Absolute Standards Research Articles

Neutron activation measurements over an extremely wide dynamic range (invited) (abstract)

The DT program at the Tokamak Fusion Test Reactor (TFTR) created requirements on 14 MeV neutron measurements to measure from ∼106 n/cm2 (for triton burnup and Ohmic tritium plasmas) to >1012 n/cm2 (characteristic of >10 MW DT plasmas) with an accuracy of 7% (one-sigma).1 To maintain an absolute calibration over this dynamic range with active neutron detectors required one to go from some absolute standard at one fluence level to a measurement at a much higher fluence. Maintaining accuracy requires an extremely linear set of measurements not systematically affected over this dynamic range. Neutron activation can provide such linearity when care is taken with a number of effects such as gamma-ray detection efficiency and sample contamination.2 Absolutely calibrated neutron yield measurements using dosimetric (well-known cross section) reactions with thin (low-mass) elemental foils will be described. This technique makes the detector comparison to an absolute standard of gamma-ray activity correspond to all neutron fluences by reducing the sample mass while keeping the activation detectors operating in a linear counting mode; that is, one always uses low count rates to minimize pileup effects. The International Thermonuclear Experimental Reactor is projected to have 1000 s burn durations at fluxes of few 1013 n/cm2 s, or more neutron fluence per second than entire TFTR discharges. Extrapolating neutron activation to these higher fluences will require yet more care. Some of the issues at such high fluences will be discussed.3 The National Ignition Facility (NIF) is projected to yield 10 MJ of fusion energy, or up to 1012 n/cm2 at the vacuum vessel wall, similar to TFTR DT conditions. However, it is expected that much interesting physics will be performed at yields far less than those from ignition, possibly covering an even greater dynamic range than needed on TFTR. Thin foil techniques do not have the sensitivity required at low fluences. Absolutely calibrated neutron yield measurements using associated particle calibrations of thick (large mass) foils on accelerators4 will be compared. Using both thin and thick foil approaches can cover the dynamic range required for NIF.

Genetic typing by capillary electrophoresis with the allelic ladder as an absolute standard.

We demonstrate a genetic typing method based on capillary electrophoresis/laser-induced fluorescence (CE-LIF). VNTR polymorphism in the human D1S80 locus was studied. A pooled allelic ladder, which contains the 27 most common human alleles, was used as the absolute standard. Extracted genomic DNA from an individual was amplified by polymerase chain reaction (PCR). Typing can be accomplished by co-injection of the PCR product and the D1S80 ladder and then running CE. Separation by a polymer solution of poly(ethylene oxide) in uncoated fused-silica capillaries allows high-resolution, repeated runs in the same capillary. Sensitive detection with minimal sample preparation is possible by using ethidium bromide as the intercalating dye. Statistical analysis of the data indicates a high level of confidence in matching the bands despite variations in the injection process or in the CE system. Future adaptation to a multiple-capillary array system should allow high-speed, high-throughput operation.

Rarefaction and Compressibility Effects in Gas Microflows

Gas microflows are encountered in many applications of Micro-Electro-Mechanical Systems (MEMS). Computational modeling and simulation can provide an effective predictive capability for heat and momentum transfer in microscales as well as means of evaluating the performance of a new microdevice before hardware fabrication. In this article, we present models and a computational methodology for simulating gas microflows in the slip-flow regime for which the Knudsen number is less than 0.3. The formulation is based on the classical Maxwell/Smoluchowski boundary conditions that allow partial slip at the wall. We first modify a high-order slip boundary condition we developed in previous work so that it can be easily implemented to provide enhanced numerical stability. We also extend a previous formulation for incompressible flows to include compressibility effects which are primarily responsible for the nonlinear pressure distribution in micro-channel flows. The focus of the paper is on the competing effects of compressibility and rarefaction in internal flows in long channels. Several simulation results are presented and comparisons are provided with available experimental data. A specific set of benchmark experiments is proposed to systematically study compressibility, rarefaction and viscous heating in microscales in order to provide validation to the numerical models and the slip-flow theory in general as well as to establish absolute standards in this relatively young field of fluid mechanics.

