bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of null-space and minimal null-space control algorithms
Authors: Nemec Bojan , Žlajpah Leon , Omrčen Damir
Published: February 2007

This paper deals with the stability of null-space velocity control algorithms in extended operational space for redundant robots. We compare the performance of the control algorithm based on the minimal null-space projection and generalized-inverse-based projection into the Jacobian null-space. We show how the null-space projection affects the performance of the null-space tracking algorithm. The results are verified with the simulation and real implementation on a redundant mobile robot composed of 3 degrees of freedom (DOFs) mobile platform and 7-DOF robot arm.
Editorial
Authors: ROKEM FREDDIE
Published: February 2007

Chris Balme, having served as senior editor of TRI for three years, has passed over the editorship to me. I really want to thank him for the excellent job he has done during his period as editor, while I have been watching the action from the wings, waiting to step in. At the same time Elaine Aston from the University of Lancaster has joined me as the new assistant editor of the journal. As a person and as a scholar she makes a huge difference, and I am looking forward to working with her. This means that three years from now she will be taking over as the senior editor of TRI. Kristina Hagström Ståhl, a graduate student from UC Berkeley, finishing her dissertation as we were working on the final touches for this issue of TRI, has joined as editorial assistant and I am very pleased to work with her as well. Finally, I also want to thank Janelle Reinelt, IFTR president, and Brian Singleton, IFTR vice president for publications, for their trust and support.
History without a Past: On the Significance of a Non-event and the Researcher's Position in History Writing
Authors: KORSBERG HANNA
Published: February 2007

The article discusses a non-event as evidence for history writing, as well as the role of historians as constructors of histories, especially those historians who have taken part in the events they are writing about. These historiographical questions are intertwined in a case study of the Finnish National Theatre's intended visit to Berlin in May 1943. Although the visit was carefully planned, it never happened, due to a change in the political situation between Finland and Germany during the Second World War. This journey, which never took place, and its absence in the history of the Finnish National Theatre, are an indication of the complex bonding between theatre, history and politics.
The Lives and Deaths of Zakia: How AIDS Changed African Community Theatre and Vice Versa
Authors: JOHANSSON DR OLA
Published: February 2007

This article discusses the functions of African community theatre in general, and its preventive capacity in the HIV/AIDS epidemic in particular. By delineating the parallel developments of community theatre and HIV prevention, the reciprocal needs of the practices are assessed in light of certain cases in Tanzania. This country has taken a leading position in the implementation of sustainable and locally owned theatre projects, but the challenges of the AIDS epidemic have proven so vast that the previously assumed purposes of community theatre must be called into question. Rather than being viewed as a means in itself, or a means for rapid change, community theatre is viewed as a relational means in coordinated programmes against AIDS. However, in spite of functioning as an exceptional relational agency for the most exposed cohort in the epidemic (women aged between fifteen and twenty-four), the social, gender and epidemic predicaments will persist as long as policy-makers do not fully recognize the status of young people and the capacity of community theatre.
Survey of the use of peripherally inserted central venous catheters in neonates with critical congenital cardiac disease
Authors: Tan Lin-Hua , Hess Beth , Diaz Laura K. , Cassady Christopher I. , Ming Xu Zhuo , Chiara Luca Di , Fraser Charles D. , Andropoulos Dean , Chang Anthony C. , Glen Seidel F.
Published: February 2007

Neonates with congenital cardiac disease are a special population. They are often critically ill, and need prolonged intravenous access. To date, no study has evaluated the efficacy and safety of peripherally inserted central venous catheters placed in this unique population. Our goal was to evaluate the use of such catheters in neonates with critical congenital cardiac disease, and to study features such as duration of use, reasons for removal of catheters, and complications. We inserted a total of 124 catheters in 115 neonates with critical congenital cardiac disease who were admitted to the Intensive Care Unit at Texas Children's Hospital from August 2002 to August 2004. The patients had a mean age of 10 days, and a mean weight of 3.1 kilograms. The peripherally inserted catheters were in place for a mean of 22.3 days. Therapy was completed in 76.6% patients at the time of removal of the catheter. The incidence of occlusion, dislodgement, and thrombus was 4.0%, 2.4%, and 1.6%, respectively. The infection rate was 3.6 per 1000 catheter-days, with a median onset on 37 days after placement. We conclude that central venous catheters, when inserted peripherally, provide reliable and safe access for prolonged intravenous therapy in neonates with critical congenital cardiac disease.
A simple screening method for determining knowledge of the appropriate levels of activity and risk behaviour in young people with congenital cardiac conditions
Authors: Kendall Lynne , Parsons Jonathan M. , Sloper Patricia , Lewin Robert J. P.
Published: February 2007

Objective: To assess a novel method for assessing risk and providing advice about activity to children and young people with congenital cardiac disease and their parents. Design and setting: Questionnaire survey in outpatient clinics at a tertiary centre dealing with congenital cardiac disease, and 6 peripheral clinics. Interventions: Children or their parents completed a brief questionnaire. If this indicated a desire for help, or a serious mismatch between advised and real level of activity, they were telephoned by a physiotherapist. Main measures of outcome: Knowledge about appropriate levels of activity, and identification of the number exercising at an unsafe level, the number seeking help, and the type of help required. Results: 253/258 (98.0%) questionnaires were returned, with 119/253 (47.0%) showing incorrect responses in their belief about their advised level of exercise; 17/253 (6.7%) had potentially dangerous overestimation of exercise. Asked if they wanted advice 93/253 (36.8%) said “yes”, 43/253 (17.0%) “maybe”, and 117/253 (46.2%) “no”. Of those contacted by phone to give advice, 72.7% (56/77) required a single contact and 14.3% (11/77) required an intervention that required more intensive contact lasting from 2 up to 12 weeks. Of the cohort, 3.9% (3/77) were taking part in activities that put them at significant risk. Conclusions: There is a significant lack of knowledge about appropriate levels of activity, and a desire for further advice, in children and young people with congenital cardiac disease. A few children may be at very significant risk. These needs can be identified, and clinical risk reduced, using a brief self-completed questionnaire combined with telephone follow-up from a suitably knowledgeable physiotherapist.
Respiratory syncytial virus as a trigger of a pulmonary hypertensive crisis after operative correction of aortic coarctation
Authors: Castelli Jussara B. , Maeda Wilma T. , Aiello Vera D.
Published: February 2007

