platinum

Platinumis a chemical elementwith the chemical symbolPtand an atomic numberof 78. It is a dense, malleable, ductile, highly unreactive, precious, gray-white transition metal. Its name is derived from the Spanish termplatina, which is literally translated into "little silver". [ 1 ] [ 2 ] Platinum is a member of the platinum groupof elements and group 10of the periodic table of elements. It has six naturally occurring isotopes. It is one of the rarest elements in the Earth's crustwith an average abundance of approximately 5 μg/kg. It occurs in some nickeland copperores along with some nativedeposits, mostly in South Africa, which accounts for 80% of the world production. Because of its scarcity in the earth's crust, only a few hundred tonnesare produced annually, and is therefore highly valuable and is a major precious metal commodity. Platinum is the least reactive metal. It has remarkable resistance to corrosion, even at high temperatures, and is therefore considered a noble metal. Consequently, platinum is often found chemically uncombined as native platinum. Because it occurs naturally in the alluvial sandsof various rivers, it was first used by pre-ColumbianSouth American natives to produce artifacts. It was referenced in European writings as early as 16th century, but it was not until Antonio de Ulloapublished a report on a new metal of Colombianorigin in 1748 that it became investigated by scientists. Platinum is used in catalytic converters, laboratory equipment, electricalcontacts and electrodes, platinum resistance thermometers, dentistryequipment, and jewellery. Being a heavy metal, it leads to health issues upon exposure to its salts, but due to its corrosion resistance, it is not as toxic as some metals. [ 3 ]Compounds containing platinum, most notably cisplatin, are applied in chemotherapyagainst certain types of cancer. [ 4 ] Characteristics Physical Pure platinum is a lustrous, ductile, and malleable, silver-white metal. [ 5 ]Platinum is more ductilethan gold, silver or copper, thus being the most ductile of pure metals, but it is less malleable than gold. [ 6 ] [ 7 ]Pure platinum is slightly harder than pure iron.[ citation needed]The metal has excellent resistance to corrosion, is stable at high temperatures and has stable electrical properties. It does not oxidize at any temperature, although it is corroded by halogens, cyanides, sulfur, and caustic alkalis. Platinum is insoluble in hydrochloricand nitric acid, but dissolves in hot aqua regiato form chloroplatinic acid, H2PtCl6.Blog Directory at OnToplist.comBlog Directory | Submit to Directories and Promote your BlogsBlog Directory at OnToplist.com

Diamond

In mineralogy,diamond(from the ancient Greekαδάμας –adámas"unbreakable") is a metastable allotrope of carbon, where the carbon atomsare arranged in a variation of the face-centered cubiccrystal structure called a diamond lattice. Diamond is less stablethan graphite, but the conversion rate from diamond to graphite is negligible at standard conditions. Diamond is renowned as a material with superlative physical qualities, most of which originate from the strong covalent bondingbetween its atoms. In particular, diamond has the highest hardnessand thermal conductivityof any bulk material. Those properties determine the major industrial application of diamond in cutting and polishing tools and the scientific applications in diamond knivesand diamond anvil cells. Because of its extremely rigid lattice, it can be contaminated by very few types of impurities, such as boronand nitrogen. Small amounts of defects or impurities (about one per million of lattice atoms) color diamond blue (boron), yellow (nitrogen), brown ( lattice defects), green (radiation exposure), purple, pink, orange or red. Diamond also has relatively high optical dispersion(ability to disperse light of different colors). Most natural diamonds are formed at high temperature and pressure at depths of 140 to 190 kilometers (87 to 118 mi) in the Earth's mantle. Carbon-containing minerals provide the carbon source, and the growth occurs over periods from 1 billion to 3.3 billion years (25% to 75% of the age of the Earth). Diamonds are brought close to the Earth's surface through deep volcanic eruptionsby a magma, which cools into igneous rocksknown as kimberlitesand lamproites. Diamonds can also be produced synthetically in a high-pressure high-temperatureprocess which approximately simulates the conditions in the Earth's mantle. An alternative, and completely different growth technique is chemical vapor deposition(CVD). Several non-diamond materials, which include cubic zirconiaand silicon carbideand are often called diamond simulants, resemble diamond in appearance and many properties. Special gemologicaltechniques have been developed to distinguish natural and synthetic diamondsand diamond simulants.Blog Directory at OnToplist.com

