bluuebunny/crossref_metadata_2025 huggingface dataset:
In Vitro Effects of Osteotomy Angle and Osteotomy Reduction on Tibial Angulation and Rotation During the Tibial Plateau‐Leveling Osteotomy Procedure
Authors: Wheeler Jason L. , Cross Alan R. , Gingrich Wade
Published: October 2010

Objective—To determine the effect of osteotomy angle, reduction technique, and tibial plateau rotation angle on angular and rotational limb deformities.

Study Design—Geometric comparison using bone models.

Methods—Rotational osteotomies were made in the proximal metaphysis of artificial tibias at 0°, 10°, 20°, −10°, and −20° from perpendicular with respect to either the proximodistal and craniocaudal tibial axes. Negative‐numbered angles represented osteotomies made from distal to proximal or caudal to cranial. Changes in tibial angulation and torsion were measured using a 3‐dimensional digitizing instrument at tibial plateau rotation angles from 0° to 30° at 5° increments. Two osteotomy reduction techniques were used: complete osteotomy reduction and alignment of the medial cortex. The mean of 5 measurements of torsional and angular tibial deformity for each of the 9 osteotomy orientations in each reduction technique group was obtained.

Results—All had increasing angular and rotational deformity as tibial plateau rotation angle increased. In the medially aligned cortex group, all tibias had valgus deformity, and 8 of 9 tibias were internally rotated. In the reduced osteotomy group, minimal angular deformity was seen in tibias with osteotomy variation along the proximodistal axis; however, tibias with osteotomy variation along the craniocaudal axis had angular deformity ranging from 6.0° of varus deformity to 14.3° of valgus deformity. Rotational deformity was affected similarly by osteotomy variation along either axis. Reduction technique had greater affect on angular and rotational deformity than osteotomy angle variation.

Clinical Relevance—These results suggest that osteotomy reduction may play a greater role in angular and rotational deformity than osteotomy angle, although extreme osteotomy angles should be avoided. To decrease the severity of deformity, we recommend that the osteotomy be made perpendicular to the craniocaudal and proximodistal axes and be completely reduced with less regard for alignment of the medial cortex.
Radiation Synovectomy With Holmium‐166 Ferric Hydroxide Macroaggregate in Equine Metacarpophalangeal and Metatarsophalangeal Joints
Authors: Mäkelä Olli , Sukura Antti , Penttilä Pirkko , Hiltunen Jukka , Tulamo Riitta‐Mari
Published: October 2010

Objectives—To evaluate the effects of radiation synovectomy (RSYN) with holmium‐166 ferric hydroxide macroaggregate (Ho‐166 FHMA) on synovium and synovial fluid in normal metacarpo‐ and metatarsophalangeal joints of horses and to determine intraarticular distribution of radioactivity after Ho‐166 FHMA treatment.

Study Design—Either Ho‐166 FHMA or nonradioactive Ho‐165 FHMA was injected into metacarpo‐ or metatarsophalangeal joints.

Animals—Six adult mixed‐breed horses without any clinical evidence of metacarpo‐ or metatarsophalangeal joint disease.

Methods—Joints were injected with a single high dose of Ho‐166 FHMA (mean, 1,000 MBq/joint) or a nonradioactive Ho‐165 FHMA preparation (controls). Clinical examination, arthroscopy, synovial fluid analyses, and histologic studies were performed to detect effects of RSYN. Scintigraphy was used to localize intraarticular distribution of Ho‐166 FHMA.

Results—Ho‐166 FHMA treatment induced joint inflammation leading to regional edema, effusion, and scar tissue formation. Scintigraphy revealed the highest intensity of radioactivity in the proximal plantar joint pouch, at which the Ho‐166 FHMA treatment caused multifocal necrosis. In the dorsal joint pouch, however, arthroscopic study and histologic analysis showed very little effect of RSYN. There was no regeneration of synovium evident within 2 months. Synovial fluid protein concentration was significantly (P< .01) elevated, and some residual radioactivity remained for 5 days after Ho‐166 FHMA injection.

Conclusions—Injection of a single high dose of Ho‐166 FHMA caused multifocal necrosis of synovium and deep, soft‐tissue injury in equine fetlock joints.

Clinical Relevance—Inflamed equine joints with synovial lining hyperplasia could benefit from Ho‐166 FHMA‐induced radiation synovectomy if excessive scar tissue formation can be avoided.
Deep Circumflex Iliac Cutaneous Free Flap in Cats
Authors: Jackson Andrew H. , Degner Daniel A. , Jackson Ian T. , Miyawaki Takeshi , Silverberg Boris , Bradford Melinda , Andrus Lee
Published: October 2010

Objective—To develop and assess the survival of a microvascular cutaneous free flap based on the ventral branch of the deep circumflex iliac (DCI) artery and vein in cats.

Study Design—Experimental study.

Animals—Phase 1: 6 feline cadavers; Phase 2: 2 adult cats; Phase 3: 10 adult cats.

