T cells

A T cell is a leukocyte which belongs to the lymphocytes group. This white blood cell is called T cell because it matures in the thymus, which is a small organ located in the chest cavity. T cells are differentiated from other lymphocyte cells, such as B cells and natural killer cells, by the presence of a special receptor on their cell surface. This receptor is called T cell receptors, or TCR.

T cells are subdivided into three types of T cells: T helper cell, or Th cell; T suppressor cell, or Ts cell; T cytotoxic cell, or Tc cell. T helper cells assist other leukocytes in immunological processes. T suppressor cells shut down T cell-mediated immunity toward the end of an immune reaction and stop specific immune reactions from occurring. T cytotoxic cells kill virally infected cells and cancerous cells.

T helper cells: they establish and maximize the capabilities of the immune system. T helper cells do not have cytotoxic or phagocytic activity. They do not kill infected host cells or pathogens, and without other immune cells they would be useless against an infection. Nevertheless T helper cells activate and direct other immune cells, such as natural killer cells, macrophage cells, and T cytotoxic cells, to carry out the task of destroying foreign microorganisms.

Natural Killer Cell

A natural killer cell is a type of lymphocyte, which is a white blood cell that play an important role in the immune system. A natural killer cell (NK cell) is a cytotoxic lymphocyte, that is to say a toxin-containing white blood cell whose main function is to detect and kill virus-infected cells and cancer cells. In order to perform their job, natural killer cells need an activating signal, such as cytokines, which are stress-molecules released by cells when they are infected by viruses. The cytokines activate natural killer cells. Natural killer cells also act in response to chemical messages which are released from Helper T-cells (a type of white blood cells).

Natural killer cells have two type of toxic proteins in their cytoplasm, such as perforin and granzymes. When perforin is released by a NK cell, it makes pores in the cell membrane of the virus-infected cell. Once these pores have been made, the granzymes enters the target cell body, inducing apoptosis, which is the process of cell distruction, leading to the destruction of the virus inside the target cell.

Natural Killer Cells

Monocytes

A monocyte is a type of phagocytic leukocyte which plays an important role in the human immune system. Monocytes replenish resident macrophages and dendritic cells under normal states, and in response to inflammation signals, monocytes move quickly, between 8 to 12 hours, to sites of infection in the tissues and divide and differentiate into macrophages and dendritic cells to elicit an immune response. Half of monocytes are stored in the spleen. Monocytes are usually identified in stained smears by their large bilobate nucleus.

Monocytes are produced from myelo-monocytic stem cells in the bone marrow. When they then go into blood stream, they circulate for a few days, then move into tissues. In the tissue they further mature into macrophages. Monocytes make up about 8% of the white blood cells. They are closely related to neutrophils. Monocytes process foreign antigens and present them to the immunocompetent lymphocytes. They are also capable of phagocytosis.

Granulocytes

Granulocytes are leukocytes which contain granules in their cytoplasms. These granules have important proteins in them. Also called polymorphonuclear leukocytes, granulocytes have a nucleus, which is lobed into two or three segments. Granulocytes include neutrophils, eosinophils, and basophils. They are produced in the bone marrow by the regulatory complement proteins. They fight bacterial and fungal infection. The most abundant granulocyte is the neutrophil, which has neutrally-staining cytoplasmic granules.

Basophil

A basophil is a type of Leukocyte which is characterized by granules in its cytoplasm. Ganules-containing leukocytes are called granulocytes. Basophils secrete a biologically active substance such as histamine and proteoglycans. Basophils show up in specific types of inflammatory reactions, specially those which trigger allergic symptoms. Basophils produce anticoagulant heparin, which prevents blood from clotting too quickly.

A basophil measures between 12 and 15 microns in diameter. A basophile mature nucleus has 2 or 3 lobes. Basophils are produced by stem cells in the bone marrow. Their function is to phagocytate foreign particles and produce heparin and histamine.

