Aperture Sentence Examples

From far away, the opening of the cave looked like a mere aperture in the rock wall.

The small aperture in the wall let in enough of the outside light to create shadows all around the room.

After taking the camera back to the store, they determined that the damage was in the aperture.

Compatible only with Mac OS X and being somewhat reminiscent of the operating system's iPhoto application, Aperture 3 is an excellent tool for organizing photos into libraries and projects.

The outer wall of the capsule is incomplete at one pole, leaving an aperture through which the thread is discharged.

At the front is a large slab, sometimes carved, with a small aperture in it, through which offerings might be inserted.

The nest is an inch and more in diameter, with a small aperture for an entrance.

It is necessary that the aperture of the pupil be accommodated to the angular extent of the spectrum, or reciprocally.

If a distal pore or aperture is present, it is excretory in function; suck varieties have been termed " cystons " by Haeckel.

The former are for the most part concerned with questions relating to the theory of light, arising out of his professorial lectures, among which may be specially mentioned his paper "On the Diffraction of an Object-Glass with Circular Aperture."

J Right (archaic left) nephri dium's aperture.

If an aperture for ingress and egress, for purposes of feeding, were left in the wall of such a chamber, there would arise in a rudimentary form what is known as the tubular nest or web; and the next important step was possibly the adoption of such a nest as a permanent abode for the spider., Some spiders, like the Drassidae and Salticidae, have not advanced beyond this stage in architectural industry; but next to the cocoon this simple tubular retreat - whether spun in a crevice or burrow or simply attached to the lower side of a stone - is the most constant feature to be observed in the spinning habits of spiders.

In both there are species which form no nest or burrow, others which construct a simple silk-lined tunnel in the soil, and others which close the aperture of the burrow with a hinged door; while both share the habit of lining the burrow with silk to prevent the infall of loose sand or mould; and the species which make an open burrow close the aperture with a sheet of silk in the winter during hibernation and open it again in the spring.

Be that as it may, the snare in many instances, as in that of the Agalenidae (Tegenaria, Agalena), a family closely allied to the Lycosidae, is a horizontal sheet of webbing, upon which the spider runs, continuous with the lower half of the aperture of the tube, of which it is simply an extension.

When a current is passed through the wire forming the coil, the fragment of iron is drawn more into the aperture of the coil where the field is stronger and so displaces an index needle over a scale.

The shell of Clausilia is sinistral and its aperture is provided with a hinged plate.

In the Auriculidae the aperture is denticulated.

The pseudo-deltidium (so named by Bronn in 1862) is a single plate which grows from the apex of the delthyrium downwards, and may completely close the aperture.

By the crushing action of their pincers, and an alternate backward and forward movement, they bring the soft blood-holding tissues of the victim close to the minute pin-hole aperture which is the scorpion's mouth.

The sperm is removed by the male from the genital aperture into a special receptacle on the terminal segment P FIG.

Thus held out at some distance from the body, it is cautiously advanced by the male spider to the genital aperture of the female.

A movable membranous j oint between the prosoma and the opisthosoma, the generative aperture opening upon the ventral side of the membrane.

Opisthosoma confluent throughout its breadth with the prosoma, with the dorsal plate of which its anterior tergal plates are more or less fused; at most ten opisthosomatic somites traceable; the generative aperture thrust far forwards between the basal segments of the 6th appendages.

When light passes through a small circular or annular aperture, the illumination at any point along the axis depends upon the precise relation between the aperture and the distance from it at which the point is taken.

If, as in the last paragraph, we imagine a system of zones to be drawn commencing from the inner circular boundary of the aperture, the question turns upon the manner in which the series terminates at the outer boundary.

If the aperture be such as to fit exactly an integral number of zones, the aggregate effect may be regarded as the half of those due to the first and last zones.

The amplitude of the light at any point in the axis, when plane waves are incident perpendicularly upon an annular aperture, is, as above, cos k(at-r 1)-cos k(at-r 2) =2 sin kat sin k(r1-r2), r2, r i being the distances of the outer and inner boundaries from the point in question.

The incident waves are thus plane, and are limited to a plane aperture coincident with a wave-front.

In experiment under ordinary circumstances it makes no difference whether the collecting lens is in front of or behind the diffracting aperture.

If the wave-length remains unchanged, similar effects are produced by an increase in the scale of the aperture.

We will now apply the integrals (2) to the case of a rectangular aperture of width a parallel to x and of width b parallel to y.

We readily find (with substitution for k of 27r/X) a2b S n J s in fl „2a2E2 „2b2n2 f2X2 f2X2 as representing the distribution of light in the image of a mathematical point when the aperture is rectangular, as is often the case in spectroscopes.

If the aperture be increased, not only is the total brightness over the focal plane increased with it, but there is also a concentration of the diffraction pattern.

The contraction of the diffraction pattern with increase of aperture is of fundamental importance in connexion with the resolving power of optical instruments.

This indefiniteness of images is sometimes said to be due to diffraction by the edge of the aperture, and proposals have even been made for curing it by causing the transition between the interrupted and transmitted parts of the primary wave to be less abrupt.

At the focal point (E =o, n = o) all the secondary waves agree in phase, and the intensity is easily expressed, whatever be the form of the aperture.

From the general formula (2), if A be the area of aperture, 102 = A2 / x2 f (7) The formation of a sharp image of the radiant point requires that the illumination become insignificant when, n attain small values, and this insignificance can only arise as a consequence of discrepancies of phase among the secondary waves from various parts of the aperture.

In the particular case of a rectangular aperture the course of things can be readily followed, especially if we conceive f to be infinite.

