bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub- or Intertrochanteric Fracture Following Screw Fixation of an Intracapsular Proximal Femoral Fracture: True Complication or Technical Error?
Authors: Pelet  , Leyvraz  , Garofalo  , Borens  , Mouhsine
Published: January 2006

Purpose: To review, retrospectively, the possible causes of sub- or intertrochanteric fractures after screw fixation of intracapsular fractures of the proximal femur. Methods: Eighty-four patients with an intracapsular fracture of proximal femur were operated between 1995 and 1998 by using three cannulated 6.25mm screws. The screws were inserted in a triangular configuration, one screw in the upper part of the femoral neck and two screws in the inferior part. Between 1999 and 2001, we use two screws proximally and one screw distally. Results: In the first series, two patients died within one week after operation. Sixty-four fractures healed without problems. Four patients developed an atrophic non-union; avascular necrosis of the femoral head was found in 11 patients. Three patients (3.6%) suffered a sub- and/or intertrochanteric fracture after a mean postoperative time of 30 days, in one case without obvious trauma. In all three cases surgical revision was necessary. Between 1999 and 2001 we did not observe any fracture after screwing. Conclusion: Two screws in the inferior part of the femoral neck create a stress riser in the subtrochanteric region, potentially inducing a fracture in the weakened bone. For internal fixation for proximal intracapsular femoral fracture only one screw must be inserted in the inferior part of neck.
Coil-Embolization of the Splenic Artery after a Penetrating Gunshot Injury
Authors: Schertler  , Pfammatter  , Eid  , Wildermuth
Published: January 2006

Die moderne Computer-Tomographie (CT) ist heutzutage für das Management schwerverletzter Patienten im Notfall nicht mehr wegdenkbar. Zudem ist die abdominelle CT eine zuverlässige Methode zur Identifizierung von Milzverletzungen und kann weitere intraabdominelle oder thorakale Verletzungen ausschliessen. Stumpfe und penetrierende Milzverletzungen benötigen unverzüglich therapeutische Massnahmen. Prinzipiell gelten als Voraussetzungen für eine nicht-operative Therapie die hämodynamische Stabilität des Patienten, das Fehlen zusätzlicher Verletzungen der abdominellen Hohlorgane und des Schädels sowie das Fehlen vorangegangener Baucheingriffe. Die konventionelle Angiographie kann einerseits zur Diagnosestellung und anderseits zur Embolisierung traumatisch bedingter Verletzungen der Milzgefässe sämtlicher Schweregrade, welche mittels CT diagnostiziert und nicht-operativ therapiert wurden, verwendet werden. Der vorliegende Fall demonstriert einen Patienten mit Schussverletzung des linken Hemiabdomens. Aufgrund der hämodynamischen Stabilität des Patienten sowie der persönlichen Anamnese mit bereits stattgehabtem abdominellen Eingriff und aufgrund fehlender weiterer Verletzungen des Abdomens und des Schädels wurde ein nicht-operativer Therapieansatz gewählt mit Embolisierung der proximalen Milzarterie.
Spontaneous Splenic Rupture - A Rare Complication of Amyloidosis
Authors: Khan  , Escofet  , Roberts  , Salman
Published: January 2006

We present a case of spontaneous rupture of the spleen, an uncommon complication of systemic amyloidosis. Amyloid deposition leading to capsular distension and increased vascular fragility is thought to predispose the spleen to rupture spontaneously.
Factors Influencing Healing of Anastomoses
Authors: Wagner  , Egger
Published: January 2006

In der Darmchirurgie ist die Anastomoseninsuffizienz eine der am meisten gefürchteten und bedeutendsten Komplikation. Die Rate der klinisch manifesten, intestinalen Anastomoseninsuffizienz liegt je nach Literatur zwischen 3.4% und 12%, und mindestens ein Drittel der perioperativen Mortalität ist auf ein Leck im Bereiche der Anastomose zurückzuführen. In diesem Kontext erscheinen die Kenntnisse der Faktoren, welche die Anastomosenheilung beeinflussen umso bedeutender. Neben chirurgisch-technischen (Nahttechnik, Nahtmaterial) und chirurgisch-taktischen Faktoren (primäre Anastomose vs. Diskontinuitätsoperation oder protektives Stoma usw.), sind die Kenntnisse der endogenen (Diabetes, Infektion, Sepsis, Malnutrition und andere) und exogenen Faktoren (Steroide, Strahlentherapie, Darmvorbereitung und andere), welche die Anastomosenheilung begünstigend bzw. beeinträchtigend beeinflussen, entscheidend. Um diese Faktoren identifizieren zu können, sind Studien im Tiermodell und auch Qualitätskontrollen bei den eigenen Patienten ungemein wichtig. Kürzlich konnte z.B. gezeigt werden, dass Mycophenolat Mofetil (Cellcept, MMF), ein Immunsuppressivum, welches vor allem in der Transplantation und auch bei chronisch entzündlichen Erkrankungen eingesetzt wird, eine nachweislich beeinträchtigende Wirkung auf die mechanische Stabilität der heilenden Anastomose hat. Im Gegensatz dazu führen z.B. Keratinozytenwachstumsfaktor (KGF) und Insulin-ähnlicher Wachstumsfaktor-I (IGF-I) zu einer Beschleunigung der Anastomosenheilung mit deutlicher Verbesserung der frühpostoperativen mechanischen Stabilität im Tiermodell. Diese Studien zur Identifizierung von weiteren, die Anastomosenheilung beeinflussenden Faktoren und Medikamenten sind von Bedeutsamkeit, weil sie grosse klinische Implikationen haben könnten. Die traditionelle Anlage von protektiven Ileostomatas nach koloanalen und ileopouch-analen Anastomosen, sowie Diskontinuitätsresektionen nach Hartmann, könnten selbst bei immunsupprimierten und anderen Hochrisiko-Patienten vermieden werden.
The Continuous Single-Layer Anastomosis in the Gastrointestinal Tract
Authors: Steinke  , Leippold  , Schweizer
Published: January 2006