A high precision technique for pressure lineshift measurements: application to NH 3 and HCN

High precision pressure-induced lineshifts have been measured by a technique involving an infrared diode laser which is frequency stabilized on the absorption peak of the molecular line under study. The corresponding frequency shifts of the stabilized laser are discriminated by means of a reference absorbing cell filled with the same active gas set at a fixed pressure. This avoids any reference to absolute or secondary frequency standards and allows a very high sensitivity for the determination of small lineshift parameters (down to 10 kHz Torr −1 with a 10 Torr explored pressure range). As an application, H 2, He and self-induced lineshifts of the v 2 and (2 v 2− v 2) band of NH 3 and of the v 2 band of HCN have been determined.

Municipal effluent standards in the Czech Republic

The paper explains the need for proper wastewater treatment in the Czech Republic and the development of legislation for effluent standards. A step-wise development from environmental quality standards to emission effluent standards is described. The necessity of retaining the environmental quality standards in the new legislation under specific conditions of the Czech Republic is explained. The paper describes the proposal by the Czech Association of Wastewater Treatment Experts to change the absolute effluent standards to standards with a stochastic character. The numerical values of effluent standards in the Czech Republic depend on the wastewater treatment plant size. Thus the wastewater treatment processes characteristic of individual size categories are described.

Organic Conductors as Novel “Molecular Rulers” for Advanced Manufacturing Processes

Abstract Future advanced manufacturing equipment used in high technology programs will require ultra-high precision and associated machining tool operations that require placement accuracy of ∼1–100 nm (1nm = 10 A). There is consensus amongst engineers that this equipment will be based on STM (Scanning Tunneling Microscope) technology. All such STM-based “drivers” must contain a metrology system that requires absolute length standards referenced to atomic spacings for calibration.1 Properly designed organic conductor substrate crystals have the potential to be molecular rulers for STM-based advanced manufacturing equipment.

Monitoring mortality as an indicator of influenza in Catalonia, Spain.

This study aimed to investigate the behaviour of two indicators of influenza activity in the area of Barcelona and to evaluate the usefulness of modelling them to improve the detection of influenza epidemics. Descriptive time series study using the number of deaths due to all causes registered by funeral services and reported cases of influenza-like illness. The study concentrated on five influenza seasons, from week 45 of 1988 to week 44 of 1993. The weekly number of deaths and cases of influenza-like illness registered were processed using identification of a time series ARIMA model. Six large towns in the Barcelona province which have more than 60,000 inhabitants and funeral services in all of them. For mortality, the proposed model was an autoregressive one of order 2 (ARIMA (2,0,0)) and for morbidity it was one of order 3 (ARIMA (3,0,0)). Finally, the two time series were analysed together to facilitate the detection of possible implications between them. The joint study of the two series shows that the mortality series can be modelled separately from the reported morbidity series, but the morbidity series is influenced as much by the number of previous cases of influenza reported as by the previous mortality registered. The model based on general mortality is useful for detecting epidemic activity of influenza. However, because there is not an absolute gold standard that allows definition of the beginning of the epidemic, the final decision of when it is considered an epidemic and control measures recommended should be taken after evaluating all the indicators included in the influenza surveillance programme.

Income distribution and mortality: cross sectional ecological study of the Robin Hood index in the United States.

To determine the effect of income inequality as measured by the Robin Hood index and the Gini coefficient on all cause and cause specific mortality in the United States. Cross sectional ecological study. Households in the United States. Disease specific mortality, income, household size, poverty, and smoking rates for each state. The Robin Hood index was positively correlated with total mortality adjusted for age (r = 0.54; P < 0.05). This association remained after adjustment for poverty (P < 0.007), where each percentage increase in the index was associated with' an increase in the total mortality of 21.68 deaths per 100,000. Effects of the index were also found for infant mortality (P = 0.013); coronary heart disease (P = 0.004); malignant neoplasms (P = 0.023); and homicide (P < 0.001). Strong associations were also found between the index and causes of death amenable to medical intervention. The Gini coefficient showed very little correlation with any of the causes of death. Variations between states in the inequality of income were associated with increased mortality from several causes. The size of the gap between the wealthy and less well off--as distinct from the absolute standard of living enjoyed by the poor--seems to matter in its own right. The findings suggest that policies that deal with the growing inequities in income distribution may have an important impact on the health of the population.

