bluuebunny/crossref_metadata_2025 huggingface dataset:
Can the Outcome of Carpal Tunnel Release be Predicted?
Authors: REGE A. J. , SHER J. L.
Published: September 2002

Between 1994 and 1996 we performed a prospective study on the effect of carpal tunnel release on the health status of 96 patients. The Nottingham Health Profile, a validated global scoring system, was used to assess quality of life before, and at 4 months after surgery. Carpal tunnel syndrome had a significant impact on the health status of our patients. There were significant improvements in the scores for pain, energy and sleep. Patients who were dissatisfied following surgery had significantly higher pre-operative scores, indicating poor perceived health status. Our findings show that outcome assessment tools have predictive value in identifying patients who may not benefit from surgery, or in whom a poor result might be anticipated.
Primary Ulnar Head Prosthesis for the Treatment of an Irreparable Ulnar Head Fracture Dislocation
Authors: GRECHENIG W. , PEICHA G. , FELLINGER M.
Published: September 2002

We report the case of an irreparable fracture – dislocation of the ulnar head with a concomitant fracture of the radius (Galeazzi lesion), treated by implantation of a Herbert Ulnar Head Prosthesis®. A stable distal radio-ulnar joint was achieved by careful dissection of a posterior soft tissue flap and accurate reduction of the radius.
EXTRA-ARTICULAR TRANSVERSE FRACTURES OF THE BASE OF THE DISTAL PHALANX (SEYMOUR’S FRACTURE) IN CHILDREN AND ADULTS
Authors: AL-QATTAN M. M.
Published: September 2002

A series of 25 extra-articular transverse fractures of the base of the distal phalanx (Seymour’s fracture) in children, adolescents and adults are presented. Prior to closure of the distal phalangeal epiphysis, the fracture line is usually entirely through the metaphyses, 1 to 2 mm distal to the growth plate. In adults, the fracture line is just distal to the insertion of the extensor tendon. Eighteen of these fractures were treated by closed reduction and splinting and one of these developed an infection and three had mild residual flexion deformities of the finger. Five fractures were treated by K-wire fixation and all healed without complications. Two adult patients presented 4 to 5 weeks after injury with malunion, and of these one underwent refracturing and K-wire fixation with an excellent result.
The Open Finger Technique for the Release of Syndactyly
Authors: WITHEY S. J. , KANGESU T. , CARVER N. , SOMMERLAD B. C.
Published: September 2002

A new technique of syndactyly release is described. The technique differs from the standard methods in that more digital flaps are used, and these are longer and are not defatted. A single stitch is applied to secure the tip of the flap and the defects between the flaps are not closed or grafted, hence the term “open” technique. Eight patients had 12 webs released using this operation. We compare this technique with 12 patients who had a total of 19 webs released using the standard technique. Patients were assessed for six parameters of operative success.
Acutrak Screw Fixation Versus Cast Immobilisation for Undisplaced Scaphoid Waist Fractures
Authors: ADOLFSSON L. , LINDAU T. , ARNER M.
Published: September 2002

Fifty-three patients with less than 14 day-old, undisplaced fractures of the waist of the scaphoid were randomized to two groups. Twenty-eight patients were treated by immobilisation in a below elbow plaster cast for 10 weeks while 25 were treated by percutaneous insertion of an Acutrak standard screw. There were no statistically significant differences between the two treatment groups with regard to either the rate of union or the time to union. Patients who underwent surgery had a significantly better range of motion at 16 weeks but there were no significant differences for grip strength. Acute percutaneous internal fixation of undisplaced scaphoid waist fractures using the Acutrak screw allows early mobilisation without adverse effects on fracture healing.
Closed Traumatic Rupture of the Flexor Pulleys of a Long Finger Associated with Avulsion of the Flexor Digitorum Superficialis
Authors: VANDEPUTTE G. , DUBERT T.
Published: September 2002

We report a closed rupture of the second, third and fourth annular pulleys associated with avulsion of the flexor digitorum superficialis tendon in the ring finger of a healthy, 48-year-old patient. It was caused by sudden and violent flexion of the finger and led to a serious impairment of the proximal interphalangeal joint motion, despite physiotherapy and dynamic splinting. The patient was treated surgically, 3 months after the injury, with reconstruction of the second (A2) and fourth (A4) annular pulleys and excision of the distal portion of the superficialis tendon. The final functional result was satisfactory.
The Long Term Recovery Curve in Adults after Median or Ulnar Nerve Repair: A Reference Interval
Authors: ROSÉN B. , LUNDBORG G.
Published: September 2002

This study presents a predicted five-year reference interval for the outcome following repair of the median or ulnar nerve in adults. Forty-four patients were examined with the use of a recently introduced model instrument for documentation after nerve repair that includes “sensory”, “motor”, and “pain/discomfort” outcomes which together constitute a summarized “total score”. Analysis of the “total score” showed that follow-up time and age significantly influence the outcome. There were obvious inferior “motor” results after ulnar nerve injury, but these did not significantly influence the “total score”. Significant improvements in the “total score” were seen throughout the follow-up period.
Treatment of De Quervain’s Disease: Role of Conservative Management
Authors: LANE L. B. , BORETZ R. S. , STUCHIN S. A.
Published: September 2002