We discuss a 9-month-old male baby, submitted to surgery for correction of aortic coarctation, who showed severe bronchospasm, hypoxaemia, and cardio-respiratory arrest, and who died on the fifth postoperative day. The autopsy revealed histological signs of severe pulmonary vasoconstriction, possibly as a consequence of hypoxaemia secondary to bronchiolitis due to infection with the respiratory syncytial virus. This supposition was confirmed when viruses were detected in pulmonary tissue by immunohistochemistry and electron microscopy.
Acute and intermediate outcomes, and evaluation of injury to the aortic wall, as based on 15 years experience of implanting stents to treat aortic coarctation
Authors: Qureshi Athar M. , McElhinney Doff B. , Lock James E. , Landzberg Michael J. , Lang Peter , Marshall Audrey C.
Published: February 2007

Background: Stenting for aortic coarctation has been shown to be effective in the short term. The safety and longer term efficacy of transcatheter therapy, however, must be well established if the technique is to be widely accepted as an alternative to surgery. In order to determine the frequency, spectrum, and outcome of injury to the aortic wall caused by angioplasty or stenting of aortic coarctation, the nomenclature of mural injury in these patients must be adapted to the conditions of transcatheter therapy. Methods and Results: Between 1989 and July 2005, we inserted stents in 153 patients with aortic coarctation, their median age being 15.8 years. Prior aortic interventions had been performed in 98 patients, and preexisting aneurysms were observed in 19. Stenting resulted in a significant reduction of the gradient across the site of coarctation, from a median of 30 millimetres of mercury to zero (p less than 0.001), with a residual gradient within the aortic arch of 20 millimetres of mercury or more in 5% of patients. Acute injuries to the aortic wall, other than therapeutic tears, were observed in 3 patients (2%), none of whom required surgery. At median follow-up of 2.5 years, this being more than 5 years in 30 patients, 4 patients had died, albeit none from complications relating to stenting or catheterization. Acute injuries to the aortic wall did not progress, and new aneurysms were observed in 6% of patients subsequent to follow-up imaging. Stent fractures, and jailed or partially covered brachiocephalic vessels, were observed in 12, and 49, patients, respectively, but did not result in haemodynamic or embolic complications. Conclusions: Stenting for aortic coarctation results in consistent relief of the gradient, and few serious complications in the short and intermediate term. Serious injuries to the aortic wall are uncommon in our experience, and can be minimized with a focus on technical measures, such as pre-dilation before stenting.
Bilateral multiple pulmonary arteriovenous fistulas and duplicated renal collecting system in a child with Noonan's syndrome
Authors: Semizel Evren , Bostan Ozlem M. , Saglam Halil
Published: February 2007

Noonan's syndrome involves the association of multiple congenital abnormalities, with a variety of cardiac defects. We describe here the association of Noonan's syndrome with multiple pulmonary arteriovenous fistulas and bilateral duplicated renal collecting systems. To the best of our knowledge, this is the first reported case of an association of the Noonan phenotype with pulmonary arteriovenous fistulas.
Serotonin and energy balance: molecular mechanisms and implications for type 2 diabetes
Authors: Lam Daniel D. , Heisler Lora K.
Published: February 2007

The neurotransmitter serotonin is an important regulator of energy balance. In the brain, serotonergic fibres from midbrain raphe nuclei project to key feeding centres, where serotonin acts on specific receptors to modulate the activity of various downstream neuropeptide systems and autonomic pathways and thus affects ingestive behaviour and energy expenditure. Serotonin, released by intestinal enterochromaffin cells, also appears to regulate energy homeostasis through peripheral mechanisms. Serotonergic effects on energy balance lead to secondary effects on glucose homeostasis, based on a well-established link between obesity and insulin resistance. However, serotonergic pathways may also directly affect glucose homeostasis through regulation of autonomic efferents and/or action on peripheral tissues. Several serotonergic compounds have been evaluated for clinical use in the treatment of obesity and type 2 diabetes; results of these trials are discussed here. Finally, future directions in the elucidation of serotonergic metabolic regulation are discussed.
PDI Improves Secretion of Redox‐Inactive β‐Glucosidase
Authors: Powers Sara Lawrence , Robinson Anne Skaja
Published: February 2007

Although manipulation of the endoplasmic reticulum (ER) folding environment in the yeast Saccharomyces cerevisiae has been shown to increase the secretory productivity of recombinant proteins, the cellular interactions and processes of native enzymes and chaperones such as protein disulfide isomerase (PDI) are still unclear. Previously, we reported that overexpression of the ER chaperone PDI enabled up to a 3‐fold increase in secretion levels of the Pyrococcus furiosus β‐glucosidase in the yeast S. cerevisiae. This result was surprising since β‐glucosidase contains only one cysteine per monomer and no disulfide bonds. Two possible mechanisms were proposed: PDI either forms a transient disulfide bond with the lone cysteine residue of the nascent β‐glucosidase during the folding and assembly process or acts as a chaperone to aid in proper folding. To discern between the two mechanisms, the single cysteine residue was mutated to serine, and the secretion of the two protein variants was determined. The serine mutant still showed increased secretion in vivo when PDI levels were elevated. When the folding bottleneck is removed by increasing expression temperatures to 37 °C rather than 30 °C, PDI no longer has an improvement on secretion. These results suggest that, unexpectedly, PDI acts in a chaperone‐like capacity or possibly cooperates with the cellapos;s folding or degradation mechanisms regardless of whether the protein is redox‐active.
Variable Stoichiometry during the Laccase‐Catalyzed Oxidation of Aqueous Phenol
Authors: Kurniawati Selvia , Nicell James A.
Published: February 2007