Municipal Effluent Standards in the Czech Republic

The paper explains the need for proper wastewater treatment in the Czech Republic and the development of legislation for effluent standards. A step-wise development from environmental quality standards to emission effluent standards is described. The necessity of retaining the environmental quality standards in the new legislation under specific conditions of the Czech Republic is explained. The paper describes the proposal by the Czech Association of Wastewater Treatment Experts to change the absolute effluent standards to standards with a stochastic character. The numerical values of effluent standards in the Czech Republic depend on the wastewater treatment plant size. Thus the wastewater treatment processes characteristic of individual size categories are described.

Ethical Inclinations of Tomorrow's Advertising Practitioners

This study, which examines the ethical inclinations of undergraduate advertising students (N = 257) who indicate career interests in advertising, finds that student responses to four scenarios about advertising ethics tend not to indicate an application of absolute moral standards. A factor analysis of student responses to 17 statements about the ethics of advertising practices show three underlying dimensions; these are labeled, respectively, Advertising Claims and Standards, Agencies' Public Responsibility, and Agencies' Moral Standards. This study also offers suggestions for research.

In Vitro Testing of Dry Powder Inhalers

There is increasing focus on the development of dry powder inhalers (DPIs) for the delivery of therapeutic entities to the lungs. In vitro testing of metered-dose inhalers (MDIs) has evolved through the years and general tests and methods have been published through USP general chapter <601>, monographs, and guidelines issued by the FDA. In contrast, very few guidelines have been established for the testing of dry powder inhaler systems. In fact, these systems may prove to be more difficult to propose general tests for because they are based on different principles leading to a greater diversity in the number of types of devices and formulations in comparison to the MDIs. To form absolute standards at this stage will be difficult and this paper will present a comparison of the in vitro test methods of MDIs to some of the DPIs that are commercially available and suggests some guidelines to follow.

感性と感覚のセンシング 人間の主観評価を加味した目の形態分類ニューラルネットの検討

A neural net approach is proposed to classify the eye shape with the respect to the three dominant features obtained from the subjective evaluation standard. The neural network is composed of eighteen physical features of the eye used as input data and the three features in the subjective tests used as output data. From the experiments, it can be concluded that these features combined can best represent various subjective impressions of human eyes. It can also be shown that unknown data can be classified by using k-neighbor interpolation training, where neighboring data are chosen based on the criterion of absolute standard of learning data.

Tell Es-Sultan (Jericho): Radiocarbon Results of Short-Lived Cereal and Multiyear Charcoal Samples from the End of the Middle Bronze Age

Samples from Tell es-Sultan, Jericho, were selected for high-precision 14C dating as a contribution toward the establishment of an independent radiocarbon chronology of Near Eastern archaeology. The material derives from archaeological excavations conducted by K. M. Kenyon in the 1950s. We present here the results of 18 samples, associated stratigraphically with the end of the Middle Bronze Age (MBA) at Tell es-Sultan. Six short-lived samples consist of charred cereal grains and 12 multiyear samples are composed of charcoal. The weighted average 14C date of the short-lived grains is 3306 ± 7 bp. The multiyear charcoal yielded, as expected, a somewhat older average: 3370 ± 6 bp. Both dates are more precise than the standard deviation (a) of the calibration curves and the absolute standard of oxalic acid. Calibration of the above Jericho dates is a bit premature, because several groups are currently testing the accuracy of both the 1986 and 1993 calibration curves. Nevertheless, preliminary calibration results are presented for comparison, based on 4 different calibration curves and 3 different computer programs. Wiggles in the calibration curves translate the precise bp dates into rather wide ranges in historical years. The final destruction of MBA Jericho occurred during the late 17th or the 16th century bc. More definite statements about the calibrated ages cannot be made until the accuracy of available calibration curves has been tested. Development of calibration curves for the Eastern Mediterranean region would be important.

