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Old 2020-02-14, 20:49   #2696
masser
 
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Ugh. I'm certain that countless teachers have discovered the exact same approach. Most of them had the humility and sense not to squawk about such a near-triviality.

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He even found out that a math teacher in Sudbury, Canada, named John Savage came up with a similar approach 30 years ago. An article by Mr. Savage in the journal The Mathematics Teacher in 1989 laid out almost the same procedure, although Dr. Loh filled in some nuances of logic in explaining why it works.

“I honestly can’t remember exactly where the eureka moment was,” Mr. Savage said in a phone interview. But it seemed to be an improvement over the usual way of teaching the subject.

He continued using that approach, as did some other teachers he knew. But the internet was still in its infancy, and the idea faded away.

“It never caught on,” Mr. Savage said. “Looking back on it, I should have pushed it a little more. I think it’s so much easier than the traditional way.”

Mr. Savage said he was excited to see the same idea revived 22 years after he had retired. “I was quite interested to read it now,” he said of Dr. Loh’s paper. “It’s quite interesting that he basically came up with the same idea.”
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Old 2020-02-14, 21:03   #2697
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Betelgeuses shenanigans just got weirder, only part of it is dimming
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Old 2020-02-14, 22:06   #2698
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It's near-criminal for articles such as this to omit mention of Kolmogorov's associated 1941 turbulent-microscale theory. Wikipedia describes the connection between the 2 scaling regimes:
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Similar to the Kolmogorov microscales, which describe the smallest scales of turbulence before viscosity dominates; the Batchelor scale describes the smallest length scales of fluctuations in scalar concentration that can exist before being dominated by molecular diffusion. It is important to note that for Sc>1, which is common in many liquid flows, the Batchelor scale is small when compared to the Kolmogorov microscales. This means that scalar transport occurs at scales smaller than the smallest eddy size.
It's winking at us! "Hiya, sailor - looking for a shoulder to cry on?"

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Old 2020-02-16, 20:25   #2699
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Scientists discover largest bacteria-eating virus. It blurs line between living and nonliving. | LiveScience
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...the researchers searched through a DNA database that they created from samples they and their colleagues collected from nearly 30 different environments around the world, ranging from the guts of people and Alaskan moose to a South African bioreactor and a Tibetan hot spring, according to a statement.

From that DNA, they discovered 351 huge phages that had genomes four or more times larger than the average genome of phages. Among those was the largest phage found to date with a genome of 735,000 base pairs — the pairs of nucleotides that make up the rungs of the DNA molecule's "ladder" structure — or nearly 15 times larger than the average phage. (The human genome contains about 3 billion base pairs.)

These phages are "hybrids between what we think of as traditional viruses and traditional living organisms," such as bacteria and archaea, senior author Jill Banfield, a University of California, Berkeley, professor of Earth and planetary science and of environmental science, policy and management, said in the statement. This huge phages' genome is much larger than the genomes of many bacteria, according to the statement.

The authors found that many of the genes coded for proteins that are yet unknown to us. They found that the phages had a number of genes that are not typical of viruses but are typical of bacteria, according to the statement. Some of these genes are part of a system that bacteria use to fight viruses (and was later adapted by humans to edit genes, a technique called CRISPR-Cas9).

Scientists don't know for sure, but they think that once these phages inject their DNA into bacteria, the phages' own CRISPR system strengthens the CRISPR system of the bacteria. In that way, the combined CRISPR system could help to target other phages (getting rid of the competition).

What's more, they found that some of the phages had genes that coded for proteins necessary for the functioning of ribosomes — a cellular machine that translates genetic material into proteins (the proteins are the molecules that carry out DNA's instructions). These proteins aren't typically found in viruses, but they are found in bacteria and archaea, according to the statement.

Some of these newfound phages may also use the ribosomes in their bacteria host to make more copies of their own proteins, according to the statement.

"Typically, what separates life from nonlife is to have ribosomes and the ability to do translation; that is one of the major defining features that separate viruses and bacteria, nonlife and life," co-lead author Rohan Sachdeva, a research associate at UC Berkeley, said in the statement. "Some large phages have a lot of this translational machinery, so they are blurring the line a bit."

