Tuesday, April 15, 2014

Meteor speed and heat relation

For following calculations i used 2 calculators.

Speed-heat relationship was calculated with this calculator using iron (amu = ~56) and most probable speeds are mentioned here. Lighter elements are faster with same heat.

Calculator for finding relation between electronvolts and temperature.
Kinetic energy calculations were done with mass in kg times speed in meters per second squared.

From perspective of meteor the atmosphere would be coming towards meteor with approximately speed of meteor.

1000 C may be achieved at ~600m/s.
1510 C (melting point of steel) has atom speeds of 727 m/s. 
2750 C (boiling point of steel) at 945 m/s.
10 000 C at 1740 m/s.
Common orbiting objects move ~6-8 km/s and 7,7 km/s could heat iron up to 200 000 C.
Escape velocity is about 11 km/s and such objects could heat to 400 000 C. Obviously any satellite flying through atmosphere is highly likely to boil away to metal vapour unless it descents almost horizontally so it could slow down in thin atmosphere. 

Helios satellite may is one of the fastest satellites made with speed of 70 km/s which could heat up to 17 million C which in turn can be hot enough to cause x-rays (~1400 eV). It's mass is 370 kg so it has ~900 billion joules of kinetic energy. In comparison lightning strike can be 1 billion joules and 1,4 billion joules is theoretical minimum needed to melt ton of steel.

As humans can create satellites with such speeds it is possible that they may be used as weapons considering 1 ton of random material could release energy comparable to thousands of lightning strikes released within couple of seconds. Helios 2 took about 3 months to get close to sun and in this time in picked up speed partly from gravity of nearby massive bodies. Another way to get them fast would be to send a lot of rocket fuel in space and build a giant military "meteor" to speed up quickly (within hour) as rockets can reach from zero to orbiting speed in ~10 minutes.

Andromeda galaxy is moving towards milky way with speed of ~300 km/s. This could heat iron up to 3 billion degrees. While collisions may be unlikely due to huge distances between stars and planets it would still be destructive to galaxies to have such high intensity collision as those which happen are hot enough to create x-rays and gamma rays. 1 gram of matter moving with 300 km/s has about 45 gigajoules of energy and those on planets in colliding galaxies are likely to see even single grams worth of dust brighten the sky with ~50 lightning strikes worth of energy.
Antennae galaxies have been colliding long enough for widespread x ray production. Most of that skull shaped structure has huge patches where heat is high enough for x-ray production.
This may be also how Andromeda and Milky way start looking when their planets and stars hit each other so fast that their atoms fly apart in every direction with more than escape velocity. That leaves behind quickly expanding debris zones which may destroy other nearby stars and planets or at least heat atmospheres too much for life.

Also this 300 km/s speed may be enough to cause nuclear reactions. Stars that reach about 3 billion degrees burn silicon to iron and other metals. If tiny icy comet hit atmosphere at 300 km/s then small amount of it could turn to metals leaving behind cloud of metals and silicon. 3 billion degrees is about 0,25 MeV but each proton and neutron is bound to nucleus with up to ~9 MeV binding energy. Hydrogen fusion can happen at about 1 billion degrees so if those 2 galaxies met and 2 watery planets collided then they could release fusion energy.

To break apart all nucleons with ~8 MeV heat energy would need about 100 billion degrees and even metals could vaporize to hydrogen (protons) and neutrons. 100 billion degrees could be achieved with ~6000 km/s in case of iron.

Thursday, February 13, 2014

Topological insulators and Hall effect

Topological insulators are partial insulators that are insulators inside themselves but are very good conductors on their sides or edges. Quality of topological insulators (TI) usually improves if internal content is not conductive and surface should preferrably have higher density of electrons than inside. Some researchers even consider TIs potential room temperature superconductors. Mostly they are combination of different elements like most insulators but at least in case of graphene, which is conductor, can also become topological insulator which only conducts on edges but for that it has to be cooled to 0,3C above absolute zero and also be in 35 Tesla magnetic field. 

