Follow Slashdot blog updates by subscribing to our blog RSS feed

 



Forgot your password?
typodupeerror
For the out-of-band Slashdot experience (mostly headlines), follow us on Twitter, or Facebook. ×

Comment: Android disasters and atrocity (Score 1) 96 96

Disasters and atrocity... exactly describes Android Lollipop on Nexus 7.

They can fucking prescribe sensitivity when they stop rendering perfectly good customer owned equipment nearly unusable. How could they ever have released such a miserable crock of shit?

Comment: Molecularly interesting, applications not so much (Score 2) 64 64

It's an interesting curiosity in a molecular sense, but is it really justified for application? Why not let room lighting be done with something optimized for luminous efficiency and subjective color, and data transfer be done in the infrared where we have cheap emitters and optical filters? Why burden a bulk illumination power supply with also being a modulator in the 10^8Hz realm?

Comment: Re:the good old days... (Score 1) 784 784

At age 10 I would walk maybe 3 miles with a 13 year old friend, with one or the other of us openly carrying an actual firearm (.22 rifle) toward a local hill to go plinking. This was in Southern California. I once bought (at a liquor store) ammunition as a birthday gift for my friend. The clerk phoned my parents to see if it was OK. They told him that they knew about it and it was OK, and he sold me the ammo.

Today this would bring a couple of helicopters, a SWAT team, and news crews.

Comment: Re: Ironic coming from ACM (Score 1) 149 149

I quit ACM years back when CACM went from a typographically elegant and content relevant general survey, to a ragged-right ugly pile of pedagogical hand wringing. Whether I am being fair in blaming P.J. Denning for this is worth arguing, but I recall its happening on his watch.

Comment: Re:Math author dies rich... (Score 2) 170 170

Stewart might have been a singular phenomenon. How many textbook authors even do well, much less become wealthy?

In some sense his book evolved not to be his book, but a brand name and industry. It exists in numerous editions, some functionally variant ("Early Transcendentals"), and some specifically formulated for one institution, in addition to the arisen phenomenon of annual editions that seem cynically designed to kill the used textbook market.

Price and physical weight (clay coated paper) aside, as a returned adult undergrad I found Stewart to be a good calculus text. So, though was Hughes-Hallett, and she probably does not live in an exceptional custom house/concert hall. And there are ways in which 1970s editions of e.g. Thomas present and illuminate the subject, that were greatly helpful.

Comment: Re:I don't think it's 1% (Score 1) 40 40

The emission is fluorescence. Some fraction of the incoming photons that get captured by the chlorophyll antenna system are absorbed, but have that energy re-radiated (at a somewhat longer wavelength after some energy loss) rather than having the energy used in photosynthesis or just absorbed and dissipated thermally. When the incident light stops, the fluorescence stops. The photosynthetic system can also emit a small amount of light after incident light stops (essentially run backwards, converting stored chemical energy back to photons), but that is not what is being measured here.

Comment: Re:Helium is non renewable (Score 1) 296 296

In second semester undergrad physics, one of our homework problems was to examine the tail of the Maxwell-Boltzmann distribution for helium at ordinary temperatures, relative to Earth escape velocity.

Nothing can replace helium, and once released to the atmosphere, it will 1) become too dilute to economically recover from the atmosphere, and 2) eventually escape into space.

Nothing especially (apart perhaps from magnetic and optical manipulations in very limited circumstances) can replace 3He as an ultimate refrigerant. Some 3He comes from natural He reservoirs, but most comes from 3H (tritium) production and decay. The decline of tritium production for nuclear weapons, has brought a corresponding decline in availability of 3He. One of my professors was in a dispute with his former institution over who owned a small cylinder of 3He from his former lab. It was at the time valued at around $16000, and was languishing uselessly in some provost's office.

Comment: Not the first helium fillled drive (Score 5, Interesting) 296 296

In the late 1960s, DDC of San Diego made head-per-track disk drives that operated with a helium atmosphere. These units had a cylinder of helium fastened to the baseplate (the units were 19" rack mount), and the documentation included procedures for replacing the cylinder and for purging from a full-sized cylinder if it was ever necessary to open the unit for repairs.

I had driven down to San Diego circa 1978 to buy a cylinder of refill helium from DDC for one of these in a hand-me-down system, but never got around to replacing the cylinder on the drive. The cylinder sat in my garage for years. Thirty years later I was a returned adult physics student. My professor was using a similar helium cylinder to purge a cryostat for a superconducting magnet. He ran out of helium, and the department had no other helium. I told him "wait 20 minutes, I'll be back." I retrieved the cylinder from my garage, and the professor was both delighted and baffled. When connected to the regulator, the cylinder proved to have maintained a remarkable fraction of its original pressure, and the professor was able to complete his procedure. Sadly, another part of the magnet failed and suffered a gas pressure explosion as it was being cooled.

In a remarkable coincidence, I noted that the department's helium cylinder and mine were identical, all the way down to a part number stenciled on them.

Comment: 1975: original MITS Altair (8080) (Score 2) 391 391

In 1975 I assembled a MITS Altair kit. I still have the machine, though I have not powered it up in many years. Discrete wiring of the front panel was memorably tedious and error-prone.

The machine had 256 bytes of static RAM on a board separate from the CPU board.

MITS later sold a 4K DRAM board, which if I recall correctly, tried to rely upon RC timed one-shots for its timing, and an incredibly poor PCB layout with numerous jumper wires. This board was a total botch. MITS later came out with a different board designed with synchronous logic that might have been better. Eventually MITS and others came out with larger static RAM boards that worked reliably.

My coolest project with that machine was to use an A/D / D/A board and some code hand-assembled to binary (and keyed in through the front panel switches), to make an audio delay line, whose delay time was controlled by the front panel switches. Running a radio straight into one side of stereo headphones, and the delayed audio into the other side, made for an amusing experience.

Comment: Entrepreneurship vs. mental illness: distinct? (Score 3, Informative) 257 257

One model claims that manic depressive tendency is under-recognized and over-represented among entrepreneurs. This sounds intriguing, but I must admit not being aware of any data that directly support the claim.

Another factor is post-mission depression. Here, we have something in common with military people, aid workers, and religious missionaries returning from deployment. One's life was for a time directed by a highly directed sense of purpose and mission, held in common with one's principal cohort. This often was within an organizational structure that made high demands, but diverted attention toward the mission and away from unknowns and uncontrollables. When the mission ends, the coherence and structure end with it.

Startup culture can reward what in other contexts would be seen as manic and obsessive/compulsive behaviors. In a bubble market with an IPO pending or recently made, it can be difficult to distinguish reality from illusion from delusion. For a while, one's life can evolve toward an obsessive focus upon one number: a stock price.

Spoken from experience.

"Love is a snowmobile racing across the tundra and then suddenly it flips over, pinning you underneath. At night, the ice weasels come." --Matt Groening

Working...