Temporal and spatial trends of particulate
n-alkanes C
24–C
33 have been investigated at urban-fringe and traffic exposed inner urban sites of a larger European city. The annual average sum of
...n-alkanes at the four sampling sites ranged from 21 to 31
ng
m
−3. The urban impact factor was ∼30% averaged over the year. The seasonal biogenic emissions of the uneven
n-alkanes cause a considerable seasonal variation in the distribution pattern of the alkanes in PM10 both in the city and at the suburban sites. The trends in the distribution pattern can be summarized using the odd carbon preference index CPI
odd and the plant wax number %WNA, both of which show clear maxima in summer pointing to important biogenic sources of
n-alkanes. The biogenic contributions to the total
n-alkanes were around 9% in winter (DJF), and 37% in summer (JJA) at the urban-fringe sites. At the inner city sites, the urban impact is dominated by
n-alkanes from combustion sources at all seasons. A comparison of two approaches to determine the contribution of the “plant debris” source to ambient PM10 indicates two different mechanisms to form atmospheric “plant debris”. The observed relative contributions of plant debris to PM10 are well in the same range but exhibit differences in the seasonal trend. Considering the different underlying concepts, the agreement of the derived plant debris contributions to PM10 is noteworthy.
As part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) study in the Mexico City Metropolitan Area in March 2006, we measured particulate polycyclic aromatic ...hydrocarbons (PAHs) and other gaseous species and particulate properties, including light absorbing carbon or effective black carbon (BC), at six locations throughout the city. The measurements were intended to support the following objectives: to describe spatial and temporal patterns in PAH concentrations, to gain insight into sources and transformations of PAHs and BC, and to quantify the relationships between PAHs and other pollutants. Total particulate PAHs at the Instituto Mexicano del Petróleo (T0 supersite) located near downtown averaged 50 ng m−3, and aerosol active surface area averaged 80 mm2 m−3. PAHs were also measured on board the Aerodyne Mobile Laboratory, which visited six sites encompassing a mixture of different land uses and a range of ages of air parcels transported from the city core. A combination of analyses of time series, back trajectories, concentration fields, pollutant ratios, and correlation coefficients supports the concept of T0 as an urban source site, T1 as a receptor site with strong local sources, Pedregal and PEMEX as intermediate sites, Pico Tres Padres as a vertical receptor site, and Santa Ana as a downwind receptor site. Weak intersite correlations suggest that local sources are important and variable and that exposure to PAHs and BC cannot be represented by a single regional-scale value. The relationships between PAHs and other pollutants suggest that a variety of sources and ages of particles are present. Among carbon monoxide, nitrogen oxides (NOx), and carbon dioxide, particulate PAHs are most strongly correlated with NOx. Mexico City's PAH/BC mass ratio of 0.01 is similar to that found on a freeway loop in the Los Angeles area and approximately 8–30 times higher than that found in other cities. Evidence also suggests that primary combustion particles are rapidly coated by secondary aerosol in Mexico City. If so, their optical properties may change, and the lifetime of PAHs may be prolonged if the coating protects them against photodegradation or heterogeneous reactions.
Surface properties of aerosols in the Mexico City metropolitan area have been measured in a variety of exposure scenarios related to vehicle emissions in 2002, using continuous, real-time ...instruments. The objective of these experiments is to describe ambient and occupational particulate polycyclic aromatic hydrocarbon (PAH) concentrations associated with vehicular traffic and facilities using diesel vehicles. Median total particulate PAH concentrations along Mexico City's roadways range from 60 to 910 ng m-3, averaged over a minimum of 1 h. These levels are approximately 5 times higher than concentrations measured in the United States and among the highest measured ambient values reported in the literature. The ratio of particulate PAH concentration to aerosol active surface area is much higher along roadways and in other areas of fresh vehicle emissions, compared to ratios measured at sites influenced more by aged emissions or noncombustion sources. For particles freshly emitted by vehicles, PAH and elemental carbon (EC) concentrations are correlated because they both originate during the combustion process. Comparison of PAH versus EC and active surface area concentrations at different locations suggests that surface PAH concentrations may diminish with particle aging. These results indicate that exposure to vehicle-related PAH emissions on Mexico City's roadways may present an important public health risk.
