bluuebunny/crossref_metadata_2025 huggingface dataset:
Transnasal Endoscopic Repair of Choanal Atresia: Why Stent?
Authors: Schoem Scott R.
Published: October 2004

OBJECTIVE

To analyze the outcome of transnasal endoscopic repair of choanal atresia in children without stenting.

DESIGN

Retrospective review.

SETTING

Academic pediatric referral center.

PATIENTS

Thirteen children ages 2 days to 13 years old (mean 45 months) who presented with unilateral (8) or bilateral (5) choanal atresia and underwent transnasal endoscopic surgery between January 1997 and May 2002. No stents were used. All patients received combinations of oral steroids, topical nasal steroids, and oral antibiotics. Patency was defined as less than 50% restenosis.

RESULTS

The 4 patients who underwent office serial examination alone after surgery remained patent. Seven of the 9 patients who underwent reexamination under general anesthesia had varying amounts of emerging granulation tissue or minor synechia formation that resolved with microdebrider excision. All serial office endoscopies demonstrated no restenoses. No office dilations were performed. There were no long‐term complications. One patient (2 days old) who underwent tracheoesopha‐geal fistula repair and bilateral choanal atresia repair on the same day required a blood transfusion. Both patients with tracheostomies were decannu‐lated.

CONCLUSIONS

Transnasal endoscopic repair of choanal atresia, both unilateral and bilateral, is safe, and is effective without stenting. Postoperative failure of endoscopic approaches may be a result of prolonged mucosal trauma from stenting rather than any deficiency inherent in the surgical technique. Adjuctive therapy may not offer any advantage in promoting patency.
Proton Pump Inhibitor Therapy for Chronic Laryngo‐Pharyngitis: A Randomized Placebo‐Control Trial
Authors: Steward David L. , Wilson Keith M. , Kelly Dan H. , Patil Mona S. , Schwartzbauer Heather R. , Long John D. , Welge Jeff A.
Published: October 2004

OBJECTIVE

To determine the efficacy of proton‐pump inhibitor (PPI) therapy for chronic laryngo‐pharyngitis treated with lifestyle modification.

STUDY DESIGN AND METHODS

Double‐blind, randomized trial comparing two‐month Rabeprazole (20 mg b.i.d.) to placebo control.

RESULTS

Compared to baseline, both PPI and control patients had significant improvement in total reflux symptoms (P = 0.002 and P = 0.03 respectively), with significant improvement in “laryngo‐pharyngeal” but not “typical” reflux symptoms. No significant difference was noted for change in reflux symptoms between PPI‐treated and control patients (P = 0.44). Significant global improvement was noted by 50% of control and 53% of PPI‐treated patients (P = 1.0). No significant differences were noted within or between treatment groups for change in health status or videostrobolaryngoscopy grade. Lifestyle modification compliance correlated significantly with global improvement.

CONCLUSION

Compared to baseline, lifestyle modification for 2 months significantly improved chronic laryngo‐pharyngitis symptoms. When compared to control, treatment with a PPI failed to demonstrate significantly greater improvement in reflux symptoms, health status, or laryngeal appearance.
The Role of Agger Nasi Air Cells in Patients Requiring Revision Endoscopic Frontal Sinus Surgery
Authors: Bradley Dewayne T. , Kountakis Stilianos E.
Published: October 2004

OBJECTIVES

To determine the association of agger nasi air cell disease with frontal rhinosinusitis, assessed by computed tomography (CT), in patients who require revision functional endoscopic sinus surgery (FESS).

METHODS

We prospectively collected data on patients undergoing revision FESS at a tertiary care medical center over an 18‐month period. Sinus CT scans were graded as per Lund‐Mackay. Frontal sinus findings on CT scan were correlated with the presence or absence of disease in agger nasi air cells.

RESULTS

Eighty patients underwent revision FESS in an 18‐month period. A total of 160 sides were evaluated by sinus CT scan with agger nasi being present in all but 11 sides (93%). One patient did not have a pneumatized frontal sinus on 1 side and so 148 sides were available for study. Frontal sinus disease was present in 119 and absent in 29 sides. The average CT grade of patients with frontal rhinosinusitis was 8.4 while it was only 3.0 in patients without frontal rhinosinusitis (P = 0.000). Agger nasi air cell disease was present in only 3 of 29 (10%) sides in patients without frontal rhinosinusitis and was present in all 119 (100%) sides of patients with frontal rhinosinusitis (P = 0.0000).

CONCLUSION

Agger nasi air cells are a common anatomic feature, present in 93% of our patients. Agger nasi air cell disease correlates strongly with frontal sinus disease as assessed by sinus CT scan in patients undergoing revision FESS. In addition, frontal sinus disease correlates with the severity of overall sinus disease as determined by sinus CT scan.
Functional Surgical Approach to the Level I for Staging Early Carcinoma of the Lower Lip
Authors: Guney E. , Yigitbasi O. G.
Published: October 2004

OBJECTIVE

The management of the neck in patients with T1‐T2 carcinoma of the lower lip (LLC) remains controversial. Suprahyoid neck dissection seems a reliable diagnostic approach, although it sacrifices the submandibular gland and its vascularity.

STUDY DESIGN AND SETTING

This study was a prospective, randomized study. Patients with previously untreated T1 or T2 primary LLC underwent either classical suprahyoid neck dissection (CSHD) or functional suprahyoid neck dissection (FSHD) in continuity with the resection of the cancer of the lip.