Methods—Phase 1: Selective angiographic study of the deep circumflex iliac artery was completed in 6 feline cadavers. After injection of the DCI artery with barium, high‐detail radiographs were made of skin flaps harvested from the lateral flank and thigh region. The extent of the cutaneous angiosome was mapped with regard to the underlying anatomical landmarks. Phase 2: An island flap based on anatomic boundaries of the DCI angiosome derived from phase 1 of the study was elevated in 2 cats. Flaps were observed for 3 weeks for survival. Phase 3: Free skin flaps based on the DCI vessels were harvested in 10 cats and transferred to the dorsal interscapular region. Flaps were evaluated for 2 weeks for survival. Tissue samples were collected for histopathology, and angiograms of the flaps were completed.

Results—Phase 1: Angiograms revealed a large primary cutaneous angiosome of the DCI artery located over the lateral femoral region, which extended from the iliac crest to the level of the patella. Phase 2: All island flaps survived for 3 weeks. Phase 3: Six free flaps survived for 2 weeks, and 4 flaps failed completely. Failure of 1 flap occurred because of avulsion of the venous and arterial anastomosis postoperatively. Another cat had intraoperative hemorrhage, which resulted in anemia and hypovolemia and likely caused the flap to fail. The other 2 flaps that failed had poor perfusion intraoperatively and had the longest ischemia times.

Conclusions—The cutaneous DCI free flap in cats may be clinically useful in reconstruction of large cutaneous wounds. The length of ischemia time for successful cutaneous free flap transfer in the cat may be shorter than in other species.

Clinical Relevance—Large wounds created by trauma or oncologic ablative surgery in cats could be reconstructed with cutaneous microvascular free flap. Additional studies assessing the critical ischemia time of cutaneous flaps in cats and evaluating the use of this flap clinically are needed.
Hamstring Graft Technique for Stabilization of Canine Cranial Cruciate Ligament Deficient Stifles
Authors: Lopez Mandi J. , Markel Mark D. , Kalscheur Vicki , Lu Yan , Manley Paul A.
Published: October 2010

Objective—To investigate the harvest and application of hamstring grafts for canine cranial cruciate ligament (CrCL) reconstruction.

Study Design—Experimental study.

Animals—Four adult female hounds, weighing 26.3 ± 1.6 kg (mean ± SEM).

Methods—One stifle in each dog was randomly chosen for hamstring graft CrCL reconstruction after native CrCL transection. Arthroscopy was performed to evaluate graft integrity at 12 weeks. Gait analysis and stifle radiographs were performed preoperatively and up to 52 weeks after graft placement. Dogs were killed 12 (n = 2) or 52 weeks (n = 2) after CrCL reconstruction. Tissues were evaluated grossly and with light and confocal laser microscopy.

Results—Hamstring grafts were intact in all stifles at 12 weeks (n = 4) and 52 weeks (n = 2). Grossly, there was no osteoarthritis in stifles at 12 weeks and only chondrophytes along the trochlear ridges at 52 weeks. Minimal radiographic evidence of osteoarthritis developed in stifles with grafts during the study. Lameness in limbs with grafts resolved by 52 weeks. Graft tissue was highly vascular, ligamentized, and undergoing active remodeling at 12 weeks. Fifty‐two weeks after graft placement, intraarticular graft tissue was well vascularized, mature, and encapsulated by synovium, and graft‐bone interfaces were characterized by Sharpey's fiber insertions. There was no evidence of graft necrosis using confocal laser microscopy at either time point.

Conclusions—The hamstring graft technique may be a viable method of canine CrCL reconstruction.

Clinical Relevance—Hamstring grafts may be an alternative technique for canine CrCL reconstruction. Further study is needed before clinical application.
Complications and Outcome After Thoracodorsal Axial Pattern Flap Reconstruction of Forelimb Skin Defects in 10 Dogs, 1989–2001
Authors: Aper Rhonda , Smeak Daniel
Published: October 2010

Objective—To determine (1) the frequency and extent of complications associated with thoracodorsal axial pattern flap reconstruction of forelimb skin defects in dogs and (2) outcome after treatment of such complications.

Study Design—Retrospective clinical study.

Sample Population—Ten dogs.

Methods—Medical records for 10 dogs that had a thoracodorsal axial pattern skin flap reconstruction of a forelimb skin defect were reviewed.

Results—Three dogs had complete flap survival. Partial necrosis of the distal flap, ranging from an estimated 2% to 53% (mean, 21%) of the flap surface area, occurred in 7 dogs. Six dogs required surgical management of the skin necrosis, resulting in successful resolution in 5 dogs, whereas, in 2 dogs, the wound healed by second intention. Positive bacterial cultures were obtained from 3 dogs with distal flap necrosis. Seroma formation was noted in 2 dogs; the entire flap survived in 1 dog, whereas the second dog developed distal flap necrosis. Edema and bruising of the distal portion of the flap were noted in 8 dogs; distal flap necrosis subsequently developed in 7 dogs. Partial incisional dehiscence, which healed by second intention, occurred in 2 dogs. Of 6 owners available for follow‐up, all were satisfied with the functional outcome, but 1 owner was not satisfied with the cosmetic appearance.

Conclusions—Partial flap necrosis was a frequent complication of thoracodorsal axial pattern flap reconstruction of forelimb skin defects and required additional wound care or surgical intervention to achieve healing.

