bluuebunny/crossref_metadata_2025 huggingface dataset:
Venous pressure gradients in the lower extremity and the hemodynamic consequences
Authors: Recek
Published: November 2010

Pressure differences play an important role in the hemodynamics of both arterial and venous circulation. Venous ambulatory pressure gradient of about 35 mm Hg arises during the activity of the calf muscle venous pump between the veins in the thigh and the lower leg; this is the initiator launching venous reflux in varicose vein patients. The hemodynamic consequence of venous reflux is interference with the physiological decrease in venous pressure in the lower leg and foot and the occurrence of ambulatory venous hypertension, the degree of which depends on the magnitude of refluxing blood. Pressure difference occurring between the femoral vein and the remnant of great saphenous vein after high ligation or crossectomy during calf pump activity may be the activator of the process leading to the building of new venous communicating channels, the consequence of which is recurrent reflux. Neovascularization is apparently triggered by this hemodynamic factor, not by the surgical procedure itself, because neovascularization does not occur after harvesting of the great saphenous vein in the groin in people without varicose veins. Venous pressure potentials developing in the lower leg during the calf pump activity force the blood to flow from deep into superficial veins during muscle contraction and in the opposite direction during muscle relaxation. An untoward event caused by venous pressure difference is presented - spontaneous bypassing of a competent valve in the saphenous remnant after crossectomy, which converted a favourable hemodynamic situation into a harmful one. Possible explanation of this undesirable event is offered.
Evidence of carotid atherosclerosis in orthopantomograms and the risk for future cardiovascular events
Authors: Hoke  , Schmidt  , Schillinger  , Kluger  , Wiesbauer  , Mlekusch  , Minar  , Schillinger
Published: November 2010

Background: Evidence of carotid atherosclerosis can be detected in 3 to 5 % of orthopantomogram (OPG) investigations. The clinical impact of these findings is unknown. We investigated the association of OPG findings of carotid atherosclerosis with the occurrence of future cardiovascular adverse events. Patients and methods: We randomly selected 411 of 1268 participants with pre-existent cardiovascular disease from the prospective Inflammation in Carotid Arteries Risk for Arthrosclerosis Study (ICARAS) and assessed their OPGs for the presence of calcified atherosclerotic lesions or indirect signs of atherosclerosis, such as surgical clips or intravascular stents. The degree of carotid stenosis was measured by duplex ultrasound investigations. Patients were then followed for median 39 months (interquartile range 33 to 44 months) for the occurrence of major adverse cardiovascular events (MACE) including myocardial infarction, coronary revascularisation, stroke and death. Results: We found no statistically significant association between the presence of carotid atherosclerosis detected on OPGs and the presence of a significant carotid stenosis (left carotid artery kappa = 0.08; right carotid artery kappa = 0.12), or the degree of carotid stenosis (P = 0.20). Furthermore, the presence of OPG signs of carotid atherosclerosis was not statistically significant associated with future MACE (adjusted hazard ratio 0.92, 95 % confidence interval 0.59 to 1.42; P = 0.70). Conclusions: Evidence of carotid plaque revealed by OPGs in patients with previously known cardiovascular disease is no useful prognostic marker for MACE. Detection of carotid atherosclerosis by OPGs in these patients therefore has no clinical consequence.
Endovascular treatment for chronic atherosclerotic occlusive mesenteric disease: Is stenting superior to balloon angioplasty?
Authors: Daliri  , Grunwald  , Jobst  , Szucs-Farkas  , Diehm  , Kickuth  , Do  , Hoppe
Published: November 2010

Background: Endovascular treatment is an increasingly used therapeutic option in patients with chronic atherosclerotic occlusive mesenteric disease. Purpose of this study was evaluation of patency and mortality in patients treated with visceral artery percutaneous transluminal angioplasty (PTA) or stenting including follow-up. Patients and methods: A retrospective review of 17 consecutive patients (4 women, 13 men) with endovascular treatment for symptomatic chronic mesenteric ischemia from 1998 to 2004 was performed. Mean follow-up period was 42 months. Patient demographics, interventional details, primary and/or secondary patency and mortality were recorded. Cumulative mortality and patency rates were determined using Kaplan-Meier life table analysis. Results: Twenty-six interventions (PTA alone n = 13, PTA and stenting n = 13) were performed in 17 patients. Interventions were performed in the superior mesenteric artery (n = 13) and celiac artery (n = 13). The re-intervention rate was 30 % (6/26). Re-interventions were performed for the superior mesenteric artery (n = 4) and celiac artery (n = 2). Cumulative overall 1-year results were primary patency rate 81 %, secondary patency rate 94 %, and survival rate 82 %. Cumulative 10-year results were primary patency rate 73 %, secondary patency rate 94 %, and survival rate 65 %. The 10-year secondary patency rate was 100 % in patients post initial stenting and 86 % in patients post initial PTA. Conclusions: Long-term follow-up post endovascular treatment for chronic mesenteric ischemia demonstrated a considerable overall secondary patency rate of 94 %. However, the long-term secondary patency rate was higher in patients post initial stenting compared to PTA alone.
Endovascular repair of common celiomesenteric trunk stenosis
Authors: Tasleem  , Younas  , Syed  , Mohuiddin
Published: November 2010

