Least-squares finite-element scheme for the lattice Boltzmann method on an unstructured mesh.

A numerical model of the lattice Boltzmann method (LBM) utilizing least-squares finite-element method in space and the Crank-Nicolson method in time is developed. This method is able to solve fluid flow in domains that contain complex or irregular geometric boundaries by using the flexibility and numerical stability of a finite-element method, while employing accurate least-squares optimization. Fourth-order accuracy in space and second-order accuracy in time are derived for a pure advection equation on a uniform mesh; while high stability is implied from a von Neumann linearized stability analysis. Implemented on unstructured mesh through an innovative element-by-element approach, the proposed method requires fewer grid points and less memory compared to traditional LBM. Accurate numerical results are presented through two-dimensional incompressible Poiseuille flow, Couette flow, and flow past a circular cylinder. Finally, the proposed method is applied to estimate the permeability of a randomly generated porous media, which further demonstrates its inherent geometric flexibility.

Least-squares finite-element lattice Boltzmann method.

A new numerical model of the lattice Boltzmann method utilizing least-squares finite element in space and Crank-Nicolson method in time is presented. The new method is able to solve problem domains that contain complex or irregular geometric boundaries by using finite-element method's geometric flexibility and numerical stability, while employing efficient and accurate least-squares optimization. For the pure advection equation on a uniform mesh, the proposed method provides for fourth-order accuracy in space and second-order accuracy in time, with unconditional stability in the time domain. Accurate numerical results are presented through two-dimensional incompressible Poiseuille flow and Couette flow.

Quantitative estimation of the degree of derivatization: an alternative methodology using 1-D and 2-D NMR experiments.

The precise estimation of the degree of derivatization of functional groups in polymers is important for determining their macroscopic properties. In this work, the quantitative estimation of the extent of esterification of novolac copolymers with di-tert-butyl dicarbonate was studied. Although the extent of esterification has been calculated previously by quantifying the signals from FT-IR and UV-Vis spectroscopy, these were restricted to monitoring the progress of the derivatization process. The 13C NMR signal intensities from the inverse-gated 1H-decoupled NMR spectrum have been used recently for the quantitative estimation of the degree of esterification of polymers. An alternative methodology has been suggested by us based on the fully relaxed 1H chemical shift intensities. However, since the proton signals of novolac resins are generally broad and overlapping, the proton decoupled 13C NMR spectrum was used to identify the 1H NMR signals using the 2-D HSQC technique. A TOCSY experiment was also performed to confirm further the 1H NMR signal assignments and, finally, the deconvoluted 1H NMR spectrum was used for the calculation of the extent of derivatization.

Changes in the corneal Na-K ATPase levels in eyes stored in moist chamber at 4 degrees C.

This report deals with a chronological measurement of Na-K ATPase enzyme activity in human and bovine corneas stored in a moist chamber at 4 degrees C. Paired human and bovine eyes were sterilized by the standard eye bank procedure and stored up to 6 days. At the desired time, the corneal endothelium was assayed for Na-K ATPase activity. The protein content of each tissue sample was also determined. In a parallel set of experiments, the viability of identical stored corneas was determined by trypan blue and alizarin red staining technique, and morphometric analysis was done to quantify the extent of the corneal endothelial damage. The human corneas showed that there was a significant progressive decrease in the Na-K ATPase activity as the storage time increased. The decrease was related to morphological endothelial damage.

A review of methods for storage of corneas for keratoplasty.

This article reviews the various methods used for the storage of the donor cornea for keratoplasty. The methods have been classified in terms of the duration of storage as (a) short-term (b) intermediate term (c) long-term and (d) very long-term. The practical importance of the moist-chamber method of short-term storage has been discussed. A short report on a new intermediate-term corneal storage medium using steroid as a lysosome membrane stabilizer has also been included. Organ culture of corneas for long-term storage is not popular in the developing countries due to lack of appropriate storage facilities. Cryopreservation as a long-term storage technique still attracts researchers' attention.

Collision tumor of gastrointestinal tract.

A rare combination of multiple adenomatous polyps of the colon and carcinoid tumor of the ileum in a 54-year-old man is reported.

Iodine therapy for thyroidectomy patients exhibiting high thyroid-stimulating hormone values: a randomised study.

