A precise measurement of the two -photon exchange effect

The two-photon exchange phenomenon is believed to be responsible for the discrepancy observed between the ratio of proton electric and magnetic form factors, measured by the Rosenbluth and polarization transfer methods. This disagreement is about a factor of three at Q 2 of 5.6 GeV2. The precise knowledge of the proton form factors is of critical importance in understanding the structure of this nucleon. The theoretical models that estimate the size of the two-photon exchange (TPE) radiative correction are poorly constrained. This factor was found to be directly measurable by taking the ratio of the electron-proton and positron-proton elastic scattering cross sections, as the TPE effect changes sign with respect to the charge of the incident particle. A test run of a modified beamline has been conducted with the CEBAF Large Acceptance Spectrometer (CLAS) at Thomas Jefferson National Accelerator Facility. This test run demonstrated the feasibility of producing a mixed electron/positron beam of good quality. Extensive simulations performed prior to the run were used to reduce the background rate that limits the production luminosity. A 3.3 GeV primary electron beam was used that resulted in an average secondary lepton beam of 1 GeV. As a result, the elastic scattering data of both lepton types were obtained at scattering angles up to 40 degrees for Q2 up to 1.5 GeV2. The cross section ratio displayed an &epsis; dependence that was Q2 dependent at smaller Q2 limits. The magnitude of the average ratio as a function of &epsis; was consistent with the previous measurements, and the elastic (Blunden) model to within the experimental uncertainties. Ultimately, higher luminosity is needed to extend the data range to lower &epsis; where the TPE effect is predicted to be largest.

A Review of the Effects of Altered Hydrology and Salinity on Vertebrate Fauna and Their Habitats in Northeastern Florida Bay

Estuarine productivity is highly dependent on the freshwater sources of the estuary. In Florida Bay, Taylor Slough was historically the main source of fresh water. Beginning in about 1960, and culminating with the completion of the South Dade Conveyance System in 1984, water management practice began to change the quantity and distribution of flow from Taylor Slough into Northeastern Florida Bay. These practices altered salinity and hydrologic parameters that had measurable negative impacts on vertebrate fauna and their habitats. Here, I review those impacts from published and unpublished literature and anecdotal observations. Almost all vertebrates covered in this review have shown some form of population decline since 1984; most of the studies implicate declines in food resources as the main stressor on their populations. My conclusion is that the diversion of fresh water resulted in an ecological cascade starting with hydrologic stresses on primary then secondary producers culminating in population declines at the top of the food web.

Socio-ecological vulnerability to climate change in South Florida

Awareness of extreme high tide flooding in coastal communities has been increasing in recent years, reflecting growing concern over accelerated sea level rise. As a low-lying, urban coastal community with high value real estate, Miami often tops the rankings of cities worldwide in terms of vulnerability to sea level rise. Understanding perceptions of these changes and how communities are dealing with the impacts reveals much about vulnerability to climate change and the challenges of adaptation. ^ This empirical study uses an innovative mixed-methods approach that combines ethnographic observations of high tide flooding, qualitative interviews and analysis of tidal data to reveal coping strategies used by residents and businesses as well as perceptions of sea level rise and climate change, and to assess the relationship between measurable sea levels and perceptions of flooding. I conduct a case study of Miami Beach's storm water master planning process which included sea level rise projections, one of the first in the nation to do so, that reveals the different and sometimes competing logics of planners, public officials, activists, residents and business interests with regards to climate change adaptation. By taking a deeply contextual account of hazards and adaptation efforts in a local area I demonstrate how this approach can be effective at shedding light on some of the challenges posed by anthropogenic climate change and accelerated rates of sea level rise. ^ The findings highlight challenges for infrastructure planning in low-lying, urban coastal areas, and for individual risk assessment in the context of rapidly evolving discourse about the threat of sea level rise. Recognition of the trade-offs and limits of incremental adaptation strategies point to transformative approaches, at the same time highlighting equity concerns in adaptation governance and planning. This new impact assessment method contributes to the integration of social and physical science approaches to climate change, resulting in improved understanding of socio-ecological vulnerability to environmental change.^

Avaliação do impacto socioambiental de indústrias têxteis no rio Jundiaí - Macaíba/RN/Brasil