A common celiomesenteric trunk (CMT) is one of the several anatomic variations in the mesenteric circulation and occurs when the celiac and superior mesenteric arteries originate from a single common trunk. Because of its rarity, few lesions of the CMT have been reported. We herein present a case of atherosclerotic stenosis of the CMT of an 81-year-old female who presented with symptoms of mesenteric angina. To our knowledge, this represents the first reported case of endovascular treatment of CMT stenosis.
Angiography catheter based bleeding complication at the access site related to Neurofibromatosis I
Authors: Gorny  , Mildner  , Fraedrich  , Greiner
Published: November 2010

Neurofibromatosis Type I (NF-I) is one of the most common inherited human diseases with an incidence of 1/3000. Besides the cardinal features, all organs or body structures as well as several arterial regions can occasionly be affected. We present an unusual case of an access-site hematoma following percutaneous transluminal coronary angioplasty in a patient suffering from NF-1. After exposure of the vessels, excessive bleeding from surrounding proliferations of supposedly neurofibromatous or ganglioneuromatous tissue was identified as the sole source of the hematoma. Patients with neurofibromatosis are at considerable risk of obtaining catheter interventions over the years. In this group, we strongly recommend an ultrasound examination of the arterial segment where the arterial access is planned. In case of suspicious findings an alternative approach should be preferred to avoid bleeding complications.
Studiendesign und Methodik des Epidemiologischen Suchtsurveys 2009
Authors: Kraus Ludwig , Pabst Alexander
Published: November 2010

Hintergrund: Der Epidemiologische Suchtsurvey (ESA) 2009 untersucht den Konsum und Missbrauch von psychoaktiven Substanzen in der deutschen Allgemeinbevölkerung. Ziel: Beschreibung der Stichprobenziehung, der eingesetzten Instrumente, der Datenerhebung, Ausschöpfung und Gewichtung des Surveys. Durchführung einer Nonresponse- und Modus-Effekt-Analyse. Methodik: Die Stichprobe wurde disproportional zur Verteilung der Geburtskohorten in der Bevölkerung in einem zweistufigen, zufallsgesteuerten Auswahlverfahren aus den Einwohnermelderegistern gezogen. Ergebnisse: Insgesamt nahmen 8.030 Personen (3.731 schriftlich, 3.376 telefonisch und 927 online) im Alter zwischen 18 und 64 Jahren teil. Die Antwortrate betrug 50.1 %. Die verwendete Design- und Poststratifikationsgewichtung erzielte eine Effektivität von 83.5 %. Abweichungen von der Grundgesamtheit bestehen in der gewichteten Stichprobe hinsichtlich Staatsbürgerschaft und Schulbildung. An der telefonischen oder schriftlichen Kurzbefragung nahmen 8 % aller Nichtantworter teil. Die Vergleiche zeigen, dass Nichtteilnehmer seltener Alkohol- und Drogenkonsum berichteten als Teilnehmer. Modus-Effekte deuten im Vergleich zu schriftlich Befragten auf eine geringere Verbreitung von Cannabiskonsum unter telefonisch Befragten und eine geringere Prävalenz von Alkoholkonsum unter Online-Teilnehmern hin. Schlussfolgerungen: Der eingesetzte Methodenmix aus schriftlicher, telefonischer und Online-Befragung wirkte sich positiv auf die Teilnahmebereitschaft aus, was sich in einer gestiegenen Antwortrate im Vergleich zu früheren ESA-Studien zeigt.
Neuropsychologische Korrelate aggressiv-dissozialen Verhaltens
Authors: Witthöft Jan , Koglin Ute , Petermann Franz
Published: November 2010

Bei der Erforschung aggressiv-dissozialen Verhaltens wurde die Bedeutung von neuropsychologischen Funktionen bisher vergleichsweise selten berücksichtigt – zudem sind die Ergebnisse heterogen. Mit einer umfangreichen Literatursuche wurden Studien identifiziert, die die Zusammenhänge von neuropsychologischen Leistungen und aggressiv-dissozialem Verhalten bei Jugendlichen untersuchten. Die Befunde werden differenziert nach Subtypen aggressiv-dissozialen Verhaltens dargestellt (Störung des Sozialverhaltens, physisch-aggressives Verhalten, straffälliges Verhalten und Psychopathie). Insgesamt weisen sie auf die Bedeutung der sprachlichen und exekutiven Funktionen hin. Defizite in diesen Funktionsbereichen sind insbesondere bei früh auftretendem stabilen und gewalttätigen Verhalten nachweisbar. Sprache, exekutive Funktionen und ihr Zusammenspiel werden in ihrer Bedeutung für sozial-kompetentes und aggressiv-dissoziales Verhalten diskutiert und die Ergebnisse werden vor dem Hintergrund der verwendeten Methodik, Einfluss von ADHS und Intelligenz kritisch besprochen. Abschließend werden neuropsychologische Defizite und biosoziale Risikofaktoren in der Entwicklung aggressiv-dissozialen Verhaltens miteinander in Beziehung gesetzt und Schlussfolgerungen für die klinische Praxis dargestellt.
Breitbandverfahren klinischer Ratingskalen zur Messung von Psychosyndromen im Kindes- und Jugendalter
Authors: Barkmann Claus , Schulte-Markwort Michael , Brähler Elmar
Published: November 2010