This retrospective study compares two methods used to treat de Quervain’s disease: splintage with oral non-steroidal anti-inflammatory drugs (NSAIDs) and steroid injection. Patients were separated into three groups based on symptom severity: group I-minimal, group II-mild, and group III-moderate or severe. Three hundred and nineteen wrists in 300 patients were followed from one to six years. Fifteen of 17 patients with minimal symptoms were relieved with splintage and NSAIDs. However, only seven of 20 in Group II and two of eight in Group III treated similarly were relieved. Of the 249 patients in Group III treated with injections, 76% were completely relieved, 7% were improved, and 4% were not improved. We conclude that classification of patients’ with de Quervain’s disease based on their pre-treatment symptoms may assist surgeons in selecting the most efficacious treatment and in providing prognostic information to their patients.
Locking of the Proximal Interphalangeal Joint of the Little Finger
Authors: COSTELLO C. H. , LAM D. G. K. , GIELE H. P.
Published: September 2002

Locking of the metacarpophalangeal joints is well documented, but locking of other joints in the finger has not been described. We present a case of locking of the little finger proximal interphalangeal joint due to an osteophyte impinging on the extensor tendon.
Lipofibromatous Hamartoma of the Median Nerve and its Associated Conditions
Authors: AL-QATTAN M. M.
Published: September 2002

This study reports on ten cases of lipofibromatous hamartoma of the median nerve, with specific references to its associated conditions. Macrodactyly was the most common associated condition and was seen in 6 cases. Two cases had associated fatty tumours and another two had bony tumours. The literature was reviewed and a classification of the sites of involvement of the median nerve and its associated conditions is suggested.
Pilonidal Sinus of the Finger Pulp
Authors: GRANT I. , MAHAFFEY P. J.
Published: September 2002

A case of pilonidal sinus of the finger-tip pulp in a male barber is reported. The site appears to be previously unreported for this condition.
Dorso-Ulnar Osteocutaneous Reverse Flow Flap of the Thumb
Authors: PELISSIER P. , PISTRE V. , CASOLI V. , LIM A. , MARTIN D. , BAUDET J.
Published: September 2002

Three cases of distal thumb reconstruction with a reverse pedicled osteocutaneous flap taken from the dorso-ulnar aspect of the first metacarpal are presented. Even though the indications are rare, this flap is useful for the reconstruction of distal osteocutaneous defects of the thumb where more complex procedures are not feasible or considered as excessive.
MRI Assessment of the Proximal Pole of the Scaphoid after Internal Fixation with a Titanium Alloy Herbert Screw
Authors: GANAPATHI M. , SAVAGE R. , JONES A. R.
Published: September 2002

We report a series of scaphoid fractures fixed with titanium alloy Herbert screws in which postoperative Magnetic Resonance Imaging (MRI) was used to assess the marrow signal in the proximal pole of the scaphoid and thus detect the presence of avascular necrosis. The artefact produced by the titanium alloy Herbert screw did not preclude this assessment.
The Mexican Hat Splint – A New Splint for the Treatment of Closed Mallet Finger
Authors: WILSON S. W. , KHOO C. T. K.
Published: September 2002

A new splint for the treatment of closed mallet finger injuries is described. This is a modified aluminium-foam (‘Zimmer’) splint, which takes account of the skin circulation at the distal interphalangeal joint, and is specifically designed to alleviate the potential problems which can be seen with the traditional ‘mallet finger’ splints.
A Biomechanical Analysis of the Modified Tsuge Suture Technique for Repair of Flexor Tendon Lacerations
Authors: LABANA N. , MESSER T. , LAUTENSCHLAGER E. , NAGDA S. , NAGLE D.
Published: September 2002

Thirty-six flexor tendons from fresh frozen cadavers were randomized to three types of repairs: a Kessler-Tajima, a 4-strand modified Tsuge, and a 6-strand modified Tsuge. All repairs were accompanied by a standard epitendinous suture. The repaired tendons were then tested to initial gap and ultimate failure in an Instron machine. The average forces to ultimate failure were 31.8 N (SD, 8.8), 48.4 N (SD, 10.7), and 64.2 N (SD, 11.0) respectively. The 6-strand modified Tsuge suture was significantly stronger than the other repairs and the 4-strand modified Tsuge was significantly stronger than the 2-strand Kessler-Tajima. The 6-strand and 4-strand modified Tsuge repairs appear strong enough to withstand the forces generated during early active range of motion flexor tendon rehabilitation protocols. Clinical trials are required to evaluate the usefulness of these repairs.
A Modified Technique of Four-Bone Fusion for Advanced Carpal Collapse (Slac/Snac Wrist)
Authors: GARCIA-LÖPEZ A. , PEREZ-UBEDA M. J. , MARCO F. , MOLINA M. , LÖPEZ-DURAN L.
Published: September 2002

This study reports the outcome of 16 patients treated with a modified four-bone fusion for symptomatic stage II and III advanced carpal collapse. The technique is based on fusion of the capitate, lunate, hamate and triquetrum using an autogenous corticocancellous bone-graft fixed with screws. The void left behind after scaphoid excision was filled with an extensor carpi radialis longus anchovy. After an average follow up of 3 years; there were 13 excellent and three good outcomes. In every patient pain relief was achieved with preservation of joint motion and grip strength. All the patients were able to return to their previous activities and jobs. Radiographic evaluation showed bone fusion in all 16 patients with a slight decrease in carpal height but a well preserved radiolunate joint space. In conclusion, this technique provides immediate stable fixation and early mobilization and assures bone fusion.
Carpal Tunnel Release for Advanced Disease in Patients 70 Years and Older: Does Outcome from the Patient’s Perspective Justify Surgery?
Authors: TOMAINO M. M. , WEISER R. W.
Published: September 2002

