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1.
J Gen Intern Med ; 37(11): 2759-2767, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35091925

RESUMO

BACKGROUND: The coronavirus disease 2019 pandemic has contributed to growing demand for mental health services, but patients face significant barriers to accessing care. Direct-to-consumer(DTC) telemedicine has been proposed as one way to increase access, yet little is known about its pre-pandemic use for mental healthcare. OBJECTIVE: To characterize patients, providers, and their use of a large nationwide DTC telemedicine platform for mental healthcare. DESIGN: Retrospective cross-sectional study. SETTING: Mental health encounters conducted on the American Well DTC telemedicine platform from 2016 to 2018. PARTICIPANTS: Patients and physicians. MAIN MEASURES: Patient measures included demographics, insurance report, and number of visits. Provider characteristics included specialty, region, and number of encounters. Encounter measures included wait time, visit length and timing, out-of-pocket payment, coupon use, prescription outcome, referral receipt, where care otherwise would have been sought, and patient satisfaction. Factors associated with five-star physician ratings and prescription receipt were assessed using logistic regression. KEY RESULTS: We analyzed 19,270 mental health encounters between 6708 patients and 1045 providers. Visits were most frequently for anxiety (39.1%) or depression (32.5%), with high satisfaction (4.9/5) across conditions. Patients had a median 2.0 visits for psychiatry (IQR 1.0-3.0) and therapy (IQR 1.0-5.0), compared to 1.0 visit (IQR 1.0-1.0) for urgent care. High satisfaction was positively correlated with prescription receipt (OR 1.89, 95% CI 1.54-2.32) and after-hours timing (aOR 1.18, 95% CI 1.02-1.36). Prescription rates ranged from 79.6% for depression to 32.2% for substance use disorders. Prescription receipt was associated with increased visit frequency (aOR 1.95, 95% CI 1.57-2.42 for ≥ 3 visits). CONCLUSIONS: As the burden of psychiatric disease grows, DTC telemedicine offers one solution for extending access to mental healthcare. While most encounters were one-off, evidence of some continuity in psychiatry and therapy visits-as well as overall high patient satisfaction-suggests potential for broader DTC telemental health use.


Assuntos
COVID-19 , Serviços de Saúde Mental , Telemedicina , COVID-19/epidemiologia , COVID-19/terapia , Estudos Transversais , Humanos , Satisfação do Paciente , Estudos Retrospectivos
2.
Chemistry ; 27(34): 8694-8697, 2021 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-33938064

RESUMO

Soft template designing is the most promising strategy for the synthesis of zeolite nanosheets. MFI nanosheets directed by soft templates (containing long-chain alkyl groups or aromatic groups as hydrophobic component) can be found frequently; however, so far, MFI nanosheets synthesized by soft templates with aromatic heterocycle groups (e. g., s-triazine groups) are rare. Herein, a nanosheet-stacked hierarchical MFI zeolite (NSHM) has been synthesized by using a triply branched s-triazine-based surfactant as a bifunctional organic structure-directing agent. On the basis of a geometrical match relationship, a formation model has been proposed. Synthesized NSHM had abundant mesopores stacked by nanosheets and exhibited a high surface area (430 m2 ⋅ g-1 ). The 1 wt% Pd/NSHM attained a significant increase in yield of cyclohexanol/cyclohexanone mixture (from 66 to 85 %) in the oxidation of cyclohexane compared with Silicalite-1 and SBA-15 as supports.

