bluuebunny/crossref_metadata_2025 huggingface dataset:
Perceptions and needs of patients with migraine: a focus group study.
Authors: Cottrell CK , Drew JB , Waller SE , Holroyd KA , Brose JA , O'Donnell FJ
Published: January 2004

J Fam Pract. 2002;51:142‐147.

OBJECTIVE: This study's purpose was to identify the areas that people find most difficult in living with migraines and, in that regard, what kinds of assistance would be most helpful to them and to other people who have migraine headaches. STUDY DESIGN: Four focus groups, each consisting of 4 to 8 participants, were held. Discussions, which were recorded and organized according to category and theme, focused on problems in living with migraines and effective treatment of migraines. POPULATION: Participants were 24 people who had been experiencing 1 to 2 migraines a month, each lasting 1 to 2 days, for at least 6 months. RESULTS: Five themes emerged: (1) impact on family, (2) misunderstanding by others, (3) effect on work, (4) physician care issues, and (5) issues related to medical insurance and drug companies. A majority of participants identified early treatment as the most important consideration for new migraine sufferers. Many participants preferred to have a relationship with their physicians in which they developed a treatment plan together rather than receiving generic educational materials. CONCLUSIONS: Results suggest that patients are interested in understanding their migraines and securing relevant information in addition to obtaining pain relief. Patients desired collaborative relationships with their physicians and a team approach to treatment. Suggestions for physicians who treat patients who have migraines are reviewed.

Comment: This small study based on focus groups builds on earlier work by Russell Packard and John Edmeads that was intended to determine what patients really want from a healthcare consultation. In this era of direct‐to‐consumer (DTC) advertising of pharmaceuticals, it would be interesting to pursue further the issues raised by patients relating to medical insurance and drug companies. DSM

Despite its small size, the article is a useful reminder from Dr. Holroyd's group that information is what patients seek most urgently, with treatment second. SJT
Self‐awareness of migraine: interpreting the labels that headache sufferers apply to their headaches.
Authors: Lipton RB , Stewart WF , Liberman JN
Published: January 2004

Neurology. 2002;58(9 suppl 6):S21‐S26.

Although people with migraine are aware of their headaches they are often not aware that they have migraine. This can lead to inappropriate or ineffective use of treatments, delays in seeking appropriate care, and miscommunication during clinical encounters. This article assesses self‐recognition of migraine and identifies terms used by migraine sufferers to describe their migraine headaches. Individuals were selected for telephone interview by random digit dialing in several large United States cities as a part of a clinical trials recruiting initiative. Individuals (n  =  30  758) aged 18 to 65 years of age were interviewed about their headaches using a validated computer‐assisted telephone interview. Among the 23  564 respondents who reported headache, their headaches were classified as migraine (with or without aura) by the criteria of the International Headache Society (IHS). The relationships among the terms subjects used for their headaches and their IHS diagnosis of migraine were assessed. Of the 23  564 respondents, 4967 individuals called their headache migraine and 3074 individuals reported headache that met the IHS criteria for migraine. The positive predictive value for self‐assessed migraine is 33.1%; the negative predictive value for a self‐assessment other than migraine is 92.3%. Therefore, individuals who called their headaches migraine were about three times more likely to meet IHS criteria for migraine. Among the 3074 individuals meeting IHS criteria for migraine, only 53.4% recognized their headaches as migraine (sensitivity 54%; specificity 83.8%). Among migraineurs, stress headaches (n  =  345) and sinus headaches (n  =  365) were the most common erroneous labels reported. Age influenced the erroneous terminology. Individuals less than 40 years of age were more likely to misidentify their migraine as stress headaches, whereas individuals 40 years of age and older were more likely to misidentify their migraines as sinus headaches. In a population sample, 54% of individuals with IHS migraine did not know that their headaches are migraine. Those who called their headaches migraine were much more likely to have migraine. Migraine awareness programs that rely solely on the term “migraine” may miss individuals who urgently need to be reached. Therefore, public education should target people with severe or disabling headache and aim to create awareness of the diagnostic possibilities.

Comment: In the general population, and in contrast to the doctor's office, episodic tension‐type headache is more common than migraine. When a person in the general population self‐diagnoses nonmigraine, the diagnosis is likely to be correct. These tension or “stress” headaches do not frequently rise to a level that compels those afflicted to seek medical attention. SJT
Neurosurgical treatment of short‐lasting, unilateral, neuralgiform hemicrania with conjunctival injection and tearing.
Authors: Hannerz J , Linderoth B
Published: January 2004

Br J Neurosurg. 2002;16:55‐58.

Trigeminal neuralgia solely involving the upper trigeminal nerve branch is rare. The SUNCT syndrome (short‐lasting, unilateral, neuralgiform hemicrania with conjunctival injection and tearing) in which the periorbital pain lasts for 60‐120 s, and is accompanied by conjunctival injection and tearing is even less common. Unlike trigeminal neuralgia, SUNCT is usually not relieved by medication. Three patients with SUNCT were treated with retrogasserian glycerol rhizolysis, two of them twice. All five treatments provided complete pain relief and the duration of the effects was 2 to more than 4 years. One of these three patients also had a third treatment with compression of retroganglionic fibres with a Fogarthy balloon, according to Mullan, of the upper trigeminal nerve with excellent results.