Kawazulite is natural example of TI. Like artificial ones they commonly have a metallic reflective appearance. Like many TIs it contains bismuth, tellurium and selenium.
Overview of Hall effect which is related topic to TIs. When current goes through magnetic field (B) then electrons get pushed to one side due to Lorentz force. If electrodes get connected to these sides then these gathering of electron on one side causes measurable voltage difference (VH) between sides.

Above illustration shows quantum Hall effect in semiconductor but it also describes closely how electrons behave in TI. Inside electrons orbit in circles but near border they skip along like stones on water as they keep on trying to circle but keep deflecting from edge. Inner structure of material can push electrons to move and when this moving is in circles then material may get enough internal magnetic field to start moving other electrons around these magnetic field lines and in TI's it is called spin quantum Hall effect. One difference between this and usual Hall effect is that spin quantum version causes oppositely moving electrons on sides.

Applying high pressure (~100 000 atmospheres) to semiconductors turns at least one of them to topological insulator.

TI could be superconducting unless there are excess electrons inside material but doping surface with electronegative substance to attract electrons there can reduce that problem.

Bismuth tellurochloride (BiTeCl) is maybe 1st topological insulator discovered which has one side positive and other negative due to inner structure.  Electrical currents flowed on upper side but not on other sides. Semiconducting transistors and most TIs materials are either n or p type but by layering many alternating layers of bismuth, tellurium and chlorine on top of each other, BiTeCl starts to have those charge differences within same piece. One of the hopes with such material is that their sides could function as p-n junctions where current is one directional. Outside magnetic fields can create channels on the sides that seem to conduct electricity with no resistance.

Illustration of graphene in conditions that make it TI. Electrons with certain spin can move along edge (shown with blue arrows) but electrons with opposite spins (red arrows) get blocked on these sides so in general currents flow around graphene flakes either clockwise or counterclockwise.

While graphene is conductor in room temperature it could behave slightly like TI under intense (35 tesla) magnetic field (to cause Hall effect) and 0,3 C above absolute zero which allows it to transport electrons with different spins in different directions. Magnetic field lines could be perpendicular to surface graphene or also parallel to surface and both caused these spin dependent flow current.

Common use for TIs according to maybe most articles i read about TIs is their supposed good use in quantum computers or spintronics devices. So far the only example of spin use in any computer part i could understand is illustrated below.
A) with usual current there is similar amount of up and down spins which spread evenly on both sides but voltage between these sides stays 0 because there is even number of electron on both sides. B) by using ferromagnet (FM) electrons can be sent with same spin. Opposite spin electrons shown red are created on other side (maybe also with ferromagnets but turned 180 degrees) and electrons with opposite spins can flow on same edge if they are going in opposite direction. This way electrons can concentrate on same side and create voltage differences. According to authors this time spins were separated due to Spin Hall effect, where opposite spins move to opposite sign of material without need for outside magnetic field. In this case outer magnetic field not needed and it can even disrupt electron flow by making them rotate in small circles. These spin differences can be measured with light as different electron spins give differently polarized light.

Above example with spins influencing light polarization may be usable in computer security by pushing certain secret amount of electron on certain regions and letting suitably polarized light expose data (maybe with interference exposing data on some screen or letting light push important electron on transistors in direction to some other transistor that gives data signal). Circular polarization keeps rotating its polarization direction depending how much it has traveled so bumpy surface may shine with differently polarized light on different heights which has potential for secret data storage.

Wednesday, September 25, 2013

Essay on possibility of x-ray and gamma ray band communication

As more primitive civilizations are mainly experienced with radio waves and visible light they may be "left in dark" by other advanced species that are using frequencies people can’t use in communication like x-rays and gamma rays. As illustrated above observers on ground can mainly detect visible light and some radio waves but other radiation types get mostly absorbed by atmosphere. Gamma ray bursts were discovered by early satellites that were designed to detect nuclear explosions but also happened to detect gamma ray bursts from space.

High energy radiation including x-rays release electrons (e) from atoms they hit and lose energy in process. Gamma rays and high energy ions from space can cause release of many electrons, protons and if they have enough energy then also some gamma ray and x-ray photons (image source). This would scramble, weaken and distort any message sent in form of ionizing radiation. 

