bluuebunny/crossref_metadata_2025 huggingface dataset:
Endoscopic Management of Retained Airgun Projectiles in the Paranasal Sinuses
Authors: Brinson George M. , Senior Brent A. , Yarbrough Wendell G.
Published: January 2004

OBJECTIVES/HYPOTHESIS

This article presents 3 cases to illustrate the appropriate management of airgun injuries with retained projectiles in the paranasal sinuses. The indications, techniques, and potential complications of removal of these foreign bodies from the paranasal sinuses are discussed. STUDY DESIGN: We conducted a case series consisting of 3 patients and a review of the literature. METHODS: Three consecutive patients who sustained airgun injuries to the face with retained bullets in the paranasal sinuses are presented. Projectiles were present in the maxillary, ethmoid, and sphenoid sinuses. The literature pertaining to this subject is reviewed.

RESULTS

All retained projectiles were removed endoscopically without complications. Stereotactic guidance was used in 2 cases.

CONCLUSIONS

Airgun injuries to the paranasal sinuses are relatively uncommon. Projectiles can safely be removed using endoscopic techniques in selected cases. When possible, foreign bodies in the paranasal sinuses should be removed to prevent long‐term sequelae.
Endoscopic Dacryocystorhinostomy: Modified Technique
Authors: Massegur Humbert , Trias Enric , Ademà Juan Manuel
Published: January 2004

BACKGROUND

Dacryocystorhinostomy (DCR) is a surgical technique that has been increasingly used by otolaryngologists in recent years due to the improved endonasal approach with endoscopes. Although it was first described in 1893 by Caldwell, it has been performed by ophthalmologists.

OBJECTIVES

Even though permeability results are similar in long‐term follow‐up, we present some modifications that in our opinion contribute to the improvement of the results and the simplification of the surgical technique: mucosal flap design that helps to improve the postoperative mucosal recovery, careful dissection of the bony suture between the frontal process of the maxillary bone and the lacrimal bone, and osteotomy using a Smith‐Kerrison forceps.

STUDY DESIGN AND SETTING

Two groups are compared. In the first group (96 DCRs), patients underwent chisel osteotomies without a mucosal flap of the lacrimal duct, and in the second group (40 DCRs), the modified technique was applied.

RESULTS

Final permeability results are similar (92.7% versus 87.5%). No major complications were found, and the most common minor complication was postoperative eyelid hematoma in cases where orbital fat was exposed (5 cases versus 7 cases).

CONCLUSIONS

There are no differences in final results, but the modified technique is easier to perform, improves postoperative mucosal recovery, is more functional and less aggressive, and improves the cost‐benefit ratio.
CD40 Monoclonal Antibody Activation of Antigen‐Presenting Cells Improves Therapeutic Efficacy of Tumor‐Specific T Cells
Authors: Bergstrom Richard T. , Silverman Damon A. , Chambers Kathleen , Kim Julian A.
Published: January 2004

OBJECTIVE

The goal of this study was to determine whether CD40 ligation of antigen presenting cells (APCs) enhances the anti‐tumor effector function of tumor draining lymph node (TDLN) T lymphocytes in an adoptive immunotherapy model.

STUDY DESIGN

MCA 205 TDLNs were culture activated both in the presence and absence of a stimulatory anti‐CD40 monoclonal antibody (mAb) and effector cell phenotype, cytokine secretion in vitro and therapeutic efficacy in vivo were compared.

RESULTS

Anti‐CD40 mAb induced upregulation of APC cell surface activation markers that promoted generation of T cells that demonstrated an increase in tumor‐specific IFN‐gamma secretion and a statistically significant reduction in the number of pulmonary tumors (p< 0.01) after adoptive transfer.

CONCLUSION

CD40 ligation of APCs in vitro results in the generation of T cells with enhanced effector function against established pulmonary tumors in vivo.

SIGNIFICANCE

These findings have direct implications in the development of effective T cell‐based immunotherapy of malignant conditions in human beings.
Integrin β1 subunit overexpressed in the SMMC‐7721 cells regulates the promoter activity of p21CIP1 and enhances its transcription
Authors: Liang Yu-Long , Fu Yi , Chen Si-Gang , Cai Xiu-Mei , Su Jian-Min , Jin Jia-Wei , Ma Dong-Zhu , Li Zeng-Xia , Zhang Wen , Zha Xiliang
Published: January 2004

Evidence has been emerging to suggest that integrin could induce growth inhibition in some cell types. Some of the molecular mechanisms underlying growth arrest have been elucidated. We reported here that overexpression of integrin β1 imposed a growth inhibitory effect on the hepatocellular carcinoma cell line SMMC‐7721, and this phenomenon was mainly attributed to the cyclin‐dependent kinase inhibitor p21CIP1. Furthermore, our findings suggested that transcription activity of the p21CIP1 gene could be upregulated in the integrin β1‐overexpressing cells, and possibly controlled by the cis‐elements in the core region of the p21CIP1 promoter.
The solution structure of the SODD BAG domain reveals additional electrostatic interactions in the HSP70 complexes of SODD subfamily BAG domains
Authors: Brockmann Christoph , Leitner Dietmar , Labudde Dirk , Diehl Annette , Sievert Volker , Büssow Konrad , Kühne Ronald , Oschkinat Hartmut
Published: January 2004