Comment: Although lamotrigine has shown promise, no pharmacologic treatment has been found to work consistently for SUNCT. Are we really at the surgical juncture? SJT
The role of concomitant headache types and non‐headache co‐morbidities in the underdiagnosis of migraine.
Authors: Diamond ML
Published: January 2004

Neurology. 2002;58(9 suppl 6):S3‐S9.

That migraine is significantly underdiagnosed in the United States and other countries is well established. New data from a follow‐up survey to the American Migraine Study II reveal that the presence of concomitant headache types and co‐morbid conditions significantly affects the ability to detect and diagnose migraine. This article describes these data and explores the contribution of concomitant headache types and co‐morbidities to the problem of underdiagnosis of migraine. Migraine continues to be underdiagnosed because of failure to recognize it (missed diagnosis) and because of misdiagnosis of migraine as another headache type. First, a diagnosis of migraine may be missed in the presence of other headache types that occur proportionally more frequently than migraine and thereby overshadow migraine. Second, migraine may be misdiagnosed when health‐care providers inappropriately interpret specific symptoms and co‐morbid conditions as indicators of the presence of a non‐migraine headache type such as sinus or tension. By becoming aware of these diagnostic pitfalls and being more judicious and deliberate in diagnosing migraine and other headache types, health‐care providers can improve the diagnosis of migraine and patients to receive appropriate therapy.

Comment: The diagnosis of migraine is less likely to be made if the patient has several types of headache presentations over time. Thus, a patient with the full spectrum of migraine, from episodic tension‐type through migrainous (probable migraine) headache and on to migraine per se is far less likely to receive a diagnosis of migraine than a patient who experiences attacks of “pure” migraine. SJT
The co‐occurrence of headache and musculoskeletal symptoms amongst 51 050 adults in Norway.
Authors: Hagen K , Einarsen C , Zwart JA , Svebak S , Bovim G
Published: January 2004

Eur J Neurol. 2002;9:527‐533.

We have evaluated the association between headache and musculoskeletal symptoms in a large cross‐sectional population‐based study. Between 1995 and 1997, all 92 566 adults in Nord‐Trondelag County in Norway were invited to participate in a health survey. A total of 51  050 (55%) responded to questions concerning headache and musculoskeletal symptoms. Both migraine and non‐migrainous headache were strongly associated with musculoskeletal symptoms. However, frequency of headache had a higher impact than headache diagnosis on this association. Thus, the prevalence of chronic headache (headache>14 days/month) was more than four times higher (OR  =  4.6; 95% CI 4.0‐5.3) in the group of individuals with musculoskeletal symptoms than in those without. Individuals with neck pain were more likely to suffer from headache as compared with those with musculoskeletal symptoms in other restricted areas. In conclusion, there was a strong association between chronic headache and musculoskeletal symptoms, which may have implications for the choice of treatment.

Comment: This study describes an important association between frequent headache and cervical musculoskeletal pain. Further work to explore the relationship between fibromyalgia and headache may help our understanding and treatment of these common and often disabling conditions. DSM
Genetic and environmental influences on expression of recurrent headache as a function of the reporting age in twins.
Authors: Svensson DA , Larsson B , Waldenlind E , Pedersen NL
Published: January 2004

Twin Res. 2002;5:277‐286.

To explore age‐related mechanisms in the expression of recurrent headache, we evaluated whether genetic and environmental influences are a function of the reporting age using questionnaire information that was gathered in 1973 for 15‐ to 47‐year‐old Swedish twins (n  =  12,606 twin pairs). Liability to mixed headache (mild migraine and tension‐type headache) was explained by non‐additive genetic influences (49%) in men aged from 15 to 30 years and additive genetic plus shared environmental influences (28%) in men aged from 31 to 47 years. In women, the explained proportion of variance, which was mainly due to additive genetic effects, ranged from 61% in adolescent twins to 12% in twins aged from 41 to 47 years, whereas individual specific environmental variance was significantly lower in twins aged from 15 to 20 years than in twins aged from 21 to 30 years. Liability to migrainous headache (more severe migraine) was explained by non‐additive genetic influences in men, 32% in young men and 45% in old men, while total phenotypic variance was significantly lower in young men than in old men. In women, the explained proportion of variance ranged from 91% in the youngest age group to 37% in the oldest age group, with major contributions from non‐additive effects in young and old women (15‐20 years and 41‐47 years, respectively) and additive genetic effects in intermediate age groups (21‐40 years). While total variance showed a positive age trend, genetic variance tended to be stable across age groups, whereas individual specific environmental variance was significantly lower in adolescent women as compared to older women.

Comment: Does this mean that most of the genetic contribution to headache in women is likely to occur during adolescence, which would be in agreement with the peak incidence? Some clinical interpretation would be helpful here. DSM
The Quality Standards Subcommittee of the American Academy of Neurology, The Practice Committee of the Child Neurology Society. Practice parameter: evaluation of children and adolescents with recurrent headaches: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society.
Authors: Lewis DW , Ashwal S , G et al. Dahl
Published: January 2004

Neurology. 2002;59:490‐498.

