bluuebunny/crossref_metadata_2025 huggingface dataset:
An analytical solution for two slender bodies of revolution translating in very close proximity
Authors: WANG Q. X.
Published: June 2007

The irrotational flow past two slender bodies of revolution at angles of yaw, translating in parallel paths in very close proximity, is analysed by extending the classical slender body theory. The flow far away from the two bodies is shown to be a direct problem, which is represented in terms of two line sources along their longitudinal axes, at the strengths of the variation rates of their cross-section areas. The inner flow near the two bodies is reduced to the plane flow problem of the expanding (contracting) and lateral translations of two parallel circular cylinders with different radii, which is then solved analytically using conformal mapping. Consequently, an analytical flow solution has been obtained for two arbitrary slender bodies of revolution at angles of yaw translating in close proximity. The lateral forces and yaw moments acting on the two bodies are obtained in terms of integrals along the body lengths. A comparison is made among the present model for two slender bodies in close proximity, Tuck & Newman's (1974) model for two slender bodies far apart, and VSAERO (AMI)–commercial software based on potential flow theory and the boundary element method (BEM). The attraction force of the present model agrees well with the BEM result, when the clearance,h0, is within 20% of the body length, whereas the attraction force of Tuck & Newman is much smaller than the BEM result whenh0is within 30% of the body length, but approaches the latter whenh0is about half the body length. Numerical simulations are performed for the three typical manoeuvres of two bodies: (i) a body passing a stationary body, (ii) two bodies in a meeting manoeuvre (translating in opposite directions), and (iii) two bodies in a passing manoeuvre (translating in the same direction). The analysis reveals the orders of the lateral forces and yaw moments, as well as their variation trends in terms of the manoeuvre type, velocities, sizes, angles of yaw of the two bodies, and their proximity, etc. These irrotational dynamic features are expected to provide a basic understanding of this problem and will be beneficial to further numerical and experimental studies involving additional physical effects.
Direct numerical simulation of stenotic flows. Part 1. Steady flow
Authors: VARGHESE SONU S. , FRANKEL STEVEN H. , FISCHER PAUL F.
Published: June 2007

Direct numerical simulations (DNS) of steady and pulsatile flow through 75% (by area reduction) stenosed tubes have been performed, with the motivation of understanding the biofluid dynamics of actual stenosed arteries. The spectral-element method, providing geometric flexibility and high-order spectral accuracy, was employed for the simulations. The steady flow results are examined here while the pulsatile flow analysis is dealt with in Part 2 of this study. At inlet Reynolds numbers of 500 and 1000, DNS predict a laminar flow field downstream of an axisymmetric stenosis and comparison to previous experiments show good agreement in the immediate post-stenotic region. The introduction of a geometric perturbation within the current model, in the form of a stenosis eccentricity that was 5% of the main vessel diameter at the throat, resulted in breaking of the symmetry of the post-stenotic flow field by causing the jet to deflect towards the side of the eccentricity and, at a high enough Reynolds number of 1000, jet breakdown occurred in the downstream region. The flow transitioned to turbulence about five diameters away from the stenosis, with velocity spectra taking on a broadband nature, acquiring a -5/3 slope that is typical of turbulent flows. Transition was accomplished by the breaking up of streamwise, hairpin vortices into a localized turbulent spot, reminiscent of the turbulent puff observed in pipe flow transition, within which r.m.s. velocity and turbulent energy levels were highest. Turbulent fluctuations and energy levels rapidly decayed beyond this region and flow relaminarized. The acceleration of the fluid through the stenosis resulted in wall shear stress (WSS) magnitudes that exceeded upstream levels by more than a factor of 30 but low WSS levels accompanied the flow separation zones that formed immediately downstream of the stenosis. Transition to turbulence in the case of the eccentric stenosis was found to be manifested as large temporal and spatial gradients of shear stress, with significant axial and circumferential variations in instantaneous WSS.
Experimental study on resonantly forced interfacial waves in a stratified circular cylindrical basin
Authors: WAKE GEOFFREY W. , HOPFINGER EMIL J. , IVEY GREGORY N.
Published: June 2007

Laboratory experiments have been performed on resonantly forced interfacial waves in a circular cylindrical basin containing a two-layer stratified fluid. The results of this shallow-water study exhibit a number of similarities to previous shallow-water studies performed in single-layer fluids, such as the generation of a large-amplitude response over a frequency bandwidth offset from the primary resonance, generation of a swirling mode at the observed resonant condition, and the significant contribution of higher harmonics. The two-layer experiments also produce results that are unique to stratified domains. In particular, the observed negative nonlinearity of the resonant condition at shallow water depth, mixing of the density interface resulting in detuning the forced response from the resonant condition, the enhanced role of viscous dissipation, and an alternative pathway for the nonlinear generation of higher-frequency waves when the layer depths are disparate. The results of this study are considered with regard to their implications for enclosed basins at the geophysical scale that are subject to near resonant forcing.
A conditionally cubic-Gaussian stochastic Lagrangian model for acceleration in isotropic turbulence
Authors: LAMORGESE A. G. , POPE S. B. , YEUNG P. K. , SAWFORD B. L.
Published: June 2007