RESULTS

A total of 48 suprahyoid neck dissections were performed in 36 patients. Among these dissections, 27 were CSHD and 21 were FSHD. The average number of dissected lymph nodes was similar for both classical and functional type operations. The overall follow‐up period was 40.5 months.

CONCLUSIONS

The end result of this series supports the idea that FSHD is a reliable diagnostic method for the management of level I lymph nodes in LLC. FSHD can avoid undertreatment or overtreatment of the patients with early LLC while preserving the submandibular gland.
Complications of Metallic Stents in the Pediatric Airway
Authors: Lim Lynne H. Y. , Cotton Robin T. , Azizkhan Richard G. , Wood Robert E. , Cohen Aliza P. , Rutter Michael J.
Published: October 2004

OBJECTIVE

Our aim was to present our experience with complications caused by placement of metallic stents in the pediatric airway.

DESIGN AND SETTING

We conducted a retrospective study of the medical records of patients with complications resulting from metallic stent placement, managed by the senior authors between 1993 and 2002.

RESULTS

Nine children had complications associated with the placement of metallic airway stents. Of these, 8 children required stent removal. Granulation tissue and tracheal stenosis were seen in all 7 children with long standing stent placement. There was 1 stent death in this series.

CONCLUSIONS

Metallic airway stents can cause significant complications in the pediatric airway. These complications may supersede the airway compromise that necessitated their initial placement. As such, metallic stent placement should be approached with caution. The likelihood and severity of complications increase with time, as do the difficulties encountered upon removal. The proportion of patients in whom metallic stents may be placed “permanently” without complications is not known. Therefore we recommend that metallic airway stents be considered a temporizing measure of limited duration.
Multivariate Predictors of Occult Neck Metastasis in Early Oral Tongue Cancer
Authors: Sparano Anthony , Weinstein Gregory , Chalian Ara , Yodul Mike , Weber Randal
Published: October 2004

OBJECTIVES

The elective dissection of cervical lymph nodes from patients with early oral tongue cancer and a clinically negative neck (T1/T2N0), remains an unsettled issue that continues to be investigated. This study examines clinical and histopathologic factors through univariate and multi‐variate analysis to correlate the risk of neck micrometastasis in patients with T1/T2N0 squamous cell carcinoma of the oral tongue.

STUDY DESIGN AND METHODS

The clinical files and histologic sections of tumor from 45 clinically determined N0 patients were retrospectively analyzed. The factors examined include degree of tumor cell differentiation, T1/T2 staging, presence of perineural invasion, presence of angiolymphatic invasion, type of invasion front, depth of muscle invasion, and tumor thickness.

RESULTS

Independent correlates of positive occult neck metastasis included greater tumor thickness (P = 0.01), greater depth of muscle invasion (P = 0.01), T2 stage (P = 0.01), poorly differentiated tumors (P = 0.007), infiltrating‐type invasion front (P = 0.03), presence of perineural invasion (P = 0.001), and presence of angiolymphatic invasion (P = 0.005). The final multivariate model for estimation of an increased probability of occult neck disease included greater tumor thickness, presence of perineural invasion, infiltrating‐type invasion front, poorly differentiated tumors, and T2 stage.

CONCLUSIONS

The clinical and histopathologic factors studied herein permit greater selectivity and more informed decision‐making than does presurgical evaluation, when addressing elective neck treatment for early N0 oral tongue cancer. The multivariate model derived from this study appears to be a more reliable method for determining the patients most likely to benefit from elective neck dissection.
Efficacy of Routine Bilateral Neck Dissection in the Management of Supraglottic Cancer
Authors: Chiu Robert J. , Myers Eugene N. , Johnson Jonas T.
Published: October 2004

OBJECTIVE

In a previous study, we reported that the contralateral undissected neck was the most common site of failure in patients treated for squa‐mous cell carcinoma of the supraglottic larynx. Since then, we have altered our treatment of all patients with T2‐T4 supraglottic cancer and selective T1 cases to include routine bilateral neck dissection. In the present study, we compare the long‐term efficacy of routine bilateral neck dissections to historic controls in the treatment of patients with supraglottic cancer.

STUDY DESIGN AND SETTING

A retrospective chart review on all patients undergoing primary surgery for supraglottic carcinoma between 1989 and 2000 was performed. All had undergone routine bilateral neck dissection. The most proximal area of recurrent disease was identified as the site of recurrence. Rates of recurrence, 2‐year overall survival, and 2‐year disease‐specific survival were calculated. Results were compared to historical data using Fisher's exact test.

RESULTS

Of 180 patients identified, 115 patients with minimum 2‐year follow‐up and meeting exclusion criteria were included in the analysis. Four patients (3.5%) experienced local recurrence, 9 patients (7.8%) had cervical recurrence, and 8 patients had distant spread (7.0%). Recurrence in the neck (7.8%) has been significantly reduced from the historical recurrence rate (20%) prior to instituting routine bilateral neck dissections (P = 0.009). The 2‐year survival increased from 72% to 82.6% (P = 0.0408).

