воскресенье, 21 апреля 2019 г.

Image of the Week — April 22, 2018CIL:39036 -…

Image of the Week — April 22, 2018

CIL:39036 http://cellimagelibrary.org/images/39036

Description: A photomicrograph of a stained semi-thin section of mouse ovary, showing a maturing Graafian follicle. The ovary contains many follicles that contain immature oocytes (egg cells). The follicle is important to support maturation and also develops through a number of stages as the ooctye matures. This process of folliculogenesis includes; the immature dormant primordial follicle, primary follicle, secondary follicle and tertiary stage follicle before ovulation occurs. The tertiary stage follicle is also called an antral or Graafian follicle characterised by a large fluid filled space (or antrum). The Graafian follicle also contains a fully mature oocyte at its full size complete with zona pellucida.

Author: Spike Walker

Licensing: Attribution-NonCommercial-NoDerivs 2.0 UK: England & Wales (CC BY-NC-ND 2.0 UK)

Archive link

Mobile Sim Today’s smartphones are as powerful as some…

Mobile Sim

Today’s smartphones are as powerful as some computers, and technology is constantly improving. Here their pocket-sized processors are being put to good use for doctors – never without their phones to access records and messages – doing something that requires a little more power. Mathematical models simulate beating hearts (grey) – highlighting waves of electrical activity in each ventricle chamber in rainbow colours. Each virtual ventricle compares with similar patterns seen in living hearts (to the right) from pigs (top row) and rabbits (middle). Tweaking the model’s settings produces simulations to match human patients (bottom), potentially giving doctors a portable visual tool for studying, discussing and treating irregular beats, or arrhythmias. Heart simulations have their origins in the 1960s, when a computer the size of a small car might have been required to run much simpler models, begging the question – given another 60 years, what will smartphones be able to do for us?

Written by John Ankers

You can also follow BPoD on Instagram, Twitter and Facebook

Archive link

2019 April 21 Spiral Aurora over Icelandic Divide Image Credit…

2019 April 21

Spiral Aurora over Icelandic Divide
Image Credit & Copyright: Juan Carlos Casado (TWAN, StarryEarth)

Explanation: Admire the beauty but fear the beast. The beauty is the aurora overhead, here taking the form of great green spiral, seen between picturesque clouds with the bright Moon to the side and stars in the background. The beast is the wave of charged particles that creates the aurora but might, one day, impair civilization. In 1859, following notable auroras seen all across the globe, a pulse of charged particles from a coronal mass ejection (CME) associated with a solar flare impacted Earth’s magnetosphere so forcefully that they created the Carrington Event. A relatively direct path between the Sun and the Earth might have been cleared by a preceding CME. What is sure is that the Carrington Event compressed the Earth’s magnetic field so violently that currents were created in telegraph wires so great that many wires sparked and gave telegraph operators shocks. Were a Carrington-class event to impact the Earth today, speculation holds that damage might occur to global power grids and electronics on a scale never yet experienced. The featured aurora was imaged in 2016 over Thingvallavatn Lake in Iceland, a lake that partly fills a fault that divides Earth’s large Eurasian and North American tectonic plates.

∞ Source: apod.nasa.gov/apod/ap190421.html

Stonehenge, 21.4.19.

Stonehenge, 21.4.19.

Source link

Original Prehistoric Capel Garmon Firedogs and Recreation, St Fagans National Museum,...

Original Prehistoric Capel Garmon Firedogs and Recreation, St Fagans National Museum, Cardiff, 14.4.19.

Source link

A closer look at Mercury’s spin and gravity reveals the planet’s inner solid...

How do you explore the interior of a planet without ever touching down on it? Start by watching the way the planet spins, then measure how your spacecraft orbits it — very, very carefully. This is exactly what NASA planetary scientists did, using data from the agency’s former mission to Mercury.

A closer look at Mercury's spin and gravity reveals the planet's inner solid core
This colourful view of Mercury was produced by using images from the color base map imaging campaign during
MESSENGER’s primary mission [Credit: NASA/Johns Hopkins University Applied Physics Laboratory/
Carnegie Institution of Washington]

It has long been known that Mercury and the Earth have metallic cores. Like Earth, Mercury’s outer core is composed of liquid metal, but there have only been hints that Mercury’s innermost core is solid. Now, in a new study, scientists from NASA’s Goddard Space Flight Center in Greenbelt, Maryland have found evidence that Mercury’s inner core is indeed solid and that it is very nearly the same size as Earth’s inner core.

