bluuebunny/crossref_metadata_2025 huggingface dataset:
Anaesthetic management during awake craniotomy in a 12‐year‐old boy
Authors: TOBIAS JOSEPH , JIMENEZ DAVID
Published: November 2003

We present our approach to the preoperative preparation and anaesthetic management for awake craniotomy in a 12‐year‐old boy. Management included conscious sedation with a propofol infusion plus local anaesthetic infiltration of the scalp, periosteum, and dura. The complications which may be encountered during such procedures and their treatments are reviewed.
Perioperative management of children with third degree heart block undergoing pacemaker placement: a ten year review
Authors: BENNIE RUTH , DIERDORF STEPHEN , HUBBARD JOYCE
Published: November 2003

It has been suggested that children with third degree heart block require insertion of a temporary pacemaker prior to general anaesthesia. This recommendation needs to be reevaluated with the availability of noninvasive transcutaneous cardiac pacing. We undertook a retrospective ten‐year chart review of anaesthesia in children with third degree heart block undergoing pacemaker insertion or revision. Forty‐eight children with complete heart block underwent seventy anaesthetics of which fifty three were in children without pacemakers or with nonfunctioning pacemakers. One child had a temporary pacemaker placed preoperatively following asystole in the emergency room. In children who were not being paced, 60% had baseline heart rates less than 60 bpm. Complications seen in this study, including hypotension, would not have been prevented by temporary pacemaker placement. We conclude that there is no benefit to routine preoperative temporary pacing in children with third degree heart block.
Oral midazolam compared with diazepam‐droperidol and trimeprazine as premedicants in children
Authors: PATEL D , MEAKIN G
Published: November 2003

Ninety children were assigned randomly to one of three groups for premedication with oral midazolam 0.5 mg·kg−1, diazepam 0.25 mg·kg−1 with droperidol 0.25 mg·kg−1, or trimeprazine 2 mg·kg−1. On arrival at the anaesthetic room, anxiolysis was satisfactory in 26 out of 29 (90%) children who received midazolam compared with 23 out of 29 (79%) who received diazepam‐droperidol and 18 out of 29 (62%) who received trimeprazine (P<0.05); at induction of anaesthesia these proportions were 24 out of 29 (83%), 16 out of 29 (55%) and 11 out of 29 (40%) respectively (P<0.001). When individual groups were compared, anxiolysis was significantly greater in the midazolam group compared with the trimeprazine group on arrival in the anaesthetic room (P<0.05) and significantly greater in the midazolam group than in either the diazepam‐droperidol or the trimeprazine groups at induction of anaesthesia (P<0.05 and P<0.001 respectively). There were no significant differences in times to early recovery between the groups (25.4, 24.4 and 28.5 min). Analysis of behavioural questionnaires completed two weeks after hospitalization showed a trend towards fewer postoperative behavioural disturbances in children who received midazolam or diazepam‐droperidol compared with trimeprazine (47 and 44%vs 75%); when the results for the benzodiazepine‐containing premedicants were combined, the difference between these groups and trimeprazine was statistically significant (P<0.05).
Intermittent positive ventilation through a laryngeal mask in children: does it cause gastric dilatation?
Authors: SELBY I.R. , MORRIS P.
Published: November 2003

After obtaining Ethics Committee approval and informed consent, sixty children, ASA Grade 1 or 2 and aged six months to ten years, were randomly allocated to receive intermittent positive pressure ventilation through either a laryngeal mask or a tracheal tube. Inflation pressures were maintained below 20 cm H2O, and gas aspirated from the stomach via an orogastric tube over a one h period. No large volumes were aspirated and no differences were detected between the groups. We conclude that healthy children over the age of six months can be safely ventilated through the laryngeal mask airway without gastric distension.
Freeman‐Sheldon (whistling face) syndrome. Anaesthetic and airway management
Authors: MUNRO HAMISH , BUTLER PATRICK , WASHINGTON EDWARD
Published: November 2003

We describe the anaesthetic management of Freeman‐Sheldon syndrome in a two‐and‐a‐half year old undergoing club foot correction. Following an inhalational induction using halothane, tracheal intubation by direct laryngoscopy proved impossible. A laryngeal mask airway was inserted and intubation with a 4.5 tracheal tube was successfully achieved using a fibreoptic bronchoscope passed through the LMA. The child had an uneventful anaesthetic course. A caudal epidural was used for postoperative analgesia and the child was discharged home on day two. The anaesthetic and airway management options of this syndrome are outlined.
A survey of pentobarbital sedation for children undergoing abdominal CT scans after oral contrast medium
Authors: SANDERSON PETER MARK
Published: November 2003

Radiologists have traditionally been responsible for the sedation of children undergoing radiological investigations. Anaesthetists are becoming increasingly involved in providing sedation and/or anaesthesia in this environment. The sedation of a child for a CT scan who has recently been given oral contrast medium (OCM) may pose anaesthetists a number of dilemmas. This is a retrospective survey of 149 intravenous pentobarbital sedations administered by radiologists to children (age range three months to seven years three months, weight range 5 kg to 28.9 kg) undergoing upper abdominal CT after recent ingestion of OCM. The average patient received pentobarbital 4.6 mg·kg−1. 141 patients (94.6%) received pentobarbital as the only sedative agent, whereas eight patients (5·4%) required supplementary sedation (midazolam±fentanyl). There were no failed sedations. 36 complications occurred during 22 sedations (14·7% of total), with the most common being desaturation, vomiting, airway secretions, airway obstruction, coughing and bronchospasm.
An audit of paediatric day care surgery in a District General Hospital
Authors: JOLLIFFE D.M.
Published: November 2003

