bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulent wake of an inclined cylinder with water running
Authors: ALAM MD. MAHBUB , ZHOU Y.
Published: March 2008

This paper presents the results of an experimental study of fluid dynamics around an inclined circular cylinder with and without water running over its surface, covering water rivulet formation, fluid forces on the cylinder, near wake and their interrelationships. The cylinder inclination angle (α) with respect to incident flow was between 55° and 80°. It has been found that water running over the cylinder surface may behave quite differently, depending on the Reynolds number (Re), and subsequently impact greatly upon the fluid dynamics around the cylinder. As such, five flow categories are classified. CategoryA: one water rivulet was observed, irrespective of α, at the leading stagnation point at a smallRe. CategoryB: the rivulet splits into two, symmetrically arranged about the leading stagnation line, onceReexceeds a critical value that depends on α. The two rivulets may further switch back to one, and vice versa. CategoryC: two symmetrical straight rivulets occur. CategoryD: the two rivulets shift towards the flow separation line with increasingReand oscillate circumferentially. The oscillation reaches significant amplitude when the rivulets occur at about 70° from the leading stagnation point. This increased amplitude is coupled with a rapid climb in the mean and fluctuating drag and lift, by a factor of near 5 for the fluctuating lift at α = 80°. Meanwhile, the flow structure exhibits a marked variation. For example, Strouhal number and vortex formation length decrease, along with an increase in spanwise vorticity concentration, velocity deficit, and coherence between vortex shedding and fluctuating lift. All these observations point to the occurrence of a ‘lock-in’ phenomenon, i.e. the rivulet oscillation synchronizing with flow separation. A rivulet–vortex-induced instability is proposed to be responsible for the well reported rain–wind-induced vibration associated with the stay cables of cable-stayed bridges. CategoryE: the two rivulets shift further downstream just beyond the separation line; the shear layers behind the rivulets become highly turbulent, resulting in weakened vortex shedding, flow fluctuating velocities and fluctuating fluid forces. Based on the equilibrium of water rivulet weight, aerodynamic pressure and friction force between fluid and surface, an analysis is developed to predict the rivulet position on the cylinder, which agrees well with measurements.
Large-scale features in turbulent pipe and channel flows
Authors: MONTY J. P. , STEWART J. A. , WILLIAMS R. C. , CHONG M. S.
Published: March 2008

In recent years there has been significant progress made towards understanding the large-scale structure of wall-bounded shear flows. Most of this work has been conducted with turbulent boundary layers, leaving scope for further work in pipes and channels. In this article the structure of fully developed turbulent pipe and channel flow has been studied using custom-made arrays of hot-wire probes. Results reveal long meandering structures of length up to 25 pipe radii or channel half-heights. These appear to be qualitatively similar to those reported in the log region of a turbulent boundary layer. However, for the channel case, large-scale coherence persists further from the wall than in boundary layers. This is expected since these large-scale features are a property of the logarithmic region of the mean velocity profile in boundary layers and it is well-known that the mean velocity in a channel remains very close to the log law much further from the wall. Further comparison of the three turbulent flows shows that the characteristic structure width in the logarithmic region of a boundary layer is at least 1.6 times smaller than that in a pipe or channel.
On the periodically excited plane turbulent mixing layer, emanating from a jagged partition
Authors: KIT E. , WYGNANSKI I. , FRIEDMAN D. , KRIVONOSOVA O. , ZHILENKO D.
Published: March 2008

The flow in a turbulent mixing layer resulting from two parallel different velocity streams, that were brought together downstream of a jagged partition was investigated experimentally. The trailing edge of the partition had a short triangular ‘chevron’ shape that could also oscillate up and down at a prescribed frequency, because it was hinged to the stationary part of the partition to form a flap (fliperon). The results obtained from this excitation were compared to the traditional results obtained by oscillating a two-dimensional fliperon. Detailed measurements of the mean flow and the coherent structures, in the periodically excited and spatially developing mixing layer, and its random constituents were carried out using hot-wire anemometry and stereo particle image velocimetry.

The prescribed spanwise wavelength of the chevron trailing edge generated coherent streamwise vortices while the periodic oscillation of this fliperon locked in-phase the large spanwise Kelvin–Helmholtz (K-H) rolls, therefore enabling the study of the inter- action between the two. The two-dimensional periodic excitation increases the strength of the spanwise rolls by increasing their size and their circulation, which depends on the input amplitude and frequency. The streamwise vortices generated by the jagged trailing edge distort and bend the primary K-H rolls. The present investigation endeavours to study the distortions of each mode as a consequence of their mutual interaction. Even the mean flow provides evidence for the local bulging of the large spanwise rolls because the integral width (the momentum thickness, θ), undulates along the span. The lateral location of the centre of the ensuing mixing layer (the location where the mean velocity is the arithmetic average of the two streams,y0), also suggests that these vortices are bent. Phase-locked and ensemble-averaged measurements provide more detailed information about the bending and bulging of the large eddies that ensue downstream of the oscillating chevron fliperon. The experiments were carried out at low speeds, but at sufficiently high Reynolds number to ensure naturally turbulent flow.
Are cascading flows stable?
Authors: THORPE S. A. , OZEN B.
Published: March 2008

The stability of flows cascading down slopes as dense inclined plumes is examined, with particular reference to flows observed in Lake Geneva during winter periods of severe cooling. A previous conjecture by Turner that the flow may be in a state of marginal stability is confirmed: the observed mean velocity and density profiles are unstable to Kelvin–Helmholtz instability, but only marginally so; the growth rates of the most unstable small disturbances to the cascading flow in Lake Geneva are small, with e-folding periods of about 2 h. A reduction in the maximum velocity by about 20% is required to stabilize the flow.

