Ο Nichοlas Bakalar έψαξε (και βρήκε) στα παλιά φύλλα της εφημερίδας "The New York Times" τις πρώτες αναφορές σχετικά με την θεωρία της Μεγάλης Έκρηξης. To 1927, o Georges Lemaître, ένας ρωμαιοκαθολικός ιερέας και αστρονόμος από το Βέλγιο, πρότεινε μια νέα θεωρία για τη γέννηση του Σύμπαντος, την «υπόθεση του πρωταρχικού ατόμου» . Η θεωρία αυτή βελτιώθηκε…
Berlin-based scientists have sequenced the complete genome of all five identified strains of the gibbon ape leukemia virus (GALV). The scientists were able to prove that selection has shaped parts of the genome of this group ...
Each year, billions of people get infected with viruses–with common ones like influenza and cold viruses, and rarer ones like polio and Ebola. The viruses don’t stay all that long inside of us. In most cases, our immune systems wipe them out, except for a few refugees that manage to escape to a new host and keep their species alive. In some cases, the viruses kill their unfortunate hosts, and end their own existence as well. But in some exquisitely rare cases, viruses meld with the genome of their hosts and become part of the genetic legacy their hosts pass down to future generations.
Scientists know this melding has happened because viruses have distinctive genes. When scientists scan the human genome, they sometimes come across a stretch of DNA that bears the hallmarks of viruses. The easiest type of virus to recognize are retroviruses, a group that includes HIV. Retroviruses make copies of themselves by infecting cells and then using an enzyme to insert their genes into their host cell’s DNA. The cell then reads the inserted DNA and makes new molecules that assemble into new viruses.
Humans carry about 100,000 pieces of DNA that came from retroviruses–known as endogenous retroviruses. All told, they come to an estimated 5 to 8 percent of the entire human genome. That’s several times more DNA that makes up all 20,000 of our protein-coding genes.
Gkikas Magiorkinis, a University of Oxford virologist, and his colleagues have now carried out large-scale survey of endogenous retroviruses in humans, apes, and Old World monkeys–a group of species that all descend from a common primate ancestor that lived some 40 million years ago. They catalogued the viruses in each species and compared them to the versions in the other primates. They were able to reconstruct the history of our viral DNA in unprecedented detail, even coming up with estimates for the rate at which the viruses inserted new copies into our genome.
The scientists can trace our viral DNA to 30 to 35 separate invasions. Once each virus established itself in our ancestors’ DNA, it produced copies of itself scattered through the genome. The rate at which new copies were inserted rose and fell over time, and at different rates in different branches of the primate tree. Here’s an overall look at the history of the viruses.
Our monkey-like ancestors 40 million years ago acquired new virus copies at a fast clip–much faster than in our own lineage in the past couple million years. One virus in particular, known as HERV-H, was responsible for most of the new copies. It may have evolved adaptations that made it into a superspreader inside the genome.
In the past million years, only a single virus has continued to multiply–known as HERV-K. Today, you can find some HERV-K copies in some people and not in others. The pattern of these copies suggests that as recently as 250,000 years ago, HERV-K was still making new copies.
It’s possible that HERV-K is completely dead now. There’s no evidence that HERV-K or any other endogenous retrovirus is actively spreading or causing cancer. It’s hard to say at this point why humans have put the brakes on endogenous retroviruses. But Magiorkinis has one suggestion: our ancestors may have reduced their odds of picking up new viruses.
Το ερώτημα στον τίτλο είναι ένα από τα τρία πιο σημαντικά ερωτήματα προκειμένου να μπορέσουμε να εκτιμήσουμε επιστημονικά την πιθανότητα να υπάρχει ζωή κάπου στο σύμπαν. Αυτό γράφει ο Χάρης Βάρβογλης, ομότιμος καθηγητής Τμήματος Φυσικής ΑΠΘ (Τομέας Αστρονομίας και Αστροφυσικής) στο εξαιρετικά κατατοπιστικό και ενδιαφέρον προλογικό σημείωμά του στον τόμο «Πέντε δισεκατομμύρια χρόνια μοναξιά» του…
... από τον επικεφαλής του Τμήματος Εκπαίδευσης και Διάχυσης των Επιστημών του Ευρωπαϊκού Νότιου Αστεροσκοπείου (ΕSO) Lars Lindberg Christensen Εκδήλωση στο Νέο Ψηφιακό Πλανητάριο, την Δευτέρα 19 Σεπτεμβρίου 2016 Με αφορμή την φθινοπωρινή ισημερία το Νέο Ψηφιακό Πλανητάριο έχει προσκαλέσει τον επικεφαλής του Τμήματος Εκπαίδευσης και Διάχυσης των Επιστημών του Ευρωπαϊκού Νότιου Αστεροσκοπείου (European Southern…
Πριν από λίγες ημέρες τέθηκε ξανά σε λειτουργία ο LHC, ο μεγαλύτερος σωματιδιακός επιταχυντής που υπάρχει πάνω στη Γη. Οι ένα δισεκατομμύριο συγκρούσεις πρωτονίων το δευτερόλεπτο -6 φορές μεγαλύτερος αριθμός δεδομένων απ’ ό,τι το 2015!- ίσως να επιτρέψουν στους φυσικούς να λύσουν το αίνιγμα της σύστασης της σκοτεινής ύλης.