At a 620 bed District General Hospital, questionnaires were issued to the patients of 142 consecutive paediatric day surgery cases and the nurses involved in the care of these children. Most of the children were not upset by day case surgery, although nearly a quarter were distressed by changing into a theatre gown. Postoperatively, pain was more of a problem than nausea and vomiting. Relatively minor problems occurred at home. The majority of the 93 parents who replied were happy with the overall care of their child. They valued being present for induction of anaesthesia and would have liked to be present in recovery when their child was awake, although the nurses felt this would not have been helpful. Nonclinical matters also influenced their assessment of the quality of care.
Intranasal ketamine preinduction of paediatric outpatients
Authors: DIAZ JAMES
Published: November 2003

A double‐blinded, placebo‐controlled study compared the outcomes of intranasal ketamine premedication with placebo in outpatients. Forty paediatric outpatients were assigned randomly in a prospective fashion to one of two separate study groups of equal size (20 patients per group). A placebo group received 2 ml of intranasal saline, 1 ml per naris. The study group received intranasal ketamine, 3 mg·kg−1, diluted to 2 ml with saline, 1 ml per naris. Using a cooperation index, a play therapist scored resistance to nasal instillation, separation of the child from parents at ten min, and acceptance of anaesthesia monitors and face mask at 15 min. Differences in age, weight, episodes of vomiting, recovery and discharge times among the two groups were not significant. Intranasal ketamine, 3 mg·kg−1, was asssociated with a significantly better (P=0.013) cooperation index than intranasal placebo. Intranasal ketamine, permitted pleasant and rapid separation of children from their parents, cooperative acceptance of monitoring and of mask inhalation induction, and did not cause prolonged postanaesthetic recovery or delayed discharge home.
Does thiopentone delay recovery in children premedicated with midazolam?
Authors: MORLEY‐FORSTER PATRICIA , McALLISTER JOHN , VANDENBERGHE HILDE , THIESSEN JAKE , WHITE ANN , TAYLOR MICHAEL , KNOPPERT DAVID
Published: November 2003

This prospective, randomized trial of paediatric surgical outpatients, premedicated with oral midazolam, was designed to determine if an intravenous thiopentone induction of anaesthesia prolongs postoperative recovery compared to an inhalation induction with halothane. One hundred children, one to ten years of age, undergoing ENT surgical procedures of 30–60 min duration received midazolam 0.5 mg·kg−1 with atropine 0.03 mg·kg−1 and were randomized to either halothane (Group 1, n=50) or a thiopentone induction (Group 2, n=50) technique, followed by a standardized anaesthetic‐protocol. Time to extubation was significantly greater in the thiopentone group (8.8±4 min vs 7.1±3 min, P<0.05). Patients receiving thiopentone were also more sedated than the halothane group on arrival in the PARR (3.9±1.5, 3.3±1.7, respectively P<0.05), but the differences disappeared after 30 min. Children premedicated with oral midazolam who receive an intravenous thiopentone induction have a slightly prolonged emergence from anesthesia compared to children induced with halothane.
A Critical Appraisal of COX‐2 Selective Inhibition and Analgesia: How Good So Far?
Authors: Bejarano Pedro F. , Herrero Juan F.
Published: December 2003

Abstract:  The development of COX‐2 selective inhibitors has opened a new era of clinical investigation in NSAIDs. Discussion of the established concepts of inflammation and therapeutical uses of these drugs has changed the rationale for its clinical use and therapeutic labeling of these drugs. A comprehensive discussion across basic science and clinical areas involved in each of these concepts is presented. This led to a remarkable re‐evaluation of our insights on their traditionally proposed mechanisms of analgesia, their side‐effects, and the clinical indication of NSAIDs as “over the counter” pain killers. This may shift physicians toward a more rational use of this drug class.
Who Will Prescribe? A Proposal for Specialized Opioid Management Clinics
Authors: Loder Elizabeth
Published: December 2003

Abstract:  There is currently no uniform system of providing care for patients with chronic nonmalignant pain who require ongoing opioid maintenance therapy. Some patients receive care in a general practice setting, while others are managed in pain clinics where opioid management is only one of many services provided. Current events involving increased abuse and diversion of opioid medications suggest the need for improved case management and coordination when opioids are used for chronic nonmalignant pain. Based on the model of anticoagulation clinics, the author proposes the development of specialized opioid management clinics. These clinics would: 1) evaluate patient‐specific risks and benefits of therapy; 2) supervise the mechanics of opioid prescribing; 3) provide systematic and secure monitoring of patient adherence to therapy; 4) assess goals of therapy and progress towards them; 5) coordinate opioid treatment with other pain‐related treatment; 6) supply education to patients, family members and caregivers about the appropriate use of opioids; 7) maintain communication with other caregivers and pharmacists; and 8) provide regular psychological assistance and support for patients.
Comparison of Epidural Depo‐Medrol vs. Aqueous Betamethasone in Patients with Low Back Pain
Authors: Noe Carl E. , Haynsworth Robert F.
Published: December 2003

Abstract:  Despite the popularity of epidural steroid injections for low back pain, there still remains a lack of consensus on which type of steroid to inject. Most comparison studies regarding epidural steroids are based on an assumption that different types of steroids are equal as long as equipotent doses are utilized.