The possibility that stationary hydraulic jumps may occur in the observed flow is also considered. Several plausible flow states downstream of transitions are examined, allowing for mixing and density changes to occur, ranging from one that preserves the shape of the density and velocity profiles to one in which, as a consequence of mixing, the velocity and density become uniform in depth within the cascading flow. Neither of these extreme states is found to conserve the fluxes of volume, mass and momentum through a transition in which the energy flux does not increase, and to be unique or ‘stable’ in the sense that no further transition is possible to a similar flow state without more entrainment. Stable transitions to intermediate downstream flows that conserve flow properties and reduce energy flux are, however, found, although the smallest value of the flow parameter, Fr≡ Umax2/gΔ h (where Umax is the maximum flow speed, g is the acceleration due to gravity, Δ is a fractional density difference within the flow and h is the flow thickness) at which transitions may occur is only slightly less than that of the cascading flow in Lake Geneva. In this sense, the observed flow is marginally unstable to a finite-amplitude transition or hydraulic jump. Velocity and density profiles of possible flows downstream of a transition are found. The amplitudes of possible transitions and the flux of water entrained from the ambient overlying water mass are limited to narrow ranges.
Spectroscopic studies of Ca plasma generated by the fundamental, second, and third harmonics of a Nd:YAG laser
Authors: Hafeez S. , Shaikh N. M. , Baig M. A.
Published: March 2008

The ablation of calcium sample has been studied by the optical emission spectroscopy of the evolving plasma using the fundamental, second, and third harmonic of a Nd:YAG laser, which reveals numerous transitions due to neutral and singly ionized calcium. The measurements have been performed to determine the electron temperature and electron number density and their spatial behavior. In addition, the behavior of the electron temperature and number density as a function of laser irradiance and ambient gas pressure has been studied. The processes of laser photon absorption in the plasma through inverse bremsstrahlung and photoionization have also been discussed.
Dynamic analysis of AGV control under dead-reckoning algorithm
Authors: Azenha Abílio , Carvalho Adriano
Published: March 2008

In this paper, dead-reckoning localization errors for automated guided vehicles (AGVs) in indoors quasi-structured environments are studied. Based on error ellipse localization analysis, dead-reckoning errors arising from mismatched AGV wheels radius are investigated. The dynamic model for a differential-drive AGV type with mismatched wheels radius is also derived. The developed rationale shows that sensor fusion is a key feature for minimizing AGV localization errors. Two simulation scenarios and one experiment are presented to show system performance under AGV proportional-derivative (PD)-type control.
MAXIMIZING THE THROUGHPUT OF TANDEM LINES WITH FLEXIBLE FAILURE-PRONE SERVERS AND FINITE BUFFERS
Authors: Andradóttir Sigrún , Ayhan Hayriye , Down Douglas G.
Published: March 2008

Consider a tandem queuing network with an infinite supply of jobs in front of the first station, infinite room for completed jobs after the last station, finite buffers between stations, and a number of flexible servers who are subject to failures. We study the dynamic assignment of servers to stations with the goal of maximizing the long-run average throughput. Our main conclusion is that the presence of server failures does not have a major impact on the optimal assignment of servers to stations for the systems we consider. More specifically, we show that when the servers are generalists, any nonidling policy is optimal, irrespective of the reliability of the servers. We also provide theoretical and numerical results for Markovian systems with two stations and two or three servers that suggest that the structure of the optimal server assignment policy does not depend on the reliability of the servers and that ignoring server failures when assigning servers to stations yields near-optimal throughput. Finally, we present numerical results that illustrate that simple server assignment heuristics designed for larger systems with reliable servers also yield good throughput performance in Markovian systems with three stations and three failure-prone servers.
Screening methods in alveolar echinococcosis: a follow-up study comparing Emc- and Emf-ELISA with Em2plus-ELISA and ultrasonography
Authors: HÄNLE M. M. , BANZHAF H.-M. , FORSBACH-BIRK V. , KIRCH A. , AKINLI A. S. , MASON R. A. , REUTER S. , KRATZER W.
Published: March 2008

The purpose of the present study was to identifyEchinococcus multilocularisinfection in follow-up of 95 subjects initially seropostive by Emc-ELISA or Emf-ELISA antibody assays and to compare the utility of these assays with specific Em2plus-ELISA and ultrasound screening forE. multilocularisinfection. At follow-up seven subjects were seropositive with both methods, while three were seropositive only with Emc-ELISA and 11 only with Emf-ELISA. All subjects were seronegative with Em2plus-ELISA. There were no manifestations ofE. multilocularisinfestation by ultrasonographic screening. Seropositivity on Emc-ELISA and Emf-ELISA screening tests does not appear to correlate with manifest alveolar echinococcosis identified by ultrasound. A recommendation for further follow-up of subjects found to be seropositive with Emc-ELISA and Emf-ELISA but with no sonographic evidence of disease is not justified at this time.
The perspective of ventricular noncompaction as seen by a nonagenarian
Authors: Lurie Paul R.
Published: March 2008