The oxidation of aqueous phenol through the catalytic action of laccase from Trametes versicolor was studied over a wide range of phenol concentrations and enzyme activities. The stoichiometric ratio, which is defined as the molar ratio of phenol transformed to oxygen consumed in the catalytic reaction, was found to increase with phenol concentration in the reaction mixture from a theoretical lower limit of 1 and to approach a theoretical upper limit of 4. A logistic equation was proposed to relate reaction stoichiometry to substrate concentration and was successfully used to relate these parameters over a range of phenol concentrations extending from approximately 0.15 to 8 mM. This expression was incorporated into two kinetic models in order to account for variations in reaction stoichiometry during the reaction and to extend the range over which the models may be accurately applied. The new models demonstrated an improved ability to predict concentrations of phenol and oxygen over time in a closed batch reaction system.
Symptomatische Therapie mit Antidepressiva bei Traurigkeit, Burn-out und Schmerzen
Authors: Siebert  , Wanner
Published: February 2007

Der Einsatz von Antidepressiva kann auch bei nicht-klassischen Indikationen wie Traurigkeit, Burn-out oder Schmerzen sinnvoll sein, wenn eine sich daraus entwickelnde depressive Episode behandelt oder zusätzliche Effekte wie z.B. Schmerzmodulation therapeutisch genutzt werden sollen. Aufgrund des Nebenwirkungsspektrums und des Interaktionspotenzials muss das Antidepressivum unter sorgsamer Berücksichtigung bereits bestehender Erkrankungen und Medikation sowie des klinischen Erscheinungsbildes gewählt werden. Eine eingehende Information und Begleitung des Patienten ist für den Aufbau und die Erhaltung der Compliance wichtig. Dabei gilt es, die skeptische Haltung vieler Patienten gegenüber Psychopharmaka ernst zu nehmen und die tatsächlich vorhandenen Risiken zu beachten.
Fieber – nützliches oder schädliches, zu behandelndes Symptom?
Authors: Schaffner
Published: February 2007

Fieber ist eine phylogenetisch uralte Reaktion auf Infektionen und andere Noxen. Infizierte poikylotherme Tiere erhöhen ihre Körpertemperatur durch Aufsuchen einer wärmeren Umgebung und verbessern dadurch ihre Aussicht zu überleben. Bei endothermen Organismen führt Fieber durch endogen Wärmeproduktion zu erhöhtem Energieverbrauch. Trotz diesem Aufwand eines febrilen Organismus wurde die Fieberreaktion in der Evolution konserviert, allem Anschein nach wegen der Bedeutung von Fieber für die Infektabwehr. Die Bedeutung von Fieber in der Überwindung banaler Infekte ist jedoch marginal und eine große Studie, die den Einfluss einer Antipyrese mit Ibuprofen bei schwerer Sepsis untersuchte, zeigte weder positive noch negative Auswirkungen auf Verlauf und Prognose. Demgegenüber wird eine Fiebersenkung mit nichtsteroidalen Antirheumatika, beispielsweise bei Influenza-ähnlichen Erkrankungen, als Linderung empfunden. Bei ausgewählten Patientengruppen wie Kleinkindern mit anamnestischen Fieberkrämpfen oder Patienten mit Hirnverletzungen hat eine Antipyrese keinen positiven Effekt. Für Patienten mit kardialer oder respiratorischer Insuffizienz gibt es keine vergleichenden Untersuchungen zur Frage ob eine Verringerung der metabolischen Rate durch Fiebersenkung günstig ist. Einzige gültige Indikation zur Fiebersenkung scheint eine Verbesserung des Wohlgefühls des Patienten zu sein, der unter Fieber leidet.
Kopfschmerzen durch Überkonsum an Medikamenten
Authors: Meienberg
Published: February 2007

Durch Medikamenten-Überkonsum verursachte Kopfschmerzen (MUK) kommen bei rund 1% der Gesamtbevölkerung vor. Mit einer starken Zunahme der Prävalenz in den kommenden Jahren ist zu rechnen, da mehr und mehr auch Jugendliche einen MUK betreiben. Die revidierte Internationale Klassifikation der Kopfschmerzen enthält detaillierte diagnostische Kriterien für Kopfschmerzen, welche durch bestimmte Substanzgruppen verursacht werden. Mit deren Hilfe lassen sich MUK durch Ergotamine, Triptane, Analgetika und Opioide leichter erkennen und voneinander abgrenzen. MUK kommen praktisch nur bei Patienten mit langjähriger Migräne oder chronischen Spannungstypkopfschmerzen vor, was eine genetische Disposition dazu vermuten lässt. Therapie der Wahl ist der Entzug des verursachenden Medikamentes. Medikamentöse Langzeitprophylaxen gegen Kopfschmerzen sind unwirksam, solange der Überkonsum an Akutschmerzmitteln anhält. Die Rückfallquote nach eingestelltem Medikamenten-Überkonsum ist je nach Substanz sehr unterschiedlich, teils relativ hoch. Deshalb sollte prophylaktisch bereits bei Patienten mit Migräne oder Spannungstypkopfschmerzen, welche noch keine MUK haben, sorgfältig darauf geachtet werden, dass es nicht zu einem Überkonsum an Akutschmerzmitteln kommt.
Perkutane transluminale Angioplastie – symptomatische oder kausale Therapie?
Authors: Biedermann
Published: February 2007

