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Abstract
We present the formulation, simulations, and results for multicomponent mutual diffusion coefficients in the warm, dense matter regime. While binary mixtures have received considerable attention for mass transport, far fewer studies have addressed ternary and more complex systems. We therefore explicitly examine ternary systems utilizing the Maxwell-Stefan formulation that relates diffusion to gradients in the chemical potential. Onsager coefficients then connect the macroscopic diffusion to microscopic particle motions, evinced in trajectories characterized by positions and velocities, through various autocorrelation functions (ACFs). These trajectories are generated by molecular dynamics (MD) simulations either through the Born-Oppenheimer approximation, which treats the ions classically and the electrons quantum-mechanically by an orbital-free density-functional theory, or through a classical MD approach with Yukawa pair-potentials, whose effective ionizations and electron screening length derive from quantal considerations. We employ the reference-mean form of the ACFs and determine the center-of-mass coefficients through a simple reference-frame-dependent similarity transformation. The Onsager terms in turn determine the mutual diffusion coefficients. We examine a representative sample of ternary mixtures as a function of density and temperature from those with only light elements (D-Li-C, D-Li-Al) to those with highly asymmetric mass components (D-Li-Cu, D-Li-Ag, H-C-Ag). We also follow trends in the diffusion as a function of number concentration and evaluated the efficacy of various approximations such as the Darken approximation.
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Affiliation(s)
- A J White
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C Ticknor
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - E R Meyer
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - J D Kress
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - L A Collins
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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2
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Baillie D, Bisset RN, Ticknor C, Blakie PB. Number fluctuations of a dipolar condensate: anisotropy and slow approach to the thermodynamic regime. Phys Rev Lett 2014; 113:265301. [PMID: 25615347 DOI: 10.1103/physrevlett.113.265301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Indexed: 06/04/2023]
Abstract
We present a theory for the number fluctuations of a quasi-two-dimensional (quasi-2D) dipolar Bose-Einstein condensate measured with finite resolution cells. We show that when the dipoles are tilted to have a component parallel to the plane of the trap, the number fluctuations become anisotropic, i.e., depend on the in-plane orientation of the measurement cell. We develop analytic results for the quantum and thermal fluctuations applicable to the cell sizes accessible in experiments. We show that as cell size is increased the thermodynamic fluctuation result is approached much more slowly than in condensates with short range interactions, so experiments would not require high numerical aperture imaging to observe the predicted effect.
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Affiliation(s)
- D Baillie
- Jack Dodd Centre for Quantum Technology, Department of Physics, University of Otago, Dunedin 9016, New Zealand
| | - R N Bisset
- Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - C Ticknor
- Center for Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - P B Blakie
- Jack Dodd Centre for Quantum Technology, Department of Physics, University of Otago, Dunedin 9016, New Zealand
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3
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Ticknor C, Herring SD, Lambert F, Collins LA, Kress JD. First principles nonequilibrium plasma mixing. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 89:013108. [PMID: 24580347 DOI: 10.1103/physreve.89.013108] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Indexed: 06/03/2023]
Abstract
We have performed nonequilibrium classical and quantum-mechanical molecular dynamics simulations that follow the interpenetration of deuterium-tritium (DT) and carbon (C) components through an interface initially in hydrostatic and thermal equilibrium. We concentrate on the warm, dense matter regime with initial densities of 2.5-5.5 g/cm3 and temperatures from 10 to 100 eV. The classical treatment employs a Yukawa pair-potential with the parameters adjusted to the plasma conditions, and the quantum treatment rests on an orbital-free density functional theory at the Thomas-Fermi-Dirac level. For times greater than about a picosecond, the component concentrations evolve in accordance with Fick's law for a classically diffusing fluid with the motion, though, described by the mutual diffusion coefficient of the mixed system rather than the self-diffusion of the individual components. For shorter times, microscopic processes control the clearly non-Fickian dynamics and require a detailed representation of the electron probability density in space and time.
