A wideband acoustic method for direct assessment of bubble-mediated methane flux

The bubble-mediated transport and eventual fate of methane escaping from the seafloor is of great interest to researchers in many fields. Acoustic systems are frequently used to study gas seep sites, as they provide broad synoptic observations of processes in the water column. However, the visualization and characterization of individual gas bubbles needed for quantitative studies has routinely required the use of optical sensors which offer a limited field of view and require extended amounts of time for deployment and data collection. In this paper, we present an innovative method for studying individual bubbles and estimating gas flux using a calibrated wideband split-beam echosounder. The extended bandwidth (16 – 26 kHz) affords vertical ranges resolution of approximately 7.5 cm, allowing for the differentiation of individual bubbles in acoustic data. Split-aperture processing provides phase-angle data used to compensate for transducer beam-pattern effects and to precisely locate bubbles in the transducer field of view. The target strength of individual bubbles is measured and compared to an analytical scattering model to estimate bubble radius, and bubbles are tracked through the water column to estimate rise velocity. The resulting range of bubble radii (0.68-8.40 mm in radius) agrees with those found in other investigations with optical measurements, and the rise velocities trends are consistent with published models. Together, the observations of bubble radius and rise velocity offer a measure of gas flux, requiring nothing more than vessel transit over a seep site, bypassing the need to deploy time-consuming and expensive optical systems

Experiential Learning Process: Exploring Teaching and Learning of Strategic Management Framework Through The Winter Survival Exercise

This article examines an attempt to introduce experiential learning methods in a business strategy course. In organizational behavior and industrial/organizational psychology, experiential teaching methods have been so widely adopted that some authors have suggested dropping the distinction between experiential and traditional teaching. Although intuitively appealing, experiential methods have not yet become popular among professors teaching strategy to traditional-age undergraduate students. It seems that heavy reliance on case-based teaching has resulted in a lack of emphasis on experiential learning tools for strategic management. In this study, the Winter Survival Exercise was used to introduce, concisely and effectively, the strategic management framework to 97 traditional-age undergraduate strategic management students in three different sections over three semesters. Statistical analysis supported the efficacy of this teaching method. Implications for teaching business strategy using experiential methods as a complement to rather than a substitute for traditional case studies are discussed

Potential links between Baltic Sea submarine terraces and groundwater seeping

Submarine groundwater discharge (SGD) influences ocean chemistry, circulation, and the spreading of nutrients and pollutants; it also shapes sea floor morphology. In the Baltic Sea, SGD was linked to the development of terraces and semicircular depressions mapped in an area of the southern Stockholm archipelago, Sweden, in the 1990s. We mapped additional parts of the Stockholm archipelago, areas in Blekinge, southern Sweden, and southern Finland using high-resolution multibeam sonars and sub-bottom profilers to investigate if the sea floor morphological features discovered in the 1990s are widespread and to further address the hypothesis linking their formation to SGD. Sediment coring and sea floor photography conducted with a remotely operated vehicle (ROV) and divers add additional information to the geophysical mapping results. We find that terraces, with general bathymetric expressions of about 1 m and lateral extents of sometimes > 100 m, are widespread in the surveyed areas of the Baltic Sea and are consistently formed in glacial clay. Semicircular depressions, however, are only found in a limited part of a surveyed area east of the island of Asko, southern Stockholm archipelago. While submarine terraces can be produced by several processes, we interpret our results to be in support of the basic hypothesis of terrace formation initially proposed in the 1990s; i.e. groundwater flows through siltier, more permeable layers in glacial clay to discharge at the sea floor, leading to the formation of a sharp terrace when the clay layers above seepage zones are undermined enough to collapse. By linking the terraces to a specific geologic setting, our study further refines the formation hypothesis and thereby forms the foundation for a future assessment of SGD in the Baltic Sea that may use marine geological mapping as a starting point. We propose that SGD through the submarine sea floor terraces is plausible and could be intermittent and linked to periods of higher groundwater levels, implying that to quantify the contribution of freshwater to the Baltic Sea through this potential mechanism, more complex hydrogeological studies are required.Peer reviewe

