bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of solar activity on the morphology of 7320 Å dayglow emission
Authors: Sunil Krishna M. V. , Singh V.
Published: June 2010

Abstract. A comprehensive model is developed to study the 7320 Å dayglow emission. The emission profiles are obtained with the help of the recently developed Solar2000 EUV (Extreme Ultra Violet) flux model. These emission profiles are used to construct the morphology of this emission between equator and 45° N in the Northern Hemisphere. A span of five years (2001–2005) is chosen to study the effect of solar activity on the morphology of this emission. The morphology is studied on 3 April which lies under the equinox conditions. In 2001, the solar F10.7 index on the chosen date was as high as 223.1 which is the case of solar maximum. It is found that the intensity of this emission does not vary linearly with the F10.7 solar index. The morphology shows that the region of maximum emission expands towards the higher latitudes as the F10.7 index increases.
SMEI direct, 3-D-reconstruction sky maps, and volumetric analyses, and their comparison with SOHO and STEREO observations
Authors: Jackson B. V. , Hick P. P. , Buffington A. , Bisi M. M. , Clover J. M.
Published: June 2010

Abstract. In this paper we present the results of the analysis of the late January 2007 Coronal Mass Ejection (CME) events recorded by the Solar Mass Ejection Imager (SMEI), the Solar TErrestrial RElations Observatory (STEREO), and the SOlar and Heliospheric Observatory (SOHO) spacecraft. This period occurs when the two STEREO spacecraft views are from close to Earth, and thus the views from both SMEI and the STEREO outer Heliospheric Imagers (HI-2s) coincide. Three-dimensional (3-D) analyses derived from SMEI data show many CMEs that have also been studied by others using short-term image subtractions (image-differencing techniques). During this interval we map several CME structures that are observed in both SMEI and the STEREO-A HI instruments. SMEI brightness analyses provided by short-term image subtractions ("difference images") and, alternatively, subtractions of a mean-brightness fit over a long-time duration, both show the extents of the CMEs travelling outward above the East limb that erupted from the Sun on 24 and 25 January 2007. The SMEI 3-D-reconstructions not only enhance distinct features within the CME events, but also reconcile difference-imaging results with those where a long-term base has been removed. In the January 2007 example the structure as mapped by CME difference images traces the sharp intensity gradients at the front of the CMEs; generally brighter ejected material follows behind the location of the CME front, but shows poorly in these because of its larger angular extent. Using the long-duration background removal enables SMEI's 3-D analysis to determine a mass for this CME sequence North of the ecliptic.
On the nonlinear shaping mechanism for gravity wave spectrum in the atmosphere
Authors: Chunchuzov I. P.
Published: June 2010

Abstract. The nonlinear mechanism of shaping of a high vertical wave number spectral tail in the field of a few discrete internal gravity waves in the atmosphere is studied in this paper. The effects of advection of fluid parcels by interacting gravity waves are taken strictly into account by calculating wave field in Lagrangian variables, and performing a variable transformation from Lagrangian to Eulerian frame. The vertical profiles and vertical wave number spectra of the Eulerian displacement field are obtained for both the case of resonant and non-resonant wave-wave interactions. The evolution of these spectra with growing parameter of nonlinearity of the internal wave field is studied and compared to that of a broad band spectrum of gravity waves with randomly independent amplitudes and phases. The calculated vertical wave number spectra of the vertical displacements or relative temperature fluctuations are found to be consistent with the observed spectra in the middle atmosphere.
Titan's ionosphere in the magnetosheath: Cassini RPWS results during the T32 flyby
Authors: Garnier P. , Wahlund J-E. , Rosenqvist L. , Modolo R. , Ågren K. , Sergis N. , Canu P. , Andre M. , Gurnett D. A. , Kurth W. S. , Krimigis S. M. , Coates A. , Dougherty M. , Waite J. H.
Published: June 2010

Abstract. The Cassini mission has provided much information about the Titan environment, with numerous low altitude encounters with the moon being always inside the magnetosphere. The only encounter taking place outside the magnetopause, in the magnetosheath, occurred the 13 June 2007 (T32 flyby). This paper is dedicated to the analysis of the Radio and Plasma Wave investigation data during this specific encounter, in particular with the Langmuir probe, providing a detailed picture of the cold plasma environment and of Titan's ionosphere with these unique plasma conditions. The various pressure terms were also calculated during the flyby. The comparison with the T30 flyby, whose geometry was very similar to the T32 encounter but where Titan was immersed in the kronian magnetosphere, reveals that the evolution of the incident plasma has a significant influence on the structure of the ionosphere, with in particular a change of the exo-ionospheric shape. The electrical conductivities are given along the trajectory of the spacecraft and the discovery of a polar plasma cavity is reported.
Different magnetospheric modes: solar wind driving and coupling efficiency
Authors: Partamies N. , Pulkkinen T. I. , McPherron R. L. , McWilliams K. , Bryant C. R. , Tanskanen E. , Singer H. J. , Reeves G. D. , Thomsen M. F.
Published: June 2010

Abstract. This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC) intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential), particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to) the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY). Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading–unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations) during geomagnetically active conditions.
Mid-latitude solar eclipses and their influence on ionospheric current systems
Authors: Tomás A. T. , Lühr H. , Rother M.
Published: June 2010

