bluuebunny/crossref_metadata_2025 huggingface dataset:
Differences between adolescents' and parents' reports of health‐related quality of life in cystic fibrosis
Authors: Britto Maria T. , Kotagal Uma R. , Chenier Thomas , Tsevat Joel , Atherton Harry D. , Wilmott Robert W.
Published: January 2004

Our objective was to determine the magnitude and direction of differences between adolescents with cystic fibrosis (CF) and their parents' reports of the adolescents' health‐related quality of life (HRQOL) as measured by the adolescent and parent versions of the Child Health Questionnaire (CHQ). Sixty‐two adolescents (mean age, 13.7 years; 46% female; mean forced expired volume in 1 sec, 73%) completed the 87‐item adolescent form, and their parents (79% mothers; 77% working full or part time) completed the 50‐item parent form of the CHQ during a routine clinic visit. For each scale, ANOVA was used to determine pairwise differences between adolescent and parent scale scores. For scales in which a significant parent‐adolescent difference existed, ANCOVA was used to determine disease and demographic factors independently associated with differences in scores. Finally, responses for each pair were compared only on similarly worded items within each scale. For the full CHQ scales, adolescents rated their HRQOL significantly better than did their parents with regard to General Health (mean difference, 12.4 points), Role Function/Physical (mean difference, 9.0 points), Behavior (mean difference, 4.8 points), and Physical Function (mean difference, 4.0 points). No demographic or health factor was associated consistently with differences in parent‐adolescent scores. When only similarly worded items were compared, adolescents still tended to rate their HRQOL better, but the difference was significant only for General Health (P = 0.0005), where adolescents rated themselves less susceptible to illness and less worried about their health than their parents. In conclusion, optimal measurement of adolescent HRQOL will likely require determining both parent and adolescent perceptions of HRQOL. Pediatr Pulmonol. 2004; 37:165–171. © 2004 Wiley‐Liss, Inc.
A comparison between classical robust stability conditions
Authors: Paoletti S. , Grasselli O. M. , Menini L.
Published: January 2004

The paper is focused on the comparison between some classical robust stability conditions for continuous‐time linear time‐invariant systems. Such conditions are given as lemmas in the paper, since their statements include some generalizations, needed in order to better compare (and use) them. The analysis is carried out by comparing pairwise the families of systems whose stabilization through a given compensator is guaranteed by each of the considered robust stability conditions. Some properties of the families are formally derived and stated, and some very simple examples arc exhibited in order to illustrate the presented properties and comparisons. A theorem, representing an extension of one of the considered conditions, is proposed in order to overcome some difficulties arising in the use of the classical result. Copyright © 2004 John Wiley & Sons, Ltd.
Nonlinear quantitative stability
Authors: Baños Alfonso , Horowitz Isaac M.
Published: January 2004

This work makes use of the Schauder fixed point theorem to develop a quantitative approach to the stability problem of non‐linear QFT designs. The method is applied to non‐linear systems having a linear high‐frequency behaviour, allowing nonlinearities in the input and output, and is especially well suited for systems with hard memoryless nonlinearities. Copyright © 2004 John Wiley & Sons, Ltd.
Dynamic models of economic systems and industrial organizations
Authors: Forrester Jay W.
Published: January 2004

In the material that follows, I comment on model building from the viewpoint of its effectiveness in predicting economic behavior and its value as a guide to the management of industrial organizations and the establishment of operating policies and organizational structure. I am referring throughout to models describing sequences of events progressing in time and not mathematical models for describing a static set of relationships.

Although the text is written in a somewhat critical manner, I look on most of the statements as propositions for further consideration and discussion rather than as facts which I accept at face value. While my general propositions suggest that current economic model design techniques are not progressing in the most fruitful direction, it is certainly true that those avenues needed to be explored, that most of the efforts represent some progress, and that they provide a foundation from which we can hope to build a better system of economic and industrial ﬁrm models using techniques and machines which have become available in the last decade. Copyright © 2003 John Wiley & Sons, Ltd.
A systemic approach to entrepreneurial learning: an exploration using storytelling
Authors: Warren Lorraine
Published: January 2004

The promotion of entrepreneurial activity is high on the educational agenda, reflecting economic and political interest and support. However, the study of entrepreneurial learning is characterized by a diffuse and fragmented literature which spans policy, individual learning and business development, with conclusions based on a plethora of methodological approaches. In this paper, a systemic schema is modified and developed to provide a frame of reference for the study of entrepreneurial learning. The paper is based on a study of women's narratives of their experience as small/micro‐enterprise owner/managers in the UK. Theoretical developments concerning the potential usefulness of the schema are discussed; practical implications for the design of entrepreneurship development programmes are also presented. Copyright © 2004 John Wiley & Sons, Ltd.
Systems thinking and knowledge management: positional assertions and preliminary observations
Authors: Kawalek J. P.
Published: January 2004

In recent years, there has been significant interest in [knowledge management]. However, the plethora of both conceptual and practitioner literature has provided little consistency regarding key definitions or methodologies that can act to guide practice. This can result in practitioners selecting particular ideas, constructs or language that has weak conceptual grounding and result in ephemeral and [ad hoc] practices. This paper analyses the use of systems thinking for [knowledge management] practices because it is argued to have the potential to provide methodological guidance for practitioners. The context of the research in the paper is in the humanitarian sector, and in operations that are often politically messy and complex, where there are often many unknown factors. It is a context in which knowledge in a broad sense of the word, as in any human activity, plays an instrumental role. Copyright © 2004 John Wiley & Sons, Ltd.
The problem of knowledge imposition: Paulo Freire and critical systems thinking
Authors: Mejía Andrés
Published: January 2004

