Increased Photosynthesis Offsets Costs of Allocation to Sapwood in An Arid Environment

We assessed the effect that varying patterns of biomass allocation had on growth of ponderosa pine (Pinus ponderosa) growing in the desert climate of the Great Basin and the montane climate of the eastern Sierra Nevada. Prior work established that desert trees have lower leaf:sapwood area ratios than montane trees (0.104 and 0.201 m2/cm2, respectively) and proportionally greater stem respiration. Sapwood:leaf mass ratios are also greater and increase more as a function stem diameter in desert than in montane trees. We hypothesized that this increased allocation of carbon to stem sapwood and stem respiration in large trees could decrease growth rates in the desert compared to the montane environment, in addition to any growth reduction imposed by drought on physiology and growth processes. Trees of all diameters (dbh) in the desert environment had lower relative growth rates (RGRs) than montane trees (e.g., for a 30 cm dbh tree, RGR = 0.012 vs. 0.021 kg·kg−1·yr−1, respectively). However, growth rates of desert and montane trees declined similarly with increasing dbh and did not reflect diverging sapwood:leaf mass ratios. Alternatively, we hypothesized that desert trees may increase rates of photosynthetic carbon accumulation (per unit leaf area) with diameter, thereby compensating for increased sapwood respiration. Leaf nitrogen (N) concentration and stable-carbon isotope composition (δ13C) were measured to examine size-dependent and seasonally integrated photosynthetic capacity within desert and montane environments. Nitrogen concentration was correlated with photosynthetic capacity. Leaf nitrogen (N) concentration and δ13C values were greater in the desert (e.g., in 1-yr-old needles, desert = 1.11% and −22.96‰; montane = 0.94% and −24.20‰) and differed between desert and montane trees as a function of dbh. In desert trees, leaf nitrogen concentration in 1-yr-old through 5-yr-old needles increased with dbh, and carbon isotope composition in 1-yr-old needles increased with dbh, suggesting increased photosynthetic capacity and photosynthetic rates with increasing tree size. Needle nitrogen concentration and δ13C values decreased or remained constant with dbh in montane trees. Desert trees had greater light extinction coefficients and retained fewer needle cohorts. Our results suggest that increased allocation to heterotrophic stem tissue at the expense of photosynthetic tissue does not always incur a reduction in tree growth as predicted by current models of forest productivity

Protease Cleavage Leads to Formation of Mature Trimer Interface in HIV-1 Capsid

During retrovirus particle maturation, the assembled Gag polyprotein is cleaved by the viral protease into matrix (MA), capsid (CA), and nucleocapsid (NC) proteins. To form the mature viral capsid, CA rearranges, resulting in a lattice composed of hexameric and pentameric CA units. Recent structural studies of assembled HIV-1 CA revealed several inter-subunit interfaces in the capsid lattice, including a three-fold interhexamer interface that is critical for proper capsid stability. Although a general architecture of immature particles has been provided by cryo-electron tomographic studies, the structural details of the immature particle and the maturation pathway remain unknown. Here, we used cryo-electron microscopy (cryoEM) to determine the structure of tubular assemblies of the HIV-1 CA-SP1-NC protein. Relative to the mature assembled CA structure, we observed a marked conformational difference in the position of the CA-CTD relative to the NTD in the CA-SP1-NC assembly, involving the flexible hinge connecting the two domains. This difference was verified via engineered disulfide crosslinking, revealing that inter-hexamer contacts, in particular those at the pseudo three-fold axis, are altered in the CA-SP1-NC assemblies compared to the CA assemblies. Results from crosslinking analyses of mature and immature HIV-1 particles containing the same Cys substitutions in the Gag protein are consistent with these findings. We further show that cleavage of preassembled CA-SP1-NC by HIV-1 protease in vitro leads to release of SP1 and NC without disassembly of the lattice. Collectively, our results indicate that the proteolytic cleavage of Gag leads to a structural reorganization of the polypeptide and creates the three-fold interhexamer interface, important for the formation of infectious HIV-1 particles. © 2012 Meng et al

Competition and Facilitation: Contrasting Effects of Artemisia Tridentata on Desert vs Montane Pines

