bluuebunny/crossref_metadata_2025 huggingface dataset:
Generation of a transgenic mouse line expressing GFP‐Cre protein from a Hoxb4 neural enhancer
Authors: Rivkin Elena , Cordes Sabine P.
Published: February 2008

Here, we describe a transgenic mouse line, in which expression of green fluorescent protein fused to Cre recombinase (GFP‐Cre) is directed by the early neuronal enhancer (ENE) of Hoxb4. In E9.0–13.5 transgenic embryos, Cre activity coincided with endogenous Hoxb4 throughout the neural tube up to the r6/r7 boundary in the hindbrain, the dorsal root ganglia, and the Xth cranial ganglia. Unexpectedly, Cre activity was also consistently detected in the trigeminal (Vth) cranial nerve, which is devoid of endogenous Hoxb4 expression. Strong GFP dependent fluorescence appeared slightly later in E9.5–E11.5 embryos, and reflected the later expression pattern expected for Hoxb4‐ENE directed expression in the neural tube up to the r7/r8 not r6/r7 boundary. Thus, with the exception of the trigeminal nerve, this reporter faithfully reproduces endogenous embryonic neural Hoxb4 expression, and provides an excellent reagent for in vivo gene manipulations in neuronal Hoxb4 positive cells as well as the developing trigeminal nerve. This transgenic mouse line should prove especially useful for determining the fate map of neuronal populations arising in rhombomeres 7 and 8 on its own and in combination with the small set of other existing rhombomere‐specific Cre recombinase expressing lines. genesis 46:119–124, 2008. © 2008 Wiley‐Liss, Inc.
First Evidence of Proline Acting as a Bifunctional Catalyst in the Baylis–Hillman Reaction Between Alkyl Vinyl Ketones and Aryl Aldehydes
Authors: Gruttadauria Michelangelo , Giacalone Francesco , Lo Meo Paolo , Mossuto Marculescu Adriana , Riela Serena , Noto Renato
Published: February 2008

Proline in the presence of sodium hydrogen carbonate has been found to be an effective catalyst for the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and aryl aldehydes. Screening of several amine catalysts showed that an ionizable carboxylic function directly linked to the secondary amine catalyst plays an important role in the synthesis of the desired product in good yield. The data obtained has allowed us to suggest, for the first time, that proline, sarcosine, pipecolinic acid and homoproline may act as bifunctional catalysts via a bicyclic enaminolactone species as intermediate. Quantum‐mechanical calculations (PM3/COSMO and ab initio 3‐21G/COSMO) support this mechanism and give more insight into the role of hydrogen carbonate.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Improved upsampling filter design for spatially scalable video coding
Authors: Wang Zhang , Liu Jian
Published: February 2008

Scalable video coding is an ongoing standard, and the current working draft (WD) is to be finalized as an extension of H.264/AVC. It provides scalability at the bit stream level with good compression efficiency and allowing free combinations of spatial, temporal and quality scalability. In the WD, a uniform up‐sampling filter is employed to interpolate the base layer frames. This technique achieves high interpolated precision for both luma component and chroma components, but it results in extremely large encoding time which obstructs it from practical use. This paper proposes an improved up‐sampling filter design for spatially scalable video coding. It makes use of a basic characteristic of human vision system and intends to assign different filters for different components. Specifically, current usage of the 6‐tap up‐sampling filter is only for luma component, but for chroma components, much more simplified filter such as 4‐tap filter or 2‐tap filter should be used instead. Experimental results show that improved up‐sampling filter design reduces the computational complexity significantly with negligible coding loss and bit‐rate increases. © 2008 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 17, 315–319, 2007
Regenerative potential of human periodontal ligament derived stem cells on three‐dimensional biomaterials: A morphological report
Authors: Trubiani O. , Orsini G. , Zini N. , Di Iorio D. , Piccirilli M. , Piattelli A. , Caputi S.
Published: February 2008

Recent studies have shown that mesenchymal stem cells obtained from periodontal ligament (PDL‐MSCs) are multipotent cells that have similar features of the bone marrow and dental pulp MSCs and are capable of proliferating and producing different types of tissue such as bone and tooth associated‐tissues. Human PDL‐MSCs expanded ex vivo were induced to osteogenesis, seeded in three‐dimensional biocompatible scaffolds (fibrin sponge, bovine‐derived substitutes) and examined using light, scanning and transmission electron microscopy. Morphological observations showed extensive growth of cellular biomass partially covering the scaffolds after 4 weeks of incubation in mineralization medium. These findings indicate that periodontal ligament can be an easily and efficient autologous source of stem cells with a high expansion capacity and ability to differentiate in osteogenic cells that can colonize and grow connected to bio‐compatible scaffold. It can be suggested that the use of PDL‐MSCs for generating graft biomaterials is advantageous for bone tissue engineering in regenerative dentistry. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2008
Hemocompatibility and antibacterial properties of lanthanum oxide films synthesized by dual plasma deposition
Authors: Jing F. J. , Huang N. , Liu Y. W. , Zhang W. , Zhao X. B. , Fu R. K. Y. , Wang J. B. , Shao Z. Y. , Chen J. Y. , Leng Y. X. , Liu X. Y. , Chu P. K.
Published: February 2008

