Interfragment Distance Research Articles

Quantitative evaluation of posterior talar subluxation in posterior malleolar fractures: A preliminary study

BackgroundsAlthough ankle posterior subluxation is one of the major mechanisms by which posterior malleolar fractures (PMF) contribute to a worse prognosis, there is no parameter to address it quantitatively. So, we suggest a method that can evaluate posterior talar subluxation quantitatively in PMF. MethodsWe retrospectively analyzed 37 patients with posterior malleolar fractures. The patients were divided into two groups: PMF without posterior talar subluxation (n = 18) and with posterior talar subluxation (n = 19). We measured the distance between the arc center of the talus and the anterior tibia (TAD), the percentage of articular involvement of the fracture fragment, the inter-fragment distance (IFD) and articular step-off. We analyzed significant differences and the correlations between the two groups for each index. The estimated area of the receiver operating characteristic (ROC) curve was calculated, and cutoff values were suggested to discriminate posterior talar subluxation. ResultsTAD, IFD, and articular step-off were significantly greater in patients with posterior talar subluxation. (TAD: 14.3 vs. 2.8 mm, p < 0.001, IFD: 7.8 vs. 4.0 mm, p < 0.001, articular step-off: 3.6 vs. 2.0 mm, p = 0.004). The ROC curve showed that TAD was most useful to determine cutoff values for posterior talar subluxation. The area under the curve for TAD was 1.000, and the appropriate cutoff value was 5 mm. When a TAD of > 5 mm was used as a threshold, a sensitivity of 100% and a specificity of 100% were achieved in determining the presence of posterior talar subluxation. Also, higher TAD was correlated with IFD and articular step-off. ConclusionsTAD can be a useful parameter for evaluating the posterior talar subluxation in PMF. It can reflect not only the degree of fracture displacement but also posterior talar subluxation quantitatively.

Potentials and limitations of Integra® flowable wound matrix seeded with adipose tissue-derived microvascular fragments.

Adipose tissue-derived microvascular fragments (ad-MVF) represent promising vascularisation units for bioengineered Integra® matrix wound dressing (MWD). However, due to the sheet-like structure with small pore sizes, the seeding of this matrix with ad-MVF is mainly limited to its surface. Integra® flowable wound matrix (FWM) may be suitable to achieve a more homogeneous distribution and, thus, improved vascularisation, because this gel-like matrix allows for the direct admixture of ad-MVF during sample preparation. To test this hypothesis, we seeded MWD and FWM with an identical number of ad-MVF and assessed their distribution and inter-fragment distance within both matrices. Moreover, ad-MVF-seeded MWD and FWM were implanted into full-thickness skin defects within mouse dorsal skinfold chambers to analyse their vascularisation, epithelialisation and tissue incorporation using intravital fluorescence microscopy, histology and immunohistochemistry. Seeded FWM exhibited a more homogeneous ad-MVF distribution, when compared to MWD. This resulted in a significantly increased inter-fragment distance, preventing the reassembly of ad-MVF into new microvascular networks. Accordingly, the vascularisation of FWM was diminished after implantation, as indicated by a reduced functional microvessel density and blood perfusion. This was associated with a decreased tissue incorporation and epithelialisation of the matrix, when compared to ad-MVF-seeded MWD. Hence, the use of FWM as a carrier system may require a tremendous amount of ad-MVF to shorten their inter-fragment distance and, thus, to maintain their vascularisation capacity for tissue engineering applications.

Does Land Fragmentation Increase the Cost of Cultivation? Evidence from India

To appreciate overall impacts of fragmentation, underlying channels, and potential heterogeneity by holding size, we distinguish average fragment size and mean inter-fragment distance as two aspects of this phenomenon. Estimating a cost function with associated input demand equations on a large nationally representative Indian survey, robust to endogeneity, suggests that fragmentation’s main impact is to reduce mean plot size below the threshold for mechanisation. Higher inter-fragment distances increase costs for larger holdings, but by a much smaller magnitude. Implications as to when programmes to consolidate holdings may make sense and ways to ensure their sustainability are discussed.