Some scientists compare Mercury to a cannonball because its metal core fills nearly 85 percent of the volume of the planet. This large core — huge compared to the other rocky planets in our solar system — has long been one of the most intriguing mysteries about Mercury. Scientists had also wondered whether Mercury might have a solid inner core.

The findings of Mercury’s solid inner core, described in Geophysical Research Letters, certainly adds to a better understanding of Mercury, but there are larger ramifications. Just how similar, and how different, the cores of the planets are may give us clues about how the solar system formed and how rocky planets change over time.

«Mercury’s interior is still active, due to the molten core that powers the planet’s weak magnetic field, relative to Earth’s,» said Antonio Genova, an assistant professor at the Sapienza University of Rome who led the research while at NASA Goddard. «Mercury’s interior has cooled more rapidly than our planet’s. Mercury may help us predict how Earth’s magnetic field will change as the core cools.»

To figure out what the core of Mercury is made of, Genova and his colleagues had to get, figuratively, closer. The team used several observations from the MESSENGER (Mercury Surface, Space Environment, GEochemistry and Ranging) mission to probe the interior of Mercury. The researchers looked, most importantly, at the planet’s spin and gravity.

The MESSENGER spacecraft entered orbit around Mercury in March 2011, and spent four years observing this nearest planet to our Sun until it was deliberately brought down to the planet’s surface in April 2015.

Radio observations from MESSENGER were used to determine the gravitational anomalies (areas of local increases or decreases in mass) and the location of its rotational pole, which allowed scientists to understand the orientation of the planet.

A closer look at Mercury's spin and gravity reveals the planet's inner solid core
A graphical representation of Mercury’s internal structure
[Credit: Antonio Genova]

Each planet spins on an axis, also known as the pole. Mercury spins much more slowly than Earth, with its day lasting about 58 Earth days. Scientists often use tiny variations in the way an object spins to reveal clues about its internal structure. In 2007, radar observations made from Earth revealed small shifts in the spin of Mercury, called librations, that proved some of Mercury’s core must be liquid-molten metal. But observations of the spin rate alone were not sufficient to give a clear measurement of what the inner core was like. Could there be a solid core lurking underneath, scientists wondered?

Gravity can help answer that question. «Gravity is a powerful tool to look at the deep interior of a planet because it depends on the planet’s density structure,» said Sander Goossens, a Goddard researcher who worked with Genova on this study.

As MESSENGER orbited Mercury over the course of its mission, and got closer and closer to the surface, scientists recorded how the spacecraft accelerated under the influence of the planet’s gravity. The density structure of a planet can create subtle changes in a spacecraft’s orbit. In the later parts of the mission, MESSENGER flew about 120 miles above the surface, and less than 65 miles during its last year. The final low-altitude orbits provided the best data yet, and allowed for Genova and his team to make the most accurate measurements about the internal structure of Mercury yet taken.

Genova and his team put data from MESSENGER into a sophisticated computer program that allowed them to adjust parameters and figure out what the interior composition of Mercury must be like to match the way it spins and the way the spacecraft accelerated around it. The results showed that for the best match, Mercury must have a large, solid inner core. They estimated that the solid, iron core is about 1,260 miles (about 2,000 kilometers) wide and makes up about half of Mercury’s entire core (about 2,440 miles, or nearly 4,000 kilometers, wide). In contrast, Earth’s solid core is about 1,500 miles (2,400 kilometers) across, taking up a little more than a third of this planet’s entire core.

«We had to pull together information from many fields: geodesy, geochemistry, orbital mechanics and gravity to find out what Mercury’s internal structure must be,» said Goddard planetary scientist Erwan Mazarico, who also helped Genova reveal Mercury’s solid core.

The fact that scientists needed to get close to Mercury to find out more about its interior highlights the power of sending spacecraft to other worlds. Such accurate measurements of Mercury’s spin and gravity were simply not possible to make from Earth. Additionally, this result used data collected by MESSENGER over several years, information that’s available for all scientists to use. New discoveries about Mercury are practically guaranteed to be waiting in MESSENGER’s archives, with each discovery about our local planetary neighborhood giving us a better understanding of what lies beyond.

«Every new bit of information about our solar system helps us understand the larger universe,» said Genova.

