Upwelling regime off the Cabo Frio region in Brazil and impact on acoustic propagation

This work introduces a description of the complex upwelling regime off the Cabo Frio region in Brazil and shows that ocean modeling, based on the feature-oriented regional modeling system (FORMS) technique, can produce reliable predictions of sound speed fields for the corresponding shallow water environment. This work also shows, through the development of simulations, that the upwelling regime can be responsible for the creation of shadow coastal zones, in which the detection probability is too low for an acoustic source to be detected. The development of the FORMS technique and its validation with real data, for the particular region of coastal upwelling off Cabo Frio, reveals the possibility of a sustainable and reliable forecast system for the corresponding (variable in space and time) underwater acoustic environment. (C) 2018 Acoustical Society of AmericaBrazilian Navy; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)/Ciencias Sem Fronteiras [400671/2014-0]; European Union [OAEX-230855]; Fundacao de Amparo a Pesquisa (FAPERJ) [E-26/110.327/2012

On the Effects of Increased Vertical Mixing on the Arctic Ocean and Sea Ice

Against the backdrop of Arctic sea ice decline, vertical mixing in the interior Arctic Ocean will most likely change, but it is still unclear how the Arctic Ocean and sea ice will respond. In this paper, a sea ice‐ocean model with a simple parameterization for interior background mixing is used to investigate the Arctic Ocean and sea ice response to a scenario of increased vertical mixing. It is found that more vertical mixing reduces sea ice thickness all year round and decreases summertime sea ice concentration. More vertical mixing leads to a cooling of the Arctic halocline layer and Atlantic Water layer below. The increased vertical mixing speeds up vertical heat and salinity exchange, brings the underlying warm and saline water into the surface layer, and contributes to the sea ice decline. Vertical salinity gradient of the Arctic halocline layer reduces together with a much fresher Atlantic Water layer, and more volume of saline water enters the deep ocean below the Atlantic Water layer. As a result, the reduced Arctic Ocean stratification leads to an adjustment of the circulation pattern. Cyclonic circulation anomalies occur in the surface layer shallower than 20m depth and in the interior ocean deeper than 700m depth, while anticyclonic circulation anomalies occur between these depths. Our study suggests that the extra heat and salinity exchange induced by more vertical mixing will have a noticeable impact on the upper ocean structure, ocean circulation, and sea ice in a changing Arctic Ocean

The cost-effectiveness of long-term antiviral therapy in the management of HBeAg-positive and HBeAg-negative chronic hepatitis B in Singapore

The purpose of this study was the economic evaluation of short-duration treatments of chronic hepatitis B (CHB) and longer duration antiviral treatment for up to 5 years. Two 10-health state Markov models were developed for hepatitis B e antigen (HBeAg)-positive and HBeAg-negative CHB patients respectively. The perspective of this economic evaluation was the Singapore healthcare system and CHB patient. The models followed cohorts of HBeAg-positive and HBeAg-negative CHB patients, respectively, over a period of 40 years, by which time the majority of the cohorts would have died if left untreated. Costs and benefits were discounted at 5% per annum. Annual rates of disease progression and the magnitude of treatment effects were obtained from the literature, with a focus on data obtained in Asian patients and meeting the criteria for therapy as described in internationally recognized management guidelines. Short-course therapy with α-interferon, or 1-year treatment with pegylated interferon α-2a, lamivudine or adefovir had limited impact on disease progression. In contrast, treatment of CHB with antiviral therapy for 5 years substantially decreased the rate of disease progression. Treatment with lamivudine for 1-year is highly cost-effective compared with no treatment of CHB but has limited effect on reducing the rate of disease progression. Compared with 1-year treatment with lamivudine, sequential antiviral therapies for up to 5 years (i.e. lamivudine plus adefovir on emergence of lamivudine resistance or adefovir plus lamivudine on emergence of adefovir resistance) are highly cost-effective by international standards. These conclusions are robust to uncertainties in model inputs and are consistent with the findings of other recently published studies

