bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model of the seismic wavefield in gas-charged magma: application to Soufrière Hills Volcano, Montserrat
Authors: Neuberg J. , O'Gorman C. 
Published: August 2007

Abstract
Abstract: A stationary two-phase magma model is used to derive the relationship between gas mass and volume fractions, gas and magma bulk densities, temperature and pressure as a function of depth. In turn, these parameters are used to obtain the vertical seismic velocity profile in the gas-charged magma. A two-dimensional finite-difference model of a magma-filled conduit embedded in an elastic medium is then employed to generate the seismic wavefield in and around the conduit. The high impedance contrast between gas-rich magma and surrounding rock results in the seismic energy being efficiently trapped in the conduit; this leads to the generation of a long-lived resonance of tens of seconds commonly observed as low-frequency earthquakes and harmonic tremor. During a single seismic event, a variety of different seismic radiation patterns along the conduit is observed, leading to the occurrence of several distinct seismic phases in the synthetic seismograms. Observations from several volcanoes show peaked amplitude spectra with integer harmonic overtones that exhibit a time-dependent gliding. These features are successfully modelled by varying the excess pressure and, consequently, the gas volume fraction and the seismic velocity, representing sudden degassing events, such as the reduction of pressure by ash-venting, a dome collapse or a Vulcanian explosion, or, in turn, the pressurization of the conduit prior to such events.
Variation in HCl/SO
2
gas ratios observed by Fourier transform spectroscopy at Soufrière Hills Volcano, Montserrat
Authors: Oppenheimer C. , Edmonds M. , Francis P. , Burton M. 
Published: August 2007

Abstract

We present here the results of open-path Fourier transform infrared (FTIR) spectroscopy of gases emitted from the lava dome of Soufrière Hills Volcano. Although measurement campaigns have been discontinuous, they do span a three-year period and provide strong evidence of secular change in the HCl/SO
2
molar ratio from ≥5 in 1996 to <0.5 in 1999. The post-1996 spectral data represent the only available measurements of gas ratios for the volcano's summit emissions, and complement SO
2
emission rate data obtained by ultraviolet correlation spectroscopy (COSPEC), enhancing the interpretation of degassing at the volcano. The long-term decreasing HCl/SO
2
ratio accompanied an increasing SO
2
emission rate, and suggests a transition from degassing of andesitic to basaltic magma, or progressive tapping of a sulphur-rich vapour phase that was introduced by mafic magma, or that was already resident within the andesite magma reservoir. On timescales of minutes to hours, we observed variations in HCl/SO
2
ratios associated with dome collapses. On 27 July 1998, for example, the HCl/SO
2
ratio dropped from about 0.7 to 0.4 within minutes of a minor dome collapse. A much larger collapse event on 26 October 1998 was followed by a decrease in HCl/SO
2
from 0.6 to 0.1, some 14 hours later. These changes are suggestive of transient degassing from a sulphur-rich source region - larger collapses resulted in tapping of deeper sources, with exsolved gases taking longer to reach the surface. The sustained degassing and response to dome collapse events suggest a permeable upper conduit system established by syneruptive vesiculation, and efficient transfer of volatiles out of the magma chamber by degassing-driven convection in the lower part of the central conduit. Open-path FTIR spectroscopy represents a means for remote geochemical surveillance when access to vent regions is restricted for safety reasons, yielding valuable insights into degassing mechanisms.
Modelling of conduit flow dynamics during explosive activity at Soufrière Hills Volcano, Montserrat
Authors: Melnik O. , Sparks R. S. J. 
Published: August 2007

Abstract
Magmatic explosive activity at Soufrière Hills Volcano involved a sub-Plinian eruption, on 17 September 1996 and two series of repetitive short-lived (c. 1 min) Vulcanian explosions in 1997. Explosive activity followed major collapses of the dome. We have modelled unsteady conduit flow in explosive eruptions after unloading. Two cases are investigated: (i) equilibrium between gas dissolved in the melt and bubbles for sustained sub-Plinian eruption; and (ii) no mass transfer between pre-existing gas bubbles and melt for Vulcanian explosions. The models for Vulcanian explosions agree with observations of erupted volumes, eruption durations (tens of seconds), typical drawdown depths (a few hundred metres to c. 2 km), exit velocities and discharge rates. Explosive mixtures are predicted to have high densities consistent with the occurrence of fountain collapse. The models for sub-Plinian eruption show good agreement with observed erupted volumes and drawdown depths (c. 4 km). Three fragmentation criteria were studied, namely fragmentation at fixed porosity, at a critical gas overpressure, and at a critical elongation strain rate. Results are similar for the three cases, but the critical overpressure and critical strain-rate criteria both predict strong pulsations, whereas the fixed-porosity criterion predicts continuous fragmentation. Pulsations are caused by feedback, with the threshold conditions for magma fragmentation being repeatedly crossed. Pulsations are indicated from seismic and video observations.
Antiapoptotic Effects of Progastrin on Pancreatic Cancer Cells Are Mediated by Sustained Activation of Nuclear Factor-κB
Authors: Rengifo-Cam William , Umar Shahid , Sarkar Shubhashish , Singh Pomila 
Published: August 2007