Lanthanum oxide (La2O3) films with good hemocompatibility and antibacterial properties have been fabricated using dual plasma deposition. X‐ray photoelectron spectroscopy (XPS) shows that La exists in the +3 oxidation state. The band gap of the materials is determined to be 3.6 eV. Activated partial thromboplastin time (APTT) and blood platelet adhesion tests were used to evaluate the blood compatibility. The bacteria, Staphylococcus aureus, were used in plate counting tests to determine the surface antibacterial properties. The APTT is a little longer than those of blood plasma and stainless steel (SS). Furthermore, the numbers of adhered, aggregated, and morphologically changed platelets are reduced compared with those on low‐temperature isotropic carbon and SS. The antibacterial plate‐counting test indicates that La2O3 has good antibacterial activity against S. aureus. These unique hemocompatibility and antibacterial properties make La2O3 useful in many biomedical applications. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res 2008
Influence of hemoglobin vesicles, cellular‐type artificial oxygen carriers, on human umbilical cord blood hematopoietic progenitor cellsin vitro
Authors: Yamaguchi Miki , Fujihara Mitsuhiro , Wakamoto Shinobu , Sakai Hiromi , Takeoka Shinji , Tsuchida Eishun , Azuma Hiroshi , Ikeda Hisami
Published: February 2008

Hemoglobin vesicles (HbVs), liposomal oxygen carriers containing human hemoglobin, are candidates for development as clinically useful blood substitutes. Although HbVs are shown to distribute transiently into the bone marrow in animal models, the influence of HbVs on human hematopoietic stem/progenitor cells has not yet been studied. Therefore, we investigated the influence of HbVs at a concentration of up to 3 vol/vol % on the clonogenic activity (in semisolid culture) and proliferative activity (in liquid culture) of human hematopoietic progenitor cells derived from umbilical cord blood (CB)in vitro. Continuous exposure of CB mononuclear cells to HbVs tended to decrease the number and size of mature‐committed colonies and most notably reduced the number of colonies of high‐proliferative potential colony‐forming cells (HPP‐CFC). In contrast, exposure to HbVs for 20 h or 3 days, which is more relevant to the clinical setting, had no effect on the number of mature‐committed colonies and only modestly decreased the number of HPP‐CFC. Continuous exposure (10 days) to HbVs significantly suppressed the cellular proliferation and differentiation of both the erythroid and myeloid lineages in liquid culture. Again, short exposure (20 h or 3 days) did not affect these parameters. Thus, our results show that HbVs, under conditions relevant to the clinical setting, have no adverse effect on human CB hematopoietic progenitor activityin vitro. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Doppler sonography of the superior mesenteric artery in children with recurrent abdominal pain
Authors: Koktener Asli , Yilmaz Ayse Esra , Catal Ferat , Eminoglu Sancar
Published: February 2008

Purpose.

Abdominal pain is one of the most common conditions in childhood and adolescence. The aim of this study was to evaluate the superior mesenteric artery (SMA) Doppler findings in children with recurrent abdominal pain.

Method.

Duplex Doppler sonographic measurements were performed in 20 patients with recurrent abdominal pain and in 34 controls.

Results.

The mean blood flow velocities, blood flow volume, and diameter of the SMA were significantly lower in patients with recurrent abdominal pain than in controls.

Conclusion.

Insufficient development and/or vasoconstriction of the SMA vascular bed may be involved in recurrent abdominal pain, but further studies on larger groups are needed to test this hypothesis. © 2008 Wiley Periodicals, Inc. J Clin Ultrasound, 2008.
Quasi‐one‐dimensional systems: fluctuations, transport and interplay
Authors: Plyukhin A. V.
Published: February 2008

In a one dimensional lattice thermal fluctuations destroy the long‐range order making particles of the lattice move on a scale much larger than the lattice spacing. We discuss the assumption that this motion may be responsible for the transport of localized electrons in a system of weakly coupled chains. The model with diffusing localization sites gives a temperature‐independent mobility with a crossover to an activated dependence at high temperature. This prediction is consistent with and might account for experimental results on discotic liquid crystals and certain biopolymers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Models for transport properties of polymer thin films
Authors: Rentzsch R. , Ionov A. N.
Published: February 2008

We have observed that thin films of different undoped non‐conjugated polymers exhibit high conductivity in metal–polymer–metal (M‐P‐M) structures. Below the critical temperature, Tc of the superconductivity of the contacts, a supercurrent in superconductor–polymer–superconductor (S‐P‐S) structures was obtained. Investigations of the current‐voltage characteristics as a function of contact diameter at different locations on the polymer showed that only in some small channels does a high conductivity appear, whereas at other places a reversible on/off switching was obtained. We postulate that the conductivity effect is connected with the phenomenon of electrification. The electrons or holes are supplied by the electrodes which are in contact with the polymer. These injected charge carriers accumulate in localised states on different locations in the polymer matrix. As a result, a large inner electrical field appears in the polymer giving rise to local changes between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). In the high field region the forbidden gap can vanish, resulting in small channels with a high “metallic‐like” conductivity of the polymer. At present, there exists no theory explaining all the peculiarities of the electrical transport observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of electronic correlations on the frequency‐dependent hopping transport in Si:P
Authors: Ritz Elvira , Dressel Martin
Published: February 2008

At low energy scales charge transport in the insulating Si:P is dominated by activated hopping between the localized donor electron states. Thus, theoretical models for a disordered system with electron‐electron interaction are appropriate to interpret the electric conductivity spectra.With a newly developed technique we have measured the complex broadband microwave conductivity of Si:P from 100 MHz to 5 GHz in a broad range of phosphorus concentration n /nc from 0.56 to 0.95 relative to the critical value nc = 3:5 × 1018 cm–3 corresponding to the metal‐insulator transition driven by doping.