In the direction (suppose horizontal) for which n=o, /f=sin 0, the phases of the secondary waves range over a complete period when sin 0 =X/a, and, since all parts of the horizontal aperture are equally effective, there is in this direction a complete compensation and consequent absence of illumination.

The reason of the augmentation of resolving power with aperture will now be evident.

The larger the aperture the smaller are the angles through which it is necessary to deviate from the principal direction in order to bring in specified discrepancies of phase - the more concentrated is the image.

The definition of a fine vertical line, and consequently the resolving power for contiguous vertical lines, is thus independent of the vertical aperture of the instrument, a law of great importance in the theory of the spectroscope.

We conclude that a double line cannot be fairly resolved unless its components subtend an angle exceeding that subtended by the wave-length of light at a distance equal to the horizontal aperture.

If the angle subtended by the components of a double line be twice that subtended by the wave-length at a distance equal to the horizontal aperture, the central bands are just clear of one another, and there is a line of absolute blackness in the middle of the combined images.

The resolving power of a telescope with circular or rectangular aperture is easily investigated experimentally.

Merely to show the dependence of resolving power on aperture it is not necessary to use a telescope at all.

The (8), A function of the telescope is in fact to allow the use of a wider, and therefore more easily measurable, aperture.

Since the limitation of the width of the central band in the image of a luminous line depends upon discrepancies of phase among the secondary waves, and since the discrepancy is greatest for the waves which come from the edges of the aperture, the question arises how far the operation of the central parts of the aperture is advantageous.

Theory and experiment alike prove that a double line, of which the components are equally strong, is better resolved when, for example, one-sixth of the horizontal aperture is blocked off by a central screen; or the rays quite at the centre may be allowed to pass, while others a little farther removed are blocked off.

It has already been suggested that the principle of energy requires that the general expression for I 2 in (2) when integrated over the whole of the plane, n should be equal to A, where A is the area of the aperture.

It is thus sufficient to determine the intensity along the axis of p. Putting q = o, we get C = ffcos pxdxdy=2f+Rcos 'px 1/ (R2 - x2)dx, R being the radius of the aperture.

The value of C for an annular aperture of radius r and width dr is thus dC =271-Jo(Pp)pdp, (12).

The first dark ring in the diffraction pattern of the complete circular aperture occurs when r/f = 1.2197 XO /2R (15).

Again, if we compare the complete circle with a narrow annular aperture of the same radius, we see that in the latter case the first dark ring occurs at a much smaller obliquity, viz.

It has been found by Sir William Herschel and others that the definition of a telescope is often improved by stopping off a part of the central area of the object-glass; but the advantage to be obtained in this way is in no case great, and anything like a reduction of the aperture to a narrow annulus is attended by a development of the external luminous rings sufficient to outweigh any improvement due to the diminished diameter of the central area.'

It may be instructive to contrast this with the case of an infinitely narrow annular aperture, where the brightness is proportional to Jo 2 (z).

The diminution of the star disks with increasing aperture was observed by Sir William Herschel, and in 1823 Fraunhofer formulated the law of inverse proportionality.

Foucault, who employed a scale of equal bright and dark alternate parts; it was found to be proportional to the aperture and independent of the focal length.

The illumination at B due to P then becomes comparatively small, indeed for some forms of aperture evanescent.

The denominator sin a is the quantity well known (after Abbe) as the " numerical aperture."

If 2R be the diameter of the objectglass and D the distance of the object, the angle subtended by AP is E/D, and the angular resolving power is given by X/2 D sin a = X/2 R (3) This method of derivation (substantially due to Helmholtz) makes it obvious that there is no essential difference of principle between the two cases, although the results are conveniently stated in different forms. In the case of the telescope we have to deal with a linear measure of aperture and an angular limit of resolution, whereas in the case of the microscope the limit of resolution is linear, and it is expressed in terms of angular aperture.

Since at these points the resultant due to the whole aperture is zero, any two portions into which the whole may be divided must give equal and opposite resultants.

Consider now the light diffracted in a direction many times more oblique than any with which we should be concerned, were the whole aperture uninterrupted, and take first the effect of a single small aperture.

The light in the proposed direction is that determined by the size of the small aperture in accordance with the laws already investigated, and its phase depends upon the position of the aperture.

If we take a direction such that the light (of given wave-length) from a single aperture vanishes, the evanescence continues even when the whole series of apertures is brought into contemplation.

Hence, whatever else may happen, there must be a system of dark rings formed, the same as from a single small aperture.

The diffraction pattern is therefore that due to a single aperture, merely brightened n times.

The aberration is here unsymmetrical, the wave being in advance of its proper place in one half of the aperture, but behind in the other half.

The function of a lens in forming an image is to compensate by its variable thickness the differences of phase which would otherwise exist between secondary waves arriving at the focal point from various parts of the aperture.

But, as we have seen, such an error of phase causes no sensible deterioration in the definition; so that from this point onwards the lens is useless, as only improving an image already sensibly as perfect as the aperture admits of.

Throughout the operation of increasing the focal length, the resolving power of the instrument, which depends only upon the aperture, remains unchanged; and we thus arrive at the rather startling conclusion that a telescope of any degree of resolving power might be constructed without an object-glass, if only there were no limit to the admissible focal length.

To get an idea of the magnitudes of the quantities involved, let us take the case of an aperture of 1 in., about that of the pupil of the eye.

As the minimum focal length increases with the square of the aperture, a quite impracticable distance would be required to rival the resolving power of a modern telescope.

Even for an aperture of 4 in., f 1 would have to be 5 miles.

