bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Migraine Disability Using the Migraine Disability Assessment (MIDAS) Questionnaire: A Comparison of Chronic Migraine With Episodic Migraine
Authors: Bigal Marcelo E. , Rapoport Alan M. , Lipton Richard B. , Tepper Stewart J. , Sheftell Fred D.
Published: January 2004

Background.—Chronic migraine is the most common type of chronic daily headache seen in headache tertiary care centers. Most patients with chronic migraine report their ability to function and feeling of well‐being as severely impaired.

Objective.—To measure the headache‐related disability of patients with chronic migraine using the Migraine Disability Assessment (MIDAS) Questionnaire, comparing it with that obtained in a control group of patients with episodic migraine.

Methods.—The clinical records of 703 patients with chronic daily headache treated in a headache specialty clinic were reviewed to identify 182 with chronic migraine who were evaluated using the MIDAS at their initial visit. Our control group consisted of 86 patients with episodic migraine.

Results.—Of the 182 patients with chronic migraine, 127 (69.8%) were overusing acute‐care medication. Patients were predominantly women (72.5%), with a mean age of 38.3 years. The group with episodic migraine consisted of 59 women (68.6%), with a mean age of 36.1 years. No statistically significant demographic differences were observed between the two groups. The group with chronic migraine had more total headache days over 3 months (66.7 versus 15.5, P<.001), missed more days of work or school (5.3 versus 2.3, P  =  .0007), had more reduced effectiveness days at work or school (11.9 versus 4.6, P  =  .0001), missed more days of housework (16.5 versus 3.3, P<.0001), and missed more days of family, social, or leisure activities (7.0 versus 5.5, P  =  .03). The group with chronic migraine was more likely to be in MIDAS grade IV (64.3% versus 43.2%, P  =  .001), reflecting the great likelihood of severe disability in this group. The average total MIDAS score was 34.9 in the group with chronic migraine versus 19.3 in the group with episodic migraine (P<.001).

Conclusion.—In subspecialty centers, patients with chronic migraine demonstrate remarkable impairment of their daily activities and are severely burdened by their headache syndrome, reflected by their high MIDAS scores. The chronicity and pervasiveness of migraine thus is associated with increased functional impairment as well as increase in headache frequency.
Reliability and Validity of the Japanese Migraine Disability Assessment (MIDAS) Questionnaire
Authors: Iigaya Miho , Sakai Fumihiko , Kolodner Kenneth B. , Lipton Richard B. , Stewart Walter F.
Published: January 2004

Objective.—This study was designed to assess the test‐retest reliability, internal consistency, and validity of a Japanese translation of the Migraine Disability Assessment (MIDAS) Questionnaire in a sample of Japanese patients with headache.

Background.—Previous studies have demonstrated that the English‐language version of the MIDAS Questionnaire is a reliable and valid instrument for the assessment of migraine‐related disability. Any translations of the MIDAS Questionnaire must also be assessed for reliability and validity.

Methods.—Study participants were recruited from the patient population attending either the Neurology Department of Kitasato University or an affiliated clinic. Participants were eligible for study entry if they had 6 or more primary headaches per year. For reliability testing, participants completed the MIDAS Questionnaire on 2 occasions, exactly 2 weeks apart. To assess validity, patients were also invited to participate in a 90‐day daily diary study. Composite measures from the 90‐day diaries were compared to equivalent MIDAS measures (ie, 5 questions on headache‐related disability and 1 question each on average pain intensity and headache frequency in the last 3 months) and to the total MIDAS score obtained from a third MIDAS Questionnaire completed at the end of this 90‐day period.

Results.—One hundred one patients between the ages of 21 and 77 years were recruited (81 women and 20 men). Ninety‐nine patients (80 women and 19 men) participated in the diary study. At baseline, 46.5% of patients were MIDAS grade I or II (minimal, mild, or infrequent disability), 22.2% were MIDAS grade III (moderate disability), and 31.3% were MIDAS grade IV (severe disability). Test‐retest Spearman correlations for the 5 disability questions and the questions on average pain intensity and headache frequency ranged from 0.59 to 0.80 (P<.0001). The test‐retest Spearman correlation coefficient for the total MIDAS score was 0.83 (P<.0001). The degree to which individual MIDAS questions correlated with the diary‐based measures ranged from 0.36 to 0.88. The correlation between the total MIDAS score and the equivalent diary‐based measure was 0.66. In general, the mean and median values for the MIDAS items and total MIDAS score were similar to the means and medians for the diary‐based measures. However, the mean MIDAS scores for the number of days on which headache was experienced and the number of missed workdays were significantly different compared to the diary‐based estimates for these items (P<.05). In addition, the mean MIDAS score for the number of days of missed housework was significantly higher than the corresponding diary‐based estimate (P<.01).

