The impact of population on community stratification structure

Status consistency was used as an aggregate measure to examine the effects of population size and change, postulated by Durkheim, on the overall community stratification structure. Communities of at least 25,000 persons in 1950 but were not the central city of an SMA in 1950 were used. Size and change did not impact the structure; the hypotheses were not supported. However, with a redefinition of a community population as that generally described as the labor force, size is related to the summary measure of community status, although population changes remains unrelated. In examining the diminishing amount of accumulated variance explained by the labor-force population variable, we ascertained that greater detail in the measurement of the status components within a community will be required. The research supports the continued examination of status consistency summary scores as a measurement tool for aggregates and the refinement of Durkheim\u27s suggestions

Differing requirements for flavonoids during the formation of lateral roots, nodules and root knot nematode galls in Medicago truncatula

In this study, we tested whether the organogenesis of symbiotic root nodules, lateral roots and root galls induced by parasitic root knot nematodes (Meloidogyne javanica) was regulated by the presence of flavonoids in the roots of Medicago truncatula. Flavonoids accumulate in all three types of root organ, and have been hypothesized previously to be required for secondary root organogenesis because of their potential role as auxin transport regulators. • Using RNA interference to silence the flavonoid biosynthetic pathway in M. truncatula, we generated transformed flavonoid-deficient hairy roots which were used to study flavonoid accumulation, cell division and organogenesis of nodules, lateral roots and root galls. • Flavonoid-deficient roots did not form nodules, as demonstrated previously, but showed altered root growth in response to rhizobia. By contrast, flavonoid-deficient roots showed no difference in the number of lateral roots and root galls. Galls on flavonoid-deficient roots formed normal giant cells, but were shorter, and were characterized by reduced numbers of dividing pericycle cells. • We rejected the hypothesis that flavonoids are required as general regulators of the organogenesis of secondary root organs, but flavonoids appear to be necessary for nodulation. Possible reasons for this difference in the requirement for flavonoids are discussed

Pattern and scale: evaluating generalities in crab distributions and marsh dynamics from small plots to a national scale

The generality of ecological patterns depends inextricably on the scale at which they are examined. We investigated patterns of crab distribution and the relationship between crabs and vegetation in salt marshes at multiple scales. By using consistent monitoring protocols across 15 U.S. National Estuarine Research Reserves, we were able to synthesize patterns from the scale of quadrats to the entire marsh landscape to regional and national scales. Some generalities emerged across marshes from our overall models, and these are useful for informing broad coastal management policy. We found that crab burrow distribution within a marsh could be predicted by marsh elevation, distance to creek and soil compressibility. While these physical factors also affected marsh vegetation cover, we did not find a strong or consistent overall effect of crabs at a broad scale in our multivariate model, though regressions conducted separately for each site revealed that crab burrows were negatively correlated with vegetation cover at 4 out of 15 sites. This contrasts with recent smaller-scale studies and meta-analyses synthesizing such studies that detected strong negative effects of crabs on marshes, likely because we sampled across the entire marsh landscape, while targeted studies are typically limited to low-lying areas near creeks, where crab burrow densities are highest. Our results suggest that sea-level rise generally poses a bigger threat to marshes than crabs, but there will likely be interactions between these physical and biological factors. Beyond these generalities across marshes, we detected some regional differences in crab community composition, richness, and abundance. However, we found striking differences among sites within regions, and within sites, in terms of crab abundance and relationships to marsh integrity. Although generalities are broadly useful, our findings indicate that local managers cannot rely on data from other nearby systems, but rather need local information for developing salt marsh management strategies

Meteorites on Mars observed with the Mars Exploration Rovers

Reduced weathering rates due to the lack of liquid water and significantly greater typical surface ages should result in a higher density of meteorites on the surface of Mars compared to Earth. Several meteorites were identified among the rocks investigated during Opportunity’s traverse across the sandy Meridiani plains. Heat Shield Rock is a IAB iron meteorite and has been officially recognized as ‘‘Meridiani Planum.’’ Barberton is olivine-rich and contains metallic Fe in the form of kamacite, suggesting a meteoritic origin. It is chemically most consistent with a mesosiderite silicate clast. Santa Catarina is a brecciated rock with a chemical and mineralogical composition similar to Barberton. Barberton, Santa Catarina, and cobbles adjacent to Santa Catarina may be part of a strewn field. Spirit observed two probable iron meteorites from its Winter Haven location in the Columbia Hills in Gusev Crater. Chondrites have not been identified to date, which may be a result of their lower strengths and probability to survive impact at current atmospheric pressures. Impact craters directly associated with Heat Shield Rock, Barberton, or Santa Catarina have not been observed, but such craters could have been erased by eolian-driven erosion.Additional co-authors: DW Ming, RV Morris, PA de Souza Jr, SW Squyres, C Weitz, AS Yen, J Zipfel, T Economo

Assessing tidal marsh resilience to sea-level rise at broad geographic scales with multi-metric indices