Eosinophils

Eosinophil is a type of white blood cell that fights parasites and bacteria. Eosinophils belong to the group of leukocytes (white blood cells) known as granulocytes, which means that they are characterized by the presence of large red granules in their cytoplasms. When foreign microorganisms enter the body, lymphocytes and neutrophils (types of leukocytes) release certain substances that attract eosinophils which release toxic substances to kill the invaders.

Eosinophils are transparent, but they show brick-red under the microscope after staining with eosin, a dye, using the Romanowsky method. They measure between 12 and 17 micrometers in size. Only 6% of white blood cells are eosinophils. Aside from destroying bacteria, eosinophils attack parasitic larvae and their number increase in the presence of certain parasites. Eosinophils along with basophils are also important mediators of allergic responses and asthma pathogenesis. Eosinophils are produced in the bone marrow.

Neutrophils

A Neutrophil is a type of leukocyte (white blood cell) whose cytoplasm is filled with staining granules. Neutrophils play an important role in the immune system as they constitute the first line defense against bacterial and fungal infection. A neutrophil is essential for phagocytosis and proteolysis. The name "neutrophil" comes from the fact that it does not get stained strongly by either acid or basic dyes but get stained readily by neutral dyes.

Neutrophils have an average diameter of 12-15 micrometers (µm). The average half-life of neutrophils in the circulation is 12 hours when they are not activated. But when they are activated, they live between 1 and 2 days. When a bacterium or a virus first enters the organism, it first encounters a neutrophil. When bacteria enter the body, neutrophils migrate to the site of infection or inflammation through the blood vessels, then through intertial tissue. Neutrophils are produced in the bone marrow and are fully mature when they are released into the blood stream.

Erythrocyte

Erythrocyte is the most abundant type of blood cell whose function is to transport oxygen, carbon dioxide, and nutrients throughout the body. Also called red blood cells because of their color, erythrocytes take up oxygen in the lungs and release it to the rest of the body and take the carbon dioxide from the body tissues and carry it to the lungs. An erythrocyte looks like a red biconcave disk. This shape allows it to have a large surface in relation to its volume, helping the exchange of oxygen and carbon dioxide between the inside of the erythrocyte and the blood plasma.

An erythrocyte is a cell without a nucleus and organelles; it contains only the cell membrane, a cytoskeleton and enzymes. It is composed of 97% of hemoglobin, which is a molecule that contains iron and has the oxygen-binding capacity. Erythrocytes are produced in the bone marrow and have an average life cycle of 120 days. A healthy adult has about 4 to 5 million erythrocytes per cubic millimeter of blood. If someone has less than that amount, it is said that he suffers from anemia, or is anemic, and must eat iron-rich food, such as red meat, eggs, and green vegatable.

Globin

A globin is a group of four globulin protein molecules that become bound by the iron in heme molecules to form hemoglobin or myoglobin. The Globins are a related family of proteins, all of which have similar amino acid sequence and folding. Globin is a constituent of the hemoglobin molecule and is composed of two alpha and two beta chains. The two alpha chains differ slightly from the beta chains in the amino acid sequence.

A globin molecule is a coiled polypeptide chain. It becomes associated with an iron-containing group which attracts oxygen; this group is called heme group. Four globin molecules and four heme groups make up hemoglobin.

Heme

Heme is a molecule that is synthesized by the sequential actions of eight enzymes and is everywhere in nature. A heme is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are known as hemoproteins. As a prosthetic group, heme mediates reversible binding of oxygen by hemoglobin.

The heme synthesis begins in the mitochondria and continues in the cytoplasm. The process begins in the mitochondria because one of the precursors is found only there. Since this reaction is regulated in part by the concentration of heme, the final step which produces the heme is mitochondrial. Most of the intermediate steps are cytoplasmic. Heme is also catabolized to yield biliverdin, one atom of iron, and one molecule of carbon monoxide and is subsequently reduced to bilirubin.