Biogeochemical modelling of dissolved oxygen in a changing ocean

Secular decreases in dissolved oxygen concentration have been observed within the tropical oxygen minimum zones (OMZs) and at mid- to high latitudes over the last approximately 50 years. Earth system model projections indicate that a reduction in the oxygen inventory of the global ocean, termed ocean deoxygenation, is a likely consequence of on-going anthropogenic warming. Current models are, however, unable to consistently reproduce the observed trends and variability of recent decades, particularly within the established tropical OMZs. Here, we conduct a series of targeted hindcast model simulations using a state-of-the-art global ocean biogeochemistry model in order to explore and review biases in model distributions of oceanic oxygen. We show that the largest magnitude of uncertainty is entrained into ocean oxygen response patterns due to model parametrization of pCO2-sensitive C : N ratios in carbon fixation and imposed atmospheric forcing data. Inclusion of a pCO2-sensitive C : N ratio drives historical oxygen depletion within the ocean interior due to increased organic carbon export and subsequent remineralization. Atmospheric forcing is shown to influence simulated interannual variability in ocean oxygen, particularly due to differences in imposed variability of wind stress and heat fluxes

Spin‐up of UK Earth System Model 1 (UKESM1) for CMIP6

For simulations intended to study the influence of anthropogenic forcing on climate, temporal stability of the Earth's natural heat, freshwater and biogeochemical budgets is critical. Achieving such coupled model equilibration is scientifically and computationally challenging. We describe the protocol used to spin‐up the UK Earth system model (UKESM1) with respect to pre‐industrial forcing for use in the 6th Coupled Model Intercomparison Project (CMIP6). Due to the high computational cost of UKESM1's atmospheric model, especially when running with interactive full chemistry and aerosols, spin‐up primarily used parallel configurations using only ocean/land components. For the ocean, the resulting spin‐up permitted the carbon and heat contents of the ocean's full volume to approach equilibrium over ~5000 years. On land, a spin‐up of ~1000 years brought UKESM1's dynamic vegetation and soil carbon reservoirs towards near‐equilibrium. The end‐states of these parallel ocean‐ and land‐only phases then initialised a multi‐centennial period of spin‐up with the full Earth system model, prior to this simulation continuing as the UKESM1 CMIP6 pre‐industrial control (piControl). The realism of the fully‐coupled spin‐up was assessed for a range of ocean and land properties, as was the degree of equilibration for key variables. Lessons drawn include the importance of consistent interface physics across ocean‐ and land‐only models and the coupled (parent) model, the extreme simulation duration required to approach equilibration targets, and the occurrence of significant regional land carbon drifts despite global‐scale equilibration. Overall, the UKESM1 spin‐up underscores the expense involved and argues in favour of future development of more efficient spin‐up techniques

Immunogenicity of Wild Type and Mutant Hepatitis B Surface Antigen Virus-like Particles (VLPs) in Mice with Pre-Existing Immunity against the Wild Type Vector

Virus-like particles (VLPs), composed of the small hepatitis B virus surface antigen (HBsAgS), are the antigenic components of the hepatitis B virus (HBV) vaccine and represent the backbones for a chimeric anti-malaria vaccine and various vaccine candidates. Biological vectors have to face pre-existing anti-vector immune responses due to previous immune exposure. Vector recognition after natural infections or vaccinations can result in unwarranted outcomes, with compromising effects on clinical outcomes. In order to evaluate the impact of a pre-existing anti-HBsAgS immune response, we developed mutant VLPs composed of subunits with reduced HBsAgS-specific antigenicity. The insertion of a Plasmodium falciparum circumsporozoite protein (CSP)-derived epitope as a read-out allowed the assessment of wild type (wt) and mutant VLPs in the context of a pre-existing immune response. Mutant and wt VLP platforms with a CSP-epitope insert are immunogenic and have the ability to generate anti-CSP antibody responses in both naïve BALB/c mice and mice with a pre-existing anti-HBsAgS immune response, but with superior anti-CSP responses in mice with a pre-existing immunity. The data indicate that previous HBsAgS exposure facilitates enhanced antibody responses against foreign epitopes delivered by the HBsAgS platform, and, in this context, the state of immune sensitization alters the outcome of subsequent vaccinations

