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PubMed2001

Nurses' use of professional distancing in the appropriation of CAM: a text analysis.

Despite the depth of interest in complementary and alternative medicines (CAM) within the nursing community, the intersection between nurses, nursing and CAM has largely avoided sociological analysis. This paper presents findings from one part of an ongoing exploratory study of how nurses present and interpret the apparent affinity of their profession with CAM. A text analysis of papers published from within the nursing community on CAM was conducted. Within the broad area of professional identity, differentiation and development, two dominant themes emerged from the analysis. Firstly, the use of professional distancing to underpin the legitimacy of the nursing/CAM axis; and second, the potential offered by the relationship for a reconstruction of lines of professional authority. As one dimension of the way in which nursing's intersection with CAM is being constructed and perpetuated, the relationship with medicine appears to be of significance and requires further attention.

Attitude of Health Personnel↗

PubMed1999

[Calculating the localization and dimension of the real pupil in keratoconus with ray tracing of corneal topography data].

BACKGROUND: It is crucial to center surgical procedures for optical indications on the pupil or the optical axis of the eye. In keratoconus the pupil appears to be dislocated due to optical aberrations of corneal topography. The purpose of this study was to evaluate the real pupil structure from the virtual image using exact raytracing techniques. PATIENTS AND METHODS: Eighty-eight patients with keratoconus (46 with mild and 42 with severe clinical signs) and a control group of 40 normal subjects were included in this study. Topographic height data were calculated from refraction data of a commercially available topographer (TMS-1) using a local approximation algorithm and a convex surface was modelled using a subdivision scheme. For the posterior corneal surface we postulated an aspherical surface with a central radius of curvature of 6.5 mm using Navarro's model eye. At the virtual pupil outline a bundle of parallel rays were intersected with the anterior and posterior corneal surface and refracted into the anterior chamber. The intersections of these rays with the pupil plane was defined as the real pupil outline. We assessed the amount and direction of pupil dislocation, the ratio between the virtual and real pupil size for each group and correlated these parameters with the central corneal power. RESULTS: The size of the virtual pupil exceeded the reference value of the real pupil in the normal group by 11%, in the group with mild keratoconus by 19% and in the group with severe keratoconus by 35%. The center of the virtual pupil was decentered 0.06 mm in the normal group, 0.49 in the group with mild keratoconus and 1.24 mm in the group with severe keratoconus. Whereas the direction of decentration was randomly in the normal group, we measured a preferred decentration to the inferior quadrants in mild keratoconus and a systematic decentration to the temporal inferior quadrant in severe keratoconus. Correlation of the optical dislocation did not correlate with central corneal power in any group. CONCLUSIONS: In keratoconic eyes the pupil outline is distorted and dislocated due to optical aberrations of the cornea. Exact raytracing technique allows the calculation of the real pupil outline from the virtual image and the topographic height of both corneal surfaces. Knowledge about the real pupil position may have an impact on adequate centration of keratorefractive surgery and penetrating keratoplasty.

Adult↗

PubMedDate not supplied

[Effect of the Hoffa fat pad on revascularization of the ruptured anterior cruciate ligament. A histologic study of the rabbit model].

After intersection of anterior cruciate ligament both ends were stitched together again. In group A the ligament was surrounded by a flap of fat pad, whereas in control group B the intersected ligament just was sutured. Postoperative the leg was immobilised by cast from 4 to 8 weeks. After that time intraarterial injection by Romeis method was performed, the bone-ligament-bone block was fixed in paraffine and the histological investigation followed. All ligament blocks of group A (n12) showed an intact anterior cruciate surrounded by well vascularized soft tissue which has been transformed from the fat pad. Ligaments of group B did not heal and where regressive changed.

Adipose Tissue↗

PubMed2003

Itinerant memory dynamics and global bifurcations in chaotic neural networks.

We have considered itinerant memory dynamics in a chaotic neural network composed of four chaotic neurons with synaptic connections determined by two orthogonal stored patterns as a simple example of a chaotic itinerant phenomenon in dynamical associative memory. We have analyzed a mechanism of generating the itinerant memory dynamics with respect to intersection of a pair of alpha branches of periodic points and collapse of a periodic in-phase attracting set. The intersection of invariant sets is numerically verified by a novel method proposed in this paper.

