Rotation Of Fragment Research Articles

Miocene rise of the Shillong Plateau and the beginning of the end for the Eastern Himalaya

A common feature of convergent plate boundaries is the self-organization of strain, exhumation and topography along discrete, arcuate boundaries. Deviations from this geometry can represent first-order changes in stress applied at a plate boundary that must affect how strain is partitioned within the interior of an orogen. The simplicity of the Himalayan fold and thrust belt seen along its central portion breaks down along the eastern extremity of the arc where the 400 km-long Shillong Plateau has developed. This change in strain partitioning affects nearly 25% of the arc and has not previously been considered to be important to the orogen's development. New low-temperature thermochronometry data suggest this structure initiated in mid to late Miocene time, significantly earlier than was previously estimated from the sedimentary record alone. Development of the Shillong Plateau may be linked to a number of kinematic changes within the Himalayan and Burman collision zones that occur at the same time. These events include the onset of E–W extension in central Tibet, eastward expansion of high topography of the Tibetan Plateau, onset of rotation of crustal fragments in southeastern Tibet, and re-establishment of eastward subduction beneath the Indo-Burman ranges. We suggest that the coincidence of these tectonic events is related to the ‘dismemberment’ of the eastern Himalayan arc, signifying a change in regional stress applied along the India–Eurasia–Burma plate boundaries. Discrepancies between vertical long-term faulting rates and geodetically derived far-field convergence rates suggest that the collisional boundary in the eastern Himalayan system may be poorly coupled due to introduction of oceanic and transitional crust into the eastern plate boundary. The introduction of dense material into the plate boundary late in the orogen's history may explain regional changes in the strain field that affect not only the Himalaya, but also the deformation field more than 1000 km into the Tibetan Plateau.

Evolution and dynamics of the Cenozoic tectonics of the South Balkan extensional system

The South Balkan extensional system consists of normal faults and associated sedimentary basins within southern Bulgaria, Macedonia, eastern Albania, northern Greece, and northwestern Turkey. Extensional tectonism began during the final convergence across the Vardar, Intra-Pontide, and Izmir-Ankara suture zones, where oceanic regions closed between continental Europe and continental fragments that make up the Pelagonian, Sakar, and western Anatolian tectonic units. Earliest extension of latest Cretaceous– middle Eocene age appears to have occurred within a regional convergent tectonic setting and may be related to an increase in gravitation potential energy within a thickening continental lithosphere. Following diachronous closure across the suture zone, from the middle Eocene to late Oligocene, the transition from a regionally convergent to a regionally extensional tectonic setting occurred and was associated with abundant magmatism and formation of sedimentary basins. Extension was associated with lithospheric thinning probably related to changes in geometry of the subducted slab, dynamics of the mantle wedge, and beginning of slab rollback along the Hellenic subduction zone. A short period of local and diachronous (?) shortening (during latest Oligocene–early Miocene time) occurred in the Thrace basin of northwestern Turkey and in some basins in western Bulgaria and eastern Macedonia. Regional extension began in middle Miocene time and was related to the regional extensional tectonic setting that has dominated the Aegean extensional region to the present. Trench rollback was the dominant dynamic process, but during late Miocene time it was modified by the formation of the western part of the North Anatolian fault zone that partially decoupled the South Balkan extensional system from the Aegean extensional region. During late Cenozoic time, east-west–striking normal faults and associated sedimentary basins in the eastern part of the South Balkan extensional system propagated westward in tandem with westward migration of north-south–striking normal faults and sedimentary basins from western Bulgaria into eastern Albania. This migration was caused by evolution of the Hellenic subduction zone as it increased its curvature during trench rollback and clockwise and counterclockwise rotation of crustal fragments in the west and east, respectively. After formation of the western part of the North Anatolian fault zone, extension within the eastern part of the South Balkan extensional system was related to southward movement of its lithosphere at a slower rate than the extension within the Aegean extensional region. Active extension and basin formation show two provinces of extension that are nearly at right angles to one another and their overlap in the central South Balkan extensional system: east-west extension in central Albania to eastern Macedonia and north-south extension from northwestern Greece and eastern Macedonia to eastern Bulgaria and northwestern Turkey.