Assessment of HBV flare in a randomized clinical trial in HIV/HBV coinfected subjects initiating HBV-active antiretroviral therapy in Thailand

BACKGROUND: Hepatic Flare (HF) after initiation of highly active antiretroviral therapy (HAART) in HIV-HBV coinfected individuals is well recognized but prospective data on predictors and subsequent outcome are limited. METHODS: The Tenofovir in HIV-HBV coinfection study was a randomized clinical trial of HBV-active HAART including lamivudine and/or tenofovir in antiretroviral naïve HIV-HBV individuals in Thailand. RESULTS: Early HF (EHF) was defined as ALT > 5 × ULN during the first 12 weeks. EHF was observed in 8 (22%) of individuals at a median of 56 days. 6/8 EHF cases were asymptomatic and resolved with HAART continuation, however one subject with underlying cirrhosis died following rapid hepatic decompensation. EHF was significantly associated with higher baseline ALT (79 IU/L vs 36 IU/L non-EHF, p = 0.008) and HBV DNA (9.9 log10 c/ml vs 8.4 log10 c/ml non EHF, p = 0.009), and subsequent serological change. HBeAg loss occurred in 75% of EHF cases versus 22% in non-EHF (p = 0.04), and HBsAg loss in 25% of EHF cases versus 4% of non-EHF (p = 0.053). CONCLUSION: EHF after HBV active HAART initiation was frequently observed in this population. Timing of EHF, association with elevated ALT and HBV DNA and high rate of seroconversion are all consistent with immune restoration as the likely underlying process. CLINICAL TRIAL NUMBER: NCT00192595

Silicon isotopes in an EMIC's ocean: Sensitivity to runoff, iron supply, and climate

The isotopic composition of Si in biogenic silica (BSi), such as opal buried in the oceans' sediments, has changed over time. Paleorecords suggest that the isotopic composition, described in terms of δ30Si, was generally much lower during glacial times than today. There is consensus that this variability is attributable to differing environmental conditions at the respective time of BSi production and sedimentation. The detailed links between environmental conditions and the isotopic composition of BSi in the sediments remain, however, poorly constrained. In this study, we explore the effects of a suite of offset boundary conditions during the Last Glacial Maximum (LGM) on the isotopic composition of BSi archived in sediments in an Earth System Model of intermediate complexity (EMIC). Our model results suggest that a change in the isotopic composition of Si supply to the glacial ocean is sufficient to explain the observed overall low(er) glacial δ30Si in BSi. All other processes explored trigger model responses of either wrong sign or magnitude or are inconsistent with a recent estimate of bottom water oxygenation in the Atlantic Sector of the Southern Ocean. Caveats, mainly associated with generic uncertainties in today's pelagic biogeochemical modules, remain.publishedVersio

The Lombard effect in singing humpback whales : source levels increase as ambient ocean noise levels increase

Funding: Office of Naval Research (Code 322, Marine Mammals and Biology), Commander, U.S. Pacific Fleet (Code N465JR), and the Naval Facilities Engineering Command Living Marine Resources Program.Many animals increase the intensity of their vocalizations in increased noise. This response is known as the Lombard effect. While some previous studies about cetaceans report a 1 dB increase in the source level (SL) for every dB increase in the background noise level (NL), more recent data have not supported this compensation ability. The purpose of this study was to calculate the SLs of humpback whale song units recorded off Hawaii and test for a relationship between these SLs and background NLs. Opportunistic recordings during 2012-2017 were used to detect and track 524 humpback whale encounters comprised of 83 974 units on the U.S. Navy's Pacific Missile Range Facility hydrophones. Received levels were added to their estimated transmission losses to calculate SLs. Humpback whale song units had a median SL of 173 dB re 1 μ Pa at 1 m, and SLs increased by 0.53 dB/1 dB increase in background NLs. These changes occurred in real time on hourly and daily time scales. Increases in ambient noise could reduce male humpback whale communication space in the important breeding area off Hawaii. Since these vocalization changes may be dependent on location or behavioral state, more work is needed at other locations and with other species.Publisher PDFPeer reviewe