The optimisation of higher order resampling methods in a multiprocessor environment

The processing of images obtained from satellites often involves highly repetitive calculations on very large amounts of data. This processing is extremely time consuming when these calculations are performed on sequential machines. Parallel computers are well suited to handling computationally expensive operations such as higher order interpolations on large data sets. This paper decribes work undertaken to develop parallel implementations of a set of resampling procedures on an Alliant VFX/4. Each resampling procedure implemented has been optimised in three stages. First, the algorithm has been restructured, where two-dimensional resampling is performed by two one-dimensional resampling operations. Second, each procedure has been reprogrammed in such a way that the autoparallelisation provided by the FX/Fortran compiler has been exploited. Thirdly, data dependent analysis of each procedure has been performed in order to achieve full optimization of each procedure; each procedure has been restructured where appropriate to circumvent vectorisation and concurrency inhibiting data dependencies. The nature and extent of the code optimization achieved for each procedure is presented in this paper. The original code for the most computationally expensive procedure, as targeted at a sequential machine, was found to have an execution time of 4900 seconds on the Alliant VFX/4 when compiled with regular compiler optimization options. Following algorithmic redesigning and reprogramming of the code, as indicated in stage 1 and stage 2, the execution time was reduced to 248 seconds. Restructuring of the code following data dependency analysis indicated in stage 3 in order to avoid data dependencies and allow concurrency and vectorisation, further reduced execution time to 162 seconds. The consequence of this work is that higher-order resampling methods which had not previous been practical are now routinely performed on the Alliant VFX/4 at the University of Dundee.     

Rate of cerebrospinal fluid formation, resistance to reabsorption of cerebrospinal fluid, brain tissue water content, and electroencephalogram during desflurane anesthesia in dogs

Propofol decreases intraocular pressure (IOP) and the IOP response to laryngoscopy and intubation, but the mechanisms responsible for this effect have not been reported. The present study examined the effect of propofol on IOP, intraocular fluid formation and outflow facility, and intraocular compliance. Twenty-two white New Zealand rabbits were anesthetized with halothane (0.8%-1.0% inspired concentration) in nitrous oxide (2 L/min) and oxygen (1 L/min). Muscle paralysis was established with pancuronium, and the lungs were mechanically ventilated through a tracheal tube. Twelve rabbits examined under these conditions served as controls. In the treatment group (n = 10), 6 mg/kg propofol followed by 18 mg.kg-1 x h-1 propofol intravenously was added to halothane/nitrous oxide/oxygen anesthesia. In both groups, a series of intraocular infusions was made via a 30-gauge needle in the anterior chamber, and IOP, the rate of aqueous humor formation (Fa), and trabecular outflow facility (Ctr) were determined using conventional analysis. These same measures, as well as intraocular compliance, were determined using a new method of analysis adapted from the manometric technique for determining cerebrospinal fluid dynamics. IOP was 11.3 +/- 1.8 mm Hg (mean +/- SD) in halothane-anesthetized controls and decreased to 9.4 +/- 2.2 mm Hg when propofol was added to halothane anesthesia (P < 0.05). By conventional analysis, Fa was 2.82 +/- 0.94 microL/min and Ctr was 0.121 +/- 0.044 microL.min-1 x mm Hg-1 in controls. After addition of propofol, Fa decreased by 24% to 2.15 +/- 0.62 microL/min (P < 0.05) and Ctr decreased by 18% to 0.099 +/- 0.034 microL.min-1 x mm Hg-1 (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Salt-tolerant and thermostable alkaline protease from Bacillus subtilis NCIM no. 64

The proteolytic activity produced by a Bacillus subtilis isolated from a hot spring was investigated. Maximum protease production was obtained after 38 h of fermentation. Effects of various carbon and nitrogen sources indicate the requirement of starch and bacteriological peptone to be the best inducers for maximum protease production. Requirement for phosphorus was very evident, and the protease was secreted over a wide range of pH 5-11. The partially purified enzyme was stable at 60 degrees C for 30 min. Calcium ions were effective in stabilizing the enzyme, especially at higher temperature. The enzyme was extremely salt tolerant and retained 100% activity in 5M NaCl over 96 h. The molecular weight of the purified enzymes as determined by SDS-PAGE was 28,000. The enzyme was completely inactivated by PMSF, but little affected by urea, sodium dodecyl sulfate, and sodium tripoly phosphate.     