Calculation shows that, if the aperture be s in., an achromatic lens has no sensible advantage if the focal length be greater than about II in.

If we suppose the focal length to be 66 ft., a single lens is practically perfect up to an aperture of 1 .

When parallel rays fall directly upon a spherical mirror the longitudinal aberration is only about one-eighth as great as for the most favourably shaped single lens of equal focal length and aperture.

If the grating be composed of alternate transparent and opaque parts, the question may be treated by means of the general integrals (§ 3) by merely limiting the integration to the transparent parts of the aperture.

If, however, we assume the theory of a simple rectangular aperture (§ 3); the results of the ruling can be inferred by elementary methods, which are perhaps more instructive.

If now we suppose the aperture AB to be covered by a great number of opaque strips or bars of width d, separated by transparent intervals of width a, the condition of things in the directions just spoken of is not materially changed.

If it were possible to introduce at every part of the aperture of the grating an arbitrary retardation, all the light might be concentrated in any desired spectrum.

All the errors, except that depending on a, and especially those depending on -y and S, can be diminished, without loss of resolving power, by contracting the vertical aperture.

If the semi-angular aperture (w) be T 36, and tan 0' might be as great as four millions before the error of phase would reach 4X.

It is as far as possible from being true that a body emitting homogeneous light would disappear on merely covering half the aperture of vision with a half-wave plate.

A fraction of a second later the aperture occupies a bright place, and the star reappears.

The aperture of the unretarded beam may thus be taken to be limited by x = - h, x = o, y= - 1, y= +1; and that of the beam retarded by R to be given by x =o, x =h, y = - 1, y = +l.

Black bands will be too fine to be well seen unless the aperture (2h) of the pupil be somewhat contracted.

The aperture and the number of bands being both fixed, the condition of blackness determines the angular magnitude of a band and of the spectrum.

If a telescope be employed there is a distinction to be observed, according as the half-covered aperture is between the eye and the ocular, or in front of the object-glass.

If, however, the half-covered aperture be in front of the object-glass, the phenomenon is magnified as a whole, and the desirable relation between the (unmagnified) dispersion and the aperture is the same as without the telescope.

Suppose now that the plate is introduced so as to cover half the aperture and that it retards those pulses which would otherwise arrive first.

As this increases from zero, the two processions which correspond to the two halves of the aperture begin to overlap, and the overlapping gradually increases until there is almost complete superposition.

If the eye, provided if necessary with a perforated plate in order to reduce the aperture, be situated inside the shadow at a place where the illumination is still sensible, and be focused upon the diffracting edge, the light which it receives will appear to come from the neighbourhood of the edge, and will present the effect of a silver lining.

Indeed, if the aperture is very small, this method gives the correct result, save as to a constant factor.

The price, however, rapidly increases with the total bulk of perfect glass required in one piece, so that large disks of glass suitable for telescope objectives of wide aperture, or blocks for large prisms, become exceedingly costly.

Round disks made of these substances were placed in a closely fitting cylindrical cavity drilled in a block of steel, the cavity having a circular aperture of two or four centimetres below.

He had discovered a contraction in the vein of fluid (vena contracta) which issued from the orifice, and found that, at the distance of about a diameter of the aperture, the section of the vein was contracted in the subduplicate ratio of two to one.

He seems to have been well acquainted with the projection of images of objects through small apertures, and to have been the first to show that the arrival of the image of an object at the concave surface of the common nerve - or the retina - corresponds with the passage of light from an object through an aperture in a darkened place, from which it falls upon a surface facing the aperture.

Leonardo also discussed the old Aristotelian problem of the rotundity of the sun's image after passing through an angular aperture, but not so successfully as Maurolycus.

The sun shining, he fixed a round glass speculum (orbem e vitro) in a window-shutter, and then closing it the images of outside objects would be seen transmitted through the aperture on to the opposite wall, or better, a white paper screen suitably placed.

He discloses as a great secret the use of a concave speculum in front of the aperture, to collect the rays passing through it, when the images will be seen reversed, but by prolonging them beyond the centre they would be seen larger and unreversed.

The second edition, in which he in the same words discloses the use of a convex lens in the aperture as a secret he had intended to keep, was not published till 1589, thirty-one years after the first.

In the Diversarum Speculationum Mathematicarum et Physicarum (1585), by the Venetian Giovanni Battista Benedetti, there is a letter in which he discusses the simple camera obscura and mentions the improvement some one had made in it by the use of a double convex lens in the aperture; he also says that the images could be made erect by reflection from any plane mirror.

There is no mention whatever of a portable box or construction beyond the darkened room, nor is there in his later work, De Refractione Optices Parte (1593), in which he discusses the analogy between vision and the simple dark room with an aperture, but incorrectly.

At one end of it paper was stretched, and at the other a convex lens was fitted in a hole, the image being viewed through an aperture at the top of the box.

Usually this aperture is median, but occasionally asymmetrical.

The excretory system is highly developed; the larger collecting ducts are elaborately looped and open posteriorly by a single terminal aperture.

In the other venomous snakes (viperines and crotalines) the maxillary bone is very short, and is armed with a single very long curved fang with a canal and aperture at each end.

In the limiting case of a long fine tube, the bore of which varies in such a manner that U is constant, the state of the substance along a line of flow may be represented by the line of constant total heat, d(E+pv) = o; but in the case of a porous plug or small throttling aperture, the steps of the process cannot be followed, though the final state is the same.

The discharge of the comminuted material takes place through an aperture, which is covered by a thin steel plate perforated with numerous slits about Ath in.

Here is the Porta dell' Arco, a gate of the old wall, with an aperture 15 ft.