Abstract. Using CHAMP magnetic field data we study the behaviour of the geomagnetic field during two mid latitude eclipses on 21 June 2001 and 22 September 2006. The possible influence of the eclipses on different ionospheric current systems, as seen in the magnetic field measured by CHAMP, is discussed. It is expected that the blocking of solar radiation during an eclipse causes a reduction of the ionospheric conductivity and therefore has an effect on the different current systems. We address in particular the effects of the eclipses on the inter-hemispheric field-aligned currents and on the Sq current system. The two events studied occur under different seasonal conditions, e.g. June solstice and September equinox, therefore quite different aspects can be investigated. We find that the eclipses might affect the direction and intensity of the inter-hemispheric currents and possibly influence the direction of zonal winds, therefore changing the direction of the prevailing F-region dynamo currents. The eclipse in the Southern Hemisphere during September equinox caused inter-hemispheric currents similar to those observed in northern summer. Reverse inter-hemispheric currents were recorded after the end of the eclipse. A large variety of atypical currents was observed during the June event. Most of them might be related to a reversed F-region dynamo in the morning sector and an enhanced conductivity difference between the hemispheres. The eclipse in the south seems to enhance the June solstice conditions considerably.
Field line distribution of density at L=4.8 inferred from observations by CLUSTER
Authors: Denton R. E. , Décréau P. , Engebretson M. J. , Darrouzet F. , Posch J. L. , Mouikis C. , Kistler L. M. , Cattell C. A. , Takahashi K. , Schäfer S. , Goldstein J.
Published: June 2010

Abstract. For two events observed by the CLUSTER spacecraft, the field line distribution of mass density ρ was inferred from Alfvén wave harmonic frequencies and compared to the electron density ne from plasma wave data and the oxygen density nO+ from the ion composition experiment. In one case, the average ion mass M≈ρ/ne was about 5 amu (28 October 2002), while in the other it was about 3 amu (10 September 2002). Both events occurred when the CLUSTER 1 (C1) spacecraft was in the plasmatrough. Nevertheless, the electron density ne was significantly lower for the first event (ne=8 cm−3) than for the second event (ne=22 cm−3), and this seems to be the main difference leading to a different value of M. For the first event (28 October 2002), we were able to measure the Alfvén wave frequencies for eight harmonics with unprecedented precision, so that the error in the inferred mass density is probably dominated by factors other than the uncertainty in frequency (e.g., magnetic field model and theoretical wave equation). This field line distribution (at L=4.8) was very flat for magnetic latitude |MLAT|≲20° but very steeply increasing with respect to |MLAT| for |MLAT|≳40°. The total variation in ρ was about four orders of magnitude, with values at large |MLAT| roughly consistent with ionospheric values. For the second event (10 September 2002), there was a small local maximum in mass density near the magnetic equator. The inferred mass density decreases to a minimum 23% lower than the equatorial value at |MLAT|=15.5°, and then steeply increases as one moves along the field line toward the ionosphere. For this event we were also able to examine the spatial dependence of the electron density using measurements of ne from all four CLUSTER spacecraft. Our analysis indicates that the density varies with L at L~5 roughly like L−4, and that ne is also locally peaked at the magnetic equator, but with a smaller peak. The value of ne reaches a density minimum about 6% lower than the equatorial value at |MLAT|=12.5°, and then increases steeply at larger values of |MLAT|. This is to our knowledge the first evidence for a local peak in bulk electron density at the magnetic equator. Our results show that magnetoseismology can be a useful technique to determine the field line distribution of the mass density for CLUSTER at perigee and that the distribution of electron density can also be inferred from measurements by multiple spacecraft.
Outflowing protons and heavy ions as a source for the sub-keV ring current
Authors: Giang T. T. , Hamrin M. , Yamauchi M. , Lundin R. , Nilsson H. , Ebihara Y. , Rème H. , Dandouras I. , Vallat C. , Bavassano-Cattaneo M. B. , Klecker B. , Korth A. , Kistler L. M. , McCarthy M.
Published: June 2010

Abstract. Data from the Cluster CIS instrument have been used for studying proton and heavy ion (O+ and He+) characteristics of the sub-keV ring current. Thirteen events with dispersed heavy ions (O+ and He+) were identified out of two years (2001 and 2002) of Cluster data. All events took place during rather geomagnetically quiet periods. Three of those events have been investigated in detail: 21 August 2001, 26 November 2001 and 20 February 2002. These events were chosen from varying magnetic local times (MLT), and they showed different characteristics. In this article, we discuss the potential source for sub-keV ring current ions. We show that: (1) outflows of terrestrial sub-keV ions are supplied to the ring current also during quiet geomagnetic conditions; (2) the composition of the outflow implies an origin that covers an altitude interval from the low-altitude ionosphere to the plasmasphere, and (3) terrestrial ions are moving upward along magnetic field lines, at times forming narrow collimated beams, but frequently also as broad beams. Over time, the ion beams are expected to gradually become isotropised as a result of wave-particle interaction, eventually taking the form of isotropic drifting sub-keV ion signatures. We argue that the sub-keV energy-time dispersed signatures originate from field-aligned terrestrial ion energising and outflow, which may occur at all local times and persist also during quiet times.
The influence of humidity fluxes on offshore wind speed profiles
Authors: Barthelmie R. J. , Sempreviva A. M. , Pryor S. C.
Published: June 2010