At our base temperature of T = 1.1 K the samples are in the zero‐phonon regime where they show a super‐linear frequency dependence of the conductivity indicating the influence of the Coulomb gap in the density of the impurity states. At higher doping n → nc , an abrupt drop in the conductivity power law σ1(ω) ∼ ωα is observed. The dielectric function ε1 increases upon doping following a power law in (1 – n /nc ). Dynamic response at elevated temperatures has also been investigated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Specific features of the low‐temperature microwave magnetoresistance in nondegenerate p‐Ge
Authors: Veinger A. I. , Zabrodskii A. G. , Tisnek T. V. , Goloshchapov S. I.
Published: February 2008

Low‐temperature microwave magnetoristance in lightly doped (nondegenerate) p‐Ge has been studied using the method of electron spin resonance (ESR) by recording the derivative of the microwave absorption with respect to magnetic field. An improvement of the experimental procedure made it possible to precisely determine the position of the zero magnetic field in the field dependence of the derivative and to obtain, by integrating this dependence, the field dependence of the microwave conductivity in the temperature range 10–120 K. A positive magnetoconductance (negative magnetoresistance) and separate manifestation of the magnetoresistances and different temperature dependences of magnetoconductance for light and heavy holes are observed in p‐Ge in weak fields. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Path coupling using stopping times and counting independent sets and colorings in hypergraphs
Authors: Bordewich Magnus , Dyer Martin , Karpinski Marek
Published: February 2008

We analyse the mixing time of Markov chains using path coupling with stopping times. We apply this approach to two hypergraph problems. We show that the Glauber dynamics for independent sets in a hypergraph mixes rapidly as long as the maximum degree Δ of a vertex and the minimum size m of an edge satisfy m ≥ 2Δ + 1. We also show that the Glauber dynamics for proper q‐colorings of a hypergraph mixes rapidly if m ≥ 4 and q > Δ, and if m = 3 and q ≥ 1.65Δ. We give related results on the hardness of exact and approximate counting for both problems. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008
Ersatz der Rechenbrücke des denkmalgeschützten Rheinkraftwerks Eglisau
Authors: Zerjeski Bernhard , Graf Ernst , Hardock Dieter , Mensinger Martin
Published: February 2008

Die neue Außenrechenbrücke am denkmalgeschützten Rheinkraftwerk Eglisau in der Schweiz befindet sich zur Zeit im Bau. Das sechsfeldrige Bauwerk ersetzt die vorhandene ca. 156 m lange Brücke. Während des Baus der Unterwasserpfeiler und der Montage der neuen Brücke soll der Außenrechen möglichst übergangslos von der bestehenden Konstruktion aus gereinigt werden. Die Stromproduktion des Kraftwerks muss während der gesamten Bauzeit und des Querverschubs der Brücke aufrechterhalten werden. Der vorliegende Aufsatz beschreibt die statischen, konstruktiven und montagetechnischen Besonderheiten des zum Teil im Wasser liegenden Bauwerks.
Is three‐dimensional power Doppler ultrasound useful in the assessment of placental perfusion in normal and growth‐restricted pregnancies?
Authors: Guiot C. , Gaglioti P. , Oberto M. , Piccoli E. , Rosato R. , Todros T.
Published: February 2008

Objectives

To investigate three‐dimensional (3D) power Doppler ultrasound indices in the assessment of placental perfusion and their relationship to gestational age (GA), placental position and umbilical artery Doppler flow velocity waveform (FVW) patterns in normal and intrauterine growth‐restricted (IUGR) pregnancies.

Methods

Forty‐five pregnant women at 23–37 weeks' gestation were studied, of whom 30 had IUGR and 15 were controls. Nine of the IUGR group had normal umbilical FVWs (NED), nine had abnormal patterns but positive end‐diastolic velocities (PED) and 12 had absent or reversed end‐diastolic velocities (AED). Placental position was assessed as being posterior, anterior or lateral. 3D power Doppler indices related to placental perfusion (vascularization index (VI), vascularization flow index (VFI) and flow index (FI)) were obtained from five different sampling sites in each placenta.

Results

VI, VFI and FI were not significantly dependent on GA or placental position. VI and VFI were significantly lower in PED and AED cases compared with controls, while FI was reduced in the AED group only. VI and VFI showed high variability between different sampling sites within each placenta, while the variability of FI was much lower.

