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    Optical Build a ballast for an Osram Hg-Cd/10 spectral lamp

    I am looking for a layout for a ballast for driving an Osram Hg-Cd/10 spectral lamp: Thank you! Florian
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    Source of chloride in seawater

    Most of the salt in seawater is sodium chloride. From my understanding, the primary source of sodium is the errosion of magmatic rocks, which contain lots of feldspars, the most abundant mineral in earth crust. On the other hand, I don't know any abundant magmatic mineral which contains...
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    A permutation question

    Remark: This is not homework Given a vector a of permuted numbers from 1 to n, I want to construct the vector b which contains in the ith position the number of elemets of a_j with j <i which are larger than a_i. E.g. a=(5,2,3,1,4), b=(0,1,1,3,1). Is there an algorithm which scales faster...
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    What is a "lumachelic limestone"?

    In the description of a fosil site, I ran into the term "lumachelic limestone". Does anybody know, what this means?
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    A Soft photons and the ETH interpretation of QM

    As the thread on Jürg Fröhlich's paper on the "ETH interpretation" of QM has been closed, I want to consider here a specific point. Fröhlich points out that this interpretation requires the inclusion of massless particles and I think this is the key to getting a physical understanding...
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    Where has the "physics news" link has gone to?

    Where has the "physics news" tab has gone to?
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    The making of vintage precision instruments

    Ever when I see one of these beautiful brass scientific instruments, like microscopes, telescopes, goniometers etc. from the 19th century, I wonder how they have been actually made and whether I could learn how to do this. I think that most of gears used in the construction of these pieces were...
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    NurdRage finally got Pyrimethamine from household chemicals

    I wanted to bring to your attention what I think this is one of the most ambitious chemistry projects to be found on youtube: A guy with the pseudonym of NurdRage or Dr. Butyllithium tried to synthesise a medication called Pyrimethamine or Daraprim which is effective against Toxoplasmosis from...
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    Unknown cretaceous fossil

    Today, I found the following fossil in calcareous deposits from cental spain which are probably from the upper cretaceous. The little pores visible on the outside, make me think off a coral. What do you think?
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    Stimulated Raman in linear regime

    In the course of another thread I was lend to think about the Raman effect. I also read about the stimulated Raman effect and found that it is usually described as a third order nonlinear effect where a power of two of E is assumed to drive the nuclear vibration. I don't quite see why this is...
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    Java Editable html table and javascript

    Hi, I would like to provide a tool for some calculation as a html table whose values the user may change and subsequently submit a JS script which uses these values as input. Do you know of some easy to use library to get the data from the table into JS? Thank you, DrDu
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    A Nonlinear regression which can be partially reduced to linear regression

    I encountered several times the following problem: Say I have a variable y dependent in a nonlinear way on m parameters ##\{x_i\}##, with ##i \in \{1,m\}##. However there is a linear relation between n>m functions ##f_j\in{x_i}##, i.e., ##y=\sum_j z_j f_j##. So I can get a solution of my problem...
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    How to access the news on mobile phone

    I enjoy very much reading the new "news" on my pc, but the tags forums, videos, news, insights info and search aren't shown on my smartphone. I simply use the browser to view the site and not the PF application. How can I access the news?
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    I Combinatorics problem on drawing sample with given mean

    I am faced with a problem in combinatorics while trying to set up a pool. Instead of explaining my real problem, I prefer to give you a simplified example: Say I am given a population of N persons of varying height ##h_i##. The height of each person ##i## in the population is known to me. Now I...
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    A Cauchy convolution with other distribution

    I have a set of data which are probably convolutions of a Cauchy distribution with some other distribution. I am looking for some model for this other distribution so that a tractable analytic formula results. I know that the convolution Cauchy with Cauchy is again Cauchy, but I want the other...
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    Looking for a movie on spies and a TV show from the 50's

    I am looking for the name of a movie which was an absurd combination of spy stuff and a TV show from the 50ies where young couples could win travels and fridges in a quiz. Any help?
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    I Basic Design of Experiments

    I need to build up knowledge about Design of Experiments and have a fundamental question about the real goal of DoE. Most classical texts start with discussing in considerable detail full factorial design plans where each factor only has two levels. The underlying statistical model is...
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    News Bus accident killed 13 Erasmus students in Catalonia

    Maybe you have heard about this horrible accident in the spanisch province catalonia. While there has been some speculation about whether the driver has fallen asleep, I would like to draw attention to another point: The driver seemingly has only been injured slightly. I guess that the students...
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    Antibodies against hormones of the own body

    Recently I came upon the description of medical tests for hormones like cortisole, or tyroid hormones like T3 and T4, which use polyclonal antibodies from hamsters, pigs, sheep or thelike. As far as I know, they are obtained by vacunating these animals and harvesting the antibodies from their...
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    Question on declaration and definition

    When I am creating an object via car audi audi=new car() what does the first line actually do? In non object oriented languages, some declaration like int mynumber to reserve a certain kind of bytes. But how does the compiler know what to reserve for the variable audi knowing it is of...
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    Event for scheduler when samba starts in windows 7

    I want to start a program with the event sheduler in windows 7 when samba establishes a connection for a network drive. I am not a windows guy. How do I do this?
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    Help with numerical integration

    I want to integrate a function numerically from 0 to infinity where for small x ##f(x)\sim x^{-5/2} \exp(-a/x)## and for large x ##f(x) \sim \exp(-bx)##. How do I best treat the steep rise for small x?
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    Any SAS users (beside me) in this forum?

    I am using SAS (sweat and suffer) for many years now on a daily basis in work and it would be nice to be able to exchange here some problems. However, searching for "SAS" in physics forums only turns up tons of post related to science advisors (SAs).
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    Characterization of a gauge theory in terms of observables

    Although I have a good understanding of how to do calculations in gauge field theory, I am still dissatisfied with my understanding of why we use them in the first place. From a philosophical point, it should be possible to characterize a gauge theory in terms of observables only. I suppose one...
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    Can't connect via the android app

    For some days now, I can't connect via the android app. I only get a message "trying to connect to the server".
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    Understanding a Colpitts oscillator

    As I was playing around with a small AM oscillator, I thought it would be time to understand how they actually work. I am referring to the 3rd picture on this page (base mode): Given the working point of the transistor, I describe its...
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    News Basel II: Numerical instabilities to stabilize banks?

    Oops, I was to quick here. At least, there is no instability. Nevertheless I would write ##\mathrm{Corr}(R)=0.12(1+\exp(-50 \mathrm{PD}))## instead of Correlation (R) = 0.12 × (1 – EXP (-50 × PD)) / (1 – EXP (-50)) + 0.24 × [1 - (1 - EXP(-50 × PD))/(1 - EXP(-50))]
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    History: Equations of a gyrostatic aether

    I would be interested in the equations of a gyrostatic ether as brought up by McCullach and Lord Kelvin, best in a modern notation. Before people jump on me: I an not interested in questioning modern theories like SR but rather in the extensions of continuum mechanics these theories go in hand with.
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    Calculating microscopic permittivity

    It has been quite some years since I last used quantum chemistry software. Now I would like to use some program which allows the calculation of the microscopic omega and k-dependent dielectric function (tensor) for periodic crystals. Any proposals?
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    Negative refraction, meta materials, no quest for chemists?

    Recently, I have read a lot about the physics behind negative refraction, super lenses, meta-materials and the like and I think I understood the theory to quite some detail. Negative refraction was predicted first by sowiet physicists around Mandelshtam [1,2], and, a paper by Veselago [3,4]...