Phytoplankton and Hydrography of the Kennebec Estuary, Maine, USA

The biomass, abundance and species composition of phytoplankton in the Kennebec estuary, Maine, USA, were investigated in relation to hydrography and Light regime during 7 seasonal survey cruises. The salinity distribution ranged from 32 at the mouth to between 0 and 5 at the head, depending on the magnitude of freshwater discharge at the time of each survey. Maximum Vertical salinity and temperature gradients were observed at the mouth. while local tidal mixing, combined with the freshwater flow, produced a well-mixed water column at the head of the estuary. The middle portion of the estuary was stratified on flooding and ebbing tides, but was vertically well mixed at high and low tides. Phytoplankton biomass was lowest in winter (chlorophyll a approximate to 1 mu g l(-1)) and highest in summer (up to 10 mu g l(-1)) The phytoplankton species assemblages at the seaward and the riverine ends of the estuary were made up of taxa with corresponding salinity preferences. Both cell numbers and biomass (chlorophyll a) exhibited a bimodal distribution along the length of the estuary in the warmer months, with the middle portions of the estuary having depressed phytoplankton standing stocks compared with the seaward and landward ends. This bimodal distribution was related to Light limitation and nutrient regeneration in the middle portion of the estuary and to the production of and advective contributions of phytoplankton from both the freshwater and seaward ends

How “Dependent” Are We? A Spatiotemporal Analysis of the Young and the Older Adult Populations in the US

The shifting of a country’s age structure has far-reaching socioeconomic and policy implications. In the US, the changing age structure at the sub-national level has received little research attention. To address this gap, we examine age dependencies across states in the US between 1990 and 2010 using decennial census data. We find that dependency changes have been gradual with a distinct graying of states during this period. Within this overarching trend, the sources of states’ dependencies follow complicated trajectories without clear spatiotemporal patterns. Nevertheless, changes in states’ old-age dependency contributions to respective total dependencies are geographically clustered and the inverse link between old-age dependency and economic productivity across states may be waning. Additional research is justified to further unravel these trends in old-age dependencies. The analytic framework that we apply can be adopted to conduct sub-national age dependency studies for other countries, including some European nations with relatively large proportions of older adults and many developing nations with an increasing share of older adults

Changing Age Segregation in the US: 1990 to 2010

Age segregation adversely impacts health and wellbeing. Prior studies, although limited, report increasing age segregation of the US. However, these studies are dated, do not comprehensively examine the spatiotemporal patterns and the correlates of intergenerational segregation, or suffer from methodological limitations. To address these gaps, we assess the spatiotemporal patterns of age segregation between 1990 and 2010 using census-tract data to compute the dissimilarity index (D) at the national, state, and county levels. Results contradict previous findings providing robust evidence of decreasing age segregation for most parts of the country and across geographical levels. We also examine factors explaining adult-older adult segregation across counties between 1990 and 2010. Higher levels of rurality indicated lower levels of adult-older adult segregation but this association diminished over time. Percent of older adults and percent of population in group quarters were inversely related to adult-older adult segregation, contrary to results from previous decades

No More “Social Distancing” But Practice Physical Separation

Though not a new term, “social distancing” exploded onto the global stage as an expression to publicize the only means currently available to control the transmission of COVID-19. This term is increasingly being adopted and translated into the vernacular to inform and guide public behavior in most, if not all, countries around the world. However, any effective global response requires direct and unambiguous communication and sharing of ideas across communities with different cultural backgrounds as well as between researchers and responders across the disciplinary spectrum. Unfortunately, social distancing is a misnomer. The current use of social distancing – separating ourselves physically to avoid infection – is not consistent with what the term actually means. Consequently, as a diktat, social distancing is not self-explanatory, conceptually ambiguous, practically misleading, and intellectually misplaced. To highlight these problems, we present arguments from multiple perspectives, calling governments, public health officials, and the media to abandon the use of social distancing, replacing it with more intuitively accurate and meaningful terms. Such a move would ensure clear consistent messaging that is critical to retain public trust especially during global public health crises

Age-Race-Ethnicity Segregation in the United States: Where do Minority Older Adults Stand?

