An anonymous reader writes:
Google, Qualcomm, and Samsung "are among 80 tech companies joining forces to develop a new open-source chip design for new technologies like self-driving vehicles," writes Seeking Alpha, citing a (pay-walled) report on The Information. "Western Digital and Nvidia also plan to use the new chip design for some of their products," while Tesla "has joined the RISC-V Foundation and is considering using the tech in its new chip efforts."
MIT Technology Review adds that while Arm had hoped to bring their low-power/high performance processors to AI and self-driving cars, "The company that masterminded the processor inside your smartphone may find that a set of free-to-use alternative designs erode some of its future success."
Whether you’ve been dreaming about space all your life, or just like the idea of a car on its way to Mars, there’s no denying that space exploration continues to be a fascination for many.
While joining the NASA engineering team may be impossible for most, these backyard space projects have all been produced in the homes, garages, and gardens of amateur rocket engineers and enthusiasts. 3… 2… 1… lift off!
This incredible mission control desk was built by Jeff Highsmith from Make. Using a variety of switches, knobs, lights, and dials, this incredible project looks and sounds just like the real thing.
Using an iPad to play space videos, and a Raspberry Pi in conjunction with an Arduino, all of the controls actually work. With factually accurate labels for oxygen levels, altitude, speed, and more, there’s not much you can’t do.
In addition to the cool buttons, Jeff programmed simulations of real historical space glitches, complete with accurate solutions! Unfortunately, this desk doesn’t control a real spaceship—but there’s no reason it couldn’t with a bit of re-programming.
When Apollo 11 landed on the Moon in 1969, the astronauts left something bigger than footprints behind. The surface of the moon contains a 2 foot wide panel covered in 100 mirrors. By using a laser and several pieces of sensitive electronics, you can fire a laser at the moon, bounce it off the mirror array, and detect the returning beam.
Admittedly, you’ll need a very powerful laser, a large telescope, and some specialist equipment, but there’s nothing stopping you renting time in a local observatory. You won’t be able to reuse your old laser pointer 6 Uses For An Old Laser Pointer
The premise is simple. Attach a camera, parachute, and GPS to a weather balloon. Send it soaring into space and then go pick up the pieces!
This particular tutorial comes from YouTube channel Dechert 360, but there are hundreds if not thousands of high altitude balloon projects.
While you may need permission to launch, a high altitude photography launch is one of the easiest projects you can work on, and the few specialist parts are inexpensive and easily obtainable.
This space project idea comes directly from YouTube creator Practical Engineering. This mechanical marvel uses an Arduino compatible development board at its heart, and simply points to the location of the International Space Station.
While this project does use a stepper motor and several specialist mounting points, the ISS tracker code on GitHub should be enough to get you started, regardless of your specific hardware configuration.
This impressive telescope breaks down into two pieces for ease of transporting, and is capable of producing impressive images of the moon and nearby planets!
Produced by the Experiment at Home YouTube channel, this video tutorial covers everything you need to know about constructing your own telescope at home.
The Best 3D Printer for Your Budget in 2017 If you’re looking for a 3D printer, we’ve got you covered. We’ve covered the overall best 3D printer, the smallest, the fastest, and the cheapest — and for all budgets, starting at $300! Read More
Ultimate Beginner’s Guide to 3D Printing 3D printing was supposed to be the new “Industrial Revolution.” It hasn’t taken over the world yet, but I’m here to talk you through everything you need to know to get started. Read More
should help you out here.
This impressive project was built by YouTube channel The Thought Emporium. Built using a satellite and a set of 3D printed gears, this project can track satellites over 20,000 miles away—impressive!
While this project does involve manipulation of microwave frequency bands, it’s not as complex as it sounds. Detailed instructions and implementation specifics are outlined in the video above, and with over 120,000 views, there’s sure to be someone else who’s attempted this project.
8 Awesome Kerbal Space Program Mods Have you ever wanted to design your own rockets, launch them into space, and send astronauts to the moon (or beyond)? Now you can with Kerbal Space Program, a unique game and digital toy that… Read More
, then the next logical step is to build a simulator control console.
Powered by a Raspberry Pi, this shiny interface is a remote controller for your virtual spacecraft. Produced by YouTuber Steven Marlowe, this console outputs real time rocket statistics, and features several lights, buttons, and switches. You could easily expand this into a whole flight deck if you wanted to.