Zusammenfassung. Theoretischer Hintergrund: Bislang existiert kein Überblick über Breitbandverfahren psychometrischer Ratingskalen, die Erlebens- oder Verhaltensweisen der klinischen Psychosyndrome des Kindes- und Jugendalters erfassen. Fragestellung: Wie lässt sich der aktuelle Bestand dieser Verfahren beschreiben und klassifizieren? Methode: Im Rahmen eines systematischen Reviews wurden diese Instrumente von Experten beschrieben und aggregiert analysiert. Ergebnisse: Die n = 14 identifizierten Verfahren sind überwiegend in einer Mischung rationaler, externaler und induktiver Strategien konstruiert worden und erfragen auf etwa vier Seiten im Mittel 87 vierstufig zu beantwortende Items. Die mittlere interne Konsistenz von Subskalen fällt unbefriedigend, die von Metaskalen dagegen gut aus. Fast alle Instrumente sind in ihrer Konstruktvalidität an deutschsprachigen Stichproben geprüft. Gut die Hälfte ist in ihrer Kriteriumsvalidität geprüft und/oder normiert. Schlussfolgerungen: Insgesamt fällt der Bestand quantitativ und qualitativ besser aus als aufgrund bisheriger Testsammlungen erwartet werden konnte, reicht aber nicht aus, um für die Fülle verschiedener Anwendungssituationen ein jeweils geeignetes und valides Instrument vorzuhalten.
Reply to Comments on “What Is the Atmosphere's Effect on Earth's Surface Temperature?”
Authors: Zeng Xubin
Published: November 2010

I thank Gerald Stanhill and Spencer Weart for their interest in my Forum (Eos, 91(15), 134–135, 13 April 2010). Strictly speaking, I agree with Stanhill that the terms “greenhouse effect” and “greenhouse gases” are inaccurate, as the atmospheric greenhouse effect is different from the effect in a greenhouse, in which a glass cover warms the air inside primarily by preventing the warm air from mixing with the air outside. My more moderate suggestion in the Forum is to drop the related and confusing phrase “greenhouse effect of clouds.”
Board Adds Two New Members With Expertise in Communication and Science Policy
Authors: McEntee Christine W.
Published: November 2010

AGU's Board of Directors approved two new members during a special teleconference on 8 November. The appointments are related to AGU's strategic plan goal of addressing science and society. Specifically, they add to AGU's expertise in science communication and policy outreach. Author Chris Mooney and policy advisor Floyd DesChamps join AGU's Board of Directors immediately and will serve the remainder of the 2010–2012 term.
Lin Receives 2010 Natural Hazards Focus Group Award for Graduate Research
Authors: Anonymous
Published: November 2010

Ning Lin has been awarded the Natural Hazards Focus Group Award for Graduate Research, given annually to a recent Ph.D. recipient for outstanding contributions to natural hazards research. Lin's thesis is entitled “Multi‐hazard risk analysis related to hurricanes.” She is scheduled to present an invited talk in the Extreme Natural Events: Modeling, Prediction, and Mitigation session (NH20) during the 2010 AGU Fall Meeting, held 13–17 December in San Francisco, Calif. Lin will be formally presented with the award at the Natural Hazards focus group reception on 14 December 2010.
X-ray crystallographic snapshots of reaction intermediates in the G117H mutant of human butyrylcholinesterase, a nerve agent target engineered into a catalytic bioscavenger
Authors: Nachon Florian , Carletti Eugenie , Wandhammer Marielle , Nicolet Yvain , Schopfer Lawrence M. , Masson Patrick , Lockridge Oksana
Published: November 2010

OPs (organophosphylates) exert their acute toxicity through inhibition of acetylcholinesterase, by phosphylation of the catalytic serine residue. Engineering of human butyrylcholinesterase, by substitution of a histidine residue for the glycine residue at position 117, led to the creation of OP hydrolase activity. However, the lack of structural information and poor understanding of the hydrolytic mechanism of the G117H mutant has hampered further improvements in the catalytic activity. We have solved the crystallographic structure of the G117H mutant with a variety of ligands in its active site. A sulfate anion bound to the active site suggested the positioning for an OP prior to phosphylation. A fluoride anion was found in the active site when NaF was added to the crystallization buffer. In the fluoride complex, the imidazole ring from the His117 residue was substantially shifted, adopting a relaxed conformation probably close to that of the unliganded mutant enzyme. Additional X-ray structures were obtained from the transient covalent adducts formed upon reaction of the G117H mutant with the OPs echothiophate and VX [ethyl ({2-[bis(propan-2-yl)amino]ethyl}sulfanyl](methyl)phosphinate]. The position of the His117 residue shifted in response to the introduction of these adducts, overlaying the phosphylserine residue. These structural data suggest that the dephosphylation mechanism involves either a substantial conformational change of the His117 residue or an adjacent nucleophilic substitution by water.
Renin, (pro)renin and receptor: an update
Authors: Nguyen Genevieve
Published: November 2010