Abstract. Wind energy developments offshore focus on larger turbines to keep the relative cost of the foundation per MW of installed capacity low. Hence typical wind turbine hub-heights are extending to 100 m and potentially beyond. However, measurements to these heights are not usually available, requiring extrapolation from lower measurements. With humid conditions and low mechanical turbulence offshore, deviations from the traditional logarithmic wind speed profile become significant and stability corrections are required. This research focuses on quantifying the effect of humidity fluxes on stability corrected wind speed profiles. The effect on wind speed profiles is found to be important in stable conditions where including humidity fluxes forces conditions towards neutral. Our results show that excluding humidity fluxes leads to average predicted wind speeds at 150 m from 10 m which are up to 4% higher than if humidity fluxes are included, and the results are not very sensitive to the method selected to estimate humidity fluxes.
The exchange across the tropical tropopause in overshooting convective cores
Authors: Rao T. N. , Radhakrishna B. , Mohan Satyanarayana T. , Satheesh Kumar S.
Published: June 2010

Abstract. Coordinated measurements of Indian MST radar and radiosonde during the passage of overshooting convective cores in SAFAR pilot campaign (May–November 2008) are utilized to quantify the mass flux across the tropopause and strength of the turbulence in up- and down-draft cores. The distribution of retrieved mass flux is found to be wide, ranging from −0.6 (downward flux) to 0.8 kg m−2 s−1 (upward flux). The net mass flux, is, however, from the troposphere to stratosphere, in spite of the existence of significant amount of downward flux. For the first time, the turbulence strength in the vicinity of the tropopause in convective cores is quantified. Large spectral widths with magnitudes >4 m s−1 are observed during convection. However, such large spectral widths are rare and are observed only for 1.6% of total observations. The average spectral width (and also the variation or standard deviation) in draft cores is found to be ~4.5 times larger than that in fair-weather. The turbulence strength in updraft cores is much higher than that of in downdraft cores. The mean (median) spectral width in updraft cores is larger by ~0.8 m s−1 (a factor of ~2) than that of in downdraft cores. The turbulence strength does not show any systematic variation with the intensity of convection in both up- and down-draft cores. The distributions and mean values of mass flux and turbulence strength obtained in the present study will be useful to quantify the STE due to direct intrusion of mass by overshooting convection and the exchange of constituents (in particular water vapor) due to turbulence in a better way.
Distortions of the magnetic field by storm-time current systems in Earth's magnetosphere
Authors: Ganushkina N. Yu. , Liemohn M. W. , Kubyshkina M. V. , Ilie R. , Singer H. J.
Published: June 2010

Abstract. Magnetic field and current system changes in Earth's inner magnetosphere during storm times are studied using two principally different modeling approaches: on one hand, the event-oriented empirical magnetic field model, and, on the other, the Space Weather Modeling Framework (SWMF) built around a global MHD simulation. Two storm events, one moderate storm on 6–7 November 1997 with Dst minimum about −120 nT and one intense storm on 21–23 October 1999 with Dst minimum about −250 nT were modeled. Both modeling approaches predicted a large ring current (first partial, later symmetric) contribution to the magnetic field perturbation for the intense storm. For the moderate storm, the tail current plays a dominant role in the event-oriented model results, while the SWMF results showed no strong tail current in the main phase, which resulted in a poorly timed storm peak relative to the observations. These results imply that the the development of a ring current depends on a strong force to inject the particles deep into the inner magnetosphere, and that the tail current is an important external source for the distortions of the inner magnetospheric magnetic field for both storms. Neither modeling approach was able to reproduce all the variations in the Bx and By components observed at geostationary orbit by GOES satellites during these two storms: the magnetopause current intensifications are inadequate, and the field-aligned currents are not sufficiently represented. While the event-oriented model reproduces rather well the Bz component at geostationary orbit, including the substorm-associated changes, the SWMF field is too dipolar at these locations. The empirical model is a useful tool for validation of the first-principle based models such as the SWMF.
The Alfvén resonator revisited
Authors: Hamza A. M. , Lyatsky W.
Published: June 2010

