bluuebunny/crossref_metadata_2025 huggingface dataset:
Positional cyanosis in infants: an unusual presentation of right-sided cardiac masses
Authors: Levitas Aviva , Gross Gil , Zucker Nili , Zalzstein Eli
Published: September 2008

Positional cyanosis is an uncommon finding in young patients. We report three infants who presented with positional cyanosis due to a pedunculated tumour in the right heart. Arterial desaturation was the result of right-to-left shunting at the level of the oval foramen caused by obstruction and/or insufficiency of the tricuspid valve. The obstruction at the level of the tricuspid valve was variable because of the pedunculated nature of the tumours, which gave them considerable mobility. Hence, the degree of right-to-left shunting was dependent on the position of the patient. In all the patients, surgical resection of the tumours resolved the cyanosis.
Use of covered Cheatham-Platinum stents in aortic coarctation and recoarctation
Authors: Qureshi Shakeel A , Zubrzycka Maria , Brzezinska-Rajszys Grazyna , Kosciesza Andrzej , Ksiazyk Joanna
Published: September 2008

We inserted covered Cheatham-Platinum stents in 4 patients, ranging in age from 12 to 19 years, who weighed between 45 and 94 kg. All the patients had aortic coarctation, with surgical repair having been attempted previously in one, and with balloon dilation having been performed as the primary treatment in two, resulting in formation of aneurysms. The fourth patient had not received any treatment. The gradients were reduced from 10 to 40 mmHg before insertion of the stent to 0 to 5 mmHg after stenting. No complications were encountered. All the patients are well at an interval of 3 to 14 months after stenting.
The Warden procedure for partially anomalous pulmonary venous connection to the superior caval vein
Authors: DiBardino Daniel J. , McKenzie E. Dean , Heinle Jeffrey S. , Su Jason T. , Fraser Charles D.
Published: September 2008

Purpose:When there is partially anomalous pulmonary venous connection to the superior caval vein, intracardiac repair alone can result in obstruction. Although the Warden procedure involving translocation of the superior caval vein is commonly performed as an alternative to atriocavoplasty, follow-up of a larger number of patients in the modern era is lacking. We report and discuss the experience of a single institution with the Warden procedure for correction of partially anomalous pulmonary venous connection to the superior caval vein.Methods:Since 1995, all 16 patients presenting with partially anomalous pulmonary venous connection to the superior caval vein underwent the Warden procedure at a mean age of 7.1 ± 4.2 years, with a range from 0.2 to 14.3 years, and a mean weight of 24.7 ± 14.0 kg, with a range from 4.1 to 52.9 kg. There were 9 males and 7 females. In 8 patients, we performed 10 concomitant procedures, including closure of an atrial or ventricular septal defect in 7, and advancement of the aortic arch in the other.Results:There were no deaths, and only one episode of postoperative sinus bradycardia with intermittent junctional rhythm, which resolved spontaneously during temporary atrial pacing. All patients were discharged home in normal sinus rhythm at an average of 4.1 ± 2.2 days after the procedure, with a range from 2 to 10 days. All are currently in the first grade of the New York Heart Association up to 5.6 years postoperatively. There is currently no evidence of sinus nodal dysfunction, nor obstruction of the superior caval vein, in any patient.Conclusion:The Warden procedure for partially anomalous pulmonary venous connection to the superior caval vein produces excellent results, preserves the function of the sinus node, and should be routinely considered for the repair of this lesion.
Prevalence of arrhythmias and conduction disturbances in large population-based samples of children
Authors: Niwa Koichiro , Warita Naomi , Sunami Yuko , Shimura Akimitsu , Tateno Shigeru , Sugita Katsuo
Published: September 2008

The aim of our study is to provide data on the prevalence of disturbances of rhythm in the general population of children. Accurate estimates of true prevalence of such disturbances of rhythm from large samples are mandatory if we are to interpret properly electrocardiographic abnormalities. We analysed prevalence of disturbances of rhythm in a population of 152,322, comprised of 71,855 elementary school students, 36,692 males and 35,163 females, aged from 5 to 6 years, and 80,467 students of junior high school, 41,842 males and 38,625 females, aged from 12 to 13 years. We analysed the prevalence of premature atrial and ventricular contractions, first, second and third degree atrioventricular block, incomplete and complete right bundle branch block, Wolff-Parkinson-White syndrome, and prolongation of the QT interval. The prevalence of disturbances of rhythm in total rose with age, being found in 1.25% of elementary school students and 2.32% of junior high school students, and was higher in males than females, at 2.00% as opposed to 1.38%, both values being statistically significant at a level of less than 0.0001. Prevalences of all types of rhythmic disturbances were higher in junior high school students than elementary school students (p < 0.0001). Premature atrial and ventricular contractions and prolongation of the QT interval were higher in female than male students, at percentages of 0.089, 0.497, and 0.02 for males, and 0.123, 0.534 and 0.027 in females (p < 0.0001). In contrast, incomplete and complete right bundle branch blocks were higher in males than females, at 0.983% and 0.083% in males versus 0.410% and 0.161% in females (p < 0.0001). Disturbances of rhythm increased with age, and conduction disturbances were higher in male students than female, although premature atrial and ventricular contractions and prolongation of the QT interval were more frequent in female. These data may be useful for future comparative studies of disturbance of rhythm in children.
Aortic-right atrial tunnel
Authors: Moraes Fernando , Lapa Santos Cleusa , Moraes Carlos R.
Published: September 2008