PRR [(pro)renin receptor] was named after its biological characteristics, namely the binding of renin and of its inactive precursor prorenin, that triggers intracellular signalling involving ERK (extracellular-signal-regulated kinase) 1/2. However the gene encoding for PRR is named ATP6ap2 (ATPase 6 accessory protein 2) because PRR was initially found as a truncated form co-purifying with V-ATPase (vacuolar H+-ATPase). There are now data showing that this interaction is not only physical, but also functional in the kidney and the heart. However, the newest and most fascinating development of PRR is its involvement in both the canonical Wnt/β-catenin and non-canonical Wnt/PCP (planar cell polarity) pathways, which are essential for adult and embryonic stem cell biology, embryonic development and disease, including cancer. In the Wnt/β-catenin pathway, it has been shown that PRR acts as an adaptor between the Wnt receptor LRP5/6 (low-density lipoprotein receptor-related protein 5/6) and Fz (frizzled) and that the proton gradient generated by the V-ATPase in endosomes is necessary for LRP5/6 phosphorylation and β-catenin activation. In the Wnt/PCP pathway, PRR binds to Fz and controls its asymetrical subcellular distribution and therefore the polarization of the cells in a plane of a tissue. These essential cellular functions of PRR are independent of renin and open new avenues on the pathophysiological role of PRR. The present review will summarize our knowledge of (pro)renin-dependent functions of PRR and will discuss the newly recognized functions of PRR related to the V-ATPase and to Wnt signalling.
Research Priorities for Neotropical Dry Forests1
Authors: Sánchez‐Azofeifa G. Arturo , Quesada Mauricio , Rodríguez Jon Paul , Nassar Jafet M. , Stoner Kathryn E. , Castillo Alicia , Garvin Theresa , Zent Egleé L. , Calvo‐Alvarado Julio C. , Kalacska Margaret E.R. , Fajardo Laurie , Gamon John A. , Cuevas‐Reyes Pablo
Published: November 2010

Our understanding of the human and biophysical dimensions of tropical dry forest change and its cumulative effects is still in the early stages of academic discovery. The papers in this special section on Neotropical dry forests cover a wide range of sites and problems ranging from the use of multispectral and hyperspectral remote sensing platforms to the impact of hurricanes on tropical dry forest regeneration. Here, we present to the scientific community the results of a workshop on which research priorities for tropical dry forests were discussed. This discussion focuses on the need to develop linkages between remote sensing, ecological, and social science research. The incorporation of social sciences into ecological research could contribute dramatically to our understandings of tropical dry forests by providing important contextual information to ecologists, and by helping to develop an important science–policy–public nexus on which environmental management can succeed.
Effects of H1 antihistamines on adhesion molecules: a possible rationale for long‐term treatment
Authors: Ciprandi G. , Passalacqua G. , Canonica G. W.
Published: November 2010

Our knowledge of the mechanisms underlying the allergic reaction has increased rapidly and has revealed a complex network of cells, mediators and cytokines. The intercellular adhesion system (and the ICAM‐1 molecule in particular) appeared to play a pivotal role in the accumulation of inflammatory cells at the site of allergic reaction. The new antihistamines have been demonstrated to be capable of affecting several phenomena of the allergic inflammation, including mediator release, cellular activation and adhesion molecule expression. Taking into consideration the central role of adhesion molecules, the modulation of their expression may represent an important therapeutic target. The nasal and the conjunctival challenges represent two useful models for the in vivo study of the antiallergic activity of drugs, as they allow investigation of a wide variety of parameters: inflammatory infiltrate, ICAM‐1 expression, concentration of soluble mediators.
Maternal ethnic origin and fetal nasal bones at 11–14 weeks of gestation
Authors: Prefumo Federico , Sairam Shanthi , Bhide Amarnath , Penna Leonie , Hollis Brian , Thilaganathan Baskaran
Published: November 2010

Objectives  Failure to visualise the fetal nasal bones at 11–14 weeks of gestation is associated with a significant increase in the risk for trisomy 21. However, it is not known whether the ethnic origin of the mother has any effect on the fetal profile and the prevalence of this marker.

Design  Prospective study.

Setting  London Teaching Hospital.

Population  Four thousand and four hundred and ninety‐two consecutive fetuses undergoing routine first trimester ultrasound scanning at 11–14 weeks of gestation in a multiethnic population.

Methods  Examination of the nasal bones was attempted in the fetuses.

Main outcome measure  Rate of visualisation of the fetal nasal bones.

Results  Five hundred fetuses were excluded from the analysis because of chromosomal abnormalities or a technically unsatisfactory examination. In the remaining 3992 fetuses, the maternal ethnic origin was African in 13.0%, Asian in 15.3% and Caucasian in 66.0%. Compared with Caucasians, the failure to visualise the fetal nasal bones was significantly higher in women of African (P= 0.0001) but not Asian origin (P= 0.24). A multivariable logistic regression model showed that having a mother of African origin is still significantly associated with an increased likelihood of absent fetal nasal bones compared with Caucasians (odds ratio 2.33), even after correcting for maternal age, parity and crown–rump length.

Conclusion  There is a significant difference in the rate of visualisation of the fetal nasal bones in the first trimester in mothers of different ethnic origin. This suggest that corrections for maternal ethnicity will be required to ensure equity of fetal nasal bone screening in multiracial populations. Whether corrections are required for the father's ethnic origin remains to be determined.
Mifepristone and misoprostol versus dilation and evacuation for midtrimester abortion: a pilot randomised controlled trial
Authors: Grimes David A. , Smith M. Susan , Witham Angela D.
Published: November 2010

Objective  To test the feasibility of mounting a randomised controlled trial comparing mifepristone–misoprostol versus dilation and evacuation (D&E) for midtrimester abortion.

Design  Pilot randomised controlled trial.

Setting  University of North Carolina Hospitals, Chapel Hill, North Carolina.

Population  Women aged 18 years or older and without prior uterine operations who requested abortion at 14–19 menstrual weeks of gestation from January 2002 to January 2003.

Methods  Participants received either mifepristone 200 mg by mouth followed in two days by vaginal then oral misoprostol (Aberdeen regimen) or D&E after one or two days of laminaria preparation. Care was provided by residents under faculty supervision.

