bluuebunny/crossref_metadata_2025 huggingface dataset:
Interrogating Flow Fields with Radar and Laser Sources
Authors: Harris J.
Published: November 2015

The main concern is with the applications of a radar dopplermeter which has recently become available. Laboratory trials have been carried out to investigate its use in the process industries especially as a potential interrogating unit in a control system.

Useful features, and some of the disadvantages are exposed and comparisons are made between dapplermeters using radar and laser sources. These and other techniques are under patent application.
Rotameters and Turbine Flowmeters in Pulsating Flow Measurement
Authors: Dijstelbergen H. H.
Published: November 2015

The equations of motion for the rotameter and turbinemeter are derived and the errors resulting from pulsating flow are investigated. Measurements of errors are given and the application of the results to practical problems is indicated.
Progress in the Design of Multivariable Control Systems
Authors: Rosenbrock H. H.
Published: November 2015

Frequency-response methods have not widely been applied to multivariable systems in which interaction is significant. The paper describes some recent progress in using computers with graphic output for this purpose.
Hydraulic Gap Control on Strip Rolling Mills
Authors: Collinson C. D.
Published: November 2015

Early applications of hydraulic loading were confined to foil rolling mills but recent developments have been rapid. Prestressed mills were adopted to obtain high stiffness and stability. The addition of modern quickly-responding electro-hydraulic equipment and accurate transducers has given these mills even higher effective stiffness and resulted in very good gauge control. The proving of hydraulic load and position controls in service on these mills has enabled them to be applied with confidence to ‘pure’ (screwless) hydraulic mills which are less costly than conventional mills and give improved performance. They are being widely adopted.

Control methods, the requirements for transducers, hydraulic systems, etc., and the essential functions of a hydraulic gauge control are described herein.
A Drag Plate Flowmeter for Pulsating Flow
Authors: Hunter J. J. , Green W. L.
Published: November 2015

A survey of recent articles shows that drag plate flowmeters, in one form or another, have been about the most popular devices for indicating transient flows.

Design principles are given and features discussed, which affect performance in transient or pulsating flow.

Where a transient flowmeter has an electrical output it is quîte easy to process the output signal so as to obtain the average flow under pulsating conditions of flow. Thus the drag plate flowmeter is of interest for this important application.

Up to the present the transient performance of these flowmeters has been inferred from the examination of the output waveform and from the comparison of the indicated flow with true average flow under pulsating conditions. Details of frequency analysis tests of a drag flowmeter are given.
Hydraulic Load Contents Gauge for a Mobile Liquid Nitrogen Storage Tank
Authors: Woodley M J A
Published: November 2015

This paper describes a simple modification to a mobile liquid nitrogen storage tank, which continuously measures the tank contents.
On-Line Analysis of Exponential Time Functions
Authors: Gray J O , Palmer J P
Published: November 2015

A hybrid computer configuration has been devised for the fast on-line estimation of the parameters of a second order exponential time function. Experimental results are given for a range of time constant ratios and the effect of signal noise is considered.
An Average Wavelength Parameter for Surface Metrology
Authors: Spragg R C , Whitehouse D J
Published: November 2015

The new International Standard for the assessment of surface texture is based on the Arithmetic Average Height Index Ra. This parameter, although extremely valuable for quality control in manufacture, takes little or no account of the openness or closeness of the texture. Recently an additional parameter, the Average Wavelength Λa has been defined which is wavelength conscious and which supplements the information given by Ra. This paper shows how this new parameter can be derived and measured, and gives some practical examples of the application to surface texture measurement.
The Measurement of Engine Volumetric Efficiency Using a Pressure Transducer
Authors: Clarke P H , Khayat M N , Harrow G A
Published: November 2015

A method of estimating the volumetric efficiency of an engine by using a piezo-electric pressure transducer to measure the compression pressure during a non-firing engine cycle is described and the results obtained are compared with those derived from a direct measurement of air flow. The results produced by the two techniques agree to within ±3% at speeds up to 2500 rpm and are in good agreement with those obtained from an infra-red exhaust gas analysis when the engine was firing.
Digital Simulation of the Dynamics of a Fixed-Bed Catalytic Reactor
Authors: Norton J P , Smith W
Published: November 2015

A dynamic model of the process whereby acetone is made from isopropanol in a fixed-bed catalytic reactor is derived from the material and heat balances and the kinetics of the reaction. The difficulties arising during the construction and use of a digital simulation of this kind of model are discussed. In particular, it is shown that stability depends on the order in which the independent variables are integrated and that the use of a single step integration algorithm is possible.
A Fluidic Clock or Pulse Generator
Authors: Burrows C R , Lowe L
Published: November 2015

