Relative merits of ultrasonography, computed tomography and cholangiography in patients of surgical obstructive jaundice

Fifty consecutive patients with surgical obstructive jaundice were evaluated prospectively with ultrasonography (US), computed tomographic scans (CT scan) and cholangiography-percutaneous transhepatic cholangiography (PTC) or endoscopic retrograde cholangio-pancreaticography (ERCP). The diagnostic accuracy of ultrasound in defining the level of obstruction was 86% as compared to 86% and 94.8% for CT scan and cholangiography, respectively. To measure the etiology of the obstruction, the accuracy of ultrasound, CT scan and cholangiography were 84%, 86% and 75%, respectively. The sensitivity of CT scans and cholangiography in the diagnosis of choledocholithiasis was 100%, 81.8% and 90%, respectively, whereas specificity was 97%, 100% and 100%, respectively. Sensitivity for a diagnosis of malignant disease was 100% for both US and CT scans whereas specificity was 90% and 81%, respectively. Ultrasonography as a single radiological investigation is sufficient in the evaluation of the majority of patients with surgical obstructive jaundice. CT scan and cholangiography should be done only when US gives equivocal findings or if concomitant therapeutic procedures like basketing and stenting are also planned.     

Image interpretation using Bayesian networks

The problem of image interpretation is one of inference with the help of domain knowledge. In this paper, we formulate the problem as the maximum a posteriori (MAP) estimate of a properly defined probability distribution function (PDF). We show that a Bayesian network can be used to represent this PDF as well as the domain knowledge needed for interpretation. The Bayesian network may be relaxed to obtain the set of optimum interpretations     

Water flow through helical coils in turbulent condition

Experimental data on pressure drop across six helical coils made of rough transparent PVC pipes for flow of water in turbulent condition are presented. A correlation for predicting the friction factor has been developed.     

Uphill permeation model of gold(III) and its separation from base metals using thiourea derivatives as ionophores across a liquid membrane

This work deals with carrier-facilitated membrane transport of Au(III) from chloride media across a polymer-immobilised liquid membrane (PILM) using as organic reagents N-(thiocarbamoyl)benzamide derivatives and N-benzoylthiourea derivatives, denoted as 2a–c and 3a–f, respectively. Both the composition of the organic membrane solvent and the type of carrier have a marked effect on gold permeation. Recovery and permeability of gold using 2a–c and 3a–f across a PILM proceed in the following order: 3e≈3d≈3c?3f>3b≈3a≈2a≈2b≈2c. In view of the performance of these carriers, 3c was selected as a metal receptor for detailed studies of Au(III) in permeation. A model is presented for the permeation of Au(III) (61 μM) in 0.5 M Cl⁻ at pH 2.5 using 3c as a membrane carrier. The mathematical equations describing the rate of permeation are derived to correlate the membrane permeability coefficient with diffusional and equilibrium parameters. The mass transfer coefficient was calculated from the described model as 1.1×10⁻⁵ m s⁻¹, and the thickness of the aqueous boundary was later calculated to be 65 μm. Several polymeric supports were tested for impregnation of the organic extractant, and Durapore (Millipore) afforded the maximum flux for Au(III), yielding a value of 1.1×10⁻¹⁴ mol m⁻² s. The relationship between flux and support characteristics is derived and a mathematical equation is presented. Of the several diluents used, cumene had the most satisfactory performance in terms of PILM stability and metal transport. Of the different reagents used, 0.5 M sodium thiocyanate in 0.5 M NaCl at pH 2.5 served most efficiently as the stripping agent. More than 80% of the Au(III) could be readily separated using 3c in the presence of various metals such as Cu(II), Fe(III) and Zn(II).     

Influence of zeolite on electrochemical and physicochemical properties of polyethylene oxide solid electrolyte

A composite polymer electrolyte of polyethyleneoxide-LiBF₄ containing fine particles of zeolite was studied using electrochemical impedance spectroscopy, cyclic voltammetry, differential scanning calorimetry, infrared spectroscopy and scanning electron microscopy. When compared with the polymer electrolyte without zeolite, the specific conductivity of the composite electrolyte film is higher by about two orders of magnitude at room temperature. The increase in specific conductivity is explained as due to increased amorphocity which is reflected in the thermal studies. The nature of the cyclic voltammograms and infrared spectra is discussed.Part of this work was presented at the Electrochemical Society Meeting, Honolulu, Hawai (May 1993).     

Triplex formation at physiological pH by oligonucleotides incorporating 5-Me-dC-(N4-spermine)

Oligonucleotide (ODN) directed triplex formation has therapeutic importance and depends on Hoogsteen hydrogen bonds between a duplex DNA and a third strand. While T*A:T triplets are formed at neutral pH, C+*G:C are favoured at acidic pH. Herein it is shown that 18-mer ODN containing spermine conjugated to 5-Me-dC at N4 (1-5), form triplexes with complementary 24-mer duplex 8:9 at neutral pH (7.3, 100 mM NaCl). Under such conditions, control ODN's carrying dC (6) or 5-Me-dC (7) did not show any triple helix formation. Remarkably, the triplexes from spermine-conjugates (1-5) have foremost stability at neutral pH (7.1), unlike the behavior of normal ODN's where optimal stability is at acidic pH (5.5). These results have importance in designing oligonucleotides for antigene applications.