This ambitious project comes from crowdfunded enterprise Copenhagen Suborbitals. With a dream of sending an amateur astronaut into space, this project is definitely on the complex side!
It’s possible to start your own space mission, but you’re probably better off donating to this one if you’re that interested. The team at Copenhagen Suborbitals have got a solid handle on the very basics required for their dream, but even so there’s a long road ahead.
If you need any more convincing that this rocket launch will be a success, then take a look at the rocket gallery, where the impressive engineering work on prototype rockets is documented.
Not just a movie prop, but this suit actually works. Or, at least it would do if it ever went into orbit. After dreaming about space as child, Cameron Smith decided to research and build his own, working space suit.
Eventually teaming up with the previously mentioned Copenhagen Suborbitals, Cameron’s suit has been selected to be used as the official suit of the homemade space mission. Not only that, but the suit is something of an open-source design, or it will be once completed.
What better way to contribute to a space program than to work on a space suit?
This outstanding scale model of the Saturn 5 rocket was produced by Steve Eves. Measuring 36 feet tall, and weighing over 1600 lbs, this model holds the world record for the largest amateur rocket ever successfully launched.
While there’s no doubt that this is an incredibly complicated space project, it shows just what’s possible with a bit of creative thinking. The real Saturn 5 is a complex piece of kit, but that’s not to say that a working scale model isn’t without its challenges.
If you’re a beginner to amateur rocket construction, then you may want to start with something a bit smaller, like the Estes Tandem-X, which measures a more manageable 30 inches tall.
As these projects show, space projects can be produced by more than just the NASA scientists. Whether you’re into functional operating equipment, or bedroom sized replicas, there’s nothing stopping you from attempting some of these projects!
In this blog post, we’ll look at using ProxySQL and VIRTUAL columns to solve ORM issues.
There are a lot of web frameworks all around. Programmers and web designers are using them to develop and deploy any website and web application. Just to cite some of the most famous names: Drupal, Ruby on Rails, Symfony, etc.
Web frameworks are very useful tools. But sometimes, as with many human artifacts, they have issues. Any framework has its own queries to manage its internal tables. While there is nothing wrong with that, but it often means these queries are not optimized.
Here is my case with Symfony 2 on MySQL 5.7, and how I solved it.
The sessions table issue
Symfony has a table to manage session data for users on the application. The table is defined as follow:
CREATETABLE`sessions`(
`sess_id`varchar(126)COLLATEutf8_binNOT NULL,
`sess_data`blobNOT NULL,
`sess_time`int(10)unsignedNOT NULL,
`sess_lifetime`mediumint(9)NOT NULL,
PRIMARY KEY(`sess_id`)
)ENGINE=InnoDBDEFAULTCHARSET=utf8COLLATE=utf8_bin
The expiration time of the user session is configurable. The developers decided to configure it to be one month.
Symfony was serving a high traffic website, and very soon that table became very big. After one month, I saw it had more than 14 million rows and was more than 3GB in size.
Developers noticed the web application sometimes stalling for a few seconds. First, I analyzed the slow queries on MySQL and I discovered that sometimes Symfony deletes inactive sessions. It issued the following query, which took several seconds to complete. This query was the cause of the stalls in the application:
Every DELETE query was a full table scan of more than 14 million rows. So, let’s try to improve it.
First workaround
Looking around on the web and discussing it with colleagues, we’ve found some workarounds. But none of them was the definitive solution:
Reduce expiration time in Symfony configuration. Good idea. One month is probably too long for a high traffic website. But we kept the expiration time configured at one month because of an internal business policy. But even one week wouldn’t have solved the full table scan.
Using a different database solution. Redis was proposed as an alternative to MySQL to manage session data. This might be a good solution, but it could involve a long deployment time. We planned a test, but the sysadmins suggested it was not a good solution to have another database system for such a simple task.
Patching Symfony code. It was proposed to rewrite the query directly into the Symfony code. Discarded.
Create indexes. It was proposed to create indexes on sess_time and sess_lifetime columns. The indexes wouldn’t get used because of the arithmetic addition on the where clause. This is the only condition we have on the query.
So, what do we do if everything must remain the same? Same configuration, same environment, same query issued and no indexes added?