Clinical Relevance—Thoracodorsal axial pattern flaps can provide full‐thickness skin coverage of extensive skin defects of the forelimb, but owners should be aware of the likelihood of local wound complications.
Popliteal and Mesenteric Lymph Node Injection With Methylene Blue for Coloration of the Thoracic Duct in Dogs
Authors: Enwiller Tara M. , Radlinsky Maryann G. , Mason Diane E. , Roush James K.
Published: October 2010

Objective—To describe and compare the time of onset and intensity of thoracic duct coloration after injection of methylene blue into a mesenteric or popliteal lymph node.

Study Design—Experimental study.

Animals—Twenty adult dogs.

Methods—A right tenth intercostal thoracotomy, a right paracostal laparotomy, and an approach to the right popliteal lymph node were performed on each dog. Methylene blue (0.5 mg/kg of a 1% solution, maximum 10 mg) was injected into either a mesenteric (group M, 10 dogs) or popliteal (group P, 10 dogs) lymph node. Thoracic duct color was graded (0 to 3) every 5 minutes for 60 minutes. Statistical analysis was performed on mean thoracic duct color grade data, on number of successful outcomes between groups M and P, and between weight groups.

Results—Coloration of the thoracic duct occurred in all group M dogs and 6 group P dogs. Coloration was first recorded 0 to 10 minutes after injection in all dogs and persisted for 60 minutes in 15 dogs. Mean thoracic duct color grade was significantly increased postinjection compared with preinjection at all times in group M. More successful outcomes occurred in group M (P= .03).

Conclusions—Methylene blue injected into mesenteric or popliteal lymph nodes was successful in coloring the thoracic duct, but both mean grade and number of successful outcomes were significantly higher after mesenteric injection.

Clinical Relevance—Thoracic duct coloration after lymph node injection occurred within 10 minutes and persisted for 60 minutes. This information is useful in planning thoracic duct ligation in cases of chylothorax when observation of the duct is desired. Injection of both lymph node sites was successful, but mesenteric node injection was a more reliable technique.
Comparison of Tibial Plateau Angles in Normal and Cranial Cruciate Deficient Stifles of Labrador Retrievers
Authors: Reif Ullrich , Probst Curtis W.
Published: October 2010

Objective—To investigate tibial plateau angles (TPA) in normal and cranial cruciate ligament (CCL) deficient stifles of Labrador retrievers.

Study Design—Prospective clinical study.

Animals—Eighty‐one client‐owned purebred Labrador retrievers.

Methods—Lateral radiographs of the tibia were obtained from 2 groups of dogs. Group I (42 dogs) had CCL rupture diagnosed by arthrotomy or arthroscopy. Group II (39 dogs) had no history of orthopedic problems, no radiographic evidence of CCL rupture, and dogs were >8 years of age. The tibial axis and the tibial plateau were determined on the radiographs, and the TPA was measured using image measurement software. The TPA measurement results of groups I and II were compared.

Results—Group I (CCL rupture) had a mean TPA (±SD) of 23.5 (±3.1) degrees, and group II (normal) had a mean TPA (±SD) of 23.6 (±3.5) degrees. With aPvalue of .97, no statistical difference was detected between the 2 groups.

Conclusions—No correlation between the magnitude of TPA and CCL rupture was identified in this group of Labrador retrievers.

Clinical Relevance—In Labrador retrievers, TPA should not be used as a predictor of CCL rupture.
Mechanical comparison of 3 different clamp and 2 different rod types of a new veterinary internal fixation system, 4.5/5.5‐mm VetFix
Authors: Haerdi Christina , Costa Riccardo Dalla , Auer Joerg A. , Linke Berend , Steiner Adrian
Published: October 2010

Objective—To compare the gripping force of a standard clamp with click‐on and T clamps of the 4.5/5.5‐mm VetFix (AO Research Institute, Davos, Switzerland), mounted on smooth and roughened rods.

Study Design—In vitro mechanical study.

Methods—Rods were mounted on a clamp‐holding device. Each clamp type was tested on a materials‐testing machine in groups of 6 specimens for torsional and axial load stability on smooth and roughened rods (total, 72 specimens). The variable evaluated was the discontinuity point (DP) as a measure for gliding resistance of the clamp on the rod. Means (±SD) were calculated for all groups separately. For statistical comparison, a multiple regression model was fitted with level of significance set atP= .05.

Results—The direction of torsion had a significant effect on DP for both asymmetric clamps (standard, click‐on). In torsion and axial load, the roughened rod had significantly higher DP levels than the smooth rod for the standard clamp. Rods differed only in axial load for the T clamp, again favoring the roughened rod. The click‐on clamp did not reach 10% of the values achieved by the other clamps, independent from the rods and loading conditions. Compared with the T clamp, standard clamp DP values were significantly higher in torsion on the roughened rod as well as in axial load on both rod types.

Conclusions—The roughened rod with a standard clamp was mechanically superior. For the T clamp, the small loss of gripping force may be compensated for by the possibility of inserting 2 more screws.