Conclusions.—The results from this study show that the Japanese translation of the MIDAS Questionnaire is comparable with the English‐language version in terms of reliability and validity.
Migraine Headache Recurrence: Relationship to Clinical, Pharmacological, and Pharmacokinetic Properties of Triptans
Authors: Géraud Gilles , Keywood Charlotte , Senard Jean Michel
Published: January 2004

Background and Objectives.—Triptan use is associated with headache recurrence, and this has been cited as an important reason for patient dissatisfaction with the treatment. The mechanism by which recurrence occurs is not clear, and the incidence of recurrence varies with the triptan used. In order to explore the pharmacological and physiological interaction of triptans and migraine headache recurrence further, some specific clinical, pharmacological, and pharmacokinetic factors that might influence migraine recurrence were evaluated in a review of the major efficacy data for the drugs in the triptan class. These factors were 5‐HT1B and 5‐HT1D receptor activities, the pharmacokinetic elimination half‐life of each triptan, and the clinical efficacy of each compound, determined by the proportion of patients with headache relief and the therapeutic gain over placebo.

Methods.—Clinical data were derived from 31 triptan, placebo‐controlled, major efficacy studies used in a previous meta‐analysis. The mean recurrence rate, mean headache response, and therapeutic gain were calculated using the results from the individual clinical studies. Mean headache response and therapeutic gain were calculated at the time point used to define recurrence in each study. Data for binding affinity and potency were taken from a direct‐comparison in vitro pharmacology study, and the elimination half‐life quoted in the data sheet for each triptan was used. Rank correlation with recurrence rate was performed for each of the test parameters.

Results.—Mean headache recurrence rates ranged from 17% for frovatriptan 2.5 mg to 40% for rizatriptan. Elimination half‐life and recurrence were inversely correlated (r  =  −1.0, P  =  .0016). There was also a significant inverse correlation between 5‐HT1B receptor potency and recurrence (r  =  −0.68, P  =  .034), but 5‐HT1D receptor potency was not correlated with recurrence (r  =  −0.20, P  =  .54). In addition, the binding affinities for the 5‐HT1B and 5‐HT1D receptors were not correlated to headache recurrence. Importantly, it also was demonstrated that initial clinical efficacy was not correlated to headache recurrence. The correlation coefficient for headache response was 0.18 (P  =  .53) and for therapeutic gain, −0.11 (P  =  .71).

Conclusion.—The incidence of migraine headache recurrence varies between drugs in the triptan class. Migraine recurrence does not appear to be related to initial clinical efficacy, but is influenced by the pharmacological and pharmacokinetic properties of the individual triptans. The triptans with longer half‐lives and greater 5‐HT1B receptor potency had the lowest rates of headache recurrence.
Headache Following Cervical Sympathectomy and Results of a Blood Flow Study in the Cat
Authors: Spierings Egilius L. H.
Published: January 2004

Background.—A patient developed severe, continuous, unilateral headache that was “vascular” in nature, following cervical sympathectomy.

Objective.—To determine the changes in cranial blood flow in the cat following lesioning and stimulation of the cervical sympathetic nerve.

Method.—Carotid blood flow was determined by electromagnetic flowmetry and its tissue distribution by intra‐arterial injection of 15‐μm radioactive microspheres.

Results.—Following sympathetic lesioning, an increase in carotid blood flow was observed and reversed with stimulation. The distribution of carotid blood flow changed for the brain only, maintaining relatively constant tissue perfusion.

Conclusion.—An increase in cerebral blood flow could not have accounted for the sympathectomy‐induced headache. Dilation of major cerebral arteries and cranial noncerebral vasodilation probably constitutes its mechanism.
Acute migraine headache: possible sensitization of neurons in the spinal trigeminal nucleus?
Authors: Kaube H , Katsarava Z , Przywara S , Drepper J , Ellrich J , Diener HC
Published: January 2004

Neurology. 2002;58:1234‐1238.

OBJECTIVE: To investigate trigeminal sensory processing in patients with migraine using a novel “nociception‐specific” blink reflex. METHODS: Seventeen patients with unilateral migraine headache were studied within 6 hours of onset. Blink reflexes were elicited with a standard stimulating electrode (standard blink reflex) and concentric stimulating electrode (nociception‐specific blink reflex) during the acute migraine attack, after treatment with IV lysine acetylsalicylate (1,000 mg) or oral zolmitriptan (5 mg) and interictally. RESULTS: After standard stimulation, no differences were detected for the R1 and R2 onset latencies and areas under the curve (AUC) between the different time points and the headache and nonheadache side. Nociception‐specific stimulation revealed a shortening of R2 onset latencies (44.3  ±  5.4 ms for headache side vs 48.9  ±  5.8 ms for nonheadache side) during the acute migraine attack compared with the headache‐free interval (49.8  ±  5.3 vs 49.8  ±  4.5 ms). The AUC of the R2 increased on the headache side by 680% and on the nonheadache side by 230% compared with the headache‐free interval. Drug treatment parallel to pain relief increased the onset latencies (zolmitriptan: 48.0  ±  8.2 ms for headache side vs 52.3  ±  7.6 ms for nonheadache side; lysine acetylsalicylate: 48.0  ±  5.0 ms for headache side vs 51.2  ±  5.6 ms for nonheadache side) and reduced the AUC of R2 (zolmitriptan by 45% and lysine acetylsalicylate by 48%). CONCLUSION: The data suggest temporary sensitization of central trigeminal neurons during acute migraine attacks.

