and 5, isotropic, nematic, smectic-A, and hexatic phases are found. The location of the phase boundaries as well as the equation of state of the fluid and further thermodynamical and structural parameters are discussed and contrasted to the Kihara fluid. In comparison to this latter fluid, the model induces the formation of ordered liquid crystalline phases at lower packing fractions and it favors, in particular, the appearance of layered hexatic ordering as a consequence of the greater attractive interaction assigned to the parallel side-to-side molecular pair configurations. The results contribute to the evaluation of the role of specific interaction energies in the mesogenic behavior of prolate molecular liquids in dense environments.
Water mobility in heterogeneous emulsions determined by a new combination of confocal laser scanning microscopy, image analysis, nuclear magnetic resonance diffusometry, and finite element method simulation
Authors: Lorén N. , Hagslätt H. , Nydén M. , Hermansson A.-M.
Published: December 2004

Nuclear magnetic resonance (NMR) diffusometry and confocal laser scanning microscopy (CLSM) were combined in a quantitative way in finite element calculations of water propagation in CLSM images obtained from a very heterogeneous emulsion. The propagators calculated on the basis of microstructure were Fourier transformed and subsequently compared with the echo decays obtained by the NMR diffusometry method. The results showed very good agreement between microstructure based calculations and experiments, indicating that the short gradient pulse approximation in the NMR diffusometry experiment holds for a certain q range. Furthermore, the CLSM was able to achieve a relevant two-dimensional microstructure although some discrepancy at low q values was noted. This effect is attributed to the inherent three-dimensional connectivity between the water domains in this type of structures, making the calculations slightly underestimate the water diffusion at longer distances.
Slow dynamics of thin nematic films in the presence of adsorbed nanoparticles
Authors: Grollau S. , Guzmán O. , Abbott N. L. , de Pablo J. J.
Published: December 2004

Recent experiments indicate that liquid crystals can be used to optically report the presence of biomolecules adsorbed at solid surfaces. In this work, numerical simulations are used to investigate the effects of biological molecules, modeled as spherical particles, on the structure and dynamics of nematic ordering. In the absence of adsorbed particles, a nematic in contact with a substrate adopts a uniform orientational order, imposed by the boundary conditions at this surface. It is found that the relaxation to this uniform state is slowed down by the presence of a small number of adsorbed particles. However, beyond a critical concentration of adsorbed particles, the liquid crystal ceases to exhibit uniform orientational order at long times. At this concentration, the domain growth is characterized by a first regime where the average nematic domain size LD obeys the scaling law LD(t)∼t1/2; at long times, a slow dynamics regime is attained for which LD tends to a finite value corresponding to a metastable state with a disordered texture. The results of simulations are consistent with experimental observations.