In the spring of 2002, a national shortage of all depo steroids allowed the authors to compare epidural methylprednisolone (Depo‐Medrol) to a non depo form of betamethasone in patients with low back pain. Patients who received epidural methylprednisolone (Depo‐Medrol) reported significant reduction in pain ratings as well as disability scores after 4 weeks, while patients receiving betamethasone showed no significant difference in pain or disability scores.

This study shows that the aqueous steroid betamethasone is not an effective alternative to the commonly used depo‐steroid methylprednisolone (Depo‐Medrol) when injected epidurally in patients with lumbar pain. The study also shows that the anti‐inflammatory effect of a depo‐steroid can be greater than a non‐depo steroid, even at equipotent doses. This should be an important factor to consider when reviewing epidural steroid outcome studies, where the type of steroid might affect results as much as other variables such as route of administration, volume of injectate, or use of fluoroscopy.
Sharp Versus Blunt Needle: A Comparative Study of Penetration of Internal Structures and Bleeding in Dogs
Authors: Heavner James E. , Racz Gabor B. , Jenigiri Bharat , Lehman Travis , Day Miles R.
Published: December 2003

Background and Objectives:  Complications associated with interventional pain procedures have raised questions regarding the relative safety of sharp vs. blunt needles. It has been speculated that the incidence of hemorrhage, intraneural and/or intravascular injections may be reduced by the use of blunt needles. In this study we compared penetration and bleeding associated with sharp vs. blunt needle punctures.

Methods:  Attempts were made to insert blunt and sharp needles (18‐, 20‐, 22‐, and 25‐gauge) directly or percutaneously into kidney, liver, renal artery, intestine or spinal nerve/nerve root of anesthetized dogs. Penetration and bleeding were ascertained by direct vision through a surgical wound.

Results:  All attempts to directly puncture the kidney and liver with sharp needles were successful. All but one attempt to puncture a spinal nerve/nerve root with 20‐, 22‐, and 25‐gauge sharp needles were successful but half or less attempts to puncture the intestines were successful. All attempts to puncture the renal artery with sharp needles were successful. Blunt needles never punctured the renal artery, spinal nerve/nerve root and intestines and rarely penetrated the kidney (22‐ and 25‐gauge one time each). All attempts to puncture the liver with blunt needles were successful. Bleeding scores for kidney punctures were generally higher for larger sharp needles than for smaller ones. Bleeding scores for blunt needle punctures of the liver were generally smaller than for sharp needle puncture.

Conclusion:  Blunt needles are less likely than sharp ones to enter vital structures and/or produce hemorrhage. Thus, blunt needles may be preferable to sharp ones for performing interventional pain procedures.
Pulsed Mode Radiofrequency Lesioning to Treat Chronic Post‐tonsillectomy Pain (Secondary Glossopharyngeal Neuralgia)
Authors: Shah Rinoo V. , Racz Gabor B.
Published: December 2003

Abstract:  Glossopharyngeal neuralgia (GPN) is an uncommon orofacial pain syndrome. Primary GPN is idiopathic, whereas secondary GPN has identifiable causes: tonsillectomy, peritonsillar abscesses, invasive cancer, and trauma. Despite these differences, both types of GPN present similarly and can recur. Pulsed mode radiofrequency lesioning is a safe, non‐destructive treatment method and hence, useful in neuropathic pain conditions. We present the first case of chronic post‐tonsillectomy pain (secondary glossopharyngeal neuralgia), that was successfully managed with pulsed radiofrequency lesioning.
Diagnosis and Management of the Painful Ankle/Foot Part 1: Clinical Anatomy and Pathomechanics
Authors: Sizer Phillip S. , Phelps Valerie , James Roger , Matthijs Omer
Published: December 2003

Abstract: Distinctive anatomical features can be witnessed in the ankle/foot complex, affording specific pathological conditions. Disorders of the ankle/foot complex are multifactoral and features in both the clinical anatomy and biomechanics contribute to the development of ankle/foot pain. The superior tibiofibular, distal tibiofibular, talocrural, subtalar, and midtarsal joint systems must all participate in function of the ankle/foot complex, as each biomechanically contributes to functional movements and clinical disorders witnessed in the lower extremity. A clinician's ability to effectively evaluate, diagnose, and treat the distal lower extremity is largely reliant upon a foundational understanding of the clinical anatomy and biomechanics of this complex complex. Thus, clinicians are encouraged to consider these distinctions when examining and diagnosing disorders of the ankle/foot.
Excited-state charge transfer dynamics in systems of aromatic adsorbates on TiO2 studied with resonant core techniques
Authors: Schnadt J. , O’Shea J. N. , Patthey L. , Kjeldgaard L. , Åhlund J. , Nilson K. , Schiessling J. , Krempaský J. , Shi M. , Karis O. , Glover C. , Siegbahn H. , Mårtensson N. , Brühwiler P. A.
Published: December 2003

Resonant core spectroscopies are applied to a study of the excited electron transfer dynamics on a low-femtosecond time scale in systems of aromatic molecules (isonicotinic acid and bi-isonicotinic acid) adsorbed on a rutile TiO2(110) semiconductor surface. Depending on which adsorbate state is excited, the electron is either localized on the adsorbate in an excitonic effect, or delocalizes rapidly into the substrate in less than 5 fs (3 fs) for isonicotinic acid (bi-isonicotinic acid). The results are obtained by the application of a variant of resonant photoemission spectroscopy.
Effect of reaction time and P content on mechanical strength of the interface formed between eutectic Sn–Ag solder and Au/electroless Ni(P)/Cu bond pad
Authors: Alam M. O. , Chan Y. C. , Tu K. N.
Published: December 2003