Comment: This abstract from Dr. Chris Diener's group reports large changes in the AUC for onset latencies between headache affected and nonaffected sides. Drug treatment effects were small. No statistical comparisons were reported. This noninvasive technique may be useful in further exploring the mechanisms which underlie the temporary sensitization of central trigeminal neurons during acute migraine attacks. DSM
Cortical spreading depression and gene regulation: relevance to migraine.
Authors: Choudhuri R , Cui L , C et al. Yong
Published: January 2004

Ann Neurol. 2002;51:499‐506.

Cortical spreading depression (CSD) may be the underlying mechanism of migraine aura. The role of CSD in initiating a migraine headache remains to be determined, but it might involve specific changes in gene expression in the brain. To examine these changes, four episodes of CSD at 5‐minute intervals were induced in the mouse brain by application of 300 mM KCl, and gene expression was examined 2 hours later using cDNA array and reverse transcriptase‐polymerase chain reaction. Controls consisted of groups that received anesthesia only, attachment of recording electrodes only, and application of 0.9% NaCl. Of the over 1180 genes examined in our experiments, those consistently regulated by CSD included vasoactive peptides; the vasodilator atrial natriuretic peptide was induced by CSD, while the vasoconstrictor neuropeptide Y was downregulated. Other genes specifically regulated by CSD were involved in oxidative stress responses (major prion protein, glutathione‐S‐transferase‐5, and apolipoprotein E). L‐type calcium channel mRNA was upregulated. In summary, CSD regulates genes that are intrinsic to its propagation, that identify accompanying vascular responses as a potential source of pain, and that protect against its potential pathological consequences. We believe these observations have strong relevance to the mechanisms of migraine and its outcomes.

Comment: Dr. Welch's group is systematically searching for gene expression targets which may lead to improvement both in understanding migraine at a molecular level and in development of new treatment strategies. SJT
Orbital myositis posing as cluster headache.
Authors: Lee MS , Lessell S
Published: January 2004

Arch Neurol. 2002;59:635‐636.

OBJECTIVE: To describe the case of a patient with recurrent orbital myositis who was thought to have cluster headaches for 6 years. DESIGN AND SETTING: Case report in an outpatient neuro‐ophthalmology clinic. PATIENT: A 24‐year‐old man developed unilateral supraorbital pain, lacrimation, conjunctival hyperemia, nasal congestion, proptosis, and painful eye movements. The pain intensity varied over the course of each day and disappeared after 1 month. He had multiple attacks responsive to prednisone that were separated by months over the ensuing 6 years. Neuroimaging revealed an enlarged extraocular muscle. CONCLUSIONS: Overlap in symptoms between recurrent orbital myositis and cluster headache delayed the diagnosis in this patient. Orbital myositis should be considered in patients with atypical cluster headache characterized by proptosis, painful eye movements, and pain that does not completely resolve after 3 hours.

Comment: Cluster has numerous mimics. Because of this, I favor one good imaging study for each patient with presumed cluster. SJT
Transmission electron microscopy specimen holder for simultaneous in situ heating and electrical resistance measurements
Authors: Verheijen M. A. , Donkers J. J. T. M. , Thomassen J. F. P. , van den Broek J. J. , van der Rijt R. A. F. , Dona M. J. J. , Smit C. M.
Published: January 2004

A transmission electron microscopy (TEM) specimen holder has been developed for the measurement of the electrical resistance of a TEM sample as a function of temperature. A custom TEM heating holder was modified for this purpose. Eight feedthrough wires were passed through the specimen holder; (i) providing current to the heater, (ii) allowing for the measurement of the hot stage temperature, and (iii) enabling the measurement of the electrical resistance of the sample. This configuration creates the opportunity to directly correlate changes in the resistance to microstructural changes as a function of temperature. The working of the holder is demonstrated by studies on a phase transformation in Al–Ge films. In this way, a direct correlation was found between changes in resistance and microstructure as a function of temperature.
Shielded electrostatic probe for nonperturbing plasma measurements in Hall thrusters
Authors: Staack D. , Raitses Y. , Fisch N. J.
Published: January 2004

Electrostatic probes are widely used to measure spatial plasma parameters of the quasineutral plasma in Hall thrusters and similar E×B electric discharge devices. Significant perturbations of the plasma induced by such probes can mask the actual physics involved in the operation of these devices. In Hall thrusters, probe-induced perturbations can produce changes in the discharge current and plasma parameters on the order of their steady-state values. These perturbations are explored by varying the material, penetration distance, and residence time of various probe designs. A possible cause of these perturbations appears to be the secondary electron emission, induced by energetic plasma electrons, from insulator ceramic tubes in which the probe wire is inserted. A new probe in which a low secondary electron emission material, such as metal, shields the probe ceramic tube, is shown to function without producing such large perturbations. A segmentation of this shield further prevents probe-induced perturbations, by not shortening the plasma through the conductive shield. In a set of experiments with a segmented shield probe, the thruster was operated in the input power range of 500 W–2.5 kW and discharge voltages of 200–500 V, while the probe-induced perturbations of the discharge current were below 4% of its steady-state value in the region in which 90% of the voltage drop takes place.
Out-of-plane displacement measurement by means of endoscopic moiré interferometry
Authors: Martı́nez-Celorio R. A. , Dirckx Joris J. J. , Martı́-López Luis , Peña-Lecona Francisco G.
Published: January 2004