Effect of breakup and transfer on complete and incomplete fusion in6Li+209Bi reaction in multi-body classical molecular dynamics calculation

The effect of breakup and transfer in 6 Li+209 Bi reaction is studied in a multi-body classical molecular dynamics approach in which the weakly-bound projectile 6 Li is constructed as a 2-body cluster of 4 He and 2 H in a configuration corresponding to the observed breakup energy. This 3-body system with their individual nucleon configuration in their ground state is dynamically evolved with given initial conditions using Classical Rigid Body Dynamics (CRBD) approach up to distances close to the barrier when the rigid-body constraint on the target, inter-fragment distance, and 2 H itself are relaxed, allowing for possible breakup of 2 H which may result in incomplete fusion following the transfer of the n or p . Relative probabilities of the possible events such as scattering with and without breakup, DCF, SCF, ICF(x ) where x may be 4 He, 2 H, 4 He+n , 4 He+p , n , p are calculated. Comparison of the calculated event-probabilities, complete, and incomplete fusion cross sections with the calculation in which 2 H is kept rigid demonstrates the effect of the transfer reactions on complete and incomplete fusion in the 4-body reaction. Events ICF(4 He+n ) corresponding to nstripping followed by breakup of the resultant 5 Li to 4 He+p are found to contribute significantly in the fusion process in agreement with a recent experimental observation of direct reaction processes in breakup of weakly-bound projectiles.

Quantum dynamics of ultrafast charge transfer at an oligothiophene-fullerene heterojunction

Following up on our recent study of ultrafast charge separation at oligothiophene-fullerene interfaces [H. Tamura, I. Burghardt, and M. Tsukada, J. Phys. Chem. C 115, 10205 (2011)], we present here a detailed quantum dynamical perspective on the charge transfer process. To this end, electron-phonon coupling is included non-perturbatively, by an explicit quantum dynamical treatment using the multi-configuration time-dependent Hartree (MCTDH) method. Based upon a distribution of electron-phonon couplings determined from electronic structure studies, a spectral density is constructed and employed to parametrize a linear vibronic coupling Hamiltonian. The diabatic coupling is found to depend noticeably on the inter-fragment distance, whose effect on the dynamics is here investigated. MCTDH calculations of the nonadiabatic transfer dynamics are carried out for the two most relevant electronic states and 60 phonon modes. The electron transfer process is found to be ultrafast and mediated by electronic coherence, resulting in characteristic oscillatory features during a period of about 100 fs.

Microscopic cold fission yields ofCf252

We show that the sharp maximum corresponding to $^{107}\mathrm{Mo}$ in the fragment distribution of the $^{252}\mathrm{Cf}$ cold fission is actually a Sn-like radioactivity, similar to other decay processes in which magic nuclei are involved, namely $\ensuremath{\alpha}$ decay and heavy cluster emission, also called Pb-like radioactivity. It turns out that the mass asymmetry degree of freedom has a key role in connecting initial Sn with the final Mo isotopes along the fission path. We investigate the cold rearrangement of nucleons within the framework of the two-center shell model in order to compute the cold valleys in the charge equilibrated fragmentation potential. The fission yields are estimated by using the semiclassical penetration approach. We consider 5 degrees of freedom, namely the interfragment distance, the shapes of fragments, the neck parameter, and mass asymmetry. We found an isomeric minimum between the internal and external barriers. It turns out that the inner cold valley of the total potential energy is connected to the doubly magic isotope $^{132}\mathrm{Sn}$.