After thyroidectomy there is an appreciable incidence of hypothyroidism as judged by FT4I estimates. Pharmacological doses of iodine (10-300 mg/day) usually suppress, whereas physiological doses of iodine (< 5 mg/day) have been reported to both decrease and increase thyroid function. The value of iodine supplementation in preventing post-thyroidectomy hypothyroidism was assessed in a prospective randomised trial. A series of 55 patients with a TSH > 6 mU/l 1 month after bilateral subtotal thyroidectomy or unilateral lobectomy for benign disease were randomised to receive either chloroform water 5 ml/day (placebo) or chloroform water 5 ml/day with 1 mg of iodine to be taken for 20 weeks. With placebo, 62% of bilateral subtotal thyroidectomies were euthyroid at 6 months on no thyroid replacement, while with iodine all were hypothyroid as judged by FT4I. After bilateral subtotal thyroidectomy, the recovery of remnant function is delayed by an iodine supplement of 1 mg/day.

Significance of serum immunoglobulin levels in conglomeration with trans-sternal phlebography in the phlebography management of breast cancer.

The study was conducted on 63 patients with breast lump and twenty normal healthy females. In benign breast disease, a significant (P < 0.001) rise in serum IgA, significant (P < 0.001) decrease in IgG and no change in IgM levels was seen before operation. A significant decrease (P < 0.001) in serum IgA and significant increase in IgG and IgM was observed post operatively. In carcinoma breast, a significant (P < 0.001) elevation in IgA, IgG and IgM levels was found pre-operatively with a concomitant decrease in serum IgA and IgG and increase in serum IgM levels, post operatively. Trans-sternal phlebography (TSP) carried out with 95.23% success has revealed significant (P < 0.001) change in the staging of carcinoma breast. The increased levels of serum immunoglobulins associated with the patients of carcinoma breast with metastasis has led to conclude that these levels, if punctuated with TSP findings can lead to better assessment of the staging of carcinoma breast and thereby its management.

Toxicity and pharmacokinetics of intravitreally injected ciprofloxacin in rabbit eyes.

To assess the toxicity of intraocular injection of ciprofloxacin, 22 New Zealand white rabbits received midvitreal injections of 100, 200, 400, 800 or 3200 micrograms of ciprofloxacin in 0.1 mL of distilled water (39 eyes) or 0.1 mL of distilled water only (5 eyes). The ocular pharmacokinetics of intravitreally injected ciprofloxacin was determined by aqueous humour and vitreous sampling 1, 2, 4, 8, 12, 18 or 24 hours after midvitreal injection of 100 micrograms of the drug in one eye each of 25 New Zealand white rabbits. The samples were analysed by means of a disc diffusion bioassay. No ocular damage was noted on ophthalmoscopy at any of the concentrations tested. Histologic study showed mild, transient vacuolation of the nerve-fibre layer in all eyes, including the control eyes, 2 hours after injection; at 24 hours no vacuolation was evident except at concentrations of 800 and 3200 micrograms, at which plexiform layer damage was evident. Peak aqueous and vitreous levels of ciprofloxacin were obtained at 1 hour (0.59 and 27.26 micrograms/mL respectively); the vitreous level fell to below 1.0 micrograms/mL 12 hours after injection. We conclude that intravitreally injected ciprofloxacin may be a safe and useful antibiotic in the treatment of aminoglycoside-resistant bacterial endophthalmitis.

Geometric and material property study of the human lumbar spine using the finite element method.

In using the finite element method to examine certain aspects of the mechanical behavior of the human lumbar spine, most investigators have made numerous simplifying assumptions regarding the geometric and material data used to build a model of the spine. Since there are no specific rules for choosing geometric and material data for a "normal" human lumbar spine, considerably different types of models have been used by investigators in their finite element studies. In this study, variations in model geometric and material properties are shown to significantly affect the finite element results of an axisymmetric model of the human lumbar spine under axial compression. The Young's moduli of the cancellous bone and intervertebral disc annulus, Poisson's ratios of the cartilaginous end-plate and disc annulus, the width of the disc annulus, the height of the disc, and the ratio of the disc nucleus pressure and axial pressure are recognized as the parametric variables that most significantly affect the finite element solution.

Quantitative determination of the melanin contents in ocular tissues from human blue and brown eyes.

This paper deals with our findings on the quantities of melanin in the tissues from blue and brown eyes. The amount of melanin in the iris, ciliary body and retinal pigment epithelium-choroid was separately determined. The results are expressed as the amount of melanin in mg tissue as well as the amount of melanin in the whole tissue. The results showed that there was no statistically significant difference between the melanin content of the iris in blue and brown eyes. However the ciliary body and retinal pigment epithelium-choroid from brown eyes had more melanin than the corresponding tissues from blue eyes. Blue and brown eyes with higher colour intensity had more melanin than the corresponding eyes with lesser intensity of colour. It is suggested that the differences between brown and blue eyes in their melanin content may have relevance to the pharmacokinetics of drugs that bind to melanin. This would mean that the larger amounts of melanin would decrease the initial levels of the drugs and would increase the drug levels after prolonged periods.