Über die Frage der besten oder "richtigen" Technik bei gastrointestinalen Anastomosen wird seit je diskutiert. Die Ansprüche an eine gute Anastomosentechnik sind: Gute Durchblutung, Wasserdichtigkeit, Spannungsfreiheit, Sicherheit, leichte Durchführbarkeit, wenig Unruhe und Verschmutzung im Operationsgebiet und geringe Kosten. Die Operationstechnik der extramukösen, fortlaufenden Anastomosentechnik im Gastrointestinaltrakt wird in Wort und Bild erläutert. Anhand einer Pilotstudie, einer randomisierten Vergleichsstudie, einer Schweizer Multizenterstudie und schliesslich einer 5-jährigen Qualitätskontrollstudie wird gezeigt, dass diese "Schweizer"-Technik allen Anforderungen zur Durchführung einer "idealen" Anastomose gerecht wird und an fast allen intestinalen Lokalisationen verwendet werden kann.
Significance of Medical Therapy in Inflammatory Bowel Disease
Authors: Seibold
Published: January 2006

Der akute Schub einer chronisch entzündlichen Darmerkrankung wird primär medikamentös behandelt. Dabei kommen in der Regel Cortisonpräparate, bei leichteren Schüben auch 5-Aminosalizylate zum Einsatz. Der anti-TNF alpha-Antikörper Infliximab kann bei therapierefraktären Crohn-Patienten verwendet werden. Die Rezidivrate ist nach medikamentöser und chirurgischer Therapie sehr hoch. Aus diesem Grunde sollte bei Patienten mit häufigen Schüben oder aggressivem Verlauf frühzeitig eine remissionserhaltende Therapie mit Immunsuppressiva (Azathioprin, 6-Mercaptopurin, Methotrexat) eingeleitet werden. Bei Patienten mit Colitis ulcerosa sollte die Remissionserhaltung primär durch 5-Aminosalizylate erfolgen. Zur Therapie der Fisteln beim M.Crohn stehen neben der Chirurgie Immunsuppressiva, Antibiotika und Infliximab zur Verfügung.
Standard Procedure in Colorectal Cancer Surgery
Authors: Buchmann
Published: January 2006

Wer über Standards schreibt, muss sich zunächst fragen: was ist ein Standard, wie kommt er zustande, wer legt ihn fest und wie verbindlich ist er? Ein Standard darf nur als Richtschnur oder als Bereich zwischen Leitplanken, niemals aber als Dogma verstanden werden, da sonst jeder operativ technische oder therapeutische Fortschritt verhindert wird. Anhand der onko-chirurgischen Richtlinien für das Kolorektalkarzinom wird dargelegt, wie Standards ins Wanken geraten können. Die nach Turnbull benannte "no-touch isolation technique" hält den Kriterien der Evidence-based Medicine nicht stand. Der Nutzen einer hohen Venenligatur und der Darmocclusion sind durch keine Studien belegt und die zentrale Ligatur der Arteria mesenterica inferior bei der Linksresektion nach neueren anatomischen Erkenntnissen falsch. Durch die aortennahe Absetzung kommt es zwangsläufig zur Verletzung des Plexus hypogastricus. Tierexperimentelle Untersuchungen sind in Bezug auf die Tumorzellaussaat beim Quetschen des Krebses kontrovers. Und eine prospektive kontrollierte Studie zeigt keinen Vorteil der Einhaltung der Turnbull-Kriterien. Unabhängige prognostische Faktoren sind der Chirurg, die Häufigkeit der Durchführung eines Eingriffes im jeweiligen Spital, das pT- und N-Stadium, die R-0-Resektion und nach den amerikanischen Pathologen der präoperative CEA-Titer. Im Weiteren werden die Infiltration von Venen und Lymphbahnen, Mikrometastasen in Lymphknoten und das Grading erwähnt. Die Resektion soll wenn immer möglich in anatomischen Schichten stattfinden, was vor allem für das Mesorektum zutrifft. Was in den distalen 8cm bis zum Beckenboden zu geschehen hat, ist bis heute nicht geklärt. Hingegen hat die laparoskopische Technik auch in der onkologischen Chirurgie definitiv Einzug gehalten. Die Diskussionen um Port-Metastasen und Tumorzelldissemination durch das Pneumoperitoneumgas sind verstummt. Bereits werden zum Teil bessere Langzeitergebnisse erwähnt. Die Eckpfeiler der Standardtechnik der onkologischen Kolorektalchirurgie sind Anfang 2003 bei uns neben der orthograden Darmspülung, der präoperativen niedermolekularen Heparinisierung und Antibiotikaprophylaxe, die R-0 en bloc-Resection offen oder laparoskopisch, der minimale Sicherheitsabstand im tiefen Rektum von 1cm, die Ligatur der Arteria mesenterica inferior 2 bis 3cm distal des Abganges aus der Aorta bei der Linksresektion, respektive der Arteria ileocolica am Abgang aus der Arteria mesenterica superior bei der Rechtsresektion, die zytotoxische Darmspülung bei der Linksresektion, und die Ausspülung der Abdominalhöhle sowie der Troicart-Kanäle mit Taurolin 0.5%. Eine neoadjuvante Radio-Chemotherapie wird beim Rektumkarzinom uT3 oder uN+, und eine adjuvante Chemotherapie beim nodal positiven Kolonkarzinom durchgeführt.
Intestinal Barotrauma in a SCUBA Diver - Mechanical Small Bowel Obstruction after Strangulation of the Last Ileal Loop Between a Mobile Caecum and a Long Sigmoid Loop
Authors: Haller  , Guenot  , Azagury  , Rosso
Published: January 2006

