Monday, September 29, 2008

Bluetooth 1.2

  • Faster Connection and Discovery
  • Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
  • Higher transmission speeds in practice, up to 721 kbit/s, as in 1.1.
  • Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets, and may optionally increase audio latency to provide better support for concurrent data transfer.
  • Host Controller Interface (HCI) support for three-wire UART.
  • Ratified as IEEE Standard 802.15.1-2005.

Tuesday, September 23, 2008


The next major advance in "beam based" navigation system was the use of two signals that varied not in sound, but in phase. In these systems, known as VHF omnidirectional range, or VOR, a single master signal is sent out continually from the station, and a highly directional second signal is sent out that varies in phase 30 times a second compared to the master. This signal is timed so that the phase varies as the secondary antenna spins, such that when the antenna is 90 degrees from north, the signal is 90 degrees out of phase of the master. By comparing the phase of the secondary signal to the master, the angle can be determined without any physical motion in the receiver. This angle is then displayed in the cockpit of the aircraft, and can be used to take a fix just like the earlier RDF systems, although it is, in theory, easier to use and more accurate.

Tuesday, September 16, 2008


Sight or vision is the ability of the brain and eye to detect electromagnetic waves within the visible range (light) interpreting the image as "sight." There is disagreement as to whether this constitutes one, two or three senses. Neuroanatomists generally regard it as two senses, given that different receptors are responsible for the perception of colour (the frequency of photons of light) and brightness (amplitude/intensity - number of photons of light). Some argue[citation needed] that stereopsis, the perception of depth, also constitutes a sense, but it is generally regarded as a cognitive (that is, post-sensory) function of brain to interpret sensory input and to derive new information. The inability to see is called blindness.

Monday, September 08, 2008

Notable paleontologists

History includes a number of prominent paleontologists. Fossils were systematically studied in the 11th century by the Persian naturalist, Ibn Sina (known as Avicenna in Europe), in The Book of Healing (1027), and by the Chinese naturalist, Shen Kuo (1031-1095). In particular, Ibn Sina's theory on fossils was accepted by most naturalists in medieval Europe and the medieval Near East by the 16th century.

The modern discipline of paleontology begins in the 19th century, when Charles Darwin collected fossils of South American mammals during his trip on the Beagle and examined petrified forests in Patagonia. Mary Anning was a notable early paleontologist. She found several landmark fossils, in her home town of Lyme Regis. Although self-taught, she collected and described them in a very systematic way. William Buckland, Richard Owen, Gideon Mantell, Georges Cuvier and Thomas Huxley were important early pioneers, in the field of paleontology. Thomas Jefferson took a keen interest in mammoth bones. Edward Drinker Cope and Othniel Charles Marsh waged a famously fierce competition known as the Bone Wars in the late 19th century that involved some questionable practices, but which significantly advanced the understanding of the natural history of North America and vertebrate paleontology. Professor Earl Douglass of the Carnegie University in Pittsburgh, Pennsylvania, opened the fossil quarry protected today by Dinosaur National Monument in Utah. Douglass' fossils are in several Natural History Museums. Meanwhile, Baron Franz Nopcsa, a pioneer paleobiologist, argued that dinosaurs might have been both warm-blooded and ancestral to birds.

Besides looking at mammal teeth and unearthing penguin skeletons, George Gaylord Simpson played a crucial role in bringing together ideas from biology, paleontology and genetics, to help create the 'Modern Synthesis' of evolutionary biology. His book "Tempo and Mode" is a classic in the field. Prominent names in invertebrate paleontology include Steven M. Stanley, Stephen Jay Gould, David Raup, Rousseau H. Flower and Jack Sepkoski, who have done much to expand our understanding of long-term patterns in the evolution of life on earth. Large names in the field of paleoanthropology include Louis, Mary and Richard Leakey, Raymond Dart, Robert Broom, C.K. 'Bob' Brain, Kenneth Oakley, Robert Ardrey and Tim White. In recent times, Mongolian paleontologist Rinchen Barsbold has done much to expand our understanding of dinosaur and bird evolution. Paul Sereno of the University of Chicago has made several important dinosaur finds in areas such as the Sahara, where fossil hunting has been uncommon.

Tuesday, September 02, 2008

Panic disorder

In panic disorder, a person suffers from brief attacks of intense terror and apprehension that cause trembling and shaking, confusion, dizziness, nausea, difficulty breathing, and feelings of impending doom or a situation that would be embarrassing. One who is often plagued by sudden bouts of intense anxiety might be said to be afflicted by this disorder. The American Psychiatric Association (2000) defines a panic attack as fear or discomfort that arises abruptly and peaks in 10 minutes or less, and can occasionally last hours.

Although panic attacks sometimes seem to occur out of nowhere, they generally happen after frightening experiences, prolonged stress, or even exercise. Many people who have panic attacks (especially their first one) think they are having a heart attack and often end up at the doctor or emergency room. Even if the tests all come back normal the person will still worry, with the physical manifestations of anxiety only reinforcing their fear that something is wrong with their body. Heightened awareness (hypervigilance) of any change in the normal function of the human body will be noticed and interpreted as a possible life threatening illness by an individual suffering from panic attacks.

Normal changes in heartbeat, such as when climbing a flight of stairs will be noticed by a panic sufferer and lead them to think something is wrong with their heart or they are about to have another panic attack. Some begin to worry excessively and even quit jobs or refuse to leave home to avoid future attacks. Panic disorder can be diagnosed when several apparently spontaneous attacks lead to a persistent concern about future attacks.