bluuebunny/crossref_metadata_2025 huggingface dataset:
Tuning and parameter variation effects in MRAS based speed estimator for sensorless vector controlled induction motor drives
Authors: Wang M. , Levi E.
Published: July 2007

A frequently applied method of speed‐sensorless rotor flux oriented control of induction machines relies on utilisation of model reference adaptive system (MRAS) based speed estimation, where the outputs of the reference and the adjustable model are selected as rotor flux space phasors. Accuracy of the method heavily depends on correct setting of the machine parameters and adjustment of the filter and Pl controller parameters within the estimator. The paper at first describes tuning of various parameters of the estimator, using purely experimental data. The speed estimator is operated in parallel with a commercially available rotor flux oriented induction motor drive with speed sensor and sampled stator voltages and currents are used to tune induction motor parameters, various filters and the Pl controller within the estimator. The procedure is described and illustrated using a comparison between the measured actual speed response during acceleration transients and the corresponding speed estimate obtained from the speed estimator. In the second part of the paper, speed estimation error that will take place in the base speed region due to incorrect setting and/or variation of the parameters of the machine (stator resistance, rotor resistance and magnetising inductance) within the speed estimator is assessed using experimentally recorded data. The experimental results are found to be in very good agreement with previously published theoretical results.
On the correlation between line outages and active losses in power transmission security assessment process
Authors: Sohtaoǧlu N. H.
Published: July 2007

In this paper, the correlation between transmission line outages and power transmission network losses in the corresponding network configurations have been probed in the context of electric power transmission system security assessment process. The effects of transmission line outages and active losses on power systems have been investigated, and contingency ranking of the line outages in order of importance has been performed. Masking effects on system performance index are also included. Test studies have been carried out using linearized power flow model on the IEEE 24‐Bus Reliability Test System to examine the relations between transmission line outages and total active losses, and detailed results are presented.
Application of neural networks to static equivalent networks
Authors: Müller V. , Nelles D.
Published: July 2007

The radial basis functions RBF are described as a special form of artificial neural networks ANN and are tested, if they are applicable as static equivalent networks for power systems. Starting out from equivalent networks for power systems with one coupling node to the internal network, the method is extended up to six coupling nodes. The accuracy of ANN‐equivalent networks will not only be considered for small deviations from the actual operating state (normal operation), also unrealistic high deviations are simulated to show that ANN‐equivalent networks are applicable for the examination of large disturbances.
Leakage field distribution of a transformer for conventional and superconducting conditions
Authors: Raitsios P. , Papadopoulos D. P.
Published: July 2007

The overall distribution of leakage field and current density in a transformer model with cylindrical windings in proximity to the core yokes is investigated from a different viewpoint than that of Kapp or Rogowski, i.e. by taking into consideration the conductivity of the conductive material. Using Maxwell's differential equations and the vector potential and by considering the conductivity of the conductive material, general equations are obtained for the components of the magnetic induction in a two dimensional space. From these components the leakage inductance is calculated and its application for conventional and superconducting conditions is examined. The distribution of current density in the windings is obtained from the vector potential.
A genetic approach to the optimization of automatic generation control parameters for power systems
Authors: Demirören A. , Kent S. , Günel T.
Published: July 2007

This paper presents a method based on genetic algorithm for the automatic generation control of power systems. The technique is applied to control a system, which includes two areas tied together through a power line. As a consequence of continuously load variation, the frequency of the power system changes with time. In conventional studies, frequency transients are minimized by using integral controllers and thus zero steady‐state error is obtained. In this paper, integral controller gains and frequency bias factors are determined by using genetic algorithm. The results of simulation reveal the application of the genetic algorithm having easy implementation to find the global optimum values of the control parameters.
Steel pipe cables with reduced operating frequency
Authors: Brakelmann H. , Rasquin W. , Steinbrich K.
Published: July 2007

The article describes the effects of operating frequency reduction on the transmission behaviour of steel pipe cables. In many countries the external/internal gas pressure cables as well as the oilostatic cables are of a greater interest. Retrofitting of such cables is done by exchanging the old cable cores by new cores with synthetic (e.g. XLPE‐) insulations, thus building so‐called “city cables”. Possible effects of a frequency reduction on the current ratings and losses of external gas pressure cables as well as of city‐cables are discussed. Furthermore the city‐cable is compared with a superconducting cable.
Testing of insulation systems with respect to high‐frequency voltage stress
Authors: Paede M. , Pfeiffer W. , Plessow R.
Published: July 2007

Due to the increasing use of power electronics high frequency working voltages are occurring rather frequently. This means a very high stress for any kind of insulatation. This situation is further aggravated by decreasing dimensions due to miniaturization. Therefore this situation has to be taken into account during dimensioning and testing. Different test methods with respect to withstand and partial discharge inception are described. The necessary test equipment and the dimensioning of the test circuits are specified. The aspects of periodic non‐sinusoidal voltages are taken into account by harmonic analysis.
The role of methylnaphthalene in EHV cable oil as related to oil breakdown and discharge velocity
Authors: Al‐Sulaiman A. , Qureshi M. I.
Published: July 2007

