On the variation of a.c. susceptibility with temperature for some Cu-Li ferrites

The a.c. susceptibility vs. temperature of the system (Li_0·5Fe_0·5)_1−x Cu _x Fe₂O₄, for 0⩽x⩽1·0 has been studied. While pure CuFe₂O₄ (x=1) shows a dramatic peak in susceptibility just before its Curie temperature (T _c), the same is supressed with the addition of a small amount of Li to the system. The variation of lattice parameter with Li content has also been investigated. Samples up tox=0·4 show tetragonal structure while those withx>0·4 are cubic. This change of structure can be explained on the basis of reduction ofdsp ² bonding of Cu ions on B-sites of the spinel lattice.     

Molecular weight distributions for reversible nylon-6 polymerizations in batch reactors

The reversible polymerization of nylon-6 including ring opening, polycondensation, polyaddition and cyclization reactions as well as the reaction with monofunctional acids, has been modelled. Molecular weight distributions and their moments have been obtained for various initial conditions and at two temperatures, 235° and 265°C, for a batch reactor. The cyclic oligomer concentrations have also been computed. It is found that even though the cyclization step has little influence on the monomer conversion, it does affect the molecular weight distribution and its moments.     

A second signal supplied by insulin-like growth factor II in oncogene-induced tumorigenesis

Transgenic mice expressing the simian virus-40 large T-antigen (Tag) under the control of the insulin gene regulatory region offer a useful model for tumorigenesis. All the islets of Langerhans express Tag, although there is at first no aberrant proliferation. Over half of the islets become hyperplastic, however, and neovascularization of a further subset (about 10%)3 leads eventually to formation of highly vascularized solid tumours in 1-2% of islets by about 14 weeks of age. Here we show that the initial proliferative switch is correlated with focal activation of insulin-like growth factor II (IGF-II). Transfection with an antisense oligonucleotide to the IGF-II messenger RNA interferes with tumour cell proliferation in vitro, and transgenic mice homozygous for a disruption of the IGF-II gene develop tumours with reduced malignancy and a higher incidence of apoptosis. Several signals, in this case including an oncoprotein and a growth/survival factor, thus appear to be needed to elicit hyperproliferation.     

Failure analysis of high-density CMOS SRAMs: using realistic defectmodeling and IDDQ testing

A rapid failure analysis method for high-density CMOS static RAMs (SRAMs) that uses realistic defect modeling and the results of functional and I_DDQ testing is presented. The key to the method is the development of a defect-to-signature vocabulary through inductive fault analysis. Results indicate that the method can efficiently debug the multimegabit-memory manufacturing process     

The strength design method for reinforced concrete around the world

In the 40 years since the American Concrete Institute (ACI) 318-56 Code introduced the ultimate strength design method, it has become the primary method for reinforced concrete design in the United States. The concept of ultimate or limit state design has also been incorporated into building codes around the world. However, the codes of different countries do not agree on the factors used to relate the service loads to ultimate loads. This article reviews the basis for the strength design method and compares the treatment of the strength design concept by codes around the world.     

Correspondence of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography

OBJECTIVES: This study assessed the agreement of left ventricular ejection fraction determinations from two-dimensional echocardiography, radionuclide angiography and contrast cineangiography. BACKGROUND: Previously published reports suggest that two-dimensional echocardiography, radionuclide angiography and contrast cineangiography are equally acceptable methods of assessing left ventricular ejection fraction on the basis of high coefficients of correlation. However, correlation of methods does not necessarily imply agreement. METHODS: In a prospective analysis, 25 consecutive subjects all had two-dimensional echocardiography and radionuclide angiography performed within 10 days of each other in the cardiology department of metropolitan community hospital. A retrospective computer search (Medline) revealed seven studies, using the coefficient of correlation (r), comparing two-dimensional echocardiographic left ventricular ejection fraction (n = 268) with radionuclide angiographic (n = 174) or contrast cineangiographic (n = 119) left ventricular ejection fractions. RESULTS: The eight individual studies (n = 293) comparing two-dimensional echocardiography with either radionuclide angiography or contrast cineangiography exhibited coefficients of correlation ranging from 0.78 to 0.93. Agreement analysis using the method of Bland and Altman was performed by averaging the results obtained from the two techniques and determining how disparate any single ejection fraction was (with 95% confidence limits) from the mean value. Agreement ranged from 23% to 42% around the mean ejection fraction. The average lack of agreement between the two methods for all studies involved was 17%, with an average r value of 0.86. CONCLUSIONS: Left ventricular ejection fraction determinations by means of two-dimensional echocardiography, radionuclide angiography and contrast cineangiography exhibit high correlation and only moderate agreement. High correlation does not always imply high agreement. These results suggest that, when validated by agreement analysis, multiple studies may not be necessary in appropriate clinical situations, potentially reducing costs.     

Forced flow evaporative cooling of a volumetrically heated porous layer

In this paper, the temperature rise and pressure drop experienced by an evaporating coolant flowing through a volumetrically heated porous layer have been studied experimentally. Experimental data for the temperature distribution and the two-phase pressure drop along the direction of flow is obtained for water flowing through layers of inductively heated steel particles. Spherical steel particles varying in size from 590 to 4763 μm are used to form porous layers in 5 and 10 cm dia. glass jars. In these experiments the data are obtained for layer depths varying from 9 to 81 cm, volumetric heat generation rate varying from 1.44 to 44.0 W/cm³ and the mass flow rate of water varying from 510 to 18200 kg/m² h.A theoretical model for the temperature profile in the liquid region and the two phase region has been made and is found to compare well with the measurements. Vapor channels are observed to form in porous layers of particle diameter less than 1600 μm. Separate semi-theoretical models have been developed for the two phase pressure drop in particles with diameter less than and greater than 1600 μm.     

Thirteen years of follow-up of 100 smear positive leprosy cases after completion of multidrug therapy

A pediatric patient with diabetic ketoacidosis (DKA) was found to have a pneumomediastinum and a small pneumothorax. Because some of the signs and symptoms of pneumomediastinum may be confused with those of the patient's primary disease process, this complication may be present more frequently than has been previously described.