OBJECTIVE: The Quality Standards Subcommittee of the American Academy of Neurology and the Practice Committee of the Child Neurology Society develop practice parameters as strategies for patient management based on analysis of evidence. For this parameter, the authors reviewed available evidence on the evaluation of the child with recurrent headaches and made recommendations based on this evidence. METHODS: Relevant literature was reviewed, abstracted, and classified. Recommendations were based on a four‐tiered scheme of evidence classification. RESULTS: There is inadequate documentation in the literature to support any recommendation as to the appropriateness of routine laboratory studies or performance of lumbar puncture. EEG is not recommended in the routine evaluation, as it is unlikely to define or determine an etiology or distinguish migraine from other types of headaches. In those children undergoing evaluation for recurrent headache found to have a paroxysmal EEG, the risk for future seizures is negligible; therefore, further investigation for epilepsy or treatments aimed at preventing future seizures is not indicated. Obtaining a neuroimaging study on a routine basis is not indicated in children with recurrent headaches and a normal neurologic examination. Neuroimaging should be considered in children with an abnormal neurologic examination or other physical findings that suggest CNS disease. Variables that predicted the presence of a space‐occupying lesion included 1) headache of less than 1‐month duration; 2) absence of family history of migraine; 3) abnormal neurologic findings on examination; 4) gait abnormalities; and 5) occurrence of seizures. CONCLUSIONS: Recurrent headaches occur commonly in children and are diagnosed on a clinical basis rather than by any testing. The routine use of any diagnostic studies is not indicated when the clinical history has no associated risk factors and the child's examination is normal.

Comment: An important paper which summarizes the evidence for reaching a clinical diagnosis in children with recurrent headaches, while at the same time avoiding unnecessary and potentially harmful investigations. DSM
Contrasts in cortical magnesium, phospholipid and energy metabolism between migraine syndromes.
Authors: Boska MD , Welch KM , Barker PB , Nelson JA , Schultz L
Published: January 2004

Neurology. 2002;58:1227‐1233.

BACKGROUND: Previous single voxel (31)P MRS pilot studies of migraine patients have suggested that disordered energy metabolism or Mg(2+) deficiencies may be responsible for hyperexcitability of neuronal tissue in migraine patients. These studies were extended to include multiple brain regions and larger numbers of patients by multislice (31)P MR spectroscopic imaging. METHODS: Migraine with aura (MWA), migraine without aura (MwoA), and hemiplegic migraine patients were studied between attacks by (31)P MRS imaging using a 3‐T scanner. RESULTS: Results were compared with those in healthy control subjects without headache. In MwoA, consistent increases in phosphodiester concentration [PDE] were measured in most brain regions, with a trend toward increase in [Mg(2+)] in posterior brain. In MWA, phosphocreatine concentration ([PCr]) was decreased to a minor degree in anterior brain regions and a trend toward decreased [Mg(2+)] was observed in posterior slice 1, but no consistent changes were found in phosphomonoester concentration [PME], [PDE], inorganic phosphate concentration ([Pi]), or pH. In hemiplegic migraine patients, [PCr] had a tendency to be lower, and [Mg(2+)] was significantly lower than in the posterior brain regions of control subjects. Trend analysis showed a significant decrease of brain [Mg(2+)] and [PDE] in posterior brain regions with increasing severity of neurologic symptoms. CONCLUSIONS: Overall, the results support no substantial or consistent abnormalities of energy metabolism, but it is hypothesized that disturbances in magnesium ion homeostasis may contribute to brain cortex hyperexcitability and the pathogenesis of migraine syndromes associated with neurologic symptoms. In contrast, migraine patients without a neurologic aura may exhibit compensatory changes in [Mg(2+)] and membrane phospholipids that counteract cortical excitability.

Comment: If the theory of hyperexcitability of migraine brain is correct, basic scientists will need to find clear markers for the neuronal abnormalities that underlie this excitability. Using their techniques, these researchers could not find such markers. SJT
Sensitization of trigeminal nociception specific for migraine but not pain of sinusitis.
Authors: Katsarava Z , Lehnerdt G , Duda B , Ellrich J , Diener HC , Kaube H
Published: January 2004

Neurology. 2002;59:1450‐1453.

Trigeminal pain processing was studied in 14 patients with unilateral migraine attacks and 14 age‐ and sex‐matched patients with comparable unilateral headache from frontal sinusitis. Using a nociception‐specific blink reflex method (nBR), a facilitation of nBR responses predominantly on the headache side was observed in migraine, but not in sinusitis. The facilitation of trigeminal nociception may be specific for migraine rather than a consequence of peripheral pain such as frontal sinusitis.

Comment: Here we have evidence for the central hyperexcitability of migraine, not found in the previously cited article by Boska et al. SJT
Median nerve somatosensory evoked potentials in migraine.
Authors: Ozkul Y , Uckardes A
Published: January 2004

Eur J Neurol. 2002;9:227‐232.

