Pre-Mesozoic Palinspastic Reconstruction of the Eastern Great Basin (Western United States)

The Great Basin of the western United States has proven important for studies of Proterozoic and Paleozoic geology [2500 to 245 million years ago (Ma)] and has been central to the development of ideas about the mechanics of crustal shortening and extension. An understanding of the deformational history of this region during Mesozoic and Cenozoic time (245 Ma to the present) is required for palinspastic reconstruction of now isolated exposures of older geology in order to place these in an appropriate regional geographic context. Considerable advances in unraveling both the crustal shortening that took place during Mesozoic to early Cenozoic time (especially from about 150 to 50 Ma) and the extension of the past 37 million years have shown that earlier reconstructions need to be revised significantly. A new reconstruction is developed for rocks of middle Proterozoic to Early Cambrian age based on evidence that total shortening by generally east-vergent thrusts and folds was at least 104 to 135 kilometers and that the Great Basin as a whole accommodated ∼250 kilometers of extension in the direction 287° ± 12° between the Colorado Plateau and the Sierra Nevada. Extension is assumed to be equivalent at all latitudes because available paleomagnetic evidence suggests that the Sierra Nevada experienced little or no rotation with respect to the extension direction since the late Mesozoic. An estimate of the uncertainty in the amount of extension obtained from geological and paleomagnetic uncertainties increases northward from ±56 kilometers at 36°30N to -87+108 kilometers at 40°N. On the basis of the reconstruction, the original width of the preserved part of the late Proterozoic and Early Cambrian basin was about 150 to 300 kilometers, about 60 percent of the present width, and the basin was oriented slightly more north-south with respect to present-day coordinates

Tectonic Subsidence of the Early Paleozoic Passive Continental Margin in Eastern California and Southern Nevada

Quantitative analysis of tectonic subsidence in Cambrian and Ordovician platform carbonates and associated strata exposed in the Spring Mountains (Nevada) and the Nopah, Funeral, and Inyo Ranges (California) indicates that subsidence associated with this segment of the early Paleozoic passive continental margin is exponential in form, consistent with thermal contraction of the lithosphere following extension. As in other parts of the North American Cordillera, continental separation in the southern Great Basin appears to have taken place between 590 and 545 Ma. These results are not sensitive to uncertainties in stratigraphic thickness, biostratigraphic age control, or paleobathymetry. Uncertainties in the Cambrian time scale lead to predictable variations in the inferred time of onset of thermal subsidence, but they have no effect on the inferred stratigraphic position of the rift to post-rift transition. A younger age for the base of the Middle Cambrian results in a younger inferred age of onset of thermal subsidence accompanied by greater rates of subsidence during the Cambrian, whereas a significantly older estimate of the onset of thermal subsidence can be obtained only if the base of the Middle Cambrian is substantially older than 540 Ma, a possibility that is inconsistent with available data. Results of the subsidence analysis are particularly significant because this is one of the few regions along the length of the North American Cordillera where they can be compared directly to the geologic evidence for syn-rift and post-rift deposition. Basement-involved faulting associated with the Amargosa basin ("aulacogen") ceased during deposition of the Noonday Dolomite, which is thought to be older than 700-680 Ma on the basis of stromatolites of late Riphean affinity. The overlying Johnnie Formation contains supposed Vendian stromatolites (younger than 700-680 Ma). If it is assumed that our results indicate the timing of the final rift to post-rift transition, then either the ages inferred from stromatolites are incorrect or the lithosphere was thinned regionally after deposition of the Noonday. The latter possibility is supported by limited geologic evidence for extension in latest Proterozoic and Early Cambrian time. The lack of appreciable physical evidence for crustal extension after deposition of the Noonday, however, may imply that (1) a uniform extension model for lithospheric thinning is inappropriate for this part of the margin or that (2) some or all of the localities studied are continentward of the hinge zone, and that the observed subsidence is exaggerated by flexural loading in a deeper basin to the west

Phonological Neighborhood Density Effects on Treatment of Naming in Aphasia

Phonological treatments to improve naming ability in aphasia focus on re-strengthening connections within the phonological system.  In this study, a participant with a phonologically-based impairment demonstrated a greater improvement in naming ability on words trained from high density neighborhoods. Stimulus parameters, such as neighborhood density, may play a critical role in the effectiveness of treatment protocols

Apathy, cognitive impairment, and social support contribute to participation in cognitively demanding activities poststroke

