Deliberating performance targets workshop: Potential paths for emerging PM2.5 and O3 air sensor progress.

The United States Environmental Protection Agency held an international two-day workshop in June 2018 to deliberate possible performance targets for non-regulatory fine particulate matter (PM2.5) and ozone (O3) air sensors. The need for a workshop arose from the lack of any market-wide manufacturer requirement for Ozone documented sensor performance evaluations, the lack of any independent third party or government-based sensor performance certification program, and uncertainty among all users as to the general usability of air sensor data. A multi-sector subject matter expert panel was assembled to facilitate an open discussion on these issues with multiple stakeholders. This summary provides an overview of the workshop purpose, key findings from the deliberations, and considerations for future actions specific to sensors. Important findings concerning PM2.5 and O3 sensors included the lack of consistent performance indicators and statistical metrics as well as highly variable data quality requirements depending on the intended use. While the workshop did not attempt to yield consensus on any topic, a key message was that a number of possible future actions would be beneficial to all stakeholders regarding sensor technologies. These included documentation of best practices, sharing quality assurance results along with sensor data, and the development of a common performance target lexicon, performance targets, and test protocols.

Anthropogenic control over wintertime oxidation of atmospheric pollutants.

During winter in the mid-latitudes, photochemical oxidation is significantly slower than in summer and the main radical oxidants driving formation of secondary pollutants, such as fine particulate matter and ozone, remain uncertain, owing to a lack of observations in this season. Using airborne observations, we quantify the contribution of various oxidants on a regional basis during winter, enabling improved chemical descriptions of wintertime air pollution transformations. We show that 25-60% of NOx is converted to N2O5 via multiphase reactions between gas-phase nitrogen oxide reservoirs and aerosol particles, with ~93% reacting in the marine boundary layer to form >2.5 ppbv ClNO2. This results in >70% of the oxidizing capacity of polluted air during winter being controlled, not by typical photochemical reactions, but from these multiphase reactions and emissions of volatile organic compounds, such as HCHO, highlighting the control local anthropogenic emissions have on the oxidizing capacity of the polluted wintertime atmosphere.

Tropospheric Emissions: Monitoring of Pollution (TEMPO).

TEMPO was selected in 2012 by NASA as the first Earth Venture Instrument, for launch between 2018 and 2021. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO observes from Mexico City, Cuba, and the Bahamas to the Canadian oil sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (~2.1 km N/S×4.4 km E/W at 36.5°N, 100°W). TEMPO provides a tropospheric measurement suite that includes the key elements of tropospheric air pollution chemistry, as well as contributing to carbon cycle knowledge. Measurements are made hourly from geostationary (GEO) orbit, to capture the high variability present in the diurnal cycle of emissions and chemistry that are unobservable from current low-Earth orbit (LEO) satellites that measure once per day. The small product spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO takes advantage of a commercial GEO host spacecraft to provide a modest cost mission that measures the spectra required to retrieve ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), formaldehyde (H2CO), glyoxal (C2H2O2), bromine monoxide (BrO), IO (iodine monoxide),water vapor, aerosols, cloud parameters, ultraviolet radiation, and foliage properties. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides these near-real-time air quality products that will be made publicly available. TEMPO will launch at a prime time to be the North American component of the global geostationary constellation of pollution monitoring together with the European Sentinel-4 (S4) and Korean Geostationary Environment Monitoring Spectrometer (GEMS) instruments.

Ozone production chemistry in the presence of urban plumes.

Ozone pollution affects human health, especially in urban areas on hot sunny days. Its basic photochemistry has been known for decades and yet it is still not possible to correctly predict the high ozone levels that are the greatest threat. The CalNex_SJV study in Bakersfield CA in May/June 2010 provided an opportunity to examine ozone photochemistry in an urban area surrounded by agriculture. The measurement suite included hydroxyl (OH), hydroperoxyl (HO2), and OH reactivity, which are compared with the output of a photochemical box model. While the agreement is generally within combined uncertainties, measured HO2 far exceeds modeled HO2 in NOx-rich plumes. OH production and loss do not balance as they should in the morning, and the ozone production calculated with measured HO2 is a decade greater than that calculated with modeled HO2 when NO levels are high. Calculated ozone production using measured HO2 is twice that using modeled HO2, but this difference in calculated ozone production has minimal impact on the assessment of NOx-sensitivity or VOC-sensitivity for midday ozone production. Evidence from this study indicates that this important discrepancy is not due to the HO2 measurement or to the sampling of transported plumes but instead to either emissions of unknown organic species that accompany the NO emissions or unknown photochemistry involving nitrogen oxides and hydrogen oxides, possibly the hypothesized reaction OH + NO + O2 → HO2 + NO2.

