bluuebunny/crossref_metadata_2025 huggingface dataset:
The Clinical Efficacy of Topical and Systemic Therapy for the Treatment of Feline Ocular Chlamydiosis
Authors: Sparkes A H , Caney S M A , Sturgess C P , Gruffydd-Jones T J
Published: March 2004

Twenty-four specific-pathogen-free-derived cats aged four to 11 months were challenged by ocular application of a field isolate of Chlamydia psittaci to evaluate the effect of topical and systemic therapy on the course of disease. The cats were monitored for 35 days post-challenge, with severity of clinical signs being measured using a scoring system, and ocular shedding of the organism monitored by culture of conjunctival swabs. All cats developed active C psittaci infection, and after 7 days the cats were randomly assigned to one of four treatment groups: Group P (placebo) was given twice-daily ophthalmic tear-replacement ointment; group F was given twice-daily topical 1% fusidic acid ophthalmic viscous drops; group C was given twice-daily topical 1% chlortetracycline ophthalmic ointment; and group D was given doxycycline at 10 mg/kg daily per os in addition to twice-daily topical 1% fusidic acid ophthalmic ointment. Within 24 h of commencement of therapy, group D had significantly lower median clinical scores than group P, and with the exception of day 16, this trend was maintained throughout the observation period. Median clinical scores of cats in group F were not appreciably different to those in group P, whereas the median scores of cats in group C generally fell between those of groups P and D. The median duration of C psittaci shedding was 10 and 15 days for groups D and C respectively, but four of the six cats in groups F and P were still shedding organisms at the end of the study (day 35). In this study, systemic therapy with doxycycline proved superior to topical therapy in the treatment of feline chlamydiosis.
Efficacy of Oral Terbinafine in Feline Dermatophytosis Due to Microsporum Canis
Authors: Mancianti Francesca , Pedonese Francesca , Millanta Francesca , Guarnieri Leonardo
Published: March 2004

Microsporum canis is the dermatophyte most commonly responsible for ringworm in cats. The purpose of this paper was to evaluate the in vivo efficacy of oral terbinafine (Lamisil; Sandoz) in the treatment of feline ringworm caused by M canis, and to consider this drug as an alternative to griseofulvin or imidazoles. Fifteen cats infected with M canis were treated orally once daily with 30 mg/kg of terbinafine over a 2-week period. All treated animals were checked for dermatophytes on the last day of treatment, a month later and 3 months after the last administration of the drug. Only 12 cats could be used in the whole trial and 11 of these (92%) showed a complete cure. Terbinafine could be an effective alternative to griseofulvin when fungal resistance or idiosyncrasic intolerance are shown and, compared with griseofulvin, could give a faster rate of cure and less relapses.
Intrathoracic Tracheal Rupture
Authors: Lawrence D T , Lang J , Culvenor J , Mischol G , Haynes S , Swinney G
Published: March 2004

This paper reports five new cases of intrathoracic tracheal rupture in cats, and summarizes these cases in conjunction with 11 cases from the literature. Most cats had no obvious respiratory signs at the time of injury, and in half of them the tracheal rupture was the only injury. The interval from trauma to onset of dyspnoea ranged from 1 to 28 days (median 12.5 days). Radiographic findings include loss of continuity of the trachea, often with a gas-filled diverticulum present between separated tracheal rings. With careful attention to surgical technique and anaesthetic management the prognosis for these cats is excellent. All eight of the cats reported in the last 14 years having surgical correction survived and returned to normal. The surgical anatomy, approach and tracheal anastomosis technique is described and recommendations for anaesthetic management are made.
Obstructive Inflammatory Laryngeal Disease in Three Cats
Authors: Tasker S , Foster D J , Corcoran B M , Whitbread T J , Kirby B M
Published: March 2004

Three cats with upper respiratory tract obstruction due to laryngeal inflammation are presented. Cervical radiography showed the presence of a soft tissue mass in the laryngeal region in all cases, and laryngoscopy allowed direct visualization of a mass associated with the larynx. Laryngeal samples were obtained by a combination of fine needle aspiration, cutting biopsy forceps, by ventral laryngotomy, and at post-mortem. Histopathology of the laryngeal samples showed the presence of a predominantly granulomatous inflammation, with macrophage and lymphocyte infiltration. One case was euthanased due to severe dyspnoea. The remaining two cases underwent combined medical (corticosteroid and antibiotic) and surgical (permanent tracheostomy or excision of laryngeal tissue by ventral laryngotomy) treatment. One case died of an undetermined cause 15 weeks after surgery while the other case remains clinically well 20 months after diagnosis. Recognition of the existence of granulomatous laryngitis is important as clinical signs and radiographic findings are indistinguishable from laryngeal neoplasia.
Hereditary and Congenital Ocular Disease in the Cat
Authors: Narfström K
Published: March 2004

The aim of this review of hereditary and congenital ocular disease in cats is to present an overview of the most common disorders seen in this species, the pathogenesis of the problems and wherever possible, how they are treated. Several defects are common in breeds such as the Persian, Himalayan and Burmese cats and affect the anterior segment of the eye. Examples are agenesis of the eyelids, dermoids, entropion and corneal sequestrum. Other problems such as cataracts, lens luxation and retinal dysplasia, cause problems of the intraocular structures, but are less common in cats compared to dogs. Finally, various parts of the retina and in some diseases other parts of the eye, are specifically affected by hereditary diseases. Examples of these are lysosomal storage disease, Chediak-Higashi syndrome and progressive rod cone degeneration and rod cone dysplasia. Research of the latter two hereditary diseases, both described in the Abyssinian breed of cat, have made affected individuals important animal models for research into comparable diseases of humans.
Current Understanding of Feline Diabetes: Part 1, Pathogenesis
Authors: Rand J
Published: March 2004

