The endless knot or eternal knot is a symbolic knot found in Tibet and Mongolia. The motif is used in Tibetan Buddhism, and may also be found in Chinese art as one of the Eight Auspicious Symbols.

The endless knot has been described as an ancient symbol representing the interweaving of the spiritual path and the flowing of time and movement within that which is eternal. All existence, it says, is bound by time and change, yet ultimately rests serenely within the divine and the eternal.

Various interpretations of the symbol are the inter-twining of wisdom and compassion, and the interplay and interaction of the opposing forces in the dualistic world of manifestation, leading to their union, and ultimately to harmony in the universe. The Endless knot iconography also symbolises Samsara, or the endless cycle of suffering or birth, death and rebirth within Tibetan Buddhism.

Endless knots as mystic and mythological symbols have developed independently in various cultures. A well-known example is the various Celtic knots. Since the knot has no beginning or end it symbolizes infinite wisdom.

Tree houses are buildings constructed among the branches, around or next to the trunk of one or more mature trees, and are raised above the ground. Tree houses can be used for recreation, work space, habitation or as temporary retreats. In some areas the wildlife, climate and illumination on ground level in areas of dense close-canopy forest is not well suited for human habitation, and tree houses are constructed to create improved conditions.

Because they do not require a clearing of a certain area of forest, tree houses are an option for building eco-friendly facilities in remote forest areas. In some parts of the tropics, ordinary houses are built in trees or elevated on stilts to keep the living quarters above hazards at ground level, and to keep the occupants and any stored food out of reach of scavenging animals. The Korowai, a Papuan tribe in the southeast of Irian Jaya, live in tree houses, some nearly 40 metres (130 ft) high, as protection against a tribe of neighbouring head-hunters, the Citak.

The tree house has been central to various environmental protest communities around the world, in a technique known as tree sitting. This method may be used in protests against proposed road building or old growth forestry operations. Tree houses are used as a method of defense from which it is difficult and costly to safely evict the protesters and begin work. Julia Butterfly Hill is a particularly well known tree sitter who occupied a Californian Redwood for 738 days, saving the tree and others in the immediate area. Her accommodation consisted of two 29 square foot platforms 200ft above the ground.

A very small number of planning departments have specific regulations for tree houses, which set out clearly what may be built and where. In some cases tree houses are given exemption from normal building regulations, as they are not considered to be a building in the normal sense of the word. There may be restrictions on height, distance from boundaries and privacy for nearby properties.

Raymond Kurzweil is an inventor and futurist. He’s involved in fields as diverse as optical character recognition, text-to-speech synthesis, and electronic keyboard instruments. He is the author of several books on health, artificial intelligence, transhumanism, technological singularity, and futurism.

Kurzweil first began speculating about the future when he was a child, but only later as an adult did he become seriously involved with trying to accurately forecast future events. Kurzweil came to realize that his success as an inventor depended largely on proper timing: His new inventions had to be released onto the market only once many other, supporting technologies had come into existence. A device issued too early and without proper refinement would lack some key element of functionality, and a device put out too late would find the market already flooded with a different product, or consumers demanding something better.

It thus became imperative for Kurzweil to have an understanding of the rates and directions of technological development. He has, throughout his adult life, kept close track of advances in the computer and machine industries, and has precisely modeled them. By extrapolating past trends into the future, Kurzweil formed a method of predicting the course of technological development.

After several years of closely tracking these trends, Kurzweil came to a realization that the innovation rate of computer technology was increasing not linearly but rather exponentially. As a computer scientist, Kurzweil also understood that there was no technical reason that this type of performance growth could not continue well into the 21st century.

Kurzweil projects that between now and 2050 technology will become so advanced that medical advances will allow people to radically extend their lifespans while preserving and even improving quality of life as they age. The aging process could at first be slowed, then halted, and then reversed as newer and better medical technologies became available. Kurzweil argues that much of this will be a fruit of advances in medical nanotechnology, which will allow microscopic machines to travel through one’s body and repair all types of damage at the cellular level.

Negative affectivity is a general dimension of subjective distress and unpleasurable engagement that subsumes a variety of aversive mood states, including anger, contempt, disgust, guilt, fear, and nervousness. Individuals high in negative affectivity are characterized by distress, un-pleasurable engagement, and nervousness. Low negative affect is characterised by a state of calmness and serenity.

It has been defined as a mood-dispositional dimension that reflects pervasive individual differences in negative emotionality and self-concept. People who express high negative affectivity view themselves and a variety of aspects of the world around them in generally negative terms. Negative affectivity may influence the relationships between variables in organizational research.

Negative affectivity represents an affective state dimension. Research has demonstrated that individuals differ in negative emotional reactivity. Trait negative affectivity roughly corresponds to the dominant personality factor of anxiety and neuroticism within the major personality traits. Research shows that negative affectivity relates to different classes of variables: Self-reported stress and poor coping skills, health complaints, and frequency of unpleasant events.

Individuals high in negative affect will exhibit, on average, higher levels of anxiety and dissatisfaction, and tend to focus on the unpleasant aspects of themselves, the world, the future, and other people. In fact, the content similarities between these affective traits and life satisfaction have led some researchers to view negative affectivity and life satisfaction as specific indicators of the broader construct of subjective well-being.

Diablo wind is a relatively recent term for a hot, dry offshore wind from the northeast that typically occurs in the San Francisco Bay Area of Northern California during the Autumn. The same wind pattern also affects other parts of California’s coastal ranges. 

The winds are created by the combination of strong high pressure at the surface over the Great Basin, strongly sinking air aloft, and lower pressure off the California coast. The air descending from aloft as well as from the Coast Ranges compresses at sea level where it warms as much as 20 °F, and loses humidity.

