Calculus Textbook Author James Stewart Has Died
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.
Satellite Captures Glowing Plants From Space
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.
Satellite Captures Glowing Plants From Space
Chlorophyll fluorescence tends to be deep red, say 680-740 nm.
WD Announces 8TB, 10TB Helium Hard Drives
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.
WD Announces 8TB, 10TB Helium Hard Drives
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.
Hemp Fibers Make Better Supercapacitors Than Graphene
How about this recently published gem: Preparation of energy storage material derived from a used cigarette filter for a supercapacitor electrode .
How long ago did you last assemble a computer?
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.
NASA Names Building For Neil Armstrong
Soviet Union congratulated US for obviating own staged moon landing and exposure of inferior cinematic technology.
Start-Up Founders On Dealing With Depression
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.
$1 Billion Mission To Reach the Earth's Mantle
I recall watching some incredibly awful movie on TV in the 1960s, where there were unexpected results from deep drilling project: giant chickens emerged from the bowels of the Earth and terrorized the population.
WD Builds High-Capacity, Helium-Filled HDDs
It took only microseconds for head switching, but rotational latency was the usual 8.33ms average. The impact of rotational latency could be reduced, depending upon the application and controller hardware, by ordering operations according to the upcoming sector boundary.
We used these in realtime bank transaction processing (for ATMs and POS terminals) circa 1977, to look up card numbers and a very limited amount of associated information (much like the credit card deny-list book that merchants used to keep at the cash register).
WD Builds High-Capacity, Helium-Filled HDDs
These drives are not the first. Circa 1969, Digital Development Corporation of San Diego sold a line of head-per-track disks that used a helium atmosphere. A typical unit took around 24 inches vertical height in a 19-inch rack. Given the difficulties of sealing anything against helium leakage, these drives required a small helium cylinder and pressure regulator to maintain a small positive pressure within the enclosure, and had a pop-off valve to vent excess pressure. The electronics consisted of about a dozen circuit cards built with discrete transistors. The capacities of these units were amusingly small by modern standards: the first one that I had direct experience with, held something like 128K bytes.
BMW Cars Vulnerable To Blank Key Attack
My '73 2002 was great fun (on good days at least), but by 1988 it had become difficult to obtain certain parts (like the original air cleaner) needed to pass California emissions visual inspection, much less functional tests.
Finally, it developed mysterious electrical problems that made it stop running at inopportune moments. Despite the fact that the car was dead simple by comparison with anything modern, I never was able to diagnose the problem, and ended up giving that car up in favor of a Honda.
That 1988 Honda now has mysterious electrical problems that make it stop running at inopportune moments. Some of these clearly are due to deterioration of wiring insulation and electrical connectors on the maze of emissions and fuel injection components. Connectors for e.g. thermal sensors onto the wiring harness, are arcane proprietary things that eventually fail and are not available as separate replacement parts. This necessitates improvised reconstruction.
Canadian Scientists Bind High-Temp Superconductor Components With Scotch Tape
Interfacial effects in electronic materials are interesting.
Alves et al reported [Nature Materials 7, 574 (2008)] high conductivity (metallic-like, not superconductive) at a junction obtained by simply placing the faces of thin crystals of two very poor organic conductors (TTF and TCNQ) into contact and allowing the crystals to self-laminate.
Interesting questions arise, including whether the conductivity is nearly 2-dimensional rather than fully 3-dimensional.
I tried to investigate this in an undergrad project, but a number of technical difficulties could not be surmounted within the available time and resources.
What's your usual coffee-making method?
Actually it's PSVT: paroxysmal supraventricular tachycardia. Paroxysmal: sudden. Supraventricular: originates in some part of the heart above the ventricles. Tachycardia: rapid heart rate.
One cause can be small lesions that disrupt the normal organization and smooth evolution of electrical flow through the heart cycle. The effect can be like a not-quite-stable oscillator suddenly beginning to run at a harmonic rather than the intended fundamental frequency.
It's not usually especially dangerous but it can be very frightening. I feel that the anxiety around episodes can make them longer and worse.
Ask Slashdot: How Many of You Actually Use Math?
I have lived on both sides of the fence, having written code for 35 years having failed second quarter calculus and thus the entire university program. After 35 years, I took a break from work, went back to school, passed 4 semesters of calculus and many other courses, and came out with a BS in Physics at an amusingly advanced age.
In the course of my first-segment career, there was were a couple of projects where I had to rely upon someone with greater math background and an expensive MATLAB DSP application package.
The first project was a low-jitter timing subsystem, where a device needed to synchronize to timing derived from a signal from a master device. I coded it, then used a combination of fragmentary digital filter experience that I'd picked up on a couple of silly personal projects over the years, and partially informed intuition, to run the filter algorithm at two different rates: a high (but CPU-expensive) rate for acquisition (where the abstract design failed), and a lower rate, exactly according to the abstract design, for tracking.
The background that I received from 4 semesters of calculus (that included a skeletal introduction to differential equations) might have helped here, but it would not have been sufficient.
The second project was a digital payload processor / modulator. I initiated and functionally specified much of the project (which mostly was an implementation of certain published standards), but it required contributions from 3 PhD researchers with evolving expertise in CIC filter design, to make the implementation feasible in a modern FPGA with integrated multiplier/accumulator blocks.
My contribution consisted mostly of generic software, but there was one area where I had to quickly try to teach myself some mathematics, and it was mathematics that would not be taught in undergrad physics, and most likely is not universally taught in other than cursory treatment, in undergrad comp. sci. programs: finite field arithmetic (error control coding). The objective here was to examine whether a legacy implementation whose design rationale had not been adequately documented, was truly equivalent to a published standard (it was, but I discovered a subtle gotcha), and to validate a proposed implementation against the standard.
What arguably has been most valuable after emerging from even a late and rudimentary education in a scientific discipline, back into software work, is having been exposed and held to a scientific standard of rigor. This stands in devising a sufficient and feasible scheme of measurement, in collecting sufficient data, in formulating claims that are supported by data rather than mere belief, and in making clear when the line between data and belief must be drawn and crossed. At times it turns me into an organizationally inconvenient holy terror. It also allows me to deeply examine and locate defects that are potential product and reputation killers, to endure hypothesis-destroying experiments, and to emerge with a clear understanding of the nature of the defect, and how to cure it.
I do wish that I'd had time and energy for more math: a practical course in statistics and design of experiments, preferably one designed to teach students who are well along in some field of study, rather than as an early weed-out for weak students in oversubscribed majors. The introductory statistics course at my university, which mercifully is not required in the physics major, is of the latter type and is generally reviled, even by the capable.
Managing Servers In the Frigid Cold
Circuits must be specifically designed and qualified for low temperature operation.
Common low-cost ceramic capacitor dielectrics (Z5U) are rated only to +15C and are useless by 0C. Y5P/Y5V are rated to -30C. X5R / X7R will get you to -55C.
Aluminum electrolytics are useless at low temperature; tantalum is required.
Neutrino-Powered Financial Trading In Our Future?
Either I don't understand the consequences of a neutrino:nucleon reaction cross-section on the order of 10^-43 m^2, or a technology writer is bafflegabbing.
I most recently switched ISPs ...
How Do You Cool Your Data Center / Server Room?
Delivered by sharks with frickin' laser beams attached to their heads.