An endoscopic moiré technique is proposed for measuring out-of-plane displacements in difficult to reach places. The Ronchi grid is projected onto the tilted object with one endoscope with a 0° viewing angle. The object with the projected grid is imaged by a second endoscope with a 30° viewing angle onto a charge-coupled device. The captured images are stored in a PC, and are used to calculate the out-of-plane displacement of the object with a phase stepping technique. A computer generated grating method is used instead of a physical phase-shift device in the optical setup. This allows designing a set of three reference grids with profiles closely similar to the projected grating. The technique is robust against problems associated with the temporal shifting method, such as nonlinear phase shift and noise. To test the feasibility of the technique the measurement of out-of-plane displacements of about 35 μm of a latex membrane under deformation is demonstrated. The advantages and disadvantages are discussed.
Fast infrared array spectrometer with a thermoelectrically cooled 160-element PbSe detector
Authors: Ji Jun , Gore Jay P. , Sivathanu Yudaya R. , Lim Jongmook
Published: January 2004

A fast infrared array spectrometer (FIAS) with a thermoelectrically cooled 160-element PbSe detector was demonstrated using measurements of instantaneous infrared radiation intensities simultaneously over the 1.8–4.9 μm wavelength range at a sampling rate of 390 Hz. A three-point second-degree Lagrange interpolation polynomial was constructed to calibrate the FIAS because of the nonlinear response of the infrared array detector to the incident radiation beam. This calibration method gave excellent measurements of blackbody radiation spectra except for a narrow band at wavelength of 4.3 μm due to absorption by room carbon dioxide, which is one of the two major gas radiation peaks (2.7 and 4.3 μm) from the lean premixed hydrocarbon/air combustion products in the midinfrared spectrum. Therefore, the absorption coefficient of room carbon dioxide was conveniently measured on site with the blackbody reference source, and was used in the calibration of the FIAS and also in the calculations of the radiation spectra. Blackbody tests showed that this procedure was effective in correcting for the room carbon dioxide absorption in the radiation spectra measured by the FIAS. For an example of its application, the calibrated FIAS was used to measure spectral radiation intensities from three lean premixed laminar flames and a premixed turbulent jet flame for which reference data with a grating spectrometer were available for comparison. The agreement between the FIAS measurements and the reference data was excellent.
Gain and loss in an optically pumped mid-infrared laser
Authors: Ongstad A. P. , Kaspi R. , Moeller C. E. , Tilton M. L. , Chavez J. R. , Dente G. C.
Published: January 2004

We report on measurements of the temperature dependence of the gain and internal waveguide loss of a 3.4 μm, optically pumped InAs/InGaSb, type II, W laser. A high-resolution Fourier transform infrared spectrometer was used to measure the laser mode spectra below threshold. To obtain an accurate determination of the gain, a full-curve fit to the spectral output of the Fabry–Pérot cavity was utilized. Our results indicate very low waveguide loss (a≈3 cm−1) at 78 K, with no apparent increase up to at least 120 K. Additional measurements of the gain properties of the device reveal a rapidly decreasing differential gain (dG/dP) and a rapidly increasing transparency pump power with increasing temperature. Moreover, measurements of the peak gain at constant pumping show a rapid decline with increasing temperature. Theoretical superlattice-empiricalpseudopotential-model-based calculations suggest that the substantial differences between the conduction and valence subband in-plane curvatures contribute to the rapid decline in gain with increasing temperature.
Theoretical and numerical results for spin coating of viscous liquids
Authors: Schwartz Leonard W. , Roy R. Valery
Published: January 2004

A mathematical model is developed for fluid flow in the spin coating process. Spin coating employs centrifugal force to produce coatings of uniform thickness. The long-wave or lubrication approximation is used for the flow of thin liquid layers that are exposed to the air and lie on a spinning horizontal solid substrate. For low rotation rates, steady axisymmetric drop shapes can be found analytically. The stability of these drops is investigated, using an energy method, both with and without the long-wave approximation. For industrially relevant high-speed motions, we formulate and solve a theoretical and numerical model for the three-dimensional time-dependent motion of the deforming drop. We pay particular attention to the formation of “fingers” at the expanding front. The model includes viscous, capillary, gravitational, centrifugal, Coriolis, and finite-contact-angle effects. Both homogeneous and chemically heterogeneous substrates are considered. In agreement with published experiments, the model demonstrates that imperfect wetting behavior is the principal cause of fingering during spin coating. Features of the finger profiles are in close agreement with experimental observations.
Vibration signal processing for interferometric optical fiber sensor
Authors: Cao Zhengyuan , Fang Ruhua , Zhao Hong , Zhao Bing , Feng Ping
Published: January 2004