This paper presents some preliminary results of an experimental investigation of a novel fluidic pulse generator. The experiments were performed to establish the useful working range of the device, and to examine the feasibility of constructing a variable frequency generator.
Basic Pneumatics
Authors: Mott J E
Published: November 2015

This paper was included in the programme of the Hertfordshire Local Section with the prime objective of interesting people new to the process control field, but the author has blended into the framework views which will engage the interest of the more experienced also. The paper is not designed as a substitute for text book study.
Pressure Regulation in the Natural Gas Grid
Authors: Dexter A L
Published: November 2015

A sub-optimal control scheme is proposed to regulate pressures throughout the Natural Gas Grid. In the scheme, the pressures at certain optimally chosen grid locations are dynamically controlled to achieve good overall regulation throughout the grid. Acknowledging the random nature of the load disturbances, the design of the regulators is based on stochastic control theory. To assess the performance of the scheme, experiments are performed on a lumped-parameter model of the grid system. Results suggest that introduction of the scheme, could substantially improve on the present method of pressure regulation.
Optimal Control Theories in the Design of Aircraft Stability Augmentation and Control Systems
Authors: Healey Martin
Published: November 2015

This paper outlines modern optimal control theory and its possible application to the design of some aircraft control systems. Both continuous and discrete control laws are considered. Deterministic linear systems with a quadratic index of performance (state feedback) are discussed and extended to real and implicit model-following. Output feedback control laws are introduced using gain matrices and state observers, leading to the (Stochastic) Kalman-Bucy filter. The effects of plant parameter variation with flight condition are related to the design of ‘desensitised’ control laws. Comment is also made on suitable state variable models.
Applying the Concepts of Control
Authors: Bishop David M.
Published: November 2015

Introducing his Address, Mr Bishop said that since it had been decided that the President should not necessarily give his address in London, he had no hesitation in selecting Teesside, where he lives and works, and where his own Local Section resides. Moreover, Teesside won the David Nutting Award for its contributions last year to the affairs of the Institute.

Mr Bishop also spoke of the recently announced granting by Her Majesty The Queen of a Royal Charter, which he saw as recognising the standing of the Institute. He said:

It might be thought by some that the standing of this Institute has been enhanced by the granting of a Royal Charter. In the formal sense this is no doubt true, but as I see it what has happened is that our standing has been recognised and that we are now in a position which we have earned by our achievements. But with this recognition we are also given increased responsibility, and we must see to it that we respond, and that we justify the trust placed upon us. If we wish to further enhance our standing we shall not do so by resting on our laurels, or by mere talk. If we are to become well-regarded, not just by our fellow scientists and engineers, but by the world at large, then we will have to do things which beneficially affect the world at large to the point that people notice and wish to applaud.

The President also paid tribute to the work of a Past-President, Mr David Nutting, and the Secretary, Mr Edgar Eden, for their efforts in preparing and presenting the petition.
Modelling a Loaded Two-Way Pneumatic Actuator
Authors: Chitty A. , Lambert T. H.
Published: November 2015

This paper describes experiments on a low-pressure pneumatic actuator and load. An impulse test is described, in which the transient behaviour of a loaded actuator, operating in a particularly simple mode, was observed. The results are used to explain the nature of the expansion and compression processes in the actuator and to aid understanding of the effects of piston leakage and friction. Numerical values are obtained for the poly tropic gas constant and for the friction and piston leakage coefficients. The conclusions are shown to be relevant to an actuator operating in more complex modes and as a component of a pneumatic servomechanism.
Control Problems Associated with an Open Loop Unstable Chemical Reactor
Authors: While C.
Published: November 2015

A batch reaction is carried out in a water-cooled reactor on a small pilot scale plant. Control problems arose because of the inherent one loop instability of the reactor due to insufficient heat transfer area between the reactor contents and the cooling water in the jacket. This paper describes how a control system was designed which stabilised the reactor.
On the Design of a Specific Kalman Filter with Identification of Noise Covariances
Authors: Amer A. F. , Hanafy A. A. R. , Sakr M. F.
Published: November 2015

In the present paper a well-posed optimisation problem is formulated using a quadratic error index where incremental corrections ΔQ and ΔR are obtained at the end of each of progressive overlapping observation intervals. For each new obtained value of Q and R a new value for the steady-state optimum Kalman filter gain is computed. At the end of the optimisation procedure a specific Kalman filter is obtained where the resulting constant gain is the correct steady-state optimum Kalman filter gain. When comparing the developed algorithm with an alternative one where the constant filter gain is computed directly without identifying the unknown noise covariances, the results show the sensitivity of the latter method to the initial guesses of the filter gain, a difficulty that is not existent in the present algorithm.
Gain Settings for Specified Time Responses
Authors: Hind E. C.
Published: November 2015