We describe an asymptomatic 1-year-old boy who presented a continuous murmur, and was found to have a tunnel between the right atrium and the aorta. The definitive diagnosis was established by both echocardiography and aortography, and surgical interruption of the tunnel was successful. We emphasise the rarity of this condition, and discuss its major features.
Intraoperative rescue by placement of a stent following a surgical coronary arterial injury in a child
Authors: Duncan Walter J. , LeBlanc Jacques G. , Human Derek G.
Published: September 2008

An acute injury to a coronary artery was recognized during the surgical construction of the Fontan circulation. Surgical manipulation of the site of injury was not successful in restoring normal myocardial blood flow. A stent was therefore placed intraoperatively under direct vision, with restoration of normal coronary arterial flow acutely and at short-term follow-up.
Anomalous origin of the circumflex coronary artery in a patient with atrial and ventricular septal defects
Authors: Dogan Abdullah , Gedikli Omer , Ozaydin Mehmet
Published: September 2008

We report a patient in whom the circumflex coronary artery arose anomalously from the right aortic sinus. The patient also had atrial and ventricular septal defects in the setting of Eisenmenger physiology. We recommended transplantation of the heart and lungs.
Echocardiographic characteristics of venous air embolism presenting as reversible pulmonary atresia in a premature neonate
Authors: Divekar Abhay , Cases Rebecca , Soni Reeni
Published: September 2008

Air embolism secondary to mechanical ventilation is a rare but well-described complication in premature infants. We describe the echocardiographic appearance of venous air embolism manifesting as acute obstruction of the right ventricular outflow tract in such a premature infant, and review the pathophysiology of acute obstruction of the right ventricular outflow tract secondary to the “air lock” phenomenon. Awareness of the pathophysiology and echocardiographic appearance of venous air embolism may aid in prompt recognition and potential therapy for this lethal complication of mechanical ventilation.
Resection of a cardiac aneurysm in an infant with anomalous origin of the left coronary artery from the pulmonary trunk
Authors: Grotenhuis Heynric B. , Backx Ad , Nijveld Aagje
Published: September 2008

We describe an infant with an anomalous left coronary artery arising from the pulmonary trunk leading to myocardial ischaemia and development of an apical aneurysm of the left ventricle.

Clinical presentation in general is based on myocardial hypoperfusion resulting in ischaemia and infarction. When presenting in infancy, however, then the features, as in our patient, may be tachypnea, dyspnea, failure to thrive and irritability, especially during feeding. Then, again as in our patient, it is possible to miss the definitive diagnosis, which is made by echocardiography and cardiac catheterization. Reimplantation of the anomalous left coronary artery into the aorta usually results in improvement of left ventricular function over time. In our patient, the myocardial infarction was complicated by formation of an aneurysm, and reimplantation alone was not sufficient to restore cardiac function. Resection of the aneurysm greatly improved the hemodynamics.
Stress conditions for the propagation of discrete compaction bands in porous sandstone
Authors: Tembe Sheryl , Baud Patrick , Wong Teng‐fong
Published: September 2008

Compaction bands are a compactant failure mode in porous rock, forming thin tabular structures normal to the maximum compressive stress with negligible shear offset. We investigated the conditions involved in the development of compaction bands in sandstone, including the influence of composition and the geometric attributes of the bands across a range of length scales. To extend beyond existing laboratory data on the relatively pure quartz Bentheim sandstone, a suite of triaxial experiments were conducted on Diemelstadt and Bleurswiller arkoses. Mechanical data and microstructural observations demonstrate that compaction bands can develop in compositionally heterogeneous rock and are the dominant failure mode in the transitional regime from brittle faulting to cataclastic flow. Synthesis of field and laboratory data on band dimensions in five sandstones over four orders of magnitude revealed a quadratic scaling relation between the thickness and length of compaction bands, wherein thickness is proportional to the square root of the band length. Using an anticrack/antidislocation fracture mechanics model, we obtained a scaling relation in which the stress level is inversely proportional to band thickness. We show that this relation provides a mechanical basis for interpreting discrepancies between laboratory and field data. Together, the laboratory and field data constrain the critical strain energy release rate in the model to be on the order of 2–80 kJ/m2, comparable with laboratory measurements.
Postseismic displacement of the 1999 Athens earthquake retrieved by the Differential Interferometry by Synthetic Aperture Radar time series
Authors: Atzori Simone , Manunta Michele , Fornaro Gianfranco , Ganas Athanassios , Salvi Stefano
Published: September 2008