A method for processing vibration signal for an interferometric optical fiber sensor is proposed in this article. A spatial correlation technique combined with a digital image approach based on the number and direction of fringe motion is suggested for random signal processing. A quantitative physical analysis is formulated, and a signal processing system including acquiring images, analyzing and displaying software is developed. The random signal analysis is carried out by determining the strain-time curve which is based on and is calibrated by the strain-time curve in a stationary vibration. The experiment results are in good agreement with the theoretical one with a maximum difference of 3.5%. The current method is suitable for measuring low frequency vibration. The low frequency is limited due to the limitation of correlation method and the image-sampling rate. For high frequency stationary vibration the method of spectra analysis can be used, but it cannot measure random vibration. High frequency random vibration response may be measured when a high speed photography system combined with a digital image processing setup and software developed in this article are used. This research provides an approach for monitoring vibration for the purpose of making structural engineering studies.
A simple and compact mechanical velocity selector of use to analyze/select molecular alignment in supersonic seeded beams
Authors: Pirani F. , Cappelletti D. , Vecchiocattivi F. , Vattuone L. , Gerbi A. , Rocca M. , Valbusa U.
Published: January 2004

A light and compact mechanical velocity selector, of novel design, for applications in supersonic molecular-beam studies has been developed. It represents a simplified version of the traditional, 50 year old, slotted disks velocity selector. Taking advantage of new materials and improved machining techniques, the new version has been realized with only two rotating slotted disks, driven by an electrical motor with adjustable frequency of rotation, and thus has a much smaller weight and size with respect to the original design, which may allow easier implementation in most of the available molecular-beam apparatuses. This new type of selector, which maintains a sufficiently high velocity resolution, has been developed for sampling molecules with different degrees of rotational alignment, like those emerging from a seeded supersonic expansion. This sampling is the crucial step to realize new molecular-beam experiments to study the effect of molecular alignment in collisional processes.
High-pressure cell for small- and medium-angle neutron scattering measurements up to 300 MPa
Authors: Bonetti M. , Calmettes P.
Published: January 2004

We describe a high-pressure cell designed for small- and medium-angle neutron scattering measurements on fluid samples under hydrostatic pressure up to 300 MPa. The cell is fitted up with two thick sapphire windows with a large forward optical aperture. For a neutron beam of 7 mm in diameter the maximum forward scattering angle is 15°. With a neutron wavelength of 0.41 nm this allows scattering spectra to be recorded for wave-number transfers up to 4 nm−1. The optical path length was 5 mm. However, it can be easily varied according to the sample under study.
An inverse photoemission system with large solid angle of detection and adjustable optical bandpass
Authors: Lipton-Duffin J. A. , Mark A. G. , Mullins G. K. , Contant G. E. , McLean A. B.
Published: January 2004

A high-brightness, low energy electron source and dual Geiger–Müller-type isochromat photon detectors are combined to create a versatile new inverse photoemission system. The bandpass of the photon detector can be set to one of the following discrete values: 0.37±0.02, 0.43±0.02, 0.56±0.02, or 0.73±0.04 eV by using ethanol, 1-propanol, 1-butanol, or a dimethyl ether/ethanol mixture, respectively, as the detection gas(es). All of the alcohols are self-quenching and do not require the addition of a quench gas. The design of the photon detectors, the electron gun, and the circuits that perform the dead time gating are described in detail. The capabilities of the new system are illustrated using spectra from both metal (Cu) and semiconductor (Si) surfaces.
Quantitative characterization of friction coefficient using lateral force microscope in the wearless regime
Authors: Bilas P. , Romana L. , Kraus B. , Bercion Y. , Mansot J. L.
Published: January 2004

Absolute quantitative data from atomic force microscopy (AFM)/lateral force microscopy experiments are always difficult to obtain mainly due to the need of the normal force FN and the friction force FF calibration. In this article, we developed an experimental method which allows us to extract absolute quantitative friction data without calibrating any force when the relation between FN and FF is linear or only calibrating the normal force when the relationship is nonlinear. The technique reported here, is suitable for an atomic force microscope that has the cantilever attached to the piezotube translator and an unguided incident laser beam on the cantilever. We take advantage of the piezotube bending during a large scan (5 μm×5 μm), generally considered as an undesirable effect, to calculate a detection factor that allows the determination of quantitative tribological data. The validity of our experimental method is checked on the extensively AFM studied materials, such as muscovite, silicon, and highly oriented pyrolytic graphite. The experiments are carried out in a load range where the shear stress τ can be expressed as τ=τ0+μP, where μ is the friction coefficient, P is the mean contact pressure, and τ0 is a parameter related to the tip/sample adhesion. The value of μ is found to be independent of the tip geometry and the pull-off force, and always constant for a given tip/sample couple in the load range investigated.
Single-sweep detection of relaxation kinetics by submicrosecond midinfrared spectroscopy
Authors: Ma Hairong , Ervin John , Gruebele Martin
Published: January 2004

We present a design for the detection of relaxation kinetics by midinfrared transient spectroscopy. Spectra can be collected with 150 ns time resolution after a single pump pulse. This eliminates the need for flowing samples and the shot-to-shot background noise common in pump–probe spectroscopy. Difference frequency generation from a Ti:sapphire oscillator with a dual-wavelength profile produces broadband femtosecond IR pulses tunable below 1800 cm−1 at 91 MHz repetition rate. This pulse train probes a sample by direct absorption, followed by dispersion of the 200 cm−1 wide spectra in a double-prism spectrometer onto a fast multichannel mercury cadmium telluride detector. In our setup, sample relaxation is initiated by a single temperature jump. We present the fast folding dynamics of the protein λ repressor as an application.
Development of an electrostatic dust detector for use in a tokamak reactor
Authors: Bader A. , Skinner C. H. , Roquemore A. L. , Langish S.
Published: January 2004