This experimental investigation explores the effect of high voltage lightning surges on the insulating oil used in the oil filled extra high voltage cables that serve electric power networks worldwide. Using non‐uniform electrode configuration, the breakdown voltage and corresponding discharge propagation velocities in oil samples that are doped with trace amounts of 1‐Methylnaphthalene are investigated under both polarities of applied stresses in gap spacing of up to 10 mm. Two distinct ranges of additive concentrations are observed which effect these characteristics. Generally, the positive discharge growth decreases with increase in gap spacing while the negative ones show opposite behaviour. Anomalous behaviour of discharge growth is observed at an optimum concentration of additive, as it attains supersonic velocity which increases with the increase in gap spacing. A correlation between the positive impulse breakdown voltage and the discharge propagation velocity is also established.
A wide‐band lumped circuit model of the terminal and internal electromagnetic response of coaxially insulated windings mounted on a core
Authors: Holmberg P. , Leijon M.
Published: July 2007

This paper presents a wide‐band lumped circuit model of coaxially insulated windings mounted on a core. The polyphase model can be used to simulate the terminal and internal electromagnetic response in DryformerTM, a new oil‐free power transformer, and similar electromagnetic power devices. The circuit parameters are based on geometrical and material data. The simulated frequency and transient response of the lumped circuit is compared to measurements on a 20 MVA 140/6.6 kV three‐phase transformer of the DryformerTM type. The comparison shows that the model can be used to estimate resonance frequencies and transient overvoltages in the transformer, although the damping is not accurately modelled. The influence of the core is discussed and investigated.
Computer simulation of responses of earth‐return circuits to the AC and DC external excitation
Authors: Czarnywojtek P. , Machczyński W.
Published: July 2007

The use of the circuit simulation package SPICE (Simulation Program with Integrated Circuit Emphasis) permits the complex analysis of the EMI (electromagnetic interference) on earth‐return circuits. In the approach presented, the earth‐return circuit with excitation by AC signals and transients, as well as with DC energization is modelled as a large multinode electrical equivalent circuit. The circuit is a chain of basic circuits, which are equivalents of homogenous sections of the earth‐return circuit with uniform exposure to the primary interfering electric field associated with the inductive and the conductive influence. The application of controlled voltage and current sources in the basic circuits permit the modelling of coupling effects in systems of earth‐return circuits. Contrary to the analytical methods the SPICE simulation enables one to solve the EMI problems in practical cases connected with: topological complexity of the system considered, non‐homogeneous geometrical and electrical parameters of the earth‐return circuits, non‐homogeneous earth, application of insulating flanges, bonds, earth electrodes in a system of earth‐return circuits, non‐linearity of the system, etc. The SPICE simulation is an alternative and a useful approach to the analysis of EMI problems in earth‐return circuits, when comparing with existing analytical and numerical solutions. The usefulness of the SPICE simulation has been illustrated by examples.
Behaviour of single‐phase full‐wave rectifier
Authors: Herraiz S. , Sainz L. , Pedra J.
Published: July 2007

This paper describes the line side behaviour of single‐phase uncontrolled rectifiers with AC‐side reactance and capacitive load, depending on the short‐circuit ratio at the valve side of the rectifier. The influence of both finite DC link capacitance and AC ohmic resistance is considered in the analysis too. As a result of the study, a set of graphics was generated. This allows a user‐friendly estimation of the line current consumed by the device (fundamental and harmonic currents).
Loss determination for long three‐phase high‐voltage submarine cables
Authors: Brakelmann H.
Published: July 2007

For the planned, great offshore‐wind farms with extended medium‐voltage cable networks and distances to the onshore grid connection point of 100 km or more, the costs of the cables and their losses play an important role. In this paper basic equations are developed to determine the losses of long three‐phase AC cables, taking into account the longitudinal distributions of current and temperature. It is shown, that the determination of cable losses by means of the line equations based on the nominal ohmic resistance, i.e. in neglecting the temperature‐dependence, may lead to essential errors, with the risk of counterfeited valuations of the installation devices under technical and economical aspects. The relations derived in this paper allow a fast determination of the load‐ and temperature‐dependent cable losses by means of a few, only cable‐specific parameters.
The transformer thermal loss of life: Part 1 ‐ improved deterministic approach for thermal and ageing models
Authors: Resende M. J. , Pierrat L. , Santana J.
Published: July 2007