Model study of atmospheric transport using carbon 14 and strontium 90 as inert tracers

The observed excess carbon 14 in the atmosphere from 1963 to 1970 provides unique, but limited, data up to an altitude of about 35 km for testing the air motions calculated by 11 multidimensional atmospheric models. Strontium 90 measurements in the atmosphere from 1964 to mid‐1967 provide data that have more latitude coverage than those of carbon 14 and are useful for testing combined models of air motions and aerosol settling. Model calculations for carbon 14 begin at October 1963, 9 months after the conclusion of the nuclear bomb tests; the initial conditions for the calculations are derived by three methods, each of which agrees fairly well with measured carbon 14 in October 1963 and each of which has widely different values in regions of the stratosphere where there were no carbon 14 measurements. The model results are compared to the stratospheric measurements, not as if the observed data were absolute standards, but in an effort to obtain new insight about the models and about the atmosphere. The measured carbon 14 vertical profiles at 31°N are qualitatively different from all of the models; the measured vertical profiles show a maximum mixing ratio in the altitude range of 20 to 25 km from October 1963 through July 1966, but all modeled profiles show mixing ratio maxima that increase in altitude from 20 km in October 1963 to greater than 40 km by April 1966. Both carbon 14 and strontium 90 data indicate that the models differ substantially among themselves with respect to stratosphere‐troposphere exchange rate, but the modeled carbon 14 stratospheric residence times indicate that differences among the models are small with respect to transport rate between the middle stratosphere and the lower stratosphere. Strontium 90 data indicate that aerosol settling is important up to at least 35 km altitude. Relative to the measurements, about three quarters of the models transport carbon 14 from the lower stratosphere to the troposphere too rapidly, and all models with all three sets of initial conditions appear to sweep carbon 14 out of the midstratosphere (above 28 km) much more slowly than was observed from 1963 to 1970. Atmospheric dynamicists should seriously consider what the carbon 14 measurements imply with respect to advection in the midstratosphere.

A birth weight adjusted comparison of perinatal mortality in the Faroe Islands and Denmark

The objectives were to compare perinatal mortality (PNM) in the Faroes and Denmark while accounting for the high birth weights in the Faroes, and to discuss methodological aspects related to this task. We applied conventional methods employing absolute birth weight standards, and the Wilcox-Russell way of comparing relative birth weights. During 1977-85 perinatal mortality (PNM) in the Faroes was 14.7 (98 cases) per 1,000 births, and 1.57 times higher than that in Denmark. Conventional method: birth weight-standardised risk ratio for PNM in the Faroes v Denmark was 1.95; the risk ratio declined with increasing birth weight. Wilcox-Russell model: the risk tended to be more uniformly increased across the birth weight distribution when babies with same relative birth weights were compared; the residual component of the birth weight distribution (i.e. the excess of observed births in the lower tail beyond what could be predicted by a Gaussian distribution) was 2.1% in the Faroes and 3.6% in Denmark, which does not fit with the model assumption that the size of the residual component is a strong determinant of a population's PNM.

