bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasma Lactic Acid and Pyruvic Acid Levels in Migraine and Tension‐Type Headache
Authors: Okada Hiroko , Araga Shigeru , Takeshima Takao , Nakashima Kenji
Published: May 2003

We examined the lactic and pyruvic acid levels in the plasma of 14 patients with migraine, 17 patients with tension‐type headache, and 12 normal controls. The lactic and pyruvic acid levels in the plasma of the migraine patients were significantly higher than those of the normal controls (9.6 ± 5.0 mg/dL and 0.51 ± 0.30 mg/dL versus 3.3 ± 1.9 mg/dL and 0.26 ± 0.20 mg/dL, respectively). There were no significant differences in the levels between the patients with tension‐type headache and normal controls. Our results suggest that migraine patients may have functional abnormalities in mitochondrial energy metabolism.
Derangement of Serotonin System in Migrainous Patients With Analgesic Abuse Headache: Clues From Platelets
Authors: Srikiatkhachorn Anan , Maneesri Supang , Govitrapong Piyarat , Kasantikul Vira
Published: May 2003

Accumulating evidence indicates that serotonin (5‐HT) may be involved in the process of analgesic‐induced headache transformation. In order to clarify this hypothesis, we investigated the 5‐HT system in migraine patients with analgesic abuse headache by using platelets as a neuronal model. Our results revealed a significant decrease in platelet 5‐HT content in these patients compared to migraine patients and nonheadache controls (179.24 ± 10.18, 451.22 ± 14.35, and 480.22 ± 13.98 ng/109 platelets, respectively; P<0.001). This biochemical result was well correlated with a significant decrease (P<O.OOl) in platelet dense body number observed in these patients (5.9 ± 0.4 and 9.2 ± 0.6 granules/10 platelets, for migraine patients with and without analgesic abuse headache, respectively). Beside the 5‐HT depletion, the presence of numerous large intracytoplasmic vacuoles formed from the surface‐connecting canaliculi system was found in this condition. Such a finding has not been previously described. The total area occupied by these vacuoles was significantly greater (P<0.01) in migraine patients with analgesic overuse than in migraine patients and nonheadache controls (249.2 ± 19.5, 164.1 ± 19.5, and 183.1 ± 20.3 nm2/cells, respectively). As this canaliculi system plays a significant role in the platelet secretory response, such dilatation may imply an excessive release of substances from this system. Based on this platelet model, we suggest that excessive use of analgesics alters the central 5‐HT system by depleting 5‐HT from its storage sites and results in the hyposerotonergic state. This analgesic‐induced 5‐HT alteration may be a possible mechanism of headache transformation observed in this condition.
Migraine Triggered by Rubbing the Eyes
Authors: Jacome Daniel E.
Published: May 2003

A patient with recurrent exertional headaches was able, on multiple occasions, to trigger his typical headaches within 30 minutes of rubbing his eyes gently and inducing bilateral photopsias. No intracranial or orbital lesions were identified. His EEG, obtained while rubbing his eyes and inducing photopsias, did not show epileptic discharges or background changes. His ophthalmologic examination, including visual field testing, was normal. Ocular pressure and massage of the carotid sinuses failed to cause bradycardia to imply vagal mediation of his physically induced headaches. It is hypothesized that in this patient mechanical displacement of the eyes precipitated retinal auras leading to migraines.
Acute and delayed hemolytic transfusion reactions secondary to HLA alloimmunization
Authors: Benson Kaaron , Agosti Steven J. , Latoni‐Benedetti Gerardo E. , Leparc German F.
Published: May 2003

BACKGROUND: HLA antibodies may be directed against HLA antigens on RBCs, but these antibodies are generally not considered to be clinically significant in transfusion practice. A case of a multiparous woman who had hemolytic transfusion reactions due to HLA‐related Bg antibodies is reported.

CASE REPORT: A 37‐year‐old woman was admitted with anemia. No unexpected RBC antibodies were identified. Two group O, D+ RBC units were transfused. Ten days later she returned with hemolysis and anemia. Two more RBC units were ordered, no unexpected RBC antibodies were identified, and two crossmatch‐compatible units were issued. During the transfusion, the patient developed symptoms of an acute reaction, and the posttransfusion sample showed evidence of intravascular hemolysis.

RESULTS: Repeat RBC antibody screen showed anti‐Bg. HLA antibody screen identified anti‐HLA‐A2, A28, B7, B7 cross‐reactive group (CREG). The two RBC units from the first transfusion episode and one RBC unit from the second transfusion episode were HLA incompatible with the patient. No other cause for the hemolytic reactions was identified. The patient was later successfully transfused with one RBC unit from an HLA‐compatible donor.

CONCLUSION: HLA antibodies should be considered in patients with hemolytic transfusion reactions when RBC‐specific antibodies are not found to be the etiology.
Differences in the perception of blood transfusion risk between laypeople and physicians
Authors: Lee D.H. , Mehta M.D. , James P.D.
Published: May 2003

BACKGROUND: There is little objective evidence to support the commonly held belief that laypeople perceive blood transfusion risk differently from physicians. Acknowledging and characterizing such differences may improve risk communication. The objective of this study was to characterize how laypeople and physicians perceive the risks of blood transfusion in comparison with a wide variety of other hazards.