A method is shown for the determination of gain settings for specified time responses from the open loop frequency responses. It is based on the use of the contour of constant closed loop phase angle, α = −90°. The method primarily yields the value of the static loop gain or velocity constant which is required so that the closed loop response will have a specified value of relative damping. For most systems, the solution is simple and direct.
Thermocouples above 600°C: Infra-Red Thermometers and Optical Pyrometers
Authors: Barber R. , Brown M. E.
Published: November 2015

This paper outlines the important features in the calibration of all types of thermocouples and infra-red thermometers using the established methods of calibration. The International Practical Temperature Scale of 1968 is described with reference to the fixed points and methods of interpolation between them. The principle of traceability is described and also the various traceability routes via Absolute, Secondary and Transfer Standards which can be employed.

Importance is placed on the provision of written procedures, schedules for routine checking and maintenance of full and accurate records. This work should be the responsibility of a co-ordinating expert. Descriptions are given of temperature sources and ancilliary equipment necessary for establishing a works laboratory which requires traceability to National Standards. The normally attainable levels of uncertainty are given for a number of examples.
Improvements in the Design and Operation of a Suction Pyrometer
Authors: Wojtan M. S. , Jones K. A. G.
Published: November 2015

There is a need to make reliable gas temperature measurements in combustion research. Conventional suction pyrometers and the associated methods of estimating their error do not always give satisfactory results.

A new suction pyrometer has been developed to meet the requirements of a specific project at the Coal Research Establishment of the NCB. The unit incorporates a means of estimating directly the error in the pyrometer reading at the time the gas temperature is measured. The pyrometer has been used to measure gas temperatures in a wide range of environments. The results demonstrate the advantages of using the new pyrometer.
‘Square One’ — Instrument and Control Checklist
Authors: Smith R. J.
Published: November 2015

‘Square One’ is a series intended primarily for the younger practitioner of our art but which, we feel, may well find readers of more mature years. The intention is to supplement more formal education and training with practical advice and explanation. Although early articles are written more for those employed by instrument users, much of the advice may be of value to manufacturers and contractors. Suggestions for subjects to be covered in this series would be particularly welcome.
Communications in Process Control (Part 1)
Authors: Matthews P. R.
Published: November 2015

The last decade has seen many new measurement and control techniques developed. This has been principally due to the development of low cost electronic circuits and, more recently, the microprocessor. As a result of this rapid development the instrument and process control engineer is faced with the arduous task of interfacing new and old equipment with differing transmission and communication requirements. The situation is further complicated by the numerous transmission and communication techniques that are available and the usual dogma of finding differing communication interfaces at either end of the connecting cable.

This paper provides an insight to the array of transmission and communication techniques currently in use and looks at new techniques which are being developed. The application of the transmission and communication techniques to process control systems is a subject which is now under careful scrutiny as the establishment of an effective transmission and communication configuration can result in an appreciable cost advantage and increased transmission efficiency. A number of these configurations (networks) are discussed.
On-Line Analytical Instrumentation in the Water Industry — Problems and Practical Solutions
Authors: Briggs R.
Published: November 2015

Part 1 of this article was published in the March issue and dealt with problems. It covered the background, needs and priorities in the water industry, also overall system considerations and developments in measurement technology.
Controlling the British Gas Grid System
Authors: March A D N
Published: November 2015

This paper was orginally presented at the East of Scotland Section of the Institute of Measurement and Control on 2 April 1985.
Some Thoughts on the Economic Justification of Flow Measurement
Authors: Hinton James R B
Published: November 2015

James Hinton reminds us that the development of ‘good ideas’ cannot be justified today without economic arguments. In this article he discusses, from his own experience, the levels of instrumentation which must be considered in designing a process plant and the relative cost and advantages of various meters.
Control Engineering Education in Belgium
Authors: van Cauwenberghe A , Noldus E , Williams J L
Published: November 2015

The present report gives an overview of the engineering education system in Belgian universities, and includes a more detailed discussion on control engineering education.
Pipeline Instrumentation: The British Gas National Transmission System
Authors: Gilbert P
Published: November 2015

The transmission and distribution system operated by British Gas plc is the largest integrated pipeline system in Europe. The whole system comprises a national transmission system which carries gas from five terminals to the twelve gas regions. Each region in turn carries the gas through a regional transmission system into a distribution grid and thence onto its customers. The national, regional and distribution system all present the instrument engineer with different technical challenges because of the way in which they have been built and are operated, however, it is simplest to characterise them by their process conditions. The operating pressure is highest in the national transmission system being up to 75 bar, in the regional transmission system the pressure is usually less than 37 bar, and in the distribution grid it is less than 7 bar. In general, the pipe diameters decrease from the national system downwards, and the measured flowrates are lowest in the distribution grids.