In September 1999, a moderate (Mw = 5.9) earthquake struck the Attica plain, causing unexpected and extensive damage to Athens and its population. In this work, we exploit the potential of multitemporal Differential Interferometry by Synthetic Aperture Radar (DInSAR) analysis, using about a hundred European Remote Sensing (ERS) 1/2 images to calculate the displacement time series from 1992 to 2002. This analysis allows us to clearly separate a strictly coseismic signal from a postseismic gradual subsidence, reaching a maximum value of about 3 cm in the following 2.5 years. We model this signal in terms of afterslip on the seismogenic fault. The afterslip distribution, retrieved by linear inversion, reflects the coseismic slip distribution and occurs mainly downdip of the area that ruptured during the main shock. The analysis of the static stress transfer suggests that the afterslip was triggered by the main shock, then it propagated aseismically through the fault plane. A partial overlap between the coseismic and aseismic slip area at the hypocentral region indicates that the 1999 rupture surface was not “healed” at least until the date of the last postseismic image (April 2002). The results obtained with a time series approach for this moderate magnitude earthquake suggest that multitemporal DInSAR analysis should become an important methodology for the study of large earthquake ruptures.
On the mechanism of the cyclonic circulation in the Gulf of Tonkin in the summer
Authors: Wu Dexing , Wang Yue , Lin Xiaopei , Yang Jiayan
Published: September 2008

The circulation in the Gulf of Tonkin had been traditionally considered to be anticyclonic in the summer. This view was challenged recently by results from reanalyzing observational data, which clearly revealed that the circulation is cyclonic in all seasons. The surface wind stress is monsoonal, southwesterly in the summer and reversed in the winter. It remains unexplained why the circulation is always cyclonic, while the surface forcing reverses seasonally. In this study, we hypothesize that the inflow through Qiongzhou Strait, a shallow and narrow channel between Hainan Island and the Chinese mainland, is responsible for maintaining the cyclonic circulation in the summer. Besides the requirements of mass conservation and bathymetry constraint, this flow, even with a rather small transport, carries a considerable amount of potential vorticity (PV) into the gulf, and the integral constraint of PV requires the presence of a frictional torque to be associated with a cyclonic circulation. Several numerical experiments with a three‐dimensional model have been conducted to test this hypothesis. When the westward flow through Qiongzhou Strait is blocked, the model simulates an anticyclonic circulation in the summer. When the westward flow through Qiongzhou Strait is allowed, the circulation changes to a cyclonic one, consistent with our hypothesis.
Diffusion barriers at Mars surface conditions: Salt crusts, particle size mixtures, and dust
Authors: Hudson Troy L. , Aharonson Oded
Published: September 2008

The diffusion coefficient of water vapor through porous media at Mars‐like surface conditions is measured for a variety of complex particle size distributions and soil compositions. Micron‐sized dust simulants, mixtures of sand‐ and dust‐sized particles, and salt‐encrusted sand are examined. We find that while the value of the diffusion coefficient,D, can be reduced by up to a factor of 10 for heavily salt‐encrusted soils (minimum observedD= 0.4 ± 0.04 cm2s−1), moderate amounts of salt only produce minor reductions inD. Mechanical packing of pure dust can lowerDby a similar amount, while mixtures of dust with sand‐sized particles produce at most a factor of ∼4 reduction. We conclude that present‐day processes of aeolian redistribution, moderate levels of salt encrustation, and volatile loss from dirty ice would be inefficient at producing soil deposits and lags on Mars that pose significant barriers to diffusion. Therefore, subsurface ice deposits that are thermally unstable would not be protected against sublimative loss by such materials.
Drill Bit Noise Illuminates the San Andreas Fault
Authors: Vasconcelos Ivan , Snieder Roel , Sava Paul , Taylor Tom , Malin Peter , Chavarria Andres
Published: September 2008

Extracting the vibration response of the subsurface from noise is a rapidly growing field of research [Curtis et al., 2006; Larose et al., 2006]. We carried out broadside imaging of the San Andreas fault zone (SAFZ) using drill bit noise created in the main hole of the San Andreas Fault Observatory at Depth (SAFOD), near Parkfield, Calif. Imaging with drill bit noise is not new, but it traditionally requires the measurement of the vibrations of the drill stem [Rector and Marion, 1991]; such measurements provide the waves radiated by the drill bit. At SAFOD, these measurements were not available due to the absence of an accelerometer mounted on the drill stem. For this reason, the new technique of deconvolution interferometry was used [Vasconcelos and Snieder, 2008]. This technique extracts the waves propagating between seismometers from recordings of incoherent noise.
Radar and Lidar Measurement of Terrestrial Processes
Authors: Donnellan Andrea , Zebker Howard , Ranson K. Jon
Published: September 2008

Earth's land surface is constantly changing and interacting with its interior and its atmosphere. In response to the interior, plate tectonics deform the surface, causing earthquakes, volcanoes, mountain building, and erosion—including landslides. These events can be violent and damaging. Forests, growing on the land surface, store carbon, which can be released into the atmosphere through logging and burning. Our ice sheets, sea ice, and glaciers are key indicators of our climate, and they have been undergoing dramatic changes. These land surface processes can be characterized and monitored from space using synthetic aperture radar (SAR) and light detection and ranging (lidar).
Who Really Failed New Orleans?
Authors: Barrow Thomas D.
Published: September 2008

I read with unusual interest the Forum “Earth Scientists and Public Policy: Have We Failed New Orleans?” in the 4 March issue of Eos (89(10), 2008). As an Earth scientist who lived in New Orleans during most of the early 1960s, I believe strongly that Earth scientists did not fail to recognize infrastructure problems. Further, they tried to communicate these problems and potential dangers to civic leaders in New Orleans and to government officials in Baton Rouge and Washington.

