Plenum Cable

Plenum cable /ˈplɛnəm/ is electrical cable that is laid in the plenum spaces of buildings. In the United States, plastics used in the construction of plenum cable are regulated under the National Fire Protection Association standard NFPA 90A: Standard for the Installation of Air Conditioning and Ventilating Systems. All materials intended for use on wire and cables to be placed in plenum spaces are designed to meet rigorous fire safety test standards in accordance with NFPA 262 and outlined in NFPA 90A.

Plenum cable is jacketed with a fire-retardant plastic jacket of either a low-smoke polyvinyl chloride (PVC) or a fluorinated ethylene polymer (FEP).  Polyolefin formulations, specifically based on polyethylene compounding had been developed by at least two companies in the early to mid-1990s; however, these were never commercialized, and development efforts continue in these yet-untapped product potentials. Development efforts on a non-halogen plenum compound were announced in 2007 citing new flame-retardant synergist packages that may provide an answer for a yet-underdeveloped plenum cable market outside the United States.

In 2006, significant concern developed over the potential toxicity of FEP and related fluorochemicals including the process aid perfluorooctanoic acid (PFOA) or C8 such that California has proposed some of these materials as potential human carcinogens. The NFPA Technical Committee on Air Conditioning, in response to public comment, has referred the issue of toxicity of cabling materials to the NFPA Committee on Toxicity for review before 2008.

In 2007, a development program specifically targeting the production of a non-halogen plenum cable compound was announced to specifically address lingering toxicity concerns presented by halogenated compounds for use in European and other global markets.

DVD

DVD (an abbreviation of digital versatile disc) is a digital optical disc storage format invented and developed in 1995. The medium can store any kind of digital data and is widely used for software and other computer files as well as video programs watched using DVD players. DVDs offer higher storage capacity than compact discs while having the same dimensions.

CD Video released in 1987 used analog video encoding on optical discs matching the established standard 120 mm (4.7 in) size of audio CDs. Video CD (VCD) became one of the first formats for distributing digitally encoded films in this format, in 1993. In the same year, two new optical disc storage formats were being developed. One was the Multimedia Compact Disc (MMCD), backed by Philips and Sony (developers of the CD and CD-i), and the other was the Super Density (SD) disc, supported by Toshiba, Time Warner, Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. By the time of the press launches for both formats in January 1995, the MMCD nomenclature had been dropped, and Philips and Sony were referring to their format as Digital Video Disc (DVD).

Capacity

4.7 GB (single-sided, single-layer – common)
8.5 GB (single-sided, double-layer)
9.4 GB (double-sided, single-layer)
17.08 GB (double-sided, double-layer) Up to four layers are possible in a standard form DVD.

APM

Apple Partition Map

For accessing volumes, both APM and GUID partitions can be used in a standard manner with Mac OS X Tiger (10.4) and higher. For starting an operating system, PowerPC-based systems can only boot from APM disks whereas Intel-based systems generally boot from GUID disks.

Intel-based models that came with Mac OS X Tiger (10.4) or Leopard (10.5) preinstalled had to be able to boot from both APM and GUID disks due to the installation media for these universal versions of Mac OS X, which are APM partitioned in order to remain compatible with PowerPC-based systems. However, the installation of OS X on an Intel-based Mac demands a GUID partitioned disk or will refuse to continue, the same way installation on a PowerPC-based system will demand an APM partitioned destination volume. Cloning an already installed OS X to an APM partition on Intel systems will remain bootable even on 2011 Intel-based Macs. Despite this apparent APM support, Apple never officially supported booting from an internal APM disk on an Intel-based system. The one exception for a universal version of Mac OS X (Tiger or Leopard) is an official Apple document describing how to set up a dual bootable external APM disk for use with PowerPC and Intel.

dark web

The dark web is the World Wide Web content that exists on darknets, overlay networks that use the Internet but require specific software, configurations, or authorization to access. The dark web forms a small part of the deep web, the part of the Web not indexed by web search engines, although sometimes the term deep web is mistakenly used to refer specifically to the dark web.

The darknets which constitute the dark web include small, friend-to-friend peer-to-peer networks, as well as large, popular networks like Tor, Freenet, I2P, and Riffle operated by public organizations and individuals. Users of the dark web refer to the regular web as Clearnet due to its unencrypted nature. The Tor dark web may be referred to as onionland, a reference to the network's top-level domain suffix .onion and the traffic anonymization technique of onion routing.

hexadecimal

In mathematics and computing, hexadecimal(also base 16, or hex) is a positional numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols "0"–"9" to represent values zero to nine, and "A"–"F" (or alternatively "a"–"f") to represent values ten to fifteen.