Silver nanoparticles (AgNPs) are gaining attention from the academic and regulatory communities, not only because of their antimicrobial effects and subsequent product applications, but also because ...of their potential health and environmental risks. Whereas AgNPs in the aqueous phase are under intensive study, those in the atmosphere have been largely overlooked, although it is well established that inhalation of nanoparticles is associated with adverse health effects. This review summarizes the present state of knowledge concerning airborne AgNPs to shed light on the possible environmental exposure scenarios that may accompany the production and popularization of silver nanotechnology consumer products. The current understanding of the toxicity of AgNPs points toward a potential threat via the inhalation exposure route. Nano-particle size, chemical composition, crystal structure, surface area, and the rate of silver ion release are expected to be important variables in determining toxicity. Possible routes of aerosolization of AgNPs from the production, use, and disposal of existing consumer products are presented. It is estimated that approximately 14% of silver nanotechnology products that have been inventoried could potentially release silver particles into the air during use, whether through spraying, dry powder dispersion, or other methods. In laboratory and industrial settings, six methods of aerosolization have been used to produce airborne AgNPs: spray atomization, liquid-flame spray, thermal evaporation-condensation, chemical vaporization, dry powder dispersion, and manual handling. Fundamental uncertainties remain about the fate of AgNPs in the environment, their short- and long-term health effects, and the specific physical and chemical properties of airborne particles that are responsible for health effects. Thus, to better understand the risks associated with silver nanotechnology, it is vital to understand the conditions under which AgNPs could become airborne.
Forty-eight Holstein cows, entering second or later lactation, were utilized to determine the effects of 2-hydroxy-4-(methylthio)-butanoic acid (HMB) on milk production, hepatic lipid metabolism, and ...gluconeogenesis during the periparturient period. Cows were fed one of 3 diets as TMR starting 21 d before expected calving. These diets contained 0 (the basal diet), 0.09 (+HMB), or 0.18 (++HMB)% HMB. From parturition to 84 DIM, cows were fed diets that contained 0, 0.13, or 0.20% HMB. Prepartum and postpartum dry matter intakes were similar among cows fed the basal diet, +HMB and ++HMB. There was a quadratic effect on milk yield such that cows fed +HMB had the greatest milk yield; yields of milk by cows fed the basal diet and ++HMB were similar. This led to trends for increased yields of 3.5% fat-corrected milk and total solids when cows were fed +HMB. Percentages of fat, protein, and total solids in milk were not affected by treatment. Despite differences in milk yield, calculated energy balance was not affected by treatment. Plasma concentrations of NEFA, β-hydroxybutyrate, and glucose were not different among treatments. Liver triglyceride content was similar among treatments on d 1 postpartum and was increased for cows consuming +HMB on d 21 postpartum compared with the other dietary treatments. Capacities for metabolism of 1-14Cpalmitate by liver slices in vitro were not affected by treatment; however, conversion of 1-14Cpropionate to CO2 and glucose decreased as the amount of HMB consumed by cows increased on d 21 postpartum. Cows consuming +HMB had greater days to first ovulation compared with cows consuming the basal diet and ++HMB as measured by plasma progesterone concentrations. These data suggest that adding HMB to low Met diets to achieve a predicted Met supply of approximately 2.3% of metabolizable protein supply is beneficial for increasing milk production but does not appear to benefit hepatic energy metabolism during early lactation.
Aim: Many plants, especially at high latitudes, have both widespread and highly discontinuous geographical distributions. To increase understanding of how such patterns originate, we examine genetic ...patterns in the arctic-alpine plant Sibbaldia procumbens. We evaluate the contributions of réfugia and the role of long-distance dispersal in shaping the current range of this species. Location: Northern Hemisphere, especially North America. Methods: We sampled Sibbaldia from 176 localities, including 168 for S. procumbens. We analysed sequence variation in three plastid DNA non-coding regions (the atpl-atpH and trnL-trnY intergenic spacers and the trnL · intron), performed Bayesian phylogenetic analyses and statistical parsimony analyses on the combined sequences, and analysed the geographical patterns of haplotype distribution and genetic diversity using data from all populations. Results: Sibbaldia procumbens probably originated in the mountains of South and East Asia. We identified highly distinct clades in Europe and North America, which overlapped on oceanic islands of the North Atlantic indicating long-distance dispersal capability. The North American dade included two lineages, one in California and the other widely distributed across the continent and North Atlantic.Haplotype diversity in the latter lineage was markedly higher to the south, suggesting mid-late Pleistocene southward displacement of North American populations with subsequent migration northwards into previously glaciated regions. In Europe, disjunct geographical regions generally harboured distinct haplotypes. Main conclusions: Multiple Pleistocene réfugia for S. procumbens occurred in both North America and Europe. North American réfugia existed in California and in the southern Rocky Mountains, but in contrast with most widespread arctic—alpine species we found no evidence for a Beringian refugium. Cryptic réfugia may have existed within the Cordilleran Ice Sheet. Episodes of range expansion and contraction and long-distance dispersal have all contributed to the genetic structure and widespread but fragmented distribution of this species.