STUDY DESIGN AND METHODS: A total of 161 laypeople and 91 physicians and medical trainees were surveyed in Kingston, Ontario, between March and August 2000. The perceived riskiness and other qualitative characteristics of blood transfusion and 9 other hazards were measured by psychometric scaling and principal components analysis.

RESULTS: The overall return rate was 100 percent, with 86 percent of surveys having no missing responses. Physicians perceived the risks of blood transfusion and most other hazards to be less dreaded and severe, but also less understood and controllable than laypeople.

CONCLUSION: Laypeople and physicians perceive risk differently for blood transfusion, but this perceptual gap between the groups for blood transfusion may be representative of a more generalized phenomenon that spans different types of hazards, both medical and nonmedical. Awareness of such differences may facilitate risk communication and shared decision making between physicians and their patients.
Methodologic issues in the use of bleeding as an outcome in transfusion medicine studies
Authors: Heddle Nancy M. , Cook Richard J. , Webert Kathryn E. , Sigouin Christopher , Rebulla Paolo ,   in collaboration with the Biomedical Excellence for Safer Transfusion (BEST) Working Party of the International Society for Blood Transfusion
Published: May 2003

BACKGROUND: Prophylactic platelet transfusions are given to thrombocytopenic patients to prevent bleeding. The benefit of platelet transfusions has frequently been assessed by measuring the count increment; however, more recently, an assessment of bleeding has been used because it is a more clinically relevant outcome measure. The purpose of this study was to identify platelet transfusion trigger studies that used bleeding as an outcome measure, compare and contrast methods used to document bleeding and analyze bleeding outcomes, and identify and discuss methodologic issues to consider when bleeding is used as a study outcome.

STUDY DESIGN AND METHODS: A systematic search to identify platelet transfusion trigger studies was performed. Relevant articles were reviewed to identify how bleeding data was captured and analyzed, and methodologic considerations were identified.

RESULTS: Seven articles meeting the predefined entry criteria were identified. Methods used to document bleeding included chart review and clinical assessment. The frequency of assessment and the type of personnel performing the assessment were variable. Four approaches to analysis were identified: descriptive; comparison of the proportions of patients having at least one bleed; comparison of patient days with bleeding expressed as a proportion of the total days at risk of bleeding; and time‐to‐event (first bleed) analysis.

CONCLUSION: Methodologic issues for consideration when designing a clinical study with bleeding as the outcome measure included approaches to minimize bias in the documentation and classification of bleeding and selection of an analysis approach that is appropriate to the question being asked. The need for development of a valid and reliable bleeding scale was also identified.
A comparison of the host preference of monarch butterflies (Danaus plexippus) for milkweed (Asclepias syriaca) over dog‐strangler vine (Vincetoxicum rossicum)
Authors: Mattila Heather R. , Otis Gard W.
Published: May 2003

Observations in the field indicate that monarch butterflies will oviposit on dog‐strangler vine, an invasive introduced species in the same family as milkweed (Asclepias spp.), the principal larval host of monarchs. The potential impact of this behaviour depends on the strength of the preference of monarch adults to oviposit on these two hosts and the relative ability of larvae to survive on each. We determined the preference for milkweed vs. dog‐strangler vine of ovipositing adults and first instar larvae in choice and no‐choice tests. We also compared the ability of larvae to consume, develop, and survive on either host. In the presence of both hosts, adults exhibited a strong preference to oviposit on milkweed over dog‐strangler vine (mean 80.7 eggs compared to 0.4 eggs over 48 h, respectively). In the absence of milkweed, adults ceased oviposition (mean 0.9 eggs in 48 h), but resumed oviposition when the dog‐strangler vine was replaced with milkweed (mean 99.1 eggs in 48 h). Given a choice between hosts over 24 h, 92% of larvae moved to milkweed leaves and consumed 3.94 cm2 of milkweed leaves compared to 2% of larvae that moved to dog‐strangler vine and consumed negligible amounts of leaf material (0.01 cm2). Without a choice, larvae on dog‐strangler vine never consumed more than mean 0.02 cm2 larva−1 in a 24‐h period, did not develop beyond the first instar, and died within 96 h. We obtained no data in support of an effect of the presence of dog‐strangler vine on monarch butterfly populations.
Relative impact of spider predation and cover crop on population dynamics of Erythroneura variabilis in a raisin grape vineyard
Authors: Hanna Rachid , Zalom Frank G. , Roltsch William J.
Published: May 2003

Experimental and correlative evidence has steadily mounted over the past 30 years implicating spiders in the suppression of insect herbivore pests in crop fields. A large body of evidence has also shown that increasing agroecosystem vegetation diversity often influences the abundance of herbivores and their natural enemies. In previous experiments, the abundance of several species of spiders on grapevines in a raisin grape vineyard was twofold enhanced in vineyard plots vegetationally diversified with a cover crop. A concomitant reduction in the abundance of the leafhopper pest Erythroneura variabilis Beamer was observed on grapevines in the diversified plots, but a causal relationship was not established. In the present study, we simultaneously manipulated spider densities (in open‐vine spider exclusion and vine‐shoot enclosures) and ground cover to determine their relative impact on E. variabilis population dynamics. Open‐vine spider exclusion resulted in an average 35% increase in the density of E. variabilis the greatest effect with occurring during the first and second leafhopper generations. The negative impact of spiders on E. variabilis densities was corroborated with vine‐shoot enclosure experiments. Under the conditions of the present study, the cover crop per se did not affect the dynamics of E. variabilis populations on grapevines, despite a 1.6‐fold increase in spider densities on vines in cover crop plots, compared with vines in bare ground plots, probably due to insufficient spider enhancement and low overall E. variabilis abundance during the summer months. The cover crop had little effect on vine macronutrient status (and presumably vine water status). While this study provided further support for the hypothesis that vegetation diversity can enhance spider abundance, this enhancement does not always lead to lower pest densities, thus underscoring the complexity and variability that exists in interactions involving cover crop, spiders, and crop plants and their herbivore pests.
Female sex pheromone components of Helicoverpa gelotopoeon: first heliothine pheromone without (Z)‐11‐hexadecenal
Authors: Cork Alan , Lobos Enrique A.
Published: May 2003