Main outcome measures  Enrolment rate and acceptability of and adverse events associated with methods.

Results  The trial was stopped at one year because of slow enrolment. Of 47 women eligible for the trial, 29 (62%) declined participation, primarily because of a preference for D&E abortion. Among the 18 participants enrolled, nine were randomised to treatment with mifepristone–misoprostol and 9 to D&E. Compared with D&E, mifepristone–misoprostol abortion caused more pain and adverse events, although none was serious.

Conclusions  Our findings concerning acceptability and adverse events should be considered hypothesis‐generating; they may prove useful in planning a larger randomised controlled trial. Such a trial will be difficult to mount in the US. Hence, we suggest that it be done in a setting where labour‐induction abortion is the norm.
Extension of Transcatheter Coil Occlusion to the Treatment of Complex Coronary Fistulas
Authors: FLETCHER SCOTT , AWADALLAH SAMI , AMIN ZAHID
Published: November 2010

Coronary fistulas can be a source of myocardial Ischemia when they are large. In this case series, we describe four complex coronary fistulas treated by transcatheter occlusion. The first two with Gianturco coils and the other two with an Amplatzer PDA device. Transcatheter closure of coronary fistulas can be accomplished in most cases. (J Interven Cardiol 2003;16:165–169)
Surface plasmon resonator: Design, construction, and observation in the farfield
Authors: Arca Ahmet , Clark Matt , Somekh Mike
Published: November 2010

We have studied the behavior of surface plasmons (SPs) in valley like structures [Schroter et al., Ultramicroscopy 68, 223 (1997)] and found that SPs traveling in both directions in such a cavity yield interference patterns in the farfield, which can be measured as specular and retroreflection. We have studied and designed the structures using finite element method in addition to a heuristic model, fabricated the devices using photolithography and experimentally verified the operation of the resonators, by observing the interference patterns of the specular and retroreflection in the farfield. We have found that the experimental results agree with the simulations, and explained the discrepancies. These structures can be useful in the study of the propagation length of SPs via observation in the farfield of the specular and the retroreflected light in laser industry and could be miniaturized to yield small biosensors.
Laboratory detection of protonated SO2 in two isomeric forms
Authors: Lattanzi Valerio , Thaddeus Patrick , McCarthy Michael C. , Thorwirth Sven
Published: November 2010

By means of Fabry–Pérot Fourier transform microwave spectroscopy, the rotational spectrum of protonated sulfur dioxide in two distinct isomeric forms, a cis- and a trans-geometry, is reported. The search for both isomers was based on theoretical structures obtained at the CCSD(T)/cc-pwCVQZ level of theory corrected for zero-point vibrational effects. At a similarly high level of theory, the cis-isomer is calculated to be the global minimum on the potential energy surface, but the trans-isomer is predicted to lie only a few kcal/mol higher in energy. A total of seven lines, including a- and b-type transitions, has been observed for both isomers, and precise rotational constants have been derived. Because sulfur dioxide, SO2, is a widespread and very abundant astronomical species, and because it possesses a large proton affinity, HOSO+ is an excellent candidate for radioastronomical detection.
A simple method to measure phase difference between sinusoidal signals
Authors: Bertotti Fabio Luiz , Hara Marcos Santos , Abatti Paulo Jose
Published: November 2010

In this paper, a novel and simple method to measure the phase difference between two sinusoidal signals is presented. Basically, the method consists of subtracting two sinusoidal signals with same frequencies and measuring the resulting signal amplitude: this amplitude being a minimum whenever there is a coincidence between both signal phases. In order to test this method, an adjustable phase reference signal has been generated using a direct digital synthesizer device. Employing this reference signal, it can be demonstrated that the phase difference between two signals can be evaluated with errors smaller than 0.3° for signals with frequencies up to 1.25 MHz.
Study of electric field enhanced emission rates of an electron trap in n-type GaN grown by hydride vapor phase epitaxy
Authors: Ashraf H. , Arshad M. Imran , Faraz S. M. , Wahab Q. , Hageman P. R. , Asghar M.
Published: November 2010

Electric field-enhanced emission of electrons from a deep level defect in GaN grown by hydride vapor phase epitaxy has been studied. Using the field dependent mode of conventional deep level transient spectroscopy (DLTS), several frequency scans were performed keeping applied electric field (12.8–31.4 MV/m) and sample temperature (300–360 K) constant. Arrhenius plots of the resultant data yielded an activation energy of the electron trap E ranging from Ec−0.48±0.02 eV to Ec−0.35±0.02 eV, respectively. The extrapolation of the as-measured field dependent data (activation energy) revealed the zero-field emission energy (pure thermal activation energy) of the trap to be 0.55±0.02 eV. Various theoretical models were applied to justify the field-enhanced emission of the carriers from the trap. Eventually it was found that the Poole–Frenkel model associated with a square well potential of radius r=4.8 nm was consistent with the experimental data, and, as a result, the trap is attributed to a charged impurity. Earlier, qualitative measurements like current-voltage (I-V) and capacitance-voltage (C-V) measurements were performed, and screening parameters of the device were extracted to ascertain the reliability of DLTS data.
Suppression of eddies in films over topography
Authors: Wierschem A. , Pollak T. , Heining C. , Aksel N.
Published: November 2010

