scholarly journals Measurement of NO<sub><i>x</i></sub> and NO<sub><i>y</i></sub> with a thermal dissociation cavity ring-down spectrometer (TD-CRDS): Instrument characterisation and first deployment

2020 ◽  
Author(s):  
Nils Friedrich ◽  
Ivan Tadic ◽  
Jan Schuladen ◽  
James Brooks ◽  
Eoghan Darbyshire ◽  
...  
Keyword(s):  
Thermal Dissociation ◽  
Arabian Gulf ◽  
Complete Removal ◽  
Ambient Conditions ◽  
High Particle ◽  
Dry Conditions ◽  
Air Sample ◽  
Recombination Reactions ◽  
Rule Out ◽  
Cavity Ring Down

Abstract. We present a newly constructed, two channel Thermal Dissociation Cavity Ring-Down Spectrometer (TD-CRDS) for the detection of NOx (NO + NO2), NOy (NOx + HNO3 + RO2NO2 + N2O5 etc.), NOz (NOy – NOx) and particulate nitrate (pNit). NOy-containing trace gases are detected as NO2 by CRDS at 405 nm following sampling through inlets at ambient temperature (NOx), or at 850 °C (NOy). In both cases, O3 was added to the air sample directly upstream of the cavities to convert NO (either ambient, or formed in the 850 °C oven) to NO2. An activated carbon denuder was used to remove gas-phase components of NOy when sampling pNit. Detection limits (1 minute averaging) for NOx, NOy and NOz are 98, 51 and 110 pptv, respectively. The total measurement uncertainties (at 50 % RH) in the NOx and NOy channels are 11 % + 10 pptv and 16 % + 14 pptv for NOz, respectively. Thermograms of various NOz species (peroxyacetyl nitrate, isopropyl nitrate, and HNO3) confirm stoichiometric conversion to NO2 (and/or NO) at the oven temperature and rule out significant interferences from NH3 detection or radical recombination reactions under ambient conditions. While fulfilling the requirement of high particle transmission and essentially complete removal of reactive nitrogen under dry conditions, the denuder suffered from NOx breakthrough and memory effects (i.e. release of stored NOy) under humid conditions. NOx measurements obtained from a ship sailing through the Red Sea, Indian Ocean and Arabian Gulf (NOx levels from

scholarly journals Measurement of NO<sub><i>x</i></sub> and NO<sub><i>y</i></sub> with a thermal dissociation cavity ring-down spectrometer (TD-CRDS): instrument characterisation and first deployment

2020 ◽  
Vol 13 (10) ◽  
pp. 5739-5761
Author(s):  
Nils Friedrich ◽  
Ivan Tadic ◽  
Jan Schuladen ◽  
James Brooks ◽  
Eoghan Darbyshire ◽  
...  
Keyword(s):  
Road Traffic ◽  
Trace Gases ◽  
Thermal Dissociation ◽  
Arabian Gulf ◽  
Complete Removal ◽  
Ambient Conditions ◽  
Data Set ◽  
High Particle ◽  
The Impact ◽  
Cavity Ring Down

