- 行业: Printing & publishing
- Number of terms: 178089
- Number of blossaries: 0
- Company Profile:
McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A mechanism for lifting and supporting loads, usually of large size. A screw jack mechanism consists of a thrust collar and a nut which rides on a bolt; the threads between the nut and bolt normally have a square shape. A standard form of screw jack has a heavy metal base with a central threaded hole into which fits a bolt capable of rotation under a collar thrusting against the load. Screw jacks are also used for positioning mechanical parts on machine tools in order to carry out manufacturing processes. These jacks are small in size and have standard V threads. Load and stress calculations may be performed on screw jacks in the same manner as in power screws and screw fastenings.
Industry:Science
A mechanism for the transfer of genetic material between cells. The material is transferred by virus particles called bacteriophages (in the case of bacteria), or phages. The transfer method differentiates transduction from transformation. In transformation the genetic material (deoxyribonucleic acid) is extracted from the cell by chemical means or released by lysis.
Industry:Science
A mechanism in which a toothed wheel engages alternate pallets attached to an oscillating member. The escapement is found principally in timepieces but may be employed wherever oscillating motion is required. Its origins are ancient and obscure.
Industry:Science
A mechanism of orientation by means of which an animal moves in a direction related to a source of stimulation. There exists a widely accepted terminology in which the nature of the stimulus is indicated by a prefix such as phototaxis, chemotaxis, geotaxis (gravity), thigmotaxis (contact), rheotaxis (water current), and anemotaxis (air current). The directions toward or away from the stimulus are expressed as positive or negative, respectively. Finally, the sensory and locomotory mechanisms by means of which the orientation is achieved are denoted by a second type of prefix forming a compound noun with taxis. Positive phototropotaxis thus describes a mechanism by means of which an animal carries out a directed movement toward a source of light along a path which permits the animal's paired eyes to receive equal intensities of light throughout the movement. The following are examples of various types of taxes.
Industry:Science
A mechanism that produces a straight-line (or nearly so) output motion from an input element that rotates, oscillates, or moves in a straight line. Common machine elements, such as linkages, gears, and cams, are often used in ingenious ways to produce the required controlled motion. The more elegant designs use the properties of special points on one of the links of a four-bar linkage.
Industry:Science
A mechanism that stitches cloth, leather, book pages, and other material by means of a double-pointed needle or an eye-pointed needle. In ordinary two-threaded machines, a lock stitch is formed (see <b>illus</b>.). An eye-pointed reciprocating needle carries an upper thread through the layers of fabric, forming a loop beneath the material. A shuttle carrying a bobbin of under thread passes through the loop. Alternatively, a rotary hook takes the loop of upper thread and passes it around the bobbin of under thread. The needle withdraws, and a thread take-up lever pulls the stitch tight. The machine carries out these necessary motions and also feeds the material past the needle intermittently between each pass of the needle. A presser foot held against the material with a yielding spring adjusts itself automatically to variations in thickness of material and allows the operator to turn the material as it feeds through the machine. A cluster of cams, any one of which can be selected to guide the needle arm, makes possible a variety of stitch patterns.
Industry:Science
A mechanism which permits a rear axle to turn corners with one wheel rolling faster than the other. An automobile differential is located in the case carrying the rear-axle drive gear (see <b>illus.</b>).
Industry:Science
A medical specialty that uses x-rays, gamma rays, high-frequency sound waves, and magnetic fields to produce images of organs and other internal structures of the body. In diagnostic radiology the purpose is to detect and diagnose disease, while in interventional radiology, imaging procedures are combined with other techniques to treat certain diseases and abnormalities.
Industry:Science
A medication capable of producing a mild state of inhibition of the central nervous system (CNS) associated with reduced awareness of external stimuli. Numerous pharmacologic agents can induce different degrees of sedation, depending on the following variables: dosage; route of administration; absorption, metabolism, and excretion rates of the compound; specific receptor sites in the central nervous system that are affected by the agent; environmental setting; and state of the patient.
Industry:Science
A medium used to record, distribute, and play video information. The video disk exists in three major forms: the Digital Video Disk (DVD; sometimes also called the Digital Versatile Disk); the Laser Video disk (sometimes called the Laser Vision disk); and the Video CD. There is an audio version of the DVD, called the Digital Audio Disk, that is based on the same digital principles as the DVD.
Industry:Science