We study inertial film flow down undulated inclines. With increasing Reynolds number, eddies are formed in the troughs of the bottom undulation. Further increase leads to a diminution of the eddies until they vanish completely. At even higher Reynolds numbers, they reappear yielding an eddy-free window of Reynolds numbers. Within this window, the free-surface shape changes abruptly. The change comes along with a sudden decrease in the mean film thickness and an abrupt transition of the surface shape type from anharmonic with a strong indentation to harmonic. The anharmonic surface shape shows typical features of a hydraulic jump, which vanishes during the transition. We find that the eddies disappear at Reynolds numbers where the first harmonic of the free-surface contour is sufficiently strong regardless of the exact surface shape. Numerical calculations are in good agreement with the experimental findings.
Molecular dynamics study of the crystallization of nitromethane from the melt
Authors: Siavosh-Haghighi Ali , Sewell Thomas D. , Thompson Donald L.
Published: November 2010

The crystallization of nitromethane, CH3NO2, from the melt on the (100), (010), (001), and (110) crystal surfaces at 170, 180, 190, 200, 210, and 220 K has been investigated using constant-volume and -temperature (NVT) molecular dynamics simulations with a realistic, fully flexible force field [D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 104, 8406 (2000)]. The crystallization process and the nature of the solid-liquid interface have been investigated by computing the molecular orientations, density, and radial distribution functions as functions of time and location in the simulation cell. During crystallization the translational motion of the molecules ceases first, after which molecular rotation ceases as the molecules assume proper orientations in the crystal lattice. The methyl groups are hindered rotors in the liquid; hindrance to rotation is reduced upon crystallization. The width of the solid-liquid interface varies between 6 and 13 Å (about two to five molecular layers) depending on which crystal surface is exposed to the melt and which order parameter is used to define the interface. The maximum rate of crystallization varies from 0.08 molecules ns−1 Å−2 for the (010) surface at 190 K to 0.41 molecules ns−1 Å−2 for the (001) surface at 220 K.
Effects of random link removal on the photonic band gaps of honeycomb networks
Authors: Florescu Marian , Torquato Salvatore , Steinhardt Paul J.
Published: November 2010

We explore the effects of random link removal on the photonic band gaps of honeycomb networks. Missing or incomplete links are expected to be common in practical realizations of this class of connected network structures due to unavoidable flaws in the fabrication process. We focus on the collapse of the photonic band gap due to the defects induced by the link removal. We show that the photonic band gap is quite robust against this type of random decimation and survives even when almost 58% of the network links are removed.
Analytical and semianalytical solutions to the kinetic equation with Coulomb collision term and a monoenergetic source function
Authors: Goncharov P. R. , Kuteev B. V. , Ozaki T. , Sudo S.
Published: November 2010

Analytical and semianalytical solutions have been obtained using a practical dimensionless form of Boltzmann kinetic equation assuming spatial homogeneity, azimuthal symmetry, and Maxwellian distributions of target plasma species. In contrast with formerly considered simplified equations with truncated collision terms, the exact Landau–Boltzmann collision operator is used, which conserves the number of particles, nullifies the collision term at statistical equilibrium, and describes the Maxwellization process naturally observed in correct solutions. A comparison with previous stationary and time-dependent analytical solutions is given. The new semianalytical results can be used in numerical modeling, for verification of solutions in more complex models, and in experimental data analysis, especially concerning nuclear processes and advanced localized, angle-resolved suprathermal particle diagnostics.
Stochastic theory of large-scale enzyme-reaction networks: Finite copy number corrections to rate equation models
Authors: Thomas Philipp , Straube Arthur V. , Grima Ramon
Published: November 2010

Chemical reactions inside cells occur in compartment volumes in the range of atto- to femtoliters. Physiological concentrations realized in such small volumes imply low copy numbers of interacting molecules with the consequence of considerable fluctuations in the concentrations. In contrast, rate equation models are based on the implicit assumption of infinitely large numbers of interacting molecules, or equivalently, that reactions occur in infinite volumes at constant macroscopic concentrations. In this article we compute the finite-volume corrections (or equivalently the finite copy number corrections) to the solutions of the rate equations for chemical reaction networks composed of arbitrarily large numbers of enzyme-catalyzed reactions which are confined inside a small subcellular compartment. This is achieved by applying a mesoscopic version of the quasisteady-state assumption to the exact Fokker–Planck equation associated with the Poisson representation of the chemical master equation. The procedure yields impressively simple and compact expressions for the finite-volume corrections. We prove that the predictions of the rate equations will always underestimate the actual steady-state substrate concentrations for an enzyme-reaction network confined in a small volume. In particular we show that the finite-volume corrections increase with decreasing subcellular volume, decreasing Michaelis–Menten constants, and increasing enzyme saturation. The magnitude of the corrections depends sensitively on the topology of the network. The predictions of the theory are shown to be in excellent agreement with stochastic simulations for two types of networks typically associated with protein methylation and metabolism.
Hydrogenated amorphous silicon deposited under accurately controlled ion bombardment using pulse-shaped substrate biasing
Authors: Wank M. A. , van Swaaij R. A. C. M. M. , Kudlacek P. , van de Sanden M. C. M. , Zeman M.
Published: November 2010

