Category Archives: History

Egypt Looters Ransack Archaeological Sites | @pritheworld

Since Hosni Mubarak’s government fell last year, many of Egypt’s museums have been looted.

And the looting has gone beyond museums — now criminals are digging up archaeological sites and stealing their treasures.

Anchor Marco Werman speaks with Carol Redmount, an archaeologist at the University of California, about her efforts to stop the looting in Egypt.

Redmount described the looters stealing from El-Hibeh’s archaeological dig as “essentially a gang of criminals, headed by a master criminal, who escaped from jail after the revolution.”

via Egypt Looters Ransack Archaeological Sites | @pritheworld.

Photo Gallery: Parts with Tin Whiskers

What are Tin Whiskers?

Tin whiskers are electrically conductive, crystalline structures of tin that sometimes grow from surfaces where tin (especially electroplated tin) is used as a final finish.  Tin whiskers have been observed to grow to lengths of several millimeters (mm) and in rare instances to lengths in excess of 10 mm.  Numerous electronic system failures have been attributed to short circuits caused by tin whiskers that bridge closely-spaced circuit elements maintained at different electrical potentials.


Tin whiskers are not a new phenomenon.  Indeed, the first published reports of tin whiskers date back to the 1940s and 1950s. Tin is only one of several metals that is known to be capable of growing whiskers.  Other examples of metals that may form whiskers include some tin alloys, zinc, cadmium, indium, antimony, silver among others . 


People sometimes confuse the term “whiskers” with a more familiar phenomenon known as “dendrites” commonly formed by electrochemical migration processes.  Therefore, it is important to note here that whiskers and dendrites are two very different phenomena. A “Whisker” generally has the shape of a very thin, single filament or hair-like protrusion that emerges outward (z-axis) from a surface.  “Dendrites”, on the other hand, form in fern-like or snowflake-like patterns growing along a surface (x-y plane) rather than outward from it.  The growth mechanism for dendrites is well-understood and requires some type of moisture capable of dissolving the metal (e.g., tin) into a solution of metal ions which are then redistributed by electromigration in the presence of an electromagnetic field.  While the precise mechanism for whisker formation remains unknown, it is known that whisker formation does NOT require either dissolution of the metal NOR the presence of electromagnetic field

via Photo Gallery: Parts with Tin Whiskers.

IMSLP/Petrucci Music Library: Free Public Domain Sheet Music

IMSLP stands for International Music Score Library Project. The logo is a capital letter A, taken from the very first press-printed book of polyphonic music, theHarmonice Musices Odhecaton, published in 1501. Its printer, Ottaviano Petrucci, is this library’s namesake.

Browse scores

IMSLP/Petrucci Music Library: Free Public Domain Sheet Music.

Statistical methods for assessing agreement between two methods of clinical measurement


In clinical measurement comparison of a new measurement technique with an established one is often needed to see whether they agree sufficiently for the new to replace the old. Such investigations are often analysed inappropriately, notably by using correlation coefficients. The use of correlation is misleading. An alternative approach, based on graphical techniques and simple calculations, is described, together with the relation between this analysis and the assessment of repeatability.


Clinicians often wish to have data on, for example, cardiac stroke volume or blood pressure where direct measurement without adverse effects is difficult or impossible. The true values remain unknown. Instead indirect methods are used, and a new method has to be evaluated by comparison with an established technique rather than with the true quantity. If the new method agrees sufficiently well with the old, the old may be replaced. This is very different from calibration, where known quantities are measured by a new method and the result compared with the true value or with measurements made by a highly accurate method. When two methods are compared neither provides an unequivocally correct measurement, so we try to assess the degree of agreement. But how?

The correct statistical approach is not obvious. Many studies give the product-moment correlation coefficient (r) between the results of the two measurement methods as an indicator of agreement. It is no such thing. In a statistical journal we have proposed an alternative analysis, [1] and clinical colleagues have suggested that we describe it for a medical readership.

Most of the analysis will be illustrated by a set of data (Table 1) collected to compare two methods of measuring peak expiratory flow rate (PEFR).



The second step is usually to calculate the correlation coefficient (r) between the two methods. For the data in fig 1, r = 0.94 (p < 0.001). The null hypothesis here is that the measurements by the two methods are not linearly related. The probability is very small and we can safely conclude that PEFR measurements by the mini and large meters are related. However, this high correlation does not mean that the two methods agree:

(1) r measures the strength of a relation between two variables, not the agreement between them. We have perfect agreement only if the points in fig 1 lie along the line of equality, but we will have perfect correlation if the points lie along any straight line.

(2) A change in scale of measurement does not affect the correlation, but it certainly affects the agreement. For example, we can measure subcutaneous fat by skinfold calipers. The calipers will measure two thicknesses of fat. If we were to plot calipers measurement against half-calipers measurement, in the style of fig 1, we should get a perfect straight line with slope 2.0. The correlation would be 1.0, but the two measurements would not agree — we could not mix fat thicknesses obtained by the two methods, since one is twice the other.

(3) Correlation depends on the range of the true quantity in the sample. If this is wide, the correlation will be greater than if it is narrow. For those subjects whose PEFR (by peak flow meter) is less than 500 l/min, r is 0.88 while for those with greater PEFRs r is 0.90. Both are less than the overall correlation of 0.94, but it would be absurd to argue that agreement is worse below 500 l/min and worse above 500 l/min than it is for everybody. Since investigators usually try to compare two methods over the whole range of values typically encountered, a high correlation is almost guaranteed.

