Measurement of Aerosol Organic Compounds Using a Novel Collection/Thermal-Desorption PTR-ITMS Instrument

We report the development and characterization of a proton-transfer-reaction ion trap mass spectrometer for the speciated measurement of organic compounds in atmospheric aerosols and show results from its first field deployment. The instrument uses an aerosol collection inlet to accumulate aerosol mass followed by rapid thermal desorption to volatilize the organic compounds for in situ analysis. We have performed laboratory studies to characterize instrument performance and the instrument was deployed aboard a NOAA research vessel during the Texas Air Quality Study 2006/Gulf of Mexico Atmospheric Composition and Climate Study (TexAQS 2006/GoMACCS) in August–September 2006. The laboratory-determined detection limit for glutaric acid in mixed glutaric acid/NH ₄ HSO ₄ test aerosols was 0.22 ng collected mass, which corresponds to an estimated detection limit of 12 ng m^?3 for a 10 min sample based on the instrument sample flow rate of 1.8 L min^?1. During TexAQS 2006/GoMACCS, signals well above the detection limit were observed at a number of mass to charge ratios, mostly occurring during an extended period of active pollution photochemistry, but also including detection of possible primary emissions of aerosol-phase pyridine.     

Piezoelectric properties of the high temperature MPB xPbTiO3 - (1−x)[BiScO3 + Bi(Ni1/2Ti1/2)O3] composition

The ternary perovskite xPbTiO₃ - (1?x)[BiScO₃ + Bi(Ni_1/2Ti_1/2)O₃] (PT-BS-BNiT), where x?=?0.54 is the morphotropic phase boundary composition, was studied for high temperature ferroelectric applications. Polycrystalline ceramics were prepared using the standard solid-state methods. The stoichiometric ceramic was found to have room temperature dielectric permittivity and loss values at 1 kHz of 1490 and 0.049 respectively. Piezoelectric properties, of the stoichiometric composition, measured included: P_r?=?31.0 μC/cm², E_c?=?25.0 kV/cm, d₃₃?=?340 pC/N, d₃₃ ^*?=?896 pm/V, and a bipolar electromechanical strain of 0.25 %. From these data, the Curie temperature was T_C?=?370 °C and the depoling temperature was T_D?=?325 °C. Processing ceramics with excess bismuth improved the low field piezoelectric coefficients with a maximum of d33?=?445 pC/N, while increasing the lead content increased the transition temperatures. The depoling and Curie temperatures of all compositions were measured to be between 275 and 400 °C.     

NUMERICAL SIMULATIONS OF DUCTILE MACHINING OF SILICON NITRIDE WITH A CUTTING TOOL OF DEFINED GEOMETRY

Recent experiments involving machining of silicon nitride at the micrometer scale has shown that silicon nitride behaves in a ductile fashion under high pressures and when the depth of cut is small. In this paper, a preliminary study of ductile machining of Silicon Nitride (Si₃N₄) using numerical simulations is reported. The commercial software package ADVANTEDGE is used to model the cutting process. The numerical simulations involve a parametric study carried out to understand the effects of cutting speed, feed, rake angle and tooltip radius to evaluate conditions that are conducive to brittle-to-ductile phase transition. The feed, tooltip radius and depth of cut are of the order of tens of micrometers and the cutting speeds range from 0.5 m/min to 300 m/min. The results indicate that machining of silicon nitride may be carried out in a ductile fashion for small tooltip radii, high negative rake angles and small depths of cut.     

Competing for consciousness: Prolonged mask exposure reduces object substitution masking.