Proximal Oblique Slide Closing Wedge Metatarsal Osteotomy With Plate Fixation for Severe Hallux Valgus Deformities

Proximal metatarsal osteotomies are generally recommended for severe hallux valgus deformities. The most common problems encountered with these osteotomies are overcorrection, that is, hallux varus and dorsal malunion because of either technical errors or fixation failure. We report our first 12 cases of severe hallux valgus deformities treated with a modified proximal metatarsal osteotomy fixed with angular stable plates, with an average American Orthopaedic Foot and Ankle Society preoperative score of 50 points, average intermetatarsal angle of 15 degrees, and metatarsophalangeal angle of 36 degrees. The osteotomy was performed from the dorsal to the plantar aspect of the bone, removing a small bone wedge laterally as determined in the preoperative planning, and translating laterally the distal fragment. In this way, rotation and lateral displacement of the distal fragment was performed until intraoperative parallelism between the first and second metatarsal bone was obtained. The osteotomy was fixed with an angular stable plate, with 2 locked screws proximally and 3 distal nonlocked screws. The geometric model of the osteotomy, preoperative planning, technique, early results, and complications are shown.

Residual strain recovery, molecular mobility, and plasticity of solid aromatic copolyesters of p-hydroxybenzoic acid with poly(ethylene terephthalate)

The processes of thermally stimulated recovery of internal energy stored by a specimen during deformation and of residual strain ɛres in weakly oriented liquid-crystalline 80: 20 and 60: 40 (by mole) copolyesters of p-hydroxybenzoic acid with PET, as well as in nonoriented (amorphous and crystalline) PET, were studied. All the materials were deformed via uniaxial compression at room temperature. It was shown that ɛres is built up in all phases that coexist in the materials: the glassy, crystalline, and intermediate phases, of which the last presumably contains imperfect crystals of a small size. Excess energy of strain is stored in the glassy phase with a built-in LC order and, probably, in copolyester crystallites. The main deformation processes in the glassy component of the materials are the nucleation and development of small-scale shear transformations in exactly the same manner as in the earlier studied glassy polymers that do not form an LC structure. Consequently, enhanced rigidity of the polyesters chains and their LC order have no qualitative effect on the mechanism of plastic deformation of the copolyester glasses. However, the LC structure leads to a decrease in the yield stress σy and the compression and shear moduli of the copolyesters in comparison with those of conventional glassy polymers i.e., reduces the resistance of the materials toward plastic deformation. With an increase in strain, various forms of Brownian motion of chains, beginning from the rotation of p-hydroxybenzoic acid fragments, become successively involved in the process of their deformation at room temperature. Correspondingly, the thermally stimulated recovery of ɛres exhibits peaks of small-scale motions of aromatic chain fragments in the glassy phase of copolyesters, a phenomenon that is not observed in PET and other aliphatic polymer glasses. The intensity of these peaks depends on the value of ɛres built up by the specimen. Even small strains (≈5−40%) in the specimens irreversibly destroy the initial orientation of chains in copolyesters. To explain this effect, the concept of domain disorientation of their structure is proposed.

The conformation and dynamic behaviour of tetrathiacalix[4]arenes functionalized by hydrazide and hydrazone groups

The 1H, 13C and 15N NMR data, conformation and dynamic behaviour of the new tetrathiacalix[4]arenes functionalized by hydrazide and hydrazone groups are reported and compared with the result of earlier investigations of 4- tert-butylphenoxyacetylhydrazones. The unusual fact of formation of N, N′-diacetylhydrazine bridge and factors leading to its formation in the cone conformer of calixarene has been discussed. The barriers of rotation of hydrazone fragments of tetrathiacalix[4]arenes were determined by NMR-measurements at various temperatures. The structure of 1,3- alternate conformer of 5,11,17,23-tetra- tert-butyl-25,26,27,28-tetrakis[hydrazinocarbonylmethyl]-2,8,14,20-tetrathiacalix[4]arene in solution is compared with crystal structure obtained by the X-ray analysis.

