Carl Sagan

American astronomer, cosmologist, astrophysicist, astrobiologist, author, science popularizer, and science communicator in astronomy and other natural sciences, Carl Edward Sagan was born November 9, 1934. Sagan First became interested in science and astronomy when parents took him to the 1939 New York World’s Fair when he was four years old. The exhibits became a turning point in his life. He later recalled the moving map of the America of Tomorrow exhibit which showed beautiful highways and cloverleaves and little General Motors cars all carrying people to skyscrapers, buildings with lovely spires and, flying buttresses. At other exhibits, he remembered how a flashlight that shone on a photoelectric cell created a crackling sound, and how the sound from a tuning fork became a wave on an oscilloscope. He also witnessed the future media technology that would replace radio: television.

Soon after entering elementary school he began to express a strong inquisitiveness about nature. Sagan recalled taking his first trips to the public library alone, at the age of five, when his mother got him a library card. He wanted to learn what stars were, since Nobody else could give him a clear answer. He and a close friend took trips to the American Museum of Natural History across the East River in Manhattan. While there, they went to the Hayden Planetarium and walked around the museum’s exhibits of space objects, such as meteorites, and displays of dinosaurs and animals in natural settings. His parents bought him chemistry sets and reading materials. His interest in space, however, was his primary focus, especially after reading science fiction stories by writers such as H. G. Wells and Edgar Rice Burroughs, which stirred his imagination about life on other planets such as Mars. In 1947 he discovered Astounding Science Fiction magazine, which introduced him to more hard science fiction speculations than those in Burroughs’s novels. That same year inaugurated the “flying saucer” mass hysteria with the young Carl suspecting the “discs” might be alien spaceships.

Sagan lived in Bensonhurst where he went to David A. Boody Junior High School. He had his bar mitzvah in Bensonhurst when he turned 13. In 1948, his family moved to the nearby town of Rahway, New Jersey for his father’s work, where Sagan then entered Rahway High School. He graduated in 1951. Sagan was made president of the school’s chemistry club, and set up his own laboratory at home, teaching himself about molecules by making cardboard cutouts to help him visualize how molecules were formed and also remained interested in astronomy.

Sagan attended the University of Chicago. Its Chancellor, Robert Hutchins, structured the school as an “ideal meritocracy,” with no age requirement. The school also employed a number of the nation’s leading scientists, including Enrico Fermi and Edward Teller, along with operating the famous Yerkes Observatory. Sagan worked in the laboratory of the geneticist H. J. Muller and wrote a thesis on the origins of life with physical chemist Harold Urey. Sagan joined the Ryerson Astronomical Society, received a B.A. degree in self-proclaimed “nothing” with general and special honors in 1954, and a B.S. degree in physics in 1955. He went on to earn a M.S. degree in physics in 1956, before earning a Ph.D. degree in 1960 with the dissertation “Physical Studies of Planets” submitted to the Department of Astronomy and Astrophysics. From 1960 to 1962 Sagan was a Miller Fellow at the University of California, Berkeley. he also published an article in 1961 in the journal Science on the atmosphere of Venus, while also working with NASA’s Mariner 2 team, and served as a “Planetary Sciences Consultant” to the RAND Corporation.

After the publication of Sagan’s Science article, in 1961 Harvard University astronomers Fred Whipple and Donald Menzel offered Sagan the opportunity to give a colloquium at Harvard, and they subsequently offered him a lecturer position at the institution. Sagan instead asked to be made an assistant professor. Sagan lectured, performed research, and advised graduate students at the institution from 1963 until 1968, as well as working at the Smithsonian Astrophysical Observatory, both located in Cambridge, Massachusetts. Cornell University astronomer Thomas Gold then asked Sagan to move to Ithaca, New York and join the faculty at Cornell. and remained a faculty member at Cornell for nearly 30 years until his death in 1996. Following two years as an associate professor, Sagan became a full professor at Cornell in 1970, and directed the Laboratory for Planetary Studies there. From 1972 to 1981, he was associate director of the Center for Radiophysics and Space Research (CRSR) at Cornell. In 1976, he became the David Duncan Professor of Astronomy and Space Sciences.