The persistence of so-called spongy myocardium was first reported in humans in the 1960s. Subsequently, a few reports described the condition, utilizing inconsistent facts and terminology. In 1990 the first report appeared using the term “noncompaction”, and detailed its clinical implications. Following this report, more descriptions of patients with noncompaction entered the literature. Prior to the availability of high resolution cross-sectional echocardiography, most cases of noncompacted myocardium escaped detection, as few patients underwent angiography. In this essay, I seek to adjudicate and clarify several confusions and controversies in the current literature including the acquired nature of hypertrabeculation, the fate of the so-called sinusoids, the relationship to coronary arteries, and noncompaction as another congenital malformation. The embryonic timing of cessation and reinitiation of compaction is conjectured as an explanation of the varied configurations of noncompaction as seen as a clinical entity. The clinical outcomes of decreased contractility, arrhythmia, and thromboembolism, have been stressed in the current literature, but more study is needed of the gray area between the normal variant and minimal noncompaction. A plea is made for the standardization of methods and terminology.
Protein–protein interactions as targets for small-molecule therapeutics in cancer
Authors: White Alex W. , Westwell Andrew D. , Brahemi Ghali
Published: March 2008

Small-molecule inhibition of the direct protein–protein interactions that mediate many important biological processes is an emerging and challenging area in drug design. Conventional drug design has mainly focused on the inhibition of a single protein, usually an enzyme or receptor, since these proteins often contain a clearly defined ligand-binding site with which a small-molecule drug can be designed to interact. Designing a small molecule to bind to a protein–protein interface and subsequently inhibit the interaction poses several challenges, including the initial identification of suitable protein–protein interactions, the surface area of the interface (it is often large), and the location of ‘hot spots’ (small regions suitable for drug binding). This article reviews the general approach to designing inhibitors of protein–protein interactions, and then focuses on recent advances in the use of small molecules targeted against a variety of protein–protein interactions that have therapeutic potential for cancer.
Le Groupe Prévention et Traitement des Plaies des Hospices-CHUV
Authors: Charbonneau L. , Mangin N.
Published: March 2008

Die Wundpflege stellt in der Betreuung einer immer älter werdenden Population mit chronischen Erkrankungen eine tägliche Herausforderung für Pflegende aller Disziplinen dar. Seit einigen Jahren gibt es im CHUV, Lausanne, eine interdisziplinäre Gruppe, welche die Pflegenden speziell in der Wundpflege unterstützt. Es wurden verschiedene Entscheidungshilfen und Richtlinien sowie ein Programm mit regelmässigen Weiterbildungsveranstaltungen erarbeitet. In dieser Übersicht berichten die Autorinnen über den Aufbau dieser Gruppe und die Erfahrungen in den ersten beiden Jahren.
Lesen oder Fernsehen?
Authors: Möller Jens , Retelsdorf Jan
Published: March 2008

Zusammenfassung. Ausgehend vom Erwartungs-Wert-Modell der Lesemotivation wird an einer für Schleswig-Holstein repräsentativen Stichprobe von Fünftklässlern (N = 1455) untersucht, wie sich Präferenzen für akademische und nicht-akademische Tätigkeiten von Schülerinnen und Schülern erklären lassen. Dafür wurden diese Vorlieben regressionsanalytisch auf vorangegangene Leistungserfahrungen sowie lesebezogene Erwartungs- und Wertkomponenten zurückgeführt. Die Präferenzen für das Lesen von Sachtexten und das Lesen von Geschichten werden vom Leseinteresse und der Leselust beeinflusst. Darüber hinaus zeigen sich negative Zusammenhänge der intrinsischen Aspekte der Lesemotivation mit Präferenzen für nicht-akademische Tätigkeiten wie das Fernsehen. Die Ergebnisse werden im Rahmen der Erwartungs-Wert-Theorie und mit Blick auf mögliche Konsequenzen für die Leseförderung diskutiert.
Identitätsbedrohung durch positives schulisches Leistungsfeedback
Authors: Kessels Ursula , Warner Lisa M. , Holle Julia , Hannover Bettina
Published: March 2008

Zusammenfassung. In zwei Experimenten wurde die Annahme überprüft, dass positive Leistungsrückmeldungen im schulischen Kontext unter Umständen für Jugendliche eine Bedrohung von wichtigen Identitätsaspekten (von Erwachsenen unabhängig sein; die eigene Geschlechtsrolle ausfüllen) implizieren, weshalb sie positives Feedback zurückweisen. In beiden Studien wurde nach einem Leistungstest falsches Feedback gegeben. In Studie 1 (N = 132 15-Jährige) wurde variiert, ob bei einem sehr positiven fachunspezifischen Leistungsfeedback dem Feedback-Empfänger im Beisein von Klassenkameraden gleichzeitig eine besondere Nähe zur Lehrkraft unterstellt wurde oder nicht. Erwartungsgemäß gaben die Jugendlichen nach der Unterstellung einer großen Nähe zur Lehrkraft an, weniger Hausaufgaben zu machen. In Studie 2 (N = 135 15-Jährige) wurde variiert, ob Jugendlichen eine sehr große oder nur durchschnittliche Begabung für ein geschlechtstypisiertes Schulfach (Physik) zurückgemeldet wurde. Erwartungskonform äußerten nur Jungen nach der Rückmeldung einer großen Physik-Begabung größeres Interesse an physikbezogenen Themen als nach dem durchschnittlichen Leistungsfeedback, wohingegen Mädchen kein Interesse an physikbezogenen Themen, nur an typischen “Mädchenthemen“ äußerten.
Geschlechtsspezifische Entwicklung der Anatomie und Gangdynamik im Kindes- und Jugendalter
Authors: König Andrej , Schölmerich Axel , Troje Nikolaus F.
Published: March 2008