Abstract
Progastrin (PG) exerts proliferative and antiapoptotic effects on intestinal epithelial and colon cancer cells via Annexin II (ANX-II). In here, we show that ANX-II similarly mediates proliferative and antiapoptotic effects of PG on a pancreatic cancer cell line, AR42J. The role of several signaling molecules was examined in delineating the biological activity of PG. PG (0.1–1.0 nmol/L) caused a significant increase (2- to 5-fold) in the phosphorylation of phosphatidylinositol 3-kinase (PI3K), Akt (Thr308), p38 mitogen-activated protein kinase (MAPK; Thr180/Tyr182), extracellular signal-regulated kinases (ERK; Thr202/Tyr204), IκB kinase α/β (IKKα/β; Ser176/180), IκBα (Ser32), and p65 nuclear factor-κB (NF-κB; Ser536). Inhibition of p44/42 ERKs (PD98059), p38 MAPK (SB203580), Akt, and PI3K (LY294002), individually or combined, partially reversed antiapoptotic effects of PG. The kinetics of phosphorylation of IKKα/β in response to PG matched the kinetics of phosphorylation and degradation of IκBα and correlated with phosphorylation, nuclear translocation, and activation of p65 NF-κB. NF-κB essential modulator–binding domain peptide (an inhibitor of IKKα/β) effectively blocked the activity of p65 NF-κB in response to PG. Activation of p65 NF-κB, in response to PG, was 70% to 80% dependent on phosphorylation of MAPK/ERK and PI3K/Akt molecules. Down-regulation of p65 NF-κB by specific small interfering RNA resulted in the loss of antiapoptotic effects of PG on AR42J cells. These studies show for the first time that the canonical pathway of activation of p65 NF-κB mediates antiapoptotic effects of PG. Therefore, targeting PG and/or p65 NF-κB may be useful for treating cancers, which are dependent on autocrine or circulating PGs for their growth. [Cancer Res 2007;67(15):7266–74]
Genetic Abnormalities Associated with Chemoradiation Resistance of Head and Neck Squamous Cell Carcinoma
Authors: van den Broek Guido B. , Wreesmann Volkert B. , van den Brekel Michiel W.M. , Rasch Coen R.N. , Balm Alfons J.M. , Rao Pulivarthi H. 
Published: August 2007

Abstract
Purpose: To identify reliable predictors of chemoradiation resistance of advanced head and neck squamous cell carcinoma (HNSCC).
Experimental Design: We did a matched-pair analysis of 20 chemoradiation-resistant and 20 sensitive HNSCCs, identified among a series of 104 consecutively treated cases. We compared the global DNA copy number profiles derived from comparative genomic hybridization analysis of both groups to identify genetic markers associated with chemoradiation resistance.
Results: Although sensitive and resistant case groups were characterized by a similar total number of genetic aberrations, high-level amplifications were more frequent in resistant tumors. Resistant tumors were characterized by a different profile of genetic changes. Gains of 3q11-q13, 3q21-q26.1, and 6q22-q27 and losses of 3p11-pter and 4p11-pter were significantly associated with chemoradiation resistance. High-level amplifications unique to resistant cases involved the chromosomal regions 1p32, 3q24, 7p11.1, 7p11.2-12, 8p11.1, 8p11.1-12, 12q15, 13q21, 15q12, 18p11.3, and 18q11.
Conclusions: Sensitive and resistant HNSCCs are characterized by divergent genomic profiles. These profiles may be valuable as predictive markers of treatment failure.
Toll-like Receptor 3 Expressed by Melanoma Cells as a Target for Therapy?
Authors: Salaun Bruno , Lebecque Serge , Matikainen Sampsa , Rimoldi Donata , Romero Pedro 
Published: August 2007