Sagan was associated with the U.S. space program from its inception. From the 1950s onward, he worked as an advisor to NASA, where one of his duties included briefing the Apollo astronauts before their flights to the Moon. Sagan contributed to many of the robotic spacecraft missions that explored the Solar System, arranging experiments on many of the expeditions. Sagan assembled the first physical message that was sent into space: a gold-anodized plaque, attached to the space probe Pioneer 10, launched in 1972. Pioneer 11, also carrying another copy of the plaque, was launched In 1973. He continued to refine his designs; the most elaborate message he helped to develop and assemble was the Voyager Golden Record that was sent out with the Voyager space probes in 1977. Sagan often challenged the decisions to fund the Space Shuttle and the International Space Station at the expense of further robotic missions.

He became known for his work as a science popularizer and communicator. His best known scientific contribution is research on extraterrestrial life, including experimental demonstration of the production of amino acids from basic chemicals by radiation. Sagan assembled the first physical messages sent into space: the Pioneer plaque and the Voyager Golden Record, universal messages that could potentially be understood by any extraterrestrial intelligence that might find them. Sagan argued the now accepted hypothesis that the high surface temperatures of Venus can be attributed to and calculated using the greenhouse effect.

Sagan published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. He wrote many popular science books, such as The Dragons of Eden, Broca’s Brain and Pale Blue Dot, and narrated and co-wrote the award-winning 1980 television series Cosmos: A Personal Voyage. The most widely watched series in the history of American public television, Cosmos has been seen by at least 500 million people across 60 different countries. The book Cosmos was published to accompany the series. He also wrote the science fiction novel Contact, the basis for a 1997 film of the same name. His papers, containing 595,000 items, are archived at The Library of Congress.

Sagan advocated scientific skeptical inquiry and the scientific method, pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI). He spent most of his career as a professor of astronomy at Cornell University, where he directed the Laboratory for Planetary Studies. Sagan and his works received numerous awards and honors, including the NASA Distinguished Public Service Medal, the National Academy of Sciences Public Welfare Medal, the Pulitzer Prize for General Non-Fiction for his book The Dragons of Eden, and, regarding Cosmos: A Personal Voyage, two Emmy Awards, the Peabody Award and the Hugo Award. He married three times and had five children. After suffering from myelodysplasia, Sagan died of pneumonia at the age of 62, on December 20, 1996.


International Day of Radiology

International Day of Radiology (IDoR) is celebrated annually on November 8th to promote the role of medical imaging in modern healthcare and mark the anniversary of the discovery of x-rays on November 8th 1895 by Wilhelm Conrad Röntgen, who effectively layed the foundation for the new medical discipline of radiology.

It was first introduced in 2012, as a joint initiative, by the European Society of Radiology (ESR), the Radiological Society of North America (RSNA), and the American College of Radiology (ACR). The International Day of Radiology is a successor to the European Day of Radiology which was launched in 2011. The first and only European Day of Radiology was held on February 10, 2011 to commemorate the anniversary of Röntgen’s death. The European day was organised by the ESR, who later entered into cooperation with the RSNA and the ACR to establish the International Day of Radiology.

The International Day of Radiology marks the anniversary of Röntgen’s discovery of x-rays and the main theme was medical imaging in oncology. The day was celebrated with events in many countries, mostly organised by national professional societies which represent radiologists. Many public lectures on the role of imaging in oncology took place across Europe. In the UK, the Royal College of Radiologists organised a free public lecture at the Wellcome Collection by Dr. Phil O’Connor, who served as head of musculoskeletal imaging at the London 2012 Olympics. The ESR also published two booklets to mark the occasion, ‘The Story of Radiology’, which was created in cooperation with the International Society for the History of Radiology, and ‘Making Cancer Visible: the role of cancer in oncology’