Algorithms↗

PubMed2004

On the peculiarities of the diabatic framework: new insight.

In this article we consider the electronic diabatic presentation of a two-state system with the aim of earning insight regarding the distribution of conical intersections in a given region. In this process we revealed explicit relationship between the diabatic potentials and the locations of conical intersections. The study is accompanied with numerical examples as worked out for a model and ab initio potential energy surfaces of the Na+H2 system.

Journal Article↗

PubMed2004

Derivation of the electronic nonadiabatic coupling field in molecular systems: an algebraic-vectorial approach.

In this Communication it is suggested that various elements of the nonadiabatic coupling matrix, tau(jk)(s) are created by the singular nonadiabatic coupling terms of the system. Moreover, given the spatial distribution of these coupling terms in the close vicinity of their singularity points yields, according to this approach, the integrated intensity of the field at every point in the region of interest. To support these statements we consider the conical intersections of the three lower states of the H+H(2) system: From an ab initio treatment we obtain the nonadiabatic coupling terms around each conical intersection separately (at its close vicinity) and having those, create the field at every desired point employing vector-algebra. This approach is also used to calculate the intensity of the Curl of those matrix elements that lack their own sources [tau(13)(s) in the present case]. The final results are compared with relevant ab initio calculations.

Journal Article↗

PubMed2004

A time-dependent wave packet study of the vibronic and spin-orbit interactions in the dynamics of Cl((2)P)+H(2)-->HCl(X (1)Sigma(g) (+))+H((2)S) reaction.

We investigate the vibronic and spin-orbit (SO) coupling effects in the state-selected dynamics of the title reaction with the aid of a time-dependent wave packet approach. The ab initio potential energy surfaces of Capecchi and Werner [Science 296, 715 (2002)] have been employed for this purpose. Collinear approach of the Cl((2)P) atom to the H(2) molecule splits the degeneracy of the (2)P state and gives rise to (2)Sigma and (2)Pi electronic states. These two surfaces form a conical intersection at this geometry. These states transform as 1 (2)A('), 1 (2)A("), and 2 (2)A('), respectively, at the nonlinear configurations of the nuclei. In addition, the SO interaction due to Cl atom further splits these states into (2)Sigma(1/2), (2)Pi(3/2), and (2)Pi(1/2) components at the linear geometry. The ground-state reagent Cl((2)P(3/2))+H(2) correlates with (2)Sigma(1/2) and (2)Pi(3/2), where as the SO excited reagent Cl(*)((2)P(1/2))+H(2) correlates with (2)Pi(1/2) at the linear geometry. In order to elucidate the impact of the vibronic and SO coupling effects on the initial state-selected reactivity of these electronic states we carry out quantum scattering calculations based on a flux operator formalism and a time-dependent wave packet approach. In this work, total reaction probabilities and the time dependence of electronic population of the system by initiating the reaction on each of the above electronic states are presented. The role of conical intersection alone on the reaction dynamics is investigated with a coupled two-state model and for the total angular momentum J=0 (neglecting the electronic orbital angular momentum) both in a diabatic as well as in the adiabatic electronic representation. The SO interaction is then included and the dynamics is studied with a coupled three-state model comprising six diabatic surfaces for the total angular momentum J=0.5 neglecting the Coriolis Coupling terms of the Hamiltonian. Companion calculations are carried out for the uncoupled adiabatic and diabatic surfaces in order to explicitly reveal the impact of two different surface coupling mechanisms in the dynamics of this prototypical reaction.

Journal Article↗

PubMed2004

Ab initio calculations and vibrational energy level fits for the lower singlet potential-energy surfaces of C3.