Clinical Relevance—The roughened rod may enhance the bending, compressive, and torsional properties of the 4.5/5.5‐mm VetFix system by reducing the risk of clamp gliding on the rod. The standard clamp is the clamp of choice, except for the metaphyseal or epiphyseal region, at which use of a T clamp may be indicated to increase the number of screws inserted at the end of the rod.
The relationship between limb function and radiographic osteoarthrosis in dogs with stifle osteoarthrosis
Authors: Gordon Wanda J. , Conzemius Michael G. , Riedesel Elizabeth , Besancon Michael F. , Evans Richard , Wilke Vicki , Ritter Matthew J.
Published: October 2010

Objective—To evaluate the relationship between limb function and radiographic evidence of stifle osteoarthrosis (OA) in dogs.

Study Design—The relationship between force platform data and radiographic OA score was evaluated on 2 separate days using regression analysis. Interday variation was also assessed.

Animals—Forty‐one dogs with visible lameness and radiographic evidence of stifle OA.

Methods—Force platform data were collected at a velocity of 1.7 to 2.0 m/s for 5 trials on day 1 and day 8. Radiographs taken on day 1 were scored using a previously reported OA scoring system.

Results—No significant relationship was found between force platform data and OA score. No significant differences were found between any day 1 and day 8 force platform values.

Conclusions—Although radiographic evidence of stifle OA provides evidence of pathology, it does a poor job of representing limb function. In addition, the absence of significant differences between day 1 and day 8 values in this population of dogs supports use of only a single force platform evaluation before measuring a treatment effect.

Clinical Relevance—The presence of OA in the stifle joint does not correlate with clinical function; radiographic outcome should be used cautiously as a predictor of clinical outcome.
Healing characteristics of deep digital flexor tenorrhaphy within the digital sheath of horses
Authors: Jann Henry , Blaik Margaret , Emerson Robert , Tomioka Michiko , Stein Larry , Moll David
Published: October 2010

Objective—To describe the healing characteristics of deep digital flexor tenorrhaphy within the digital sheath.

Study Design—Experimental study.

Animals—Five mature horses.

Methods—Right thoracic limb, deep digital flexor tenorrhaphy was performed within the digital sheath. Limbs were cast in partial flexion using a short limb cast for 6 weeks. Next, extended heel shoes were used for limb support for 14 weeks. Healing was evaluated by sequential ultrasonographic examinations, and limb use was evaluated by force plate analysis. At 26 weeks, mechanical strength and morphologic characteristics of the repair site were evaluated.

Results—Gap (mean, 0.93 cm.) formation was evident in unloaded limbs at 3 weeks. This increased markedly by 6 weeks and was 5 cm at 26 weeks. Demarcation between the deep and superficial flexor tendons decreased as the transected ends adhered to the dorsal surface of the superficial flexor tendon. The intrathecal space was reduced by fibrous tissue. Mean maximum load to failure of the repair tissue was 4,616 ± 3,556 N, with a mean stress of 12.99 ± 2.78 MPa. The repair consistently failed at the adhesion between the transected tendon and the superficial flexor tendon.

Conclusions—Intrathecal tenorrhaphy with external coaptation (in partial limb flexion) for 6 weeks resulted in gap healing, fibrous adhesion between the deep and superficial flexor tendons, fibrous tissue reduction of the intrathecal space, and a pasture‐sound horse at 26 weeks.

Clinical Relevance—Without improved methods for immobilizing the deep digital flexor tendon, intrathecal tenorrhaphy is unlikely to result in first intention tendon healing.
Diagnostics for the Plasma Liner Experiment
Authors: Lynn A. G. , Merritt E. , Gilmore M. , Hsu S. C. , Witherspoon F. D. , Cassibry J. T.
Published: October 2010

The goal of the Plasma Liner Experiment (PLX) is to explore and demonstrate the feasibility of forming imploding spherical “plasma liners” via merging high Mach number plasma jets to reach peak liner pressures of ∼0.1 Mbar using ∼1.5 MJ of initial stored energy. Such a system would provide HED plasmas for a variety of fundamental HEDLP, laboratory astrophysics, and materials science studies, as well as a platform for experimental validation of rad-hydro and rad-MHD simulations. It could also prove attractive as a potential standoff driver for magnetoinertial fusion. Predicted parameters from jet formation to liner stagnation cover a large range of plasma density and temperature, varying from ni∼1016 cm−3, Te≈Ti∼1 eV at the plasma gun mouth to ni>1019 cm−3, Te≈Ti∼0.5 keV at stagnation. This presents a challenging problem for the plasma diagnostics suite which will be discussed.
Millimeter-wave spectroscopy of H2CCD: Tunneling splitting and ortho-para mixing interaction
Authors: Hayashi Masato , Harada Kensuke , Lavrich Richard , Tanaka Takehiko , Tanaka Keiichi
Published: October 2010