In visual evoked potential studies, habituation during stimulus repetition with the same stimulus at a constant intensity has been found to be abnormal in migraineurs between attacks. The purpose of this study was to investigate habituation of somatosensory evoked potentials (SEPs) and the effects of migraine on them. Eighty‐five subjects were included in the study: 30 healthy volunteers (HVs) and 55 migraineurs [30 with migraine without aura (MO), 25 with migraine with aura (MA)]. During continuous stimulation at 3 Hz, four blocks of 100 responses were sequentially averaged of Erb's point (N9), cervical (N13), and cortical (N20) median nerve SEPs. Mean amplitude changes in the second, third and fourth blocks are expressed as percentages of the first block. There was habituation to N13 and N20 in the second, third and fourth blocks in HVs. In the migraine groups, there was no habituation; on the contrary, potentiation was found. This potentiation was statistically significant only in the second blocks for N13 (MO P  =  0.007, MA P  =  0.01 versus HVs). However, in both migraineur groups, the rate of N20 potentiations was statistically significant versus that in HVs for all blocks (all P< 0.05). It is concluded that whilst physiological habituation occurs in HVs for cervical and cortical SEPs, in migraine patients there is an interictal deficit of habituation of this sensory modality.

Comment: This interesting study confirms the lack of habituation to repetitive stimuli reported in migraineurs between attacks and extends this finding to somatosensory evoked potentials using median nerve stimulation. One might speculate that migraineurs lack a protective mechanism which modulates both cervical and cortical sensory inputs. DSM
Simultaneous surface acoustic wave and surface plasmon resonance measurements: Electrodeposition and biological interactions monitoring
Authors: Friedt J.-M , Francis L. , Reekmans G. , De Palma R. , Campitelli A. , Sleytr U. B.
Published: January 2004

We present results from an instrument combining surface acoustic wave propagation and surface plasmon resonance measurements. The objective is to use two independent methods, the former based on adsorbed mass change measurements and the latter on surface dielectric properties variations, to identify physical properties of protein layers, and more specifically their water content. We display mass sensitivity calibration curves using electrodeposition of copper leading to a sensitivity in liquid of 150±15 cm2/g for the Love mode device used here, and the application to monitoring biological processes. The extraction of protein layer thickness and protein to water content ratio is also presented for S-layer proteins under investigation. We obtain, respectively, 4.7±0.7 nm and 75±15%.
Transport relaxation phenomena in superconducting Y1Ba2Cu3O7−δ
Authors: Kiliç K. , Kiliç A. , Yetiş H. , Çetin O.
Published: January 2004

Transport relaxation measurements (V-t) were carried out in bulk superconducting Y1Ba2Cu2O7−δ ceramic samples as a function of driving current (I), temperature (T), and external magnetic field (H). The evolution of the V-t curve strongly depends on I, T, and H. The V-t characteristics exhibit several features revealing the details of the evolution of the penetrated state associated with different flow patterns. Analysis of the V-t data showed that the relaxation process originates mainly from the intergranular region. The results provide direct evidence for the relaxation of vortices which are of Josephson-type. From the magnetic field dependence of the V-t curves, we found that there is a transition evolving from the Josephson vortices to the Abrikosov ones. We showed that both the driving current and external magnetic field have determining effects on the shape of the V-t curve and anneal the dynamical states by serving as an effective temperature.
C49-C54 phase transition in nanometric titanium disilicide grains
Authors: Alessandrino M. S. , Privitera S. , Grimaldi M. G. , Bongiorno C. , Pannitteri S. , La Via F.
Published: January 2004

The formation of single C49-TiSi2 grains embedded in a polycrystalline Si matrix has been studied in detail by means of in-situ sheet resistance, x-ray diffraction measurements, and energy filtered transmission electron microscopy characterization. The C49 clusters were obtained by starting from a 3 nm-Ti/40 nm-Si multilayer structure. After the C49 clusters formation, increasing the temperature in the 800–1100 °C range, the first-order C49-C54 transition has been therefore investigated in a system without triple grains boundaries. At each temperature the C54 fraction initially increases with the annealing time until it reaches a maximum constant value within ∼80 s. The maximum value of the converted C54 fraction increases linearly with the annealing temperature in the studied range. The nucleation sites density in these samples is ∼2×1011 cm−2, several orders of magnitude higher than in continuous TiSi2 films, where this value is about 4×106 cm−2.
X-ray characterization of Si microstructures with high spatial resolution
Authors: Cedola A. , Lagomarsino S. , Scarinci F. , Servidori M. , Stanic V.
Published: January 2004

With the advent of the nanolithographic technologies, the demand of a local strain/stress analysis with submicrometer resolution is increasing. In particular, the aim of this work was the study of a patterned Si wafer subjected to preliminary process flow for 0.15 μm complementary metal oxide semiconductor generation. The main purpose was to follow the production of strain induced in the Si substrate during the shallow trench isolation process and subsequent formation of active stripes. The determination of structural parameters with very high spatial resolution in one dimension (300 nm) has been obtained using a scanning x-ray microscope whose main element is a waveguide for medium and high energy x-rays (8–30 keV). The experiment, which takes advantage of a nondispersive geometry, required neither a two-dimensional highly sensitive detector nor an insertion device beamline, but it has been carried out on bending magnet beamlines with relatively low flux.
Modification of the optical properties of Ag-implanted silica by annealing in two different atmospheres
Authors: Roiz J. , Oliver A. , Muñoz E. , Rodrı́guez-Fernández L. , Hernández J. M. , Cheang-Wong J. C.
Published: January 2004

