The effects of nail bending-yield stress and biological deterioration on the cyclic performance of shearwalls

Key parts of the lateral force resisting system in wood-frame buildings are the shearwafls and the connections. The connections in wooden buildings are the primary source of ductility and energy dissipation; these are essential properties when buildings are exposed to lateral forces, such as wind and earthquakes. Shearwall design is based on new materials and a monotonic testing method, which departs from the actual situation because buildings age and are subjected to cyclic loads during wind and earthquake events. After the property losses experienced in the Loma Prieta and Northridge earthquakes, the engineering community realized there was a need to further investigate wooden shearwall performance especially with respect to condition and cyclic loading. Individual sheathing-framing connections can be designed with respect to capacity and yield mode by using the yield mode equations. However, the relationship between individual connection characteristics and the performance of a shearwall remains unclear. The objective of this study was to investigate the relationship between individual connections and shearwall performance where nail bending-yield stress (fyb) and biological deterioration of the wood were sources of variation in physical and simulation experiments

Sheathing Nail Bending-Yield Stress: Effect on Cyclic Performance of Wood Shear Walls

This study investigated the effects of sheathing nail bending-yield stress (fyb) on connection properties and shear wall performance under cyclic loading. Four sets of nails were specially manufactured with average fyb of 87, 115, 145, and 241 ksi. Nail bending-yield stress and the hysteretic behavior of single-nail lateral connections were determined. The parameters of the lateral nail tests were used in a numerical model to predict shear wall performance and hysteretic parameters. The competency of the numerical model was assessed by full-scale cyclic tests of shear walls framed with Douglas-fir lumber and sheathed with oriented strandboard (OSB). The parameters of the shear wall model were used in another program to predict shear wall performance for a suite of seismic ground motions. The single-nail connection tests and wall model computations suggested that increased fyb of the sheathing nails should lead to improved wall stiffness and capacity. In both single-nail lateral connection and shear wall tests, the probability of nonductile failure modes increased as fyb increased. The peak capacity of the walls increased as fyb of the sheathing nails increased up to 145 ksi, but wall initial stiffness, displacement at peak capacity, and energy dissipation were not significantly affected by fyb. Sheathing nail fyb greater than 145 ksi did not enhance the overall cyclic behavior of wood shear walls

Theoretical and experimental infrared spectra of hydrated and dehydrated sulfonated poly(ether ether ketone)

Time-dependent FT-IR spectra of sulfonated poly(ether ether ketone) during dehydration show diminishing 1081 cm−1 and 1023 cm−1 band intensities concurrent with the emergence and shifting of bands at 1362 cm−1 and 898 cm−1. Animations of density functional theory calculated normal modes enable assignment of the 1081 cm−1 and 1023 cm−1 bands as group modes that include a sulfonate exchange site with C3v local symmetry, while the 1362 cm−1 and 898 cm−1 bands are assigned as group modes that include an associated sulfonic acid with no local symmetry (C1). In contrast to analogously assigned Nafion group mode bands, the SPEEK C3v and C1 bands coexist throughout the entire dehydration–hydration cycle, suggesting the presence of associated and dissociated exchange sites in SPEEK at all states-of-hydration. This supports a morphological model for SPEEK featuring branched hydrophilic domains and dead-end aqueous confines

Unusual Case of Pump Thrombosis in LVAD Patient with COVID-19 — Diagnostic Challenges

We present the first reported case of left ventricular assist device (LVAD) pump thrombosis in the setting of the coronavirus pandemic. We describe the clinical features of the case which helped to differentiate coronavirus disease 19 (COVID-19) from LVAD pump thrombosis. The patient is 56-year-old female supported by destination LVAD therapy. She was originally implanted with a HeartMate II device in 2015 and underwent two pump exchanges in 2017 and 2019 for pump thrombosis, despite medication adherence. Shortly after routine lab work revealed near doubling of her lactate dehydrogenase (LDH) levels, she tested positive for COVID-19. She then developed power spikes and symptomatic heart failure, which prompted hospital admission. An initial computed tomography (CT) scan showed bilateral ground glass opacities, but repeat testing was negative for COVID-19. Her LVAD pump thrombosis was treated with aspirin, unfractionated heparin, and cangrelor, which was guided by thromboelastogram. Over several weeks, her LDH returned to baseline, and she was transitioned from cangrelor to ticagrelor and from heparin to warfarin. A repeat CT scan after several days of IV diuresis showed resolution of the ground glass opacities

scMRI Reveals Large-Scale Brain Network Abnormalities in Autism

Autism is a complex neurological condition characterized by childhood onset of dysfunction in multiple cognitive domains including socio-emotional function, speech and language, and processing of internally versus externally directed stimuli. Although gross brain anatomic differences in autism are well established, recent studies investigating regional differences in brain structure and function have yielded divergent and seemingly contradictory results. How regional abnormalities relate to the autistic phenotype remains unclear. We hypothesized that autism exhibits distinct perturbations in network-level brain architecture, and that cognitive dysfunction may be reflected by abnormal network structure. Network-level anatomic abnormalities in autism have not been previously described. We used structural covariance MRI to investigate network-level differences in gray matter structure within two large-scale networks strongly implicated in autism, the salience network and the default mode network, in autistic subjects and age-, gender-, and IQ-matched controls. We report specific perturbations in brain network architecture in the salience and default-mode networks consistent with clinical manifestations of autism. Extent and distribution of the salience network, involved in social-emotional regulation of environmental stimuli, is restricted in autism. In contrast, posterior elements of the default mode network have increased spatial distribution, suggesting a ‘posteriorization’ of this network. These findings are consistent with a network-based model of autism, and suggest a unifying interpretation of previous work. Moreover, we provide evidence of specific abnormalities in brain network architecture underlying autism that are quantifiable using standard clinical MRI