World Radiography Day also takes place to mark the anniversary of the discovery of X-rays in 1895. The purpose of this day is to raise public awareness of radiographic imaging and therapy, which play a crucial role in the diagnosis and the treatment of patients and, most importantly, ensuring radiation is kept to the minimum required, hence improving the quality of patient care. The day is celebrated worldwide by various national radiographers’ associations and societies, including Nigeria’s Association of Radiographers of Nigeria, United Kingdom’s Society of Radiographers (SoR), among others. [1]The International Society of Radiographers and Radiological Technologists have celebrated 8 November as World Radiography Day since 2007.

German mechanical engineer and physicist Wilhelm Konrad Röntgen was born 27 March 1845. He attended high school in Utrecht, Netherlands. However In 1865, he was expelled from high school and Without a high school diploma, Röntgen could only attend university in the Netherlands as a visitor. In 1865, he tried to attend Utrecht University without having the necessary credentials required for a regular student. Upon hearing that he could enter the Federal Polytechnic Institute in Zurich (today known as the ETH Zurich), he passed its examinations, and began studies there as a student of mechanical engineering. In 1869, he graduated with a Ph.D. from the University of Zurich; once there, he became a favorite student of Professor August Kundt, whom he followed to the University of Strassburg.

In 1874, Röntgen became a lecturer at the University of Strassburg. In 1875, he became a professor at the Academy of Agriculture at Hohenheim, Württemberg. He returned to Strassburg as a professor of physics in 1876, and in 1879, he was appointed to the chair of physics at the University of Giessen. In 1888, he obtained the physics chair at the University of Würzburg, and in 1900 at the University of Munich, by special request of the Bavarian government. Although Röntgen accepted an appointment at Columbia University in New York City the outbreak of World War I changed his plans and he remained in Munich for the rest of his career.

During 1895, Röntgen was investigating the external effects from the various types of vacuum tube equipment — apparatuses from Heinrich Hertz, Johann Hittorf, William Crookes, Nikola Tesla and Philipp von Lenard — when an electrical discharge is passed through them.[5][6] In early November, he was repeating an experiment with one of Lenard’s tubes in which a thin aluminium window had been added to permit the cathode rays to exit the tube but a cardboard covering was added to protect the aluminium from damage by the strong electrostatic field that produces the cathode rays. He knew the cardboard covering prevented light from escaping, yet Röntgen observed that the invisible cathode rays caused a fluorescent effect on a small cardboard screen painted with barium platinocyanide when it was placed close to the aluminium window. It occurred to Röntgen that the Crookes–Hittorf tube, which had a much thicker glass wall than the Lenard tube, might also cause this fluorescent effect.

On 8 November 1895, Röntgen decided to test his idea. He carefully constructed a black cardboard covering similar to the one he had used on the Lenard tube. He covered the Crookes–Hittorf tube with the cardboard and attached electrodes to a Ruhmkorff coil to generate an electrostatic charge. Before setting up the barium platinocyanide screen to test his idea, Röntgen darkened the room to test the opacity of his cardboard cover. As he passed the Ruhmkorff coil charge through the tube, he determined that the cover was light-tight and turned to prepare the next step of the experiment. It was at this point that Röntgen noticed a faint shimmering from a bench a few feet away from the tube. To be sure, he tried several more discharges and saw the same shimmering each time. Striking a match, he discovered the shimmering had come from the location of the barium platinocyanide screen he had been intending to use next.

Röntgen speculated that a new kind of ray might be responsible. 8 November was a Friday, so he took advantage of the weekend to repeat his experiments and made his first notes. In the following weeks he ate and slept in his laboratory as he investigated many properties of the new rays he temporarily termed “X-rays”, using the mathematical designation (“X”) for something unknown. The new rays came to bear his name in many languages as “Röntgen rays” (and the associated X-ray radiograms as “Röntgenograms”). At one point while he was investigating the ability of various materials to stop the rays, Röntgen brought a small piece of lead into position while a discharge was occurring. Röntgen thus saw the first radiographic image, his own flickering ghostly skeleton on the barium platinocyanide screen. He later reported that it was at this point that he determined to continue his experiments in secrecy, because he feared for his professional reputation if his observations were in error.