Tidal marshes and the ecosystem services they provide may be at risk from sea-level rise (SLR). Tidal marsh resilience to SLR can vary due to differences in local rates of SLR, geomorphology, sediment availability and other factors. Understanding differences in resilience is critical to inform coastal management and policy, but comparing resilience across marshes is hindered by a lack of simple, effective analysis tools. Quantitative, multi-metric indices are widely employed to inform management of benthic aquatic ecosystems, but not coastal wetlands. Here, we develop and apply tidal marsh resilience to sea-level rise (MARS) indices incorporating ten metrics that contribute to overall marsh resilience to SLR. We applied MARS indices to tidal marshes at 16 National Estuarine Research Reserves across the conterminous U.S. This assessment revealed moderate resilience overall, although nearly all marshes had some indication of risk. Pacific marshes were generally more resilient to SLR than Atlantic ones, with the least resilient marshes found in southern New England. We provide a calculation tool to facilitate application of the MARS indices to additional marshes. MARS index scores can inform the choice of the most appropriate coastal management strategy for a marsh: moderate scores call for actions to enhance resilience while low scores suggest investment may be better directed to adaptation strategies such as creating opportunities for marsh migration rather than attempting to save existing marshes. The MARS indices thus provide a powerful new approach to evaluate tidal marsh resilience and to inform development of adaptation strategies in the face of SLR

Selected Papers on Protoplanetary Disks

Three papers present studies of thermal balances, dynamics, and electromagnetic spectra of protoplanetary disks, which comprise gas and dust orbiting young stars. One paper addresses the reprocessing, in a disk, of photons that originate in the disk itself in addition to photons that originate in the stellar object at the center. The shape of the disk is found to strongly affect the redistribution of energy. Another of the three papers reviews an increase in the optical luminosity of the young star FU Orionis. The increase began in the year 1936 and similar increases have since been observed in other stars. The paper summarizes astronomical, meteoric, and theoretical evidence that these increases are caused by increases in mass fluxes through the inner portions of the protoplanetary disks of these stars. The remaining paper presents a mathematical-modeling study of the structures of protostellar accretion disks, with emphasis on limits on disk flaring. Among the conclusions reached in the study are that (1) the radius at which a disk becomes shadowed from its central stellar object depends on radial mass flow and (2) most planet formation has occurred in environments unheated by stellar radiation

Physical Activity and the Health of Wheelchair Users: A Systematic Review in Multiple Sclerosis, Cerebral Palsy, and Spinal Cord Injury

Objective To understand the benefits and harms of physical activity in people who may require a wheelchair with a focus on people with multiple sclerosis (MS), cerebral palsy (CP), and spinal cord injury (SCI). Data Sources Searches were conducted in MEDLINE, Cumulative Index to Nursing and Allied Health, PsycINFO, Cochrane CENTRAL, and Embase (January 2008 through November 2020). Study Selection Randomized controlled trials, nonrandomized trials, and cohort studies of observed physical activity (at least 10 sessions on 10 days) in participants with MS, CP, and SCI. Data Extraction We conducted dual data abstraction, quality assessment, and strength of evidence. Measures of physical functioning are reported individually where sufficient data exist and grouped as “function” where data are scant. Data Synthesis No studies provided evidence for prevention of cardiovascular conditions, development of diabetes, or obesity. Among 168 included studies, 44% enrolled participants with MS (38% CP, 18% SCI). Studies in MS found walking ability may be improved with treadmill training and multimodal exercises; function may be improved with treadmill, balance exercises, and motion gaming; balance is likely improved with balance exercises and may be improved with aquatic exercises, robot-assisted gait training (RAGT), motion gaming, and multimodal exercises; activities of daily living (ADL), female sexual function, and spasticity may be improved with aquatic therapy; sleep may be improved with aerobic exercises and aerobic fitness with multimodal exercises. In CP, balance may be improved with hippotherapy and motion gaming; function may be improved with cycling, treadmill, and hippotherapy. In SCI, ADL may be improved with RAGT. Conclusions Depending on population and type of exercise, physical activity was associated with improvements in walking, function, balance, depression, sleep, ADL, spasticity, female sexual function, and aerobic capacity. Few harms of physical activity were reported in studies. Future studies are needed to address evidence gaps and to confirm findings

J/Psi mass shift in nuclear matter

The $J/\Psi$ mass shift in cold nuclear matter is computed using an effective Lagrangian approach. The mass shift is computed by evaluating $D$ and $D^*$ meson loop contributions to the $J/\Psi$ self-energy employing medium-modified meson masses. The modification of the $D$ and $D^*$ masses in nuclear matter is obtained using the quark-meson coupling model. The loop integrals are regularized with dipole form factors and the sensitivity of the results to the values of form-factor cutoff masses is investigated. The $J/\Psi$ mass shift arising from the modification of the $D$ and $D^*$ loops at normal nuclear matter density is found to range from -16 MeV to -24 MeV under a wide variation of values of the cutoff masses. Experimental perspectives for the formation of a bound state of $J/\Psi$ to a nucleus are investigated.Comment: 9 pages, latex file, 6 figures. Version published in Phys. Lett.