Zusammenfassung. Im Verlauf der Kindheit werden Unterschiede zwischen Jungen und Mädchen im Körperbau und der Bewegungsdynamik sichtbar. Die Entwicklung von Körperproportionen und der Gangdynamik wurde an einer Querschnittsstichprobe von 27 Mädchen und 27 Jungen im Alter von 4 bis 16 Jahren analysiert. Zur Synthese digitalisierter Point-Light Modelle wurden die Gangmuster der Probanden im dreidimensionalen Raum erfasst. Lineare Diskriminanzfunktionen der Bewegungsinformation erlauben die überzufällig korrekte Zuordnung individueller Gangmuster nach Alter und Geschlecht, wobei die Präzision mit dem Alter ansteigt. Berechnet man die Diskriminanzfunktion als altersspezifische Funktion innerhalb von drei Altersgruppen, ergibt sich zusätzlich zur dynamischen Identifikation eine korrekte Zuordnung auf Grund der strukturellen anatomischen Information. Korrelative Zusammenhänge zwischen altersspezifischen Körperproportionen und dynamischen Aspekten treten dabei für Mädchen und Jungen in unterschiedlichen Entwicklungsphasen auf. Diese Ergebnisse werfen ein neues Licht auf die bisherigen Erkenntnisse der anthropometrischen Forschung und die Entwicklung von geschlechtsspezifischen Bewegungsmustern.
Entwicklung eines Fragebogens zur Erfassung von Aufmerksamkeitsdefizit-/Hyperaktivitätsstörungen (ADHS) bei Vorschulkindern im Eltern- und im Erziehungsurteil
Authors: Breuer Dieter , Döpfner Manfred
Published: March 2008

Zusammenfassung. Fragestellung: Zur Erfassung von Aufmerksamkeitsdefizit-/Hyperaktivitätsstörungen (ADHS) im Kindergarten- und Vorschulalter wurde die Validität und Reliabilität einer altersangepassten Version des Fremdbeurteilungsbogens für Hyperkinetische Störungen (FBB-HKS), der Fremdbeurteilungsbogen für Aufmerksamkeitsdefizit-/Hyperaktivitätsstörungen im Vorschulalter (FBB-ADHS-V) geprüft. Methodik: Bundesweit nahmen 708 Patienten (2,9 bis 7,3 Jahre) aus 103 Arztpraxen teil, die im Rahmen von kinderärztlichen Vorsorgeuntersuchungen vorgestellt (U8/U9, n = 521) oder vom Arzt als expansiv auffällig eingeschätzt wurden (AUF, n = 187). Eltern- und Erzieherbögen wurden ergänzt durch nachgeordnete, eher deskriptive ärztliche Beurteilungen. Ergebnisse: Durch konfirmatorische Faktorenanalysen konnte sowohl im Eltern- als auch im Erzieherurteil eine zweifaktorielle Lösung analog zu den DSM-IV-Subkategorien für ADHS (hyperaktiv/impulsiv; unaufmerksam) ermittelt werden. Die internen Konsistenzen aller Skalen liegen beurteilerübergreifend im guten Bereich. Die Trennschärfekoeffizienten der geänderten Items sind zufrieden stellend. Die Korrelationen zwischen den Beurteilerperspektiven liegen im mittleren Bereich und belegen damit die Ergebnisse internationaler und deutscher Studien in anderen Altersgruppen. Eltern beurteilen ihre Kinder etwas auffälliger als Erzieherinnen im Kindergarten. Jungen zeigen höhere Auffälligkeitswerte als Mädchen. Die Symptomausprägung korreliert deutlich mit Funktionseinschränkungen. Schlussfolgerungen: Der FBB-ADHS-V kann als reliables und valides Instrument zur Erfassung von ADHS-Symptomatik im Vorschulalter eingesetzt werden.
The depositional web on the floodplain of the Fly River, Papua New Guinea
Authors: Day Geoff , Dietrich William E. , Rowland Joel C. , Marshall Andrew
Published: March 2008

Floodplain deposition on lowland meandering rivers is usually interpreted as either lateral accretion during channel migration or overbank deposition. Previous studies on the Fly River in Papua New Guinea suggest, however, that floodplain channels (consisting of tie channel and tributary channels) play an important role in conveying sediment out across the floodplain. Here we report the results of an intensive field study conducted from 1990 to 1998 that documents the discharge of main stem water from the Fly River onto its floodplain and maps the spatial pattern of sediment deposition on the floodplain (using as a tracer elevated particulate copper introduced into the system by upstream mining). An extensive network of water level recorders demonstrates significant hydraulic heads from the main stem out the floodplain channels. For the monitoring period 1995–1998, net water discharge into the floodplain channels was about 20% of the flow. Another 20% is estimated to spill overbank from the main stem in wet years. Annual floodplain coring from 1990 to 1994 obtained over 800 samples across the 3500 km2 Middle Fly floodplain for use in documenting temporal and spatial patterns of sediment deposition. Early samples record the rapid spread of sediment up to 10 km away from the main stem via floodplain channels. Later, more intensive coring samples documented a well‐defined exponential decline in sediment deposition from the nearest channel (which differed little between floodplain and main stem channels). Deposition, averaging about 6–9 mm/a, occurred in a 1 km corridor either side of these channels and effectively ceased beyond that distance. About 40% of the total sediment load was deposited on the floodplain, with half of that being conveyed by the over 900 km of floodplain channels (equal to about 0.09% sediment deposition/km of main stem channel length). Levee topographies along the main stem and floodplain channels are similar but cannot be explained by the observed exponential functions. Channel margin shear flow during extended periods of flooding may give rise to the localized levee deposition. Our study demonstrates that tie and tributary floodplain channels can inject large volumes of sediment‐laden main stem waters great distances across the floodplain where they spill overbank, forming a narrow band of deposition, thereby creating a depositional web.
Dimethylsulfide emissions over the multi‐year ice of the western Weddell Sea
Authors: Zemmelink H. J. , Dacey J. W. H. , Houghton L. , Hintsa E. J. , Liss P. S.
Published: March 2008