The modelling of fluid-particle acceleration in homogeneous isotropic turbulence in terms of stochastic models for the Lagrangian velocity, acceleration and a dissipation rate variable is considered. The basis for the Reynolds model (A. M. Reynolds, Phys. Rev. Lett. vol. 91, 2003, 084503) is reviewed and examined by reference to direct numerical simulations (DNS) of isotropic turbulence at Taylor-scale Reynolds number (Rλ) up to about 650. In particular, we show DNS data that support stochastic modelling of the logarithm of pseudo-dissipation as an Ornstein–Uhlenbeck process and reveal non-Gaussianity of the acceleration conditioned on fluctuations of the pseudo-dissipation rate. The DNS data are used to construct a new stochastic model that is exactly consistent with Gaussian velocity and conditionally cubic-Gaussian acceleration statistics. This model captures the effects of small-scale intermittency on acceleration and the conditional dependence of acceleration on pseudo-dissipation (which differs from that predicted by the refined Kolmogorov hypotheses). Non-Gaussianity of the conditionally standardized acceleration probability density function (PDF) is accounted for in terms of model nonlinearity. The large-time behaviour of the new model is that of a velocity-dissipation model that can be matched with DNS data for conditional second-order Lagrangian velocity structure functions. As a result, the diffusion coefficient for the new model incorporates two-time information and its Reynolds-number dependence as observed in DNS. The resulting model predictions for conditional and unconditional velocity autocorrelations and time scales are shown to be in very good agreement with DNS.
Passive scalar mixing in vortex rings
Authors: SAU RAJES , MAHESH KRISHNAN
Published: June 2007

Direct numerical simulation is used to study the mixing of a passive scalar by a vortex ring issuing from a nozzle into stationary fluid. The ‘formation number’ (Gharibet al. J. Fluid Mech.vol. 360, 1998, p. 121), is found to be 3.6. Simulations are performed for a range of stroke ratios (ratio of stroke length to nozzle exit diameter) encompassing the formation number, and the effect of stroke ratio on entrainment and mixing is examined. When the stroke ratio is greater than the formation number, the resulting vortex ring with trailing column of fluid is shown to be less effective at mixing and entrainment. As the ring forms, ambient fluid is entrained radially into the ring from the region outside the nozzle exit. This entrainment stops once the ring forms, and is absent in the trailing column. The rate of change of scalar-containing fluid is found to depend linearly on stroke ratio until the formation number is reached, and falls below the linear curve for stroke ratios greater than the formation number. This behaviour is explained by considering the entrainment to be a combination of that due to the leading vortex ring and that due to the trailing column. For stroke ratios less than the formation number, the trailing column is absent, and the size of the vortex ring increases with stroke ratio, resulting in increased mixing. For stroke ratios above the formation number, the leading vortex ring remains the same, and the length of the trailing column increases with stroke ratio. The overall entrainment decreases as a result.
Application of joint error maximum mutual compensation for hexapod robots
Authors: Veryha Yauheni , Petersen Henrik Gordon
Published: June 2007

A good practice to ensure high-positioning accuracy in industrial robots is to use joint error maximum mutual compensation (JEMMC). This paper presents an application of JEMMC for positioning of hexapod robots to improve end-effector positioning accuracy. We developed an algorithm and simulation framework in MatLab to find optimal hexapod configurations with JEMMC. Based on a real hexapod model, simulation results of the proposed approach are presented. Optimal hexapod configurations were found using the local minimum of the infinity norm of hexapod Jacobian inverse. JEMMC usage in hexapod robots can improve hexapod end-effector positioning accuracy by two times and more.
Opening Remarks on the History of Science in Yiddish
Authors: Métraux Alexandre
Published: June 2007

When introducing a collection of essays on Yiddish, Joseph Sherman asserted, among other things, that:
Although the Nazi Holocaust effectively destroyed Yiddish together with the Jews of Eastern Europe for whom it was a lingua franca, the Yiddish language, its literature and culture have proven remarkably resilient. Against all odds, Yiddish has survived to become a focus of serious intellectual, artistic and scholarly activity in the sixty-odd years that have passed since the end of World War II. From linguistic and literary research in the leading universities of the world to the dedicated creativity of contemporary novelists and poets in Israel and America, from the adaptation of Yiddish words and phrases to the uses of daily newspapers in English to the elevation of Yiddish as a new loshn koydesh by Hasidic sects, from the publication of new writing to the translation of its established canonical works into modern European languages, Yiddish is continually reminding the world of its vibrancy, relevance and importance as a marker of Jewish identity and survival. (Sherman 2004, 9)
A Study in Red: Jewish Scholarship in the 1920s Soviet Union
Authors: Shneer David
Published: June 2007

Argument

In the 1920s the Soviet Union invested a group of talented, mostly socialist, occasionally Communist, Jewish writers and thinkers to use the power of the state to remake Jewish culture and identity. The Communist state had inherited a multiethnic empire from its tsarist predecessors and supported the creation of secular cultures for each ethnicity. These cultures would be based not on religion, but on language and culture. Soviet Jews had many languages from which to choose to be their official Soviet language, but Yiddish, the vernacular of eastern European Jewry, won the battle and served as the basis of secular Soviet Jewish culture. Soviet Jewish scholars, writers, and other cultural activists remade Jewish culture by creating a usable Jewish past that fit the socialist present, reforming the “wild” vernacular of Yiddish into a modern language worthy of high culture, and transforming Jews into secular Soviet citizens.
“On the Social-Economic Front”: The Polemics of Shtetl Research during the Stalin Revolution
Authors: Yalen Deborah
Published: June 2007

