Math Is Fun Forum

2462) Selman Waksman

Gist:

Work

After Robert Koch discovered that tuberculosis is caused by a bacterium, the hunt for a cure began. In 1939 Selman Waksman and colleagues began systematic studies of how microorganisms in soil affect tubercle bacteria. They found that their growth was impeded by another bacterium, Streptomyces grisues. In 1943 Waksman's colleague, Albert Schatz, isolated streptomycin from this bacterium, which proved an effective medicine against tuberculosis.

Summary

Selman Abraham Waksman (born July 22, 1888, Priluka, Ukraine, Russian Empire [now Pryluky, Ukraine]—died August 16, 1973, Hyannis, Massachusetts, U.S.) was a Ukrainian-born American biochemist who was one of the world’s foremost authorities on soil microbiology. After the discovery of penicillin, he played a major role in initiating a calculated, systematic search for antibiotics among microbes. His screening methods and consequent co-discovery of the antibiotic streptomycin, the first specific agent effective in the treatment of tuberculosis, brought him the 1952 Nobel Prize for Physiology or Medicine.

A naturalized U.S. citizen (1916), Waksman spent most of his career at Rutgers University, New Brunswick, New Jersey, where he served as professor of soil microbiology (1930–40), professor of microbiology and chairman of the department (1940–58), and director of the Rutgers Institute of Microbiology (1949–58). During his extensive study of the actinomycetes (filamentous, bacteria-like microorganisms found in the soil), he extracted from them antibiotics (a term he coined in 1941) valuable for their killing effect not only on gram-positive bacteria, such as the tubercle bacillus (Mycobacterium tuberculosis, which unlike other gram-positive microbes is insensitive to penicillin), but also on gram-negative bacteria, such as the organisms that cause cholera (Vibrio cholerae) and typhoid fever (Salmonella typhi).

In 1940 Waksman, along with his graduate student H. Boyd Woodruff, isolated actinomycin from soil bacteria. Although the substance was effective against strains of gram-negative and gram-positive bacteria, including M. tuberculosis, it was extremely toxic when given to test animals. Four years later Waksman and graduate students Albert Schatz and Elizabeth Bugie published a paper describing their discovery of the relatively nontoxic streptomycin, which they extracted from the actinomycete Streptomyces griseus. They found that the antibiotic exercised repressive influence on tuberculosis. In combination with other chemotherapeutic agents, streptomycin has become a major factor in controlling the disease. Waksman also isolated and developed several other antibiotics, including neomycin, that have been used in treating many infectious diseases of humans, domestic animals, and plants.

Among Waksman’s books are Principles of Soil Microbiology (1927), regarded as one of the most exhaustive works on the subject, and My Life with the Microbes (1954), an autobiography.

Details

Selman Abraham Waksman (July 22, 1888 – August 16, 1973) was a Russian-born American inventor, biochemist and microbiologist, whose research into the decomposition of organisms that live in soil enabled the discovery of streptomycin and several other antibiotics. For his work he won the 1952 Nobel Prize in Physiology or Medicine.

Waksman emigrated to the United States in 1910 and became a naturalized U.S. citizen in 1916. A professor of biochemistry and microbiology at Rutgers University for four decades, he discovered several antibiotics (and introduced the modern sense of that word to name them), and he introduced procedures that have led to the development of many others. The proceeds earned from the licensing of his patents funded a foundation for microbiological research, which established the Waksman Institute of Microbiology located at the Rutgers University Busch Campus in Piscataway, New Jersey (USA). After receiving the Nobel Prize, Waksman and his foundation later were sued by Albert Schatz, one of his Ph.D. students and the discoverer of streptomycin, for minimizing Schatz's role in the discovery.

In 2005, Waksman was granted an ACS National Historic Chemical Landmark in recognition of the significant work of his lab in isolating more than 15 antibiotics, including streptomycin, which was the first effective treatment for tuberculosis.

Early life and education

Selman Waksman was born on July 22 [O.S. July 8] 1888, to Jewish parents, in Nova Pryluka, Kiev Governorate, Russian Empire, now Vinnytsia Oblast, Ukraine. He was the son of Fradia (London) and Jacob Waksman. In 1910, shortly after receiving his diploma from the Fifth Gymnasium in Odessa, he immigrated to the United States and became a naturalized American citizen in 1916.

Waksman attended Rutgers College (now Rutgers University), where he graduated in 1915 with a Bachelor of Science in agriculture. He continued his studies at Rutgers, receiving a Master of Science the following year, in 1916. During his graduate study, he worked under J. G. Lipman at the New Jersey Agricultural Experiment Station at Rutgers performing research in soil bacteriology. Waksman spent some months in 1915–1916 at the United States Department of Agriculture in Washington, DC under Charles Thom, studying soil fungi.  He was appointed as a research fellow at the University of California, Berkeley, and in 1918 he was awarded his doctor of philosophy in biochemistry.