Quelques heures après une plongée sous-marine à 30 mètres de profondeur, un homme de 49 ans a présenté des douleurs abdominales diffuses avec des nausées et des vomissements. Une laparotomie a été pratiquée à 36 heures d'évolution d'un traitement conservateur en raison d'un iléus mécanique du grêle persistant. Elle a montré une incarcération du grêle distal entre un caecum mobile et une longue boucle sigmoïdienne chez ce patient sans antécédents chirurgicaux. Compte tenu de l'absence de souffrance intestinale, seule une caecopexie a été pratiquée et l'évolution post-opératoire a été simple. La distension des gaz intestinaux pendant la remontée suivant la loi de Boyle-Mariotte et leur répartition a provoqué chez ce patient avec une anatomie particulière un iléus mécanique du grêle. Le traitement du caecum mobile et la littérature des barotraumatismes abdominaux en plongée sous-marine ont été revus.
Idiopathic Spontaneous Haemoperitoneum
Authors: Vionnet  , Rostan
Published: January 2006

L'hémopéritoine est habituellement associé aux traumatismes, à la rupture d'un anévrisme, à une grossesse extra-utérine, à un follicule ovarien hémorragique ou à une tumeur hépatique. L'hémopéritoine spontané idiopathique est une pathologie extrêmement rare qui se manifeste le plus souvent par des douleurs abdominales diffuses, associées à une instabilité hémodynamique qui peut aller jusqu'au collapsus vasculaire. Nous décrivons le cas d'une jeune patiente de 28 ans avec un hémopéritoine spontané idiopathique qui s'est manifesté par un syndrome douloureux de la fosse iliaque droite. Nous présentons une revue de la littérature sur cette entité pathologique rare que représente l'hémopéritoine spontané et proposons une attitude face à cette affection dont le diagnostic repose souvent sur un fort index de suspicion, en raison de symptômes parfois peu pathognomoniques.
Severe Gastrointestinal Bleeding with Rupture of Anastomosis as a Result of Pseudoaneurysm of Common Hepatic Artery Following Pancreato-Duodenectomy
Authors: Specker  , Wildisen  , von Flüe
Published: January 2006

Die Chirurgie des Pankreas- und Choledochuskarzinoms erfordert zwecks Radikalität und korrektem Staging eine ausgedehnte Lymphadenektomie des Ligamentum hepatoduodenale mit Ausräumung des Kompartimentes II. Infolge Skelettierung oder enzymatischer Autodigestion kann ein Pseudoaneurysma der peripankreatischen Arterien entstehen. Die Ruptur eines solchen Pseudoaneurysmas führt zu einer schweren oberen Gastrointestinalblutung. Nur wenige Fälle dieser schweren Komplikation sind in der Literatur beschrieben.
The Sorin Pericardial Bioprosthesis: The Stentless Aortic Valve with Excellent Hemodynamic Performance
Authors: Gegouskov  , Eckstein  , Kipfer  , Berdat  , Immer  , Schmidli  , Seiler  , Zobrist  , Carrel
Published: January 2006

Fragestellung: Die Sorin PericarbonTM Freedom Stentless Aortenklappe verfügt über eine sehr gute hämodynamische Funktion und eine hohe Widerstandsfähigkeit. In dieser Studie stellen wir die früh- und mittelfristigen Resultate mit dieser Klappenprothese vor. Methodik: 31 konsekutive Patienten (16 Frauen und 15 Männer) wurden nach Implantation einer Sorin PericarbonTM Freedom Stentless Aortenklappe untersucht. Das mittlere Lebensalter betrug 64 +/- 17 Jahre. Präoperativ litten fünf Patienten an einer isolierten Aortenklappenstenose, drei Patienten an einer isolierten Aortenklappeninsuffizienz, ein Patient wies ein kombiniertes Aortenvitium auf. Drei Patienten hatten zusätzlich eine Mitralklappeninsuffizienz, 14 Patienten eine koronare Herzkrankheit und ein Patient eine kongenitale Aortenisthmusstenose. Bei drei Patienten bestand eine akute Aortenklappenendokarditis. 18 Patienten wurden als Hoch-Risiko-Patienten (EuroSCORE 9 +/- 2) klassifiziert. Die mittlere linksventrikuläre Auswurfsfraktion betrug 52.5 +/- 15.0%. Ergebnisse: Alle implantierten Klappenprothesen wurden, bezogen auf die intraoperative Anulusausmessung, um 2mm grösser gewählt. 16 Patienten erhielten isolierte Klappenersatzoperationen. Als Zusatzeingriffe wurden drei Mitralklappenrekonstruktionen, 12 aorto-koronare Bypass-Operationen und eine Resektion einer Aortenisthmusstenose in Kombination mit einem VSD-Verschluss durchgeführt. Drei Eingriffe waren Re-Operationen. Die postoperative Früh-Mortalität war 6.4% (zwei Hoch-Risiko-Patienten). Beide Todesfälle waren nicht klappenbedingt. Vier Patienten entwickelten postoperativ ein Low-Output-Syndrom und erhielten eine intra-aortale Ballon-Pumpe. Die sechs Monate postoperativ durchgeführte Echokardiographie erbrachte tiefe transvalvuläre Mean- und Peak-Gradienten (9.6 +/- 4.4 bzw. 20.6 +/- 5.9mmHg) sowie eine signifikante Regression der linksventrikulären Hypertrophie(linksventrikulärer Massenindex 126.5 +/- 27.3 vs. 189.6 +/- 45.3g/m2, p = 0.0313) und eine Verbesserung der systolischen Auswurfsfraktion (58 +/- 9.8 vs. 52.5 +/- 15.0%, p = 0.9749). Schlussfolgerungen: Die Sorin PericarbonTM Freedom Stentless Aortenklappe zeigte eine hervorragende hemodynamische Funktion, die nach sechs Monaten durch tiefe transvalvulären Gradienten, Regression der linksventrikulären Hypertrophie sowie Anstieg der systolischen Auswurfsfraktion charakterisiert ist. Aussagen bezüglich Lebensdauer und Abnützung des biologischen Gewebes können erst nach Durchführung von Langzeit-Untersuchungen erhoben werden.
Frequency of Trainee Operations in General Surgery at a Non-University Teaching Hospital
Authors: Derungs  , Nussbaumer  , Sommer  , Leutenegger  , Furrer
Published: January 2006