The solution structure of an N‐terminally extended construct of the SODD BAG domain was determined by nuclear magnetic resonance spectroscopy. A homology model of the SODD‐BAG/HSP70 complex reveals additional possible interactions that are specific for the SODD subfamily of BAG domains while the overall geometry of the complex remains the same. Relaxation rate measurements show that amino acids N358–S375 of SODD which were previously assigned to its BAG domain are not structured in our construct. The SODD BAG domain is thus indeed smaller than the homologous domain in Bag1 defining a new subfamily of BAG domains.
Functional silencing of hepatic microsomal glucose‐6‐phosphatase gene expression in vivo by adenovirus‐mediated delivery of short hairpin RNA
Authors: Huang Alan , Chen Yan , Wang Xinzhong , Zhao Shanchuan , Su Nancy , White David W
Published: January 2004

An expression cassette containing mouse U6 polymerase III promoter directing expression of short hairpin RNA (shRNA) targeting murine microsomal glucose‐6‐phosphatase (G6P) transcript was generated. This construct was packaged into an adenoviral (AdV) backbone and viral stocks generated. Mice injected intravenously with AdV‐G6PshRNA exhibited a significant reduction in postprandial glucose levels and had significantly elevated steady‐state hepatic glycogen stores. Target gene silencing was confirmed by measurements demonstrating a significant reduction in both hepatic G6P transcript level and phosphohydrolase activity. These findings provide evidence that AdV delivery of expressed shRNA can be a productive tool to explore gene function in vivo.
Altered channel gating mechanism for CFTR inhibition by a high‐affinity thiazolidinone blocker
Authors: Taddei Alessandro , Folli Chiara , Zegarra-Moran Olga , Fanen Pascale , Verkman A.S , Galietta Luis J.V
Published: January 2004

The thiazolidinone CFTRinh‐172 was identified recently as a potent and selective blocker of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel. Here, we characterized the CFTRinh‐172 inhibition mechanism by patch‐clamp and short‐circuit analysis using cells stably expressing wild‐type and mutant CFTRs. CFTRinh‐172 did not alter CFTR unitary conductance (8 pS), but reduced open probability by >90% with K
i≈0.6 μM. This effect was due to increased mean channel closed time without changing mean channel open time. Short‐circuit current experiments indicated similar CFTRinh‐172 inhibitory potency (K
i≈0.5 μM) for inhibition of Cl− current in wild‐type, G551D, and G1349D CFTR; however, K
i was significantly reduced to 0.2 μM for ΔF508 CFTR. Our studies provide evidence for CFTR inhibition by CFTRinh‐172 by a mechanism involving altered CFTR gating.
The risks and benefits of teaching purely functional programming in first year
Authors: CHAKRAVARTY MANUEL M. T. , KELLER GABRIELE
Published: January 2004

We argue that teaching purely functional programming as such in freshman courses is detrimental to both the curriculum as well as to promoting the paradigm. Instead, we need to focus on the more general aims of teaching elementary techniques of programming and essential concepts of computing. We support this viewpoint with experience gained during several semesters of teaching large first-year classes (up to 600 students) in Haskell. These classes consisted of computer science students as well as students from other disciplines. We have systematically gathered student feedback by conducting surveys after each semester. This article contributes an approach to the use of modern functional languages in first year courses and, based on this, advocates the use of functional languages in this setting.
Attenuation correction constraint for single‐polarisation weather radar
Authors: Nicol J. C. , Austin G. L.
Published: January 2004

A new method of constraining divergent attenuation corrections for weather radar systems is presented. This was motivated by the need for reliable attenuation corrections when making quantitative precipitation estimates using a small, mobile X‐band radar at short range. The approach is suitable for systems requiring attenuation correction in real‐time and requires no auxiliary data. An outline of the literature on attenuation and its correction for single‐polarisation weather radar is presented. The traditional form of correction is known to be problematic due to the divergence, which may occur in its estimation. The form of constraint presented is based on the representation of attenuation correction originally derived for space‐borne radar configurations. This method determines when divergent estimates will occur and allows a more realistic application of the constrained correction. Examples of attenuation correction applied to X‐band radar observations in comparison with ground clutter returns are presented, showing good agreement and hence good absolute calibration. Selected profiles are then used to determine the influence of measurement errors on attenuation estimation in the context of this representation. The paper concludes with a discussion of the practical limitations and considerations in applying an attenuation correction to quantitative weather radar rainfall estimates. Copyright © 2003 Royal Meteorological Society.
Seasonality in the statistics of surface air temperature and the pricing of weather derivatives
Authors: Jewson Stephen , Caballero Rodrigo
Published: January 2004

The pricing of weather derivatives motivates the need to build accurate statistical models of daily temperature variability.Current published models are shown to be inaccurate for locations that show strong seasonality in the probability distribution and autocorrelation structure of temperature anomalies. With respect to the first of these problems, we present a new transform that allows seasonally varying non‐normal temperature anomaly distributions to be cast into normal distributions. With respect to the second, we present a new parametric time‐series model that captures both the seasonality and the slow decay of the autocorrelation structure of observed temperature anomalies. This model is valid when the seasonality is slowly varying. We also present a simple non‐parametric method that is accurate in all cases, including extreme non‐normality and rapidly varying seasonality. Application of these new methods in some realistic weather derivative valuation examples shows that they can have a very large impact on the final price when compared to existing methods. Copyright © 2003 Royal Meteorological Society.
The Theory and Practice of Chinese Grassroots Governance: Five Models
Authors: HE BAOGANG
Published: January 2004