When I first moved to New Orleans in 1959, I studied existing topographic information carefully. After numerous conversations about the levee system with a cousin who worked for the U.S. Army Corps of Engineers, I concentrated my house search in the uptown section southwest of Tulane University, which was clearly the highest part of town. I bought a raised cottage (these are fairly common) after determining that the first floor above the ground‐level basement was 2 feet higher than the top of the levee. I reasoned that even if a levee break did occur, my house would be slightly above flood level.
Organic Carbon in the Ocean's Twilight Zone: Controls on Organic Carbon Export and Twilight Zone Remineralization; Brussels, Belgium, 28–30 May 2008
Authors: Dehairs Frank , de Brauwere Anouk , Elskens Marc
Published: September 2008

Today, the key role played by oceans in the Earth's carbon cycle is widely recognized. The important boundary to consider is not the ocean‐atmosphere interface, across which the carbon dioxide (CO2) concentration gradient is small, but the seasonal and permanent thermoclines, whose positions range from about 20 to 300 meters in depth. Once CO2 is delivered to depths beyond these thermoclines, the sequestration efficiency for CO2 is increased.

Both physical and biological pumps act to increase the amount of carbon stored in the deep sea. For the latter process, more than 90% of the organic carbon exported (10–12 gigatons per year) to the deeper mesopelagic waters (i.e., the region below the upper mixed layer down to about 1000 meters, also called the twilight zone) is again respired to form CO2. Only a very small fraction of this organic carbon (<1%) eventually reaches the seafloor, where it is sequestered on longer timescales. The mechanisms controlling carbon export and its fate are still insufficiently understood to allow an informed assessment of its variability.
Geological Approaches to Coral Reef Ecology
Authors: Kench Paul
Published: September 2008

Tropical coral reef systems cover an estimated 284,300 square kilometers of the Earth's surface and are considered among the most valuable ecosystems on Earth. The reef systems are zones of high biological diversity, habitat for about one quarter of all known marine species, and important components of the global carbon cycle. In addition, they provide the physical foundation for a number of mid‐ocean nation states. Coral reefs worldwide are considered to be in serious ecological decline due to anthropogenic impacts, natural stresses, and climate change. However, these gloomy projections for coral reefs are based largely on analysis of short‐term changes in their ecological condition.
Assessing sedimentary records of paleohurricane activity using modeled hurricane climatology
Authors: Woodruff Jonathan D. , Donnelly Jeffrey P. , Emanuel Kerry , Lane Philip
Published: September 2008

Patterns of overwash deposition observed within back‐barrier sediment archives can indicate past changes in tropical cyclone activity; however, it is necessary to evaluate the significance of observed trends in the context of the full range of variability under modern climate conditions. Here we present a method for assessing the statistical significance of patterns observed within a sedimentary hurricane‐overwash reconstruction. To alleviate restrictions associated with the limited number of historical hurricanes affecting a specific site, we apply a recently published technique for generating a large number of synthetic storms using a coupled ocean‐atmosphere hurricane model set to simulate modern climatology. Thousands of overwash records are generated for a site using a random draw of these synthetic hurricanes, a prescribed threshold for overwash, and a specified temporal resolution based on sedimentation rates observed at a particular site. As a test case we apply this Monte Carlo technique to a hurricane‐induced overwash reconstruction developed from Laguna Playa Grande (LPG), a coastal lagoon located on the island of Vieques, Puerto Rico in the northeastern Caribbean. Apparent overwash rates in the LPG overwash record are observed to be four times lower between 2500 and 1000 years B.P. when compared to apparent overwash rates during the last 300 years. However, probability distributions based on Monte Carlo simulations indicate that as much as 65% of this drop can be explained by a reduction in the temporal resolution for older sediments due to a decrease in sedimentation rates. Periods of no apparent overwash activity at LPG between 2500 and 3600 years B.P. and 500–1000 years B.P. are exceptionally long and are unlikely to occur (above 99% confidence) under the current climate conditions. In addition, breaks in activity are difficult to produce even when the hurricane model is forced to a constant El Niño state. Results from this study continue to support the interpretation that the western North Atlantic has exhibited significant changes in hurricane climatology over the last 5500 years.
On westward transport processes off central California revealed by RAFOS floats
Authors: Ivanov L. M. , Collins C. A. , Margolina T. M. , Piterbarg L. I. , Eremeev V. N.
Published: September 2008

Westward transport processes off central California are quantified by exit time statistics for RAFOS floats launched at mid‐depths (275–375 m). The random displacement model in the diffusion limit was used to interpret results. The alongshore‐averaged westward motion of floats represented inhomogeneous eddy diffusion interspersed with short‐duration advective motions. The across‐shore diffusion coefficient grew as a power law with distance from the coastline (the power exponent was close to one). This is evidence for offshore growth of eddy kinetic energy and may be explained through flow barotropization accompanied by a quasi‐geostrophic turbulent regime. Typical values of the float drift velocity were about 1.8–2 cm/s but, offshore, drift velocities were as high as 4–6 cm/s during the upwelling season. Between 150 and 250 km from shore, a transition zone between nearshore and offshore was clearly identified in spring but was either very narrow or undetectable in other seasons.
Modelling Circumpolar Deep Water intrusions on the Amundsen Sea continental shelf, Antarctica
Authors: Thoma Malte , Jenkins Adrian , Holland David , Jacobs Stan
Published: September 2008