There are several biologically important kinds of heme; the most common type is heme B; other important types include heme A and heme C. Isolated hemes are commonly designated by capital letters while hemes bound to proteins are designated by lower case letters.

Porphyrins

Porphyrins are a group of organic compounds that occur in nature, specially as the pigment in red blood cells. They are cyclic macromolecules called macrocycles that are characterized by the presence of four modified pyrrole subunits interconnected at their a carbon atoms via methine bridges (=CH-). Porphyrins are aromatic, and they obey Hückel's rule for aromaticity in that they possess 4n+2 pi electrons that are delocalized over the macrocycle. The macrocycles, therefore, are highly-conjugated system and consequently are deeply colored - the name porphyrin comes from a Greek word for purple. The macrocycle has 26 pi electrons. The parent porphyrin is porphine, and substituted porphines are called porphyrins.

Hemoglobin

Hemoglobin is the protein that is found in the red blood cells of vertebrates. Its function is to pick up and transport oxygen from the lungs to the rest of the body, delivering it to the tissues cells, and return carbon dioxide from the tissues cells to the lungs to be exhaled. Hemoglobin makes up 97% of a red blood cell.

Structurally, hemoglobin consists of four protein molecules (globins) that are connected together. Each one of these molecules contains 2 alpha-globulin chains and 2 beta-globulin chains. Each globulin chain holds the heme molecule. Wrapped by the heme molecule is an iron atom, which is the most important part of hemoglobin, for it is responsible to transport the oxygen and carbon dioxide in our blood. The iron contained in hemoglobin is also responsible for the red color of blood.

Hemoglobin is also found in nonerythroid cells including the A9 dopaminergic neurons in the substantia nigra, macrophages, alveolar cells, and mesangial cells in the kidney. In these tissues, it has a non-oxygen carrying function as an antioxidant and a regulator of iron metabolism.

Multiverse Theory

The multiverse theory is the hypothetical existence of a set of multiple possible universes, which includes our universe. These multiple universes are composed of everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that rule them. These different universes contained within the multiverse are sometimes called parallel universes. The structure of the multiverse, and the nature of each universe held within it, depend on the specific multiverse hypothesis considered.

Multiverses have been hypothesized in physics, astronomy, and philosophy. The word "multiverse" was coined in 1895 by psychologist William James.

Multiverse Theory

IC 2118 Witch Head Nebula

IC 2118 Witch Head Nebula is an ancient supernova remnant or gas cloud which is located in the constellation of Eridanus and is illuminated by nearby supergiant Rigel in Orion. The IC 2118 lies 900 light-years away from Earth, in the Eridanus constellation. Its dust particles reflect blue light better than red; hence the Witch Head blue color. The Witch Head Nebula glows mainly by light reflected from Rigel. The same physical process makes the Earth's daytime sky to appear blue. The IC 2118 lies at 2.6° to the west of Rigel.

Cosmic Inflation

Cosmic inflation is the exponential expansion of the universe at the end of the grand unification epoch, 10-36 seconds after the Big Bang. This exponential expansion was driven by a negative-pressure vacuum energy density. Cosmic inflation theory states that the primeval universe went through a phase of exponential expansion, ballooning almost instantaneously from less than the size of an atom to about golf-ball size. The term "inflation" is also used to refer to the hypothesis that inflation occurred, to the theory of inflation, or to the inflationary epoch. As a direct consequence of this expansion, all of the observable universe originated in a small causally connected region.

Cosmic inflation answers the conundrum of the big bang theory: why does the universe appear flat, homogeneous and isotropic in accordance with the cosmological principle when one would expect, on the basis of the physics of the big bang, a highly curved, heterogeneous universe? Cosmic inflation predicts the existence of gravity waves, as well as fluctuations in the density and temperature of radiation left over from the big bang. Inflation also explains the origin of the large-scale structure of the cosmos. Quantum fluctuations in the microscopic inflationary region, magnified to cosmic size, become the seeds for the growth of structure in the universe.