This paper is concerned only with instrumentation on the national transmission system. The discussion will cover current technology which is typical of that being installed at present, and concentrates on the more commonly found instrumentation. The paper begins with a brief history of development of the national transmission system and a description of how it is operated. This is followed by a discussion on the application of computers to the control of unmanned installations. A section concerning the measurement of pressure and its application to the control of the system comes next. The main part of the paper contains an analysis of high accuracy flowmetering and the paper concludes with some comments on developments in instrumentation and their application to changing operation of the national transmission system.
The Present and Future Status of Fibre Optic Sensors in Industry
Authors: Medlock R S
Published: November 2015

The applicational requirements of sensors for the industrial market are discussed. The advantages and disadvantages of fibre optic industrial sensors are reviewed against these requirements and against the competitive advantages of electronic sensors. It is concluded that the high performance and sensitivity of some fibre optic sensors will favour their acceptance in the market place as discrete devices. Their future in large sensor systems for the process control industry seems less assured. Battery assisted sensors may provide an interim solution.
Control Engineering Education in Denmark
Authors: Larsen P Martin
Published: November 2015

The aim of the article is to present the structure of the engineering educational system in Denmark with special emphasis on control engineering education at university level. In comparison with other European countries, the Danish system is unique in including four types of engineering schools: Technical University, Ålborg University Center, Engineering Academy, and Engineering Colleges. The curricula are based on the module systems, which in principle gives students great freedom in selection and combination of courses. For each engineering school the specific requirements and options are listed for lines/branches, which offer specialisation in automatic control. In conclusion the Danish engineering system is briefly compared with the systems in the other Scandinavian countries.
Intrinsic Safety Rules OK for Process Instrumentation — Part 1
Authors: Hutcheon I C
Published: November 2015

The technique of intrinsic safety was originated in England for mine signalling, following a serious mine disaster in 1913. The first surface certificate was issued in 1936 and the first formal standard in 1945, but it was not until the 1960s that the technique came into its own for process measurement and control, with the development of the shunt-diode safety barrier based on the Zener diode.

This paper outlines the development of the technique and describes some typical applications of the shunt-diode barrier and its more recent companion, the isolating interface device. It also looks briefly at the new IS instruments being made possible by advances in low-power semiconductor technology.
Measurement, Models and Medicine: Computer Modelling in hEalth Care Delivery
Authors: Carson Ewart R
Published: November 2015

Computational modelling is becoming of increasing importance in assisting with, and enhancing, the processes of decision-making in clinical medicine and in health care delivery, processes which depend upon the effective interpretation of data yielded by measurement practice. Using conceptual models of health care delivery, a framework can be established within which the role of specific computational modelling paradigms can be clearly identified. Some of the methodological issues which underpin computer modelling are considered across the range of realizations (mathematical, logical, statistical and graphical) that find application in the clinical and health care domains. Examples are given of both quantitative modelling and qualitative model-based reasoning as important adjuncts to measurement practice.
Instrumentation and Control Systems for Sizewell B
Authors: Boettcher D B , Hickling E M
Published: November 2015

Sizewell B is the first nuclear power station to be built in the UK using the pressurized water reactor system. Although the design is based on that of pressurized water reactor stations constructed in the United States, many changes and new features have been introduced to suit British practice and licensing requirements. Among the novel features of Sizewell B are entirely new designs for the man-machine interfaces in the main control and auxiliary shutdown rooms, and for the control and instrumentation systems. These new designs incorporate lessons learned by Nuclear Electric as an electrical utility and nuclear power station operator. This paper describes the development of the designs for the control rooms, and instrumentation and control systems, explaining some of the thinking that lay behind the design decisions. It also contrasts the practices employed on Sizewell B with some of the latest thinking coming out of the United States.
Development of an IC Engine Simulator
Authors: O'Reilly P , Thompson S , Gong C
Published: November 2015

After demonstrating the need for real-time simulation, it is shown that a transputer-based system can be used to mimic the functional elements of an analogue computer. This analogue approach to the modelling of dynamical systems, combined with the transputer's inherent digital mode of operation, results in a low-cost quasihybrid computer. In particular, it is shown how the quasi-hybrid computer is used to simulate an internal combustion (IC) engine model.
Mechanical Characterization of Extended-Chain Polyethylene (ECPE) Fiber-Reinforced Composites
Authors: Sloan Forrest , Nguyen Huy
Published: November 2015