Type-1 diabetes, resulting from immune-mediated destruction of beta cells, appears to be rare in cats. Type-2 diabetes, characterised by inadequate insulin secretion and impaired insulin action, is the most common form of diabetes in cats. Other specific forms of diabetes constitute a substantial minority of cases. The most common is pancreatic destruction from pancreatic adenocarcinoma. Less frequent causes are insulin resistance from other endocrinopathies including acromegaly. Diabetes in cats is characterised by variable loss of insulin secretory capacity and insulin resistance. Glucose toxicity, islet amyloid-deposition, and pancreatitis contribute to further loss of beta cells and failure of insulin secretion. A significant number of cats undergo remission of their diabetes, usually 1–3 months after good glycaemic control is instituted. Obesity, old age, and Burmese breed are recognised risk factors for the development of diabetes in cats.
Feline Inflammatory Bowel Disease: A Review
Authors: Willard M D
Published: March 2004

Inflammatory bowel disease (IBD), while a popular diagnosis, may not occur as commonly as it is diagnosed. It is a diagnosis of exclusion, meaning that it is important to eliminate diseases that mimick it. Dietary intolerance or allergy in particular, can have the same clinical and histologic appearance as IBD. Likewise, well-differentiated alimentary lymphosarcoma can also be confused with it. Intestinal biopsies are useful, but must be taken carefully and then evaluated by someone with interest and expertise in alimentary tract pathology. Therefore, it behoves the clinician to carefully consider the diagnosis instead of starting multiple drug therapy in a cavalier fashion. Well constructed dietary therapy can often be beneficial for both dietary problems and IBD.
Vegetative Endocarditis in Six Cats
Authors: Malik R , Barrs V R , Church D B , Zahn A , Allan G S , Martin P , Wigney D I , Love D N
Published: March 2004

Between 1990 and 1997 vegetative endocarditis was diagnosed in six neutered cats (three males, three females) aged between 3 and 9 years. Two cats were purebred (one Persian and one Tonkinese), the remaining four being domestic short haired cats. The diagnosis was made using echocardiography (five cases) or at necropsy (one case). Concurrent involvement of the aortic and mitral valve was noted in four cats, the aortic valve alone was affected in one case, and the tricuspid valve in another. A likely microbiological diagnosis was obtained in three cats: a Bartonella species in two cats based on positive blood culture and a Streptococcus species in one cat based on Gram stain of valve lesions at necropsy. In another cat, Gram-positive cocci were demonstrated histologically in tricuspid vegetations. Invariably, cats had signs of congestive heart failure (left-sided in five cats, right-sided in one), and this was the major factor contributing to mortality in four cases. Signs referable to sepsis were prominent in only two patients. Appropriate medical therapy, consisting of antimicrobials and drugs to treat congestive heart failure, resulted in survival for 5 and 11 months, respectively, in two cases. The other cats died within 2 weeks of diagnosis, including two which received aggressive treatment in hospital.
Circulating Lupus Anticoagulant and Probable Systemic Lupus Erythematosus in a Cat
Authors: Lusson D , Billiemaz B , Chabanne J L
Published: March 2004

An adult domestic short hair cat was presented in a critical condition with icterus. Various investigations demonstrated the presence of haemolytic anaemia and hepatic abnormalities, as well as significant coagulation defects. Systemic lupus erythematosus (SLE) was suggested as a possible cause.
Elastic beam over an adhesive wavy foundation
Authors: Carbone Giuseppe , Decuzzi Paolo
Published: March 2004

The adhesive behavior of a thin infinitely long elastic beam resting over a wavy rigid foundation with wavelength λ is studied. Three governing parameters have been identified describing the physical and geometrical properties of the system: the dimensionless surface energy γ̃=γ/Es, the dimensionless amplitude h̃=h/λ of the substrate, and thickness of the beam s̃=s/λ. Analyzing the variation of the total energy of the system as a function of the governing parameters three different adhesive regimes have been individuated: full adhesion, partial adhesion, and no adhesion (point contact). An effective surface energy has been considered showing that the effect of surface waviness could be beneficial in increasing the adhesive strength of the system. In particular for γ̃=1.0 and s̃=0.1, it has been evaluated a maximum effective interface energy of about 1.4γ under full contact conditions. Larger amplifications are expected for higher γ̃ and smaller s̃.
Study of GaN light-emitting diodes fabricated by laser lift-off technique
Authors: Chu Chen-Fu , Lai Fang-I , Chu Jung-Tang , Yu Chang-Chin , Lin Chia-Feng , Kuo Hao-Chung , Wang S. C.
Published: March 2004