3.
J Gen Intern Med ; 35(3): 643-648, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31667749

RESUMO

BACKGROUND: Urinary tract infections (UTI) are a common reason for seeking care via direct to consumer (DTC) telemedicine, yet patterns of care, including antibiotic prescribing, have not been reported. OBJECTIVE: To describe management of UTI in a large nationwide DTC telemedicine platform. DESIGN: Cross-sectional observational study. PARTICIPANTS: Patients seeking care for or diagnosed with UTI via DTC telemedicine between July 2016 and July 2018. MAIN MEASURES: Patient measures included age, sex, geographic region, satisfaction with care, and patient-reported call reason. High-risk patients were defined as males, patients over 65 years, or those diagnosed with pyelonephritis. Physician measures included specialty and geographic region. Antibiotic prescription was assessed overall and by antibiotic type. Variation in antibiotic prescriptions was assessed by patient and physician factors, including geographic region of both parties. KEY RESULTS: Of the 20,600 patients diagnosed with a UTI during the study period, 96% were female. Most (84%) stated their call reason was a UTI. Overall, 94% of UTI patients received an antibiotic; 56% got nitrofurantoin, 29% got trimethoprim-sulfamethoxazole, and 10% got a quinolone. Receipt of an antibiotic was associated with higher satisfaction with care (p < 0.001). While nitrofurantoin was the most common antibiotic for all physician regions, antibiotic type varied by physician region. Of the 6% of the study population defined as high risk, 69% received an antibiotic: 72% of males, 91% of women over 65, and 21% of patients diagnosed with pyelonephritis. CONCLUSIONS: Management of UTI via DTC telemedicine appears to be appropriate for average-risk patients, and most are able to self-diagnose. Most patients received guideline-concordant care, but over half of high-risk patients received antibiotics. DTC telemedicine offers convenient, low-cost care that is generally appropriate. Efforts should be made to ensure high-risk patients get proper follow-up.


Assuntos
Telemedicina , Infecções Urinárias , Adolescente , Adulto , Idoso , Antibacterianos/uso terapêutico , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Infecções Urinárias/diagnóstico , Infecções Urinárias/tratamento farmacológico , Infecções Urinárias/epidemiologia , Adulto Jovem
4.
J Gen Intern Med ; 35(9): 2600-2606, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32632788

RESUMO

BACKGROUND: Patient satisfaction measures have important implications for physicians. Patient bias against non-White physicians may impact physician satisfaction ratings, but this has not been widely studied. OBJECTIVE: To assess differences in patient satisfaction by physician race/ethnicity. DESIGN: A cross-sectional observational study. PARTICIPANTS: Patients seeking care on a large nationwide direct to consumer telemedicine platform between July 2016 and July 2018 and their physicians. MAIN MEASURES: Patient satisfaction was ascertained immediately following the encounter on scales of 1 to 5 stars and scored two ways: (1) top-box satisfaction (5 stars versus fewer) and (2) dissatisfaction (2 or fewer stars versus 3 or more). To approximate the information patients would use to make assumptions about physician race/ethnicity, four reviewers classified physicians into categories based on physician name and photo. These included White American, Black American, South Asian, Middle Eastern, Hispanic, and East Asian. Mixed effects logistic regression was used to assess differences in patient top-box satisfaction and patient dissatisfaction by physician race/ethnicity, controlling for patient characteristics, prescription receipt, physician specialty, and whether the physician trained in the USA versus internationally. KEY RESULTS: The sample included 119,016 encounters with 390 physicians. Sixty percent were White American, 14% South Asian, 7% Black American, 7% Hispanic, 6% Middle Eastern, and 6% East Asian. Encounters with South Asian physicians (aOR 0.70; 95% CI 0.54-0.91) and East Asian physicians (aOR 0.72; 95% CI 0.53-0.99) were significantly less likely than those with White American physicians to result in top-box satisfaction. Compared to encounters with White American physicians, those with Black American physicians (aOR 1.72; 95% CI 1.12-2.64), South Asian physicians (aOR 1.77; 95% CI 1.23-2.56), and East Asian physicians (aOR 2.10; 95% CI 1.38-3.20) were more likely to result in patient dissatisfaction. CONCLUSIONS: In our study, patients reported lower satisfaction with some groups of non-White American physicians, which may have implications for their compensation, professional reputation, and job satisfaction.