Because more advanced stages of nerve compression are likely to result in intraneural changes including intrinsic fibrosis and axon loss, we hypothesised that carpal tunnel release for advanced carpal tunnel syndrome might not result in satisfactory resolution of symptoms. We were particularly interested in evaluating a population of elderly patients 70 years and older for whom relief of symptoms is the overwhelming objective of surgery. Our retrospective assessment of symptom resolution and patient satisfaction in 13 patients with advanced carpal tunnel syndrome utilized a validated self-administered questionnaire and revealed minimal symptoms in 11 patients. Although carpal tunnel release is unlikely to result in the total elimination of symptoms when performed in elderly patients with advanced disease, outcome from the patient’s perspective appears to be satisfactory and the surgery quite justified.
Type 5 Avulsion of the Insertion of the Flexor Digitorum Profundus Tendon
Authors: AL-QATTAN M. M.
Published: September 2002

Four cases of avulsion of the insertion of the flexor digitorum profundus tendon with an osseous fragment are presented. In each case, there was another significant fracture of the distal phalanx. The current classification system for flexor profundus avulsions is reviewed and an extended classification is offered which considers such avulsions.
Radial Closing Wedge Osteotomy for Kienböck’s Disease: an Over 10 Year Clinical and Radiographic Follow-Up.
Authors: WADA A. , MIURA H. , KUBOTA H. , IWAMOTO Y. , UCHIDA Y. , KOJIMA T.
Published: September 2002

Thirteen patients with Kienböck’s disease who had undergone a radial closing wedge osteotomy were reviewed clinically and radiologically at a follow-up mean of 14 years. Good long-term results were obtained in all patients. Their levels of pain were improved, and significant increases were seen in the range of motion and grip strength. Radiographic stage, as assessed by Lichtman’s classification, improved in one, did not change in four, and advanced in eight patients. The radial inclination angle significantly decreased and the carpal-ulnar distance and lunate covering ratios both increased, demonstrating that radial shift in the alignment of the carpal bones occurs and that the joint contact area of the lunate increases in proportion to the decrease in radial inclination. The preoperative radiolunate and radioscaphoid angles, which were significantly larger than those of the unaffected wrist, did not change postoperatively which shows that this technique was not able to correct the flexion deformity of the lunate and the scaphoid.
Duplicated Longitudinal Bracketed Epiphysis ‘Kissing Delta Phalanx’ in the Hand
Authors: WOOD V. E. , SHUREN N.
Published: September 2002

The duplicated longitudinal bracketed epiphysis (“kissing delta”) phalanx has been described rarely. These delta bones have a bizarre appearance and are often associated with other developmental abnormalities such as central polydactyly. We have seen a total of 13 kissing delta phalanges in the hands. We discuss their natural history, look at the associated anomalies and consider the treatment options for this very rare congenital anomaly.
Subchondral Bone Mineral Density Patterns Representing the Loading History of the Wrist Joint
Authors: HOOGBERGEN M. M. , NIESSEN W. J. , SCHUURMAN A. H. , SPAUWEN P. H. M. , KAUER J. M. G.
Published: September 2002

Ten cadaver wrists were examined with CT-Absorptiometry in order to assess bone density in the subchondral bone. In normal wrists the distal radius contained two centroids of bone density, one in the lunate fossa and another in the scaphoid fossa. Pathologically altered wrists showed a shift in bone density towards the scaphoid fossa, with the subchondral bone in the lunate fossa and distal ulna becoming less dense. Bone density patterns in the wrist reflect the long-term force transmission. As bone density alters according to loading conditions, this method can be used to determine force transmission patterns before and after wrist surgery.
Modified “On-Top-Plasty” Technique for Restoring Length to Amputation Stumps
Authors: PISTRE V. , PELISSIER P. , BALLANGER A. , MARTIN D. , BAUDET J.
Published: September 2002

Five patients were successfully treated with a modified “on-top-plasty” technique, in which a finger stump is lengthened by transfer of an adjacent amputation stump with a reverse blood flow fingerstump. This technique can be performed in the acute phase or as a secondary procedure. A conventional on-top-plasty can be performed by transfer of a partially amputated index or ring finger to the “top” of the proximal phalanx of an amputated middle finger. Alternatively, the transferred part may be used in an intercalated fashion to reconstruct the middle phalanx, using a prosthesis to reconstruct the proximal interphalangeal joint. The results, complications and disadvantages of the technique are reported. We propose this procedure for the reconstruction of the middle ring finger when a free microneurovascular toe-to-hand transfer is contraindicated or refused by the patient.
Simultaneous Toe-to-Hand Transfer and Lower Extremity Amputations for Severe Upper and Lower Limb Defects: The Use of Spare Parts
Authors: CHANG J. , JONES N. F.
Published: September 2002

From 1995 to 2000, five microvascular toe-to-hand transfers were performed in three children who were simultaneously undergoing lower extremity amputations. Their ages at time of transfer ranged from 4 to 10 years and the types of lower extremity amputation included toe amputation, foot amputation and through-knee amputation. The resulting toe-to-hand transfers included three great toe-to-thumb transfers and one combined great and second toe-to-hand transfer. The toe-to-hand transfers were all successful and all the lower extremity amputations healed without complications. In all cases, improved hand function and lower extremity function was noted by the families. These unique cases represent the ultimate use of spare parts in congenital hand surgery.
The Role of Human-Derived Fibrin Sealant in the Reduction of Postoperative Flexor Tendon Adhesion Formation in Rabbits
Authors: JONES M. E. , BURNETT S. , SOUTHGATE A. , SIBBONS P. , GROBBELAAR A. O. , GREEN C. J.
Published: September 2002