Author: Michelle Thaller | Source: NASA’s Goddard Space Flight Center [April 17, 2019]



Iron Age Battersea and Witham Decorative Shields, The British Museum, London, 20.4.19.

Iron Age Battersea and Witham Decorative Shields, The British Museum, London, 20.4.19.

Source link

They dream to grow the vine on the Martian soil

Georgian Technical University (GTU) logo.

April 20, 2019

With their experience on Earth, Georgians want to be the first to produce wine on the red planet.

Red Planet Vine, vintage 2040

Image above: Crater «Spirit of St. Louis» scene from the panoramic camera (Pancam) on NASA’s Mars Exploration Rover Opportunity (MER-B). The bottle is a photo-montage (Illustration).

A glass of wine after a day of exploring Mars? If the idea seems to be science fiction, it aims to study the possibility of cultures on this planet where Americans have promised to send men in the decades to come. «Georgians were the first winemakers in history and now we hope to become pioneers in viticulture on another planet,» says Nikoloz Doborjguinidze, co-founder of this ambitious project.

The first traces of wine production date back to 8000 years ago in this country wedged between the Caucasus Mountains and the Black Sea. Building on this tradition, a group of researchers and entrepreneurs came together to respond to a call from NASA to imagine a «sustainable human presence» on Mars. Objective: greenhouse production of vine and grape varieties that can be grown on the Red Planet …

Biologist Marika Tarasashvili

One of the project’s scientists, biologist Marika Tarasashvili, is developing a bacterium that could turn the arid soil of Mars into fertile soil.

Regions with «extreme ecosystems»

The researchers collected bacteria from areas with «extreme ecosystems», including hot springs, and claim to have created strains of bacteria that can withstand harsh Martian conditions.

Greenhouse: could feed astronauts on Mars

They are also testing the skin of the 525 varieties of grapes found in Georgia to determine which will best withstand high levels of radiation.

Georgian Technical University (Tbilissi): http://gtu.ge/Eng/

Images, Text, Credits: AFP/Georgian Technical University/NASA/Orbiter.ch Aerospace/Roland Berga.

Cheers, Orbiter.chArchive link

Bronze Age 3500 year old Boiling Tank made from a single piece of Oak, St Fagans National...

Bronze Age 3500 year old Boiling Tank made from a single piece of Oak, St Fagans National Museum, Cardiff, 14.4.19.

This tank was used for boiling water or for textile production. The axe marks are visible and it is thought that the wood served a previous existence as a boat too.

Source link

Bronze Age Chariot Fittings, St Fagans National Museum, Cardiff, 14.4.19.

Bronze Age Chariot Fittings, St Fagans National Museum, Cardiff, 14.4.19.

Source link

Prehistoric Decorated Funerary Pottery, St Fagans National Museum, Cardiff, 14.4.19.

Prehistoric Decorated Funerary Pottery, St Fagans National Museum, Cardiff, 14.4.19.

Source link

Elusive molecule, first in Universe, detected in space

In the beginning, more than 13 billion years ago, the Universe was an undifferentiated soup of three simple, single-atom elements. Stars would not form for another 100 million years.

Elusive molecule, first in Universe, detected in space
Illustration of planetary nebula NGC 7027 and helium hydride molecules. In this planetary nebula, SOFIA detected
helium hydride, a combination of helium (red) and hydrogen (blue), which was the first type of molecule to ever
 form in the early universe. This is the first time helium hydride has been found in the modern universe
[Credit: NASA/SOFIA/L. Proudfit/D.Rutter]

But within 100,000 years of the Big Bang, the very first molecule emerged, an improbable marriage of helium and hydrogen known as a helium hydride ion, or HeH+.

«It was the beginning of chemistry,» said David Neufeld, a professor at John Hopkins University and co-author of a study published in Nature detailing how — after a multi-decade search — scientists finally detected the elusive molecule in space.

«The formation of HeH+ was the first step on a path of increasing complexity in the Universe,» as momentous a shift as the one from single-cell to multicellular life on Earth, he told AFP.

Theoretical models had long since convinced astrophysicists that HeH+ came first, followed — in a precise order — by a parade of other increasingly complex and heavy molecules.

HeH+ had also been studied in the laboratory, as early as 1925. But detected HeH+ in its natural habitat had remained beyond their grasp.

«The lack of definitive evidence of its very existence in interstellar space has been a dilemma for astronomy for a long time,» said lead author Rolf Gusten, a scientist at the Max Planck Institute for Radioastronomy in Bonn.