We have applied pulse-shaped biasing to the expanding thermal plasma deposition of hydrogenated amorphous silicon at substrate temperatures ∼200 °C and growth rates around 1 nm/s. Substrate voltage measurements and measurements with a retarding field energy analyzer demonstrate the achieved control over the ion energy distribution for deposition on conductive substrates and for deposition of conductive materials on nonconductive substrates. Presence of negative ions/particles in the Ar–H2–SiH4 plasma is deduced from a voltage offset during biasing. Densification of the material at low Urbach energies is observed at a deposited energy <4.8 eV/Si atom and attributed to an increase in surface mobility of mobile species as well as well as surface atom displacement. The subsequent increase in Urbach energy >4.8 eV/Si atom is attributed to bulk atom displacement in subsurface layers. We make the unique experimental abservation of a decreasing Tauc band gap at increasing total hydrogen concentration—this allows to directly relate the band gap of amorphous silicon to the presence of nanovoids in the material.
Characterization of traps in the gate dielectric of amorphous and nanocrystalline silicon thin-film transistors by 1/f noise
Authors: Ioannidis E. G. , Tsormpatzoglou A. , Tassis D. H. , Dimitriadis C. A. , Templier F. , Kamarinos G.
Published: November 2010

The low frequency noise technique is used to obtain the volume profile of traps in the SiNx gate dielectric of hydrogenated amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si:H) thin film transistors (TFTs). In both a-Si:H and nc-Si:H TFTs, within the range of probing depth in the gate dielectric, the traps have a uniform spatial distribution which is consistent with the observed pure 1/f noise. The experimental results show that the gate dielectric trap properties near the interface are dependent on the channel material with the trap density in nc-Si:H TFTs being much smaller in comparison with the a-Si:H TFTs.
Thickness dependent magnetic reversal process and hysteresis loops in exchange-coupled hard-soft trilayers
Authors: Zhao G. P. , Deng Y. , Zhang H. W. , Chen L. , Feng Y. P. , Bo N.
Published: November 2010

The demagnetization process of a hard/soft/hard sandwich has been investigated systematically within a self-contained micromagnetic model, with particular attention on the cases with small hard layer thickness. The microscopic and macroscopic hysteresis loops, as well as the angular distributions of the magnetization between nucleation and pinning have been obtained numerically, with the formula for the nucleation field derived. It is found that both nucleation and pinning fields, as well as the gap in between decrease as the hard layer thickness reduces. The hard layer thickness has great effect on the hysteresis loops only when the thickness is very small, where the hysteresis loop is nearly square and the dominant coercivity mechanism is the nucleation. The thickness regions at which the theoretical and practical giant energy products can be achieved have been discussed. In most cases, the hard layer can be taken as sufficiently thick so that the magnetization at its surface obeys a simple coherent rotation model. In these cases, the calculation can be simplified significantly, with only the influence of the soft layer thickness accounted.
Contained modes in mirrors with sheared rotation
Authors: Fetterman Abraham J. , Fisch Nathaniel J.
Published: November 2010

In mirrors with E×B rotation, a fixed azimuthal perturbation in the laboratory frame can appear as a wave in the rotating frame. If the rotation frequency varies with radius, the plasma-frame wave frequency will also vary radially due to the Doppler shift. A wave that propagates in the high rotation plasma region might therefore be evanescent at the plasma edge. This can lead to radially localized Alfven eigenmodes with high azimuthal mode numbers. Contained Alfven modes are found both for peaked and nonpeaked rotation profiles. These modes might be useful for alpha channeling or ion heating, as the high azimuthal wave number allows the plasma wave frequency in the rotating frame to exceed the ion cyclotron frequency.
A multi-channel structure to enhance the performance of a sequential lateral solidification thin-film transistor
Authors: Kang Myung-Koo , Kim Si Joon , Kim Hyun Jae
Published: November 2010

Sequential lateral solidification (SLS) thin-film transistors (TFTs) offer higher performance than conventional excimer laser-annealed TFTs. However, their performance has an anisotropy originating from the polycrystalline silicon (p-Si) microstructure. The properties of TFTs with channel direction parallel to the lateral growth (parallel TFTs) are superior to those of TFTs with a perpendicular channel direction (perpendicular TFTs). The multi-channel structure proposed in this paper, which directly incorporates a parallel component in a perpendicular TFT, exhibits greatly improved properties. This MC structure can be applied not only to p-Si produced by SLS, but also to any material with property anisotropy.
Resistive switching in NiSi gate metal-oxide-semiconductor transistors
Authors: Li X. , Liu W. H. , Raghavan N. , Bosman M. , Pey K. L.
Published: November 2010

Both unipolar and bipolar resistive switchings are demonstrated on NiSi gate transistors after gate dielectric percolation. Nanoscale Ni filaments and oxygen ion conduction are found in the percolation path as the physical defects responsible for resistive switching. Memory cells can be fabricated together with the metal gate transistors for ease of integration.
Threshold voltage control of oxide nanowire transistors using nitrogen plasma treatment
Authors: Park Jin-Woo , Baik Hong-Koo , Lim Taekyung , Ju Sanghyun
Published: November 2010

In developing complementary metal-oxide semiconductor logic circuits using N-type semiconducting nanowires, threshold voltage (Vth) control is crucial because the driving voltage should be established in relation to the Vth dispersion of transistors. In this study, using N2 plasma treatment, positive shifts of SnO2 nanowire transistor (NWT) devices were produced as desired without degrading the nanowire surfaces. The NWT devices exhibited positive Vth shifts of ∼0.9 and ∼1.5 V and decreases in on-currents of ∼20% and ∼40% at plasma source powers of 200 and 400 W, respectively, without any changes in subthreshold slope or off-current. The positive Vth shifts and decreases in on-current can be explained by assuming that nitrogen ions (N3−) filled in for the existing oxygen vacancies (Vo, Vo+, and Vo++) and that consequently, the amount of oxygen vacancies playing a role in electron-trapping decreased.
Species traits and resilience of meiofauna to floods and drought in a Mediterranean stream
Authors: Gaudes Ainhoa , Artigas Joan , Muñoz Isabel
Published: November 2010