CONCLUSION AND SIGNIFICANCE

Routine bilateral neck dissection decreases cervical recurrence and appears to improve survival in the management of supraglottic cancer.
Contacting Passengers after Exposure to Measles on an International Flight: Implications for Responding to New Disease Threats and Bioterrorism
Authors: Lasher Lara E. , Ayers Tracy L. , Amornkul Pauli N. , Nakata Michele N. , Effler Paul V.
Published: October 2004

On May 21, 2000, a passenger with measles traveled from Japan to Hawai'i on a seven-hour flight. When the flight landed, the U.S. Public Health Service (USPHS) Quarantine Station in Honolulu alerted passengers that a suspected case of measles had been identified, but they were not detained. The next day, to offer appropriate post-exposure prophylaxis, the Hawai'i Department of Health (HDOH) attempted to contact all passengers from the flight using information from the airline, U.S. Customs declaration forms, and tour agencies. Of 335 total passengers, 270 (81%) were successfully reached and provided complete information. The mean time from exposure to contact for all respondents was 61 hours (95% confidence interval 57, 66). A total of 202 (75%) of the responding passengers were contacted within 72 hours after exposure, the time period during which administration of measles vaccine would have provided protection for susceptible individuals. The time-to-contact was significantly longer for passengers who did not stay in hotels than for hotel guests. Customs forms proved to be of limited utility in contacting international travelers. This experience highlights the need for more complete and timely methods of contacting passengers potentially exposed to infectious agents aboard flights.
Fatal Traumatic Brain Injury, West Virginia, 1989–1998
Authors: Adekoya Nelson , Majumder Ranjit
Published: October 2004

Objective.

The objective of this study was to describe fatal cases of traumatic brain injury (TBI) among West Virginia residents.

Methods.

The authors analyzed data from the National Center for Health Statistics Multiple Cause of Death tapes for the period 1989–1998. They compared West Virginia's annualized average TBI death rate with the rates of other states and with the rate among U.S. residents for the same period. U.S. Bureau of Census population estimates were used as denominators.

Results.

A total of 4,416 TBI deaths occurred in West Virginia in 1989–1998, for an annual average death rate of 23.6 per 100,000 population. From 1989 to 1998, TBI death rates declined 5% ( p=0.4042). Seventy-five percent ( n=3,315) of fatalities occurred among men. Adults ⩾65 years of age accounted for the highest percentage of fatal injuries ( n = 1,135). The leading external causes of fatal TBI were: firearm-related (39% of reported fatalities), motor vehicles–related (34%), and fall-related (10%). Firearm-related TBI became the leading cause of TBI fatalities in 1991, surpassing motor vehicle-related TBI. Seventy-five percent of firearm-related TBI deaths were suicides ( n = 1,302). West Virginia's TBI death rate (23.6 per 100,000) was higher than the national rate (20.6 per 100,000). In 23 states, the average TBI death rates over the 10-year period were higher than West Virginia's. Whereas modest declines in TBI death rates occurred for motor vehicle-related and firearm-related causes in West Virginia, a concomitant 38% increase occurred in the fall-related TBI death rate during the decade.

Conclusion.

Data presented in this report can be used to develop targeted prevention programs in West Virginia.
Worsening Trends in Adult Health-Related Quality of Life and Self-Rated Health—United States, 1993–2001
Authors: Zack Matthew M. , Moriarty David G. , Stroup Donna F. , Ford Earl S. , Mokdad Ali H.
Published: October 2004

Objectives.

Health-related quality of life and self-rated health complement mortality and morbidity as measures used in tracking changes and disparities in population health. The objectives of this study were to determine whether and how health-related quality of life and self-rated health changed overall in U.S. adults and in specific sociodemographic and geographic groups from 1993 through 2001.

Methods.

The authors analyzed data from annual cross-sectional Behavioral Risk Factor Surveillance System surveys of 1.2 million adults from randomly selected households with telephones in the 50 states and the District of Columbia.

Results.

Mean physically and mentally unhealthy days and activity limitation days remained constant early in the study period but increased later on. Mean unhealthy days increased about 14% during the study period. The percentage with fair or poor self-rated health increased from 13.4% in 1993 to 15.5% in 2001. Health-related quality of life and self-rated health worsened in most demographic groups, especially adults 45–54 years old, high school graduates without further education, and those with annual household incomes less than $50,000. However, adults 65 years old or older and people identified as non-Hispanic Asian/Pacific Islander reported stable or improving health-related quality of life and self-rated health. In 18 of the states and the District of Columbia, mean unhealthy days increased, while only North Dakota reported a decrease.

Conclusion.

Population tracking of adult health-related quality of life and self-rated health identified worsening trends overall and for many groups, suggesting that the nation's overall health goals as identified in the Healthy People planning process are not being met.
Ungewissheitstoleranz, Belastung und Befinden bei BerufsschullehrerInnen
Authors: König Silvio , Dalbert Claudia
Published: October 2004

Zusammenfassung. Mit einer Längsschnittstudie konnte die Hypothese einer positiven Beziehung zwischen Ungewissheitstoleranz und dem beruflichen sowie allgemeinen Befinden von Lehrenden berufsbildender Schulen (N = 94) belegt werden. Für einen Zeitraum von 10 Monaten konnte ein adaptiver Einfluss der Ungewissheitstoleranz auf den positiven Affekt und das berufliche Befinden (Arbeitsunzufriedenheit, Leistungsmangel) nachgewiesen werden. Gleichzeitig ging eine ausgeprägte Ungewissheitstoleranz jedoch mit einem vermehrten Kontrolliertheitserleben sowie mehr negativem Affekt einher. Der Einfluss der Ungewissheitstoleranz auf das Befinden der Lehrenden blieb auch nach Kontrolle anderer Personmerkmale (Selbstwert, Ängstlichkeit, Selbstwirksamkeit) erhalten. Die Ergebnisse sprechen insgesamt dafür, dass Ungewissheitstoleranz eine Ressource im Lehrerberuf darstellt. Sie weisen aber gleichzeitig darauf hin, dass sich die ungewissheitstoleranten Lehrenden stärker durch das Schulsystem kontrolliert fühlen.
Sprache und Theory of Mind:
Authors: Lockl Kathrin , Schwarz Stefanie , Schneider Wolfgang
Published: October 2004