ELECTRO CONDUCTIVE THREAD

On a pound-per-pound basis, carbon nanotube-based fibers invented at Rice University have greater capacity to carry electrical current than copper cables of the same mass, according to new research. While individual nanotubes are capable of transmitting nearly 1,000 times more current than copper, the same tubes coalesced into a fiber using other technologies fail long before reaching that capacity.Credit: Illustration by Tanyia Johnson [Click to enlarge image] On a pound-per-pound basis, carbon nanotube-based fibers invented at Rice University have greater capacity to carry electrical current than copper cables of the same mass, according to new research. While individual nanotubes are capable of transmitting nearly 1,000 times more current than copper, the same tubes coalesced into a fiber using other technologies fail long before reaching that capacity. But a series of tests at Rice showed the wet-spun carbon nanotube fiber still handily beat copper, carrying up to four times as much current as a copper wire of the same mass. Scanning electron microscope images show typical carbon nanotube fibers created at Rice University and broken into two by high-current-induced Joule heating. Rice researchers broke the fibers in different conditions -- air, argon, nitrogen and a vacuum -- to see how well they handled high current. The fibers proved overall to be better at carrying electrical current than copper cables of the same mass. (Credit: Kono Lab/Rice University) That, said the researchers, makes nanotube-based cables an ideal platform for lightweight power transmission in systems where weight is a significant factor, like aerospace applications. The analysis led by Rice professors Junichiro Kono and Matteo Pasquali appeared online this week in the journalAdvanced Functional Materials. Just a year ago the journal Science reported that Pasquali's lab, in collaboration with scientists at the Dutch firm Teijin Aramid, created a very strong conductive fiber out of carbon nanotubes. Present-day transmission cables made of copper or aluminum are heavy because their low tensile strength requires steel-core reinforcement. Scientists working with nanoscale materials have long thought there's a better way to move electricity from here to there. Certain types of carbon nanotubes can carry far more electricity than copper. The ideal cable would be made of long metallic "armchair" nanotubes that would transmit current over great distances with negligible loss, but such a cable is not feasible because it's not yet possible to manufacture pure armchairs in bulk, Pasquali said. In the meantime, the Pasquali lab has created a method to spin fiber from a mix of nanotube types that still outperforms copper. The cable developed by Pasquali and Teijin Aramid is strong and flexible even though at 20 microns wide, it's thinner than a human hair. Pasquali turned to Kono and his colleagues, including lead author Xuan Wang, a postdoctoral researcher at Rice, to quantify the fiber's capabilities. Pasquali said there has been a disconnect between electrical engineers who study the current carrying capacity of conductors and materials scientists working on carbon nanotubes. "That has generated some confusion in the literature over the right comparisons to make," he said. "Jun and Xuan really got to the bottom of how to do these measurements well and compare apples to apples." The researchers analyzed the fiber's "current carrying capacity" (CCC), or ampacity, with a custom rig that allowed them to test it alongside metal cables of the same diameter.