Importance. Individuals with chronic stroke experience decreased participation in activities with cognitive demands across all areas of occupation. Objective. To understand the extent to which apathy, cognition, and social support predict participation in activities with cognitive demands. Design. Prospective, quantitative correlational, cross-sectional study. Setting. Outpatient treatment centers and community stroke support groups located in St. Louis, MO, and Boston, MA. Participants. 81 community-dwelling individuals≥6-month poststroke with and without aphasia. Measures. Participants completed the Activity Card Sort (ACS), Apathy Evaluation Scale (AES), Medical Outcomes Study Social Support Survey (MOS-SSS), and Delis-Kaplan Executive Function System (DKEFS) Design Fluency and Trail-Making subtests. Results. Cognitive deficits limit participation in activities with high cognitive demands. Apathy and positive social interaction influence participation, regardless of high or low cognitive demands. Poststroke aphasia did not impact return to participation in activities with high and low cognitive demands. Conclusions and Relevance. Cognitive deficits seen poststroke contribute to participation only for activities with high cognitive demands. Apathy has a significant and negative influence on participation overall. Social support is a modifiable contextual factor that can facilitate participation. Poststroke apathy can be detrimental to participation but is not well recognized. The availability of companionship from others to enjoy time with can facilitate participation

C-Speak Aphasia alternative communication program for people with severe aphasia: Importance of executive functioning and semantic knowledge

Learning how to use a computer-based communication system can be challenging for people with severe aphasia even if the system is not word-based. This study explored cognitive and linguistic factors relative to how they affected individual patients’ ability to communicate expressively using C-Speak Aphasia, (CSA), an alternative communication computer program that is primarily picture-based. Ten individuals with severe non-fluent aphasia received at least six months of training with CSA. To assess carryover of training, untrained functional communication tasks (i.e., answering autobiographical questions, describing pictures, making telephone calls, describing a short video, and two writing tasks) were repeatedly probed in two conditions: 1) using CSA in addition to natural forms of communication, and 2) using only natural forms of communication, e.g., speaking, writing, gesturing, drawing. Four of the ten participants communicated more information on selected probe tasks using CSA than they did without the computer. Response to treatment also was examined in relation to baseline measures of non-linguistic executive function skills, pictorial semantic abilities, and auditory comprehension. Only nonlinguistic executive function skills were significantly correlated with treatment response

Two-year follow-up of macaques developing intermittent control of the human immunodeficiency virus homolog simian immunodeficiency virus SIVmac251 in the chronic phase of infection

Off-therapy control of viremia by HIV-infected individuals has been associated with two likely players: a restricted viral reservoir and an efficient cell-mediated immune response. We previously showed that a combination of highly suppressive antiretroviral therapy and two experimental drugs, i.e., auranofin and buthionine sulfoximine, was able to reduce the viral reservoir, elicit efficient cell-mediated antiviral responses, and induce intermittent posttherapy viral load control in chronically SIVmac251-infected macaques. We here show that the macaques that had received this drug combination and then stopped antiretroviral therapy were also able to maintain low numbers of activated CD4(+) T cells at viral rebound. Moreover, these macaques consistently displayed low-level simian immunodeficiency virus (SIV) diversity, which was in line with the strong and broadly reactive cell-mediated immune responses against conserved Gag antigens. Extended follow-up showed that the two macaques that had received the complete drug combination remained healthy and did not develop AIDS in 2 years of follow-up after therapy suspension. This disease-free survival is longer than twice the average time of progression to AIDS in SIVmac251-infected rhesus macaques. These results suggest that limited numbers of activated T cells at viral rebound and subsequent development of broadly reactive cell-mediated responses may be interrelated in reducing the viral reservoir

Transcranial magnetic stimulation as a complementary treatment for aphasia

Functional brain imaging with nonfluent aphasia patients has shown increased cortical activation (perhaps ‘‘overactivation’’) in right (R) hemisphere language homologues. These areas of overactivation may represent a maladaptive strategy that interferes with, rather than promotes, aphasia recovery. Repetitive transcranial magnetic stimulation (rTMS) is a painless, noninvasive procedure that utilizes magnetic fields to create electric currents in discrete brain areas affecting about a 1-cm square area of cortex. Slow frequency, 1 Hz rTMS reduces cortical excitability. When rTMS is applied to an appropriate cortical region, it may suppress the possible overactivation and thus modulate a distributed neural network for language. We provide information on rTMS and report preliminary results following rTMS application to R Broca’s area (posterior, R pars triangularis) in four stroke patients with nonfluent aphasia (5–11 years after left hemisphere stroke). Following 10 rTMS treatments, significant improvement in naming pictures was observed. This form of rTMS may provide a novel, complementary treatment for aphasia.This research was supported by NIH grant DC05672 from the National Institute on Deafness and Other Communication Disorders, Bethesda, MD; and in part by the Medical Research Service, Department of Veterans Affairs, Washington, DC; and NIH grant NCRR MO1 RR01032 to the Harvard-Thorndike General Clinical Research Center at the Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA; and NIH NIDCD grant P30 DC05207 to the Harold Goodglass Aphasia Research Center, Boston University School of Medicine, Boston, MAMedicin

Systemic Racism and Health Disparities: A Statement from Editors of Family Medicine Journals