Results are presented from an isopycnic coordinate model of ocean circulation in the Amundsen Sea, focusing on the delivery of Circumpolar Deep Water (CDW) to the inner continental shelf around Pine Island Bay. The warmest waters to reach this region are channeled through a submarine trough, accessed via bathymetric irregularities along the shelf break. Temporal variability in the influx of CDW is related to regional wind forcing. Easterly winds over the shelf edge change to westerlies when the Amundsen Sea Low migrates west and south in winter/spring. This drives seasonal on‐shelf flow, while inter‐annual changes in the wind forcing lead to inflow variability on a decadal timescale. A modelled period of warming following low CDW influx in the late 1980's and early 1990's coincides with a period of observed thinning and acceleration of Pine Island Glacier.
Observations of wintertime arctic mesosphere cooling associated with stratosphere baroclinic zones
Authors: Thayer J. P. , Livingston J. M.
Published: September 2008

A regional wintertime mesosphere cooling of 30–40 K is observed over the Sondrestrom facility near Kangerlussuaq, Greenland (67.0°N, 309.1°E) during multiple weeks in December 2000 where temperatures from the ground to 90 km were uniquely observed. The negative excursions in mesosphere temperature were observed during times when no thermal changes are observed below 10 hPa (∼30 km), but strong temperature changes are observed above this pressure surface. These thermal features are associated with middle atmosphere disturbances that may occur prior to, or independently of, major stratospheric warmings. They are regionally confined, deviate significantly from ambient conditions, and are likely caused by adiabatic cooling/heating due to strong vertical velocities. We propose that these types of mesosphere cooling events are related to stratospheric baroclinic zones and a Q‐vector analysis of stratospheric geopotential and temperature fields can be used to help identify and describe regional occurrences of significant cooling in the mesosphere.
An extensive western Mediterranean deep water renewal between 2004 and 2006
Authors: Schroeder K. , Ribotti A. , Borghini M. , Sorgente R. , Perilli A. , Gasparini G. P.
Published: September 2008

The deep waters of the western Mediterranean are known to have an almost constant trend towards higher salinity and temperature values since the 1950s. Recent observations have shown an acceleration of this tendency, which has been attributed by some authors to the effect of the propagation of the signal of the Eastern Mediterranean Transient, from east to west. From 2004 to 2006 five basin‐scale oceanographic cruises evidenced a relevant change in the deep structure of the western Mediterranean. In less than two years almost the whole deep basin has been filled with highly saline and warm new deep water, which substantially renewed the resident deep water. The paper shows evidence of the rapid basin‐wide extension of the event, giving insights into the origin and the propagation of the new deep water towards the basin interior and showing the evolution of the deep characteristics.
Intraplate deformation of the Indian subcontinent
Authors: Banerjee P. , Bürgmann R. , Nagarajan B. , Apel E.
Published: September 2008

While deformation at the Earth's surface primarily occurs along tectonic plate boundaries, major earthquakes have shaken regions deep within continental interiors. Three of the largest (M > 7.5) historic intraplate earthquakes occurred within the Indian subcontinent, suggesting the possibility of significant intraplate deformation. We consider surface velocities determined from new GPS data collected at 29 continuous GPS stations and 41 survey‐mode GPS stations in India between 1995 and 2007 to find a north‐south shortening rate of 0.3 ± 0.05 nanostrain yr−1, which may be accommodated by 2 ± 1 mm/yr of more localized convergence across central India. Southward motions at 4–7 mm/yr of sites on the Shillong plateau in northeast India reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau. The width and magnitude of the elastic strain accumulation field across the Himalaya varies little from ∼76°–90° longitude, but the strain is more broadly distributed and convergence rates are higher along the eastern ∼200 km of the range.
Thermospheric meridional winds as deduced from ionosonde chain at low and equatorial latitudes and their connection with midnight temperature maximum
Authors: Maruyama Takashi , Saito Susumu , Kawamura Masabumi , Nozaki Kenro
Published: September 2008

Multipoint ionosonde observation was conducted in Southeast Asia to study ionosphere‐thermosphere coupling. For this observation three ionosondes were installed along the magnetic meridian at 100°E (Southeast Asia Low‐latitude Ionospheric Network: SEALION); two of them were at magnetic conjugate points and the third was near the magnetic equator. The F layer virtual height, h′F, was scaled from nighttime ionograms obtained from September 2004 to August 2005, close to the solar minimum. The height variations at the three locations were used to derive thermospheric winds in the magnetic meridional plane for transequatorial and convergent/divergent components (with respect to the magnetic equator). During northern winter months, a prominent 6‐hr periodic variation of a transequatorial component was found. During northern summer months, a diurnal or semidiurnal variation was dominant. Convergent winds toward the magnetic equator were associated with the occurrence of the midnight temperature maximum at the latitudes between the two conjugate stations as observed by satellite instruments during the solstices. However, no clear evidence was found of abatement of the wind due to the pressure bulge associated with the midnight temperature maximum.
Changing sea ice melt parameters in the Canadian Arctic Archipelago: Implications for the future presence of multiyear ice
Authors: Howell Stephen E. L. , Tivy Adrienne , Yackel John J. , Else Brent G. T. , Duguay Claude R.
Published: September 2008