Nearly two weeks after his discovery, he took the very first picture using X-rays of his wife Anna Bertha’s hand. When she saw her skeleton she exclaimed “I have seen my death!” Röntgen’s original paper, “On A New Kind Of Rays” (Ueber eine neue Art von Strahlen), was published on 28 December 1895. On 5 January 1896, an Austrian newspaper reported Röntgen’s discovery of a new type of radiation. Röntgen was awarded an honorary Doctor of Medicine degree from the University of Würzburg after his discovery. He published a total of three papers on X-rays between 1895 and 1897. Today, Röntgen is considered the father of diagnostic radiology, the medical speciality which uses imaging to diagnose disease. A collection of his papers is held at the National Library of Medicine in Bethesda, Maryland.

Marie Curie

Best known for her pioneering research in the field of radioactivity, the World famous Polish–French physicist and chemist Marie Skłodowska Curie was born 7th Novemer in 1867 in Warsaw, Poland. Maria’s paternal grandfather, Józef Skłodowski, had been a respected teacher in Lublin, where he taught the young Bolesław Prus,who became a leading figure in Polish literature.Her father, Władysław Skłodowski, taught mathematics and physics, subjects that Maria was to pursue, and was also director of two Warsaw gymnasia for boys.After Russian authorities eliminated laboratory instruction from the Polish schools, he brought much of the laboratory equipment home, and instructed his children in its use.

The father was eventually fired by his Russian supervisors for pro-Polish sentiments, and forced to take lower-paying posts. the family also lost money on a bad investment, and eventually chose to supplement their income by lodging boys in the house. Maria’s mother Bronisława operated a prestigious Warsaw boarding school for girls; she resigned from the position after Maria was born.She died of tuberculosis in May 1878, when Maria was ten years old. Less than three years earlier, Maria’s oldest sibling, Zofia, had died of typhus contracted from a boarder.

When she was ten years old, Maria began attending the boarding school of J. Sikorska; next she attended a gymnasium for girls, from which she graduated on 12 June 1883 with a gold medal. After an illness she spent the following year in the countryside with relatives of her father, and the next year with her father in Warsaw, where she did some tutoring. Unable to enroll in a regular institution of higher education because she was a woman, she and her sister Bronisława became involved with the clandestine Flying University, a Polish patriotic institution of higher learning that admitted women students.

At a Warsaw laboratory, in 1890–91, Maria Skłodowska did her first scientific work and made an agreement with her sister, Bronisława, that she would give her financial assistance during Bronisława’s medical studies in Paris, in exchange for similar assistance two years later. Maria took a position as governess: first as a home tutor in Warsaw; then for two years as a governess in Szczuki with a landed family, the Żorawskis, who were relatives of her father and fell in love with their son, Kazimierz Żorawski, a future eminent mathematician.Who soon earned a doctorate and pursued an academic career as a mathematician, becoming a professor and rector of Kraków University. Sadly his parent rejected his relationship with Maria.

She lived inWarsaw until the age of 24, when she followed her older sister Bronisława to study in Paris, where she earned her higher degrees and conducted her subsequent scientific work. She was also the first person honored with two Nobel Prizes—in both physics and chemistry, In 1903 she won the Nobel Prize in Physics which She shared with her husband Pierre Curie (and with Henri Becquerel), and In 1911 She became the sole winner of the 1911 Nobel Prize in Chemistry which she shared with Her daughter Irène Joliot-Curie and son-in-law, Frédéric Joliot-Curie, and is the only woman to date to win in two fields, and the only person to win in multiple sciences.