Query optimization using a virtual column
I focused on how to optimize the query. Since I was using 5.7, I thought about a generated virtual column. I decided to add a virtual column in the sessions table, defined as sess_time+sess_lifetime (the same as the condition of the query):
Any virtual column can have an index on it. So, I created the index:
mysql>ALTERTABLEsessionsADDINDEX(sess_delete);
Note: I first checked that the INSERT queries were well written in Symfony (with an explicit list of the fields to insert), in make sure this modification wouldn’t cause more issues. Making a schema change on a table that is in use by any framework, where the queries against the table are generally outside of your control, can be a daunting task.
So, let’s EXPLAIN the query rewritten as follows, with the condition directly on the generated indexed column:
The query now can to use the index, and the number of rows selected are the exact number of the session that we have to delete.
So far, so good. But will Symfony execute that query if we don’t want to modify the source code?
Using ProxySQL to rewrite the query
Fortunately, we already had ProxySQL up and running in our environment. We were using it just to manage the master MySQL failover.
One of the very useful features of ProxySQL is the ability to rewrite any query it receives into another one based on rules you can define. You can create queries from very simple rules, like changing the name of a field, to very complex queries that use a chain of rules. It depends on how complex the translation is that you have to do. In our case, we just needed to translate sess_time + sess_lifetime into sess_delete. The rest of the query was the same. We needed to define a very simple rule.
–>‘^DELETE FROM sessions WHERE sess_lifetime + sess_time < (.*)’,
–>0,
–>‘CASELESS’,
–>‘DELETE FROM sessions WHERE sess_delete < \1’,
–>0,
–>1);
The two fields I want to focus on are:
match_pattern: it defines the query to be matched using the regular expression notation. The + symbol must be escaped using because it’s a special character for regular expressions
replace_pattern: it defines how to rewrite the matched query. 1 is the value of the parameter matched by match_pattern into (.*)
Once created, we have to save the rule to disk and put it on runtime to let it run effectively.
Admin>SAVEMYSQLQUERYRULESTODISK;
Admin>LOADMYSQLQUERYRULESTORUNTIME;
After that, the proxy began to filter the query and rewrite it to have a better execution plan using the index on the virtual column.
Note: pay attention when you need to upgrade the framework. If it needs to rebuild the database tables, you will lose the virtual column you’ve created. Just remember to recreate it and check it after the upgrade.
Conclusion
Developers love using web frameworks because they are very powerful in simplifying development and deployment of complex web applications. But for DBAs, sometimes internal queries can cause a bit of a headache because it is not well optimized or because it was not supposed to run in your “huge” database. I solved my case using ProxySQL and VIRTUAL columns with a minimal impact on the architecture of the system we had and avoided any source code patching.
Take this post as a tip in case you face similar issues with your application framework.
Prior to joining Percona as a Senior Consultant, Corrado spent more than 20 years in developing web sites and designing and administering MySQL. He is a MySQL enthusiast since version 3.23 and his skills are focused on performances and architectural design. He’s also a trainer and a MongoDB consultant.
Every gun owner should own at least one .22lr firearm. The ammo is ubiquitous, and I don’t know of any other cartridge that you can regularly get for $.05/round.
.22 Long Rifle can be used for hunting, target shooting, practice, plinking, and even defending yourself in a pinch. There are even competitions you can enter with rimfire firearms like the .22lr that can be loads of fun.
There are few things more fun than ripping holes in a target with a .22LR handgun.
Now, we’ve talked about the best .22lr RIFLES before, and I’ve talked about my competition Browning Buckmark before, but we’ve never gone over the best .22lr handguns, other than the occasional mention of things like the awesome NAA revolvers for pocket carry options.
Today, that changes.
I want to go over the best .22lr handguns to own for more than just the purposes of pocket carry. These guns are perfect for everything from last-ditch survival options to fun range toys.
For the impatient among you, here are my top picks:
They’re also great first guns for kids, and wonderful training tools. And unlike kids, they’re incredibly cheap to feed, with 5000+ round cases regularly coming in under $300 if you catch them on sale.
So, let’s go over how I chose these particular guns, and why they stand out (and why you should own at least one of them).
Choosing a 22LR Handgun
For me, there’s a few things I’m looking for in a .22LR handgun.
