The House Observations of Microbial and Environmental Chemistry (HOMEChem) study is a collaborative field investigation designed to probe how everyday activities influence the emissions, chemical ...transformations and removal of trace gases and particles in indoor air. Sequential and layered experiments in a research house included cooking, cleaning, variable occupancy, and window-opening. This paper describes the overall design of HOMEChem and presents preliminary case studies investigating the concentrations of reactive trace gases, aerosol particles, and surface films. Cooking was a large source of VOCs, CO
2
, NO
x
, and particles. By number, cooking particles were predominantly in the ultrafine mode. Organic aerosol dominated the submicron mass, and, while variable between meals and throughout the cooking process, was dominated by components of hydrocarbon character and low oxygen content, similar to cooking oil. Air exchange in the house ensured that cooking particles were present for only short periods. During unoccupied background intervals, particle concentrations were lower indoors than outdoors. The cooling coils of the house ventilation system induced cyclic changes in water soluble gases. Even during unoccupied periods, concentrations of many organic trace gases were higher indoors than outdoors, consistent with housing materials being potential sources of these compounds to the outdoor environment. Organic material accumulated on indoor surfaces, and exhibited chemical signatures similar to indoor organic aerosol.
The House Observations of Microbial and Environmental Chemistry (HOMEChem) study was a large-scale collaborative experimental investigation probing indoor air composition and chemistry.
ABSTRACT
In 2019 November, MAXI detected an X-ray outburst from the known Be X-ray binary system RX J0209.6−7427 located in the outer wing of the Small Magellanic Cloud. We followed the outburst of ...the system with NICER, which led to the discovery of X-ray pulsations with a period of 9.3 s. We analysed simultaneous X-ray data obtained with NuSTAR and NICER, allowing us to characterize the spectrum and provide an accurate estimate of its bolometric luminosity. During the outburst, the maximum broad-band X-ray luminosity of the system reached (1–2) × 1039 erg s−1, thus exceeding by about one order of magnitude the Eddington limit for a typical 1.4 M⊙ mass neutron star (NS). Monitoring observations with Fermi/GBM and NICER allowed us to study the spin evolution of the NS and compare it with standard accretion torque models. We found that the NS magnetic field should be of the order of 3 × 1012 G. We conclude that RX J0209.6−7427 exhibited one of the brightest outbursts observed from a Be X-ray binary pulsar in the Magellanic Clouds, reaching similar luminosity level to the 2016 outburst of SMC X-3. Despite the super-Eddington luminosity of RX J0209.6−7427, the NS appears to have only a moderate magnetic field strength.
The prediction of a supersonic solar wind
was first confirmed by spacecraft near Earth
and later by spacecraft at heliocentric distances as small as 62 solar radii
. These missions showed that plasma ...accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy
. Magnetic tension forces the corona to co-rotate with the Sun, but any residual rotation far from the Sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams
. Here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii
, well within the distance at which stream interactions become important. We find that Alfvén waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating S-like bends in the magnetic-field lines. We detect an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second-considerably above the amplitude of the waves. These flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age
.
Micronized dehydrated human amnion/chorion membrane (μ-dHACM) is derived from donated human placentae and has anti-inflammatory, low immunogenic and anti-fibrotic properties. The objective of this ...study was to quantitatively assess the efficacy of μ-dHACM as a disease modifying intervention in a rat model of osteoarthritis (OA). It was hypothesized that intra-articular injection of μ-dHACM would attenuate OA progression.
Lewis rats underwent medial meniscal transection (MMT) surgery to induce OA. Twenty four hours post-surgery, μ-dHACM or saline was injected intra-articularly into the rat joint. Naïve rats also received μ-dHACM injections. Microstructural changes in the tibial articular cartilage were assessed using equilibrium partitioning of an ionic contrast agent (EPIC-μCT) at 21 days post-surgery. The joint was also evaluated histologically and synovial fluid was analyzed for inflammatory markers at 3 and 21 days post-surgery.
There was no measured baseline effect of μ-dHACM on cartilage in naïve animals. Histological staining of treated joints showed presence of μ-dHACM in the synovium along with local hypercellularity at 3 and 21 days post-surgery. In MMT animals, development of cartilage lesions at 21 days was prevented and number of partial erosions was significantly reduced by treatment with μ-dHACM. EPIC-μCT analysis quantitatively showed that μ-dHACM reduced proteoglycan loss in MMT animals.