This study assessed the role of a novel fibrin sealant (Vivostat®) in adhesion reduction after flexor tendon surgery. The deep flexor tendons of the 2nd and 4th digits of the left paw of 20 rabbits were exposed and a standard partial injury was performed on each. The rabbits were randomized to either immediate post-injury treatment with Vivostat® or no treatment. In each case active movement of the 2nd digit was prevented while the 4th digit was allowed to move normally. The two groups were assessed at 14 days for adhesion formation with a tensiometer. The right paw acted as the unoperated control. Results showed that there was no significant difference in the force needed to remove the tendon from its sheath when comparing the two Vivostat®-treated groups to the unoperated controls. There was, however, a highly significant difference in this force between the non-Vivostat®-treated groups and the unoperated controls. This suggests a beneficial effect of Vivostat® in reducing post surgical tendon adhesion formation.
Callus Resection for Brachial Plexus Compression Following Stress-Induced First Rib Fracture
Authors: SEKI H. , SAITOH S. , HATA Y. , MURAKAMI N. , SHIMIZU T. , TAKAOKA K.
Published: September 2002

A 27-year-old man presented with a lower trunk brachial plexus injury due to excessive callus formation following a stress-induced first rib fracture. The callus, but not the first rib, was resected through a supraclavicular approach. His symptoms resolved in 2 months, and no recurrence was seen at 2 years follow-up.
Hyaluronidase Versus Surgical Excision of Ganglia: A Prospective, Randomized Clinical Trial
Authors: JAGERS OP AKKERHUIS M. , VAN DER HEIJDEN M. , BRINK P. R. G.
Published: September 2002

This prospective, randomized clinical trial compared the treatment of ganglia by either hyaluronidase injection and aspiration or surgical excision. Fifty patients were randomly allocated to each group and 46 patients in the hyaluronidase group and 43 in the surgical group were available for follow-up at 1 year. Patients with ganglia treated with hyaluronidase had a recurrence rate of 77%, which was significantly higher ( P<0.01) than the recurrence rate after surgery (24%).
Electromechanical and elastic isotropy in the (011) plane of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 crystals: Inhomogeneous shearing of polarization
Authors: Viehland D. , Li J. F. , Amin A.
Published: September 2002

Temperature dependent electromechanical investigations of 〈110〉, 〈001〉, and 〈111〉 oriented morphotropic phase boundary compositions of Pb(Mg1/3Nb2/3)O3-PbTi03 crystals have been performed. Softening of the dielectric constant, piezoelectric constant, and Young’s modulus was found for all three orientations, near a ferroelectric rhombohedral to ferroelectric tetragonal transformation. However, the value of Young’s modulus was an order of magnitude higher along 〈111〉, than either 〈001〉 or 〈110〉. An unusual electromechanical and elastic equivalence was found between the 〈110〉 and 〈001〉 directions. This result demonstrates that the enhanced electromechanical performance of oriented piezocrystals is not constrained to the 〈001〉 orientation, but rather to the (011) plane.
Continuum model of thin film deposition incorporating finite atomic length scales
Authors: O'Sullivan Peter L. , Baumann Frieder H. , Gilmer George H. , Torre Jacques Dalla , Shin Chan-Soo , Petrov Ivan , Lee Tae-Yoon
Published: September 2002

We show that surface evolution resulting from the deposition of discrete particles is intrinsically different from that produced by continuum processes. The atomistic effects have major consequences, even when observed at macroscopic length scales. We have elucidated some of the atomistic effects by comparing: (i) numerical simulations of thin film deposition using the continuum model, (ii) atomistic (Monte Carlo) models, and (iii) experiments on the sputter deposition of Ta onto a substrate containing etched vias. We have therefore developed a continuum model which incorporates finite atomic length scales. The model incorporates effects of atomic interactions, which lead to the capture of impinging atoms that pass near a point on the film. This capture effect results in “breadloafing” at sharp convex corners where the curvature is high. We have validated our model in idealized two-dimensional simulations and obtained improved qualitative agreement with both experiment and Monte Carlo atomistic simulations. In the case of deposition into a trench, the model predicts that the protruding material from breadloafing eventually merges above the trench, leaving an enclosed void. This effect is observed in experiments, but is not reproduced when using the standard continuum model. Finally, we have also developed and implemented a more general three-dimensional model which successfully results in the breadloafing effect.
Adsorption behavior of Lander molecules on Cu(110) studied by scanning tunneling microscopy
Authors: Schunack M. , Rosei F. , Naitoh Y. , Jiang P. , Gourdon A. , Lægsgaard E. , Stensgaard I. , Joachim C. , Besenbacher F.
Published: September 2002

The adsorption of a large organic molecule, named Lander, has been studied on a Cu(110) substrate by scanning tunneling microscopy (STM). At low temperatures three different conformations of the molecule are observed on the flat surface terraces. At room temperature the Lander molecules are highly mobile and anchor preferentially to step edges. There the molecules cause a rearrangement of the Cu step atoms leading to the formation of Cu nanostructures that are adapted to the dimension of the molecule, as revealed directly by STM manipulation experiments. Upon annealing to 500 K the molecules order at higher coverages partially into small domains. In all cases the exact adsorption conformation of the molecules was identified through an interplay with elastic scattering quantum chemistry calculations.
General theory for pulse propagation in two-photon active media
Authors: Baev Alexander , Gel’mukhanov Faris , Macák Peter , Luo Yi , Ågren Hans
Published: September 2002