Fecal Incontinence in US Adults: Epidemiology and Risk Factors

The study aims were to estimate the prevalence of different types and frequencies of fecal incontinence (FI), describe demographic factors, and identify risk factors

A conserved myotubularin-related phosphatase regulates autophagy by maintaining autophagic flux

Macroautophagy (autophagy) targets cytoplasmic cargoes to the lysosome for degradation. Like all vesicle trafficking, autophagy relies on phosphoinositide identity, concentration, and localization to execute multiple steps in this catabolic process. Here, we screen for phosphoinositide phosphatases that influence autophagy in Drosophila and identify CG3530. CG3530 is homologous to the human MTMR6 subfamily of myotubularin-related 3-phosphatases, and therefore, we named it dMtmr6. dMtmr6, which is required for development and viability in Drosophila, functions as a regulator of autophagic flux in multiple Drosophila cell types. The MTMR6 family member MTMR8 has a similar function in autophagy of higher animal cells. Decreased dMtmr6 and MTMR8 function results in autophagic vesicle accumulation and influences endolysosomal homeostasis

Parasite fate and involvement of infected cells in the induction of CD4+ and CD8+ T cell responses to Toxoplasma gondii

During infection with the intracellular parasite Toxoplasma gondii, the presentation of parasite-derived antigens to CD4+ and CD8+ T cells is essential for long-term resistance to this pathogen. Fundamental questions remain regarding the roles of phagocytosis and active invasion in the events that lead to the processing and presentation of parasite antigens. To understand the most proximal events in this process, an attenuated non-replicating strain of T. gondii (the cpsII strain) was combined with a cytometry-based approach to distinguish active invasion from phagocytic uptake. In vivo studies revealed that T. gondii disproportionately infected dendritic cells and macrophages, and that infected dendritic cells and macrophages displayed an activated phenotype characterized by enhanced levels of CD86 compared to cells that had phagocytosed the parasite, thus suggesting a role for these cells in priming naïve T cells. Indeed, dendritic cells were required for optimal CD4+ and CD8+ T cell responses, and the phagocytosis of heat-killed or invasion-blocked parasites was not sufficient to induce T cell responses. Rather, the selective transfer of cpsII-infected dendritic cells or macrophages (but not those that had phagocytosed the parasite) to naïve mice potently induced CD4+ and CD8+ T cell responses, and conferred protection against challenge with virulent T. gondii. Collectively, these results point toward a critical role for actively infected host cells in initiating T. gondii-specific CD4+ and CD8+ T cell responses

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference

The layer that did not swim away : Broadband acoustic discrimination and characterization of ocean stratification

Ocean stratification plays a critical role in many oceanographic processes. The magnitude of mixing between stable water masses is regulated, in part, by the intensity of stratification. As such, stratification modulates the vertical transport of heat and many important dissolved constituents in the water column, influencing such processes as ocean ventilation, and ocean heat and carbon uptake. As human induced climate change alters oceanic stratification a thorough understanding of its distribution and variability is critical in the study of the world’s oceans. However, traditional methods are limited in terms of spatial context and rapid, near-synoptic observational methods, such as those provided by active acoustic systems, are needed to fill in the gaps. Broadband acoustic water column data have already been used to observe ocean structure and commercial systems are becoming increasingly available. However, broadband acoustic methods for characterizing oceanic stratification are not well developed, limiting of applicability of broadband data to the study, quantification, and monitor ocean stratification as the world warms. This thesis aims to develop quantitative acoustic methods for characterization of ocean stratification using active broadband acoustic systems. This work leveraged the high range resolution and signal to noise ratios, as well as the frequency-modulated scattering response of broadband acoustic systems. Broadband acoustic methods were developed and established through 1) the analysis of field data from different ocean basins and 2) the development and application of acoustic scattering models. This work will provide the means to better understand the physical mechanisms responsible for acoustic backscattering from stratification, working towards rapid, remote, high-resolution measurements of ocean stratification through acoustic inversion, in order to monitor and quantify changes in ocean structure