The contamination of aquatic environments is a phenomenon that dates back the origins of human civilizations and was amplified by the advent of industrial processes. The Jundiaí river , Macaíba's main water source, suffering discharge of effluents from various industries. The study work´s in two fronts, the environmental perception front was conducted through semistructured interviews whose textile effluent was appointed by the population as the main problem in the river. It was observed that nearly all respondents had concerns about the environment. In addition, there is an inclusion of individuals as the cause of the problem, because a significant part recognizes that its activities may cause damage to the environment and people's health. In other front, the experimental monitoring of water quality was conducted through ecotoxicological tests and physiochemical analysis that proposed to assess Pomacea lineata .Mysidopsis juniae isolated effect of textile effluent and its influence on the river compared with the limits established by Brazilian law. Although the physio-chemical analysis shows is inconclusive about the participation of the textile effluent in environmental contamination of the river, the ecotoxicological tests have shown to blunt the signal that the effluent may present a risk to aquatic organisms and consequently to human health. Thus, an interdisciplinary way it was possible to study the cause of the environmental problem identified by the population in the realization phase and measurable effect on water quality analysis in the river by means of the tests mentioned.

Serviço de nuvem pública e sua relação com os arranjos de governança de TI e o alinhamento estratégico

Increasingly, the Information Technology (IT) has been used to sustain the business strategies, causing increased its relevance. Therefore IT governance is seen as one of the priorities of organizations at the time. The search for strategic alignment between business and IT is debated as a factor for business success, but even with that importance, usually the main business managers are reluctant to take responsibility for decisions involving IT, mainly due to the complexity of your infrastructure. Since cloud computing is being seen as an element capable of assisting in the implementation of organizational strategies, because their characteristics enable greater efficiency and agility in IT, and is considered as a new computing paradigm. The main objective of the analyze the relationship between IT governance arrangements and strategic alignment with the infrastructure as a service (IaaS) of public cloud computing. Therefore, an exploratory, descriptive and inferential was developed, with approach to the problem of quantitatively research, with descriptive survey method and cross section. An electronic questionnaire that was applied to the ISACA chapters Associates of São Paulo and the Distrito Federal, totaling 164 respondents was used. The instrument used based on the theories of Weill and Ross (2006) for array of IT governance arrangement; Henderson and Venkatraman (1993) and Luftman (2000), for maturity of the strategic alignment model; and NIST (2011 b), ITGI (2007) and CSA (2010) for infrastructure maturity as a service (IaaS) public in its essential characteristics. As regards the main results, this research proved that with public IaaS decision-making structures have changed, with a greater participation of senior executives in all five key IT decisions (IT governance arrangement array) including more technical decisions as architecture and IT infrastructure. With increased participation of senior executives the decrease was also observed in the share of IT specialists, characterizing the decision process with the duopoly archetype (shared decision). With regard to strategic alignment, it was observed that it changes with cloud computing, and organizations with public IaaS, a maturity of strategic alignment with statistically significant and greater difference when compared to organizations without IaaS. The maturity of public IaaS is at the intermediate level (level 3 - "defined process"), with the elasticity and measurement achieved level 4 - "managed and measurable" It was also possible to infer in organizations with public IaaS, there are positive correlations between the key decisions and the maturity of IaaS, especially at the beginning, architecture and infrastructure, and the archetypes involving senior executives and IT specialists. In the correlation between the maturity and mature strategic alignment of public IaaS therefore the higher the strategic alignment, the greater the maturity of the public IaaS and vice versa.