First, accuracy. The humble .22LR is a surprisingly accurate little round at close ranges, so it’s worth getting a gun that can hit what you aim it at. You’ll have a lot more fun hitting those cans setup on a hill than you will watching shots land juuuuust a hair away from them.
Next, shootability and ergonomics. I want something that I’m going to enjoy shooting, not something that’s difficult and forces you to be accurate in spite of it. This is one of my problems with the NAA mini-revolvers.
Pictured: Neat and convenient, not easy to shoot.
Sure, they’re also surprisingly accurate, but anyone who tells you they’re easy to shoot is lying to you, or has never experienced the wonder of a full-size firearm firing .22LR.
Finally, availability and aftermarket support. There’s nothing worse than a $200 gun with $50 mags. I want something that has a lot of support and options available.
As far as aftermarket support, rimfire handguns and rifles (particularly the Ruger 10/22) have a ridiculous number of aftermarket manufacturers making improved triggers, stocks, conversion kits, sights, extractors, magazines, mag releases…the list goes on and on.
And with the low cost of entry (usually sub-$400) to a rimfire firearm, you can experiment a little more and really go all out on the upgrades and accessories, without much worry that you’re going to ruin something expensive.
I highly recommend either the SW-22 Victory, Browning Buckmark, or Ruger 10/22 if you’re looking to start doing any kind of gunsmithing as they’re great platforms to learn on, and you can get really creative with the stuff you can build these guns into.
The Best .22LR Handguns
Alright, here are the guns I’d suggest looking at if you’re trying to decide on a .22LR handgun.
Some of these guns will work for a CCW, in particular the ATI, Beretta, and Walther options make good little guns for folks with low hand strength or for those who are very recoil sensitive, but that’s not why I chose them.
Also, I know there’s roughly a billion other options out there and I can already hear the comments like “what about this Bersa” and “what about that NAA” etc, etc. Now, I don’t want to discourage those comments (quite the opposite) but I can only make this list so long, and I have to start drawing lines somewhere.
So, if I’ve missed an option you think is really good, or there’s something not on the list that you want to know about, be sure to drop a comment below and we can talk about it. Maybe the gun you remembered and I forgot will be exactly what someone else needed.
Alright, I’ve run my mouth long enough, let’s look at some guns.
Ruger Mark IV
Ruger Mark IV
There are a number of excellent .22LR pistols with designs that harken back to the iconic Luger shape (of 9mm Luger fame).
This design is as robust as it is prolific, and has a long development history that began almost a decade before John Moses Browning’s masterwork, the 1911.
The Ruger Mark IV is perhaps one of the finest examples of this design, managing to capture the classic lines, while updating the older toggle-lock design to a simple, but modern blowback design.
It is a 10+1 capacity, magazine fed gun that is a pleasure to hold and shoot, and the heavy bull barrel makes recoil management a cinch. If you’re used to shooting centerfire cartridges of any size, this gun is going to feel like an absolute pushover by comparison.
Long plagued by complaints from owners that the Ruger Mark X series was a pain to take down, the new Mark IV solves that problem effortlessly.
In previous models, reinstalling the frame was relatively easy, but then you had to try and finagle the bolt-stop pin back in, and it was a nightmare fit to make a grown man weep in frustration.
Now, press a button on the rear of the slide, and the gun opens up almost like an AR-15, ready to be cleaned, lubed, and reassembled without fuss.
Like the other two Luger-centric pistols on this list, the Mark IV is as accurate as the ammo and your skill will allow, so don’t try blaming the gun for your misses. Fortunatley, as with any .22LR, practice is cheap, and so is good ammo (relatively speaking) so no excuses.
SW-22 Victory
The SW-22 Victory is the newest of the three Luger-inspired guns on this list, and S&W have approached the design with their typical eye on quality of materials and design.
Of the three, I’d call it the most reliable, even if only by a little bit, especially with mixed ammo. I was shooting ammo that came from a ziplock bag, several different bullet types and manufacturers present, and I had not the first issue with the Victory.
Smith & Wesson SW22 Victory
Like the Mark IV, it’s a 10+1 capacity, mag-fed firearm with a bull barrel, typically a 5.5 inch one, but there are a host of options available from Smith and others.