Helicoverpa gelotopoeon Dyar is a very important pest of economic importance on cotton in Argentina. Analysis of female pheromone gland extracts prepared from 1‐ to 2‐day‐old virgin female moths demonstrated the presence of a 1 : 0.84 blend of hexadecanal (16:Ald) and (Z)‐9‐hexadecenal (Z9‐16:Ald), with trace quantities of tetradecanal in some samples, 2.4% of 16:Ald. The average quantity of Z9‐16:Ald extracted per female was estimated to be 33 ng, with a range of 18.9–46.4 ng per female when collected 2–3 h into the scotophase. In field trials conducted in both cotton and tomato crops in Santiago del Estero, Argentina 1 : 1 blends of 16:Ald and Z9‐16:Ald caught significantly more male H. gelotopoeon than Z9‐16:Ald alone, although there was no significant difference between blends containing between a 0.2 : 1 and 2 : 1 ratio of 16:Ald and Z9‐16:Ald. There was no analytical evidence for the presence of (Z)‐11‐hexadecenal (Z11‐16:Ald) in pheromone gland extracts, although this compound has been identified in all female sex pheromones of Heliothinae to date. In field trials, the addition of Z11‐16:Ald at the 1% level to either a 1 : 1 blend of 16:Ald and Z9‐16:Ald or Z9‐16:Ald alone significantly reduced the catch of male H. gelotopoeon. Sympatric Heliothis virescens were not caught in any of the blends tested for H. gelotopoeon, but were caught in low numbers in traps baited with a 4 : 100 blend of (Z)‐9‐tetradecenal and (Z)‐11‐hexadecenal.
Effect of diet and feeding history on flight of Colorado potato beetle, Leptinotarsa decemlineata
Authors: MacQuarrie Chris J. K. , Boiteau Gilles
Published: May 2003

We evaluated the hypothesis that Colorado potato beetle (Leptinotarsa decemlineata Say) (CPB) flight frequency is related to diet, and that it changes with duration of food unavailability or exposure to poor quality food by exposing adult overwintered and summer CPB populations to an acceptable host plant (conventional foliage), a poor host (insect resistant transgenic foliage expressing Bacillus thuringiensis tenebrionis[Btt] Cry3a toxin) and no host. Exposure to poor host and no host treatments (with or without water) decreased mean daily flight frequencies and the overall number of overwintered CPB flying, but increased the mean daily flight frequency and number of summer population CPB that flew. Overwintered CPB did not react to an absence of plants at emergence whereas summer CPB increased mean daily flight frequencies when plants and water were not available. The flight response to insect resistant foliage was similar to that for starvation treatments in both populations indicating that flight may not be triggered by Btt toxins but by starvation brought on by feeding on poor quality food. Flight was observed in all treatments for the duration of the test with two exceptions; overwintered beetles fed insect resistant foliage ceased flying after day 17 and summer beetles starved without water ceased after day 8 of a 29‐day study.
Attraction of the specialist parasitoid Cotesia rubecula to Arabidopsis thaliana infested by host or non‐host herbivore species
Authors: Van Poecke Remco M. P. , Roosjen Mara , Pumarino Lorena , Dicke Marcel
Published: May 2003

In this study we investigated whether in a two‐choice set‐up the parasitoid Cotesia rubecula (Marshall) (Hymenoptera, Braconidae) distinguishes between volatiles emitted by Arabidopsis thaliana (L.) Heynh. (Brassicaceae) infested with its host, Pieris rapae (L.) (Lepidoptera: Pieridae) and Arabidopsis infested with non‐host herbivores. Four non‐host herbivore species were tested: the caterpillars Plutella xylostella (L.) (Lepidoptera: Plutellidae) and Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), both chewing insects, the spider mite Tetranychus urticae (Koch) (Acari: Tetranychidae), which punctures parenchymal cells, and the aphid Myzus persicae (Sulzer) (Hemiptera: Aphidoidea), which is a phloem‐feeder. Compared with undamaged plants, C. rubecula females were more attracted to Arabidopsis plants infested by P. rapae, P. xylostella, S. exigua, or T. urticae, but not to plants infested by M. persicae. The parasitoids preferred host‐infested plants to spider mite‐ or aphid‐infested plants, but not to plants infested with non‐host caterpillars (P. xylostella or S. exigua). The data show that when Arabidopsis plants are infested with a leaf tissue‐damaging herbivore they emit a volatile blend that attracts C. rubecula females and the wasps only discriminate between a host and non‐host herbivore when the type of damage is different (chewing vs. piercing). When Arabidopsis is infested with a herbivore that hardly damages leaf tissue, C. rubecula females are not attracted. These results may be explained by differences in the amount of damage and in the relative importance of different signal‐transduction pathways induced by different types of herbivores.
Spectroscopic properties of Er3+ and Eu3+ doped acentric LaBO3 and GdBO3
Authors: Giesber Henry , Ballato John , Chumanov George , Kolis Joseph , Dejneka Matthew
Published: May 2003