Organic nitrate chemistry and its implications for nitrogen budgets in an isoprene- and monoterpene-rich atmosphere: constraints from aircraft (SEAC4RS) and ground-based (SOAS) observations in the Southeast US.

Formation of organic nitrates (RONO2) during oxidation of biogenic volatile organic compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NOx), but the chemistry of RONO2 formation and degradation remains uncertain. Here we implement a new BVOC oxidation mechanism (including updated isoprene chemistry, new monoterpene chemistry, and particle uptake of RONO2) in the GEOS-Chem global chemical transport model with ∼25 × 25 km2 resolution over North America. We evaluate the model using aircraft (SEAC4RS) and ground-based (SOAS) observations of NOx, BVOCs, and RONO2 from the Southeast US in summer 2013. The updated simulation successfully reproduces the concentrations of individual gas- and particle-phase RONO2 species measured during the campaigns. Gas-phase isoprene nitrates account for 25-50% of observed RONO2 in surface air, and we find that another 10% is contributed by gas-phase monoterpene nitrates. Observations in the free troposphere show an important contribution from long-lived nitrates derived from anthropogenic VOCs. During both campaigns, at least 10% of observed boundary layer RONO2 were in the particle phase. We find that aerosol uptake followed by hydrolysis to HNO3 accounts for 60% of simulated gas-phase RONO2 loss in the boundary layer. Other losses are 20% by photolysis to recycle NOx and 15% by dry deposition. RONO2 production accounts for 20% of the net regional NOx sink in the Southeast US in summer, limited by the spatial segregation between BVOC and NOx emissions. This segregation implies that RONO2 production will remain a minor sink for NOx in the Southeast US in the future even as NOx emissions continue to decline.

Right-sided congenital diaphragmatic hernia: A tertiary centre's experience over 25 years.

AIMS: To provide analysis on infants treated for right-sided congenital diaphragmatic hernia (RCDH) including mortality, neonatal morbidities, and associated congenital anomalies. METHODS: We reviewed records of infants admitted with RCDH from 1985 to 2010. RESULTS: A total of 160 infants with CDH were identified; of them 22 infants had RCDH, 14 (64%) were male and eight (36%) were female. Eleven of the 22 infants died (50%), of which seven (64%) were male, and four (36%) were female. Three infants (13.6%) were diagnosed prenatally, and 19 (86.4%) were diagnosed postnatally. A statistically significant association with mortality was observed for low five minute Apgar score (OR = 8; 95% CI: 1.24-51.5), and high alveolar-arterial gradient >400 (OR = 25.7; 95% CI: 2.2-298.5). Fourteen infants (64%) underwent surgical correction, three (21.4%) infants who underwent surgery died. Three infants were discharged with oxygen supplementation and tube feeding at home, and one on sildenafil. No statistical significance was observed between other variables and mortality/morbidity. We observed a change in practice in relation to timing of surgery allowing stabilisation of patient prior to surgery. Average in-patient stay for RCDH infants was 23.5 days (range: 0-112), compared with the total in-patient mean stay of 10.5 days. CONCLUSIONS: Low five minute Apgar score, and high alveolar-arterial gradient were significant predictors of mortality. RCDH is associated with high mortality (50%), prolonged length of stay and other anomalies. In recent years, we observed an improving trend for survival.

Evidence for NO(x) control over nighttime SOA formation.

Laboratory studies have established a number of chemical pathways by which nitrogen oxides (NO(x)) affect atmospheric organic aerosol (OA) production. However, these effects have not been directly observed in ambient OA. We report measurements of particulate organic nitrates in Bakersfield, California, the nighttime formation of which increases with NO(x) and is suppressed by high concentrations of organic molecules that rapidly react with nitrate radical (NO(3))--evidence that multigenerational chemistry is responsible for organic nitrate aerosol production. This class of molecules represents about a third of the nighttime increase in OA, suggesting that most nighttime secondary OA is due to the NO(3) product of anthropogenic NO(x) emissions. Consequently, reductions in NO(x) emissions should reduce the concentration of organic aerosol in Bakersfield and the surrounding region.

Use of personal digital assistants for data collection in a multi-site AIDS stigma study in rural south Nyanza, Kenya.