(4) The test of significance may show that the two methods are related, but it would be amazing if two methods designed to measure the same quantity were not related. The test of significance is irrelevant to the question of agreement.

(5) Data which seem to be in poor agreement can produce quite high correlations. For example, Serfontein and Jaroszewicz [2] compared two methods of measuring gestational age. Babies with a gestational age of 35 weeks by one method had gestations between 34 and 39.5 weeks by the other, but r was high (0.85). On the other hand, Oldham et al. [3] compared the mini and large Wright peak flow meters and found a correlation of 0.992. They then connected the meters in series, so that both measured the same flow, and obtained a “material improvement” (0.996). If a correlation coefficient of 0.99 can be materially improved upon, we need to rethink our ideas of what a high correlation is in this context. As we show below, the high correlation of 0.94 for our own data conceals considerable lack of agreement between the two instruments.


It is most unlikely that different methods will agree exactly, by giving the identical result for all individuals. We want to know by how much the new method is likely to differ from the old: if this is not enough to cause problems in clinical interpretation we can replace the old method by the new or use the two interchangeably. If the two PEFR meters were unlikely to give readings which differed by more than, say, 10 l/min, we could replace the large meter by the mini meter because so small a difference would not affect decisions on patient management. On the other hand, if the meters could differ by 100 l/min, the mini meter would be unlikely to be satisfactory. How far apart measurements can be without causing difficulties will be a question of judgment. Ideally, it should be defined in advance to help in the interpretation of the method comparison and to choose the sample size.

The first step is to examine the data. A simple plot of the results of one method against those of the other (fig 1) though without a regression line is a useful start but usually the data points will be clustered near the line and it will be difficult to assess between-method differences. A plot of the difference between the methods against their mean may be more informative. Fig 2 displays considerable lack of agreement between the large and mini meters, with discrepancies of up to 80 l/min, these differences are not obvious from fig 1. The plot of difference against mean also allows us to investigate any possible relationship between the measurement error and the true value. We do not know the true value, and the mean of the two measurements is the best estimate we have. It would be a mistake to plot the difference against either value separately because the difference will be related to each, a well-known statistical artefact. [4]

via Statistical methods for assessing agreement between two methods of clinical measurement.

Comparing methods of measurement: why plotting difference against standard method is misleading

My reasons for jumping into stats was to directly compare two measurement methods… with multiple trials, on multiple ILDs (inter-landmark distances).  I don’t really go for “funny name, lol” things, but when Bland and Borg are cited in the same paper on stats (which I long thought of [cluelessly/ignorantly] as boring).  Eponysterical.

But getting real, the issues raised by Bland and Altman sound pretty interesting, and they raise the issue that many tests of this sort may be using misleading information… I have tried to duplicate their methods in my own little H.T.-UGR/Inquiry Study.




When comparing a new method of measurement with a standard method, one of the things we want to know is whether the difference between the measurements by the two methods is related to the magnitude of the measurement. A plot of the difference against the standard measurement is sometimes suggested, but this will always appear to show a relationship between difference and magnitude when there is none. A plot of the difference against the average of the standard and new measurements is unlikely to mislead in this way. This is shown theoretically and illustrated by a practical example using measurements of systolic blood pressure.


In earlier papers [1,2] we discussed the analysis of studies of agreement between methods of clinical measurement. We had two issues in mind: to demonstrate that the methods of analysis then in general use were incorrect and misleading, and to recommend a more appropriate method. We saw the aim of such a study as to determine whether two methods agreed sufficiently well for them to be used interchangeably. This led us to suggest that the analysis should be based on the differences between measurements on the same subject by the two methods. The mean difference would be the estimated bias, the systematic difference between methods, and the standard deviation of the differences would measure random fluctuations around this mean. We recommended 95% limits of agreement, mean difference plus or minus 2 standard deviations (or, more precisely, 1.96 standard deviations), which would tell us how far apart measurements by the two methods were likely to be for most individuals.


via Comparing methods of measurement: why plotting difference against standard method is misleading.

Bertrand Russell and F.C. Copleston Debate the Existence of God, 1948 | Open Culture

On January 28, 1948 the British philosophers F.C. Copleston and Bertrand Russell squared off on BBC radio for a debate on the existence of God. Copleston was a Jesuit priest who believed in God. Russell maintained that while he was technically agnostic on the existence of the Judeo-Christian God–just as he was technically agnostic on the existence of the Greek gods Zeus and Poseidon–he was for all intents and purposes an atheist.

via Bertrand Russell and F.C. Copleston Debate the Existence of God, 1948 | Open Culture.

The Horse, the Wheel, and Language – David W. Anthony – Book Review – New York Times

Prepare for a massive series on PIE.  Many folks love PIE.  Renfrew, Anatolia, Kurgan culture Gimbutas, Mallory… Will try to hit it all (just because this article is first, has no bearing on “ranking” of positions.  Just have to start somewhere (yeah, this is a poor place to start, didn’t want to bookmark, or lose the link, so hey!)  Actually, I will return and resequence/recontextualize once I decide on more articles to use.

Where Proto-Indo-European came from and who originally spoke it has been a mystery ever since Sir William Jones, a British judge and scholar in India, posited its existence in the late 18th century. As a result, Anthony writes, the question of its origins was “politicized almost from the beginning.” Numerous groups, ranging from the Nazis to adherents of the “goddess movement” (who saw the Indo-Europeans as bellicose invaders who upended a feminine utopia), have made self-interested claims about the Indo-European past.

via The Horse, the Wheel, and Language – David W. Anthony – Book Review – New York Times.