OBJECTIVE:We report the results of the investigation of safety and efficacy of venous angioplasty in patients with multiple sclerosis (MS) with findings of extracranial venous anomalies, considered ...hallmarks of chronic cerebrospinal venous insufficiency (CCSVI), in a 2-phase study (ClinicalTrials.gov NCT01450072).
METHODS:Phase 1 was an open-label safety study (10 patients); phase 2 was sham-controlled, randomized, and double-blind (10 sham procedure, 9 treated). All study patients fulfilled venous hemodynamic screening criteria indicative of CCSVI. Assessment was at 1, 3, and 6 months postprocedure with MRI, clinical, and hemodynamic outcomes. Primary endpoints were safety at 24 hours and 1 month, venous outflow restoration >75% at 1 month, and effect of angioplasty on new lesion activity and relapse rate over 6 months. Secondary endpoints included changes in disability, brain volume, cognitive tests, and quality of life.
RESULTS:No perioperative complications were noted; however, one patient with history of syncope was diagnosed with episodic bradycardia requiring placement of a pacemaker before discharge. Doppler evidence-based venous hemodynamic insufficiency severity score (VHISS) was reduced >75% compared to baseline in phase 1 (at 1 month) but not phase 2. In phase 2, higher MRI activity (cumulative number of new contrast-enhancing lesions 19 vs 3, p = 0.062 and new T2 lesions 17 vs 3, p = 0.066) and relapse activity (4 vs 1, p = 0.389) were identified as nonsignificant trends in the treated vs sham arm over 6 months. Using analysis of covariance, significant cumulative new T2 lesions were related to larger VHISS decrease (p = 0.028) and angioplasty (p = 0.01) over the follow-up. No differences in other endpoints were detected.
CONCLUSION:Venous angioplasty is not an effective treatment for MS over the short term and may exacerbate underlying disease activity.
CLASSIFICATION OF EVIDENCE:This is a Class I study demonstrating that clinical and imaging outcomes are no better or worse in patients with MS identified with venous outflow restriction who receive venous angioplasty compared to sham controls who do not receive angioplasty. This study also includes a Class IV phase 1 study of safety in 10 patients receiving the angioplasty procedure.
Objective. Examine the influence of knee positions and gender on the Ober test for the length of the iliotibial band.
Design. A cross-sectional comparative repeated measures design.
Background. The ...Ober test is in widespread use, yet the influence of knee positions and gender on the test has not been reported. Such information is needed to help clarify test results.
Methods. The Ober test was administered with the knee flexed to 90° and extended to 0° to the right lower limb of 26 women and 23 men. The limb was lowered from abduction and the end point of hip abduction (positive angle) or hip adduction (negative angle) was measured in relation to neutral.
Results. The hip adduction movement was restricted more with the knee flexed than with the knee extended for both genders (
P<0.009). With the knee flexed the mean hip abduction angle was less for men (+4°) than for women (+6°) (
P<0.001), and with the knee extended the mean hip adduction angle was greater for men (−9°) than for women (−4°) (
P<0.001).
Conclusion. The Ober test with the knee flexed limited hip adduction more than with the knee extended for both men and women, and women had greater limitations than men.
Relevance
The Ober test with the knee flexed and with the knee extended yielded different results and may be considered different tests. Normal Ober test values for the two knee positions should be defined separately for men and women in order to understand how deviations from normal are related to pathologies.
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