Conclusions

3D power Doppler sonography can provide new insights into placental pathophysiology. FI, which identifies the most severe cases of placental impairment, appears to be the most reliable index because of its low intraplacental variability. Further studies are needed to verify its accuracy when applied in clinical practice as a substitute for or an adjunct to umbilical artery Doppler studies. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
The use of inversion mode and 3D manual segmentation in volume measurement of fetal fluid‐filled structures: comparison with Virtual Organ Computer‐aided AnaLysis (VOCAL™)
Authors: Kusanovic J. P. , Nien J. K. , Gonçalves L. F. , Espinoza J. , Lee W. , Balasubramaniam M. , Soto E. , Erez O. , Romero R.
Published: February 2008

Objective

Volume measurements by three‐dimensional (3D) ultrasonography are considered more accurate than those performed by two‐dimensional (2D) ultrasonography. The purpose of this study was to compare the agreement of three techniques, as well as the inter‐ and intraobserver agreements for volume measurements of fetal fluid‐filled structures.

Methods

Fifty 3D volume datasets of fetal stomachs and bladders were explored. Volume measurements were performed independently by two observers using: (1) Virtual Organ Computer‐aided AnaLysis (VOCAL™); (2) inversion mode; and (3) ‘manual segmentation’. Reliability was evaluated using intraclass correlation coefficient (ICC), and Bland–Altman plots were generated to examine bias and agreement. The time required to complete the measurements was compared using Student's t‐test or the Wilcoxon Signed Rank Test, and P‐values < 0.025 or < 0.05 were considered statistically significant.

Results

All volume datasets could be measured using the three techniques. A high degree of reliability was observed between: (1) VOCAL and inversion mode (ICC, 0.995; 95% CI, 0.992–0.997); (2) VOCAL and manual segmentation (ICC, 0.997; 95% CI, 0.995–0.998); and (3) inversion mode and manual segmentation (ICC, 0.995; 95% CI, 0.992–0.997). There was good agreement between VOCAL and inversion mode (mean, − 2.4%; 95% limits of agreement, − 20.1 to 15.3%), VOCAL and manual segmentation (mean, − 8.3%; 95% limits of agreement, − 28.8 to 12.2%) as well as between inversion mode and manual segmentation (mean, 5.9%, 95% limits of agreement: − 14.3 to 26%). Manual segmentation and inversion mode measurements were obtained significantly faster than those by VOCAL.

Conclusions

Volume measurements of fetal fluid‐filled structures of relatively regular shape with inversion mode and manual segmentation are feasible. Both techniques have good agreement with VOCAL and are significantly faster than VOCAL. Inversion mode is a reliable method for volume calculations of fluid‐filled organs, whereas manual segmentation can be used when volume measurements by VOCAL or inversion mode are technically difficult to obtain, such as solid structures with poorly defined borders as the volume dataset is rotated, like the uterine cervix. Copyright © 2008 ISUOG. Published by John Wiley & Sons, Ltd.
Virtual kinship in ancient Chinese society
Authors: Yuanlu XIE
Published: February 2008

Virtual kinship in ancient Chinese society mainly includes two types: brothers without kinship and father and son without kinship. From the Wei and Jin to the Sui and Tang dynasties, when the clan society and the imperial regimes were declining or on the edge of disintegration, virtual kinship became an important choice for marginalized families and lower strata of society in forming new social groups. After the Song Dynasty, virtual brothers without kinship was severely suppressed and even forbidden by authorities because of its tremendous threat to the stability of the dynasty. Due to its low social cost and high efficiency in forming a new social group, it became the main organization pattern of the secret folk society in the Ming and Qing dynasties.
The Western European witch-hunt in the 16th and 17th centuries
Authors: Qihong LU
Published: February 2008

The European witch-trials became numerous in the sixteenth and seventeenth centuries. A large number of witches were imprisoned and many of them were executed at the stake. The ubiquitous social strain brought on the witch-hunt, and the witch became the scapegoat. Study on the witch-hunt provides a special perspective on the transition of Western Europe in the sixteenth and seventeenth centuries.
Establishment of a national database to link epidemiological and molecular data from norovirus outbreaks in Ireland
Authors: KELLY S. , FOLEY B. , DUNFORD L. , COUGHLAN S. , TUITE G. , DUFFY M. , MITCHELL S. , SMYTH B. , O'NEILL H. , McKEOWN P. , HALL W. , LYNCH M.
Published: February 2008

A prospective study of norovirus outbreaks in Ireland was carried out over a 1-year period from 1 October 2004 to 30 September 2005. Epidemiological and molecular data on norovirus outbreaks in the Republic of Ireland (ROI) and Northern Ireland (NI) were collected and combined in real time in a common database. Most reported outbreaks occurred in hospitals and residential institutions and person-to-person spread was the predominant mode of transmission. The predominant circulating norovirus strain was the GII.4-2004 strain with a small number of outbreaks due to GII.2. This study represents the first time that enhanced epidemiological and virological data on norovirus outbreaks in Ireland have been described. The link established between the epidemiological and virological institutions during the course of this study has been continued and the data is being used as a source of data for the Foodborne Viruses in Europe Network (DIVINE-NET).
Glacial isostatic adjustment observed using very long baseline interferometry and satellite laser ranging geodesy
Authors: Argus Donald F. , Peltier W. Richard , Watkins Michael M.
Published: February 2008