Among her many achievements are the theory of radioactivity (a term that she coined), She also developed techniques for isolating radioactive isotopes, and discovered two radioactive elements, polonium (Which was named after her native country) and radium. She was also the first female professor at the University of Paris andUnder her direction, the world’s first studies were conducted into the treatment of neoplasms, using radioactive isotopes. In 1932, she founded a Radium Institute (now the Maria Skłodowska–Curie Institute of Oncology) in her home town, Warsaw. Which was headed by her physician-sister Bronisława.

Unfortunately though Marie Curie died on 4th July 1934 of aplastic anemia, a condition which was undoubtedly brought on by her lifelong exposure to radiation, however her pioneering research has led the way for many improvements in the fields of Science, Chemistry and Medicine and in 1995 she became the first woman to be entombed on her own merits in the Paris Panthéon.

Bill Gates

American business magnate, software executive and philanthropist William Henry “Bill” Gates III was born October 28th, 1955. Bill Gates is the former chief executive and current chairman of Microsoft, the world’s largest personal-computer software company, which he co-founded with Paul Allen. He is consistently ranked among the world’s wealthiest people and was the wealthiest overall from 1995 to 2009, excluding 2008, when he was ranked third; in 2011 he was the third wealthiest American and the second wealthiest person. During his career at Microsoft, Gates held the positions of CEO and chief software architect, and remains the largest individual shareholder, with 6.4 percent of the common stock. He has also authored or co-authored several books.Gates is one of the best-known entrepreneurs of the personal computer revolution. Gates has been criticized for his business tactics, which have been considered anti-competitive, an opinion which has in some cases been upheld by the courts. In the later stages of his career, Gates has pursued a number of philanthropic endeavors, donating large amounts of money to various charitable organizations and scientific research programs through the Bill & Melinda Gates Foundation, established in 2000.

Gates stepped down as chief executive officer of Microsoft in January 2000. He remained as chairman and created the position of chief software architect. In June 2006, Gates announced that he would be transitioning from full-time work at Microsoft to part-time work, and full-time work at the Bill & Melinda Gates Foundation. He gradually transferred his duties to Ray Ozzie, chief software architect, and Craig Mundie, chief research and strategy officer. Gates’s last full-time day at Microsoft was June 27, 2008. He remains at Microsoft as non-executive chairmanthiest American and the second wealthiest person. During his career at Microsoft, Gates held the positions of CEO and chief software architect, and remains the largest individual shareholder, with 6.4 percent of the common stock. He has also authored or co-authored several books.

Gates is one of the best-known entrepreneurs of the personal computer revolution. Gates has been criticized for his business tactics, which have been considered anti-competitive, an opinion which has in some cases been upheld by the courts. In the later stages of his career, Gates has pursued a number of philanthropic endeavors, donating large amounts of money to various charitable organizations and scientific research programs through the Bill & Melinda Gates Foundation, established in 2000.Gates stepped down as chief executive officer of Microsoft in January 2000. He remained as chairman and created the position of chief software architect. In June 2006, Gates announced that he would be transitioning from full-time work at Microsoft to part-time work, and full-time work at the Bill & Melinda Gates Foundation. He gradually transferred his duties to Ray Ozzie, chief software architect, and Craig Mundie, chief research and strategy officer. Gates’s last full-time day at Microsoft was June 27, 2008. He remains at Microsoft as non-executive chairman.

World Polio Day

World Polio Day occurs annually on 24 October. It was established by Rotary International to commemorate the birth of Jonas Salk, who led the first team to develop a vaccine against poliomyelitis. Use of this inactivated poliovirus vaccine and subsequent widespread use of the oral poliovirus vaccine developed by Albert Sabin led to establishment of the Global Polio Eradication Initiative (GP) in 1988. Since then, GPEI has reduced polio worldwide by 99 percent. The term derives from the Ancient Greek poliós (πολιός), meaning “grey”, myelós (µυελός “marrow”), referring to the grey matter of the spinal cord, and the suffix -itis, which denotes inflammation., i.e., inflammation of the spinal cord’s grey matter, although a severe infection can extend into the brainstem and even higher structures, resulting in polioencephalitis, producing a lack of ability to breathe that requires mechanical assistance such as an iron lung.