Due to computers' widespread, models used in Power Engineering reached an unthinkable complexity and precision. However, the nature of the problem has changed: we rarely use fully the precision of nowadays models, because parameters and operating conditions are submitted to uncertainty. Apart from a limiting range of rated values, realistic operating conditions are not completely known, which is as evident as long the device is alife. In this context, the estimation of the distribution transformer loss of life is a pertinent problem that we propose to solve by developing and illustrating a new appropriate methodology. Because of the subject extent, we considered three successive aspects: first, an improved deterministic approach for thermal and ageing models; second, a probabilistic extension considering functional variability and model structural uncertainty and the third one, an application to the power derating problem in case of harmonic distortion load. This paper corresponds to the first aspect.
A new combinatorial algorithm for the optimal planning of distribution urban medium voltage cable networks
Authors: Minic S. , Rajakovic N.
Published: July 2007

In this paper a new combinatorial algorithm for the optimal planning of distribution urban medium voltage cable networks is presented. Realistic modeling requirements and an improved combinatorial method have resulted into an interactive software package with the proven performance on some actual distribution cable networks.
A flexible dynamic model of multiproduct technology for the West German economy
Authors: Nakamura Shinichiro
Published: July 2007

This paper tests symmetry and negativity of the Slutsky matrix for a system of demand functions derived from an aggregate model of multi product technology within a flexible dynamic framework. The model considers three inputs and three outputs, including imports and exports of intermediate goods. We derive a static demand model from a trans log cost function and specify the data generation process by a stationary ARX (1, 1) model. Results based on West German quarterly data indicate that the integrability conditions are not rejected when imposed on the ARX (1, 1) model, whereas they are rejected for all the less general dynamic models considered.
Differential mortality in Rural Bangladesh
Authors: McIntosh James , Satchell Stephen , Nasim Anjum
Published: July 2007

Discrete regression methods are used to analyse sample survey data from two villages in two different regions of Bangladesh. No significant mortality differentials by socio‐economic class are found.
Macroeconometric model comparison and evaluation techniques: A practical appraisal
Authors: Parke William R.
Published: July 2007

This paper examines four model comparison techniques in the setting of an actual large‐scale U.S. macroeconomic model. The techniques include formal hypothesis tests, mean squared error analysis, and two new tests based on the complementary conditions that the structural and reduced form disturbances should be orthogonal to the predetermined variables. The latter two tests can be conveniently implemented by regressing either structural residuals or reduced form forecasting errors on a vector of predetermined variables. The empirical example tests restrictions on the simultaneous feedback effects of prices, wage rates, and interest rates.
Minute by minute: Efficiency, normality, and randomness in intra‐daily asset prices
Authors: Feinstone Lauren J.
Published: July 2007

In this study we test the efficiency of asset markets at intervals as short as 30 seconds. We also describe the properties of a simple new stochastic process as a potential model of the behaviour of asset prices and test it on intra‐daily Deutsche Mark futures prices. According to this process, asset prices are constant between economically relevant events, which occur at the random times generated by a Poisson process. At the moments of these events, prices jump to new values; the size of the jump is drawn from a normal distribution. Tests of this process indicate that it cannot be rejected for most of the days in the sample.
A keynesian macro‐econometric model of the UK: 1955–1984
Authors: Desai Meghnad , Weber Guglielmo
Published: July 2007

In this paper we present a small Keynesian macro‐economic model in which wage‐price determination is linked to the working of goods and money markets. By explicitly treating the Keynes effect we derive a general expression for the employment‐money supply elasticity, and draw the IS‐LM loci in the employment‐interest rate space

Our empirical specification allows for short‐run disequilibrium dynamic adjustments around the static long‐run relations predicted by the theoretical model. By careful use of our specification search strategy we obtain a statistically sound econometric model, which exhibits sensible long‐run properties. A remarkable finding implied by our estimates is that equilibrium unemployment is negatively affected by both money supply and incomes policy.
Money stock targeting and money supply: An intertemporal optimization approach (with an application to Canada)
Authors: Mercenier Jean , Sekkat Khalid
Published: July 2007

We propose a model of the short‐term behaviour of the monetary authorities of a small open economy that is willing to stabilize, to some extent, its bilateral exchange rate vis‐à‐vis a dominant partner. The optimal money supply strategy is derived using intertemporal optimization arguments, in a rational expectations environment, The model is formulated so as to avoid the time inconsistency problem stressed by Kydland and Prescott (1977). It allows econometric estimation of the optimal money supply rule as well as of the parameters of the intertemporal utility function, and of the function that defines the intermediate target money stock. The model is successfully estimated on Canadian quarterly data, using maximum‐likelihood techniques.
The climacteric in late victorian Britain and France: A reappraisal of the evidence
Authors: Crafts N. F. R. , Leybourne S. J. , Mills T. C.
Published: July 2007

The paper investigates the question of whether the trend rate of growth of GDP slowed down in Britain or France in the nineteenth century. We establish that real GDP belongs to the trend‐stationary process class of time‐series in each case rather than the difference‐stationary process and using Kalman filter techniques, analyse trends in a model incorporating time‐varying parameters without specifying breakpoints in advance. We find, contrary to the literature, that neither country experienced a climacteric. Our results suggest that economic historians have been prone to exaggerated views of variations in trend economic growth.
Survival analysis software on MS/PC‐DOS computers
Authors: Goldstein Richard , Anderson Jennifer , Ash Arlene , Craig Ben , Harrington David , Pagano Marcello
Published: July 2007

