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Volume 9, Issue 9, September 2008, Pages 378-380
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The metric system of units is more appropriate than the imperial system for scientific applications because of its decimal basis. The metric system originated in France in 1791 and used fundamental or base units of the centimetre, gram and second (CGS), before changing to the metre, kilogram and second (MKS), ampere, candela and kelvin in 1954, and finally moved to an internationally agreed standard, Le Système International (SI) d’Unités, in 1960, which incorporated a non-gravitationally The seven fundamental units of the SI system are dimensionally independent. Six of the fundamental units are based on the physical properties of defined systems and are therefore reproducible to a high degree of certainty in any suitably equipped laboratory. The unit of mass (the kilogram) is still dependent on comparison with a physical standard (Table 1). There are two supplementary units which are used in definitions of derived units, but have no dimensions themselves and are therefore not regarded as base units. The radian (rad) is the unit of plane angle, defined as the plane angle between two radii which, on the circumference of a circle, cuts an arc equal in length to the radius. The steradian (sr) is the unit of solid angle, defined as the solid angle which has its apex at the centre of a sphere and which describes on the surface of the Almost all the units required in scientific work can be derived from the algebraic expressions of the fundamental SI units. Twenty-two of the derived units have been given special names and symbols for ease of use. Some of the derived units of relevance to anaesthesia are given below (Table 2).
The concept of temperature describes whether objects are in thermal equilibrium. Heat describes the transfer of energy due to a difference in temperature. The Celsius temperature scale uses the ice and
An SI prefix is a name or associated symbol that precedes a unit of measurement or its symbol (without space or punctuation) to form a decimal multiple or submultiple and reduce the quantity of zeros in calculations (Table 3). The prefixes are never combined: a millionth of a kilogram is a milligram not a microkilogram. SI prefixes are governed by the BIPM and are the product of four resolutions dating from 1960 to 1991.
The SI allows retention of some quantities which are in common use and can be defined in terms of the base units. The SI unit of volume is the cubic metre, but the litre (l; 1 l = 10−3 cubic metres) is a necessary convenience in medicine, otherwise we would find ourselves measuring cardiac output in cubic metres per second. The bar is a pressure close to atmospheric pressure and is useful in meteorology and in the gas industry. The electron volt (eV; 1 eV ≈ 1.602189 × 10−19 J) is the kinetic
Several non-SI units have been retained, but may be reconsidered in future. Of relevance to medicine are millimetres of mercury (mm Hg; 1 mm Hg = 133.322 Pa) and the standard atmosphere (atm; 1 atm = 101.325 Pa) for pressure, the angstrom (Å; 1 Å = 10−10 m) for wavelength, and the calorie (cal; 1 cal = 4.18 J) for energy. Note that calorie spelt with a capital ‘C’ (e.g. when describing the energy content of foods) represents 1000 calories (1 kcal). Also temporarily retained are some CGS units
Force (F) is the property that causes an object to accelerate. It is a vector quantity, that is, it has magnitude and direction. If the vector sum (the net or resultant force) exerted on an object is zero, the acceleration of the object is zero, its velocity is constant and the object is said to be in equilibrium. Forces may involve physical contact (contact forces, e.g. the force exerted by pushing on an object or by gas molecules pushing on the wall of a container) or may act without contact
This article is an overview of the key mathematical concepts required to understand computer science, physics and physiology as applied to anaesthesia. Topics include classification of numbers, base systems, scientific notation and rounding, logarithms, plain geometry, conic sections, graphical representation and periodic functions. Particular emphasis is given to exponential curves, as these relate to many phenomena in anaesthesia including uptake and elimination of drugs, and the flow of heat, gases, liquids and electrical current. The role of complex functions such as calculus and Fourier analysis is described; however a detailed understanding of these topics is not necessary to appreciate their application.