Ab initio multireference configuration interaction potential energy surfaces are computed for the eight lowest singlet surfaces of C(3). These reveal several important features, including several conical intersections in linear, nonlinear, and equilateral triangle geometries. These intersections are important because, particularly for the excited A (1)Pi(u) state, reasonable ab initio results could only be obtained by including nearby, near degenerate, (1)Sigma(u) (-) and (1)Delta(u) states that cross the A (1)Pi(u) state around 4500 cm(-1) above the equilibrium geometry, and a (1)Pi(g) state whose potential in turn crosses the other states about 2000 cm(-1) further up. These states are probably responsible for the complexity of the shorter wavelength UV absorption spectrum of C(3). The computed potential energy surface for the ground, X (1)Sigma(g) (+), state and for the lowest two excited singlet surfaces (which both correlate with the A (1)Pi(u) state in a collinear geometry) are fitted to analytic functional forms. Vibrational energy levels are calculated for both states, taking account of the Renner-Teller coupling in the excited A (1)Pi(u) state. The potential parameters for both states are then least-squares fitted to experimental data. The ground-state fit covers a range of approximately 8500 cm(-1) above the lowest level, and reproduces 100 observed vibrational levels with an average error of 2.8 cm(-1). The A (1)Pi(u) state surfaces cover a range of 3250 cm(-1) above the zero-point level, and reproduce the 44 observed levels in this range with an average error of 2.8 cm(-1).

Journal Article↗

PubMed2004

Photochemistry of ethylene: a multireference configuration interaction investigation of the excited-state energy surfaces.

Multireference configuration interaction with singles and doubles (MR-CISD) calculations have been performed for the optimization of conical intersections and stationary points on the ethylene excited-state energy surfaces using recently developed methods for the computation of analytic gradients and nonadiabatic coupling terms. Basis set dependence and the effect of various choices of reference spaces for the MR-CISD calculations have been investigated. The crossing seam between the S0 and S1 states has been explored in detail. This seam connects all conical intersections presently known for ethylene. Major emphasis has been laid on the hydrogen-migration path. Starting in the V state of twisted-orthogonal ethylene, a barrierless path to ethylidene was found. The feasibility of ethylidene formation will be important for the explanation of the relative yield of cis and trans H2 elimination.

Journal Article↗

PubMed2004

A study of the adiabatic connection for two-electron systems.

Some aspects of the adiabatic connection method are studied for two-particle spherically symmetric systems. Ground-state wave functions that are constrained by means of a set of moments to have the same density as a corresponding fully interacting system are obtained for noninteracting or partially interacting systems. Local one-body potentials that support these constrained wave functions are generated using a simple method. We examine an interacting two-particle system with a parameter-dependent one-body potential, which for a particular value of that parameter exhibits an intersection between the (3)S and the (3)P states, whereas the 2s and 2p eigenvalues of the corresponding Kohn-Sham potentials do not intersect along with the total energies. These results show that there do exist cases where occupying the orbitals from below in energy may not lead to the ground state, and that the inherent assumptions behind the adiabatic connection can sometimes be violated.

Journal Article↗

PubMed2005

Cyclic-N3. II. Significant geometric phase effects in the vibrational spectra.

An accurate theoretical prediction of the vibrational spectra for a pure nitrogen ring (cyclic-N(3)) molecule is obtained up to the energy of the (2)A(2)/(2)B(1) conical intersection. A coupled-channel approach using the hyperspherical coordinates and the recently published ab initio potential energy surface [D. Babikov, P. Zhang, and K. Morokuma, J. Chem. Phys. 121, 6743 (2004)] is employed. Two independent sets of calculations are reported: In the first set, the standard Born-Oppenheimer approximation is used and the geometric phase effects are totally neglected. In the second set, the generalized Born-Oppenhimer approximation is used and the geometric phase effects due to the D(3h) conical intersection are accurately treated. All vibrational states are analyzed and assigned in terms of the normal vibration mode quantum numbers. The magnitude of the geometric phase effect is determined for each state. One important finding is an unusually large magnitude of the geometric phase effects in the cyclic-N(3): it is approximately 100 cm(-1) for the low-lying vibrational states and exceeds 600 cm(-1) for several upper states. On average, this is almost two orders of magnitude larger than in the previously reported studies. This unique example suggests a favorable path to experimental validation.

Journal Article↗

PubMed2005

Statistical and nonstatistical nonadiabatic photodissociation from the first excited state of the hydroxymethyl radical.

Photodissociation of hydroxymethyl (H(2)COD) from the first excited state, a Rydberg 3s state, can produce either H+HCOD or H(2)CO+D. These processes involve a seam of conical intersections. An analysis of the seam is reported based on a pointwise determination of the three gradient vectors that characterize a conical intersection: the energy difference gradient and the coupling gradient, which span the branching space, and the gradient of the average energy. These data are used to understand why H, but not D is produced at energies near threshold, the difference in the recoil anisotropy for H and D dissociation, and whether H or D will be produced impulsively or after formation of an intermediate complex.