A new adiabatic approach to the photodissociation of polyatomic molecules

An adiabatic theory of polyatomic photodissociation is developed that explicitly treats the interaction between the relative and internal motion and leads to an expression for the nuclear wavefunction of the final dissociative state which differs considerably from the zeroth-order distorted-wave approximation. The vibrational frequencies ..omega../sub i/ of the fragments are found to depend on the interfragment distance. In the evaluation of the matrix element needed to describe the energy distribution of the fragments, it is found necessary to use values of ..omega../sub i/ different from the frequencies of the free fragments. These values of ..omega../sub i/ can be expressed in terms of the force constants of the precursor system. Inverse vibrational distributions are obtained from this theory in accord with recent experimental data.

Charge localization and Jahn–Teller distortions in the benzene dimer cation

Jahn-Teller (JT) distortions and charge localization in the benzene dimer cation are analyzed using the equation-of-motion coupled cluster with single and double substitutions for ionization potential (EOM-IP-CCSD) method. Ionization of the dimer changes the bonding from noncovalent to covalent and induces significant geometrical distortions, e.g., shorter interfragment distance and JT displacements. Relaxation along interfragment coordinates lowers the energy of the t-shaped and displaced sandwich isomers by 0.07 and 0.23 eV, respectively, whereas JT displacements result in additional 0.18 and 0.23 eV. Energetically, the effect of JT distortion on the dimer is similar to the monomer where JT relaxation lowers the energy by 0.18 eV. While the change in the interfragment distance has dramatic spectroscopic consequences, the JT distortion causes only a small perturbation in the electronic spectra. The two geometrical relaxations in the t-shaped isomer lead to opposing effects on hole localization. Intermolecular relaxation leads to an increased delocalization, whereas JT ring distortion localizes the charge. In the sandwich isomers, breaking the symmetry by ring rotation does not induce considerable charge localization. The optimization and property calculations were performed using a new implementation of EOM-IP-CCSD energies and gradients in the Q-CHEM electronic structure package.

Structures and interaction energies of stacked graphene–nucleobase complexes

The noncovalent interactions of nucleobases and hydrogen-bonded (Watson-Crick) base-pairs on graphene are investigated with the DFT-D method, i.e., all-electron density functional theory (DFT) in generalized gradient approximation (GGA) combined with an empirical correction for dispersion (van der Waals) interactions. Full geometry optimization is performed for complexes with graphene sheet models of increasing size (up to C(150)H(30)). Large Gaussian basis sets of at least polarized triple-zeta quality are employed. The interaction energies are extrapolated to infinite lateral size of the sheets. Comparisons are made with B2PLYP-D and SCS-MP2 single point energies for coronene and C(54)H(18) substrates. The contributions to the binding (Pauli exchange repulsion, electrostatic and induction, dispersion) are analyzed. At a frozen inter-fragment distance, the interaction energy surface of the rigid C(96)H(24) and base monomers is explored in three dimensions (two lateral and one rotational). Methodologically and also regarding the results of an energy decomposition analysis, the complexes behave like other pi-stacked systems examined previously. The sequence obtained for the interaction energy of bases with graphene (G > A > T > C > U) is the same for all methods and supports recent experimental findings. The absolute values are rather large (about -20 to -25 kcal mol(-1)) but in the expected range for pi-systems of that size. The relatively short equilibrium inter-plane distance (about 3 A) is consistent with atomic force microscopy results of monolayer guanine and adenine on graphite. In graphene ... Watson-Crick pair complexes, the bases lie differently from their isolated energy minima leading to geometrical anti-cooperativity. Together with an electronic contribution of 2 and 6%, this adds up to total binding anti-cooperativities of 7 and 12% for AT and CG, respectively, on C(96)H(24). Hydrogen bonds themselves are merely affected by binding on graphene.