In this work, we apply the fractional order theory of thermoelasticity to a 2D problem for a half-space. The surface of the half-space is taken to be traction free and is subject to heating. There are no body forces or heat sources affecting the medium. Laplace and exponential Fourier transform techniques are used to solve the problem. The inverse Laplace transforms are obtained using a numerical technique. The predictions of the theory are discussed and compared with those for the generalized theory of thermoelasticity. We also study the effect of the fractional derivative parameter on the behavior of the solution. Numerical results are computed and represented graphically for the temperature, displacement and stress distributions. The generation rate of ultrasonically atomized droplets and the alcohol concentration in droplets were estimated by measuring the flow rate and the alcohol concentration of vapors from a bulk solution with a fountain. The effect of the alcohol concentration in the bulk solution on the generation rate of droplets and the alcohol concentration in droplets were investigated. The ultrasonic frequency was 2.4 MHz, and ethanol and methanol aqueous solutions were used as samples. The generation rate of droplets for ethanol was smaller than that for methanol at the same alcohol molar fraction in the bulk solution. For both solutions, at low alcohol concentration in the bulk solution, the alcohol concentration in droplets was lower than that in vapors and the atomized droplets were visible. On the other side, at high concentration, the concentration in droplets exceeded that in vapors and the atomized droplets became invisible. These results could be explained that the alcohol-rich clusters in the bulk solution were preferentially atomized by ultrasonic irradiation. The concentration in droplets for ethanol was higher than that for methanol at low alcohol concentration because the amount of alcohol-rich clusters was larger. When the alcohol molar fraction was greater than 0.6, the atomized droplets almost consisted of pure alcohol. Good state of charge estimation in lithium-sulfur batteries (Li-S) is vital, as the simplest convention methods commonly used in lithium-ion batteries – open-circuit voltage measurement and ‘coulomb counting’ – are often ineffective for Li-S. Since Li-S is a new battery chemistry, there are few published techniques. Existing techniques based on the extended Kalman filter and the unscented Kalman filter have shown some promise, existing work has explored only one of many possible estimator architectures: a single filter based on a pre-calibrated behavioural reparameterization of an equivalent circuit network whose parameters vary as a function of state of charge and temperature. Such filters have been shown to be reasonably effective in practical cases, but they can converge slowly if initial conditions are unknown, and they can become inaccurate with changes in current density. It is desirable to understand whether other possible estimator architectures offer improved performance. One such alternative architecture is the ‘dual extended Kalman filter’, which uses voltage and current measurements to estimate into a short-term dynamic circuit parameters then uses the outputs of this in a slower-acting state-of-charge estimator. This paper develops a ‘behavioural’ form of the dual extended Kalman filter, and applies this to a lithium-sulfur battery. The estimator is adapted with a term to model circuit current dependence, and demonstrated using pulse-discharge tests and scaled automotive driving cycles including some with initially partially discharged batteries. Compared to the published state-of-the-art, the new estimators were are found to be between 16.4% and 28.2% more accurate for batteries that are initially partially discharged to a 60% SoC level; the new estimators also converge faster. The resulting estimators have the potential to be extended to state-of-health measures, and the ‘behavioural’ circuit reparameterization is likely to be of use for other battery chemistries beside lithium-sulfur. Realistic assessment of existing masonry structures requires the use of detailed nonlinear numerical descriptions with accurate model material parameters. In this work, a novel numerical-experimental strategy for the identification of the main material parameters of a detailed nonlinear brick-masonry mesoscale model is presented. According to the proposed strategy, elastic material parameters are obtained from the results of diagonal compression tests, while a flat-jack test, purposely designed for in-situ investigations, is used to determine the material parameters governing the nonlinear behaviour. The identification procedure involves: a) the definition of a detailed finite element (FE) description for the tests; b) the development and validation of an efficient metamodel; c) the global sensitivity analysis for parameter reduction; and d) the minimisation of a functional representing the discrepancy between experimental and numerical data. The results obtained by applying the proposed strategy in laboratory tests are discussed in the paper. These results confirm the accuracy of the developed approach for material parameter identification, which can be used also in combination with in-situ tests for assessing existing structures. Practical and theoretical aspects related to the proposed flat-jack test, the experimental data to be considered in the process and the post-processing methodology are critically discussed. To better understand the regional tephra stratigraphy and chronology of northern Nevada and southern Oregon, tephras in archived cores, taken as part of the Steens Mountain Prehistory Project from four lakes, Diamond Pond, Fish and Wildhorse lakes in southeastern Oregon and Blue Lake in northwestern Nevada, were reexamined using more advanced electron microprobe analytical technology. The best preserved and most complete core from Fish Lake along with Wildhorse Lake hosted two tephras from Mt. Mazama (Llao Rock and the Climactic Mazama), a mid-Holocene basaltic tephra from Diamond Craters, Oregon, two Medicine Lake tephras and an unexpected late Holocene Chaos Crags (Mt. Lassen volcanic center) tephra which was also found in the other lakes. Blue Lake was the only lake that hosted a Devils Hill tephra from the Three Sisters volcano in west central Oregon. Another tephra from the Three Sisters Volcano previously reported in sediments of Twin Lakes in NE Oregon, has now been confirmed as Rock Mesa tephra. The Chaos Crags, Devils Hill and Rock Mesa tephras are important late Holocene stratigraphic markers for central and eastern Oregon and northwestern Nevada. Lysosomes are organelles with an acidic lumen containing hydrolases, whose role is to break down macromolecules into their subunits. Cathepsins, which are lysosomal proteases, have important roles in cancer. Enhanced cathepsin activity out of the cell is linked to tumor growth, whereas such activity inside the cell is linked to tumor growth inhibition. Recently published studies on the opposing roles of cathepsin in cancer have investigated their potential as biochemical and nanotechnological therapeutic targets.