Two different ways can be distinguished in which the problem of imposition of knowledge has been addressed by Paulo Freire's radical educational proposal: (1) through an examination of formal aspects of the interactions in which knowledge is produced and/or reproduced—the problem of interactions—and (2) through the provision of critical tools with which the validity of any proposed knowledge can be questioned—the problem of validity. In that proposal, these strategies appear represented by Freire's notions of dialogue—on the side of interactions—and critical consciousness—on the side of validity. There appears, however, a tension between them, as the critical tools provided to question validity and develop a critical consciousness might go against the beliefs held by the students whose reasoning autonomy is to be developed, making it necessary to manipulate interactions and therefore promote a non‐genuine dialogue. In critical systems thinking, the ways in which knowledge imposition occurs or is prevented through the use of both boundary critique—represented in Ulrich's CSH—and critical pluralism—represented in Jackson's TSI—are analysed in relation to the use of the same or similar strategies to those found in Freire's work, and to the tension between them. Copyright © 2004 John Wiley & Sons, Ltd.
Where is ENSO stress balanced?
Authors: Münnich Matthias , Neelin J. David
Published: January 2004

The zonal surface torque budget associated with the tropical wind stress anomalies during El Niño/Southern Oscillation is analyzed. Mountain and surface stress torques over South America are found to play a prominent role. Local momentum change is negligible for 6 month averages allowing the balance among regional contributions to the torque anomalies to be compared. During El Niño, eastward torque anomalies over the central equatorial Pacific are largely compensated by westward anomalies elsewhere in the equatorial band, notably over South America. Torque anomalies over South America and the Pacific in latitude bands north and south of the equator are both westward and are not compensated within the band, implying an export of eastward momentum to higher latitudes. Copyright © 2003 Royal Meteorological Society. Published by Elsevier Ltd. All rights reserved.
Searching for circulation patterns affecting North Europe annual temperature
Authors: Kryjov Vladimir N.
Published: January 2004

Statistical analysis of Northern Europe annual temperature against monthly pressure fields reveals that the circulation modes resembling North Atlantic/Arctic Oscillation significantly contribute to annual temperature only in January and February. In November, significant contribution is associated with the Labrador–Scandinavia teleconnection pattern. The January–February and November circulation modes are significantly (negatively) correlated with each other. Copyright © 2003 Royal Meteorological Society. Published by Elsevier Ltd. All rights reserved.
N‐acetyl‐GLP‐1: a DPP IV‐resistant analogue of glucagon‐like peptide‐1 (GLP‐1) with improved effects on pancreatic β‐cell‐associated gene expression
Authors: Liu Hui‐Kang , Green Brian D. , Gault Victor A. , McCluskey Jane T. , McClenaghan Neville H. , O'Harte P. M. Finbarr , Flatt Peter R.
Published: January 2004

Glucagon‐like peptide‐1(7‐36)amide (GLP‐1) is a key insulinotropic hormone with the reported potential to differentiate non‐insulin secreting cells into insulin‐secreting cells. The short biological half‐life of GLP‐1 after cleavage by dipeptidylpeptidase IV (DPP IV) to GLP‐1(9‐36)amide is a major therapeutic drawback. Several GLP‐1 analogues have been developed with improved stability and insulinotropic action. In this study, the N‐terminally modified GLP‐1 analogue, N‐acetyl‐GLP‐1, was shown to be completely resistant to DPP IV, unlike native GLP‐1, which was rapidly degraded. Furthermore, culture of pancreatic ductal ARIP cells for 72 h with N‐acetyl‐GLP‐1 indicated a greater ability to induce pancreatic β‐cell‐associated gene expression, including insulin and glucokinase. Further investigation of the effects of stable GLP‐1 analogues on β‐cell differentiation is required to assess their potential in diabetic therapy.
Neuronal primary cilia: a review
Authors: Fuchs Jannon L. , Schwark Harris D.
Published: January 2004

Primary cilia in neurons have often been regarded as rare, vestigial curiosities. However, neuronal cilia are now gaining recognition as ubiquitous organelles in the mammalian brain, raising speculation about what their functions may be. They might have some features tailored for the nervous system and others that serve needs shared by a spectrum of other cell types. Here we review clues from the literature and present new data supporting several possibilities for the significance of neuronal cilia. Our immunocytochemical results show regional heterogeneity in neuronal cilia. Brain regions nearer to the cerebral ventricles had longer cilia, suggesting that they might sense chemicals such as peptides, originating from cerebrospinal fluid. In mutant Tg737orpkmice, most brain regions appeared to be missing cilia. The importance of intraflagellar transport proteins establishes a functional link between neuronal cilia and other primary cilia.
Endothelial dysfunction in congestive heart failure: ACE inhibition vs. angiotensin II antagonism
Authors: Schäfer Andreas , Fraccarollo Daniela , Tas Piet , Schmidt Isabel , Ertl Georg , Bauersachs Johann
Published: January 2004

Background:

Endothelial dysfunction of the vasculature contributes to the elevated peripheral resistance and reduced myocardial perfusion in congestive heart failure (CHF). The present study systematically investigated the effect of angiotensin II (AT1)‐ receptor blockade on vascular superoxide (O2−) production and endothelial dysfunction.