Initial results from a novel device to detect dust particles settling on remote surfaces are presented. Dust particle inventories are a concern in next-step fusion devices. The increase in duty cycle will lead to a scale-up in the amount of particles generated by plasma material interactions. These particles will be chemically and radiologically hazardous and it will be important to establish that the in-vessel particle inventory is within regulatory limits. The detection device consists of two interlocking combs of closely spaced conductive traces on a Teflon circuit board. When a direct current bias is applied, impinging dust creates a transient short circuit between the traces. The increase in bias current generates a signal pulse that is counted by standard nuclear counting electronics. We present data on the response of the device in air and vacuum to carbon particles.
Calibration of optical cantilever deflection readers
Authors: Hu Zhiyu , Seeley Tim , Kossek Sebastian , Thundat Thomas
Published: January 2004

Because of its ultrahigh sensitivity, the optical lever detection method similar to that used in the atomic force microscope (AFM) has been widely employed as a standard technique for measuring microcantilever deflection. Along with the increasing interest in using the microcantilever as a sensing platform, there is also a requirement for a reliable calibration technique. Many researchers have used the concept of optical lever detection to construct microcantilever deflection readout instruments for chemical, physical, and biological detection. However, without an AFM piezo z scanner, it is very difficult to precisely calibrate these instruments. Here, we present a step-by-step method to conveniently calibrate an instrument using commercially available piezoresistive cantilevers. The experimental results closely match the theoretical calculation. Following this procedure, one can easily calibrate any optical cantilever deflection detection system with high reproducibility, precision, and reliability. A detailed discussion of the optical lever readout system design has been addressed in this article.
Wide-field spectroscopy for optical characterization of the pulsed laser deposition plume
Authors: Pérez-Tijerina E. , Machorro R. , Bohigas J.
Published: January 2004

A technique to study several regions of plasma produced by laser ablation in a single laser pulse is presented. The technique is based on a field spectrograph, an instrument where the image of the plasma is captured with a number of fibers in a user defined array, and then projected into the one-dimensional slit of a spectrograph. With this instrument, we can obtain the spectra of a discrete number of regions in the plume and reconstruct the image of the plasma at different wavelengths. Several examples of interest in the field of pulsed laser deposition are given.
High-density and low electron temperature direct current reflex plasma source
Authors: Toader E. I. , Covlea V. , Graham W. G. , Steen P. G.
Published: January 2004

A new type of direct current, high-density, and low electron temperature reflex plasma source, obtained as a hybrid between a modified hollow-cathode discharge and a Penning ionization gauge discharge is presented. The plasma source was tested in argon, nitrogen, and oxygen over a range pressure of 1.0–10−3 mbar, discharge currents 20–200 mA, and magnetic field 0–120 Gauss. Both external parameters, such as breakdown potential and the discharge voltage–current characteristic, and its internal parameters, like the electron energy distribution function, electron and ion densities, and electron temperature, were measured. Due to the enhanced hollow-cathode effect by the magnetic trapping of electrons, the density of the bulk plasma is as high as 1018 m−3, and the electron temperature is as low as a few tenths of electron volts. The plasma density scales with the dissipated power. Another important feature of this reflex plasma source is its high degree of uniformity, while the discharge bulk region is free of an electric field.
Magnetoresistance behavior of single castellated Ni80Fe20 nanowires
Authors: Adeyeye A. O. , White R. L.
Published: January 2004

We have studied in a systematic way the magnetization reversal processes of single castellated Ni80Fe20 nanowires fabricated by advanced electron beam lithography. The structures consist of two 5 μm wide Ni80Fe20 support wires bridged with a castellated nanowire of width in the range from 80 to 150 nm. We have used the anisotropic magnetoresistance (AMR) effect as a probe of the spin orientations and hence magnetization reversal processes in these complex magnetic structures. When the applied fields are along the horizontal legs of the castellated nanowire, we observe a unique MR response due to the creation of magnetic local easy and hard axes resulting in a number of discontinuous jumps in the magnetoresistance. The magnetoresistance behavior is strongly influenced by spin states at corners of the nanowire for field applied parallel or perpendicular to horizontal legs. These results are in agreement with simple micromagnetic simulations.
Spatially-resolved photoluminescence studies of V-shaped pits on Al0.16Ga0.84N
Authors: Huang H. Y. , Ku C. S. , Ke W. C. , Tang N. E. , Peng J. M. , Chen W. K. , Chen W. H. , Lee M. C. , Lee H. Y.
Published: January 2004

We have studied optical properties of V-shaped pits on Al0.16Ga0.84N. The microphotoluminescence spectrum from the pit center shows a broader and stronger emission at 350 nm than the near-band-edge emission at 336 nm from nonpit regions. The results indicated specific defect levels associated with the V-shaped pits. Furthermore, after using atomic force microscopy to probe the surface electrical potential with a conductive tip, the pit’s potential was ∼0.2 V lower than its surrounding region. A simplified energy diagram is tentatively proposed to interpret our observation.
Deuterium storage in nanocrystalline magnesium thin films
Authors: Checchetto R. , Bazzanella N. , Miotello A. , Brusa R. S. , Zecca A. , Mengucci A.
Published: January 2004

