Atmospheric oxidation capacity in the summer of Houston 2006: Comparison with summer measurements in other metropolitan studies

Both similarities and differences in summertime atmospheric photochemical oxidation appear in the comparison of four field studies: TEXAQS2000 (Houston, 2000), NYC2001 (New York City, 2001), MCMA2003 (Mexico City, 2003), and TRAMP2006 (Houston, 2006). The compared photochemical indicators are OH and HO₂ abundances, OH reactivity (the inverse of the OH lifetime), HO_x budget, OH chain length (ratio of OH cycling to OH loss), calculated ozone production, and ozone sensitivity. In terms of photochemical activity, Houston is much more like Mexico City than New York City. These relationships result from the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NO_x), which are comparable in Houston and Mexico City, but much lower in New York City. Compared to New York City, Houston and Mexico City also have higher levels of OH and HO₂, longer OH chain lengths, a smaller contribution of reactions with NO_x to the OH reactivity, and NO_x-sensitivity for ozone production during the day. In all four studies, the photolysis of nitrous acid (HONO) and formaldehyde (HCHO) are significant, if not dominant, HO_x sources. A problematic result in all four studies is the greater OH production than OH loss during morning rush hour, even though OH production and loss are expected to always be in balance because of the short OH lifetime. The cause of this discrepancy is not understood, but may be related to the under-predicted HO₂ in high NO_x conditions, which could have implications for ozone production. Three photochemical indicators show particularly high photochemical activity in Houston during the TRAMP2006 study: the long portion of the day for which ozone production was NO_x-sensitive, the calculated ozone production rate that was second only to Mexico City's, and the OH chain length that was twice that of any other location. These results on photochemical activity provide additional support for regulatory actions to reduce reactive VOCs in Houston in order to reduce ozone and other pollutants.     

The Northwest U.S. Dam Breaching Decision: Factors, Costs and Benefits

Northwestern United States' salmon populations have fallen precipitously. Attempts at salmon restoration are going on and dam breaching is being considered. Costs associated with the continued restoration attempts including hatchery stocking, barging and trucking salmon around the dams are high while benefits are unclear. Those costs may be greater than dam breaching. An additional impetus for dam removal is the revival of the commercial salmon fishing industry. This may not occur for both ecological and economic reasons. Ecologically complete restoration may not be feasible. Economically, the rise of competitively priced salmon aquaculture will reduce the value of any future commercial catch. A statistical relationship between falling prices for wild salmon and rising salmon aquaculture output is shown.     

Dust Deposit Profiles in a High Velocity Pulse-Jet Fabric Filter

Dust deposit profiles in a pilot-scale pulse-jet fabric filter were measured using a beta gauge. Fly ash was collected on polyester needled felt bags, and the dust profiles were measured after the test system was operated to equilibrium at superficial filtration velocities of 50, 75,100,125, and 150 mm/s. The profiles measured show that a large mass of dust is retained on the fabric of a pulse-jet filter when operated at high filtration velocities. This dust mass retention can be caused by two mechanisms: the failure to remove dust from the fabric during a cleaning pulse, and the redeposition of suspended dust onto the fabric after a cleaning pulse. The dust deposit measured at the highest test velocity was found to be much different from the deposits measured at all other velocities. The deposit found at 150 mm/s had almost twice the average areal density and was more evenly distributed than the deposits found at lower velocities.     

Prenatal diagnosis of cleft lip and/or palate: What do we tell prospective parents?

Cleft lip and/or palate (CL/CP) is the most common congenital craniofacial anomaly and parents often ask, “how did this happen?” Patients and families may benefit from access to a multidisciplinary team (MDT) from prenatal diagnosis into early adulthood. Multiple factors can contribute to the development of a cleft. We discuss the epidemiology and risk factors that increase the likelihood of having a newborn with a cleft. The purpose of this article is to review the prenatal investigations involved in the diagnosis and workup of these patients in addition to postpartum treatment, prognostic factors, and counseling families regarding future recurrence risk.     

In vivo assessment of the biomechanical properties of the uterine cervix in pregnancy

Measuring the stiffness of the cervix might be useful in the prediction of preterm delivery or successful induction of labor. For that purpose, a variety of methods for quantitative determination of physical properties of the pregnant cervix have been developed. Herein, we review studies on the clinical application of these new techniques. They are based on the quantification of mechanical, optical, or electrical properties associated with increased hydration and loss of organization in collagen structure. Quasi-static elastography determines relative values of stiffness; hence, it can identify differences in deformability. Quasi-static elastography unfortunately cannot quantify in absolute terms the stiffness of the cervix. Also, the current clinical studies did not demonstrate the ability to predict the time point of delivery. In contrast, measurement of maximum deformability of the cervix (e.g. quantified with the cervical consistency index) provided meaningful results, showing an increase in compliance with gestational age. These findings are consistent with aspiration measurements on the pregnant ectocervix, indicating a progressive decrease of stiffness along gestation. Cervical consistency index and aspiration measurements therefore represent promising techniques for quantitative assessment of the biomechanical properties of the cervix. © 2013 John Wiley & Sons, Ltd.