Abstract
Purpose: The immunomodulatory properties of Toll-like receptors (TLR) agonists have inspired their use as experimental adjuvants for vaccination of cancer patients. However, it is now well recognized that TLR expression is not restricted to immune cells but can also be found in many cell types, including those giving rise to tumors. It is therefore mandatory to explore the potential effects of TLR triggering directly on tumor cells.
Experimental Design: In the present work, we have investigated TLR3 protein expression in melanoma cell lines derived from patients, and analyzed the effects of TLR3 agonists on tumor cell survival. Moreover, we used RNA interference to stably knock down TLR3 expression and study the involvement of this receptor in dsRNA-induced effects on melanoma cells viability.
Results: Human melanoma cells can express functional TLR3 protein. Interestingly, the engagement of the receptor by TLR3 agonists can directly inhibit cell proliferation and induce tumor cell death when combined to treatment with either type I IFN or protein synthesis inhibitors. These effects were shown by RNA interference to be largely dependent on TLR3. Moreover, TLR3-mediated cell death involves the activation of caspases and engages both extrinsic and intrinsic apoptotic pathways.
Conclusion: TLR3 protein can be expressed in human melanoma cells, where it can deliver proapoptotic and antiproliferative signaling. Altogether, these results suggest that TLR3 agonists represent very promising adjuvants for cancer vaccines not only based on their well-described immunostimulatory properties, but also due to their newly identified cytostatic and cytotoxic effects directly on tumor cells.
Selecting Patients for Treatment with Epidermal Growth Factor Tyrosine Kinase Inhibitors
Authors: Bonomi Philip D. , Buckingham Lela , Coon John 
Published: August 2007

Abstract
Identification of objective tumor regressions with epidermal growth factor receptor tyrosine kinases (EGFR TKI) in non–small cell lung cancer (NSCLC) patients has resulted in intense, worldwide clinical and basic research directed toward finding the optimal use of EGFR TKIs in NSCLC. EGFR TKI clinical trials have shown that higher response rates and longer survival are associated with specific patient characteristics and that using conventional chemotherapy simultaneously with EGFR TKIs in unselected patients does not increase survival. Molecular studies have revealed that EGFR-activating mutations and high EGFR gene copy number are frequently found in patients who have the best outcomes with EGFR TKIs. More recent studies suggest that KRAS mutations may identify the subset of patients who have the worst outcome with the EGFR TKI treatment. Currently, investigators are trying to determine the optimal approach to selecting patients for treatment with EGFR TKIs. Studies that have evaluated the potential predictive value of clinical features and/or molecular profiles in EGFR TKI-treated NSCLC patients are discussed in this review.
South Atlantic Variability Arising from Air–Sea Coupling: Local Mechanisms and Tropical–Subtropical Interactions
Authors: Trzaska Sylwia , Robertson Andrew W. , Farrara John D. , Mechoso Carlos R. 
Published: August 2007

Abstract
Interannual variability in the southern and equatorial Atlantic is investigated using an atmospheric general circulation model (AGCM) coupled to a slab ocean model (SOM) in the Atlantic in order to isolate features of air–sea interactions particular to this basin. Simulated covariability between sea surface temperatures (SSTs) and atmosphere is very similar to the observed non-ENSO-related covariations in both spatial structures and time scales. The leading simulated empirical coupled mode resembles the zonal mode in the tropical Atlantic, despite the lack of ocean dynamics, and is associated with baroclinic atmospheric anomalies in the Tropics and a Rossby wave train extending to the extratropics, suggesting an atmospheric response to tropical SST forcing. The second non-ENSO mode is the subtropical dipole in the SST with a mainly equivalent barotropic atmospheric anomaly centered on the subtropical high and associated with a midlatitude wave train, consistent with atmospheric forcing of the subtropical SST.
The power spectrum of the tropical mode in both simulation and observation is red with two major interannual peaks near 5 and 2 yr. The quasi-biennial component exhibits a progression between the subtropics and the Tropics. It is phase locked to the seasonal cycle and owes its existence to the imbalances between SST–evaporation and SST–shortwave radiation feedbacks. These feedbacks are found to be reversed between the western and eastern South Atlantic, associated with the dominant role of deep convection in the west and that of shallow clouds in the east. A correct representation of tropical–extratropical interactions and of deep and shallow clouds may thus be crucial to the simulation of realistic interannual variability in the southern and tropical Atlantic.
Comments on “Testing the Fidelity of Methods Used in Proxy-Based Reconstructions of Past Climate”
Authors: Zorita Eduardo , Gonzalez-Rouco Fidel , von Storch Hans 
Published: August 2007