CONDUCTIVE TEXTILE

Aconductive textileis a fabricwhich can conduct electricity. Conductive textiles can be made with metal strands woveninto the construction of the textile. There is also an interest in semiconducting textiles, made by impregnating normal textiles with carbon- or metal-based powders. [ 1 ] Conductive fibers consist of a non-conductive or less conductive substrate, which is then either coated or embedded with electrically conductive elements, often carbon, nickel, copper, gold, silver, or titanium. Substrates typically include cotton, polyester, nylon, and stainless steelto high performance fibers such as aramids and PBO. Straddling the worlds of textiles and wires, conductive fibers are sold either by weight or length, and measured in denieror AWG. Because of the rapid growth in the kinds of conductive fibers and the uses of these fibers, a trade association has been formed to increase awareness, utilization, and possibly standarize terminology. The association is Conductive Fiber Manufacturers Council. [ 2 ] Applications Uses for conductive fibers and textiles may include staticdissipation, EMI shielding, [ 3 ]signal and power transfer in low resistanceversions, and as a heating elementin higher resistance versions. Their benefits over solid or stranded metal wires come from conductive fibers' flexibility and ability to use them in existing textile and wire machinery (weaving, knitting, braiding, etc.) Another more recent use is in the production of 'Stun gun' or Taser proof clothing, where the conductive textile is used as a sort of Faraday shield in a layer of the garment in question. Conductive fabric can also be used to make electrodesfor EEGand other medical applications; [ 4 ]such electrodes were used in a commercially-available sleep-monitoring device made by former company Zeo, Inc.Highly conductive stainless steel fiber is available.

CNT CARBON NANOTUBE

Carbon nanotubes(CNTs) are allotropes of carbonwith a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, [ 1 ]significantly larger than for any other material. These cylindrical carbon moleculeshave unusual properties, which are valuable for nanotechnology, electronics, opticsand other fields of materials scienceand technology. In particular, owing to their extraordinary thermal conductivityand mechanical and electricalproperties, carbon nanotubes find applications as additives to various structural materials. For instance, nanotubes form a tiny portion of the material(s) in some (primarily carbon fiber) baseball bats, golf clubs, or car parts. [ 2 ] Nanotubes are members of the fullerenestructural family. Their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene. These sheets are rolled at specific and discrete (" chiral") angles, and the combination of the rolling angle and radius decides the nanotube properties; for example, whether the individual nanotube shell is a metalor semiconductor. Nanotubes are categorized as single-walled nanotubes(SWNTs) and multi-walled nanotubes(MWNTs). Individual nanotubes naturally align themselves into "ropes" held together by van der Waals forces, more specifically, pi-stacking. Applied quantum chemistry, specifically, orbital hybridizationbest describes chemical bonding in nanotubes. The chemical bondingof nanotubes is composed entirely of sp 2 bonds, similar to those of graphite. These bonds, which are stronger than the sp 3 bondsfound in alkanesand diamond, provide nanotubes with their unique strength. Types of carbon nanotubes and related structures Terminology There is no consensus on some terms describing carbon nanotubes in scientific literature: both "-wall" and "-walled" are being used in combination with "single", "double", "triple" or "multi", and the letter C is often omitted in the abbreviation; for example, multi-walled carbon nanotube (MWNT) Most single-walled nanotubes (SWNT) have a diameter of close to 1 nanometer, with a tube length that can be many millions of times longer. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite called graphene into a seamless cylinder. The way the graphene sheet is wrapped is represented by a pair of indices (n,m). The integersnandmdenote the number of unit vectorsalong two directions in the honeycomb crystal latticeof graphene. Ifm= 0, the nanotubes are called zigzag nanotubes, and ifn=m, the nanotubes are called armchair nanotubes. Otherwise, they are called chiral. The diameter of an ideal nanotube can be calculated from its (n,m) indices as follows wherea= 0.246 nm. SWNTs are an important variety of carbon nanotube because most of their properties change significantly with the (n,m) values, and this dependence is non-monotonic (see Kataura plot). In particular, their band gapcan vary from zero to about 2 eV and their electrical conductivity can show metallic or semiconducting behavior. Single-walled nanotubes are likely candidates for miniaturizing electronics. The most basic building block of these systems is the electric wire, and SWNTs with diameters of an order of a nanometer can be excellent conductors. [ 3 ] [ 4 ]One useful application of SWNTs is in the development of the first intermolecular field-effect transistors(FET). The first intermolecular logic gateusing SWCNT FETs was made in 2001. [ 5 ]A logic gate requires both a p-FET and an n-FET.