Orações relativas no português brasileiro em perspectiva histórica

In this study, we focus on the relativization strategies, in diachronic corpus of Brazilian Portuguese (BP). Generally speaking, we aim to investigate the use of the relative in a historical perspective on BP, focusing on semantic-cognitive and discursive-pragmatic motivations involved and the correlation with the discursive traditions. The theoretical perspective underlying our study is the North-American Functional Linguistics, inspired by Talmy Givón, Sandra Thompson, Paul Hopper, Joan Bybee, Elizabeth Traugott, Mario Martelotta, Angelica Furtado da Cunha, among others, combined with contributions of Discursive Traditions, based on authors such as Kabatek, Koch and Oesterreicher. As for the methodology, our research is eminently qualitative, in the sense that it seeks to elucidate semantic-cognitive and discursive-pragmatic motivations related to the use of relativization strategies in BP; and it has quantitative support, with respect to measurable data aspect and characterization of the object of study and its frequency of use. For this investigation, we use the corpora of the project Para a História do Português Brasileiro (PHPB), more specifically, the particular, official, reader and redactor letters written between the eighteenth and twentieth centuries, from four states: Minas Gerais, Paraná, Pernambuco and Rio de Janeiro. The results of this research reveal the variation in relativization strategies, in view of the increase in the relativa cortadora (prepositional chopping strategy) percentage in the corpus of this investigation, even though the occurrence of this strategy is more restricted to private letters. In addition, we found factors of cognitive nature such as reduction in cognitive cost and economy related to the occurrence of that relative strategy, principally in private letters; aspects such as the need for expressiveness and clearness related to the use, even if infrequent, of the relativa copiadora (resumptive strategy), especially in official letters; and factors of communicative order such as the public sphere of circulation of the sample letters, as in the redactor and reader letters, and the gap between the parties most directly involved in the use of the standard relative of our sample.

SLA-Based Guidelines for Database Transitioning

Component-based Software Engineering (CBSE) and Service-Oriented Architecture (SOA) became popular ways to develop software over the last years. During the life-cycle of a software system, several components and services can be developed, evolved and replaced. In production environments, the replacement of core components, such as databases, is often a risky and delicate operation, where several factors and stakeholders should be considered. Service Level Agreement (SLA), according to ITILv3’s official glossary, is “an agreement between an IT service provider and a customer. The agreement consists on a set of measurable constraints that a service provider must guarantee to its customers.”. In practical terms, SLA is a document that a service provider delivers to its consumers with minimum quality of service (QoS) metrics.This work is intended to assesses and improve the use of SLAs to guide the transitioning process of databases on production environments. In particular, in this work we propose SLA-Based Guidelines/Process to support migrations from a relational database management system (RDBMS) to a NoSQL one. Our study is validated by case studies.

(Table 1) Physical oceanography during Lance cruise LA99/2 in the marginal ice zone of the Barents Sea

Zooplankton was studied on eight stations in the marginal ice zone (MIZ) of the Barents Sea, in May 1999, along two transects across the ice edge. On each station, physical background measurements and zooplankton samples were taken every 6 h over a 24 h period at five discrete depth intervals. Cluster analysis revealed separation of open water stations from all ice stations as well as high similarity level among replicates belonging to particular station. Based on five replicates per station, analysis of variance (ANOVA) confirmed significant differences (P < 0.05) in abundances of the main mesozooplankton taxa among stations. Relations between the zooplankton community and environmental parameters were established using redundancy analysis (CANOCO). In total, 55% of mesozooplankton variability within studied area was explained by eight variables with significant conditional effects: depth stratum, fluorescence, temperature, salinity, bottom depth, latitude, bloom situation, and ice concentration. GLM models supported supposition about clear and negative relationship between concentration of Oithona similis, and overall mesozooplankton diversity The analyses showed a dynamic relationship between mesozooplankton distribution and hydrological conditions on short-term scale. Furthermore, our study demonstrated that variability in the physical environment of dynamic MIZ of the Barents Sea has measurable effect on the Arctic pelagic ecosystem.

Prioritizing tropical habitats for long-distance migratory songbirds: an assessment of habitat quality at a stopover site in Colombia

Long-distance migratory birds are declining globally and migration has been identified as the primary source of mortality in this group. Despite this, our lack of knowledge of habitat use and quality at stopovers, i.e., sites where the energy for migration is accumulated, remains a barrier to designing appropriate conservation measures, especially in tropical regions. There is therefore an urgent need to assess stopover habitat quality and concurrently identify efficient and cost-effective methods for doing so. Given that fuel deposition rates directly influence stopover duration, departure fuel load, and subsequent speed of migration, they are expected to provide a direct measure of habitat quality and have the advantage of being measurable through body-mass changes. Here, we examined seven potential indicators of quality, including body-mass change, for two ecologically distinct Neotropical migratory landbirds on stopover in shade-coffee plantations and tropical humid premontane forest during spring migration in Colombia: (1) rate of body-mass change; (2) foraging rate; (3) recapture rate; (4) density; (5) flock size; (6) age and sex ratios; and (7) body-mass distribution. We found higher rates of mass change in premontane forest than in shade-coffee in Tennessee Warbler Oreothlypis peregrina, a difference that was mirrored in higher densities and body masses in forest. In Gray-cheeked Thrush Catharus minimus, a lack of recaptures in shade-coffee and higher densities in forest, also suggested that forest provided superior fueling conditions. For a reliable assessment of habitat quality, we therefore recommend using a suite of indicators, taking into account each species’ ecology and methodological considerations. Our results also imply that birds stopping over in lower quality habitats may spend a longer time migrating and require more stopovers, potentially leading to important carryover effects on reproductive fitness. Evaluating habitat quality is therefore imperative prior to defining the conservation value of newly identified stopover regions.