Cosmic inflation was proposed almost simultaneously by by Alan Guth in the United States and Alexei Starobinski in the Soviet Union.

Rigel

Rigel is a star in the constellation Orion. With visual magnitude 0.18, it is the sixth brightest star in the sky. Rigel is moving through a region of nebulosity and lights up several dust clouds in its vicinity, the most notable being the IC 2118, which is called the Witch Head Nebula.

Rigel is a contrasting blue supergiant. The theory of stellar structure and evolution shows that Rigel has a mass 18 times that of the Sun. With a dead helium core, it is still in a swelling and cooling phase. It is located at 850 light years away from the Solar System. Rigel should eventually expand to become a red supergiant very much like Betelgeuse.

NGC 147

NGC 147 is a Dwarf spheroidal galaxy which is located in the constellation Cassiopeia, 2.58 million light years away from Earth . NGC 147 is a satellite galaxy of Andromeda (M31) and belongs to the Local group of galaxies. It forms a physical pair with the nearby galaxy NGC 185, another remote satellite of M31. It is fainter but slightly larger than NGC 185, but they are both visible in small telescopes.

NGC 147 was discovered by John Herschel in September 1829 and the membership of NGC 147 in the Local Group was confirmed by Walter Baade in 1944 when he was able to resolve the galaxy into individual stars with the 100-inch (2.5 m) telescope at Mount Wilson near Los Angeles.

NGC 147 DDO3

Ursa Major I Dwarf

Ursa Major I Dwarf, or UMa I dSph, is a dwarf spheroidal galaxy which belongs to the Local Group and is satallite of the Milky Way galaxy. It measures only a few thousand light-years in diameter. The Ursa Major Dwarf is the second least luminous galaxy known to the Boötes Dwarf (absolute magnitude -5.7). The absolute magnitude of the galaxy is estimated to be only -6.75, meaning that it is less luminous than some stars in the Milky Way. It has been described as similar to the Sextans Dwarf Galaxy. Both galaxies are ancient and metal-deficient.

Ursa Major Dwarf galaxy lies at 330,000 light-years (100 Kpc) away from the Earth; twice the distance to the Large Magellanic Cloud; the largest and most luminous satellite galaxy of the Milky Way. It was discovered by Beth Willman in 2005.

One must not mistake the other celestial object which is also called Ursa Major Dwarf, discovered by Edwin Hubble in 1949. It was designated as Palomar 4, which, due to its peculiar look, was temporary suspected to be either a dwarf spheroidal or elliptical galaxy. Nevertheless, it has since been found to be a very distant (about 360,000 ly) globular cluster belonging to our galaxy.

Dwarf Spheroidal Galaxy

A dwarf spheroidal galaxy is a low luminosity type of galaxy which is found as a satellite galaxy of the Milky Way and the Andromeda Galaxy M31. It is spheroidal in shape, lower luminosity, and similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust. Dwarf spheroidal galaxies belong to the Local Group. Up until 2005, there were nine dwarf spheroidal galaxies in the Local Group, but the Sloan Digital Sky Survey has discovered eleven more. These types of galaxies might be the most common galaxies in the universe.

A dwarf spheroidal galaxy has extremely large amounts of dark matter. In the past, most astronomers believed that a dwarf spheroidal galaxy was merely a large, low density globular cluster. Nevertheless detailed studies in the last 20 years have revealed that the dwarf spheroidal galaxies have a more diverse set of properties and contain more complex stellar populations than the globular cluster analogy would predict.

Ursa Minor Dwarf

The Ursa Minor Dwarf is a dwarf elliptical galaxy which is a small satellite galaxy of the our Milky Way. It was discovered by A.G. Wilson of the Lowell Observatory in 1954. The Ursa Minor Dwarf is part of the Ursa Minor constellation. It is composed of older stars. Apparantly there is little star formation in the Ursa Minor Dwarf galaxy. It is located at 240,000 light years from our Solar System.