Theories of governance and Chinese understandings

There is a vast and eclectic literature about many forms of governance, including markets, bureaucratic hierarchies, associations and different types of networks. The Commission on Global Governance, for example, defines governance as ‘the sum of the many ways individuals and institutions, public and private, manage their common affairs. It is a continuing process through which conflicting or diverse interests may be accommodated and cooperative action may be taken. It includes formal institutions and regimes empowered to enforce compliance, as well as informal arrangements that people and institutions either have agreed to or perceive to be in their interest’. Thus, ‘at the global level, governance has been viewed primarily as intergovernmental relationships, but it must now be understood as also involving non-governmental organizations (NGOs), citizens' movements, multinational corporations and the global mass of dramatically enlarged influence’.
Regional Governance: Lessons from European Involvement in Yugoslav Conflicts
Authors: SADAKATA MAMORU
Published: January 2004

The fragmentation of Yugoslavia has wrought extensive political and social change in the Balkans and Europe more generally. After the collapse of communism and the breakup of Yugoslavia, many Balkan countries have transformed their political systems. European states have attempted to engage and manage this breakup on an individual and collective basis. The involvement of the international community, and above all of EU countries adjacent to the Balkans, has greatly influenced processes of conflict resolution and post-conflict reconstruction in the region.
Regional Governance and East Central Europe: The EU, NATO and the Consolidation of Democracy
Authors: WOLCHIK SHARON L.
Published: January 2004

Over a decade has passed since the heady days of 1989 and 1990 when communist governments fell one after the other and almost all political parties taking part in elections shared the same goals: Democracy, the Market, and Back to Europe. In December 2002, the efforts of the new leaders of these countries to ‘return to Europe’ bore fruit in an event that many had in 1989 regarded as too farfetched to imagine, the invitation of most of the countries in the region to join the EU in 2004 or 2007. The culmination of a decade-long process of harmonization and negotiation, this invitation symbolized the success of these countries in instituting political democracies and market economies. But how complete is this process, particularly in the political realm?
The Legislative Record: The Japan National Diet in 2003
Authors: HIROSE JUNKO
Published: January 2004

The performance of the Japanese Diet in 2003 indicates that a new political era may have begun. The rate at which government sponsored bills were passed in 2003 was 11 per cent higher than in 2002. The unity of government parties, especially the unified support of the Komei Party, the high approval rates of Koizumi Cabinet, and changes in the Democratic Party of Japan (DPJ), the largest opposition party, all contributed to this high passage rate. Most notable was a change in the treatment of national security issues. The confrontational style of the 1955 regime gave way to a new political era of discussion and compromise through the Diet deliberation. The Koizumi cabinet demonstrated strong leadership over the government parties, and the cabinet made many substantial policy decisions.
Overview of the Issue
Authors: BROWN JEFFREY , HABERMAN STEVEN , MILEVSKY MOSHE , ORSZAG MIKE
Published: January 2004

This issue features four articles and a book review section. The first article in the issue is by Stefan Engström (Stockholm School of Economics) and Anna Westerberg (National Social Insurance Board) and examines “Which Individuals Make Active Decisions in the New Swedish Pension System?” The vast majority of empirical evidence on how individuals make decisions in defined contribution plans has been based on US experience and the unique choices available within 401(k) plans. Therefore, the paper by Engström and Westerberg, which examines the situation in Sweden where the institutional details and investment choices are somewhat different, is a most welcome contribution to the literature.
INDO-JAPAN COOPERATIVE VENTURES IN MATCH MANUFACTURING IN INDIA: MUSLIM MERCHANT NETWORKS IN AND BEYOND THE BENGAL BAY REGION 1900–1930
Authors: Oishi Takashi
Published: January 2004

This paper discusses the role of Indian merchants, especially Muslims, in the match trade between Japan and India, and situates the cooperative ventures set up in the middle of the 1920s between Indian merchants and Japanese manufacturers in the context of the economy of the Bengal Bay region. Their inter-regional networks and partnerships were important not just for trade, but also for manufacturing based on the flow of technology, ideas, information, and natural resources. The paper also shows that such ventures unexpectedly caused conflicts with movements in India to promote domestic industry and with the logic of territorial nationalism that lay behind them.
Racial Discrimination and Racial Identity as Risk or Protective Factors for Violent Behaviors in African American Young Adults
Authors: Caldwell Cleopatra Howard , Kohn-Wood Laura P. , Schmeelk-Cone Karen H. , Chavous Tabbye M. , Zimmerman Marc A.
Published: February 2004

This study examined the influences of racial discrimination and different racial identity attitudes on engaging in violent behavior among 325 African American young adults. The contributions of racial discrimination and racial identity attitudes in explaining violent behavior during the transition into young adulthood while controlling for the influences of prior risk behaviors at ninth grade were examined separately for males and females. In addition, the buffering effects of racial identity attitudes on the relationship between racial discrimination and violent behavior were tested. Results indicated that experience with racial discrimination was a strong predictor of violent behavior, regardless of gender. The centrality of race for males and the meaning others attribute to being Black for both males and females were moderators of the influence of racial discrimination on violent behavior.
Zur Brauchbarkeit des Differentiellen Leistungsangst Inventars (DAI) bei Studenten: Faktorielle Struktur und psychometrische Kennwerte
Authors: Schilling Susanne R. , Rost Detlef H. , Schermer Franz J.
Published: February 2004