In this work, shear strengths of the solder joints for Sn–Ag eutectic alloy with the Au/electroless Ni(P)/Cu bond pad were measured for three different electroless Ni(P) layers. Sn–Ag eutectic solder alloy was kept in molten condition (240 °C) on the Au/electroless Ni(P)/Cu bond pad for different time periods ranging from 0.5 min to 180 min to render the ultimate interfacial reaction and the consecutive shear strength. After the shear test, fracture surfaces were investigated by scanning electron microscopy equipped with energy dispersed x ray. Cross-sectional studies of the interfaces were also conducted to correlate with the fracture surfaces. It was found that formation of crystalline phosphorous-rich Ni layer at the solder interface of Au/electroless Ni(P)/Cu bond pad with Sn–Ag eutectic alloy deteriorates the mechanical strength of the joints significantly. It was also noticed that such weak P-rich Ni layer appears quickly for high-P content electroless Ni(P) layer. However, when this P-rich Ni layer disappears from a prolonged reaction, the shear strength increases again.
Room-temperature 1.54 μm photoluminescence from Er-doped Si-rich silica layers obtained by reactive magnetron sputtering
Authors: Gourbilleau F. , Dufour C. , Levalois M. , Vicens J. , Rizk R. , Sada C. , Enrichi F. , Battaglin G.
Published: December 2003

Er-doped Si-rich silica layers were obtained by reactive magnetron sputtering and both structural and room-temperature photoluminescence properties were investigated. The controlled introduction of hydrogen in the plasma was found to play a critical role in the microstructure and distribution of the Si nanograins formed after annealing. Concomitant density increase and size decrease of these nanograins mostly amorphous were noticed upon increasing the hydrogen partial pressure in the plasma. This was accompanied by a systematic enhancement of the Er emission indicating that both crystallized and amorphous silicon nanoparticles are similarly efficient sensitizers for Er emission. The lifetime of the latter was found as high as 5–6 ms.
Measurement of the electro-optic properties of poled polymers at λ=1.55 μm by means of sandwich structures with zinc oxide transparent electrode
Authors: Michelotti F. , Belardini A. , Larciprete M. C. , Bertolotti M. , Rousseau A. , Ratsimihety A. , Schoer G. , Mueller J.
Published: November 2003

We report on the measurement of the electro-optic properties of poled polymers at λ=1.55 μm via the Teng and Man technique. Measurements of the electro-optic coefficient obtained for two different sandwich structures, using either indium tin oxide (ITO) or aluminum doped zinc oxide (ZnO:Al) semitransparent electrodes, are compared. The experimental results show that the use of ITO electrodes can lead to a largely wrong evaluation of the electro-optic coefficient r33, with respect to that obtained when using ZnO:Al electrodes, whose plasma resonance is shifted to longer wavelengths. Results on the disperse red 1/methyl-metacrylate based sidechain benchmark system are reported.
A theoretical investigation of valence and Rydberg electronic states of acrolein
Authors: Aquilante Francesco , Barone Vincenzo , Roos Björn O.
Published: December 2003

The main features of the ultraviolet spectrum of acrolein have been studied by a multireference perturbative treatment and by a time dependent density functional approach. The valence and Rydberg transition energies have been calculated and the assignment of the experimental bands has been clarified. The different relaxation trends of the three lowest singlet and triplet excited states have been analyzed by unconstrained geometry optimizations. This has allowed, in particular, the characterization of a twisted (ππ*)3 state, which is crucial for the interesting photophysics and photochemistry of the acrolein molecule and, more generally, of the α,β-enones. Solvatochromic shifts in aqueous solution have been investigated using a combined discrete/continuum approach based on the so called polarizable continuum model. The experimental trends are well reproduced by this approach and a closer degeneracy in the triplet manifold has been detected in solution with respect to gas phase.
Depletion interactions induced by flexible polymers in solutions of rod-like macromolecules
Authors: Wang Xiaoling , Chatterjee Avik P.
Published: December 2003

An analytic integral equation treatment is developed for the entropic depletion attractions induced by flexible polymers in dilute solutions of rigid rod-like macromolecules. The polymer-induced changes in the pair correlation functions between rod-like molecules and the rod–rod second virial coefficient are compared with results derived from a scaling approach. Results from both approaches predict that, for flexible coil-like depletants with radii of gyration sufficiently large compared to the rod lengths, the rod–rod second virial coefficient shows a nonmonotonic dependence on the coil concentration with a minimum located near the semidilute threshold. Our results are analogous to prior findings for athermal mixtures of flexible coils and hard spheres, and the predicted nonmonotonicities in the second virial coefficients between dispersed particles have the same physical origins.
Dielectric properties of BaTiO3/SrTiO3 superlattices measured with interdigital electrodes and electromagnetic field analysis
Authors: Harigai Takakiyo , Tanaka Daisuke , Kakemoto Hirofumi , Wada Satoshi , Tsurumi Takaaki
Published: December 2003