This study, conducted in December 2004, is the first to present observations of DMS in a snow pack covering the multi‐year sea ice of the western Weddell Sea. The snow layer is important because it is the interface through which DMS needs to be transported in order to be emitted directly from the ice to the overlying atmosphere. High concentrations of DMS, up to 6000 nmol m−3, were found during the first weeks of December but concentrations sharply decline as late spring‐early summer progresses. This implies that DMS contained in sea ice is efficiently vented through the snow into the atmosphere. Indeed, field measurements by relaxed eddy accumulation indicate an average release of 11 μmol DMS m−2 d−1 from the ice and snow throughout December.
Chlorophyll blooms in the Antarctic Zone south of Australia and New Zealand in reference to the Antarctic Circumpolar Current fronts and sea ice forcing
Authors: Sokolov Serguei
Published: March 2008

Using new high‐resolution maps of the frontal structure of the Antarctic Circumpolar Current (ACC) derived from satellite altimetry, the relationship between circulation, sea ice concentrations, availability of light, and surface chlorophyll in the Southern Ocean south of Australia and New Zealand is investigated. South of the Polar Front, in the Antarctic Zone (AZ), there is a distinct spring bloom, which occurs earlier, persists for longer, and reaches higher maximum values farther south near Antarctica. The seasonal changes in chlorophyll pattern in this zone are predominantly driven by the sea ice meltwater flux which improves the irradiance‐mixing regime via formation of a very shallow mixed layer and provides an additional source of iron which triggers the chlorophyll blooms. There is a clear and consistent increase of about fivefold in both mean and maximum chlorophyll concentrations in regions of largest decrease in monthly mean sea ice concentrations. The seasonal signal in chlorophyll concentrations related to the ice melting is particularly strong between the southern ACC front and the southern boundary of the ACC. The changes in wind‐driven mixed layer depth in the AZ in summer do not explain adequately the elevated surface chlorophyll concentrations observed between these two ACC fronts. Reduction in the cloud cover and consequent increase in photosynthetically active radiation near the Antarctic coast in the summer could also support higher phytoplankton concentrations within the seasonal sea ice zone and costal polynyas.
Particle properties and water content of noctilucent clouds and their interannual variation
Authors: Baumgarten G. , Fiedler J. , Lübken F.‐J. , von Cossart G.
Published: March 2008

Noctilucent clouds (NLC) have been observed by a multicolor lidar in northern Norway (69°N, 16°E). From three backscatter coefficients we calculate the parameters of a monomodal particle size distribution. We deduce the mean of the size distribution, the width, and the average number density of the ensemble. Using the backscatter coefficients at the peak of the layer the particle size above ALOMAR is investigated by comparing the observations with model results for spherical and aspherical particles assuming either lognormal or Gaussian size distribution. From the analysis of 645 particle size soundings (142 h of measurements) we find that the average size of all NLC particles above ALOMAR from 1998 to 2005 is 47.7 ± 1 nm for cylinders with Gaussian distribution while it is 39.7 ± 1 nm for the traditional model having spherical particles with lognormal distribution. The distribution width is 16.6 ± 0.5 nm for Gaussian distributed cylinders while the particle number density is 85 ± 6 cm−3. We compare our results in detail to previously published measurements and find a satisfying agreement between the observations taking into account the limitations of previous studies and the different locations of the measurements. From the particle properties we calculate a mean surface density of (4.4 ± 0.2) × 10−8 cm2/cm3 and a mean volume density of (6.0 ± 0.2) × 10−14 cm3/cm3. The mean volume density of faint and strong clouds is 1.6 × 10−14 cm3/cm3 and 7.9 × 10−14 cm3/cm3, respectively. From the volume density we calculate the year‐to‐year variation of the seasonal mean cloud water content to be about 40% and the average observable NLC ice mass flux through 70°N to be about 11 kilotons.
Performance metrics for climate models
Authors: Gleckler P. J. , Taylor K. E. , Doutriaux C.
Published: March 2008

Objective measures of climate model performance are proposed and used to assess simulations of the 20th century, which are available from the Coupled Model Intercomparison Project (CMIP3) archive. The primary focus of this analysis is on the climatology of atmospheric fields. For each variable considered, the models are ranked according to a measure of relative error. Based on an average of the relative errors over all fields considered, some models appear to perform substantially better than others. Forming a single index of model performance, however, can be misleading in that it hides a more complex picture of the relative merits of different models. This is demonstrated by examining individual variables and showing that the relative ranking of models varies considerably from one variable to the next. A remarkable exception to this finding is that the so‐called “mean model” consistently outperforms all other models in nearly every respect. The usefulness, limitations and robustness of the metrics defined here are evaluated 1) by examining whether the information provided by each metric is correlated in any way with the others, and 2) by determining how sensitive the metrics are to such factors as observational uncertainty, spatial scale, and the domain considered (e.g., tropics versus extra‐tropics). An index that gauges the fidelity of model variability on interannual time‐scales is found to be only weakly correlated with an index of the mean climate performance. This illustrates the importance of evaluating a broad spectrum of climate processes and phenomena since accurate simulation of one aspect of climate does not guarantee accurate representation of other aspects. Once a broad suite of metrics has been developed to characterize model performance it may become possible to identify optimal subsets for various applications.
Detection of layering in the upper cloud layer of Venus northern polar atmosphere observed from radio occultation data
Authors: Gubenko Vladimir N. , Andreev Vitali E. , Pavelyev Alexander G.
Published: March 2008