Significant changes in the optical properties of nanometer-size Ag clusters embedded in high-purity silica were obtained. Samples were prepared by 2 MeV Ag-ion implantation with fluences in the 2.8–3.8×1016 ions/cm2 range and subsequent annealing at various temperatures in air (oxidizing atmosphere) or in a hydrogen-rich atmosphere (reducing atmosphere). Changes consisted of large and small blueshifts of the resonance surface plasmon peak position, light absorption modification in the ultraviolet (UV) region, increased optical extinction in all the spectrum wavelength range, and different resonance peak height depending on annealing atmosphere. Optical property changes were analyzed in terms of Ag cluster size, interaction at cluster–matrix interface, cluster hydrogen content, diffusivity and conductivity. Bands in the UV region are reported.
Electro-optic characteristics of 90° twisted nematic liquid crystal display driven by fringe-electric field
Authors: Song I. S. , Shin S. S. , Kim H. Y. , Song S. H. , Lee S. H.
Published: January 2004

We investigated the electro-optic characteristics of a fringe-field driven twisted nematic (TN) display. In the absence of an electric field, the liquid crystals (LCs) are initially twisted 90° from the top to the bottom substrate under parallel polarizers so that the cell appears to be black. In the presence of a fringe-electric field, the LCs with negative dielectric anisotropy are rotated toward a plane that is almost perpendicular to the horizontal component of the fringe field, above the entire electrode surface. The cell then appears to be white, and shows high transmittance. In addition, the cell displays a wide viewing angle and has excellent color characteristics over a wide viewing range due to almost in-plane switching, unlike a conventional TN device where the LC director tilts upward in only one direction and results in a narrow viewing angle.
Growth and characterization of hydrogenated amorphous silicon thin films from SiH2 radical precursor: Atomic-scale analysis
Authors: Sriraman Saravanapriyan , Aydil Eray S. , Maroudas Dimitrios
Published: January 2004

Molecular-dynamics (MD) simulations of hydrogenated amorphous silicon (a-Si:H) film growth on an initially H-terminated Si(001)-(2×1) substrate at T=500 K was studied through repeated impingement of SiH2 radicals to elucidate the effects of this species on the structural quality of the deposited films. A detailed analysis of the radical–surface interaction trajectories revealed the important reactions contributing to film growth. These reactions include (i) adsorption of SiH2 onto the deposition surface, (ii) insertion of SiH2 into surface Si–Si bonds, (iii) surface dimerization of adsorbed SiH2 groups, (iv) formation of polysilane chains and islands, (SiH2)n, n⩾2, on the surface, (v) formation of higher surface hydrides through the exchange of hydrogen, and (vi) dangling-bond-mediated dissociation of surface hydrides. The MD simulations of a-Si:H film growth predict an overall surface reaction probability of 39% for the SiH2 radical. Structural and chemical characterization of the deposited films was carried out through a detailed analysis of the evolution of the structure of the film, surface morphology, and roughness, surface reactivity, and surface composition. The analysis revealed that the deposited films exhibit a high concentration of H and columnar surface morphologies. In particular, islands or polysilane chains form on the growth surface and are believed to be responsible for the columnar structural features in the deposited film. Such polysilane chain formation may have significant effects on the structural, morphological, and optical properties of the a-Si:H films.
Matrix-assisted laser deposition of a sorbent oligomer using an infrared laser
Authors: Bubb D. M. , O’Malley S. M. , Antonacci C. , Simonson D. , McGill R. A.
Published: January 2004

Fluoropolyol, a sorbent chemoselective oligomer, has been deposited using a matrix-assisted laser-based deposition technique. A comparison of films deposited with infrared (2.94 μm) and ultraviolet (UV) (193 nm) radiation shows that photochemical and/or photothermal modification of the oligomer occurs for the UV-deposited films while the IR-deposited films appear to be identical to the starting material. In addition, it is shown that even ablating the matrix alone causes a film to be deposited when using a UV laser. Therefore, unless photochemical interactions are a desired outcome, the use of a UV laser for most matrix-assisted laser ablation and deposition techniques is unfavorable.
Ion-beam irradiation of Co/Cu nanostructures: Effects on giant magnetoresistance and magnetic properties
Authors: Cai M. , Veres T. , Schiettekatte F. , Roorda S. , Cochrane R. W.
Published: January 2004

We have studied the effects of ion irradiation at low doses (<5×1014 ions/cm2) on the structural properties, giant magnetoresistance (GMR), and interlayer magnetic coupling in Co/Cu multilayers. X-ray analysis combined with magnetic and resistivity measurements reveal that intermixing is promoted by ion irradiation while the periodic structure and crystallographic properties of the multilayers are not significantly altered. The GMR ratio of a multilayer decreases monotonically with ion dose. However, thermal annealing on an irradiated multilayer results in sharp recovery of the reduced GMR, and can be associated with a backdiffusion process in metastably intermixed regions. Hence, using ion irradiation and subsequent annealing, the GMR of a single multilayer can be altered reversibly over a wide range. The variation of GMR upon irradiation (or annealing) is accompanied by significant suppression (or improvement) of the antiferromagnetic interlayer coupling. The correlation between GMR and AF coupling, as well as the role of enhanced electron scattering at interfaces during these processes are discussed.
Structural evolution of Co/Cu nanostructures under 1 MeV ion-beam irradiation
Authors: Cai M. , Veres T. , Roorda S. , Schiettekatte F. , Cochrane R. W.
Published: January 2004