There exist more than a dozen MS/PC‐DOS programs with the capability of performing some form of survival analysis. Most of these are reviewed here, with respect to (1) the survival analysis methods they cover, (2) their ease of use and flexibility, (3) their user interface, (4) their graphics capabilities, and (5) their computational accuracy.
The problem of not observing small expenditures in a consumer expenditure survey
Authors: Alessie Rob , Gradus Raymond , Melenberg Bertrand
Published: July 2007

In consumer expenditure surveys one often faces the problem that full information on small consumption expenditures is not available. Suppose a panel of households is available, which is divided into two subsamples, say, A and B. For subsample B all expenditures are registered, but from subsample A only expenditures above some fixed amount, say Z dollars. Suppose, furthermore, that in some economic analysis the use of the sum of all expenditures of each single observation in the sample is required. It is then evident that the use of the (observed) sum of expenditures above Z dollars instead of the (unobserved) sum of all expenditures in case of observations in subsample A will lead to understimation of the sum of all expenditures. To correct for this underestimation one could, for instance, make use of blow‐up factors, computed with subsample B, or one could construct a Tobit model explaining the sum of expenditures below Z dollars and use this model, after estimating it with subsample B, to predict the sum of expenditures belwo Z dollars in subsample A. In this paper we propose an alternative method to correct for the underestimation. The method consists of constructing a model, which explains the sum of expenditures below Z dollars, by explicitly taking into account that each one of these is below Z dollars. This model is estimated on the subsample B data and can then be used to compute the expected values of the sum of expenditures below Z dollars made by households in subsample A. We apply this and the other two methods to a Dutch panel where the above‐mentioned situation actually occurred. The sample consists of two subsamples; for one subsample all expenditures are registered, but for the other subsample only expenditures above 10 Dutch guilders.
Describing the separability properties of empirical demand systems
Authors: Baccouche Rafiq , Laisney François
Published: July 2007

In empirical demand analysis separability restrictions are usually imposed as maintained hypotheses. The separability inflexibility of most functional forms makes parametric tests of these restrictions appear problematic. We follow Pudney (1981) in stressing the usefulness of a description of the separable structure of preferences underlying an estimated model, and propose a non‐iterative method for the production of such a description. An illustration with different models estimated for nine categories of goods on French aggregate time‐series data is presented.
Demand for durable and nondurable goods, environmental policy and consumer welfare
Authors: Conrad K. , Schröder M.
Published: July 2007

If a tax on energy affects the demand for a nondurable good, the stock of a durable good, and the proportion of the energy consumption per unit of service of the durable good, an integrated approach for investigating consumer demand for durables and nondurables is required. The purpose of this paper is to employ the concept of a variable expenditure function with quasi‐fixed durable goods as arguments in order to derive a demand system for nondurable goods in prices of the nondurables, in the stocks of durables, and in variable expenditure. From the envelope condition desired stocks of durables can be calculated and investment demand for durables can be determined. For an application we choose a variable expenditure function based on the almost ideal demand specification, and evaluate alternative environmental policy measures using the equivalent variation for comparing the welfare effects.
The stationarity of British economic and productivity growth 1856–1913
Authors: Greasley D.
Published: July 2007

Characterization of late nineteenth‐century British economic performance rests heavily on identifying trends and turning points in GDP and productivity growth. Crafts, Leybourne and Mills (1989) provide the most sophisticated study in this genre, deploying a time‐varying parameter model, to severely dent the notion of a climacteric. This paper argues the linear trend approach to assessing the climacteric may be otiose. Investigating the order of integration of the GDP series, and the cointegration of GDP and factor input growth, suggests both GDP and productivity growth tended to revert to a constant mean rate within the period 1856–1913, and undermines the notion of a climacteric.
Alternative estimators for factor garch models—A monte carlo comparison
Authors: Lin Wen‐Ling
Published: July 2007

This paper proposes four estimators for factor GARCH models: two‐stage univariate GARCH (2SUE), two‐stage quasi‐maximum likelihood (2SML), quasi‐maximum likelihood with known factor weights (RMLE), quasi‐maximum likelihood with unknown factor weights (MLE). A Monte‐Carlo study is designed for bivariate one‐factor GARCH models to examine the finite sample properties. Results are presented for biases, ratios of standard errors to standard deviations, ratios of variances, coverage of confidence intervals, effects of misspecified factor weights, and finite sample properties of the 2SUE for factor GARCH‐in‐mean models.
Stochastic trends and economic fluctuations in a small open economy
Authors: Mellander E. , Vredin A. , Warne A.
Published: July 2007

