Misplaced Pages

#957042

42-564: The garden is jointly administered by Northern Beaches Council and a voluntary advisory committee. The garden also receives support in the form of public donations, and volunteers who care for the garden. The garden also hosts an annual Spring Festival. Officially opened in 1961 as the Stony Range Flora Reserve, the Stony Range Botanic Garden is so named due to its location on the site of an old stone quarry. The site

84-487: A stationary phase . In column chromatography , the stationary phase is most often composed of silica gel particles of 40–63 μm. Different particle sizes are used for different kinds of column chromatography as the particle size is related to surface area. The differences in particle size dictate if the silica gel should be used for flash or gravity chromatography. In this application, due to silica gel's polarity, non-polar components tend to elute before more polar ones, hence

126-655: A desiccant (drying agent). Silica gel is often described as "absorbing" moisture, which may be appropriate when the gel's microscopic structure is ignored, as in silica gel packs or other products. However, material silica gel removes moisture by adsorption onto the surface of its numerous pores rather than by absorption into the bulk of the gel. Silica gel is able to adsorb up to 37% of its own weight in moisture in high-humidity environments. This moisture can be released upon heating at 120 °C for extended periods of time. This makes it reusable multiple times with very little, if any, loss of efficiency. Once saturated with water,

168-460: A developed industrial park may vary greatly from a wooded park nearby, as natural flora in parks absorb light and heat in leaves that a building roof or parking lot just radiates back into the air. Advocates of solar energy argue that widespread use of solar collection can mitigate overheating of urban environments by absorbing sunlight and putting it to work instead of heating the foreign surface objects. A microclimate can offer an opportunity as

210-497: A drop in temperature and/or humidity can be attributed to different sources or influences. Often a microclimate is shaped by a conglomerate of different influences and is a subject of microscale meteorology . Examples of the cold air pool (CAP) effect are Gstettneralm Sinkhole in Austria (lowest recorded temperature −53 °C (−63 °F)) and Peter Sinks in the US. The main criterion on

252-461: A few millimeters in diameter. Some grains may contain small amounts of indicator substance that changes color when they have absorbed some water. Small paper envelopes containing silica xerogel pellets, usually with a "do not eat" warning, are often included in dry food packages to absorb any humidity that might cause spoilage of the food. 'Wet' silica gel, as may be freshly prepared from alkali silicate solutions, may vary in consistency from

294-599: A few square meters or smaller (for example a garden bed , underneath a rock, or a cave) or as large as many square kilometers. Because climate is statistical , which implies spatial and temporal variation of the mean values of the describing parameters , microclimates are identified as statistically distinct conditions which occur and/or persist within a region. Microclimates can be found in most places but are most pronounced in topographically dynamic zones such as mountainous areas, islands, and coastal areas. Microclimates exist, for example, near bodies of water which may cool

336-467: A garden in Australia is a stub . You can help Misplaced Pages by expanding it . This New South Wales geography article is a stub . You can help Misplaced Pages by expanding it . Microclimate A microclimate (or micro-climate ) is a local set of atmospheric conditions that differ from those in the surrounding areas, often slightly but sometimes substantially. The term may refer to areas as small as

378-405: A microclimate study. Microclimates can also refer to purpose-made environments, such as those in a room or other enclosure. Microclimates are commonly created and carefully maintained in museum display and storage environments. This can be done using passive methods, such as silica gel , or with active microclimate control devices. Usually, if the inland areas have a humid continental climate ,

420-577: A moisture indicator that gradually changes its color when it transitions from the anhydrous (dry) state to the hydrated (wet) state. Common indicators are cobalt(II) chloride and methyl violet . Cobalt (II) chloride is deep blue when dry and pink when wet, but it is toxic and carcinogenic, and was reclassified by the European Union in July 2000 as a toxic material. Methyl violet may be formulated to change from orange to green, or orange to colorless. It also

462-433: A negative effect on the microclimates as well as on the geological and archeological findings. Factors that play into the deterioration of these environments include nearby deforestation, agriculture operations, water exploitation, mining, and tourist operations. The speleogenetic effect of normal caves tends to show a slow circulation of air. In unique conditions where acids are present, the effects of erosion and changes to