Probing Tissue Microstructure Using Susceptibility Contrast Magnetic Resonance Imaging

Magnetic resonance imaging is a research and clinical tool that has been applied in a wide variety of sciences. One area of magnetic resonance imaging that has exhibited terrific promise and growth in the past decade is magnetic susceptibility imaging. Imaging tissue susceptibility provides insight into the microstructural organization and chemical properties of biological tissues, but this image contrast is not well understood. The purpose of this work is to develop effective approaches to image, assess, and model the mechanisms that generate both isotropic and anisotropic magnetic susceptibility contrast in biological tissues, including myocardium and central nervous system white matter.

This document contains the first report of MRI-measured susceptibility anisotropy in myocardium. Intact mouse heart specimens were scanned using MRI at 9.4 T to ascertain both the magnetic susceptibility and myofiber orientation of the tissue. The susceptibility anisotropy of myocardium was observed and measured by relating the apparent tissue susceptibility as a function of the myofiber angle with respect to the applied magnetic field. A multi-filament model of myocardial tissue revealed that the diamagnetically anisotropy α-helix peptide bonds in myofilament proteins are capable of producing bulk susceptibility anisotropy on a scale measurable by MRI, and are potentially the chief sources of the experimentally observed anisotropy.

The growing use of paramagnetic contrast agents in magnetic susceptibility imaging motivated a series of investigations regarding the effect of these exogenous agents on susceptibility imaging in the brain, heart, and kidney. In each of these organs, gadolinium increases susceptibility contrast and anisotropy, though the enhancements depend on the tissue type, compartmentalization of contrast agent, and complex multi-pool relaxation. In the brain, the introduction of paramagnetic contrast agents actually makes white matter tissue regions appear more diamagnetic relative to the reference susceptibility. Gadolinium-enhanced MRI yields tensor-valued susceptibility images with eigenvectors that more accurately reflect the underlying tissue orientation.

Despite the boost gadolinium provides, tensor-valued susceptibility image reconstruction is prone to image artifacts. A novel algorithm was developed to mitigate these artifacts by incorporating orientation-dependent tissue relaxation information into susceptibility tensor estimation. The technique was verified using a numerical phantom simulation, and improves susceptibility-based tractography in the brain, kidney, and heart. This work represents the first successful application of susceptibility-based tractography to a whole, intact heart.

The knowledge and tools developed throughout the course of this research were then applied to studying mouse models of Alzheimer’s disease in vivo, and studying hypertrophic human myocardium specimens ex vivo. Though a preliminary study using contrast-enhanced quantitative susceptibility mapping has revealed diamagnetic amyloid plaques associated with Alzheimer’s disease in the mouse brain ex vivo, non-contrast susceptibility imaging was unable to precisely identify these plaques in vivo. Susceptibility tensor imaging of human myocardium specimens at 9.4 T shows that susceptibility anisotropy is larger and mean susceptibility is more diamagnetic in hypertrophic tissue than in normal tissue. These findings support the hypothesis that myofilament proteins are a source of susceptibility contrast and anisotropy in myocardium. This collection of preclinical studies provides new tools and context for analyzing tissue structure, chemistry, and health in a variety of organs throughout the body.

Can a Broader Education Narrow the Gap? Evidence on Non-Academic Features of Schooling

Empirical studies of education programs and systems, by nature, rely upon use of student outcomes that are measurable. Often, these come in the form of test scores. However, in light of growing evidence about the long-run importance of other student skills and behaviors, the time has come for a broader approach to evaluating education. This dissertation undertakes experimental, quasi-experimental, and descriptive analyses to examine social, behavioral, and health-related mechanisms of the educational process. My overarching research question is simply, which inside- and outside-the-classroom features of schools and educational interventions are most beneficial to students in the long term? Furthermore, how can we apply this evidence toward informing policy that could effectively reduce stark social, educational, and economic inequalities?