In this paper we describe how restricted vector autoregressions can be employed to examine the sources of macroeconomic fluctuations. We show how cointegration restrictions can be used to identify a VAR system with common stochastic trends subject to transitory and permanent changes in average growth, and how we may investigate the system's responses to permanent shocks, i.e. to innovations to the trends. Theoretical cointegration vectors are derived from a small open economy growth model for terms of trade, real GDP, real consumption, and real investments. Applying these methods to Swedish annual data (1875–1986) we find that permanent real (supply) shocks account for most of the fluctuations in GDP, even in the short run.
Aggregate shocks and macroeconomic fluctuations: A bayesian approach
Authors: Koop G.
Published: July 2007

This paper describes Bayesian techniques for analysing the effects of aggregate shocks on macroeconomic time‐series. Rather than calculate point estimates of the response of a time‐series to an aggregate shock, we calculate the whole probability density function of the response and use Monte‐Carlo or Gibbs sampling techniques to evaluate its properties. The proposed techniques impose identification restrictions in a way that includes the uncertainty in these restrictions, and thus are an improvement over traditional approaches that typically use least‐squares techniques supplemented by bootstrapping. We apply these techniques in the context of two different models. A key finding is that measures of uncertainty, such as posterior standard deviations, are much larger than are their classical counterparts.
Threshold arch models and asymmetries in volatility
Authors: Rabemananjara R. , Zakoian J. M.
Published: July 2007

This paper attempts to enlarge the class of Threshold Heteroscedastic Models (TARCH) introduced by Zakoían (1991a). We show that it is possible to relax the positivity constraints on the parameters of the conditional variance. Unconstrained models provide a greater generality of the paths allowing for nonlinearities in the volatility. Cyclical behaviour is permitted as well as different relative impacts of positive and negative shocks on volatility, depending on their size. We give empirical evidence using French stock returns.
Bayesian inference in limited dependent variable models. An application to measuring strike duration
Authors: Dejong D. N.
Published: July 2007

This paper presents a straightforward set of Bayesian techniques for analyzing models involving limited dependent variables; the techniques are demonstrated in an analysis of Kennan's (1985) data on contract strikes in US manufacturing. The data are analyzed by deriving posterior distributions—including probability distributions—of hazard functions for strike duration using numerical Monte Carlo methods. The distributions are employed to derive coverage intervals for hazard functions, to assess the relative plausibility of nonnested hypotheses concerning the shape of the functions, and to assess the impact of industrial production on duration.
Structural shifts in the manufacturing export performance of oecd economies
Authors: Landesmann M. , Snell A.
Published: July 2007

This paper identifies structural shifts in manufacturing export performance of the major OECD economies. The particular emphasis of this study is to see whether the longer‐run responses of a country's exports to the growth in world demand have undergone trend changes. The econometric work focuses on the time variation in income elasticities from an export demand model over the period 1963–89. It thus covers a period in which there was a substantial slow‐down in world economic growth and in which the manufacturing sectors in advanced economies underwent substantial restructuring in the wake of the two oil‐price shocks and the competitive challenges of Japan and the NICs. The exercise attempted to evaluate the relative successes and failures of the different OECD economies to maintain or improve their positions in the ‘higher quality’ (income elastic) segments of world trade. Evidence was found for trend improvements in the income elasticity for UK exports from the early 1980s onwards and a trend decline for that of the US over the same period. The effects of non‐tariff protection against Japanese exports also showed up in our results and an attempt was made to separately identify its effects.
An adjustment cost model of long‐term employment in Japan
Authors: Nakamura S.
Published: July 2007

A dynamic factor demand model is presented which pays special attention to the prevalence of a long‐term employment relationship in Japan. The model is based on the representation of technology by a variable cost function with adjustment costs for employment and capital stock, where the variable cost consists of the sum of overtime costs and materials costs. With employment being quasi‐fixed and scheduled hours institutionally regulated, short‐run adjustments are mostly made by overtime hours. Application to a time‐series data on the Japanese electrical machinery industry indicates quasi‐fixity of capital and employment and reproduces short‐run overshooting of overtime hours to compensate for the sluggish adjustment of employment.
Testing the proportional hazards assumption in the presence of unmeasured heterogeneity
Authors: McCall B. P.
Published: July 2007

This paper develops a discrete‐time hazard model which accounts for unmeasured hetergeneity while allowing the coefficients of the regressors to vary over time. Sufficient conditions for nonparametric identifiability of the unmeasured heterogeneity distribution are derived. Testing for time‐varying coefficients in this model is, under suitable conditions, equivalent to testing the proportionality assumption of the underlying continuous‐time hazard model. Some Monte Carlo evidence is presented regarding the small‐sample properties of this test. As an illustration, these tests are applied to the joblessness durations of displaced workers.
Allocation of individuals to job levels under rationing
Authors: Hartog J. , Ridder G. , Visser M.
Published: July 2007