The year 2020 has been marked by historic protests across the United States and the globe sparked by the deaths of George Floyd, Ahmaud Arbery, Breonna Taylor, and so many other Black people. The protests heightened awareness of racism as a public health crisis and triggered an antiracism movement. The editors of several North American family medicine publications have come together to address this call to action and share resources on racism across our readerships.http://deepblue.lib.umich.edu/bitstream/2027.42/163331/1/Final Statement on Systemic Racism- with acknowledgements.pdf-1Description of Final Statement on Systemic Racism- with acknowledgements.pdf : Main ArticleSEL

Population Bottlenecks as a Potential Major Shaping Force of Human Genome Architecture

The modern synthetic view of human evolution proposes that the fixation of novel mutations is driven by the balance among selective advantage, selective disadvantage, and genetic drift. When considering the global architecture of the human genome, the same model can be applied to understanding the rapid acquisition and proliferation of exogenous DNA. To explore the evolutionary forces that might have morphed human genome architecture, we investigated the origin, composition, and functional potential of numts (nuclear mitochondrial pseudogenes), partial copies of the mitochondrial genome found abundantly in chromosomal DNA. Our data indicate that these elements are unlikely to be advantageous, since they possess no gross positional, transcriptional, or translational features that might indicate beneficial functionality subsequent to integration. Using sequence analysis and fossil dating, we also show a probable burst of integration of numts in the primate lineage that centers on the prosimian–anthropoid split, mimics closely the temporal distribution of Alu and processed pseudogene acquisition, and coincides with the major climatic change at the Paleocene–Eocene boundary. We therefore propose a model according to which the gross architecture and repeat distribution of the human genome can be largely accounted for by a population bottleneck early in the anthropoid lineage and subsequent effectively neutral fixation of repetitive DNA, rather than positive selection or unusual insertion pressures

Pelagic Functional Group Modeling: Progress, Challenges and Prospects

In this paper, we review the state of the art and major challenges in current efforts to incorporate biogeochemical functional groups into models that can be applied on basin-wide and global scales, with an emphasis on models that might ultimately be used to predict how biogeochernical cycles in the ocean will respond to global warming. We define the term biogeochemical functional group to refer to groups of organisms that mediate specific chemical reactions in the ocean. Thus, according to this definition, functional groups have no phylogenetic meaning-these are composed of many different species with common biogeochemical functions. Substantial progress has been made in the last decade toward quantifying the rates of these various functions and understanding the factors that control them. For some of these groups, we have developed fairly sophisticated models that incorporate this understanding, e.g. for diazotrophs (e.g. Trichodesmium), silica producers (diatoms) and calcifiers (e.g. coccolithophorids and specifically Emiliania huxleyi). However, current representations of nitrogen fixation and calcification are incomplete, i.e., based primarily upon models of Trichodesmium and E huxleyi, respectively, and many important functional groups have not yet been considered in open-ocean biogeochemical models. Progress has been made over the last decade in efforts to simulate dimethylsulfide (DMS) production and cycling (i.e., by dinoflagellates and prymnesiophytes) and denitrification, but these efforts are still in their infancy, and many significant problems remain. One obvious gap is that virtually all functional group modeling efforts have focused on autotrophic microbes, while higher trophic levels have been completely ignored. It appears that in some cases (e.g., calcification), incorporating higher trophic levels may be essential not only for representing a particular biogeochemical reaction, but also for modeling export. Another serious problem is our tendency to model the organisms for which we have the most validation data (e.g., E huxleyi and Trichodesmium) even when they may represent only a fraction of the biogeochemical functional group we are trying to represent. When we step back and look at the paleo-oceanographic record, it suggests that oxygen concentrations have played a central role in the evolution and emergence of many of the key functional groups that influence biogeochemical cycles in the present-day ocean. However, more subtle effects are likely to be important over the next century like changes in silicate supply or turbulence that can influence the relative success of diatoms versus dinoflagellates, coccolithophorids and diazotrophs. In general, inferences drawn from the paleo-oceanographic record and theoretical work suggest that global warming will tend to favor the latter because it will give rise to increased stratification. However, decreases in pH and Fe supply could adversely impact coccolithophorids and diazotrophs in the future. It may be necessary to include explicit dynamic representations of nitrogen fixation, denitrification, silicification and calcification in our models if our goal is predicting the oceanic carbon cycle in the future, because these processes appear to play a very significant role in the carbon cycle of the present-day ocean and they are sensitive to climate change. Observations and models suggest that it may also be necessary to include the DMS cycle to predict future climate, though the effects are still highly uncertain. We have learned a tremendous amount about the distributions and biogeochemical impact of bacteria in the ocean in recent years, yet this improved understanding has not yet been incorporated into many of our models. All of these considerations lead us toward the development of increasingly complex models. However, recent quantitative model intercomparison studies suggest that continuing to add complexity and more functional groups to our ecosystem models may lead to decreases in predictive ability if the models are not properly constrained with available data. We also caution that capturing the present-day variability tells us little about how well a particular model can predict the future. If our goal is to develop models that can be used to predict how the oceans will respond to global warming, then we need to make more rigorous assessments of predictive skill using the available data