# Foci Sentence Examples

The excitable

**foci**of the cerebral cortex are well myelinated long before the unexcitable are so.Confocal conics are conics having the same

**foci**.Johann Kepler had proved by an elaborate series of measurements that each planet revolves in an elliptical orbit round the sun, whose centre occupies one of the

**foci**of the orbit, that the radius vector of each planet drawn from the sun describes equal areas in equal times, and that the squares of the periodic times of the planets are in the same proportion as the cubes of their mean distances from the sun.A line became continuous, returning into itself by way of infinity; two parallel lines intersect in a point at infinity; all circles pass through two fixed points at infinity (the circular points); two spheres intersect in a fixed circle at infinity; an asymptote became a tangent at infinity; the

**foci**of a conic became the intersections of the tangents from the circular points at infinity; the centre of a conic the pole of the line at infinity, &c. In analytical geometry the line at infinity plays an important part in trilinear co-ordinates.The orbit of the moon around the earth, though not a fixed curve of any class, is elliptical in form, and may be represented by an ellipse which is constantly changing its form and position, and has the earth in one of its

**foci**.AdvertisementThis theory he founded on 2 Kings xxii.; and ever since, this chapter has been one of the recognized

**foci**of Biblical criticism.Let AA' be the axis and S, S' the

**foci**.It has stronger anticonvulsant properties than most other barbiturates, and may be preferentially concentrated in metabolically active epileptic

**foci**.The right kidney parenchyma was thinned and irregular and contained low attenuation areas and tiny

**foci**of calcification.Thus it has a real centre, two

**foci**, two directrices and two vertices; the transverse axis, joining the vertices, corresponds to the major axis of the ellipse, and the line through the centre and perpendicular to this axis is called the conjugate axis, and corresponds to the minor axis of the ellipse; about these axes the curve is symmetrical.AdvertisementCalling the

**foci**S, S', the real vertices A, A', the extremities of the conjugate axis B, B' and the centre C, the positions of B, B' are given by AB = AB' = CS.If the law of attraction is that of gravitation, the orbit is a conic section - ellipse, parabola or hyperbola - having the centre of attraction in one of its

**foci**; and the motion takes place in accordance with Kepler's laws (see Astronomy).Since we have now to integrate for the whole illumination at a particular point 0 due to all the components which have their

**foci**in its neighbourhood, we may conveniently regard 0 as origin.By embolism is meant the more or less sudden stoppage of a vessel by a plug of solid matter carried thither by the current of the blood; be it a little clot from the heart or, what is far more pernicious, an infective fragment from some focus of infection in the body, by which messengers new

**foci**of infection may be scattered about the body.The extension of the image away from the axis or size of field available for covering a photographic plate with fair definition is a function in the first place of the ratio between focal length and aperture, the longer focus having the greater relative or angular covering power, and in the second a function of the curvatures of the lenses, in the sense that the objective must be free from coma at the

**foci**of oblique pencils or must fulfil the sine condition (see Aberration).AdvertisementThe earlier arrangement of two lenses of the Huygenian eye-piece (see Microscope) having

**foci**with ratio of 3 to I, gives a fairly large flat field of view approximately free from distortion of tangential lines and from coma, while the Mittenzw ?As the ellipse degenerates into the straight line joining its

**foci**, the contracted parts of the unduloid become narrower, till at last the figure becomes a series of spheres in contact.By compounding two lenses or lens systems separated by a definite interval, a system is obtained having a focal length considerably less than the focal lengths of the separate systems. If f and f' be the focal lengths of the combination, and f2, f2 the focal lengths of the two components, and A the distance between the inner

**foci**of the components, then f = - f,f2/4, f' =fi f27 0 (see Lens).The approach could also potentially help eliminate local

**foci**for trypanosomes causing sleeping sickness in humans.These

**foci**will be combined with transect survey of the entire area, which we intend to cover with a 12% sample.AdvertisementThese are typical of the kinds of changes found in the broader range of chronic epileptic

**foci**.Negative values of n must be interpreted by a streaming motion on a parallel plane at a level slightly different, as on a double Riemann sheet, the stream passing from one sheet to the other across a cut SS' joining the

**foci**S, S'.The motor field, therefore, though absolutely larger, forms a smaller fraction of the whole cortex of the brain than in the lower forms. The statement that in the anthropoid (orang-outan) brain the groups of