Career

He joined the faculty at Rutgers University in the Department of Biochemistry and Microbiology.

At Rutgers, Waksman's team discovered several antibiotics, including actinomycin, clavacin, streptothricin, streptomycin, grisein, neomycin, fradicin, candicidin, candidin. Waksman co-discovered streptomycin with Albert Schatz. Streptomycin was the first effective drug against gram-negative bacteria and the first antibiotic used to cure tuberculosis. Waksman is credited with coining the term antibiotics to describe antibacterials derived from other living organisms, for example penicillin, though the term was used by the French dermatologist François Henri Hallopeau, in 1871 to describe a substance opposed to the development of life.

In 1931, Waksman organized the division of Marine Bacteriology at the Woods Hole Oceanographic Institution (WHOI) in addition to his task at Rutgers. He was appointed a marine bacteriologist there and served until 1942. He was elected a trustee at WHOI and finally a Life Trustee.

In 1951, using half of his patent royalties, Waksman created the Waksman Foundation for Microbiology. At a meeting of the board of trustees of the foundation, held in July 1951, he urged the building of a facility for work in microbiology, named the Waksman Institute of Microbiology, which is located on the Busch Campus of Rutgers University in Piscataway, New Jersey. The foundation's first president, Waksman, was succeeded in this position by his son, Byron H. Waksman, from 1970 to 2000.

2525) Sulfur Dioxide

Gist

Sulfur dioxide (SO2) is a colorless, pungent, and toxic gas composed of sulfur and oxygen, primarily produced by burning fossil fuels and volcanic activity. It is a major air pollutant known to cause respiratory issues, such as difficulty breathing and asthma exacerbation. Industrially, it is crucial for manufacturing sulfuric acid and used as a preservative in food and wine.

Sulfur dioxide (SO2) is an industrial chemical used primarily as a precursor for sulfuric acid production, a preservative (especially for dried fruits and wine), a bleaching agent in paper/pulp manufacturing, and a disinfectant. It acts as a reducing agent in chemical processes and a refrigerant in industrial cooling systems.

Summary

Sulfur dioxide (SO2), is an inorganic compound, a heavy, colorless, poisonous gas. It is produced in huge quantities in intermediate steps of sulfuric acid manufacture.

Sulfur dioxide has a pungent, irritating odor, familiar as the smell of a just-struck match. Occurring in nature in volcanic gases and in solution in the waters of some warm springs, sulfur dioxide usually is prepared industrially by the burning in air or oxygen of sulfur or such compounds of sulfur as iron pyrite or copper pyrite. Large quantities of sulfur dioxide are formed in the combustion of sulfur-containing fuels.

Sulfur dioxide pollution carries serious health and environmental risks and is one of the six criteria air pollutants regulated by the U.S. Environmental Protection Agency and other regulatory agencies around the world. In the atmosphere sulfur dioxide can combine with water vapor to form sulfuric acid, a major component of acid rain; in the second half of the 20th century, measures to control acid rain were widely adopted. Most of the sulfur dioxide released into the environment comes from coal-fired power plants and petroleum refineries. Paper pulp manufacturing, cement manufacturing, and metal smelting and processing facilities are other important sources.

Sulfur dioxide is a precursor of the trioxide (SO3) used to make sulfuric acid. In the laboratory the gas may be prepared by reducing sulfuric acid (H2SO4) to sulfurous acid (H2SO3), which decomposes into water and sulfur dioxide, or by treating sulfites (salts of sulfurous acid) with strong acids, such as hydrochloric acid, again forming sulfurous acid.

Details

Sulfur dioxide (SO2) is a pungent, toxic gas that is the primary product of burning elemental sulfur. It exists widely in nature, mostly from volcanic activity and burning fossil fuels. It is found elsewhere in the solar system, as a gas in the atmospheres of Venus and Jupiter’s moon Io and as an ice on the other Galilean moons.

The major use of SO2 is in the manufacture of sulfuric acid (H2SO4), the most-produced chemical worldwide. Elemental sulfur and oxygen react to form SO2, which is catalytically oxidized with additional oxygen to make sulfur trioxide (SO3). The SO3 is mixed with existing H2SO4 to produce oleum (fuming sulfuric acid), which is added to water in a strongly exothermic process to make concentrated H2SO4. This is known as the contact process; it dates to an 1831 patent by British inventor Peregrine Phillips.

In chemical laboratories, it has multiple functions, including as a reducing agent, as a reagent in sulfonylation reactions, and as a low-temperature solvent. SO2 is also used to preserve dried fruits such as raisins and prunes and to prevent spoilage in wine.

The hazard information table shows that SO2 is pretty nasty stuff; but, in addition to its value as a chemical, it has another positive side: Volcanoes that emit the gas can have a beneficial effect on climate change. When SO2 spews into the stratosphere, it reacts photochemically with oxygen to form H2SO4 aerosols, which in turn reflect solar radiation and cool the atmosphere. But, as might be expected, even this has a downside because SO2 and H2SO4 contribute to acid rain.