Co/Cu multilayers with composition wavelength ranging from 2 to 10 nm have been deposited and irradiated at various doses from 1×1014 to 3×1016 ions/cm2 using 1 MeV Si+ ions. The ion-beam-induced variation in structural properties such as interfacial mixing, interface roughness, crystallographic texture, and grain size, are characterized by a variety of x-ray scattering techniques. Irradiating Co/Cu multilayers generate metastable Co–Cu alloys whose electrical and magnetic properties have been found to be very similar to the Co–Cu alloys fabricated by other nonequilibrium methods. Fitting to the low-angle x-ray reflectivity spectra using a standard optical model yields a mixing efficiency comparable to the prediction of a ballistic ion-beam mixing model, and interfacial mixing widths consistent with the values estimated from saturation magnetization measurements.
Enhancement of superconducting transition temperature via Ba doping in RuSr2−xBaxGdCu2O8 (x⩽0.1)
Authors: Yang L. T. , Liang J. K. , Liu Q. L. , Luo J. , Song G. B. , Liu F. S. , Feng X. M. , Rao G. H.
Published: January 2004

The crystal structure and superconducting properties of RuSr2−xBaxGdCu2O8 (0⩽x⩽0.1) have been investigated. X-ray powder diffraction (XRD) patterns show that the solid solution range is 0⩽x⩽0.1. The superconducting transition temperature was raised up to 35 K (zero) and 62 K (onset) for x=0.07, from 16 K (zero) and 45 K (onset) for x=0.0, and then TC decreases with x when x>0.07. Rietveld refinement for XRD data of RuSr2−xBaxGdCu2O8 show that the apical Cu–O(1) bond length increases with an increase of x, while the Ru–O(1) bond length decreases, This may account for the enhancement of the superconducting transition temperature.
On two incompatible models for dispersion in ionic conductors
Authors: Macdonald J. Ross
Published: January 2004

The two models considered are the widely used 1973 original modulus formalism (OMF) of Moynihan and associates, and the later corrected modulus formalism (CMF). Both approaches involve a dispersive frequency-response model derived from Kohlrausch stretched-exponential temporal response, the KWW1 model, also termed the K1. A brief summary of the derivation of this model is followed by consideration of the small but crucial differences between OMF and CMF analysis approaches and the reasons why the OMF and an inferred physical basis for its behavior, variable correlation between mobile ions, are inappropriate. After discussions of some prior criticisms of the OMF approach, results of accurate least-squares fitting of experimental frequency-response data to OMF and CMF models for a variety of ionic materials illustrate these differences and demonstrate a crucial inconsistency of the OMF, one that critically falsifies it.
Dependence of the stress–temperature coefficient on dislocation density in epitaxial GaN grown on α-Al2O3 and 6H–SiC substrates
Authors: Ahmad I. , Holtz M. , Faleev N. N. , Temkin H.
Published: January 2004

We report measurements of stress in GaN epitaxial layers grown on 6H–SiC and α-Al2O3 substrates. Biaxial stresses span +1.0 GPa (tensile) to −1.2 GPa (compressive). Stress determined from curvature measurements, obtained using phase-shift interferometry (PSI) microscopy, compare well with measurements using accepted techniques of x-ray diffraction (XRD) and Raman spectroscopy. Correlation between XRD and Raman measurements of the E22 phonon gives a Raman-stress factor of −3.4±0.3 cm−1/GPa. We apply PSI microscopy for temperature dependent stress measurements of the GaN films. Variations found in the stress–temperature coefficient correlate well with threading dislocation densities. We develop a phenomenological model which describes the thermal stress of the epitaxial GaN as a superposition of that for ideal GaN and the free volume existing in the layers due to the threading dislocations. The model describes well the observed dependence.
Dependence on liquid temperature and purity of light emission characteristics in single cavitation bubble luminescence
Authors: Barbaglia Mario O. , Bonetto Fabián J.
Published: January 2004

We produced single bubbles in water using a visible pulsed laser and studied the characteristics of the light emitted during the bubble collapse time as a function of the water temperature for different water purity values. The water temperature ranged from freezing point (0 °C) to near boiling. We measured the luminescence pulse for the mentioned temperature range at various purity values. We also obtained the average bubble lifetime and the average luminescence pulse emitted as a function of water temperature. The main conclusion was that the luminescence can be modified by the water quality and by the water temperature. Maximum luminescence was obtained near the water freezing point.
Numerical simulation of laser-generated ultrasound by the finite element method
Authors: Xu Baiqiang , Shen Zhonghua , Ni Xiaowu , Lu Jian
Published: January 2004