OBJECTIVES: To describe the development, cost effectiveness and implementation of a PDA based electronic system to collect, verify and manage data from a multi-site study on HIV/AIDS stigma and pregnancy in a rural, resource-poor area. METHODS: We worked within a large prevention of mother-to-child-transmission (PMTCT) program in nine rural health facilities to implement a PDA-based data collection system and to study the feasibility of its use in a multisite HIV research study in rural Kenya. The PDAs were programmed for collecting screening and eligibility data, and responses to structured interviews on HIV/AIDS stigma and violence in three local languages. RESULTS: Between November 2007 and December 2008, nine PDAs were used by Clinic and Community Health Assistants to enrol 1,270 participants on to the PMTCT program. Successes included: capacity-building of interviewers, low cost of implementation, quick turnaround time of data entry with good data quality, and convenience. CONCLUSION: Our study demonstrated the feasibility of utilizing PDAs for data collection in a multi-site observational study on HIV/AIDS stigma conducted in remote rural health facilities in Kenya. However, appropriate and frequent data backup protocols need to be established and paper forms are still needed as backup tools in resource-poor settings.

Kinetics of NO and NO2 evolution from illuminated frozen nitrate solutions.

The release of NO and NO2 from frozen aqueous NaNO3 irradiated at 313 nm was studied using time-resolved spectroscopic techniques. The kinetic behavior of NO and NO2 signals during on-and-off illumination cycles confirms that NO2 is a primary photoproduct evolving from the outermost ice layers and reveals that NO is a secondary species generated deeper in the ice, whence it eventually emerges due to its inertness and larger diffusivity. NO is shown to be more weakly held than NO2 by ice in thermal desorption experiments on preirradiated samples. The partial control of gaseous emissions by mass transfer, and hence by the morphology and metamorphisms of polycrystalline ice, is established by (1) the nonmonotonic temperature dependence of NO and NO2 signals upon stepwise warming under continuous illumination, (2) the fact that the NO, NO2 or NOx (NOx identical with NO + NO2) amounts released in bright thermograms performed under various heating ramps fail to scale with photon dose, due to irreversible losses in the adsorbed state. Because present NO/NO2 ratios are up to 10-fold smaller than those determined over sunlit snowpacks, we infer that the immediate precursors to NO mostly absorb at lambda > lambda(max) (NO3-) approximately 302 nm.

Photochemical production and release of gaseous NO2 from nitrate-doped water ice.

Temperature-programmed NO2 emissions from frozen aqueous NaNO3 solutions irradiated at 313 nm were monitored as function of nitrate concentration and heating rate, H, above -30 degrees C. Emissions increase nonmonotonically with temperature, displaying transitions suggestive of underlying metamorphic transformations. Thus, NO2 emissions surge at ca. -8 degrees C in frozen [NO3-] > 200 microM samples warmed at H = 0.70 degrees C min(-1) under continuous irradiation, and also in the dark from samples that had been photolyzed at -30 degrees C. The amounts of NO2 released in individual thermograms, SigmaN, increase less than linearly with [NO3-] or the duration of experiments, revealing the significant loss of photogenerated NO2. The actual SigmaN proportional, variant [NO3-]1/2 dependence (at constant H) is consistent with NO2 hydrolysis: 2NO2 + H2O --> NO3- + NO2- + 2H+, overtaking NO2 desorption, even below the eutectic point (-18 degrees C for aqueous NaNO3). The increasingly larger NO2 losses detected in longer experiments (at constant [NO3-]) are ascribed to secondary photolysis of trapped NO2. The relevance of present results to the interpretation of polar NO2 measurements is briefly analyzed.

Local hydration environments of amino acids and dipeptides studied by X-ray spectroscopy of liquid microjets.

The nitrogen K-edge spectra of aqueous proline and diglycine solutions have been measured by total electron yield near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at neutral and high pH. All observed spectral features have been assigned by comparison to the recently reported spectrum of aqueous glycine and calculated spectra of isolated amino acids and hydrated amino acid clusters. The sharp preedge resonances at 401.3 and 402.6 eV observed in the spectrum of anionic glycine indicate that the nitrogen terminus is in an "acceptor-only" configuration, wherein neither amine proton is involved in hydrogen bonding to the solvent, at high pH. The analogous 1s --> sigma(NH) preedge transitions are absent in the NEXAFS spectrum of anionic proline, implying that the acceptor-only conformation observed in anionic glycine arises from steric shielding induced by free rotation of the amine terminus about the glycine CN bond. Anionic diglycine solutions exhibit a broadened 1s --> pi(CN) resonance at 401.2 eV and a broad shoulder resonance at 403 eV, also suggesting the presence of an acceptor-only species. Although this assignment is not as unambiguous as for glycine, it implies that the nitrogen terminus of most proteins is capable of existing in an acceptor-only conformation at high pH. The NEXAFS spectrum of zwitterionic lysine solution was also measured, exhibiting features similar to those of both anionic and zwitterionic glycine, and leading us to conclude that the alpha amine group is present in an acceptor-only configuration, while the end of the butylammonium side chain is fully solvated.

pH dependence of the electronic structure of glycine.