Argument

This article explores the relationship between ideology and statistical knowledge in Soviet Yiddish scholarship during the first Five-Year Plan and Cultural Revolution. Specifically, it examines the political status of Yiddish-language socioeconomic research as a tool of state building in the shtetls (small market towns) of the former Pale of Jewish Settlement. Historically, many Jewish inhabitants of the shtetl worked as economic middlemen between city and countryside, a function that became politically untenable after 1917. The Soviet regime sponsored Yiddish socioeconomic data collection in order to monitor its efforts to transform the occupational structure of shtetl Jewry. Accordingly, this data was expected to demonstrate the steady self-disintegration of the shtetl as an obsolete artifact of the old regime. In fact, these Soviet Yiddish narratives inadvertently highlighted the endurance of the shtetl in Soviet life at both the concrete and discursive levels. A close reading of these sources provides insight into how a segment of the Soviet Jewish intelligentsia attempted to align itself within the new state's scientific establishment by fusing modern Jewish social scientific knowledge with Marxist-Leninist principles. In the polemics of the “shtetl problem” we find an example of how Soviet yidishe visnshaft registered the constantly shifting perceptions of ideological orthodoxy and deviation among Jewish Communists, and provoked international debate among Jewish demographers and economists as to the political use and abuse of statistics.
Classical Text in Translation The Tasks of Yiddish Philology>
Authors: Borochov Ber
Published: June 2007

Judeo-German developed, like any popular dialect, according to unconscious and natural laws. No gardener nursed and tended it, nobody cut back its wild shoots. (Ph. Mansch 1888)
Effectiveness of control measures during the SARS epidemic in Beijing: a comparison of theRtcurve and the epidemic curve
Authors: COWLING B. J. , HO L. M. , LEUNG G. M.
Published: June 2007

One of the areas most affected by SARS was Beijing with 2521 reported cases. We estimate the effective reproductive numberRtfor the Beijing SARS epidemic, which represents the average number of secondary cases per primary case on each day of the epidemic and is therefore a measure of the underlying transmission dynamics. Our results provide a quantitative assessment of the effectiveness of public health control measures. More generally, our results illustrate how changes inRtwill reflect changes in the epidemic curve.
The burden of acute gastrointestinal illness in Ontario, Canada, 2005–2006
Authors: SARGEANT J. M. , MAJOWICZ S. E. , SNELGROVE J.
Published: June 2007

A retrospective, cross-sectional telephone survey (n=2090) was conducted in Ontario, Canada, between May 2005 and April 2006, to determine the burden of acute gastrointestinal illness in the population. The 4-week prevalence was 8·56% (95% CI 7·36–9·76); in households with more than one resident, 35% of cases reported someone else in their household had similar symptoms at the same time. The annual adjusted incidence rate was 1·17 (95% CI 0·99–1·35) episodes per person-year, with higher rates in females, rural residents, and in the winter and spring. Health care was sought by 22% of cases, of which 33% were asked to provide a stool sample. Interestingly, 2·2% of cases who did not visit a health-care provider reported self-administering antibiotics. Overall, acute gastrointestinal illness appears to pose a significant burden in the Ontario population. Further research into the specific aetiologies and risk factors is now needed to better target intervention strategies.
Epidemiology of vertebral osteomyelitis (VO) in France: analysis of hospital-discharge data 2002–2003
Authors: GRAMMATICO L. , BARON S. , RUSCH E. , LEPAGE B. , SURER N. , DESENCLOS J. C. , BESNIER J. M.
Published: June 2007

Vertebral osteomyelitis (VO) is a rare event. To estimate the incidence of VO in France for 2002–2003, national hospital-discharge data were used. Hospital stays were categorized as definite, probable or possible VO. Unique patient identification numbers allowed the investigators to link patients with multiple hospital stays and to analyse data for individual patients. A sample of medical records was reviewed to assess the specificity of the VO case definition. In 2002–2003, 1977 and 2036 hospital stays corresponding to 1422 and 1425 patients (median age 59 years, male:female ratio 1·5) were classified as definite (64%), probable (24%) and possible (12%) VO. The overall incidence of VO was 2·4/100 000. Incidence increased with age: 0·3/100 000 (<20 years), 3·5/100 000 (50–70 years) and 6·5/100 000 (>70 years). The main infectious agents reported wereStaphylococcusspp. (38%) andMycobacterium tuberculosis(31%). The most frequent comorbidities were septicaemia (27%) and endocarditis (9%). Three percent of patients died. A review of 90 medical records confirmed the diagnosis of VO in 94% of cases. Using a hospital database and a specific case definition, nationwide surveillance of VO is possible.
Epidemiological characteristics of reported sporadic and outbreak cases of E. coli O157 in people from Alberta, Canada (2000–2002): methodological challenges of comparing clustered to unclustered data
Authors: PEARL D. L. , LOUIE M. , CHUI L. , DORÉ K. , GRIMSRUD K. M. , MARTIN S. W. , MICHEL P. , SVENSON L. W. , McEWEN S. A.
Published: June 2007