Einleitung: Auch nach Einführung des neuen Weiterbildungsreglements zum Facharzt Chirurgie, stellt die Erfüllung des Operationskatalogs die wohl wichtigste Anforderung dar. Anhand unserer Operationszahlen soll untersucht werden, ob an einer nicht-universitären Ausbildungsklinik der Kategorie A die Facharztanwärter (= Assistenzärzte ohne Facharzt-Titel) mit unserem gegenwärtigen Konzept die geforderten Eingriffe durchführen können. Methode: Für acht Tracereingriffe wurden die Fallzahlen der nicht zusatzversicherten Patienten im Zeitraum 1998-2002 retrospektiv erfasst und bezüglich Weiterbildungsstand des Operateurs untersucht. Das Team umfasste in diesem Zeitraum insgesamt 51 Assistenzärzte (71 Weiterbildungsjahre), davon 18 Facharzt-Anwärter (35 Weiterbildungsjahre, inklusive Rotationen auf die Intensivstation, den Notfall und in andere chirurgische Fachbereiche, wie z.B. die Urologie). Resultate: Bezüglich aller Tracereingriffe werden die Medianwerte (= Anzahl Eingriffe pro Ausbildungsjahr pro Facharztanwärter) erreicht, welche zur Erfüllung des Ausbildungsziels im Sinne der "Chirurgie des Häufigen" nach vier Jahren Weiterbildung nötig sind: Appendektomie 8.9, laparoskopische Cholezystektomie 7.3, offene Inguinalhernienoperation 9.4, Varizenoperation 12.1, offene Sigmaresektion 3.2, Osteosynthesen hüftnahe Fraktur und Malleolarfraktur 6.9, Strumektomie 5.0. Schlussfolgerung: Die Weiterbildungsziele im Hinblick auf die Erfüllung des Operationskataloges wurden erreicht. Mit einer weiterhin konsequenten Umsetzung unseres strukturierten Weiterbildungskonzeptes und gleichbleibenden Fallzahlen dürften die Anforderungen an unsere chirurgische Weiterbildungsstätte auch in Zukunft erfüllt werden können. Noch nicht absehbar ist, inwieweit sich die neuen Arbeitsverträge mit der Arbeitszeitreduktion auf die Facharztausbildung auswirken werden.
Fuzzy unit hydrograph
Authors: Bárdossy András , Mascellani Gianluca , Franchini Marco
Published: January 2006

The unit hydrograph method, frequently used for representing the rainfall‐runoff transformation, is subject to a number of uncertainties related both to the model assumption and data acquisition, despite them usually being disregarded. A methodology to account for these uncertainties based on the fuzzy approach is proposed and illustrated. It is assumed that the unit hydrograph can be represented through a fuzzy schematization, and effective precipitation is also considered a fuzzy series; by applying the extension principle to the convolution integral a fuzzy runoff is obtained. In particular, the Nash cascade parametric form of the unit hydrograph is used, and its parameters are considered fuzzy numbers. The general methodology and the assessment of the parameters are explained using a case study relevant to the subcatchments of the Neckar catchment (southwest Germany). The proposed procedure enables bands to be calculated that describe the range of possible hydrographs for predefined h levels. The uncertainty in the runoff calculation is thus represented in terms of fuzzy vagueness by the width of these bands. The bands decrease with the increase of the h level. The calibrated parameters are then used with the extension principle for calculating the vagueness of different runoff characteristics, such as flood peak discharge and time to peak, as fuzzy numbers.
Assessing measurement uncertainty of first‐order degradation rates in heterogeneous aquifers
Authors: Bauer Sebastian , Beyer Christof , Kolditz Olaf
Published: January 2006

The principal idea of this paper is to simulate and evaluate the determination of first‐order degradation rate constants at heterogeneous contaminated sites under realistic conditions. First, a set of heterogeneous and contaminated synthetic aquifers is generated; second, the spreading of a solute plume subject to first‐order degradation is simulated. Third, this plume is investigated using “monitoring wells” placed along the presumed plume center line. Using only piezometric heads, concentrations and hydraulic conductivities obtained at these monitoring wells, first‐order degradation rate constants are calculated by methods typically used in field applications. The estimated rate constants are compared to the “real” value known from the simulations. This comparison is conducted for different degrees of heterogeneity, represented by lognormally distributed random conductivity fields. The results indicate that, with increasing degree of heterogeneity, “measured” degradation rate constants become uncertain with a high variability around the true constant. Measured rate constants tend to overestimate the true constant by up to one order of magnitude. A sensitivity analysis of the influences of source width, transport velocity, and dispersivity shows that (1) with increasing source width, measured rate constants decrease their relative error and increase their accuracy; (2) the choice of dispersivity can produce both over‐ and under‐estimation of the true rate constant; and (3) that large‐scale measurements of hydraulic conductivity yield better estimates of flow velocities as compared to local scale measurements. These results explain in part the high variability of field measured degradation rate constants reported in the literature.
Lithospheric flexure and the evolution of the dichotomy boundary on Mars
Authors: Watters Thomas R. , McGovern Patrick J.
Published: January 2006

