Many people find it difficult to remember the difference between defuse and diffuse, and when faced with the need for one of these words simply grab whichever one first comes to mind. Although these word sound quite similar, their meanings are rather distinct. Defuse means "to make less harmful, potent, or tense"; the word has another, helpfully literal, meaning, which is "to remove the fuse from." Diffuse means "not concentrated or localized"; it comes from the Latin word diffūsus ("spread over a wide area").
Diffuse is commonly found used as both adjective ("not concentrated or localized") and verb ("to pour out and permit or cause to spread freely," "to scatter"), while infuse is almost entirely restricted to use as a verb. While the meannings of diffuse are mainly concerned with outward movement, those of infuse are inward; the word has such meanings as "to steep in liquid (such as water) without boiling so as to extract the soluble constituents or principles," "to administer or inject by infusion," and "to cause to be permeated with something (such as a principle or quality) that alters usually for the better."
Please notify us if you see diffuse knapweed growing in King County. Our program staff can provide the property owner or appropriate public agency with site-specific advice on how best to remove it. We map all known locations of regulated noxious weeds such as diffuse knapweed in order to help us and others locate new infestations in time to control them.
Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection. An ideal diffuse reflecting surface is said to exhibit Lambertian reflection, meaning that there is equal luminance when viewed from all directions lying in the half-space adjacent to the surface.
A surface built from a non-absorbing powder such as plaster, or from fibers such as paper, or from a polycrystalline material such as white marble, reflects light diffusely with great efficiency. Many common materials exhibit a mixture of specular and diffuse reflection.
Diffuse reflection from solids is generally not due to surface roughness. A flat surface is indeed required to give specular reflection, but it does not prevent diffuse reflection. A piece of highly polished white marble remains white; no amount of polishing will turn it into a mirror. Polishing produces some specular reflection, but the remaining light continues to be diffusely reflected.
The most general mechanism by which a surface gives diffuse reflection does not involve exactly the surface: most of the light is contributed by scattering centers beneath the surface,[2][3] as illustrated in Figure 1.If one were to imagine that the figure represents snow, and that the polygons are its (transparent) ice crystallites, an impinging ray is partially reflected (a few percent) by the first particle, enters in it, is again reflected by the interface with the second particle, enters in it, impinges on the third, and so on, generating a series of "primary" scattered rays in random directions, which, in turn, through the same mechanism, generate a large number of "secondary" scattered rays, which generate "tertiary" rays, and so forth.[4] All these rays walk through the snow crystallites, which do not absorb light, until they arrive at the surface and exit in random directions.[5] The result is that the light that was sent out is returned in all directions, so that snow is white despite being made of transparent material (ice crystals).
For simplicity, "reflections" are spoken of here, but more generally the interface between the small particles that constitute many materials is irregular on a scale comparable with light wavelength, so diffuse light is generated at each interface, rather than a single reflected ray, but the story can be told the same way.
Few materials do not cause diffuse reflection: among these are metals, which do not allow light to enter; gases, liquids, glass, and transparent plastics (which have a liquid-like amorphous microscopic structure); single crystals, such as some gems or a salt crystal; and some very special materials, such as the tissues which make the cornea and the lens of an eye. These materials can reflect diffusely, however, if their surface is microscopically rough, like in a frost glass (Figure 2), or, of course, if their homogeneous structure deteriorates, as in cataracts of the eye lens.
A surface may also exhibit both specular and diffuse reflection, as is the case, for example, of glossy paints as used in home painting, which give also a fraction of specular reflection, while matte paints give almost exclusively diffuse reflection.
Most materials can give some specular reflection, provided that their surface can be polished to eliminate irregularities comparable with the light wavelength (a fraction of a micrometer). Depending on the material and surface roughness, reflection may be mostly specular, mostly diffuse, or anywhere in between. A few materials, like liquids and glasses, lack the internal subdivisions which produce the subsurface scattering mechanism described above, and so give only specular reflection. Among common materials, only polished metals can reflect light specularly with high efficiency, as in aluminum or silver usually used in mirrors. All other common materials, even when perfectly polished, usually give not more than a few percent specular reflection, except in particular cases, such as grazing angle reflection by a lake, or the total reflection of a glass prism, or when structured in certain complex configurations such as the silvery skin of many fish species or the reflective surface of a dielectric mirror. Diffuse reflection can be highly efficient, as in white materials, due to the summing up of the many subsurface reflections.