Using multivariable models, we compared whether there were significant differences between reported outbreak and sporadic cases in terms of their sex, age, and mode and site of disease transmission. We also determined the potential role of administrative, temporal, and spatial factors within these models. We compared a variety of approaches to account for clustering of cases in outbreaks including weighted logistic regression, random effects models, general estimating equations, robust variance estimates, and the random selection of one case from each outbreak. Age and mode of transmission were the only epidemiologically and statistically significant covariates in our final models using the above approaches. Weighing observations in a logistic regression model by the inverse of their outbreak size appeared to be a relatively robust and valid means for modelling these data. Some analytical techniques, designed to account for clustering, had difficulty converging or producing realistic measures of association.
Folate status and mood: is there a relationship?
Authors: Williams Emma , Stewart-Knox Barbara , McConville Chris , Bradbury Ian , Armstrong Nicola C , McNulty Helene
Published: June 2007

Objective

To explore the relationship between subjective mood, folate status and homocysteine in healthy individuals.

Design

Subjective mood assessments were completed twice daily over the course of one week using the Positive and Negative Affect Scale (PANAS). The PANAS is a validated scale which considers mood state on two distinct continua, one reflecting positive mood and the other negative mood, each requiring response to 10 adjectives on a Likert scale. A blood sample was taken on one occasion at the start of the week during which subjective mood was assessed and analysed for red-blood-cell (RBC) folate, serum folate and plasma homocysteine concentrations.

Subjects

Male volunteers aged 19–47 years (n= 58) were recruited from local industries.

Results

High concentrations of RBC folate were associated with less variability (lower standard deviation) in negative mood (P= 0.023). Subjective mood, however, was not related to serum folate or homocysteine.

Conclusions

This study appears to be the first to uncover an association between long-term folate status and subjective mood (employing the PANAS) in healthy males. More research is needed to further explore the relationship between nutritional status and mood.
Personal and lifestyle characteristics predictive of the consumption of fast foods in Australia
Authors: Mohr Philip , Wilson Carlene , Dunn Kirsten , Brindal Emily , Wittert Gary
Published: June 2007

Objective

To identify key predictors of fast-food consumption from a range of demographic, attitudinal, personality and lifestyle variables.

Methods

We analysed data from a nationwide survey (n= 20 527) conducted in Australia by Nielsen Media Research. Items assessing frequency of fast-food consumption at (1) eat in and (2) take away were regressed onto 12 demographic, seven media consumption, and 23 psychological and lifestyle variables, the latter derived from factor analysis of responses to 107 attitudinal and behavioural items.

Results

Stepwise multiple regression analyses explained 29.6% of the variance for frequency of take-away and 9.6% of the variance for frequency of eat-in consumption of fast foods. Predictors of more frequent consumption of fast food at take away (and, to a lesser extent, eat in) included lower age – especially under 45 years, relative indifference to health consequences of behaviour, greater household income, more exposure to advertising, greater receptiveness to advertising, lesser allocation of time for eating, and greater allocation of time to home entertainment. There were no effects for occupational status or education level.

Conclusions

The effects for age suggest that fast-food take-away consumption is associated with a general cultural shift in eating practices; individual differences in attitudinal and lifestyle characteristics constitute additional, cumulative, predictive factors. The role of advertising and the reasons for the lesser explanatory value of the eat-in models are important targets for further research.
Positive sentinel lymph nodes should be followed by axillary lymph node dissection
Authors: Hoehne F. , Mabry H. , Giuliano A. E.
Published: June 2007

The use of sentinel lymph node biopsy (SLNB) has revolutionized breast surgery for early stage breast cancer. SLNB accurately stages the axilla without the morbidity of axillary lymph node dissection (ALND). While allowing those patients with No disease to avoid a potentially morbid dissection, SLNB is a diagnostic procedure which identifies nodal disease and is not designed to replace ALND in patients with metastatic disease in the axilla. ALND provides regional disease control, assists physicians in making decisions for patients regarding systemic therapy, and may or may not have a survival advantage. The American College of Surgeons Oncology Group Z0011 study was constructed to determine whether there was a survival difference between completion ALND vs. observation in patients with a positive sentinel lymph node (SLN). Without strong data from randomized, controlled trials regarding the locoregional and long-term survival of patients who undergo observation after a positive SLN, patients should be offered completion ALND for a positive SLNB although ALND may offer no survival advantage.
Machen SSRI suizidal?
Authors: Bridler  , Straub
Published: June 2007

Selektive Serotonin-Wiederaufnahmehemmer (SSRI) gehören weltweit zu den am häufigsten verordneten Psychopharmaka. Kurz nach ihrer Einführung erschienen erste Berichte, welche die Einnahme von SSRI in den Zusammenhang mit einer erhöhten Suizidgefahr brachten. Die Mini-Review stellt die seither zum Thema SSRI und Suizidalität gewonnenen Erkenntnisse anhand von Metaanalysen, Populations-basierten Untersuchungen und Beobachtungsstudien dar und gibt konkrete Empfehlungen zum Einsatz von SSRI ab.
Leistenschwellung und Knöchelödem nach Inguinal-hernien-OP
Authors: Oettl  , Tzankov  , Ramseier
Published: June 2007