NICHROME

Nichromeis a non-magnetic alloyof nickel, chromium, and often iron, usually used as a resistance wire. History Patented in 1905, it is the oldest documented form of resistance heating alloy. A common alloy is 80% nickel and 20% chromium, by mass, but there are many others to accommodate various applications. It is silvery-grey in colour, is corrosion-resistant, and has a high melting pointof about 1,400 °C(2,550 °F). Due to its resistance to oxidationand stability at high temperatures, it is widely used in electric heating elements, such as in appliances and tools. Typically, nichrome is wound in coils to a certain electrical resistance, and current is passed through it to produce heat. Uses Nichrome is used in the explosivesand fireworksindustry as a bridgewirein electric ignition systems, such as electric matchesand model rocketigniters. Industrial and hobby hot-wire foam cuttersuse nichrome wire. Nichrome wire is commonly used in ceramicas an internal support structure to help some elements of claysculptures hold their shape while they are still soft. Nichrome wire is used for its ability to withstand the high temperatures that occur when clay work is fired in a kiln. Nichrome wire can be used as an alternative to platinumwire for flame testingby colouring the non-luminous part of a flame to detect cationssuch as sodium, potassium, copper, calcium etc. The alloytends to be expensive due to its high nickelcontent. Distributor pricing is typically indexed to commodity market prices for nickel. Other areas of usage include motorcycle silencers, in certain areas in the microbiological lab apparatus, and as the heating element of plastic extruders by the RepRap3D printing community. For heating, resistance wire must be stable in air when hot. Nichrome wire forms a protective layer of chromium oxide. [ 1 ] Nichrome may be also used as the coils of electronic cigarettes for vaping. Properties The properties of nichrome vary depending on its alloy. Figures given are representative of typical material and are accurate to expressed significant figures. Any variations are due to different percentages of nickel or chromium. Material propertyValueUnit Modulus of elasticity2.2 × 1011Pa Density8400kg/m3 Melting point1400 °C Electrical resistivity at room temperature(1.0—1.5) × 10−6Ω·m Specific heat450J/(kg· K) Thermal conductivity11.3W/(m·K) Thermal expansion14 × 10−6K−1 Standard ambient temperature and pressure used unless otherwise noted. Table 1: Resistance per inch (Ω), closed helix, 80/20 alloy. [ 2 ] Wire Gauge ( B&SNo. / AWG)Outside Diameter of Helix(inches) 3/45/81/23/81/47/323/165/321/83/321/161/32 140.4460.3650.2830.2020.1210.101 150.6380.5230.4080.2930.1780.1480.120 160.8950.7350.5750.4150.2550.2150.1750.135 171.321.080.8510.6170.3830.3250.2660.2080.150 181.891.561.220.8910.5590.4750.3920.3090.226 192.602.141.691.230.7790.6650.5510.4380.324 203.723.072.421.781.130.9670.8050.6440.482 214.533.582.631.681.451.210.9710.7330.496 224.983.672.362.031.701.371.05.719 237.025.183.342.882.421.961.511.05 237.025.183.342.882.421.961.511.05 244.694.053.412.782.141.60.865 256.875.945.024.103.172.251.32