Zusammenfassung. Die vorliegende Längsschnittstudie hat sich zum Ziel gesetzt, die Kausalrichtung der Beziehung zwischen sprachlichen Kompetenzen und Theory of Mind systematisch zu analysieren und dabei einen möglichen Einfluss des Arbeitsgedächtnisses zu berücksichtigen. Insgesamt wurden 179 dreijährige Kindergartenkinder zweimal im Abstand von 7 Monaten mit den gleichen Aufgaben zur Sprachentwicklung, zu Theory of Mind und zum Arbeitsgedächtnis konfrontiert. In Übereinstimmung mit Befunden aus dem englischen Sprachraum stellte sich heraus, dass frühere sprachliche Kompetenzen einen guten Prädiktor für spätere Theory of Mind-Leistungen darstellen, während eine umgekehrte Vorhersage nicht möglich war. Individuelle Unterschiede im Arbeitsgedächtnis konnten hierbei nicht im Sinne einer Drittvariablen die Fortschritte in der Sprachentwicklung und in den Theory of Mind-Leistungen erklären. Insgesamt sprechen die Ergebnisse dafür, dass der Erwerb sprachlicher Fähigkeiten eine wichtige Grundlage für die Theory of Mind-Entwicklung bildet.
Sensation Seeking, gesundheitsbezogene Kognitionen und Partizipation am Risikosport
Authors: Schumacher Jörg , Roth Marcus
Published: October 2004

Zusammenfassung. In der vorliegenden Untersuchung wird der Frage nachgegangen, welchen Stellenwert das persönlichkeitspsychologische Konstrukt Sensation Seeking (SS) sowie gesundheitsbezogene Kognitionen (Risikowahrnehmung, Konsequenz- und Selbstwirksamkeitserwartung) für die Erklärung der Partizipation am Risikosport besitzen. Mittels Fragebogen wurden dazu N = 228 Studierende befragt. Zur Erfassung von SS kamen die SSS-V sowie das AISS zum Einsatz. Die gesundheitsbezogenen Kognitionen wurden mittels selbst entwickelter Skalen erhoben. Im Ergebnis zeigte sich, dass SS negativ mit der Risikowahrnehmung und positiv mit der Selbstwirksamkeitserwartung korreliert. Gemeinsam können diese Variablen einen signifikanten Beitrag zur Vorhersage der Risikosportpartizipation leisten. Darüber hinaus sind Wechselbeziehungen zwischen SS und den gesundheitsbezogenen Kognitionen zu beachten.
Gewichtsbezogene Lebensqualität bei Schulkindern:
Authors: Warschburger Petra , Fromme Carmen , Petermann Franz
Published: October 2004

Zusammenfassung. Gewicht und Figur spielen bereits im Kindes- und Jugendalter eine zentrale Rolle. Das Gewicht stellt einen wichtigen Marker für die soziale Stellung innerhalb der Gruppe und das psychische Wohlbefinden dar. Dementsprechend ist das psychische Wohlbefinden von adipösen Kindern und Jugendlichen im Vergleich zu normalgewichtigen oftmals vermindert; dies gilt vor allem für klinische Stichproben. Gewichtsbezogene Lebensqualitätsinstrumente für Kinder und Jugendliche fehlen größtenteils ebenso wie Angaben darüber, ob für klinische Gruppen entwickelte Messinstrumente sich auch für die Allgemeinbevölkerung eignen. Der folgende Beitrag beschreibt die Validierung eines gewichtsbezogenen Lebensqualitätsinstrumentes für übergewichtige Kinder und Jugendliche (GW-LQ-KJ) in einer populationsbezogenen Stichprobe. 936 Schüler im Alter von 8 bis 18 Jahren füllten neben dem GW-LQ-KJ die deutsche Version des STAI für Kinder, einen Fragenbogen zum Meidungsverhalten auf Grund des Körperbildes (BIAQ) sowie Subskalen des Child Health Questionnaire (CHQ) zur Erhebung der allgemeinen Lebensqualität aus. Die Akzeptanz des Fragebogens ist als gut zu bezeichnen. Hypothesenkonform ergaben sich Unterschiede in der gewichtsbezogenen Lebensqualität zwischen verschiedenen Gewichtsgruppen. Die Ergebnisse dieser Studie deuten darauf hin, dass der GW-LQ-KJ auch in nicht-klinischen Gruppen die gewichtsbezogene Lebensqualität von Kindern und Jugendlichen valide erfassen kann.
Modeled and measured optical transmittance of snow‐covered first‐year sea ice in Kongsfjorden, Svalbard
Authors: Hamre Børge , Winther Jan‐Gunnar , Gerland Sebastian , Stamnes Jakob J. , Stamnes Knut
Published: October 2004