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Affiliation(s)
- C Ticknor
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - S D Herring
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - F Lambert
- CEA, DAM, DIF, F-91297 Arpajon, France
| | - L A Collins
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - J D Kress
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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4
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Burakovsky L, Ticknor C, Kress JD, Collins LA, Lambert F. Transport properties of lithium hydride at extreme conditions from orbital-free molecular dynamics. Phys Rev E Stat Nonlin Soft Matter Phys 2013; 87:023104. [PMID: 23496628 DOI: 10.1103/physreve.87.023104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 11/26/2012] [Indexed: 06/01/2023]
Abstract
We have performed a systematic study of lithium hydride (LiH), using orbital-free molecular dynamics, with a focus on mass transport properties such as diffusion and viscosity by extending our previous studies at the lower end of the warm, dense matter regime to cover a span of densities from ambient to 10-fold compressed and temperatures from 10 eV to 10 keV. We determine analytic formulas for self- and mutual-diffusion coefficients, and viscosity, which are in excellent agreement with our molecular dynamics results, and interpolate smoothly between liquid and dense plasma regimes. In addition, we find the orbital-free calculations begin to agree with the Brinzinskii-Landau formula above about 250 eV at which point the medium becomes fully ionized. A binary-ion model based on a bare Coulomb interaction within a neutralizing background with the effective charges determined from a regularization prescription shows good agreement above about 100 eV with the orbital-free results. Finally, we demonstrate the validity of a pressure-based mixing rule in determining the transport properties from the pure-species quantities.
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Affiliation(s)
- L Burakovsky
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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5
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Feist J, Nagele S, Ticknor C, Schneider BI, Collins LA, Burgdörfer J. Attosecond two-photon interferometry for doubly excited states of helium. Phys Rev Lett 2011; 107:093005. [PMID: 21929238 DOI: 10.1103/physrevlett.107.093005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Indexed: 05/31/2023]
Abstract
We show that the correlation dynamics in coherently excited doubly excited resonances of helium can be followed in real time by two-photon interferometry. This approach promises to map the evolution of the two-electron wave packet onto experimentally easily accessible noncoincident single-electron spectra. We analyze the interferometric signal in terms of a semianalytical model which is validated by a numerical solution of the time-dependent two-electron Schrödinger equation in its full dimensionality.
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Affiliation(s)
- J Feist
- ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA.
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6
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Blakie PB, Ticknor C, Bradley AS, Martin AM, Davis MJ, Kawaguchi Y. Numerical method for evolving the dipolar projected Gross-Pitaevskii equation. Phys Rev E Stat Nonlin Soft Matter Phys 2009; 80:016703. [PMID: 19658834 DOI: 10.1103/physreve.80.016703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Indexed: 05/28/2023]
Abstract
We describe a method for evolving the projected Gross-Pitaevskii equation (PGPE) for an interacting Bose gas in a harmonic-oscillator potential, with the inclusion of a long-range dipolar interaction. The central difficulty in solving this equation is the requirement that the field is restricted to a small set of prescribed modes that constitute the low-energy c -field region of the system. We present a scheme, using a Hermite-polynomial-based spectral representation, which precisely implements this mode restriction and allows an efficient and accurate solution of the dipolar PGPE. We introduce a set of auxiliary oscillator states to perform a Fourier transform necessary to evaluate the dipolar interaction in reciprocal space. We extensively characterize the accuracy of our approach and derive Ehrenfest equations for the evolution of the angular momentum.
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Affiliation(s)
- P B Blakie
- Department of Physics, Jack Dodd Centre for Quantum Technology, University of Otago, Dunedin 9016, New Zealand
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7
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Davis JA, Dao LV, Wen X, Ticknor C, Hannaford P, Coleman VA, Tan HH, Jagadish C, Koike K, Sasa S, Inoue M, Yano M. Suppression of the internal electric field effects in ZnO/Zn(0.7)Mg(0.3)O quantum wells by ion-implantation induced intermixing. Nanotechnology 2008; 19:055205. [PMID: 21817603 DOI: 10.1088/0957-4484/19/05/055205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Strong suppression of the effects caused by the internal electric field in ZnO/ZnMgO quantum wells following ion-implantation and rapid thermal annealing, is revealed by photoluminescence, time-resolved photoluminescence, and band structure calculations. The implantation and annealing induces Zn/Mg intermixing, resulting in graded quantum well interfaces. This reduces the quantum-confined Stark shift and increases electron-hole wavefunction overlap, which significantly reduces the exciton lifetime and increases the oscillator strength.
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Affiliation(s)
- J A Davis
- Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Melbourne 3122, Australia
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8
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Inouye S, Goldwin J, Olsen ML, Ticknor C, Bohn JL, Jin DS. Observation of heteronuclear Feshbach resonances in a mixture of bosons and fermions. Phys Rev Lett 2004; 93:183201. [PMID: 15525160 DOI: 10.1103/physrevlett.93.183201] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2004] [Indexed: 05/24/2023]
Abstract
Three magnetic-field induced heteronuclear Feshbach resonances were identified in collisions between bosonic 87Rb and fermionic 40K atoms in their absolute ground states. Strong inelastic loss from an optically trapped mixture was observed at the resonance positions of 492, 512, and 543+/-2 G. The magnetic-field locations of these resonances place a tight constraint on the triplet and singlet cross-species scattering lengths, yielding (-281+/-15)a(0) and (-54+/-12)a(0), respectively. The width of the loss feature at 543 G is 3.7+/-1.5 G wide; this broad Feshbach resonance should enable experimental control of the interspecies interactions.