Additional Information:

What Is Sulfur Dioxide?

Sulfur dioxide (SO2) is a gaseous air pollutant composed of sulfur and oxygen. SO2 forms when sulfur-containing fuel such as coal, petroleum oil, or diesel is burned. Sulfur dioxide gas can also change chemically into sulfate particles in the atmosphere, a major part of fine particle pollution, which can blow hundreds of miles away.

What Are the Health Effects of Sulfur Dioxide Pollution?

Sulfur dioxide causes a range of harmful effects on the lungs:

* Wheezing, shortness of breath and chest tightness and other problems, especially during exercise or physical activity. Rapid breathing during exercise helps SO2 reach the lower respiratory tract, as does breathing through the mouth.
* Long-term exposure at high levels increases respiratory symptoms and reduces the ability of the lungs to function.
* Short exposures to peak levels of SO2 in the air can make it difficult for people with asthma to breathe when they are active outdoors.
* Increased risk of hospital admissions or emergency room visits, especially among children, older adults and people with asthma.

What Are the Sources of Sulfur Dioxide Emissions?

As of 2020, human-made sources in the U.S. emit about 1.8 million short tons of sulfur dioxide per year (down from just over 6 million short tons per year in 2011) mainly from burning fuels. Power plants, commercial and institutional boilers, internal combustion engines, manufacturing, and industrial processes such as petroleum refining and metal processing are the largest sources of emissions, followed by diesel engines in old buses and trucks, locomotives, ships, and off-road equipment such as construction vehicles. Emissions of sulfur dioxide will decline as cleanup of many of these sources continue in future years.

Where Do High SO2 Concentrations Occur?

Coal-fired power plants remain one of the biggest sources of sulfur dioxide in the U.S. Columns of emissions (plumes) such as from chimneys of a coal-fired power plant are moved by wind over long distances before touching down at ground level at far away sites. These plumes could also get trapped at the ground level by unusual weather conditions such as a layer of warmer air occurring higher up in the atmosphere (inversion).

Ports, smelters, and other sources of sulfur dioxide also cause high concentrations of emissions nearby.

People who live and work near these large sources get the highest exposure to SO2.

What Can We Do about it?

SO2 levels have improved over time, thanks to policies requiring cleaner fuels and pollution controls on power plants. The nation achieved major reductions in this pollutant through its successful program to reduce acid rain.

However, it remains a health concern. What’s more, even with pollution controls installed, high levels can occur when a polluting source such as a power plant is starting up or shutting down its operation or if its equipment malfunctions.

Individuals can take steps to protect themselves on days with unhealthy levels of air pollutants and also ask policymakers at all levels of government to continue to require cleanup of air pollution.

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#6003. What does the adjective odious mean?

#6004. What does the noun oenophile mean?

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#9884.

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2738.

2524) Microchip

Gist

Microchips (integrated circuits) are tiny silicon devices containing millions or billions of transistors that process, store, and manage data within electronics. They act as the "brains" or "nervous system" for devices ranging from smartphones and computers to cars, medical devices, and household appliances.

Microchips, also known as integrated circuits or computer chips, are the tiny, powerful devices at the heart of nearly every device we use today. These chips are essential building blocks in all modern technology: from smartphones and computers to cars and medical devices.

Summary

Microchips, those unassuming slivers of silicon, are more than just components; they are the linchpins of modern technology. Fundamentally, a microchip, or an integrated circuit, is a convergence of numerous electronic elements—transistors, resistors, capacitors—meticulously integrated onto a tiny silicon chip. This integration represents more than just a triumph in making things smaller; it stands as a powerful demonstration of human creativity and skill in the field of electronics.

The true value of microchips lies not in their physical form but in their pervasive influence across various technological domains. From the smartphone in your pocket to the satellites orbiting our planet, microchips are the unsung heroes, silently orchestrating the digital symphony that underpins our daily lives.

As we delve into the workings of microchips, this article aims to transcend the fleeting trends of the tech world, focusing instead on the enduring principles that make microchips a cornerstone of innovation. We'll explore their fundamental concepts, steering clear of ephemeral specifics, to appreciate their lasting impact on technology.

Details

A microchip is an electronic device made of a small, flat piece of semiconductor material modified with other dopants, oxides, and metals to create electronic components, including transistors, diodes, resistors, and capacitors connected in a circuit.

Microchips are also called:

* Integrated circuits (ICs)
* Computer chips
* Semiconductors
* Chips

Integrated circuits have replaced assemblies of discrete components attached by wires or printed circuit boards (PCBs) because they are a single monolithic device that is much smaller, uses much less power, and can be mass produced at a significantly lower cost.