Dynamical Constraints and Adiabatic Invariants in Chemical Reactions

For long-range electrostatic potentials and, more generally, when the topography of the potential energy surface is locally simple, the reaction path coordinate is adiabatically separable from the perpendicular degrees of freedom. For the ion-permanent dipole and ion-quadrupole interactions, the Poisson bracket of the adiabatic invariant decreases with the interfragment distance more rapidly than the electrostatic potential. The smaller the translational momentum, the moment of inertia of the neutral fragment, and the dipole or quadrupole moments are, the more reliable the adiabatic approximation is, as expected from the usual argumentation. Closed-form expressions for an effective one-dimensional potential in an adiabatic Hamiltonian are given. Connection with a model where the decoupling is exact is obtained in the limit of an infinitely heavy dipole. The dynamics is also constrained by adiabatic invariance for a harmonic valley about a curved reaction path, as shown by the reaction path Hamiltonian method. The maximum entropy method reveals that, as a result of the invariance properties of the entropy, constraints whose validity has been demonstrated locally only subsist in all parts of phase space. However, their form varies continuously, and they are not necessarily expressed in simple terms as they are in the asymptotic region. Therefore, although the influence of adiabatic invariance has been demonstrated at asymptotically large values of the reaction coordinate only, it persists in more interesting ranges.

Electronic structure of the benzene dimer cation

The benzene and benzene dimer cations are studied using the equation-of-motion coupled-cluster model with single and double substitutions for ionized systems. The ten lowest electronic states of the dimer at t-shaped, sandwich, and displaced sandwich configurations are described and cataloged based on the character of the constituent fragment molecular orbitals. The character of the states, bonding patterns, and important features of the electronic spectrum are explained using qualitative dimer molecular orbital linear combination of fragment molecular orbital framework. Relaxed ground state geometries are obtained for all isomers. Calculations reveal that the lowest energy structure of the cation has a displaced sandwich structure and a binding energy of 20 kcal/mol, while the t-shaped isomer is 6 kcal/mol higher. The calculated electronic spectra agree well with experimental gas phase action spectra and femtosecond transient absorption in liquid benzene. Both sandwich and t-shaped structures feature intense charge resonance bands, whose location is very sensitive to the interfragment distance. Change in the electronic state ordering was observed between sigma and piu states, which correlate to the B and C bands of the monomer, suggesting a reassignment of the local excitation peaks in the gas phase experimental spectrum.

Electronic quenching of OH AΣ+2 radicals in single collision events with molecular hydrogen: Quantum state distribution of the OH XΠ2 products

We report a combined experimental and theoretical investigation of the nonreactive quenching channel resulting from electronic quenching of OH A 2Sigma+ by molecular hydrogen. The experiments utilize a pump-probe scheme to determine the OH X 2Pi population distribution following collisional quenching in a pulsed supersonic expansion. The pump laser excites OH A 2Sigma+ (nu'=0, N'=0), which has a significantly reduced fluorescence lifetime due to quenching by H2. The probe laser monitors the OH X 2Pi (nu", N") population via laser-induced fluorescence on various A-X transitions under single collision conditions. The experiments reveal a high degree of rotational excitation (N") of the quenched OH X 2Pi products observed in nu"=1 and 2 as well as a pronounced propensity for quenching into the Pi(A') Lambda-doublet level. These experiments have been supplemented by extensive multireference, configuration-interaction calculations aimed at exploring the topology of the relevant potential energy surfaces. Electronic quenching of OH A 2Sigma+ by H2 proceeds through conical intersections between two potentials of A' reflection symmetry (in planar geometry) that correlate with the electronically excited A 2Sigma+ and ground X 2Pi states of OH. The conical intersections occur in high-symmetry geometries, in which the O side of OH points toward H2. Corroborating and extending earlier work of Hoffman and Yarkony [J. Chem. Phys. 113, 10091 (2000)], these calculations reveal a steep gradient away from the OH-H2 conical intersection as a function of both the OH orientation and interfragment distance. The former will give rise to a high degree of OH rotational excitation, as observed for the quenched OH X 2Pi products.