The H2CCD isotopic species of vinyl radical produced in a supersonic jet expansion by ultraviolet laser photolysis was studied by millimeter-wave spectroscopy. Due to the tunneling motion of the α deuteron, the ground state is split into two components, 0+ and 0−. Tunneling-rotation transitions connecting the lower (0+) and upper (0−) components of the tunneling doublet were observed in the frequency region of 184–334 GHz, including three R- and two Q-branch transitions. Three and two pure rotational transitions in the Ka=0 and 1 stacks, respectively, were also observed for each of the 0+ and 0− states in the frequency region of 52–159 GHz. Least-squares analysis of the observed frequencies for the tunneling-rotation and pure rotational transitions with well resolved hyperfine structures yielded a set of precise molecular constants, among which the tunneling splitting in the ground state was determined to be ΔE0=1187.234(17) MHz, which is 1/14 that for H2CCH. The potential barrier height derived from the observed tunneling splitting by an analysis of the tunneling dynamics using a one-dimensional model is 1545 cm−1, consistent with the value 1568 cm−1 obtained for the normal vinyl. The observed spectrum was found to be perturbed by a hyperfine interaction connecting ortho and para levels. The constant for the interaction, which we call the ortho-para mixing Fermi contact interaction, has been determined to be δaF(β)=68.06(53) MHz. This is believed to be the first definite detection of such an interaction. By this interaction the ortho and para states of H2CCD are mixed up to about 0.1%. The constant is more than 1000 times larger than spin-rotation interaction constants that cause ortho-para mixing in closed shell molecules and suggests extremely rapid conversion between the ortho and para nuclear spin isomers of H2CCD.
High-performance time-resolved fluorescence by direct waveform recording
Authors: Muretta Joseph M. , Kyrychenko Alexander , Ladokhin Alexey S. , Kast David J. , Gillispie Gregory D. , Thomas David D.
Published: October 2010

We describe a high-performance time-resolved fluorescence (HPTRF) spectrometer that dramatically increases the rate at which precise and accurate subnanosecond-resolved fluorescence emission waveforms can be acquired in response to pulsed excitation. The key features of this instrument are an intense (1 μJ/pulse), high-repetition rate (10 kHz), and short (1 ns full width at half maximum) laser excitation source and a transient digitizer (0.125 ns per time point) that records a complete and accurate fluorescence decay curve for every laser pulse. For a typical fluorescent sample containing a few nanomoles of dye, a waveform with a signal/noise of about 100 can be acquired in response to a single laser pulse every 0.1 ms, at least 105 times faster than the conventional method of time-correlated single photon counting, with equal accuracy and precision in lifetime determination for lifetimes as short as 100 ps. Using standard single-lifetime samples, the detected signals are extremely reproducible, with waveform precision and linearity to within 1% error for single-pulse experiments. Waveforms acquired in 0.1 s (1000 pulses) with the HPTRF instrument were of sufficient precision to analyze two samples having different lifetimes, resolving minor components with high accuracy with respect to both lifetime and mole fraction. The instrument makes possible a new class of high-throughput time-resolved fluorescence experiments that should be especially powerful for biological applications, including transient kinetics, multidimensional fluorescence, and microplate formats.
Terahertz instability of surface optical-phonon polaritons that interact with surface plasmon polaritons in the presence of electron drift
Authors: Sydoruk O. , Shamonina E. , Kalinin V. , Solymar L.
Published: October 2010

Traveling-wave interaction between optical phonons and electrons drifting in diatomic semiconductors has potential for amplification and generation of terahertz radiation. Existing models of this interaction were developed for infinite materials. As a more practically relevant configuration, we studied theoretically a finite semiconductor slab surrounded by a dielectric. This paper analyzes the optical-phonon instability in the slab including the Lorentz force and compares it to the instability in an infinite material. As the analysis shows, the slab instability occurs because of the interaction of surface optical-phonon polaritons with surface plasmon polaritons in the presence of electron drift. The properties of the instability depend on the slab thickness when the thickness is comparable to the wavelength. For large slab thicknesses, however, the dispersion relation of the slab is similar to that of an infinite material, although the coupling is weaker. The results could be used for the design of practical terahertz traveling-wave oscillators and amplifiers.
A guided-ion beam study of the reactions of Xe+ and Xe2+ with NH3 at hyperthermal collision energies
Authors: Levandier Dale J. , Chiu Yu-Hui
Published: October 2010

We have measured the absolute cross sections for reactions of Xe+ and Xe2+ with NH3 at collision energies in the range from near-thermal to ∼34 and ∼69 eV, respectively. For Xe+, the cross section for charge transfer, the only exothermic channel, decreases from ∼200 Å2 below 0.1 eV to ∼12 Å2 at the highest energies studied. The production of NH3+ is the only channel observed below 5 eV, above which a small amount of NH2+ is also formed. In Xe2+ reactions, the main products observed are NH3+ and NH2+. The charge transfer cross section decreases monotonically from ∼80 to ∼6 Å2 over the studied energy range. The NH2+ cross section is similar to the charge transfer cross section at the lowest energies, and exhibits a second component above 0.4 eV, with a maximum of 65 Å2 at 0.7 eV, above which the cross section decreases to ∼30 Å2 at the highest energies studied. At energies above 10 eV, a small amount of NH+ is also observed in Xe2+ collisions. Product recoil velocity distributions were determined at selected collision energies, using guided-ion beam time-of-flight methods.
Giant electric field effect on the second hyperpolarizability of symmetric singlet diradical molecules
Authors: Nakano Masayoshi , Champagne Benoît , Botek Edith , Ohta Koji , Kamada Kenji , Kubo Takashi
Published: October 2010