Zusammenfassung. Überprüft wird, inwieweit das für Gymnasiasten konzipierte “Differentielle Leistungsangst Inventar“ (DAI, Rost & Schermer, 1997 ) zur Diagnostik von Leistungsängstlichkeit bei Studenten eingesetzt werden kann. N = 480 Studierende der Rechtswissenschaften (n1 = 239) und der Medizin (n2 = 241) bearbeiteten die DAI-Kurzform. Das Differentielle Leistungsangst Inventar erweist sich auch in einer studentischen Stichprobe als faktoriell valides Verfahren mit guten teststatistischen Kennwerten aller 12 Subskalen. Mittelwertsunterschiede zwischen Studierenden der Fachrichtungen “Medizin“ und “Jura“ sowie zwischen der studentischen Stichprobe und der DAI-Eichstichprobe legen eine Normierung für Studierende nahe.
Immediate and Delayed Recall of Visually Presented Sentences:
Authors: Rummer Ralf
Published: January 2004

Abstract. The lure intrusion effect refers to the observation that lexical priming affects recall of sentences. This effect is taken as evidence against the contribution of surface information, even with immediate sentence recall. Recently, Rummer and Engelkamp (2003a ) demonstrated that this effect, which is usually observed under rapid serial visual presentation (RSVP), does not appear under immediate recall of auditorily presented sentences. This finding indicates that surface information (i.e., phonological or acoustic-sensory information) can contribute to immediate sentence recall. So far, however, the findings do not allow for a decision on whether phonological and/or acoustic-sensory information is used in immediate sentence recall. In order to dissociate the two kinds of surface information, an experiment was conducted in which immediate and delayed recall were tested for sentences that were visually presented for a longer period of time than in RSVP. This kind of presentation should support phonological representations, but does not allow for acoustic-sensory representations. The findings showed a smaller intrusion effect for immediate than for delayed recall. This indicates that, if available, phonological information is involved in immediate sentence recall thereby reducing the lure intrusion effect. Furthermore, the findings support the assumption that the phonological trace provided via RSVP reading is weaker than in normal reading.
Predicted net efflux of radiocarbon from the ocean and increase in atmospheric radiocarbon content
Authors: Caldeira Ken , Rau Greg H. , Duffy Philip B.
Published: February 2004

Prior to changes introduced by man, production of radiocarbon (14C) in the stratosphere nearly balanced the flux of 14C from the atmosphere to the ocean and land biosphere, which in turn nearly balanced radioactive decay in these 14C reservoirs. This balance has been altered by land‐use changes, fossil‐fuel burning, and atmospheric nuclear detonations. Here, we use a model of the global carbon cycle to quantify these radiocarbon fluxes and make predictions about their magnitude in the future. Atmospheric nuclear detonations increased atmospheric 14C content by about 80% by the mid‐1960's. Since that time, the 14C content of the atmosphere has been diminishing as this bomb radiocarbon has been entering the oceans and terrestrial biosphere. However, we predict that atmospheric 14C content will reach a minimum and start to increase within the next few years if fossil‐fuel burning continues according to a “business‐as‐usual” scenario, even though fossil fuels are devoid of 14C. This will happen because fossil‐fuel carbon diminishes the net flux of 14C from the atmosphere to the oceans and land biosphere, forcing 14C to accumulate in the atmosphere. Furthermore, the net flux of both bomb and natural 14C into the ocean are predicted to continue to slow and then, in the middle of the next century, to reverse, so that there will be a net flux of 14C from the ocean to the atmosphere. The predicted reversal of net 14C fluxes into the ocean is a further example of human impacts on the global carbon cycle.
Accurate and efficient FDTD modeling of ground‐penetrating radar antenna radiation
Authors: Holliger Klaus , Bergmann Tim
Published: February 2004

We present a 3‐D finite‐difference time domain (FDTD) solution of Maxwell's equations for modeling the near‐field radiation of dipole antennas in ground‐penetrating radar surveys. The antenna is represented as a conducting wire with a narrow gap in the middle. The electromagnetic field in the immediate vicinity of the wire is evaluated by numerical solution of an integral representation of Maxwell's equations. Integration contours and surfaces are defined by the finite‐difference cells surrounding the wire. Everywhere else the electromagnetic wavefield is calculated using conventional FDTD approximations of Maxwell's equations. The accuracy of the algorithm has been tested by comparing the simulated near‐field radiation of a dipole antenna between two dielectric media with corresponding experimental observations.
Long term dynamic radiation belt model for low energy protons
Authors: Boscher Daniel , Bourdarie Sebastien , Friedel Reiner , Korth Axel
Published: February 2004