Συνέντευξη στον Μάκη Προβατά (ΒΗΜΑ FM) (από το 2:90 έως 18:05) Με την ευκαιρία να αναφέρουμε ότι η ανακοίνωση της ανίχνευσης των βαρυτικών κυμάτων από το LIGO συνοδεύθηκε από μια δεύτερη ανακοίνωση από το διαστημικό τηλεσκόπιο ακτινοβολίας γ Fermi. Σύμφωνα με αυτή 0,4 δευτερόλεπτα μετά την παρατήρηση των βαρυτικών κυμάτων που προκλήθηκαν από την συγχώνευση των μαύρων…
Dr. Melanie Mormile, professor of biological sciences at Missouri S&T, and her team discovered the bacterium "Halanaerobium hydrogeninformans" in Soap Lake, Washington. It can "produce hydrogen under saline and alkaline conditions in amounts that rival genetically modified organisms," Mormile says.
"Usually, I tend to study the overall microbial ecology of extreme environments, but this particular bacterium has caught my attention," Mormile says. "I intend to study this isolate in greater detail."
Mormile, an expert in the microbial ecology of extreme environments, wasn't searching for a bacterium that could produce hydrogen. Instead, she first became interested in bacteria that could help clean up the environment, especially looking at the extremophiles found in Soap Lake.
An extremophile is a microorganism that lives in conditions of extreme temperature, acidity, alkalinity or chemical concentration. Living in such a hostile environment, "Halanaerobium hydrogeninformans" has metabolic capabilities under conditions that occur at some contaminated waste sites.
With "Halanaerobium hydrogeninformans," she expected to find an iron-reducing bacterium and describe a new species. What she found was a new species of bacterium that can produce hydrogen and 1, 3-propanediol under high pH and salinity conditions that might turn out to be valuable industrially. An organic compound, 1, 3-propenediol can be formulated into industrial products including composites, adhesives, laminates and coatings. It's also a solvent and can be used as antifreeze.
The infrastructure isn't in place now for hydrogen to replace gasoline as a fuel for planes, trains and automobiles. But if hydrogen becomes an alternative to gasoline, "Halanaerobium hydrogeniformans," mass-produced on an industrial scale, might be one solution – although it won't be a solution anytime soon.
To avoid the spread of Ebola and far worse scenarios, quick and forceful implementation of control interventions are necessary, according to new research published today in the scientific journal Eurosurveillance.
Analyzing Ebola cases in Nigera, a country that has had success in containing the disease, researchers estimated the rate of fatality, transmission progression, proportion of health care workers infected and the impact of control interventions on the size of the epidemic.
The study's findings show that Ebola transmission is dramatically influenced by how rapidly control measures are put in place.
"Rapid and forceful control measures are necessary, as is demonstrated by the Nigerian success story," said Arizona State University's Gerardo Chowell, senior author of the paper. "This is critically important for countries in the West African region that are not yet affected by the Ebola epidemic, as well as for countries in other regions of the world that risk importation of the disease."
The largest Ebola outbreak to date is ongoing in West Africa, with approximately 8,011 reported cases that include more than 3,857 deaths as of Oct. 5. However, just 20 Ebola cases have been reported in Nigeria, with no new cases reported since Sept.5.
Ebola transmission is dramatically influenced by how rapidly control measures are put in place, as researchers found that the projected effect of control interventions in Nigeria ranged from 15-106 cases when interventions are put in place on day 3; 20-178 cases when implemented on day 10; 23-282 cases on day 20; 60-666 cases on day 30; 39-1599 cases on day 40; and 93-2771 on day 50.
"There is brief window of time when a rapid and forceful intervention in terms of relentless contact tracing and isolation pays off handsomely and the transmission is effectively halted and the outbreak dies out," said co-author professor Lone Simonsen, of the Milken Institute School of Public Health at the George Washington University in Washington D.C.
The person who was initially infected generated 12 secondary cases, in the first generation of the disease; five secondary cases were generated from those 12 in the second generation; and two secondary cases in the third generation, leading to a rough empirical estimate of the reproduction number according to disease generation declining from 12 during the first generation, to approximately 0.4 during the second and third disease generations. Recent estimates of the reproduction number for the ongoing Ebola epidemic in Sierra Leone and Liberia range between 1.5 and 2 (two new cases for each single case), indicating that the outbreak is yet to be brought under control.
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