Biomechanical comparison of two side plate fixation techniques in an unstable intertrochanteric osteotomy model: Sliding Hip Screw and Percutaneous Compression Plate

Our objective was to determine the biomechanical primary stability of two different side plate fixation devices in an unstable intertrochanteric cadaver model: the Sliding Hip Screw with an additional derotation screw was compared with the Percutaneous Compression Plate. Eight pairs of human cadaver femurs were tested for comparison of the primary stability of the two implants in two modes: (a) cyclic loading up to 200 N, 400 N, 600 N, 800 N, and 1000 N, respectively. In vitro combined axial and bending loads were applied. Angular displacements of the proximal head fragment during loading were recorded in rotational, varus-valgus, and anterior-posterior directions. (b) The load to failure was determined. Specimens fixed with the Percutaneous Compression Plate showed higher displacements in the varus during loading up to 200 N (P=0.033), and 400 N (P=0.001), compared to the Sliding Hip Screw. A similar tendency was observed for higher loads. The Percutaneous Compression Plate allowed more external rotation of the proximal fragment only at loads up to 800 N (P=0.019). No statistical difference could be found for the slight migrations in the posterior direction. Load to failure also revealed no statistical difference between the two implants. The Percutaneous Compression Plate as a double-axis fixation device with a sliding capability allows higher displacements in the varus direction and also in external rotation at 800 N loading compared to the Sliding Hip Screw as a single-axis fixation device combined with an additional derotation screw. While both implants are successful used in clinical practice, this should be considered in treatment of unstable intertrochanteric fractures with inferior comminution in osteoporotic patients.

Calix[4]arenequinazolinones. Synthesis and structure

The synthesis of calix[4]arenes bearing two quinazolin-4-ones group at the upper rim is decribed. 1H NMR spectra and quantum chemical calculations make it possible to suggest that calix[4]arenequinazolinones form three rotamers in solutions at room temperature, due to the restricted rotation of the quinazolinone fragments. The X-ray structure investigation indicates that quinazolin-4-onecalix[4]arene exists in the crystal state as the methanol 1:1 inclusion complex.

Dissociative versus molecular adsorption of phenol onSi(100)2×1: A first-principles calculation

We investigated the competitive adsorption of a bifunctional molecule, phenol, on $\mathrm{Si}(100)2\ifmmode\times\else\texttimes\fi{}1$ by ab initio calculations. We performed geometry optimizations of phenol adsorbed either molecularly or dissociatively, on five possible sites (top, bridge, valley bridge, cave, and pedestal), in the low coverage regime. We found that the dissociative adsorption of phenol on top of a silicon dimer is the most favorable adsorption configuration. In the group of dissociative adsorption the phenol initially placed on the bridge or the valley-bridge sites ends up as a toplike local minima. The pedestal and cave sites remain as low-adsorption energy ``open'' sites. In the group of molecular adsorption, a higher adsorption energy is associated to the adsorption through an addition reaction and loss of the aromatic character (bridge, valley-bridge, and pedestal sites). Standard butterfly or diagonal butterfly are the corresponding optimized geometries. Retention of aromatic character and lower adsorption energy are associated to the adsorption on the top and cave sites. The ordering of adsorption sites according to the adsorption energy shows a mixture of the dissociative and the molecular sites. In the case of adsorption on the top site, the adsorption energies after a rotation of the phenoxy fragment along the bonding axis and hydrogen migration on the surface are very similar. The bend of the phenoxy fragment on the surface, instead, is not favored (the adsorption energy is $1.004\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ lower compared to the vertical position). Different electron density maps were calculated for different adsorption sites and modes. Finally, we investigated the possibility that molecularly adsorbed phenol behaves as a precursor for the dissociative one by nudged elastic band calculations. We found a barrier of the same order of magnitude of the thermodynamic energy at room temperature for the conversion of the valley-bridge molecular into the top dissociative site.

Chain structure and stiffness of Teflon AF glassy amorphous fluoropolymers

The structure of the amorphous perfluorinated polymer Teflon AF 2400 and other structurally close perfluoropolymers was studied by means of a quantum chemistry method. The electronic and structural characteristics of the repeating unit and polymer models with ten and nine monomer units were obtained. It was found that two nonplanar isomers can exist for different models of the perfluorinated dioxole ring with a difference of their energy minimums of 10.8 kJ/mol. The orthogonal-block structure of the polymer chain of the perfluorodioxole homopolymer and its copolymer with tetrafluoroethylene was proposed, the block size was found, and a possible diameter of the void formed by two neighboring polymer chains was evaluated. Potential energy curves for the rotation of certain chain fragments about different bonds of the polymer main chain were constructed, and the polymer stiffness was shown to substantially depend on the molar ratio between perfluorodioxole and tetrafluoroethylene units in the copolymer and on the geometry of the perfluorodioxole ring.