The boundary of the Martian crustal dichotomy in the eastern hemisphere is one of the most striking topographic features on the planet. The long wavelength topography of much of the boundary is expressed by a broad rise and an arched ramp that slopes downward from the southern highlands into the northern lowlands and often ends in a steep scarp. Lithospheric flexure of the southern highlands for both a continuous and broken plate boundary with the northern lowlands lithosphere is modeled. We find that the long wavelength topography of the boundary is best fit by a lithospheric deflection profile of a broken lithosphere for reasonable values of the flexural parameter. The lithosphere near the dichotomy boundary may have been weakened by tectonic stress associated with the formation of the crustal dichotomy by subcrustal transport caused by overturn of an early magma ocean.
Static stability of the Jovian atmospheres estimated from moist adiabatic profiles
Authors: Sugiyama Ko‐ichiro , Odaka Masatsugu , Kuramoto Kiyoshi , Hayashi Yoshi‐Yuki
Published: January 2006

The dependency of static stability N2 of the Jovian atmospheres on the abundances of condensible elements is considered by calculating the moist adiabatic profiles. An optimal minimization method of the Gibbs free energy is utilized to obtain equilibrium compositions in order to cover a variety of basic elements. It is shown that CH4 is one of the dominant contributors to producing a stable layer in the Uranian atmosphere. On Jupiter, R. K. Achterberg and A. P. Ingersoll (1989) have shown that, at low water abundances, N2 is proportional to the H2O abundance. In the present study, we show that this relationship does not hold when the H2O abundance is larger than approximately 5 × solar. A rough estimation of wave speed indicates that the abundance of 10 × solar is marginal to explain the SL9‐induced wave speed as that of an internal gravity wave.
Characteristics of sea ice floe size distribution in the seasonal ice zone
Authors: Toyota Takenobu , Takatsuji Shinya , Nakayama Masashige
Published: January 2006

The size distribution of sea ice floes was observed by coordinated Landsat imagery and video monitoring conducted from an icebreaker and a helicopter for an area 38 km × 26 km in seasonal sea ice in the southern Sea of Okhotsk in February 2003. The combination of imagery on several scales allowed measurements of ice floes over three orders of magnitude, from 1 m to 1.5 km. Two different regimes were observed: floes larger than about 40 m have a power‐law number density with an exponent of −1.87, in the lower range of earlier results. Below 40 m, the power law exponent is −1.15. The cause of these two different regimes is hypothesized to lie in the effects of swell on floes of different sizes and thicknesses. The importance of the floe size distribution for lateral melting is elucidated.
Use of a portable topographic mapping millimetre wave radar at an active lava flow
Authors: Macfarlane D. G. , Wadge G. , Robertson D. A. , James M. R. , Pinkerton H.
Published: January 2006

A ground‐based millimetre wave radar, AVTIS (All‐weather Volcano Topography Imaging Sensor), has been developed for topographic monitoring. The instrument is portable and capable of measurements over ranges up to ∼7 km through cloud and at night. In April and May 2005, AVTIS was deployed at Arenal Volcano, Costa Rica, in order to determine topographic changes associated with the advance of a lava flow. This is the first reported application of mm‐wave radar technology to the measurement of lava flux rates. Three topographic data sets of the flow were acquired from observation distances of ∼3 km over an eight day period, during which the flow front was detected to have advanced ∼200 m. Topographic differences between the data sets indicated a flow thickness of ∼10 m, and a dense rock equivalent lava flux of ∼0.20 ± 0.08 m3s−1.
Features of glacial valley profiles simply explained
Authors: Anderson Robert S. , Molnar Peter , Kessler Mark A.
Published: January 2006

Glacial occupation of alpine valleys results in a distinct signature in the long‐valley profile, including steepening of the profile in the headwaters, flattening at lower elevations, and a step in the profile at the convergence of headwater tributaries. We present analytic results for glacial erosion patterns by making the following assumptions: (1) the initial profile is linear, (2) the width of the valley is uniform, (3) the annual mass balance varies linearly with elevation, (4) the glacier at any time is quasi‐steady, (5) the erosion rate is proportional to ice discharge per unit valley width, and (6) glacial erosion rates far exceed fluvial erosion rates. A steady glacier under these conditions would erode a parabolic divot in the longitudinal valley profile, with its maximum depth coinciding with the down‐valley position of the equilibrium line altitude (ELA). The calculated flattening of the valley floor down valley of the ELA and the steepening of it up valley captures the essence of the glacial signature. When a reasonable probability distribution of ELAs is allowed, the predicted erosion peaks at 30–40% of the down‐valley distance to the glacial limit, and the pattern merges smoothly with the steeper fluvial profile downstream of the glacial limit. Profiles of mass balance that are capped at a maximum value produce shorter glaciers and a slight asymmetry in the expected erosion pattern. Only when we mimic the tributaries of glacial headwaters by specifying a valley width distribution do we obtain the upper step observed in many valley profiles.
Interpolating moving least-squares methods for fitting potential-energy surfaces: Further improvement of efficiency via cutoff strategies
Authors: Kawano Akio , Tokmakov Igor V. , Thompson Donald L. , Wagner Albert F. , Minkoff Michael
Published: January 2006

In standard applications of interpolating moving least squares (IMLS) for fitting a potential-energy surface (PES), all available ab initio points are used. Because remote ab initio points negligibly influence IMLS accuracy and increase IMLS time-to-solution, we present two methods to locally restrict the number of points included in a particular fit. The fixed radius cutoff (FRC) method includes ab initio points within a hypersphere of fixed radius. The density adaptive cutoff (DAC) method includes points within a hypersphere of variable radius depending on the point density. We test these methods by fitting a six-dimensional analytical PES for hydrogen peroxide. Both methods reduce the IMLS time-to-solution by about an order of magnitude relative to that when no cutoff method is used. The DAC method is more robust and efficient than the FRC method.
Polyene photoisomerization rates: Are they distinct in aqueous block copolymer micellar solutions and gels?
Authors: Mali K. S. , Dutt G. B. , Mukherjee T.
Published: January 2006

