The use of disjunct eddy sampling methods for the determination of ecosystem level fluxes of trace gases

The concept of disjunct eddy sampling (DES) for use in measuring ecosystem-level micrometeorological fluxes is re-examined. The governing equations are discussed as well as other practical considerations and guidelines concerning this sampling method as it is applied to either the disjunct eddy covariance (DEC) or disjunct eddy accumulation (DEA) techniques. A disjunct eddy sampling system was constructed that could either be combined with relatively slow sensors (response time of 2 to 40 s) to measure fluxes using DEC, or could also be used to accumulate samples in stable reservoirs for later laboratory analysis (DEA technique). Both the DEC and DEA modes of this sampler were tested against conventional eddy covariance (EC) for fluxes of either CO2 (DEC) or isoprene (DEA). Good agreement in both modes was observed relative to the EC systems. However, the uncertainty in a single DEA flux measurement was considerable (40%) due to both the reduced statistical sampling and the analytical precision of the concentration difference measurements. We have also re-investigated the effects of nonzero mean vertical wind velocity on accumulation techniques as it relates to our DEA measurements. Despite the higher uncertainty, disjunct eddy sampling can provide an alternative technique to eddy covariance for determining ecosystem-level fluxes for species where fast sensors do not currently exist

A steady-state continuous flow chamber for the study of daytime and nighttime chemistry under atmospherically relevant NO levels

Experiments performed in laboratory chambers have contributed significantly to the understanding of the fundamental kinetics and mechanisms of the chemical reactions occurring in the atmosphere. Two chemical regimes, classified as high-NO vs. zero-NO conditions, have been extensively studied in previous chamber experiments. Results derived from these two chemical scenarios are widely parameterized in chemical transport models to represent key atmospheric processes in urban and pristine environments. As the anthropogenic NO_x emissions in the United States have decreased remarkably in the past few decades, the classic high-NO and zero-NO conditions are no longer applicable to many regions that are constantly impacted by both polluted and background air masses. We present here the development and characterization of the NCAR Atmospheric Simulation Chamber, which is operated in steady-state continuous flow mode for the study of atmospheric chemistry under intermediate NO conditions. This particular chemical regime is characterized by constant sub-ppb levels of NO and can be created in the chamber by precise control of the inflow NO concentration and the ratio of chamber mixing to residence timescales. Over the range of conditions achievable in the chamber, the lifetime of peroxy radicals (RO_2), a key intermediate from the atmospheric degradation of volatile organic compounds (VOCs), can be extended to several minutes, and a diverse array of reaction pathways, including unimolecular pathways and bimolecular reactions with NO and HO_2, can thus be explored. Characterization experiments under photolytic and dark conditions were performed and, in conjunction with model predictions, provide a basis for interpretation of prevailing atmospheric processes in environments with intertwined biogenic and anthropogenic activities. We demonstrate the proof of concept of the steady-state continuous flow chamber operation through measurements of major first-generation products, methacrolein (MACR) and methyl vinyl ketone (MVK), from OH- and NO_3- initiated oxidation of isoprene

A steady-state continuous flow chamber for the study of daytime and nighttime chemistry under atmospherically relevant NO levels

Experiments performed in laboratory chambers have contributed significantly to the understanding of the fundamental kinetics and mechanisms of the chemical reactions occurring in the atmosphere. Two chemical regimes, classified as high-NO vs. zero-NO conditions, have been extensively studied in previous chamber experiments. Results derived from these two chemical scenarios are widely parameterized in chemical transport models to represent key atmospheric processes in urban and pristine environments. As the anthropogenic NO_x emissions in the United States have decreased remarkably in the past few decades, the classic high-NO and zero-NO conditions are no longer applicable to many regions that are constantly impacted by both polluted and background air masses. We present here the development and characterization of the NCAR Atmospheric Simulation Chamber, which is operated in steady-state continuous flow mode for the study of atmospheric chemistry under intermediate NO conditions. This particular chemical regime is characterized by constant sub-ppb levels of NO and can be created in the chamber by precise control of the inflow NO concentration and the ratio of chamber mixing to residence timescales. Over the range of conditions achievable in the chamber, the lifetime of peroxy radicals (RO_2), a key intermediate from the atmospheric degradation of volatile organic compounds (VOCs), can be extended to several minutes, and a diverse array of reaction pathways, including unimolecular pathways and bimolecular reactions with NO and HO_2, can thus be explored. Characterization experiments under photolytic and dark conditions were performed and, in conjunction with model predictions, provide a basis for interpretation of prevailing atmospheric processes in environments with intertwined biogenic and anthropogenic activities. We demonstrate the proof of concept of the steady-state continuous flow chamber operation through measurements of major first-generation products, methacrolein (MACR) and methyl vinyl ketone (MVK), from OH- and NO_3- initiated oxidation of isoprene

