Rolling

Rolling is a type of motion that combines rotation (commonly, of an axially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact with each other without sliding.

Rolling where there is no sliding is referred to as pure rolling. By definition, there is no sliding when the instantaneous velocity of the rolling object in all the points in which it contacts the surface is the same as that of the surface; in particular, for a reference plane in which the rolling surface is at rest, the instantaneous velocity of the point of contact of the rolling object is zero.

In practice, due to small deformations near the contact area, some sliding and energy dissipation occurs. Nevertheless, the resulting rolling resistance is much lower than sliding friction, and thus, rolling objects, typically require much less energy to be moved than sliding ones. As a result, such objects will more easily move, if they experience a force with a component along the surface, for instance gravity on a tilted surface, wind, pushing, pulling, or torque from an engine. Unlike most axially symmetrical objects, the rolling motion of a cone is such that while rolling on a flat surface, its center of gravity performs a circular motion, rather than linear motion. Rolling objects are not necessarily axially-symmetrical. Two well known non-axially-symmetrical rollers are the Reuleaux triangle and the Meissner bodies. The oloid and the sphericon are members of a special family of developable rollers that develop their entire surface when rolling down a flat plane. Objects with corners, such as dice, roll by successive rotations about the edge or corner which is in contact with the surface.

Leukocyte extravasation

Leukocyte extravasation, less commonly called diapedesis, is the movement of leukocytes out of the circulatory system and towards the site of tissue damage or infection. This process forms part of the innate immune response, involving the recruitment of non-specific leukocytes. Monocytes also use this process in the absence of infection or tissue damage during their development into macrophages.

Overview

Leukocyte extravasation occurs mainly in post-capillary venules, where haemodynamic shear forces are minimised. This process can be understood in several steps, outlined below as "chemoattraction", "rolling adhesion", "tight adhesion" and "(endothelial) transmigration". It has been demonstrated that leukocyte recruitment is halted whenever any of these steps is suppressed.

White blood cells (leukocytes) perform most of their functions in tissues. Functions include phagocytosis of foreign particles, production of antibodies, secretion of inflammatory response triggers (histamine and heparin), and neutralization of histamine. In general, leukocytes are involved in the defense of an organism and protect it from disease by promoting or inhibiting inflammatory responses. Leukocytes use the blood as a transport medium to reach the tissues of the body. Here is a brief summary of each of the four steps currently thought to be involved in leukocyte extravasation:

Rolling (metalworking)

In metalworking, rolling is a metal forming process in which metal stock is passed through one or more pairs of rolls to reduce the thickness and to make the thickness uniform. The concept is similar to the rolling of dough. Rolling is classified according to the temperature of the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is known as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is known as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process, and cold rolling processes the most tonnage out of all cold working processes.Roll stands holding pairs of rolls are grouped together into rolling mills that can quickly process metal, typically steel, into products such as structural steel (I-beams, angle stock, channel stock, and so on), bar stock, and rails. Most steel mills have rolling mill divisions that convert the semi-finished casting products into finished products.

Eggman

Eggman or Egg Man may refer to:

Doctor Eggman

Doctor Ivo "Eggman" Robotnik (ドクター・エッグマン, Dokutā Egguman, ロボトニック Robotonikku) is a video game character and the main antagonist of the Sonic the Hedgehog series created by Sega. He is a rotund mad scientist with an IQ of 300, who plans to conquer the world in order to build his own Eggman Empire, and is the archenemy of Sonic the Hedgehog. His original character designer was Naoto Ohshima, and while he has gone through several major and minor appearance changes throughout the series, his in-game designs retain several basic characteristics, such as his egg-shaped body, red-black-yellow clothing, pince-nez sunglasses, and large mustache.

Eggman has appeared in almost every Sonic the Hedgehog video game since his first appearance in the 1991 title Sonic the Hedgehog, and is also a prominent character in other Sonic media, including comics, novels, animated TV series and an original video animation.

Concept and inspiration

In April 1990, Sega commissioned its AM8 R&D department to create a character who would replace Alex Kidd as the company's mascot, as well as compete against Nintendo's flagship character, Mario. The idea of an egg-shaped character became the basis of the visual design for Eggman. In creating the "bad guy" for the Sonic series, the development team wanted a character who was "the opposite of Sonic;" a character who represented "machinery" and "development" to play on the then-growing debate between developers and environmentalists. The character was also designed to be easy for children to draw.