A new simple model for equatorialy mirroring protons, based on classical radial diffusion, is used here to understand the global long term dynamics of the ring current ion population. The convection access for low energy particles coming from the plasmasheet is used as a source population. Then magnetospheric acceleration processes are reproduced by using a Kp dependent radial diffusion coefficient. Comparing the results with CRRES satellite energetic ion measurements from the fifteen months of the total mission yields very good quantitative agreement for ∼80 keV ring‐current protons and good qualitative agreement with ∼300 keV ions.
Bromine activation in the troposphere by the dark reaction of O3 with seawater ice
Authors: Oum K. W. , Lakin M. J. , Finlayson‐Pitts B. J.
Published: February 2004

There is increasing evidence that bromine atoms play a role in tropospheric chemistry in the marine boundary layer. In addition, they are believed to lead to rapid depletion of surface level ozone in the Arctic at polar sunrise. While mechanisms have been proposed for recycling bromine atoms from sea salt particles, the initial reaction(s) leading to the formation of bromine atom precursors is not known. We report here the formation of gaseous Br2 from the reaction of seawater ice with O3 in the dark. These observations suggest that this reaction is a potential source of tropospheric photolyzable bromine in high latitude coastal regions in winter. In addition, it may be the source of the photolyzable bromine gas measured recently in the Arctic by Impey et al. (1997), which is believed to be responsible for the ozone destruction at polar sunrise.
Global scale decadal climate variability
Authors: Meehl Gerald A. , Arblaster Julie M. , Strand Warren G.
Published: February 2004

Analysis of observations and results from a global coupled climate model show that coherent decadal climate variability extends over the entire Pacific basin, is associated with processes in the Atlantic and Indian Ocean regions to contribute to global patterns of decadal climate variability, and encompasses regional decadal mechanisms noted in previous studies. Ocean heat content anomalies embedded in the gyre circulations of the Pacific, Atlantic and Indian Oceans are associated with global decadal timescale “El Niño‐like” signals in atmosphere and ocean with consequent global energy balance variations. Large‐scale tropical‐midlatitude interactions act to replenish the ocean heat content anomalies. Maxima in decadal timescale globally averaged surface temperature occur in conjunction with periodic arrangements of SST anomalies, in association with the heat content anomalies embedded in the various ocean gyre circulations, in a global “El Niño‐like” pattern that is highly correlated with such maxima. The decadal timescale in the model is approximately set by the circuit times of the ocean gyre circulations.
Regional metamorphic dehydration and seismic hazard
Authors: Ague J. J. , Park Jeffrey , Rye D. M.
Published: February 2004

We use a one‐dimensional model of coupled heat transport, fluid transport, porosity feedback, and metamorphism to investigate how dehydration reactions, proceeding during burial of hydrous rocks in the footwall of thrusts or the hanging wall of normal faults, may influence the temporal evolution of pore fluid pressure (Pf). Based on a new interpretation of existing kinetic data for the dehydration of model serpentinite, we advance the hypothesis that Pf buildup to tensile failure may be possible within decades of the onset of dehydration in low permeability metamorphic rocks of the middle crust. This model contrasts with both: 1) typical earthquake nucleation models which involve preexisting fluids that play a passive role, responding to tectonic stresses rather than generating them and 2) conventional treatments of Pf generation based on equilibrium thermodynamics and constant rates of dehydration, which require 10³–106 years to produce significant Pf increases. Our results suggest that repeated cycles dehydration‐induced seismicity are plausible in low permeability areas of the mid‐crust, and can be sustained throughout an orogenic episode if fresh hydrous minerals descend into the metamorphic zone along the downgoing face of a thrust‐ or normal‐fault system.
Tropospheric sulfur dioxide observed by the ERS‐2 GOME instrument
Authors: Eisinger Michael , Burrows John P.
Published: February 2004

Since July 1995, the Global Ozone Monitoring Experiment (GOME) onboard ESA's 2nd European Remote Sensing Satellite (ERS‐2) provides continuous spectral measurements of nadir backscattered earth radiances and solar irradiances in the UV/visible wavelength range. From these, column amounts of sulfur dioxide have been derived for the December 1996 eruption of Nyamuragira volcano, Zaire, and the ongoing activity of Popocatépetl volcano, Mexico. Maximal column densities of 33 DU for Nyamuragira and 6 DU for Popocatépetl have been found. Popocatépetl results compare well with the activity reported for this volcano. Furthermore, GOME observed enhanced SO2 over Southeast Europe which is attributed to lignite combustion in local power plants. The results demonstrate a high sensitivity and specificity of this new sensor for sulfur dioxide. For cloud‐free scenes at low solar zenith angles, the detection limit for SO2 is estimated to be 0.4 DU.
Upper mantle S velocities beneath Afar and Western Saudi Arabia from Rayleigh wave dispersion
Authors: Knox Ronald P. , Nyblade Andrew A. , Langston Charles A.
Published: February 2004

Two‐station methods are employed to determine Rayleigh wave phase velocities along three paths crossing the Afro‐Arabian dome. Phase velocities are modeled using a grid‐search technique, and the range of successful models indicate that the uppermost mantle beneath Afar and western Saudi Arabia is characterized by pronounced negative S wave velocity gradients and S wave velocities that are 0.2–0.8 km/s lower than PREM at 100 km depth. These results are consistent with a thermal plume model for Afar, provided that there is a few percent of partial melt present within the mantle. The low velocity anomaly beneath western Saudi Arabia could be caused by migrating plume material from Afar, upwelling mantle material associated with Red Sea rifting, or isolated small‐scale convection.
Experimental evidence that excited ozone is a source of nitrous oxide
Authors: Zipf E. C. , Prasad S. S.
Published: February 2004