The fabrication process and performance characteristics of the laser lift-off (LLO) GaN light-emitting diodes (LEDs) were investigated. The LLO-GaN LEDs were fabricated by lifting off the GaN LED wafer structure grown on the original sapphire substrate by a KrF excimer laser at 248 nm wavelength with the laser fluence of 0.6 J/cm2 and transferring it onto a Cu substrate. The LLO-GaN LEDs on Cu show a nearly four-fold increase in the light output power over the regular LLO-LEDs on the sapphire substrate. High operation current up to 400 mA for the LLO-LEDs on Cu was also demonstrated. Based on the emission wavelength shift with the operating current data, the LLO-LEDs on Cu show an estimated improvement of heat dissipation capacities by nearly four times over the light-emitting devices on sapphire substrate. The LLO process should be applicable to other GaN-based LEDs in particular for those high light output power and high operation current devices.
Large-eddy simulation of conductive flows at low magnetic Reynolds number
Authors: Knaepen Bernard , Moin Parviz
Published: March 2004

Using the method of large-eddy simulation, we study decaying homogeneous turbulence of a conductive flow under the influence of an applied external magnetic field at low magnetic Reynolds number. In order to assess the performance of large-eddy simulation, comparison with high resolution (5123) direct numerical simulation is performed. Results show that the modeling of subgrid scales using the dynamic Smagorinsky model is very effective in the present context.
Second-order optical nonlinearity and change in refractive index in silica glasses by a combination of thermal poling and x-ray irradiation
Authors: Kameyama Akihiro , Yokotani Atsushi , Kurosawa Kou
Published: March 2004

Second-order optical nonlinearity was found to be generated in high-purity silica glasses when they were exposed to x-ray radiation and then thermally poled. Two kinds of second-order optical nonlinearity, near-surface nonlinearity localized in a thin layer near the sample surface and bulk nonlinearity spreading throughout the whole sample, were observed. The maximum χ33(2) values of near-surface and bulk nonlinearity were 0.20 and 0.43 pm/V, respectively. Further, a change in refractive index of Δn=4×10−3 was also observed in the sample. The χ33(2) value of the bulk nonlinearity and the change in refractive index increased with the x-ray intensity. On the other hand, the χ33(2) value of the near-surface nonlinearity had a tendency to saturate when the intensity was higher than 1.3 mW/cm2. Based on absorption spectra of the samples, both the bulk nonlinearity and the refractive index change were found to be associated with point defects such as the E′ center (≡Si⋅) and nonbridging oxygen ions (NBO−,≡Si–O−).
Toward making layered films using selective ionization in InSb and GaSb laser ablation plumes
Authors: Kelly Michael C. , Gomlak Geoff , Panayotov Valentin G. , Koplitz Brent
Published: March 2004

The 308 nm laser ablation of InSb and GaSb has been investigated with the goal being to exert macroscopic control over the ablation plume. By taking advantage of the lower ionization potential of the group III element, In or Ga can be selectively ionized within the ablation plume by a 193 nm (6.4 eV) photon. The ionized species are removed from the plume with an electric field. As shown by x-ray photoelectron spectra, films subsequently deposited are diminished in In or Ga. A three-cycle deposition study demonstrates that a depleted layer of InSb can be deposited between two nondepleted layers of InSb.
Ultrafast polarization modulation induced by the “virtual excitation” of spin-polarized excitons in quantum wells: Application to all-optical switching
Authors: Gansen Eric J. , Smirl Arthur L.
Published: March 2004

The operation of an all-optical coherent polarization switch that makes use of spin-polarized virtual excitons in unstrained quantum wells is thoroughly investigated experimentally over a wide range of excitation intensities. The device is shown to exhibit a 415 fs switching time and a contrast ratio of >300:1 at ∼100 K in a thin (40 well) sample. The switching mechanisms are discussed in terms of the circular optical selection rules and the virtual excitation is studied by performing differential measurements for various input polarizations. The polarization state changes induced by the spin-polarized virtual population are measured and their contributions to the switch signal separated using a combination of time-averaged, time-resolved, and spectrally resolved ellipsometric techniques.
Comparison of mixed anion, InAsyP1−y and mixed cation, InxAl1−xAs metamorphic buffers grown by molecular beam epitaxy on (100) InP substrates
Authors: Hudait M. K. , Lin Y. , Palmisiano M. N. , Tivarus C. , Pelz J. P. , Ringel S. A.
Published: March 2004

The structural, morphological, and defect properties of mixed anion, InAsyP1−y and mixed cation, InxAl1−xAs metamorphic step-graded buffers grown on InP substrates are investigated and compared. Two types of buffers were grown to span the identical range of lattice constants and lattice mismatch (∼1.1–1.2%) on (100) InP substrates by solid source molecular beam epitaxy. Symmetric relaxation of ∼90% in the two orthogonal 〈110〉 directions with minimal lattice tilt was observed for the terminal InAs0.4P0.6 and In0.7Al0.3As overlayers of each graded buffer type, indicating nearly equal numbers of α and β dislocations were formed during the relaxation process and that the relaxation is near equilibrium and hence insensitive to asymmetric dislocation kinetics. Atomic force microscopy reveals extremely ordered crosshatch morphology and very low root mean square (rms) roughness of ∼2.2 nm for the InAsP relaxed buffers compared to the InAlAs relaxed buffers (∼7.3 nm) at the same degree of lattice mismatch with respect to the InP substrates. Moreover, phase decomposition is observed for the InAlAs buffers, whereas InAsP buffers displayed ideal, step-graded buffer characteristics. The impact of the structural differences between the two buffer types on metamorphic devices was demonstrated by comparing identical 0.6 eV band gap lattice-mismatched In0.69Ga0.31As thermophotovoltaic (TPV) devices that were grown on these buffers. Clearly superior device performance was achieved on InAsyP1−y buffers, which is attributed primarily to the impact of layer roughness on the carrier recombination rates near the front window/emitter interface of the TPV devices.
Light-induced modification of a-SiOx II: Laser crystallization
Authors: Janotta Andreas , Dikce Yavuz , Schmidt Matthias , Eisele Christopher , Stutzmann Martin , Luysberg Martina , Houben Lothar
Published: March 2004