Journal Article↗

PubMed2005

A new pathway for the rapid decay of electronically excited adenine.

Combined density functional and multireference configuration interaction methods have been used to calculate the electronic spectrum of 9H-adenine, the most stable tautomer of 6-aminopurine. In addition, constrained minimum energy paths on excited potential energy hypersurfaces have been determined along several relaxation coordinates. The minimum of the first (1)[n-->pi*] state has been located at an energy of 4.54 eV for a nuclear arrangement in which the amino group is pyramidal whereas the ring system remains planar. Close by, another minimum on the S(1) potential energy hypersurface has been detected in which the C(2) center is deflected out of the molecular plane and the electronic character of S(1) corresponds to a nearly equal mixture of (1)[pi-->pi*] and (1)[n-->pi*] configurations. The adiabatic excitation energy of this minimum amounts to 4.47 eV. Vertical and adiabatic excitation energies of the lowest n-->pi* and pi-->pi* transitions as well as transition moments and their directions are in very good agreement with experimental data and lend confidence to the present quantum chemical treatment. On the S(1) potential energy hypersurface, an energetically favorable path from the singlet n-->pi* minimum toward a conical intersection with the electronic ground state has been identified. Close to the conical intersection, the six-membered ring of adenine is strongly puckered and the electronic structure of the S(1) state corresponds to a pi-->pi* excitation. The energetic accessibility of this relaxation path at about 0.1 eV above the singlet n-->pi* minimum is presumably responsible for the ultrafast decay of 9H-adenine after photoexcitation and explains why sharp vibronic peaks can only be observed in a rather narrow wavelength range above the origin. The detected mechanism should be equally applicable to adenosine and 9-methyladenine because it involves primarily geometry changes in the six-membered ring whereas the nuclear arrangement of the five-membered ring (including the N(9) center) is largely preserved.

Journal Article↗

PubMed2006

Multistate multimode vibronic dynamics: entanglement of electronic and vibrational degrees of freedom in the benzene radical cation.

An earlier theoretical treatment of multimode and multistate vibronic coupling in the benzene radical cation [Koppel et al., J. Chem. Phys. 117, 2657 (2002)] is extended to investigate also the behavior of the nuclear degrees of freedom and to include additional electronic states. The five lowest doublet electronic states are considered which have been shown earlier to be all interconnected through a series of conical intersections of their potential-energy surfaces. In the most extensive calculations, they are all included simultaneously in the quantum dynamical calculations performed, which represent a system of unprecedented complexity treated in this way. The results are compared with various reduced-dimensionality treatments (i.e., employing reduced vibrational and electronic function spaces). The different temporal behavior of the various electronic populations is emphasized and traced to the different locations of the various seams of conical intersections: due to the coherent oscillations of the time-dependent wave packet this leads to an oscillatory behavior in some cases and to monotonous behavior in others. A seemingly irreversible behavior of the system dynamics in this strictly microscopic treatment is confirmed. The importance of this benchmark system to highlight complex, entangled multimode, and multistate vibronic dynamics is pointed out.

Journal Article↗

PubMed2006

Generalized trajectory surface hopping method based on the Zhu-Nakamura theory.

We present a generalized formulation of the trajectory surface hopping method applicable to a general multidimensional system. The method is based on the Zhu-Nakamura theory of a nonadiabatic transition and therefore includes the treatment of classically forbidden hops. The method uses a generalized recipe for the conservation of angular momentum after forbidden hops and an approximation for determining a nonadiabatic transition direction which is crucial when the coupling vector is unavailable. This method also eliminates the need for a rigorous location of the seam surface, thereby ensuring its applicability to a wide class of chemical systems. In a test calculation, we implement the method for the DH(2) (+) system, and it shows a remarkable agreement with the previous results of C. Zhu, H. Kamisaka, and H. Nakamura, [J. Chem. Phys. 116, 3234 (2002)]. We then apply it to a diatomic-in-molecule model system with a conical intersection, and the results compare well with exact quantum calculations. The successful application to the conical intersection system confirms the possibility of directly extending the present method to an arbitrary potential of general topology.