Photoisomerization of 3,3′-diethyloxadicarbocyanine iodide (DODCI) has been investigated in water, 5% and 30% aqueous triblock copolymer, poly(ethylene oxide)20−poly(propylene oxide)70−poly(ethylene oxide)20 (P123) by measuring the fluorescence quantum yields and lifetimes in the temperature range 293–318 K. Reports available in literature indicate that 5% aqueous P123 exists as micellar solution, whereas 30% aqueous P123 forms gel due to micelle-micelle entanglement. This study has been undertaken to find out how the polyene photoisomerization rates are influenced in the sol and gel phases. It has been observed that 60%–70% of DODCI is located in the palisade layer of the micelles in the sol as well as gel phases and the photoisomerization rate of this component is identical in both the phases at a particular temperature. The remainder of the probe is located in the interfacial region and isomerization rates of this fraction are slower by a factor of 1.4–1.1 in the gel phase compared with the micellar solution. The retardation of the isomerization rate in the gel phase has been explained on the basis of enhancement in the friction experienced by the probe due to micelle-micelle entanglement at the interface. Compared to the isomerization rates in water, the rates of photoisomerization of DODCI located in the palisade layer, interfacial region of micellar solution, and interfacial region of the micelles in the gel phase are slower by factors of 3.5, 1.5–1.9, and 2, respectively. The outcome of this study validates the point that in organized media photoisomerization rates are sensitive to the localized friction, which is not uniform unlike in a homogeneous solution.
Spectroscopic and spin-orbit calculations on the SO+ radical cation
Authors: Ben Houria A. , Ben Lakhdar Z. , Hochlaf M.
Published: January 2006

Highly correlated ab initio methods were used in order to generate the potential-energy curves of the SO+ electronic states correlating to S+(Su4)+O(Pg3) and S+(Du2)+O(Pg3). These curves were used for deducing accurate spectroscopic properties for these electronic states. Our calculations predict the existence of a Φ2 state lying close in energy to the well-characterized b̃Σ−4 state and several weakly bound quartet and doublet states located in the 6–9 eV internal energy range not identified yet. The spin-orbit integrals between these electronic states were evaluated using these highly correlated wave functions, allowing the discussion of the metastability and the predissociation processes forming S++O in their electronic ground states. Multistep spin-orbit-induced predissociation pathways are suggested. More specifically, the experimentally determined dissociative potential-energy curve [H. Bissantz et al., Z. Phys. D 22, 727 (1992)] proposed to explain the rapid SO+(b̃Σ−4,v⩾13)→S+(Su4)+O(Pg3) reaction is found to coincide with the 2Π4 potential-energy curve for short internuclear distances and with the repulsive 1Π6 state for longer internuclear separations.
Phase formation and work function tuning in fully silicided Co–Ni metal gates with variable Co:Ni ratios
Authors: Liu J. , Kwong D. L.
Published: January 2006

Dual work function metal gates fabricated by full silicidation of a Co–Ni bilayer with different Co:Ni ratios were investigated by both physical and electrical measurements. Full silicidation, sheet resistance and phase confirmation of CoxNi1−xSi2 were studied by physical characterizations. Complementary metal-oxide-semiconductor work functions were extrapolated by electrical characterization and correlated with dopant accumulation at the gate/oxide interface. The quality of underlying oxide was measured by gate leakage current density and found to be impacted by the Co:Ni ratio in CoxNi1−xSi2.
Wide-band gap oxide alloy: BeZnO
Authors: Ryu Y. R. , Lee T. S. , Lubguban J. A. , Corman A. B. , White H. W. , Leem J. H. , Han M. S. , Park Y. S. , Youn C. J. , Kim W. J.
Published: January 2006

A wide-band gap oxide alloy, BeZnO, is proposed and studied in this letter. The BeZnO films were deposited on sapphire substrates by our hybrid beam deposition growth method. The value of the energy band gap of BeZnO can be efficiently engineered to vary from the ZnO band gap (3.4 eV) to that of BeO (10.6 eV). BeZnO can be used for fabricating films and heterostructures of ZnO-based electronic and photonic devices and for other applications. Changes in the measured energy band gap and lattice constant values with Be content are described for BeZnO alloys.
Local structure around Mn atoms in cubic (Ga,Mn)N thin films probed by fluorescence extended x-ray absorption fine structure
Authors: He Bo , Zhang Xinyi , Wei Shiqiang , Oyanagi Hiroyuki , Novikov Sergei V. , Edmonds Kevin W. , Foxon C. Thomas , Zhou Gui’en , Jia Yunbo
Published: January 2006

The local structures of Mn atoms incorporated in zinc-blende (Ga,Mn)N thin films have been investigated by fluorescence extended x-ray absorption fine structure analysis (EXAFS). The EXAFS results provide direct evidence for the substitution of the majority of Mn atoms in Ga sites of GaN at 2.5% doping. On the other hand, the simulation result of 10% doped (Ga,Mn)N shows that secondary phases—Mn clusters—are formed. The long-range-order crystal structures of (Ga,Mn)N are also studied by x-ray diffraction. The broadening of rocking curve of 10% doped (Ga,Mn)N is attributed to the existence of mosaic block, which resulted from the earlier mentioned secondary phases. How Mn dopants affect the properties of GaN films is discussed as well.
Gas diffusion barriers on polymers using Al2O3 atomic layer deposition
Authors: Groner M. D. , George S. M. , McLean R. S. , Carcia P. F.
Published: January 2006

Thin films of Al2O3 grown by atomic layer deposition (ALD) were investigated as gas diffusion barriers on flexible polyethylene naphthalate and Kapton® polyimide substrates. Al2O3 ALD films with thicknesses of 1–26nm were grown at 100–175°C. For Al2O3 ALD films with thicknesses ⩾5nm, oxygen transmission rates were below the MOCON instrument test limit of ∼5×10−3cc∕m2∕day. Applying a more sensitive radioactive tracer method, H2O-vapor transmission rates of ∼1×10−3g∕m2∕day were measured for single-sided Al2O3 ALD films with thicknesses of 26nm on the polymers. Ultrathin gas diffusion barriers grown by Al2O3 ALD may enable organic displays and electronics on permeable, flexible polymer substrates.
Ba
5
SiO
4
Cl
6
:
Eu
2
+
: An intense blue emission phosphor under vacuum ultraviolet and near-ultraviolet excitation
Authors: Zeng Qinghua , Tanno Hiroaki , Egoshi Kiichirou , Tanamachi Nobutsugu , Zhang Shuxiu
Published: January 2006