In Mediterranean streams, droughts and floods are mainly seasonal and predictable, occurring twice or three times a year. Under these conditions, multivoltinism and short life-cycles would be favoured, particularly for organisms with low migratory capacity. The meiofaunal community is therefore hypothesised to have species traits adapted to these hydrological perturbations. However, meiofauna have been neglected in many lotic studies. The present study examined the temporal variability of meiofaunal density and biomass over a 2-year period in three reaches of a low-order Mediterranean stream. Relationships between biological traits and hydrological and environmental characteristics were investigated. Resilience of meiofauna to floods was quantified using regression. Small differences in basin drainage resulted in different responses. The abundance and resilience of the meiofauna were higher in the upstream reach than those in the downstream communities. A small, worm-shaped body and active locomotor structures conferred higher resilience in the face of natural hydrological disturbances. Low-order reaches are refugia for functionally important meiofauna that can eventually repopulate downstream reaches.
Neural signatures of autism
Authors: Kaiser Martha D. , Hudac Caitlin M. , Shultz Sarah , Lee Su Mei , Cheung Celeste , Berken Allison M. , Deen Ben , Pitskel Naomi B. , Sugrue Daniel R. , Voos Avery C. , Saulnier Celine A. , Ventola Pamela , Wolf Julie M. , Klin Ami , Vander Wyk Brent C. , Pelphrey Kevin A.
Published: November 2010

Functional magnetic resonance imaging of brain responses to biological motion in children with autism spectrum disorder (ASD), unaffected siblings (US) of children with ASD, and typically developing (TD) children has revealed three types of neural signatures: (
i
) state activity, related to the state of having ASD that characterizes the nature of disruption in brain circuitry; (
ii
) trait activity, reflecting shared areas of dysfunction in US and children with ASD, thereby providing a promising neuroendophenotype to facilitate efforts to bridge genomic complexity and disorder heterogeneity; and (
iii
) compensatory activity, unique to US, suggesting a neural system–level mechanism by which US might compensate for an increased genetic risk for developing ASD. The distinct brain responses to biological motion exhibited by TD children and US are striking given the identical behavioral profile of these two groups. These findings offer far-reaching implications for our understanding of the neural systems underlying autism.
Dental evidence for ontogenetic differences between modern humans and Neanderthals
Authors: Smith Tanya M. , Tafforeau Paul , Reid Donald J. , Pouech Joane , Lazzari Vincent , Zermeno John P. , Guatelli-Steinberg Debbie , Olejniczak Anthony J. , Hoffman Almut , Radovčić Jakov , Makaremi Masrour , Toussaint Michel , Stringer Chris , Hublin Jean-Jacques
Published: November 2010

Humans have an unusual life history, with an early weaning age, long childhood, late first reproduction, short interbirth intervals, and long lifespan. In contrast, great apes wean later, reproduce earlier, and have longer intervals between births. Despite 80 y of speculation, the origins of these developmental patterns in
Homo sapiens
remain unknown. Because they record daily growth during formation, teeth provide important insights, revealing that australopithecines and early
Homo
had more rapid ontogenies than recent humans. Dental development in later
Homo
species has been intensely debated, most notably the issue of whether Neanderthals and
H. sapiens
differ. Here we apply synchrotron virtual histology to a geographically and temporally diverse sample of Middle Paleolithic juveniles, including Neanderthals, to assess tooth formation and calculate age at death from dental microstructure. We find that most Neanderthal tooth crowns grew more rapidly than modern human teeth, resulting in significantly faster dental maturation. In contrast, Middle Paleolithic
H. sapiens
juveniles show greater similarity to recent humans. These findings are consistent with recent cranial and molecular evidence for subtle developmental differences between Neanderthals and
H. sapiens
. When compared with earlier hominin taxa, both Neanderthals and
H. sapiens
have extended the duration of dental development. This period of dental immaturity is particularly prolonged in modern humans.
Hippo signaling regulatesDrosophilaintestine stem cell proliferation through multiple pathways
Authors: Ren Fangfang , Wang Bing , Yue Tao , Yun Eun-Young , Ip Y. Tony , Jiang Jin
Published: November 2010

Intestinal stem cells (ISCs) in theDrosophilaadult midgut are essential for maintaining tissue homeostasis and replenishing lost cells in response to tissue damage. Here we demonstrate that the Hippo (Hpo) signaling pathway, an evolutionarily conserved pathway implicated in organ size control and tumorigenesis, plays an essential role in regulating ISC proliferation. Loss of Hpo signaling in either midgut precursor cells or epithelial cells stimulates ISC proliferation. We provide evidence that loss of Hpo signaling in epithelial cells increases the production of cytokines of the Upd family and multiple EGFR ligands that activate JAK-STAT and EGFR signaling pathways in ISCs to stimulate their proliferation, thus revealing a unique non–cell-autonomous role of Hpo signaling in blocking ISC proliferation. Finally, we show that the Hpo pathway mediator Yorkie (Yki) is also required in precursor cells for injury-induced ISC proliferation in response to tissue-damaging reagent DSS.