The brightness of the image is sometimes in creased by silvering the glass; and on removing a small portion of the silver the observer can Object see the image with part of the pupil while he sees the paper through the unsilvered aperture with the remaining part.

The object-glass has an aperture of 62 in.

Dawes found the best method for the purpose in question was to limit the aperture of the object-glass by a diaphragm having a double circular aperture, placing the line joining the centres of the circles approximately in the position angle under measurement.

Dawes successfully employed the double circular aperture also with Amici's micrometer.

The size of the discharge aperture can be varied by means of a flexible wooden shutter sliding in a groove in a cast iron plate, curved to the slope of the casing.

Almost the only characters they possess in common are the short and spike-like horns of the bucks, which are ringed at the base, with smooth tips, and the large size of the face-gland, which opens by a circular aperture.

The duikers, or duikerboks (Cephalophus), of Africa, which range in size from a large hare to a fallow-deer, typify the subfamily Cephalophinae, characterized by the spike-like horns of the bucks, the elongated aperture of the face-glands, the naked muzzle, the relatively short tail, and the square-crowned upper molars; lateral hoofs being present.

The blanks fall through an aperture after having been heated for a few minutes.

Thecurrent being alternately transmitted and shut off, as a hole passes on and off the aperture of the tube or bellows, causes a vibratory motion of the air, whose frequency depends on the number of times per second that a perforation passes the mouth of the tube.

The dome has a small aperture in the top which remains open to preclude accumulation of pressure.

Aperture, and a Selection from the Observations of Nebulae made with them," with numerous engravings.

The foot is very large and powerful; it can be protruded from the anterior aperture between the mantle edges, and its outer part is bent sharply forwards and terminates in a point.

A second closely-allied genus of this family is Pseudobranchus, differing in having a single branchial aperture on each side instead of three, and only three fingers.

Aperture by which the left auricle joins the ventricle.

When the edges of the mantle ventral to the inhalant orifice are united, an anterior aperture is left for the protrusion of the foot, and thus there are three pallial apertures altogether, and species in this condition are called " Tripora."

When the pedal aperture is small and far forward there may be a fourth aperture in the region of the fusion behind the pedal aperture.

The genital duct opens by a pore into the urino-genital groove of the oyster (the same arrangement being repeated on each side of the body) close to but distinct from the aperture of the nephridial canal.

In the most primitive Lamellibranchs there is no separate generative aperture but the gonads discharge into the renal cavity, as in Patella among Gastropods.

These forms are hermaphrodite, with an ovary and testis completely separate from each other on each side of the body, each having its own duct and aperture.

The special gland of the musk-deer, which has made the animal so well known, and has proved the cause of unremitting persecution to its possessor, is found in the male only, and is a sac about the size of a small orange, situated beneath the skin of the abdomen, the orifice being immediately in front of the preputial aperture.

This opening in a uterus which has never been pregnant is a narrow transverse slit, rarely a circular aperture, but in those uteri in which pregnancy has occurred the slit is much wider and its lips are thickened and gaping and often scarred.

In the higher forms the opening of the gonad is shifted more and more towards the external aperture of each kidney until finally it is situated on the external surface, and thus the gonad secondarily acquires an independent aperture.

These conditions may be generally satisfied by projecting the image of the source on the slit with a lens of sufficient aperture.

When the slit is narrow light is lost through diffraction unless the angular aperture of this condensing lens, as viewed from the slit, is considerably greater than that of the collimator lens.

Meinert, open to the exterior by a median aperture, the terminal part of the duct being single, either by the fusion of the primitive paired ducts or by the suppression of one of them.

A simple gonaduct on each side arises from the gonad near its posterior end and passes first forwards, then backwards, and lastly outwards to the external opening in the pallial groove, anterior to the renal aperture.

The chief difference is that the gonad or generative portion of the coelom is single and median, opening into the pericardium by a single posterior aperture.

Pieces which vary materially in cross section from point to point in their length cannot well be made by rolling, because the cross section of the piece as it emerges from the rolls is necessarily that of the aperture between the rolls from which it is emerging, and this aperture is naturally of constant size because the rolls are cylindrical.

The setting in the meridian is effected by turning the instrument after setting for latitude until a pin-hole aperture s and a small screen P, placed so that Ps is parallel to CO, are in a line with the sun.

When all is taken into consideration it is scarcely possible to reduce the secondary colour aberration at the focus of such a double object-glass to less than a fourth part of that prevailing at the focus of a double objective of the same aperture and focus, but made of the ordinary crown and flint glasses.

Silvered mirrors have also some advantage in light grasp over those of speculum metal, though, aperture for aperture, the former are inferior to the modern object-glass.

In these telescopes the photographic objectglass has an aperture of 13 in.

If steam or vapour is " wire-drawn " or expanded through a porous plug or throttling aperture without external loss or gain of heat, the total heat (E+pv) remains constant (Thermodynamics, § I I), provided that the experiment is arranged so that the kinetic energy of flow is the same on either side of the throttle.

Another beautiful illustration is easily obtained by cutting with a sharp knife a very small T aperture in a piece of note paper.

The collapse of the gold-leaf is observed through an aperture in the case by a miscroscope, and the time taken by the goldleaf to fall over a certain distance is proportional to the ionizing current, that is, to the intensity of the radio-activity of the substance.

Any divergence or collapse of the gold-leaf can be viewed by a microscope through an aperture in the side of the case.

The vestibule of the mouth is the space bounded by the oral hood; this arises by secondary downgrowth of lid-like folds over the true oral aperture, and is provided with a fringe of tentacular cirri, each of which is supported by a solid skeletal axis.