The first study of three assesses mechanisms by which the Fast Track project, a randomized intervention in the early 1990s for high-risk children in four communities (Durham, NC; Nashville, TN; rural PA; and Seattle, WA), reduced delinquency, arrests, and health and mental health service utilization in adolescence through young adulthood (ages 12-20). A decomposition of treatment effects indicates that about a third of Fast Track’s impact on later crime outcomes can be accounted for by improvements in social and self-regulation skills during childhood (ages 6-11), such as prosocial behavior, emotion regulation and problem solving. These skills proved less valuable for the prevention of mental and physical health problems.

The second study contributes new evidence on how non-instructional investments – such as increased spending on school social workers, guidance counselors, and health services – affect multiple aspects of student performance and well-being. Merging several administrative data sources spanning the 1996-2013 school years in North Carolina, I use an instrumental variables approach to estimate the extent to which local expenditure shifts affect students’ academic and behavioral outcomes. My findings indicate that exogenous increases in spending on non-instructional services not only reduce student absenteeism and disciplinary problems (important predictors of long-term outcomes) but also significantly raise student achievement, in similar magnitude to corresponding increases in instructional spending. Furthermore, subgroup analyses suggest that investments in student support personnel such as social workers, health services, and guidance counselors, in schools with concentrated low-income student populations could go a long way toward closing socioeconomic achievement gaps.

The third study examines individual pathways that lead to high school graduation or dropout. It employs a variety of machine learning techniques, including decision trees, random forests with bagging and boosting, and support vector machines, to predict student dropout using longitudinal administrative data from North Carolina. I consider a large set of predictor measures from grades three through eight including academic achievement, behavioral indicators, and background characteristics. My findings indicate that the most important predictors include eighth grade absences, math scores, and age-for-grade as well as early reading scores. Support vector classification (with a high cost parameter and low gamma parameter) predicts high school dropout with the highest overall validity in the testing dataset at 90.1 percent followed by decision trees with boosting and interaction terms at 89.5 percent.

Non-Pharmacological Approaches for Pain Management in Sickle Cell Disease: Development of a Mindfulness-Based Intervention

Background: Sickle Cell Disease (SCD) is a genetic hematological disorder that affects more than 7 million people globally (NHLBI, 2009). It is estimated that 50% of adults with SCD experience pain on most days, with 1/3 experiencing chronic pain daily (Smith et al., 2008). Persons with SCD also experience higher levels of pain catastrophizing (feelings of helplessness, pain rumination and magnification) than other chronic pain conditions, which is associated with increases in pain intensity, pain behavior, analgesic consumption, frequency and duration of hospital visits, and with reduced daily activities (Sullivan, Bishop, & Pivik, 1995; Keefe et al., 2000; Gil et al., 1992 & 1993). Therefore effective interventions are needed that can successfully be used manage pain and pain-related outcomes (e.g., pain catastrophizing) in persons with SCD. A review of the literature demonstrated limited information regarding the feasibility and efficacy of non-pharmacological approaches for pain in persons with SCD, finding an average effect size of .33 on pain reduction across measurable non-pharmacological studies. Second, a prospective study on persons with SCD that received care for a vaso-occlusive crisis (VOC; N = 95) found: (1) high levels of patient reported depression (29%) and anxiety (34%), and (2) that unemployment was significantly associated with increased frequency of acute care encounters and hospital admissions per person. Research suggests that one promising category of non-pharmacological interventions for managing both physical and affective components of pain are Mindfulness-based Interventions (MBIs; Thompson et al., 2010; Cox et al., 2013). The primary goal of this dissertation was thus to develop and test the feasibility, acceptability, and efficacy of a telephonic MBI for pain catastrophizing in persons with SCD and chronic pain.