Assuntos
Médicos , Telemedicina , Estudos Transversais , Etnicidade , Hispânico ou Latino , Humanos , Satisfação do Paciente
5.
Environ Res ; 168: 319-328, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30384226

RESUMO

A series of batch experiments were conducted to obtain the optimal adsorption condition for removing aqueous Hg from actual lime-based wet flue gas desulfurization (WFGD) wastewater with sulfur-containing activated carbon (SAC). The experimental results showed that SAC1 had an average 0.32 µg mg-1 larger aqueous Hg adsorption capacity and 21% larger Hg removal than the CS2-treated SAC1 (i.e., SAC2) in all tested pH values, confirming that greater sulfur content associated with effective sulfur functional group (i.e., elemental S) caused the larger Hg adsorption capacity. Furthermore, as increasing pH from 4 to 7, the Hg adsorption capacity of SAC1 decreased by 22% (i.e., 0.27 µg mg-1). The equilibrium Hg adsorption capacity was well fitted with linear and Freundlich adsorption isotherms. Kinetic simulations showed that both pseudo-second order and Elovich equations could well describe the chemisorption behavior of Hg to SAC1. Thermodynamic parameter calculation confirmed that Hg adsorption by SAC1 was thermodynamically spontaneous and exothermic. Re-emission of gaseous Hg markedly decreased by 88% as SO32- addition increased from 0 to 0.01 mM. Notably, by the addition of SAC1, zero re-emission of gaseous Hg was achieved. These experimental results confirm that the capture of aqueous Hg2+ and the inhibition of gaseous Hg0 re-emission can be successfully and simultaneously achieved in actual WFGD wastewater via the addition of SAC.


Assuntos
Carvão Vegetal/química , Mercúrio , Eliminação de Resíduos Líquidos , Águas Residuárias/química , Adsorção , Carbono , Enxofre
6.
J Gen Intern Med ; 33(10): 1768-1773, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30112737

RESUMO

BACKGROUND: Despite its rapid expansion, little is known about use of direct to consumer (DTC) telemedicine. OBJECTIVE: To characterize telemedicine patients and physicians and correlates of patient satisfaction DESIGN: Cross-sectional study PARTICIPANTS: Patients and physicians of a large nationwide DTC telemedicine service MAIN MEASURES: Patient characteristics included demographics and whether or not they reported insurance information. Physician characteristics included specialty, board certification, and domestic versus international medical training. Encounter characteristics included time of day, wait time, length, coupon use for free or reduced-cost care, diagnostic outcome, prescription receipt, and patient/physician geographic concordance. Patients rated satisfaction with physicians on scales of 0 to 5 stars and reported where they would have sought care had they not used telemedicine. Logistic regression was used to assess factors associated with 5-star physician ratings. KEY RESULTS: The analysis included 28,222 encounters between 24,040 patients and 277 physicians completed between January 2013 and August 2016. Sixty-five percent of patients were under 40 years and 32% did not report insurance information. Family medicine was the most common physician specialty (47%) and 16% trained at a non-US medical school. Coupons were used in 24% of encounters. Respiratory infections were diagnosed in 35% of encounters and 69% resulted in a prescription. Had they not used telemedicine, 43% of patients reported they would have used urgent care/retail clinic, 29% would have gone to the doctor's office, 15% would have done nothing, and 6% would have gone to the emergency department. Eighty-five percent of patients rated their physician 5 stars. High satisfaction was positively correlated with prescription receipt (OR 2.98; 95%CI 2.74-3.23) and coupon use (OR 1.47; 95%CI 1.33-1.62). CONCLUSIONS: Patients were largely satisfied with DTC telemedicine, yet satisfaction varied by coupon use and prescription receipt. The impact of telemedicine on primary care and emergency department use is likely to be small under present usage patterns.


Assuntos
Aceitação pelo Paciente de Cuidados de Saúde/estatística & dados numéricos , Satisfação do Paciente/estatística & dados numéricos , Telemedicina/organização & administração , Adulto , Idoso , California , Competência Clínica , Estudos Transversais , Atenção à Saúde/organização & administração , Atenção à Saúde/normas , Feminino , Pesquisas sobre Atenção à Saúde , Pesquisa sobre Serviços de Saúde/métodos , Humanos , Masculino , Pessoa de Meia-Idade , Relações Médico-Paciente , Fatores Socioeconômicos , Telemedicina/normas , Telemedicina/estatística & dados numéricos
7.
Environ Sci Technol ; 51(13): 7581-7589, 2017 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-28562025