The propagation of laser pulses of different lengths in nonlinear media of organic absorbers is described starting out from a recently suggested dynamical theory for two-photon absorption (TPA) of molecules in solutions [J. Opt. Soc. Am. B 19, 937 (2002)]. The roles of saturation effects and pulse duration on the suppression of TPA are emphasized. The numerical simulations of the pulse propagation are performed for a two-photon active charge transfer molecule using molecular parameters obtained from first principle calculations.
Magnetoultrasonic studies in liquids for the influence of magnetic fields on frequency and amplitude
Authors: Singh O. Gourakishwar
Published: September 2002

Investigations are made for the changes in both frequency and amplitude of ultrasonic waves propagating in liquids in the presence of magnetic fields. Methods for Fourier analysis and transformation are used to estimate the characteristic changes of both shear and longitudinal waves. Experimental and analytical results in water at room temperature are in agreement qualitatively suggesting for the intensification of magnetic fields by the excitation of ultrasonic waves in conducting liquids and would lead to studies of sound velocities related to the physical structure of liquids and molecular interaction in electrolytic solutions under the influence of magnetic fields.
Fluctuation–dissipation considerations for phenomenological damping models for ferromagnetic thin films
Authors: Smith Neil
Published: September 2002

Dissipation properties of ferromagnetic thin films are traditionally characterized by phenomenological damping models related to ferromagnetic resonance (FMR) linewidths. They may also be analyzed in terms of thermal magnetization fluctuations, the connection being made through the fluctuation–dissipation theorem. This article describes how fluctuation–dissipation relations provide a means for discriminating between alternative phenomenological magnetic damping models in ways that are not obvious using traditional uniform-magnetization descriptions appropriate to FMR experiments. In particular, it is shown that recently proposed alternatives to the well-known Gilbert damping model lead to physically untenable predictions/contradictions when analyzed in this light, unlike the traditional Gilbert model itself.
Morphology and effects of hydrogen etching of porous SiC
Authors: Sagar Ashutosh , Lee C. D. , Feenstra R. M. , Inoki C. K. , Kuan T. S.
Published: September 2002

The morphology of the porous network in porous SiC has been studied. It has been found that pore formation starts with a few pores on the surface and then the porous network grows in a V-shaped branched structure below the surface. The hydrogen etching rates of porous and nonporous SiC have been measured. Etch rates of porous and nonporous wafers of various miscuts are found to be equal within a factor of two, indicating that the rate-limiting step in the etching process arises from the supply of active etching species from the gas phase. The porous SiC etches slightly faster than the nonporous SiC, which is interpreted simply in terms of the reduced average density of the porous material.
Linewidth determination in local oxidation nanolithography of silicon surfaces
Authors: Tello Marta , Garcı́a Fernando , Garcı́a Ricardo
Published: September 2002

We measure the linewidth of structures fabricated by local oxidation lithography on silicon surfaces. Two different structures, isolated and arrays of parallel lines have been generated. The oxide structures have been fabricated in the proximity of sexithiophene islands whose size is comparable to the oxide motives. The comparison between local oxides and sexithiophene islands reveals that atomic force microscopy (AFM) images faithfully reproduce the size and shape of local silicon oxides. The oxide lines have a trapezoidal shape with a flat section at the top. AFM images of the oxide structures show rather small slopes ∼0.05–0.15 which imply angles with the horizontal between 3° and 8°. The shallow angles imply a minimum feature size of 14 nm at the base for an oxide thickness of 1 nm. Linewidths of 7 nm and 20 nm at the top and base, respectively, have been fabricated. We have also demonstrated the ability to pack structures with a periodicity of 13 nm.
Unipolar “V-shaped” switching in chiral smectic C (Sm–C*) liquid crystals bounded by an ion-store film
Authors: Strangi Giuseppe , Versace Carlo , Scaramuzza Nicola , Bruno Vincenzo
Published: September 2002

We present experimental evidence of polarity dependent thresholdless switching in ferroelectric chiral smectic C liquid crystals (Sm-C*) confined by an ion-store electrochromic film. The interaction between high polarization Sm-C* liquid crystals and a mixed conductor film of tungsten oxide is responsible for unipolar hysteretic electro-optic behavior. According to Clark’s model [N. A. Clark et al., Liq. Cryst. 27, 985 (2000)], in the limit of high spontaneous polarization, the electro-optics of Sm-C* liquid crystals are dominated by electrostatics. Here, we discuss the ion store film’s influence on analogue “V-shaped” switching due to different electrostatic contributions for each polarity of the applied field.
Double injection of charge carriers in chemical vapor deposited diamond-based diodes
Authors: Weima J. A. , von Borany J. , Meusinger K. , Horstmann J. , Fahrner W. R.
Published: September 2002