Bei einer schnell wachsenden inguinalen Raumforderung haben wir die Diagnose eines aggressiven Non-Hodgkin-Lymphoms (diffus grosszelliges B-Zell-Lymphom) gestellt. Nach einer inguinalen Lymphknotenbiopsie stellt sich erfahrungsgemäss nur etwa ein Drittel als malignes Lymphom heraus, gerade dann ist jedoch die ausreichende Gewebegewinnung entscheidend für die exakte Diagnose und die daraus resultierende Therapie. Mit dem IPI-Score kann eine prognostische Schätzung zum Überleben gegeben werden. Obwohl es sich um einen aggressiven Tumor handelt, konnte die Heilungsrate mit Einführung des R-CHOP-Schemas im Jahre 2002 auf über 50% verbessert werden.
Dimethylsulphide, clouds, and phytoplankton: Insights from a simple plankton ecosystem feedback model
Authors: Cropp Roger , Norbury John , Braddock Roger
Published: June 2007

The hypothesis that marine plankton ecosystems may effectively regulate climate by the production of dimethylsulphide (DMS) has attracted substantial research effort over recent years. This hypothesis suggests that DMS produced by marine ecosystems can affect cloud properties and hence the averaged irradiance experienced by the phytoplankton that produce DMS's precursor dimethylsulphoniopropionate (DMSP). This paper describes the use of a simple model to examine the effects of such a biogenic feedback on the ecosystem that initiates it. We compare the responses to perturbation of a simple marine nitrogen‐phytoplankton‐zooplankton (NPZ) ecosystem model with and without biogenic feedback. Our analysis of this heuristic model reveals that the addition of the feedback can increase the model's resilience to perturbation and hence stabilize the model ecosystem. This result suggests the hypothesis that DMS may play a role in stabilizing marine plankton ecosystem dynamics through its effect on the atmosphere.
The composition and horizontal homogeneity of E region plasma layers
Authors: Roddy P. A. , Earle G. D. , Swenson C. M. , Carlson C. G. , Bullett T. W.
Published: June 2007

A series of four NASA sounding rockets launched from Wallops Island, VA (37.84°N, 75.48°W), on 29–30 June 2003 between the hours of 23:19 and 3:07 EST observed an intermediate layer and a plasma density enhancement possibly associated with an internal gravity wave. Ion composition measurements were made by the third payload at 2:50 EST from 80‐ to 220‐km altitude and included observations of three separate regions having high concentrations of metallic ions: a sporadic E layer at 105 km, an intermediate layer at 118 km, and the region above 160 km. The remaining payloads measured electron densities and made TMA chemical tracer releases at 23:19, 1:41, and 3:07 EST, respectively. This sequence of measurements shows that intermediate layers cannot be treated as flat layers over a scale of hundreds of kilometers and that internal gravity waves may lead to the formation of plasma layers in the nighttime lower F and upper E region ionosphere. The composition observations demonstrate that metallic ions may be a significant source of ionization in the nighttime E and F region ionosphere at midlatitudes, and that the relative ion composition within intermediate layers may fluctuate significantly over horizontal scales of hundreds of kilometers.
Prediction of the AL index using solar wind parameters
Authors: Li Xinlin , Oh Kap Soo , Temerin M.
Published: June 2007

Two empirical models, one simple, one more complex, are introduced to predict the AL index, a measure of the Earth’s auroral activity derived from magnetometers in the Northern hemisphere. Both models are based on solar wind and magnetometer data from the year 1995. The simple model predicts the 10‐min averaged AL index for 1995 using only solar wind measurements with a prediction efficiency of 0.644 and a linear correlation of 0.803. The more complex model has a prediction efficiency of 0.723 and a linear correlation of 0.850. The simple model forward integrates with a 10‐min time step the model AL term using a driver term on the basis of the solar wind magnetic field magnitude and direction, solar wind velocity and density, and a nonlinear decay term whose amplitude depends on the model AL amplitude. The more complex model adds annual, semiannual, and diurnal variations, saturation, and some time delays and an additional term that is a direct function of the solar wind magnetic field and velocity. Though both models were optimized to predict the 10‐min averaged AL index, both models predict a longer‐averaged AL index substantially better (prediction efficiency of 0.736 and 0.825, respectively, for the 2‐hour averaged AL using the simple and complex models) while predicting the difference between 2‐hour averaged AL and the 10‐min AL poorly (prediction efficiency of 0.083 and 0.136, respectively) implying much less predictability for shorter timescale variations. The models show that the AL index is strongly dependent on the solar wind magnetic field and velocity but is practically independent of the solar wind density.
Energetic ion composition during reconfiguration events in the Jovian magnetotail
Authors: Radioti A. , Woch J. , Kronberg E. A. , Krupp N. , Lagg A. , Glassmeier K.‐H. , Dougherty M. K.
Published: June 2007