Semiconductor materials were discovered in 1821 by Thomas Johann Seebeck, and the first working semiconductor transistors were created by Willam Shockley in 1947. The components and all their interconnects were then combined into a single device in 1959 by Robert Noyce. The key to this invention and all that followed was the planar manufacturing process, which used photolithography to deposit and remove materials one layer at a time in a precise manner.

Integrated circuits are an integral part of modern life, providing electronics for devices ranging from toys to deep space probes. In 2023, the worldwide revenue from microchip sales was $526.9 billion. That year’s sales also saw further growth in chip usage beyond computers: 32% were for communication, 17% for automotive applications, 14% for industrial devices, 11% for consumer electronics, and only 25% for computing.

Driven by Moore’s Law, which states that the number of transistors in an IC will double every two years, the growing complexity of the circuits and the ever-decreasing size of components make designing and manufacturing microchips more challenging with each generation of chips.

The general size of individual elements on a chip, referred to as feature size, is measured in nanometers (nm), or one-billionth of a meter. Current semiconductor manufacturers use 14-nm, 10-nm, 7-nm, 5-nm, and 3-nm processes, with 2-nm technologies coming online. For scale, a grain of rice is 5 million nanometers long.

In 2023, researchers created a record-breaking microprocessor containing 1.2 trillion transistors. Intel’s line of CPUs in 2024 include more than 100 million transistors on a single chip.

The Elements of a Typical Microchip

Integrated circuits are made from semiconductor material, usually silicon, stacked in overlapping layers. Here are the most common elements in a microchip:

* Silicon substrate: The base pure silicon crystal layer from which the other layers are constructed by removing or depositing other materials or doping the crystal material.
Silicon Wafer
* Layers: Electronic circuits are created on individual layers. Layers are modified with photolithography, etching, and deposition to produce the desired components and interconnections. Some layers also serve as electrical insulators.
* Vias: A conducting zone, usually cylindrical, used to transmit electrical signals between layers.
* Components: The electronic devices that make up the desired circuit. In most ICs, these consist of transistors, capacitors, diodes, resistors, and sometimes inductors.
* Interconnects: Metalized paths on a given layer that conduct electricity between components or to vias.
* Packaging: Once completed, the IC is placed inside an assembly called a semiconductor package that protects and insulates the delicate silicon chip, can connect multiple chips, and provides a way to connect the chip or chips to a larger electronics circuit.

How Microchips Are Manufactured

There are three steps to microchip manufacturing. Each step is highly optimized and automated to minimize cost, ensure quality, and maximize efficiency. Engineers designing ICs need to have a good understanding of the manufacturing process because each step determines the size, shape, and spacing of the components.

Step 1: Wafer Production

Making blank silicon wafers is the first step in semiconductor manufacturing. This process begins by growing a monocrystalline cylindrical ingot, called a boule, of semiconductor material, usually pure silicon. The boule is then sliced into a thin wafer, machined to create a flat surface, chemically etched to remove any damage from the machining, and polished. Electronic wafers are usually 100 to 450 mm in diameter. The most common size is 300 mm across and 755 µm thick.

Step 2: Fabrication

The circuitry, with all its components and interconnects, is created in a semiconductor fabrication facility, usually called a fab. Each layer and the topology of the circuitry is created in a series of highly controlled steps. Robots move wafers from machine to machine in clusters. Most chip fabrication processes follow these steps for each layer:

* Grow a silicon dioxide layer to cover the layer completely (also called passivation).
* Add a photoresist coating.
* Expose the photoresist layer to ultraviolet light in the pattern of the geometry you want to create. The photoresist layer is then developed, and the material exposed to light is removed. This is called photolithography.
* Use chemicals, usually a strong acid, to remove the oxide layer where the photoresist was removed. This is referred to as etching.
* Remove the undeveloped photoresist material.
* If doping is needed for the layer, ion implantation of contaminants into the crystal structure creates the desired semiconductor behavior for transistors and other components.
* For other materials, various forms of chemical or vapor deposition are used to create interconnects, vias, and other components.

Step 3: Packaging

Once each layer has been constructed and the wafer is cleaned and tested, it is cut into individual chips called dies. One or more dies are then attached to a structure through bonding, and the IC is encapsulated in different materials, depending on the application. Some packages contain a single chip, but the current trend is to combine multiple dies in a single package.

Microchip Types and Uses

The types and uses of integrated circuits are growing every year. Early ICs often performed a single function. But as the manufacturing technology and design tools have improved, chips have shifted to being multifunction.

Smartphones are a great example of how multiple types of chips can be combined in a single device for different uses. They contain radio frequency (RF) chips for the 5G radio and GPS, optoelectrical chips for the cameras, LED chips for the display, digital ICs for the processing units, micro-electromechanical systems (MEMS) chips for the accelerometer, and a dozen other integrated circuits to sense, control, and modify a vast number of uses.