A recent study shows that among the three age groups of youth, adult and older adult, youth-older adult has the highest age segregation while youth-adult has the lowest. Similar to many previous age segregation studies, racial-ethnic differences, an important population axis in segregation studies, were not considered. Prior studies are also limited to using two-group measures, failing to compare multiple groups together. We explore the complexity in measuring intersectional segregation focusing on the two axes of age and race-ethnicity and propose a conditional approach to measure age segregation by racial-ethnic groups, and racial-ethnic segregation by age groups. Using this approach, we empirically study the 2010 age-race-ethnic segregation at the county and state levels in the United States, using census tracts as the basic units. Both the two and multigroup dissimilarity indices were used. Results show that the racial-ethnic axis had been a stronger force in segregation than the age axis. Results also show disparities of racial-ethnic segregation across age groups with the highest levels present among older adults and in urban counties. For all three age groups, segregation levels involving Natives and Asians tend to be higher than those without them. In contrast, age segregation was the highest between youths and older adults, and the levels varied across racial-ethnic groups with Natives at the highest levels. Although age segregation was significantly different between urban and rural counties, higher segregation in urban areas were mostly involving Whites as opposed to higher segregation in rural counties involving minority racial groups. Studying age segregation should not be colour blinded, as nonwhite older adults in rural counties were more likely to experience higher levels of age segregation than other groups

How do UK-based foreign exchange dealers think their market operates?

This paper summarises the results of a survey of UK based foreign exchange dealers conducted in 1998. It addresses topics in three main areas: The microeconomic operation of the foreign exchange market; the beliefs of dealers regarding the importance, or otherwise, of macroeconomic fundamental factors in affecting exchange rates; microstructure factors in FX. We find that heterogeneity of traders’ beliefs is evident from the results but that it is not possible to explain such disagreements in terms of institutional detail, rank or trading technique (e.g. technical analysts versus fundamentalists). As expected, nonfundamental factors are thought to dominate short horizon changes in exchange rates, but fundamentals are deemed important over much shorter horizons that the mainstream empirical literature would suggest. Finally, market ‘norms’ and behavioural phenomena are very strong in the FX market and appear to be key determinants of the bid-ask spread

Grain Physics and Rosseland Mean Opacities

Tables of mean opacities are often used to compute the transfer of radiation in a variety of astrophysical simulations from stellar evolution models to proto-planetary disks. Often tables, such as Ferguson et al. (2005), are computed with a predetermined set of physical assumptions that may or may not be valid for a specific application. This paper explores the effects of several assumptions of grain physics on the Rosseland mean opacity in an oxygen rich environment. We find that changing the distribution of grain sizes, either the power-law exponent or the shape of the distribution, has a marginal effect on the total mean opacity. We also explore the difference in the mean opacity between solid homogenous grains and grains that are porous or conglomorations of several species. Changing the amount of grain opacity included in the mean by assuming a grain-to-gas ratio significantly affects the mean opacity, but in a predictable way.Comment: 19 pages, 6 figures, accepted for publication in Ap

Cortical Circuitry Associated With Reflex Cardiovascular Control in Humans: Does the Cortical Autonomic Network Speak or Listen During Cardiovascular Arousal

Beginning with clinical evidence of fatal cardiac arrhythmias in response to severe stress, in epileptic patients, and following stroke, the role of the cerebral cortex in autonomic control of the cardiovascular system has gained both academic and clinical interest. Studies in anesthetized rodents have exposed the role of several forebrain regions involved in cardiovascular control. The introduction of functional neuroimaging techniques has enabled investigations into the conscious human brain to illuminate the temporal and spatial activation patterns of cortical regions that are involved with cardiovascular control through the autonomic nervous system. This symposia report emphasizes the research performed by the authors to understand the functional organization of the human forebrain in cardiovascular control during physical stressors of baroreceptor unloading and handgrip exercise. The studies have exposed important associations between activation patterns of the insula cortex, dorsal anterior cingulate, and the medial prefrontal cortex and cardiovascular adjustments to physical stressors. Furthermore, these studies provide functional anatomic evidence that sensory signals arising from baroreceptors and skeletal muscle are represented within the insula cortex and the medial prefrontal cortex, in addition to the sensory cortex. Thus, the cortical pathways subserving reflex cardiovascular control integrate viscerosensory inputs with outgoing traffic that modulates the autonomic nervous system. © 2012 Wiley Periodicals, Inc.