Radical Cations of Branched Alkanes As Observed in Irradiated Solutions by the Method of Time-Resolved Magnetic Field Effect

Spin dynamics in radical ion pairs formed under ionizing irradiation of n-hexane solutions of two branched alkanes 2,3-dimethylbutane and 2,2,4-trimethylpentane has been studied by the method of time-resolved magnetic field effect in recombination fluorescence. Experimental curves of the magnetic field effect are satisfactorily described by assuming that the spin dynamics is determined by the hyperfine interactions in the radical cation (RC) of branched alkane under study with hyperfine coupling (HFC) constants averaged by internal rotations of RC fragments. The HFC constants determined from the magnetic field effect curves are close to those estimated within DFT B3LYP approach. Analysis of the results indicates that at room temperature the lifetimes of the RC of the studied branched alkanes amount to, at least, tens of nanoseconds.

Anterior or posterior obliquity of the lag screw in the lateral view—Does it affect the sliding characteristics on unstable trochanteric fractures?

We investigated the sliding pattern characteristics of proximal fragment in 16 proximal femur models of 31-A2.1 type trochanteric fractures fixed with dynamic hip screw system under load. In eight models, the lag screw was inserted with an anterior-to-posterior vector within the neck and the head of femur (group 1). The other eight had a posterior-to-anterior vector (group 2). A force of 500 N (30 cycles) was applied to the fracture fragment-plate complex using the Instron 6022. No significant difference was noted in the sliding distance between the two groups (p=0.17). However, the mean angle of rotation of the proximal fragment was twice as great in group 1 (16+/-3.7 degrees ) than that in group 2 (8.1+/-1.5 degrees ) (p<0.001). In group 1, early eccentric contact in the anterior aspect of the intertrochanteric area caused internal rotation of the proximal fragment. Breakage of the anterior cortex of the lateral wall was noted in five out of the eight cases in group 1 and no case in group 2 (p=0.026). Fracture of the anterior cortices significantly threatened the integrity of the lateral wall in group 1.

Structural model of the rare mineral tacharanite and a possible process of its formation

A large number of samples of the poorly studied tacharanite mineral have been comprehensively investigated. A model of the tacharanite structure is derived from the tobermorite structure. A new zeolite-like structure is derived from the tacharanite structure by removing calcium atoms and subsequent shifts and rotations of the silicon-oxygen fragments forming the tacharanite structure. The IR spectral features have been considered, which made it possible not only to show the inhomogeneity of the system studied but also to propose a hypothesis about the conditions of its formation, taking into account the overall close presence of zeolite as the initial material.

Archaeoseismological investigation of the ancient Ayla site in the city of Aqaba, Jordan

Many tens of severe earthquake damage patterns were revealed at the ancient city of Ayla. The seismic deformation patterns are of various types, including systematic tilting of walls, systematic shifting and rotation of wall fragments and individual stones, arch deformations and joints crossing two or more stones. Features of later repair, supporting walls and secondary use of building stones suggest that the damage patterns can be explained by two historical devastating earthquakes: (I) revealed in the constructions built during the late Rashidun period (644–656 A.D.); (II) revealed in the structures restored and/or built during the Fatimid period (1050–1116 A.D.). The maximum observed intensity of both earthquakes at the studied site was not less than IX (EMS98 scale). The sources of the seismic events were probably the Dead Sea Transform and Wadi Araba Faults that cross the site obliquely. The last 1995 Nuweiba earthquake with maximum observed intensity VIII has also left its clear traces in the excavated ancient Ayla buildings. The severity of the destruction was significantly increased because of site effects.