The different types of chips can be categorized by the signaling they carry out.

Analog Integrated Circuits

Analog signals carry voltage across a continuous voltage range, not just a high or a low voltage signal. They are used to amplify, filter by frequency, and mix signals. The frequency and power of an analog IC can vary greatly, and higher frequencies and higher powers present significant design challenges.

Common uses for analog ICs include:

* Optical, thermal, and audio sensors
* Power management circuits
* Operational amplifiers (op-amps)
* Audio and video signal processing
* Telecommunications, including radio communication and optical signal processing
* RF circuits
* Signal conditioning
* Machine controllers

Digital Integrated Circuits

Digital ICs are logic devices that contain millions or billions of logic gates made of transistors. A signal running at a fixed clock frequency is modified or measured as either high or low, zero or one. By combining different logic devices, very complex calculations can be done with very little power used.

Some of the most common uses for digital ICs include:

* Logic ICs or processors
** Microprocessors
** Microcontrollers
** Application-specific integrated circuits (ASICs)
* Memory chips
* Field programmable gate arrays (FPGAs)
* Digital power management devices
* System-on-a-chip (SoC) devices
* Multi-die chips

Mixed-signal Integrated Circuits

Some integrated circuits combine circuitry to handle analog and digital signals and convert between the two to create mixed-signal integrated circuits. They are used when an analog signal is sensed or created and logical operations are needed to read, create, or modify that signal.

Some of the most common uses for mixed-signal ICs are:

* SoC devices
* Data acquisition chips
* RF CMOS circuits
* Clock/timing ICs
* Switched capacitor circuits
* Electro-optical devices
* MEMS devices

Future Trends in Microchip Technology

The future of microchips looks like the past, with more capabilities in smaller sizes while constantly driving the cost down. Advances in manufacturing will also create new opportunities for better performance and new applications.

Trends that will drive electrical engineering design and simulation in the near future include:

Shift to Fabless Design and Foundries

The industry has shifted over the years to a model where companies can design their own ICs and then outsource the manufacturing to a company that just makes chips. This is called fabless design, and the contract manufacturers are called foundries. This enables companies like Apple and Qualcomm to design innovative new products without the capital investment of building their own fabrication facilities. Engineers must design to the manufacturing processes and standards of the foundry they will use.

Smaller Feature Size

Feature sizes continue to shrink, creating power and signal integrity issues. To stay competitive, electrical engineers need to design using these new capabilities, as well as leveraging simulation and design best practices to avoid issues.

Electronic Device Complexity and Combined Functionality

With time, an increasing number of designers of electronic devices are looking for greater functionality in a single chip. Internet of Things (IoT) devices, new solid-state long-term storage, and GPU chips are examples of integrated circuits that will not only add new features and capabilities in the same chip, but the interaction between those functions will also become more sophisticated. Engineers need design and simulation tools to drive designs in which the industry is pulling the technology. Biomedical electronics like implanted microchips will be another area in which several capabilities are needed on a single chip.

Higher Clock Speeds and Frequencies

Increased performance demands and advances in RF technology are driving up clock speeds for digital ICs and frequencies for analog and mixed-signal chips. Both create issues with signal integrity and power management.

Greater Computer Power With Increased Energy Efficiency

The growth of data centers for high-performance computing to support trends like artificial intelligence, cryptocurrency mining, and IoT applications is driving demand for increased performance for microprocessors. These applications are pushing the industry for improvements in FPGAs, solid-state hard drives, memory, and GPUs, along with all the chips needed to connect everything at increasing data transfer speeds.

More Use Beyond Computing

The trend of increased microchip use in automotive, consumer electronics, and industrial applications will continue. Almost all products will be designed as smart devices with connectivity to broadband, sensors, and computing power — all of which need microchips.

Simulation in the Design of Microchips

The complexity and expense of microchip manufacturing make physically prototyping designs impractical. Instead, engineers use virtual prototyping through simulation to drive their design, verify the performance, and identify and solve problems before production begins. Simulation is also used to design packaging and optimize the semiconductor manufacturing machines that make the chips.

Using simulation for digital microchips begins with verifying the logical functionality of the digital design at an abstract level with RTL design. This includes a first look at power management with PowerArtist™ software. This tool can assess the power needs of a design early in the process and help drive a more power-efficient design.

Once the physical design is laid out, engineers can use RedHawk-SC™ software, the trusted industry leader for power noise and reliability for digital ICs, to assess voltage drop and electromigration in their designs.

On the analog and mixed-signal side of things, Totem™ software can be brought into the process for power integrity and reliability signoff. The industry’s trusted gold standard for electromigration multiphysics, it is certified by all major foundries down to 3 nm. It also works with PathFinder-SC™ software to calculate electrostatic discharge.