These can’t go far in air and are therefore mainly reachable by some intelligent life form operating in vacuum of space.
Although destructive to whatever they hit x-rays and gamma rays have high frequency that may be used to carry more data. For example x-rays have 3×1016 Hz to 3×1019 Hz and gamma rays have higher frequency. Good enough control of x-rays would allow passing of up to 3×1016 to 3×1019 data values every second which could mean up to 30 thousand to 30 million terabytes per second which could allow civilizations to send out almost all their recordings very fast and overview of their species within a second.

Creating such beam of data could be achievable by humans already but recording this data may not be possible yet.

Sources for x-ray and gamma ray data. At least x-ray signals may be achieved by irradiating different elements that pass some intense electron beam source to create resonance x-ray signal (K-alpha and K-beta) which depends on element and every element would release different x-ray frequencies and energies.
Overview of x-rays different elements release can be found in this table. Energies vary from 800 eV (electronvolt) x-rays in neon to ~100 000 eV gamma rays in plutonium where lightest elements have lowest energy radiations and heavier radioactive substances like uranium producing ~100 000 eV radiation. At first every extra proton increases radiation energy by ~200 eV but it gradually increases to 2000 eV with each proton. Due to wide range of energy levels these different elements could be used to create different data points. These don't have to be restricted to bits or even bytes as there are over 100 elements available and each could be used to send some symbol from numbers to letters and other needed symbols. X-ray antenna may be particle accelerator that sends particles into strong electron beam that causes release of x-rays which are then directed towards desired location with opening in radiation shielding. These elements may need to be very close to each other in this particle accelerator as x-rays have wavelength of 10-0,01 nanometers and that lower end is about half of atomic diameter. If different atoms could be accelerated with 1 nanometer between them with speed of light then they may create x-rays with ~1 nanometer wavelength but easier way may be to use several accelerators working together with serious precision to get many separate x-ray beams directed to intended location in space.   

Something analogous could be used to create gamma ray beams. Neutron radiation or just collision of atoms moving near speed of light can create nuclear fission with certain energy/frequency and that depend on isotope which could be sent in orderly line towards neutron stream. Different isotopes (about 3000 are known including very short lived isotopes) could be used to create different gamma ray photons and with thousands of isotopes to work with each isotope collision could create 1 value out of thousands which may easily be letters in many alphabets, numbers, pixel data etc. so even if they create 1 billion collisions per second they could still send several bytes worth of data with every collision. If 1000 isotopes were usable then 1000 in binary is 10 bits long. 3000 isotopes could carry 22 bits with each isotope.

Data readers and recorders.Trickiest part is counting signals from x-ray or gamma ray source. Easiest way to separate signals would be to use radiation detectors behind different radiation shields. For example one shield allowing any photon with over 800 eV to pass, another for those with 1000 eV and so on for every energy level different elements could create. When capturing high enough energy gamma rays then there is likelihood of atoms splitting to new elements and different elements need different minimum energy amount to go through fission. Resulting radiation and formation of elements could also have some role as data reader.

Overview of several gamma ray bursts. Most last several seconds but few last for milliseconds. More powerful photons can activate all detectors behind weaker shields but one way to have some order would be to create bursts that start strongest or weakest and move to opposite extreme with detectors recording most powerful recent photons. Most of them have somewhat gradual fall in intensity which may help record their content as they often jump to some maximum, then fall until jumping up in intensity again and that could help with reading most energetic photons as detectors and also constantly change which electrode is going to transmit signal from most powerful photon.

In case there is intelligent life causing gamma ray burst and they want to be found then it's likely they use elements, energy levels and timing that is different from natural sources. For example using wolfram (x-ray machines use wolfram due to heat resistance) and other heat resistant elements which are unlikely to randomly be concentrated but likely to be used by creatures wanting to have heat resistant components. Maybe sign of one pure element, then another and like that for around a minute. In case they want to hide and intimidate they may wait until there is distant galaxy behind them and send high energy burst towards some planet where locals may think the source was several billion light years away and hopelessly hard to reach while also seemingly having some scary energy bursts coming from that far.