On the basis of input from in situ measurements of key parameters determining optical properties (i.e., snow grain size, density, ice salinity, ice temperature, etc.) we calculate the transmittance of shortwave radiation (280 nm < λ < 800 nm) through first‐year sea ice with and without snow cover. We use a multistream radiative transfer code that takes into account the coupling between two strata with different indices of refraction (i.e., the atmosphere‐snow stratum and the ice‐ocean stratum). Also, we give a detailed description of the parameterization used to calculate the optical properties for shortwave radiation in the atmosphere, snow, ice, and ocean. Through comparisons between calculated and in situ measured transmittances we tune the model to obtain consistency. We find that for the type of snow and ice considered in this study a 2.5‐cm‐thick layer of snow is less transparent than a 61‐cm‐thick layer of ice. Also, the diffuse attenuation coefficient for snow Kd varies considerably with the snow thickness, emphasizing the need for accurate radiative transfer modeling. Our model not only provides accurate transmittances but also gives accurate values for ultraviolet and visible light versus depth in the atmosphere, snow, ice, and ocean. This makes it a suitable tool for both calculating energy deposition in icy polar waters and predicting effects on polar aquatic ecology due to changes in the light conditions.
Oceanic forcing of interannual and multidecadal climate variability in the southwestern Indian Ocean: Evidence from a 160 year coral isotopic record (La Réunion, 55°E, 21°S)
Authors: Pfeiffer Miriam , Timm Oliver , Dullo Wolf‐Christian , Podlech Steffen
Published: October 2004

We have developed a new 163‐year bimonthly coral δ18O record from La Réunion (55°E, 21°S). Interannual variations in coral δ18O are coherent with the Southern Oscillation Index but not with regional sea surface temperature (SST). Correlations with the global SST field suggest more negative seawater δ18O (δ18Osw) during La Niña years. We propose that the signal results from changes in the strength of the South Equatorial Current and the Indonesian throughflow, which carry low salinity water. Multidecadal variations in coral δ18O are coherent with regional SST, but the sign is of opposite sense as expected from the coral δ18O‐temperature relationship. This requires multidecadal changes in salinity large enough to overprint the SST contribution in the coral δ18O record. Our results suggest that multidecadal salinity variations result from modulations in the transport of the South Equatorial Current, which varies in response to the surface wind field and/or the Indonesian throughflow.
A model for the variation in permeability of clay‐bearing fault gouge with depth in the brittle crust
Authors: Faulkner D. R.
Published: October 2004

A model of the variation in permeability of clay‐bearing fault gouge in the brittle crust is presented. Factors affecting the permeability from laboratory experiments are considered and quantified. These are pressure, temperature and permeating fluid. Effective pressure () and temperature (T) effects on permeability (k) are described by k = k0exp(−0.01Δ)exp(−0.01ΔT) where k0 is a reference permeability at a particular temperature and pressure. At low temperatures (<80°C), with aqueous pore fluids, the above relation is modified to k = k0exp(−0.01Δ)exp(−0.01ΔT) in order to describe low temperature (less than a critical temperature, Tc, of 80°C) inferred physicochemical interactions between pore fluids and the fault gouge. The model is used to predict the variation in permeability as a function of depth for different ratios (λ) of pore fluid pressure to confining pressure.
Solar proton events of October–November 2003: Ozone depletion in the Northern Hemisphere polar winter as seen by GOMOS/Envisat
Authors: Seppälä A. , Verronen P. T. , Kyrölä E. , Hassinen S. , Backman L. , Hauchecorne A. , Bertaux J. L. , Fussen D.
Published: October 2004

Observations of O3 and NO2 made by the GOMOS instrument on board European Space Agency's Envisat satellite have been used to monitor the increase of NO2 and depletion of ozone due to the solar proton events of October–November 2003. For the first time this phenomenon was measured in polar winter conditions by a satellite instrument. Results show NO2 enhancement of several hundred per cent and tens of per cent ozone depletion between 36 and 60 km, an effect which lasts several months after the events. A comparison of the after‐event concentrations of NO2 and ozone reveals a strong negative correlation.
The effects of connectivity, coherence, and trapping on energy transfer in simple light-harvesting systems studied using the Haken-Strobl model with diagonal disorder
Authors: Gaab Kevin M. , Bardeen Christopher J.
Published: October 2004

The problem of electronic energy transfer in a network of two-level systems coupled to a single trapping site is investigated using a simple Haken-Strobl model with diagonal disorder. The goal is to illustrate how the trapping time Ttrap, coherence time Td, and molecular topology all affect the overall efficiency of a light-harvesting network. Several issues are identified that need to be considered in the design of an optimal energy transfer network, including the dephasing-induced decoupling the trap from the rest of the network, the nonlinear dependence of trapping rate on the coherence time, and the role of network size and connectivity in determining the effect of the coherence time on efficiency. There are two main conclusions from this work. First, there exists an optimum combination of trapping time and coherence time, which will give the most rapid population transfer to the trap. These values are not in general the shortest trapping time and the longest coherence time, as would be expected based on rate equation models and/or simple considerations from previous analytical results derived for the Haken-Strobl model in an infinite system. Second, in the coherent regime, where Td is longer than the other relevant timescales, population trapping in a finite system can be suppressed by quantum interference effects, whose magnitude is sensitive to the molecular geometry. Suggestions for possible methods of observing such effects are discussed. These results provide a qualitative framework for quantum coherence and molecular topology into account for the design of covalent light-harvesting networks with high energy transfer efficiencies.
AXUV bolometer and Lyman-α camera systems on the TCV tokamak
Authors: Degeling A. W. , Weisen H. , Zabolotsky A. , Duval B. P. , Pitts R. A. , Wischmeier M. , Lavanchy P. , Marmillod Ph. , Pochon G.
Published: October 2004

