Parallel pointer machines

The parallel pointer machine is a synchronous collection of finite state transducers, each transducer receiving its inputs via pointers to the other transducers. Each transducer may change its input pointers dynamically by pointer jumping. These machines provide a simple example of a parallel model with a time-varying processor inter-connection structure, and are sufficiently powerful to simulate deterministic spaceS(n) within timeO(S(n)).     

Correlation of high-pressure diffusion and viscosity coefficients for n-alkanes

Self-diffusion coefficient and viscosity coefficient data for liquid n-alkanes over the whole pressure range at different temperatures are satisfactorily correlated simultaneously by a method which is just an extension of that previously used to apply the smooth hard-sphere theory of transport properties to individual transport coefficients. Universal curves are developed for reduced quantities D ^* and ^* as a function of reduced volume. A consistent set of values is derived for the characteristic volume V ₀ and for parameters R _D and R , introduced to account for effects of nonspherical molecular shape and molecular roughness. On this basis, accurate calculation can be made of self-diffusion and viscosity coefficients for other members of the n-alkane series, for which data are at present limited.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Testing the hypothesis that amphiphilic antineoplastic lipid analogues act through reduction of membrane curvature elastic stress

The alkyllysophospholipid (ALP) analogues Mitelfosine and Edelfosine are anticancer drugs whose mode of action is still the subject of debate. It is agreed that the primary interaction of these compounds is with cellular membranes. Furthermore, the membrane-associated protein CTP: phosphocholine cytidylyltransferase (CCT) has been proposed as the critical target. We present the evaluation of our hypothesis that ALP analogues disrupt membrane curvature elastic stress and inhibit membrane-associated protein activity (e.g. CCT), ultimately resulting in apoptosis. This hypothesis was tested by evaluating structure–activity relationships of ALPs from the literature. In addition we characterized the lipid typology, cytotoxicity and critical micelle concentration of novel ALP analogues that we synthesized. Overall we find the literature data and our experimental data provide excellent support for the hypothesis, which predicts that the most potent ALP analogues will be type I lipids.     

Bearing damage analysis in a large oil-ring-lubricated inductionmachine

In this paper, an alternative method of online detection capable of discerning machine failure modes resulting in shaft current is proposed. The relationship between shaft current and fault conditions such as asymmetrical flux due to joints in the lamination segments, broken rotor bars, air-gap eccentricity, saturation, and slot harmonics are investigated. The diagnostic equipment used in the investigation of a three-phase medium-voltage squirrel-cage induction machine is described. The experimental results using the alternative method of online detection of shaft current are presented     

Locked-rotor and acceleration testing of large inductionmachines-methods, problems, and interpretation of the results

The measurement of locked-rotor current, torque, and power factor has been a standard test for induction machines for many years. Measurement of torque has evolved from using a brake, a dynamometer, a torque arm, and scale, through strain gauges and load cells to acceleration tests. The test must be of short duration to prevent damage to the machine and large machines present problems because of facility limitations in either kilovoltampere or torque measurement. A single test at reduced voltage when prorated to operating voltage by the square of the ratio of rated voltage to test voltage neglects the impact of saturation and results in significantly lower values of predicted torque and current. This paper discusses several methods for performing the locked-rotor and the speed-torque tests on large machines. It also discusses some of the problems associated with the test methods and shows how the tests can be performed and the results evaluated to account for saturation effects. Finally, the paper shows how to extract some machine circuit parameters from the test data     

Instrumentation, testing, and analysis of electric machine rotor steady-state heating

It is not a simple task to measure temperatures on the rotors or rotor components of large induction and synchronous machines during steady-state operation. The single greatest obstacle to obtaining these data is related to getting the data from the rotating element. Other problems are associated with instrumentation noise, sensor type, and attachment. This paper describes a number of techniques that have been used by the authors and their associates over the last 30 years. Test and calculated temperatures are presented for one machine. Also, test data from a number of machines are presented that show, for this particular population of enclosures and ventilation schemes, the steady-state temperatures at the design load can range from the value of the stator rise to greater than 70/spl deg/C higher.     

Correlation and prediction of dense fluid transport coefficients. VII. Refrigerants

A recently developed scheme, based on considerations of hard-sphere theory, is used for the simultaneous correlation of the coefficients of viscosity and thermal conductivity for the refrigerants R11, R12, R22, R32. R124, R125, R134a, R141b, and R152a in excellent agreement with experiment, over extended temperature and pressure ranges. Values for the roughness factors and correlations for the characteristic volume are presented. The overall average absolute deviations of the experimental viscosity and thermal conductivity measurements from those calculated by the correlation are 2.1 and 2.3%, respectively, over a temperature range from 200 to about 10 K below the critical temperature and a pressure range from saturation to about 40 MPa. Since the proposed scheme is based on recent and accurate density values, a Tail-type equation was also employed to correlate successfully the density of the refrigerants. The overall average absolute deviation of the experimental density measurements from those calculated by the correlation is ±0.08%.Invited paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Conditioned suppression in a virtual environment

Virtual environments (VEs) provide an inexpensive way of conducting ecologically valid psychological research. The present study used a VE to demonstrate conditioned suppression, a behavioral model of anxiety, in a first-person perspective video game. During operant training, participants learned to shoot crates to find gold bars and thus score points in the game. Next, during Pavlovian conditioning, a colored light (i.e., conditioned stimulus: CS+) was followed by a white noise unconditioned stimulus (US) while a different colored light (CS−) was not paired with the US. Probe trials in a final testing phase were then used to assess suppression. We found significant suppression of accurate responding (shots hitting the designated targets) during the presence of the CS+ relative to the CS−, both in terms of total hits and hits as a proportion of total shots. Importantly, this effect emerged despite the overall level of operant responding being undiminished during the CS+. Our findings are consistent with related studies examining human behavior in real environments, and demonstrate the potential of VEs in combination with a modestly aversive CS to allow a detailed behavioral profile of anxiety to emerge.     

An in vivo ratio control mechanism for phospholipid homeostasis: evidence from lipidomic studies

While it is widely accepted that the lipid composition of eukaryotic membranes is under homeostatic control, the mechanisms through which cells sense lipid composition are still the subject of debate. It has been postulated that membrane curvature elastic energy is the membrane property that is regulated by cells, and that lipid composition is maintained by a ratio control function derived from the concentrations of type II and type 0 lipids, weighted appropriately. We assess this proposal by seeking a signature of ratio control in quantified lipid composition data obtained by electrospray ionization mass spectrometry from over 40 independent asynchronous cell populations. Our approach revealed the existence of a universal ‘pivot’ lipid, which marks the boundary between type 0 lipids and type II lipids, and which is invariant between different cell types or cells grown under different conditions. The presence of such a pivot species is a distinctive signature of the operation in vivo, in human cell lines, of a control function that is consistent with the hypothesis that membrane elastic energy is homeostatically controlled.     

Measurements of the viscosity of toluene + mesitylene mixtures at pressures up to 55 MPa

New absolute measurements of the viscosity of mesitylene and binary mixtures of toluene + mesitylene are presented. The measurements were performed in a vibrating-wire instrument and cover a temperature range of 295–330 K and pressures up to 55 MPa. The concentrations studied were 40 and 70%, by weight, of toluene. The overall uncertainty in the reported data is estimated to be ±0.5%. A recently extended semiempirical scheme for the prediction of the viscosity of mixtures from the pure components is used to predict successfully the viscosity of these mixtures, as a function of composition, temperature, and pressure.