Observations of radio wave scintillations represent an important tool for measuring of small‐scale irregularities in the atmosphere of Venus. Prominent features of enhanced scintillation located in the 60‐km region were observed in Mariners 5 and 10, Venera 9, and Pioneer Venus occultations. It is possible that the enhanced scintillations are due to the random turbulence in the upper region which is caused by trapped small‐scale gravity waves. However, other interpretations are possible. Thin stable layers, which are commonly observed in the Earth stratosphere under cloud‐free conditions, could also contribute to scattering in the Venus stratosphere. If scintillations observed in different occultations are correlated, then these scintillations may be attributed to the persistent layers. Cross correlations of 32‐cm radio wave amplitude fluctuations have been determined for seven radio occultation measurements of Venus's northern polar atmosphere using Venera 15 and 16. Significant cross correlations were found between 59.0 and 61.5 km in four different radio occultations. Layering is revealed in the upper layer of the Venus clouds at altitudes of 59.0–61.5 km, which is specified by enhanced turbulence of the atmosphere. It is found that the lifetime of the small‐scale layered irregularities is 2 d or more and that their horizontal extension in the meridional direction can exceed 180 km. A possible cause of emergence of the layered structures inside the upper layer of polar clouds of Venus is discussed.
Statistical and process‐based modeling analyses of tree growth response to climate in semi‐arid area of north central China: A case study of Pinus tabulaeformis
Authors: Shi Jiangfeng , Liu Yu , Vaganov Eugene A. , Li Jinbao , Cai Qiufang
Published: March 2008

Statistical modeling techniques and the Vaganov‐Shashkin (VS) forward model of tree ring formation were used to investigate tree growth response of Pinus tabulaeformis to climate variations in semi‐arid north central China. Both statistical and process‐based modeling techniques were shown to be capable of simulating and evaluating climate‐tree growth relationships for the study area, but the process‐based VS model produced results that were more physically interpretable. Statistical modeling results indicate that both moisture and temperature have significant effects on tree growth during the growing season, with the most important months being May–August. The VS modeled results validated the above statistical modeling results, and further clarified the effects on tree growth of the seasonal distribution of temperature and soil moisture, soil moisture status prior to the growing season, and the start and end dates of the growing season. Under current and projected climate scenarios, our modeling results suggest significant tree growth reduction in north central China, and the possibility that regional forests may reduce their capacity to sequester carbon.
Cellular origin of the Bufo arenarum sperm receptor gp75, a ZP2 family member: its proteolysis after fertilization
Authors: Scarpeci Sonia L. , Sanchez Mercedes L. , Cabada Marcelo O.
Published: March 2008

Background information. The egg envelope is an extracellular matrix that surrounds oocytes. In frogs and mammals, a prominent feature of envelope modification following fertilization is the N‐terminal proteolysis of the envelope glycoproteins, ZPA [ZP (zona pellucida) A]. It was proposed that ZPA N‐terminal proteolysis leads to a conformational change in egg envelope glycoproteins, resulting in the prevention of polyspermy. Bufo arenarum VE (vitelline envelope) is made up of at least four glycoproteins: gp120 (glycoprotein 120), gp75, gp41 and gp38. The aim of the present study was to identify and characterize the baZPA (B. arenarum ZPA homologue). Also, our aim was to evaluate its integrity and functional significance during fertilization.

Results. VE components were labelled with FITC in order to study their sperm‐binding capacity. The assay showed that gp75, gp41 and gp38 possess sperm‐binding activity. We obtained a full‐length cDNA of 2062 bp containing one ORF (open reading frame) with a sequence for 687 amino acids. The predicted amino acid sequence had close similarity to that of mammalian ZPA. This result indicates that gp75 is the baZPA. Antibodies raised against an N‐terminal sequence recognized baZPA and inhibited sperm—baZPA extracted from VE binding. This protein does not induce the acrosome reaction in homologue sperm. Northern‐blot studies indicated that the transcript is exclusively expressed in the ovary. In situ hybridization studies confirmed this and pointed to previtellogenic oocytes and follicle cells surrounding the oocyte as the source of the transcript. baZPA was cleaved during fertilization and the N‐terminal peptide fragment remained disulfide bonded to the glycoprotein moiety following proteolysis.