Circumstantial evidence suggests that Artemisia tridentata may out-compete Pinus ponderosa and P. jefferyi for water at ecotones between shrub steppe and montane forest vegetation in the Great Basin. Other studies indicate that within the shrub steppe Artemisia may act as a nurse plant for a third species of pine, P. monophylla. We used field experiments to study these contrasting effects of Artemisia on P, ponderosa and P. monophylla within the contest of the distributional patterns in western Nevada of all three species on andesite, and on sites where hydrothermal activity has altered the andesite. At intermediate elevations in the Great Basin Artemisia and P. monophylla are restricted to unaltered desert soils, whereas P. ponderosa is restricted to acidic, nutrient-poor altered andesite. Although mature P. monophylla were virtually absent in our study plots on altered andesite, first- and second-year seedlings were common. On adjacent unaltered andesite, all size classes of P. monophylla occurred, and P. monophylla seedlings were associated with Artemisia shrubs. Pinus ponderosa and P. jefferyi adults and seedlings were rare on unaltered andesite, but a wide range of size classes was found on altered andesite. In experiments, all P. ponderosa seedlings on unaltered andesite were consumed by predators regardless of positive or negative spatial association with shrubs. Of the P, monophylla seedlings that germinated on unaltered andesite, all that were under shrubs survived, but only 6% of those that germinated in the intershrub spaces survived, On the open altered andesite the mortality of P. monophylla seedlings due to abiotic stress was high, with a final survival of only 3%, whereas 25% of P, ponderosa seedlings survived the iir-st growing season on altered andesite. On unaltered andesite, survival and conductance of P. ponderosa saplings was enhanced by shrub removal, but P. monophylla survival was significantly higher under shrubs than in shrub-removal plots or in intershrub spaces, In Artemisia-removal experiments, we found that Artemisia competed with P. ponderosa seedlings and saplings for water. Removal of Artemisia decreased water use efficiency (WUE) of P. monophylla seedlings. The absence of Artemisia may restrict Pinus monophylla from out-crops of altered andesite in the Great Basin, but provide refuges for P. ponderosa

Monte Carlo Transmission Line Modeling of Multilayer Optical Coatings for Performance Sensitivity of a Dichroic Filter for the ARIEL Space Telescope

Dichroic beamsplitters, or dichroics, are filters that rely on the optical interference that occurs within thin layers to ensure the transmission and reflection of selective wavelengths of an incident beam of light. These optical components consist of a substrate coated on one or both surfaces with multiple layers of thin films, the spectral design and construction of which determine the isolation of particular wavebands. Discrepancies between the measured and expected spectral performance of optical elements with such coatings can largely be attributed to depositions errors and uncertainties in the refractive indices of the materials. Our model uses two-dimensional transmission line modeling to evaluate the transmittance of light through multilayer coatings deposited on a substrate material for given materials, angle of incidence and polarisation. This model allows us to perform Monte Carlo simulations to obtain statistical information about the tolerance of the coating performance to systematic and random uncertainties from the manufacturing process, as well as from environmental changes in space. With the aid of accurate manufacturing recipes and uncertainty amplitudes from commercial manufacturers, this tool can predict variations in the optical performance that result from the propagation of each of these uncertainties for various hypothetical scenarios. One particular application of this study are the dichroics of the ARIEL space telescope. We compare the predicted optical performance with transmission measurements at cryogenic temperatures for one of the ARIEL dichroics, which show the specification compliance of this prototype after many thermal cycles

Educating Health Professionals about Disability: A Review of Interventions

Health professionals need to understand the human rights and health needs of disabled people. This review of evidence on interventions demonstrates that a range of often innovative approaches have been trialled. Lectures by faculty are less effective in changing attitudes than contact with disabled people themselves. Existing examples of good practice need to be scaled up, and better and more long-term evaluations of impact are required

An Exact Formula for the Average Run Length to False Alarm of the Generalized Shiryaev-Roberts Procedure for Change-Point Detection under Exponential Observations