Where it falls short of the other Luger-style guns here is in aftermarket support (just barely) and accuracy, although it’s certainly a close thing and it could very well just have been me having an off day as I only tested it during one range trip following what I will charitably call a late night.
Fortunately for the SW-22, it also has one of the lower MSRPs of any of the Lugeresque options here, so if you’re looking for something that’ll get the job done without breaking the bank, this is certainly a strong contender.
The one other thing I’ll note is that Smith and Wesson took a beating for a while on their M&P triggers in their handguns (something that has been rectified in the 2.0 series). The triggers were not good, certainly not by comparison to S&W’s other triggers, particularly in their revolvers.
The SW-22, despite coming out around the same time as the older generation M&Ps, was not cursed with such an affliction.
The trigger on this thing is damn good, and while aftermarket options and some carefully applied gunsmithing knowledge can certainly make it better, it’s perfectly adequate for most folks out of the box.
SW22 taken down.
Browning Buckmark
Next, we have the final Luger-style gun on the list, and my personal favorite, the Browning Buckmark.
The Buckmark is mostly my favorite because it was one of the first guns I purchased for myself, many years ago, but there are other, more objective reasons as well.
First, it has the nicest trigger of the three out of the box, which for me was big benefit. I really enjoy a nice, crisp trigger that makes accuracy easy, and the Buckmark certainly has that.
It also has a ton of factory options available, which makes it easy to find the Buckmark that best suits your needs.
The one area that really drags it down is, well, taking it down.
To clean the other two Luger knockoffs, you have either a button to push or a pin to rotate, and that’s pretty much it. Baddabing, baddaboom, you’re done.
The Buckmark requires you to remove the slide bridge which is annoying enough by itself but it also means you need tools, yes tools, plural, to take the thing down.
Tandemkross Everything Kit on Buckmark
Yes, it’s just two allen wrenches, and no, it’s not particularly difficult, but it is needlessly complicated, and it leaves me feeling guilty every time I take it to the range because I know all that dirty rimfire shooting I just did is going to make my gun a pain in the ass to clean.
Of course, the Buckmark also excels in other areas, and like just about every mag-fed gun on this list, comes in a 10+1 capacity, and like the Mark IV and the victory, it also comes with a 5.5 inch bull barrel. For aftermarket accessories, I’d have to again recommend Tandemkross, just like I would for the Ruger and the Smith above.
Reliability wise, I’d put it above the Mark IV and below the Victory, and looks-wise, I’d put it at the top of the heap, but you may think differently. That’s fine, this is America and you’re absolutely free to be wrong.
Walther P22 QD
The legendary Walther P22 was noted for it’s awesome trigger, clean design, and tactical styling.
All in all, it was an excellent little gun save one thing: it only worked when it felt like it, and overly-tight tolerances meant you got maybe one mag of reliable function out of it before it needed to be cleaned again.
Come on, don’t lie. That thing looks sexy as all hell.
The new QD model solves this issue, and updates the classic design while keeping the amazingly nice trigger that blows most other factory pistol triggers out of the water.
Best of all, the P22 is a DA/SA pistol so you have that second-strike capability if you have a light primer strike, which is a common issue with .22LR ammo.
In DA mode, you’ll be dealing with a stiff but smooth 11lb trigger pull, and with the hammer back you’ll get an incredibly crips break right at 4lbs of pressure.
Honestly, this is the gun I’d have if I could only own one from this list. It has a 10+1 capacity just the like the other mag-fed options here, and while it doesn’t have a lot of aftermarket support, it doesn’t need a whole lot.
If you’re going to carry an easy-to-shoot .22, this is the way to go as well as it is one of the more reliable options, while being a reasonable size to carry, unlike the 34-38oz behemoths we’ve covered so far.
The slide serrations also make it easy for those with low hand strength to rack in a round, and the sights, while kind of a cheap polymer, are more than accurate enough for self-defense distances.
That being said, the gun is great fun to shoot at the range, and its quite the looker. Walther certainly didn’t skimp in the design department on this thing.
Like most of their guns, there’s a little bit of the James Bond about it, and I really like that. Plus, it’s usually found under $250 and I’d call anyone charging much more than that a ripoff, so there’s really no reason not to have one.
Heritage Rough Rider .22
If you’re looking for something a little more classic, but just as fun, the Heritage Rough Rider is a strong contender. A single-action six shot like those wielded by your favorite Western heroes, the Rough Rider might just have the best fun-to-money ratio of any gun on the list.