The results obtained from the finite element model of laser-generated ultrasound are presented in terms of temperature and displacement. According to thermoelastic theory, considering the temperature dependence of the thermophysical parameters of the material, the transient temperature field can be precisely calculated by using the finite element method; then, laser-generated surface acoustic wave forms are calculated in Al plates of various thicknesses. The elastic waves excited by a pulsed laser in a thin plate are typical Lamb waves, and the numerical results demonstrate that the surface vibration is mainly determined by the lower frequency components of the symmetric mode s0 and antisymmetric mode a0 of the lowest order in very thin plate materials. It is also indicated that, when the sample thickness increases, both the higher frequency components of the lower Lamb wave modes and the higher order Lamb wave modes should be considered. In a relatively thicker plate, the numerical model can still capture the significant details of the transient features taking place in the plates. The surface skimming longitudinal and shear waves are relatively stronger in the near field, distorting the observed wave form of the Rayleigh wave. These effects must be considered when the quantitative near field is applied to determining elastic parameters or residual stresses.
Comment on “Schottky diodes with a δ-doped near-surface layer” [J. Appl. Phys. 90, 6205 (2001)]
Authors: Shashkin V. , Murel A.
Published: January 2004

The influence of planar δ-doping on the effective parameters of Schottky diodes was modeled by J. Osvald [J. Appl. Phys. 90, 6205 (2001)]. In this Comment we emphasize that the proposed analysis based on the drift-diffusion model does not seem to be fully correct for the system in question. Neglect of the tunneling effects in Schottky diode with isotype δ-layer inserted near the metal–semiconductor interface leads to wrong speculations about the effective barrier height and ideality factor.
Molecular dynamics simulations of the effects of defects on martensite nucleation
Authors: Li B. , Zhang X. M. , Clapp P. C. , Rifkin J. A.
Published: January 2004

The effects of various lattice defects, such as a single edge dislocation, dislocation configurations, a low-angle grain boundary, and a high-angle grain boundary, on martensite nucleation and growth were investigated by performing molecular dynamics simulations, using EAM interatomic potentials for Ni–Al alloy. Stress induced and thermally activated martensitic transformations were studied in the cases that various defects were introduced into the simulated system. The simulation results show that the nucleation patterns were closely related to the stresses of the dislocation configurations, in the sense that the locations where stresses assist the lattice distortion of the transformation are favorable for martensite nucleation. A symmetric, tilt low-angle grain boundary is not favorable for martensite nucleation, because the stresses of the constituent dislocations cancel one another and stresses that assist the lattice distortion cannot be produced. The low-angle boundary hinders the martensite growth due to the high stability of this type of dislocation configuration. A relaxed, high-angle grain boundary (coincident site lattice) is also not favorable for martensite nucleation, because of the lack of long-range stress field.
Barrier-limited surface diffusion in atom lithography
Authors: te Sligte E. , van der Stam K. M. R. , Smeets B. , van der Straten P. , Scholten R. E. , Beijerinck H. C. W. , van Leeuwen K. A. H.
Published: January 2004

Thermally activated surface diffusion has a strong influence on structure widths in atom lithography. We investigate the effects of two barriers to thermally activated atomic diffusion on atom lithography: a thermally activated Ehrlich–Schwoebel (ES) barrier, and pollution from the residual gas in the vacuum system. We performed kinetic Monte Carlo simulations using a one-dimensional surface grid. We find that the ES barrier fails to explain the lack of temperature dependence observed experimentally [W. R. Anderson et al., Phys. Rev. A 59, 2476 (1999)]. The dependencies of the structure width on temperature, vacuum conditions, and beam characteristics can be explained using the pollutant adatom hypothesis. Only the variation of structure width with deposition duration was not entirely reproduced by this model. We attribute this to the one-dimensional nature of our simulations. These results demonstrate that barrier-limited diffusion can play an important role in atom lithography, and that pollutant adatoms are a likely candidate barrier.
Experimental verification of the effect of depletion-region modulation on photoconductance lifetime measurements
Authors: Cousins Peter J. , Neuhaus Dirk H. , Cotter Jeffrey E.
Published: January 2004

Depletion-region modulation (DRM) has recently been identified as a mechanism that influences photoconductance lifetime measurements. The effect is observed in semiconductor samples containing a depletion-region (i.e., p-n junction solar cells). Experimental measurements presented within demonstrate that the DRM effect dominates the conductance measurement at low excess carrier concentrations, resulting in an overestimation of the effective lifetime by several orders of magnitude. The influence of substrate thickness on the DRM effect is experimentally verified. The previously developed analytical equation for DRM is in agreement with our experimental data and can be used to correct DRM affected photoconductance lifetime measurements. Finally, the impact on the sensitivity of a photoconductance measurement is discussed for the DRM corrected case.
Effect of temperature on carbon nanotube diameter and bundle arrangement: Microscopic and macroscopic analysis
Authors: Hinkov I. , Grand J. , Lamy de la Chapelle M. , Farhat S. , Scott C. D. , Nikolaev P. , Pichot V. , Launois P. , Mevellec J. Y. , Lefrant S.
Published: January 2004

The diameter distribution of the nanotubes produced by electric-arc discharge are measured using Raman spectroscopy at various wavelengths. These measurements agree with the results provided by two other techniques: high-resolution transmission electron microscopy and x-ray diffraction. The mean tube diameter shifts more than 0.1 nm with the increase of argon in the inert atmosphere. Some argon concentrations favored the synthesis of metallic tubes with specific diameters. Furthermore, the background gas influences the macroscopic characteristics of nanotube yield and bundle size, as determined by Brunauer–Emmett–Teller surface area measurements and x-ray diffraction. The information collected on nanotube diameter and arrangement is correlated with temperatures calculated using a numerical model of the plasma generated between the two electrodes. Indeed, plasma temperature control during the production process is achieved using argon–helium mixtures as buffer gases. The variation of the gas mixture from pure argon to pure helium changes the plasma temperature and hence the nanotube diameter.
Young’s modulus of silicon nitride used in scanning force microscope cantilevers
Authors: Khan A. , Philip J. , Hess P.
Published: January 2004