Unlike the Santa Ana wind which drains surface air off the high deserts, the so-called Diablo wind mainly originates from areas of strongly sinking air aloft, associated with the development of high atmospheric pressure inland following the passage of storms just north and east of California. The similar, though distinctive mechanisms can be distinguished by where the strongest winds in each type of event occur.

Typically, Santa Anas are strongest in canyons whereas a Diablo wind is first noted and blows strongest atop the various mountain peaks and ridges around the Bay Area. In both cases, as the air sinks, it heats up by compression and its humidity drops. This heat is in addition to, and usually greater than, any heat picked up by the wind as it crosses the Central Valley and the Diablo Valley. This is the reverse of the normal summertime weather pattern in which a trough of low rather than high pressure lies east of the Bay Area, drawing in cooler, more humid air from the ocean.

If the pressure gradient is large enough, the dry offshore wind can become quite strong with gusts reaching speeds of 40 mph or higher, particularly along and in the lee of the ridges of the Coast Range where the higher wind speed aloft acts like a pump, drawing warm, dry surface air from the windward eastern side up and over the ridgelines. This effect is especially dangerous with respect to wildfires as it can enhance the updraft generated by the heat in such fires.

Tides are the rising of Earth’s ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans.Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams, making prediction of tides important for coastal navigation. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides.

The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the bathymetry of oceans, seas and estuaries. Besides the ocean, tidal phenomena can occur in other systems whenever a gravitational field that varies in time and space is present.

In addition to oceanic tides, there are atmospheric tides as well as earth tides. All of these are continuum mechanical phenomena, the first two being fluids and the third being essentially the thin solid Earth’s crust on top of the semi-liquid Earth’s interior.

Atmospheric tides are negligible from ground level and aviation altitudes, drowned by the much more important effects of weather. Atmospheric tides are both gravitational and thermal in origin and are the dominant dynamics from about 80 km to 120 km where the molecular density becomes too small to behave as a fluid.

Earth tides or terrestrial tides affect the entire mass of the Earth, which can be viewed as a liquid gyro with a very thin crust. The Earth’s crust shifts in response to the Moon’s and Sun’s gravitation, ocean tides, and atmospheric loading. While negligible for most human activities, the semidiurnal amplitude of terrestrial tides can reach about 55 cm at the equator which is important in GPS calibration.

When oscillating tidal currents in the stratified ocean flow over uneven bottom topography, they generate internal waves with tidal frequencies. Such waves are called internal tides. The galactic tide is the tidal force exerted by galaxies on stars within them and satellite galaxies orbiting them. The effects of the galactic tide on the Solar System’s Oort cloud are believed to be the cause of 90 percent of all observed long-period comets.

Nasturtium, literally “nose-twister” or “nose-tweaker” as a common name, refers to a genus of roughly 80 species of annual and perennial herbaceous flowering plants in the genus Tropaeolum. They have showy, often intensely bright flowers and rounded, shield-shaped leaves with the petiole in the center. The intense color can make macrophotography quite difficult. The flowers have five petals and a funnel-shaped nectar tube in the back. The most common use of the nasturtium plant in cultivation is as an ornamental flower. It grows easily and prolifically, and is a self-seeding annual.

In cultivation, most varieties of nasturtiums prefer to be grown in direct or indirect sunlight, with a few preferring partial shade. All parts of the plant are edible. The flower has most often been consumed, making for an especially ornamental salad ingredient. It has a slightly peppery taste reminiscent of watercress, and is also used in stir fry. The unripe seed pods can be harvested and pickled with hot vinegar, to produce a condiment and garnish, sometimes used in place of capers, although the taste is strongly peppery.

Nasturtiums are also considered widely useful companion plants. They repel a great many cucurbit pests, like squash bugs, cucumber beetles, and several caterpillars. They have a similar range of benefits for brassica plants, especially broccoli and cauliflower. They also attract black fly aphids, and are sometimes planted in the hope of saving crops susceptible to them as a trap crop. They may also attract beneficial, predatory insects.

Multistable perceptual phenomena are a rare form of visual perception phenomena which is characterized by an unpredictable sequence of spontaneous subjective changes.

Perceptual multistability can be evoked by visual patterns that are too ambiguous for the human visual system to recognise with one unique interpretation. Famous examples include the Necker cube, structure from motion, monocular rivalry and binocular rivalry, but many more visually ambiguous patterns are known. Since most of these images lead to an alternation between two mutually exclusive perceptual states, they are sometimes also referred to as bistable perception.

Transitions from one percept to its alternative are called perceptual reversals. They are spontaneous and stochastic events which cannot be eliminated by intentional efforts, although some control over the alternation process is learnable. Reversal rates vary drastically between stimuli and observers, and has been found to be slower for people with Bipolar disorder due to “sticky” interhemispheric switch in bipolar disorder. 

Human interest in these phenomena can be traced back to antiquity. The fascination of multistable perception probably comes from the active nature of endogenous perceptual changes or from the dissociation of dynamic perception from constant sensory stimulation. Multistable perception was a common feature in the artwork of the Dutch lithographer M. C. Escher, who was strongly influenced by mathematical physicists such as Roger Penrose. 

Photographs of craters, from either the moon or other planets including our own, can exhibit this phenomenon. Craters, in stereo imaging, such as our eyes, should appear to be pit-like structures. However in mono-vision, such as that of photographs, the elimination of our depth perception causes multistable perception to take over, and this can cause the craters to inverse their depth values and instead look like plateaus rather than pits. Sometimes rotating the image so that the photographic direction of the source of light matches a light source in the room can cause the correct perception to suddenly switch.