Artificial BaTiO3(BTO)/SrTiO3(STO) superlattices on STO substrates were fabricated by the molecular beam epitaxy process. The capacitance and the complex admittance of superlattices with interdigital electrode structures were measured at 1–110 MHz. The dielectric properties of the superlattices were evaluated by the electromagnetic analysis. It was found that the dielectric permittivity changed with the structure of superlattices and the highest permittivity of 33 000 was obtained for [(BTO)10/(STO)10]4 superlattice from 1 to 110 MHz.
Orange-emitting frequency-doubled GaAsSb/GaAs semiconductor disk laser
Authors: Gerster Eckart , Ecker Irene , Lorch Steffen , Hahn Christian , Menzel Susanne , Unger Peter
Published: December 2003

We report on an orange-emitting intracavity frequency-doubled semiconductor disk laser based on the material system GaAsSb/GaAs. The infrared fundamental wavelength of λ=1220 nm corresponds to a second-harmonic wavelength of λ=610 nm. The second-harmonic generation is done using a lithium–triborate crystal as the nonlinear material. We have achieved an orange continuous-wave frequency-doubled laser output power of 30 mW in the fundamental transverse mode at a wavelength of λ=610 nm.
On the negative value of dielectric permittivity of the water surface layer
Authors: Cherpak N. T. , Barannik A. A. , Prokopenko Yu. V. , Smirnova T. A. , Filipov Yu. F.
Published: November 2003

The present letter reports on experimental measurements of a resonant frequency shift of a radially two-layer quasioptical dielectric resonator with whispering gallery wave modes when the internal layer is water or benzine. The sign of the shift indicates that the real part of dielectric permittivity of the water surface layer adjacent to a solid-state dielectric becomes negative (ε′<0). The measurements were carried out at room temperature in microwave K band.
Absolute entropy and free energy of fluids using the hypothetical scanning method. I. Calculation of transition probabilities from local grand canonical partition functions
Authors: Szarecka Agnieszka , White Ronald P. , Meirovitch Hagai
Published: December 2003

The hypothetical scanning (HS) method provides the absolute entropy and free energy from a Boltzmann sample generated by Monte Carlo, molecular dynamics or any other exact simulation procedure. Thus far HS has been applied successfully to magnetic and polymer chain models; in this paper and the following one it is extended to fluid systems by treating a Lennard-Jones model of argon. With HS a probability Pi approximating the Boltzmann probability of system configuration i is calculated with a stepwise reconstruction procedure, based on adding atoms gradually layer-by-layer to an initially empty volume, where they are replaced in their positions at i. At each step a transition probability (TP) is obtained from local grand canonical partition functions calculated over a limited space of the still unvisited (future) volume, the larger this space the better the approximation. Pi is the product of the step TPs, where ln Pi is an upper bound of the absolute entropy, which leads to upper and lower bounds for the free energy. We demonstrate that very good results for the entropy and the free energy can be obtained for a wide range of densities of the argon system by calculating TPs that are based on only a very limited future volume.
Monte Carlo wave-function approach to the quantum-phase dynamics of a dissipative molecular system interacting with a single-mode amplitude-squeezed field
Authors: Nakano Masayoshi , Kishi Ryohei , Nitta Tomoshige , Yamaguchi Kizashi
Published: December 2003

We investigate the quantum-phase dynamics of a dissipative molecular system interacting with a single-mode amplitude-squeezed field (with a sub-Poissonian photon-number distribution) using the Monte Carlo wave-function method. As quantum dissipation, we consider molecular coherent (phase) and population relaxations, which are caused by nuclear vibration, and cavity relaxation (the dissipation of an internal single mode to outer mode). In this study, we elucidate the effects of these dissipations on the unique quantum dynamical behaviors of this coupled system, e.g., collapse-revival behavior of Rabi oscillations, using the quasiprobability (Q function) distribution of a single-mode field and the off-diagonal molecular density matrix. It is found that although the amplitude-squeezed field exhibits a distinct revival with larger amplitudes of molecular population in the presence of the molecular phase and population relaxations as compared to the coherent field, a very slight cavity relaxation suppresses the revival of molecular population and the increase in the magnitude of off-diagonal molecular density matrices during the quiescent region in the amplitude-squeezed field case more significantly than in the coherent field case. These features are shown to be closely related to the difference in the dynamics of Q function distributions between amplitude-squeezed and coherent fields.
Equilibration in two chambers connected by a capillary
Authors: Dagdug Leonardo , Berezhkovskii Alexander M. , Shvartsman Stanislav Y. , Weiss George H.
Published: December 2003

A problem common to biophysics, chemical engineering, physical chemistry, and physiology relates to a description of the kinetics of particle transport between two or more chambers. In this paper we analyze the case of two chambers connected by a cylindrical capillary. We derive general solutions for the Laplace transforms of the relaxation functions describing the equilibration of particles between the two chambers and the capillary. These solutions show how the relaxation functions depend on geometric parameters (volumes of the two chambers, the length and radius of the capillary) as well as diffusion coefficients in the three compartments. The general solutions are used to analyze the reduction to single-exponential kinetics which describes equilibration of the particles when the capillary is not too long. When all of the diffusion constants are equal we derive simple expressions for the average relaxation times. Brownian dynamics simulations were run to check the accuracy of approximations used to derive the results. We found excellent agreement between the theoretical predictions and numerical results.
Bonding configuration and density of defects of SiOxHy thin films deposited by the electron cyclotron resonance plasma method
Authors: San Andrés E. , del Prado A. , Mártil I. , González-Dı́az G. , Bravo D. , López F. J. , Fernández M. , Bohne W. , Röhrich J. , Selle B. , Sieber I.
Published: December 2003