Composite materials reinforced with extended-chain polyethylene (ECPE) fibers are unlike typical stiff and brittle composite materials such as graphite/epoxy or fiberglass. The high ductility and energy absorption capacity of the ECPE reinforcing fibers gives these composites a unique mechanical response which makes them ideally suited for a variety of applications. However, this dissimilarity with more common materials requires special consideration of mechanical properties testing. In this paper, the mechanical behavior of ECPE-fiber-reinforced composites is investigated using standard composite test methods. Results of these tests are presented and discussed based on the properties of the ECPE reinforcing fibers and on the assumptions inherent in the test methods. ECPE/epoxy composites are characterized by high ultimate tensile strength, high tensile modulus, low shear modulus and strength, and viscoelastic response to loading. The highest available combination of fiber strength and strain-to-failure gives this material ductility and energy absorption capacity significantly higher than other common composite materials. Applications of ECPE composites are discussed.
Pathophysiology of Cystic Fibrosis with Emphasis on Salivary Gland Involvement
Authors: Davis P. B.
Published: November 2015

Cystic fibrosis (CF) is a fatal autosomal recessive disorder which affects all exocrine glands, or perhaps all epithelial surfaces. The three organs most consistently affected are the eccrine sweat gland, which produces excessively salty sweat; the lung, in which chronic obstructive pulmonary disease invariably develops and is usually the cause of mortality; and the pancreas, which fails to produce adequate bicarbonate ion and water in nearly all patients, and produces in-adequate digestive enzymes in most, giving rise to pancreatic insuf-ficiency. However, the liver, reproductive tracts, intestine, sinuses, and salivary glands are also regularly affected. In the sweat gland and in the airways, passive chloride permeability is reduced, accounting for the salty sweat and probably contributing to the dehydrated mucus in the airways. In organs apart from the sweat gland, a common feature of the disease is the plugging of glandular acini and ductules by precipitated secretions. Salivary glands have been extensively studied in CF because of both the accessibility of the glands and their products, and the mix of mucous and serous components in the salivary glands. However, there is no unanimity in the results from parotid and submandibular glands. In the labial (mucous) glands, the sodium content of secreted product and in the secretory granules is markedly elevated, and histologically the acini are plugged with eosinophilic material. Functional studies of CF salivary glands have also yielded inconsistent data. Cultured cell systems combined with molecular biologic approaches offer promise in tracing the funda-mental CF defect in salivary and other epithelial systems.
Relationship of Total Fluoride Intake to Beneficial Effects and Enamel Fluorosis
Authors: Pendrys D.G. , Stamm J.W.
Published: November 2015

Recent studies indicate that the prevalence of very mild to moderate dental fluorosis, as classified by Dean, has increased relative to that found in earlier investigations. To date, fluoridated water, fluoride supplements, the diet, fluoride dentifrices, and other topical fluoride applications have been identified as sources of systemic fluoride. Recent evidence suggests that there is a strong association between mild to moderate enamel fluorosis and the use of fluoride supplements during early childhood, and that the presently recommended supplementation schedule for U. S. children above the age of 2 years may be too high. Evidence also suggests that there is a strong association between fluoride dentifrice use during early childhood and enamel fluorosis in fluoridated populations. These findings support the need for a careful review of existing supplementation schedules and early oral hygiene practices. There is a pressing need for additional analytical epidemiological studies to confirm existing findings and to determine whether other fluoride sources may be associated with enamel fluorosis. Further, since exposure to combinations of individual risk factors has been shown to carry more than merely an additive increase in the risk of fluorosis, these studies must be multifactorial in design. There is also a need for more fluorosis prevalence and severity data to be gathered, so that the development of enamel fluorosis as a public health problem can be assessed, and so that the success of measures implemented to maximize efficacy while minimizing unwanted side-effects can be monitored.
Pharmacokinetics of Fluoride in Man and its Clinical Relevance
Authors: Ekstrand J. , Spak C.-J. , Vogel G.
Published: November 2015

A large number of parameters will influence and mediate the activity and the pharmacological response of dental fluoride products after systemic or topical treatment. This report reviews some aspects of the pharmacokinetics of fluoride in man, fluoride bio-availability, plasma kinetics, and kinetics of fluoride in saliva and plaque fluid. Pharmacokinetic studies in growing dogs show that 90% of a single injected fluoride dose is retained shortly after birth, but at maturity it decreases to about 50%. The degree of fluoride accumulating in cal-cifying tissues seems to be strongly related to age. The bio-availability of fluoride from swallowed fluoride toothpaste is shown to be decreased if the toothpaste is ingested close to a meal. Several studies show that fluoride exerts its cariostatic effects through the liquid phase surrounding the enamel. The importance of fluoride in the fluid environment of the teeth and the kinetics of fluoride in saliva are discussed. Clinical studies using different slow-release fluoride systems indicate that they are promising cariostatic agents—in particular in-tra-dural slow-release devices and lozenges. A new micro-analytical method to study the kinetics of fluoride in plaque fluid collected from single tooth sites has been developed. Preliminary studies show that the clearance of fluoride from plaque fluid is slowest in the upper incisor region, followed by the molar region, and faster in the lower incisor region. A site-by-site study of the concentration of fluoride in plaque fluid after topical fluoride administration could be extremely beneficial in optimization of the methods and recommended safety regimens for fluoride therapy.
Structural Events in the Caries Process in Enamel, Cementum, and Dentin
Authors: Frank R.M.
Published: November 2015