SECTION 10

#1733085751958

504-688: A small growing region for crops that cannot thrive in the broader area; this concept is often used in permaculture practiced in northern temperate climates. Microclimates can be used to the advantage of gardeners who carefully choose and position their plants. Cities often raise the average temperature by zoning , and a sheltered position can reduce the severity of winter. Roof gardening , however, exposes plants to more extreme temperatures in both summer and winter. In an urban area, tall buildings create their own microclimate, both by overshadowing large areas and by channeling strong winds to ground level. Wind effects around tall buildings are assessed as part of

546-518: A soft transparent gel , similar to gelatin or agar , to a hard solid, namely a water-logged xerogel. It is sometimes used in laboratory processes, for example to suppress convection in liquids or prevent settling of suspended particles. Silica gel was in existence as early as the 1640s as a scientific curiosity. It was used in World War I for the adsorption of vapors and gases in gas mask canisters . The synthetic route for producing silica gel

588-807: Is allowed to be added to food in the USA at up to 2% as permitted under 21 CFR 172.480. In the EU, it can be in up to 5% concentrations. In 2018, a re-evaluation by the EFSA Panel on Food Additives and Nutrient Sources added to Food found no indications of toxicity even at the highest estimates of exposure level. Listed uses include: anticaking agent , defoaming agent, stabilizer, adsorbent, carrier, conditioning agent, chill proofing agent, filter aid, emulsifying agent, viscosity control agent, and anti-settling agent. Silica can be found commonly in foods including baked goods, spices and herbs, dairy products, cocoa products, and more. Given

630-518: Is also used as cat litter , by itself or in combination with more traditional materials, such as clays including bentonite . It is non-tracking and virtually odorless. Silica gel, also referred to as silicon dioxide or synthetic amorphous silica (SAS), is listed by the FDA in the United States as generally recognized as safe (GRAS), meaning it can be added to food products without needing approval. Silica

672-402: Is commonly described as a way to remove moisture from phones and electronics accidentally exposed to water, but there are no known controlled studies that compare its actual efficacy compared to simple air or fan exposure. The average person is also unlikely to have a sufficient quantity of ready-to-use activated or regenerated silica gel. In chemistry, silica gel is used in chromatography as

714-480: Is non-toxic, and non-reactive and stable with ordinary usage. It will react with hydrogen fluoride , fluorine , oxygen difluoride , chlorine trifluoride , strong acids, strong bases, and oxidizers. Silica gel is irritating to the respiratory tract and may cause irritation of the digestive tract. Dust from the beads may cause irritation to the skin and eyes, so precautions should be taken. Crystalline silica dust can cause silicosis , but synthetic amorphous silica gel

756-470: Is toxic and potentially carcinogenic, but is safe enough to have medicinal uses. Ferric and ferrous salts, sometimes combined with small amounts of sodium hydroxide , provide a better alternative. In particular, ferric sulfate and double salts like ammonium iron(III) sulfate (iron alum), ammonium iron(II) sulfate , and potassium iron(III) sulfate all result in a color change from amber/yellow when dry to colorless/white when saturated. Silica gel

798-719: The Grotta Grande del Vento cave in Ancona, Italy . As pointed out by Rudolf Geiger in his book not only climate influences the living plant but the opposite effect of the interaction of plants on their environment can also take place, and is known as plant climate . This effect has important consequences for forests in the midst of a continent; indeed, if forests were not creating their own clouds and water cycle with their efficient evapotranspiration activity, there would be no forest far away from coasts, as statistically, without any other influence, rainfall occurrence would decrease from

840-414: The ability to remove metal ions selectively from aqueous solutions. Chelating groups can be covalently bound to polyamines that have been grafted onto a silica gel surface producing a material of greater mechanical integrity. Silica gel is also combined with alkali metals to form a M-SG reducing agent . (See SiGNa chemistry ) Silica gel is not expected to biodegrade in either water or soil. Silica gel

882-516: The air in industrial compressed air systems. Air from the compressor discharge flows through a bed of silica gel beads. The silica gel adsorbs moisture from the air, preventing damage at the point of use of the compressed air due to condensation or moisture. The same system is used to dry the compressed air on railway locomotives, where condensation and ice in the brake air pipes can lead to brake failure. Prior to widespread use of air-conditioning, salt shakers with caps containing silica gel beads to keep