The atrial region extends from the mouth over about twothirds of the length of the body, terminating at a large median ventral aperture, the atriopore; this is the excurrent orifice for the respiratory current of water and also serves for the evacuation of the generative products.

At the top of each of these pouches there is a minute orifice, the aperture of a small tubule lying above each pouch in the dorsal coelom.

If the system be entirely behind the aperture stop, then this is itself the entrance pupil (" front stop "); if entirely in front, it is the exit pupil (" back stop ").

This distance replaces the angle u in the preceding considerations; and the aperture, i.e.

With a considerable aperture, the neighbouring point N will be reproduced, but attended by aberrations comparable in magnitude to ON.

Both the aberration of axis points, and the deviation from the sine condition, rapidly increase in most (uncorrected) systems with the aperture.

If the above errors be eliminated, the two astigmatic surfaces united, and a sharp image obtained with a wide aperture - there remains the necessity to correct the curvature of the image surface, especially when the image is to be received upon a plane surface, e.g.

It requires the middle of the aperture stop to be reproduced in the centres of the entrance and exit pupils without spherical aberration.

In the mathematical sense, however, this selection is arbitrary; the reproduction of a finite object with a finite aperture entails, in all probability, an infinite number of aberrations.

This number is only finite if the object and aperture are assumed to be " infinitely small of a certain order"; and with each order of infinite smallness, i.e.

Each of the four co-ordinates, n', x', y are functions of %, rj, x, y; and if it be assumed that the field of view and the aperture be infinitely small, then, n, x, y are of the same order of infinitesimals; consequently by expanding ', ii', x', y in ascending powers of E, rt, x, y, series are obtained in which it is only necessary to consider the lowest powers.

The existence of an optical system, which reproduces absolutely a finite plane on another with pencils of finite aperture, is doubtful; but practical systems solve this problem with an accuracy which mostly suffices for the special purpose of each species of instrument.

The rays with an angle of aperture smaller than u* would not have the same distance of intersection and the same sine ratio; these deviations are called "zones," and the constructor endeavours to reduce these to a minimum.

Spherical aberration and changes of the sine ratios are often represented graphically as functions of the aperture, in the same way as the deviations of two astigmatic image surfaces of the image plane of the axis point are represented as functions of the angles of the field of view.

The final form of a practical system consequently rests on compromise; enlargement of the aperture results in a diminution of the available field of view, and vice versa.

For infinitely distant objects the radius of the chromatic disk of confusion is proportional to the linear aperture, and independent of the focal length (vide supra," Monochromatic Aberration of the Axis Point "); and since this disk becomes the less harmful with an increasing image of a given object, or with increasing focal length, it follows that the deterioration of the image is proportional to the ratio of the aperture to the focal length, i.e.

After escaping from the genital aperture they find their way into the infra-branchial part of the mantle cavity of the parent, probably by passing through the suprabranchial chamber to the posterior extremity of the gills, and then being conducted by the inhalent current caused by the cilia of the gills into the infra-branchial chamber.

This aperture is not the original mouth, the latter being a chasm a quarter of a mile north of it, and leading into what is known as Dixon's cave.

The disturbances by which equilibrium is upset are impressed upon the fluid as it leaves the aperture, and the continuous portion of the jet represents the distance travelled during the time necessary to produce disintegration.

The right and left margins of the mantle are united ventrally, leaving an anterior and posterior aperture to the mantle cavity.

The edge of the mantle at the anterior aperture is very thick and muscular; at the posterior aperture also there is a circular muscle, and here the edge is interrupted by a ventral sinus and is provided internally with a dorsal and ventral valve which can be applied to each other so as to close the aperture.

The captacula are tactile and prehensile and can be protruded from the anterior aperture of the mantle.

The foot is elongated and cylindrical, and can be protruded from the anterior aperture to serve as a burrowing organ.

The head is situated on the dorsal side of the body anteriorly within the anterior aperture of the mantle, from which it cannot be protruded.

Shell curved with greatest diameter at anterior aperture and diminishing gradually to posterior.

Foot expanded distally into a symmetrical disk with a crenate edge or simple and vermiform without well-developed lateral processes; shell often contracted towards the anterior aperture.

The mouth and cloacal aperture are generally at opposite ends of the ventral surface.

The aperture of the ear is exceedingly minute; the eyes are of moderate size and the blow-hole is crescent-shaped.

The rate of increase of velocity towards any isolated aperture through which water passes into the side of a well sunk in a deep bed of sand is, in the neighbourhood of that aperture, inversely proportional to the square of the distance therefrom.

The arc being struck in the usual way between two carbons, a concave mirror, placed close behind it, caused a large part of the radiation to be directed through an aperture in the camera and concentrated to a focus outside.

In front of the aperture were placed a plate of transparent rock-salt, and a flat cell of thin glass containing a solution of iodine in carbon bisulphide.

Lankester (2) was the first to suggest that (as is actually the fact in the Nauplius larva of the Crustacea) the prae-oral somites or prosthomeres and their appendages were ancestrally postoral, but have become prae-oral " by adaptational shifting of the oral aperture."

The original stock, like that of the last grade, has a gnathobase on every post-oral appendage, but three prosthomeres are now present, in consequence of the movement of the oral aperture from the third to the fourth somite.

In fact, we have to suppose that the actual somite which in grades 1 and 2 bore the mandibles lost those mandibles, developed their rami as tactile organs, and came to occupy a position in front of the mouth, whilst its previous jaw-bearing function was taken up by the next somite in order, into which the oral aperture had passed.

Benham describes backward shifting of the oral aperture in certain Chaetopods, Proc. Zoolog.