Kidney Stone

Kidney stone Classification and external resources A kidney stone, 8 millimeters (0.31 in) in diameter ICD- 10 N 20.0– N 20.9 ICD- 9 592.0, 592.1, 592.9 DiseasesDB 11346 MedlinePlus 000458 eMedicine med/1600 MeSH D007669 Akidney stone, also known as arenal calculus(from the Latinrēnēs, "kidneys," and calculus, "pebble"), is a solid concretionor crystalaggregation formed in the kidneys from dietary mineralsin the urine. Urinary stonesare typically classified by their location in the kidney(nephrolithiasis), ureter(ureterolithiasis), or bladder( cystolithiasis), or by their chemical composition( calcium-containing, struvite, uric acid, or other compounds). About 80% of those with kidney stones are men. Kidney stones typically leave the body by passage in the urine stream, and many stones are formed and passed without causing symptoms. If stones grow to sufficient size (usually at least 3 millimeters (0.12 in)) they can cause obstruction of the ureter. Ureteral obstruction causes postrenal azotemiaand hydronephrosis(distension and dilation of the renal pelvisand calyces), as well as spasmof the ureter. This leads to pain, most commonly felt in the flank(the area between the ribs and hip), lower abdomen, and groin(a condition called renal colic). Renal colic can be associated with nausea, vomiting, fever, blood in the urine, pusin the urine, and painful urination. Renal colic typically comes in waves lasting 20 to 60 minutes, beginning in the flank or lower back and often radiating to the groin or genitals. The diagnosisof kidney stones is made on the basis of information obtained from the history, physical examination, urinalysis, and radiographicstudies. Ultrasound examinationand blood testsmay also aid in the diagnosis. When a stone causes no symptoms, watchful waitingis a valid option. For symptomatic stones, pain controlis usually the first measure, using medications such as nonsteroidal anti-inflammatory drugsor opioids. More severe cases may require surgical intervention. For example, some stones can be shattered into smaller fragments using extracorporeal shock wave lithotripsy. Some cases require more invasiveforms of surgery. Examples of these are cystoscopicprocedures such as laser lithotripsyor percutaneoustechniques such as percutaneous nephrolithotomy. Sometimes, a tube ( ureteral stent) may be placed in the ureter to bypass the obstruction and alleviate the symptoms, as well as to prevent ureteral stricture after ureteroscopic stone removal. Signs and symptoms Diagram showing the typical location of renal colic, below the rib cage to just above the pelvis The hallmark of stones that obstruct the ureter or renal pelvis is excruciating, intermittent pain that radiates from the flank to the groin or to the inner thigh. [ 1 ]This particular type of pain, known as renal colic, is often described as one of the strongest pain sensations known. [ 2 ]Renal colic caused by kidney stones is commonly accompanied by urinary urgency, restlessness, hematuria, sweating, nausea, and vomiting. It typically comes in waves lasting 20 to 60 minutes caused by peristalticcontractions of the ureter as it attempts to expel the stone. [ 1 ]The embryologicallink between the urinary tract, the genital system, and the gastrointestinal tractis the basis of the radiation of pain to the gonads, as well as the nausea and vomiting that are also common in urolithiasis. [ 3 ] Postrenal azotemiaand hydronephrosis can be observed following the obstruction of urine flow through one or both ureters.

Kidney Stone

Kidney stone Classification and external resources A kidney stone, 8 millimeters (0.31 in) in diameter ICD- 10 N 20.0– N 20.9 ICD- 9 592.0, 592.1, 592.9 DiseasesDB 11346 MedlinePlus 000458 eMedicine med/1600 MeSH D007669 Akidney stone, also known as arenal calculus(from the Latinrēnēs, "kidneys," and calculus, "pebble"), is a solid concretionor crystalaggregation formed in the kidneys from dietary mineralsin the urine. Urinary stonesare typically classified by their location in the kidney(nephrolithiasis), ureter(ureterolithiasis), or bladder( cystolithiasis), or by their chemical composition( calcium-containing, struvite, uric acid, or other compounds). About 80% of those with kidney stones are men. Kidney stones typically leave the body by passage in the urine stream, and many stones are formed and passed without causing symptoms. If stones grow to sufficient size (usually at least 3 millimeters (0.12 in)) they can cause obstruction of the ureter. Ureteral obstruction causes postrenal azotemiaand hydronephrosis(distension and dilation of the renal pelvisand calyces), as well as spasmof the ureter. This leads to pain, most commonly felt in the flank(the area between the ribs and hip), lower abdomen, and groin(a condition called renal colic). Renal colic can be associated with nausea, vomiting, fever, blood in the urine, pusin the urine, and painful urination. Renal colic typically comes in waves lasting 20 to 60 minutes, beginning in the flank or lower back and often radiating to the groin or genitals. The diagnosisof kidney stones is made on the basis of information obtained from the history, physical examination, urinalysis, and radiographicstudies. Ultrasound examinationand blood testsmay also aid in the diagnosis. When a stone causes no symptoms, watchful waitingis a valid option. For symptomatic stones, pain controlis usually the first measure, using medications such as nonsteroidal anti-inflammatory drugsor opioids. More severe cases may require surgical intervention. For example, some stones can be shattered into smaller fragments using extracorporeal shock wave lithotripsy. Some cases require more invasiveforms of surgery. Examples of these are cystoscopicprocedures such as laser lithotripsyor percutaneoustechniques such as percutaneous nephrolithotomy. Sometimes, a tube ( ureteral stent) may be placed in the ureter to bypass the obstruction and alleviate the symptoms, as well as to prevent ureteral stricture after ureteroscopic stone removal. Signs and symptoms Diagram showing the typical location of renal colic, below the rib cage to just above the pelvis The hallmark of stones that obstruct the ureter or renal pelvis is excruciating, intermittent pain that radiates from the flank to the groin or to the inner thigh. [ 1 ]This particular type of pain, known as renal colic, is often described as one of the strongest pain sensations known. [ 2 ]Renal colic caused by kidney stones is commonly accompanied by urinary urgency, restlessness, hematuria, sweating, nausea, and vomiting. It typically comes in waves lasting 20 to 60 minutes caused by peristalticcontractions of the ureter as it attempts to expel the stone. [ 1 ]The embryologicallink between the urinary tract, the genital system, and the gastrointestinal tractis the basis of the radiation of pain to the gonads, as well as the nausea and vomiting that are also common in urolithiasis. [ 3 ] Postrenal azotemiaand hydronephrosis can be observed following the obstruction of urine flow through one or both ureters.