Elusive molecule, first in Universe, detected in space
Spectrum of HeH+ as observed with GREAT on board of SOFIA towards the planetary nebula NGC 7027. In the underlying
 image from the Hubble/NICMOS camera, the sharp transition zone between the ionized HII region (white-yellow) and the
cool envelope (red colour) is nicely visible. It is in this ionization front where HeH+ is formed (marked by an artist’s
concept of the molecular structure). The sky area covered by the GREAT instrument with a size of 14.3 arcsec includes
 most of the nebula’s emission. The spectral line width of the HeH+ profile is determined by the motion of the
expanding envelope [Credit: Composition: NIESYTO design; Image NGC 7027: William B. Latter
(SIRTF Science Center/Caltech) and NASA/ESA; Spectrum: Rolf Güsten/MPIfR, Nature 2019]

Researchers knew where to look. Already in the 1970s, models suggested that HeH+ should exist in significant quantities in the glowing gases ejected by dying Sun-like stars, which created conditions similar to those found in the early Universe.

The problem was that the electromagnetic waves given off by the molecule were in a range — far-infrared — cancelled out by Earth’s atmosphere, and thus undetectable from the ground.

So NASA and the German Aerospace Center joined forces to create an airborne observatory with three main components: a massive 2.7-metre telescope, an infrared spectrometer, and a Boeing 747 — with a window-like square cut away from it fuselage — big enough to carry them.

From a cruising altitude of nearly 14,000 metres (45,000 feet), the Stratospheric Observatory for Infrared Astronomy, or SOFIA, avoided 85 percent of the atmospheric «noise» of ground-based telescopes.

Data from a series of three flights in May 2016 contained the molecular evidence scientists had long sought, interlaced in the planetary nebula NGC 7027 some 3,000 light years away.»

The discovery of HeH+ is a dramatic and beautiful demonstration of Nature’s tendency to form molecules,» said Neufeld.

In this case, it did so despite inauspicious circumstances. Even though temperatures in the young Universe fell rapidly after the Big Bang, they were still in the neighbourhood of 4,000 degrees Celsius, a hostile environment for molecular bonding.

Moreover, helium — a «noble» gas — «has a very low proclivity for form molecules,» Neufeld explained.

It’s union with ionised hydrogen was fragile, and did not persist for very long, replaced by progressively more robust and complex molecular bonds.

Heavier elements such as carbon, oxygen and nitrogen — and the many molecules they gave rise to — were formed later still by the nuclear reactions that power stars.

Author: Marlowe Hood | Source: AFP [April 17, 2019]



Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare ten times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter. The star is the coolest and smallest to give off a rare white-light superflare, and by some definitions could be too small be considered a star.

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun
A superflare on an L-dwarf [Credit: University of Warwick/Mark Garlick]

The discovery, funded by the Science and Technology Facilities Council, is published in the Monthly Notices of the Royal Astronomical Society: Letters sheds light on the question of how small a star can be and still display flaring activity in its atmosphere. Flares are thought to be driven by a sudden release of magnetic energy generated in the star’s interior. This causes charged particles to heat plasma on the stellar surface, releasing vast amounts of optical, UV and X-ray radiation.

Lead author James Jackman, a PhD student in the University of Warwick’s Department of Physics, said: «The activity of low mass stars decreases as you go to lower and lower masses and we expect the chromosphere (a region of the star which support flares) to get cooler or weaker. The fact that we’ve observed this incredibly low mass star, where the chromosphere should be almost at its weakest, but we have a white-light flare occurring shows that strong magnetic activity can still persist down to this level.

«It’s right on the boundary between being a star and a brown dwarf, a very low mass, substellar object. Any lower in mass and it would definitely be a brown dwarf. By pushing this boundary we can see whether these type of flares are limited to stars and if so, when does this activity stop? This result takes us a long way to answering these questions.»

The L dwarf star located 250 light years away, named ULAS J224940.13-011236.9, is only a tenth of the radius of our own sun, almost the same size as Jupiter in our solar system. It was too faint for most telescopes to observe until the researchers, led by the University of Warwick, spotted the massive stellar explosion in its chromosphere in an optical survey of the surrounding stars.

Using the Next Generation Transit Survey (NGTS) facility at the European Southern Observatory’s Paranal Observatory, with additional data from the Two Micron All Sky Survey (2MASS) and Wide-field Infrared Survey Explorer (WISE), they observed the brightness of the star over 146 nights.