Last fiddled with by ewmayer on 2020-02-16 at 20:26
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Old 2020-02-19, 20:03   #2701
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I still use paper star maps on a night to night basis, despite the availability of alternatives on the interweb thingy which are in full colour and go much fainter.

Whether it's Norton's for simple orientation, finder charts for specific variable stars, or the Millennium Star Atlas for breadth of coverage, sometimes paper maps are so much more practical and convenient. They tend to be better annotated, for a start.
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Old 2020-02-20, 21:13   #2702
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o The First Molecule in the Universe | Scientific American -- Another article on helium hydride.

o ‘Radical Change’ Needed After Latest Neutron Star Collision | Quanta
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Last summer, the gravitational wave observatory known as LIGO caught its second-ever glimpse of two neutron stars merging. The collision of these incredibly dense objects — the hulking cores of long-ago supernova explosions — sent shudders through space-time powerful enough to be detected here on Earth. But unlike the first merger, which conformed to expectations, this latest event has forced astrophysicists to rethink some basic assumptions about what’s lurking out there in the universe…. Based on the recent observation, LIGO scientists estimate that these heavy pairings should be almost as common as the lighter binary star systems that astronomers have been studying for decades. Big neutron star pairs should be all over the universe, including our own Milky Way. Why, then, have they never been spotted before?
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Old 2020-02-20, 22:58   #2703
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Originally Posted by xilman View Post
I still use paper star maps on a night to night basis, despite the availability of alternatives on the interweb thingy which are in full colour and go much fainter.

Whether it's Norton's for simple orientation, finder charts for specific variable stars, or the Millennium Star Atlas for breadth of coverage, sometimes paper maps are so much more practical and convenient. They tend to be better annotated, for a start.
I whole-heartedly agree- the bindings on my Uranometria volumes of charts are falling apart, but I never have the telescope out without them. They seem much easier to use than a computer screen, plus I've made many notations over the years about especially nice fields of view, or tracking a comet's progress across the pages. Just can't imagine a program and screen being as useful and pleasant as a good star chart.

Norm
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Old 2020-02-21, 08:34   #2704
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Quote:
Originally Posted by Spherical Cow View Post
I whole-heartedly agree- the bindings on my Uranometria volumes of charts are falling apart, but I never have the telescope out without them. They seem much easier to use than a computer screen, plus I've made many notations over the years about especially nice fields of view, or tracking a comet's progress across the pages. Just can't imagine a program and screen being as useful and pleasant as a good star chart.

Norm
I never write anything on my charts. If I need hard-copy for annotation I scan and print the relevant portion.
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Old 2020-02-21, 13:00   #2705
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o ‘Radical Change’ Needed After Latest Neutron Star Collision | Quanta
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<snip>
Based on the recent observation, LIGO scientists estimate that these heavy pairings should be almost as common as the lighter binary star systems that astronomers have been studying for decades. Big neutron star pairs should be all over the universe, including our own Milky Way. Why, then, have they never been spotted before?
This may be a silly question, but -- what exactly do you look for?

A neutron star with a visible binary companion can be detected by its effect on the motion of the visible companion, whether its radiation sweeps over the earth or not.

But if you've got two neutron stars orbiting each other and no visible companion, there may not be much to see from Earth. If you're lucky, the directional "pulses" of one or the other will be detected, and if you're very lucky, pulses from both will be visible. [It is AFAIK possible that the rotation axes will be forced to align, making this an all-or-nothing proposition.]

It is also possible that, assuming the neutron stars formed in situ (rather than the binary system being formed by orbital capture), the nebula from two supernovas occurring at different times but spatially nearby might have some distinctive properties.
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Old 2020-02-22, 08:06   #2706
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It is also possible that, assuming the neutron stars formed in situ (rather than the binary system being formed by orbital capture), the nebula from two supernovas occurring at different times but spatially nearby might have some distinctive properties.
Unfortunately that is not very likely to occur. The production of the first SN releases so much gravitational energy that the system becomes unbound, often to the extent that the remaining star takes off at high velocity. A number of so-called "runaway stars" have been identified and their high space velocities attributed to this process.
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