Abstract
Mann et el. found that a version of the Regularized Expectation Maximization (RegEM) method to reconstruct the temperatures of the last millennium showed similar results to previous reconstructions in one of their earlier papers. They also tested the RegEM method in the surrogate climate of a simulation with the Climate System Model (CSM) and found no attenuation of the pseudoreconstructed centennial variability of the Northern Hemisphere mean temperature compared to the one simulated by the model. This is in contrast with the results by von Storch et al., who found, in a simulation with ECHO-G model, that the earlier Mann et al. method underestimates the centennial temperature variability of the Northern Hemisphere temperature. The newer paper by Mann et al. explains that this difference is in part due to the unrealistic character of the ECHO-G simulation. However, it is shown here that similar results to those of von Storch et al. are also found in an ECHO-G simulation that closely resembles the CSM simulation used by Mann et al. Therefore, it is argued here that this discrepancy could be related to other factors, probably to the use of a longer calibration period and to the difference between RegEM and the original method by Mann et al.
Cluster Analysis of Typhoon Tracks. Part I: General Properties
Authors: Camargo Suzana J. , Robertson Andrew W. , Gaffney Scott J. , Smyth Padhraic , Ghil Michael 
Published: August 2007

Abstract
A new probabilistic clustering technique, based on a regression mixture model, is used to describe tropical cyclone trajectories in the western North Pacific. Each component of the mixture model consists of a quadratic regression curve of cyclone position against time. The best-track 1950–2002 dataset is described by seven distinct clusters. These clusters are then analyzed in terms of genesis location, trajectory, landfall, intensity, and seasonality.
Both genesis location and trajectory play important roles in defining the clusters. Several distinct types of straight-moving, as well as recurving, trajectories are identified, thus enriching this main distinction found in previous studies. Intensity and seasonality of cyclones, though not used by the clustering algorithm, are both highly stratified from cluster to cluster. Three straight-moving trajectory types have very small within-cluster spread, while the recurving types are more diffuse. Tropical cyclone landfalls over East and Southeast Asia are found to be strongly cluster dependent, both in terms of frequency and region of impact.
The relationships of each cluster type with the large-scale circulation, sea surface temperatures, and the phase of the El Niño–Southern Oscillation are studied in a companion paper.
Physical Processes Associated with the Tropical Atlantic SST Gradient during the Anomalous Evolution in the Southeastern Ocean
Authors: Hu Zeng-Zhen , Huang Bohua 
Published: August 2007

Abstract
This work is focused on the evolution of the dominant air–sea coupled mode in the equatorial and southeastern tropical Atlantic and the associated physical processes. It is shown that in June–August (JJA) the evolution of the dominant mode is mainly dynamically driven and displays a coherent warming or cooling pattern extending from the Angola coast toward the equator in the Gulf of Guinea. For anomalies peaking in JJA, the warming (cooling) is initiated near the Angola coast in March–May. It is suggested that SST anomalies along the coast and near the equator are physically connected. The air–sea interaction along the coast may be a major factor in triggering the development of SST anomalies near the equator, which is intensified by local positive feedbacks that may include Bjerknes and Ekman processes. In return, the warming or cooling near the equator weaken the SST anomalies along the coast by changing the direction of anomalous wind. Slow westward Rossby wave propagation may also play a role in stimulating the equatorial feedback. The thermodynamic processes affect the evolution of this mode. On average, the net surface latent heat flux anomalies are the leading damping factor, and the net surface sensible heat flux plays the same role on a smaller scale, while the net surface shortwave (longwave) radiation heating has a negative (positive) contribution to the SST variation. However, although on average the surface heat flux damps the SST anomalies, the role played by the heat flux varies with regions and components. Spatially, the latent and sensible heat flux as well as the longwave radiation damp air–sea coupling in the eastern South Atlantic near the Gulf of Guinea and amplify the coupling in the western equatorial ocean. The situation is opposite for the solar radiation.
Coupled Decadal Variability in the North Pacific: An Observationally Constrained Idealized Model*
Authors: Qiu Bo , Schneider Niklas , Chen Shuiming 
Published: August 2007