The flare occurred on the night of 13 August 2017 and gave off energy equivalent to 80 billion megatonnes of TNT, ten times as much energy as the Carrington event in 1859, the highest energy event observed on our sun. Solar flares occur on our Sun on a regular basis, but if the Sun were to superflare like this star the Earth’s communications and energy systems could be at serious risk of failing.

It is one of the largest flares ever seen on an L dwarf star, making the star appear 10,000 times brighter than normal.

James adds: «We knew from other surveys that this kind of star was there and we knew from previous work that these kinds of stars can show incredible flares. However, the quiescent star was too faint for our telescopes to see normally — we wouldn’t receive enough light for the star to appear above the background from the sky. Only when it flared did it become bright enough for us to detect it with our telescopes.»

James’s PhD supervisor Professor Peter Wheatley said: «Our twelve NGTS telescopes are normally used to search for planets around bright stars, so it is exciting to find that we can also use them to find giant explosions on tiny, faint stars. It is particularly pleasing that detecting these flares may help us to understand the origin of life on planets.»

L dwarfs are among the lowest mass objects that could still be considered to be a star, lying in the transition region between stars and brown dwarfs. Brown dwarfs are not massive enough to fuse hydrogen into helium as stars do. L dwarfs are also very cool compared to the more common main sequence stars, such as red dwarfs, and emit radiation mostly in the infra-red, which may affect their ability to support the creation of life.

James adds: «Hotter stars will emit more in the optical spectrum, especially towards the UV. Because this star is cooler, around 2000 kelvin, and most of its light is towards the infra-red, when it flares you get a burst of UV radiation that you wouldn’t normally see.

«To get chemical reactions going on any orbiting planets and to form amino acids that form the basis of life, you would need a certain level of UV radiation. These stars don’t normally have that because they emit mostly in the infra-red. But if they produced a large flare such as this one that might kickstart some reactions.»

Professor Wheatley adds: «It is amazing that such a puny star can produce such a powerful explosion. This discovery is going to force us to think again about how small stars can store energy in magnetic fields. We are now searching giant flares from other tiny stars and push the limits on our understanding of stellar activity.»

Source: University of Warwick [April 17, 2019]



Neotropical cloud forests to lose what most defines them: Clouds

In as few as 25 years, climate change could shrink and dry 60-80% of Western Hemisphere cloud forests, finds a study published today. If greenhouse gas emissions continue increasing as they have been, 90% of Western Hemisphere cloud forests would be affected as early as 2060. The current cloud and frost environment of the highly diverse alpine ecosystems above these equatorial cloud forests, known as páramo, will nearly disappear.

Neotropical cloud forests to lose what most defines them: Clouds
Elfin cloud forest in the El Yunque National Forest of Puerto Rico
[Credit: María Rivera]

Cloud forests are the misty forests found high on tropical mountains. Frequently cloud-enshrouded, many are reminiscent of fairy-tale forests, having twisted, stunted old trees covered in moss and ferns. But their importance is real.

Their trees, and the plants and lichens living on them, intercept water vapor that can supply 75% of the stream water in drier places. And they are among the most biodiverse ecosystems on Earth. Thousands of unique species evolved where fog and mist have created strikingly wetter habitat isolated on mountains.

The effects are near. In Mexico, Central America and the Caribbean, warming would reduce cloud immersion in 100% of cloud forests. Monarch butterflies spend their winters, by the millions, in cloud forests of Central Mexico and in the forests just below them, where they depend on clouds to stabilize temperatures.

In the Caribbean, the U.S. National Forest El Yunque harbors the threatened Elfin Woods Warbler, found only in Puerto Rico’s mountains. It is named after the mossy, mysterious «elfin» cloud forests on mountaintops. In Central America, tourists from around the world visit the Monteverde Cloud Forest Reserve in Costa Rica.

While traversing treetop walkways there, they can feel the strength of trade winds forcing humid air up mountains and hear the ethereal songs of Nightingale Thrushes. All of these cloud forests will be affected from fewer or thinner clouds that form at higher elevations, and from drier conditions.

Neotropical cloud forests to lose what most defines them: Clouds
The Federally Threatened Elfin Woods Warbler occurs only in Puerto Rico’s mountains.
Cloud forests dominate its range [Credit: Gloria Archilla]

This study is the first to quantify these potential changes across continents. To do so, scientists from U.S. Forest Service labs in Puerto Rico and Fort Collins, Colorado, and from Colorado State University developed a new approach.