Ab initio potential energy surface, infrared spectra, and dynamics of the ion-molecule complexes between Br− and H2, D2, and HD

A three-dimensional potential energy surface (PES) for the Br(-)-H(2) complex is computed using the ab initio CCSD(T) method and an extended basis set. The PES has two equivalent minima at the linear geometries (equilibrium interfragment distance R(e)=3.34 A and interaction energy D(e)=670 cm(-1)) separated by the barrier at the T-shaped configuration (interfragment distance R(e)=4.03 A and barrier height of 610 cm(-1)). Ab initio points are fitted to a flexible analytical form and used in the variational rovibrational energy level calculations. Simulated infrared spectra of the Br(-)-H(2) and Br(-)-D(2) complexes in the monomer stretching excitation region are in good agreement with the measured ones. Nonstatistical intensity ratios of the complexes of para- and ortho-monomers are qualitatively explained by monomer ligand exchange reactions. Predissociation of the complexes containing vibrationally excited monomers is analyzed and shown to proceed through the near-resonant vibration-to-rotation energy transfer. For complexes involving Br(-) and the HD monomer, two energetically low-lying states are predicted, corresponding predominately to the Br(-)-DH and Br(-)-HD isomeric forms. The results demonstrate the close similarity of the bromide containing complexes to their analogs containing the chloride anion.

Objective definition of interaction degree between residues in globular proteins

A new measure of the interaction between two molecular fragments, contact intensity (ContI), is defined as the ratio X/( Y+ Z), where X is the average inter-fragment inter-atomic distance and Y and Z are the average intra-fragment inter-atomic distances. Its prominent advantages, relative to alternatives, are the following: ContI does not need a priori assumptions or parameterization and it is intrinsically standardized, to take into account the variability of shape and dimension amongst different molecular moieties. The reliability of ContI is demonstrated by the fact that it allows one to well describe fundamental properties of globular proteins.

Cold valleys of superheavy elements with deformed targets and projectiles

The dependence of the cold driving potential on the deformation of the incoming target and projectile is investigated in the case of the synthesis of the superheavy nuclei 256No, 286112, 292114, 296116, and 306122. The occurrence of valleys in the driving potential as a function on the interfragment distance and the mass asymmetry is studied for different fixed orientations of the colliding nuclei such as the pole-pole, pole-equator, equator-equator, and equator-equator-crossed and compared to the case when the nuclei are assumed to be spherical or when the potential is averaged over the orientation.

Role of fragment orientations in the formation of fusion valleys of superheavy elements

The dependence of the heavy-ion interaction on the orientation is investigated for the cold fusion of two (spherical or deformed) nuclei leading to a superheavy element. In contrast to the case of cold fission, when the fragments are exclusively emerging at scission in pole-pole configuration, in the case of cold fusion the fragments are not necessarily limited to a particular reciprocal orientation and capture can occur also for configurations other than the pole-pole configuration. The occurrence of minima in the driving potential as a function of the interfragment distance and of the mass asymmetry is discussed for several orientations.

The dynamics of hazel grouse (Bonasa bonasia L.) occurrence in habitat fragments

The aim of this study was to evaluate the effects of habitat fragment size and isolation on the dynamics of hazel grouse (Bonasa bonasia L.) occurrence. Habitat fragments surrounded by nonhabitat coniferous forest, in an intensively managed forested landscape, were censused during seven seasons. None of the 33 habitat fragments were occupied in all seven seasons and 7 were never occupied. Turnover occurred in 79% of the habitat fragments. The most common occupation of a habitat fragment was by only one hazel grouse male (84%). Thus, the dynamics of hazel grouse occurrence in the habitat fragments was basically monitored on the scale of individuals. Large and less isolated habitat fragments with a high amount of cover were occupied significantly more often than small, isolated fragments. The effect of size appeared most clearly when analyzing the total number of hazel grouse occupying a habitat fragment. The appearance of hazel grouse in the habitat fragments was best explained by the amount of cover, distance to the nearest suitable habitat, and size of the habitat fragment. The effects of interfragment distance on the occurrence and appearance of hazel grouse implies that the habitat has become functionally disconnected for hazel grouse and suggests that the amount of suitable hazel grouse habitat left in this landscape has fallen below a critical level.