Estimates of annual sea ice melt onset, freeze onset, and melt duration are made within the Canadian Arctic Archipelago (CAA) using SeaWinds/QuikSCAT data from 2000 to 2007. The average date of melt onset occurred on day 150, the average freeze onset occurred on day 266, and the average number of days of melt was 116. Melt onset occurred first, and freeze onset occurred last within the Amundsen, Western Arctic Waterway, and Eastern Parry Channel regions, whereas the reverse occurred in the Queen Elizabeth Islands (QEI) and the M'Clure and Viscount‐Melville regions. Multiyear sea ice (MYI) increases occurred from 2000 to 2004 because of dynamic import and first‐year sea ice (FYI) being promoted to MYI, but this replenishment virtually stopped from 2005 to 2007, coincident with longer melt seasons. Only after two consecutive long melt seasons (2005–2006) and almost no replenishment were regions to the south of the QEI cleared of MYI. We argue that this is because MYI must slowly ablate on the underside while in transit within the CAA from the small oceanic heat flux and can therefore survive for several years in southern regions without replenishment. Net positive dynamic MYI import into the CAA was observed in 2007 following MYI removal during 2005–2006. Longer melt seasons will continue to reduce the inventory of FYI in the CAA following the melt season. Longer melt seasons within the CAA will likely not reduce MYI dynamic import, but it remains to be seen whether or not this MYI will be able to survive longer melt seasons as it migrates to the southern regions.
Proton cyclotron waves in the solar wind at Venus
Authors: Delva M. , Zhang T. L. , Volwerk M. , Vörös Z. , Pope S. A.
Published: September 2008

Magnetometer data from two Venus years of the Venus Express mission in orbit are investigated for the occurrence of ion cyclotron waves. Proton cyclotron waves were recently detected in the upstream region of Venus by the spacecraft, indicating pickup of planetary protons from Venus's exosphere by the solar wind and loss of hydrogen to interplanetary space. A study of representative cases illustrates the waveform, spectrum, duration, and higher‐order resonances of the transverse waves with left‐hand circular polarization and propagation nearly along the magnetic field; their properties in the magnetic field principal axes system are determined. A statistical approach studies the wave properties as a function of the angle between the solar wind and magnetic field direction, as a function of their occurrence in space, and with respect to the motional solar wind electric field. Proton cyclotron waves are found up to 9 Venus radii from the planet, for a large range of angles between the solar wind and magnetic field direction, independent from foreshock geometry and independent from the direction of the motional electric field. This reveals that cyclotron wave generation from local pickup of neutral hydrogen is efficient over a large volume of space upstream of the planet and imposes the existence of an extended reservoir of planetary neutral hydrogen at Venus.
Calabrian Arc oroclinal bending: The role of subduction
Authors: Cifelli Francesca , Mattei Massimo , Della Seta Marta
Published: September 2008

Paleomagnetic data collected in the last 30 years indicate that a simple orocline model is not sufficient to describe the complex evolution of the Calabrian Arc. Present‐day curvature of the Calabrian Arc is the result of a different tectonic history between the edges of the arc, namely the Southern Apennines and Sicily, and its core, the Calabria‐Peloritani Domain. These differences mirror the structural architecture and deep lithospheric configuration of the Calabrian Arc, which are related to the geometry and evolution of the Ionian subduction system. In particular, the presence of lateral heterogeneities in the subducting lithosphere and the subsequent progressive decrease in width of the trench during subduction are likely the main causes of Calabrian Arc formation and of its present‐day narrow tight shape.
Reducing uncertainty in predictions in ungauged basins by combining hydrologic indices regionalization and multiobjective optimization
Authors: Zhang Zhenxing , Wagener Thorsten , Reed Patrick , Bhushan Rashi
Published: September 2008

Approaches to predictions in ungauged basins have so far mainly focused on a priori parameter estimates from physical watershed characteristics or on the regionalization of model parameters. Recent studies suggest that the regionalization of hydrologic indices (e.g., streamflow characteristics) provides an additional way to extrapolate information about the expected watershed response to ungauged locations for use in continuous watershed modeling. This study contributes a novel multiobjective framework for identifying behavioral parameter ensembles for ungauged basins using suites of regionalized hydrologic indices. The new formulation enables the use of multiobjective optimization algorithms for the identification of model ensembles for predictions in ungauged basins for the first time. Application of the new formulation to 30 watersheds located in England and Wales and comparison of the results with a Monte Carlo approach demonstrate that the new formulation will significantly advance our ability to reduce the uncertainty of predictions in ungauged basins.
Stability of delta distributary networks and their bifurcations
Authors: Edmonds D. A. , Slingerland R. L.
Published: September 2008

