Sunday, June 29, 2008


Morphogenesis (from the Greek morphê shape and genesis creation),( literally, "beginning of the shape"), is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation. Morphogenesis is concerned with the shapes of tissues, organs and entire organisms and the positions of the various specialized cell types. Cell growth and differentiation can take place in cell culture or inside of tumor cell masses without the normal morphogenesis that is seen in an intact organism. The study of morphogenesis involves an attempt to understand the processes that control the organized spatial distribution of cells that arises during the embryonic development of an organism and that give rise to the characteristic forms of tissues, organs, and overall body anatomy. In the human embryo, the change from a cluster of nearly identical cells at the blastula stage to a post-gastrulation embryo with structured tissues and organs is controlled by the genetic "program" and can be modified by environmental factors. The term morphogenesis can also be used to describe the development of unicellular life forms that do not have an embryonic stage in their life cycle, or to refer to the evolution of a body structure within a taxonomic group. Morphogenetic responses may be induced in organisms by hormones, by environmental chemicals ranging from substances produced by other organisms to toxic chemicals or radionuclides released as pollutants, and other plants, or by mechanical stresses induced by spatial patterning of the cells.

Sunday, June 22, 2008


Mitosis is the process by which a cell separates the chromosomes in its cell nucleus, into two identical sets in two daughter nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing roughly equal shares of these cellular components. Mitosis and cytokinesis together define the mitotic (M) phase of the cell cycle - the division of the mother cell into two daughter cells, genetically identical to each other and to their parent cell.

Mitosis occurs exclusively in eukaryotic cells, but occurs in different ways in different species. For example, animals undergo an "open" mitosis, where the nuclear envelope breaks down before the chromosomes separate, while fungi such as Aspergillus nidulans and Saccharomyces cerevisiae (yeast) undergo a "closed" mitosis, where chromosomes divide within an intact cell nucleus. Prokaryotic cells, which lack a nucleus, divide by a process called binary fission.
The process of mitosis is complex and highly regulated. The sequence of events is divided into phases, corresponding to the completion of one set of activities and the start of the next. These stages are prophase, prometaphase, metaphase, anaphase and telophase. During the process of mitosis the pairs of chromosomes condense and attach to fibers that pull the sister chromatids to opposite sides of the cell. The cell then divides in cytokinesis, to produce two identical daughter cells.

Because cytokinesis usually occurs in conjunction with mitosis, "mitosis" is often used interchangeably with "mitotic phase". However, there are many cells where mitosis and cytokinesis occur separately, forming single cells with multiple nuclei. This occurs most notably among the fungi and slime moulds, but is found in various different groups. Even in animals, cytokinesis and mitosis may occur independently, for instance during certain stages of fruit fly embryonic development. Errors in mitosis can either kill a cell through apoptosis or cause mutations that may lead to cancer.

Sunday, June 15, 2008


The first integrated circuits contained only a few transistors. Called "Small-Scale Integration" (SSI), they used circuits containing transistors numbering in the tens.

SSI circuits were crucial to early aerospace projects, and vice-versa. Both the Minuteman missile and Apollo program needed lightweight digital computers for their inertial guidance systems; the Apollo guidance computer led and motivated the integrated-circuit technology, while the Minuteman missile forced it into mass-production.

These programs purchased almost all of the available integrated circuits from 1960 through 1963, and almost alone provided the demand that funded the production improvements to get the production costs from $1000/circuit (in 1960 dollars) to merely $25/circuit (in 1963 dollars).[citation needed] They began to appear in consumer products at the turn of the decade, a typical application being FM inter-carrier sound processing in television receivers.
The next step in the development of integrated circuits, taken in the late 1960s, introduced devices which contained hundreds of transistors on each chip, called "Medium-Scale Integration" (MSI).

They were attractive economically because while they cost little more to produce than SSI devices, they allowed more complex systems to be produced using smaller circuit boards, less assembly work (because of fewer separate components), and a number of other advantages.

Further development, driven by the same economic factors, led to "Large-Scale Integration" (LSI) in the mid 1970s, with tens of thousands of transistors per chip.
Integrated circuits such as 1K-bit RAMs, calculator chips, and the first microprocessors, that began to be manufactured in moderate quantities in the early 1970s, had under 4000 transistors. True LSI circuits, approaching 10000 transistors, began to be produced around 1974, for computer main memories and second-generation microprocessors.

Sunday, June 08, 2008

Trance production

Trance employs a 4/4 time signature, a tempo of 130 to 160 BPM, and 32 beat phrases, somewhat faster than house music but usually not as fast as rave music. Psychedelic Trance is sometimes faster and earlier tracks were sometimes slower. A kick drum is placed on every downbeat and a regular open hi-hat is often placed on the upbeat. Some simple extra percussive elements are usually added, and major transitions, builds or climaxes are often foreshadowed by lengthy 'snare rolls' - a quick succession of equally spaced snare drum hits that builds in volume towards the end of a measure or phrase.

Synthesizers form the central elements of most trance tracks, with simple sawtooth-based sounds used both for short pizzicato elements and for long, sweeping string sounds. As with other genres of electronic music, important synthesizers are the Roland TR-808, TR-909, and TB-303, which is the source of the "acid" sound. There are also several synthesizer sounds that are almost completely unique to its genre. One of these sounds is the "supersaw", a waveform was made famous by such classic trance synthesizers as the Roland JP-8000, the Novation Supernova, and the Korg MS2000. A technique called "gating" is often employed in creating lead sounds (turning the volume up and down rapidly in rhythm with the piece to create a stuttered, chopped sound). Rapid arpeggios and minor scales are common features. Trance tracks often use one central "hook" melody which runs through almost the entire song, repeating at intervals anywhere between 2 beats and several bars.

While many trance tracks contain no vocals at all, other tracks rely heavily on vocals, and thus a sub-genre has developed. The sound and quality of the production relies to a large degree upon the technology available. Vintage analog equipment still holds a place in the hearts of many producers and enthusiasts, with names such as Moog, Roland and Oberheim staples in the trance sound palette. However, the mainstream availability of digital technology has allowed a whole new group of producers to emerge because while top shelf digital (or analog modeling) synthesizers cost thousands of US dollars, high demand and a small supply of clean vintage analog synthesizers causes them to be extremely expensive.

Trance records are often heavily loaded with reverb and delay effects on the synthesizer sounds, vocals and often parts of the percussion section. This provides the tracks with the sense of vast space that trance producers tend to look for in order to achieve the genre's epic quality. Flangers, phasers and other effects are also commonly used at extreme settings - in trance there is no need for sounds to resemble any real-world instrument, and so producers have free rein.

Monday, June 02, 2008

Psychoactive mushrooms

Psilocybin mushrooms possess psychedelic properties. They are commonly known as "magic mushrooms" "mush" or "shrooms" and are available in smart shops in many parts of the world, though some countries have outlawed their sale. A number of other mushrooms are eaten for their psychoactive effects, such as fly agaric, which is used for shamanic purposes by tribes in northeast Siberia, Russia. They have also been used in the West to potentiate, or increase, religious experiences. Because of their psychoactive properties, some mushrooms have played a role in native medicine, where they have been used in an attempt to effect mental and physical healing, and to facilitate visionary states. One such ritual is the Velada ceremony. A practitioner of traditional mushroom use is the shaman and curandera (priest-healer) María Sabina.