We augment an ordered response model for the job level at which individuals desire to work with allowance for individual reporting of a discrepancy between actual and desired job level, and we also investigate possible biases from restricting the observations to the employed, and omitting the unemployed. We find that the latter bias can be ignored and interpret this as evidence that the unemployed are not choosier than the employed. People claiming inadequate capability utilization are not markedly differently allocated than those claiming a proper match. Women's lower job levels cannot be explained from rationing by capability utilization.
Certificate‐of‐need regulation and the diffusion of innovations: A random coefficient model
Authors: Caudill Steven B. , Ford Jon M. , Kaserman David L.
Published: July 2007

In this paper, we examine empirically the effect that certificate‐of‐need regulation by state health planning organizations has had on the speed of diffusion of a relatively new medical technology—haemodialysis. Specifically, we test the hypothesis that a requirement that investments be subject to certificate‐of‐need review has significantly slowed the rate of adoption of this particular treatment modality. In subjecting this hypothesis to empirical verification, we estimate a random coefficient model. This approach allows us to make more efficient use of the available data than the traditional two‐stage approach to modelling diffusion processes wherein separate logistic functions are first estimated over the time series observations followed by hypothesis tests conducted over the cross‐sectional observations. We find evidence that certificate‐of‐need regulation slows the spread of haemodialysis technology.
American Society for Apheresis, Society of Hemapheresis Specialists and Francis S. Morrison, MD, revisited
Authors: Strauss Ronald G.
Published: July 2007

The histories of the American Society for Apheresis (ASFA) and the Society for Hemapheresis Specialists (SHS) are intimately intertwined with Francis S Morrison, MD. Because many of the relevant historical events are not recorded as written documents, it is useful to revisit them via the memory of those who lived‐through the growth and development of ASFA. ASFA began in 1982 as an organization of physicians interested in automated hemapheresis—actually, meetings of ASFA perse were preceded in the late 1970s by apheresis symposia sponsored by the American Red Cross Blood Services in Chicago. Concurrently, SHS formed as an organization of nurses and “operators” performing hemapheresis procedures and held meetings separate from ASFA. Following a number of turbulent years, ASFA and SHS merged. Trusting my memory and a few personal documents, I will touch on many of the notable events of ASFA and SHS history. Because of the leadership of Dr. Fran Morrison during many crucial events in ASFA history, I will make special efforts to remember his contributions to ASFA as an organization and the ways in which he touched the lives of many ASFA members. J. Clin. Apheresis., 2007 © 2007 Wiley‐Liss, Inc.
Improved syntheses of acridines. Part V. The dechlorination of 5‐chloroacridines and a new synthesis of acridine
Authors: Albert Adrien , Willis John Bryan
Published: July 2007

B‐Chloroacridine (II) was converted to acridine in 80% yiold by hydrogenation in the presence of potassium hydroxide and ranoy‐nicked catalyst at atmospheric picture followed by oxidation of the resulting acridnn (III) with chromic acid. The scope of the now reaction for the preparation of substituted acridities is discussed, with examples. A critical comparison is made of the various methods available for the preparation of acridine.
Studies in coal tar bases. I. Separation of β‐ and γ picolines and 2:6‐lutidine
Authors: Coulson E. A. , Jones J. Idris
Published: July 2007

Tar base fractions commonly described as “commercial β‐picoline” are mixtures containing β‐ and γ‐picoline and 2 : 6‐lutidine in variable, if usually roughly equal proportions. Many methods for the separation of one or more of the individual components have been proposed yet few are suitable for commercial exploitation. In the present paper it is shown that by azeotropic fractional distillation the three bases may be readily separated in purities of 95‐98% and with little loss, if acetic or propionic acids are used as azeotropic‐formers, and it is possible to recover for re‐use the acids from the separate base‐acid azeotropes with the aid of a suitable hydrocarbon entrainer.

It is also shown that the hydrochlorides of the bases differ very markedly in physical properties and can be easily separated.

Pure specimens of the three bases were obtained by fractional freezing of 95‐88% pure materials : 2 : 6‐lutidine, b.p. 144°, f.p. −5·97°; β‐picoline b.p. 1447middot;0°, f.p. −177middot;77°; γ‐picoline b.p. 145·37°, f.p. + 47middot;3°.
Determination of plastic and brittle states of “pool” bitumens
Authors: Lethersich W.
Published: July 2007

This paper deals with the determination of the plastic and brittle states of bitumens by means of three mechanical tests, viz., tensile strength, ductility and impact.

Brittleness is defined us failure due to the hydrostatic component of stress whereas plastic failure is duo to the shear component. This definition leads to suitable tests for brittleness of materials.

The ductility teat is applicable to the determination of the strain which the material can conveniently accommodate, whereas the tensile strength test is directly applicable to the matter under consideration, since brittleness deepends on rate of loading and this factor is controlled in this form of test.