The structural events observed in enamel, cementum, and dentin during the caries process have been reviewed. In incipient enamel lesions, the prevailing concept of an almost intact surface layer has been seriously challenged by SEM and TEM observations demonstrating structural pathways (such as enlarged prism junctions or sheaths) from the enamel surface to the subsurface lesion. The destruction in this latter location consisted of (I) enlarged prism junctions, (2) diffuse mineral destruction in the prism cores, and (3) destruction of the interprismatic substance. In root caries, the destruction of cementum started along junctions between calcified layers of extrinsic (Sharpcyj and intrinsic collagen fibers as well as along incremental lines. Invasion of Gram-positive micro-organisms followed these enlarged junctions. Dentin caries was similar in coronal and root caries. It consisted of sclerosis of the lumens of the dentinal tubules, followed by an important gradient of demineralization of intertubular dentin and destruction of occluded tubular lumens and peritubular dentin. Bacterial penetration occurred initially in the dentinal tubules and was followed by bacterial invasion and destruction of the intertubular dentin. Various phenomena of crystalline remineralization were described in enamel and dentin. Whereas in enamel and dentin caries, an important gradient of demineralization was observed before bacterial invasion, a simultaneous destruction of the mineral and organic components seemed to occur in cementum.
Effects of Fluoride on Caries Development and Progression Using Intraoral Models
Authors: Wefel J.S.
Published: November 2015

This paper reviews the use of Intraoral model systems to help elucidate the role of fluoride and. its mechanism of action in caries prevention. The Intraoral models currently in use were found to be of three general types. The most widely used system has consisted of a removable appliance that relies on the use of dacron gauze or a recessed sample to enhance plaque formation. Similarly, the banding model of Øgaard requires the presence of orthodontic band material to produce a plaque accumulation niche for demineralization, while the crown single-section technique relies mainly on placement of the sections in plaque-retentive areas (below contact points). In general, the models may be used for the assessment of food cariogenicity, an evaluation of de- and re-mineralization, and measurement of fluoride incorporation into enamel or root substrates.

On evaluation of lesion initiation and progression in vivo, it is apparent that few non-destructive in vivo techniques are available that offer the sensitivity of laboratory-based analysis. Thus, the use of Intraoral models that allow lesion formation and progression to occur in the oral environment, but can be measured with the sensitivity of in vitro techniques, has been extremely important. Although the magnitude of the fluoride dose, the longevity of fluoride in the oral environment, and the time required for remineralization are different from those found in vitro, it is apparent that the presence of fluoride in the aqueous phase is now thought to be of primary importance. Mechanistically, the presence of fluoride will both inhibit demineralization by acid and promote remineralization under more neutral conditions. Thus, one of fluoride's major contributions is to affect the rates of lesion formation and progression. It was concluded that low-concentration fluoride agents with a high frequency of application would best fulfill the above needs.
Fluoride in Dental Plaque and its Effects
Authors: Tatevossian A.
Published: November 2015

Total plaque fluoride is in the range 5–10 mg/kg (ppm) on a wet-weight basis. The variability of literature data on plaque fluoride is partly ascribed to analytical problems, many assays being close to or below the concentration detection limit of the fluoride electrode. A change in classification of plaque fluoride compartments is necessary, since recent work indicates that there are two pools of plaque F: <5% of the total F is in plaque fluid as the free ion, and the large remaining portion of total plaque F is designated as bound F, with the total F being >95% extractable by cold 0.5 mol/L perchloric acid.

Sources of plaque fluoride include the diet, saliva, and crevicular fluid; enamel is unlikely to be a regular source for plaque F unless it is either coated daily with labile fluoride compounds, such as calcium fluoride, or released by demineralization.

The location and nature of plaque bound F are not established, but the present evidence is consistent with an intracellular location. Bound F may be released by acids produced in plaque during sugar fermentation, but it is unlikely to reach ion concentrations high enough for sufficient time periods to exert significant inhibition of plaque acidogenesis. Epidemiological evidence showing correlations between pooled plaque F concentrations and caries prevalence in the plaque donors does not exclude the possibility of coincidental effects of water F on both caries and plaque F concentrations.

