Light limitation of primary production in high latitude reservoirs

International audienceTo explore the effects of vertical mixing on the primary production in a northern reservoir, a Lagrangian particle dispersion model was coupled to a 1-D reservoir model where the vertical mixing was calculated using a k-? model together with an empirically-based deep-water eddy viscosity. The primary production of each phytoplankton cell is assumed to be a function of the ambient light and not to be nutrient limited. The photoadaption follows first-order kinetics where the photoadaptive variables, a, b, and Pm, describe the coefficients of the photosynthesis-irradiance curve. The model is applied to the northern reservoir Akkajaure, which is strongly regulated with a mean and maximum depth of 30 m and 100 m respectively. Based on the release of 1000 particles (plankton), the model calculated the mean primary production of each plankton, during four different growing seasons. Vertical mixing has a substantial effect on the vertical distribution of phytoplankton and, thus, on the primary production in a reservoir. It was found that primary production was greater in a cold summer with weak stratification than in a warm summer when the reservoir was more stratified

Weathering rates and origin of inorganic carbon as influenced by river regulation in the boreal sub-arctic region of Sweden

International audienceMajor environmental stressors of boreal and sub-arctic rivers are hydrological changes and global warming and both factors will significantly influence the future evolution of the river chemistry in high latitudes. We tested the hypothesis whether lower concentrations of dissolved constituents observed in regulated rivers come along with lower weathering rates, though specific discharge as a major force for physical erosion and weathering is often higher in regulated river systems. In this study the river chemistry, weathering rates and related carbon dioxide consumption in two large watersheds in the sub arctic region of Sweden, one regulated river (Lule River) and one unregulated river (Kalix River), was investigated. Weathering rates of silicates in the two watersheds are shown to be different; the silicate weathering rate in Kalix River catchment is almost 30% higher than in the Lule River catchment. This is most likely a result of constructing large reservoirs in the former river valleys inundating the alluvial deposits and thus decreasing soil/water contact resulting in lower weathering rates. Furthermore, the difference observed in weathering rates between lowland regions and headwaters suggests that weathering in sub arctic boreal climates is controlled by the residence time for soil water rock interactions followed by lithology. The chemistry in the two rivers shows weathering of silicates as the origin for 68% of the inorganic carbon in the Lule River and 74% for Kalix River. The study clearly shows that river regulation significantly decreases alkalinity export to the sea because lower weathering rates gives less carbon dioxide ending up as DIC. By considering sources for inorganic carbon we here report that the inorganic carbon load that originates from respiration of organic matter in soils makes up of 30% and 35% of the total C export for the watersheds of the Kalix River and Lule River, respectively. Therefore, both the inorganic (i.e. the origin of carbon in DIC) and organic carbon load carbon must be considered when studying climate changes on the organic carbon load since effects from increased degradation of organic matter may lead to more weathering (higher production of DIC)

Transformation Optics for Plasmonics

A new strategy to control the flow of surface plasmon polaritons at metallic surfaces is presented. It is based on the application of the concept of Transformation Optics to devise the optical parameters of the dielectric medium placed on top of the metal surface. We describe the general methodology for the design of Transformation-Optical devices for surface plasmons and analyze, for proof-of-principle purposes, three representative examples with different functionalities: a beam shifter, a cylindrical cloak and a ground-plane cloak.Comment: 15 pages, 3 figure

The Goldberger-Treiman Discrepancy in SU(3)

The Goldberger-Treiman discrepancy in SU(3) is analyzed in the framework of heavy baryon chiral perturbation theory (HBChPT). It is shown that the discrepancy at leading order is entirely given by counterterms from the order p^3 Lagrangian, and that the first subleading corrections are suppressed by two powers in the HBChPT expansion. These subleading corrections include meson-loop contributions as well as counterterms from the order p^5 Lagrangian. Some one-loop contributions are calculated and found to be small. Using the three discrepancies (pi-N-N, K-N-Lambda and K-N-Sigma) which can be extracted from existing experimental data, we find that the HBChPT calculation favors the smaller g(pi-N-N) values obtained in recent partial wave analyses.Comment: 16 pages,2 figures, revte

Generalized h-index for Disclosing Latent Facts in Citation Networks

What is the value of a scientist and its impact upon the scientific thinking? How can we measure the prestige of a journal or of a conference? The evaluation of the scientific work of a scientist and the estimation of the quality of a journal or conference has long attracted significant interest, due to the benefits from obtaining an unbiased and fair criterion. Although it appears to be simple, defining a quality metric is not an easy task. To overcome the disadvantages of the present metrics used for ranking scientists and journals, J.E. Hirsch proposed a pioneering metric, the now famous h-index. In this article, we demonstrate several inefficiencies of this index and develop a pair of generalizations and effective variants of it to deal with scientist ranking and with publication forum ranking. The new citation indices are able to disclose trendsetters in scientific research, as well as researchers that constantly shape their field with their influential work, no matter how old they are. We exhibit the effectiveness and the benefits of the new indices to unfold the full potential of the h-index, with extensive experimental results obtained from DBLP, a widely known on-line digital library.Comment: 19 pages, 17 tables, 27 figure

Social interaction anxiety and personality traits predicting engagement in risky sexual behavior