This contribution reveals the effects of a static electric field on the static second hyperpolarizability γ of symmetric singlet diradical molecules using the valence configuration interaction scheme. It is found that under the effect of a field, the component of γ along the axis joining the two radical sites can be gigantically (approximately two to three orders) enhanced for symmetric diradicals having intermediate diradical characters with respect to those of closed-shell and pure diradical molecules in the absence of a field. Moreover, this electric field enhancement of γ increases as a function of the diradical character. These results and their analysis propose therefore a new strategy to design materials with exceptional nonlinear optical responses.
Grazing incidence wide angle x-ray scattering at the wiggler beamline BW4 of HASYLAB
Authors: Perlich J. , Rubeck J. , Botta S. , Gehrke R. , Roth S. V. , Ruderer M. A. , Prams S. M. , Rawolle M. , Zhong Q. , Körstgens V. , Müller-Buschbaum P.
Published: October 2010

We present an upgrade of the available measurement techniques at the wiggler beamline BW4 of the Hamburger Synchrotronstrahlungslabor (HASYLAB) to grazing incidence wide angle x-ray scattering (GIWAXS). GIWAXS refers to an x-ray diffraction method, which, based on the measurement geometry, is perfectly suited for the investigation of the material crystallinity of surfaces and thin films. It is shown that the overall experimental GIWAXS setup employing a movable CCD–detector provides the capability of reliable and reproducible diffraction measurements in grazing incidence geometry. Furthermore, the potential usage of an additional detector enables the simultaneous or successive measurement of GIWAXS and grazing incidence small angle x-ray scattering (GISAXS). The new capability is illustrated by the microbeam GIWAXS measurement of a thin film of the conjugated polymer poly(3-octylthiophene) (P3OT). The investigation reveals the semicrystalline nature of the P3OT film by a clear identification of the wide angle scattering reflexes up to the third order in the [100]-direction as well as the first order in the [010]-direction. The corresponding microbeam GISAXS measurement on the present morphology complements the characterization yielding the complete sample informa-tion from subnanometer up to micrometer length scales.
Fast magnetic reconnection in low-density electron-positron plasmas
Authors: Bessho Naoki , Bhattacharjee A.
Published: October 2010

Two-dimensional particle-in-cell simulations have been performed to study magnetic reconnection in low-density electron-positron plasmas without a guide magnetic field. Impulsive reconnection rates become of the order of unity when the background density is much smaller than 10% of the density in the initial current layer. It is demonstrated that the outflow speed is less than the upstream Alfvén speed, and that the time derivative of the density must be taken into account in the definition of the reconnection rate. The reconnection electric fields in the low-density regime become much larger than the ones in the high-density regime, and it is possible to accelerate the particles to high energies more efficiently. The inertial term in the generalized Ohm’s law is the most dominant term that supports a large reconnection electric field. An effective collisionless resistivity is produced and tracks the extension of the diffusion region in the late stage of the reconnection dynamics, and significant broadening of the diffusion region is observed. Because of the broadening of the diffusion region, no secondary islands, which have been considered to play a role to limit the diffusion region, are generated during the extension of the diffusion region in the outflow direction.
Theoretical consideration of osmotic pressure in aqueous protein/salt systems based on extended hard core Lennard-Jones potential
Authors: Pai Sung Jin , Bae Young Chan
Published: October 2010

A simple and analytical pair potential function was developed to represent the osmotic pressures in aqueous protein/salt systems under various conditions. Based on a hard core Lennard-Jones (HCLJ) potential model, the new potential function considers various interactions by extending the attractive Lennard-Jones potential. A temperature-dependent coefficient term was introduced to take into account the specific properties of given materials. Comparison of the new potential function with the HCLJ model in hydrocarbon and water systems showed that consideration of the temperature dependence in the potential function was effective, especially for strong polar systems such as water. To predict the osmotic pressures of aqueous lysozyme/(NH4)2SO4 solutions of various ionic strength and pH, the energy parameters of lysozyme were correlated with the experimental cloud point temperature. The proposed model agreed fairly well with the experimental osmotic pressure data with only previously obtained parameters.
Measurement of the force on microparticles in a beam of energetic ions and neutral atoms
Authors: Trottenberg Thomas , Schneider Viktor , Kersten Holger
Published: October 2010

The force on microparticles in an energetic ion beam is investigated experimentally. Hollow glass microspheres are injected into the vertically upward directed beam and their trajectories are recorded with a charge-coupled device camera. The net force on the particles is determined by means of the measured vertical acceleration. The resulting beam pressures are compared with Faraday cup measurements of the ion current density and calorimetric measurements of the beam power density. Due to the neutral gas background, the beam consists, besides the ions, of energetic neutral atoms produced by charge-exchange collisions. It is found that the measured composition of the drag force by an ion and a neutral atom component agrees with a beam model that takes charge-exchange collisions into account. Special attention is paid to the momentum contribution from sputtered atoms, which is shown to be negligible in this experiment, but should become measurable in case of materials with high sputtering yields.
Efficient on the fly calculation of time correlation functions in computer simulations
Authors: Ramírez Jorge , Sukumaran Sathish K. , Vorselaars Bart , Likhtman Alexei E.
Published: October 2010