SECTION 20

#1733085751958

924-440: The cave atmosphere, air pressure, geochemistry of the cave rock as well as the waste product from these species can combine to make unique microclimates within cave systems. The speleogenetic effect is an observed and studied process of air circulation within cave environments brought on by convection. In phreatic conditions the cave surfaces are exposed to the enclosed air (as opposed to submerged and interacting with water from

966-664: The coast towards inland. Planting trees to fight drought has also been proposed in the context of afforestation . Artificial reservoirs as well as natural ones create microclimates and often influence the macroscopic climate as well. Another contributing factor of microclimate is the slope or aspect of an area. South-facing slopes in the Northern Hemisphere and north-facing slopes in the Southern Hemisphere are exposed to more direct sunlight than opposite slopes and are therefore warmer for longer periods of time, giving

1008-415: The coastal areas stay much milder during winter months, in contrast to the hotter summers. This is the case in places such as British Columbia , where Vancouver has an oceanic wet winter with rare frosts, but inland areas that average several degrees warmer in summer have cold and snowy winters. Two main parameters to define a microclimate within a certain area are temperature and humidity . A source of

1050-521: The environment within that system. Air density within caves, which directly relates to the convection processes, is determined by the air temperature, humidity, and pressure. In enclosed cave environments, the introduction of bacteria, algae, plants, animals, or human interference can change any one of these factors therefore altering the microenvironment within the cave. There are over 750 caves worldwide that are available for people to visit. The constant human traffic through these cave environments can have

1092-416: The gel may be regenerated by heating it to 120 °C (248 °F) for 1–2 hours. Some types of silica gel will "pop" when exposed to enough water. This is caused by breakage of the silica spheres when contacting the water. An aqueous solution of sodium silicate is acidified to produce a gelatinous precipitate that is washed, then dehydrated to produce colorless silica gel. When a visible indication of

1134-416: The last case, the material is properly called silica xerogel . Silica xerogel with an average pore size of 2.4 nanometers has a strong affinity for water molecules and is widely used as a desiccant . It is hard and translucent , but considerably softer than massive silica glass or quartz , and remains hard when saturated with water. Silica xerogel is usually commercialized as coarse granules or beads,

1176-402: The lifespan of chemicals, like those in vitamins. Silica gel packets help by absorbing moisture and extending the life of these items. Silica gel may also be used to keep the relative humidity inside a high frequency radio or satellite transmission system waveguide as low as possible (see also humidity buffering ). Excessive moisture buildup within a waveguide can cause arcing inside

1218-545: The local atmosphere, or in heavy urban areas where brick , concrete , and asphalt absorb the sun's energy, heat up, and re-radiate that heat to the ambient air: the resulting urban heat island (UHI) is a kind of microclimate that is additionally driven by relative paucity of vegetation . The terminology "micro-climate" first appeared in the 1950s in publications such as Climates in Miniature: A Study of Micro-Climate Environment (Thomas Bedford Franklin, 1955). The area in

1260-473: The microenvironment can be drastically enhanced. One example is the effect of the presence of hydro sulfuric acid ( H 2 S ). When the oxidized hydrosulfuric acid chemically alters to sulfuric acid( H 2 SO 4 ), this acid starts to react with the calcium carbonate rock at much higher rates. The water involved in this reaction tends to have a high pH of 3 which renders the water almost unlivable for many bacteria and algae. An example of this can be found in

1302-602: The moisture content of the silica gel is required, ammonium tetrachlorocobaltate(II) (NH 4 ) 2 [CoCl 4 ] or cobalt(II) chloride CoCl 2 is added. This will cause the gel to be blue when dry and pink when hydrated. Due to a link between the cobalt chloride and cancer, it has been forbidden in Europe for use in silica gel. An alternative indicator is methyl violet which is orange when dry and green when hydrated. Moisture can cause mold and spoilage in many items. It can also damage electronics by causing condensation and shorten