Complete Genome Sequence of Geobacter sp. Strain FeAm09, a Moderately Acidophilic Soil Bacterium

A moderately acidophilic Geobacter sp. strain, FeAm09, was isolated from forest soil. The complete genome sequence is 4,099,068 bp with an average GC content of 61.1%. No plasmids were detected. The genome contains a total of 3,843 genes and 3,608 protein-coding genes, including genes supporting iron and nitrogen biogeochemical cycling

Nonlinear Krylov Acceleration Applied to a Discrete Ordinates Formulation of the k-Eigenvalue Problem

We compare variants of Anderson Mixing with the Jacobian-Free Newton-Krylov and Broyden methods applied to an instance of the k-eigenvalue formulation of the linear Boltzmann transport equation. We present evidence that one variant of Anderson Mixing finds solutions in the fewest number of iterations. We examine and strengthen theoretical results of Anderson Mixing applied to linear problems.Comment: This final revision includes results of the C5G7-MOX problem; Nonlinear Krylov Acceleration Applied to a Discrete Ordinates Formulation of the k-Eigenvalue Problem, Accepted by the Journal of Computational Physics December 201

The Sloan Digital Sky Survey Quasar Lens Search. III. Constraints on Dark Energy from the Third Data Release Quasar Lens Catalog

We present cosmological results from the statistics of lensed quasars in the Sloan Digital Sky Survey (SDSS) Quasar Lens Search. By taking proper account of the selection function, we compute the expected number of quasars lensed by early-type galaxies and their image separation distribution assuming a flat universe, which is then compared with 7 lenses found in the SDSS Data Release 3 to derive constraints on dark energy under strictly controlled criteria. For a cosmological constant model (w=-1) we obtain \Omega_\Lambda=0.74^{+0.11}_{-0.15}(stat.)^{+0.13}_{-0.06}(syst.). Allowing w to be a free parameter we find \Omega_M=0.26^{+0.07}_{-0.06}(stat.)^{+0.03}_{-0.05}(syst.) and w=-1.1\pm0.6(stat.)^{+0.3}_{-0.5}(syst.) when combined with the constraint from the measurement of baryon acoustic oscillations in the SDSS luminous red galaxy sample. Our results are in good agreement with earlier lensing constraints obtained using radio lenses, and provide additional confirmation of the presence of dark energy consistent with a cosmological constant, derived independently of type Ia supernovae.Comment: 9 pages, 3 figures, 2 tables, accepted for publication in A

Investigation of antihypertensive class, dementia, and cognitive decline: A meta-analysis

Objective High blood pressure is one of the main modifiable risk factors for dementia. However, there is conflicting evidence regarding the best antihypertensive class for optimizing cognition. Our objective was to determine whether any particular antihypertensive class was associated with a reduced risk of cognitive decline or dementia using comprehensive meta-analysis including reanalysis of original participant data. Methods To identify suitable studies, MEDLINE, Embase, and PsycINFO and preexisting study consortia were searched from inception to December 2017. Authors of prospective longitudinal human studies or trials of antihypertensives were contacted for data sharing and collaboration. Outcome measures were incident dementia or incident cognitive decline (classified using the reliable change index method). Data were separated into mid and late-life (>65 years) and each antihypertensive class was compared to no treatment and to treatment with other antihypertensives. Meta-analysis was used to synthesize data. Results Over 50,000 participants from 27 studies were included. Among those aged >65 years, with the exception of diuretics, we found no relationship by class with incident cognitive decline or dementia. Diuretic use was suggestive of benefit in some analyses but results were not consistent across follow-up time, comparator group, and outcome. Limited data precluded meaningful analyses in those ≤65 years of age. Conclusion Our findings, drawn from the current evidence base, support clinical freedom in the selection of antihypertensive regimens to achieve blood pressure goals. Clinical trials registration The review was registered with the international prospective register of systematic reviews (PROSPERO), registration number CRD42016045454.The corresponding author is funded by the Australian National Health and Medical Research Council, National Institute for Dementia Research, and Dementia Centre for Research Collaboration (NHMRC NNIDR DCRC)

Impact of natural gas extraction on PAH levels in ambient air

After publication the authors discovered a mistake in the air concentration calculations. PAH air concentrations reported in the original article are therefore incorrect. The calculation error resulted from using incorrect units of the ideal gas constant, and improper cell linkages in the spreadsheet used to adjust air concentrations for sampling temperature. Correcting this error changes air concentrations significantly relative to those reported in the published article. This correction also changes some of the conclusions reported in the original article. Due to the impact of this correction on the reported findings, all authors retract the original article. The original article was published on March 26, 2015 and retracted on June 29, 2016.Natural gas extraction, often referred to as “fracking,” has increased rapidly in the U.S. in recent years. To address potential health impacts, passive air samplers were deployed in a rural community heavily affected by the natural gas boom. Samplers were analyzed for 62 polycyclic aromatic hydrocarbons (PAHs). Results were grouped based on distance from each sampler to the nearest active well. PAH levels were highest when samplers were closest to active wells. Additionally, PAH levels closest to natural gas activity were an order of magnitude higher than levels previously reported in rural areas. Sourcing ratios indicate that PAHs were predominantly petrogenic, suggesting that elevated PAH levels were influenced by direct releases from the earth. Quantitative human health risk assessment estimated the excess lifetime cancer risks associated with exposure to the measured PAHs. Closest to active wells, the risk estimated for maximum residential exposure was 2.9 in 10,000, which is above the U.S. EPA’s acceptable risk level. Overall, risk estimates decreased 30% when comparing results from samplers closest to active wells to those farthest. This work suggests that natural gas extraction may be contributing significantly to PAHs in air, at levels that are relevant to human health