Methods and results:

Vasodilator responses and O2− production were determined in aortic rings from Wistar rats with experimental CHF 10 weeks after extensive myocardial infarction and compared with sham‐operated animals (Sham). Rats were either treated with placebo (P), with the AT1‐receptor antagonist Irbesartan (50 mg kg−1 day−1) or with the ACE inhibitor Trandolapril (0.3 mg kg−1 day−1). In CHF‐P, endothelium‐dependent, acetylcholine‐induced relaxation was significantly attenuated compared with Sham‐P. Chronic treatment with Trandolapril or Irbesartan significantly improved endothelium‐dependent relaxation. Aortic O2− formation was markedly increased in CHF, and was not significantly affected by Trandolapril treatment, while it was reduced by Irbesartan. eNOS expression was reduced in CHF and normalised by both treatments.

Conclusion:

Endothelial vasomotor function in CHF rats was normalised by long‐term treatment with an ACE inhibitor or an AT1‐antagonist. Reduced aortic eNOS expression was normalised by both treatments, whereas aortic superoxide formation was only reduced by the AT1‐antagonist Irbesartan.
Holocene annual mean temperature changes in Estonia and their relationship to solar insolation and atmospheric circulation patterns
Authors: Seppä Heikki , Poska Anneli
Published: January 2004

We reconstructed annual mean temperature (Tann) trends from three radiocarbon-dated Holocene pollen stratigraphies from lake sediments in Estonia, northern Europe. The reconstructions were carried out using a North-European pollen-climate calibration model based on weighted averaging partial least-squares regression. The cross-validated prediction error of the model is 0.89°C and the coefficient of determination between observed modernTannvalues and those predicted by the model is 0.88. In the reconstruction, the Holocene thermal maximum (HTM) is distinguishable at 8000–4500 cal yr B.P. with the expansion of thermophilous tree species andTannon average 2.5°C higher than at present. The pollen-stratigraphical data reflect progressively warmer and drier summers during the HTM. Analogously with the modern decadal-scale climatic variability in North Europe, we interpret this as an indication of increasing climatic continentality due to the intensification of anticyclonic circulation and meridional air flow. Post-HTM cooling started abruptly at around 4500 cal yr B.P. All three reconstructions show a transient (ca. 300 years) cooling of 1.5–2.0°C at 8600–8000 cal yr B.P. We tentatively correlate this cold event with the North-Atlantic “8.2 ka event” at 8400–8000 cal yr B.P. Provided that the 8.2 ka event was caused by freshening of the North-Atlantic surface water, our data provide evidence of the climatic and vegetational responsiveness of the boundary of the temperate and boreal zones to the weakening of the North-Atlantic thermohaline circulation and the zonal energy transport over Europe. No other cold events of comparable magnitude are indicated during the last 8000 years.
Highly efficient renaturation of β‐lactamase isolated from moderately halophilic bacteria
Authors: Tokunaga Hiroko , Ishibashi Matsujiro , Arakawa Tsutomu , Tokunaga Masao
Published: January 2004

Most, if not all, β‐lactamases reported to date are irreversibly denatured at 60–70°C. Here, we found that a halophilic β‐lactamase from the moderately halophilic bacterium Chromohalobacter sp. 560 was highly stable against heat inactivation: it retained ∼75% of its activity after boiling for 5 min in the presence of 0.2 M NaCl, suggesting that the protein either incompletely denatures during the boiling process or readily renatures upon cooling to the assay temperature. Circular dichroism showed a complete unfolding at 60°C and a full reversibility, indicating that the observed activity after boiling is due to efficient refolding following heat denaturation. The enzyme showed optimal activity at 50–60°C, indicating that an increase in activity with temperature offsets the thermal denaturation. The gene bla was cloned, and the primary structure of the enzyme was deduced to be highly abundant in acidic amino acid residues, one of the characteristics of halophilic proteins. Despite its halophilic nature, the enzyme refolds in low salt media after heat denaturation.
Growth hormone is a positive regulator of adiponectin receptor 2 in 3T3‐L1 adipocytes
Authors: Fasshauer Mathias , Klein Johannes , Kralisch Susan , Klier Margit , Lössner Ulrike , Blüher Matthias , Paschke Ralf
Published: January 2004

The fat‐derived protein adiponectin is an important insulin‐sensitizing adipocytokine which is downregulated in insulin resistance and obesity. Recently, two receptors of this adipose‐expressed protein called adiponectin receptor 1 (AdipoR1) and 2 (AdipoR2) have been cloned. To clarify expression and regulation of these receptors in fat cells, AdipoR1 and AdipoR2 mRNA was measured by quantitative real‐time reverse transcription‐polymerase chain reaction during differentiation of 3T3‐L1 adipocytes and after treatment with various hormones known to induce insulin resistance. Interestingly, AdipoR2 synthesis was significantly increased up to 4.8‐fold during differentiation of 3T3‐L1 preadipocytes, whereas AdipoR1 expression was only augmented up to 1.4‐fold. Furthermore, growth hormone (GH) induced AdipoR2, but not AdipoR1 mRNA by up to 2.4‐fold in a dose‐ and time‐dependent fashion with significant stimulation detectable at concentrations as low as 5 ng/ml GH and as early as 2 h after effector addition. The positive effect of GH on AdipoR2 expression could be reversed by withdrawal of the hormone for 24 h. In contrast, other key hormones involved in the regulation of insulin resistance and energy metabolism such as insulin, isoproterenol, dexamethasone, triiodothyronine, angiotensin 2, tumor necrosis factor α, and interleukin‐6 did not influence AdipoR1 and AdipoR2 synthesis in vitro. Taken together, our results suggest that AdipoR2 expression is differentiation‐dependent and selectively regulated by GH implying a potential role of this hormone in adiponectin‐associated alterations of insulin sensitivity and energy homeostasis.
Urotensin II in patients with chronic heart failure
Authors: Krüger Stefan , Graf Jürgen , Kunz Dagmar , Stickel Tina , Merx Marc W. , Hanrath Peter , Janssens Uwe
Published: January 2004