The Ursa Minor Dwarf galaxy has a right ascension of 15h 09m 08.5s, and a declination of +67° 13′ 21″.

The Hertzsprung-Russel Diagram

The Hertzsprung–Russell diagram is a scatter graph of stars which shows the relationship between the stars' absolute magnitudes and their spectral types or classifications and effective temperatures. Hertzprung-Russell diagrams are not pictures or maps of the locations of the stars. Rather, they plot each star on a graph measuring the star's absolute magnitude or brightness against its temperature and color. The Hertzsprung–Russell diagram is also referred to by the abbreviation H-R diagram or HRD. They are also known as colour-magnitude diagrams or CMD. The diagram was created circa 1910 by Ejnar Hertzsprung and Henry Norris Russell and represents a major step towards an understanding of stellar evolution or "the lives of stars".

There are several forms of the Hertzsprung–Russell diagram. The original diagram displayed the spectral type of stars on the horizontal axis and the absolute magnitude on the vertical axis. The first quantity is difficult to plot as it is not a numerical quantity and in modern versions of the chart it is replaced by the B-V color index of the stars. This type of diagram is what is often called a Hertzsprung–Russell diagram, or specifically a color-magnitude diagram, and it is often used by observers. In cases where the stars are known to be at identical distances such as with a star cluster, a color-magnitude diagram is often used to describe a plot of the stars in the cluster in which the vertical axis is the apparent magnitude.

Electron Energy Loss Spectroscopy

Electron Energy Loss Spectroscopy is an analytical technique which involves the measurement of the energy of electrons which have interacted with the specimen, in order to determine their energy loss and hence deduce the nature of the atoms with which they have interacted. In electron energy loss spectroscopy a material is exposed to a beam of electrons with a known, narrow range of kinetic energies. Some of the electrons will undergo inelastic scattering, which means that they lose energy and have their paths slightly and randomly deflected. The amount of energy loss can be measured via an electron spectrometer and interpreted in terms of what caused the energy loss. Inelastic interactions include phonon excitations, inter and intra band transitions, plasmon excitations, inner shell ionizations, and Cerenkov radiation.

Spectral Reflectance

Spectral reflectance is the fraction of incident radiation reflected by a non-transparent surface. Spectral reflectance must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength. However it is also commonly averaged over the reflected hemisphere to give the hemispherical spectral reflectivity:Spectral reflectance measures the fractional amplitude of the reflected electromagnetic field, while reflectance refers to the fraction of incident electromagnetic power that is reflected at an interface. The reflectance is thus the square of the magnitude of the reflectivity. The spectral reflectance can be expressed as a complex number as determined by the Fresnel Equations for a single layer, whereas the reflectance is always a positive real number.

The fraction of energy reflected at a particular wavelength varies for different features. Additionally, the reflectance of features varies at different wavelengths. Thus, two features that are indistinguishable in one spectral range may be very different in another portion of the spectrum. This is an essential property of matter that allows for different features to be identified and separated by their spectral signatures. A spectral signature is a unique reflectance value in a specific part of the spectrum.

Uncertainty Principle

The uncertainty principle states that the product of the uncertainty in measurement of one variable, say momentum p, multiplied by the uncertainty of measurement of another variable, say position x, can never be smaller than Planck's constant h. Then Δp Δx = h. So, if we know the position of a particle very accurately we cannot determine its momentum with great precision. The same relationship occurs between other pairs of variables such as energy and time.

The uncertainty principle was postulated by the German physicist Werner Heisenberg, who asserted that certain pairs of physical properties, like position and momentum, cannot both be known to arbitrary precision. That is, the more precisely one property is known, the less precisely the other can be known. It is impossible to measure simultaneously both position and velocity of a microscopic particle with any degree of accuracy or certainty. Heisenberg formulated the uncertainty principle in Niels Bohr's institute at Copenhagen, while working on the mathematical foundations of quantum mechanics.