RESUMO

Adsorption systems typically need gas and temperature sensors to monitor their adsorption/regeneration cycles to separate gases from gas streams. Activated carbon fiber cloth (ACFC)-electrothermal swing adsorption (ESA) is an adsorption system that has the potential to be controlled with the electrical properties of the adsorbent and is studied here to monitor and control the adsorption/regeneration cycles without the use of gas and temperature sensors and to predict breakthrough before it occurs. The ACFC's electrical resistance was characterized on the basis of the amount of adsorbed organic gas/vapor and the adsorbent temperature. These relationships were then used to develop control logic to monitor and control ESA cycles on the basis of measured resistance and applied power values. Continuous sets of adsorption and regeneration cycles were performed sequentially entirely on the basis of remote electrical measurements and achieved ≥95% capture efficiency at inlet concentrations of 2000 and 4000 ppmv for isobutane, acetone, and toluene in dry and elevated relative humidity gas streams, demonstrating a novel cyclic ESA system that does not require gas or temperature sensors. This contribution is important because it reduces the cost and simplifies the system, predicts breakthrough before its occurrence, and reduces emissions to the atmosphere.


Assuntos
Monitoramento Ambiental , Compostos Orgânicos/análise , Adsorção , Carbono , Carvão Vegetal , Gases , Temperatura
8.
Appl Opt ; 56(27): 7691-7701, 2017 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-29047749

RESUMO

Measurements from two field campaigns that employed a micropulse lidar are used to compare the near-end and the far-end lidar equation inversion methods for estimating emission factors (EFs) of particulate matter (PM) from three types of anthropogenic fugitive sources: vehicles moving on unpaved roads, open burning, and open detonation. As optical depth increased from 0 to 2, relative EF uncertainty increased from 54% to 300% using the near-end method and decreased from 69% to 42% using the far-end method. To the best of our knowledge, this research is the first to use field measurements to compare results from these methods for anthropogenic PM plumes and quantify their uncertainties.

9.
Environ Sci Technol ; 50(3): 1465-72, 2016 Feb 02.
Artigo em Inglês | MEDLINE | ID: mdl-26727459

RESUMO

A life-cycle assessment (LCA) and cost analysis are presented comparing the environmental and economic impacts of using regenerative thermal oxidizer (RTO), granular activated carbon (GAC), and activated carbon fiber cloth (ACFC) systems to treat gaseous emissions from sheet-foam production. The ACFC system has the lowest operational energy consumption (i.e., 19.2, 8.7, and 3.4 TJ/year at a full-scale facility for RTO, GAC, and ACFC systems, respectively). The GAC system has the smallest environmental impacts across most impact categories for the use of electricity from select states in the United States that produce sheet foam. Monte Carlo simulations indicate the GAC and ACFC systems perform similarly (within one standard deviation) for seven of nine environmental impact categories considered and have lower impacts than the RTO for every category for the use of natural gas to produce electricity. The GAC and ACFC systems recover adequate isobutane to pay for themselves through chemical-consumption offsets, whereas the net present value of the RTO is $4.1 M (20 years, $0.001/m(3) treated). The adsorption systems are more environmentally and economically competitive than the RTO due to recovered isobutane for the production process and are recommended for resource recovery from (and treatment of) sheet-foam-production exhaust gas. Research targets for these adsorption systems should focus on increasing adsorptive capacity and saturation of GAC systems and decreasing electricity and N2 consumption of ACFC systems.


Assuntos
Poluentes Atmosféricos/química , Poluição do Ar/prevenção & controle , Técnicas Eletroquímicas , Adsorção , Poluição do Ar/economia , Butanos/química , Carbono/química , Eletricidade , Técnicas Eletroquímicas/economia , Meio Ambiente , Têxteis
13.
J Air Waste Manag Assoc ; 64(2): 227-34, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24654390