Background:

Human Urotensin II (hU‐II) is the most potent vasoconstrictor known to date. HU‐II receptors are predominant in the human heart and arterial vessels, suggesting hU‐II to be of importance as a cardiovascular mediator.

Methods:

We studied 32 consecutive patients (60±12 years) with chronic heart failure (CHF) and 10 control subjects (54±12 years, n.s.) with cardiopulmonary exercise testing. Blood samples for the measurement of plasma hU‐II and big‐endothelin‐1 (big‐ET1) were obtained at rest and at peak exercise.

Results:

Peak VO2 was significantly higher in controls than in CHF patients (19.8±3.8 vs. 14.7±3.6 ml min−1 kg−1, P<0.001). Big‐ET1 levels were increased in CHF compared to controls at rest (2.8±1.8 vs. 1.7±0.1 fmol/ml, P<0.01) and at peak exercise (2.7±1.7 vs. 1.6±0.2 fmol/ml, P<0.005). HU‐II concentrations were comparable in patients with CHF and controls at rest (2990±1104 vs. 3290±508 pg/ml, n.s.) and peak exercise (3063±1185 vs. 3213±1188 pg/ml, n.s.). Resting hU‐II levels demonstrated no correlation with peak VO2 in controls or CHF patients.

Conclusions:

The measurement of circulating plasma levels of hU‐II does not seem to be very helpful in studying the effects of hU‐II in human cardiovascular regulation. A local paracrine or autocrine mediator effect of hU‐II in CHF is possible.
Tail current surge: New insights from a global MHD simulation and comparison with satellite observations
Authors: Ohtani Shin‐ichi , Raeder Joachim
Published: January 2004

The present study examines the tailward propagation of substorm‐associated variations of the tail current intensity. In the substorm event of 24 November 1996, the Interball and IMP 8 satellites were located in the midnight sector at X = −26 and −36 RE, respectively, and observed an increase and a decrease of the lobe magnetic field strength corresponding to the storage and release of the lobe magnetic energy. Both spacecraft observed BZ to decrease initially and then increase in the course of the decrease in ∣BX∣, a feature that was reported previously as a manifestation of the tailward expansion of the current disruption region. The delay of the signatures between the two satellites confirms that the associated current system moved tailward. Motivated by this fortuitous coordination of the satellite observation, the present study revisits a global MHD simulation previously conducted specifically for this substorm event [Raeder et al., 2001]. The most noticeable feature of the modeled tail dynamics is the repeated occurrence of tail current surges, that is, temporal intensifications of the tail current that propagate tailward. The first tail current surge is accompanied by the stretching of the tail magnetic field, which starts in the inner magnetosphere and extends tailward. The associated tailward flow redistributes the plasma pressure in such a way that the tail current is reduced in its intensity in the near‐Earth region, while the pressure gradient increases at the propagation front, which intensifies the local current. The last major tail current surge is caused by the near‐Earth reconnection. Inside a plasmoid, the pressure gradient current is intensified on the tailward side of the O‐line, and it propagates tailward as the plasmoid grows and is released. For each tail current surge, irrespective of its cause, the intensification of the tail current is followed by the reduction, and its tailward propagation creates the aforementioned phase relationship between BX and BZ. It is probably difficult to determine based on lobe magnetic field observations whether it is caused by the tail stretching or a neutral line motion. The present study not only sheds new light about tail substorm dynamics but also provides a good exercise for evaluating the potential of the modeling effort for substorm study in general.
On the warming and salinification of the Mediterranean outflow waters in the North Atlantic
Authors: Potter Rachel A. , Lozier M. Susan
Published: January 2004

Based on hydrographic data collected since 1955, Mediterranean outflow waters present in the eastern North Atlantic show a density compensated increase in both temperature and salinity. With an increase in temperature of 0.101 ± 0.024°C/decade and an increase in salinity of 0.0283 ± 0.0067 psu/decade in the Mediterranean outflow waters, the heat content gain from 1955 to 1993 is calculated to be 2.02 ± 0.31 × 106 J/m3, which surpasses the average gain in heat content of the North Atlantic basin over the latter half of the 20th century. This suggests that the Mediterranean outflow waters are an important contributor to climatological changes at intermediate depths within the mid‐latitude North Atlantic.
Toward mapping surface deformation in three dimensions using InSAR
Authors: Wright Tim J. , Parsons Barry E. , Lu Zhong
Published: January 2004