Poliomyelitis, often called polio or infantile paralysis, is an infectious disease caused by the poliovirus. In about 0.5 percent of cases there is muscle weakness resulting in an inability to move. This can occur over a few hours to a few days. The weakness most often involves the legs but may less commonly involve the muscles of the head, neck and diaphragm.Many but not all people fully recover. In those with muscle weakness about 2 to 5 percent of children and 15 to 30 percent of adults die. Another 25 percent of people have minor symptoms such as fever and a sore throat and up to 5 percent have headache, neck stiffness and pains in the arms and legs. These people are usually back to normal within one or two weeks.In up to 70 percent of infections there are no symptoms. Years after recovery post-polio syndrome may occur, with a slow development of muscle weakness similar to that which the person had during the initial infection.

Poliovirus is usually spread from person to person through infected fecal matter entering the mouth. It may also be spread by food or water containing human feces and less commonly from infected saliva.Those who are infected may spread the disease for up to six weeks even if no symptoms are present.The disease may be diagnosed by finding the virus in the feces or detecting antibodies against it in the blood. The disease only occurs naturally in humans.

Poliomyelitis is caused by infection with a member of the genus Enterovirus known as poliovirus (PV). This group of RNA viruses colonize the oropharynx and the intestine. The incubation time (to the first signs and symptoms) ranges from three to 35 days, with a more common span of six to 20 days.PV infects and causes disease in humans alone. Its structure is very simple, composed of a single (+) sense RNA genome enclosed in a protein shell called a capsid. In addition to protecting the virus’s genetic material, the capsid proteins enable poliovirus to infect certain types of cells. Three serotypes of poliovirus have been identified—poliovirus type 1 (PV1), type 2 (PV2), and type 3 (PV3)—each with a slightly different capsid protein All three are extremely virulent and produce the same disease symptoms. PV1 is the most commonly encountered form, and the one most closely associated with paralysis.

Individuals who are exposed to the virus, either through infection or by immunization with polio vaccine, develop immunity. In immune individuals, IgA antibodies against poliovirus are present in the tonsils and gastrointestinal tract, and are able to block virus replication; IgG and IgM antibodies against PV can prevent the spread of the virus to motor neurons of the central nervous system. Infection or vaccination with one serotype of poliovirus does not provide immunity against the other serotypes, and full immunity requires exposure to each serotype. A rare condition with a similar presentation, nonpoliovirus poliomyelitis, may result from infections with nonpoliovirus enteroviruses.

The term “poliomyelitis” is used to identify the disease caused by any of the three serotypes of poliovirus. Two basic patterns of polio infection are described: a minor illness which does not involve the central nervous system (CNS), sometimes called abortive poliomyelitis, and a major illness involving the CNS, which may be paralytic or nonparalytic. In most people with a normal immune system, a poliovirus infection is asymptomatic. Rarely, the infection produces minor symptoms; these may include upper respiratory tract infection (sore throat and fever), gastrointestinal trouble (nausea, vomiting abdominal pain, constipation or, rarely, diarrhea), and influenza-like illness.

The virus enters the central nervous system in about 1 percent of infections. Most patients with CNS involvement develop nonparalytic aseptic meningitis, with symptoms of headache, neck, back, abdominal and extremity pain, fever, vomiting, lethargy, and irritability.About one to five in 1000 cases progress to paralytic disease, in which the muscles become weak, floppy and poorly controlled, and, finally, completely paralyzed; this condition is known as acute flaccid paralysis. Depending on the site of paralysis, paralytic poliomyelitis is classified as spinal, bulbar, or bulbospinal. Encephalitis, an infection of the brain tissue itself, can occur in rare cases, and is usually restricted to infants. It is characterized by confusion, changes in mental status, headaches, fever, and, less commonly, seizures and spastic paralysis.