RESUMO

Emission factors (EFs) of particulate matter with aerodynamic diameter <10 microm (PM10) from the open burning/open detonation (OB/OD) of energetic materials were measured using a hybrid-optical remote sensing (hybrid-ORS) method. This method is based on the measurement of range-resolved PM backscattering values with a micropulse light detection and ranging (LIDAR; MPL) device. Field measurements were completed during March 2010 at Tooele Army Depot, Utah, which is an arid continental site. PM10 EFs were quantified for OB of M1 propellant and OD of 2,4,6-trinitrotoluene (TNT). EFs from this study are compared with previous OB/OD measurements reported in the literature that have been determined with point measurements either in enclosed or ambient environments, and with concurrent airborne point measurements. PM10 mass EFs, determined with the hybrid-ORS method, were 7.8 x 10(-3) kg PM10/kg M1 from OB of M1 propellant, and 0.20 kg PM10/kg TNT from OD of TNT. Compared with previous results reported in the literature, the hybrid-ORS method EFs were 13% larger for OB and 174% larger for OD. Compared with the concurrent airborne measurements, EF values from the hybrid-ORS method were 37% larger for OB and 54% larger for OD. For TNT, no statistically significant differences were observed for the EFs measured during the detonation of 22.7 and 45.4 kg of TNT, supporting that the total amount of detonated mass in this mass range does not have an effect on the EFs for OD of TNT.


Assuntos
Explosões , Incêndios , Material Particulado/análise , Tecnologia de Sensoriamento Remoto , Modelos Teóricos
14.
Environ Sci Technol ; 47(13): 7373-9, 2013 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-23789711

RESUMO

The use of adsorption on activated carbon fiber cloth (ACFC) followed by electrothermal swing adsorption (ESA) and postdesorption pressure and temperature control allows organic gases with boiling points below 0 °C to be captured from air streams and recovered as liquids. This technology has the potential to be a more sustainable abatement technique when compared to thermal oxidation. In this paper, we determine the process performance and energy requirements of a gas recovery system (GRS) using ACFC-ESA for three adsorbates with relative pressures between 8.3 × 10(-5) and 3.4 × 10(-3) and boiling points as low as -26.3 °C. The GRS is able to capture > 99% of the organic gas from the feed air stream, which is comparable to destruction efficiencies for thermal oxidizers. The energy used per liquid mole recovered ranges from 920 to 52,000 kJ/mol and is a function of relative pressure of the adsorbate in the feed gas. Quantifying the performance of the bench-scale gas recovery system in terms of its ability to remove organic gases from the adsorption stream and the energy required to liquefy the recovered organic gases is a critical step in developing new technologies to allow manufacturing to occur in a more sustainable manner. To our knowledge, this is the first time an ACFC-ESA system has been used to capture, recover, and liquefy organic compounds with vapor pressures as low as 8.3 × 10(-5) and the first time such a system has been analyzed for process performance and energy consumption.


Assuntos
Poluentes Atmosféricos/química , Butanos/química , Carbono/química , Gases/química , Hidrocarbonetos Fluorados/química , Adsorção , Poluição do Ar/prevenção & controle , Fibra de Carbono , Modelos Teóricos , Temperatura , Pressão de Vapor
15.
Environ Sci Technol ; 46(20): 11305-12, 2012 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-22967177

RESUMO

Electrothermal swing adsorption (ESA) of organic compounds from gas streams with activated carbon fiber cloth (ACFC) reduces emissions to the atmosphere and recovers feedstock for reuse. Local temperature measurement (e.g., with a thermocouple) is typically used to monitor/control adsorbent regeneration cycles. Remote electrical resistance measurement is evaluated here as an alternative to local temperature measurement. ACFC resistance that was modeled based on its physical properties was within 10.5% of the measured resistance values during electrothermal heating. Resistance control was developed based on this measured relationship and used to control temperature to within 2.3% of regeneration set-point temperatures. Isobutane-laden adsorbent was then heated with resistance control. After 2 min of heating, the temperature of the adsorbent with isobutane was 13% less than the adsorbent without isobutane. This difference decreased to 2.1% after 9 min of heating, showing desorption of isobutane. An ACFC cartridge was also heated to 175 °C for 900 cycles with its resistance and adsorption capacity values remaining within 3% and 2%, respectively. This new method to control regeneration power application based on rapid sensing of the adsorbent's resistance removes the need for direct-contact temperature sensors providing a simple, cost-efficient, and long-term regeneration technique for ESA systems.