The action of F in reducing caries has been considered to depend on a multiplicity of effects on enamel and dental plaque, but the range of F concentrations used for such effects in dental plaque spans five orders of magnitude. Of these, only F effects in enhancing enamel remineralization and reducing the solubility rate for enamel mineral appear likely to be of practical importance. Cationic fluoride preparations containing metal ions can reduce plaque formation in the short term, but the effect is manifested mainly by the cation rather than by the F. However, progress has been made in formulation of rinse solutions which can raise plaque fluoride levels (as well as calcium and phosphate) long enough to reduce plaque acidogenicity and its potential to demineralize enamel during fermentation.
The Future of Water Fluoridation and Other Systemic Fluorides
Authors: Horowitz H.S.
Published: November 2015

School and community water fluoridation, salt fluoridation, and use of dietary fluoride supplements have abundant scientific support as effective caries-preventive methods. Because caries has declined greatly in many developed countries from use of topical fluorides, the absolute caries reduction will be considerably smaller when systemic fluoride methods are implemented now than it was 20 to 40 years ago. For countries with most of the population living in cities with communal water supplies, community fluoridation is the most logical approach from the standpoints of cost-effectiveness and total caries-preventive impact. In countries with a mostly rural population without central water supplies, salt fluoridation is more practical. Dietary fluoride supplements can be recommended only for regions where neither water fluoridation nor salt fluoridation is possible, or as a temporary measure. Although divergent views exist concerning the relative caries-preventive effects of pre-eruptive and post-eruptive fluoride administration, the effectiveness of systemic fluoride methods for preventing dental caries remains unchallenged. Persuasive scientific and public health arguments exist to justify implementing and sustaining their use. The future of these methods will be influenced by the findings of new clinical and epidemiological research. Social, political, economic, and educational factors will be of equal, if not greater, importance. Perceptions of the current severity of dental caries as a health problem and of risks associated with preventing the problem may affect the future uses of systemic fluorides more than will recommendations of scientists.
Evaluation of Topical Fluoride Preparations
Authors: Mellberg J.R.
Published: November 2015

For practical reasons, evaluation of topical fluoride products must depend upon clinical and laboratory assessments. While not always a good predictor of clinical efficacy by itself, fluoride uptake is the most commonly used laboratory test. A consideration of the relationship between possible anticaries mechanisms of fluoride, different product types, and the meaning of various kinds of fluoride uptake data suggests that both the amount of fluoride taken up by early lesions and the amount of ambient fluoride present at a cariogenic site may play key roles in determining the efficacy of a product. While formulations applied annually or semi-annually probably depend on fluoride deposition, those used daily might not.

There are no clear data supporting the superiority of one fluoride compound over another, even for infrequently used products, although there are significant differences among them in fluoride uptake by enamel. This suggests that fluoride uptake in vivo at a cariogenic site might actually be different from that suggested by in vitro data, or that larger differences are required for a clinical effect to be observable. Clinical data support the conclusion that a large increase in the fluoride concentration of a product will somewhat increase its Anticaries effectiveness, although the increase will not be linearly related to concentration. There also are no obvious differences in clinical effectiveness caused by the addition of gelling agents to topical solutions. Fluoride varnishes are clinically effective but have not been shown to be superior to topical solutions or gels.

The abrasive, humectant, and thickener systems used in most prophylaxis pastes reduce both fluoride uptake and clinical effectiveness, even though, in some cases, the components may be chemically compatible. Precleaning prior to a topical application appears unnecessary, but a delay in rinsing after the application and longer application times appear beneficial. Mouthrinse formulations essentially differ only in fluoride source, concentration, and pH. Higher fluoride concentrations are likely to provide greater benefits, but pH differences probably will not. The stannous ion in SnF2 rinses is unstable, and its effect on anticaries activity is unknown.

This review of the composition of topical fluoride products emphasizes the lack of clear evidence for the making of definite scientific judgments regarding relative clinical efficacy. Future efforts should be directed toward the development of test models that utilize the natural oral environment, so that more precise and valid comparison of compositions may be made.
Feasibility of the Combined Use of Fluorides
Authors: König K.G.
Published: November 2015

An increase in the number of methods of fluoride administration over and above traditional modes, while offering new caries-preventive possibilities, has also created problems. These cannot be solved by the purely scientific, objective approach, since emotional resistance to fluoride has increased in some countries in parallel to environmental pollution. In most of the highly developed countries, the decrease of caries prevalence has dramatically lowered the number of children in need of concentrated preventive programs. On the other hand, dental awareness and multiple sources of fluoride have increased the risk of chronic fluoride overdosage. Means to avoid the latter problem are discussed. In addition to community-delivered fluoridation programs, individual counseling and “tailor-made” preventive measures are of increasing importance.
Effects of Fluoride on Caries Development and Progression in vivo
Authors: Øgaard B.
Published: November 2015