Impact tests show that all the bitumens tested are brittle when rapidly loaded; the most satisfactory criterion here is the impact energy or what may be determined the brittle strength.
The evaluation of the roughness of lithographic printing plates
Authors: Elton G. A. H. , MacDougall G.
Published: July 2007

The surface area, the surface void volume and the depth of the grain of lithographic printing plates have been measured.
Dehydration of magnesium chloride
Authors: Gaskin J. G. N.
Published: July 2007

An examination of the vapours evolved during the heating of magnesium chloride in the presence of ammonium chloride has shown that hydrolysis of the magnesium chloride is not prevented by the presence of the ammonium chloride. The production of anhydrous magnesium chloride is shown to be due to a second reaction occurring at a somewhat higher temperature between the basic product of the hydrolysis and the amonium monium chloride. Anhydrous magnesium chloride may be prepared from a basic chloride, the hydroxide or the oxide of magnesium by heating with ammonium chloride.
A comparison of methyl bromide and hydrogen cyanide for the fumigation of empty bags in barges
Authors: Brown W. Burns , Lewis S. E.
Published: July 2007

During two trial famigations of empty bags in barges with methyl bromide, the penetration of this gas was studied by the measurement of gas concentrations. In the second trial, the loaded barge was also treated with hydrogen cyanide, so that a strict comparison could be made between the performances of the two fumigants. The rates of airing were also compared. The data demonstrate the grater suitability of methyl bromide for the fumigation of empty bags in barges.
South African fish products. Part XXI. Recovery of vitamin A in the unsaponifiable matter of fish liver oils
Authors: Black M. M. , Lamchen M. , Rapson W. S. , Schwartz H. M. , Van Rensburg N. J.
Published: July 2007

The percentage recovery of Vitamin A in the unsaponiflable matters from commercial South African hake, soupfin shark, dogfish, kabeljou and geelbek liver oils has been determined for a large number of samples and characteristic values for each type of oil have been established. Hake liver oils were exceptional in giving recoveries not significantly different from 100%, while recoveries from the other types of oils averaged from 93‐95%, and wore unaltered when the oils wore diluted with vegetable oils such as an employed in margarineo compositions. No explanation of the different recoveries if given, but possible causes are discussed.
The spontaneous combustion of hay. II. The composition of the acidity
Authors: Firth J. B. , Stuckey R. E.
Published: July 2007

Previous work by the authors showed that an acidity developed in hay which had undergone spontaneous combustion. Further examination of such hay indicated that the acidity was composed mainly of non‐volatile acids; this fraction contained lactic, malic, and succinic acids, while acotic and formic acids were present in the volatile acidity. Methods of analysis are given.
South African fish products. Part XXIII. Variations in the oil and vitamin A contents of the liver of the cape hake (Merluccius capensis, cast.)
Authors: Roux E. R. , Molteno C. J.
Published: July 2007

Factory data collected at Cape Town and Port Elizabeth are used to demonstrate variations in the oil and vitamin A contents of the liver of the Cape hake. In addition to seasonal changes related to the sexual cycle, there are marked fluctuations from year to year, probably connected with variations in the food supply, which ultimately are related to oceanographic factors, such as sea temperatures, Migratory phenomena have an important bearing on the average size and physiological condition of the fish caught, and size of fish also markedly influences the oil and vitamin A content of the Users.
The nicotinic acid content of coffee
Authors: Hughes E. B. , Smith R. F.
Published: July 2007

From 16 to 44 μg./g. of nicotinic acid were found in samples of raw coffee beans. Nicotinic acid in produced during the roasting of coffee by the decomposition of trigonelline present in the raw beans. The production of nicotinic acid is dependent on the extent of roasting, a dark roast coffee containing more than a light roast coffee. Normal samples of roasted coffee contained from 95 to 263 μg./g. of nicotinic acid. The nicotinic acid content of coffee is not dependent on the variety of bean. The nicotinic acid is almost completely extracted in the preparation of the beverage for drinking, the amount in a cup of white coffee (200 ml, half 10% coffee decoction and half milk) being between 1 and 2 mg. The pyridine in coffee also originates from the decomposition of trigonelline.
The determination of the moisture content of cereals by measurement of specific inductive capacity
Authors: Groves L. G. , King J.
Published: July 2007

The determination of the moisture content of a material by the measurement of its specific inductive capacity is now well established, and several commercial instruments are available using this principle, generally in conjunction with electrical conductivity. An instrument easily constructed in the laboratory is described in this paper, which it is hoped will enable the principle to be more widely used. The method employed in the determination of the moisture content of various cereals is described, together with the degree of accuracy to be expected and the limitations of the method.
The estimation of sulphur compounds in crude and refined benzoles. Part I
Authors: Claxton G. , Hoffert W. H.
Published: July 2007

