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History Professor Leonard Kleinrockwith the first ARPANET Interface Message Processors at UCLA Research into packet switching started in the early 1960s and packet switched networks such as Mark I at NPL in the UK, ARPANET, CYCLADES, Merit Network, Tymnet, and Telenet, were developed in the late 1960s and early 1970s using a variety of protocols. The ARPANET in particular led to the development of protocols for internetworking, where multiple separate networks could be joined together into a network of networks. [ citation needed ] The first two nodes of what would become the ARPANET were interconnected between Leonard Kleinrock's Network Measurement Center at the UCLA's School of Engineering and Applied Scienceand Douglas Engelbart's NLS system at SRI International (SRI) in Menlo Park, California, on 29 October 1969. The third site on the ARPANET was the ...

Terminology The  Internet , referring to the specific global system of interconnected IP networks, is a proper noun and written with an initial capital letter. In the media and common use it is often not capitalized, viz.  the internet.  Some guides specify that the word should be capitalized when used as a noun, but not capitalized when used as a verb or an adjective. The Internet is also often referred to as  the Net . Historically the word  internet  was used, uncapitalized, as early as 1883 as a verb and adjective to refer to interconnected motions. Starting in the early 1970s the term  internet  was used as a shorthand form of the technical term internetwork, the result of interconnecting computer networks with special gateways or routers. It was also used as a verb meaning to connect together, especially for networks. The terms  Internet  and  World Wide Web  are often used in...

Internet This article is about the public worldwide computer network system. For other uses, see  Internet (disambiguation) . "Computer culture" redirects here. For other uses, see Cyberculture. Internet Computer network  types by spatial scope Near field (NFC) Body (BAN) Personal (PAN) Near-me (NAN) Local (LAN) Home (HAN) Storage (SAN) Campus (CAN) Backbone Metropolitan (MAN) Wide (WAN) Internet Interplanetary Internet The  Internet  is a global system of interconnected computer networks that use the standard Internet protocol suite ( TCP/IP ) to serve billions of users worldwide. It is a network of networks  that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. The Internet carries an extensive range of information resources and services, ...

The Variables of Organic Reactions In an effort to understand how and why reactions of functional groups take place in the way they do, chemists try to discover just how different molecules and ions interact with each other as they come together. To this end,  it is important to consider the various properties and characteristics of a reaction that may be observed and / or measured as the reaction proceeds  . The most common and useful of these are listed below: 1. Reactants and Reagents A. Reactant Structure:   Variations in the structure of the reactant may have a marked influence on the course of a reaction, even though the functional group is unchanged. Thus, reaction of 1-bromopropane with sodium cyanide proceeds smoothly to yield butanenitrile, whereas 1-bromo-2,2-dimethylpropane fails to give any product and is recovered unchanged. In contrast, both alkyl bromides form Grignard reagents (RMgBr) on reaction with magnesium. B. Reagent Character...

Classifying Organic Chemical Reactions If you scan any organic textbook you will encounter what appears to be a very large, often intimidating, number of reactions. These are the "tools" of a chemist, and to use these tools effectively, we must organize them in a sensible manner and look for patterns of reactivity that permit us make plausible predictions. Most of these reactions occur at special sites of reactivity known as functional groups, and these constitute one organizational scheme that helps us catalog and remember reactions. Ultimately, the best way to achieve proficiency in organic chemistry is to understand how reactions take place, and to recognize the various factors that influence their course. This is best accomplished by perceiving the reaction pathway or mechanism of a reaction. 1. Classification by Structural Change First, we identify four broad classes of reactions based solely on the  structural change  occurring in the reactant mol...

Chemical Reactivity Organic chemistry encompasses a very large number of compounds ( many millions ), and our previous discussion and illustrations have focused on their structural characteristics. Now that we can recognize these actors ( compounds ), we turn to the roles they are inclined to play in the scientific drama staged by the multitude of chemical reactions that define organic chemistry. We begin by defining some basic terms that will be used frequently as this subject is elaborated. Chemical Reaction:   A transformation resulting in a change of composition, constitution and/or configuration of a compound ( referred to as the reactant or substrate ). Reactant or Substrate:   The organic compound undergoing change in a chemical reaction. Other compounds may also be involved, and common reactive partners ( reagents ) may be identified. The reactant is often ( but not always ) the larger and more complex molecule in the reacting system. Most ( or all ) of the...

Mechanisms Of Organic Reactions A detailed description of the changes in structure and bonding that take place in the course of a reaction, and the sequence of such events is called the   reaction mechanism . A reaction mechanism should include a representation of plausible electron reorganization, as well as the identification of any intermediate species that may be formed as the reaction progresses. These features are elaborated in the following sections. 1. The Arrow Notation in Mechanisms Since chemical reactions involve the breaking and making of bonds, a consideration of the movement of bonding ( and non-bonding ) valence shell electrons is essential to this understanding. It is now common practice to show the movement of electrons with curved arrows, and a sequence of equations depicting the consequences of such electron shifts is termed a  mechanism . In general, two kinds of curved arrows are used in drawing mechanisms: A full head on the arrow ind...