The single action and loading-gate design means you have to pull back (or fan) the hammer for each shot and load and unload each round individually. No speed loaders, no slapping an ejection rod to spit all six spent shells to the ground at once.
All in all, it’s a very slow-paced, almost zen experience to shoot one, and you can really stretch a box of ammo for several afternoons at the range.
Heritage Rough Rider Revolver
It’s also a great gun for working on your accuracy as the low round count and almost-but-not-quite painfully slow reload will have you picking and placing your shots carefully.
The trigger is surprisingly good, no doubt a product of the simple single-action design more than anything, but that’s okay. It’s more than good enough for the gun’s real purpose: having the most fun for the least money.
Yeah, it’ll shoot snakes or discourage predators of the two and four-legged variety, and it’ll certainly make a good training tool for youngins and new shooters, but fun is what this gun is all about.
And the price certainly helps. You can get fancy commemorative versions, and versions with nice grips, and ones with interchangeable .22 Magnum cylinders, and all that, but the base version, with a .22lr cylinder and a 6.5” barrel will set you back between $100 and $125.
Next, we have one of the most legendary DA/SA revolvers to ever exist, the Ruger GP-100. For a long time, Ruger’s legendarily tough GP-100 was only available in a 6-shot .357 model (which I own and adore), but as of late, I’m seeing more and more .22LR versions on the shelf at my local gun store.
I can’t sing the praises of the GP-100 enough. Its rugged monolithic design means that it’ll almost certainly outlive you, and possibly your children and grandchildren as well if it’s cared for at all.
You could also probably bury it in the dirt somewhere for the sole purpose of having it dug up 200 years from now, and it’d probably still work (and be of great help to the revolution’s fight against our robot overlords circa 2200).
Ruger GP-100
The .22LR version is a ten shot model available with a 4” and 6” barrel, and its just about as accurate as you could want, something that’s in no small part due to the better-than-average trigger and factory fiber optic front sight post.
It is one of the pricier guns on this list with a typical going price of about $650, which sounds like a lot if you don’t realize you’re getting one of the best, if not the best, .22LR revolver around.
That about does it for this one. These .22LRs are sure to make you smile, and are great for everything from defense to hunting to plinking and target shooting. I own, or have owned all of these save the Victory, and I regret selling the ones I don’t have anymore.
This should about cover any use you should have for a .22LR handgun, but if you’re looking for something specific, or wanting to pick my or your fellow commenter’s brains about any of these guns, or even one that’s not on the list, be sure to drop a comment below!
For decades, scientists have debated the cause of the popping sound when we crack our knuckles. Using computer models, a research team from France may have finally reached the answer.
As the authors state in the new paper published today in Scientific Reports, the sound of knuckles cracking is caused by a “collapsing cavitation bubble in the synovial fluid inside a metacarpophalangeal joint during an articular release.” More simply, it’s the sound of microscopic gas bubbles collapsing—but not fully popping—inside the finger joint. Scientists first proposed this theory nearly 50 years ago, but this latest paper used a combination of lab experiments and a computer simulation to bolster the case.
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Seems weird, but scientists have been investigating this bodily quirk since the early 1900s, and they haven’t been able to reach consensus on the cause of the popping sound. The seemingly endless debate is the result of unconvincing experimental evidence, and the difficulty in visualizing the process in action: The whole phenomenon takes only about 300 milliseconds to unfold. What scientists have agreed upon, however, is that knuckle cracking is not something everyone is able to do, not every finger can produce the popping sound, and it takes about 20 minutes before a knuckle can be cracked again.
To help clear things up, and to add more support to existing experimental data, V. Chandran Suja and Abdul Bakarat from École Polytechnique in France took geometric representations of the metacarpophalangeal joint (MCP), where the popping happens, and converted them into mathematical equations that powered computer simulations of knuckle cracking. Or more specifically, computer simulations that showed what goes on in our fingers just prior to that popping sound.