A set of seven twin slit cameras, each containing two 20-element linear absolute extreme ultraviolet photodiode arrays, has been installed on the Tokamak à Configuration Variable. One array in each camera will operate as a bolometer and the second as a Lyman-alpha (Lα) emission monitor for estimating the recycled neutral flux. The camera configuration was optimized by simulations of tomographic reconstructions of the expected Lα emission. The diagnostic will provide spatial and temporal resolution (10 μs) of the radiated power and the Lα emission that is considerably higher than previously achieved. This optimism is justified by extensive experience with prototype systems, which include first measurements of Lα light from the divertor.
Exploiting a transmission grating spectrometer
Authors: Bell Ronald E.
Published: October 2004

The availability of compact transmission grating spectrometers now allows an attractive and economical alternative to the more familiar Czerny–Turner configuration for many high-temperature plasma applications. Higher throughput is obtained with short focal length refractive optics and stigmatic imaging. Many more spectra can be obtained with a single spectrometer since smaller, more densely packed optical input fibers can be used. Multiple input slits, along with a bandpass filter, can be used to maximize the number of spectra per detector, providing further economy. Curved slits can correct for the strong image curvature of the short focal length optics. Presented here are the governing grating equations for both standard and high-dispersion transmission gratings, defining dispersion, image curvature, and desired slit curvature, that can be used in the design of improved plasma diagnostics.
Transmitted laser beam diagnostic at the Omega laser facility
Authors: Niemann C. , Antonini G. , Compton S. , Glenzer S. H. , Hargrove D. , Moody J. D. , Kirkwood R. K. , Rekow V. , Satariano J. , Sorce C. , Armstrong W. , Bahr R. , Keck R. , Pien G. , Seka W. , Thorp K.
Published: October 2004

We have developed and commissioned a transmitted beam diagnostic (TBD) for the 2ω high intensity interaction beam at the Omega laser facility. The TBD consists of a bare-surface reflector mounted near the target, which collects and reflects 4% of the transmitted light to a detector assembly outside the vacuum chamber. The detector includes a time integrating near-field camera that measures beam spray, deflection, and the absolute transmitted power. We present a detailed description of the instrument and the calibration method and include first measurements on laser heated gas bag targets to demonstrate the performance of the diagnostic.
Diagnostic method for the measurement of coherent magnetic field fluctuations
Authors: Levinton F. M. , Fredriksen Å.
Published: October 2004

The motional Stark diagnostic has been proven to provide excellent measurements of the pitch angle of the equilibrium magnetic field in tokamaks. In this work, we explore its feasability for obtaining the pitch angle modulation of the magnetic field due to coherent fluctuations. Theoretical calculations for a signal with periodic pitch angle variation indicate that fluctuations in the magnetic pitch angle can be derived from spectral lines offset from the second harmonics of the retarder drive frequencies. The calculations agree well with laboratory simulations of magnetic fluctuations using spectral analysis.
High resolution transmission grating spectrometer for edge toroidal rotation measurements of tokamak plasmas
Authors: Graf A. , May M. , Beiersdorfer P. , Magee E. , Lawrence M. , Rice J.
Published: October 2004

We present a high throughput (f/3) visible (3500–7000 Å) Doppler spectrometer for toroidal rotation velocity measurements of the Alcator C-Mod tokamak plasma. The spectrometer has a temporal response of 1 ms and a rotation velocity sensitivity of ∼105 cm/s. This diagnostic will have a tangential view and map out the plasma rotation at several locations along the outer half of the minor radius (r/a>0.5). The plasma rotation will be determined from the Doppler shifted wavelengths of Dα and magnetic and electric dipole transitions of highly ionized impurities in the plasma. The fast time resolution and high spectral resolving power are possible due to a 6 in. diam circular transmission grating that is capable of λ/Δλ∼15 500 at 5769 Å in conjunction with a 50 μm slit.
Full-aperture backscatter measurements on the National Ignition Facility
Authors: Froula D. H. , Bower D. , Chrisp M. , Grace S. , Kamperschroer J. H. , Kelleher T. M. , Kirkwood R. K. , MacGowan B. , McCarville T. , Sewall N. , Shimamoto F. Y. , Shiromizu S. J. , Young B. , Glenzer S. H.
Published: October 2004

The National Ignition Facility’s full-aperture backscatter station (FABS) is described. The FABS uses five independent diagnostics on each of the four laser beams in the initial National Ignition Facility quad to measure the energy, power, spectrum, and near-field amplitude modulations of the stimulated Brillouin and stimulated Raman backscattered light. In initial tests CO2 and C5H12 gas-filled targets were used to create various laser–plasma interaction conditions which have shown the capability of producing ignition size laser plasmas with reflectivites on the order of 10%. Results are presented for tests in which 16 kJ on target produced between 0.3 and 2.5 kJ of backscattered light.
Implementation of a near backscattering imaging system on the National Ignition Facility
Authors: Mackinnon A. J. , McCarville T. , Piston K. , Niemann C. , Jones G. , Reinbachs I. , Costa R. , Celeste J. , Holtmeier G. , Griffith R. , Kirkwood R. , MacGowan B. , Glenzer S. H. , Latta M. R.
Published: October 2004