They mapped and projected how climate change would affect the feature that cloud forest species are uniquely adapted to: cloud immersion. The team mapped current cloud forest areas across the Western Hemisphere with data on climate and mountain size and observations from dozens of ecological studies, including historical ones dating back 50 to 60 years. They then projected cloud forest extent and relative humidity, a proxy for cloud frequency and density, with scenarios for future greenhouse gas emissions and associated climate conditions.

Before this research, studies from a handful of sites suggested that cloud immersion would increase in some cloud forests but decline in others. Cloud immersion might increase because air humidity will increase over warming oceans, implying thicker clouds forming at lower elevations and cloudier forests.

Cloud immersion might decrease because increased temperatures over land could force air to travel further up mountains before it cools enough to form clouds, reducing cloud forest area and cloudiness. The fates of the rest of cloud forests were unknown. Global climate modeling is too coarse to target effects on cloud forests.

This new study found that cloud immersion would increase for only about 1% of all Western Hemisphere cloud forests, in only a few regions of South America. Declines in cloud immersion would dominate.

The study appeared in the journal PLOS ONE.

Source: USDA Forest Service [April 17, 2019]



NASA study verifies global warming trends

A new study by researchers from NASA has verified the accuracy of recent global warming figures. The team used measurements of the ‘skin’ temperature of the Earth taken by a satellite-based infrared measurement system called AIRS (Atmospheric Infra-Red Sounder) from 2003 to 2017.

NASA study verifies global warming trends
Credit: iStock/oonal

They compared these with station-based analyses of surface air temperature anomalies — principally the Goddard Institute for Space Studies Surface Temperature Analysis (GISTEMP).

They found a high level of consistency between the two datasets over the past 15 years. Their results are published in Environmental Research Letters.

Commenting on the study, lead author Dr Joel Susskind, from NASA’s Goddard Space Flight Center, said: «AIRS data complement GISTEMP because they are at a higher spatial resolution than GISTEMP, and have more complete global coverage.

«Both data sets demonstrate the earth’s surface has been warming globally over this period, and that 2016, 2017, and 2015 have been the warmest years in the instrumental record, in that order.

«This is important because of the intense interest in the detail of how estimates of global and regional temperature change are constructed from surface temperature data, and how known imperfections in the raw data (due to station moves, gaps, instrument and practice changes, urban heat island effects) are handled.»

AIRS data reflects skin temperature at the surface of the ocean, land, and snow/ice covered regions. Surface-based data are a blend of two metre surface air data anomalies over land, and bulk sea surface temperature anomalies in the ocean.

To compare the two, the researchers constructed monthly grid point climatologies for each calendar month and for each set of data, by averaging the monthly values over 2003 to 2017, with anomalies for a given month, in a given year, defined as the difference of the grid point value for that month from its monthly climatology.

Co-author Dr Gavin Schmidt, from NASA’s Goddard Institute for Space Studies, said: «Interestingly, our findings revealed that the surface-based data sets may be underestimating the temperature changes in the Arctic. This means the warming taking place at the poles may be happening more quickly than previously thought.

«Our work also shows that complementary satellite-based surface temperature analyses serve as an important validation of surface-based estimates. They may point the way to make improvements in surface-based products that can perhaps be extended back many decades.»

Source: Institute of Physics [April 17, 2019]



The Cerrado once connected the Andes with the Atlantic Rainforest

The tropical forests of the Andes and Brazil’s Atlantic Rainforest biome are separated by almost 1,000 km of drier areas with open vegetation in the Chaco, Cerrado (Brazilian savanna), and Caatinga (Brazilian semiarid) biomes. Today, these tropical forests are not connected, but the fact that they share closely related species and lineages suggests that these biomes were connected in the past. For example, 23 rainforest bird species have been found in both the Andean and Atlantic tropical forests.

The Cerrado once connected the Andes with the Atlantic Rainforest
A genetic and computational analysis of birds suggests that the Andean and Atlantic tropical forests, which are now
 almost a thousand kilometers apart, were connected via the Cerrado in the distant past (bird species
Syndactyla rufosuperciliata) [Credit: : Gustavo Cabanne]

Several published studies reinforce such hypothesis. What scientists do not know for sure is whether this connection consisted of past gallery forests along rivers in what is now the Chaco (which spans across southern Bolivia, northern Argentina and Paraguay) or the Cerrado (in part of Bolivia, central-west Brazil and northern Paraguay).