μ-dHACM is rapidly sequestered in the synovial membrane following intra-articular injection and attenuates cartilage degradation in a rat OA model. These data suggest that intra-articular delivery of μ-dHACM may have a therapeutic effect on OA development.
Recently, a comparison between the locations of 6.7-GHz methanol masers and dust continuum emission has renewed speculation that these masers can be associated with evolved stars. The implication of ...such a scenario would be profound, especially for the interpretation of large surveys for 6.7-GHz masers, individual studies where high-mass star formation has been inferred from the presence of 6.7-GHz methanol masers and for the pumping mechanisms of these masers. We have investigated the two instances where 6.7-GHz methanol masers have been explicitly suggested to be associated with evolved stars, and we find the first to be associated with a standard high-mass star formation region, and the second to be a spurious detection. We also find no evidence to suggest that the methanol maser action can be supported in the environments of evolved stars. We thereby confirm their exclusive association with high-mass star formation regions.
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In this study, polycaprolactone (PCL)-based composite scaffolds containing 50wt% of 45S5 Bioglass® (45S5) or strontium-substituted bioactive glass (SrBG) particles were fabricated ...into scaffolds using an additive manufacturing technique for bone tissue engineering purposes. The PCL scaffolds were surface coated with calcium phosphate (CaP) to enable further comparison of the osteoinductive potential of different scaffolds: PCL (control), PCL/CaP-coated, PCL/50-45S5 and PCL/50-SrBG scaffolds. The PCL/50-45S5 and PCL/50-SrBG composite scaffolds were reproducibly manufactured with a morphology highly resembling that of PCL only scaffolds. However, 50wt% loading of the bioactive glass (BG) particles into the PCL bulk decreased the scaffold’s compressive Young’s modulus. Coating of PCL scaffolds with CaP had a negligible effect on the scaffold’s porosity and compressive Young’s modulus. When immersed in culture media, BG dissolution ions (Si and Sr) were detected for up to 10weeks in the immersion media and surface precipitates were formed on both PCL/50-45S5 and PCL/50-SrBG scaffolds’ surfaces, indicating good in vitro bioactivity. In vitro cell studies were conducted using sheep bone marrow stromal cells (BMSCs) under non-osteogenic or osteogenic conditioned media, and under static or dynamic culture environments. All scaffolds were able to support cell adhesion, growth and proliferation. However, when cultured in non-osteogenic media, only PCL/CaP, PCL/50-45S5 and PCL/50-SrBG scaffolds showed an up-regulation of osteogenic gene expression. Additionally, under a dynamic culture environment, the rate of cell growth, proliferation and osteoblast-related gene expression was enhanced across all scaffold groups. Subsequently, PCL/CaP, PCL/50-45S5 and PCL/50-SrBG scaffolds, with or without seeded cells, were implanted subcutaneously into nude rats for the evaluation of osteoinductivity potential. After 8 and 16weeks, host tissue infiltrated well into the scaffolds, but no mature bone formation was observed in any scaffolds groups.
This novelty of this research work is that it provide a comprehensive comparison, both in vitro and in vivo, between 3 different composite materials widely used in the field of bone tissue engineering for their bone regeneration capabilities. The materials used in this study include polycaprolactone, 45S5 Bioglass, strontium-substituted bioactive glass and calcium phosphate. Additionally, the composite materials were fabricated into the form of 3D scaffolds using additive manufacturing technique, a widely used technique in tissue engineering.