Once the design is optimized and verified, packaging engineers can use simulation to optimize the power, signal integrity, and robustness of the full microchip package. RedHawk-SC software is designed to handle large, multichip configurations, including system-in-package designs. Advanced semiconductor packaging uses 2.5D- and 3D-IC approaches to combine and connect multiple dies in the same package, and simulation with RedHawk-SC software is the primary way to verify and optimize the designs.

Once the electrical aspects of the design are resolved, packaging engineers can use tools like Mechanical™software and the Icepak® tool for structural reliability and thermal management.

Additional Information:

What is a microchip?

A microchip -- also called a chip, computer chip or integrated circuit (IC) -- is a unit of integrated circuitry that is manufactured at a microscopic scale using a semiconductor material, such as silicon or, to a lesser degree, germanium. Electronic components, such as transistors and resistors, are etched into the material in layers, along with intricate connections that link the components together and facilitate the flow of electric signals.

Microchip components are so small they're measured in nanometers (nm). Some components are now under 10 nm, making it possible to fit billions of components on a single chip. In 2021, IBM introduced a microchip based on 2 nm technology, smaller than the width of a strand of human DNA. A nanometer is one-billionth of a meter or one-millionth of a millimeter. At that scale, it is possible to fit up to 50 billion transistors on a microchip the size of a fingernail.

How are microchips made?

Microchip manufacturers rely on silicon for their chips because it is abundant, inexpensive and easy to work with. Also, it has proven to be a reliable semiconductor in a variety of devices. However, silicon might be reaching its practical limits as microchip technologies become smaller and more components are squeezed into the microchip in an effort to meet the ever-increasing demands for greater performance and more data. Researchers are actively working on a variety of solutions that they hope will be able to carry electronics into the future.

Microchips typically include the following types of components, which can number into the millions or even billions, depending on the type and function of the microchip:

* Transistors. Transistors are active components that control, generate or amplify electric signals within the circuitry, acting as a switch or gate. Multiple transistors can be combined into a single logic gate that compares input currents and produces a single output according to the specified logic.
* Resistors. Resistors are passive components that limit or regulate the flow of electrical current or that provide a specific voltage for an active device. Resistors control the electric signals that move between transistors.
* Capacitors. Capacitors are passive components that store electricity as an electrostatic field and release electric current. Capacitors are often used along with transistors in dynamic RAM (DRAM) to help maintain stored data.
* Diodes. Diodes are specialized components with two nodes that conduct electric current in one direction only. A diode can permit or block the flow of electric current and can be used for various roles, such as switches, rectifiers, voltage regulators or signal modulators.

What are the types of microchips?

Microchips drive all of today's electronics. Not only do these include computers, but also smartphones, network switches, home appliances, car and aircraft components, televisions and amplifiers, internet of things devices and countless other electronic systems. Microchips generally fall into one of the following two categories:

* Logic. This type of microchip does all the heavy lifting, processing the instructions and data that are fed to the device and subsequently to the chip in that device. The most common and widely used type of logic microchip is the central processing unit (CPU). However, this category also includes more specialized chips, such as graphical processing units (GPUs) and neural net processors.

* Memory. This type of microchip stores data. Data storage is either volatile or non-volatile. volatile memory chips require a constant source of power to retain their data. DRAM is a common example of a volatile memory chip. A non-volatile chip is one that can persist data even if the power supply is disrupted. A good example of non-volatile memory is NAND flash. Volatile memory devices tend to perform much better than non-volatile devices, although a number of efforts are underway to bridge the gap between the two, such as storage class memory.

Although many microchips focus on logic or memory only, other types of chips incorporate both, along with other capabilities. For example, system-on-a-chip (SoC) ICs are now widely used in devices such as smartphones and wearable technology and have begun making headway into the computer market, as evidenced by the Apple silicon series of chips. Another example is the application-specific IC, which can also include logic, memory and other capabilities, much like the SoC chip, except that the ASIC chip is customized for a specific purpose, such as medical equipment or an automotive component.

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#10795. What does the term in Geography Desertification mean?

#10796. What does the term in Geography Desire path mean?

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#2597. What does the medical term Hyperplasia mean?

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#6376.

2523) Hematite

Gist

Hematite is a common iron oxide mineral and the world's most important iron ore, containing roughly 70% iron. It is recognized by its brilliant metallic gray to dull red color and characteristic reddish-brown streak, which is used for pigments and polishing. It is abundant on Earth and causes the red coloration on Mars.

Hematite occurs in a variety of igneous and metamorphic rocks, but is most abundant in sedimentary settings. In sedimentary rocks, hematite can either have formed from have originally formed directly from direct precipitation out of marine waters, or as a concentration and enrichment deposit formed from groundwater.