Delta distributary networks are created by bifurcating channels that commonly split their discharges unequally. The origin and stability of these asymmetrical fine‐grained cohesive bifurcations are investigated here using Delft3D, a morphodynamic flow and sediment transport model. Results are compared to bifurcations on the Mossy delta, Saskatchewan, Canada, that have remained stable for decades. Over a range of channel aspect ratios, friction factors, and Shields numbers, we find three equilibrium functions relating the discharge ratio of the bifurcate arms at equilibrium to the Shields number. One function defines symmetrical configurations (equal partitioning of discharge), while the other two define asymmetrical configurations (unequal partitioning of discharge). Discharge asymmetries and morphologies of Mossy delta bifurcations are consistent with these predictions. Among the equilibrium bifurcations, only the asymmetrical type is stable to perturbations, such as a partial closing of one throat. This possibly explains why asymmetrical bifurcations are more common in nature.
Blocking Glucocorticoid and Enhancing Estrogenic Genomic Signaling Protects against Cerebral Ischemia
Authors: Cheng Michelle Y , Sun Guohua , Jin Michael , Zhao Heng , Steinberg Gary K , Sapolsky Robert M
Published: September 2008

Glucocorticoids (GCs) and estrogen can modulate neuron death and dysfunction during neurological insults. Glucocorticoids are adrenal steroids secreted during stress, and hypersecretion of GCs during cerebral ischemia compromises the ability of hippocampal and cortical neurons to survive. In contrast, estrogen can be neuroprotective after cerebral ischemia. Here we evaluate the protective potential of a herpes viral vector expressing a chimeric receptor (ER/GR), which is composed of the ligand-binding domain of the GC receptor (GR) and the DNA-binding domain of the estrogen receptor-α (ER). This novel receptor can transduce an endangering GC signal into a protective estrogenic one. Using an in vitro oxygen glucose deprivation model (OGD), GCs exacerbated neuron death in primary cortical cultures, and this worsening effect was completely blocked by ER/GR expression. Moreover, blocking GC actions with a vector expressing a dominant negative GC receptor promoted neuron survival during postischemia, but not preischemia. Thus, gene therapeutic strategies to modulate GC and estrogen signaling can be beneficial during an ischemic insult.
Hemodynamic Changes after Visual Stimulation and Breath Holding Provide Evidence for an Uncoupling of Cerebral Blood Flow and Volume from Oxygen Metabolism
Authors: Donahue Manus J , Stevens Robert D , de Boorder Michiel , Pekar James J , Hendrikse Jeroen , van Zijl Peter CM
Published: September 2008

Functional neuroimaging is most commonly performed using the blood-oxygenation-level-dependent (BOLD) approach, which is sensitive to changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and the cerebral metabolic rate of oxygen (CMRO2). However, the precise mechanism by which neuronal activity elicits a hemodynamic response remains controversial. Here, visual stimulation (14 secs flashing checkerboard) and breath-hold (4 secs exhale + 14 secs breath hold) experiments were performed in alternating sequence on healthy volunteers using BOLD, CBV-weighted, and CBF-weighted fMRI. After visual stimulation, the BOLD signal persisted for 33 ± 5 secs (n = 9) and was biphasic with a negative component (undershoot), whereas CBV and CBF returned to baseline without an undershoot at 20 ± 5 and 20 ± 3 secs, respectively. After breath hold, the BOLD signal returned to baseline (23 ±7 secs) at the same time ( P < 0.05) as CBV (21 ± 6 secs) and CBF (18 ±3 secs), without a poststimulus undershoot. These data suggest that the BOLD undershoot after visual activation reflects a persistent increase in CMRO2. These observations support the view that CBV and CBF responses elicited by neuronal activation are not necessarily coupled to local tissue metabolism.
Mushroom-bodies regulate habit formation in Drosophila
Authors: Brembs Björn
Published: September 2008

Our past experience is one of the primary sources of information when faced with a choice. We ask ourselves: "what will happen if I do this?"Accurately predicting the consequences of our actions is usually modeled by operant (instrumental) learning experiments. These types of experiments are often contrasted with classical (Pavlovian) conditioning experiments in a dichotomy. And indeed, different brain circuits mediate the acquisition of skills and habits (via operant/instrumental learning) and the acquisition of facts (via classical/Pavlovian learning). However, realistic learning situations always comprise interactions of skill- and fact-learning components (composite learning). Fixed flying Drosophila melanogaster at the torque meter provide one of the very few systems where the relationship of operant and classical predictors in composite learning can be studied with sufficient rigor. The latest experiments show that the textbook operant/classical dichotomy is misleading and that instead composite learning consists of multiple interacting memory systems. These interactions between predictive stimuli (classical component) and goal-directed actions (operant component) make composite conditioning more effective than the operant and classical components alone (learning-by-doing, generation effect). Rutabaga (rut) mutants are impaired in learning about the (classical) stimuli, but show improved (operant) behavior learning. This is the first evidence that operant and classical conditioning differ not only at the circuit, but also at the molecular level. The interaction between operant and classical components is reciprocal and hierarchical, such that the classical suppresses the operant component. Experiments with transgenic flies demonstrate that this suppression of operant learning is mediated by the mushroom-bodies and serves to ensure that the classical memories can be generalized for access by other behaviors. Extended training can overcome this suppression and transforms goal-directed actions into habitual responses. This interaction leads to efficient learning, enables generalization and prevents premature habit-formation.
Preparation and initial characterization of biodegradable particles containing gadolinium-DTPA contrast agent for enhanced MRI
Authors: Doiron Amber L. , Chu Kevin , Ali Adeel , Brannon-Peppas Lisa
Published: September 2008