Time correlation functions yield profound information about the dynamics of a physical system and hence are frequently calculated in computer simulations. For systems whose dynamics span a wide range of time, currently used methods require significant computer time and memory. In this paper, we discuss the multiple-tau correlator method for the efficient calculation of accurate time correlation functions on the fly during computer simulations. The multiple-tau correlator is efficacious in terms of computational requirements and can be tuned to the desired level of accuracy. Further, we derive estimates for the error arising from the use of the multiple-tau correlator and extend it for use in the calculation of mean-square particle displacements and dynamic structure factors. The method described here, in hardware implementation, is routinely used in light scattering experiments but has not yet found widespread use in computer simulations.
Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices
Authors: Pejović Milić M. , Denić Dragan B. , Pejović Momčilo M. , Nešić Nikola T. , Vasović Nikola
Published: October 2010

This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.
Progress toward the development and testing of source reconstruction methods for NIF neutron imaging
Authors: Loomis E. N. , Grim G. P. , Wilde C. , Wilson D. C. , Morgan G. , Wilke M. , Tregillis I. , Merrill F. , Clark D. , Finch J. , Fittinghoff D. , Bower D.
Published: October 2010

Development of analysis techniques for neutron imaging at the National Ignition Facility is an important and difficult task for the detailed understanding of high-neutron yield inertial confinement fusion implosions. Once developed, these methods must provide accurate images of the hot and cold fuels so that information about the implosion, such as symmetry and areal density, can be extracted. One method under development involves the numerical inversion of the pinhole image using knowledge of neutron transport through the pinhole aperture from Monte Carlo simulations. In this article we present results of source reconstructions based on simulated images that test the methods effectiveness with regard to pinhole misalignment.
Two-step melting of Na41+
Authors: Zamith Sébastien , Labastie Pierre , Chirot Fabien , L’Hermite Jean-Marc
Published: October 2010

The heat capacity of the mass selected Na41+ cluster has been measured using a differential nanocalorimetry method. A two-peak structure appears in the heat capacity curve of Na41+, whereas Schmidt and co-workers [M. Schmidt, J. Donges, Th. Hippler, and H. Haberland, Phys. Rev. Lett. 90, 103401 (2003)] observed, within their experimental accuracy, a smooth caloric curve. They concluded from the absence of any structure that there is a second order melting transition in Na41+ with no particular feature such as premelting. The observed difference with the latter results is attributed to the better accuracy of our method owing to its differential character. The two structures in the heat capacity are ascribed to melting and premelting of Na41+. The peak at lower temperature is likely due to an anti-Mackay to Mackay solid-solid transition.
Sequence composition and environment effects on residue fluctuations in protein structures
Authors: Ruvinsky Anatoly M. , Vakser Ilya A.
Published: October 2010

Structure fluctuations in proteins affect a broad range of cell phenomena, including stability of proteins and their fragments, allosteric transitions, and energy transfer. This study presents a statistical-thermodynamic analysis of relationship between the sequence composition and the distribution of residue fluctuations in protein-protein complexes. A one-node-per-residue elastic network model accounting for the nonhomogeneous protein mass distribution and the interatomic interactions through the renormalized inter-residue potential is developed. Two factors, a protein mass distribution and a residue environment, were found to determine the scale of residue fluctuations. Surface residues undergo larger fluctuations than core residues in agreement with experimental observations. Ranking residues over the normalized scale of fluctuations yields a distinct classification of amino acids into three groups: (i) highly fluctuating-Gly, Ala, Ser, Pro, and Asp, (ii) moderately fluctuating-Thr, Asn, Gln, Lys, Glu, Arg, Val, and Cys, and (iii) weakly fluctuating-Ile, Leu, Met, Phe, Tyr, Trp, and His. The structural instability in proteins possibly relates to the high content of the highly fluctuating residues and a deficiency of the weakly fluctuating residues in irregular secondary structure elements (loops), chameleon sequences, and disordered proteins. Strong correlation between residue fluctuations and the sequence composition of protein loops supports this hypothesis. Comparing fluctuations of binding site residues (interface residues) with other surface residues shows that, on average, the interface is more rigid than the rest of the protein surface and Gly, Ala, Ser, Cys, Leu, and Trp have a propensity to form more stable docking patches on the interface. The findings have broad implications for understanding mechanisms of protein association and stability of protein structures.
A nonlocal connection between certain linear and nonlinear ordinary differential equations: Extension to coupled equations
Authors: Pradeep R. Gladwin , Chandrasekar V. K. , Senthilvelan M. , Lakshmanan M.
Published: October 2010