The disease is preventable with the polio vaccine; however, a number of doses are required for it to be effective. The US Centers for Disease Control and Prevention recommends polio vaccination boosters for travelers and those who live in countries where the disease is occurring.Once infected there is no specific treatment. In 2016, polio affected 42 people, while there were about 350,000 cases in 1988. In 2014 the disease was only spreading between people in Afghanistan, Nigeria, and Pakistan. In 2015 Nigeria had stopped the spread of wild poliovirus but it reoccurred in 2016.

Poliomyelitis has existed for thousands of years, with depictions of the disease in ancient art. The disease was first recognized as a distinct condition by Michael Underwood in 1789and the virus that causes it was first identified in 1908 by Karl Landsteiner. Major outbreaks started to occur in the late 19th century in Europe and the United States. In the 20th century it became one of the most worrying childhood diseases in these area. The first polio vaccine was developed in the 1950s by Jonas Salk.It is hoped that vaccination efforts and early detection of cases will result in global eradication of the disease by 2018.

Mole Day

Many chemists, chemistry students and chemistry enthusiasts celebrate Mole Day annually on October 23 between 6:02 a.m. and 6:02 p.m. (making the date 6:02 10/23 in the American style of writing dates) The time and date are derived from Avogadro’s number, which is approximately 6.02 × 1023, defining the number of particles (atoms or molecules) in one mole of substance, one of the seven base SI units. Mole Day originated in an article in The Science Teacher in the early 1980s. Inspired by this article, Maurice Oehler, now a retired high school chemistry teacher from Prairie du Chien, Wisconsin, founded the National Mole Day Foundation (NMDF) on May 15, 1991. Many high schools around the United States, South Africa, Australia and in Canada celebrate Mole Day as a way to get their students interested in chemistry, with various activities often related to chemistry or moles. The American Chemical Society sponsors National Chemistry Week, which occurs from the Sunday through Saturday during October in which the 23rd falls. This makes Mole Day an integral part of National Chemistry Week.

The Avogadro constant (named after the scientist Amedeo Avogadro) is used in chemistry and physics, to determine the number of constituent particles, usually atoms or molecules, that are contained in the amount of substance given by one mole. Thus, it is the proportionality factor that relates the molar mass of a compound to the mass of a sample. The Avogadro constant, often designated with the symbol NA or L, has the value 6.022140857(74)×1023 mol−1 in the International System of Units (SI).

Previous definitions of chemical quantity involved Avogadro’s number, a historical term closely related to the Avogadro constant, but defined differently: Avogadro’s number was initially defined by Jean Baptiste Perrin as the number of atoms in one gram-molecule of atomic hydrogen, meaning one gram of hydrogen. This number is also known as Loschmidt constant in German literature. The constant was later redefined as the number of atoms in 12 grams of the isotope carbon-12 (12C), and still later generalized to relate amounts of a substance to their molecular weight. For instance, to a first approximation, 1 gram of hydrogen element (H), having the atomic (mass) number 1, has 6.022×1023 hydrogen atoms. Similarly, 12 grams of 12C, with the mass number 12 (atomic number 6), has the same number of carbon atoms, 6.022×1023. Avogadro’s number is a dimensionless quantity, and has the same numerical value of the Avogadro constant when given in base units. In contrast, the Avogadro constant has the dimension of reciprocal amount of substance. The Avogadro constant can also be expressed as 0.602214… mL⋅mol−1⋅Å−3, which can be used to convert from volume per molecule in cubic ångströms to molar volume in millilitres per mole.

Revisions in the base set of SI units necessitated redefinitions of the concepts of chemical quantity. Avogadro’s number, and its definition, was deprecated in favor of the Avogadro constant and its definition. Changes in the SI units are proposed to fix the value of the constant to exactly 6.02214X×1023 when it is expressed in the unit mol−1, in which an “X” at the end of a number means one or more final digits yet to be agreed upon.