This work studies the spectroscopic behavior of Eu3+-doped and Yb3+/Er3+-codoped single crystals of orthorhombic LaBO3 and rhombohedral GdBO3. Emissions from Er3+ at ∼1535 nm are shown to exhibit multiple narrow linewidth emissions. Luminescence from the D05→7F1, F27 transitions of Eu3+ is found to depend on the choice of LaBO3 or GdBO3 as a parent phase in a well-defined manner. Phonon sideband spectroscopy of the Eu3+ D25 excitation, corroborated using Raman spectroscopy, indicates that the highest energy phonon is less than 1400 cm−1 for the LaBO3 and less than 1010 cm−1 for the GdBO3. Further, absorption spectrum to 190 nm is provided for the GdBO3 clearly showing the I6 manifold, and the rarely seen D6 levels. Excitation of the D7/26 state at 250 nm in GdBO3 is shown to yield a strong ultraviolet emission centered at 314 nm. This work marks the lanthanide borates as candidate single crystals for active and nonlinear materials for UV, visible, and telecommunication band applications.
He
4
nanoclusters around vacancies in solid solutions of He4 in He3
Authors: Gan’shin A. N. , Grigor’ev V. N. , Maı̆danov V. A. , Penzev A. A. , Rudavskiı̆ É. Ya. , Rybalko A. S. , Syrnikov E. V.
Published: May 2003

Precise measurements of the pressure in solid solutions of 4He in 3He are performed with temperature cycling in the phase-separation range. It is found that as a result of such cycling the difference ΔP of the pressures between the minimum (≈100 mK) and maximum (≈200 mK) temperatures decreases by a factor of approximately 3 and then remains unchanged for a long time. The initial values of ΔP and the pressure P0 in a uniform solid solution 4He-3He are restored only after the sample is heated to a temperature substantially above the phase-separation point. The data obtained are explained on the basis of the hypothesis that under these conditions clusters of pure 4He form around quasiequilibrium vacancies. A thermodynamic calculation of such clusters is performed. The computational results made it possible to give a quantitative explanation of the distinctive features observed. Comparing the calculations with experiment made it possible to determine the cluster concentration, 8×10−5, and the cluster radius, which is 3–4 interatomic distances at low temperatures. The characteristic equilibration time under these conditions is determined, and it is suggested that processes occurring at cluster boundaries determine its value.
Phonon scattering in ortho-para hydrogen solid solutions (role of configurational relaxation)
Authors: Gorodilov B. Ya.
Published: May 2003

The experimental data on the thermal conductivity of ortho-para hydrogen solutions are analyzed on the basis of a relaxation-time model taking account of configurational relaxation of the ortho subsystem. The influence of configurational relaxation on the thermal conductivity is analyzed using resonance scattering of phonons by pair clusters of orthomolecules taking account of their rotational spectrum.
Motion of a probe nanoparticle in a quantum crystal with a narrow vacancy band
Authors: Levchenko A. A. , Mezhov-Deglin L. P. , Trusov A. B.
Published: May 2003

The temperature dependence of the diffusion coefficient Dp(T) of a probe particle with a diameter dp of several nanometers and moving in a quantum crystal with a narrow vacancy band Qv≪Tmelt changes substantially, as a result of interactions with thermal vacancies, with decreasing temperature in the range Tmelt⩾Ttr⩾Qv, where a transition occurs from classical thermally activated vacancy hopping to coherent motion of delocalized vacancies. Moreover, in the transitional range T≈Ttr the diffusion coefficient of a probe particle in a viscous vacancion gas can increase if the effective vacancion mean-free path length is small compared to the particle diameter lv≪dp and increases with decreasing temperature more rapidly than the concentration of thermal vacancies xv∼exp(−Ev/T). For T≪Ttr, in a rarefied vacancion gas where lv≫dp the particle diffusion coefficient Dp(T)∼xvSvp decreases as xv if the cross section Svp for the inelastic scattering of a vacancion by a probe particle is a weak function of the temperature. The model developed in this paper can be used to describe the diffusion of positive charges in He4 hcp crystals, grown at pressures above the lowest solidification pressure of helium, and negative charges in parahydrogen crystals.
On the phase diagram of the development of an instability of a massive charged surface of liquid helium
Authors: Shikin V.
Published: May 2003

The existing interpretation of the development of an instability of a massive charged helium surface requires a definite correction that identifies this phenomenon more closely with the known spinodal and binodal decomposition processes in the theory of first-order phase transformations. The distinctive features of the development of an instability of a charged helium surface, exhibiting indications of spinodal (binodal) decomposition, are discussed and a qualitative phase diagram for such transitions is constructed in the plane surface electron density—electric field above a plane charged with 2D electrons.
Nonlinear Rayleigh waves in a medium with a monatomic nonlinear coating
Authors: Kovalev A. S. , Sokolova E. S. , Mayer A. P. , Maugin G. A.
Published: May 2003