Monday, August 5, 2013

Thymus and its role in protecting body against overactive immune system


Thymus is involved in removing T cells that may attack body and if it fails then it may cause wide range of autoimmune disorders where T cells may potentially kill any cells type. T cells are produced in way which makes it possible for majority of them to attack body and this is checked in thymus as thymus produces any protein any other tissue produces including neural tissue. Immature T cells which don't have neither CD4 or CD8 receptors are not active but they get activated within thymus. In thymus large "nurse" cells swallow these T cells inside them (and after filling would not take in other T cells until old ones get removed) where they mature by getting one of those 2 receptor types. Those with CD8 would become T killer cells that attack damaged cells including cancers and those with CD4 become T helper cells which help at finding targets for T killer cells. Less commonly those with CD4 become regulatory T cells that inhibit immune system and these cells may form other T cells in case of chronic inflammation. If those large cells detect that T cells are likely to attack body or just malformed then they cause death of these T cells. About 95% of T cells get killed in thymus because they were not formed correctly or they showed potential to attack body. While T cells have lifespan lasting about weeks they may become memory cells if they they are needed during infection after which they may become T memory cells that survive about decade in bone marrow, spleen and lymphoid tissue.
Thymus produces all those different proteins mainly with few proteins. One such is AIRE (autoimmune regulatory element) which binds to silenced DNA regions which happen to have positively charged side-chains that stick to negatively charged DNA. AIRE is attached to several proteins (common to proteins involved in gene regulation) among which is CREB that adds negatively charged parts to histones which then come loose from DNA and allow RNA polymerase to express that gene. Usually AIRE causes 1 cell to express one cluster of genes and neighboring cell may produce different cluster of cells (~10% of thymic cells express neural genes including oxytocin and nerve growth factor genes). If AIRE is mutated seriously enough then this T cell selection may not happen. Similar things may happen if thymus gets removed if having heart surgery on small kids (removed because it gets in the way) and sometime tumors in thymus if cells that don't express AIRE form the tumor. AIRE has less known roles in other organs as young embryos, all internal organs from heart, liver, spleen, testis, ovaries to bone marrow and muscles produce AIRE as well although they don't have such control over immune system as thymus.

Citations and additions

Type I is autoimmune disorder where T cells cause death of insulin containing cells during childhood and at least in some cases it is associated with thymus not producing insulin within itself so cells that produce it elsewhere are attacked by T cells.
Example of APECED progression on 39 year old woman. At age 3 she developed chronic candidiasis (white fungal infection in mouth and mucus membranes) which usually starts within first few years of someone with APECED. At age 11 she got hypoparathyroidism which slows metabolism. At 23 she got diagnosed with chronic hepatitis. Addison’s disease (low adrenaline gland activity) and type 1 diabetes at 27 and in her 30s her muscles started weakening that made her bedridden by 39. This one was more rare APECED type which shows if 1 allele is mutated but most APECED cases happen if both parents had mutated version of AIRE.

Thymus grows after castration or adrenalectomy. Thymus and hypothalamus/pituitary gland seem to mutually regulate each other. Females tend to have more antibodies of all classes than men and estrogen increases levels of circulating antibodies. Estrogen also shortens time to organ rejection after transplantation. Estrogens reduce activities of natural killer and T-cells as well as release of thymic hormones. Growth hormone increases size of thymus and circulating naive T-cells in HIV patients.

Loss of AIRE is common causes for infertility in at least women as part of APECED. Alopecia is possible symptom. Some of the antigens AIRE produces in thymus are antigens that ovaries produce. Mice with AIRE knockout had delayed puberty but all had puberty.
Only 50% were able to have at least 1 litter and 16% gave birth to second litter. 83% of previously bred mice had lost all ovarian follicular reserves.  Among virgin females 25% lost follicules by week 8 and by 20th week 50-60% had lost follicules. Their ovulation and fertilization rates were normal. Autoimmunity may also cause miscarriages.  Follicle loss was associated with increased (~5 times) serum follicle-stimulating hormone levels and ovarian invasion by CD3+ T-cells. About third of those who reach menopause before 40 had autoimmunity as cause.  Part of thymic work happens through MHC I and II proteins present on surface of thymic cells and white blood cells. If T-cell show autoimmune effect then they get disabled in thymus before they could activate and cause autoimmunity.