In global space geodetic solutions, radial site motions are usually estimated relative to the geocenter (the center of figure of the solid Earth). Most geodesists estimate the motion of the geocenter assuming both that sites do not move radially and that sites move laterally as predicted by plate motion model NUVEL‐1A [DeMets et al., 1990, 1994]. Here we estimate the motion of the geocenter assuming that the plate interiors deform radially and laterally as predicted by the postglacial rebound model of Peltier [1994] or that of Peltier [1996] without assuming a priori knowledge about relative plate motion. Radial site motions estimated relative to this rebound‐adjusted geocenter are in the same reference frame as the rebound model predictions, whereas site motions estimated without adjusting for rebound are not. We further constrain the motion of the rebound‐adjusted geocenter using satellite laser ranging's sensitivity to the center of mass (of the solid Earth, the oceans, and the atmosphere) by assuming that the mean velocity between the rebound‐adjusted geocenter and the center of mass is negligible over the time period of geodetic measurement. Twenty years of observation with satellite laser ranging and very long baseline interferometry record the isostatic response of the solid Earth to the unloading of the late Pleistocene ice sheets. The misfits of the postglacial rebound model of Peltier [1994] and that of Peltier [1996] are 34% and 16% less, respectively, than the misfit of the rigid plate model. Sites at Onsala (Sweden) and Algonquin Park (Ontario) are observed to be rising at 3 mm/yr and 2 mm/yr, respectively, reflecting unloading of the Fennoscandian and Laurentide ice sheets. Sites along the east coast of the United States are subsiding at <2 mm/yr, indicating that the forebulge produced by the Laurentide ice sheet is currently collapsing very slowly. Sites beneath the margins of the ice sheets during the last glacial maximum are currently moving laterally away from the ice sheet centers at <1.5 mm/yr, in disagreement with the moderately fast outward motion predicted by the model of Peltier [1996].
Implications of shear heating and fracture zones for ridge formation on Europa
Authors: Han Lijie , Showman Adam P.
Published: February 2008

We present 2D and 3D numerical simulations of convection to test the role of shear heating and fracture zones on Europan ridge formation. Our simulations show that a pre‐existing fracture zone promotes upwelling and lithospheric thinning, leading to topographic uplift of 50 m. Shear heating also promotes lithospheric thinning and buoyant ascent, producing a ridge‐like feature with topography up to 120 m. Topography remains linear along strike even under the influence of heterogeneous 3D convection within the ice shell. Although the central trough is not reproduced in the simulations, our results support the idea that shear heating can produce ridge‐like structures on Europa.
Calculations of transmission functions in the infrared CO2 and O3 bands
Authors: Chou Ming‐Dah , Kouvaris Louis
Published: February 2008

An efficient method for computing the transmission function in the 15‐μm CO2 and the 9.6‐μm O3 bands is presented. An inhomogeneous atmospheric path is treated as homogeneous by applying simple pressure and temperature scaling approximations. The transmission functions are then derived from small precomputed tables. Because the atmospheric cooling rate is primarily contributed from adjacent layers, the simple scaling approximations can be used to accurately compute transmission functions in both the middle and lower atmosphere. Applying the parameterization to vastly different atmospheric conditions, the difference with line‐by‐line calculations is small. In the region between 0.01 mbar and the Earth's surface, the cooling rate difference is < 0.3°C/d in the 15‐μm CO2 band and < 0.1°C/d in the 9.6‐μm O3 band.
Neptune's cosmic ray cutoff
Authors: Selesnick R. S. , Stone E. C.
Published: February 2008

The Voyager 2 cosmic ray experiment observed the signature of a magnetic cutoff of cosmic ray protons immediately after the closest approach to Neptune. The cutoff signature shows that the simultaneous observation of a trapped particle dropout could not have occurred at high magnetic latitudes, but is likely to be a drift shadow of the planet caused by the large offset of the particle drift shells. The OTD2 dipole model of Neptune's magnetic field predicts a drift shadow at approximately the correct times. In addition, the cutoff signature is similar to that predicted by the OTD2 model, although the model is not accurate throughout the observation period. The similarity is consistent with small estimated corrections to the predicted signature based on the locally observed magnetic field values, indicating that the L shell values derived from the model are approximately valid after the closest approach time.
DE‐1 observations of lower hybrid waves excited by VLF whistler mode waves
Authors: Bell T. F. , Inan U. S. , Sonwalkar V. S. , Helliwell R. A.
Published: February 2008

Recent satellite data show high amplitude lower hybrid (LH) waves excited by electromagnetic (EM) whistler mode waves throughout magnetospheric regions where small scale magnetic‐field‐aligned plasma density irregularities exist. One important consequence in the auroral acceleration region is the heating of suprathermal ions by the excited LH waves. To evaluate such heating it is necessary to know the wavelength (λ) range of the waves, information not previously available since most past observations were made with long (l ≥ 75; l=antenna length) electric dipole antennas which have very poor response for λ < l. New observations using the short 9 m electric dipole antenna on the DE‐1 spacecraft show that LH waves with λ ≤ 10 m are excited by EM input waves from ground‐based VLF transmitters. Sequential observations on the short (9 m) and long (200 m) dipole antennas show that the long antenna generally has no measurable response to LH waves with λ ≤ 26 m. Since most previous correlative observations of LH waves and ion conics in the low altitude auroral acceleration region have involved long electric antennas, it is suggested that the intensity of the LH waves in this region may have been seriously underestimated.
Triaxial search coil measurements of ELF waves in the plasmasphere: Initial results from EXOS‐D
Authors: Kokubun S. , Takami M. , Hayashi K. , Fukunishi H. , Kimura I. , Sawada A. , Kasahara Y.
Published: February 2008