Die perkutane, transluminale Koronarangioplastie ist eine minimal invasive, kausale Therapie einer Koronarstenose oder eines akuten Koronarverschlusses, nicht aber der Arteriosklerose als panarterieller Krankheit. Die präzise, möglichst molekulare Charakterisierung des pathogenen Prozesses und die entsprechende Typisierung der Arteriosklerose beim einzelnen Patienten ist die Voraussetzung für eine gezielte und wirksame, d.h. remissionsinduzierende Therapie. Und manchmal sind dies sogar kausale Therapien. Erste Ansätze derartiger zielgerichteter («targeted») Behandlungsformen unterziehen sich zur Zeit der Endpunkt-kontrollierten, klinischen Prüfung.
Symptomatische Therapien in der Palliativmedizin
Authors: Büche
Published: February 2007

Palliative Care (Definition Tab. 1) befasst sich mit der Verbesserung der Lebensqualität bei Patienten in komplexen Situationen mit unheilbaren Krankheiten. Die Linderung von Symptomen steht dabei häufig im Vordergrund. Somit haben wir es in der Palliative Care meist mit symptomatischen Therapien zu tun, da an der Grunderkrankung wenig oder nichts geändert werden kann. Trotzdem ist Wissen über die Krankheit, die Therapiemöglichkeiten und die Prognose eines Leidens notwendig, damit eine gute Therapieentscheidung gefällt werden kann. An drei häufigen Symptomen soll gezeigt werden, wie Therapieentscheide zustande kommen können. Für einen neuropathischen Schmerz gibt es viele mögliche Ursachen und auch viele Therapiemöglichkeiten, leider aber keinen prospektiven Test, der voraussagt, welcher Schmerz auf welche Therapie ansprechen wird. Für die pharmakologische Therapie der Atemnot gibt es nur gute evidenz-basierte Daten für die Behandlung mit Morphin. Die Entscheidung gegen eine zusätzliche Ernährung bei fortgeschrittenem Tumorleiden oder bei dementen Patienten fällt uns einfacher, wenn wir die Datenlage kennen.
Inguinal anastomotic aneurysm due to salmonellosis treated with orthotopic reconstruction
Authors: Sigala  , Menenakos  , Baunach  , Langer  , Sigalas  , Bramis  , Sigalas  , Hepp
Published: February 2007

Femoral anastomosis following either an aortofemoral or femoropopliteal bypass, is a common site for anastomotic aneurysms occurring with an incidence of 2% to 5%. Among the factors contributing to the pathogenesis of such aneurysms, graft infection should be considered as a major one. We report the case of a 74 years old woman with history of an aorto-femoral right and -iliac left bypass with a Dacron Y-prosthetic graft due to abdominal aneurysm. The patient presented with a painful, inflammatory, and pulsating mass in her right inguinal region. She was treated surgically with wide radical resection of infected tissues including the anastomotic aneurysm, and in situ bypass reconstruction using a Silver-Dacron graft. Cultures of inflamed wound tissue, graft, and stools were positive for Salmonella typhimurium. In the postoperative period the patient was submitted to subtotal colectomy due to colon cancer and later to an iliofemoral crossover-bypass from right to left due to acute ischaemia of the left limb. Her postoperative follow up has been insignificant. Infected femoral anastomotic aneurysms due to salmonellosis are a rarity. Although their treatment of choice consist in an extra-anatomic bypass, under specific conditions in situ reconstruction may be adopted as a feasible and effective surgical technique to treat these infected aneurysms.
Symptomatische Therapie der amyotrophen Lateralsklerose (ALS)
Authors: Czaplinski  , Schweikert  , Strobel  , Steck  , Weber
Published: February 2007

Trotz der bislang unbefriedigenden kausalen Therapie der ALS im Sinne einer Lebensverlängerung sind im Laufe des letzten Jahrzehntes wirksame symptomatische Therapien entwickelt worden. Die momentane ALS-Forschung zeigt, dass sich durch ein aktives multidisziplinäres Management die Lebensqualität erhalten und die Lebensdauer verlängern lässt. Dabei kommt der Kommunikation und der Entscheidungsbefugnis von Patient und Pflegenden eine entscheidende Bedeutung zu. Es stehen zahlreiche supportive und palliative Therapieansätze wie z.B. Medikamente für den pseudobulbären Effekt, exzessiver Speichelfluss und Schlafstörungen zur Verfügung. Zudem lässt sich die Lebensqualität vieler Patienten durch die Einführung der nicht invasiven Heimbeatmung und parenteralen Ernährung deutlich bessern.
Leydig-Zell-Tumor: Klinische Überlegungen bei verfrühter Pubertätsentwicklung
Authors: Gozzi  , Flück  , Mullis
Published: February 2007

