Fresh Water Muscles Just as tissues develop from a blend of…

Fresh Water Muscles

Just as tissues develop from a blend of different cells, our cells each have sets of proteins that must work together. Looking for clues to these delicate early relationships in human life, researchers turn to simpler, but genetically similar, organisms. In this four-day-old zebrafish larva, a high-powered microscope captures fin muscles forming. Ribbon-like muscle cells (with their nuclei stained blue) contain two different types of myosins (artificially coloured red and green): elastic proteins that will help the fin to pull and flip in the water. Researchers can compare changes in such vivid pictures to measure the effects of genetic mutations – examining how different genes balance the pattern of different myosins, or form the muscle as it develops. The shaping, or morphogenesis, of early zebrafish tissues may hint at how similar genes contribute to human skeletal muscle development.

Written by John Ankers

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The ancient people in the high-latitude Arctic had well-developed trade

Russian scientists studied the Zhokhov site of ancient people, which is located in the high-latitude Arctic, and described in detail the way of life of the ancient people had lived there. It turned out that, despite the sparsely populated area, the ancient people had communicated with representatives of other territories and had even exchanged various objects with them through some kind of the fairs.

The ancient people in the high-latitude Arctic had well-developed trade
Products from obsidian found on Zhokhov site [Credit: Vladimir V. Pitulko et al. 2019]

The Arctic is the coldest part of our planet, where there are no favorable conditions for life. The Arctic regions of the Earth are hardly populated by humans, although in some countries, including Russia, the United States and Norway, there are industrial zones. These zones increase the average population density to 0.35 people / km2 but basically it does not exceed 0.03-0.04 people / km2.

Zhokhov Island, located at 76º N in the New Siberian Islands, 440 kilometers north of the modern coast of the East Siberian Sea, belongs to the High Arctic?. It was discovered here the settlement of the ancient man, Zhokhov site, considered the earliest evidence for human habitation in the High Arctic. In the settlement that existed 9300-8600 years ago, 25-50 people lived permanently.

In the remote past, Zhokhov island was a part of the vast plain formed due to drastic sea level drop during the Last Glacial maximum. Because of the post-glacial sea-level rise, this plain was flooded and eroded. At present, Zhokhov site is located in the south-western part of the modern Zhokhov island, near the foot of a low — about 120 m — hill covering it from the severe north-west wind. This place was very convenient for the ancient people. The hill served as an observation point, and because of the proximity to the coast, they always had a supply of wood, which was brought by sea.

The scientists conducted excavations in permafrost and have already investigated a significant part of the monument — 571 square meters. In the course of work, many tools were found made of stone, bones, horns, tusks and wood. These are different tools, items of hunting weapons, details of sleds and diverse home utensils.

Among the lithic artifacts there are a lot of microprismatic blades, which served as side-blades for composite tools that served as spear/dart/arrow points and knives. Most of them had been produced of various silicious rocks of local origin, while some of them were made of exotic raw materials unusual for this part of the world such as obsidian, or volcanic glass. The researchers found 79 such items.

The ancient people appreciated this material for the best splitting ability among other rocks and valued its extremely thin and sharp cutting edge. This material is also highly appreciated by the researchers because each deposit of obsidian has its own unique geochemical signature, which helps finding the source of the material. Then it is possible to see how it moves through the space and thus we can learn more about the life of ancient people.

The ancient people in the high-latitude Arctic had well-developed trade
Skull of a dog found on Zhokhov site [Credit: Vladimir V. Pitulko et al. 2019]

However, there is no obsidian source nearby Zhokhov Island. The closest area with such source locates near Krasnoye lake in the lower reaches of the Anadyr River in Chukotka, which is some 1,500 km in a straight line, and the actual travel easily could be more than 2,000 km. It would seem that the ancient people could not travel such a distance physically.

The authors studied the unearthed obsidian objects by the X-ray Fluorescence method. This is non-destructive examination method that allows to determine the geochemical properties of the samples and thus find the gives the way to locate the source of the material using the unique signatures.

«We found that particular obsidian type was coming to Zhokhov Island from the area of the Krasnoye Lake. This is a super long-distance travel, and it is hard to imagine that the ancient people could possibly make such trips some 9000 years ago. Most likely, they met other people at the intermediate points and exchanged products made of obsidian, or enjoyed primitive trade,» said one of the authors of the article, Vladimir Pitulko, RSF project’s principal investigator, Ph.D. in history, senior researcher at the Paleolithic Department of the Institute for the History of Material Culture, Russian Science Foundation.