Nanocrystalline magnesium deuteride thin films with the β-MgD2 structure were prepared by vacuum evaporation of hexagonal magnesium (h-Mg) samples and thermal annealing in 0.15 MPa D2 atmosphere at 373 K. Thermal desorption spectroscopy analysis indicated that the rate-limiting step in the deuterium desorption was given by the thermal decomposition of the deuteride phase. The activation energy Δg of the β-MgD2→h-Mg+D2 reaction scaled from 1.13±0.03 eV in 650-nm-thick films to 1.01±0.02 eV in 75-nm-thick films most likely as consequence of different stress and defect level. Positron annihilation spectroscopy analysis of the thin-film samples submitted to deuterium absorption and desorption cycles reveal the presence of a high concentration of void-like defects in the h-Mg layers after the very first decomposition of the β-MgD2 phase, the presence of these open volume defects reduces the D2 absorption capacity of the h-Mg thin film.
Source for atomic beams of metastable gases: Design and performance
Authors: DeKieviet M. , Dürr M. , Epp S. , Lang F. , Theis M.
Published: January 2004

There is an increasing interest in high flux sources of metastable species in many scientific communities, for example for lithography and quantum optics experiments. We present a simple dc discharge design, based on microstructured electrodes (MSE), for the production of truly thermal beams of metastable atoms. Even for inlet pressures above 1 atm the discharge runs stably, at relatively modest voltages. Time-of-flight data prove that the expansion is supersonic with speed ratios up to 8.5 and internal temperatures of less than 10 K. The MSE source works equally well for many different gases like He, Ne, Kr, Ar, H2, and N2. Its measured yield of ∼1014 metastable atoms s−1 sr−1 compares favorably with conventional discharge sources. In addition, its simple design holds good promise for cooling the source down to cryogenic temperatures.
Optical response of cerium-doped lutetium oxyorthosilicate coatings at shocked surfaces
Authors: Stevens G. D. , Lutz S. S. , Turley W. D. , Adams C. D. , Boat R. M. , Hull L. M.
Published: January 2004

Shock experiments were performed to characterize the triboluminescent signature of surface coatings of powdered cerium-doped lutetium oxyorthosilicate suspended in a silicate binder. This coating shows prompt, nanosecond timescale light emission when driven by explosive detonation. When properly applied to a surface, it may be used to sense the arrival of a shock, or to image the propagation of a shock front.
Simulations and measurements of the performance of a channeled neutron guide for a time-of-flight spectrometer at the NIST Center for Neutron Research
Authors: Cook Jeremy C. , Copley John R. D.
Published: January 2004

We describe the identification and analysis of the principal sources of intensity loss within the five-channeled neutron guide tube that was originally installed in the chopper section of the Disk Chopper Spectrometer at the National Institute of Standards and Technology Center for Neutron Research. (The purpose of the five channels was to optimize intensity and resolution in three different modes of operation known as “resolution modes.”) By combining measurements, Monte Carlo simulations, and analytical calculations, we have developed a model that successfully explains performance losses in the original guide. We have used this model to quantify expected returns in performance using a replacement guide in which the principal contributions to the intensity loss are reduced to the minimum achievable with current technology. We have also estimated the intensity gains that would be achieved if one of the limited number of options were adopted for modifying the original guide in a manner likely to produce such gains. We describe factors that affect the performance of the original guide and compare the measured and predicted performance of the modified guide against predictions for the optimal replacement guide. The simulations indicate that the modified guide (which has three channels rather than the original five) produces greater intensity gains over a large incident wavelength band for the low and medium resolution modes, whereas a high quality replacement guide greatly improves performance in the high resolution mode of operation. Because the low and medium resolution modes are most heavily demanded, we opted to modify the guide rather than replace it. We describe the nature of this modification and present intensity measurements that meet or exceed predictions in all resolution modes with no detectable change in the energy resolution nor increase in the instrumental background.
Measurement technique for pumping performance of a centrifugal collector under microgravity
Authors: Totani Tsuyoshi , Itami Masahiko , Nagata Harunori , Kudo Isao , Iwasaki Akira
Published: January 2004

A measurement technique for obtaining the pumping performance of a centrifugal collector under microgravity has been developed and evaluated through microgravity experiments. These tests have been conducted under conditions such that the pressure sensors cannot easily detect the pressure rise of the liquid working fluid. These conditions have a pressure increase smaller than 400 Pa. The characteristic of the head produced in a centrifugal collector calculated from experimental data agrees well with that predicted theoretically from the velocity and the pressure generated by rotation of the centrifugal collector. It is concluded from this result that the measurement technique can correctly obtain the pumping performance of the centrifugal collector under microgravity. The centrifugal collector has produced the head of 0.041 m at the rotation speed of 223 rpm under microgravity. The working fluid is silicon oil. This head corresponds to the pressure rise of approximately 390 Pa.
Improving the efficiency of a jet pump using a swirling primary jet
Authors: Guillaume D. W. , Judge T. A.
Published: January 2004

