Daylight wasting time

In South Africa, efforts to introduce summer ("daylight saving") time (DST) has and will always by stymied by the considerable east-west extent of the country. During the summer, we have the same time as Namibia - which is then on "daylight saving" time - and there is no reason for the time in Cape Town, on the same latitude as Namibia, to be different. Should the western part of the country then switch to the time zone of Namibia (UTC+1 with DST), the eastern part would surely stay on the present (UTC+2) time zone, perhaps introducing DST and perhaps not. The confusion generated by such a move would be considerable. The blog Freakonomics has furthermore just revealed the environmental effect of DST to be not negligible but actually negative. A study,

Does Daylight Saving Time Save Energy? Evidence From a Natural Experiment in Indiana by Matthew J. Kotchen and Laura E. Grant

has just revealed that DST increases the residential demand for electricity in the US state of Indiana - probably due to increase demand for heating and cooling. Ouch!

Half a day of Ubuntu blues

Like Linux geeks all over the planet, I was excited about last Friday's release of version 8.10 of Ubuntu Linux - Intrepid Ibex. I had tried pre-release versions on my Dell laptop without any problem and was very impressed by the option Auto GSM Connection in the network manager. This feature allowed me to connect to UMTS/GPRS networks using the popular Huawei E220 3G modem. All I needed to enter was the PIN for the SIM card, and the connection just appeared. Given the fragility of our monopoly fixed-line provider and the fickle network at Big U, where I collect a monthly stipend, the Auto GSM features is a great addition - even to desktops.

With almost no trepidation at all, I proceeded to update my Dell desktop in the office, using a downloaded CD image and updating additional packages over the Internet. In other words, this was not a clean install but a genuinely "hot" upgrade. After booting, though, the monitor went into hibernation after briefly showing... nothing at all. Fortunately the consoles (Ctrl-Alt-F1 and F2) were available and I tried to slowly discover what was going on. After I managed to start a graphical VNC session from my home computer, I was convinced that the problem was not serious. Nevertheless, it still took me about an hour this morning to stumble on the idea of removing all NVidia drivers. Bingo - my desktop was back in good shape, running Ibex.

Judge refuses DoC's request to appeal

The Minister of Communications, Dr Ivy Matsepe-Cassaburri, has been denied leave to appeal (see Minister scratches back below) in the judgement in favour of Altech's right to have its value-added network service (VANS) licence converted into an individual electronic communications network service (I-ECNS) licence, allowing it to deploy a telecommunications network. It is anyone's guess what she might try next, but - for now - industry and private enterprise are safe.

Sources

1. Minister scratches back http://www.cyphafrica.com/2008/09/minister-scratches-back.html
   


2. Ispa welcomes ruling on Matsepe Cassaburi’s Altech appeal http://www.engineeringnews.co.za/article.php?a_id=146686
   

Malema's matric and Home Affairs

The matric (school-leaving exam in SA) results of Mr Julius Malema, leader of the ANC Youth League, have been circulating in the country over the past week or so. This gentelman, who is famously prepared to "kill" to support "the revolution" managed to get 4% (an H symbol) in the exam in Standard Grade Mathematics. He did manage 57% in History (also on Standard Grade) which is, presumably, more important for a politician. Now, I do not doubt that there were not many opportunities for academic advancement where Mr Malema grew up and although he should perhaps have tried better nevertheless, I am most surprised that no-one has commented about the spelling of "mother tongue" with a Q on the, apparently, official print-out.

Lest anyone believe that the spelling mistake or typo indicates the Malema document not to be genuine, I present the image on the left from an official receipt from the Department of Home Affairs (for a passport application), dated earlier this month. Somehow they got the Afrikaans for "affairs" as "sakke" (meaning "bags") instead of "sake". I have to wonder whether this is the case at every office of Home Affairs or whether it is only at this office and - in that case - whether all the offices set up their cash registers or printers manually.


Also see

1. "Malema’s (lacklustre) matric results", The Sowetan, 2008-10-24, http://www.sowetan.co.za/News/Article.aspx?id=870114

Prime number formulae

Last week, I was interviewed on ClassicFM in the show The Internet Economy about GIMPS - the Great Internet Mersenne Prime Search. During the interview, I said that there was no formula for generating prime numbers, by which I meant - of course - that there is no easy formula. As Eric Weisstein writes in the authoritative MathWorld,

"all such formulas require either extremely accurate knowledge of some unknown constant, or effectively require knowledge of the primes ahead of time in order to use the formula."

He is writing about formulae that are known to produce the n-th prime p(n) on input n. There are other kinds of prime-generating formulae. Consider, for example, the formula described by Eric Rowland in a recent issue of the Journal of Integer Sequences. Rowland's sequence is defined by

a(n) = a(n-1) + gcd(n, a(n-1))

and a(1) = 7. He shows that the values taken on by a(n)-a(n-1) are always either one or prime. However, it is not known whether all primes are produced by this sequence, and I expect it not to be the case! Another approach is to consider the values taken on by a polynomial with integer coefficients and in several unknowns. There exist polynomials for which all the positive values are all prime and in fact there exist such polynomials for which all prime numbers are found among the positive values. These prime-generating polynomials (about which more in the MathWorld article cited below) are, however, not a particularly efficient way of generating prime numbers.


Sources

1. Podcast of the 3 October 2008 edition of The Internet Economy on ClassicFM http://tinyurl.com/3m2gug
   


2. Weisstein, Eric W. "Prime Formulas." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/PrimeFormulas.html
   


3. Rowland, Eric S. "A Natural Prime-Generating Recurrence." Journal of Integer Sequences, Vol. 11 (2008), Article 08.2.8 http://www.cs.uwaterloo.ca/journals/JIS/VOL11/Rowland/rowland21.html
   


4. Weisstein, Eric W. "Prime-Generating Polynomial." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Prime-GeneratingPolynomial.html