Abstract
Air–sea coupled variability is investigated in this study by focusing on the observed sea surface temperature signals in the Kuroshio Extension (KE) region of 32°–38°N and 142°E–180°. In this region, both the oceanic circulation variability and the heat exchange variability across the air–sea interface are the largest in the midlatitude North Pacific. SST variability in the KE region has a dominant time scale of ∼10 yr and this decadal variation is caused largely by the regional, wind-induced sea surface height changes that represent the lateral migration and strengthening/weakening of the KE jet. The importance of the air–sea coupling in influencing KE jet is explored by dividing the large-scale wind forcing into those associated with the intrinsic atmospheric variability and those induced by the SST changes in the KE region. The latter signals are extracted from the NCEP–NCAR reanalysis data using the lagged correlation analysis. In the absence of the SST feedback, the intrinsic atmospheric forcing enhances the decadal and longer time-scale SST variance through oceanic advection but fails to capture the observed decadal spectral peak. When the SST feedback is present, a warm (cold) KE SST anomaly works to generate a positive (negative) wind stress curl in the eastern North Pacific basin, resulting in negative (positive) local sea surface height (SSH) anomalies through Ekman divergence (convergence). As these wind-forced SSH anomalies propagate into the KE region in the west, they shift the KE jet and alter the sign of the preexisting SST anomalies. Given the spatial pattern of the SST-induced wind stress curl forcing, the optimal coupling in the midlatitude North Pacific occurs at the period of ∼10 yr, slightly longer than the basin-crossing time of the baroclinic Rossby waves along the KE latitude.
Decadal Changes of Wind Stress over the Southern Ocean Associated with Antarctic Ozone Depletion
Authors: Yang Xiao-Yi , Huang Rui Xin , Wang Dong Xiao 
Published: August 2007

Abstract
Using 40-yr ECMWF Re-Analysis (ERA-40) data and in situ observations, the positive trend of Southern Ocean surface wind stress during two recent decades is detected, and its close linkage with spring Antarctic ozone depletion is established. The spring Antarctic ozone depletion affects the Southern Hemisphere lower-stratospheric circulation in late spring/early summer. The positive feedback involves the strengthening and cooling of the polar vortex, the enhancement of meridional temperature gradients and the meridional and vertical potential vorticity gradients, the acceleration of the circumpolar westerlies, and the reduction of the upward wave flux. This feedback loop, together with the ozone-related photochemical interaction, leads to the upward tendency of lower-stratospheric zonal wind in austral summer. In addition, the stratosphere–troposphere coupling, facilitated by ozone-related dynamics and the Southern Annular Mode, cooperates to relay the zonal wind anomalies to the upper troposphere. The wave–mean flow interaction and the meridional circulation work together in the form of the Southern Annular Mode, which transfers anomalous wind signals downward to the surface, triggering a striking strengthening of surface wind stress over the Southern Ocean.
On Sub-ENSO Variability
Authors: Keenlyside Noel S. , Latif Mojib , Dürkop Anke 
Published: August 2007

AbstractMultichannel singular spectrum analysis (MSSA) of surface zonal wind, sea surface temperature (SST), 20° isotherm depth, and surface zonal current observations (between 1990 and 2004) identifies three coupled ocean–atmosphere modes of variability in the tropical Pacific: the El Niño–Southern Oscillation (ENSO), the annual cycle, and a mode with a 14–18-month period, which is referred to as sub-ENSO in this study. The sub-ENSO mode accounts for the near 18-month (near annual) variability prior to (following) the 1997/98 El Niño event. It was strongest during this El Niño event, with SST anomalies exceeding 1°C. Sub-ENSO peak SST anomalies are ENSO-like in structure and are associated with eastward propagating heat content variations. However, the SST anomalies are preceded by and in near quadrature with relatively strong remotely forced westward propagating zonal current variations, suggesting the sub-ENSO mode arises from the zonal-advective feedback.The sub-ENSO mode is found to exist also in an intermediate complexity model (ICM) of the tropical Pacific. A heat budget analysis of the model’s sub-ENSO mode shows it indeed arises from the zonal-advective feedback. In the model, both ENSO and sub-ENSO modes coexist, but there is a weak nonlinear interaction between them. Experiments also show that the observed changes in sub-ENSO’s characteristics may be explained by changes in the relative importance of zonal and vertical advection SST tendencies.