Assuntos
Carbono/química , Temperatura , Adsorção , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/química , Fibra de Carbono , Recuperação e Remediação Ambiental/instrumentação , Recuperação e Remediação Ambiental/métodos , Modelos Químicos , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/química
16.
Environ Pollut ; 294: 118597, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34848285

RESUMO

Cyclists can be easily exposed to traffic-related pollutants due to riding on or close to the road during commuting in cities. PM2.5 has been identified as one of the major pollutants emitted by vehicles and associated with cardiopulmonary and respiratory diseases. As routing has been suggested to reduce the exposures for cyclists, in this study, PM2.5 was monitored with low-cost sensors during commuting periods to develop models for identifying low exposure routes in three Asian cities: Taipei, Osaka, and Seoul. The models for mapping the PM2.5 in the cities were developed by employing the random forest algorithm in a two-stage modeling approach. The land use features to explain spatial variation of PM2.5 were obtained from the open-source land use database, OpenStreetMap. The total length of the monitoring routes ranged from 101.36 to 148.22 km and the average PM2.5 ranged from 13.51 to 15.40 µg/m³ among the cities. The two-stage models had the standard k-fold cross-validation (CV) R2 of 0.93, 0.74, and 0.84 in Taipei, Osaka, and Seoul, respectively. To address spatial autocorrelation, a spatial cross-validation approach applying a distance restriction of 100 m between the model training and testing data was employed. The over-optimistic estimates on the predictions were thus prevented, showing model CV-R2 of 0.91, 0.67, and 0.78 respectively in Taipei, Osaka, and Seoul. The comparisons between the shortest-distance and lowest-exposure routes showed that the largest percentage of reduced averaged PM2.5 exposure could reach 32.1% with the distance increases by 37.8%. Given the findings in this study, routing behavior should be encouraged. With the daily commuting trips expanded, the cumulative effect may become significant on the chronic exposures over time. Therefore, a route planning tool for reducing the exposures shall be developed and promoted to the public.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Algoritmos , Cidades , Exposição Ambiental , Monitoramento Ambiental , Material Particulado/análise , Meios de Transporte
17.
Environ Sci Technol ; 45(2): 738-43, 2011 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-21158385

RESUMO

Electrothermal swing adsorption (ESA) of organic gases generated by industrial processes can reduce atmospheric emissions and allow for reuse of recovered product. Desorption energy efficiency can be improved through control of adsorbent heating, allowing for cost-effective separation and concentration of these gases for reuse. ESA experiments with an air stream containing 2000 ppm(v) isobutane and activated carbon fiber cloth (ACFC) were performed to evaluate regeneration energy consumption. Control logic based on temperature feedback achieved select temperature and power profiles during regeneration cycles while maintaining the ACFC's mean regeneration temperature (200 °C). Energy requirements for regeneration were independent of differences in temperature/power oscillations (1186-1237 kJ/mol of isobutane). ACFC was also heated to a ramped set-point, and the average absolute error between the actual and set-point temperatures was small (0.73%), demonstrating stable control as set-point temperatures vary, which is necessary for practical applications (e.g., higher temperatures for higher boiling point gases). Additional logic that increased the maximum power application at lower ACFC temperatures resulted in a 36% decrease in energy consumption. Implementing such control logic improves energy efficiency for separating and concentrating organic gases for post-desorption liquefaction of the organic gas for reuse.


Assuntos
Poluentes Atmosféricos/química , Carbono/química , Técnicas Eletroquímicas/métodos , Calefação , Compostos Orgânicos Voláteis/química , Adsorção , Poluição do Ar/prevenção & controle , Butanos/química , Fibra de Carbono , Técnicas Eletroquímicas/economia , Técnicas Eletroquímicas/instrumentação , Gerenciamento de Resíduos/economia , Gerenciamento de Resíduos/instrumentação , Gerenciamento de Resíduos/métodos
18.
Environ Sci Technol ; 45(2): 658-65, 2011 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-21142142