The carbon, nitrogen, and oxygen K-edge spectra were measured for aqueous solutions of glycine by total electron yield near-edge X-ray absorption fine structure (TEY NEXAFS) spectroscopy. The bulk solution pH was systematically varied while maintaining a constant amino acid concentration. Spectra were assigned through comparisons with both previous studies and ab initio computed spectra of isolated glycine molecules and hydrated glycine clusters. Nitrogen K-edge solution spectra recorded at low and moderate pH are nearly identical to those of solid glycine, whereas basic solution spectra strongly resemble those of the gas phase. The carbon 1s --> pi*(C=O) transition exhibits a 0.2 eV red shift at high pH due to the deprotonation of the amine terminus. This deprotonation also effects a 1.4 eV red shift in the nitrogen K-edge at high pH. Two sharp preedge features at 401.3 and 402.5 eV are also observed at high pH. These resonances, previously observed in the vapor-phase ISEELS spectrum of glycine, have been reassigned as transitions to sigma* bound states. The observation of these peaks indicates that the amine moiety is in an acceptor-only hydrogen bond configuration at high pH. At low pH, the oxygen 1s --> pi*(C=O) transition exhibits a 0.25-eV red shift due to the protonation of the carboxylic acid terminus. These spectral differences indicate that the variations in electronic structure observed in the NEXAFS spectra are determined by the internal charge state and hydration environment of the molecule in solution.

The clinical course of fistulating Crohn's disease.

AIM: To determine the clinical characteristics, management and outcome of Crohn's fistulas from the time of first presentation. METHODS: Patients treated for fistulas 6 years previously were assessed for disease demographics, fistula characteristics and treatment from first presentation to final follow-up. RESULTS: Eighty-seven patients with active Crohn's fistulas were evaluated. The median age was 35 years and the median duration of Crohn's disease was 8 years at study entry. Disease was ileo-colonic or colonic in 85%, and 65% had rectal involvement. A single fistula was present in one-third and multiple fistulas in two-thirds; 65% of fistulas were perianal; 80% of fistulas were complex. After a median follow-up from the last treatment of 5.9 years, 68% of patients showed healing of all fistulas, 18% showed healing of some fistulas and 14% showed no healing of fistulas. The fistula site did not influence healing. Perianal and recto-vaginal fistulas took a median of 2.6 years to heal. Half of the complex fistulas required a stoma, resection or proctectomy. CONCLUSIONS: Healing is usually achieved. However, morbidity is great and healing is slow. Proctectomy is required in one-fifth of patients, and perineal healing is often slow. Defining the perianal fistula anatomy as complex or simple determines the likelihood of healing and the type of surgical approach required.

Medium-term results of permanent sacral nerve stimulation for faecal incontinence.

BACKGROUND: Anal sphincter surgery for faecal incontinence is associated with significant morbidity and a variable outcome. Sacral nerve stimulation may provide a good functional outcome with minimal morbidity. This paper reports the experience in a single centre over 5 years. METHODS: Fifteen consecutive patients (14 women), median age 60 (range 37-71) years, underwent temporary, and subsequent permanent, stimulation. All had incontinence to solid or liquid stool; the aetiology was obstetric injury (seven patients), scleroderma (four), idiopathic (two), fistula surgery (one) and repaired rectal prolapse (one). Median duration of symptoms was 6 (range 2-15) years. Clinical evaluation, endoanal ultrasonography, bowel diary, quality of life questionnaire (Short Form (SF) 36) and anorectal physiological testing were performed before and after stimulation. RESULTS: Continence had improved in all patients at median follow-up of 24 (range 3-60) months. Eleven patients were fully continent. Episodes of faecal incontinence decreased from median (range) 11 (2-30) per week before stimulation to 0 (0-4) per week after permanent stimulation (P < 0.001). Urgency improved in all patients (median (range) ability to defer less than 1 (0-1) versus 8 (1-15) min; P = 0.01). 'Social function' and 'role-physical' subscales of the SF36 improved significantly. Mean resting pressure (35 versus 49 cmH2O with temporary stimulation; P < 0.05) and squeeze pressure increment (43 versus 69 cmH2O with permanent stimulation; P < 0.01) increased. Rectal sensitivity to initial distension changed (mean 47 versus 34 ml air; P < 0.05). There were no major complications. CONCLUSION: Sacral nerve stimulation is a safe and effective treatment for faecal incontinence when conventional treatment has failed. There is minimal morbidity. The benefit is maintained in the medium term.