One of the limitations of deformation measurements made with interferometric synthetic aperture radar (InSAR) is that an interferogram only measures one component of the surface deformation — in the satellite's line of sight. We investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms, with different imaging geometries. Geometries for both current and future missions are evaluated, and their abilities to resolve the displacement vector are compared. The north component is always the most difficult to determine using data from near‐polar orbiting satellites. However, a satellite with an inclination of about 60°/120° would enable all three components to be well resolved. We attempt to resolve the 3D displacements for the 23 October 2002 Nenana Mountain (Alaska) Earthquake. The north component's error is much larger than the signal, but proxies for eastward and vertical motion can be determined if the north component is assumed negligible. Inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms, acquired on ascending and descending tracks.
A new empirical model of sea surface microwave emissivity for salinity remote sensing
Authors: Gabarró C. , Font J. , Camps A. , Vall‐llossera M. , Julià A.
Published: January 2004

SMOS (Soil Moisture and Ocean Salinity) is a European Space Agency mission that aims at generating global ocean salinity maps with an accuracy of 0.1 psu, at spatial and temporal resolution suitable for climatic studies. The satellite sensor is an L‐band (1400–1427 MHz) aperture synthesis interferometric radiometer. Sea surface salinity (SSS) can be retrieved since the brightness temperature of sea water is dependent on the frequency, angle of observation, dielectric constant of sea water, sea surface temperature and sea surface state. This paper presents a new empirical sea water emissivity model at L‐band in which surface roughness effects are parameterized in terms of wind speed and significant wave height. For the SMOS mission these parameters can be obtained from external measurements and model diagnostics. An analysis has been done on the effect on SSS retrieval of different sources for this auxiliary information.
Vertical crustal motion determined by satellite altimetry and tide gauge data in Fennoscandia
Authors: Kuo C. Y. , Shum C. K. , Braun A. , Mitrovica J. X.
Published: January 2004

We present a new method of combining satellite altimetry and tide gauge data to obtain improved estimates of absolute (or geocentric) vertical crustal motion at tide gauges within a semi‐enclosed sea. As an illustration, we combine TOPEX/POSEIDON altimetry data (1992–2001) and 25 long‐term (>40 years) tide gauge records around the Baltic Sea region of Fennoscandia, an area where crustal deformation is dominated by glacial isostatic adjustment (GIA). A comparison of the estimated vertical motion, at 1–11 mm/yr, with independent solutions from 10 collocated BIFROST GPS sites, shows a difference of 0.2 ± 0.9 mm/yr, thus verifying the accuracy and robustness of the procedure. The solution uncertainty is estimated at 0.4 mm/yr, which is significantly lower than previous analyses of this type. We conclude that our technique can potentially provide accurate vertical motion observations globally where long‐term tide gauge records exist.
Physics of multiscale convection in Earth's mantle: Evolution of sublithospheric convection
Authors: Korenaga Jun , Jordan Thomas H.
Published: January 2004

We investigate the physics of multiscale convection in Earth's mantle, characterized by the coexistence of large‐scale mantle circulation associated with plate tectonics and small‐scale sublithospheric convection. In part 2 of our study, the temporal and spatial evolution of sublithospheric convection is studied using two‐dimensional whole mantle convection models with temperature‐ and depth‐dependent viscosity and an endothermic phase transition. Scaling laws for the breakdown of layered convection as well as the strength of convection are derived as a function of viscosity layering, the phase buoyancy parameter, and the thermal Rayleigh number. Our results suggest that layered convection in the upper mantle is maintained only for a couple of overturns, with plausible mantle values. Furthermore, scaling laws for the onset of convection, the stable Richter rolls, and the breakdown of layered convection are all combined to delineate possible dynamic regimes beneath evolving lithosphere. Beneath long‐lived plates, the development of longitudinal convection rolls is suggested to be likely in the upper mantle, as well as its subsequent breakdown to whole mantle‐scale convection. This evolutionary path is suggested to be consistent with the seismic structure of the Pacific upper mantle.
Hydrothermal seepage patterns above a buried basement ridge, eastern flank of the Juan de Fuca Ridge
Authors: Spinelli G. A. , Zühlsdorff L. , Fisher A. T. , Wheat C. G. , Mottl M. , Spieß V. , Giambalvo E. R.
Published: January 2004

We use the distributions of sediment physical properties and modeled basement overpressures to estimate the spatial distribution of fluid seepage through sediments over and around the “First Ridge,” a buried basement ridge on the eastern flank of Juan de Fuca Ridge. Fluid discharge rates differ by 1 order of magnitude because of differences in sediment hydraulic properties and by 2 orders of magnitude resulting from differences in sediment thickness and basement overpressure. Sediment type distribution appears to have resulted from differences in local seafloor relief. Compression index (ease of consolidation) increases with proportion of hemipelagic material, from 0.5 at 30% hemipelagic to 1.4 at 95% hemipelagic. Permeability at 50% porosity decreases with proportion of hemipelagic material, from 2 × 10−16 m2 at 30% hemipelagic to 6 × 10−18 m2 at 95% hemipelagic. Modeled seepage rates, derived from basement overpressures and sediment physical properties, range from 0 to 27 mm/yr. The average seepage rate over the entire 11 km of ridge within our study area is 1.3 mm/yr. On the basis of the model results, half of the total volume flux of seepage from the First Ridge is contributed from 25% of the study area, with flow rates ≥1.1 mm/yr. Low seismic reflection amplitude anomalies are generally correlated with areas of high seepage rates.
Microearthquake patterns following the 1998 eruption of Axial Volcano, Juan de Fuca Ridge: Mechanical relaxation and thermal strain
Authors: Sohn Robert A. , Barclay Andrew H. , Webb Spahr C.
Published: January 2004