Kidney Stone

Kidney stone Classification and external resources A kidney stone, 8 millimeters (0.31 in) in diameter ICD- 10 N 20.0– N 20.9 ICD- 9 592.0, 592.1, 592.9 DiseasesDB 11346 MedlinePlus 000458 eMedicine med/1600 MeSH D007669 Akidney stone, also known as arenal calculus(from the Latinrēnēs, "kidneys," and calculus, "pebble"), is a solid concretionor crystalaggregation formed in the kidneys from dietary mineralsin the urine. Urinary stonesare typically classified by their location in the kidney(nephrolithiasis), ureter(ureterolithiasis), or bladder( cystolithiasis), or by their chemical composition( calcium-containing, struvite, uric acid, or other compounds). About 80% of those with kidney stones are men. Kidney stones typically leave the body by passage in the urine stream, and many stones are formed and passed without causing symptoms. If stones grow to sufficient size (usually at least 3 millimeters (0.12 in)) they can cause obstruction of the ureter. Ureteral obstruction causes postrenal azotemiaand hydronephrosis(distension and dilation of the renal pelvisand calyces), as well as spasmof the ureter. This leads to pain, most commonly felt in the flank(the area between the ribs and hip), lower abdomen, and groin(a condition called renal colic). Renal colic can be associated with nausea, vomiting, fever, blood in the urine, pusin the urine, and painful urination. Renal colic typically comes in waves lasting 20 to 60 minutes, beginning in the flank or lower back and often radiating to the groin or genitals. The diagnosisof kidney stones is made on the basis of information obtained from the history, physical examination, urinalysis, and radiographicstudies. Ultrasound examinationand blood testsmay also aid in the diagnosis. When a stone causes no symptoms, watchful waitingis a valid option. For symptomatic stones, pain controlis usually the first measure, using medications such as nonsteroidal anti-inflammatory drugsor opioids. More severe cases may require surgical intervention. For example, some stones can be shattered into smaller fragments using extracorporeal shock wave lithotripsy. Some cases require more invasiveforms of surgery. Examples of these are cystoscopicprocedures such as laser lithotripsyor percutaneoustechniques such as percutaneous nephrolithotomy. Sometimes, a tube ( ureteral stent) may be placed in the ureter to bypass the obstruction and alleviate the symptoms, as well as to prevent ureteral stricture after ureteroscopic stone removal. Signs and symptoms Diagram showing the typical location of renal colic, below the rib cage to just above the pelvis The hallmark of stones that obstruct the ureter or renal pelvis is excruciating, intermittent pain that radiates from the flank to the groin or to the inner thigh. [ 1 ]This particular type of pain, known as renal colic, is often described as one of the strongest pain sensations known. [ 2 ]Renal colic caused by kidney stones is commonly accompanied by urinary urgency, restlessness, hematuria, sweating, nausea, and vomiting. It typically comes in waves lasting 20 to 60 minutes caused by peristalticcontractions of the ureter as it attempts to expel the stone. [ 1 ]The embryologicallink between the urinary tract, the genital system, and the gastrointestinal tractis the basis of the radiation of pain to the gonads, as well as the nausea and vomiting that are also common in urolithiasis. [ 3 ] Postrenal azotemiaand hydronephrosis can be observed following the obstruction of urine flow through one or both ureters.