Abstract. Two models for a magnetosphere-ionosphere coupling feedback instability in the lower magnetosphere are studied. In both models the instability arises because of the generation of an Alfvén wave from growing arc-like structures in the ionospheric conductivity. The first model is based on the modulation of precipitating electrons by field-aligned currents of the upward moving Alfvén wave (Modulation Model). The second model takes into consideration the reflection of the Alfvén wave from a maximum of the Alfvén velocity at about 3000 km altitude (Reflection Model). The growth of structures in both models takes place when the ionization function associated with upward field aligned current is shifted from the edges of enhanced conductivity structures to their centers. Such a shift arises because the structures move along the ionosphere at a velocity different from the E×B drift velocity. As a result, field-aligned currents of upward propagating Alfvén wave at some altitude appear shifted with respect to the edges of the structures. Although both models may work, the growth rate for the first model, as based on the modulation of the precipitating accelerated electrons, for typical conditions, may be tens or more times larger than that for the second model based on the Alfvén wave reflection. The proposed models can provide the growth of both single and periodic structures. When applied to auroral arc generation the studied instability leads to high growth rates and narrow arcs. The physical mechanism is mostly suitable for the generation of auroral arcs with widths of the order of 1 km and less. The growth rate of the instability for such structures can be as large as 0.3 s−1. In the case of periodic structures, their motion must lead to the generation of magnetic pulsations with periods of about 1–6 s, which is close to the expected period of Alfvén resonant oscillations in the lower magnetosphere. However, these oscillations (for the first and most effective model MM) are not exactly Alfvén resonant oscillations. These oscillations are modulations in the ionospheric density, which propagate along the ionospheric currents and not along the magnetic field lines.
Impact of agriculture crop residue burning on atmospheric aerosol loading – a study over Punjab State, India
Authors:   Anu Rani Sharma,   Shailesh Kumar Kharol, Badarinath K. V. S. ,   Darshan Singh
Published: June 2010

Abstract. The present study deals with the impact of agriculture crop residue burning on aerosol properties during October 2006 and 2007 over Punjab State, India using ground based measurements and multi-satellite data. Spectral aerosol optical depth (AOD) and Ångström exponent (α) values exhibited larger day to day variation during crop residue burning period. The monthly mean Ångström exponent "α" and turbidity parameter "β" values during October 2007 were 1.31±0.31 and 0.36±0.21, respectively. The higher values of "α" and "β" suggest turbid atmospheric conditions with increase in fine mode aerosols over the region during crop residue burning period. AURA-OMI derived Aerosol Index (AI) and Nitrogen dioxide (NO2) showed higher values over the study region during October 2007 compared to October 2006 suggesting enhanced atmospheric pollution associated with agriculture crop residue burning.
Statistical study on the occurrence of ASAID electric fields
Authors: Liléo S. , Karlsson T. , Marklund G. T.
Published: June 2010

Abstract. The first statistical results on the occurrence of abnormal subauroral ion drifts (ASAID) are presented based on electric and magnetic field measurements from the low-altitude Astrid-2 satellite. ASAID are narrow regions of rapid eastward ion drifts observed in the subauroral ionosphere. They correspond to equatorward-directed electric fields with peak amplitudes seen to vary between 45 mV/m and 185 mV/m, and with latitudinal extensions between 0.2° and 1.2° Corrected Geomagnetic Latitude (CGLat), reaching in some cases up to 3.0° CGLat. Opposite to subauroral ion drifts (SAID) that are known to be substorm-related, ASAID are seen to occur predominantly during extended periods of low substorm activity. Our results show that ASAID are located in the vicinity of the equatorward edge of the auroral oval, mainly in the postmidnight sector between 23:00 and 03:00 magnetic local time. They are associated with a local current system with the same scale-size as the corresponding ASAID, composed by a region of downward field-aligned currents (FACs) flowing in the ASAID poleward side, and a region of upward flowing FACs in the equatorward side. The FACs have densities between 0.5 and 2.0 μA/m2. The data suggest that ASAID do not contribute significantly to the reduction of the ionospheric conductivity. ASAID are seen to have life times of at least 3.5 h. A discussion on possible mechanisms for the generation of ASAID is presented. We speculate that the proximity of the electron to the ion plasma sheet inner boundaries and of the plasmapause to the ring current outer edge, during extended quiet times, is an important key for the understanding of the generation of ASAID electric fields.
Klein-Gordon equations for toroidal hydromagnetic waves in an axi-symmetric field
Authors: McKenzie J. F. , Hu Q.
Published: June 2010

Abstract. In this paper we develop the hydromagnetic wave equations for toroidal Alfvén waves in a background axi-symmetric magnetic field. In the case where spatial variations are directed along the ambient magnetic field direction, the equations can be cast in a Klein-Gordon form in which the adiabatic-geometric amplitude factor of the perturbations varies as √ρL5sin5θ along a magnetic field line (where θ is colatitude and L the L-shell number) and the cut-off frequency, associated with the Klein-Gordon form, displays an astonishing variation with distance along a field line (see Eqs. 35 and 37 of the text), in the case of a dipole magnetic field. We compute the eigenvalues and eigenfunctions for the Earth's dipole field which are relevant to geomagnetic pulsations.
Productivity patterns and N-fixation associated with Pliocene-Holocene sapropels: paleoceanographic and paleoecological significance
Authors: Gallego-Torres D. , Martínez-Ruiz F. , Meyers P. A. , Paytan A. , Jimenez-Espejo F. J. , Ortega-Huertas M.
Published: June 2010