Ocean bottom seismic networks deployed following the 1998 eruption of Axial seamount reveal an evolving pattern of microearthquake activity associated with subsurface magmatism and thermal strain. Seismicity rates decay steadily over 15 months of observation (February 8, 1998, to April 30, 1999), consistent with a trend toward thermal and mechanical equilibrium in the shallow crust after the magmatic event. Immediately after the eruption, seismicity rates were high for about 60 days in the southeast corner of the caldera where lava flows from the 1998 eruption were mapped. A small burst of seismic activity was observed on the southeast shoulder of the volcano from 100 to 150 days after the eruption. These events, which are characterized by slip on nearly vertical faults in the shallow crust, extend about 6 km from the southeast corner of the caldera and overlie a mid‐crustal low‐velocity zone. After this episode, seismicity rates remain low until the end of the observation period, 455 days after the eruption. Shallow (∼0.7 km depth) events, consistent with thermal contraction and volume changes of ∼2 × 10−3 m3 in ∼5 m3 sources, are observed in individual clusters beneath hydrothermal vents within the 1998 lava flow at the southeast edge of the caldera. Microearthquakes observed during the last 70 days of observation are distributed around the central caldera, most likely representing small amounts of subsidence on caldera faults during the final stages of equilibration following melt withdrawal associated with the 1998 eruption.
Seismic attenuation due to wave‐induced flow
Authors: Pride S. R. , Berryman J. G. , Harris J. M.
Published: January 2004

Three P wave attenuation models for sedimentary rocks are given a unified theoretical treatment. Two of the models concern wave‐induced flow due to heterogeneity in the elastic moduli at “mesoscopic” scales (scales greater than grain sizes but smaller than wavelengths). In the first model, the heterogeneity is due to lithological variations (e.g., mixtures of sands and clays) with a single fluid saturating all the pores. In the second model, a single uniform lithology is saturated in mesoscopic “patches” by two immiscible fluids (e.g., air and water). In the third model, the heterogeneity is at “microscopic” grain scales (broken grain contacts and/or microcracks in the grains), and the associated fluid response corresponds to “squirt flow.” The model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus, crack porosity, and/or frequency is reduced to zero. It is shown that squirt flow is incapable of explaining the measured level of loss (10−2 < Q−1 < 10−1) within the seismic band of frequencies (1–104 Hz); however, either of the two mesoscopic scale models easily produces enough attenuation to explain the field data.
Retrieval of cloud pressure and oceanic chlorophyll content using Raman scattering in GOME ultraviolet spectra
Authors: Joiner Joanna , Vasilkov Alexander P. , Flittner David E. , Gleason James F. , Bhartia Pawan K.
Published: January 2004

Reliable cloud pressure estimates are needed for accurate retrieval of ozone and other trace gases using satellite‐borne hyperspectral backscatter ultraviolet (buv) instruments. The cloud pressures should be consistent with the assumptions made in the retrieval algorithms. Cloud pressure can be derived from buv instruments using the properties of rotational‐Raman scattering (RRS) and absorption by O2‐O2. Here we estimate cloud pressure using the concept of a Lambert‐equivalent reflectivity (LER) surface that is also used in many trace gas retrieval algorithms. An LER cloud pressure (PLER) algorithm is being developed for the ozone monitoring instrument (OMI) that will fly on NASA EOS Aura. As a demonstration, we apply the approach to data from the global ozone monitoring experiment (GOME) in the 355–400 nm spectral range. GOME has full spectral coverage in this range at relatively high spectral resolution with a very high signal‐to‐noise ratio. This allows for more accurate estimates of cloud pressure than were possible with its predecessors SBUV and TOMS. We also demonstrate for the first time the retrieval of oceanic chlorophyll content using oceanic Raman scattering in buv observations. We compare our retrieved PLER with cloud top pressures, Ptop, derived from the infrared ATSR‐2 instrument on the same satellite for overcast situations. The findings confirm results from previous studies that showed retrieved PLER from buv observations is systematically higher than IR‐derived Ptop. Simulations using Mie‐scattering radiative transfer algorithms with O2‐O2 absorption show that these differences can be explained by increased absorption within and below the cloud as well as between multiple cloud decks.
Existence of thresholds in proton flares and application to solar energetic particle alerts
Authors: Kubo Yūki , Akioka Maki
Published: January 2004

This article discusses our statistical investigations into the occurrence of proton events for solar energetic particle (SEP) alerts in space weather forecasts. We analyzed X‐ray flux and proton intensity data obtained with the GOES satellite in the 23rd solar cycle. We found that the total soft X‐ray flux (1–8Å) of almost all flares related to proton events exceeded a threshold value, which was ∼20 ergs cm−2. This means that there is a threshold in flare duration in regard to peak X‐ray flux and this is ∼30 min for an M1.0 flare and/or 3 min for an X1.0 flare. We also confirmed this threshold with data in the 22nd solar cycle. These results will provide some of the most important criteria for SEP alerts and solar proton event forecasts in the future.
Evaluation of longitudinal dispersivity estimates from simulated forced‐ and natural‐gradient tracer tests in heterogeneous aquifers
Authors: Tiedeman Claire R. , Hsieh Paul A.
Published: January 2004