The nonlinear dynamics of surface acoustic waves at the surface of a linear elastic half-space coated with a monolayer of a nonlinear material is investigated. A one-dimensional nonlinear integrodifferential equation describing the dynamics of such a system is derived. The model proposed is used to study Rayleigh solitons with a stationary profile. The possible phenomenological generalizations of the equations derived and their exact soliton solutions are discussed.
Local excitations in the conduction band of crystalline xenon
Authors: Belov A. G. , Tarasova E. I. , Yurtaeva E. M.
Published: May 2003

A detailed experimental investigation of the basic characteristics of the radiation of crystalline xenon with Emax=2 eV (A band) is performed as a function of temperature, impurity concentration, lattice perfection, and irradiation dose. The radiation parameters of this band are compared with the same parameters of the radiation of free excitons, localized holes Xe2+*, and impurity centers Xe2O*, whose bands were recorded in parallel. The photoexcitation spectra of the A band and the time decay curves of luminescence are analyzed. Radiation with similar structure with Emax=2.05 eV is also found in the binary crystals Ar+Xe with high (∼10%) xenon concentrations. It is concluded that the observed radiation is due to intrinsic molecular-type excited states of localized in the interior volume of the crystal and lyingnear 10 eV in the conduction band.
Heat transfer by low-frequency phonons and “diffusive” modes in molecular crystals
Authors: Konstantinov V. A.
Published: May 2003

A model where low-frequency phonons and, above the mobility limit, “diffusive” modes migrating randomly from site to site transfer heat is proposed to describe the behavior of the isochoric thermal conductivity of molecular crystals in orientationally ordered phases. The mobility limit ω0 is found from the condition that the phonon mean-free path length determined by umklapp processes cannot become less than half the wavelength. The Bridgman coefficient g=−(∂ ln Λ/∂ ln V)T is the weighted-mean over these modes, whose volume dependence differs strongly. The model proposed here is used to analyze the thermal conductivity of CO2, N2O, naphthalene C10H8, anthracene C14H10, and hexamethylenetetramine (CH2)6N4. It is shown that site-to-site rotational energy transfer must be taken into account in order to calculate the lower limit of the thermal conductivity of molecular crystals.
On the orientational relief of the intermolecular potential and the structure of domain walls in fullerite C60
Authors: Khalack J. M. , Loktev V. M.
Published: May 2003

A simple planar model for an orientational ordering of threefold molecules on a triangular lattice modeling a close-packed (111) plane of fullerite is considered. The system has 3-sublattice ordered ground state which includes 3 different molecular orientations. There exist 6 kinds of orientational domains, which are related with a permutation or a mirror symmetry. Interdomain walls are found to be rather narrow. The model molecules have two-well orientational potential profiles, which are slightly effected by a presence of a straight domain wall. The reason is a stronger correlation between neighbor molecules in the triangular lattice versus the square lattice previously considered. A considerable reduction (up to one order) of the orientational interwell potential barrier is found in the core regions of essentially two-dimensional potential defects, such as a three-domain boundary or a kink in the domain wall. For ultimately uncorrelated nearest neighbors the height of the interwell barrier can be reduced even by a factor of 102.
Intercalation of C60 fullerite with helium and argon at normal temperature and pressure
Authors: Stetsenko Yu. E. , Legchenkova I. V. , Yagotintsev K. A. , Prokhvatilov A. I. , Strzhemechnyı̆ M. A.
Published: May 2003

Powder x-ray diffractometry was used to study the effect of intercalating C60 fullerite with helium and argon atoms on the fullerite structure. The samples were saturated at room temperature and normal pressure. The dependences obtained for the lattice parameter and half-width of certain reflections on the intercalation time with helium atoms showed that the voids in the C60 lattice were filled in two stages. Helium filled the octahedral voids relatively rapidly first and then the tetrahedral subsystem, but much more slowly. Both intercalants affected the half-width and intensity of the reflections, the matrix lattice parameters, the phase transition temperature, the volume jump at the transition, and the thermal expansion coefficients of C60 fullerite.
Low-temperature thermal conductivity of solid carbon dioxide
Authors: Sumarokov V. V. , Stachowiak P. , Jeżowski A.
Published: May 2003

Preliminary measurements of the thermal conductivity of pure carbon dioxide in the temperature range 1.5–35 K are reported. The first data below 25 K have been obtained. The thermal conductivity reaches very high values, about 700 W/(m⋅K), which is unusual for simple molecular crystals. A straightforward analysis of the data shows a coarse-grained sample.
Generalized coherent states and the diagonal representation for operators
Authors: Mukunda N. , Arvind  , Chaturvedi S. , Simon R.
Published: May 2003

We consider the problem of existence of the diagonal representation for operators in the space of a family of generalized coherent states associated with a unitary irreducible representation of a (compact) Lie group. We show that necessary and sufficient conditions for the possibility of such a representation can be obtained by combining Clebsch–Gordan theory and the reciprocity theorem associated with induced unitary group representations. Applications to several examples involving SU(2), SU(3), and the Heisenberg–Weyl group are presented, showing that there are simple examples of generalized coherent states which do not meet these conditions. Our results are relevant for phase–space description of quantum mechanics and quantum state reconstruction problems.
Cubic algebraic equations in gravity theory, parametrization with the Weierstrass function and nonarithmetic theory of algebraic equations
Authors: Dimitrov Bogdan G.
Published: May 2003