Boron ion implantation of thermochemically polished chemical vapor deposited diamond films with multienergies ranging between 24 and 150 keV and a total dose of about 2×1016 cm−2 is used to get p-type conductivity. n-type conductivity is achieved by lithium ion implantation of the diamond films with a single energy of 50 keV and a dose of 2×1016 cm−2. The intrinsic areas separating the p- and n-doped regions form the active areas of the diodes into which charge carriers are simultaneously injected upon bias. Onset voltages of <10 V are due to the low concentration (∼1014 cm−3) of nitrogen related centers in the diamond films. The current–voltage (I–V) characteristics of the p-i-n diodes manifest trap filling, Frenkel–Poole emission, thermionic emission, and space charge limited current regimes. At 300 °C, currents as high as 12 mA are measured at a forward bias of 100 V. Rectification ratios of up to about four orders of magnitude are achieved. They increase with increasing width of the i region within the measured i region of 3–10 μm, as a result of the considerable decrease of the reverse bias current relative to the forward bias current.
Effects of silver doping on ferroelectric SrBi2Ta2O9
Authors: Sih B. , Jung A. , Ye Z.-G.
Published: September 2002

Silver-doped SrBi2Ta2O9 (Ag:SBT) ceramics were synthesized by solid state reactions. The reaction mechanism has been deduced based on the crystal defect chemistry. It involves the diffusion of Ag+ and O2− ions into the (Bi2O2)2+ layers between the perovskite-like units to recover the bismuth and oxygen vacancies, respectively, which were inherently present in SBT ceramics due to the volatilization of Bi2O3 at high temperatures. The Ag:SBT samples have been characterized by a variety of techniques: x-ray diffraction, dielectric and ferroelectric measurements, and impedance spectroscopy. Ag doping is found to significantly affect the structural and physical properties of SBT, including lattice parameters, Curie temperature, bulk conductivity, activation energy, and ferroelectricity. These effects have been interpreted based on the model of the recovery of oxygen and bismuth vacancies upon Ag doping. The effects of Ag diffusion should be taken into account when using Ag as electrode materials for the characterization of the electric properties of SBT and related materials.
The observation of large changes in the rotational constants of glyoxal in superfluid helium droplets upon electronic excitation
Authors: Pörtner Nikolas , Toennies J. Peter , Vilesov Andrej F.
Published: September 2002

The rotational fine structure of the vibrationless 000 band of the electronic S1←S0 transition of glyoxal in large superfluid He4 droplets (N̄4=2⋅103–2⋅104) has been interrogated with high resolution laser depletion spectroscopy. In the electronic ground singlet state S0 the rotational constants A and B̄=(B+C)/2 are less than for the free molecule by a factor of 2.87 and 2.16, respectively. In the electronic excited state S1 the rotational constant A is found to be 17% larger and the average rotational constants B̄ to be 25% smaller than in the S0 state. The unexpected large magnitudes and different signs in the observed changes are attributed to modifications in the shape of the outer electron density distribution of the molecule upon excitation. None of the previous models introduced to explain the changes in rotational constants is entirely satisfactory, presumably because of the much weaker interactions with the helium environment.
Electron spin echo envelope modulation theory for high electron spin systems in weak crystal field
Authors: Astashkin Andrei V. , Raitsimring Arnold M.
Published: September 2002

Electron spin echo envelope modulation (ESEEM) experiments with aqueous complexes of Gd3+ and Mn2+ have shown that a common and unusual feature of the primary ESEEM spectra of such high spin/weak crystal field systems is an extremely low intensity of the sum combination line. Numerical simulations of the ESEEM spectra based on the existing theory [Coffino and Peisach, J. Chem. Phys. 97, 3072 (1992); Larsen and Singel, J. Chem. Phys. 98, 6704 (1993)] could not reproduce these ESEEM spectra. In this work the theoretical description of the ESEEM was revised and corrected, and new expressions were derived for the ESEEM from high electron spin (S>1/2) systems in a weak crystal field, interacting with a nuclear spin I=1/2. The corrections primarily affected the shape and intensity of the sum combination line, whose position was found to be sensitive to the product of the crystal field and anisotropic hyperfine interaction constants. These theoretical improvements resulted in a successful simulation of the primary ESEEM from a model system, Mn2+(H2O)6 complex in a frozen glassy water–methanol solution. The results of this work show that the shape and intensity of the sum combination line in ESEEM spectra may be used for evaluating the distribution of crystal field interactions in Mn2+, Gd3+, and similar complexes.
Interfacial properties deduced from nucleation experiments: A Cahn–Hilliard analysis
Authors: Gránásy László , Pusztai Tamás , James Peter F.
Published: September 2002

We apply a single-order-parameter Cahn–Hilliard theory to deduce properties of the fluid–crystal interface from nucleation experiments: The two Cahn–Hilliard parameters (the free energy scale and the coefficient of the square-gradient term) are chosen so that the experimentally determined interfacial free energy of nuclei is recovered. The theory is then used to predict the thickness and free energy of the equilibrium planar interface, and other quantities such as the Tolman length and characteristic thickness, which describe the curvature dependence of the interfacial free energy. The accuracy of the method is demonstrated on systems (Lennard-Jones and ice-water) for which these properties are known. Experimental data available for five stoichiometric oxide glasses are then analyzed. The reduced interfacial free energy (Turnbull’s α) and the interface thickness, we obtained, cover the α=0.28–0.51 and the d=0.8–1.6 nm ranges. For oxide glasses we find that α scales with n−1/3, where n is the number of molecules per formula unit. In agreement with computer simulations, the Tolman length is strongly size dependent, while far weaker though still perceptible temperature dependence is observed for the characteristic interface thickness used in Gránásy’s phenomenological diffuse interface theory. In some cases bulk crystal properties prevail at the center of nuclei, while in other systems the nuclei are ramified, and the local properties significantly deviate from those of the macroscopic crystal. The accuracy of these results rests on a hypothesized temperature independence of the Cahn–Hilliard parameters, an assumption whose validity remains to be seen at large undercoolings.
Electron diffraction and high-resolution transmission electron microscopy of the high temperature crystal structures of GexSb2Te3+x (x=1,2,3) phase change material
Authors: Kooi B. J. , De Hosson J. Th. M.
Published: September 2002