Bladder Store

Bladder stone Classification and external resources A star-shaped urolith can be seen in the urinary bladderon this radiographof the pelvis ICD- 10 N 21.0- N 21.9 ICD- 9 594.0, 594.1, 594.2, 594.8, 594.9 DiseasesDB 31859 MedlinePlus 001275 eMedicine ped/2371 MeSH D001744 Bladderstones incidentally found in a bladder diverticulumduring transvesical prostatectomy(removal of the prostate via an incision in the bladder) Abladder stone(also called avesical calculusorcystolith) is a stonefound in the urinary bladder. The termcystolithiasisrefers to the presence of stones in the bladder. [ 1 ] Classification Urinary stones may be composed of the following substances: [ 2 ] *. Calcium oxalate monohydrate(whewellite) *. Calcium oxalate dihydrate(weddellite) *. Calcium phosphate *. Magnesium phosphate *. Ammonium phosphate *. Ammonium magnesium phosphate(struvite) *. Calcium hydroxyphosphate(apatite) *. Uric acidand its salts (urates) *. Cystine *. Xanthine *.Indigotin (rare) *. Urostealith(rare) *. Sulfonamide(rare) Signs and symptoms Bladder stones are small particles that can form in the bladder. In most cases bladder stones develop when the urine becomes very concentrated or when one is dehydrated. This allows for the minerals like calcium or magnesium to crystallize and form stones. Bladder stones vary in number, size and consistency. In some cases bladder stones do not cause any symptoms and are discovered as an incidental finding on a plain radiograph. However, when symptoms do occur, these may include severe lower abdominal and back pain, difficult urination, frequent urination at night, fever, painful urination and blood in the urine. The majority of individuals who are symptomatic will complain of pain which comes in waves. The pain may also be associated with nausea, vomiting and chills. [ 3 ] Bladder stones vary in their size, shape and texture- some are small, hard and smooth whereas others are huge, spiked and very soft. One can have one or multiple stones. Bladder stones are somewhat more common in men who have prostate enlargement. The large prostatepresses on the urethra and makes it difficult to pass urine. Over time, stagnant urine collects in the bladder and minerals like calcium start to precipitate. Other individuals who develop bladder stones include those who have had spinal cord injury, paralysis, or some type of nerve damage. When nerves to the back are damaged, the bladder cannot empty, resulting in stagnant urine. [ 4 ] Causes Bladder stones may occur whenever the kidneys, bladder, or ureters become inflamed, which may occur when the urinebecomes too concentrated or when the body becomes dehydrated. Minerals such as calcium and magnesium crystallize into the stones, which then can cause such symptoms as lower back or abdominal pain or difficulty with urination. The use of urinary cathetersmay cause a bladder stone. Individuals who are paralyzed or are unable to adequately pass urine may require the use of small plastic tubes ( catheters) placed into the bladder. The use of these tubes may lead to an infection, which irritates the bladder, resulting in stone formation. Finally, a kidney stone may travel down the ureter into the bladder and become a bladder stone. There is some evidence indicating that chronic irritation of the bladder by retained stones may increase the chance of bladder cancer. Urinary schistosomiasis, a disease caused by the digenean trematode Schistosoma haematobium, has been implicated in the development of vesical calculi. [ 5 ] [ 6 ]However, evidence accumulated thus far has not supported this hypothesis.