The composition, bonding configuration, hydrogen content, and paramagnetic defects of SiOxHy thin films were studied. Films were deposited by the electron cyclotron resonance plasma method at room temperature using SiH4 and O2 as precursor gases. The film composition was measured by heavy ion elastic recoil detection analysis and energy dispersive x-ray spectroscopy. Suboxide films with compositions ranging from SiO2 to SiH0.38 were obtained. Infrared spectroscopy showed the presence of different Si–O and Si–H vibration modes. The usual estimation of the oxygen to silicon ratio by the wave number of the Si–O–Si stretching band was not accurate for films far from stoichiometry. These off-stoichiometric films also showed a broader Si–O–Si stretching peak than the stoichiometric ones, indicating a higher bonding disorder. The position of the Si–O–Si bending and rocking modes did not depend on the film composition. On the other hand, the peak position of the Si–H modes were found strongly dependent on the Si environment. By single-wavelength ellipsometry at λ=632.8 nm the refractive index n was found to range between 1.45 (SiO2) and 2.04 (SiO0.06H0.36). Electron spin resonance measurements showed that stoichiometric films presented the well known E′ center (⋅Si≡O3) with concentrations in the 1016–1017 cm−3 range, while for Si-rich films (x≪1) the Si dangling bond center (SiDB, ⋅Si≡Si3) was the only detectable defect, with concentrations in the 1018–1019 cm−3 range. In near-stoichiometric films both E′ and SiDB centers were found.
H–Li correlation and stoichiometry of mixed phases in proton-exchanged LiNbO3 waveguides
Authors: Espeso O. , Garcı́a G. , Climent A. , Agulló-López F. , de la Paliza G. , Cabrera J. M. , Sajavaara T.
Published: December 2003

Elastic recoil detection with a time of flight discrimination method using I127 ions has been applied to the simultaneous determination of the H and Li depth profiles as well as of the stoichiometry of the mixed phases formed by thermal annealing in proton-exchanged LiNbO3 waveguides. For both, as-exchanged and annealed waveguides, a one-to-one local correlation between the H and Li profiles has been obtained so that [H]+[Li]=constant. Moreover, the stoichiometry of the HxLi1−xNbO3 compound, where x is the exchange rate, has been correlated with x-ray diffraction (rocking curves) data in order to identify the generated phases after the exchange and annealing processes. In as-exchanged guides, the value x≃0.85 is mainly associated with a broad β2-phase peak. In annealed guides, a well-defined β2-peak is associated with x≃0.5, a broad κ2-peak is associated with x≃0.40, a broad κ1-peak to x≃0.19 and 0.21, and a α-shoulder to x≃0.09 and 0.12.
Magnetic and transport properties of the V2–VI3 diluted magnetic semiconductor Sb2−xMnxTe3
Authors: Dyck J. S. , Švanda P. , Lošt’ák P. , Horák J. , Chen W. , Uher C.
Published: December 2003

We have measured electrical and magnetic properties of single crystals of Sb2−xMnxTe3 with x=0–0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2–VI3 diluted magnetic semiconductors, at least in the range of magnetic impurity and carrier concentrations studied here.
Departures from the correlation of time- and temperature-dependences of the α-relaxation in molecular glass-formers
Authors: Roland C. M. , Paluch M. , Rzoska S. J.
Published: December 2003

There is a well-known correlation between the shape of the relaxation function (nonexponentiality) and the temperature-dependence of the relaxation times (e.g., fragility), with broader relaxations associated with steeper Tg-normalized temperature dependences. Herein, exceptions to this correlation are described. Five molecular glass-formers, all having very similar relaxation functions, are found to exhibit a range of fragilities. We also show for two of these materials that, while pressure does not affect the breadth of the relaxation function, it substantially reduces the fragility.
Asymptotic relations between time-lag and higher moments of transient nucleation flux
Authors: Shneidman Vitaly A.
Published: December 2003

Exact relations between Tk, the kth temporal moments of the nucleation flux, and the derivative of its Laplace transform (LT) are established and applied to available asymptotic expressions for the LT, generalizing earlier results by Shneidman and Weinberg [J. Chem. Phys. 95, 9148 (1991); 97, 3629 (1992)] on the time-lag T0. For any k⩾2 the moments Tk are expressed through simple algebraic combinations of T0 and T1. The two lower moments can thus be used to parametrize the time-dependent flux, with parametrization being substantially different from earlier, nonasymptotic approximations. The leading asymptotic dependences are expected to be applicable to both discrete and continuous versions of the nucleation equation, and to arbitrary sizes in the growth region. Higher-order corrections at the critical size are also obtained.
Ultraviolet stimulated photocatalytic activity on polycrystalline diamond film surfaces
Authors: Apátiga L. M. , Castaño V. M.
Published: November 2003

A photocatalytic reaction produced on polycrystalline diamond film surfaces by ultraviolet (UV) light was studied by micro-Raman spectroscopy. The diamond films were specially prepared for this study by the rf-assisted chemical vapor deposition technique. The photocatalytic activity was analyzed in terms of the sharpness of the typical diamond Raman band at 1332 cm−1 and by the weak nondiamond carbon (NDC) features around 1550 cm−1. The micro-Raman spectra show a decrease of the NDC content originally codeposited on diamond film surfaces during the synthesis. This decreasing is proportional to the UV irradiation time, suggesting that the photocatalytic reaction can be controlled by the UV irradiation dose. Since a selective reduction of the NDC phase was achieved on diamond surfaces. The UV irradiation was applied continuously during 1, 2, and 3 days in open atmosphere at room temperature. The role of oxygen radicals, such as ozone (O3) and atomic oxygen (O*) on the photocatalytic reaction is discussed, as well.
Optical amplification of the cutoff mode in planar asymmetric polymer waveguides
Authors: Pauchard M. , Vehse M. , Swensen J. , Moses D. , Heeger A. J. , Perzon E. , Andersson M. R.
Published: November 2003