We derive analytically an exact closed-form formula for the standard minimax Average Run Length (ARL) to false alarm delivered by the Generalized Shiryaev-Roberts (GSR) change-point detection procedure devised to detect a shift in the baseline mean of a sequence of independent exponentially distributed observations. Specifically, the formula is found through direct solution of the respective integral (renewal) equation, and is a general result in that the GSR procedure's headstart is not restricted to a bounded range, nor is there a "ceiling" value for the detection threshold. Apart from the theoretical significance (in change-point detection, exact closed-form performance formulae are typically either difficult or impossible to get, especially for the GSR procedure), the obtained formula is also useful to a practitioner: in cases of practical interest, the formula is a function linear in both the detection threshold and the headstart, and, therefore, the ARL to false alarm of the GSR procedure can be easily computed.Comment: 9 pages; Accepted for publication in Proceedings of the 12-th German-Polish Workshop on Stochastic Models, Statistics and Their Application

Application of Focal Conflict Theory to Psychoeducational Groups: Implications for Process, Content, and Leadership

Group psychoeducation is a common group type used for a range of purposes. The literature presents balancing content and process as a challenge for psychoeducational group leaders. While the significance of group psychoeducation is supported, practitioners are given little direction for addressing process in these groups. Focal Conflict Theory (FCT) is a model for conceptualizing and intervening in group process that has been applied to therapy and work groups. This article presents the challenges of psychoeducational groups, describes FCT, and discusses its application to psychoeducational groups using case examples. Implications for leaders of psychoeducation groups are discussed

CO2 fertilization of Sphagnum peat mosses is modulated by water table level and other environmental factors

Sphagnum mosses account for most accumulated dead organic matter in peatlands. Therefore, understanding their responses to increasing atmospheric CO2 is needed for estimating peatland C balances under climate change. A key process is photorespiration: a major determinant of net photosynthetic C assimilation that depends on the CO2 to O-2 ratio. We used climate chambers to investigate photorespiratory responses of Sphagnum fuscum hummocks to recent increases in atmospheric CO2 (from 280 to 400 ppm) under different water table, temperature, and light intensity levels. We tested the photorespiratory variability using a novel method based on deuterium isotopomers (D6(S)/D6(R) ratio) of photosynthetic glucose. The effect of elevated CO2 on photorespiration was highly dependent on water table. At low water table (-20 cm), elevated CO2 suppressed photorespiration relative to C assimilation, thus substantially increasing the net primary production potential. In contrast, a high water table (similar to 0 cm) favored photorespiration and abolished this CO2 effect. The response was further tested for Sphagnum majus lawns at typical water table levels (similar to 0 and -7 cm), revealing no effect of CO2 under those conditions. Our results indicate that hummocks, which typically experience low water table levels, benefit from the 20th century's increase in atmospheric CO2

Evolving trends in aortic valve replacement: A statewide experience

BackgroundTranscatheter aortic valve replacement (TAVR) is an alternative to surgical aortic valve replacement (SAVR) for the treatment of aortic stenosis in patients at intermediate, high, and extreme risk for mortality from SAVR. We examined recent trends in aortic valve replacement (AVR) in Michigan.MethodsThe Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative (MSTCVS‐QC) database was used to determine the number of SAVR and TAVR cases performed from January 2012 through June 2017. Patients were divided into low, intermediate, high, and extreme risk groups based on STS predicted risk of mortality (PROM). TAVR patients in the MSTCVS‐QC database were also matched with those in the Transcatheter Valve Therapy Registry to determine their Heart Team‐designated risk category.ResultsDuring the study period 9517 SAVR and 4470 TAVR cases were performed. Total annual AVR volume increased by 40.0% (from 2086 to 2920), with a 13.3% decrease in number of SAVR cases (from 1892 to 1640) and a 560% increase in number of TAVR cases (from 194 to 1280). Greater than 90% of SAVR patients had PROM ≤8%. While >70% of TAVR patients had PROM ≤ 8%, they were mostly designated as high or extreme risk by a Heart Team.ConclusionsDuring the study period, SAVR volume gradually declined and TAVR volume dramatically increased. This was mostly due to a new group of patients with lower STS PROM who were designated as higher risk by a Heart Team due to characteristics not completely captured by the STS PROM score.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145246/1/jocs13740_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145246/2/jocs13740.pd