Stony Range Botanic Garden - Misplaced Pages Continue

1344-708: The name normal phase chromatography . However, when hydrophobic groups (such as C 18 groups) are attached to the silica gel then polar components elute first and the method is referred to as reverse phase chromatography . Silica gel is also applied to aluminium , glass , or plastic sheets for thin layer chromatography . The hydroxy (OH) groups on the surface of silica can be functionalized to afford specialty silica gels that exhibit unique stationary phase parameters. These so-called functionalized silica gels are also used in organic synthesis and purification as insoluble reagents and scavengers . Chelating groups have also been covalently bound to silica gel. These materials have

1386-529: The near ground temperature. On the other hand, if soil has many air pockets, then the heat could be trapped underneath the topsoil, resulting in the increased possibility of frost at ground level. Silica gel Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer -scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum . In

1428-443: The salt dry enough to prevent clumping were marketed in the USA, replacing the practice of including a few grains of rice in salt shakers to effect the same drying. Silica gel is sometimes used as a preservation tool to control relative humidity in museum and library exhibitions and storage. Other applications include diagnostic test strips, inhalation devices, syringes , drug test kits , and hospital sanitation kits. Silica gel

1470-422: The slope a warmer microclimate than the areas around the slope. The lowest area of a glen may sometimes frost sooner or harder than a nearby spot uphill, because cold air sinks, a drying breeze may not reach the lowest bottom, and humidity lingers and precipitates , then freezes . The type of soil found in an area can also affect microclimates. For example, soils heavy in clay can act like pavement, moderating

1512-448: The threshold wind speed. The presence of permafrost close to the surface in a crater creates a unique microclimate environment. Caves are important geologic formations that can house unique and delicate geologic/biological environments. The vast majority of caves found are made of calcium carbonates such as limestone . In these dissolution environments, many species of flora and fauna find home. The mixture of water content within

1554-433: The water adsorption properties of silica gel, it is used in domestic water filters. The surface structure of silica gel allows the adsorption of some minerals that are dissolved in the water, or "Ion-exchange" as it is marketed. Due to the lack of regulations for domestic water filtration products, no studies validate the manufacturer claims regarding the effectiveness of the filtration system. Silica gel may be doped with

1596-492: The water table in vadose conditions). This air circulates water particles that condense on cave walls and formations such as speleothems . This condensing water has been found to contribute to cave wall erosion and the formation of morphological features. Some examples of this can be found in the limestone walls of Grotta Giusti ; a thermal cave near Monsummano , Lucca, Italy. Any process that leads to an increase or decrease in chemical/physical processes will subsequently impact

1638-407: The waveguide itself, damaging the power amplifier feeding it. Also, the beads of water that form and condense inside the waveguide change the characteristic impedance and frequency, degrading the signal. It is common for a small compressed air system (similar to a small home aquarium pump) to be employed to circulate the air inside the waveguide over a jar of silica gel. Silica gel is also used to dry

1680-592: The wind speed v {\displaystyle v} in order to create a warm air flow penetration into a CAP is the following: where F r {\displaystyle \mathrm {Fr} } is the Froude number , N {\displaystyle N} — the Brunt–Väisälä frequency , h {\displaystyle h} — depth of the valley, and F r c {\displaystyle \mathrm {Fr} _{c}} — Froude number at

1722-697: Was patented in 1918 by Walter A. Patrick, a chemistry professor at Johns Hopkins University . Silica alumina gel - light yellow, chemically stable, flame-resistant, insoluble except in alkali or hydrofluoric acid. Superficial polarity, thermal stability, performance greater than fine-pored silica gel. Stabilizing silica gel - non-crystalline micro-porous solid powder, nontoxic, flame-resisting, used in brewery of grains for beer to improve taste, clearness, color, and foam and for removal of non-micro-organism impurities. Silica gel's high specific surface area (around 750–800 m /g (230,000–240,000 sq ft/oz)) allows it to adsorb water readily, making it useful as

Stony Range Botanic Garden - Misplaced Pages Continue

1764-474: Was revegetated and regenerated by local volunteers using local indigenous species as well as native plants from across Australia. Today, there are several microclimates within the garden: the rainforest gully, the sandstone heath, and the Federation Cascades. 33°45′28″S 151°16′58″E  /  33.75778°S 151.28278°E  / -33.75778; 151.28278 This article related to

#957042