The Young’s modulus and Poisson’s ratio of high-quality silicon nitride films with 800 nm thickness, grown on silicon substrates by low-pressure chemical vapor deposition, were determined by measuring the dispersion of laser-induced surface acoustic waves. The Young’s modulus was also measured by mechanical tuning of commercially available silicon nitride cantilevers, manufactured from the same material, using the tapping mode of a scanning force microscope. For this experiment, an expression for the oscillation frequencies of two-media beam systems is derived. Both methods yield a Young’s modulus of 280–290 GPa for amorphous silicon nitride, which is substantially higher than previously reported (E=146 GPa). For Poisson’s ratio, a value of ν=0.20 was obtained. These values are relevant for the determination of the spring constant of the cantilever and the effective tip–sample stiffness.
Approach for reducing the Rayleigh scattering loss in optical fibers
Authors: Saito K. , Yamaguchi M. , Ikushima A. J. , Ohsono K. , Kurosawa Y.
Published: January 2004

Structural relaxations in fiber cores and claddings with various F concentrations were investigated. It was found that structural relaxation in the core is strongly affected by that in the cladding. This effect leads to an approach to control structural relaxation in fiber core for reducing the Rayleigh scattering loss in optical fibers. The advantage of this approach is to avoid increase of the Rayleigh scattering due to concentration fluctuation.
Three-dimensional high-resolution reconstruction of polarization in ferroelectric capacitors by piezoresponse force microscopy
Authors: Rodriguez B. J. , Gruverman A. , Kingon A. I. , Nemanich R. J. , Cross J. S.
Published: January 2004

A combination of vertical and lateral piezoresponse force microscopy (VPFM and LPFM, respectively) has been used to map the out-of-plane and in-plane polarization distribution, respectively, of (111)-oriented Pb(Zr,Ti)O3-based (PZT) ferroelectric patterned and reactively-ion-etched capacitors. While VPFM and LPFM have previously been used to determine the orientation of the polarization vector in ferroelectric crystals and thin films, this is the first time the technique has been applied to determine the three-dimensional polarization distribution in thin-film capacitors and, as such, is of importance to the implementation of nonvolatile ferroelectric random access memory. Sequential VPFM and LPFM imaging have been performed in poled 1×1.5 μm2 PZT capacitors. Subsequent quantitative analysis of the obtained piezoresponse images allowed the three-dimensional reconstruction of the domain arrangement in the PZT layers of the capacitors. It has been found that the poled capacitors, which appear as uniformly polarized in VPFM, are in fact in a polydomain state as is detected by LPFM and contain 90° domain walls. Despite the polycrystallinity of the PZT layer, regions larger than the average PZT grain size are found to have the same polarization orientation. This technique has potential for clarifying the switching behavior and imprint mechanism in micro- and nanoscale ferroelectric capacitors.
Intersubband photoconductivity of self-assembled InAs quantum dots embedded in InP
Authors: Pettersson H. , Landin L. , Kleverman M. , Seifert W. , Samuelson L. , Fu Y. , Willander M.
Published: January 2004

In this article, we present the results from photoconductivity measurements in the infrared spectral region (3–10 μm) on ensembles of self-assembled InAs quantum dots embedded in a matrix of InP. In the spectral distribution of the photocurrent, peaks are observed which we interpret in terms of transitions from the dots’ ground- and first-excited states to the conduction band of the dots/matrix. Furthermore, we have calculated the expected photoresponse and found it to be in qualitative agreement with our experimental data.
Manipulation of vortex circulation in decentered ferromagnetic nanorings
Authors: Saitoh E. , Kawabata M. , Harii K. , Miyajima H. , Yamaoka T.
Published: January 2004

A method to control the direction of the magnetic-moment circulation in ferromagnetic nanoscale rings is presented. This method involves controlling the domain-wall (DW) motion using the gradient of the DW energy along the circumference in cooperation with an external magnetic field. Since it is free from the DW pinning and depinning process, the method is applicable even under strong thermal disturbance. Magnetic-force-microscopic observation was performed for Ni81Fe19 rings 500 nm in diameter in which the gradient of the DW energy was introduced by decentering the rings. The result indicates perfect controllability of the magnetic-moment circulation at room temperature, demonstrating its potential for a wide range of applications in magnetic memory devices.
Thermal growth of silicon oxynitride films on Si: A reaction-diffusion approach
Authors: de Almeida R. M. C. , Baumvol I. J. R. , Ganem J. J. , Trimaille I. , Rigo S.
Published: January 2004

We present some experimental results and propose a reaction-diffusion model to describe thermal growth of silicon oxynitride films on Si in NO and N2O, as well as annealing in NO of thermally grown silicon oxide films on Si. We obtain growth kinetics and N and O depth distributions for the different growth routes by changing only initial and boundary conditions of a set of nonlinear differential equations. The results suggest that the puzzling differences in film growth rate and N incorporation originate from dynamical effects, rather than in differences in chemical reactions.