More exciting Fantasy and Science Fiction novels

A Sellsword’s Compassion By Jacob Peppers

A Sellsword’s Compassion is Book One of The Seven Virtues by Jacob Peppers. It takes place in a War torn land as the sons and daughters of the late King Marcus battle over who will claim their father’s throne and able-bodied men and women flock to one cause or the other in the hopes of a better tomorrow. At least, most of them. If life has taught the jaded sellsword, Aaron Envelar, anything, it’s that hope is for fools and causes are a sure remedy for breathing.

However his latest job leads him to the corpse of a prince and a conspiracy that threatens to destroy the entire realm, Aaron is forced to choose sides in a war he doesn’t want, between forces he doesn’t understand. Thrust into a world of mythical assassins, a madman with a superhuman strength, and a nagging ball of light with a superiority complex who claims to be the embodiment of compassion, Aaron takes on his hardest job yet—staying alive.

Benjamin Ashwood by AC Cobble

Set Against the backdrop of warring political, economic, and military factions, Benjamin Ashwood is book one in an engaging fantasy adventure, series by A.C.Cobble which is Packed full of action and adventure. It features Young Benjamin who starts off as your typical orphan in a small farming town. Life is simple in Ben’s village until an unexpected attack brings the arrival of exciting strangers.

Before Ben understands what is happening, they’ve recruited his sister to go with them on an adventure to the big city where his sister enrols as a pupil at the all-female magic school. To ensure her safety, Ben accompanies her among company of mysterious swordsmen and magic-users. At the city Benjamin starts brewing beer for a living,

This goes well until he gets involved in politics of the dangerous kind and discovers that the city is ruled by unscrupulous leaders and he finds himself in a more dangerous world than he ever imagined. Mages, demons, thieves, and assassins are just a few of the perils he faces on an epic journey to a city shrouded in myth and legend. Ben and his friends end up battling a threat to all of mankind and Benjamin must decide whether to flee or stand up to them…

Trilisk Ruins Michael McCloskey

The Trilisk Ruins is the first book in the PIT series by Michael McCloskey. They feature a character named Telisa Relachik who studied to be a xenoarchaeologist in a future where humans have found alien artifacts but haven’t ever encountered live aliens. Then she discovers an Ancient race of cephalopod like aliens called Trilisk. Of all the aliens whose extinct civilizations are investigated, the Trilisks are the most advanced and the most mysterious.

Telisa refuses to join the government because of her opposition to its hard-handed policies restricting civilian investigation and trade of alien artifacts, despite the fact that her estranged father is a captain in the United Nations Space Force. However When a group of artifact smugglers recruits her, she can’t pass up the chance at getting her hands on objects that could advance her life’s work. But she soon learns her expectations of excitement and riches come with serious drawbacks as she ends up fighting for her life on a mysterious alien planet.

Valley of Embers (The Landkist Saga Book 1) by Steven Kelliher

Valley of Embers is book one of five in the epic fast-paced Landkist fantasy series by Steven Keliher. It is set in the mythical realm of Landkist where For hundreds of years, the flame-wielding Embers have been the last line of defense against the nightmare creatures from the World Apart, but the attacks are getting worse. Kole Reyna and his guards Protect Last Lake from the terrors of the night. They are the Last Line of defence, and he fears for his people’s future.

Then Kole is wounded by a demon unlike any they have seen before, and the Emberfolk believe it is a sign of an ancient enemy returned, a powerful Sage known as the Eastern Dark. Soon the besieged inhabitants of the Valley of Embers are one of only a handful of walled towns remaining as the last bastions against the night, and the dwindling population of Emberfolk struggle to defend their secluded homes from the Dark Kind. Kole has never trusted in prophecy, but with his people hanging on the precipice, he reluctantly agrees to lead the Valley’s greatest warriors in a last desperate bid for survival. They must risk everything in search of a former ally long-thought dead, to help them, and whether Kole trusts him or not, he may be the only one capable of saving them.