**foci**in the motor fields of the cortex are themselves separated one from another by surrounding inexcitable cortex, has been made and was one of great interest, but has not been confirmed by subsequent observat'on.That in man the excitable

**foci**of the motor field are islanded in excitable surface similarly and even more extensively, was a natural inference, but it had its chief basis in the observations on the orang, now known to be erroneous.Both these preparations should only be used in cases where it is possible to exclude any tuberculous

**foci**, or by their action in breaking down protective fibrous tissues they may cause a quiescent lesion to become active.AdvertisementIt will be seen, then, that the visual and photographic

**foci**are now merged in one, and the image is practically as achromatic as that yielded by a reflector.The magnifying power of the telescope is = Ff /ex, where F and f are respectively the focal lengths of the large and the small mirror, e the focal length of the eye-piece, and x the distance between the principal

**foci**of the two mirrors (=Ff in the diagram) when the instrument is in adjustment for viewing distant objects.Earthquakes are frequent all over the peninsula, but especially in the south-east and west, where the Maeander valley and the Gulf of Smyrna are notorious seismic

**foci**.Besides streets running east and west, which are named by the letters of the alphabet, and streets running north and south, which are numbered, there are avenues named for various states, which radiate from two

**foci**- the Capitol and the White House - or traverse the city without any fixed plan.Hence the locus of J relative to AB, and the locus relative to CD are equal ellipses of which A, B and C, D are respectively the

**foci**.Similarly any other property might be used as a definition; an ellipse is the locus of a point such that the sum of its distances from two fixed points (the

**foci**) is constant, &c., &c.There are in some cases points termed centres, or singular or multiple

**foci**(the nomenclature is unsettled), which are the intersections of improper tangents from the two circular points respectively; thus, in the circular cubic, the tangents to the curve at the two circular points respectively (or two imaginary asymptotes of the curve) meet in a centre.The notions of distance and of lines at right angles are connected with the circular points; and almost every construction of a curve by means of lines of a determinate length, or at right angles to each other, and (as such) mechanical constructions by means of linkwork, give rise to curves passing the same definite number of times through the two circular points respectively, or say to circular curves, and in which the fixed centres of the construction present themselves as ordinary, or as singular,

**foci**.Metrical relations between the axes, eccentricity, distance between the

**foci**, and between these quantities and the co-ordinates of points on the curve (referred to the axes and the centre), and focal distances are readily obtained by the methods of geometrical conics or analytically.Of the properties of a tangent it may be noticed that the tangent at any point is equally inclined to the focal distances of that point; that the feet of the perpendiculars from the

**foci**on any tangent always lie on the auxiliary circle, and the product of these perpendiculars is constant, and equal to the product of the distances of a focus from the two vertices.From any point without the curve two, and only two, tangents can be drawn; if OP, OP' be two tangents from 0, and S, S' the

**foci**, then the angles OSP, OSP' are equal and also SOP, S'OP'.Take a piece of thread of length AA', and fix it at its extremities by means of pins at the

**foci**.If one of the

**foci**be at infinity, the conics are confocal parabolas, which may also be regarded as parabolas having a common focus and axis.According to the laws of optics it is only possible either to portray a small object near one of the

**foci**of the system with wide pencils, or to produce an image from a relatively large object by correspondingly narrow pencils.The basal lamina along the base of the cells was damaged at several

**foci**.The accompanying simple figure indicates better than any verbal description the topography of the main groups of

**foci**in the motor field of a manlike ape (chimpanzee).In that case, however, in the compound microscope a small object may always be represented by means of wider pencils, one of the

**foci**of the objective (not of the collective system) being near it.Also the auxiliarly circle is the locus of the feet of the perpendiculars from the

**foci**on any tangent.In the monkey the proportions it assumes are still greater, and the number of

**foci**, for distinct movements of this and that member, indeed for the individual joints of each limb, are much more numerous, and together occupy a more extensive surface, though relatively to the total surface of the brain a smaller one.Larger and thicker in the rabbit, when excited it gives rise in that animal to movements of the eyes and of the fore-limbs and neck; but it is only in much higher types, such as the dog, that the cortex yields, under experimental excitation, definitely localized

**foci**, whence can be evoked movements of the fore-limb, hind-limb, neck, eyes, ears and face.Experiment shows that in the manlike (anthropoid) apes the differentiation of the

**foci**or "centres" of movement in the motor field of the cortex is even more minute.The castles of these great lords were the

**foci**of the social and political life of their respective provinces.