On the basis of the first 15 orbits of the Galileo spacecraft the composition of the energetic ion population of the Jovian magnetosphere is studied on a global scale. Analyzing data from the energetic particles detector onboard Galileo, we study the relative ion abundance ratios of S/O, S/He, O/He and p/He at various energy/nucleon values. Prominent enhancements of S/O, S/He, and O/He abundance ratios are observed in the predawn sector and are associated with substorm‐like events in the Jovian magnetotail. During these reconfiguration events, frequent small‐scale variations of the south‐north component of the magnetic field are present. Acceleration by such magnetic field variations is examined as a possible mechanism for particle energization in that region. When the timescale of the magnetic field variation is comparable to the particle gyro period, the particle is accelerated by the induced electric field. It is shown that, during the Jovian substorm‐like events, the heavier ions are more efficiently energized than the lighter leading to the observed ion abundances. Ion composition measurements in other parts of the magnetosphere have shown quasiperiodic 3‐day modulations suggesting that the internally driven processes affect the ion composition in the whole magnetosphere.
Constraining and validating the Oct/Nov 2003 X‐class EUV flare enhancements with observations of FUV dayglow and E‐region electron densities
Authors: Strickland D. J. , Lean J. L. , Daniell R. E. , Knight H. K. , Woo W. K. , Meier R. R. , Straus P. R. , Woods T. N. , Eparvier F. G. , McMullin D. R. , Christensen A. B. , Morrison D. , Paxton L. J.
Published: June 2007

Near peak activity of two X‐class solar flares, on 28 October and 4 November 2003, the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)/Solar EUV Experiment (SEE) instrument recorded order of magnitude increases in solar EUV irradiance, the TIMED/Global Ultraviolet Imager (GUVI) observed simultaneous increases in upper atmosphere far ultraviolet (FUV) dayglow, and the European Incoherent Scatter Scientific Association (EISCAT) radar and the Ionospheric Occultation Experiment onboard the PICOSat spacecraft recorded corresponding changes in E‐region electron densities. Calculations of the FUV dayglow and electron density profiles using Version 8 SEE flare spectra overestimate the actual observed increases by more than a factor of 2.0. This prompted the development of an alternative approach that uses the FUV dayglow and associated E‐layer electron density profiles to derive and validate, respectively, the increases in the solar EUV irradiance spectrum. The solar EUV spectrum required to produce the FUV dayglow is specified between 45 and 27 nm by SEE’s EGS measurements, between 27 and 5 nm by GUVI dayglow measurements, and between 5 and 1 nm using a combination of the GOES X‐ray data and the NRLEUV model. The energy fluxes in the 5‐ to 27‐nm bands (at 5–10, 10–15, 15–20, and 20–27 nm) are randomly varied in search of combinations such that the full spectrum (λ < 45 nm) replicates the GUVI dayglow observations. In contrast to the Version 8 SEE XPS observations, solar EUV spectra derived using the multiband yield approach produce electron densities that are consistent with those observed independently. The new multiband yield algorithm thus provides a unique tool for independent validation of solar EUV spectral irradiance measurements using FUV dayglow observations.
Whistler propagation in nonsymmetrical density channels
Authors: Streltsov A. V. , Lampe M. , Ganguli G.
Published: June 2007

We present results from a study of whistler propagation in plasma density channels extended along Earth's geomagnetic field and localized across it. Our study is focused on whistler guiding by channels with a nonsymmetrical density profile across the channel. Such profiles are typical for density inhomogeneities observed on/near the plasmapause formed in the Earth's magnetosphere during strong geomagnetic storms/substorms. Considering these density channels as a combination of high‐density and low‐density ducts, we analyze leakage of the electromagnetic energy from these ducts depending on various parameters of the system. Our results indicate that a whistler with a frequency less than half of the local electron gyrofrequency can propagate along a nonsymmetrical duct with a homogeneous central part, without any leakage, when the width of the duct is equal to an integral multiple of each of the two internal perpendicular wavelengths. We also show that a homogeneous ducting region is not necessary; a low‐frequency whistler can be guided along a region of appropriate density within a monotonic density gradient. This finding makes our results particularly relevant for the interpretation of intense whistler dynamics recorded in a number of satellite observations near/on the plasmapause where strong transverse density gradients are observed.
The secondary instability initiated by the three‐dimensional nonlinear evolution of the Kelvin‐Helmholtz instability
Authors: Matsumoto Yosuke , Seki Kanako
Published: June 2007

Three‐dimensional magnetohydrodynamic simulations of the Kelvin‐Helmholtz instability (KHI) are conducted. The resultant three‐dimensional evolution of the KHI possesses new signatures that cannot be obtained in two‐dimensional evolutions. It is shown that the vortex core is susceptible to the three‐dimensional secondary instability. In the early nonlinear stage, after a vortex fully develops, the three‐dimensional secondary instability starts growing inside the vortex core. The newly generated components of the magnetic field lead the two‐dimensional vortex motion to a highly structured one in the three‐dimensional space. To understand its nature, we model a one‐dimensional axisymmetric vortex core, where the centrifugal force is balanced with the gradient of the total pressure, and examine the linear response to the perturbed fields. The obtained dispersion relation shows that the eigenmode peaks off the vortex center, the linear growth rate of the unstable mode is order of the rotation period, and it only slightly changes with varying β while its wavelength gets longer as β decreases. These results suggest that a simple two‐dimensional KHI evolution cannot be applied to the magnetospheric boundary and the three‐dimensional evolution may owe a wave excitation and thus the energy transport along the closed magnetic field lines to the ionosphere.
Particle and field characteristics of broadband electrons observed by the FAST satellite during a geomagnetic storm
Authors: Nakajima A. , Shiokawa K. , Seki K. , Strangeway R. J. , McFadden J. P. , Carlson C. W.
Published: June 2007