A near backscattering imaging diagnostic system is being implemented on the first quad of beams on the National Ignition Facility. This diagnostic images diffusing scatter plates, placed around the final focus lenses on the National Ignition Facility target chamber, to quantitatively measure the fraction of light backscattered outside of the focusing cone angle of incident laser beam. A wide-angle imaging system relays an image of light scattered outside the lens onto a gated charge coupled device camera, providing 3 mm resolution over a 2 m field of view. To account for changes of the system throughput due to exposure to target debris the system will be routinely calibrated in situ at 532 and 355 nm using a dedicated pulsed laser source.
Development of magnetic field mapping via heavy ion beam spectral imaging
Authors: Demers D. R. , Connor K. A. , Schoch P. M. , Radke R. J. , Anderson J. K. , Craig D. , Den Hartog D. J.
Published: October 2004

Mapping magnetic fields via heavy ion beam spectral imaging relies upon establishing a high quality ion beam, identifying beam emission at wavelengths favorable for imaging, and designing an appropriate imaging configuration. Identifying emission lines suitable for imaging is difficult due to intense, broadband radiation of the target reversed field pinch plasma. To compensate, we have worked to raise the beam emission intensity. Simulations of the beam optics and characteristics have led to a technique that achieves a narrower beam and increased ion current at the plasma. Additionally, we are developing computer vision tools to reconstruct beam trajectories based on various camera and system configurations. We simulate charge coupled device images of the vessel interior and beam trajectories, and reconstruct three dimensional trajectories from image pairs. Analysis of the simulated images will guide the system specifications. We present results of the beam optics and camera simulations, surveys of radiation, and status of the diagnostic.
Target diagnostic technology research and development for the LLNL ICF and HED program (invited)
Authors: Bell P. M. , Landen O. L. , Weber F. A. , Lowry M. E. , Bennett C. V. , Kimbrough J. R. , Moody J. D. , Holder J. P. , Lerche R. A. , Griffith R. L. , Park H. S. , Boni R. , Jaanimagi P. A. , Davies T.
Published: October 2004

The National Ignition Facility is operational at Lawrence Livermore National Laboratory (LLNL). The inertial confinement fusion and HED programs at LLNL have formed diagnostic research and development groups to institute improvements outside the charter of core diagnostics. We will present data from instrumentation being developed. A major portion of our work is improvements to detectors and readout systems. We have efforts related to charge-coupled device (CCD) development. Work has been done in collaboration with the University of Arizona to back thin a large format CCD device. We have developed in collaboration with a commercial vendor a large format, compact CCD system. We have coupled large format CCD systems to our optical and x-ray streak cameras leading to improvements in resolution and dynamic range. We will discuss gate width and uniformity improvements to microchannel plate-based framing cameras. We will present data from single shot data link work and discuss technology aimed at improvements of dynamic range for high-speed transient measurements from remote locations.
Versatile multiwavelength imaging diagnostic in the MAST spherical tokamak
Authors: Patel A. , Carolan P. G. , Conway N. J. , Bunting C. A. , Akers R. J.
Published: October 2004

Spectral imaging diagnostics that view the full plasma cross section are used on MAST with sensor resolutions and frame rates of up to 256×512 chords and 130 Hz, respectively. The incident and solid angles of filter illumination are fully controllable. Image splitting and spectral selection with separate filters are performed in the telecentric region of the optics, whereas quasicontinuous polychromatic selection is achieved with a single filter in the convergent region. The versatility is investigated in exploiting the diagnostic techniques facilitated by neutral beam injection. Three color image dissection, detection of impurity charge exchange emission and Balmer-alpha beam emission are demonstrated. In another application it has been possible to use a single narrow band filter to image the spatially varying Doppler shifted emission from an inclined neutral beam even though the spatial variation well exceeds the filter bandwidth.
Vibrational dynamics of medium strength hydrogen bonds: Fourier transform infrared spectra and band contour analysis of the DF stretching region of (CH2)2S–DF
Authors: Goubet M. , Asselin P. , Soulard P. , Lewerenz M. , Latajka Z.
Published: October 2004

Fourier transform infrared spectra of the νs band of the (CH2)2S–DF complex have been recorded at 0.1–0.5 cm−1 resolution in a cooled cell and in a supersonic jet expansion seeded with argon. A sufficient density of (CH2)2S–DF heterodimers is produced by a double injection nozzle device, which limits the possibility of reaction between thiirane and DF before the expansion. The observation of partially resolved PQR branch structures at cell temperatures as high as 252 K indicates relatively small effective line widths, which allow a detailed analysis of the underlying vibrational couplings and of the structural properties of the complex. The analysis of cell and free jet spectra in the temperature range 50–250 K is performed with a software package for the simulation and fitting of multiple hot band progressions in asymmetric rotors. The analysis reveals that the three low frequency hydrogen-bond modes are strongly coupled to the DF stretch with anharmonic coupling constants, which indicates a strengthening of the hydrogen bond upon vibrational excitation of DF. Rovibrational parameters and a reliable upper bound for the homogeneous line width have been extracted.
A kinetic model for an argon plasma containing dust grains
Authors: Denysenko I. , Yu M. Y. , Ostrikov K. , Azarenkov N. A. , Stenflo L.
Published: October 2004

A complex low-pressure argon discharge plasma containing dust grains is studied using a Boltzmann equation for the electrons and fluid equations for the ions. Local effects, such as the spatial distribution of the dust density and external electric field, are included, and their effect on the electron energy distribution, the electron and ion number densities, the electron temperature, and the dust charge are investigated. It is found that dust particles can strongly affect the plasma parameters by modifying the electron energy distribution, the electron temperature, the creation and loss of plasma particles, as well as the spatial distributions of the electrons and ions. In particular, for sufficiently high grain density and/or size, in a low-pressure argon glow discharge, the Druyvesteyn-like electron distribution in pristine plasmas can become nearly Maxwellian. Electron collection by the dust grains is the main cause for the change in the electron distribution function.
Effect of absolute laser phase on reaction paths in laser-induced chemical reactions
Authors: Bandrauk André D. , Sedik El-Wallid S. , Matta Chérif F.
Published: October 2004