By analogy the term "to cork" is used of any such devices for sealing up a bottle or aperture.

A beam of sunlight admitted into a darkened room through a narrow aperture, and there dispersed into a vario-tinted band by the interposition of a prism, is not absolutely W continuous.

Its duct leaves the inferior anterior angle, at first descends a little, and runs forward under cover of the rounded inferior border of the lower jaw, then curves up along the anterior margin of the masseter muscle, becoming superficial, pierces the buccinator, and enters the mouth by a simple aperture opposite the middle of the crown of the third premolar tooth.

Male with four accessory glands, opening on each side of and behind the genital aperture.

When the pupil regulates the aperture of the rays producing the image the aberrations of the ordinary lenses increase considerably with the magnification, or, what amounts to the same thing, with the increase in the curvature of the surfaces.

For lenses of short focus the diameter of the pupil is too large, and diaphragms must be employed which strongly diminish the aperture of the pencils, and so reduce the errors, but with a falling off of illumination.

A diminution of the aperture, however, would injure a very much more important property, viz.

This is specially important, for otherwise pencils from points placed somewhat laterally to the axis arrive with diminished aperture at the image.

As the pencils used in the representations are of wide aperture on the object-side, only such points as are proportionately very near the focal plane can produce such small dispersion circles on the plane focused for, that they, so far as the objectiveand eyepiece-magnification permit, appear as points to the eye.

The brightnesses of image points in a median section of the pencil are proportional to the aperture of the lens, supposing that the rays are completely reunited.

The function n sin u = A, for the microscope, has been called by Abbe the numerical aperture.

On the other hand, in immersion-systems the numerical aperture can almost amount to the refractive index, for A=n sin u

If in this case the aperture of the objective be so small, or the diffraction spectra lie so far from each other, that only the pencil parallel to the axis, i.e.

From the Fraunhofer formula I =X/n sin a one can immediately deduce the limit to the diffraction constant I, so that the banding by an objective of fixed numerical aperture can be perceived.

The value n sin u equals the numerical aperture A, where n is the refractive index of the immersion-liquid, and u is the semi-aperture on the object-side.

If microscopic preparations are observed by diffused daylight or by the more or less white light of the usual artificial sources, then an objective of fixed numerical aperture will only represent details of a definite fineness.

With the best immersion-system, having a numerical aperture of 1.6, details of the size o.

As the microscopist usually estimates the resolving power according to the aperture with ordinary day-light, Kohler introduced the " relative resolving power " for ultra-violet light.

Then the denominator of the fraction, the numerical aperture, must be correspondingly increased, in order to ascertain the real resolving power.

In this way a monochromat for glycerin of a numerical aperture 1.25 gives a relative numerical aperture of 2.50.

If the magnification be greater than the resolving power demands, the observation is not only needlessly made more difficult, but the entrance pupil is diminished, and with it a very considerable decrease of clearness, for with an objective of a certain aperture the size of the exit pupil depends upon the magnification.

From the section Regulation of the Rays (above) it is seen that the resolving power is opposed to the depth of definition, which is measured by the reciprocal of the numerical aperture, I/A.

As shown in Lens and Aberration, for reproduction through a single lens with spherical surfaces, a combination of the rays is only possible for an extremely small angular aperture.

The aberrations, both spherical and chromatic, increase very rapidly with the aperture.

Owing to these aberrations, the fine structure, which in consequence of the large aperture could be resolved, could not be perceived.

The rays emitted from an axial object-point are not combined into one image-point by an ordinary biconvex lens of fixed aperture, but the central rays come to a more distant focus than the outer rays.

Correction of the spherical aberration in strong systems with very large aperture can not be brought about by means of a single combination of two lenses, but several partial systems are necessary.

A well-corrected microscope objective with a wide aperture therefore can only represent, free from aberrations, one object-element situated on a definite spot on the axis.

This system will always be aplanatic. These objectives permitted a much larger aperture than a simple achromatic system.

He had recognized that the good operation of a microscope objective depended essentially upon the size of the aperture, and he therefore endeavoured to produce systems with wide aperture and good correction.

He also showed the influence of the cover-slip on pencils of such wide aperture.

For this reason Amici constructed objectives of a similar aperture and focus for different thicknesses of glass covers.

The alteration of the focus and the aperture are little influenced.

To fully utilize the aperture of the system all dispersing rays in the object-space of the objective must be retained in the imagespace of the illuminating system.

If the aperture of the objective is increased, the diameter of the illuminating surface must also be increased so that the system is quite filled up, from which it follows that this method of illuminating soon fails.

As a rule a concave mirror of similar aperture is fitted on the other side of the plane mirror.

Hence a condenser, for lighting with very oblique cones, must have about the same aperture as the objective, and therefore be of very wide aperture; they therefore closely resemble microscope objectives in construction.

In dark field illumination care has to be taken that no direct rays reach the objective, and hence a good dark field illumination can be produced if the condenser system has a larger aperture than the objective.

This diaphragm is sometimes fixed to a handle piercing the condenser, and which can be moved up and down, so that the aperture of the oblique entering cones of rays can be altered.

On account of the slight depth definition, short focused systems of wide aperture are not at all specially suitable for stereoscopic observation, because the possibility of observing objects taking up a good deal of space is too limited when such systems are used.

The resolving power of an objective depends on its numerical aperture.

The numerical aperture can be determined in two ways.

The ratio of half the length of the visible piece of the scale to its distance from the diaphragm on the stage gives the tangent of half the angular aperture.

The sine of this angle is the numerical aperture for dry lenses.

The angular or numerical aperture can then be read off.

