Monday, August 25, 2008


Enzymes are biomolecules that catalyze (i.e. increase the rates of) chemical reactions. Almost all enzymes are proteins. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products. Almost all processes in a biological cell need enzymes in order to occur at significant rates. Since enzymes are extremely selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.

Like all catalysts, enzymes work by lowering the activation energy (Ea or ΔG‡) for a reaction, thus dramatically increasing the rate of the reaction. Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions. As with all catalysts, enzymes are not consumed by the reactions they catalyze, nor do they alter the equilibrium of these reactions. However, enzymes do differ from most other catalysts by being much more specific. Enzymes are known to catalyze about 4,000 biochemical reactions. A few RNA molecules called ribozymes catalyze reactions, with an important example being some parts of the ribosome. Synthetic molecules called artificial enzymes also display enzyme-like catalysis.

Thursday, August 21, 2008

Locative media

Locative Media are media of communication bound to a location. They are digital media applied to real places and thus triggering real social interactions. While mobile technologies such as the Global Positioning System (GPS), laptop computers and mobile phones enable locative media, they are not the goal for the development of projects in this field. Rather:

"Locative media is many things: A new site for old discussions about the relationship of consciousness to place and other people. A framework within which to actively engage with, critique, and shape a rapid set of technological developments. A context within which to explore new and old models of communication, community and exchange. A name for the ambiguous shape of a rapidly deploying surveillance and control infrastructure." (Russell, 2004)

Monday, August 11, 2008

Custom software

Custom software (also known as Bespoke software) is a type of software that is developed either for a specific organization or function that differs from or is opposite of other already available software (also called off-the-shelf or COTSsoftware). It is generally not targeted to the mass market, but usually created for companies, business entities, and organizations. Custom software is also when companies or governments pay for customized software for budget or project managing.

Examples of bespoke software include ATMs and Supermarket checkout scanners. Other examples include many web sites and web-based applications.

However, according to the US government, million and multi-million dollar projects for custom software are available to bid on. (Refer to for more information.) Multiple companies with security clearances are able to bid for these massive projects. Other companies will successfully bid on these projects and then sell the project to another company for profit.

Tuesday, August 05, 2008

Active Object

This article is about a multi-threading technique. For the lockstep protocol variant, see Active objects.

The Active Object design pattern decouples method execution from method invocation that reside in their own thread of control.s The goal is to introduce concurrency, by using asynchronous method invocation and a scheduler for handling requests.

The pattern consists of six elements:

* a proxy, which provides an interface towards clients with publicly accessible methods
* an interface which defines the method request on an active object
* a list of pending requests from clients
* a scheduler, which decides which request to execute next
* the implementation of the active object method.
* a callback or variable for the client to receive the result.