Abstract. Sapropels are organic matter enriched sediments cyclically deposited in the Eastern Mediterranean. We have studied a suite of 35 sapropel sequences from a transect of four ODP sites across the basin to explore for paleoproductivity patterns and their relationship to ecological changes in the region during their deposition. We assessed paleoproductivity variations using TOC and Babio mass accumulation rates and δ15Ntotal and δ13Corg values. Elevated Ba/Al and TOC mass accumulation rates record periods of basin-wide amplified productivity. δ15N values are dramatically lower in the sapropels than in TOC-poor background sediments indicating a major contribution from nitrogen-fixing bacteria to the higher productivity during sapropel deposition. Different degrees of denitrification occurred as a function of water column oxygen depletion. The evolution of sapropel deposition over the past 3 My is characterized by increased productivity together with enhanced preservation of organic matter during the late Pliocene, peaks in primary and export production and sedimentation rates during the middle Pleistocene, and a relatively weak increase in productivity during formation of the Holocene sapropel accompanied by high sedimentation rates. We conclude that sapropels were formed by cyclic increases in primary production of marine organic matter largely sustained by N-fixing bacteria that led to depletion of deepwater dissolved oxygen and consequently improved organic matter preservation. The increase in primary production was helped by nutrient input from continental sources climatically induced.
Objective identification of climate states from Greenland ice cores for the last glacial period
Authors: Peavoy D. J. , Franzke C.
Published: June 2010

Abstract. We present statistical methods to systematically determine climate regimes for the last glacial period using three temperature proxy records from Greenland: measurements of δ18O from the Greenland Ice Sheet Project 2 (GISP2), the Greenland Ice Core Project (GRIP) and the North Greenland Ice Core Project (NGRIP). By using Bayesian model comparison methods we find that, in two out of three data sets, a model with 3 states is very strongly supported. We interpret these states as corresponding to: a gradual cooling regime due to iceberg influx in the North Atlantic, sudden temperature decrease due to increased freshwater influx following ice sheet collapse and to the Dansgaard-Oeschger events associated with sudden rebound temperature increase after the thermohaline circulation recovers its full flux. We find that these models are far superior to those that differentiate between states based on absolute temperature differences only, which questions the appropriateness of defining stadial and interstadial climate states. We investigate the recurrence properties of these climate regimes and find that the only significant periodicity is within the Greenland Ice Sheet Project 2 data at 1450 years in agreement with previous studies.
Day 15 bone marrow driven double induction in young adult patients with acute myeloid leukemia: Feasibility, toxicity, and therapeutic results
Authors: Ferrara Felicetto , Izzo Tiziana , Criscuolo Clelia , Riccardi Cira , Celentano Maria , Mele Giuseppina
Published: June 2010

The strategy named double induction (DI) in acute myeloid leukemia (AML) consists of two courses of chemotherapy irrespective of the degree of cytoreduction in the bone marrow (BM) after the first course, unless severe complications prohibit its application. We describe treatment results from a series of 33 patients in whom DI was adopted only after demonstration of persistence of more than 10% blast cells at day 15 (D15) examination of BM. All patients received as induction idarubicin, cytarabine, and etoposide. As second induction, we administered the combination of fludarabine, intermediate dose cytarabine, and Granulocyte colony stimulating factor (G‐CSF). The median blast count at D15 was 30 (15–90). Overall, 30 of 33 patients were judged as eligible to receive DI, reasons for exclusion being in all cases active infection in the context of severe pancytopenia. Nineteen patients (63%) had unfavorable karyotype and 11 (37%) normal karyotype; seven of these had Fms‐like tyrosine kinase gene internal tandem duplication (FLT3/ITD) mutation. Overall, complete remission (CR) was achieved in 20/30 patients (67%), while eight patients (27%) were refractory and two died of infectious complications. All refractory patients had unfavorable cytogenetics. All patients achieving CR were programmed to receive allogeneic stem cell transplantation (allo‐SCT), which was actually performed in 11 patients. Our study suggest that D15 driven DI represents a feasible and effective therapeutic strategy in young adult AML patients, improving therapeutic results and not compromising feasibility of allo‐SCT. When compared with conventional DI, it offers the potential to avoid unnecessary toxicity in a consistent proportion of patients. Am. J. Hematol., 2010. © 2010 Wiley‐Liss, Inc.
No cerebrocervical venous congestion in patients with multiple sclerosis
Authors: Doepp Florian , Paul Friedemann , Valdueza José M. , Schmierer Klaus , Schreiber Stephan J.
Published: June 2010

Objective:

Multiple sclerosis (MS) is characterized by demyelination centered around cerebral veins. Recent studies suggested this topographic pattern may be caused by venous congestion, a condition termed chronic cerebrospinal venous insufficiency (CCSVI). Published sonographic criteria of CCSVI include reflux in the deep cerebral veins and/or the internal jugular and vertebral veins (IJVs and VVs), stenosis of the IJVs, missing flow in IJVs and VVs, and inverse postural response of the cerebral venous drainage.

Methods:

We performed an extended extra‐ and transcranial color‐coded sonography study including analysis of extracranial venous blood volume flow (BVF), cross‐sectional areas, IJV flow analysis during Valsalva maneuver (VM), and CCSVI criteria. Fifty‐six MS patients and 20 controls were studied.

Results:

Except for 1 patient, blood flow direction in the IJVs and VVs was normal in all subjects. In none of the subjects was IJV stenosis detected. IJV and VV BVF in both groups was equal in the supine body position. The decrease of total jugular BVF on turning into the upright position was less pronounced in patients (173 ± 235 vs 362 ± 150ml/min, p < 0.001), leading to higher BVF in the latter position (318ml/min ± 242 vs 123 ± 109ml/min; p < 0.001). No differences between groups were seen in intracranial veins and during VM. None of the subjects investigated in this study fulfilled >1 criterion for CCSVI.