We simulate three types of forced‐gradient tracer tests (converging radial flow, unequal strength two well, and equal strength two well) and natural‐gradient tracer tests in multiple realizations of heterogeneous two‐dimensional aquifers with a hydraulic conductivity distribution characterized by a spherical variogram. We determine longitudinal dispersivities (αL) by analysis of forced‐gradient test breakthrough curves at the pumped well and by spatial moment analysis of tracer concentrations during the natural‐gradient tests. Results show that among the forced‐gradient tests, a converging radial‐flow test tends to yield the smallest αL, an equal strength two‐well test tends to yield the largest αL, and an unequal strength two‐well test tends to yield an intermediate value. This finding is qualitatively explained by considering the aquifer area sampled by a particular test. A converging radial‐flow test samples a small area, and thus the tracer undergoes a low degree of spreading and mixing. An equal strength two‐well test samples a much larger area, so the tracer is spread and mixed to a greater degree. Results also suggest that if the distance between the tracer source well and the pumped well is short relative to the lengths over which velocity is correlated, then the αL estimate can be highly dependent on local heterogeneities in the vicinity of the wells. Finally, results indicate that αL estimated from forced‐gradient tracer tests can significantly underestimate the αL needed to characterize solute dispersion under natural‐gradient flow. Only a two‐well tracer test with a large well separation in an aquifer with a low degree of heterogeneity can yield a value of αL that characterizes natural‐gradient tracer spreading. This suggests that a two‐well test with a large well separation is the preferred forced‐gradient test for characterizing solute dispersion under natural‐gradient flow.
Diagnosing a distributed hydrologic model for two high‐elevation forested catchments based on detailed stand‐ and basin‐scale data
Authors: Thyer Mark , Beckers Jos , Spittlehouse Dave , Alila Younes , Winkler Rita
Published: January 2004

This study evaluates the performance and internal structure of the distributed hydrology soil vegetation model (DHSVM) using 1998–2001 data collected at Upper Penticton Creek, British Columbia, Canada. It is shown that clear‐cut snowmelt rates calculated using data‐derived snow albedo curves are in agreement with observed lysimeter outflow. Measurements in a forest stand with 50% air crown closure suggest that the fraction of shortwave radiation transmitted through the canopy is 0.18–0.28 while the hemispherical canopy view factor controlling longwave radiation fluxes to the forest snowpack is estimated at 0.81 ± 0.07. DHSVM overestimates shortwave transmittance (0.50) and underestimates the view factor (0.50). An alternative forest radiation balance is formulated that is consistent with the measurements. This new formulation improves model efficiency in simulating streamflow from 0.84 to 0.91 due to greater early season melt that results from the enhanced importance of longwave radiation below the canopy. The model captures differences in canopy rainfall interception between small and large storms, tree transpiration measured over a 6‐day summer period, and differences in soil moisture between a dry and a wet summer. While the model was calibrated to 1999 snow water equivalent (SWE) and hydrograph data for the untreated control basin, it successfully simulates forest and clear‐cut SWE and streamflow for the 3 other years and 4 years of preharvesting and postharvesting streamflow for the second basin. Comparison of model states with the large array of observations suggests that the modified model provides a reliable tool for assessing forest management impacts in the region.
The functional dyad of scorpion toxin Pi1 is not itself a prerequisite for toxin binding to the voltage-gated Kv1.2 potassium channels
Authors: MOUHAT Stéphanie , MOSBAH Amor , VISAN Violeta , WULFF Heike , DELEPIERRE Muriel , DARBON Hervé , GRISSMER Stephan , De WAARD Michel , SABATIER Jean-Marc
Published: January 2004

Pi1 is a 35-residue scorpion toxin cross-linked by four disulphide bridges that acts potently on both small-conductance Ca2+-activated (SK) and voltage-gated (Kv) K+ channel subtypes. Two approaches were used to investigate the relative contribution of the Pi1 functional dyad (Tyr-33 and Lys-24) to the toxin action: (i) the chemical synthesis of a [A24,A33]-Pi1 analogue, lacking the functional dyad, and (ii) the production of a Pi1 analogue that is phosphorylated on Tyr-33 (P-Pi1). According to molecular modelling, this phosphorylation is expected to selectively impact the two amino acid residues belonging to the functional dyad without altering the nature and three-dimensional positioning of other residues. P-Pi1 was directly produced by peptide synthesis to rule out any possibility of trace contamination by the unphosphorylated product. Both Pi1 analogues were compared with synthetic Pi1 for bioactivity. In vivo, [A24,A33]-Pi1 and P-Pi1 are lethal by intracerebroventricular injection in mice (LD50 values of 100 and 40 µg/mouse, respectively). In vitro, [A24,A33]-Pi1 and P-Pi1 compete with 125I-apamin for binding to SK channels of rat brain synaptosomes (IC50 values of 30 and 10 nM, respectively) and block rat voltage-gated Kv1.2 channels expressed in Xenopus laevis oocytes (IC50 values of 22 µM and 75 nM, respectively), whereas they are inactive on Kv1.1 or Kv1.3 channels at micromolar concentrations. Therefore, although both analogues are less active than Pi1 both in vivo and in vitro, the integrity of the Pi1 functional dyad does not appear to be a prerequisite for the recognition and binding of the toxin to the Kv1.2 channels, thereby highlighting the crucial role of other toxin residues with regard to Pi1 action on these channels. The computed simulations detailing the docking of Pi1 peptides on to the Kv1.2 channels support an unexpected key role of specific basic amino acid residues, which form a basic ring (Arg-5, Arg-12, Arg-28 and Lys-31 residues), in toxin binding.
GBPI, a novel gastrointestinal- and brain-specific PP1-inhibitory protein, is activated by PKC and inactivated by PKA
Authors: LIU Qing-Rong , ZHANG Ping-Wu , LIN Zhicheng , LI Qi-Fu , WOODS Amina S. , TRONCOSO Juan , UHL George R.
Published: January 2004