Wir beschreiben den Verlauf eines Knaben, bei dem im Alter von 8 1⁄2 Jahren ein Leydig-Zell-Tumor diagnostiziert wurde. Der Knabe präsentierte sich mit den Zeichen einer Pubertas praecox. Der Verlauf zeigt, dass die Enukleation des Tumors die Therapie der Wahl darstellt. Der nachfolgende Verlauf bis zum Abschluss des Längenwachstums wird dokumentiert und war entsprechend unauffällig. Physiologischerweise war der nachträgliche Pubertätsspurt im Vergleich mit seinen Alterskollegen vermindert, zumal dieser schon entsprechend seiner früheren Androgen-Stimulation durch die Leydig-Zellen im Alter von 7–8 Jahren eingesetzt hatte. Dies unterstreicht, dass der ganze puberale Wachstumsspurt, und somit das Total des Längenwachstums während der Pubertät, gesamthaft gesehen stabil und konstant ist. Die erreichte Endlänge entsprach der mittleren elterlichen Zielgrösse. Im Verlauf ist zehn Jahre nach der Operation kein Rezidiv aufgetreten. Es ist eine regelmässige Selbst-Kontrolle nicht ausser Acht zu lassen und eine Re-Evaluation ist bei der kleinsten, verdächtigen Abnormität unabdingbar.
Gastrointestinale Blutung bei einem 74-jährigen Mann nach Operation eines Bauchaortenaneurysmas
Authors: Luder  , Schmidli  , Greeve
Published: February 2007

Bei einem Patienten mit erstmaligem Frischblutabgang ab ano und Status nach Rohrprothesenimplantation wegen gedeckt rupturiertem Bauchaortenaneurysma wird eine aorto-duodenale Fistel gefunden. Die Abklärungsschritte sowie das Krankheitsbild werden anhand des Falles besprochen.
Observations of deep convective influence on stratospheric water vapor and its isotopic composition
Authors: Hanisco Thomas F. , Moyer E. J. , Weinstock E. M. , St. Clair J. M. , Sayres D. S. , Smith J. B. , Lockwood R. , Anderson J. G. , Dessler A. E. , Keutsch F. N. , Spackman J. R. , Read W. G. , Bui T. P.
Published: February 2007

In situ observations of H2O and HDO in the midlatitude stratosphere are used to evaluate the role of convection in determining the stratospheric water budget. The observations show that water vapor in the overworld stratosphere (potential temperature > 380 K) is isotopically heavier than expected. Measurements in an airmass with anomalously high concentrations of water vapor show isotopic water signatures that are characteristic of evaporated ice lofted from the troposphere during convective storms. Observed H2O and HDO concentrations in the plume of enhanced water and in the background stratosphere suggest that extratropical convection can account for a significant fraction of the observed water vapor in the summertime overworld stratosphere above the mid‐North American continent.
Mesospheric dynamical changes induced by the solar proton events in October–November 2003
Authors: Jackman Charles H. , Roble Raymond G. , Fleming Eric L.
Published: February 2007

The Thermosphere Ionosphere Mesosphere Electrodynamic General Circulation Model (TIME‐GCM) was used to study the atmospheric dynamical influence of the solar protons that occurred in Oct–Nov 2003, the fourth largest period of solar proton events (SPEs) measured in the past 40 years. The highly energetic solar protons produced odd hydrogen (HOx) and odd nitrogen (NOy). Significant short‐lived ozone decreases (10–70%) followed these enhancements of HOx and NOy and led to a cooling of most of the lower mesosphere. Temperature changes up to ±2.6 K were computed as well as wind (zonal, meridional, vertical) perturbations up to 20–25% of the background winds as a result of the solar protons. The solar proton‐induced mesospheric temperature and wind perturbations diminished over a period of 4–6 weeks after the SPEs. The Joule heating in the mesosphere, induced by the solar protons, was computed to be relatively insignificant for these solar storms.
Retrieval of global mesospheric sodium densities from the Odin satellite
Authors: Gumbel J. , Fan Z. Y. , Waldemarsson T. , Stegman J. , Witt G. , Llewellyn E. J. , She C.‐Y. , Plane J. M. C.
Published: February 2007

Satellite observations of the Na D dayglow at 589 nm provide a global database for the climatology of the mesospheric sodium layer. More than five years of Na D limb observations are available from the Optical Spectrograph and InfraRed Imager System onboard the Odin satellite. We describe a robust retrieval method that provides individual sodium density profiles with a typical accuracy of 20% and altitude resolution of 2 km. Retrieved column abundances and density profiles are validated against sodium resonance lidar measurements at mid‐latitudes. Examples of the seasonal and latitudinal variation of the sodium layer illustrate Odin's potential for climatological studies of mesospheric metals.
Surface phospholipids in gastric injury and protection when a selective cyclooxygenase‐2 inhibitor (Coxib) is used in combination with aspirin
Authors: Lichtenberger L M , Romero J J , Dial E J
Published: February 2007

Background and purpose:

Clinical studies demonstrate that aspirin consumption reverses the gastrointestinal (GI) benefits of coxibs, by an undefined mechanism.

Experimental approach:

Rodent models were employed to investigate the effects of combinations of celecoxib and aspirin on gastric ulcerogenesis, bleeding, surface hydrophobicity (by contact angle analysis) and ulcer healing. We also evaluated the effects of phosphatidylcholine (PC)‐associated aspirin in these rodent models and confirmed its cyclooxygenase (COX)‐inhibitory activity by measuring mucosal prostaglandin E2 (PGE2) concentration.

Key results:

We present evidence that aspirin's ability to induce gastric injury and bleeding in rats, was exacerbated in the presence of a coxib and was dependent on its ability to reduce gastric surface hydrophobicity. In contrast, co‐administration of phosphatidylcholine (PC)‐associated aspirin and celecoxib induced little or no gastric injury/bleeding and maintained the stomach's hydrophobic properties. Interestingly, aspirin and aspirin/PC equally inhibited gastric mucosal PGE2 concentration. Aspirin in combination with a coxib retarded the healing of experimentally induced gastric ulcers, whereas healing rates of rats treated with celecoxib in combination with aspirin/PC were comparable to controls.