Summary

Hematite is a heavy and relatively hard oxide mineral, ferric oxide (Fe2O3), that constitutes the most important iron ore because of its high iron content (70 percent) and its abundance. Its name is derived from the Greek word for “blood,” in allusion to its red colour. Many of the various forms of hematite have separate names. The steel-gray crystals and coarse-grained varieties have a brilliant metallic lustre and are known as specular iron ore; thin scaly types are called micaceous hematite. Much hematite occurs in a soft, fine-grained, earthy form called red ochre or ruddle. Intermediate between these types are compact varieties, often with a reniform surface (kidney ore) or a fibrous structure (pencil ore). Red ochre is used as a paint pigment; a purified form, rouge, is used to polish plate glass.

The most important deposits of hematite are sedimentary in origin. The world’s largest production (nearly 75 million tons of hematite annually) comes from a sedimentary deposit in the Lake Superior district in North America. Other important deposits include those at Minas Gerais, Brazil (where the hematite occurs in metamorphosed sediments); Cerro Bolívar, Venezuela; and Labrador and Quebec, Canada. Hematite is found as an accessory mineral in many igneous rocks; commonly as a weathering product of siderite, magnetite, and other iron minerals; and almost universally as a pigmenting agent of sedimentary and other rocks. For detailed physical properties, see oxide mineral.

Details

Hematite is one of the most abundant minerals on Earth's surface and in the shallow crust. It is an iron oxide with a chemical composition of Fe2O3. It is a common rock-forming mineral found in sedimentary, metamorphic, and igneous rocks at locations throughout the world.

Hematite is the most important ore of iron. Although it was once mined at thousands of locations around the world, today almost all of the production comes from a few dozen large deposits where significant equipment investments allow companies to efficiently mine and process the ore. Most ore is now produced in China, Australia, Brazil, India, Russia, Ukraine, South Africa, Canada, Venezuela, and the United States.

Hematite has a wide variety of other uses, but their economic significance is very small compared to the importance of iron ore. The mineral is used to produce pigments, preparations for heavy media separation, radiation shielding, ballast, and many other products.

Physical Properties of Hematite

Hematite has an extremely variable appearance. Its luster can range from earthy to submetallic to metallic. Its color ranges include red to brown and black to gray to silver. It occurs in many forms that include micaceous, massive, crystalline, botryoidal, fibrous, oolitic, and others.

Even though hematite has a highly variable appearance, it always produces a reddish streak. Students in introductory geology courses are usually surprised to see a silver-colored mineral produce a reddish streak. They quickly learn that the reddish streak is the most important clue for identifying hematite.

Hematite is not magnetic and should not respond to a common magnet. However, many specimens of hematite contain enough magnetite that they are attracted to a common magnet. This can lead to an incorrect assumption that the specimen is magnetite or the weakly magnetic pyrrhotite. The investigator must check other properties to make a proper identification.

If the investigator checks the streak, a reddish streak will rule out identification as magnetite or pyrrhotite. Instead, if the specimen is magnetic and has a reddish streak, it is most likely a combination of hematite and magnetite.

Composition of Hematite

Pure hematite has a composition of about 70% iron and 30% oxygen by weight. Like most natural materials, it is rarely found with that pure composition. This is particularly true of the sedimentary deposits where hematite forms by inorganic or biological precipitation in a body of water.

Minor clastic sedimentation can add clay minerals to the iron oxide. Episodic sedimentation can cause the deposit to have alternating bands of iron oxide and shale. Silica in the form of jasper, chert, or chalcedony can be added by chemical, clastic, or biological processes in small amounts or in significant episodes. These layered deposits of hematite and shale or hematite and silica have become known as the "banded iron formations".

Geologic Occurrence

Hematite is found as a primary mineral and as an alteration product in igneous, metamorphic, and sedimentary rocks. It can crystallize during the differentiation of a magma or precipitate from hydrothermal fluids moving through a rock mass. It can also form during contact metamorphism when hot magmas react with adjacent rocks.

The most important hematite deposits formed in sedimentary environments. About 2.4 billion years ago, Earth’s oceans were rich in dissolved iron, but very little free oxygen was present in the water. Then a group of cyanobacteria became capable of photosynthesis. The bacteria used sunlight as an energy source to convert carbon dioxide and water into carbohydrates, oxygen, and water. This reaction released the first free oxygen into the ocean environment. The new oxygen immediately combined with the iron to form hematite, which sank to the bottom of the seafloor and became the rock units that we know today as the banded iron formations.

Soon, photosynthesis was occurring in many parts of Earth’s oceans, and extensive hematite deposits were accumulating on the seafloor. This deposition continued for hundreds of millions of years - from about 2.4 to 1.8 million years ago. This allowed the formation of iron deposits hundreds to several thousand feet thick that are laterally persistent over hundreds to thousands of square miles. They comprise some of the largest rock formations in Earth’s rock record.

Many of the sedimentary iron deposits contain both hematite and magnetite as well as other iron minerals. These are often in intimate association, and the ore is mined, crushed, and processed to recover both minerals. Historically, much of the hematite was not recovered and was sent to tailings piles. More efficient processing today allows more hematite to be recovered from the ore. The tailings can also be reprocessed to recover additional iron and reduce tailings volume.