An intense blue emission of Eu2+-doped Ba5SiO4Cl6 under vacuum ultraviolet and near-ultraviolet excitation was observed. The material exhibits an emission peak at 440 nm with relative intensity 50% under 147 nm, 90% under 254 nm, 120% under 366 nm, and 220% under 405 nm excitation as compared with the commercial blue phosphor BaMgAl10O17:Eu2+. It is a very promising candidate as a blue-emitting phosphor for potential applications in display and light-emitting diode devices.
Fermi-level pinning at conjugated polymer interfaces
Authors: Tengstedt Carl , Osikowicz Wojciech , Salaneck William R. , Parker Ian D. , Hsu Che-H. , Fahlman Mats
Published: January 2006

Photoelectron spectroscopy has been used to map out energy level alignment of conjugated polymers at various organic-organic and hybrid interfaces. Specifically, we have investigated the hole-injection interface between the substrate and light-emitting polymer. Two different alignment regimes have been observed: (i) Vacuum-level alignment, which corresponds to the lack of vacuum-level offsets (Schottky–Mott limit) and (ii) Fermi-level pinning, where the substrate Fermi level and the positive polaronic level of the polymer align. The observation is rationalized in terms of spontaneous charge transfer whenever the substrate Fermi level exceeds the positive polaron/bipolaron formation energy per particle. The charge transfer leads to the formation of an interfacial dipole, as large as 2.1 eV.
Lifetime-limiting defects in n− 4H-SiC epilayers
Authors: Klein P. B. , Shanabrook B. V. , Huh S. W. , Polyakov A. Y. , Skowronski M. , Sumakeris J. J. , O’Loughlin M. J.
Published: January 2006

Low-injection minority carrier lifetimes (MCLs) and deep trap spectra have been investigated in n− 4H-SiC epilayers of varying layer thicknesses, in order to enable the separation of bulk lifetimes from surface recombination effects. From the linear dependence of the inverse bulk MCL on the concentration of Z1∕Z2 defects and from the behavior of the deep trap spectra in 4H-SiC p-i-n diodes under forward bias, we conclude that it is Z1∕Z2 alone that controls the MCL in this material.
Moments-based tight-binding calculations of local electronic structure in InAs/GaAs quantum dots for comparison to experimental measurements
Authors: Lu Jun-Qiang , Johnson H. T. , Dasika V. D. , Goldman R. S.
Published: January 2006

Local electronic properties of InAs∕GaAs nanostructures are studied using a real-space moments method sp3d5s* tight-binding approach. The order (N) method is unique because it allows for accurate and highly resolved determination of local density of states that accounts for local strain, disorder, and defects, without diagonalization of the full tight-binding Hamiltonian. The effects of free surfaces and strain are first investigated by considering pure, cuboidal GaAs nanostructures. The quantum confinement in an embedded InAs quantum dot is then shown directly through the local densities of states projected on different atoms in the structure. The relationship between effective energy band gap and quantum dot size is mapped onto a simple equation. Finally, the real-space study is applied to quantum dot structures observed experimentally using scanning tunneling microscopy. Atomic positions are obtained from the images and used as input into the tight-binding calculations in order to study interfacial effects on the local electronic structure of real embedded quantum dots.
In situ growth of Co nanofibers in In2O3–SnO2 matrix during sputtering deposition
Authors: Echigoya Jun-ichi , Sano Junichi
Published: January 2006

Co-sputtering onto (001) cubic zirconia from a target of indium tin oxide (ITO) partially covered by cobalt (Co) was carried out at substrate temperatures of 470–770K in order to investigate the growth of Co nanofibers. During film growth, Co forms fibers in the growth direction in the single-crystalline ITO matrix. The cross section of the Co fibers, the size of which depends on the substrate temperature, was a rectangle with an edge 1–5nm in length. The edge length of the Co fiber increased with the increase of the substrate temperature. The present method is attractive for application to produce magnetic recording media.
Minimising cold damage during reproductive development among temperate rice genotypes. II. Genotypic variation and flowering traits related to cold tolerance screening
Authors: Farrell T. C. , Fox K. M. , Williams R. L. , Fukai S. , Lewin L. G.
Published: January 2006

Low temperature during microspore development increases spikelet sterility and reduces grain yield in rice (Oryza sativa L.). The objectives of this study were to determine genotypic variation in spikelet sterility in the field in response to low temperature and then to examine the use of physio-morphological traits at flowering to screen for cold tolerance. Multiple-sown field experiments were conducted over 4 consecutive years in the rice-growing region of Australia to increase the likelihood of encountering low temperature during microspore development. More than 50 cultivars of various origins were evaluated, with 7 cultivars common to all 4 years. The average minimum temperature for 9 days during microspore development was used as a covariate in the analysis to compare cultivars at a similar temperature. The low-temperature conditions in Year 4 identified cold-tolerant cultivars such as Hayayuki and HSC55 and susceptible cultivars such as Sasanishiki and Doongara. After low temperature conditions, spikelet sterility was negatively correlated with the number of engorged pollen grains, anther length, anther area, anther width, and stigma area. The number of engorged pollen grains and anther length were found to be facultative traits as their relationships with spikelet sterility were identified only after cold water exposure and did not exist under non-stressed conditions.
Suppression of gross chromosomal rearrangements by yKu70-yKu80 heterodimer through DNA damage checkpoints
Authors: Banerjee Soma , Smith Stephanie , Myung Kyungjae
Published: January 2006