Identifying integrable coupled nonlinear ordinary differential equations (ODEs) of dissipative type and deducing their general solutions are some of the challenging tasks in nonlinear dynamics. In this paper we undertake these problems and unearth two classes of integrable coupled nonlinear ODEs of arbitrary order. To achieve these goals we introduce suitable nonlocal transformations in certain linear ODEs and generate the coupled nonlinear ODEs. In particular, we show that the problem of solving these classes of coupled nonlinear ODEs of any order effectively reduces to solving a single first order nonlinear ODE. We then describe a procedure to derive explicit general solutions for the identified integrable coupled ODEs, when the above mentioned first order nonlinear ODE reduces to a Bernoulli equation. The equations which we generate and solve include the two coupled versions of modified Emden equations (in second order), coupled versions of Chazy equations (in third order), and their variants, higher dimensional coupled Ricatti and Abel’s chains, as well as a new integrable chain and higher order equations.
New Products
Authors: Mandelis Andreas
Published: October 2010

In order to supplement manufacturers’ information this Department will welcome the submission by our readers of brief communications reporting measurements on the physical properties of materials which supersede earlier data or suggest new research applications.
Performance of some nucleation theories with a nonsharp droplet-vapor interface
Authors: Napari Ismo , Julin Jan , Vehkamäki Hanna
Published: October 2010

Nucleation theories involving the concept of nonsharp boundary between the droplet and vapor are compared to recent molecular dynamics (MD) simulation data of Lennard-Jones vapors at temperatures above the triple point. The theories are diffuse interface theory (DIT), extended modified liquid drop-dynamical nucleation theory (EMLD-DNT), square gradient theory (SGT), and density functional theory (DFT). Particular attention is paid to thermodynamic consistency in the comparison: the applied theories either use or, with a proper parameter adjustment, result in the same values of equilibrium vapor pressure, bulk liquid density, and surface tension as the MD simulations. Realistic pressure-density correlations are also used. The best agreement between the simulated nucleation rates and calculations is obtained from DFT, SGT, and EMLD-DNT, all of which, in the studied temperature range, show deviations of less than one order of magnitude in the nucleation rate. DIT underestimates the nucleation rate by up to two orders of magnitude. DFT and SGT give the best estimate of the molecular content of the critical nuclei. Overall, at the vapor conditions of this study, all the investigated theories perform better than classical nucleation theory in predicting nucleation rates.
CoPc adsorption on Cu(111): Origin of the C4 to C2 symmetry reduction
Authors: Cuadrado Ramón , Cerdá Jorge I. , Wang Yongfeng , Xin Ge , Berndt Richard , Tang Hao
Published: October 2010

The adsorption of phthalocyanines (Pc) to various surfaces has recently been reported to lead to a lowering of symmetry from C4 to C2 in scanning tunneling microscope (STM) images. Possible origins of the reduced symmetry involve the electronic structure or geometric deformation of the molecules. Here, the origin of the reduction is clarified from a comprehensive theoretical study of CoPc adsorbed on the Cu(111) surface along with the experimental STM data. Total energy calculations using different schemes for the exchange-correlation energy and STM simulations are compared against experimental data. We find that the symmetry reduction is only reproduced when van der Waals corrections are included into the formalism. It is caused by a deformation along the two perpendicular molecular axes, one of them coming closer to the surface by around 0.2 Å. An electronic structure analysis reveals (i) the relevance of the CoPc interaction with the Cu(111) surface state and (ii) that intramolecular features in dI/dV maps clearly discriminate a Co-derived state from the rest of the Pc states.
The Solubility of Mercury and Some Sparingly Soluble Mercury Salts in Water and Aqueous Electrolyte Solutions
Authors: Clever H. Lawrence , Johnson Susan A. , Derrick M. Elizabeth
Published: October 2010

The literature on the solubility of mercury and of the sparingly soluble salts of mercury (I) and mercury (II) in water and in aqueous electrolyte solutions has been reviewed. The solubility data have been compiled and evaluated. Recommended and tentative values of the solubilities are presented when warranted. Auxiliary thermodynamic data and crystallographic data useful in the interpretation of solubility data are given. An annotated bibliography on the solubility of some of the less common inorganic mercury compounds, with emphasis on the solubility literature published since 1950, is given.
The Homogeneous Nucleation Limits of Liquids
Authors: Avedisian C. T.
Published: October 2010

This work provides a critical compilation of the homogeneous nucleation limits of liquids. Data for 90 pure substances and 28 mixtures have been compiled over a range of pressures, nucleation rates, and compositions. Detailed descriptions of the experimental methods used to obtain the included data are given to assess the accuracy of measured values. Criteria used to select the measurements included in the final listing are discussed.
Standard Chemical Thermodynamic Properties of Alkene Isomer Groups
Authors: Alberty Robert A. , Gehrig Catherine A.
Published: October 2010

The chemical thermodynamic properties of alkene isomer groups from C4H8 to C6H12 in the ideal gas phase have been calculated from 298.15 to 1000 K from tables of Stull, Westrum, and Sinke. In the absence of literature data on all isomers of higher isomer groups, the properties of isomers of C7H14 to C8H16 have been estimated using Benson group values. Equilibrium mole fractions within isomer groups have been calculated for the ideal gas state from 298.15 to 1000 K. For isomer group properties increments per carbon atom have been calculated to show the extent to which thermodynamic properties of higher isomer groups may be obtained by linear extrapolation. Values of C○P, S°, ΔfH°, and ΔfG° are given for all species from C2H4 to C8H16 in joules for a standard state pressure of 1 bar.