Abstract. We present a newly constructed, two-channel thermal dissociation cavity ring-down spectrometer (TD-CRDS) for the measurement of NOx (NO+NO2), NOy (NOx+HNO3+RO2NO2+2N2O5 etc.), NOz (NOy−NOx) and particulate nitrate (pNit). NOy-containing trace gases are detected as NO2 by the CRDS at 405 nm following sampling through inlets at ambient temperature (NOx) or at 850 ∘C (NOy). In both cases, O3 was added to the air sample directly upstream of the cavities to convert NO (either ambient or formed in the 850 ∘C oven) to NO2. An activated carbon denuder was used to remove gas-phase components of NOy when sampling pNit. Detection limits, defined as the 2σ precision for 1 min averaging, are 40 pptv for both NOx and NOy. The total measurement uncertainties (at 50 % relative humidity, RH) in the NOx and NOy channels are 11 %+10 pptv and 16 %+14 pptv for NOz respectively. Thermograms of various trace gases of the NOz family confirm stoichiometric conversion to NO2 (and/or NO) at the oven temperature and rule out significant interferences from NH3 detection (<2 %) or radical recombination reactions under ambient conditions. While fulfilling the requirement of high particle transmission (>80 % between 30 and 400 nm) and essentially complete removal of reactive nitrogen under dry conditions (>99 %), the denuder suffered from NOx breakthrough and memory effects (i.e. release of stored NOy) under humid conditions, which may potentially bias measurements of particle nitrate. Summertime NOx measurements obtained from a ship sailing through the Red Sea, Indian Ocean and Arabian Gulf (NOx levels from <20 pptv to 25 ppbv) were in excellent agreement with those taken by a chemiluminescence detector of NO and NO2. A data set obtained locally under vastly different conditions (urban location in winter) revealed large diel variations in the NOz to NOy ratio which could be attributed to the impact of local emissions by road traffic.

scholarly journals Impact of ozone and inlet design on the detection of isoprene-derived organic nitrates by thermal dissociation cavity ring-down spectroscopy (TD-CRDS)

2021 ◽  
Author(s):  
Patrick Dewald ◽  
Raphael Dörich ◽  
Jan Schuladen ◽  
Jos Lelieveld ◽  
John N. Crowley
Keyword(s):  
Thermal Dissociation ◽  
Volume Ratio ◽  
Reaction Chamber ◽  
Organic Nitrates ◽  
Temperature Dependent ◽  
Alkyl Nitrates ◽  
Cavity Ring Down Spectroscopy ◽  
Viable Solution ◽  
Peroxy Nitrates ◽  
Cavity Ring Down

Abstract. We present measurements of isoprene-derived organic nitrates (ISOP-NITs) generated in the reaction of isoprene with the nitrate radical (NO3) in a 1 m3 Teflon reaction chamber. Detection of ISOP-NITs is achieved via their thermal dissociation to nitrogen dioxide (NO2), which is monitored by cavity ring-down spectroscopy (TD-CRDS). Using thermal dissociation inlets (TDIs) made of quartz, the temperature-dependent dissociation profiles (thermograms) of ISOP-NITs measured in the presence of ozone (O3) are broad (350 to 700 K), which contrasts the narrower profiles previously observed for e.g. isopropyl nitrate (iPN) or peroxy acetyl nitrate (PAN) under the same conditions. The shape of the thermograms varied with the TDI’s surface to volume ratio and with material of the inlet walls, providing clear evidence that ozone and quartz surfaces catalyse the dissociation of unsaturated organic nitrates leading to formation of NO2 at temperatures well below 475 K, impeding the separate detection of alkyl nitrates (ANs) and peroxy nitrates (PNs). We present a simple, viable solution to this problem and discuss the potential for interference by the thermolysis of nitric acid (HNO3), nitrous acid (HONO) and O3.

scholarly journals SURGICAL REMOVAL OF THE EPIDERMAL INCLUSION CYSTS WITH SQUEEZE TECHNIQUE: CASE REPORT

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Mehmet Eren Yuksel ◽  
Funda Tamer
Keyword(s):  
Wound Infection ◽  
Surgical Techniques ◽  
Complete Removal ◽  
Wound Infection Rate ◽  
Hair Follicles ◽  
Surgical Removal ◽  
Minimal Scarring ◽  
Trichilemmal Cyst ◽  
Slow Growing ◽  
Rule Out