Conclusions and implications:

Aspirin's gastric toxicity in combination with a coxib can be dissociated from its ability to inhibit COX‐1 and appears to be dependent, in part, on its ability to attenuate the stomach's surface hydrophobic barrier. This adverse drug interaction between aspirin and coxibs, which impacts the treatment of osteoarthritic and cardiac patients requiring cardiovascular prophylaxis, can be circumvented by the administration of phosphatidylcholine (PC)‐associated aspirin, to maintain the stomach's hydrophobic properties.

British Journal of Pharmacology (2007) 150, 913–919. doi:10.1038/sj.bjp.0707176
Ectopic activity in the rat pulmonary vein can arise from simultaneous activation of α1‐ and β1‐adrenoceptors
Authors: Maupoil V , Bronquard C , Freslon J‐L , Cosnay P , Findlay I
Published: February 2007

Background and purpose:

Atrial fibrillation (AF) is the most common electrical cardiac disorder in clinical practice. The major trigger for AF is focal ectopic activity of unknown origin in sleeves of cardiac muscle that extend into the pulmonary veins. We examined the role of noradrenaline in the genesis of ectopic activity in the pulmonary vein.

Experimental approach:

Mechanical activity of strips of pulmonary vein isolated from male Wistar rats was recorded via an isometric tension meter. Twitch contractions of cardiac myocytes were evoked by electrical field stimulation in a tissue bath through which flowed Krebs‐Heinseleit solution warmed to 36‐37°C and gassed with 95% O2 5% CO2.

Key results:

The superfusion of noradrenaline induced ectopic contractions in 71 of 76 different isolated pulmonary veins. Ectopic contractions in the pulmonary vein were not associated with electrically evoked twitch contractions. The effect of noradrenaline on the pulmonary vein could be replicated by the simultaneous, but not separate, application of the α adrenoceptor agonist phenylephrine and the β adrenoceptor agonist isoprenaline. The use of selective agonists and antagonists for adrenoceptor subtypes showed that ectopic activity in the pulmonary vein arose from the simultaneous stimulation of α1 and β1 adrenoceptors. The application of noradrenaline to isolated strips of left atrium did not induce ectopic contractions (n=10).

Conclusions:

These findings suggest an origin for ectopic activity in the pulmonary vein that requires activation of both α and β adrenoceptors. They also open new perspectives towards our understanding of the triggering of AF.

British Journal of Pharmacology (2007) 150, 899–905. doi:10.1038/sj.bjp.0707177
Measurement of the twist elastic constant of nematic liquid crystals using pi-cell devices
Authors: Brimicombe P. D. , Kischka C. , Elston S. J. , Raynes E. P.
Published: February 2007

We present a fast and accurate method for measurement of the twist elastic constant of nematic liquid crystals using pi-cell devices. We observe that there are two bifurcations during the transition from the bend state to the planar 180° twisted state, each of which leads to a voltage threshold. The Fréedericksz threshold voltage due to a tilt bifurcation occurs at a lower voltage and is “softened” by the required surface pretilt in the device. The higher of the two thresholds is due to a bifurcation between left- and right-handed 180° twisted states and we term this the T to V state threshold. This voltage threshold is independent of device thickness, and is not softened by the pretilt. We show that the T to V state threshold is highly sensitive to changes in the twist elastic constant, K22, and use this threshold to evaluate the magnitude of K22 for a variety of materials. These results show very good agreement with those obtained using the standard magnetic Fréedericksz twist threshold experiment. This method does not require a complex experimental setup and has an accuracy of better than ±8%.
High temperature Faraday balance for in situ measurement of magnetization in transition metal oxides
Authors: Baskar D. , Adler S. B.
Published: February 2007

We report the design of a Faraday balance that can be used to measure the magnetization of transition metal oxides at high temperatures and under controlled atmosphere. The instrument is sufficiently sensitive and stable to quantify the magnetic force on diamagnetic and paramagnetic samples at temperatures up to 1000°C and in oxygen partial pressures as low as 100ppm. We demonstrate the performance of the instrument by presenting preliminary magnetic measurements of lanthanum strontium cobalt oxide (La1−xSrxCoO3−δ) and aluminum oxide (Al2O3).
Analysis of latent tracks for MeV protons in CR-39
Authors: Kar S. , Borghesi M. , Romagnani L. , Takahashi S. , Zayats A. , Malka V. , Fritzler S. , Schiavi A.
Published: February 2007

For protons of energy up to a few MeV, the temporal evolution of etched latent tracks in CR-39 nuclear track detector has been numerically modeled by assuming that the electronic energy loss of the protons governs the latent track formation. The technique is applied in order to obtain the energy spectrum of high intensity laser driven proton beams, with high accuracy. The precise measurement of the track length and areal track density have been achieved by scanning short etched, highly populated CR-39 employing atomic force microscope.
Size dependence of the structures and energetic and electronic properties of gold clusters
Authors: Li Xi-Bo , Wang Hong-Yan , Yang Xiang-Dong , Zhu Zheng-He , Tang Yong-Jian
Published: February 2007

The structures and stabilities of gold clusters with up to 14 atoms have been determined by density-functional theory. The structure optimizations and frequency analysis are performed with the Perdew-Wang 1991 gradient-corrected functional combined with the effective core potential and corresponding valence basis set (LANL2DZ). The turnover point from two-dimensional to three-dimensional geometry for gold clusters occurs at Au12. The energetic and electronic properties of the small gold clusters are strongly dependent on sizes and structures, which are in good agreement with experiment and other theoretical calculations. The even-odd oscillation in cluster stability and electronic properties predicted that the clusters with even numbers of atoms were more stable than the neighboring clusters with odd numbers of atoms. The stability and electronic structure properties of gold clusters are also characterized by the maximum hardness principle of chemical reactivity and minimum polarizability principle.
Visible photoluminescence from a nanocrystalline porous silicon structure fabricated by a plasma hydrogenation and annealing method
Authors: Abdi Y. , Jamei M. , Hashemi P. , Mohajerzadeh S. , Robertson M. D. , Burns M. J. , MacLachlan J. M.
Published: February 2007