Conclusion. From the sequence analysis, it was possible to consider that gp75 is the baZPA. It is expressed by previtellogenic oocytes and follicle cells. Also, it can be considered as a sperm receptor that undergoes N‐terminal proteolysis during fertilization. The N‐terminal peptide could be necessary for sperm binding.
Cell‐penetrating peptides: from molecular mechanisms to therapeutics
Authors: Morris May C. , Deshayes Sebastien , Heitz Frederic , Divita Gilles
Published: March 2008

The recent discovery of new potent therapeutic molecules which do not reach the clinic due to poor delivery and low bioavailability have made the delivery of molecules a keystone in therapeutic development. Several technologies have been designed to improve cellular uptake of therapeutic molecules, including CPPs (cell‐penetrating peptides), which represent a new and innovative concept to bypass the problem of bioavailability of drugs. CPPs constitute very promising tools and have been successfully applied for in vivo. Two CPP strategies have been described to date; the first one requires chemical linkage between the drug and the carrier for cellular drug internalization, and the second is based on the formation of stable complexes with drugs, depending on their chemical nature. The Pep and MPG families are short amphipathic peptides, which form stable nanoparticles with proteins and nucleic acids respectively. MPG‐ and Pep‐based nanoparticles enter cells independently of the endosomal pathway and efficiently deliver cargoes, in a fully biologically active form, into a large variety of cell lines, as well as in animal models. This review focuses on the structure—function relationship of non‐covalent MPG and Pep‐1 strategies, and their requirement for cellular uptake of biomolecules and applications in cultured cells and animal models.
APC nuclear membrane association and microtubule polarity
Authors: Collin Ludovic , Schlessinger Karni , Hall Alan
Published: March 2008

Background information. Directional cell migration is a fundamental feature of embryonic development, the inflammatory response and the metastatic spread of cancer. Migrating cells have a polarized morphology with an asymmetric distribution of signalling molecules and of the actin and microtubule cytoskeletons. The dynamic reorganization of the actin cytoskeleton provides the major driving force for migration in all mammalian cell types, but microtubules also play an important role in many cells, most notably neuronal precursors.

Results. We previously showed, using primary fibroblasts and astrocytes in in vitro scratch‐induced migration assays, that the accumulation of APC (adenomatous polyposis coli; the APC tumour suppressor protein) at microtubule plus‐ends promotes their association with the plasma membrane at the leading edge. This is required for polarization of the microtubule cytoskeleton during directional migration. Here, we have examined the organization of microtubules in the soma of migrating neurons and fibroblasts.

Conclusions. We find that APC, through a direct interaction with the NPC (nuclear pore complex) protein Nup153 (nucleoporin 153), promotes the association of microtubules with the nuclear membrane.
Observation of nonmonotonic oscillatory interlayer exchange coupling in Co∕Cu∕CoO films with varying Cu spacer thickness
Authors: Song Young-Yeal , Kim Dong-Hyun , Yu Seong-Cho , Kim Petr. D. , Turpanov Igor Alexandrovic , Lee Liudmila Alexeevna , Buzmakov Afanasy Egorovic , Lee Kyu Won
Published: March 2008

We report our experimental observation of interlayer exchange coupling phenomena in CoO∕Cu∕Co trilayers with systematic variation of Cu spacer layer thickness as well as temperature. It has been found that there exists a clear indication of nonmonotonically varying oscillatory interlayer exchange coupling. The amplitude of oscillation increases, reaches to the maximum, and decreases with increasing Cu spacer thickness from 1 to 16 atomic layers for all temperature ranges between 70 and 200K.
Thermal fluctuations in magnetic nanoparticles: Numerical testing of Langevin approach
Authors: Ragusa C. , Serpico C. , Repetto M. , d’Aquino M. , Xie B. , Bertotti G.
Published: March 2008

Thermal fluctuations for fine ferromagnetic particles are studied. First, a derivation of the fluctuation-dissipation relation for the stochastic (Langevin-type) Landau–Lifshitz equation is carried out. Then, the Fokker–Planck analysis of fluctuations in uniformly magnetized particles is compared with the full micromagnetic analysis based on numerical integration of the spatially discretized Langevin–Landau–Lifshitz equation. The relevance of these results to the formulation of a meaningful “standard problem” for micromagnetic analysis of thermal fluctuations in magnetic nanoparticles is finally discussed.
Structure–magnetic property relationship in transition metal (M=V,Cr,Mn,Fe,Co,Ni) doped SnO2 nanoparticles
Authors: Van Komen C. , Thurber A. , Reddy K. M. , Hays J. , Punnoose A.
Published: March 2008

This work reports the results of an extensive search for ferromagnetism in SnO2 doped with a wide range of transition metal cations (M=V, Cr, Mn, Fe, Co, and Ni). By varying the dopant concentration in the 0–12% range, signatures of ferromagnetic behavior in varying degrees were observed with most dopants. The room temperature magnetic moments per dopant ion were low in all the systems and Co (0.13μB∕ion), Fe (0.014μB∕ion), and Cr (0.06μB∕ion) showed relatively the strongest ferromagnetic behavior. In these systems, the observed ferromagnetism initially increased reaching a maximum in the 1–12% range and then gradually weakened and eventually disappeared at higher concentration. The limiting dopant concentration xL at which ferromagnetic behavior reaches a maximum varies with dopant type and has a strong relation to structural changes revealed from detailed x-ray diffraction (XRD) analysis. The XRD data indicated that the lattice volume for every Sn1−xMxO2 system decreased with increasing x in the 0⩽xL range. However, for x>xL, the lattice volume increased dramatically indicating a significant interstitial doping which destroys the ferromagnetic behavior.
An analysis through order ℏ2 of a surface hopping expansion of the nonadiabatic wave function
Authors: Herman Michael F. , Wu Yinghua
Published: March 2008