In object substitution masking (OSM) a sparse, temporally trailing 4-dot mask impairs target identification, even though it has different contours from, and does not spatially overlap with the target. Here, we demonstrate a previously unknown characteristic of OSM: Observers show reduced masking at prolonged (e.g., 640 ms) relative to intermediate mask durations (e.g., 240 ms). We propose that with prolonged exposure, the mask's visual representation is consolidated, which allows processing of the lingering target icon to be reinitiated, thereby improving performance. Our findings suggest that when the visual system is confronted with 2 temporally contiguous stimuli, although one may initially gain access to consciousness above the other, the “losing” stimulus is not irreversibly lost to awareness. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Physicochemical characteristics of a southern Lake Michigan river plume

Riverine inputs are a major source of nutrients to the Laurentian Great Lakes and have important effects on nearshore biological processes, where mixing between river and lake water leads to formation of heterogeneous river plumes. We examined the physical and chemical characteristics of the St. Joseph River plume in southern Lake Michigan between May and October 2011, and in October 2012, June 2013 and April 2014. Specific electric conductivity and stable isotopes of water were used to quantify the fraction of river water (FRW) at sampling sites in Lake Michigan. Both tracers predicted similar patterns of FRW among sites; however, there was a systematic offset between the two methods, and specific electric conductivity method under-predicted the FRW by ~5%. We observed a distinct, seasonally varying river plume, with plume size correlated with flow rate of St. Joseph River. Within the plume, sediments and nutrients were non-conservative and exhibited significant and seasonally varying losses that we attribute to settling of particle-bound nutrients and/or nutrients in particulate phase below the plume. The characteristics and the spatiotemporal heterogeneity of the river plume documented here may have important implications for the nearshore biogeochemistry of the Great Lakes and for understanding the roles of these features in ecological processes in nearshore areas.     

Population pharmacokinetics of intravenous amiodarone and comparison with two-stage pharmacokinetic analysis

The disposition of amiodarone, an antiarrhythmic agent was evaluated after a single intravenous infusion (5 mg/kg over 15 minutes) in patients of various ages and with various degrees of renal function and left ventricular function. The plasma concentration-time data were obtained from three clinical studies with similar protocols. The data were analyzed by nonlinear mixed-effects modeling (NONMEM) to estimate the population pharmacokinetic parameters of amiodarone and to determine the significant demographic covariates affecting these parameters. The pharmacokinetic parameters of amiodarone (weight-corrected) also were calculated using two-stage analysis and were compared with the results obtained from the mixed-effects analysis. The population plasma concentration-time profile of amiodarone was best described by a four-compartment model. Demographic covariates (i.e., creatinine clearance and ejection fraction) did not improve the final pharmacostatistical model significantly. The results from the two-stage analysis showed no significant relationship between amiodarone pharmacokinetic parameters and age, gender, renal function, or ejection fraction. The results from one study, however, demonstrated that advanced age (> or = 65 years) resulted in reduced amiodarone clearance coupled with a prolonged elimination half-life. No such correlation was detected with NONMEM analysis, which may be partly attributable to the small number of elderly patients. Overall, the results from NONMEM analysis validated the results obtained from the two-stage analysis.     

Acquisition of the Ph chromosome and BCR-ABL fusion product in AML-M2 and t(8;21) leukemia: cytogenetic and FISH evidence for a late event

A patient with the M2 subtype of AML who had a 45,X,-X,t(8;21) karyotype at diagnosis was found to have the Ph chromosome in one out of 37 evaluated cells 18 months after the initial diagnosis. Interphase FISH studies utilizing a BCR-ABL dual-color probe did not detect a fusion product 4 months prior to the appearance of one Ph-positive cell. Nineteen months post diagnosis and 5 months after clinical relapse all evaluated cells had the Ph chromosome in a clone characterized by t(8;21). These observations suggest that late appearing Ph is a secondary event which may be either therapy-related or consistent with one of the later events in a multistep pathogenesis of AML.     

为音频设备提供高性能的低通30kHz贝塞尔滤波器

贝塞尔(Bessel)线性相位滤波器正是由于具有向其截止频率以下的所有频率提供等量延时的特性,才被用于音频设备中,在音频设备中,必须在不损害频带内多信号的