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Affiliation(s)
- S Inouye
- JILA, National Institute of Standards and Technology, and University of Colorado, Boulder, CO 80309, USA
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9
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Greiner M, Regal CA, Ticknor C, Bohn JL, Jin DS. Detection of spatial correlations in an ultracold gas of fermions. Phys Rev Lett 2004; 92:150405. [PMID: 15169273 DOI: 10.1103/physrevlett.92.150405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2003] [Indexed: 05/24/2023]
Abstract
Spatial correlations are observed in an ultracold gas of fermionic atoms close to a Feshbach resonance. The correlations are detected by inducing spin-changing rf transitions between pairs of atoms. We observe the process in the strongly interacting regime for attractive as well as for repulsive atom-atom interactions and both in the regime of high and low quantum degeneracy. The observations are compared with a two-particle model that provides theoretical predictions for the measured rf transition rates.
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Affiliation(s)
- M Greiner
- JILA, University of Colorado and National Institute of Standards and Technology, Department of Physics, Boulder, Colorado 80309-0440, USA.
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10
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Abstract
We have measured a p-wave Feshbach resonance in a single-component, ultracold Fermi gas of 40K atoms. We have used this resonance to enhance the normally suppressed p-wave collision cross section to values larger than the background s-wave cross section between 40K atoms in different spin states. In addition to the modification of two-body elastic processes, the resonance dramatically enhances three-body inelastic collisional loss.
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Affiliation(s)
- C A Regal
- JILA, National Institute of Standards and Technology, Boulder, Colorado 80309-0440, USA
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11
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Loftus T, Regal CA, Ticknor C, Bohn JL, Jin DS. Resonant control of elastic collisions in an optically trapped fermi gas of atoms. Phys Rev Lett 2002; 88:173201. [PMID: 12005753 DOI: 10.1103/physrevlett.88.173201] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2001] [Indexed: 05/23/2023]
Abstract
We have loaded an ultracold gas of fermionic atoms into a far-off resonance optical dipole trap and precisely controlled the spin composition of the trapped gas. We have measured a magnetic-field Feshbach resonance between atoms in the two lowest energy spin states, /9/2,-9/2> and /9/2,-7/2>. The resonance peaks at a magnetic field of 201.5+/-1.4 G and has a width of 8.0+/-1.1 G. Using this resonance, we have changed the elastic collision cross section in the gas by nearly 3 orders of magnitude.
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Affiliation(s)
- T Loftus
- JILA, National Institute of Standards and Technology, University of Colorado, Boulder, Colorado 80309, USA
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12
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You Y, Bergstrom R, Klemm M, Lederman B, Nelson H, Ticknor C, Jaenisch R, Schimenti J. Chromosomal deletion complexes in mice by radiation of embryonic stem cells. Nat Genet 1997; 15:285-8. [PMID: 9054943 DOI: 10.1038/ng0397-285] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Chromosomal deletions ("deficiencies') are powerful tools in the genetic analysis of complex genomes. They have been exploited extensively in Drosophila melanogaster, an organism in which deficiencies can be efficiently induced and selected. Spontaneous deletions in humans have facilitated the dissection of phenotypes in contiguous gene syndromes and led to the positional cloning of critical genes. In mice, deletion complexes created by whole animal irradiation experiments have enabled a systematic characterization of functional units along defined chromosomal regions. However, classical mutagenesis in mice is logistically impractical for generating deletion sets on a genome-wide scale. Here, we report a high-throughput method for generating radiation-induced deletion complexes at defined regions in the genome using ES cells. Dozens of deletions of up to several centiMorgans, encompassing a specific locus, can be created in a single experiment and transmitted through the germline. The ability to rapidly create deletion complexes along chromosomes will facilitate systematic functional analyses of the mammalian genome.