Epidermal inclusion cysts are common benign cutaneous cysts which arise from hair follicles. These cysts usually present as asymptomatic, small, smooth, firm, round, slow growing swellings on hair bearing areas such as scalp, face, neck and trunk. Epidermal inclusion cysts are easily diagnosed by their clinical features. However, trichilemmal cyst, dermoid cyst, neurofibroma, hemangioma, lipoma and liposarcoma should also be kept in mind in differential diagnosis of cutaneous cystic lesions. As malignant transformation of epidermal inclusion cysts has been reported, histopathological evaluation of epidermal inclusion cysts is mandatory in order to rule out malignancy. Moreover, giant epidermal inclusion cysts with ulceration, rapid growth, resistance to treatment, recurrence and fistula drainage may have malignant potential. Therefore, epidermal cysts should be surgically removed. There are several different types of surgical techniques to remove cutaneous cysts. A proper surgical technique should facilitate the complete removal of the cyst wall to prevent recurrence. In addition, it should provide minimal scarring and a low wound infection rate. Epidermal inclusion cysts can be easily removed surgically with squeeze technique. In this technique, the cyst is squeezed out through a small incision using both index fingers. Thus, the cyst is not ruptured. The squeeze technique allows the cyst capsule to remain intact. Therefore, the risk of wound infection, recurrence and scar formation is minimized. Hereby, we present a 48-year-old male with multiple epidermal inclusion cysts on the scalp treated surgically with squeeze technique. 

Analysis of the Contribution of Adhesion and Ploughing to Shoe-Floor Lubricated Friction in the Boundary Lubrication Regime

2011 ◽  
Author(s):  
Caitlin Moore ◽  
Kurt Beschorner ◽  
Pradeep L. Menezes ◽  
Michael R. Lovell
Keyword(s):  
Coefficient Of Friction ◽  
Boundary Lubrication ◽  
Ambient Conditions ◽  
Lubrication Regimes ◽  
Lubrication Regime ◽  
Material Hardness ◽  
Lubrication Layer ◽  
The Coefficient Of Friction ◽  
Dry Conditions ◽  
Pin On Disk

Slip and fall accidents cost billions of dollars each year. Shoe-floor-lubricant friction has been shown to follow the Stribeck effect, operating primarily in the boundary and mixed-lubrication regimes. Two of the most important factors believed to significantly contribute to shoe-floor-lubricant friction in the boundary lubrication regime are adhesion and ploughing. Experiments were conducted using a pin-on-disk tribometer to quantify adhesion and ploughing contributions to shoe-floor friction in dry and lubricated conditions. The coefficient of friction between three shoe materials and two floor materials of different hardness and roughness were considered. Experiments were conducted under six lubricants for a sliding speed of 0.01 m/sec at ambient conditions. It was found that the contribution of adhesion and ploughing to shoe-floor-lubricant friction was significantly affected by material hardness, roughness, and lubricant properties. Material hardness and roughness are known to affect adhesion, with increased hardness or increased roughness typically resulting in decreased adhesion. The smoothest shoe material, while also being the hardest, resulted in the greatest adhesional contribution to friction. The roughest material, while also being the softest, resulted in the lowest adhesional contributions under dry conditions. Canola oil consistently resulted in the lowest percent of full adhesion and water consistently resulted in the highest percent of full adhesion, presumably due to the thickness, of the boundary lubrication layer. Ploughing contribution was dependent upon the hardness of the shoe and floor materials. A positive correlation was found between the shoe and floor hardness ratio and ploughing coefficient of friction.

scholarly journals A five-channel cavity ring-down spectrometer for the detection of NO<sub>2</sub>, NO<sub>3</sub>, N<sub>2</sub>O<sub>5</sub>, total peroxy nitrates and total alkyl nitrates

2016 ◽  
Vol 9 (10) ◽  
pp. 5103-5118 ◽  
Author(s):  
Nicolas Sobanski ◽  
Jan Schuladen ◽  
Gerhard Schuster ◽  
Jos Lelieveld ◽  
John N. Crowley
Keyword(s):  
Thermal Decomposition ◽  
Thermal Dissociation ◽  
Organic Radical ◽  
Alkyl Nitrates ◽  
Mixing Ratios ◽  
Instrument Construction ◽  
Peroxy Nitrates ◽  
Field Deployment ◽  
And Performance ◽  
Cavity Ring Down