The dissolution rate of calcium-fluoride-like material from the enamel surface in vivo appears to be much slower than previously thought. This could be due to adsorption of phosphate ions and/or protein molecules to the surface of the calcium-fluoride-like particles. During cariogenic challenges, the phosphate/protein coating is released, resulting in increased solubility rate of the calcium-fluoride-like material. Due to this mechanism, calcium-fluoride-like material may be a major aspect of the cariostatic mechanism of topically applied fluoride. Topically applied neutral fluoride agents are able to inhibit caries development in enamel but not completely stop lesion development. A fluoride solution at low pH has been found to be more effective in caries model studies than neutral fluoride agents, which might be due to the formation of a larger depot of calcium fluoride. Data from fluoridated areas indicate that the fluoride ion as such has a limited effect on lesion development, and a major mechanism of the cariostatic effect may be reformation of apatite (remineralization). The product of lesion consolidation (a fluoridated apatite) may have a limited effect, since Intraoral caries model studies show that even pure fluorapatite, in the form of shark enamel, demineralizes. In fissures and around orthodontic appliances, conventional fluoride agents appear to have only a small effect.
Injecting Drug Use and HIV in Moscow: Results of a Survey
Authors: Reilley Brigg , Burrows Dave , Melnikov Vitalec , Andreeva Tatiana , Bijl Murdo , Veeken Hans
Published: November 2015

Russia has experienced a large increase in injecting drug use since the collapse of the Soviet Union. Injecting drug use is presently attributed with up to 90 perccent of newly acquired HIV. Peer educators of an outreach program conducted a survey of injecting drug users (IDUs) in Moscow. The survey was supplemented by qualitative field notes. Due to differences in settings and methods, the hospital and street survey results are presented separately. A total of 298 hospital and 126 street surveys were collected. Results showed that IDUs are young (average 20 years), and the majority were studying or working. Needles were rated as easy to get, although police pressure often deters carrying a syringe. Sharing needles was common; IDUs that used only heroin were significantly less likely to share (RR 0.38 to 0.56). IDUs that had spoken to a peer educator were also less likely to share (RR 0.55). Heroin users had lower rates of hepatitis. Self-assessed HIV risk was unclear for many IDUs. HIV prevalence was 3 percent.
Timing of Drinking Initiation: A Trend Study Predicting Drug Use among High School Seniors
Authors: Lo Celia C.
Published: November 2015

A trend study was undertaken to evaluate the relationship between onset age of drinking and the use of drugs. Despite the fact that drinking is illegal for teenagers, general acceptance of alcohol use in mid-adolescence prompts many underage individuals to drink. However, an early start in drinking not only suggests a general tolerance for deviance, it also indicates a violation of role definitions. As explained by problem behavior theory, individuals' tolerance of drug use—or the lack of it—may exert an impact on lifetime and on current drug-using behavior. It was hypothesized that the younger individuals are when they start to drink, the more frequently they will engage in drinking and also in illegal drug use. Using the repeat survey data collected in the “Monitoring the Future” project, the present study offered a new method of partially evaluating the generality of the deviance hypothesis. By comparing 21 years of trends seen in the effects of onset age of drinking on the use of different drugs, this study derived some support for the generality of deviance.
Surviving Violence: Pregnancy and Drug Use
Authors: Sales Paloma , Murphy Sheigla
Published: November 2015

In this exploratory study of pregnant drug users who have experienced one or more violent events (physical/sexual or emotional) while pregnant, the authors detail how drug use is both a survival strategy and a source of vulnerability to violence. Using a qualitative methodology, 126 women were interviewed who were or had recently been pregnant (within six months postpartum) and had used marijuana, crack, cocaine, or heroin singly or in combination (including alcohol with one or more of the above). Data concerning demographics, family, relationships, reproductive, drug use and violence histories were collected with a structured questionnaire. Of the 126 interviewees, 79% (100) were selected on the basis of their violent experiences during pregnancy for an in-depth interview that focused on their drug use and violence histories. The authors detail the ways in which women's drug use was a form of recreation, as well as a coping and survival strategy. Drug use also caused them serious problems. Women were demonized for using drugs while pregnant but not given feasible or reasonable alternatives.
I Didn't Know: Discoveries and Identity Transformation of Women Addicts in Treatment
Authors: Baker Phyllis L.
Published: November 2015

The purpose of this research was to study the efficacy of gender-sensitive substance abuse treatment programs with a focus on the perceptions of women addicts. Based on semi-structured in-depth interviews and observation of treatment groups, an analysis of the women's stories about their lives revealed transformations in their identities. These identity transformations were based on self-discoveries made during treatment that included realizations about their addiction, emotional well-being, and parenting. An analysis of their discoveries shows compliance and resistance to institutional socialization. Just as surely as the women addicts accepted the institutional socialization, they also resisted, pushed, and pulled at it, reminding us that they are not automatons of social and institutional forces.