The inactivation of either subunit of the Ku70-Ku80 heterodimer, which functions in nonhomologous end-joining and telomere maintenance, generates severe defects such as sensitivity to DNA damage, telomere shortening, and increased gross chromosomal rearrangements (GCRs) that are frequently observed in many cancers. To understand the mechanism of Ku as a genome gatekeeper, we overexpressed the yKu70-yKu80 heterodimer and monitored the formation of GCRs. Ku overexpression suppressed the formation of either spontaneously generated GCRs or those induced by treatments with different DNA damaging agents. Interestingly, this suppression depended on Ku’s interaction with DNA damage checkpoints and not through nonhomologous end-joining. We also demonstrate that the inactivation of telomerase inhibitor, Pif1 along with Ku overexpression or the overexpression of Pif1 in either
yku70
or
yku80
strains arrested the cell cycle at S phase in a DNA damage checkpoint-dependent fashion. Lastly, Ku overexpression causes cell growth delay, which depends on intact Rad27. In summary, the results presented here suggest that Ku functions as a genomic gatekeeper through its crosstalk with DNA damage checkpoints.
Prestressed F-actin networks cross-linked by hinged filamins replicate mechanical properties of cells
Authors: Gardel M. L. , Nakamura F. , Hartwig J. H. , Crocker J. C. , Stossel T. P. , Weitz D. A.
Published: January 2006

We show that actin filaments, shortened to physiological lengths by gelsolin and cross-linked with recombinant human filamins (FLNs), exhibit dynamic elastic properties similar to those reported for live cells. To achieve elasticity values of comparable magnitude to those of cells, the
in vitro
network must be subjected to external prestress, which directly controls network elasticity. A molecular requirement for the strain-related behavior at physiological conditionsis a flexible hinge found in FLNa and some FLNb molecules. Basic physical properties of the
in vitro
filamin–F-actin network replicate the essential mechanical properties of living cells. This physical behavior could accommodate passive deformation and internal organelle trafficking at low strains yet resist externally or internally generated high shear forces.
Weighting of experimental evidence in macromolecular structure determination
Authors: Habeck Michael , Rieping Wolfgang , Nilges Michael
Published: January 2006

The determination of macromolecular structures requires weighting of experimental evidence relative to prior physical information. Although it can critically affect the quality of the calculated structures, experimental data are routinely weighted on an empirical basis. At present, cross-validation is the most rigorous method to determine the best weight. We describe a general method to adaptively weight experimental data in the course of structure calculation. It is further shown that the necessity to define weights for the data can be completely alleviated. We demonstrate the method on a structure calculation from NMR data and find that the resulting structures are optimal in terms of accuracy and structural quality. Our method is devoid of the bias imposed by an empirical choice of the weight and has some advantages over estimating the weight by cross-validation.
Chemosensing in
Escherichia coli
: Two regimes of two-state receptors
Authors: Keymer Juan E. , Endres Robert G. , Skoge Monica , Meir Yigal , Wingreen Ned S.
Published: January 2006

The chemotaxis network in
Escherichia coli
is remarkable for its sensitivity to small relative changes in the concentrations of multiple chemical signals. We present a model for signal integration by mixed clusters of interacting two-state chemoreceptors. Our model results compare favorably to the results obtained by Sourjik and Berg with
in vivo
fluorescence resonance energy transfer. Importantly, we identify two distinct regimes of behavior, depending on the relative energies of the two states of the receptors. In regime I, coupling of receptors leads to high sensitivity, while in regime II, coupling of receptors leads to high cooperativity, i.e., high Hill coefficient. For homogeneous receptors, we predict an observable transition between regime I and regime II with increasing receptor methylation or amidation.
Insight into autoproteolytic activation from the structure of cephalosporin acylase: A protein with two proteolytic chemistries
Authors: Kim Jin Kwang , Yang In Seok , Shin Hye Jeong , Cho Ki Joon , Ryu Eui Kyung , Kim Sun Hwa , Park Sung Soo , Kim Kyung Hyun
Published: January 2006

Cephalosporin acylase (CA), a member of the N-terminal nucleophile hydrolase family, is activated through sequential primary and secondary autoproteolytic reactions with the release of a pro segment. We have determined crystal structures of four CA mutants. Two mutants are trapped after the primary cleavage, and the other two undergo secondary cleavage slowly. These structures provide a look at pro-segment conformation during activation in N-terminal nucleophile hydrolases. The highly strained helical pro segment of precursor is transformed into a relaxed loop in the intermediates, suggesting that the relaxation of structural constraints drives the primary cleavage reaction. The secondary autoproteolytic step has been proposed to be intermolecular. However, our analysis provides evidence that CA is processed in two sequential steps of intramolecular autoproteolysis involving two distinct residues in the active site, the first a serine and the second a glutamate.
First molecular and biochemical analysis ofin vivoaffinity maturation in an ectothermic vertebrate
Authors: Dooley Helen , Stanfield Robyn L. , Brady Rebecca A. , Flajnik Martin F.
Published: January 2006

The cartilaginous fish are the oldest phylogenetic group in which Igs have been found. Sharks produce a unique Ig isotype, IgNAR, a heavy-chain homodimer that does not associate with light chains. Instead, the variable (V) regions of IgNAR bind antigen as soluble single domains. Our group has shown that IgNAR plays an integral part in the humoral response of nurse sharks (Ginglymostoma cirratum) upon antigen challenge. Here, we generated phage-displayed libraries of IgNAR V regions from an immunized animal and found a family of clones derived from the same rearrangement event but differentially mutated during expansion. Because of the cluster organization of shark Ig genes and the paucicopy nature of IgNAR, we were able to construct the putative ancestor of this family. By studying mutations in the context of clone affinities, we found evidence that affinity maturation occurs for this isotype. Subsequently, we were able to identify mutations important in the affinity improvement of this family. Because the family clones were all obtained after immunization, they provide insight into thein vivomaturation mechanisms, in general, and for single-domain antibody fragments.