Objective: To estimate the incidence and direct medical costs for fatal and non-fatal fall injuries among US adults aged ⩾65 years in 2000, for three treatment settings stratified by age, sex, body ...region, and type of injury. Methods: Incidence data came from the 2000 National Vital Statistics System, 2001 National Electronic Injury Surveillance System-All Injury Program, 2000 Health Care Utilization Program National Inpatient Sample, and 1999 Medical Expenditure Panel Survey. Costs for fatal falls came from Incidence and economic burden of injuries in the United States; costs for non-fatal falls were based on claims from the 1998 and 1999 Medicare fee-for-service 5% Standard Analytical Files. A case crossover approach was used to compare the monthly costs before and after the fall. Results: In 2000, there were almost 10 300 fatal and 2.6 million medically treated non-fatal fall related injuries. Direct medical costs totaled $0.2 billion dollars for fatal and $19 billion dollars for non-fatal injuries. Of the non-fatal injury costs, 63% ($12 billion) were for hospitalizations, 21% ($4 billion) were for emergency department visits, and 16% ($3 billion) were for treatment in outpatient settings. Medical expenditures for women, who comprised 58% of the older adult population, were 2–3 times higher than for men for all medical treatment settings. Fractures accounted for just 35% of non-fatal injuries but 61% of costs. Conclusions: Fall related injuries among older adults, especially among older women, are associated with substantial economic costs. Implementing effective intervention strategies could appreciably decrease the incidence and healthcare costs of these injuries.
Total hydroxyl radical (OH) reactivity was measured at the PROPHET (Program for Research on Oxidants: PHotochemistry, Emissions, and Transport) forested field site in northern Michigan during the ...2009 Community Atmosphere–Biosphere INteraction EXperiment (CABINEX). OH reactivity measurements were made with a turbulent-flow reactor instrument at three heights from the forest floor above (21 and 31 m) and below (6 m) the canopy at three different time periods during the CABINEX campaign. In addition to total OH reactivity measurements, collocated measurements of volatile organic compounds (VOCs), inorganic species, and ambient temperature were made at the different heights. These ancillary measurements were used to calculate the total OH reactivity, which was then compared to the measured values. Discrepancies between the measured and calculated OH reactivity, on the order of 1–24 s−1, were observed during the daytime above the canopy at the 21 and 31 m heights, as previously reported for this site. The measured OH reactivity below the canopy during the daytime was generally lower than that observed above the canopy. Closer analysis of the measurements of OH reactivity and trace gases suggests that the missing OH reactivity could come from oxidation products of VOCs. These results suggest that additional unmeasured trace gases, likely oxidation products, are needed to fully account for the OH reactivity measured during CABINEX.
The role of chlorine atoms (Cl) in atmospheric oxidation has been traditionally thought to be limited to the marine boundary layer, where they are produced through heterogeneous reactions involving ...sea salt. However, recent observation of photolytic Cl precursors (ClNO2 and Cl2) formed from anthropogenic pollution has expanded the potential importance of Cl to include coastal and continental urban areas. Measurements of ClNO2 in Los Angeles during CalNex (California Nexus – Research at the Nexus of Air Quality and Climate Change) showed it to be an important primary (first generation) radical source. Evolution of ratios of volatile organic compounds (VOCs) has been proposed as a method to quantify Cl oxidation, but we find no evidence from this approach for a significant role of Cl oxidation in Los Angeles. We use a box model with the Master Chemical Mechanism (MCM v3.2) chemistry scheme, constrained by observations in Los Angeles, to examine the Cl sensitivity of commonly used VOC ratios as a function of NOx and secondary radical production. Model results indicate VOC tracer ratios could not detect the influence of Cl unless the ratio of OH to Cl was less than 200 for at least a day. However, the model results also show that secondary (second generation) OH production resulting from Cl oxidation of VOCs is strongly influenced by NOx, and that this effect obscures the importance of Cl as a primary oxidant. Calculated concentrations of Cl showed a maximum in mid-morning due to a photolytic source from ClNO2 and loss primarily to reactions with VOCs. The OH to Cl ratio was below 200 for approximately 3 h in the morning, but Cl oxidation was not evident from the measured ratios of VOCs. Instead, model simulations show that secondary OH production causes VOC ratio evolution to follow that expected for OH oxidation, despite the significant input of primary Cl from ClNO2 photolysis in the morning. Even though OH is by far the dominant oxidant in Los Angeles, Cl atoms do play an important role in photochemistry there, constituting 9% of the primary radical source. Furthermore, Cl–VOC reactivity differs from that of OH, being more than an order of magnitude larger and dominated by VOCs, such as alkanes, that are less reactive toward OH. Primary Cl is also slightly more effective as a radical source than primary OH due to its greater propensity to initiate radical propagation chains via VOC reactions relative to chain termination via reaction with nitrogen oxides.
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