Determination of glutamine and α-ketoglutarate concentration and specific activity in plasma using high-performance liquid chromatography

A method is described for measuring glutamine (GLN) and α-ketoglutarate (KG) concentration and specific activity (SA) using high-performance liquid chromatography (HPLC). Plasma GLN and KG are separated on miniature ion-exchange columns. KG is derivatized with O-phenylene diamine, the derivative is extracted in ethyl acetate, dried, and dissolved in pH 7 phosphate buffer. The isolated GLN is enzymatically converted to KG and analysed as such. Derivatized samples are stable for weeks at −20°C. Samples are injected onto a reversed-phase HPLC column. Absolute standards are injected to determine the nmol content of unknown samples. α-Ketoadipate and [ 3H]-glutamine are used as internal standards to quantitate KG and GLN concentrations, respectively. Collection of the entire peak of interest permits determination of the radioactivity in the GLN and KG peaks; this together with the determination of the nanomoles injected permits the calculation of the SA. Typical precision is 3.5 and 4.6% for GLN and KG concentrations and 5.3 and 3.3% for GLN and KG SA, respectively. Analysis time is ca. 7 min. Using this method, the turnover rate of GLN carbon was determined during a 5-h infusion of l-[U- 14C]glutamine in a human subject.

Measurement of iron isotopes (54Fe, 56Fe, 57Fe, and 58Fe) in submicrogram quantities of iron

Iron isotopes offer an excellent opportunity for detailed tracing of natural processes because of the range of stable isotopes (54, 56, 57, 58) and the importance of iron redox transitions in biochemical and inorganic processes. In this paper, we describe a significantly improved mass spectrometric technique for iron isotopic analysis that utilizes ion pulse counting detection and is calibrated with an absolute iron isotope abundance standard. All four stable iron isotopes are quantified in a single analysis to approximately 0.1% precision and accuracy using a low-temperature (1200[degrees]C) silica gel/boric acid technique on an improved source filament assembly composed of platinum and ceramic. Filament loads of 100-1000 ng can be utilized through implementation of an ultraclean work environment, improved chemistry, and a source designed specifically to minimize isobaric interference in the mass 50-60 region. 30 refs., 5 figs., 4 tabs.

Feasibility of Measuring Relative Right Ventricular Volumes and Ejection Fraction with Implantable Rhythm Control Devices

Ejection fraction (EF), the ratio between stroke volume (SV) and end-diastolic volume (EDV), is a valuable contractility indicator. Unlike SV, the Frank-Starling effect is automatically compensated in the calculation of EF. It was the aim of this study to evaluate the physiological behavior of impedance derived measurements of relative right ventricular (RV) volumes and EF, obtained with standard pacing leads. Seven patients were evaluated at the time of pacemaker implant or replacement. Since no absolute standard of comparison was available for RV volumes, the value of the measurements was assessed by observing their behavior under cardio-circulatory challenges. A 2.5-kHz carrier was fed to the ring and tip electrodes of standard bipolar pacing leads and the resulting voltage was digitized and stored. The peak-to-peak voltage (PPV) of the carrier at the time of QRS was used as EDV, and the largest PPV as end-systolic volume (ESV). Relative SV was the difference between EDV and ESV, and EF = SV/EDV x 100. Pacing was used to reduce EDV, and the effect of contractility was tested with isometric hand grip, recumbent leg exercise, or isoproterenol drip. Only minimal changes in EF were noted during incremental pacing; relative SV and EDV decreased as expected; and EF increased significantly during contractility challenges. A high correlation coefficient was observed between EDV and SV changes induced by incremental pacing at rest (r values from 0.62 to 0.98, P from < 0.01 to 0.001). The study revealed that impedance volumetry, utilizing conventional bipolar pacing leads, yields useful hemodynamic data related to EDV, ESV, and EF. Given the simplicity of the method, it is reasonable to conclude on the feasibility of using said impedance derived hemodynamic parameters in implantable rhythm control devices.

How well do prediction equations predict? Using receiver operating characteristic curves and accuracy curves to compare validity and generalizability.