Thin film nanocrystalline porous silicon layers have been fabricated from amorphous silicon films using dc plasma hydrogenation and subsequent annealing at temperatures about 450°C on silicon substrates. Plasma power densities about 5.5W∕cm2 were found to be suitable for etching of the silicon film and the creation of nanoporous layers. The nanoporous structures show visible luminescence at room temperature as confirmed by photoluminescence spectroscopy. The effects of plasma power and annealing temperature on the grain size and luminescence properties of these layers have been investigated by scanning electron microscopy, transmission electron microscopy, photoluminescence, and cathodoluminescence. It was observed that by lowering the temperature during the hydrogenation step, the diameter of the grains increased, whereas lowering the plasma power density caused the distribution of the porous surface structures to become less widely distributed and the formation of more packed structures. In addition, infrared spectroscopy has been used to investigate the origin of the light emitting behavior.
Demonstration of interface-scattering-limited electron mobilities in InAs∕GaSb superlattices
Authors: Szmulowicz F. , Elhamri S. , Haugan H. J. , Brown G. J. , Mitchel W. C.
Published: February 2007

The in-plane transport in InAs∕GaSb type-II superlattices (SLs) is a sensitive indicator of SL growth quality and of the eventual performance of devices made from these materials. The in-plane mobility of electrons that move predominantly in the InAs layer is affected by a number of intrinsic and extrinsic scattering mechanisms, including interface roughness scattering (IRS). The hallmark of classic IRS-limited transport in SLs and quantum wells is the sixth power dependence of mobility on layer width. While IRS-limited transport was demonstrated in a number of SL and quantum well systems, it has never been demonstrated in the important InAs∕GaSb SL material. In this paper, we perform temperature dependent Hall effect measurements on a series of InAs∕GaSb SLs with a fixed GaSb layer width and a variable InAs layer width d. The low temperature (10K) in-plane electron mobilities μ as a function of d behave as μ∝d6.20, which follows the classic sixth power dependence expected from theory. At the same time, the dominance of the IRS-limited transport indicates that our samples are less affected by other scattering mechanisms, so that mobility measurements are another indicator of sample quality.
New cryogenic environment for beamline ID22 at the European Synchrotron Radiation Facility
Authors: Martínez-Criado G. , Steinmann R. , Alén B. , Labrador A. , Fuster D. , Ripalda J. M. , Homs A. , Labouré S. , Susini J.
Published: February 2007

A compact minicryostat has been well adapted on the hard x-ray microprobe ID22 of the European Synchrotron Radiation Facility. For variable low-temperature investigations, its special technical design provides precise scanning microscopy and allows easy access for multiple detection modes. Based on x-ray excited optical luminescence technique on the micrometer scale, details of the equipment, its temperature calibration, and typical results are described. Data collections from InAs quantum heterostructures support the excellent thermal performance of the novel cryogenic device.
Electrochemical interface between an ionic liquid and a model metallic electrode
Authors: Reed Stewart K. , Lanning Oliver J. , Madden Paul A.
Published: February 2007

A molecular dynamics simulation model for an electroactive interface in which a metallic electrode is maintained at a preset electrical potential is described. The model, based on earlier work of Siepmann and Sprik [J. Chem. Phys. 102, 511 (1995)], uses variable charges whose magnitudes are adjusted on-the-fly according to a variational procedure to maintain the constant potential condition. As such, the model also allows for the polarization of the electrode by the electrolyte, sometimes described by the introduction of image charges. The model has been implemented in a description of an electrochemical cell as a pair of parallel planar electrodes separated by the electrolyte using a two-dimensional Ewald summation method. The method has been applied to examine the interfacial structure in two ionic liquids, consisting of binary mixtures of molten salts, chosen to exemplify the influences of dissimilar cation size and charge. The stronger coordination of the smaller and more highly charged cations by the anions prevents them from approaching even the negatively charged electrode closely. This has consequences for the capacitance of the electrode and will also have an impact on the rates of electron transfer processes. The calculated capacitances exhibit qualitatively the same dependence on the applied potential as has been observed in experimental studies.
Analysis of measurement error in the experiment of laser equation of state with impedance-match way and the Hugoniot data of Cu up to ∼2.24 TPa with high precision
Authors: Fu Sizu , Huang Xiuguang , Ma Minxun , Shu Hua , Wu Jiang , Ye Junjian , He Juhua , Gu Yuan , Luo Pingqing , Rong Tao , Zhang Yonghui
Published: February 2007

This article has reported the detailed analysis about the error in the experimental measurement of laser equation of state. A kind of matrix method to calculate the uncertainty of state parameter was put forward and applied to the error estimation in the experiment with Al-Cu impedance-match target. The shock adiabatic data of Cu with the pressure up to ∼2.24 TPa and the relative uncertainty of shock velocity of ∼2% have been also presented.
Crystallization kinetics of ultrathin amorphous Si film induced by Al metal layer under thermal annealing and pulsed laser irradiation
Authors: Her Yung-Chiun , Chen Chih-Wei
Published: February 2007

