Direct Emission of I_2 Molecule and IO Radical from the Heterogeneous Reactions of Gaseous Ozone with Aqueous Potassium Iodide Solution

Recent studies indicated that gaseous halogens mediate key tropospheric chemical processes. The inclusion of halogen-ozone chemistry in atmospheric box models actually closes the ~50% gap between estimated and measured ozone losses in the marine boundary layer. The additional source of gaseous halogens is deemed to involve previously unaccounted for reactions of O_3(g) with sea surface water and marine aerosols. Here, we report that molecular iodine, I_2(g), and iodine monoxide radical, IO(g), are released ([I_2(g)] > 100[IO(g)]) during the heterogeneous reaction of gaseous ozone, O_3(g), with aqueous potassium iodide, KI(aq). It was found that (1) the amounts of I_2(g) and IO(g) produced are directly proportional to [KI(aq)] up to 5 mM and (2) IO(g) yields are independent of bulk pH between 2 and 11, whereas I_2(g) production is markedly enhanced at pH < 4. We propose that O_3(g) reacts with I− at the air/water interface to produce I_2(g) and IO(g) via HOI and IOOO− intermediates, respectively

Incisional atrial reentrant tachycardia: experimental study on the conduction property through the isthmus

AbstractBackgroundIncisional atrial reentrant tachycardia is a life-threatening tachyarrhythmia after surgery for congenital heart disease. Slow conduction through an isthmus between anatomical barriers, such as a right atriotomy or the sites for cannulation, has been shown to be a prerequisite for perpetuation of the incisional atrial reentrant tachycardia. However, the conduction property through the isthmus has not been examined in detail.MethodsTo examine the conduction property, 2 tandem incisions were made on the lateral right atrium with various distances (3 to 20 mm) between the incisions in 16 canines. Four weeks after the surgery, the lateral right atrium was mapped epicardially during pacing to examine the conduction property through the isthmus. The conduction property was characterized by approximated curves of the conduction velocity through the isthmus in accordance with the pacing cycle lengths. The atrial tissue at the isthmus was examined microscopically.ResultsThe approximated curves of the conduction velocity were classified into 3 different types. Decremental conduction was observed only in the isthmi between 5 and 15 mm in width. A small amount of surviving myocardium between the scars formed the critical isthmus microscopically (decremental type). In the isthmi wider than 15 mm in width, slow conduction was not seen at any paced cycle length (nondecremental type). In the extremely narrow isthmi less than 5 mm in width, all of the atrial myocardium at the isthmus was replaced by fibrous tissue. Conduction was blocked at the isthmus and the activation detoured around the incisions (block type). There was a statistically significant difference in the approximated curves between the 3 different types of conduction properties (P < .01).ConclusionThe width of the isthmus determines the conduction property through the isthmus that contributes to the development of the incisional atrial reentrant tachycardia. Thus, the incisional atrial reentrant tachycardia may be preventable by leaving a sufficient amount of surviving myocardium between the incisions or by connecting the incisions by an ablative procedure

Extension of measurement range in OCDR based on double-modulation scheme

We extend the measurement range of optical correlation-domain reflectometry (OCDR) by modulating the laser output frequency at two frequencies, while preserving spatial resolution. We demonstrate distributed reflectivity sensing with a ten-fold extended measurement range.Comment: 4 pages, 6 figure

Diabetic Cardiovascular Disease Induced by Oxidative Stress.

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among patients with diabetes mellitus (DM). DM can lead to multiple cardiovascular complications, including coronary artery disease (CAD), cardiac hypertrophy, and heart failure (HF). HF represents one of the most common causes of death in patients with DM and results from DM-induced CAD and diabetic cardiomyopathy. Oxidative stress is closely associated with the pathogenesis of DM and results from overproduction of reactive oxygen species (ROS). ROS overproduction is associated with hyperglycemia and metabolic disorders, such as impaired antioxidant function in conjunction with impaired antioxidant activity. Long-term exposure to oxidative stress in DM induces chronic inflammation and fibrosis in a range of tissues, leading to formation and progression of disease states in these tissues. Indeed, markers for oxidative stress are overexpressed in patients with DM, suggesting that increased ROS may be primarily responsible for the development of diabetic complications. Therefore, an understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of diabetes-induced CVD. The current review focuses on the relationship between diabetes-induced CVD and oxidative stress, while highlighting the latest insights into this relationship from findings on diabetic heart and vascular disease

Fenton chemistry at aqueous interfaces

In a fundamental process throughout nature, reduced iron unleashes the oxidative power of hydrogen peroxide into reactive intermediates. However, notwithstanding much work, the mechanism by which Fe^(2+) catalyzes H_2O_2 oxidations and the identity of the participating intermediates remain controversial. Here we report the prompt formation of O=Fe^(IV)CI_3^− and chloride-bridged di-iron O=Fe^(IV)·CI·FeIICI_4^− and O=Fe^(IV)·CI·Fe^(III)CI_5^− ferryl species, in addition to Fe^(III)CI_4^−, on the surface of aqueous FeCI_2 microjets exposed to gaseous H_2O_2 or O_3 beams for 10^3 times faster than Fe(H_2O)_6^(2+) in bulk water via a process that favors inner-sphere two-electron O-atom over outer-sphere one-electron transfers. The higher reactivity of di-iron ferryls vs. O=Fe^(IV)CI_3^− as O-atom donors implicates the electronic coupling of mixed-valence iron centers in the weakening of the Fe^(IV)–O bond in poly-iron ferryl species

“Sizing” Heterogeneous Chemistry in the Conversion of Gaseous Dimethyl Sulfide to Atmospheric Particles

The oxidation of biogenic dimethyl sulfide (DMS) emissions is a global source of cloud condensation nuclei. The amounts of the nucleating H_2SO_4(g) species produced in such process, however, remain uncertain. Hydrophobic DMS is mostly oxidized in the gas phase into H_2SO_4(g) + DMSO(g) (dimethyl sulfoxide), whereas water-soluble DMSO is oxidized into H_2SO_4(g) in the gas phase and into SO_4^(2–) + MeSO_3– (methanesulfonate) on water surfaces. R = MeSO_3–/(non-sea-salt SO_4^(2–)) ratios would therefore gauge both the strength of DMS sources and the extent of DMSO heterogeneous oxidation if R_(het) = MeSO_3–/SO_4^(2–) for DMSO(aq) + ·OH(g) were known. Here, we report that R_(het) = 2.7, a value obtained from online electrospray mass spectra of DMSO(aq) + ·OH(g) reaction products that quantifies the MeSO_3– produced in DMSO heterogeneous oxidation on aqueous aerosols for the first time. On this basis, the inverse R dependence on particle radius in size-segregated aerosol collected over Syowa station and Southern oceans is shown to be consistent with the competition between DMSO gas-phase oxidation and its mass accommodation followed by oxidation on aqueous droplets. Geographical R variations are thus associated with variable contributions of the heterogeneous pathway to DMSO atmospheric oxidation, which increase with the specific surface area of local aerosols