A cubic algebraic equation for the effective parametrizations of the standard gravitational Lagrangian has been obtained without applying any variational principle. It was suggested that such an equation may find application in gravity theory, brane, string and Rundall–Sundrum theories. The obtained algebraic equation was brought by means of a linear-fractional transformation to a parametrizable form, expressed through the elliptic Weierstrass function, which was proved to satisfy the standard parametrizable form, but with g2 and g3 functions of a complex variable instead of the definite complex numbers [known from the usual (arithmetic) theory of elliptic functions and curves]. The generally divergent (two) infinite sums of the inverse first and second powers of the poles in the complex plane were shown to be convergent in the investigated particular case. Some relations were found, which ensure the parametrization of the cubic equation in its general form with the Weierstrass function.
Second harmonic generation tuning curves in quasiphase-matched potassium titanyl phosphate with narrow, high-intensity beams
Authors: Katz Mordechai , Eger David , Kim Hongki , Jankovic Ladislav , Stegeman George , Carrasco Silvia , Torner Lluis
Published: May 2003

The second harmonic generation (SHG) tuning curves with temperature and angle of incidence were measured in periodically poled KTiOPO4 for narrow fundamental beams at intensities typical of quadratic soliton generation. Mutual self-focusing of the fundamental and harmonic, cascading, and walk-off for light incidence away from the poling axis drastically distorted the SHG response curves, in good agreement with theory.
Deposition of hard magnetic rare-earth-Fe-B thin films by magnetron sputtering
Authors: Castaldi L. , Gibbs M. R. J. , Davies H. A.
Published: May 2003

We report a systematic study of the microstructural and magnetic properties of rare-earth (RE) Fe-B films, with particular emphasis on the role of the RE:Fe ratio. Strongly textured RE-Fe-B thin films having one or more of the following magnetic properties—high coercivity (820 kA/m), remanence ratio (0.84), and maximum energy product (180 kJ/m3)—were prepared by magnetron sputtering on heated, thermally oxidized Si substrates.
Evidence of phosphorus incorporation into InGaAs/InP epilayers after thermal annealing
Authors: Hernández S. , Blanco N. , Mártil I. , González-Dı́az G. , Cuscó R. , Artús L.
Published: May 2003

We report on Raman scattering measurements on annealed In0.53Ga0.47As/InP layers that reveal the outdiffusion of phosphorus from the substrate and its possible incorporation in substitutional positions in the In0.53Ga0.47As lattice. Raman signal associated with InP-like modes was detected in the annealed samples. The effect is also observed in samples where the substrate was protected by a SiNx:H capping and were annealed in arsenic atmosphere, thus ruling out the possibility of a surface contamination by atmospheric phosphorus evaporated from the InP substrate. Protruding regions of a few microns were observed on the surface, which were identified as misoriented In1−xGaxP and InP crystals by means of micro-Raman measurements.
Optimizing the spatial-harmonic millimeter-wave magnetron
Authors: Schuenemann K. , Serebryannikov A. E. , Sosnytskiy S. V. , Vavriv D. M.
Published: May 2003

A particle simulation has been carried out for an 8 mm nonrelativistic magnetron operating at the first backward spatial harmonic of a cavity eigenmode in order to study the effect of geometrical parameters of the slow-wave anode structure with sector-shaped vanes and resonators on the output characteristics. It is shown that an optimum value of the resonator opening, which corresponds to maximum output power, can be predicted from the electromagnetic characteristics of the cavity, at least if the dc voltage is close to its threshold value. The corresponding procedure is proposed. The optimum does not exist if the loaded Q factor is too large.
Interdiffusion in MnIr/NiFe exchange biased layer annealed above 300 °C in the pinned electrode of a magnetic tunnel junction
Authors: Yoon C. S. , Lee J. H. , Kim C. K.
Published: May 2003

The thermal stability of the MnIr/NiFe exchange couple in the pinned electrode of a magnetic tunnel junction was analyzed using Auger electron spectroscopy (AES) and x-ray photoelectron microscopy (XPS). When the Ta/AlOx/CoFe/MnIr/NiFe/Ta/SiO2/Si electrode was annealed at 350 °C, the magnetic properties of the electrode quickly deteriorated. AES analysis indicated that there was a large diffusion of Ni into the MnIr layer accompanied by Ir migration into the NiFe layer above 350 °C. XPS of the annealed electrode revealed that the massive migration of Ni resulted in formation of antiferromagnetic NixMn1−x within the MnIr layer. The presence of the AlOx tunnel barrier, which promoted the preferential migration of Mn, appears to be the cause of the massive migration of Ni through formation of vacancies in the MnIr lattice.
Optical and structural properties of SiOxNyHz films deposited by electron cyclotron resonance and their correlation with composition
Authors: del Prado A. , San Andrés E. , Mártil I. , González-Diaz G. , Bravo D. , López F. J. , Bohne W. , Röhrich J. , Selle B. , Martínez F. L.
Published: May 2003

