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 NO_x 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.

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 (NO_x), 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 NO_x, 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 NO_x and 15% by dry deposition. RONO₂ production accounts for 20% of the net regional NO_x sink in the Southeast US in summer, limited by the spatial segregation between BVOC and NO_x emissions. This segregation implies that RONO₂ production will remain a minor sink for NO_x in the Southeast US in the future even as NO_x emissions continue to decline.

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 NO_x-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 NO_x-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.

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.

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.

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.

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.

Photochemical Production and Release of Gaseous NO2from 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.

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 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.

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 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.

Adverse outcome of congenital diaphragmatic hernia is determined by diaphragmatic agenesis, not by antenatal diagnosis

BACKGROUND/PURPOSE

The authors studied their congenital diaphragmatic hernia (CDH) cases retrospectively to ascertain if classical CDH and diaphragmatic agenesis (DA) have separate clinical manifestations, whether antenatally diagnosed cases behave differently from those not diagnosed antenatally, and if antenatal diagnosis before 25 weeks carries a worse prognosis.

METHODS

The authors performed a retrospective review of 23 infants with CDH treated at their institution between January 1996 and March 1999. The patients were divided into 3 groups that were analyzed: DA and classical CDH, antenatally diagnosed and nonantenatally diagnosed, and antenatally diagnosed before 25 weeks and after 25 weeks.

RESULTS

There were 8 cases of DA and 11 cases of classical CDH. Four infants died without operation and could not be classified. Neonates with DA had significantly longer mean duration of preoperative stabilization compared with classical CDH (5.25+/-2.76 days v 1.36+/-1.0 days) and postoperative mechanical ventilatory support (15.7+/-3.0 days v 4.9+/-3.0 days). Fifty percent of DA patients died; all classical CDH patients survived. Twelve cases were diagnosed antenatally, 6 before 25 weeks' gestation. Antenatally diagnosed cases had no statistically significant difference in mortality rates from those not diagnosed antenatally; 50% of those diagnosed before 25 weeks survived.

CONCLUSIONS

DA cases require more preoperative preparation and postoperative ventilation and have a bad prognosis compared with classical CDH. Antenatal diagnosis of CDH does not convey a different prognosis. Fifty percent of CDH patients with antenatal diagnosis before 25 weeks survive.

Cisapride in the control of symptoms in infants with gastroesophageal reflux: A randomized, double-blind, placebo-controlled trial

OBJECTIVE

To evaluate the efficacy of cisapride in the treatment of uncomplicated gastroesophageal reflux in children younger than 36 months of age.

STUDY DESIGN

A total of 95 patients satisfied the entry criteria and were randomly assigned to double-blind treatment with either cisapride (n = 50), 0.2 mg/kg 4 times daily, or placebo (n = 45) for 2 weeks. At the end of the 2-week treatment period, symptom diary and parental evaluation with repeat 24-hour pH study were performed.

RESULTS

Sixty-eight patients completed the trial (38 in the cisapride group and 30 in the placebo group). There were no significant differences in the symptoms of crying, vomiting, or gagging; the overall symptom intensity score; or parental global evaluations. There was a significant difference (P <.03) in the percent time pH <4, the number of reflux episodes lasting more than 5 minutes, and the duration of the longest episode. No significant difference was demonstrated for the number of episodes with pH <4 or the reflux score.

CONCLUSIONS

Cisapride was no better than placebo for relief of symptoms in children with uncomplicated gastroesophageal reflux. A beneficial effect was demonstrated in the cisapride group in relation to the measured parameters for esophageal acid exposure time.

Ureteroceles in children: an ongoing challenge

The treatment of ureteroceles in children requires an individualised approach. Antenatal diagnosis is the ideal, so that postnatal urinary antibiotic prophylaxis and appropriate investigations can be organised. Postnatal investigations should assess both upper and lower urinary tract. Renal and bladder ultrasound and radiographic micturating cystourethragraphy under antibiotic cover will both detect vesicoureteric reflux and assess any bladder outlet obstruction due to the ureterocele. Renal function, particularly of the upper moiety, is best evaluated by technetium Tc99m dimercaptosuccinic acid renal scan. Both function and obstruction can be quantitated by the Tc99m-mercaptoacetyltriglycine isotope scan with intravenous volume expansion (10 ml/kg) and furosemide diuresis (1 mg/kg). Intravenous urography provides the best anatomic information when the upper moiety is functional. The surgical management is based on the clinical situation, which is often variable, and therefore needs to be tailored for each patient. The general principles include restoration of anatomy to as near normal as possible and preservation of functional renal tissue.

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.