Amorphous hydrogenated silicon suboxides (a-SiOx:H) were deposited by plasma enhanced chemical vapor deposition from the source gases SiH4, H2, and CO2. The band gap of the samples can be tuned from 1.9 to 3.0 eV by varying the oxygen content from 0 to 50 at. %. H-effused samples were irradiated by ultraviolet laser pulses with intensities up to 480 mJ/cm2. The structural changes and the crystallization behavior were investigated as a function of oxygen content and laser intensity. A decrease of the melting threshold by a factor of two with increasing oxygen content (0–44 at. %) was observed for the SiOx samples. Above the respective melting thresholds, not only a deterioration of the structural properties but also indications of a segregation of Si crystallites were found. Raman spectroscopy and transmission electron microscopy gave evidence for the existence of Si crystallites up to oxygen contents of 40 at. %. The crystal size reached an optimum for oxygen concentrations between 10 and 30 at. %.
Optical properties and microring laser of conducting polymers with Sn atoms in main chains
Authors: Yoshida Y. , Nishihara Y. , Fujii A. , Ozaki M. , Yoshino K. , Kim H. K. , Baek N. S. , Choi S. K.
Published: March 2004

Optical properties of conducting polymers with Sn atoms in main chains, such as optical absorption, photoluminescence (PL), and electroluminescence, have been studied. The electronic energy structures have been determined by optical and electrochemical measurements. Strong PL with high quantum efficiency has been clarified in the films, and photopumped multimode laser emission was demonstrated from cylindrical microcavities formed by these polymers coated around optical fibers.
Mechanisms of laser drilling of metal plates underwater
Authors: Lu J. , Xu R. Q. , Chen X. , Shen Z. H. , Ni X. W. , Zhang S. Y. , Gao C. M.
Published: March 2004

Several metal plates with different thickness including copper, iron, aluminum, and stainless steel have been drilled in the surroundings of air and water, respectively, by a Q-switched pulsed Nd:yttrium–aluminum–garnet laser. It is observed that for the same metal plate less energy is needed to drill a hole in water than that in air, and the surface morphology of hole drilled in water is improved greatly than that in air by comparison of the scanning electron micrographs. The underlying mechanisms behind the efficiency and quality enhancement in water are further investigated by means of optical beam deflection technique. The experimental results show that due to the water confinement the peak amplitude and duration of the laser-ablation-generated impact underwater is much larger than that in air. During the underwater laser drilling, besides laser ablation effect, both the first and second liquid-jet-induced impulses by cavitation bubble collapse in the vicinity of a solid boundary are also observed and their amplitudes are, respectively, about 12.4 and 5.2 times that of the laser ablation impact in air. Cavitation bubbles are the special dynamic phenomenon occurring in liquids. Therefore, it is concluded that in-air-drilling laser ablation-produced impact is a dominant mechanism; while during laser underwater drilling, it is the result of a combination of ablation-produced impact effect and liquid-jet-induced impact, especially the latter. Thus, the efficiency and quality of laser processing in the surrounding water can be greatly increased and improved compared with that in air.
Multiple scattering and nonlinear thermal emission of Yb3+, Er3+:Y2O3 nanopowders
Authors: Redmond S. , Rand S. C. , Ruan X. L. , Kaviany M.
Published: March 2004

Radiation transport and multiple scattering calculations are presented and compared with experimental observations to characterize light attenuation in high emissivity nanopowders irradiated with low power laser light at room temperature, and to explain the associated white light emission and the onset of melting. Using radiation tuned to an absorption resonance of Yb3+ dopants in Y2O3 nanopowder, we observed the onset of intense blackbody emission above a well-defined intensity threshold. Local melting of the compact above threshold leads to the formation of single crystal microtubes. Evidence is provided to show that two-flux transport theory and diffusion theory both significantly underestimate the absorption due to dependent, multiple scattering and that the threshold for the thermal runaway process responsible for this behavior is very sensitive to porosity of the random medium.
Liquid behavior inside a reflective display pixel based on electrowetting
Authors: Roques-Carmes Thibault , Hayes Robert A. , Feenstra B. J. , Schlangen L. J. M.
Published: March 2004