This letter presents experimental data and their interpretation that lend support to earlier speculations concerning the formation of nitrous oxide (N2O) by excited ozone (O3) chemistry. This is a significant new development because the discovery of an atmospheric source of N2O has important implications for its global budget and because this process may account for the mass independent N2O isotope anomaly recently observed in the troposphere and lower stratosphere.
Comment on “Empirical determination of depth‐distance corrections for mb and MW from Global Seismograph Network Stations” By Guust Nolet, Steve Krueger and Robert M. Clouser
Authors: Murphy J. R. , McLaughlin K. L.
Published: February 2004

In their recent article, Nolet et al. (1998) presented an analysis which led them to conclude that the epicentral distance and focal depth correction factors for mb which were previously published by Veith and Clawson (1972) are not accurate for events with focal depths greater than 100 km. In this brief commentary, we present some independent evidence which has led us to conclude that the Veith/Clawson (V/C) corrections are in fact quite accurate, at least for seismic events having focal depths of less than about 400 km.
Water column sediment fluxes in the Ross Sea, Antarctica: Atmospheric and sea ice forcing
Authors: Dunbar Robert B. , Leventer Amy R. , Mucciarone David A.
Published: February 2004

We measured time series of the vertical particle flux at three locations in the Ross Sea, Antarctica, between January 1990 and February 1992 as part of an interdisciplinary project focusing on the accumulation and recycling of organic C and biogenic Si on a polar shelf. We estimate area‐wide annual average fluxes through the deep water column of 5 g organic C m−2 yr−l and 30 g biogenic Si m−2 yr−1, values similar to the highest annual average fluxes to the subsurface reported for other areas of the Antarctic continental shelf. Total particle and biogenic Si fluxes are highest during January and February in the southwestern Ross Sea, beneath a seasonally recurrent bloom of the diatom Fragilariopsis curta. Organic C fluxes are highest in the central Ross Sea, consistent with a surface water algal assemblage dominated by the prymnesiophyte Phaeocystis. While organic C flux decreases with depth at all three sites, the result of remineralization within the water column, biogenic opal fluxes are higher in near‐bottom traps than at 230 m at the two western Ross Sea sites. Some biogenic opal must be supplied to these deep traps via horizontal advection and possibly resuspension. Fecal pellets and large aggregates contributed between 4 and 70% of the vertical flux and settled at rates of 60 to >400 m d−1. Maximum particle fluxes occur 2 to 10 weeks after surface waters become ice free. We discuss three hypotheses to explain lags between production and settling: (1) advection from surface waters with different ice cover characteristics, (2) lags in the development of a grazing Zooplankton community, and (3) early season windinduced inhibition of primary production. Interannual variability in surface wind stress is empirically linked to variability in biogenic fluxes. Windiness and relative phasing of the annual cycles of ice cover and air temperature may be responsible for the development of different algal communities in the central versus western Ross Sea.
Investigation of subsurface water flow along the continental margin of the Eurasian Basin using the transient tracers tritium, 3He, and CFCs
Authors: Frank Markus , Smethie William M. , Bayer Reinhold
Published: February 2004

During August–September 1993 the R/V Polarstern expedition ARK IX/4 was made to the Eurasian continental margin of the Arctic Ocean. Sections of oceanographic stations leading from the outer shelf over the continental slopes toward the deep Eurasian Basin were occupied north of the Barents and Laptev Seas. The distributions of the transient tracers CFC‐11, CFC‐12, tritium, and 3He were measured along these sections and are discussed in relation to water mass distribution and circulation along the continental margin of the Eurasian Basin. The tracer data strongly corroborate the temperature and salinity data [Schauer et al., 1997], clearly showing the inflow of Atlantic water in two branches, the Fram Strait branch and the Barents Sea branch. High CFC and tritium concen‐trations extended down to 1300 m over the Laptev continental slope, indicating strong inflow of the Barents Sea branch between Franz Josef Land and Severnaya Zemlya. The apparent ages of water in the Fram Strait branch were estimated to be about 2 years north of the Barents Sea and 6 years at the eastern end of the Nansen Basin, which corresponds to an apparent mean current speed of about 1 cm s−1. The age of the core of the Barents Sea branch was also estimated to be about 6 years over the Laptev slope region and to increase by 0.5 years as it flowed through this region. A lower limit for the inflow of newly formed Barents Sea Branch Water was estimated to be 0.5 Sv, and an overall transport for the sum of Fram Strait branch plus Barents Sea branch flow of 4 Sv was estimated from this aging. In the deep water there was clear evidence for the inflow of Norwegian Sea Deep Water through Fram Strait, but there appeared to be no significant input of shelf‐derived water from the Santa Anna Trough. If there was any shelf‐derived input to Eurasian Basin Bottom Water, it entered at a deeper depth than was sampled on the slope sections in the Laptev Sea or its flow is intermittent and was not occurring during the ARK IX/4 expedition.
Diagnosing vertical mixing in a two‐layer exchange flow
Authors: Pawlowicz Rich , Farmer David M.
Published: February 2004