Interpretation:

Our results challenge the hypothesis that cerebral venous congestion plays a significant role in the pathogenesis of MS. Future studies should elucidate the difference between patients and healthy subjects in BVF regulation. ANN NEUROL 2010;68:173–183
Kolloidale Hybridnanostrukturen: ein neuer Typ von Funktionsmaterialien
Authors: Costi Ronny , Saunders Aaron E. , Banin Uri
Published: June 2010

Die Forschung über Nanokristalle hat unter anderem die Entwicklung experimenteller Verfahren zum Ziel, mit denen Zusammensetzung und Form von Nanokristallen über vielfältige Materialkombinationen hinweg gesteuert werden können. Wenn nanometergroße Domänen metallischer, halbleitender und magnetischer Materialien zu einzelnen “Hybrid”‐Nanopartikeln kombiniert werden können, eröffnen sich faszinierende Möglichkeiten für die Herstellung von Nanomaterialien mit mehreren Funktionalitäten oder verbesserten Eigenschaften einer einzelnen Domäne. In unserem Aufsatz diskutieren wir aktuelle Strategien für die Herstellung von Halbleiter/Metall‐Hybridnanopartikeln, neue Eigenschaften dieser Mehrkomponentenmaterialien sowie ihre möglichen Anwendungen.
Colloidal Hybrid Nanostructures: A New Type of Functional Materials
Authors: Costi Ronny , Saunders Aaron E. , Banin Uri
Published: June 2010

One key goal of nanocrystal research is the development of experimental methods to selectively control the composition and shape of nanocrystals over a wide range of material combinations. The ability to selectively arrange nanosized domains of metallic, semiconducting, and magnetic materials into a single hybrid nanoparticle offers an intriguing route to engineer nanomaterials with multiple functionalities or the enhanced properties of one domain. In this Review, we focus on recent strategies used to create semiconductor–metal hybrid nanoparticles, present the emergent properties of these multicomponent materials, and discuss their potential applicability in different technologies.
Unraveling the Structure of the Ribosome (Nobel Lecture)
Authors: Ramakrishnan V.
Published: June 2010

A complex structure: The 2009 Nobel Prize was awarded for investigations into the structure and function of the ribosome, the protein factory of the cell. The Laureates describe first hand the course of the discoveries in this area, from the beginning of their research to the current detailed understanding.
Influence of wood species on the properties of biopolyurethane prepared from liquefied wood with residue
Authors: Izumo Kenji , Fukushima Masami
Published: June 2010

Biopolyurethane prepared from liquefied wood with the residue of the liquefied wood product was investigated in this article. Previous results indicated that the residue of the liquefaction product was composed mostly of compounds originated from lignin. The chemical structures of lignin in softwood and hardwood are different. The influence of soft‐ and hardwood species on the chemical structure and mechanical properties of biopolyurethane prepared from liquefied wood with residue was investigated by tensile testing and Fourier transform infrared spectroscopy. The experimental results showed that the liquefaction of softwood occurs within a shorter time than that of hardwood and the biopolyurethane prepared from softwood was harder than that prepared from hardwood, which suggests that the properties of the liquefaction product and biopolyurethane are influenced by the chemical structure of the lignin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Electrodeposition of poly(o‐toluidine) on brass from aqueous salicylate solution and its corrosion protection performance
Authors: Patil Dewyani , Patil P. P.
Published: June 2010

Poly(o‐toluidine) (POT) has been electrodeposited on brass from an aqueous salicylate solution by using cyclic voltammetry, and its corrosion protection performance has been evaluated by potentiodynamic polarization technique and electrochemical impedance spectroscopy in aqueous 3% NaCl solution. The corrosion potential was about 0.115 V vs. SCE more positive for the POT‐coated brass than that of uncoated brass and reduces the corrosion rate of brass almost by a factor of 800. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Preparation of bimodal porous copolymer containing β‐cyclodextrin and its inclusion adsorption behavior
Authors: Sun Zhao‐Yang , Shen Ming‐Xing , Cao Gui‐Ping , Deng Jie , Liu Yuan , Liu Tao , Zhao Ling , Yuan Wei‐Kang
Published: June 2010

A novel insoluble bimodal porous polymer containing β‐cyclodextrin (β‐CD) was prepared to adsorb aromatic amine compound. The process involved copolymerization of styrene and methyl methacrylate with a maleic acid derivative of β‐CD, subsequently, above formed copolymer was foamed by supercritical CO2. The chemical properties and physical structure of obtained copolymer was analyzed using Fourier transform infrared spectra, Thermal gravimetric analysis, X‐ray diffraction, scanning electron microscope, and N2 adsorption techniques. The inclusion adsorption of aromatic amine compounds on β‐CD copolymer was carried out in a batch system. The quantities of aromatic amine compounds adsorbed on β‐CD copolymer reached equilibrium within 60 min. The adsorption kinetic could be fitted to a pseudo‐second‐order kinetic equation, and the linear correlation coefficients varied from 0.9828 to 0.9935. With the influence of molecular structure and hydrophobicity of the aromatic amine compound, the sequence of quantity of aromatic amine compounds adsorbed on β‐CD copolymer is p‐toluidine > aniline > benzidine > o‐toluidine. The adsorption equilibrium data of aromatic amine compound adsorbed on β‐CD copolymer were fitted to Freundlich and Langmuir models, respectively. The linear correlation coefficients of Langmuir model varied from 0.9516 to 0.9940, and the linear correlation coefficients of Freundlich varied from 0.9752 to 0.9976. It is concluded that Freundlich model fits better than Langmuir model, because the adsorption of aromatic amine compound on β‐CD copolymer is a chemical process. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Preparation, characterization, structure, and dynamics of carboxymethyl chitosan grafted with acrylic acid sodium salt
Authors: El‐Sherbiny Ibrahim M. , Elmahdy Mahdy M.
Published: June 2010