Hematite on Mars?

NASA has discovered that hematite is one of the most abundant minerals in the rocks and soils on the surface of Mars. An abundance of hematite in Martian rocks and surface materials gives the landscape a reddish brown color and is why the planet appears red in the night sky. It is the origin of Mars' "Red Planet" nickname.

Uses of Hematite (Iron Ore)

Hematite is the world’s most important ore of iron. Although magnetite contains a higher percentage of iron and is easier to process, hematite is the leading ore because it is more abundant and present in deposits in many parts of the world.

Hematite is mined in some of the largest mines in the world. These mines require investments of billions of dollars, and some will remove over 100 million tons of ore per year. These open-pit mines can be hundreds to thousands of feet deep and several miles across by the time they have been worked to completion.

China, Australia, Brazil, India, Russia, Ukraine, South Africa, and the United States are the world’s leading producers of iron ore (includes hematite, magnetite, and other ores). Iron ore production in the United States occurs in Michigan and Minnesota.

Uses of Hematite (Pigment)

The name hematite is from the Greek word "haimatitis" which means "blood-red." That name stems from the color of hematite when it has been crushed to a fine powder. Primitive people discovered that hematite could be crushed and mixed with a liquid for use as a paint or cosmetic. Cave paintings, known as "pictographs," dating back to 40,000 years ago were created with hematite pigments.

Hematite continues to be one of the most important pigment minerals. It has been mined at many locations around the world and has been traded extensively as a red pigment. During the Renaissance when many painters began using oils and canvas, hematite was one of the most important pigments. Hematite color was opaque and permanent. It could be mixed with a white pigment to produce a variety of pink colors that were used to paint flesh.

Uses of Hematite (Gem Material)

Hematite is a minor gem material used to produce cabochons, beads, small sculptures, tumbled stones, and other items. The material used to manufacture these products is a silver-colored hematite with a solid, uniform texture. The bright silver color of hematite and its "weighty feel" make it a very popular tumbled stone.

Uses of Hematite (Healing Stone)

Some people believe that carrying pieces of tumble-polished hematite, known as "healing stones," will bring relief from certain medical problems. There is no scientific proof that this use of hematite has any positive effect beyond being a placebo. Using hematite as a "healing stone" or a "healing crystal" can actually be harmful because it diverts people from seeing a doctor who can provide proper care. Then when the person with the problem finally decides to see a doctor, their situation is more severe.

Other Uses of Hematite

Hematite is used for a number of other purposes. It is a very dense and inexpensive material that is effective at stopping x-rays. For that reason it is used for radiation shielding around medical and scientific equipment. The low cost and high density of hematite and other iron ores also makes them useful as ballast for ships.

Hematite can also be ground to a fine powder that when mixed with water will make a liquid with a very high specific gravity. These liquids are used in the "float-sink" processing of coal and other mineral material. The crushed coal, which has a very low specific gravity, is placed on the heavy liquid and the light clean coal floats, while high-specific-gravity impurities such as pyrite sink.

Finally, hematite is the material used to make polishing compounds known as "red rouge" and "jeweler's rouge." Red rouge is a hematite powder used to polish brass and other soft metals. It can be added to crushed corn cob media or crushed walnut shell media for tumble-polishing brass shell casings. Jeweler's rouge is a paste used on a soft cloth to polish gold and silver jewelry.

Additional Information

Hematite, also spelled as haematite, is a common iron oxide compound with the formula Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe2O3. It has the same crystal structure as corundum (Al2O3) and ilmenite (FeTiO3). With this crystal structure geometry it forms a complete solid solution at temperatures above 950 °C (1,740 °F).

Hematite occurs naturally in black to steel or silver-gray, brown to reddish-brown, or red colors. It is mined as an important ore mineral of iron. It is electrically conductive. Hematite varieties include kidney ore, martite (pseudomorphs after magnetite), iron rose and specularite (specular hematite). While these forms vary, they all have a rust-red streak. Hematite is not only harder than pure iron, but also much more brittle. The term kidney ore may be broadly used to describe botryoidal, mammillary, or reniform hematite.[8] Maghemite is a polymorph of hematite (γ-Fe2O3) with the same chemical formula, but with a spinel structure like magnetite.

Large deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that have still, standing water, or mineral hot springs, such as those in Yellowstone National Park in North America. The mineral may precipitate in the water and collect in layers at the bottom of the lake, spring, or other standing water. Hematite can also occur in the absence of water, usually as the result of volcanic activity.

Clay-sized hematite crystals also may occur as a secondary mineral formed by weathering processes in soil, and along with other iron oxides or oxyhydroxides such as goethite, which is responsible for the red color of many tropical, ancient, or otherwise highly weathered soils.