This article deals with the behavior of fluids inside a reflective display based on electrowetting. The advantage of using electrowetting as a principle for a reflective display has been demonstrated [R. A. Hayes and B. J. Feenstra, Nature (London) 425, 383 (2003)]. The principle is based on the controlled two-dimensional movement of an oil/water interface across a hydrophobic fluoropolymer insulator. The main objective of this article is to show experimentally the influence of the oil film curvature on the kinetics of the optical switch. For this we explore the electrowetting behavior and the fluidic motion as a function of several parameters, including addressing voltage, colored oil film thickness, oil type, and device size. The electro-optic characteristics and the switching dynamics of a single electrowetting pixel are studied. The results indicate that the competition between capillary forces and electrostatic forces governs the voltage driven oil contraction while capillary forces only drive the oil relaxation upon voltage removal. Consequently, a major parameter that controls the electrowetting behavior is the curvature of the oil/water interface. When increasing the oil film thickness or decreasing the device size, the oil film curvature increases. Hence, the capillary forces become stronger and the voltage required to achieve a particular oil contraction increases. With increasing curvature of the spherical oil cap, oil film relaxation, which is only capillary driven, is more rapid. The oil viscosity also plays a role in the speed of the oil movement. The reduction of the oil viscosity leads to an increase in the extent and speed of the oil/water interface movement. A linear relationship between the pixel capacitance and the resulting pixel white area percentage is found experimentally and is reconciled with an electrical model.
Characterization and modeling of tungsten nanoparticles generated by laser-assisted chemical vapor deposition
Authors: Landström L. , Kokavecz J. , Lu J. , Heszler P.
Published: March 2004

Tungsten nanoparticles were generated by photolytical (UV) laser-activated chemical vapor deposition from WF6/H2/Ar gas mixture. Emission spectroscopy of thermal radiation allowed temperature determination of the nanoparticles while varying the laser fluence. A model including known cooling mechanisms was used to calculate the laser-induced temperature as a function of time and laser fluence, where the only fitting parameter was the absorption efficiency of the particles, obtained from measured temperatures. Size decrease of the particles due to evaporation was modeled at different laser fluences, and connected to size-distribution measurements from transmission electron microscopy micrographs, where a maximum geometric mean diameter (for the experimental conditions used) of 10 nm was obseved at a laser fluence of ∼120 mJ/cm2. Measurements and the model calculations showed that the laser-excited particles reached the melting temperature of tungsten at ∼95 mJ/cm2. Above ∼130 mJ/cm2, very high rates of evaporation of W atoms were found, resulting in a decrease in size of the deposited particles. Crystalline, metastable β-W nanoparticles were found above ∼100 mJ/cm2 by both electron and x-ray diffraction. Below fluences of ∼100 mJ/cm2, i.e., corresponding to the value necessary for melting, amorphous nanoparticles were obtained.
Investigation of thermal effect on electrical properties of Si0.887Ge0.113 and Si0.887−yGe0.113Cy films
Authors: Feng W. , Choi W. K.
Published: March 2004

Thermal effects on the bulk and interface electrical properties of Si0.887Ge0.113 and Si0.887−yGe0.113Cy films annealed at an oxidizing or inert ambient were investigated. We found that while annealing the Si0.887−yGe0.113Cy films at an oxidizing ambient reduced the C content significantly, a significant amount of SiC precipitates was found in films annealed in an inert ambient. The high interface state value of the Al–SiO2–Si0.887Ge0.113 capacitor resulted in a low minority carrier generation lifetime and a frequency dispersion behavior at the depletion region of such a device. A good agreement in the interface state values was obtained from the capacitance versus voltage and the deep level transient spectroscopy measurements performed on the Al–SiO2–Si0.887Ge0.113 capacitors. For the capacitors fabricated on Si0.887−yGe0.113Cy substrates, the significant increase in the apparent substrate doping level was attributed to the SiC precipitates in the film caused by the high temperature oxidation process. The capacitance versus frequency measurements showed the influence of interface state and bulk defects on the frequency dependence at the depletion and inversion regions of capacitors fabricated on Si0.887−yGe0.113Cy substrates.
Control of the magnetic ground state by A-site substitution in Pr0.6Ca0.4MnO3: Impact upon the multistep-like behavior of magnetization
Authors: Zhu D. , Raveau B. , Maignan A. , Hervieu M. , Hardy V. , Martin C.
Published: March 2004

The substitution of barium and strontium for calcium in the pseudo-charge exchange (CE)-type charge ordered manganite Pr0.6Ca0.4MnO3 has been reinvestigated for low substitution levels (<10%). It is shown that Ba or Sr substitution exhibits a greater ability to induce ferromagnetism, metallicity and sharp magnetization, and resistivity multisteps at low temperature (2.5 K) in this phase, than in the CE-type manganite Pr0.5Ca0.5MnO3. The crucial role of the size of the A-site impurity is emphasized, the larger Ba2+ cation being much more efficient than Sr2+ to induce such effects. This study demonstrates that the multistep-like behavior, previously observed for Mn-site substitution in Pr0.6Ca0.4MnO3, can be obtained by A-site substitution, Ba substitution being as efficient as Cr substitution, and Sr substitution having a similar effect to Ga substitution. In the framework of the martensitic mechanism, it is suggested that the introduction of larger cations on the Ca sites, or of non-Jahn–Teller cations on the Mn3+ sites, induces “locally” around them the formation of more symmetric domains within the distorted antiferromagnetic matrix. This structural phase separation would induce the electronic phase separation, favoring the formation of ferromagnetic metallic regions in the antiferromagnetic insulating matrix.
Thickness dependent crystallization speed in thin phase change layers used for optical recording
Authors: Martens H. C. F. , Vlutters R. , Prangsma J. C.
Published: March 2004