“Mathematical modeling is particularly useful because [real-time] imaging is not sufficiently rapid to capture the phenomena involved,” Bakarat told Gizmodo. “Another advantage of the modeling is that it allows varying one parameter at a time and therefore permits determining which parameters are truly important in determining the behavior. In this regard, we found that the parameter that has the most effect on the sound generated by knuckle cracking is how hard you pull on the knuckle. How fast you pull, the geometry of the joint, and the viscosity of the fluid (which changes with age) do not have a very strong effect.”
Research from a 2015 study showing the joint before (left) and after (right) knuckle cracking.
The models showed that when the joint undergoes a certain amount of stress, the resulting pressure changes in the joint fluid causes the collapse of microscopic gas bubbles within the synovial joint fluid. This theory was first proposed by scientists from the University of Leeds in 1971, but in 2015, a PLoS Onepaper led by Greg Kawchuk from the University of Alberta’s Faculty of Rehabilitation Medicine used MRI scans to show that gas bubbles remained in the fluid even after the knuckles were cracked. So instead of collapsing bubbles causing the popping sound, Kawchuk’s team said it was the sudden growth of bubbles that produced the noise.
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But as Suja and Bakarat show, this is not a deal-breaking contradiction. According to their models, only a partial collapse of the bubbles is needed to make the pop, and that’s why bubbles can still be seen even after knuckle cracking. And to prove their point even further, the researchers recorded the sound of knuckles cracking from three test subjects, and compared the digital acoustic waves to those mathematically produced by the computer simulation. The two acoustic waveforms were extremely similar, suggesting that Suja and Bakarat’s model is providing an accurate representation of knuckle cracking, and that the cause of the popping noise is indeed the sound of bubbles collapsing.
In terms of limitations, Bakarat said his team made a number of assumptions in the study, including the presence of only a single bubble, that the bubble is perfectly spherical, that the joint has an idealized, common shape, among others. “Furthermore, a limitation of the study is that we do not model the formation of the cavitation bubble in the synovial fluid but only bubble collapse,” he said. “A possible future direction of this work is to extend the modeling to include the phase of bubble formation.”
Greg Kawchuk, the lead author of the 2015 paper, said Suja and Barakat “should be congratulated” for designing a mathematical model that creates a theoretical pre-existing bubble. He thought it was interesting that other phenomena may be involved in between the frames of the MRI video published in his earlier study. But he believes the new study doesn’t completely solve the knuckle cracking mystery.
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“First, it must be emphasized that the work presented in this new study is a mathematical model that has not yet been validated by physical experimentation—we do not yet know if this occurs in real life,” Kawchuk told Gizmodo. “Second, although the authors of the paper demonstrated that the theoretical sounds produced by a theoretical bubble collapse were similar to actual sounds produced in knuckle cracking, the authors did not test the opposing circumstance proposed previously in the literature by asking, ‘what acoustics could be generated from bubble formation?’”
Which is an excellent point—one that Bakarat himself admitted was a limitation to the research. For all we know, rapid bubble formation may be producing a very similar knuckle-cracking sound, but the new study didn’t go there.
“As such, the impact of this new study is diminished by having investigated only one possibility (collapse of a pre-formed bubble) and disregarding other alternative phenomenon such as bubble formation, multiple formation/collapse events and the lingering issue of large volumes of gas in the joint following sound production that have been visualized by many investigators,” said Kawchuk.
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This topic may seem trivial, Kawchuk said, but he believe this issue has potential importance to healthcare—it could reveal insights into preserving joint health and joint mobility on account of disease and increasing age.
As to whether or not knuckle cracking is unhealthy, this latest study doesn’t speak to that (and neither Bakarat nor Kawchuk were comfortable in answering this question). But in 2015, Robert D. Boutin from the University of California, Davis did some research showing that the habit produced no immediate pain, swelling, or disability among habitual knuckle crackers, nor among those who rarely, if ever, do it. Boutin added that “further research will need to be done to assess any long-term hazard—or benefit—of knuckle cracking,”
So for you knuckle crackers out there, you probably don’t have to worry about contracting arthritis or anything like that, but just remember that many of us non-knuckle crackers find your habit to be absolutely revolting. So stop it.
Electric arc lighters are so…hot right now. But this model from Tacklife is about the size of a USB flash drive, making it one of the smallest on the market. I own it myself, and it works great. Just $10 today with promo code C2E85A9F.
The seven-year-old startup is now announcing a $125 million Series D round led by Kleiner Perkins, with participation from Google Ventures. Veteran investor Mary Meeker will also be joining the board.