Modes with low threshold for optical gain were observed at wavelengths close to the cutoff in experiments probing the amplified spontaneous emission of light-emitting polymer thin films. The polymer was the semiconductor layer in a multilayer semiconductor–insulator–metal structure that simulates the one-dimensional waveguide characteristics in the channel of a field-effect transistor. The “cutoff” mode propagates at the polymer/gate-insulator interface, has an optical gain threshold of approximately 10 kW/cm2, and is not influenced by absorption of the gate electrode. The wavelength of the amplified emission tracks the cutoff wavelength of the asymmetric double-waveguide structure and the cutoff mode is, therefore, tunable in wavelength. Our results suggest that the light-emitting field-effect transistor architecture is a promising route for the construction of an injection laser.
Self-oscillations in reverse biased pn junction with current injection
Authors: Lukin Konstantin A. , Cerdeira Hilda A. , Maksymov Pavel P.
Published: November 2003

The dynamics of charge carriers and the electric field in reverse biased pn junction in the presence of injected current is studied within the frame of a drift-diffusion model of semiconductors accounting for impact ionization. It is shown that for asymmetrical pn junctions and strong enough injected current, the charges of electrons and holes generated due to impact ionization make noticeable distortions in the electric field and dimensions of the depleted area which leads to time modulation of the currents flowing through the junction and voltage dropping across it. Self-oscillatory regime occurs when the reverse voltage approaches the critical value of the avalanche breakdown. This effect may be used for generation of electromagnetic oscillations in millimeter and submillimeter wave bands.
Resistive switching in metal–ferroelectric–metal junctions
Authors: Rodrı́guez Contreras J. , Kohlstedt H. , Poppe U. , Waser R. , Buchal C. , Pertsev N. A.
Published: November 2003

The aim of this work is to investigate the electron transport through metal–ferroelectric–metal (MFM) junctions with ultrathin barriers in order to determine its dependence on the polarization state of the barrier. To that end, heteroepitaxial Pt/Pb(Zr0.52Ti0.48)O3/SrRuO3 junctions have been fabricated on lattice-matched SrTiO3 substrates. The current–voltage (I–V) characteristics of the MFM junctions involving a few-nanometer-thick Pb(Zr0.52Ti0.48)O3 barriers have been recorded at temperatures between 4.2 K and 300 K. Typical I–V curves exhibit reproducible switching events at well-defined electric fields. The mechanism of charge transport through ultrathin barriers and the origin of the observed resistive switching effect are discussed.
Quantum well intermixing in GaInNAs/GaAs structures
Authors: Sun H. D. , Macaluso R. , Calvez S. , Dawson M. D. , Robert F. , Bryce A. C. , Marsh J. H. , Gilet P. , Grenouillet L. , Million A. , Nam K. B. , Lin J. Y. , Jiang H. X.
Published: December 2003

We report on the characteristics of quantum well intermixing in GaInNAs/GaAs structures of differing N content. Rapid thermal annealing combined with SiO2 caps deposited on the surface of the samples is used to disorder 1.3 μm GaInNAs/GaAs multiquantum wells which have been preannealed in-situ to the stage of blueshift saturation. The different effects of two capping layer deposition techniques on the interdiffusion of In–Ga have been compared, particular regarding the role of sputtering processes. The dependence of quantum well intermixing-induced photoluminescence blueshift on N concentration has provided extra information on the intrinsic properties of the GaInNAs/GaAs material system. We found that the blueshift decreases as the N concentration increases. This finding not only rules out the possible mechanism of N–As interdiffusion, but also demonstrates the alloy stability of GaInNAs due to the strong bond between In–N.
Cation self-diffusion of Ca44, Y88, and Zr96 in single-crystalline calcia- and yttria-doped zirconia
Authors: Kilo M. , Taylor M. A. , Argirusis Ch. , Borchardt G. , Lesage B. , Weber S. , Scherrer S. , Scherrer H. , Schroeder M. , Martin M.
Published: December 2003

Self-diffusion of calcium, yttrium, and zirconium in single-crystalline YSZ and CSZ (YSZ: yttria-stabilized zirconia; containing 10 to 32 mol % Y2O3; CSZ: calcia-stabilized zirconia; containing 11 and 17 mol % CaO) was measured at temperatures between 960 and 1700 °C. For zirconium and calcium diffusion, the stable isotopes Ca44 and Zr96 were used as tracers and the samples were analyzed with secondary ion mass spectrometry. In the case of yttrium diffusion, the radioactive tracer Y88 was used and an abrasive sectioning technique was applied. Zirconium bulk diffusion is slower than yttrium and calcium bulk diffusion, and there is a nearly linear correlation of diffusion coefficient with cation radius. In YSZ, zirconium and yttrium bulk diffusivity are maximum for a stabilizer content of 10–11 mol %, while in CSZ both calcium and zirconium tracer diffusion are independent of the calcium content. The activation enthalpy of yttrium stabilizer bulk diffusion (4.2 eV) is, as in CSZ, slightly smaller than for zirconium bulk diffusion (4.5 eV). The yttrium dislocation pipe diffusivity is five to six orders of magnitude faster than the bulk diffusivity, and its activation enthalpy (3.5 eV) is also smaller than that of the bulk diffusion. From the activation enthalpy and from the concentration dependence of the cation bulk diffusion, it is concluded that the cation diffusion occurs either via free vacancies (VZr4′ in YSZ) or via bound vacancies ([VZr4′−2VO2•]x in CSZ).
Acousto-optic response of nematic liquid crystals
Authors: Greanya V. A. , Spector M. S. , Selinger J. V. , Weslowski B. T. , Shashidhar R.
Published: December 2003