Pigmented Basal Cell Carcinoma of the Nipple-Areola Complex in an Elderly Woman

Basal cell carcinoma (BCC), which frequently occurs in sun-exposed areas of the head and neck region, is the most common cutaneous malignancy. The nipple-areola complex (NAC) is an uncommon site for BCC to develop. BCCs in this region display more aggressive behavior and a greater potential to spread than when found in other anatomical sites. This paper outlines the case of 67-year-old female with a solitary asymptomatic black plaque on the right areola. The lesion was initially recognized as Paget's disease of the nipple by a general surgeon. However, the histopathological features showed a tumor mass of basaloid cells, a peripheral palisading arrangement and scattered pigment granules. Finally, the patient was diagnosed with pigmented BCC of the NAC and was referred to the department of dermatology. Positron emission tomography-computed tomography revealed the absence of distant metastasis. A wide excision was done. The lesion resolved without recurrence or metastasis during 14 months of follow-up

Antifungal drug resistance evoked via RNAi-dependent epimutations

Microorganisms evolve via mechanisms spanning sexual/parasexual reproduction, mutators, aneuploidy, Hsp90, and even prions. Mechanisms that may seem detrimental can be repurposed to generate diversity. Here we show the human fungal pathogen Mucor circinelloides develops spontaneous resistance to the antifungal drug FK506 (tacrolimus) via two distinct mechanisms. One involves Mendelian mutations that confer stable drug resistance; the other occurs via an epigenetic RNA interference (RNAi)-mediated pathway resulting in unstable drug resistance. The peptidyl-prolyl isomerase FKBP12 interacts with FK506 forming a complex that inhibits the protein phosphatase calcineurin1. Calcineurin inhibition by FK506 blocks M. circinelloides transition to hyphae and enforces yeast growth2. Mutations in the fkbA gene encoding FKBP12 or the calcineurin cnbR or cnaA genes confer FK506 resistance (FK506R) and restore hyphal growth. In parallel, RNAi is spontaneously triggered to silence the FKBP12 fkbA gene, giving rise to drug-resistant epimutants. FK506R epimutants readily reverted to the drug-sensitive wild-type (WT) phenotype when grown without drug. The establishment of these epimutants is accompanied by generation of abundant fkbA small RNA (sRNA) and requires the RNAi pathway as well as other factors that constrain or reverse the epimutant state. Silencing involves generation of a double-stranded RNA (dsRNA) trigger intermediate from the fkbA mature mRNA to produce antisense fkbA RNA. This study uncovers a novel epigenetic RNAi-based epimutation mechanism controlling phenotypic plasticity, with possible implications for antimicrobial drug resistance and RNAi-regulatory mechanisms in fungi and other eukaryotes

Experimental studies on pollen-mediated gene flow in Sorghum bicolor (L.) Moench using male-sterile bait plants

Information on the potential of pollen mediated gene flow (PMGF) in sorghum is required for ensuring varietal purity and to mitigate risk transgenic gene flow. Replicated trials were conducted in Kenya using a local landrace, 'Ochuti' as pollen donor surrounded by male-sterile pollen baits. Frequency of PMGF decreased with the increase of distance from pollen sources and was significantly influenced by wind direction and speed. Anther dehiscence correlated with increase in vapour pressure deficit in the morning. A negative exponential regression model with logarithmic transformation of PMGF and square-root transformation of distance from source field best fitted the data. Up to 50% of female florets on a male sterile (MS) plant were pollinated at 1 m from pollen source and declined to 14% at 10 m. The maximum distance of PMGF using the PMGF model, based on a threshold of one seed per MS plant, was 203 m when data above the 95th percentile is considered. However, in the presence of self-produced pollen of male-fertile target plants, the possibility of long-distance cross-pollination may be very low

Airborne Flux Measurements of BVOCs above Californian Oak Forests: Experimental Investigation of Surface and Entrainment Fluxes, OH Densities, and Damköhler Numbers

The article of record as published may be located at http://dx.doi.org/10.1175/JAS-D-13-054.1Airborne flux measurements of isoprene were performed over the Californian oak belts surrounding the Central Valley. The authors demonstrate for the first time 1) the feasibility of airborne eddy covariance measurements of reactive biogenic volatile organic compounds; 2) the effect of chemistry on the vertical transport of reactive species, such as isoprene; and 3) the applicability of wavelet analysis to estimate regional fluxes of biogenic volatile organic compounds. These flux measurements demonstrate that instrumentation operating at slower response times (e.g., 1–5 s) can still be used to determine eddy covariance fluxes in the mixed layer above land, where typical length scales of 0.5–3km were observed. Flux divergence of isoprene measured in the planetary boundary layer (PBL) is indicative of OH densities in the range of 4–7 3 106 molecules per cubic centimeter and allows extrapolation of airborne fluxes to the surface with Damk€ohler numbers (ratio between the mixing time scale and the chemical time scale) in the range of 0.3–0.9. Most of the isoprene is oxidized in the PBL with entrainment fluxes of about 10% compared to the corresponding surface fluxes. Entrainment velocities of 1–10 cm s21 were measured. The authors present implications for parameterizing PBL schemes of reactive species in regional and global models