Triaxial search coil measurements of ELF waves in the frequency range below 50 Hz have been made with the polar orbiting satellite, EXOS‐D [AKEBONO], in the plasmasphere. Single component electric field measurements were also obtained along with measurements of the magnetic field. A survey of realtime telemetry data received for the period of March – October, 1989 reveals the existence of variety of plasma waves in the frequency range around ion gyrofrequencies near the equatorial region of the plasmasphere. Electromagnetic noises with a multi‐band structure were observed mostly above the local helium gyro‐frequency (fHe+), in the region of L values of 1.5 ∼ 2.5. Multi‐band ELF emissions are common in the daytime and were observed in 49 out of 250 orbits examined here. Another type of electromagnetic ELF waves with a broad‐band spectrum are also observed in the frequency range above the helium gyrofrequency in 10 orbits. Both types of wave spectra extend above the local proton gyrofrequency, but no absorption effect is observed at the local proton gyrofrequency. The electric field measurements clearly show spectral cut‐off for both of these two types of waves near f = (1.3 ∼ 2.5) fHe+. On the other hand, several spectral bands sometimes appear between the helium and oxygen gyrofrequencies in magnetic field components of multi‐band emissions.
Middle atmosphere heating by exothermic chemical reactions involving odd‐hydrogen species
Authors: Mlynczak Martin G. , Solomon Susan
Published: February 2008

We calculate the rate of heating that occurs in the middle atmosphere (50 – 105 km) due to four exothermic reactions involving members of the odd‐hydrogen family. These reactions are O + OH → O2 + H, H + O2 + M → HO2 + M, H + O3 → OH + O2, and O + HO2 → OH + O2. The energy lost from vibrationally excited OH (produced in the third reaction) by spontaneous emission is explicitly accounted for by using detailed kinetic models, so that only a portion of the exothermicity of this reaction is converted into heat. The heating rates due to these four reactions are found to rival the oxygen‐related heating rates conventionally considered in models of the middle atmosphere, e.g., those due to O + O + M → O2 + M, O + O2 + M → O3 + M, O2 + hv → O + O, and O3 + hv → O + O2 The conversion of chemical potential energy into molecular translational energy (heat) by these odd‐hydrogen reactions is a significant source of energy in the middle atmosphere which has not been previously considered.
Ion Reflection and transmission during reconnection at the Earth's subsolar magnetopause
Authors: Fuselier S. A. , Klumpar D. M. , Shelley E. G.
Published: February 2008

Composition measurements in an accelerated flow event at the Earth's dayside magnetopause show evidence for reflection and transmission of magnetospheric and magnetosheath ion species. Furthermore, a single velocity transformation approximately tangent to the magnetopause surface orders the individual transmitted and reflected ion distributions on both sides of the magnetopause into field‐aligned flow at VA, the local Alfven speed. These observations provide strong evidence for a kinetic description of magnetic reconnection at the magnetopause.
The longitudinal dependence of whistler and chorus characteristics observed on the ground near L = 4
Authors: Smith A. J. , Carpenter D. L. , Corcuff Y. , Rash J. P. S. , Bering E. A.
Published: February 2008

Whistler activity at L ≃ 4 is known to be a function of longitude, peaking in the Weddell Sea sector of Antarctica; a combination of source and propagation factors, the latter possibly partly associated with the South Atlantic geomagnetic anomaly, is believed to be responsible. There is evidence, for example from satellite surveys, that chorus and hiss activity may also be longitude dependent. To investigate this further, we have compared VLF data from four L ≃ 4 Antarctic stations from a 2‐day period in June 1982. Siple, Halley, and Sanae form a closely spaced (∼20°–0° geomagnetic longitude) triplet, while Kerguelen is ∼120° (geomagnetic) to the east, on the opposite side of the anomaly. To a large extent there was a repeatable diurnal variation in activity at all stations on the two days. Events observed at Siple tended to be similar to those observed ∼9 hours earlier (the same MLT) at Kerguelen on the same day. There was a very marked drop‐off in both whistler and VLF emission activity between Siple and Halley on the one hand and Sanae on the other. The reason for this is not clear; it may be either a source effect such as the lower occurrence of lightning over eastern North America compared to the adjacent Atlantic Ocean, or else a wave‐particle interaction effect whereby the conditions for wave growth or amplification are more favorable, or substorm particle injections penetrate the magnetosphere more deeply, at the longitude of Siple than further east. Comparison of the spectral forms of whistler mode activity at neighboring stations suggests that wave generation occurs simultaneously over relatively wide longitude (or local time) sectors (≳30° or 2 hours). Individual interaction regions are smaller than this, ≲5° in longitude, comparable with the previously inferred sizes of whistler ducts. Data sets with longer time coverage and better spatial resolution are required to answer some of the problems raised by this limited study.
Transient auroral events near midday: Relationship with solar wind/magnetosheath plasma and magnetic field conditions
Authors: Jacobsen B. , Sandholt P. E. , Lybekk B. , Egeland A.
Published: February 2008