Urethral trauma in children.

We report our 12-year experience in the management of urethral injuries in nine children, six boys and three girls. The most common mechanisms of injury were motor vehicle accidents, followed by straddle injuries. All the injuries in boys involved the anterior urethra, and in girls the proximal or mid-urethra. There were associated injuries in five, including three pelvic fractures. All children were investigated with a retrograde urethrogram. Four were treated non-operatively with insertion of a urethral catheter. Of the remaining five, one had drainage of a penile haematoma, one cystourethroscopy, two insertion of urinary and suprapubic catheters, and one open cystotomy and passage of a guide wire with antegrade passage of a urethral catheter. Complications included one urinary tract infection, one urethral fistula, one urethrovaginal fistula, and two urethral strictures. Final outcome was satisfactory in all nine children.

Laparoscopic varicocelectomy with preservation of the testicular artery in adolescents.

PURPOSE: The aim of this study was to determine if laparoscopic varicocelectomy (LV) with preservation of the testicular artery (TA) is a satisfactory alternative to standard open surgical techniques in adolescents. METHODS: Between June 1993 and June 1999 left LV was performed on 40 boys, median age, 12 years (range, 9 to 16 years). Selection for surgical correction included size of the varicocele, symptoms, and clinical or ultrasound assessment for testicular hypotrophy. Eight patients had undergone previous left-sided inguinal surgery, 5 of these for varicocele. Three laparoscopic ports were used. The TA was identified and preserved with the aid of a Doppler flow transducer ("Smart Needle"). All the testicular veins were ligated and divided. The inferior epigastric (IE) veins also were ligated in 19 patients. The operating time was a mean of 1 hour. The postoperative follow-up for a median of 19.5 months (range, 3 to 36 months) included clinical and ultrasound assessment. RESULTS: Preoperative assessment confirmed left-sided testicular hypotrophy 35 patients (88%). Thirty-eight varicoceles were stage 3, and 2 were stage 2. Testicular discomfort was present in 13 patients. Complete correction of the varicocele was achieved in 33 (83%). At a mean of 5 months after LV open repair in 7 patients confirmed a dilated cremasteric vein connecting to the IE veins. Ligation of the IE veins at the time of LV was associated with a persistent varicocele in 3 of 19 patients (16%), similar to the nonligated group, 4 of 21 patients (19%). Five patients (12.5%) had a mild hydrocele. The left testicular volume increased 30% to 50% in 28 patients (70%) at a median of 6.5 months after repair. Testicular atrophy did not occur in any patients. The majority of patients went home within 6 hours of surgery. CONCLUSIONS: The laparoscopic technique with preservation of the TA is an acceptable alternative to open surgical treatment of varicoceles. Further, it eliminates the risk of testicular atrophy and is the technique of choice when previous inguinal surgery has been performed. Ligation of IE veins was not associated with a decrease in the persistence of varicocele postoperatively.

Antenatal detection of a pancreatic foregut duplication cyst.

Congenital pancreatic cyst is a rare cause of a cystic abdominal mass in the neonate. The authors report a case of antenatal detection of a foregut duplication cyst arising entirely from the pancreas.

Laparoscopic bladder 'wrap' technique for repair of vesicoureteric reflux in a porcine model.

PURPOSE: The aim of this study was to determine if vesicoureteric reflux (VUR) can be successfully corrected laparoscopically by a bladder "wrap" technique in a pig model. METHODS: In 15 female piglets (mean weight, 22.5 kg) bilateral VUR was created by an open technique (11 grade 3, 2 each of grades 2 and 4). Eight weeks later (range, 4to 16 weeks) VUR was confirmed by fluoroscopic cystogram, and unilateral laparoscopic correction was performed. The contralateral ureter was used as a control. The bladder was emptied, and a 3F ureteric catheter was inserted on the repair side. Four 11-mm ports were inserted transperitoneally. The ureter was dissected to the ureterovesical junction (UVJ). Commencing at the UVJ, 2 (n = 9) or 3 (n = 6) black silk sutures were placed through the bladder muscle on either side of the ureter creating a bladder wrap around the distal 2 to 4 cm of ureter. At a mean of 16 weeks (range, 4 to 24 weeks) cystograms were repeated. The animals were killed the bladder and ureters underwent histopathology examination. RESULTS: VUR was corrected in 12 animals (80%). There was persistence of VUR in 2 and ureteric obstruction in 1. The wrap was intact in all animals. CONCLUSIONS: Laparoscopic correction of VUR by the bladder wrap technique is successful in pigs. Long-term follow-up studies will determine if this will be a satisfactory alternative surgical treatment for correction of VUR in children.