SIZE CONTROL IN THE FORMATION OF EXTREMELY FINE GOETHITE PARTICLES BY OXIDATION OF ALKALINE SUSPENSIONS OF FERROUS HYDROXIDE

The kinetics for oxidation of an aqueous alkaline suspension of ferrous hydroxide leading to formation of fine goethite particles was reconfirmed. The mean size of the needle-like goethite particles can be correlated well to the oxidation rate. Phenomenologically, host nuclei are generated in the early stage of the reaction, and afterwards particle growth mainly occurs through hydrolysis of ferric hydroxo-complex (intermediate species) with the number of host nuclei held almost constant. The particle size can be expected to be approximately governed by the number of host nuclei generated in the early stage of the reaction and the initial concentration of total Fe(II). By shifting the oxygen concentration in the feed stream to a lower level at a low conversion, the size distribution of the prepared particles becomes narrow.     

Image processing and synthesis for extended depth of field of optical microscopes

An optimal microscope is useful for observing various kinds of samples. However, precise observation of an extended region in depth is difficult, because of the narrow range of depth of focus. To overcome this problem, this paper proposes a method of obtaining a pan-focused stereoscopic image. By using image processing, in-focus areas are extracted from multiple images focused on slightly different depths, and a stereoscopic image is composed with these in-focus areas. The proposed method is applied to the observation of three-dimensional distributions of soil particles, a common problem in the field of civil engineering, and the usefulness of the proposed method is demonstrated.     

Analysis of below-threshold spectrum and linewidth of surface-emitting lambda /4-shifted DFB lasers with DBR mirror

The frequency distribution of spontaneous emission noise below lasing threshold and the spectral linewidth in lasing operation are analysed for surface-emitting lambda /4-shifted distributed feedback (DFB) lasers consisting of alternating active and passive layers with a distributed Bragg reflector (DBR) mirror.<>     

Transfer-matrix formulation of spontaneous emission noise of DFBsemiconductor lasers

A unified formulation of the spontaneous emission noise in semiconductor DFB (distributed feedback) lasers is presented by using a transfer-matrix approach. Analytical expressions for the noise power per unit frequency bandwidth below threshold and the spontaneous emission rate into the lasing mode are obtained based on the Green's function method. Three DFB laser structures are analyzed: (1) a standard DFB structure with facet reflectivities, (2) a multisection DFB structure composed of n sections which models a phase-shifted DFB laser and a multielectrode (tunable) DFB laser, and (3) a periodic layered DFB structure which models a surface-emitting DFB laser. It is shown that the spontaneous emission noise of a complicated DFB laser structure can be calculated easily by the transfer matrix of each section of the structure and its derivative to frequency     

Measurement of diffusion coefficient of water and ethanol in aqueous maltodextrin solution

Capillary cell and absorption-desorption methods were used to measure the diffusion coefficients of water and ethanol in aqueous maltodextrin solution over a wide range of water content. The diffusion coefficients showed a surprisingly large dependence on water content, particularly at low water content, as reported by other workers. Free volume theory was applied to correlate the diffusion coefficients. It was found that this theory was adequate to explain their large dependence on water content. Furthermore, experimental results on ethanol retention in drying an aqueous maltodextrin droplet could be predicted well, using the present experimental results for the diffusion coefficients of water and ethanol.     

Spermatid-specific overexpression of the TATA-binding protein gene involves recruitment of two potent testis-specific promoters