The erasure rate of recorded amorphous marks in nanometers thick SbTe-alloy layers is studied as a function of layer thickness. We point out the presence of an optimum layer thickness where the crystallization speed is maximized. Analysis of the Gibbs free energy of a crystallite embedded in a thin amorphous film indicates that the height of the energy barrier for crystallization is a function of phase-change layer thickness. This barrier increases steeply in thin layers due to the larger surface energy at the crystallized phase-change surface. This suggests that the crystallization speed in thin films may be improved by modifying the interfaces of the phase-change layer.
Diffuse phase transition in NaNbO3:Gd single crystals
Authors: Raevski I. P. , Prosandeev S. A. , Abdulvakhidov K. G. , Shilkina L. A. , Raevskaya S. I. , Eremkin V. V. , Smotrakov V. G. , Jastrabik L.
Published: March 2004

Gd-doping of NaNbO3 crystals leads to gradual diffusion of an antiferroelectric phase transition. Though the permittivity maximum in crystals with a high Gd content is even more diffused than in PbMg1/3Nb2/3O3, its frequency shift is negligible in the (1–100) kHz range. We explain the diffuseness of the phase transition in NaNbO3:Gd within a Landau-type theory that includes the coupling of the order parameter with local quenched fields.
Spectroscopic properties of Er doped silica glasses
Authors: Wang Q. , Dutta N. K. , Ahrens R.
Published: March 2004

We have carried out a systematic study of optical emission in Er doped silica glass materials with different codopants. The stimulated emission cross-sections of these materials have been calculated. The wavelength dependence of emission of these materials has been studied. The different spectral shapes and hence broadening observed in this model is primarily due to different Stark splitting of the upper and lower levels of the Er ion in the glass matrix in the presence of different codopants. Inhomogeneous broadening which may be important at low temperatures is not discussed here. The peak emission cross section in Er doped pure silica glass is 5.4 pm2 and the peak wavelength is at 1535 nm. Codopants broaden the Er amplifier spectrum and vary the wavelength of peak stimulated emission cross section.
Exchange biased magnetoresistance based spin-transport sensor
Authors: Negusse Ezana , Idzerda Y. U. , Suci Peter A.
Published: March 2004

A method for measuring processes that alter the degree of exchange bias (HEX) for a thin film by monitoring HEX indirectly through the magnetoresistance (MR) is described. In unbiased magnetic films and multilayers, the positive and negative magnetic field sweep MR spectra are symmetric about zero applied field. Introducing an exchange bias to the film shifts the intersection point of these two curves away from zero to HEX. Taking the difference in the measured MR at zero field for a positive and negative field pulse (measuring ΔMR at zero field) gives a relative measure of HEX. Any variations in the exchange bias field will result in a corresponding change in the ΔMR, which, unlike HEX, can be measured with two points rather quickly, making it ideal for sensor applications. A method for selecting material parameters for increased sensitivity or operational range is given.
Recombination and lifetimes of charge carriers in semiconductors
Authors: Volovichev I. N. , Logvinov G. N. , Titov O. Yu. , Gurevich Yu. G.
Published: March 2004

In this Communication, it is shown that models used for describing generation and recombination of electrons and holes lead to disagreements with Maxwell’s electrodynamics. Self-consistent expressions, more adequately depicting the actual physical processes of electron-hole recombination in semiconductors are obtained. It is shown that the electron and hole lifetimes can be defined correctly only for the special cases when the electron and hole nonequilibrium concentrations are the same, these lifetimes being equal. The influence of temperature inhomogeneity on the recombination is also considered. The recombination rate for hot electrons is obtained in the case when the electron and hole temperatures differ.
Structural and electronic properties of wide band gap Zn1−xMgxSe alloys
Authors: Pelucchi E. , Rubini S. , Bonanni B. , Franciosi A. , Zaoui A. , Peressi M. , Baldereschi A. , De Salvador D. , Berti M. , Drigo A. , Romanato F.
Published: March 2004

We determined the properties of Zn1−xMgxSe semiconductor alloys through a combination of optical and photoelectron spectroscopy, x-ray diffraction, Rutherford backscattering spectrometry, and ab initio pseudopotential calculations. The complementary character of the techniques and the good agreement between calculated and experimental trends allowed us to explain some of the discrepancies between the reported properties of these wide band gap alloys.
Characterization of perovskite piezoelectric single crystals of 0.43BiScO3–0.57PbTiO3 with high Curie temperature
Authors: Zhang Shujun , Randall Clive A. , Shrout Thomas R.
Published: March 2004

The perovskite single crystal solid solution of 0.43BiScO3–0.57PbTiO3 (BSPT57) was reported to possess a high Curie temperature (TC∼402 °C) and rhombohedral to tetragonal phase transition temperature (TR–T∼349 °C) with excellent electromechanical properties (k33∼90%). In this work, the resonance method was used to determine all of the eleven electromechanical coefficients of the BSPT57 piezocrystals using five Z-cut samples. The complete set of materials constants, including the elastic sij, cij, piezoelectric dij, eij, gij, hij, dielectric εij, βij, and electromechanical kij values were derived from the experimental data. The BSPT57 crystal was found to be a promising material for piezoelectric applications, which is comparable to the properties of the Pb(Zn1/3Nb2/3)O3–PbTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 relaxor-PT single crystals, but has a much high-temperature stability.
Molecular simulation study of miscibility in InxGa1−xN ternary alloys
Authors: Adhikari Jhumpa , Kofke David A.
Published: March 2004