Methods: First, a telephonic MBI was developed through an informal process that involved iterative feedback from patients, clinical experts in SCD and pain management, social workers, psychologists, and mindfulness clinicians. Through this process, relevant topics and skills were selected to adapt in each MBI session. Second, a pilot randomized controlled trial was conducted to test the feasibility, acceptability, and efficacy of the telephonic MBI for pain catastrophizing in persons with SCD and chronic pain. Acceptability and feasibility were determined by assessment of recruitment, attrition, dropout, and refusal rates (including refusal reasons), along with semi-structured interviews with nine randomly selected patients at the end of study. Participants completed assessments at baseline, Week 1, 3, and 6 to assess efficacy of the intervention on decreasing pain catastrophizing and other pain-related outcomes.

Results: A telephonic MBI is feasible and acceptable for persons with SCD and chronic pain. Seventy-eight patients with SCD and chronic pain were approached, and 76% (N = 60) were enrolled and randomized. The MBI attendance rate, approximately 57% of participants completing at least four mindfulness sessions, was deemed acceptable, and participants that received the telephonic MBI described it as acceptable, easy to access, and consume in post-intervention interviews. The amount of missing data was undesirable (MBI condition, 40%; control condition, 25%), but fell within the range of expected missing outcome data for a RCT with multiple follow-up assessments. Efficacy of the MBI on pain catastrophizing could not be determined due to small sample size and degree of missing data, but trajectory analyses conducted for the MBI condition only trended in the right direction and pain catastrophizing approached statistically significance.

Conclusion: Overall results showed that at telephonic group-based MBI is acceptable and feasible for persons with SCD and chronic pain. Though the study was not able to determine treatment efficacy nor powered to detect a statistically significant difference between conditions, participants (1) described the intervention as acceptable, and (2) the observed effect sizes for the MBI condition demonstrated large effects of the MBI on pain catastrophizing, mental health, and physical health. Replication of this MBI study with a larger sample size, active control group, and additional assessments at the end of each week (e.g., Week 1 through Week 6) is needed to determine treatment efficacy. Many lessons were learned that will guide the development of future studies including which MBI strategies were most helpful, methods to encourage continued participation, and how to improve data capture.

Design and Synthesis of 4-N-Alkanoyl and 4-N-Alkyl Gemcitabine Analogues Suitable for Positron Emission Tomography

Gemcitabine is a highly potent chemotherapeutic nucleoside agent used in the treatment of several cancers and solid tumors. However, it is therapeutically limitated because of toxicity to normal cells and its rapid intracellular deamination by cytidine deaminase into the inactive uracil derivative. Modification at the 4-(N) position of gemcitabine's exocyclic amine to an -amide functionality is a well reported prodrug strategy which has been that confers a resistance to intracellular deamination while also altering pharmacokinetics of the parent drug. Coupling of gemcitabine to carboxylic acids with varying terminal moieties afforded the 4-N-alkanoylgemcitabines whereas reaction of 4-N-tosylgemcitabine with the corresponding alkyl amines gave the 4-N-alkylgemcitabines. The 4-N-alkanoyl and 4-N-alkyl gemcitabine analogues with a terminal hydroxyl group on the 4-N-alkanoyl or 4-N-alkyl chain were efficiently fluorinated either with diethylaminosulfur trifluoride or under conditions that are compatible with the synthetic protocols for 18F labeling, such as displacement of the corresponding mesylate with KF/Kryptofix 2.2.2. The 4-N-alkanoylgemcitabine analogues displayed potent cytostatic activities against murine and human tumor cell lines with 50% inhibitory concentration (IC50) values in the range of low nM, whereas cytotoxicity of the 4-N-alkylgemcitabine derivatives were in the low to modest µM range. The cytostatic activity of the 4-N-alkanoylgemcitabines was reduced by several orders of magnitude in the 2'-deoxycytidine kinase (dCK)-deficient CEM/dCK- cell line while the 4-N-alkylgemcitabines were only lowered by 2-5 times. None of the 4-N-modified gemcitabines were found to be substrates for cytosolic dCK, however all were found to inhibit DNA synthesis. As such, the 4-N-alkanoyl gemcitabine derivatives likely need to be converted to gemcitabine prior to achieving their significant cytostatic potential, whereas the 4-N-alkylgemcitabines reach their modest activity without "measurable" conversion to gemcitabine. Thus, the 4-N-alkylgemcitabines provide valuable insight on the metabolism of 4-N-modified gemcitabine prodrugs.