Graft copolymerization of different vinyl monomers onto chitosan (Cs) and its derivatives can alter their properties and consequently expands their potential applications. In this study, carboxymethyl chitosan (CMCs) was prepared and characterized. Graft copolymerization of acrylic acid sodium salt (AAs) onto CMCs was accomplished by using ammonium persulphate (APS)‐induced free radical polymerization in aqueous medium under nitrogen atmosphere. Occurrence of grafting was confirmed and the effects of [AAs], [APS], reaction time, and temperature on the extent of grafting were studied. The influence of grafting yield on the structure and dynamics was also investigated by using differential scanning calorimetry (DSC), two‐dimensional wide‐angle X‐ray scattering (2D‐WAXS), scanning electron microscopy (SEM), and dielectric spectroscopy. Preliminary study, using dielectric spectroscopy, was carried out to the CMCs‐g‐AAs copolymer with grafting percent ∼ 2900%, as an example, in a wide range of temperature (from 299 to 473 K) and frequency (from 1 × 10−2 to 1 × 105 Hz). One relaxation process with Arrhenius type was detected. This process has the characteristics of a secondary relaxation process related to local chain dynamics with activation energy of 53 ± 3 kJ/mol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Melting and crystallization behavior of poly(ethylene terephthalate) and poly(m‐xylylene adipamide) blends
Authors: Xie Fei , Lofgren Elizabeth A. , Jabarin Saleh A.
Published: June 2010

The crystallization and melting behaviors as well as the crystalline morphologies of Poly(ethylene terephthalate)/Poly(m‐xylylene adipamide) (PET/MXD6) blends have been examined and characterized with the aid of differential scanning calorimetry (DSC) and wide angle x‐ray diffraction (WAXD). The isothermal and nonisothermal crystallization behaviors of the blends were studied as functions of the contents of MXD6, catalyst concentrations, and the effects of the interchange reactions between PET and MXD6. Wide angle x‐ray scattering has been used to examine the crystalline morphologies of the PET/MXD6 blends, to characterize their crystalline and amorphous phases, and to determine crystallite sizes in the blends. Results indicate that the catalyst has both catalyzing and nucleation effects on the PET/MXD6 blends, with the extents of each effect dependent upon the content of catalyst. In addition the crystalline morphology was found to be dominated by the MXD6 content as well as the crystallization temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Synthesis and characterization of poly(3,4‐ethylenedioxythiophene) nanoparticles obtained through ultrasonic irradiation
Authors: Zhong Xinrui , Fei Guoxia , Xia Hesheng
Published: June 2010

Poly(3,4‐ethylenedioxythiophene) (PEDOT) nanoparticles with a size of 50–100 nm were prepared by the oxidation polymerization of the monomer 3,4‐ethylenedioxythiophene (EDOT) under ultrasonic irradiation. The structure and morphology of PEDOT, as well as the electrical conductivity were characterized. Compared with the conventional stirring method, the PEDOT nanoparticles prepared by ultrasonic irradiation have a smaller particle size and are more uniform and spherical due to the dispersion, emulsifying and disruption effects of ultrasound. The yield of PEDOT by ultrasonic irradiation can reach ∼ 50%, and the conductivity of PEDOT is high up to 11 S/cm. A decrease in particle size due to the ultrasonication can lead to more effective doping and enhanced conductivity. The reaction time, temperature and ultrasound power output have significant effects on the field and electrical conductivity of PEDOT. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Rheology behavior of high‐density polyethylene/diluent blends and fabrication of hollow‐fiber membranes via thermally induced phase separation
Authors: Wang Jianli , Wang Liang , Ruan Wenxiang , Zhang Cheng , Ji Jianbing
Published: June 2010

The phase‐separation behavior of high‐density polyethylene (HDPE)/diluent blends was monitored with a torque variation method (TVM). The torque variation of the molten blends was recorded with a rheometer. It was verified that TVM is an efficient way to detect the thermal phase behavior of a polymer–diluent system. Subsequently, polyethylene hollow‐fiber membranes were fabricated from HDPE/dodecanol/soybean oil blends via thermally induced phase separation. Hollow‐fiber membranes with a dense outer surface of spherulites were observed. Furthermore, the effects of the spinning temperature, air‐gap distance, cold drawing, and HDPE content on the morphology and gas permeability of the resultant membranes were examined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Crystallization kinetics, melting behavior, and morphologies of poly(butylene succinate) and poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyester
Authors: Huang Xi , Li Chuncheng , Guan Guohu , Zhang Dong , Xiao Yaonan
Published: June 2010