The crystallization kinetics of ultrathin a-Si induced by Al under thermal annealing and pulsed laser irradiation has been studied. Under thermal annealing, the crystallization temperature and activation energy for crystallization of a-Si with a thin Al metal layer was reduced to around 340°C and 3.3eV, respectively. The reaction exponent was determined to vary from 1.5 to 1.8, corresponding to a crystallization process in which grain growth occurs with nucleation, and the nucleation rate decreases with the progress of grain growth. Under high power pulsed laser irradiation, the crystallization and reamorphization of a-Si were found to take place sequentially in a-Si∕Al. The reamorphization of a-Si in contact with a thin Al metal layer can be attributed to the melting of a-Si∕Al initiated at the interface, due to the low melting temperature of Si–Al alloy and the rapid solidification that followed. Considering only the crystallization process, the activation energy for crystallization of a-Si induced by Al, estimated to be about 0.22eV, was nearly an order of magnitude lower than that under thermal annealing. This may be explained by the explosive crystallization of a-Si by mechanical impact with a high power pulsed laser. In the meantime, the reaction exponent, determined to range from 1.9 to 2.2, was slightly higher than that under thermal annealing, indicating that the decrease of nucleation rate with the progress of grain growth during crystallization was slower, and the crystallization process became more nucleation dominant.
Enhanced focusing of laser beams in semiconductor plasmas
Authors: Gupta D. N. , Suk H.
Published: February 2007

The beating of two copropagating laser beams (having frequency difference Δω≈ωp, where ωp is the plasma frequency) can resonantly excite a large amplitude plasma wave in a narrow-gap semiconductor [V. I. Berezhiani and S. M. Mahajan, Phys. Rev. B 55, 9247 (1997)]. The higher ponderomotive force on the electrons due to the plasma beat wave makes the medium highly nonlinear. As a result, the incident laser beams become self-focused due to the nonlinearity by the ponderomotive force. In this paper, we show the self-focusing and spot size evolution of the laser beams in semiconductor plasmas.
High critical current density and improved flux pinning in bulk MgB2 synthesized by Ag addition
Authors: Shekhar Chandra , Giri Rajiv , Tiwari R. S. , Srivastava O. N. , Malik S. K.
Published: February 2007

In the present investigation, we report a systematic study of Ag admixing in MgB2 prepared by solid-state reaction at ambient pressure. All the samples in the present investigation have been subjected to structural∕ microstructural characterization employing x-ray diffraction and transmission electron microscopic (TEM) techniques. The magnetization measurements were performed by physical property measurement system. The TEM investigations reveal the formation of MgAg nanoparticles in Ag admixed samples. These nanoparticles may enhance critical current density due to their size (∼5–20nm) which is compatible with the coherence length of MgB2 (∼5–6nm). In order to study the flux pinning effect of Ag admixing in MgB2, the evaluation of intragrain critical current density (Jc) has been carried out through magnetic measurements on the fine powdered version of the as synthesized samples. The optimum result on intragrain Jc is obtained for 10at.% Ag admixed sample at 5K. This corresponds to ∼9.23×107A∕cm2 in self-field, ∼5.82×107A∕cm2 at 1T, ∼4.24×106A∕cm2 at 3.6T, and ∼1.52×105A∕cm2 at 5T. However, intragrain Jc values for MgB2 sample without Ag admixing are ∼2.59×106, ∼1.09×106, ∼4.53×104, and 2.91×103A∕cm2 at 5K in self-field, 1T, 3.6T, and 5T, respectively. The high value of intragrain Jc for Ag admixed MgB2 superconductor has been attributed to the inclusion of MgAg nanoparticles into the crystal matrix of MgB2, which are capable of providing effective flux pinning centers. A feasible correlation between microstructural features and superconducting properties has been put forward.
Synchronizing fast electrically driven phenomena with synchrotron x-ray probes
Authors: Grigoriev Alexei , Do Dal-Hyun , Evans Paul G. , Adams Bernhard , Landahl Eric , Dufresne Eric M.
Published: February 2007

Time scales of long-range physical processes in solids are typically in the range of picoseconds to nanoseconds. These times are commensurate with the time resolution of structural probes based on modern synchrotron x-ray sources. Several processes of technological and scientific interest can be driven by applied electric fields, but synchronizing electrically driven phenomena with an x-ray probe poses a technical challenge. We describe the synchronization of a well-defined number of fast electrical pulses with the time structure of synchrotron x rays to probe the dynamics of thin films and nanostructures. This synchronization technique yields x-ray transient signals with 600ps transitions in ferroelectric thin films, with a contribution of approximately 320ps due to timing jitter in the synchronization.
Surface enhanced optical absorption and photoluminescence in nonbonding electrons in small poly(vinylpyrrolidone) molecules
Authors: Mishra A. , Ram S.
Published: February 2007

Molecularly dispersed poly(vinylpyrrolidone) (PVP) in water (after mechanochemical stirring in hot condition) absorbs strongly in a triplet band (π→π* electronic transitions) in the 200–400nm range. Absorption maximum shifts nonlinearly from 222nm [full width at half maximum (FWHM)∼22nm] in a dilute solution 0.1g∕dl PVP to a value as large as 247nm (FWHM∼55nm) in 10g∕dl PVP. Disobeying the Beer-Lambert relation, the absorbance increased in dilute samples. Irradiating in this region induces two emission groups; (i) 300–580nm and (ii) 600–850nm in six distinct bands in three major PVP conformers. The first band group involves an order of larger intensity in the other group. Strong electron-phonon coupling results in the CO group of pyrrolidone ring, which governs the conformation, in a vibronic band 1665cm−1 as intense as the (0,0) band. The group (ii) occurs in part of the energy loss in interactions of excited photons with surrounding in the n←π* transition [band group (i)] in the nonbonding CO (2sp4) electrons. Such transitions may be useful for optical switching and other devices.