Until recently the sulphur compounds in crude benzoles were generally considered to be chiefly carbon disulphide and thiophene, although the presence of other compounds such as sulphides, disulphides and mercaptans had been reported. With the exception of carbon disulphide, methods of estimation had not been accurately worked out and knowledge concerning the exact quantities of other sulphur compounds was scanty. Examination of a large number of crude benzoles in these laboratories had shown that normal high‐temperature benzoles contain approximately half their sulphur content as carbon disulphide. It has been customary to regard the remainder as thiophene and its derivatives, an assumption that is justified to some extent since other sulphur compounds, such as sulphides, behave in the same way as thiopheno during refining by sulphuric acid. For example, although a large number of makes and types of acid‐washed benzoic have been tested, it has always been found that the remaining sulphur, other than as carbon disulphide, was the same for a particular yield of benzole irrespective of the concentration and quantity of sulphuric acid used to obtain this yield.
The estimation of small quantities of total sulphur in benzoles
Authors: French K. H. V. , Claxton G.
Published: July 2007

The standard S.T.P.T.C* method of estimating total sulphur was designed primarily for determining sulphur in commercial products, in particular motor benzoic, of which tlio sulphur content is between 0·1 and 0·4% w/w. In connection with the estimation of individual sulphur compounds in benzolo a method is needed for quantities of sulphur of the order of 0·01% w/w. Such a method of analysis would also be, of extreme value for determining the sulphur in products such as pure benzole, now being required with low sulphur contents for synthetic processes.
Determination of the boiling‐points of liquids of low vapour pressure
Authors: Burrows G.
Published: July 2007

A boiling‐point apparatus is described and an account is given of its use for determining the boiling‐points at reduced pressures of‐ various liquids of low vapour pressure. The theoretical relationship between temperature and vapour pressure is discussed and the vapour pressures of various liquids at room temperature are derived from the data obtained. Comparisons arc made with other published figures relating to the boiling‐points and vapour pressures of various liquids used in high‐vacuum technique.
Recent developments in the microbiology of retting. Part I.—the microbial flora in different systems of retting
Authors: Allen L. A.
Published: July 2007

The general bacterial flora was found to be similar in the different processes of flax‐retting investigated. Coliform bacteria, streptococci, and spore‐forming anaerobes consistently appeared in largo numbers. Continuous aeration of tbe rotting liquor with diffused air during the course of a ret encouraged the growth of aerobic and facultativo bacteria, but did not greatly ailed the number of anaerobes. Continuous circulation of retting liquor through n percolating filter removed a large proportion of bacteria from the liquor, but loft hirgoly undisturbed those growing in or near the flax straw.
The determination of the pyrethrins in pyrethrum concentrates in mineral oil
Authors: Martin I. T. , Brightwell S. T. P.
Published: July 2007

A method is described for the determination of pyrethrin I in pyrethrum concentrates in light mid heavy mineral oils. The method is based that of Wileoxon as modified by Holaday and utilises the separation of chrysanthemum monocarboxylic acid and the reduction of Denier reagent. Modifications of the Wilcoxon‐Holaday method concerned with the initial removal of uncombined acids, the removal of the oil and the separation of the monocarboxylic acid have been introduced. The determination of the monocarboxylic acid by the reduction of Denier reagent gives results for pyrethrum I slightly in excess of those given by a modified Soil method involving separation of the monocarboxylic acid by steam distillation. pyrethrum II may be determined in oil solutions made from petroleum ether extracts of pyrethrum lowers by an application of the Soil method. Further work is required on the determination of pyrethrum II in oil solutions made from acctouo extracts of the flowers.
Insecticides: Chemical constitution and toxicity
Authors: Martin Hubert
Published: July 2007

Of the several ways of studying the relationships between molecular structure and toxicity, the analytical method, when effects of modification and dissection of the molecule are followed, is applicable to insecticides of insignificant vapour pressure at ordinary temperatures. The effect of modification of the molecular structures of nicotine, rotenone, and of the pyrethrin‐synergists allied to sesamin on their insecticidal properties is discussed. The importance of physical properties affecting the distribution of the insecticide between the biophase in which it acts and the phase in which it is applied is illustrated by the case of the aliphatic thiocyanates. The reasons why DDT is insecticidal are discussed and it is shown that the possibility of ready dehydrochlorination is requisite for inseetieidaal properties in this series, an idea now extended to other chlorinated hydrocarbons.
Liquid‐vapour equilibrium data for the systems: Methyl methacry‐late‐methanol and methyl metha‐crylate‐methacrylic acid
Authors: Woods D. E.
Published: July 2007

Liquid‐vapour equilibrium data for methyl methacrylate‐methanol and methyl methacrylate‐methacrylic acid mixtures have been determined using a modified Rosanoff apparatus at 200 mm. and 760 mm. Hg pressure. It has been found that methyl methaerylate forms constant‐boiling binary mixtures both with methanol and with water. Some physical properties of pure methyl methaerylate and mixtures with water, methanol and methacrylic acid have been determined.