The crystal structures of GeSb2Te4, Ge2Sb2Te5, and Ge3Sb2Te6 were determined using electron diffraction and high-resolution transmission electron microscopy. The structure determined for the former two crystals deviates from the ones proposed in the literature. These crystal structures were developed jointly upon cooling of liquid Ge2Sb2Te5. A stacking disorder parallel to the basal plane was observed that increases with increasing cooling rates. For the GexSb2Te3+x (x=1,2,3) crystals it is shown that an a,b,c stacking holds with an alternating stacking of x GeTe double layers identically present in binary GeTe and one Te–Sb–Te–Te–Sb– repeat unit also present in binary Sb2Te3. A stacking disorder is a logical consequence of building crystals with these two principal units. On the other hand, it is likely that all stable crystals of the Ge–Sb–Te systems are an ordered sequence of these two units. Some of the implications of these findings of the stable and metastable crystal structures that develop from amorphous Ge2Sb2Te5 are presented so as to understand the crucial crystallization process in Ge2Sb2Te5 phase change material.
Rapid thermal annealing effects on blue luminescence of As-implanted GaN
Authors: Huang H. Y. , Xiao J. Q. , Ku C. S. , Chung H. M. , Chen W. K. , Chen W. H. , Lee M. C. , Lee H. Y.
Published: September 2002

Rapid thermal annealing effects on blue luminescence of As-implanted GaN grown by metalorganic vapor phases epitaxy were investigated by means of photoluminescence and photoluminescence excitation measurements. The locations of the As-implantation induced bands and the associated transition channels for the emission were determined to characterize the As-implanted GaN. After the rapid thermal annealing treatment, the deep As-related levels become more ready to be populated by photoexcitation at low temperature so that the new blue luminescence emission peak is enhanced significantly, whose activation energy is found to be 46 meV.
Accurate quantum calculations on three-body collisions in recombination and collision-induced dissociation. I. Converged probabilities for the H+Ne2 system
Authors: Parker Gregory A. , Walker Robert B. , Kendrick Brian K. , T Pack Russell
Published: September 2002

The exact quantum theory of atomic recombination and collision-induced dissociation (CID) is presented using hyperspherical coordinates. Delves’ coordinates are emphasized, methods for doing numerically exact calculations are discussed and implemented, and fully converged dissociation probabilities (J=0) are presented for a model H+Ne2⇌H+Ne+Ne system. These are the first accurate CID calculations reported for any atomic system in the full three-dimensional physical space.
Photoinduced reactions in the Mg+–NHn(CH3)3−n complex ions: Effect of the methyl substitution
Authors: Guo Wenyue , Liu Haichuan , Yang Shihe
Published: September 2002

Photoinduced reactions in Mg+–NH2CH3 and Mg+–NH(CH3)2 have been studied in the spectral range of 230–440 nm. Although the N–H bond activation channel was found to be prominent in the photodissociation of Mg+–NH3 [Yoshida, Okai, and Fuke, Chem. Phys. Lett. 347, 93 (2001)], it is very unfavorable as the ammonia is replaced by methylamines in the complex. Instead, C–H bond cleavage products are observed from Mg+–NH2CH3(CH2NH2+) and exclusively produced from Mg+–NH(CH3)2((CH3)HN+=CH2) after photoexcitation. For Mg+–NH2CH3, the C–N bond activation product Mg+NH2 and the charge transfer product CH3NH2+ are also abundant. The action spectra of the complexes consist of two pronounced peaks on the red and blue side of the Mg+ 3 2P←3 2S atomic transition. The calculated absorption spectra of the two complexes using the optimized structures of their ground states are in good agreement with the observed action spectra. On the basis of the branching fraction data and the calculated complex structures, the C–H bond activation is invoked to account for the MgH loss channel after photoexcitation, followed by a nonadiabatic transition to the ground state by a bond-stretch mechanism. However, the formation of Mg+NH2 from photodissociation of Mg+–NH2CH3 involves the insertion of Mg+ into the C–N bond. Finally, the photoinduced charge transfer product CH3NH2+ are also identified from Mg+–NH2CH3 but not from Mg+–NH(CH3)2.
Effective pair potentials in charged molecular systems: Water mediated interactions
Authors: Bagatella-Flores N. , González-Mozuelos P.
Published: September 2002

We study the effective interactions among ions of various valences immersed in a polar solvent by determining the effective pair potentials (EPPs) obtained after “contracting” (integrating out) the degrees of freedom of the solvent molecules. This is accomplished by extending the framework of the dressed ion theory to describe the formal solution of the reference interaction site model integral equations. It is shown here that these EPPs have in the asymptotic limit the expected Coulomb form, even for finite concentrations of the solute. At shorter distances, the molecular structure of the solvent induces noticeable deviations of the EPPs from the reference potentials corresponding to an analogous model system with a structureless dielectric background. These deviations remain almost invariant over the whole range of concentrations considered here. These EPPs are therefore suitable to be used as the input for computer simulations at the McMillan–Mayer level. We also analyze with some detail the consequences of the short range behavior of the EPPs involving multivalent ions.
Charge transfer and nonadiabatic dynamics of diatomic anions in clusters
Authors: Cho Eunseog , Shin Seokmin
Published: September 2002