Abstract. We report the characteristics and performance of a newly developed five-channel cavity ring-down spectrometer to detect NO3, N2O5, NO2, total peroxy nitrates (ΣPNs) and total alkyl nitrates (ΣANs). NO3 and NO2 are detected directly at 662 and 405 nm, respectively. N2O5 is measured as NO3 after thermal decomposition at 383 K. PNs and ANs are detected as NO2 after thermal decomposition at 448 and 648 K. We describe details of the instrument construction and operation as well as the results of extensive laboratory experiments that quantify the chemical and optical interferences that lead to biases in the measured mixing ratios, in particular involving the reactions of organic radical fragments following thermal dissociation of PNs and ANs. Finally, we present data obtained during the first field deployment of the instrument in July 2015.

Field Measurement of NO2 and RNO2 by Two-Channel Thermal Dissociation Cavity Ring Down Spectrometer

2017 ◽  
Vol 30 (5) ◽  
pp. 493-498 ◽  
Author(s):  
Jian Chen ◽  
Hao Wu ◽  
An-wen Liu ◽  
Shui-ming Hu ◽  
Jingsong Zhang
Keyword(s):  
Field Measurement ◽  
Thermal Dissociation ◽  
Cavity Ring Down

scholarly journals On the Conformation of the COOH-terminal Domain of the Large Mechanosensitive Channel MscL

2003 ◽  
Vol 121 (3) ◽  
pp. 227-244 ◽  
Author(s):  
Andriy Anishkin ◽  
Vyacheslav Gendel ◽  
Neda A. Sharifi ◽  
Chien-Sung Chiang ◽  
Lena Shirinian ◽  
...  
Keyword(s):  
Osmotic Shock ◽  
Complete Removal ◽  
Size Exclusion ◽  
Ambient Conditions ◽  
Dynamic Simulations ◽  
E Coli ◽  
Terminal Domain ◽  
Reducing Conditions ◽  
Truncation Mutant

COOH-terminal (S3) domains are conserved within the MscL family of bacterial mechanosensitive channels, but their function remains unclear. The X-ray structure of MscL from Mycobacterium tuberculosis (TbMscL) revealed cytoplasmic domains forming a pentameric bundle (Chang, G., R.H. Spencer, A.T. Lee, M.T. Barclay, and D.C. Rees. 1998. Science. 282:2220–2226). The helices, however, have an unusual orientation in which hydrophobic sidechains face outside while charged residues face inside, possibly due to specific crystallization conditions. Based on the structure of pentameric cartilage protein , we modeled the COOH-terminal region of E. coli MscL to better satisfy the hydrophobicity criteria, with sidechains of conserved aliphatic residues all inside the bundle. Molecular dynamic simulations predicted higher stability for this conformation compared with one modeled after the crystal structure of TbMscL, and suggested distances for disulfide trapping experiments. The single cysteine mutants L121C and I125C formed dimers under ambient conditions and more so in the presence of an oxidant. The double-cysteine mutants, L121C/L122C and L128C/L129C, often cross-link into tetrameric and pentameric structures, consistent with the new model. Patch-clamp examination of these double mutants under moderately oxidizing or reducing conditions indicated that the bundle cross-linking neither prevents the channel from opening nor changes thermodynamic parameters of gating. Destabilization of the bundle by replacing conservative leucines with small polar residues, or complete removal of COOH-terminal domain (Δ110–136 mutation), increased the occupancy of subconducting states but did not change gating parameters substantially. The Δ110–136 truncation mutant was functional in in vivo osmotic shock assays; however, the amount of ATP released into the shock medium was considerably larger than in controls. The data strongly suggest that in contrast to previous gating models (Sukharev, S., M. Betanzos, C.S. Chiang, and H.R. Guy. 2001a. Nature. 409:720–724.), S3 domains are stably associated in both closed and open conformations. The bundle-like assembly of cytoplasmic helices provides stability to the open conformation, and may function as a size-exclusion filter at the cytoplasmic entrance to the MscL pore, preventing loss of essential metabolites.

Sign in / Sign up

Export Citation Format

Share Document