The dependence of the acousto-optic response of two nematic liquid crystals on several possible future device parameters is investigated. Several paths for possible optimization are identified. A large enhancement of the acousto-optic response is obtained through optimization of the incident angle of the acoustic wave. The power required for a given cell to reach the maximum optical intensity is also reduced by adjusting the optical angle. This reduction comes at the expense of higher zero-field intensity, and therefore lowers the overall contrast. Finally, the acousto-optic response shows a significant dependence on liquid crystal layer thickness, scaling with the theoretically predicted fifth power of the cell thickness.
Tracing the characteristics of a flux qubit with a hysteretic dc-superconducting quantum interference device comparator
Authors: Castellano M. G. , Chiarello F. , Leoni R. , Simeone D. , Torrioli G. , Cosmelli C. , Buttiglione R. , Poletto S. , Carelli P.
Published: December 2003

A hysteretic dc-superconducting quantum interference device (SQUID) is used to trace the flux characteristic of a tunable rf-SQUID, the basic element for the realization of superconducting flux qubits. This allows important simplifications of circuitry and electronics in developing devices for quantum computing, by eliminating the necessity of more complex magnetometers. A hysteretic dc-SQUID is usually operated as a comparator, distinguishing only which one of two adjacent flux states is occupied by the rf-SQUID. The necessary sensitivity, moreover, is usually reached only at temperatures in the mK range. However, by exploiting the statistical properties of the current–voltage curve in the region where the switching from the zero-voltage state occurs, it is possible to obtain an accurate tracing of the input flux, even at a relatively high temperature (a few Kelvin). In our case, the input signal is given by the internal flux of a tunable rf-SQUID, the building block of a flux qubit.
Ion concentrations in plasmas produced from 193 nm excimer laser irradiation of LiNbO3 in vacuum and gas atmospheres
Authors: Gordillo-Vázquez F. J. , Gonzalo J.
Published: December 2003

We have calculated the concentration of ions in the plasma produced upon ablation of LiNbO3 with a low fluence ArF excimer laser in vacuum and different gas environments (Ar and O2). The model shows that Li and Nb ions (with the amount of Li ions being greater than that of Nb ions) are the most abundant in the plasma with their concentrations being always above their corresponding neutral densities. In addition, we show that the concentration of excited Nb ions is relatively important while no excited Li ions are predicted. We found that the concentration of both Li and Nb ions in O2 is slightly higher than in Ar and vacuum. Moreover, the calculated spatial evolution of the ionic species suggests that a significant fraction of the predicted ion concentration is not produced by electron–atom ionization events within the plasma; on the contrary, they might have been produced in the LiNbO3 crystal through a nonthermal mechanism and then ejected from the target after the laser pulse.
Dislocation-free relaxed SiGe-on-insulator mesa structures fabricated by high-temperature oxidation
Authors: Tezuka Tsutomu , Sugiyama Naoharu , Takagi Shin-ichi
Published: December 2003

Relaxed SiGe-on-Insulator (SGOI) mesa structures were fabricated using mesa etching and successive high-temperature oxidation of SiGe layer on a Si-on-insulator (SOI) substrate for strained SOI (SSOI) metal–oxide–semiconductor field effect transistors (MOSFETs). In this procedure, the oxidation induces an increase in Ge fraction in the SiGe layer due to the rejection of Ge atoms from the oxide layer, while the mesa isolation enhances the lattice relaxation in the SiGe mesa. As a consequence, almost fully relaxed SGOI mesa structures with the Ge fraction up to 0.35 were obtained without introducing dislocations and surface undulation. Raman measurements revealed that a higher relaxation has been obtained for smaller and thicker mesas as well as at higher oxidation temperature. The experimental results were qualitatively explained by a relaxation model in which a strained SiGe island expands laterally without introducing dislocations on a plastic substrate. Based on this model, the applicability of this method to the fabrication of scaled MOSFETs was examined. In conclusion, this technique is promising for the fabrication of dislocation-free SGOI layers for scaled SSOI-MOSFETs without using any processes which are incompatible with conventional MOSFET processes.
Composition dependence of electron and hole transport in polyfluorene:[6,6]-phenyl C61-butyric acid methyl ester blend films
Authors: Pacios Roberto , Nelson Jenny , Bradley Donal D. C. , Brabec Christoph J.
Published: December 2003

We present a study of charge transport in polyfluorene:[6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend films. The electron and hole mobilities, measured via time-of-flight photocurrent experiments, show a strong dependence on the PCBM concentration. As a result, ambipolar transport can be obtained in blends of two otherwise unipolar materials. Both the magnitude of the mobility and the shape of the current transient are strongly affected by the presence of PCBM molecules in the film. Highly dispersive electron and hole transport for the pure polymer becomes nondispersive when PCBM is added.