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Affiliation(s)
- Y You
- Jackson Laboratory, Bar Harbor, Maine 04609, USA
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13
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Abstract
The function of DNA methylation in higher plants was investigated by expression of a complementary DNA encoding a cytosine methyltransferase (MET1) from Arabidopsis thaliana as an antisense RNA in transgenic plants. This expression resulted in a 34 to 71 percent reduction in total genomic cytosine methylation. Loss of methylation was observed in both repetitive DNA and single-copy gene sequences. Developmental effects included altered heterochrony, changes in meristem identity and organ number, and female sterility. Cytosine demethylation prolonged both vegetative and reproductive phases of development. These findings implicate DNA methylation in establishing or maintaining epigenetic developmental states in the meristem.
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Affiliation(s)
- M J Ronemus
- Department of Biology, Yale University, New Haven, CT 06520-8104, USA
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14
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Abstract
Transmission ratio distortion (TRD) of mouse t haplotypes occurs through the interaction of multiple distorter loci with the t complex responder (Tcr) locus. Males heterozygous for a t haplotype will transmit the t-bearing chromosome to nearly all of their offspring. This process is mediated by the production of functionally inequivalent gametes: wild-type meiotic partners of t spermatozoa are rendered functionally inactive. The Tcr locus, which is required for TRD to occur, is thought to somehow protect its host spermatid from the sperm-inactivating effects of linked distorter genes (Lyon 1984). In previous work, Tcr was mapped to a small genetic interval in t haplotypes, and a candidate gene from this region was isolated (Tcp-10bt). In this work, we further localize Tcr to a 40-kb region that contains the 21-kb Tcp-10bt gene. A cloned genomic copy of Tcp-10bt was used to generate transgenic mice. The transgene was bred into a variety of genetic backgrounds to test for non-Mendelian segregation. Abberrant segregation was observed in some mice carrying either a complete t haplotype or a combination of certain partial t haplotypes. These observations, coupled with those of Snyder and colleagues (in this issue), provide genetic and functional evidence that the Tcp-10bt gene is Tcr. However, other genotypes that were predicted to produce distortion did not. The unexpected data from a variety of crosses in this work and those of our colleagues suggest that elements to the TRD system and the Tcr locus remain to be identified.
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Affiliation(s)
- D C Bullard
- Baylor College of Medicine, Institute for Molecular Genetics, Houston, Texas 77030
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15
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Abstract
Ninety-six patients requesting psychotherapy were studied prospectively at the time of screening interview by four senior psychiatrists using a variation on Luborsky's Helping Alliance questionnaire and the Osgood Semantic Differential. Significant differences were found at the time of screening between early dropouts and continuers, among screeners' rate of early dropouts, and among patients' perceptions of screeners. The screener with a high early dropout rate was seen as being more passive and less potent, and offering less new understanding than other screeners. Patients who dropped out early experienced a less strong helping alliance, felt they gained less new understanding, liked the clinician less well, felt less well liked and less respected, and saw the interviewer as more passive and psychotherapy as less potent than did continuers.
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Affiliation(s)
- P C Mohl
- University of Texas Health Science Center, San Antonio
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16
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Abstract
A systematic review of 414 terminated cases on a semiprivate psychotherapy service revealed that 16.7% of patients never began therapy despite being accepted after an extensive and lengthy screening process. This is lower than in previous studies. Except for ethnicity, comparison between the refusers and acceptors of 42 variables failed to replicate the correlations found in previous studies. In our sample, psychotherapy refusers were characterized by (1) having less family psychiatric history, (2) being more likely to elaborate their problems, (3) having less alcohol abuse history, (4) being less likely to be offered long-term individual therapy, and (5) having waited less time for their screening appointment. Such variables as age, gender, diagnosis, severity, income, and education were all nonsignificant. Although we offer some hypotheses for our significant correlations, we suspect that the interaction with the screener is more important than patient variables in determining acceptance of psychotherapy.
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Affiliation(s)
- P C Mohl
- Department of Psychiatry, University of Texas Health Science Center, San Antonio 78284
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Mohl PC, Martinez D, Matthews KL, Ticknor C, Appleby J. A psychotherapy service: preserving a place for psychodynamic teaching. Acad Psychiatry 1989; 13:48-51. [PMID: 24442977 DOI: 10.1007/bf03341841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Striving for an educational balance between psychodynamics and psychotherapy led to the creation of a Psychotherapy Service. Psychodynamic teaching was preserved while biological teaching was increased. The history, philosophy, and structure of this service, combined with a chart review, give a picture of the kind of clinical experience and training available on such a service.
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Affiliation(s)
- P C Mohl
- Department of Psychiatry, University of Texas Health Sciences Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, Texas, 78284, USA
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