Monte Carlo molecular simulation is applied to calculate miscibility behavior of a valence force-field model of InGaN alloy as a function of temperature. Calculations find that the upper critical solution temperature is 1550 K, in good agreement with previous studies based on regular solution theory. The simulations show that the excess entropy is small, and the excess enthalpy is insensitive to temperature, indicating that the regular-solution treatment is appropriate for this system.
Effect of porosity on the electrical properties of Y2O3-doped SrTiO3 internal boundary layer capacitors
Authors: Krueger Daniel S. , Shende Rajesh V. , Lombardo Stephen J.
Published: March 2004

Compositions of 0.8 mole % Y2O3-doped SrTiO3 were sintered over a range of temperatures of 1450–1550 °C for times of 1–15 h, and the resulting internal boundary layer capacitors had relative densities ranging from 92% to 98%. The effective dielectric constant and effective conductivity were highly correlated with each other, and both electrical properties decreased strongly with increasing porosity. To account for the effect of porosity on the two electrical properties, a scaling law model was developed, which takes into account the grain size, the thickness of the grain boundary region, the pore size, and the pore aspect ratio. The model predicts a strong decrease in effective dielectric constant and effective conductivity with porosity for internal boundary layer capacitors, which is in accord with the observed trends.
Magnetic properties of cobalt and cobalt–platinum nanocrystals investigated by magneto-optical Kerr effect
Authors: Petit C. , Rusponi S. , Brune H.
Published: March 2004

Magneto-optical Kerr effect, is used to investigate the magnetization of film made of uncoalesced cobalt and cobalt–platinum nanocrystals. For the pure cobalt nanocrystals, different film morphologies are obtained through application of magnetic field during deposition. These morphologies have quite different magnetic properties, which is rationalized by considering dipolar interactions and the associated demagnetizing factor. We show that fast annealing can be used to trigger changes in the particles’ crystalline structure while largely avoiding their coalescence. With increasing the annealing temperature, 2.7 nm CoPt nanocrystals show a transition from the magnetically soft face-centered-cubic phase to the hard face-centered-tetragonal L10 phase. In particular fast annealing to 950 K is shown to produce largely uncoalesced nanocrystals ferromagnetic at room temperature. With 7 nm cobalt nanocrystals, fast annealing at 500 K equally results in ferromagnetism at room temperature without inducing coalescence between the nanocrystals in the film.
Nitridation effects on Pb center structures at SiO2/Si(100) interfaces
Authors: Miura Yoshinao , Fujieda Shinji
Published: March 2004

Interfacial defect structures of NO-nitride oxide on Si(100) were characterized by electron spin resonance spectroscopy. We confirmed that the effective g values of the Pb1 center are affected by interfacial nitridation even at a small nitrogen concentration of 5 at. %, while those of the Pb0 center proved to be unchanged. We observed that the shifted Pb1 line appeared gradually with interfacial nitrogen concentration, which suggests that the nitrogen-induced modified structure substitutes for the original Pb1 structure. Angular variations of the shifted Pb1 lines were also significantly different from those of pure oxide. Based on our analysis, we attributed the g value shift of the Pb1 center to dangling bond tilting, caused by the displacement of nearest-neighbor Si atoms.
Stabilization of liquified-inert-gas jets for laser–plasma generation
Authors: Hansson B. A. M. , Berglund M. , Hemberg O. , Hertz H. M.
Published: March 2004

We investigate the hydrodynamic properties of liquified-inert-gas jets in a vacuum with a special emphasis on their stability. Such jets have applications as targets for laser–plasma generation of soft-x-ray and extreme-ultraviolet (EUV) radiation. An important example is the liquid-xenon-jet laser-plasma source, one of the source candidates for EUV lithography. A simple hydrodynamic model in not sufficient to explain experimental observations of jet stability. Evaporation-induced cooling explains observed in-flight freezing of the jet and may be a key factor influencing jet stability. It is shown how the jet stability, and, thus, the stability of the laser–plasma x-ray and EUV emission, are improved by applying localized heating to the tip of the jet-generating nozzle.
Influence of electrical cycling on polarization reversal processes in Pb(Zn1/3Nb2/3)O3-PbTiO3 ferroelectric single crystals as a function of orientation
Authors: Ozgul Metin , Trolier-McKinstry Susan , Randall Clive A.
Published: March 2004

Pb(Zn 1/3 Nb 2/3 ) O 3 - PbTiO 3 (PZN-PT) ferroelectric single crystals with rhombohedral symmetry demonstrate a wide variety of anisotropic behavior under both unipolar and bipolar electrical switching. Specifically, PZN-4.5%PT crystals demonstrate exceptional polarization switching fatigue resistance along [001]C (C: pseudocubic), as opposed to normal fatigue in [111]C directions in the rhombohedral ferroelectric state [Takemura et al., J. Appl. Phys. 88, 7272 (2000)]. The influence of prior exposure to electrical cycling on polarization switching as a function of electric field and driving frequency was studied in both orientations. The field and frequency dependence of switching polarization can be described by a power law, in which greater electrical field strength and frequency dependence are shown for [111]C crystals. As fatigue evolves in the [111]C orientation, higher electric fields are required for switching due to the changes in microscopic switching mechanisms and buildup of local internal electric fields. However, negligible changes are observed in [001]C-oriented crystals as a function of cycling. These differences are consistent with switching current and strain-field analyses. From strain-field data, asymmetry can be detected in bipolar strain loops accompanying the suppression of the polarization-electric-field switching. The asymmetry is localized, as noted by region-to-region changes in strain-field loops across the surface of the [111]C PZN-PT crystals.
Thermal stability of ohmic contacts between Ti and Se-passivated n-type Si(001)
Authors: Udeshi Darshak , Maldonado Eduardo , Xu Yuqing , Tao Meng , Kirk Wiley P.
Published: March 2004