Most classification schemes and analyses of estuarine and exchange flows use only salinity as a tracer. Temperatures are generally ignored. However, a proper understanding of the effects of surface heating can explain observed seaward changes in the slope of temperature‐salinity correlations. A theory is proposed relating changes in temperature and salinity with transport and mixing parameters in a two‐layer exchange flow. Results show that along‐channel changes in the slope of T‐S correlations are virtually independent of vertical mixing but are directly related to horizontal layer transport. Changes in the layer salinities can be related to various ratios of horizontal and vertical transports. Combining these two features of the theory permits a diagnostic determination of Lagrangian transport and mixing from standard hydrographic observations of layer temperature and salinity and an estimate of the surface heat input. The theory is applied to observations made through the spring/neap tidal cycle of mixing in Haro Strait, British Columbia.
Climate‐induced variations in productivity and planktonic ecosystem structure from the Younger Dryas to Holocene in the Cariaco Basin, Venezuela
Authors: Werne Josef P. , Hollander David J. , Lyons Timothy W. , Peterson Larry C.
Published: February 2004

A high‐resolution molecular organic geochemical study of sediments in the anoxic Cariaco Basin indicates significant changes in primary productivity and planktonic community structure associated with the transition from the Younger Dryas to the Holocene. Variations in climate conditions over the past 12 14C kyr have induced large‐scale changes in upwelling intensity, which directly affected levels of primary productivity as reflected in accumulation rates of bulk productivity proxies. Concentrations and accumulation rates of sterol and alkenone biomarkers have been used to identify how productivity changes affected the structure of the planktonic ecosystem. A shift in the dominant primary producer from diatoms (Younger Dryas) to coccolithophores (Holocene) is identified. If productivity and ecosystem variations like those identified in the tropical upwelling zone of the Cariaco Basin region, occur throughout the tropical oceans, they have the potential to affect global climate through perturbations in the biogeochemical cycle of carbon.
Diffusion in one‐dimensional multifractal porous media
Authors: Lovejoy S. , Schertzer D. , Silas P.
Published: February 2004

We examine the scaling properties of one‐dimensional random walks on media with multifractal diffusivities, which is a simple model for transport in scaling porous media. We find both theoretically and numerically that the anomalous scaling exponent of the walk is dw=2 + K(− 1) where K(− 1) is the scaling exponent of the reciprocal spatially averaged (“dressed”) resistance to diffusion. Since K(− 1) > 0, the walk is subdiffusive; the walkers are effectively trapped in a hierarchy of barriers. The trapping is dominated by contributions from a specific order of singularity associated with a phase transition between anomalous and normal diffusion. We discuss the implications for transport in porous media.
A process‐based model for methane emission predictions from flooded rice paddies
Authors: van Bodegom P. M. , Wassmann R. , Metra‐Corton T. M.
Published: February 2004

Estimation and prediction of methane emission from flooded rice paddies is impaired by the large spatial and temporal variability in methane emissions and by the dynamic nonlinear relations between processes underlying methane emissions. This paper describes a process‐based model on methane emission prediction from flooded rice paddies that can be used for extrapolation. The model is divided into two compartments; rhizosphere, which is a function of root length density, and bulk soil. The production of carbon substrates drives methane emission and originates from soil organic matter mineralization, organic fertilizer decomposition, in both compartments, and root exudation and root decay, in the rhizosphere compartment only. It is assumed that the methanogens are completely outcompeted for acetate by nitrate and iron reducers but that competition takes place with sulfate reducers. Produced methane is transported to the root surface in the rhizosphere or the soil‐water interface in the bulk soil. Transport time coefficients are different for the two compartments. Part of the methane is oxidized, a constant fraction of produced methane in the bulk soil, whereas the oxidation fraction varies according to root activity dynamics in the rhizosphere. The remaining methane is emitted to the atmosphere. The model was validated with independent field measurements of methane emissions at sites in the Philippines, China, and Indonesia with only few generally available site‐specific input parameters. The model properly predicts methane emission dynamics and total seasonal methane emission for the sites in different seasons and under different inorganic and organic fertilizer conditions. A sensitivity analysis on model assumptions showed that the assumptions made in this model are reasonable and that the division into two compartments was necessary to obtain good results with this model. The combination of proper prediction and the necessity of few input parameters allow model application at regional and global scales.
Cold season CH4 and CO2 emission from boreal peat bogs (West Siberia): Winter fluxes and thaw activation dynamics
Authors: Panikov N. S. , Dedysh S. N.
Published: February 2004