According to a new study based on genomic and biogeographical data for two bird species (Syndactyla rufosupercilita and S. dimidiata), the past connection between Andean and Atlantic tropical forests ran through the Cerrado. Such connection may have emerged several times during the Pleistocene, the geological epoch that lasted from approximately 2.5 million years ago to 11,700 years ago.

The study was part of a research project conducted by Gustavo Cabanne, an ornithologist at Argentina’s Museum of Natural Sciences (MACN), in collaboration with Cristina Yumi Miyaki, a professor at the University of São Paulo’s Bioscience Institute (IB-USP) in Brazil. Results of the study were published in the journal Molecular Phylogenetics and Evolution.

Biogeography studies the relationships among living beings, latitude, elevation and climate over time.

Paleobiogeography focuses on species distribution and relationships in remote epochs. An understanding of the paleobiogeography of the species that inhabit certain biomes in the present can help scientists infer the distribution of these same biomes in the past.

«The main challenge in biogeographical research is integrating and interpreting the information obtained from several sources, such as data on biological components and genomes for the species analyzed, geology and paleoclimate, palynology [pollen and spores], and even remote sensing data from satellite imagery,» Miyaki said.

«We needed to collect and analyze all these kinds of data in order to investigate the hypothesis that there was an ancient connection between the Andean and Atlantic tropical forests and to test whether this connection ran through the Cerrado or the Chaco. The connection may have consisted of gallery forests that, during the Pleistocene, would have been remnants of wetland vegetation crossing more arid biomes.»

According to Cabanne, the existence of a connection between the Andean and Atlantic tropical forests is supported by palynological studies, among others, according to which both forests expanded transitorily in some regions (such as the Cerrado) toward the Andes during the most recent glacial cycle and last glacial maximum, i.e., the coldest period among the various ice ages that occurred in the past 2.5 million years (at least 11 have been identified).

«In this past biogeographical context, the Andean and Atlantic tropical forests may have served as refugia. Their dynamic history [connection and isolation cycles] may have been an important driver of speciation in the Neotropics [a region comprising Central and South America, the Caribbean and parts of Mexico and the United States],» Cabanne said.

In the present interglacial period, Cabanne explained that these biomes represent forest refugia, where isolated organisms in either biome are expected to differentiate. During the Pleistocene ice ages, both forests were connected, allowing for gene flow between forest domains.

In the study published in Molecular Phylogenetic & Evolution, researchers chose to study the Buff-browed Foliage-gleaner, a New World ovenbird whose scientific name is Syndactyla rufosuperciliata, a passerine belonging to the order Passeriformes and family Furnariidae, as do other ovenbirds, such as the Rufous hornero (Furnarius rufus) and 230 other species found in Argentina, Bolivia, Brazil, Ecuador, Paraguay, Peru and Uruguay. There are five recognized subspecies in this taxon.

«S. rufosuperciliata is an appropriate model with which to explore the Andean-Atlantic forest connection because it inhabits both the main forest domains and the areas that could have been directly involved in bridging them: the gallery forests of the eastern Chaco and some parts of the southern Cerrado,» Cabanne said.

Researchers used niche modeling to investigate the historical connectivity between the two regions. They then used DNA sequences from 71 birds and the genomic analysis of samples from other 33 specimens to evaluate the genetic structure of the population and the gene flow within the species. Lastly, they performed population model selection with the aid of approximate Bayesian computation (ABC), a method of inference based on summary statistics.

According to the researchers, their genomic analysis showed that the populations of S. rufosuperciliata now found in the Andean and Atlantic tropical forests belong to different lineages, but hundreds of thousands of years ago, the species was far more widely distributed, and its lineages were less differentiated from a genomic standpoint.

As the ice age continued and the vegetation in the Cerrado advanced and retreated, Andean and Atlantic birds became isolated from each other for tens of thousands of years, leading to diversification into two lineages.

The data also suggested new contacts between the eastern and western populations of the species during the interglacial periods of the Pleistocene, when temperatures rose and rainforests advanced, permitting cross-breeding between the two lineages and new gene exchanges.

The analysis of genomic diversity between Andean and Atlantic birds combined with paleoclimate data suggested that these gene exchanges occurred via the Cerrado to the north rather than via the Chaco further to the south.