The gene encoding the TATA-binding protein, TBP, is highly overexpressed during the haploid stages of spermatogenesis in rodents. RNase protection analyses for mRNAs containing the previously identified first, second, and eighth exons suggested that most TBP mRNAs in testis did not initiate at the first exon used in somatic cells (here designated exon 1C). Using a sensitive ligation-mediated cDNA amplification method, 5' end variants of TBP mRNA were identified, and the corresponding cDNAs were cloned from liver and testis. In liver, a single promoter/first exon is used to generate a steady-state level of roughly five molecules of TBP mRNA per diploid cell equivalent. In testis, we detect modest up-regulation of the somatic promoter and recruitment of at least five other promoters. Three of the alternative promoter/first exons, including 1C and two of the testis-specific promoter/first exons, 1D and 1E, contribute roughly equivalent amounts of mRNA which, in sum, account for greater than 90% of all TBP mRNA in testis. As a result, round spermatids contain an estimated 1000 TBP mRNA molecules per haploid cell. Testis TBP mRNA also exhibits several low abundance 5' end splicing variants; however, all detected TBP mRNA leader sequences splice onto the common exon 2 and are expected to initiate translation at the same site within exon 2. The precise locations of the three major initiation exons are mapped on the gene. The identification of the strong testis-specific promoter/first exons will be important for understanding spermatid-specific tbp gene regulation.     

Quantification of human lithostathine S2-5 forms using the antibody to the N-terminal peptide region

OBJECTIVE: To describe the various components of the delay to thrombolytic treatment for patients with acute myocardial infarction (MI) and to identify the hospital and patient characteristics related to these delays. DESIGN: Cohort analysis from a hospital registry of patients receiving thrombolytic treatment. SETTING: Forty acute care hospitals in Quebec. SUBJECTS: All 1357 patients who received thrombolysis between January 1995 and May 1996. MAIN OUTCOME MEASURES: Time from onset of symptoms to arrival at hospital and the various components of the in-hospital delay. RESULTS: The median delay before presentation to hospital was 98 (interquartile range [IR] 56 to 180) minutes and was longer for women (p < 0.001), patients over 65 years of age (p < 0.001) and patients with diabetes mellitus (p < 0.01). The median time from arrival at hospital to thrombolysis was 59 (IR 41 to 89) minutes, the medical decision-making component taking a median of 12 (IR 4 to 27) minutes. Women (p < 0.005), older patients (p < 0.001) and patients with a past history of MI (p < 0.001) had increased in-hospital delays to thrombolysis. Delays were longer in community hospitals (p < 0.05) and low-volume centres (p < 0.01) and when a cardiologist made the decision to administer thrombolysis (p < 0.001). Multivariate analysis showed that increased age (odds ratio 1.5, 95% confidence interval 1.3 to 1.7, p < 0.001) and having the medical decision made by a cardiologist (odds ratio 1.8, 95% confidence interval 1.6 to 2.0, p < 0.001) were independently associated with an increased risk of being in the upper median of in-hospital delays. CONCLUSIONS: Despite certain improvements, there remain substantial delays between symptom onset and the administration of thrombolysis for patients with acute MI. A large part of the delay is due to the hesitation of patients (particularly women, older patients and patients with diabetes) to seek medical attention. Although the median time for medical decision-making appears reasonable, care must be taken to ensure that all patient groups receive timely evaluation and therapy. The delay associated with having the treatment decision made by a cardiologist probably represents a marker for more difficult, complex cases. Methods should be developed to permit specialty consultation, if needed, while minimizing treatment delays. Community and low-volume hospitals may require special attention.     

Etiology of idiopathic scoliosis. Computational study

A review of the literature on the mechanical aspects of the etiology for idiopathic scoliosis reveals that the buckling hypothesis has been presented as a purely mechanical phenomenon. In an attempt to confirm the buckling hypothesis, a numerical simulation of growth and the resulting buckling phenomena was done by means of finite element analysis. It previously was observed that growth was induced in the T4 to T10 vertebrae. Only the sacrum was assumed to be stationary. From the growth analysis, a deformation process that mitigated thoracic kyphosis was obtained as observed in healthy children during early adolescence. From the buckling analysis, the first to the fourth buckling modes that correspond to the first side bending, first forward bending, first rotation, and second side bending modes were obtained. The shape of the fourth buckling mode (second side bending mode) was in good agreement with the clinical shape. Considering the potential for controlling these modes by posture change, it is concluded that the second bending mode in the coronal plane is one of the most likely etiologic candidates in the mechanics of thoracic idiopathic scoliosis.