RESUMO

The emissions of particulate matter (PM) from anthropogenic sources raise public concern. A new method is described here that was developed to complete in situ rapid response measurements of PM mass emissions from fugitive dust sources by use of optical remote sensing (ORS) and an anemometer. The ORS system consists of one ground-based micropulse light detection and ranging (MPL) device that was mounted on a positioner, two open path-Fourier transform infrared (OP-FTIR) spectrometers, and two open path-laser transmissometers (OP-LT). An algorithm was formulated to compute PM light extinction profiles along each of the plume's cross sections that were determined with the MPL. Size-specific PM mass emission factors were then calculated by integrating the light extinction profiles with particle mass extinction efficiencies (determined with the OP-FTIRs/OP-LTs) and the wind's speed and direction. This method also quantifies the spatial and temporal variability of the plume's PM mass concentrations across each of the plume's cross sections. Example results from three field studies are also described to demonstrate how this new method is used to determine mass emission factors as well as characterize the dust plumes' horizontal and vertical dimensions and temporal variability of the PM's mass concentration.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Material Particulado/análise , Tecnologia de Sensoriamento Remoto/métodos , Poluição do Ar/estatística & dados numéricos , Atmosfera/química , Cinética , Lasers , Luz , Modelos Químicos , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de Fourier , Vento
19.
Environ Sci Technol ; 45(2): 666-72, 2011 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-21142143

RESUMO

Quantification of emissions of fugitive particulate matter (PM) into the atmosphere from military training operations is of interest by the United States Department of Defense. A new range-resolved optical remote sensing (ORS) method was developed to quantify fugitive PM emissions from puff sources (i.e., artillery back blasts), ground-level mobile sources (i.e., movement of tracked vehicles), and elevated mobile sources (i.e., airborne helicopters) in desert areas that are prone to generating fugitive dust plumes. Real-time, in situ mass concentration profiles for PM mass with particle diameters <10 µm (PM(10)) and <2.5 µm (PM(2.5)) were obtained across the dust plumes that were generated by these activities with this new method. Back blasts caused during artillery firing were characterized as a stationary short-term puff source whose plumes typically dispersed to <10 m above the ground with durations of 10-30 s. Fugitive PM emissions caused by artillery back blasts were related to the zone charge and ranged from 51 to 463 g PM/firing for PM(10) and 9 to 176 g PM/firing for PM(2.5). Movement of tracked vehicles and flying helicopters was characterized as mobile continuous sources whose plumes typically dispersed 30-50 m above the ground with durations of 100-200 s. Fugitive PM emissions caused by moving tracked vehicles ranged from 8.3 to 72.5 kg PM/km for PM(10) and 1.1 to 17.2 kg PM/km for PM(2.5), and there was no obvious correlation between PM emission and vehicle speed. The emission factor for the helicopter flying at 3 m above the ground ranged from 14.5 to 114.1 kg PM/km for PM(10) and 5.0 to 39.5 kg PM/km for PM(2.5), depending on the velocity of the helicopter and type of soil it flies over. Fugitive PM emissions by an airborne helicopter were correlated with helicopter speed for a particular soil type. The results from this range-resolved ORS method were also compared with the data obtained with another path-integrated ORS method and a Flux Tower method.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Material Particulado/análise , Tecnologia de Sensoriamento Remoto/métodos , Poluição do Ar/estatística & dados numéricos , Aeronaves/estatística & dados numéricos , Atmosfera/química , Cinética , Lasers , Luz , Modelos Químicos , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de Fourier , Emissões de Veículos/análise , Armas/estatística & dados numéricos , Vento
20.
Environ Sci Technol ; 44(18): 7070-5, 2010 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-20722439

RESUMO

A bench-scale capture and recovery system to convert a low concentration organic gas to a liquid is described here. Adsorption of isobutane onto activated carbon fiber cloth (ACFC) followed by electrothermal desorption and subsequent liquefaction is demonstrated. Experimental conditions to condense desorbed isobutane were determined based on Dalton's law and Antoine's equation. Breakthrough curves for a gas stream containing 2000 ppm(v) isobutane in air adsorbing onto ACFC-15 demonstrate an adsorption capacity of 0.094 ± 0.017 g of isobutane/g of ACFC with >98% capture efficiency. The system described here utilizes two adsorbers, which operate cyclically to allow for continuous treatment of the isobutane. Adsorption followed by electrothermal desorption provided a concentration ratio of 240, which facilitates condensation of the isobutane after compression and cooling and is an order of magnitude greater than what has been previously demonstrated.


Assuntos
Butanos/química , Técnicas Eletroquímicas/métodos , Temperatura , Adsorção , Carbono/química , Fibra de Carbono , Carvão Vegetal/química , Pressão de Vapor
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