Broadband electrons (BBEs) are remarkable flux enhancements (>1013 eV cm−2 s−1) of precipitating electrons over a broad energy range (0.03–30 keV) near the equatorward edge of the auroral oval during geomagnetic storms. We show characteristics of particles (energy spectra and pitch angle distribution) and fields (electric field, magnetic field, and wave spectra) during a BBE event observed by the Fast Auroral SnapshoT (FAST) satellite. The BBEs were observed at an altitude of ∼2000 km at 59°–61° invariant latitudes (ILATs) and 21 h magnetic local time (MLT). The event was observed at ∼7 min after the onset of a substorm during the main phase of the Bastille Day geomagnetic storm (minimum Dst = −301 nT) on 15 July 2000. The precipitation region of the BBEs corresponded to a localized intensification of auroral emission, lasting ∼14 min, observed by the Polar UVI images at 50°–60° geomagnetic latitudes (MLATs) and 20–21 MLTs. These results suggest that rapid particle acceleration was occurring in the inner magnetosphere associated with a storm‐time substorm. The pitch angle distribution of BBEs was isotropic except for a loss cone feature around the field‐aligned upward direction at a higher energy range above ∼1 keV, while field‐aligned electron fluxes were larger than the perpendicular fluxes below ∼1 keV. These results imply that a higher energy part of the BBEs originated from higher altitudes in the inner magnetosphere and that a lower energy part was accelerated parallel to the local magnetic field at lower altitudes near the satellite. Intense fluctuations of electric and magnetic fields were observed during this BBE event. From these results, we discuss possible acceleration of the lower energy part of BBEs through wave–particle interaction.
Signature of the 29 March 2006 eclipse on the ionosphere over an equatorial station
Authors: Adeniyi J. O. , Radicella S. M. , Adimula I. A. , Willoughby A. A. , Oladipo O. A. , Olawepo O.
Published: June 2007

This study documents some results of the effect of the 29 March 2006 eclipse on the ionosphere over Ilorin, Nigeria (longitude 4.57°E, latitude 8.53°N, dip 4.1°S), an equatorial station in the West African region. The maximum obscuration of the eclipse at this station was 99 percent and it occurred before midday. True height electron density profile analysis below the F2 peak was employed in the study. The effect on the E and F1 layers was a drastic decrease in electron density, with maximum decrease percentages of 60 and 68 for the E and F1 layers, respectively. A decrease in foF2 began at about 1 hour 20 min after those in the lower layers had started. Variation of electron density with height showed that the decrease in the electron density occurred through out the E and F1 heights at about the same time while that of the F2 region began at lower heights and extended progressively toward the peak of electron density height of the layer. The recovery in the E and F1 layers has already reached an advanced stage before the effect of the eclipse got to the maximum in the F2 region. A major departure of hmF2 from the normal variation was observed and discussed.
Predictive accuracy of temperature‐nitrate relationships for the oceanic mixed layer of the New Zealand region
Authors: Sherlock V. , Pickmere S. , Currie K. , Hadfield M. , Nodder S. , Boyd P. W.
Published: June 2007

Nitrate concentrations are a major factor controlling phytoplankton growth, hence the recent interest in using remotely sensed sea surface temperature (SST) and chlorophyll concentrations (Chla) to infer nitrate concentrations and substantially improve spatiotemporal estimates of nitrate in the surface ocean. Regression models which predict mixed‐layer nitrate concentrations as a function of temperature and climatological salinity are derived for the subtropical and subantarctic waters of the New Zealand region (30°–50°S, 154°E–160°W). These models are then validated using independent in situ measurements of temperature and nitrate concentrations and remotely sensed SST and Chla. Root mean square (RMS) nitrate prediction errors vary with water mass and exhibit seasonally dependent biases. RMS errors range from 0.8 to 1.8 μM in subtropical waters, 1.6 to 1.9 μM in the Subtropical Front, and 1.4 to 2.5 μM in subantarctic waters, depending on the spatiotemporal sampling characteristics of validation data sets. Prediction errors are correlated with observed chlorophyll concentrations, and a linear chlorophyll correction reduces seasonally dependent prediction biases significantly. Nitrate prediction errors for the New Zealand region are comparable with nitrate prediction errors reported for the North Atlantic and Equatorial and North Pacific, and the regression models give a substantially better description of the seasonal variation of nitrate in the New Zealand region than an existing nitrate climatology. A comparison of predicted nitrate‐depletion temperatures with other published studies highlights the importance of detailed regional validation of temperature‐nitrate regression models.
Current system east of the Ryukyu Islands
Authors: Nagano A. , Ichikawa H. , Miura T. , Ichikawa K. , Konda M. , Yoshikawa Y. , Obama K. , Murakami K.
Published: June 2007