Development of T-cells is supervised by 2 cell types. In thymus they get engulfed by epithelial “nurse cells” (located from medulla to cortex) that remove ~95% of immature T-cells for having autoimmune potential or which are not developed enough. Outside thymus regulatory cells would restrict T-cell activity to reduce damage to healthy cells. If thymus fills with immature T-cells then new ones can’t enter until old ones get removed or leave. T-cells are guided by chemokines and held by adhesion molecules like selectins and integrins. Adhesion molecules may be expressed partially by oxytocin, androgens, estrogens, vasopressin, neurotensin, insulin growth factor 2, glucocorticoids, acetylcholine, histamine and serotonin. Thymus in mammals starts to lose mass during puberty and it can speed up with stress or steroid hormones. Castration can reduce loss of T-cell function during aging as testosterone causes apoptosis in thymus through TNF. Nurse cells release thymic hormone thymulin which is needed to produce Th1 cytokines IL-2 and interferon-gamma in tyhmus. Thymulin can be released when thymic cells are exposed to endorphins and enkephalins.  Adenosine and its receptors seem needed or causing apoptosis in T-cells. Regulatory T-cells (Treg) exit thymus similarly to other T-cells but Treg cells reduce inflammation. GABA agonists can increase weight of thymus and they increase cell division in thymus. Inducible Treg cells are formed outside of thymus commonly during chronic infections or towards antigens produced by unharmful bacteria in intestines. Glucocorticoids and nicotine stimulate activity of Treg cells.
Thymic epithelial cells (TEC) are one of two cell types that help against self immunity. TEC produce almost every hormone and substance body  produces. ~10% of TEC produce most of neural hormones and other neural proteins/peptides.

AIRE binds with all transcription sites that have RNA polymerase II. Without AIRE these RNA polymerases near un-methylated histones may have produced short RNA molecules with length of 50-100 base pairs but AIRE is needed for rest of the gene.

Thymus seems to protect from autoimmunity throughout lifespan as in case a 67 year old woman with thymic tumor got APECED type autoimmune disorders. Her tumor happened to have cells that didn’t express AIRE while her AIRE gene didn’t seem mutated.

RegulatoryT cells (containing CD25 and CD4 receptors) can suppress immune responses and they can be found in many types of cancers. T killer cells can attack damaged cells, including cancer cells, unless immunosuppressive interference keeps them from attacking cancer or other abnormal cells. In case ovarian cancer their proportion kept increasing as cancer progressed (from 0,3% in early stages to 2,5% in late stage cancer). Proportion of regulatory T cells increased twofold compared to T killer cells in that time. Loss of regulatory T cells did slow growth of tumors by up to ~80% but they still grew.

Lack of regulatory T cells seems to be involved among causes or symptoms of multiple sclerosis. Tregs produce anti-inflammatory cytokines to reduce or stop excessive inflammation.

Skin problems that ~25-40% people with APECED get include patchy hair loss, wider alopecia (hair loss) and loss of skin pigment which may turn skin black people white in patches. AIRE is produced also in urinary tract, genitals, gastrointestinal tract, respiratory tract, thyroid glands, adrenal glands and brain.AIRE production can be caused by TNF (tumor necrosis factor). TNF is relatively intensely produced in thymus and in in adults it’s mainly produced in medullary thymic cells.

TNF levelsincrease during infections. Excessive TNF can cause some thymic atrophy. After infection TNF levels rise in blood in 7 days and in thymus in ~14 days. Glucocorticoid hormones during intense stress promote apoptosis of more mature T cells in thymus. Infections stimulate movements of white blood cells from thymus to other organ like spleen and lymphoid organs several times which can be amplified by additional injection of TNF. Immature T cells are also more likely to leave thymus due to effects of TNF. TNF may act as stop signal to white blood cells as it is concentrated in place of inflammation where it binds with fibronectin that itself is involved in wound healing.