The dynamics of hazel grouse (&lt;i&gt;Bonasa bonasia&lt;/i&gt; L.) occurrence in habitat fragments

The aim of this study was to evaluate the effects of habitat fragment size and isolation on the dynamics of hazel grouse (Bonasa bonasia L.) occurrence. Habitat fragments surrounded by nonhabitat coniferous forest, in an intensively managed forested landscape, were censused during seven seasons. None of the 33 habitat fragments were occupied in all seven seasons and 7 were never occupied. Turnover occurred in 79% of the habitat fragments. The most common occupation of a habitat fragment was by only one hazel grouse male (84%). Thus, the dynamics of hazel grouse occurrence in the habitat fragments was basically monitored on the scale of individuals. Large and less isolated habitat fragments with a high amount of cover were occupied significantly more often than small, isolated fragments. The effect of size appeared most clearly when analyzing the total number of hazel grouse occupying a habi- tat fragment. The appearance of hazel grouse in the habitat fragments was best explained by the amount of cover, dis- tance to the nearest suitable habitat, and size of the habitat fragment. The effects of interfragment distance on the occurrence and appearance of hazel grouse implies that the habitat has become functionally disconnected for hazel grouse and suggests that the amount of suitable hazel grouse habitat left in this landscape has fallen below a critical level.

The effect of nonadiabatic coupling on the calculation of N(E,J) for the methane association reaction

A classic example of a barrierless reaction, CH3+H→CH4 is used as a model to test the extent of nonadiabatic coupling on the reaction rate constant. This coupling has two contributions. The first arises from the anisotropy of the CH3+H potential and the second is Coriolis coupling. A method is presented which calculates adiabats formally equivalent to those calculated by statistical adiabatic channel model (SACM) while still permitting the determination and inclusion of nonadiabatic coupling. Using the discrete variable representation (DVR) for the interfragment distance R, the ro-vibrational Hamiltonian is solved at particular R values. The eigenvalues and eigenfunctions are calculated at each of these R values to create the surface and the coupling elements used in a wave packet propagation. The dynamics of the reaction are investigated through a study of the cumulative reaction probability N(E,J) using energy resolved flux methods. We find that for J=0, 1, and 2, neglecting the coupling due to the changing anisotropy as a function of R results in a 20% error in N(E,J). Neglecting the Coriolis coupling results in average errors of 2% lending support to the helicity-conserving approximation. Finally, within the adiabatic approximation, the calculated adiabats provide a more realistic view of the barriers than the analytic functions of SACM, require no fitting parameter, and are obtained at reasonable computational cost.

The fragmented Atlantic rain forest of Brazil: size, shape and distribution of forest fragments

The geographical characteristics of a total of 1839 forest fragments surrounded by sugar cane fields were studied in the Brazilian Atlantic rain forest region of the northeastern state of Pernambuco. The size and shape of the fragments as well as inter-fragment distances and the effects of varying edge width were examined using a geographical information system. The analyses show that the fragments are relatively small and close to each other. Approximately 48% of the rain forest fragments are 100 hectares. Forest fragments are close to each other, as fragments located 50m or less apart formed groups that included ca. 50% of the total forest area. At 350m inter-fragment distance, 98% of the rain forest area was included in groups of fragments. Due to the small size and irregular shape of the fragments, the total area of edge zone exceeds that of the interior habitat when the edge width is ca. 60m. At an edge width of 300m ca. 94% of the total fragment area is edge zone. For conservation purposes, ways of establishing networks of forest fragments connected by corridors and stepping stone fragments are demonstrated using GIS. Simulations using these techniques show that reforestation of sugar cane fields between the forest fragments would considerably increase the area of interior forest habitat and connectivity between fragments.