This article investigated the crystallization kinetics, melting behavior, and morphologies of poly(butylene succinate)(PBS) and its segmented copolyester poly(butylene succinate)‐block‐poly(propylene glycol)(PBSP) by means of differential scanning calorimetry, polarized light microscopy, and wide angle X‐ray diffraction. Avrami equation was used to describe the isothermal crystallization kinetics. For nonisothermal crystallization studies, the Avrami equation modified by Jeziorny, and the model combining Avrami equation and Ozawa equation were employed. The results showed that the introduction of poly(propylene glycol) soft segment led to suppression of crystallization of PBS hard segment. The melting behavior of the isothermally and nonisothermally crystallized samples was also studied. Results showed that the isothermally crystallized samples exhibited two melting endotherms, whereas only one melting endotherm was shown after nonisothermal crystallization. The spherulitic morphology of PBSP and wide angle X‐ray diffraction showed that the polyether segments were excluded from the crystals and resided in between crystalline PBS lamellae and mixed with amorphous PBS. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Influence of collecting velocity on fiber orientation, morphology and tensile properties of electrospun PPESK fabrics
Authors: Qi Wen , Lu Chun , Chen Ping , Cui Tianfang
Published: June 2010

Poly(phthalazinone ether sulfone ketone) (PPESK) is a novel kind of soluble thermoplastic resin with excellent thermal resistance properties. In this article, PPESK nonwoven fabrics were successfully prepared using electrospinning technique, and the influence of collecting velocity on fibers orientation, morphology and tensile properties was studied by changing the collecting velocity during electrospinning process. Results indicate that collecting velocity has a strong influence on fiber orientation and mechanical performance. When the collecting linear velocity increases from 0.36 to 3.35 m/s, fiber angular standard deviation is decreased from 63.8° to 45.5°, and tensile strength of PPESK fabrics is increased from 0.0246 to 3.677 MPa. However, when collecting velocity is higher than 3.35 m/s, fabrics tensile strength shows a declining tendency due to the breaking down of the fibers at a high of collecting speed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Reactive green HE‐4BD functionalized supermacroporous poly(hydroxyethyl methacrylate) cryogel for heavy metal removal
Authors: Arpa Çiğdem , Bereli Nilay , Özdil Elif , Bektaş Sema , Denizli Adil
Published: June 2010

The aim of this study was to investigate the heavy metal adsorption performance of supermacroporous poly(hydroxyethyl methacrylate) [PHEMA] cryogel. The PHEMA cryogel was produced by cryo‐polymerization. The PHEMA cryogel was characterized by scanning electron microscopy (SEM). The PHEMA cryogel containing 385 μmol Reactive Green HE‐4BD/g were used in the adsorption studies. Adsorption capacity of the PHEMA cryogel for the metal ions, i.e., Cu2+, Cd2+, and Pb2+ were investigated in aqueous media containing different amounts of the ions (5–600 mg/L) and at different pH values (3.2–6.9). The maximum adsorption capacities of the PHEMA cryogel were 11.6 mg/g (56 μmol/g) for Pb2+, 24.5 mg/g (385 μmol/g) for Cu2+ and 29.1 mg/g (256 μmol/g) for Cd2+. The competitive adsorption capacities were 10.9 mg/g (52 μmol/g) for Pb2+, 22.1 mg/g for Cd2+ (196 μmol/g) and 23.2 mg/g (365 μmol/g) for Cu2+. The PHEMA/Reactive Green HE‐4BD cryogel exhibited the following metal ion affinity sequence on molar basis: Cu2+ > Cd2+ > Pb2+. The PHEMA/Reactive Green HE‐4BD cryogel can be easily regenerated by 50 mM EDTA with higher effectiveness. These features make the PHEMA/Reactive Green HE‐4BD cryogel a potential adsorbent for heavy metal removal. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Preparation, intermolecular motion, and thermal properties of thiodiphenyl epoxy
Authors: Chiu Yie‐Chan , Tsai Hsieh‐Chih , Chou I‐Chen , Lin Wei‐Ning , Yang Shih‐Yi , Tien Hsin‐Wen , Ma Chen‐Chi M.
Published: June 2010

The thiodiphenyl epoxy (THEP) was prepared by the 4,4′‐thiodiphenol (THDOL) and the epichlorohydrin (ECH) without using any NaOH or KOH catalysts. The THEP possessed weak hydrogen bonding in the cured THEP/DGEBA system. The intermolecular motion parameters k and q were 0.26 and −168.5, respectively, which determined by the Gordon‐Taylor and Kwei equations. The soft sulfide linkage (S) of the THEP degraded at lower temperature than cured DGEBA material, and further to form various thermal stable sulfate derivative chars. The char yields increased from 11.43 to 25.94 wt % and from 0.65 to 1.04 wt % in the nitrogen and air, respectively. Introduction of the THEP into the DGEBA could provide the antioxidation thermal property and improve the thermal stability of the DGEBA epoxy in the air. In the air atmosphere, the activation energies of the second thermal degradation were increased from 66.67 to 103.42 kJ/mol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010