The conventional chamber technique was used to measure CH4 and CO2emission to the atmosphere from snow‐covered ombrotrophic bogs (57°N, 82°E, Plotnikovo, West Siberia). The average ± standard deviation values for CH4 and CO2fluxes in mid‐February were found to be equal mg m−2 d−15.0 ± 3.7 and 69±52, respectively. The contribution of cold season to annual methane fluxes varied from 3.5 to 11% depending on the calculation method and was similar to that found in Alaska and northern Minnesota. The vertical profiles of gases in snow were linear implying the applicability of the simple diffusion equation under steady state conditions. The diffusion reduction factor due to porous resistance and tortuousity of snowpack was 0.18 and 0.29 for methane and carbon dioxide, respectively. Thus snow forms only a passive cap which controls the gas concentration at the snow‐soil interface, while gas flux into the atmosphere is controlled by gas production in the soil. The fresh samples of frozen peat soil incubated under laboratory conditions at constant temperature −16°C displayed very slow, but steady respiration varied from 0.05 to 0.2 mg CO2−C d−1 dm−3depending on peat sampling depth. Although this activity was 200‐300 times lower than soil respiration in summertime, it was enough to support the observed in situ winter CO2 emission. The thaw and subsequent peat incubation at 15°C accelerated gas formation up to 2–5 mg CO2‐C and 1.2 mg CH4‐C h−1 dm−3of peat after 3–4 days of incubation followed by a decline by 1 order of magnitude and approaching a new steady state level. Although the mechanism of freeze‐thaw activation needs further clarification, it was nevertheless possible to simulate the observed activation dynamics by a mathematical model which accounts for the burst of microbial growth on nutrients released into soil from frost‐damaged cells.
Cloud‐active particles over the central Arctic Ocean
Authors: Bigg E. Keith , Leck Caroline
Published: February 2004

Concentrations of cloud condensation (CCN) and ice forming nuclei (IFN) were measured throughout an expedition by icebreaker around the central Arctic Ocean including the North Pole from July 15 to September 23, 1996. Daily median CCN concentrations at 0.25% supersaturation were typically in the range 15 to 50 cm−3, but concentrations varied by 3 orders of magnitude over the expedition and commonly by an order of magnitude within a day. They were highest near the ice edge and fell by almost an order of magnitude in the first 36 hours of transport from the open sea into the pack ice region. For longer transport times they increased again indicating a local source, suggested to be drops injected into the air by bubbles bursting on open leads. Median concentrations of IFN ranged from 18 m−3 just inside the pack ice at the beginning of the expedition to 1 m−3 at the end. The differences with transport time from the ice edge were less marked than for CCN. Comparison of CCN measurements with simultaneously measured number size distributions showed that the median concentration active at a given supersaturation was only 71% of the number expected if all the particles had been composed of pure ammonium sulfate. Transmission electron microscope observations of individual particles suggested an evolution of many CCN from nonvolatile, nonhygroscopic particles <50 nm by acquisition of the oxidation products of dimethyl sulfide. Cloud processing added further mass. The largest primary source within the pack ice region was deduced to be film drops from bursting bubbles yielding liquid particles with a high organic content and surfactant properties. A relationship between CCN number and sulfur mass is derived which extends previous results to lower CCN numbers and indicates a greater sensitivity to change in sulfate mass than at lower latitudes. Bacteria and probable submicron fragments of marine organisms were identified in the samples and suggested to be the source of IFN.
The MVACS Surface Stereo Imager on Mars Polar Lander
Authors: Smith P. H. , Reynolds R. , Weinberg J. , Friedman T. , Lemmon M. T. , Tanner R. , Reid R. J. , Marcialis R. L. , Bos B. J. , Oquest C. , Keller H. U. , Markiewicz W. J. , Kramm R. , Gliem F. , Rueffer P.
Published: February 2004

The Surface Stereo Imager (SSI), a stereoscopic, multispectral camera on the Mars Polar Lander, is described in terms of its capabilities for studying the Martian polar environment. The camera's two eyes, separated by 15.0 cm, provide the camera with range‐finding ability. Each eye illuminates half of a single CCD detector with a field of view of 13.8° high by 14.3° wide and has 12 selectable filters between 440 and 1000 nm. The ƒ/18 optics have a large depth of field, and no focusing mechanism is required; a mechanical shutter is avoided by using the frame transfer capability of the 528×512 CCD. The resolving power of the camera, 0.975 mrad/pixel, is the same as the Imager for Mars Pathfinder camera, of which it is nearly an exact copy. Specially designed targets are positioned on the Lander; they provide information on the magnetic properties of windblown dust, and radiometric standards for calibration. Several experiments beyond the requisite color panorama are described in detail: contour mapping of the local terrain, multispectral imaging of interesting features (possibly with ice or frost in shaded spots) to study local mineralogy, and atmospheric imaging to constrain the properties of the haze and clouds. Eight low‐transmission filters are included for imaging the Sun directly at multiple wavelengths to give SSI the ability to measure dust opacity and potentially the water vapor content. This paper is intended to document the functionality and calibration of the SSI as flown on the failed lander.
Photometric properties of the lunar surface derived from Clementine observations
Authors: Kreslavsky M. A. , Shkuratov Yu. G. , Velikodsky Yu. I. , Kaydash V. G. , Stankevich D. G. , Pieters C. M.
Published: February 2004

Photometric properties of the lunar surface in visual and near‐infrared light were studied using raw images obtained with UVVIS camera during the Clementine mission. The investigation focused on several specific regions on the lunar surface, each of which was observed by Clementine at a variety of different illumination and viewing geometries. Through these observations, the dependence of the surface brightness on the observation/illumination geometry was studied. It was shown that the disk component of this dependence, that is, the variations of brightness at constant phase angle, is different for different mare areas. The color of the lunar surface also changes with changing of the observation/illumination geometry, even if under constant phase angle. The Reiner Gamma formation displays unusual photometric properties. They are consistent with the surface being smoother than the typical mare regolith surface. The UVVIS images taken at the smallest phase angles were used to study the opposition spike, that is, the sharp increase of the surface brightness near the opposition. Steepness of the phase dependence of brightness varies over a wide range for different sites.