SiO x N y H z films were deposited from O2, N2, and SiH4 gas mixtures at room temperature using the electron cyclotron resonance plasma method. The absolute concentrations of all the species present in the films (Si, O, N, and H) were measured with high precision by heavy-ion elastic recoil detection analysis. The composition of the films was controlled over the whole composition range by adjusting the precursor gases flow ratio during deposition. The relative incorporation of O and N is determined by the ratio Q=φ(O2)/φ(SiH4) and the relative content of Si is determined by R=[φ(O2)+φ(N2)]/φ(SiH4) where φ(SiH4), φ(O2), and φ(N2) are the SiH4, O2, and N2 gas flows, respectively. The optical properties (infrared absorption and refractive index) and the density of paramagnetic defects were analyzed in dependence on the film composition. Single-phase homogeneous films were obtained at low SiH4 partial pressure during deposition; while those samples deposited at high SiH4 partial pressure show evidence of separation of two phases. The refractive index was controlled over the whole range between silicon nitride and silicon oxide, with values slightly lower than in stoichiometric films due to the incorporation of H, which results in a lower density of the films. The most important paramagnetic defects detected in the films were the K center and the E′ center. Defects related to N were also detected in some samples. The total density of defects in SiOxNyHz films was higher than in SiO2 and lower than in silicon nitride films.
Molecular mean field study of rare-earth intermetallic compounds R3Co29Si4B10
Authors: Zhang Heng , Campbell S. J.
Published: May 2003

The magnetic properties and exchange interactions of magnetic components for rare-earth intermetallic compounds R3Co29Si4B10 (R=La, Tb, Er, Tm) have been investigated by magnetization and molecular mean field analysis. The 3d-interaction energy in R3Co29Si4B10 is found to increase with the unpaired f-shell electrons. The investigation indicates that the 3d interaction is the strongest of the R–R, R–Co, and Co–Co interactions. The R–Co interaction is the second largest, and the exchange energy increases with the unpaired 4f-electron number. Conversely, the smaller distance between the 4f and 5d shells results in the stronger interaction of R–Co. The R–R exchange interaction is the least significant in the three sorts of exchange interactions. The interaction feature between the magnetic components in this quaternary system is similar to those in binary and ternary systems.
Pathways of atomistic processes on TiN(001) and (111) surfaces during film growth: an ab initio study
Authors: Gall D. , Kodambaka S. , Wall M. A. , Petrov I. , Greene J. E.
Published: May 2003

Density functional methods were used to calculate binding and diffusion energies of adatoms, molecules, and small clusters on TiN(001) and TiN(111) surfaces in order to isolate the key atomistic processes which determine texture evolution during growth of polycrystalline TiN layers. The surface energy for nonpolar TiN(001), 81 meV/Å2, was found to be lower than that of both N- and Ti-terminated TiN(111) polar surfaces, 85 and 346 meV/Å2. While N2 molecules are only weakly physisorbed, Ti adatoms form strong bonds with both TiN(001), 3.30 eV, and TiN(111), 10.09 eV. Ti adatom diffusion is fast on (001), but slow on (111) surfaces, with calculated energy barriers of 0.35 and 1.74 eV, respectively. The overall results show that growth of 111-oriented grains is favored under conditions typical for reactive sputter deposition. However, the presence of excess atomic N (due, for example, to collisionally induced dissociation of energetic N2+ ions) leads to a reduced Ti diffusion length, an enhanced surface island nucleation rate, and a lower chemical potential on the (001) surface. The combination of these effects results in preferential growth of 001 grains. Thus our results provide an atomistic explanation for the previously reported transition from 111 to 001 texture observed for sputter deposition of TiN in Ar/N2 mixtures with increasing N2 partial pressure PN2 and at constant PN2 with increasing N2+/Ti flux ratios incident at the growing film.
Optical absorption spectra near the fundamental band edge in Cu2In4Se7 bulk crystals
Authors: Rincón C. , Wasim S. M. , Marı́n G. , Sánchez Pérez G.
Published: May 2003

From the analysis of the optical absorption coefficient spectra of bulk crystals of Cu2In4Se7 near the band edge as a function of temperature, two distinct absorption bands, one in the energy range from 0.8 to 1.0 eV and the other above 1.0 eV, were observed. The first band was identified as due to band tail–to–band transitions caused by a high concentration of native defects whereas the latter was attributed to the lowest band–to–band transition due to an allowed direct gap. The energy gap EG was found to be 1.020 and 0.986 eV at 10 and 300 K, respectively. From the analysis of the temperature dependence of EG in terms of the current theoretical models reported in the literature for its shift with T, the Debye temperature was estimated to be around 220 K. It was also found that the major contribution to the temperature variation of EG in this compound is apparently due to acoustic phonons.
Ferroelectric and ferromagnetic properties of BiFeO3–PrFeO3–PbTiO3 solid solutions
Authors: Kim Jeong Seog , Cheon Chae Il , Choi Yong Nam , Jang Pyong Woo
Published: May 2003