The valuation is $1.275 billion, meaning that the company is considered a “unicorn.” The round brings the total amount raised to $241 million. Existing investors include Bessemer Venture Partners, Index Ventures, Jack Dorsey and Mark Zuckerberg.
Intercom is the “next generation customer database that’s specifically built for internet businesses,” co-founder and CEO Eoghan McCabe said in an interview with TechCrunch. “Salesforce is not built for internet businesses.”
“When a business uses the Intercom Messenger, they see conversation rates increase,” McCabe claims. Intercom says that customer sales go up an average of 82%.
The startup touts its “messaging-first approach,” helping its clients with customer acquisition and support. It says it powers 500 million conversations per month across its 25,000 customers. Atlassian, New Relic and Shopify use Intercom.
Intercom says it will use the funding to further develop its customer platform. It plans to double its research and development teams. Says McCabe, Intercom is “putting our foot on the pedal.”
Intercom, which has a strong presence in both the United States and Ireland, hopes to use the capital to expand its workforce beyond 500 employees.
It also would like to further expand its geographic footprint, adding customers across Europe and Asia.
In this post, we’ll look at the MySQL 8.0 innodb_dedicated_server variable.
MySQL 8.0 introduces a new variable called innodb_dedicated_server. When enabled, it auto tunes innodb_buffer_pool_size, innodb_log_file_size and innodb_flush_method at startup (if these variables are not explicitly defined in my.cnf).
The new MySQL 8.0 variable automatically sizes the following variables based on the RAM size of the system:
innodb_buffer_pool_size:
<1G: 128M(default value if innodb_dedicated_server is OFF)
<=4G: Detected Physical RAM * 0.5
>4G: Detected Physical RAM * 0.75
innodb_log_file_size:
<1G: 48M(default value if innodb_dedicated_server is OFF)
<=4G: 128M
<=8G: 512M
<=16G: 1024M
>16G: 2G
The variable also sets the following:
innodb_flush_method:
Set to O_DIRECT_NO_FSYNC if the setting is available on the system. If not, set it to the default InnoDB flush method
These new default values are very reasonable, and the changes to these three variables show considerable performance improvements from the get-go than using the old default values. As stated in the worklog of this feature, the current MySQL version (5.7) only uses around 512M RAM with the default settings. With the new feature, these variables can easily adapt to the amount of RAM allocated to the server for the convenience of the system/database administrator.
With that said, you can achieve the best setting for these three variables by tuning it to your workload and hardware.
For InnoDB buffer pool size (based on this article), consider allocating 80% of physical RAM for starters. You can increase it to as large as needed and possible, as long as the system doesn’t swap on the production workload.
For InnoDB log file size, it should be able to handle one hour of writes to allow InnoDB to optimize writing the redo log to disk. You can calculate an estimate by following the steps here, which samples one minute worth of writes to the redo log. You could also get a better estimate from hourly log file usage with Percona Monitoring and Management (PMM) graphs.
Finally, for innodb_flush_method, O_DIRECT_NO_FSYNC prevents double buffering between the OS cache and disk, and works well with low-latency IO devices such as RAID subsystem with write cache. On the other hand, in high-latency IO devices, commonly found on deployments where MySQL is stored in SAN drives, having an OS cache with the default flush method fsync is more beneficial.
All in all, the MySQL 8.0 innodb_dedicated_server variable provides a fairly well-tuned InnoDB configuration at startup. But if it’s not enough, you can still tune these variables based on your workload and hardware. While MySQL 8.0 isn’t released yet, you can take a look at this article that helps you tune the current version (MySQL 5.7) right after installation.
And in case you missed it last week, our favorite arc lighter, the Power Practical Sparkr Mini, is still down to $19 with code L5IMQBFO. This is an updated model of the Sparkr which fixes an issue that caused the its flashlight to turn on in your pocket, and it also doesn’t make a high-pitched whine like most competing products.
OhioHealth Corp. and Nationwide Children’s Hospital were awarded $200,000 each from Ohio Third Frontier toward testing the market viability of in-house discoveries and inventions.
OhioHealth Corp. and Nationwide Children’s Hospital were awarded $200,000 each from Ohio Third Frontier toward testing the market viability of in-house discoveries and inventions.