2017 Summer.Includes bibliographical references.Social anxiety disorder is a prevalent psychiatric condition, especially among adolescents (American Psychiatric Association, 2013, p. 204). Individuals with social interaction anxiety, which pertains to interpersonal exchanges with others, ruminate on perceived failures in past interactions, withdraw from or avoid social encounters, and engage in coping behaviors in response to negative feelings (Clark & Wells, 1995; Hoffman, 2007; Kashdan, 2004; Leary, 2001). While the majority of individuals with social interaction anxiety avoid risky situations, a subset engages in risky behaviors, including more frequent sexual encounters and unprotected sex (Kashdan, Elhai, & Breen, 2008; Kashdan & Hoffman, 2008; Kashdan, McKnight, Richey, & Hoffman, 2009). The personality constructs sensation seeking, emotion dysregulation, and impulsivity predict engagement in risky sexual behavior and have been suggested in previous studies to explain the relation between social interaction anxiety and risky sexual behavior (Arnold, Fletcher, & Farrow, 2002; Gullette & Lyons, 2005, 2006; Hoyle, Fejfar, & Miller, 2000; Kalichman et al., 1994; Kashdan et al., 2008; Kashdan et al., 2009; Kashdan & Hoffman, 2008; Kashdan & McKnight, 2010; Parent & Newman, 1999). Therefore, the present study hypothesized that latent classes of social interaction anxiety and personality traits would be identified that distinguish engagement in risky sexual behaviors. Finite mixture modeling was used to discern latent heterogeneous classes of social interaction anxiety and facets of sensation seeking, emotion dysregulation, impulsivity, behavioral approach, and behavioral inhibition. Risky sexual behaviors were treated as auxiliary variables. Four classes were discerned: two low social interaction anxiety classes distinguished by facets of emotion dysregulation, positive urgency, and negative urgency (Low SIAS High Urgency and Low SIAS Low Urgency) and two high social interaction anxiety classes distinguished by positive urgency, negative urgency, risk seeking, and facets of emotion dysregulation (High SIAS High Urgency and High SIAS Low Urgency). Of importance to this study were the findings that the High SIAS High Urgency class was significantly more likely to engage in all identified risky sexual behaviors than the High SIAS Low Urgency class and that the High SIAS High Urgency class did not significantly differ from the Low SIAS High Urgency and Low SIAS Low Urgency classes in engagement in risky sexual behaviors. This study extends previous findings on the heterogeneity of social interaction anxiety by identifying the effects of social interaction anxiety and personality on engagement in risky sexual behaviors

Development and initial validation of the comprehensive HIV adherence with treatment scale

2021 Spring.Includes bibliographical references.HIV remains a significant public health concern despite decreasing rates of transmission in the U.S. (Centers for Disease Control and Prevention, 2020c). Contributing factors include low rates of treatment adherence (de Bruin et al., 2010) and high rates of comorbidities with other medical and mental health conditions (Bing et al., 2001; Gallant et al., 2017; Lerner et al., 2020). Antiretroviral therapy (ART) has significantly improved HIV health outcomes and reduced AIDS diagnoses and AIDS-related mortality (Crum et al., 2006; Glass et al., 2008; Ickovics & Meade, 2002; Paterson et al., 2000; Stone, 2001; World Health Organization, 2015). Because of ART's effectiveness, HIV is considered a chronic rather than terminal health condition for people adherent with treatment (Aberg, 2006; Swendeman, Ingram, & Rotheram- Borus, 2009). Treatment for HIV as a chronic health condition includes several pro-health behaviors in addition to ART adherence to support overall wellness. To support future research and treatment recommendations, the current study developed a measure of adherence with pro- health behavior and conducted an initial analysis of the measure's psychometric properties with a sample of 118 people living with HIV. Structural equation modeling explored relations among antecedents (personality, treatment self-efficacy, treatment information, and treatment motivation) and health outcomes of pro-health behaviors and ART adherence. Regularly assessing engagement in, as well as antecedents and outcomes of, treatment behaviors can enhance communication between providers and people living with HIV, reinforce HIV's status as a manageable chronic condition, and link people living with HIV to appropriate interventions

Determination of the pion-nucleon coupling constant and scattering lengths

We critically evaluate the isovector GMO sum rule for forward pion-nucleon scattering using the recent precision measurements of negatively charged pion-proton and pion-deuteron scattering lengths from pionic atoms. We deduce the charged-pion-nucleon coupling constant, with careful attention to systematic and statistical uncertainties. This determination gives, directly from data a pseudoscalar coupling constant of 14.11+-0.05(statistical)+-0.19(systematic) or a pseudovector one of 0.0783(11). This value is intermediate between that of indirect methods and the direct determination from backward neutron-proton differential scattering cross sections. We also use the pionic atom data to deduce the coherent symmetric and antisymmetric sums of the negatively charged pion-proton and pion-neutron scattering lengths with high precision. The symmetric sum gives 0.0012+-0.0002(statistical)+-0.0008 (systematic) and the antisymmetric one 0.0895+-0.0003(statistical)+-0.0013(systematic), both in units of inverse charged pion-mass. For the need of the present analysis, we improve the theoretical description of the pion-deuteron scattering length.Comment: 27 pages, 5 figures, submitted to Phys. Rev. C, few modifications and clarifications, no change in substance of the pape

The high-precision, charge-dependent Bonn nucleon-nucleon potential (CD-Bonn)

We present a charge-dependent nucleon-nucleon (NN) potential that fits the world proton-proton data below 350 MeV available in the year of 2000 with a chi^2 per datum of 1.01 for 2932 data and the corresponding neutron-proton data with chi^2/datum = 1.02 for 3058 data. This reproduction of the NN data is more accurate than by any phase-shift analysis and any other NN potential. The charge-dependence of the present potential (that has been dubbed `CD-Bonn') is based upon the predictions by the Bonn Full Model for charge-symmetry and charge-independence breaking in all partial waves with J <= 4. The potential is represented in terms of the covariant Feynman amplitudes for one-boson exchange which are nonlocal. Therefore, the off-shell behavior of the CD-Bonn potential differs in a characteristic and well-founded way from commonly used local potentials and leads to larger binding energies in nuclear few- and many-body systems, where underbinding is a persistent problem.Comment: 69 pages (RevTex) including 20 tables and 9 figures (ps files