Potential surfaces, dipole moments, and polarizabilities are calculated by ab initio methods [unrestricted MP2(full)/6-311++G(2d,2p)] along the reaction paths of the F+CH4 and Cl+CH4 reaction systems. It is found that in general dipole moments and polarizabilities exhibit peaks near the transition state. In the case of X=F these peaks are on the products side and in the case of X=Cl they are on the reactants side indicating an early transition state in the case of fluorine and a late transition state in the case of chlorine. An analysis of the geometric changes along the reaction paths reveals a one-to-one correspondence between the peaks in the electric properties and peaks in the rate of change of certain internal geometric coordinates along the reaction path. Interaction with short infrared intense laser fields pulses leads to the possibility of interferences between the dipole and polarizability laser-molecule interactions as a function of laser phase. The larger dipole moment in the Cl+CH4 reaction can lead to the creation of deep wells (instead of energy barriers) and new strongly bound states in the transition state region. This suggests possible coherent control of the reaction path as a function of the absolute phase of the incident field, by significant modification of the potential surfaces along the reaction path and, in particular, in the transition state region.
Coherent switching with decay of mixing: An improved treatment of electronic coherence for non-Born–Oppenheimer trajectories
Authors: Zhu Chaoyuan , Nangia Shikha , Jasper Ahren W. , Truhlar Donald G.
Published: October 2004

The self-consistent decay-of-mixing (SCDM) semiclassical trajectory method for electronically nonadiabatic dynamics is improved by modifying the switching probability that determines the instantaneous electronic state toward which the system decoheres. This method is called coherent switching with decay of mixing (CSDM), and it differs from the previously presented SCDM method in that the electronic amplitudes controlling the switching of the decoherent state are treated fully coherently in the electronic equations of motion for each complete passage through a strong interaction region. It is tested against accurate quantum mechanical calculations for 12 atom-diatom scattering test cases. Also tested are the SCDM method and the trajectory surface hopping method of Parlant and Gislason that requires coherent passages through each strong interaction region, and which we call the “exact complete passage” trajectory surface hopping (ECP-TSH) method. The results are compared with previously presented results for the fewest switches with time uncertainty and Tully’s fewest switches (TFS) surface hopping methods and the semiclassical Ehrenfest method. We find that the CSDM method is the most accurate of the semiclassical trajectory methods tested. Including coherent passages improves the accuracy of the SCDM method (i.e., the CSDM method is more accurate than the SCDM method) but not of the trajectory surface hopping method (i.e., the ECP-TSH method is not more accurate on average than the TFS method).
Molecular theory of dielectric relaxation in nematic dimers
Authors: Stocchero M. , Ferrarini A. , Moro G. J. , Dunmur D. A. , Luckhurst G. R.
Published: October 2004

This paper reports a theory for the dielectric relaxation of dimeric mesogenic molecules in a nematic liquid crystal phase. Liquid crystal dimers consist of two mesogenic groups linked by a flexible chain. Recent experimental studies [D. A. Dunmur, G. R. Luckhurst, M. R. de la Fuente, S. Diez, and M. A. Perez Jubindo, J. Chem. Phys. 115, 8681 (2001)] of the dielectric properties of polar liquid crystal dimers have found unexpected results for both the static (low frequency) and variable frequency dielectric response of these materials. The theory developed in this paper provides a quantitative model with which to understand the observed experimental results. The mean-square dipole moments of α,ω-bis[(4-cyanobiphenyl-4′-yl]alkanes in a nematic phase have been calculated using both the rotational isomeric state model and a full torsional potential for the carbon-carbon bonds of the flexible chain. The orienting effect of the nematic phase is taken into account by a parametrized potential of mean torque acting on the mesogenic groups and the segments in the flexible chain. Results of calculations using the full torsional potential are in excellent agreement with experimental results for comparable systems. The probability density peq(βA,βB) for the orientation of the mesogenic groups (A,B) along the nematic director is also calculated. The resultant potential of mean torque is a surface characterized by four deep energy wells or sites equivalent to alignment of the terminal groups A and B approximately parallel and antiparallel to the director; of course, the reversal of the director leads to equivalent sites. This potential energy surface provides the basis for a kinetic model of dielectric relaxation in nematic dimers. Solution of the Fokker-Planck equation corresponding to this four-site model gives the time dependence of the site populations, and hence the time-correlation functions for the total dipole moment along the director. In this model the end-over-end rotation of the molecule, corresponding to simulataneous reversal of both mesogenic groups, is excluded because the activation energy is too large. Results are presented for a number of cases, in which a dipole is located on one or both of the mesogenic groups, and additionally where the groups differ in size. For the latter, under particular conditions, the correlation function exhibits a biexponential decay, which corresponds to two low frequency absorptions in the dielectric spectrum. This is exactly what has been observed for nonsymmetric nematic dimers having different groups terminating a flexible chain. Experimental results over a range of temperature for the nonsymmetric dimer α-[(4-cyanobiphenyl)-4′-yloxy]-ω-(4-decylanilinebenzylidene-4′-oxy)nonane can be fitted precisely to the theory, which provides new insight into the orientational and conformational dynamics of molecules in ordered liquid crystalline phases.