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.

Tunable far-IR laser spectroscopy of jet-cooled carbon clusters: the nu 2 bending vibration of C3.

Seven rovibrational transitions of the (01(1)0) <-- (00(0)0) fundamental bending band of C3 have been measured with high precision with the use of a tunable far-infrared laser spectrometer. The C3 molecules were produced by laser vaporization of a graphite rod and cooled in a supersonic expansion. The astrophysically important nu 2 fundamental frequency is determined to be 63.416529(40) cm-1. These measurements provide the basis for studies of C3 in the interstellar medium with far-infrared astronomy.

Removal of Stratospheric O3 by Radicals: In Situ Measurements of OH, HO2, NO, NO2, ClO, and BrO.

Simultaneous in situ measurements of the concentrations of OH, HO(2), ClO, BrO, NO, and NO(2) demonstrate the predominance of odd-hydrogen and halogen free-radical catalysis in determining the rate of removal of ozone in the lower stratosphere during May 1993. A single catalytic cycle, in which the rate-limiting step is the reaction of HO(2) with ozone, accounted for nearly one-half of the total O(3) removal in this region of the atmosphere. Halogen-radical chemistry was responsible for approximately one-third of the photochemical removal of O(3); reactions involving BrO account for one-half of this loss. Catalytic destruction by NO(2), which for two decades was considered to be the predominant loss process, accounted for less than 20 percent of the O(3) removal. The measurements demonstrate quantitatively the coupling that exists between the radical families. The concentrations of HO(2) and ClO are inversely correlated with those of NO and NO(2). The direct determination of the relative importance of the catalytic loss processes, combined with a demonstration of the reactions linking the hydrogen, halogen, and nitrogen radical concentrations, shows that in the air sampled the rate of O(3) removal was inversely correlated with total NOx, loading.

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.

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.

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.

Volume expanded diuretic renography in the postnatal assessment of suspected uretero-pelvic junction obstruction.

Controversy surrounds the role of 99mTc-diethylenetriamine pentaacetic acid renography in suspected uretero-pelvic junction obstruction in early life. Accordingly, we retrospectively reviewed 18 patients (28 hydronephrotic kidneys) with a mean age of 2 mo (range: 1 wk-6 mo) who underwent a total of 36 scans using intravenous volume expansion (10 ml/kg) and furosemide diuresis (1 mg/kg). Initial scans were classified as obstructed, not obstructed or indeterminate using differential renal function, furosemide washout T 1/2 and visual assessment of tracer clearance. Those initially classified as obstructed (n = 8) have been surgically confirmed. In the indeterminate (n = 6) and nonobstructed (n = 14) groups, three and two kidneys, respectively, developed obstruction on progress scans. Mean follow-up in the nonsurgical patients was approximately 9 mo (range: 4-17 mo). A total of 13 kidneys had developed obstruction by renographic criteria, and to date 12 have surgical confirmation. Our data indicate that: (1) scans classified as obstructed correlate well with surgery; (2) an initial classification of indeterminate or nonobstructed does not exclude later development of obstruction; and (3) serial scans correctly stratify children with possible uretero-pelvic junction obstruction.

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.

A new model of tracheal stenosis and its repair with free periosteal grafts.

Stenosis of 50% to 80% of the cervical or thoracic tracheal lumen was created in 17 piglets by encircling the trachea with silicone rubber sheet for 3 to 19 days (median 14 days). In 13 animals thoracic tracheal stenosis was repaired by longitudinal incision and insertion of a free tibial periosteal graft into the defect. An omental pedicle graft was applied to the surface of the free periosteal graft to augment its blood supply in three of these animals. An endotracheal silicone rubber splint was left in place for 2 to 3 weeks after the operations. Four animals served as untreated controls. In 12 of 13 piglets respiratory obstruction was relieved. One repair failed because of graft necrosis. In two animals put to death 1 month and 2 months later, stenosis was absent and the grafts showed variable ossification. The luminal surface had epithelialized. In nine of 10 animals put to death 3 months after the operation, tracheal cross-sectional areas had doubled, stenosis and granulation tissue were absent, and all the grafts had ossified and epithelialized. A mild stenosis (24%) developed over a 2 mm length in one animal and the graft had not ossified. The omental pedicle graft did not improve vascularization of the free periosteal graft. These studies describe a model of tracheal stenosis that can be used to assess various methods of repair. The results indicate that tracheal stenosis can be successfully treated by incision and insertion of a free periosteal graft into the defect.

Intraneural ganglion of the common peroneal nerve in a 4-year-old boy.

The case history of a 4-year-old boy with an intraneural ganglion of the common peroneal nerve is presented. These lesions are rare, more commonly affect males, and typically present with a painful foot-drop. A mass is often palpable adjacent to the neck of the fibula. Our patient has made a good recovery after surgery.

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.

Diagnosis and management of massive hepatic hemangiomas in childhood.

Twelve patients diagnosed as having hepatic hemangiomas during 1960 to 1982 at the Royal Children's Hospital, Melbourne are reviewed. This rare benign vascular tumor can present considerable problems in both diagnosis and management and has a high reported mortality. Our experience over this 23-year period demonstrates some of the difficulties in diagnosis and suggests a plan of management. Eight patients were diagnosed when five weeks of age or less, the youngest was 24 hours old. One was diagnosed at four months of age. In the remaining three patients, the diagnosis was made at postmortem. Ten patients had prominent hepatomegaly, nine had congestive cardiac failure and in one of these the onset was delayed four weeks. Thrombocytopenia was present in five and jaundice in four patients. Four patients had associated cutaneous or visceral hemangiomas. Seven patients underwent selective hepatic arteriography, and two of these had prior ultrasound examinations of the liver. Management of congestive cardiac failure included steroids, radiotherapy, hepatic resection, and in one patient, hepatic artery ligation. One patient with diffuse hepatic hemangiomas did not require any specific therapy and resolved spontaneously over two years. The four patients in whom hepatic resection was performed survived.

Continuous epidural analgesia in newborn infants undergoing major surgery.

Providing safe, effective analgesia for newborn infants undergoing major surgery remains a challenge to pediatric anesthetists and surgeons. Continuous epidural analgesia (CEA) has been shown to provide safe and effective analgesia in infants and children; however, there is little reported use in neonates. We review our experience of CEA in 14 newborn infants (32 to 40 weeks gestation) aged 4 hours to 35 days undergoing major surgery, as well as a further 6 ex-preterm (25 to 29 weeks gestation) infants aged 2 to 5 months at time of surgery. In all cases effective analgesia was achieved for up to 69 hours without complication. All infants were awake and extubated uneventfully at the completion of surgery, which lasted 5 hours in one case. None of the infants developed respiratory depression or prolonged apnea. The technique has been widely accepted by surgeons, neonatal nursing staff, and neonatologists.

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.

Endoscopic laser division of an esophageal web in a child.

The authors report the first successful endoscopic laser division of a congenital esophageal web in a child in whom dilatation had failed. Laser lysis is minimally invasive and should be attempted before surgery is considered.

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.