Continuous flow contact lens delivery of gentamicin to rabbit cornea and aqueous humor.

The Morgan Therapeutic Lens (MTL) was investigated as a continuous corneal perfusion system in New Zealand white rabbits. Gentamicin concentration in the cornea and aqueous humor delivered by the MTL was compared to gentamicin drops (13.6 mg/ml) administered every 15 or 30 minutes. Gentamicin (1 mg/ml) or 5 mg/ml was perfused at 10 ml/hr for up to 4.0 hours. At each time interval of 0.5, 1, 2 and 4 hours, homogenized corneas and aqueous humour were assayed for gentamicin concentrations. The highest aqueous humour gentamicin concentrations of 57.99 +/- 12.86 micrograms/ml were significantly higher with the MTL and 5 mg/ml of gentamicin compared with the MTL and 1 mg/ml of gentamicin or than drops applied every 30 minutes, but not significantly different than drops every 15 minutes. Highest corneal concentrations of gentamicin of 496.04 +/- 101.16 micrograms/gm cornea were significantly higher with MTL and 5 mg/ml of gentamicin compared with the MTL and 1 mg/ml gentamicin or than drops applied every 30 minutes, but not significantly different than drops every 15 minutes. All mean gentamicin concentrations attained via the MTL exceeded the mean inhibitory concentration for most sensitive bacterial species. The MTL is a reliable drug delivery system with distinct advantages, and may be a useful therapeutic modality in the ocular delivery of gentamicin and other drugs.

Effect of vitrectomy on the ocular distribution of gentamicin in the rabbit.

To determine whether vitrectomy affects the ocular distribution of intravitreally injected gentamicin sulfate, 25 pigmented rabbits received an intravitreal injection of gentamicin (control group), and 25 other pigmented rabbits underwent pars plana vitrectomy followed by an intravitreal injection of gentamicin (experimental group). The animals were killed in groups of five 1, 3, 6, 12 and 24 hours after the injection. The mean retinal gentamicin levels 1 and 3 hours after the injection were significantly higher in the experimental group than in the control group (p less than 0.01). The mean gentamicin level in the aqueous humour was significantly lower in the experimental group than in the control group 1 hour (p less than 0.01), 6 hours (p less than 0.01) and 24 hours (p less than 0.001) after the injection. The mean corneal gentamicin level 24 hours after the injection was significantly lower in the experimental group than in the control group (p less than 0.05). There was no significant difference in mean choroidal gentamicin level between the two groups. We conclude that vitrectomy significantly affects the ocular distribution of gentamicin in the rabbit.

Characterization of the pigment from homogentisic acid and urine and tissue from an alkaptonuria patient.

When urine samples from alkaptonuria patients are allowed to stand, they turn black, presumably owing to the oxidation of homogentisic acid to a melanin-like substance. We report the characterization of the pigments formed by polymerization of (a) the components in the urine from a patient with alkaptonuria and (b) homogentisic acid. The absorption spectra and electron spin resonance signals of these pigments are similar to those of eumelanins. Irradiation of the pigments with nitroblue tetrazolium caused reduction of the tetrazolium; this was partially inhibited by superoxide dismutase. Irradiation of Ehrlich ascites carcinoma cells with the pigments from homogentisic acid or urine caused cell lysis. Since this lysis was inhibited by catalase, we have concluded that it was mediated by H2O2. A similar pigment was also extracted from the tissue from an alkaptonuria patient. It is suggested that the degeneration of tissue in vivo may be due to the deposition of melanin-like pigments in the tissues, probably in combination with metal ions.

The effects of donor age and cause of death on corneal graft survival.

The Ontario Corneal Recipient Registry followed 299 recipients of 326 corneal transplants performed between October 1985 and October 1987. This report describes the joint effects of donor age and cause of death on subsequent graft survival in these procedures up to two years after surgery. Cox regression analysis established that grafts from donors dying of injury experienced half the risk of graft failure of those from donors dying of heart disease or other natural causes (P less than 0.05). Although donor age differed substantially between these causes of death, controlling for donor age did not alter the association. There were no statistically or clinically significant differences in graft survival associated with either donor age or recipient age. These results suggest that the health of the donor and the circumstances surrounding death may influence the quality of corneal tissue, and deserve more attention and detailed study.