Accurate imaging of atherosclerosis is a growing necessity for timely treatment of the disease. Magnetic resonance imaging (MRI) is a promising technique for plaque imaging. The goal of this study was to create polymeric particles of a small size with high loading of diethylenetriaminepentaacetic acid gadolinium (III) (Gd-DTPA) and demonstrate their usefulness for MRI. A water-in-oil-in-oil double emulsion solvent evaporation technique was used to encapsulate the MRI agent in a poly(lactide-co-glycolide) (PLGA) or polylactide-poly(ethylene glycol) (PLA-PEG) particle for the purpose of concentrating the agent at an imaging site. PLGA particles with two separate average sizes of 1.83 μm and 920 nm, and PLA-PEG particles with a mean diameter of 952 nm were created. Loading of up to 30 wt % Gd-DTPA was achieved, and
in vitro
release occurred over 5 h. PLGA particles had highly negative zeta potentials, whereas the particles incorporating PEG had zeta potentials closer to neutral. Cytotoxicity of the particles on human umbilical vein endothelial cells (HUVEC) was shown to be minimal. The ability of the polymeric contrast agent formulation to create contrast was similar to that of Gd-DTPA alone. These results demonstrate the possible utility of the contrast agent-loaded polymeric particles for plaque detection with MRI.
Mutations alter the sodium versus proton use of a
Bacillus clausii
flagellar motor and confer dual ion use on
Bacillus subtilis
motors
Authors: Terahara Naoya , Krulwich Terry A. , Ito Masahiro
Published: September 2008

Bacterial flagella contain membrane-embedded stators, Mot complexes, that harness the energy of either transmembrane proton or sodium ion gradients to power motility. Use of sodium ion gradients is associated with elevated pH and sodium concentrations. The Mot complexes studied to date contain channels that use either protons or sodium ions, with some bacteria having only one type and others having two distinct Mot types with different ion-coupling. Here, alkaliphilic
Bacillus clausii
KSM-K16 was shown to be motile in a pH range from 7 to 11 although its genome encodes only one Mot (BCl-MotAB). Assays of swimming as a function of pH, sodium concentration, and ion-selective motility inhibitors showed that BCl-MotAB couples motility to sodium at the high end of its pH range but uses protons at lower pH. This pattern was confirmed in swimming assays of a statorless
Bacillus subtilis
mutant expressing either BCl-MotAB or one of the two
B. subtilis
stators, sodium-coupled Bs-MotPS or proton-coupled Bs-MotAB. Pairs of mutations in BCl-MotB were identified that converted the naturally bifunctional BCl-MotAB to stators that preferentially use either protons or sodium ions across the full pH range. We then identified trios of mutations that added a capacity for dual-ion coupling on the distinct
B. subtilis
Bs-MotAB and Bs-MotPS motors. Determinants that alter the specificity of bifunctional and single-coupled flagellar stators add to insights from studies of other ion-translocating transporters that use both protons and sodium ions.
Rapamycin inhibits trypanosome cell growth by preventing TOR complex 2 formation
Authors: Barquilla Antonio , Crespo José L. , Navarro Miguel
Published: September 2008

Target of rapamycin (TOR) kinases control cell growth through two functionally distinct multiprotein complexes. TOR complex 1 (TORC1) controls temporal cell growth and is sensitive to rapamycin, whereas TOR complex 2 (TORC2) is rapamycin resistant and regulates spatial cell growth. Here, we identified two TOR orthologues, TbTOR1 and TbTOR2, in the protozoan parasite
Trypanosoma brucei
, as well as orthologues of the well-known TORC1 and TORC2 partners, KOG1/raptor and AVO3/rictor. TbTOR proteins differ in their functions, subcellular localization, and rapamycin sensitivity. TbTOR1 controls cell growth by regulating cell cycle, nucleolus structure, and protein synthesis, whereas TbTOR2 coordinates cell polarization and cytokinesis. Rapamycin treatment of bloodstream trypanosomes resulted in a pronounced reduction of cell proliferation, with an EC
50
of 152 nM. Unique for a eukaryote, we observed that rapamycin acted exclusively by preventing TORC2 formation, with no effect on TORC1. Our findings on TOR signaling in this protozoan, which is located in a distal position in the eukaryotic cell lineage, highlight the clinical possibilities of rapamycin derivates and provide valuable insights into understanding rapamycin-mediated inhibition of TORC2.
Netrin-1 is a survival factor during commissural neuron navigation
Authors: Furne Céline , Rama Nicolas , Corset Véronique , Chédotal Alain , Mehlen Patrick
Published: September 2008

DCC (Deleted in Colorectal Cancer) is a putative tumor suppressor whose expression is lost in numerous cancers and whose tumor suppressor activity appears to be dependent on its ability to trigger apoptosis when disengaged by its ligand netrin-1. In this sense, netrin-1 is a survival factor that controls tumorigenesis. However, netrin-1 is also the prototypical axon guidance cue and has been shown to orient many neurons or axons, especially commissural axons, during spinal cord development. Here we show that netrin-1 is not only an attractive cue for developing commissural axons but also promotes their survival. In primary neuronal culture, in mice or in chick embryos, netrin-1 inhibits the proapoptotic activity of DCC in developing commissural neurons. Thus, adequate commissural neurons navigation requires both the attractive activity of netrin-1 and the anti-apoptotic function of this cue.