Composition of noble gases in sediments and metasediments

Solar-type helium (He) and neon (Ne) in the Earth's mantle were suggested to be the result of solarwind loaded extraterrestrial dust that accumulated in deep-sea sediments and was subducted into the Earth's mantle. To obtain additional constraints on this hypothesis, we analysed He, Ne and argon (Ar) in high pressure-low temperature metamorphic rocks representing equivalents of former pelagic clays and cherts from Andros (Cyclades, Greece) and Laytonville (California, USA). While the metasediments contain significant amounts of 4He, 21Ne and 40Ar due to U, Th and K decay, no solar-type primordial noble gases were observed. Most of these were obviously lost during metamorphism preceding 30 km subduction depth. We also analysed magnetic fines from two Pacific ODP drillcore samples, which contain solar-type He and Ne dominated by solar energetic particles (SEP). The existing noble gas isotope data of deep-sea floor magnetic fines and interplanetary dust particles demonstrate that a considerable fraction of the extraterrestrial dust reaching the Earth has lost solar wind (SW) ions implanted at low energies, leading to a preferential occurrence of deeply implanted SEP He and Ne, fractionated He/Ne ratios and measurable traces of spallogenic isotopes. This effect is most probably caused by larger particles, as these suffer more severe atmospheric entry heating and surface ablation. Only sufficiently fine-grained dust may retain the original unfractionated solar composition that is characteristic for the Earth's mantle He and Ne. Hence, in addition to the problem of metamorphic loss of solar noble gases during subduction, the isotopic and elemental fractionation during atmospheric entry heating is a further restriction for possible subduction hypotheses.

Benthos activity, abundance and biomass in surface sediments off Morocco, Northwest Africa

Macro- and meiobenthic abundance and biomass as well as metabolic activity (respiration, ETS activity) have been studied along a transect ranging from 130 to 3000 m water depth off northern Morocco (35° N) during "Meteor" cruise No. 53 (1980). The distribution of chloroplastic pigment concentration (chlorophyll a, pheophytins) in the sediment has been investigated as a measure of sedimented primary organic matter. High chloroplastic pigment concentrations were found on the shelf and around the shelf break, but values declined rapidly between 200 and 600 m depth. Below 1200 m pigment concentrations remained at a relatively uniform low level. Macrobenthic abundance and biomass (wet weight) decreased with increasing water depth and with distance from the shore. Significant changes occurred between the shelf and upper slope and below 2000 m depth. Meiobenthic abundance and biomass (ash free dry weight) followed the same general pattern, but changes were found below 400 and 800 m depth. In the depth range of 1200 to 3000 m values differ only slightly. Meiofauna abundance and biomass show a good correlation with the sedimentary chloroplastic pigment concentrations. Respiratory activity of sediment cores, measured by a shipboard technique at ambient temperatures, decreased with water depth and shows a good correlation with the pigment concentrations. ETS activity was highest on the shelf and decreased with water depth, with significant changes between 200 and 400 m, and below 1200 m depth, respectively. Activity was generally highest in the top 5 cm of the sediment and was measurable, at all stations, down to 15 cm sediment depth. Shelf and upper slope stations exhibited a vertical distribution pattern of ETS activity in the sediment column, different from that of deeper stations. The importance of biological activity measurements as an estimate of productivity is discussed. To prove the thesis that differences in benthic abundance, biomass and activity reflect differences in pelagic surface primary production, in the case of the NW-African coast caused by different upwelling intensities, the values from 35° N were compared with data from 21° N (permanent upwelling activity) and 17° N (ca. 9 months upwelling per year). On the shelf and upper slope (< 500 m) hydrographical conditions (currents, internal waves) influence the deposition of organic matter and cause a biomass minimum between 200 and 400 m depth in some regions. But, in general, macrobenthic abundance and biomass increases with enhanced upwelling activity and reaches a maximum in the area off Cape Blanc (21° N). On the shelf and in the shelf break region meiofauna densities are higher at 35° N in comparison to 21° N; but in contrast to the decreasing meiofauna abundance with increasing water depth at 35° N, an abundance maximum between 400 and 1200 m depth is formed in the Cape Blanc region; this maximum coincides with the maximum of sedimentary chloroplastic pigment equivalents. The comparison of ETS activities between 35° N and 21° N shows on the shelf activity at 21° N is up to 14 times higher and on the slope 4-9 times higher, which demonstrates that benthic activity responds to the surface productivity regime.