If the numerical aperture be known the resolving power is easily found.

Such forms he distinguished as Coelentera, and showed that they had no special affinity with echinoderms, polyzoa, &c. He divided the Coelentera into a group Hydrozoa, in which the sexually produced embryos were usually set free from the surface of the body, and a group Actinozoa, in which the embryos are detached from the interior of the body and escape generally by the oral aperture.

The oviducts are long, usually more or less convoluted tubes which open posteriorly into the cloaca, while their anterior aperture is situated far forward, sometimes close to the root of the lung; their walls secrete a gelatinous substance which invests the ova as they descend.

They are good value for money but are not optically brilliant, a small aperture essential to eliminate the aberrations of the lens.

Magellan synthetic aperture radar data is combined with radar altimetry to develop a three-dimensional map of the surface.

Thus an INNER radius of 1 means that the sky annulus starts where the object aperture ends.

The only window has a deeply splayed aperture, the sloping sill utilizing a cross slab; a modern lintel.

For a circular aperture this should be set to 0.0.

The audience enter a booth one at a time to watch a three minute performance through a small rectangular aperture.

For grasp, maximum grip aperture and time to maximum grip aperture were measured.

See the ' How can I change my AGP aperture size?

The condenser aperture controls the fraction of the beam which is allowed to hit the specimen.

However the center column shows that the rate of fall was greater for the narrower pallet aperture.

You can use the guide number to work out the lens aperture for the correct exposure at any distance.

The tiny aperture that serves as both entrance and exit to this great basilica constitutes a danger to pilgrims.

For uniform surface brightness sources, an aperture with an area of 1 square arcsec is used.

The latter is determined by the lens aperture, CCD integration time, and the sensitivity of the silicon CCD detector.

A very commonly used dry condenser has a numerical aperture (NA) of 0.9.

Figure 2. The aperture in a phase contrast plate is moved off-center in regards to the center of the sub-stage condenser.

Images are so contrasty and for the aperture the images are incredible.

I used a scanning densitometer with a very small aperture and averaged over many scans across an image of interest.

Delighted with his find he slipped in through the narrow aperture and greedily devoured it all.

The aperture diaphragm is located at the light guide end.

Köhler lighting systems have an iris or field diaphragm which controls the aperture of light going into the condenser.

Aperture If you care about taking pictures in low light look at the maximum f-stop your camera can support.

The maker's stated specification is a ' 0.25 mm aperture grill pitch ' .

Most monitors are shadow mask or aperture grille in design.

Open the substage iris diaphragm fully, since the condenser needs to be operating at maximum aperture.

They have a floating mullion fixed to one door sash, which allows the total aperture to be a clear opening with no obstructions.

The 150mm aperture enables you to observe bright nebulas in the depth of space.

The display uses a permanent magnet that is perforated to provide an aperture for each pixel.

In both modes the user may perform photometry using either the traditional aperture method or using optimal extraction.

The source counts and their errors were calculated using circular aperture photometry centered at the listed source position.

Some entries are from photoelectric aperture photometry or from CCD photometry with the Whipple Observatory 24 inch.

For instance, you might wish to change the aperture diameter for the aperture photometry.

On beamline 5D circularly polarized photons are selected by means of a defining aperture, or chopper.

For those times when creative expression is desired, the aperture priority, shutter priority or full manual settings allow greater control.

The modified Bombardier Global Express is fitted with an active synthetic aperture radar for ground surveillance.

This was to be a photographic refractor, with an object-glass of 13 inches aperture and 11 feet focus.

The aperture for the single bell has a two-centred arch with chamfered dressings in buff-yellow sandstone.

In front of the shutter button is the main dial which is used to adjust shutter button is the main dial which is used to adjust shutter speed or aperture settings.

The 12ins square dial is mounted with turban head and foliage spandrels, a silvered chapter ring, seconds ring and calendar aperture.

The sky subtraction aperture is assumed to the 5 times larger than the object aperture.

Under average seeing conditions, atmospheric turbulence limits the highest useful magnification to 25 to 30 times per unit of aperture.

This consists of passing a sail, attached to cords, and charged with oakum, wool, and other materials, under the vessel's keel, in such a manner that the suction of the leak may draw the canvas into the aperture, and thus partially stop the vent.

The instrumental equipment of that observatory was somewhat antiquated, his largest telescope being a small refractor of 73 lines aperture, but he selected a line of work to suit the instruments at his disposal, observing nebulae and variable stars and keeping a watch on comets and new planets.

The inner membrane is continuous with the wall of the hollow thread at a spot immediately below the aperture in the outer wall, so that the thread itself (f) is simply a hollow prolongation of the wall of the inner capsule inverted and pushed into its cavity.

From the open condition arises the closed condition very simply by closing up of the aperture of the pit.

The medusae In such a system the dactylo- 'gastropore, so that the entire single aperture subdivided by FIG.

The spores escape generally by means of a distinct aperture which appears in the top of the ball.

More usually, and indeed in nearly every other case among the Oligochaeta and Hirudinea, the coelomic aperture of the nephridium consists of several cells, ciliated like the nephridium itself for a greater or less extent, forming a funnel.

In this category are included (by Goodrich and Lankester) the gonad ducts of the Oligochaeta, certain funnels without any aperture to the exterior that have been detected in Nereis, &c., funnels with wide and short ducts attached to nephridia in other Polychaeta, gonad ducts in the Capitellidae, the gonad ducts of the leeches.

I I.-Liotiidae, shell globular, margin of aperture thickened.

Internally this glandular sac presents a second slit or aperture which leads into the pericardium (as is now found to be the case in all Mollusca).