Use of a circular external skeletal fixator for stabilization of a comminuted diaphyseal metatarsal fracture in an alpaca

A 3-year-old male alpaca was evaluated because of non-weight-bearing lameness (grade 5/5) in the left hind limb. Clinical and radiographic examination revealed a closed, comminuted, nonarticular, displaced diaphyseal fracture of the left third and fourth metatarsal bones. Initial attempts at treatment via reduction of the fracture under traction and subsequent application of a cast were unsuccessful, and more stable fracture fixation was pursued. The alpaca underwent closed reduction of the fracture, which was stabilized by the application of a 3-ring circular external skeletal fixator (CESF). Improved weight bearing on the affected limb was evident soon after surgery and gradually increased; full weight bearing was evident by the seventh day after discharge from the hospital (day 20 after application of the CESF). Lameness was hardly noticeable during walking at that time. After 3 months, complete fracture healing was evident and the CESF was removed; mild outward rotation of the distal fragment and metatarsophalangeal joint was present. A Robert Jones bandage was applied to the limb, and the alpaca was kept in a stall for another 4 weeks. Eleven months after CESF application, the owners and referring veterinarian reported that the alpaca was healthy, not lame, and serving as a stallion without apparent impediment. Although mostly restricted to small animals, application of a CESF can be a viable alternative for management of long bone fractures in South American camelids.

Electron-microscopic investigation of high-strain-rate deformation produced by shock waves in the pearlitic structure of the grade 40 Kh steel

Upon high-strain-rate deformation under the action of shock waves, cementite plates in thin-lamel-lar pearlite are deformed and/or destroyed. “Fragments” of broken plates change their position relative to each other. The local (in a volume of ∼2 μm) shear, tensile, and torsional deformations were determined from regular displacements and rotations of fragments found upon electron-microscopic investigation. The local strain rates of deformations were also estimated.

Torsional stability of intramedullary compression nails: Tibial osteotomy model

Studies comparing intramedullary compression nailing to conventional dynamized intramedullary nailing contend that better clinical outcomes of intramedullary compression techniques result from greater rotational stability of fracture or osteotomy sites. However, there appears to be no experimental evidence that rotational stability is improved with intramedullary nail compression. This study evaluated the effect of intramedullary nail compression on cadaveric and composite tibial fragment rotation above and below a mid-tibial transverse osteotomy. Twelve composite and four matched pairs of human cadaveric tibiae were randomized into either a compression group or a non-compressed dynamized group. A bi-axial servo-hydraulic testing machine applied 5Nm of internal and external torque (2Nm/s) under constant axial loads of 375N and 750N. Rotation along each tibia and at the osteotomy site was recorded from the trajectories of infrared emitting diodes rigidly attached along the tibial shaft. In comparison to dynamized nails, intramedullary nail compression significantly reduced the rotation at the osteotomy site in both human (8.9 degrees reduction; P=0.007) and composite tibiae (2.5 degrees reduction; P=0.039) under 750N of axial load. A similar result was noted for simulated half-body weight loads (375N) for both composite (3.0 degrees reduction; P=0.009) and human tibiae (10.5 degrees reduction; P=0.003). Intramedullary nail compression more effectively reduced tibial fragment rotation about a mid-tibial osteotomy than conventional dynamized intramedullary nails because intramedullary nails created more osteotomy site compression than the application of body weight to tibiae instrumented with dynamized intramedullary nails.

The mechanism of H-bond rupture: the vibrational pre-dissociation of C2H2–HCl and C2H2–DCl

Pair correlated fragment rovibrational distributions are presented following vibrational predissociation of the C2H2-DCl van der Waals dimer initiated by excitation of the asymmetric (asym) C-H stretch. The only observed fragmentation pathways are DCl (v= 0; j= 6-9)+ C2H2(nu2= 1; j= 1-5). These and previously reported data on the related C2H2-HCl species are analysed using the angular momentum (AM) method. Calculations accurately reproduce fragment rovibrational distributions following dissociation of the C2H2-HCl dimer initiated either by excitation of the asym C-H stretch or via the HCl stretch, and those from C2H2-DCl initiated via asym C-H stretch excitation. The calculations demonstrate that the dimer is bent at the moment of dissociation. Several geometries are found that lead to H-bond breakage via a clearly identified set of fragment quantum states. The results suggest a hierarchy in the disposal of excess energy and angular momentum between fragment vibration, rotation and recoil. Deposition of the largest portion of energy into a C2H2 vibrational state sets an upper limit on HCl rotation, which then determines the energy and AM remaining for C2H2 rotation and fragment recoil. Acceptor C2H2 vibrational modes follow a previously noted propensity, implying that the dissociating impulse must be able to induce appropriate nuclear motions both in the acceptor vibration and in rotation of the C2H2 fragment.