Solid solutions of xBiFeO3–yPrFeO3–zPbTiO3 (x+y+z=1) and (1−w)BiFeO3–wPbTiO3 have been explored for finding ferroelectromagnetic bulk material, in which ferroelectricity and ferromagnetism coexist simultaneously. The coexistence has been observed only in some ternary composition samples, that is, 0.2BiFeO3–0.2PrFeO3–0.6PbTiO3 and 0.4BiFeO3–0.2PrFeO3–0.4PbTiO3. In the ternary solid solutions, spontaneous magnetic moments disappear with the decrease of PrFeO3 content to y<0.2 independently of BiFeO3 content. When PrFeO3 content remains constant at y=0.2, the ternary solid solutions become paraelectric with the decrease of PbTiO3 content to z⩽0.2. The ferroelectromagnetic solid solutions have the noncentrosymmetric and doubled perovskite unit cell with a space group I4cm (a=b≈5.4 Å, c≈7.9 Å). Addition of Ta2O5 dopant substantially changes the polarization–electric-field and magnetization–magnetic field curves of the 0.2BiFeO3–0.2PrFeO3–0.6PbTiO3. The binary solid solutions of (1−w)BiFeO3–wPbTiO3 do not exhibit spontaneous magnetic moments down to 10 K over the entire composition range.
Characterization of electrostatic glass actuators
Authors: Moser R. , Wüthrich R. , Sache L. , Higuchi T. , Bleuler H.
Published: May 2003

Electrostatic glass actuators are a promising concept for various applications. The use of the interaction between glassy substances and electrostatic fields allows synchronous propulsion akin to the electret actuator. Even though some properties of electrostatic glass motors have been observed and described, a characterization is still missing. The authors would like to present the experimental work leading to the determination of the optimal glass blend and to the optimal electrode pattern in order to maximize the exploitable forces. An analytical model is also presented, satisfactorily close to the measured data. These measurements and models constitute a tool to design electrostatic glass actuators such as, for example, a miniature disk drive, which is presented as one of several promising applications.
Existence and stability of solitary kinetic Alfvén, ion-acoustic and electron-acoustic waves in a two electron temperature plasma
Authors: Chakraborty Debalina , Das K. P.
Published: May 2003

The Korteweg–de Vries–Zakharov–Kuznetsov equations are derived for kinetic Alfvén, ion- acoustic and electron-acoustic waves in a two electron temperature magnetized plasma. The solitary wave solutions of these equations propagating obliquely to the external uniform magnetic field are obtained. The existence of these solitary wave solutions in the parameter space is investigated and studies are made on the stabilities of these solitary waves by the Rowlands–Infeld method. The kinetic Alfvén solitons are found to be stable. The instability criterion and maximum growth rate of instability become the same for both electron-acoustic and ion-acoustic solitons.
Growth temperature and dopant species effects on deep levels in Si grown by low temperature molecular beam epitaxy
Authors: Chung Sung-Yong , Jin Niu , Rice Anthony T. , Berger Paul R. , Yu Ronghua , Fang Z-Q. , Thompson Phillip E.
Published: May 2003

Deep-level transient spectroscopy measurements were performed in order to investigate the effects of substrate growth temperature and dopant species on deep levels in Si layers during low-temperature molecular beam epitaxial growth. The structures studied were n+-p junctions using B doping for the p layer and p+-n junctions using P doping for the n layer. While the density of hole traps H1 (0.38–0.41 eV) in the B-doped p layers showed a clear increase with decreasing growth temperature from 600 to 370 °C, the electron trap density was relatively constant. Interestingly, the minority carrier electron traps E1 (0.42–0.45 eV) and E2 (0.257 eV), found in the B-doped p layers, are similar to the majority carrier electron traps E11 (0.48 eV) and E22 (0.269 eV) observed in P-doped n layers grown at 600 °C. It is hypothesized that these dominating electron traps are associated with pure divacancy defects and are independent of the dopant species.
Operating regimes for multivalued single-electron tunneling phase logic
Authors: Li Tan , Kiehl Richard A.
Published: May 2003

The dc bias range and the logic-state lifetime for multivalued single-electron tunneling phase logic are examined in computer simulations. Results for quaternary operation, which is of particular interest for compact logic circuitry, are compared with those for ternary and binary logic. Quaternary logic is shown to exhibit a rotation rule similar to binary and ternary logic and to have an optimized dc bias range of 14%, compared with 20 and 37 % for ternary and binary logic, respectively. The effects of shot noise and Nyquist noise on the logic-state lifetime are strongly influenced by the number of logic states. The ratio of tunnel resistance to series resistance required to suppress the effects of shot noise below those of Nyquist noise depends on the number of logic states. To obtain a lifetime equal to 1000 phase-locked cycles together with a maximum dc bias operating range, the ratio of Coulomb energy to thermal energy Ec/kBT must be 400, 1650, and 2830 for two, three, and four states, respectively. This corresponds to a rapid drop in the maximum operating temperature with the number of states, which can be related to an exponential dependence of lifetime on the activation energy for a thermally activated escape process. The implications of these results on the trade-offs between the operating regimes for dc bias, temperature, and junction size are discussed.
Grain-size dependence of plastic deformation in nanocrystalline Fe
Authors: Jang D. , Atzmon M.
Published: May 2003

Plastic deformation of nanocrystalline Fe was investigated by nanoindentation. Samples, synthesized by mechanical attrition, consisted of powder particles with diameters greater than 30 μm. The average grain diameters within the particles of different samples ranged from 10 nm to 10 μm. To avoid potential artifacts, samples were prepared without use of heat treatment, and measurements were conducted at a depth significantly smaller than the powder particle size. Corrections were made for the indentation-size effect and for pileup or sink in around the indent. The volume-averaged grain size was used in the analysis. The Hall-Petch relation is obeyed for grain sizes above about 18 nm, and slight softening occurs at smaller grain sizes. The strain-rate sensitivity increases monotonically with decreasing grain size. The results are consistent with grain-boundary sliding.