Although morbidity and mortality prediction equations are widely used in planning, clinical practice, and health risk appraisal, their validity and generalizability have been tested only in a limited way. Previous attempts lacked an absolute standard of performance and looked only at the equations' ability to predict who would become ill (sensitivity), not the equally important ability to predict who would remain healthy (specificity). We compared six all-cause mortality prediction equations using receiver operating characteristic curves and accuracy curves, which overcome the limitations of earlier methods and provide a concise visual representation of the results. We used equations from five prospective studies conducted in the United States (Tecumseh at 8 and 12 years of follow-up, Framingham, Chicago Gas, Chicago Western Electric, and Albany), each of which included cholesterol, smoking, and blood pressure as independent variables, to predict 12-year mortality in Tecumseh males age 40-54 years. Previous studies suggested that these equations predict equally well. Our analysis found that, although all predict better than chance, Albany, Chicago Western Electric, and Tecumseh at 8 years underestimate mortality. Receiver operating characteristic and accuracy curves are a promising technique for assessment of prediction equations.

Approaches to measurement and evaluation

Approaches utilized to appraise student progress depend upon the philosophy of education involved. Each specific philosophy uniquely determines that which learners should acquire. The testing and measurement movement stresses the utilization of predetermined objectives written in measurable terms. The objectives are written prior to instruction of learners. With appropriate learning opportunities, a student either does or does not achieve one or more precise objectives. Measuring student progress against the stated objectives emphasizes the concept of criterion referenced testing (CRT). The testing and measurement movement also advocates using norm referenced tests (NRT). Students are spread out on a continuum from highest to lowest based on test scores. Predetermined objectives tend not to exist when utilizing norm referenced tests to measure student achievement. Norm references tests spread students' results in terms of test scores much more so than criterion referenced testing. Students attempt to attain predetermined objectives with CRTs. The measurably stated objectives represent absolute standards. A high number of students might well achieve the measurably stated objectives, as the teacher usually intends. Self-evaluation by the student is an opposite approach to appraisal of learner progress as advocated by the testing and measurement movements. With self-evaluation, responsibility rests with the learner him/herself to acknowledge strengths, weaknesses, and modifications to attain at a higher level. Learners, when evaluating themselves, need to perceive the processes and products completed from the frame of reference of personal improvement. The truth resulting from evaluation may well reside within the student. Subjectivity in results is to be expected, since open-ended criteria are utilized to appraise progress. The tendency here will be not to utilize objective tests to ascertain progress. With self-evaluation, the student might well perceive increased purpose in assessing the self. The teacher is a stimulator and initiator guiding the self-evaluation process. Idealism advocates students' achievement in mental development. Mental maturity here is prized more highly than affective and psychomotor objectives. The affective dimension is salient to the point that learners attain well academically and intellectually. Students' attaining vital concepts and generalizations is of utmost importance to an idealist. To appraise learner progress effectively, the teacher must evaluate student growth in achieving worthwhile subject matter content, consisting of vital broad ideas. Discussions and essay tests, in particular, assist the idealist teacher to determine student acquisition of subject matter. Experimentalists depend upon teacher observation, basically, to evaluate student progress. The experimentalist teacher evaluates students in life-like situations in which they select information and solve problems. Hypotheses, tentative in nature, attempt to provide answers to identified problems. Since each hypothesis is to be tested within a social context, modifications or revisions may need to be made. Perennialism is a philosophy of conservation, rejecting a continually changing environment as identified and defined by experimentalists. The great ideas of thinkers of the past provide subject matter content. The abstract and academic are preferred to the concrete and the practical. Transitory ideas from the past have no place in a perennialist's curriculum. Rather, content must remain salient, vital, and significant as the decades and centuries pass. Endurance in time and in diverse geographical regions characterize that which is classic. Perennialists emphasize the liberal arts and general education for all. Preparing for jobs, careers, and the professions, has no place in such a curriculum. Vocational needs are not to be emphasized on the elementary, high school, or baccalaureate degree level, but only on graduate levels of study which should prepare the student for a niche in the world of work. Prior to that time, however, common learning should be acquired by students in the form of a liberal arts education. Liberal education, which is non-vocational, needs to emphasize as objectives of instruction the development of the mind towards maturity so that the great ideas of the past may be understood and accepted. The classics provide the intellectual system of subject matter which is offered to students. The content needs to be challenging intellectually and enable retention of major concepts and generalizations.