Schrödinger Equation

The Schrödinger equation is an equation that describes how the quantum state of a physical system changes in time. It is as central to quantum mechanics as Newton's laws are to classical mechanics. The Schrödinger equation can be mathematically transformed into Heisenberg's matrix mechanics, and into Feynman's path integral formulation. The Schrödinger equation describes time in a way that is inconvenient for relativistic theories, a problem which is not as severe in Heisenberg's formulation and completely absent in the path integral.

In the standard interpretation of quantum mechanics, the quantum state is the most complete description which can be given to a physical system. Solutions to Schrödinger's equation describe not only atomic and subatomic systems, atoms and electrons, but also macroscopic systems, possibly even the whole universe. The equation is named after Erwin Schrödinger, who constructed it in 1926.

The Schrödinger equation describes the behaviour of an electron of energy E in a potential V in terms of the wave function y. The time-independent, one-dimensional form of the equation is: d2y/dx2 + (8p2m/h2)[E - V]y = 0 where m is the electron mass and h is Planck's constant.

Electrolytic Process

The electrolytic process is the process that proceeds when an electrical charge is put on between two electrodes in a conducting electrolyte. Some examples of electrolytic aluminium surface treatments are anodising, AC-electrolytic graining and plating. Electrolytic process is the use of electrolysis in industry to refine metals or compounds at a high purity and low cost. Some examples are the Hall-Héroult process used for aluminium, or the production of hydrogen from water. Electrolysis is usually done in bulk using hundreds of sheets of metal connected to an electric power source.

Electrical Conductivity

Electrical conductivity is the capacity of matter to conduct an electric current, indicating the ease with which electrical current flows through it. When an electrical potential difference is placed across a conductor, its movable charges flow, giving rise to an electric current. The conductivity σ is defined as the ratio of the current density J to the electric field strength E.

A conductor such as a metal has high electrical conductivity and a low resistivity. An insulator like glass or plastic has low conductivity and a high resistivity. Silver, copper, gold, and aluminum have the highest electrical conductivity.

Diffraction

Diffraction is an interference effect which leads to the scattering of strong beams of radiation in specific directions. Diffraction usually refers to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Diffraction from crystals is described by the Bragg Law: n λ= 2 d sin θ; where n is an integer (the order of scattering), λ is the wavelength of the radiation, d is the spacing between the scattering entities (e.g. planes of atoms in the crystal) and θ is the angle of scattering.

Electron and X-ray diffraction are both particularly powerful because their wavelengths are smaller than the typical spacings of atoms in crystals and strong, easily measurable, diffraction occurs. The effects of diffraction can be regularly seen in everyday life. The most colorful examples of diffraction are those involving light; for example, the closely spaced tracks on a CD or DVD act as a diffraction grating to form the familiar rainbow pattern we see when looking at a disk.

Refraction

Refraction is the change in direction of a beam of light. Refraction occurs when a light ray changes mediums. This is most commonly observed when a ray or beam of light passes from one medium to another, as when light traveling from air goes into water. The speed of the light beam changes when it changes mediums, and so does the direction of the light beam.

If someone half-submerges a pencil into a glass of water, he will notice that the straight pencil appears bent at the point it gets into the water. This optical effect is caused by refraction. When light passes from one transparent medium to another, it changes speed, and bends. How much it appears to bend depends on the refractive index of the mediums and the angle between the light ray and the line perpendicular (normal) to the surface separating the two mediums.

In 1621, Willebrord Snell, a Dutch physicist, derived the relationship between the different angles of light as it passes from one transperent medium to another. When light passes from one transparent medium to another, it bends according to Snell's law which states: Ni * Sin(Ai) = Nr * Sin(Ar). where: Ni is the refractive index of the medium the light is leaving; Ai is the incident angle between the light ray and the normal to the meduim to medium interface; Nr is the refractive index of the medium the light is entering; Ar is the refractive angle between the light ray and the normal to the meduim to medium interface.

Refraction