Acetabular Cysts Heal after Successful Periacetabular Osteotomy

The presence of subchondral bone cysts reflects degeneration or defects of the articular cartilage and elevated local stresses in the subchondral bone. We asked whether the presence of acetabular cysts deleteriously influenced the clinical and radiographic results of periacetabular osteotomy for treatment of dysplastic hips. We retrospectively reviewed 46 hips in 43 patients with cartilage narrowing who had periacetabular osteotomies. Of the 46 hips, 21 had acetabular cysts (cyst group) and 25 did not (control group). The average followups were 5.8 and 5.4 years in the cyst and control groups, respectively. We compared the Harris hip score and coverage of the femoral head between the two groups. The clinical results were similar between the two groups. There were no differences in radiographic evaluations between the two groups at the latest followup. In the cyst group, complete or partial healing of the cysts was observed in 17 of the 21 hips. A postoperative increase in the center-edge angle of 20 degrees or greater was found in 14 of the 17 hips. The preoperative presence of acetabular cysts did not influence the results of periacetabular osteotomy. Adequate rotation of the acetabular fragment induced cyst remodeling.

Osteosynthesis of a triplane fracture under arthroscopic control in a bilateral case

There are various types of ankle triplane fractures; they may be lateral and medial with two, three or four fragments. Some are described as extra-articular. We describe an exceptional bilateral case occurring after a trampoline accident of a displaced articular and an extra-articular fracture. The extra-articular fracture was treated by closed reduction and percutaneous fixation under fluoroscopic control. For the displaced articular fracture, an arthroscopically assisted reduction and percutaneous fixation was performed. The degree of rotation of the antero-lateral fragment of the articular triplane fracture, during percutaneous screw fixation, was not visible under image intensifier but could be corrected under arthroscopic control. Several portals can be made to enhance articular fracture reduction. This surgical procedure offers reliability and safety to the reduction and the synthesis of this articular fracture. It allows surgery to be less invasive in young patients, while decreasing the risk of malunion and poor long-term clinical results.

Complex history of a zircon aggregate from lunar breccia 73235

Results are reported of an investigation of the age and origin of the exceptional zircon aggregate in an anorthositic clast from lunar breccia 73235. Cathodoluminescence and birefringence images show that the aggregate consists of numerous angular fragments of sector zoned primary zircon in a matrix of secondary zircon with an overall texture that resembles a pseudotachylite. SIMS U–Pb analyses of the primary fragments and the matrix yielded two clearly defined ages, an age of 4.315 ± 0.015 Ga and initial Th/U ratio of 0.21–0.35 for the primary zircon and an age of 4.187 ± 0.011 Ga and Th/U of 0.04–0.17, for the secondary zircon matrix. A Raman spectroscopic study the secondary matrix zircon was undertaken to investigate its structure. Results showed that the matrix has a zircon structure but there is also evidence for the presence of an amorphous component. Implications of the structural and U–Pb age data are discussed in terms of the origin and evolution of the aggregate and the history of lunar events. It is proposed that an original single, millimetre-sized, sector zoned zircon, formed at 4.31 Ga, was subjected to a severe shock event at 4.18 Ga. This event resulted in the fracturing of the zircon, the displacement and rotation of fragments, the compression of the aggregate to a lensoid shape, and the shock reduction of zircon to sub-micron-sized and amorphous granules in crush zones in the mosaic of fractures. Volatilisation loss of Pb and the addition of U to the secondary zircon is attributed to processes activated by the extreme thermal pulse which accompanied the 4.18 Ga shock event. Shock effects are seen in some of the primary fragments but Raman spectra of the primary and secondary zircon show no evidence for pressure-induced transformation of zircon to a scheelite structure. The zircon U–Pb system has not been affected by the ca. 3.95 Ga thermal pulse that accompanied formation of the host breccia although this event has largely reset the K–Ar systems.