Tuesday, August 26, 2008


Adenoviruses are viruses that carry their genetic material in the form of double-stranded DNA. They cause respiratory (especially the common cold), intestinal, and eye infections in humans. When these viruses infect a host cell, they introduce their DNA molecule into the host. The genetic material of the adenoviruses is not incorporated (transient) into the host cell's genetic material. The DNA molecule is left free in the nucleus of the host cell, and the instructions in this extra DNA molecule are transcribed just like any other gene. The only difference is that these extra genes are not replicated when the cell is about to undergo cell division so the descendants of that cell will not have the extra gene. As a result, treatment with the adenovirus will require readministration in a growing cell population although the absence of integration into the host cell's genome should prevent the type of cancer seen in the SCID trials. This vector system has shown real promise in treating cancer and indeed the first gene therapy product to be licensed to treat cancer is an adenovirus.

Friday, August 22, 2008

Data stream

This article is about the more general meaning of the term "data stream". For the UK-specific DSL technology called "Datastream", also see the IP Stream article.

In telecommunications and computing, a data stream is a sequence of digitally encoded coherent signals (packets of data or datapackets) used to transmit or receive information that is in transmission.

In electronics and computer architecture, a data stream determines for which time which data item is scheduled to enter or leave which port of a systolic array, a Reconfigurable Data Path Array or similar pipe network, or other processing unit or block. Often the data stream is seen as the counterpart of an instruction stream, since the von Neumann machine is instruction-stream-driven, whereas its counterpart, the Anti machine is data-stream-driven.

Tuesday, August 12, 2008

Assisted GPS

Conventional GPS has difficulty providing reliable positions in poor signal conditions. For example when surrounded by tall buildings (as a result of multipath), or when the satellite signals are weakened by being indoors or under trees. Some newer receivers are better at handling these situations.

In addition, when first turned on in these conditions, some non-assisted GPS units may not be able to download the almanac and ephemeris information from the GPS satellites, rendering them unable to function until a clear signal can be received continuously for up to one minute.

An A-GPS receiver can address these problems in several ways, using an Assistance Server:

* The Assistance Server can locate the phone roughly by what cell site it is connected to on the cellular network.
* The Assistance Server has a good satellite signal, and lots of computation power, so it can compare fragmentary signals relayed to it by cell phones, with the satellite signal it receives directly, and then inform the cell phone or emergency services of the cell phone's position.
* It can supply orbital data for the GPS satellites to the cell phone, enabling the cell phone to lock to the satellites when it otherwise could not, and autonomously calculate its position.
* By having accurate, surveyed coordinates for the cell site towers, it can have better knowledge of ionospheric conditions and other errors affecting the GPS signal than the cell phone alone, enabling more precise calculation of position. (See also Wide Area Augmentation System)

Some A-GPS solutions require an active connection to a cell phone (or other data) network to function, in others it simply makes positioning faster and more accurate, but is not required.

As an additional benefit, it can reduce both the amount of CPU and programming required for a GPS Phone by offloading most of the work onto the assistance server. (This is not a large amount for a basic GPS – many early GPSs utilized Intel 80386-class 16MHz CPUs or similar hardware.)

High Sensitivity GPS is an allied technology that addresses some of the same issues in a way that does not require additional infrastructure. However, unlike some forms of A-GPS, high sensitivity GPS cannot provide instant fixes when the phone has been off for some time.

Wednesday, August 06, 2008

Video blogging

Video blogging, sometimes shortened to vlogging is a form of blogging for which the medium is video. Entries are made regularly and often combine embedded video or a video link with supporting text, images, and other metadata.

Video logs (vlogs) also often take advantage of web syndication to allow for the distribution of video over the Internet using either the RSS or Atom syndication formats, for automatic aggregation and playback on mobile devices and personal computers

Vlogging saw a strong increase in popularity beginning in 2005. The Yahoo! Videoblogging Group saw its membership increase dramatically in 2005 . The most popular video sharing site to date, YouTube, founded in February 2005, was publicly launched between August and November 2005. The BBC launched their first official video blog in October 2006, with a feature allowing children to name a new Blue Peter puppy. Many open source content management systems, like WordPress or Drupal, enable posting of video content allowing bloggers to host and administer their own video blogging sites. Moreover, convergence of mobile phones with digital cameras allow publishing of video content to the Web almost as it is recorded.