Ground‐based observations of auroral/geomagnetic transient events near magnetic midday and magnetosheath magnetic field and plasma observations from spacecraft IMP 8 are presented. One category of event is characterized by a sequence of discrete auroral arc fragments moving westward along the poleward boundary of the persistent cusp arc, accompanied by an isolated magnetic pulse at latitudes close to the auroral event. This phenomenon occurs mainly during intervals of southward directed magnetosheath/interplanetary magnetic field. The auroral display in the second category of event is separated in two components, possibly associated with the cusp and the cleft/low‐latitude boundary layer. Intensification of the cleft aurora and magnetic perturbations over a wide latitudinal range were observed after a sharp northward magnetosheath magnetic field transition and a large variation in plasma density. It is suggested that these different events are ionospheric footprints of different time‐dependent coupling processes near/in the magnetopause boundary layer. However, the specific mechanism involved (e.g., flux transfer events or pressure pulses/ boundary waves) may not be uniquely inferred from these observations.
Phase and amplitude perturbations on subionospheric signals produced by a moving patch of artificially heated ionosphere
Authors: Dowden R. L. , Adams C. D. D. , Rietveld M. T. , Stubbe P. , Kopka H.
Published: February 2008

The Ionospheric Heating Facility (1‐MW HF transmitter and steerable array) at Ramfjordmoen, Norway, was used to generate a localized and steerable discontinuity in the Earth‐ionosphere waveguide for scattering Omega signals. The phase of the scattered signal (“echo”) relative to the direct signal varied with position of the heated patch of ionosphere (the discontinuity) in proportion to the change in echo path length. Previous results by Barr et al. (1985), using the same technique, Omega signals and path, show very similar behavior when looked at in this way. In this respect, both experiments simulated the phase and amplitude perturbations (“trimpis”) produced by lightning‐induced (via electron precipitation) changes in the waveguide and show that measurements of the varying echo phase of trimpis can be used to track lightning‐induced perturbations. The steerable discontinuity can also be used as a waveguide probe to measure the phase velocity of the strongest waveguide mode received on the ground by such scattering.
An approximate description of field‐aligned currents in a planetary magnetic field
Authors: Southwood David J. , Kivelson Margaret G.
Published: February 2008

Field‐aligned currents play a central role in the study of the magnetized plasmas of the solar terrestrial environment. In particular, if perturbations of flow develop on one part of a flux tube, field‐aligned currents must flow in order to communicate the changes to the entire flux tube. Field‐aligned currents cause the field to twist or shear, a feature that can be described in terms of the displacement of field lines from an unperturbed orientation. In this paper we derive expressions for the field‐aligned current density in a magnetized plasma that illuminate die relationship between twist or shear and current flow parallel to the background magnetic field. We show that the time evolution of the field displacements is closely linked to equations for Alfvén wave displacements and that they are driven by pressure gradient terms of the sort that are encountered in computations of interchange motions. We find that in the magnetosphere or in any other collisionless plasma regime, the field‐aligned current density is related closely to the time integral of the parallel vorticity. We make use of the fact that the field‐aligned current density in the ionosphere is related to the vorticity itself, not its time integral. Continuity relates the currents in the two regions and implies a decay time for the magnetospheric current inversely proportional to the ionospheric resistivity. The decay depends only on a magnetospheric scale length but on no other magnetospheric parameters and resembles the decay of current in an inductance caused by resistivity somewhere in the circuit.
A comparison of ULF fluctuations in the solar wind, magnetosheath, and dayside magnetosphere: 2. Field and plasma conditions in the magnetosheath
Authors: Lin N. , Engebretson M. J. , McPherron R. L. , Kivelson M. G. , Baumjohann W. , Luehr H. , Potemra T. A. , Anderson B. J. , Zanetti L. J.
Published: February 2008

Data from three spacecraft (AMPTE IRM, AMPTE CCE, and ISEE 1 or 2) are used to study the correlation among the field and plasma conditions in the subsolar magnetosheath region, ULF wave activity in the magnetosphere, and the cone angle of the IMF. A disturbance parameter, R, which is the magnitude of the normalized resultant of unit vectors (calculated from measurements of the magnetic field or the plasma bulk velocity in a time interval), is used to describe the disturbance of the magnetosheath region. A “quiet” state has R values close to unity. We have studied five time intervals and found that when the R values of the magnetosheath magnetic field were below 0.8, indicative of a disturbed magnetosheath near local noon, transverse harmonic oscillations of magnetic field lines in the Pc 3, 4 range were observed in the magnetosphere and small cone angles were observed in the solar wind. We have also investigated the variation of other magnetosheath parameters (such as the magnetic pressure, the thermal pressure, the dynamic pressure, and the perturbation energy, etc.) under various magnetosheath conditions by comparing them with the disturbance parameter. It is found that the thermal beta (the ratio of the thermal pressure to the magnetic pressure) and the perturbation energy increase greatly as R decreases (i.e., as the magnetosheath region becomes more disturbed). The total pressure, which is the sum of the magnetic, thermal, and dynamic pressure of the subsolar magnetosheath region, decreases as the region becomes more disturbed. The dynamic pressure and the dynamic beta (the ratio of the dynamic pressure to the magnetic pressure) measured in the magnetosheath are poorly correlated with R, indicating that the changes in magnitude of the plasma bulk velocity in the subsolar magnetosheath have little effect on the occurrence of Pc 3‐4 waves in the outer magnetosphere. All magnetosheath parameters we examined became more variable during disturbed periods than during quiet ones. The implication of the above results to the transport of wave energy from the solar wind to the magnetosphere is discussed.
Extension of the MSIS Thermosphere Model into the middle and lower atmosphere
Authors: Hedin A. E.
Published: February 2008