The Ryukyu Current System (RCS) is a northeastward current southeast of the Ryukyu Islands. The variation of current structure in the RCS region was investigated on the basis of the absolute geostrophic velocity estimated by inverse calculation using hydrographic data. Three realizations of the RCS are examined from cruises in May, September, and October 2002. It was found that the current structure in the RCS region is divided into upper and lower layers by an isopycnal surface of 26 σθ. The currents in both layers proceed northeastward along the eastern slope, east of the Ryukyu Islands. The current in the upper layer merges with the inflow from the interior region, resulting in larger northeastward volume transport southeast of Amami‐Oshima Island than southeast of Okinawa Island. The volume transport from the east reaches more than 40% of that southeast of Amami‐Oshima Island. On the other hand, the current in the lower layer is not affected by inflow from the east. It is also found that the upper RCS gains heat mainly through the advection of warm water from the east, resulting in an increase in the downstream temperature by about 0.5°C on average.
Influence of large‐scale atmospheric circulation on climate variability in the Greater Alpine Region of Europe
Authors: Efthymiadis Dimitrios , Jones Philip D. , Briffa Keith R. , Böhm Reinhard , Maugeri Maurizio
Published: June 2007

The climatic variability in the Greater Alpine Region (GAR) of Europe has a diverse character: it exhibits differences between winter and summer, and between its individual subregions. The large‐scale atmospheric circulation, as expressed by the mean sea level pressure (MSLP) patterns in the wider Euro‐Atlantic region, plays a significant role in the climate variability in winter, but less in summer. In winter, high‐altitude temperatures are markedly linked with the Northern Hemisphere (NH) zonal circulation, as expressed by the NH annular mode (NAM), whereas the low‐level temperature field is associated more with the circulation over the NE Atlantic. The Alpine mountain chain delimits the different winter precipitation regimes between the northern and southern side of the GAR. While a British Isles‐centered pressure pattern plays the principal role in influencing northern Alpine precipitation, the North Atlantic Oscillation (NAO), and in particular its Mediterranean component, is the large‐scale atmospheric mode affecting precipitation over the southern Alpine region. The impact of the El Niño/Southern Oscillation (ENSO) phenomenon on GAR climate is weak, though it is distinctly manifested within intermittent multidecadal periods. The most pronounced impact is found for late‐autumn and early‐winter temperature and late‐winter precipitation. In these cases, GAR climate exhibits significant correlations with ENSO state of the preceding early autumn and late summer. The ENSO impact is associated with atmospheric pressure anomaly patterns in the European region indicating modifications of large‐scale circulation whose effects are also found in the climates of larger areas of Europe.
A new high precision 14CO2 time series for North American continental air
Authors: Turnbull Jocelyn C. , Lehman Scott J. , Miller John B. , Sparks Rodger J. , Southon John R. , Tans Pieter P.
Published: June 2007

We develop a high precision Δ14CO2 measurement capability in 2‐5 L samples of whole air for implementation within existing greenhouse gas flask sampling networks. The long‐term repeatability of the measurement is 1.8‰ (1‐sigma), as determined from repeated analyses of quality control standards and replicate extraction and measurement of authentic field samples. In a parallel effort, we have begun a Δ14CO2 measurement series from NOAA/ESRL’s (formerly NOAA/CMDL) surface flask sampling site at Niwot Ridge, Colorado, USA (40.05°N, 105.58°W, 3475 masl) in order to monitor the isotopic composition of carbon dioxide in relatively clean air over the North American continent. Δ14CO2 at Niwot Ridge decreased by 5.7‰/yr from 2004 to 2006, with a seasonal amplitude of 3‐5‰. A comparison with measurements from the free troposphere above New England, USA (41°N, 72°W) indicates that the Δ14CO2 series at the two sites are statistically similar at timescales longer than a few days to weeks (i.e., those of synoptic scale variations in transport), suggesting that the Niwot Ridge measurements can be used as a proxy for North American free tropospheric air in future carbon cycle studies.
A fast radiative transfer model for SSMIS upper atmosphere sounding channels
Authors: Han Yong , Weng Fuzhong , Liu Quanhua , van Delst Paul
Published: June 2007

Special Sensor Microwave Imager/Sounder (SSMIS) on board the Defense Meteorology Satellite Program (DMSP) F‐16 satellite probes the atmospheric temperature from surface to 100 km. SSMIS channels 19–22 are significantly affected by Zeeman splitting, which is dependent on the Earth’s magnetic field. Thus, in satellite data assimilation or retrieval systems, SSMIS brightness temperatures and their Jacobians (or gradient with respect to temperature) must be computed with a fast radiative transfer (RT) scheme that takes into account the Zeeman‐splitting effect. In this study, an averaged transmittance within the channel frequency passbands is parameterized and predicted with atmospheric temperature, geomagnetic field strength, and the angle between the geomagnetic field vector and the electromagnetic wave propagation direction. The coefficients of predictors are trained with a line‐by‐line (LBL) radiative transfer model that accurately computes the monochromatic transmittances at fine frequency steps within each passband. The new radiative transfer scheme is compared to the results from the line‐by‐line model for the dependent and independent data sets. It is shown that the differences between the two models are well below the instrument noise levels but the new scheme is much faster. It is also shown that the SSMIS measurements agree well with the simulations that are based on the atmospheric profiles from the sounding of the atmosphere using broadband emission radiometry (SABER) on the Thermosphere‐lonosphere‐Mesosphere Energetics and Dynamics satellite and the COSPAR international reference atmosphere (CIRA) model.