Journal Article↗

PubMed2006

Amplification of molecular traffic control in catalytic grains with novel channel topology design.

We investigate the conditions for reactivity enhancement of catalytic processes in porous solids by the use of molecular traffic control (MTC). With dynamic Monte-Carlo simulations and continuous-time master equation theory applied to the high concentration regime, we obtain a quantitative description of the MTC effect for a network of intersecting single-file channels in a wide range of grain parameters and for optimal external operating conditions. Implementing the concept of MTC in models with specially designed alternating bimodal channels, we find the efficiency ratio (compared with a topologically and structurally similar reference system without MTC) to be enhanced with increasing grain diameter, a property verified for the first time for a MTC system. Even for short intersection channels, MTC leads to a reactivity enhancement of up to approximately 65%. This suggests that MTC may significantly enhance the efficiency of a catalytic process for small as well as large porous particles with a suitably chosen binary channel topology.

Journal Article↗

PubMed2006

Photodissociation of methane: exploring potential energy surfaces.

The potential energy surface for the first excited singlet state (S(1)) of methane is explored using multireference singles and doubles configuration interaction calculations, employing a valence triple zeta basis set. A larger valence quadruple zeta basis is used to calculate the vertical excitation energy and dissociation energies. All stationary points found on the S(1) surface are saddle points and have imaginary frequencies for symmetry-breaking vibrations. By studying several two-dimensional cuts through the potential energy surfaces, it is argued that CH(4) in the S(1) state will distort to planar structures. Several conical intersection seams between the ground state surface S(0) and the S(1) surface have been identified at planar geometries. The conical intersections provide electronically nonadiabatic pathways towards products CH(3)((approximately)X (2)A"(2))+H, CH(2)((approximately)a (1)A(1))+H(2), or CH(2)((approximately)X (3)B(1))+H+H. The present results thereby make it plausible that the CH(3)((approximately)X (2)A"(2))+H and CH(2)((approximately)a (1)A(1))+H(2) channels are major dissociation channels, as has been observed experimentally.

Journal Article↗

PubMed2006

Towards a highly efficient theoretical treatment of Jahn-Teller effects in molecular spectra: the 1 2A and 2 2A electronic states of the ethoxy radical.

Nonadiabatic effects in the two lowest electronic states of the ethoxy radical, the 1 (2)A and 2 (2)A states, are considered, using multireference configuration interaction (MRCI) wave functions comprised of over 15x10(6) configuration state functions. The lowest point on the seam of conical intersection is located. Using this point as the origin, a quasidiabatic Hamiltonian suitable for use in a multimode vibronic coupling treatment of the coupled 1 (2)A and 2 (2)A electronic states is determined. The Hamiltonian includes all contributions from all internal coordinates through second order in displacements from the origin and is comprised of over 500 parameters. By using the average energy gradient, the energy difference gradients, and the derivative couplings, all of which are obtained at little additional cost once the requisite eigenstates are known, the second order Hamiltonian is determined from MRCI calculations at only 35 nuclear configurations. This is essentially the same number of points required to obtain the frequencies for the ground state equilibrium structure using centered differences of gradients. The diabatic Hamiltonian provides a good description of the seam space, the (N(int)-2)-dimensional space of conical intersection points, continuously connected to the minimum energy crossing point, enabling, for the first time, an analysis of the changes in the branching plane induced by seam curvature in the full seam space. Comparing the diabatic representation and MRCI results we find a good agreement for the ground state equilibrium structure, R(eq)(1 (2)A), as well as the ground state energy and vertical excitation energy. In good agreement with the available experimental data are the ground state equilibrium structure and the excitation energy to the A (2)A state, predicted here to involve a cone state level. Agreement between the harmonic frequencies at R(eq)(1 (2)A) computed from the MRCI wave function and from the diabatic Hamiltonian is excellent for all but the three lowest energy normal modes where significant deviations are observed indicating the need for selected cubic and/or quartic terms. For the low-lying vibrational levels, the diabatic representation can be used to partition the normal modes into two groups, those that involve inter(diabatic) state coupling and those that are spectators as far as nonadiabatic effects are concerned. The spin-orbit coupling interaction is determined using the Breit-Pauli approximation and its incorporation into the diabatic Hamiltonian is discussed.

Journal Article↗