The MSIS‐86 empirical model has been revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating temperature and density profiles representative of the climatological average for various geophysical conditions. Tabulations from the Handbook for MAP 16 are the primary guide for the lower atmosphere and are supplemented by historical rocket and incoherent scatter data in the upper mesosphere and lower thermosphere. Low‐order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and simplified local time and longitude variations. While month to month details cannot be completely represented, lower atmosphere temperature data are fit to an overall standard deviation of 3 K and pressure to 2%. Comparison with rocket and other data indicates that the model represents current knowledge of the climatological average reasonably well, although there is some conflict as to details near the mesopause.
Turbulent upwelling of the mid‐latitude ionosphere: 1. Observational results by the MU radar
Authors: Fukao Shoichiro , Kelley Michael C. , Shirakawa Tatsuya , Takami Tomoyuki , Yamamoto Mamoru , Tsuda Toshitaka , Kato Susumu
Published: February 2008

In this paper we present the detailed results of a series of experiments designed to study the coherent backscatter of 50‐MHz radar waves from the mid‐latitude F region. Data were obtained with the active phased‐array MU radar in Japan and include some auxiliary E region coherent echoes as well. As in other turbulent ionospheric phenomena the intense nonthermal scatter comes from irregularities oriented parallel to B. The strongest echoes correspond to irregularities at least 20 dB stronger than thermal backscatter at the same frequency from typical F region densities at the same range. Simultaneous observations with ionosondes show that these echoes occur during strong mid‐latitude spread F. As defined by ionosondes, the latter phenomenon is certainly much more widespread than the turbulent upwelling events described here, but we believe that in some sense these correspond to the most violent mid‐latitude spread F. The strongest echoes occur in large patches which display away Doppler shifts corresponding to irregularity motion upward and northward from the radar. At the edges of these patches there is often a brief period of toward Doppler before the echoing region ceases. On rare occasions comparable patches of strong away and toward Doppler are detected, although in such cases the Doppler width of the toward echoes is much narrower than that of the away echoes. The away patches often are characterized by mean velocities well over 250 m/s and Doppler widths (full width at half maximum) of 50 m/s. The multiple beam capability at MU allowed us to track the patches in the zonal direction on two days. The patches moved east to west in both cases at velocities of 125 m/s and 185 m/s, respectively. There is a distinct tendency for the bottom contour of the scattering region to be modulated at the same period as the patch occurrence frequency as well as at higher frequencies. This higher‐frequency component may correspond to substructures in the large patches and to the E region coherent scatter patches which were detected simultaneously in several multiple beam experiments. In the companion paper (Kelley and Fukao, this issue), we explore a number of possible explanations for this phenomenon in more detail.
Ionospheric closure of small‐scale Birkeland Currents
Authors: Forget B. , Cerisier J.‐C. , Berthelier A. , Berthelier J.‐J.
Published: February 2008

In this paper, we study the relationship between the spatial variations of the perpendicular electric field observed in the topside ionosphere and those of the magnetic field induced by the associated field‐aligned currents. The mapping of the magnetospheric electric field down to the ionosphere depends upon the spatial scale of its variations and, consequently, also the amplitude of the perpendicular currents and their divergence. This mapping is modeled using realistic conductivity profiles, and the dependence of the electric and magnetic fields upon the spatial scale is analyzed. We compare the effective integrated Pedersen conductivity ΣP,eff defined in our model to ΔB/μo ΔE, where Delta;E and ΔB are the correlated variations of the mutually orthogonal electric and magnetic fields in the topside ionosphere. We have studied the variation of ΣP,eff as a function of the scale of ΔE and ΔB fluctuations. ΣP,eff is constant and equal to the classical integrated Pedersen conductivity for scales larger than ≈5 km. At smaller scales, it shows a steep decrease down to the lowest scales considered of 0.1 km. The good agreement between observations made on board the AUREOL 3 satellite and this model calculation suggests that the ULF electromagnetic turbulence observed frequently in the cusp and auroral zone may be essentially due to the crossing of spatially structured field‐aligned currents. The limits of the present model and its possible improvements are discussed.
Some remarks on the structure of intermediate magnetohydrodynamic shocks
Authors: Freistühler Heinrich
Published: February 2008

Though being unstable in the framework of ideal dynamics, intermediate MHD shocks can often be realized in the presence of dissipative effects. Numerical experiments by Wu which predict this phenomenon have an analytical counterpart: Mathematical proofs are reported here for the fact that for arbitrary positive values of the four dissipation coefficients (two coefficients of fluid viscosity, one for electrical resistivity, and one for heat conductivity) many shocks of the types 0 → 3, 0 → 2, and 1 → 2 possess structure. Consequently, this is the case for physically interesting values of these coefficients.