Up to this point white objects have been discussed, which do not absorb light. But the above scheme continues to be valid in the case that the material is absorbent. In this case, diffused rays will lose some wavelengths during their walk in the material, and will emerge colored.
And, when a colored object has both diffuse and specular reflection, usually only the diffuse component is colored. A cherry reflects diffusely red light, absorbs all other colors and has a specular reflection which is essentially white (if the incident light is white light). This is quite general, because, except for metals, the reflectivity of most materials depends on their refractive index, which varies little with the wavelength (though it is this variation that causes the chromatic dispersion in a prism), so that all colors are reflected nearly with the same intensity.
The vast majority of visible objects are seen primarily by diffuse reflection from their surface.[7][8]Exceptions include objects with polished (specularly reflecting) surfaces, and objects that themselves emit light. Rayleigh scattering is responsible for the blue color of the sky, and Mie scattering for the white color of the water droplets in clouds.
Diffuse interreflection is a process whereby light reflected from an object strikes other objects in the surrounding area, illuminating them. Diffuse interreflection specifically describes light reflected from objects which are not shiny or specular. In real life terms what this means is that light is reflected off non-shiny surfaces such as the ground, walls, or fabric, to reach areas not directly in view of a light source. If the diffuse surface is colored, the reflected light is also colored, resulting in similar coloration of surrounding objects.
In 3D computer graphics, diffuse interreflection is an important component of global illumination. There are a number of ways to model diffuse interreflection when rendering a scene. Radiosity and photon mapping are two commonly used methods.
Additional symptoms depend on the size and location of the tumor, which may impact specific neurological functions. For example, a diffuse astrocytoma near the motor cortex (which controls body movement) may cause slowly progressive weakness on one side of the body.
Diffuse astrocytoma is the second most common glioma, after glioblastoma, accounting for about 2-5% of all primary brain tumors in adults.1 In 2017, an estimated 1,410 new cases were diagnosed in the United States.1 Most cases of diffuse astrocytoma occur in adults, although they occasionally develop in children as well.
Diffuse astrocytoma can be further classified into more specific subtypes based on genetic characteristics. Specifically, diffuse astrocytomas can have abnormal genetic signatures, including mutations in the IDH1 or IDH2 genes. The presence of these genetic differences can affect prognosis and treatment, and are classified accordingly:
Typically, complete surgical removal of the tumor offers the best patient outcomes for long-term survival. However, diffuse astrocytoma can recur after surgery, so patients are regularly monitored for both tumor recurrence and progression to a higher grade tumor.
Grade II diffuse gliomas, often referred as low-grade gliomas, are slow-growing tumors and hold a better prognosis than grade III-IV diffuse gliomas, which are high-grade gliomas, and progress more rapidly.
Hereditary diffuse gastric cancer (HDGC) is an inherited disorder that greatly increases the chance of developing a form of stomach(gastric) cancer. In this form, known as diffuse gastric cancer, there is no solid tumor. Instead cancerous (malignant) cells multiply underneath the stomach lining, making the lining thick and rigid. The invasive nature of this type of cancer makes it highly likely that these cancer cells will spread (metastasize) to other tissues, such as the liver or nearby bones.
Symptoms of diffuse gastric cancer occur late in the disease and can include stomach pain, nausea, vomiting, difficulty swallowing (dysphagia), decreased appetite, and weight loss. If the cancer metastasizes to other tissues, it may lead to an enlarged liver, yellowing of the eyes and skin (jaundice), an abnormal buildup of fluid in the abdominal cavity (ascites), firm lumps under the skin, or broken bones.
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