This Note presents a unique means of increasing the efficiency of a jet pump. Much research has been devoted to the study of swirl jets and their ability to increase the amount of fluid entrainment. Since the efficiency of a jet pump is directly related to the ability of the primary jet to entrain fluid, a jet pump is an obvious potential application for a swirl jet. In this study, the entrainment flow and efficiency of a jet pump is measured with and without swirl in the primary jet of a centrally driven jet pump. At moderate swirl, the jet pump is shown to have an approximate 4.5% increase in entrainment flow and a 5% increase in efficiency when compared to the same pump without swirl.
Time-resolved measurement system of electrofluorescence spectra
Authors: Tsushima Minoru , Ushizaka Tsuyoshi , Ohta Nobuhiro
Published: January 2004

A time-resolved measurement system for electrofluorescence spectra (plots of electric-field-induced change in fluorescence intensity as a function of wavelength) has been constructed by combining the time-correlated single-photon-counting system for emission decay measurement with modulated electric field as a sample bias. Four fluorescence decays, which correspond to positive, zero, negative, and zero sample bias, respectively, can be measured simultaneously, and a small field-induced change in decay profile can be detected precisely by using the constructed system. Measurements of time-resolved electrofluorescence spectra have been performed in electron donor–acceptor compounds which show a photoinduced electron transfer.
Development of a high-temperature and high-pressure nuclear magnetic resonance probe for studies of chemical reactions in supercritical water
Authors: Amita Fujitsugu , Oka Hiroyuki , Mukaide Masanobu , Urasaki Yohei , Takegoshi Kiyonori , Terao Takehiko , Kajimoto Okitsugu
Published: January 2004

A high-temperature and high-pressure nuclear magnetic resonance (NMR) probe has been developed to investigate chemical reactions in supercritical water up to 50 MPa and 500 °C. The NMR probe is of a continuous flow type with a high-pressure sample tube made of hot-pressed Si3N4 and a specially designed heat-resistant high-pressure seal. A mixing method was utilized to quickly realize the supercritical condition. The NMR probe can be used for in situ investigation of rapid reactions with several hundreds of ms half lives in continuously flowing supercritical water as well as slow equilibria under a stopped-flow condition.
Heavy ions dynamic simulations in CYTRACK cyclotron
Authors: Denisov Yu. N. , Kalinichenko V. V. , Karamysheva G. A.
Published: January 2004

The basic results of numeric simulations of heavy-ion motion in cyclotron CYTRACK are presented. Computer modeling confirms the possibility of ion acceleration and effective extraction. The experimental data completely support theoretical results presented.
Bias conditions of dc-SQUID for a time-domain SQUID multiplexer
Authors: Beyer Jörn , Drung Dietmar , Irwin Kent D.
Published: January 2004

We have analyzed the biasing of the first-stage dc superconducting quantum interference devices (SQUIDs) of a time-domain dc-SQUID multiplexer (SQUID MUX) and find that the bias conditions of first-stage SQUIDs significantly affect the performance of the SQUID MUX in terms of total multiplexer noise and bandwidth. We present an experimental study of the operational parameters of a first-stage SQUID under varied bias conditions. Our measurements include a direct determination of the first-stage SQUID dynamic resistance RDYN1 and the flux noise of the first-stage SQUID biased over the range from voltage bias to current bias. Our measurements show that matching the bias resistors RS1 of the first-stage SQUIDs to RDYN1 improves the SQUID MUX noise performance as well as the first-stage bandwidth.
In situ mechanical characterization of square microfabricated elastomeric membranes using an improved microindentation
Authors: Liu Kuo-Kang , Khoo Hwa Seng , Tseng Fan-Gang
Published: January 2004

A testing method has been developed for in situ mechanical characterizations of square microfabricated elastomeric membranes, using a tailored microindentation instrument. Such a depth-sensing microindentation system, incorporated with a long-focal microscope for capturing the side view image, provides accurate load–displacement measurements and complete profiles of deformed membranes. The deformations of square silicon rubber membranes with various thicknesses were examined under different degrees of external central microindentation forces. These membranes were integrated and supported by SU-8 photoresist frames, with openings of 2 mm×2 mm. A theoretical model was applied to quantitatively correlate the membrane elasticity to the measured compliance under such indentation. Through comparing the simulated and experimental results, the average values of Young’s modulus for these membranes were reasonably extracted and determined. Viscoelasticity of the membranes used was acknowledged; however, it showed no significant effect on the determination of the Young’s modulus of the membranes in the current work. The good agreement between the experimental results and the theoretical analyses demonstrates the successful in situ mechanical characterizations of microfabricated elastomeric films, particularly for the square shape membrane, which is the most common structure or component for microfabricated devices.
Improvement of detected intensity in confocal microscopy by using reflecting optical system
Authors: Kang DongKyun , Seo JungWoo , Gweon DaeGab
Published: January 2004

In confocal microscopy, the level of the detected intensity is low, which reduces the contrast of the images. We propose a reflecting optical system to improve the detected intensity. The result of the optimal design is presented and the performance of the resulting reflecting optical system is evaluated. A numerical simulation of the effect of the reflecting optical system on the total system performance is also presented. A standard specimen is imaged to show the benefits of the proposed reflecting optical system. The results in this Note demonstrate a 37% increase of the detected intensity and better contrast of the image.