The activities of PP1 (protein phosphatase 1), a principal cellular phosphatase that reverses serine/threonine protein phosphorylation, can be altered by inhibitors whose activities are themselves regulated by phosphorylation. We now describe a novel PKC (protein kinase C)-dependent PP1 inhibitor, namely GBPI (gut and brain phosphatase inhibitor). The shorter mRNA that encodes this protein, GBPI-1, is expressed in brain, stomach, small intestine, colon and kidney, whereas a longer GBPI-2 splice variant mRNA is found in testis. Human GBPI-1 mRNA encodes a 145-amino-acid, 16.5 kDa protein with pI 7.92. GBPI contains a consensus PP1-binding motif at residues 21–25 and consensus sites for phosphorylation by enzymes, including PKC, PKA (protein kinase A or cAMP-dependent protein kinase) and casein kinase II. Recombinant GBPI-1-fusion protein inhibits PP1 activity with IC50=3 nM after phosphorylation by PKC. Phospho-GBPI can even enhance PP2A activity by >50% at submicromolar concentrations. Non-phosphorylated GBPI-1 is inactive in both assays. Each of the mutations in amino acids located in potential PP1-binding sequences, K21E+K22E and W25A, decrease the ability of GBPI-1 to inhibit PP1. Mutations in the potential PKC phosphoacceptor site T58E also dramatically decrease the ability of GBPI-1 to inhibit PP1. Interestingly, when PKC-phosphorylated GBPI-1 is further phosphorylated by PKA, it no longer inhibits PP1. Thus, GBPI-1 is well positioned to integrate PKC and PKA modulation of PP1 to regulate differentially protein phosphorylation patterns in brain and gut. GBPI, its closest family member CPI (PKC-potentiated PP1 inhibitor) and two other family members, kinase-enhanced phosphatase inhibitor and phosphatase holoenzyme inhibitor, probably modulate integrated control of protein phosphorylation states in these and other tissues.
Both N- and C-terminal regions are essential for cinnamomin A-chain to deadenylate ribosomal RNA and supercoiled double-stranded DNA
Authors: HE Wen-Jun , LIU Wang-Yi
Published: January 2004

Cinnamomin is a type II ribosome-inactivating protein and its A-chain exhibits RNA N-glycosidase activity to remove an adenine in the conserved sarcin/ricin loop of the largest RNA in ribosome, arresting protein synthesis at the elongation step. In this report, deadenylation of both rRNA and supercoiled DNA by native and recombinant cinnamomin A-chain expressed in Escherichia coli was demonstrated. However, the mutants of cinnamomin A-chain devoid of N-terminal 52 or/and C-terminal 51 amino acid residues lost both the activity of RNA N-glycosidase and the ability to release adenines from supercoiled DNA. Additionally, supercoiled DNA could not be cleaved into nicked and linear forms by these mutants. These results indicate that both N- and C-terminal regions are essential for the cinnamomin A-chain to deadenylate rRNA and supercoiled DNA. It was suggested that phosphodiester bonds in the extensively deadenylated region of supercoiled DNA would become fragile and liable to be broken spontaneously owing to the existence of tension in the supercoiled DNA.
The nucleotide-binding domain of the Zn2+-transporting P-type ATPase from Escherichia coli carries a glycine motif that may be involved in binding of ATP
Authors: OKKERI Juha , LAAKKONEN Liisa , HALTIA Tuomas
Published: January 2004

In P-type ATPases, the nucleotide-binding (N) domain is located in the middle of the sequence which folds into the phosphorylation (P) domain. The N domain of ZntA, a Zn2+-translocating P-type ATPase from Escherichia coli, is approx. 13% identical with the N domain of sarcoplasmic reticulum Ca2+-ATPase. None of the Ca2+-ATPase residues involved in binding of ATP are found in ZntA. However, the sequence G503SGIEAQV in the N domain of ZntA resembles the motif GxGxxG, which forms part of the ATP-binding site in protein kinases. This motif is also found in Wilson disease protein where several disease mutations cluster in it. In the present work, we have made a set of disease mutation analogues, including the mutants G503S (Gly503→Ser), G505R and A508F of ZntA. At low [ATP], these mutant ATPases are poorly phosphorylated. The phosphorylation defect of the mutants G503S and G505R can, however, be partially (G503S) or fully (G505R) compensated for by using a higher [ATP], suggesting that these mutations lower the affinity for ATP. In all three mutant ATPases, phosphorylation by Pi has become less sensitive to the presence of ATP, also consistent with the proposal that the Gly503 motif plays a role in ATP binding. In order to test this hypothesis, we have modelled the N domain of ZntA using the sarcoplasmic reticulum Ca2+-ATPase structure as a template. In the model, the Gly503 motif, as well as the residues Glu470 and His475, are located in the proximity of the ATP-binding site. In conclusion, the mutagenesis data and the molecular model are consistent with the idea that the two loops carrying the residues Glu470, His475, Gly503 and Gly505 play a role in ATP binding and activation.