Characterization of polyphosphates by electrospray mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was applied for the characterization of inorganic polyphosphates [orthophosphate, pyrophosphate, tripolyphosphate, trimetaphosphate, and tetrapolyphosphatel. The high selectivity of ESI-MS allows the detection of different polyphosphate species without preseparation by ion chromatography or capillary electrophoresis. Furthermore, ESI-MS does not require the incorporation of UV-absorbing chromophores into the analytical method for the detection of phosphates, unlike conventional UV-chromatographic methods. Limits of detection by ESI-MS were estimated to range from approximately 1 to 10 ng/mL. The quantification of polyphosphate samples as single-component and multicomponent mixtures was investigated. Linear signal response for single-component samples ranged from the limit of detection to approximately 10 microg/mL Quantification of polyphosphate in streamwater is demonstrated using the standard addition method. The effect of multi-polyphosphate components and salts on signal response was also studied. For concentrations less than 2.0 microg/mL, signal response from a tetrapolyphosphate sample was comparable to those obtained from tetrapolyphosphate-tripolyphosphate mixtures. Signal response obtained from tetrapolyphosphate in the presence of tripolyphosphate or NH4NO3 at higher concentrations (approximately 50 microg/mL and 35 microg/mL, respectively) was significantly lower relative to single-component standards (approximately 40%-70%).     

Ultrasound measurement of brachial flow-mediated vasodilator response

Brachial artery flow-mediated vasodilation is increasingly used as a measure of endothelial function. High resolution ultrasound provides a noninvasive method to observe this flow-mediated vasodilation by monitoring the diameter of the artery over time following a transient flow stimulus. Since hundreds of ultrasound images are required to continuously monitor brachial diameter for the 2-3 min during which the vasodilator response occurs, an automated diameter estimation is desirable. However, vascular ultrasound images suffer from structural noise caused by the constructive and destructive interference of the backscattered signals, and the true boundaries of interest that define the diameter are frequently obscured by the multiple-layer structure of the vessel wall. These problems make automated diameter estimation strategies based on the detection of the vessel wall boundary difficult. We obtain a robust automated measurement of the vasodilator response by automatically locating the artery using a variable window method, which gives both the lumen center and width. The vessel wall boundary is detected by a global constraint deformable model, which is insensitive to the structural noise in the boundary area. The ambiguity between the desired boundary and other undesired boundaries is resolved by a spatiotemporal strategy. Our method provides excellent reproducibility both for interreader and intrareader analyzes of percent change in diameter, and has been successfully used in analyzing over 4000 brachial flow-mediated vasodilation scans from several medical centers in the United States.     

Determination of end groups of synthetic polymers by matrix-assisted laser desorption/ionization: high-energy collision-induced dissociation

Matrix-assisted laser desorption/ionization has been combined with high-energy collision-induced dissociation for the analysis of poly(ethylene glycols) with butanoyl, benzoyl and acetyl end groups, using novel technology comprising a magnetic-sector mass spectrometer and ion buncher with an in-line quadratic-field ion mirror. High-energy (>8 keV) collision-induced dissociation facilitated unambiguous end-group determination of these polymers, providing masses of end groups and structural information. The high-energy collision-induced dissociation also provided information regarding repeat units.     

Ultrasonic inspection of studs (bolts) using dynamic predictive deconvolution and wave shaping

Bolt degradation has become a major issue in the nuclear industry since the 1980's. If small cracks in stud bolts are not detected early enough, they grow rapidly and cause catastrophic disasters. Their detection, despite its importance, is known to be a very difficult problem due to the complicated structures of the stud bolts. This paper presents a method of detecting and sizing a small crack in the root between two adjacent crests in threads. The key idea is from the fact that the mode-converted Rayleigh wave travels slowly down the face of the crack and turns from the intersection of the crack and the root of thread to the transducer. Thus, when a crack exists, a small delayed pulse due to the Rayleigh wave is detected between large regularly spaced pulses from the thread. The delay time is the same as the propagation delay time of the slow Rayleigh wave and is proportional to the site of the crack. To efficiently detect the slow Rayleigh wave, three methods based on digital signal processing are proposed: wave shaping, dynamic predictive deconvolution, and dynamic predictive deconvolution combined with wave shaping.     

Prototypes of facial attributes developed through image averaging techniques

Image capture and quantification has proven useful in a variety of scientific applications, for example, biology, medicine, geology, meteorology and forensics. The objective of this research was to utilize this technology to quantify clinical- and consumer-perceivable changes in facial attributes. A panel of expert assessors was trained, and, in a large consumer study, consumer facial attributes were identified and grading scales for each attribute were established. These experts then rated over 240 subjects on a total of 19 different facial attributes. Based on methodology developed by Perrett et al., facial averages or prototypes were computed from panelists rated high or low for each attribute. Prototypes were developed in a 3 step process: 1) selection of 224 predefined feature points; 2) calculation of average face shape; and 3) 'morphing' individual faces into that shape and blending the images together. Naive assessors could readily appreciate the differences in facial appearance of the prototypes. In addition, expert graders were able to identify the general class of attribute affected. This method provides a powerful tool for assessing the effects of skin care technologies.     

Design of an integrating cavity absorption meter

The design of integrating cavity absorption meters of general geometry is analyzed for cases in which the incident illumination of the cavity is spatially uniform and isotropic, such as the meter of Fry et al. [Appl. Opt. 31, 2055 (1992)]. The analysis by Kirk [Appl. Opt. 34, 4397 (1995)] for the probability of photon survival in a spherical meter is extended to general geometries. An estimate of the effect of the shape of the cavity on the estimated absorption coefficient is given.     

Encoding amplitude information onto phase-only filters

We report a new, to our knowledge, technique for encoding amplitude information onto a phase-only filter with a single liquid-crystal spatial light modulator. In our approach we spatially modulate the phase that is encoded onto the filter and, consequently, spatially modify the diffraction efficiency of the filter. Light that is not diffracted into the first order is sent into the zero order, effectively allowing for amplitude modulation of either the first-order or the zero-order diffracted light. This technique has several applications in both optical pattern recognition and image processing, including amplitude modulation and inverse filters. Experimental results are included for the new technique.     

合适旋转开关的选用

合适旋转开关的选用这件事似简单，做起来并不容易，需要协调许多设计参数，以求得合理的理衡。Ｇｒａｙｈｉｌｌ公司ＤＡＮ　Ｍ．ＯＴＴ简单地说，旋转开关是一种引导电流进入选定的导通路径的机械手段，它是人和机器之间的直接而又确实的接口。常见的旋转开关的用途是：...     

Circuitry for the contactless detection of superconducting transitions

Complete circuitry is presented for the detection of the superconducting transition in powders, or specimens for which the standard four-point resistance measurement cannot be performed. Specimens are placed within an inductance coil, and the change in the coil reactance is monitored as a function of temperature. The sensitivity is sufficient to detect the superconducting transition in 10(-3) cm(3) of lead, and only four integrated circuit packages are required.