It is shown that a surface hopping expansion of the semiclassical wave function formally satisfies the time independent Schrödinger equation for many-state, multidimensional problems. This wave function includes terms involving hops between different adiabatic quantum states as well as momentum changes without change of state at each point along classical trajectories. The single-state momentum changes correct for the order ℏ2 errors due to the semiclassical approximation that are present even in single surface problems. A prescription is provided for the direction of this momentum change and the amplitude associated with it. The direction of the momentum change for energy conserving hops between adiabatic states is required to be in the direction of the nonadiabatic coupling vector. The magnitude of the posthop momentum in this direction is determined by the energy, but the sign is not. Hops with both signs of this momentum component are required in order for the wave function to formally satisfy the Schrödinger equation. Numerical results are presented which illustrate how the surface hopping expansion can be implemented and the accuracy that can be obtained.
Ultrasmooth Ni thin films evaporated on polyethylene naphthalate films for spin quantum cross devices
Authors: Kaiju Hideo , Ono Akito , Kawaguchi Nobuyoshi , Ishibashi Akira
Published: March 2008

Surface morphology of Ni thin films vacuum-deposited on polyethylene naphtalate (PEN) organic films has been investigated as a function of Ni film thickness for spin quantum cross devices. The surface roughness of the Ni films decreases from 1.3nm, being the roughness of PEN films, down to 0.69nm as the thickness of Ni films increases up to 41nm. As a result of the scaling investigation of the surface roughness, the surface roughness for Ni films of sub-10-nm thickness, in the scanning scale of the film thickness, is less than 0.23nm, corresponding to one atomic layer thickness. These experimental results indicate that Ni thin films on PEN films are suitable as a candidate of metal/insulator hybrid materials used for spin quantum cross devices and may open up a novel research field on the electric characteristics of a few atoms or molecules, which leads to high-density memories.
Phase transition processes and magnetocaloric effect in Ni2.15Mn0.85−xCoxGa alloys
Authors: Bao B. , Long Y. , Duan J. F. , Shi P. J. , Wu G. H. , Ye R. C. , Chang Y. Q. , Zhang J. , Rong C. B.
Published: March 2008

Phase transition processes and magnetocaloric effect in Ni2.15Mn0.85−xCoxGa (x=0.03, 0.04, 0.05, and 0.06) alloys were investigated. The alloys exhibit nonmodulated tetragonal martensitic structure at room temperature. According to experiment results, Ni2.15Mn0.85−xCoxGa alloys undergo a magnetostructural phase transition on the heating process when electron concentration is in the range from 7.633 to 7.643. The alloys also show large magnetic entropy changes. With increasing Co content, the magnetic entropy change decreases.
Eliminating spin contamination in auxiliary-field quantum Monte Carlo: Realistic potential energy curve of F2
Authors: Purwanto Wirawan , Al-Saidi W. A. , Krakauer Henry , Zhang Shiwei
Published: March 2008

The use of an approximate reference state wave function ∣Φr⟩ in electronic many-body methods can break the spin symmetry of Born–Oppenheimer spin-independent Hamiltonians. This can result in significant errors, especially when bonds are stretched or broken. A simple spin-projection method is introduced for auxiliary-field quantum Monte Carlo (AFQMC) calculations, which yields spin-contamination-free results, even with a spin-contaminated ∣Φr⟩. The method is applied to the difficult F2 molecule, which is unbound within unrestricted Hartree–Fock (UHF). With a UHF ∣Φr⟩, spin contamination causes large systematic errors and long equilibration times in AFQMC in the intermediate, bond-breaking region. The spin-projection method eliminates these problems and delivers an accurate potential energy curve from equilibrium to the dissociation limit using the UHF ∣Φr⟩. Realistic potential energy curves are obtained with a cc-pVQZ basis. The calculated spectroscopic constants are in excellent agreement with experiment.
Performance of the M06 family of exchange-correlation functionals for predicting magnetic coupling in organic and inorganic molecules
Authors: Valero Rosendo , Costa Ramon , de P. R. Moreira Ibério , Truhlar Donald G. , Illas Francesc
Published: March 2008

The performance of the M06 family of exchange-correlation potentials for describing the electronic structure and the Heisenberg magnetic coupling constant (J) is investigated using a set of representative open-shell systems involving two unpaired electrons. The set of molecular systems studied has well defined structures, and their magnetic coupling values are known experimentally. As a general trend, the M06 functional is about equally as accurate as B3LYP or PBE0. The performance of local functionals is important because of their economy and convenience for large-scale calculations; we find that M06-L local functional of the M06 family largely improves over the local spin density approximation and the generalized gradient approximation.
Infrared spectra of (HCOOH)2 and (DCOOH)2 in rare gas matrices: A comparative study with gas phase spectra
Authors: Ito Fumiyuki
Published: March 2008

Infrared absorption spectra of (HCOOH)2 and (DCOOH)2 in solid argon, krypton, and xenon matrices have been measured and each fundamental band has been assigned. Spectra in Ar and Kr matrices showed notable splitting in contrast to those in Xe, which suggests a difference in structure of the trapping sites. A comparison with the reported jet-cooled spectra has shown that vibrational structures of the spectra of (HCOOH)2 and (DCOOH)2 in the OH stretching region are preserved in the matrices. On the other hand, the CO stretching band of (HCOOH)2 shows a drastic change upon matrix isolation, wherein the Fermi-triad feature observed in gas phase [F. Ito, Chem. Phys. Lett. 447, 202 (2007)] could not be identified. No substantial change of the vibrational structure has been found for matrix-isolated (DCOOH)2. The differences of the vibrational structures in the matrix-isolation spectra and in the jet-cooled spectra have been qualitatively accounted for using the idea of anharmonic couplings among “matrix-shifted harmonic states.”