We have studied the photodissociation and recombination dynamics of diatomic anions in size-selected clusters by using simple model systems. The main purpose of the study is to provide a theoretical background for a better understanding of the salient features of the charge transfer and nonadiabatic transitions involved in the dynamics of solvated molecular ions. Calculations have been performed on the photodissociation and recombination of the model diatomic anion X2− embedded in N2O and CO2 clusters. The homonuclear diatomic anion is modeled as one-electron system consisting of two identical nuclei and an extra electron. The nuclear and electronic dynamics of X2− are treated quantum mechanically, while the motions of the solvent molecules are described by classical dynamics. Nonadiabatic theoretical calculations, in which the electronic and the nuclear dynamics are treated simultaneously, can reveal the importance of nonadiabatic effects by including intrinsically all electronic states. It is found that extensive nonadiabatic transitions between ground and excited electronic states are involved in the dynamics of X2− in molecular clusters. It is suggested that changes in anion electronic structures and corresponding charge switching can lead to a multitude of pathways for dissociation-recombination dynamics. The results of the present study illustrate the microscopic details of the electronically nonadiabatic processes which control the photodissociation dynamics of molecular ions in clusters.
Acoustic and optical properties of (Li2O)0.2−x(Na2O)x(TeO2)0.8 glasses
Authors: Roychoudhury P. , Batabyal Sudip K. , Paul A. , Basu C. , Mukherjee S. , Goswami K.
Published: September 2002

We study the ultrasonic properties of five different samples of Na2O-Li2O-TeO2 glass system within the temperature range 140–420 K (for longitudinal polarization) and 140–300 K (for transverse polarization). The variation of ultrasonic velocity of all samples shows negative gradient with temperature and has been explained by the existing theories. No well defined broad peak has been observed in the temperature variation of attenuation and a mixed alkali type peak starts growing at temperature ≈350 K. Composition dependence of elastic properties and density shows maximum or minimum at a critical concentration of Na2O. Optical transmission and reflection spectra were recorded in the UV-visible region at room temperature. The physical quantities such as optical energy gap, refractive index and optical dielectric constant were evaluated from the spectra. The theoretical fitting of the optical absorption indicates that the present glass system behaves as indirect gap semiconductor.
Excitation of Tm3+ by resonant energy transfer from Si nanocrystals
Authors: Watanabe Kei , Tamaoka Hiroyuki , Fujii Minoru , Hayashi Shinji
Published: September 2002

Photoluminescence (PL) properties and PL decay dynamics of SiO2 films containing Si nanocrystals (nc-Si) and Tm3+ were studied. The samples exhibited a broad PL at around 1.5 eV due to the recombination of excitons in nc-Si, and rather sharp PL at 1.58, 0.84, and 0.69 eV corresponding to the intra-4f shell transitions of Tm3+. The correlation between the intensities of nc-Si and Tm3+ related PL was studied as a function of the Tm concentration, the size of nc-Si, and the temperature. It was found that the intensity of Tm3+ related PL depends strongly on the size of nc-Si. At low temperatures, the spectral shape of nc-Si PL was strongly modified by doping Tm. From analysis of the modified spectral shape, a resonant energy transfer from nc-Si to Tm3+ is discussed.
Enhancement of switching stability of tunneling magnetoresistance systems with artificial ferrimagnets
Authors: You Chun-Yeol , Bader S. D.
Published: September 2002

In the study of spin dependent magnetic tunneling junctions, the switching stability of the magnetically hard layer is a crucial issue for long-term use in magnetic random access memory. After N switching cycles of the soft layer, the hard layer would be demagnetized due to the stray field from the domain wall created during switching of the soft layer. Therefore, reducing the stray field from the soft layer is the way to increase switching stability. In this study, we propose a structure which replaces the usual soft layer (typically permalloy, Fe, or Co) with an artificial ferrimagnet to reduce the stray field. The artificial ferrimagnet consists of a trilayer with an interlayer that antiferromagnetically couples two ferromagnetic layers of unequal thickness. The total stray field from the artificial ferrimagnet structure can be approximated as the sum of the stray fields from the two ferromagnetic layers. Since the sign of the stray field of the two layers is opposite, due to antiferromagnetic coupling, the total stray field is reduced due to cancellation. Since the magnitude of the stray field depends on the magnetic properties and the thickness of each layer and the distance from the magnetic layer, we can tailor the two magnetic layers of the artificial ferrimagnet structure to minimize the total stray field.
Semimetal–semiconductor transition in Bi1−xSbx alloy nanowires and their thermoelectric properties
Authors: Lin Yu-Ming , Rabin O. , Cronin S. B. , Ying Jackie Y. , Dresselhaus M. S.
Published: September 2002

The resistivity of Bi1−xSbx nanowire arrays exhibits complex variations as a function of Sb content x and temperature T due to the unique semimetal-to-semiconductor (SM–SC) transition experienced by the nanowires. Seebeck coefficient measurements show enhanced thermopower due to Sb alloying and the reduction in wire diameter. The theoretical model not only explains these transport measurements, but also suggests a useful technique to experimentally determine (i) whether the wire is semimetallic or semiconducting, (ii) the carrier concentration, and (iii) the conditions for the SM–SC transition.