The thermal stability of the interface between Ti and Se-passivated n-type Si(001) is investigated. As-deposited Ti contacts show ohmic characteristics. After annealing at temperatures from 200 °C to 480 °C in air, the Se-passivated samples are much more resistant to Schottky transition as compared to the bare samples. The bare samples turn to Schottky below 300 °C, whereas the passivated samples are ohmic all the way to 400 °C. A difference of over 100 °C is observed between the two types of samples. Schottky barrier heights are determined using capacitance–voltage and activation–energy methods. The bare samples reach a maximum barrier height of 0.39 eV as determined by activation–energy measurements, while the passivated samples maximize at 0.19 eV. We deduce that a monolayer of Se suppresses silicidation between Ti and Si by eliminating dangling bonds on Si(001).
Solid C60 doped with C70: Order-to-disorder transition studied with dielectric and 13C nuclear magnetic resonance spectroscopies
Authors: Wu Jian , Gu Min , Liu Dawei , Keung Sharon S. K. , Tang Tong B.
Published: March 2004

C 60 crystals containing C70 at various dopant levels from 0% to 10% have been grown via a method of “solvent dilution.” Their crystallographic structures as revealed by x-ray diffraction exhibit an extra hcp lattice, and this stacking fault character increases with C70 concentration. The same trend applies to the shift of transition temperature in dielectric spectra, and in 13C nuclear magnetic resonance spectra, an additional resonance appeared besides the primary resonance in doped samples. We explain such phenomena as follows. The additional resonance arises from a diamagnetic ring-current effect in C70. C60 and C70 molecules in an hcp phase undergo a cylindrical motion around their threefold axis, which is parallel to the crystallographic sixfold axis, instead of “spherical” motion in fcc C60 crystal. The lower molecular rotations correspond to lower free energy of the high-temperature phase. The free energy barrier between the high- and the low-temperature phases thus decreases, accounting for the suppression of orientational order–disorder transition temperature.
Nondestructive evaluation of micrometric diamond films with an interferometric picosecond ultrasonics technique
Authors: Rossignol C. , Perrin B. , Laborde S. , Vandenbulcke L. , De Barros M. I. , Djemia P.
Published: March 2004

Synthetic diamond thin or thick films are suitable materials for many applications because of their weak friction coefficient and their large hardness, Young modulus, and thermal conductivity. A series of diamond thin films of variable quality obtained by plasma-assisted chemical vapor deposition lying on titanium alloy substrates has been studied by picosecond ultrasonics. Femtosecond laser pulses allow the generation and detection of picosecond acoustic pulses that can be used to study the elastic properties of thin micrometric and submicrometric films. Acoustic fields generated in the substrate and propagating in the transparent diamond film are detected by an interferometric technique; they give rise to oscillations and abrupt step-like changes in the transient reflectivity variations. An analysis of these different features allows the determination of various characteristics of these films, such as longitudinal elastic constant, thickness, and roughness in terms of the diamond quality.
Electromagnetic wake-field due to surface roughness in an optical structure
Authors: Banna S. , Schieber D. , Schächter L.
Published: March 2004

In this study we investigate the properties of the electromagnetic wake-field generated by an electron bunch moving in the vicinity of an optical structure of finite roughness. The model employed consists of a metallic cylindrical waveguide to which grooves of random width, height, and location are attached. Based on this model analytic expressions have been developed for the average energy emitted per groove and for its standard deviation. As expected, both quantities are virtually independent of the momentum in a highly relativistic regime and the average energy emitted per groove is proportional to the roughness parameter. Moreover, it has been found that the standard deviation of the energy emitted per groove is proportional to the standard deviation of the roughness parameter to the power of 1/4. The cumulative effect of surface roughness was studied resorting to both periodic and quasiperiodic structures—significant differences in the spectrum have been observed only for low frequencies.
Influence of nitride and oxide cap layers upon the annealing of 1.3 μm GaInNAs/GaAs quantum wells
Authors: Liu H. F. , Peng C. S. , Likonen J. , Jouhti T. , Karirinne S. , Konttinen J. , Pessa M.
Published: March 2004

Effects of thermal annealing on optical and structural properties of GaInNAs/GaAs quantum well (QW) heterostructures, which were coated with dielectric films, were studied using photoluminescence, x-ray diffraction (XRD), and secondary-ion mass spectrometry (SIMS). A sample having no dielectric coating exhibited a rapid saturable blueshift in the beginning of annealing. A Si3N4 cap layer prevented the line shift, while a SiO2 cap enhanced the shift. The XRD and SIMS spectra provided evidence that the large blueshift for the SiO2-capped sample originated from Ga/In interdiffusion across the QW walls, and from a local reorganization of N-bonding configuration within the QW. The inhibition of blueshift for the Si3N4-capped sample was likely due to an improved stability of Ga–N bonds during annealing.