Detection of sodium and potassium in single human red blood cells by 193-nm laser ablative sampling: a feasibility demonstration

The feasibility of quantifying sodium and potassium in single human erythrocytes was demonstrated by spectrochemical analysis of emissions from plasmas produced by 193-nm laser ablation of blood cells confined in a sheath flow. In one scheme, single blood cells that happened to be in the ablation volume were sampled. In another scheme, individual blood cells were first sighted and then synchronously ablated downstream. Plasma emission spectra of single ablated cells were captured, and the ratios of the analyte line intensity to the root-mean-square fluctuation of the continuum background were measured to be about 18 for sodium and 30 for potassium.     

Analysis of solids by laser ablation and resonance-enhanced laser-induced plasma spectroscopy

An analytical technique based on resonance-enhanced laser-induced plasma spectroscopy was demonstrated. Pellets of potassium iodate containing trace amounts of sodium were ablated by a 532-nm laser pulse in air. After 30 ns, the plasma plume was intercepted by a 404.4-nm laser pulse to resonantly photoionize the potassium atoms in the vapor plume. The 589-nm emissions of the sodium were found to be significantly enhanced. The enhancement was shown to depend critically on the profile of the 532-nm beam as well as the spatial overlap of the two laser pulses. Using this double-pulse scheme, the mass detection limit for sodium was estimated to be about 200 pg, which was five times better than that obtained by using the 532-nm laser pulse alone.     

Very-high-speed all-optical code-division multiplexing systems using a 2n prime code

We demonstrate experimental all-optical code-division multiplexing (AO-CDM) systems using 64-ps optical pulses and a 2" prime code of n = 3. A distinguishing feature of this experiment is that the modulation of an ultrashort optical clock stream by electrical data is realized without using any optical intensity modulator at each transmitter. Moreover, only low-cost optical 2 x 2 couplers and fiber delay lines are employed to implement all-serial encoders and decoders for a 2n prime code.     

Anti-plane shear problem for an edge crack in a finite orthotropic plate

The problem of an edge crack in a finite orthotropic plate under anti-plane shear is considered. The boundary collocation method is used to calculate the mode III stress intensity factor (SIF). For the case in which the material is isotropic, the present results agree very well with those obtained by using the integral equation method. Furthermore, the method can be extended readily for general cases with arbitrary geometrical and boundary loading conditions and material properties.     

Colour-difference ellipsoids for five CIE colour centres

Following the CIE guidelines for coordinated research on colour-difference evaluation, sets of dyed wool samples were produced near each of the five CIE reference colours, the colour differences within each set ranging from 1 to 9 CIE-LAB units. Ratio assessments were used to determine discrimination ellipsoids for illuminants D₆₅ and A. Ratio and grey-scale assessments involving pairs from all five colours were used to bring the visual data onto a common scale consistent with previous results. The ellipsoids for the red and green centres were compared with those obtained previously for the same centres. The agreement was rather better for the green colour, even though the substrates and sizes of colour-differences were different in this case. The chromaticity-discrimination ellipses generally agreed well with those obtained earlier for similar colours. The CMC (1 : 1) formula agreed better with the experimental results than did the CIELAB formula.     

Growth kinetics of Pd2Si from evaporated and sputter-deposited films

The growth kinetics of Pd₂Si formed by palladium films either vacuum deposited or sputter deposited onto vacuum-evaporated, sputter-deposited or single-crystal silicon substrates were investigated by backscattering spectrometry (BS). The impurity contents of the films and substrates were characterized by both secondary ion mass spectrometry and BS. In all cases, Pd₂Si is the only silicide phase detected after vacuum annealing up to 300°C and the growth mechanism is always diffusion limited. The rate of the diffusion was found to differ and the activation energies for Pd₂Si formation varied between 0.9 and 1.5 eV. These changes are correlated with the presence of impurities in the deposited palladium and silicon films. Also, sputtered palladium films do not form epitaxial Pd₂Si layers on (111) Si substrates as vacuum-deposited palladium films do. The conclusion is that rates of reaction and morphology of Pd₂Si layers grown by thermal annealing depend on the deposition system.     

Direct effect of endotoxin on the gastric mucosal microcirculation and electrical gradient

The effects of intra-arterial infusion of E. coli endotoxin at 1.0 mg. per minute on the gastric total and mucosal blood flows, electrical potential difference, and ionic fluxes across the gastric mucosa were studied in an exteriorized, chambered preparation of canine fundic stomach. Gamma-labelled microsphere technique was used in addition to venous drainage and plasma aminopyrine clearance for the measurement of total and mucosal blood flow, respectively. In spite of normal systemic blood pressure throughout the experiment, E. coli endotoxin infusion caused a significant decrease in total gastric blood flow and in the fractional distribution of flow to the mucosae. There was no significant arteriovenous shunting of microspheres. Significant reduction in potential difference and hydrogen-ion back diffusion also was noted after endotoxin infusion, possibly as a consequence of reduced mucosal blood flow. The results indicate that significant gastric mucosal ischemia can occur and may represent a mechanism in the development of gastric erosions in endotoxemia, even in the absence of systemic hypotension.     

Controllable porosity hydroxyapatite ceramics as spine cage: fabrication and properties evaluation

A procedure was designed to prepare porosity-graded hydroxyapatite (HA) ceramics simulating the bimodal structure of natural bone, which could be used to build a cage that would promote the reconstruction of the anterior column after vertebrectomy or corpectomy in tumor and trauma surgery. HA ceramics with controllable pore size distribution and porosity were developed by using chitosan and Poly(vinyl alcohol) (PVA) as the pore-forming agents. HA ceramics with worthwhile properties such as a wide range of volume porosity (10-50%) and pore size (nanometer to 400 microm) can be obtained from this method, which allows the fabrication of HA ceramics with desirable porous characteristics simulating the bimodal natural bone architecture expected to provide advantages for bony fusion in the intervertebral foramina. When coated with chitosan-gelatin network, the bending strength of the porous HA ceramics significantly improved. The polymer network coated porous HA have potential application in the construction of cages for spinal operations.