As contrasted r', Aperture of the neph with the Aspidobranchia, we find that in ridium (kidney).

The aperture, which was formerly supposed to be an aquiferous pore, leads into an extensive and often ramified cavity surrounded by glandular tubules.

No ctenidium, pallial cavity transformed into a lung; aperture of shell circular; terrestrial.

Shell depressed, with rounded aperture; cephalic tentacles long.

Shell with numerous tuberculated whorls; aperture canaliculated anteriorly; short pallial siphon.

Shell conical; aperture slightly canaliculated; siphon slightly developed.

Shell elongated; aperture expanded; siphon very short.

Shell ventricose, with short spire, and wide aperture; no varices and no operculum; foot very broad, with projecting anterior angles; siphon long.

Shell fusiform and solid, aperture elongated, columella folded; no operculum; eyes on sides of tentacles.

Spire of shell prominent, aperture narrow, canal very short, columella crenelated; foot large.

Shell turriculated, with numerous whorls; aperture and operculum oval; eyes at summits of tentacles; siphon long.

In the most primitive condition the genital duct is single throughout its length and has a single external aperture; it is therefore said to be monaulic. The hermaphrodite aperture is on the right side near the opening of the pallial cavity, and a ciliated groove conducts the spermatozoa to the penis, which is situated more anteriorly.

In some cases while the original aperture remains undivided, the seminal groove is closed and so converted into a canal.

Originally in this condition the female aperture is at some distance from the male, as in the Basommatophora and in other cases; but in some forms the female aperture itself has shifted and come to be contiguous with the male opening and penis as in the Stylommatophora.

In front of the osphradium is the single genital pore, the aperture of the common or hermaphrodite duct.

Hermaphrodite genital aperture, connected with the penis by a ciliated groove, except in Actaeon, Lobiger and Cavolinia longirostris, in which the spermiduct is a closed tube.

Cephalic shield broad, thick and simple; shell wholly internal, thin, spire much reduced, aperture very large.

The ctenidium is atrophied, and the edge of the mantle-skirt is fused to the dorsal integument by concrescence, except at one point which forms the aperture of the mantle-chamber, thus converted into a nearly closed sac. Air is admitted to this sac for respiratory and hydrostatic purposes, and it thus becomes a lung.

The shell of the Pulmonata, though always light and delicate, is in many cases a well-developed spiral " house," into which the creature can withdraw itself; and, although the foot possesses no operculum, yet in Helix the aperture of the shell is closed in the winter by a complete lid, the " hybernaculum," more or less calcareous in nature, which is secreted by the froot.

Terrestrial and usually littoral; genital duct monaulic, the penis being connected with the aperture by an open or closed groove; shell with a prominent spire, the internal partitions often absorbed and the aperture denticulated.

Shell with short spire, and wide oval aperture; tentacles short.

Shell ovoid, with short spire, wide aperture and folded columella; inferior pallial lobe thick; visceral commissure still twisted.

Visceral mass and shell sinistrally coiled; shell thin, with narrow aperture; no inferior pallial lobe.

Shell with medium spire, external or partly covered by the mantle; genital aperture below the right posterior tentacle; genital apparatus generally provided with a dart-sac and multifid vesicles.

Shell external, spiral, generally ornamented with ribs; borders of aperture thin and not reflected; radula with square teeth; genital ducts without accessory organs.

Shell oval, elongated, with narrow aperture; neck very long; labial palps prominent.

Helix hibernates in a torpid condition for about four months, and during this period the aperture of the shell is closed by a calcareous membrane secreted by the foot.

The linear dimension of the diffraction pattern is inversely as that of the aperture, and the brightness at corresponding points is as the square of the area of aperture.

If we imagine the aperture reduced to two equal narrow slits bordering its edges, compensation will evidently be complete when the projection on an oblique direction is equal to 2X, instead of X as for the complete aperture.

Since A' is in some sense the area of the diffraction pattern, it may be considered to be a rough criterion of the definition, and we infer that the definition of a point depends principally upon the area of the aperture, and only in a very secondary degree upon the shape when the area is maintained constant.

In telescopes of the best construction and of moderate aperture the performance is not sensibly prejudiced by outstanding aberration, and the limit imposed by the finiteness of the waves of light is practically reached.

If, however, as in practice, the light be heterogeneous, the source of finite area, the obstacles in motion, and the discrimination of different directions imperfect, we are concerned merely with the mean brightness found by varying the arbitrary phase-relations, and this is obtained by simply multiplying the brightness due to a single aperture by the number of apertures (n) (see Interference Of Light, § 4).

The results in the second case show that an increase of aperture up to that corresponding to an extreme aberration of half a period has no ill effect upon the central band (§ 3), but it increases unduly the intensity of one of the neighbouring lateral bands; and the practical conclusion is that the best results will be obtained from an aperture giving an extreme aberration of from a quarter to half a period, and that with an increased aperture aberration is not so much a direct cause of deterioration as an obstacle to the attainment of that improved definition which should accompany the increase of aperture.

If, on the other hand, we suppose the aperture given, we find that aberration begins to be distinctly mischievous when it amounts to about a quarter period, i.e.

If it were desired to use an angular aperture so large that the aberration according to (13) would be injurious, Rowland points out that on his machine there would be no difficulty in applying a remedy by making v slightly variable towards the edges.

Oughtred's English edition (1633) of the Recreations mathematiques (1627) of Jean Leurechon ("Henry van Etten") there is a quaint description, with figures, of the simple dark chamber with aperture, and also of a sort of tent with a lens in it and the projection on an inner wall of the face of a man standing outside.