«Our results showed that the Andean and Atlantic tropical forests were refugia and that populations of the species from both regions made contact via the Cerrado,» Cabanne said. «This suggests that the historical dynamics of the Andean and Atlantic forests played an important role in the evolution of forest birds in the region.»

«Our findings are consistent with studies of other organisms and may indicate a more general pattern of connectivity among biomes in the Neotropics,» Miyaki added.

In addition, this new study and previous research by the same group «point to high levels of cryptic diversity [meaning morphologically similar but genetically diverse species] between the Andes and Atlantic Rainforest biomes and suggest that the Andean population of S. rufosuperciliata should be recognized as an independent species», Cabanne added.

Source: Fundação de Amparo à Pesquisa do Estado de São Paulo [April 17, 2019]



Mesopotamian King Sargon II envisioned ancient city Karkemish as western Assyrian capital

In a new study published in the Journal of Near Eastern Studies, Gianni Marchesi translates a recently discovered inscription of the Assyrian King Sargon II found at the ruins of the ancient city of Karkemish. The inscription, which dates to around 713 B.C., details Sargon’s conquest, occupation, and reorganization of Karkemish, including his rebuilding the city with ritual ceremonies usually reserved for royal palaces in capital cities. The text implies that Sargon may have been planning to make Karkemish a western capital of Assyria, from which he could administer and control his empire’s western territories.

Mesopotamian King Sargon II envisioned ancient city Karkemish as western Assyrian capital
Sargon II, founder of the Sargonid dynasty, the final and greatest ruling house of Assyria
[Credit: WikiCommons]

The cuneiform inscription was found on fragments from three different clay cylinders in 2015 as part of the Nicolò Marchetti-led Turco-Italian Archaeological Expedition at Karkemish. Now in ruins, the site is located on the Euphrates river on the border between present day Syria and Turkey.

Marchesi analyzed and translated the total of thirty-eight lines of partially broken Akkadian text, using reference material, academic literature and other inscribed Assyrian artifacts as reference points for filling in the gaps. The lines of text ranged from two-thirds complete to much less, and no line of text was completely intact.

«Even so, we can grasp much of the original text, which turns out to be very informative,» Marchesi writes. «In fact, unlike other Sargon cylinders, which contain relatively standard ‘summary’ inscriptions or annalistic accounts of the events of Sargon’s reign, the Karkemish Cylinder provides us with a completely new inscription, dealing almost exclusively with the newly conquered city on the Euphrates in a highly-elaborated, literary style.»

In the inscription, Sargon tells of the «betrayal» of Pirisi, the Hittite King of Karkemish who exchanged hostile words about Assyria with its enemy, King Midas of Phrygia. Sargon invades Karkemish, deports Pisiri and his supporters, destroys his palace, seizes his riches as booty and incorporates Pisiri’s army into his own. He resettles the city with Assyrians. Having previously blocked the water supply to Karkemish, the meadows «let go fallow, like a wasteland,» Marchesi translates, he now reactivates the irrigation system, planting orchards and botanical gardens. «I made the scent of the city sweeter than the scent of a cedar forest.»

He also details an inauguration ceremony where he received gifts from Assyrian provinces and sacrifices them to deities. «My lords the gods Karhuha and Kubaba, who dwell in Karkemish, I invited them into my palace,» Marchesi translates. «Strong rams of the stable, geese, ducks and flying birds of the sky I offered before them.»

Marchesi was struck by the attention that Sargon paid to Karkemish, in particular the elaborate inauguration ceremony and construction of botanical gardens, both indicative not of a typical provincial capital but of a royal palace.

«Because of its glorious past and strategic position, Karkemish was fully entitled to become a sort of western capital of the Assyrian Empire: a perfect place in which to display the grandeur of Assyria, and from which to control the western and north-western territories of the empire,» Marchesi writes.

This vision of Karkemish was short-lived, however. Though much care was taken to detail the city’s rise in these texts, the city is not mentioned in any known inscriptions of Sargon’s successors.

«The unthinkable, ominous death of Sargon on the battlefield in Tabal probably prevented this project from being accomplished, and negatively marked the destiny of Karkemish itself, which no longer attracted the interest of Assyrian kings who followed after him,» Marchesi writes.

Source: University of Chicago Press Journals [April 19, 2019]




    Солнечное затмение 14 декабря 2020 года  — полное  солнечное затмение  142  сароса , которое лучше всего будет видно в юго-восточной час...