The researchers also analyzed more than 54 000 faunal remains of hunting and reconstructed the yearly economic cycle of the inhabitants of the Zhokhov site. The occupants of the site were classic terrastrial hunters who practiced reindeer hunting. However, in the winter time they hunted polar bears sleeping in bear lairs. For them, that was reliable and stable way of getting food supply, because there were quite a lot of the bear dens in this area.

Previously, scientists investigated the bones of medium-sized canids; they indicate the presence of a well-formed dog that lived together with the people of Zhokhov site. In addition, these animals are similar in size and body weight to the modern breed of sled dogs. Findings of parts of sleds in the form of runners prove that the inhabitants of these territories had a well developed transport system. Thanks to that system, the inhabitants of Zhokhov site travelled to the nearby territories, which were still part of the mainland at that time, and maintained relations with their inhabitants.

Vladimir Pitulko also noted that sites in the mouths of Kolyma and Indigirka rivers could serve as the intermediate points in that trade. In this case, the distance between the exchange points was about 700 km, which is quite possible to travel in early spring by sled dogs.

Such «meetings» turned into fairs later on as the inhabitants of the north of Eastern Siberia organized them in the 18th-19th centuries, but not only for the exchange of goods. The exchange of various information was considered to be of much more importance. In any case, the material evidence on Zhokhov island is presented with a minimum of findings. Probably an important result of such meetings was the marriage contacts necessary secure biological stability of small groups of people who lead a rather isolated life.

«The results of our research indicate a high level of sociocultural relations that existed among the ancient population of the Arctic in Eastern Siberia 9000 years ago, and about the engagement of people from the Zhokhov site. These people who lived on the edge of the earth were not isolated. On the contrary, contacts within these societies were much more developed than it used to be thought,» concluded Vladimir Pitulko.

The study is published in the journal Antiquity.

Source: AKSON Russian Science Communication Association [February 22, 2019]

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Meteor Activity Outlook for February 23-March 1, 2019

This photograph of a bright fireball, provided by Daniel Bush, occurred on February 1, 2018 at 7:07 UT, from Auburn, Missouri. © Daniel Bush.

During this period the moon will reach its last quarter phase on Tuesday February 26th. At this time the moon will be located 90 degrees west of the sun and will rise near 0100 local standard time (LST). Useful meteor observations can be carrier out during the more active morning hours as long as you keep the moon out of your field of view. This weekend will be more difficult to view meteor activity as the gibbous moon will rise earlier and also be brighter than later in the week. Hourly meteor rates for evening observers this week is near 3 as seen from mid-northern latitudes (45N) and 4 as seen from tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 5 as seen from mid-northern latitudes and 9 from the southern tropics. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Rates are  reduced during the morning hours due to moonlight. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brighter meteors will be visible from such locations.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning February 23/24 . These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies near the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

Radiant Positions at 7:00pm Local Standard Time

Radiant Positions at 12:00am Local Standard Time

Radiant Positions at 5:00am Local Standard Time

These sources of meteoric activity are expected to be active this week.

The center of the large Anthelion (ANT) radiant is currently located at 11:12 (168) +11. This position lies in southeastern Leo, 2 degrees southwest of the 4th magnitude star known as sigma Leonis) Due to the large size of this radiant, Anthelion activity may also appear from western Virgo and Sextans as well as Leo. This radiant is best placed near 0100 local standard time (LST), when it lies on the meridian and is located highest in the sky. Rates at this time should be near 2 per hour as seen from the northern hemisphere and 1 per hour from south of the equator. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

The February Mu Virginids (FMV) were discovered by Damir Šegon and the Croatian Meteor Network team based on studying SonotaCo and CMN observations (SonotaCo 2007-2011, CMN 2007-2010). These meteors are active from February 17 through March 5 with maximum activity occurring on February 26. The current radiant position lies near 16:16 (244) -02, which actually places it on the border of Ophiuchus and Sepens Caput, 3 degrees north of the pair of stars known as “Yeds” (epsilon and delta Ophiuchi). Rates are expected to be less than 1 per hour no matter your location. These meteors are best seen near 0500 LST when the radiant lies highest above the horizon. At 62 km/sec. the February Mu Virginids would produce mostly swift meteors.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 3 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 2 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 8 per hour as seen from rural observing sites and 3 per hour during the evening hours. Morning rates are reduced due to moonlight. Locations between these two extremes would see activity between the listed figures.

SHOWER DATE OF MAXIMUM ACTIVITY CELESTIAL POSITION ENTRY VELOCITY CULMINATION HOURLY RATE CLASS
RA (RA in Deg.) DEC Km/Sec Local Standard Time North-South
Anthelion (ANT) 11:12 (168) +11 30 01:00 2 – 1 II
February mu Virginids (FMV) Feb 26 16:16 (244) -02 62 07:00 <1 – <1 IV

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