Large specimen bone embedment and cement line staining

Undecalcified embedment of large bone specimens is often challenging. A method is presented here that is suitable for methacrylate embedment of sections of canine vertebrae while retaining the ability to localize tartrate-resistant acid phosphatase and alkaline phosphatase activity. Specimens also retained tetracycline labelling, and sectioned preparations were readily stained with routine bone procedures. A modification of the Bodian silver stain, used for examining the nerves and spinal cord in these specimens, provided a useful stain for canaliculi and cement lines in trabecular and cortical bone. This stain is advantageous when both bone and nerve tissue are of interest, as in spinal fusion studies.     

Validation of a Three-Dimensional Computational Fluid Dynamics Model of a Contact Tank

A three-dimensional (3D) computational fluid dynamics (CFD) model of a contact tank is presented in this paper. The model results are compared against 3D velocities and flow through curve (FTC) data, representing a tracer concentration profile, from a 1:8 scale physical model. The objective is to demonstrate that CFD models can simulate both the FTC and the 3D velocity field quite well. Simultaneous validation of velocities and FTC is important in ascertaining the predictive capabilities of CFD models, as physical model studies indicate that different baffle arrangements can lead to similar FTCs. Therefore, a good prediction of only FTC, as presented in previous 3D CFD model studies, does not necessarily imply a correct simulation of the flow field.     

Magnetic resonance findings in skeletal muscle tears

Magnetic resonance (MR) images of skeletal muscle tears can clearly delineate the severity of muscle injury. Although MR imaging is seldom necessary in patients with acute muscle trauma, it can be helpful in deciding on clinical management. The two major MR findings in acute muscle tears are deformity of the muscle and the presence of abnormal signal reflecting hemorrhage and edema. In acute tears, methemoglobin within the extravascular blood causes high-signal areas on both T1- and T2-weighted images. With partial tears, the blood may dissect in a distinctive linear pattern along the muscle bundles and fibers. As healing begins, the muscle signal diminishes, first on the T1-weighted images and then on the T2-weighted images. When there is residual abnormal signal on images obtained more than several months after the injury, it is presumed to represent hemorrhage from recurrent tears. In patients with a questionable history of a remote injury, the clinical presentation may be that of persistent pain or a soft tissue mass. In these cases MR imaging may identify the cause of the pain and can exclude a neoplasm by proving that the mass is a hypertrophied or retracted muscle. Thus, MR imaging has a limited, but occasionally important role in selected patients with skeletal muscle tears.     

A study of neutron and gamma radiation effects on transmission of various types of glasses, optical coatings, cemented optics and fiber

A study of radiation effects on various types of glasses, dielectric optical coatings, cemented optics and fiber was undertaken with a view to select them for extreme radiation environments. Samples were exposed to different radiation doses in the Pakistan Research Reactor-I (PARR-I) for neutron and Cobalt 60 source for gamma irradiation. Transmissions were measured before and after irradiation. The dielectric coatings were subjected to additional tests (adhesion, abrasion and humidity, etc.) as per MIL-M-13508C and MIL-C-675C. All 15 glasses studied showed varying amounts of transmission loss as expected, with negligible degradation for three types. Recovery of transmissions with time/ageing was also studied, with more or less complete recovery with temperature annealing. A faster bleaching of darkened/brown glasses was achieved by using UV lamps or UV laser. The dielectric coatings (HR, AR) and one of the two commercial optical cements showed excellent resistance to neutrons and gamma radiations, and could be good candidates for the fabrication and utilization of optical components in extreme radiation environments. The data allowed several Chinese glasses to be studied for the first time.