Tuesday, May 7, 2013
Friday, May 3, 2013
Great article from 1941 on the Varian brothers
http://upload.wikimedia.org/wikipedia/commons/6/61/The_Klystron_boys%2C_Radio%27s_miracle_makers_in_Saturday_Evening_Post_Feb_8%2C_1941.pdf
Great article on the Varian brothers from 1941. Reminded me of the book Tuxedo Park by Jennet Conant.
Great article on the Varian brothers from 1941. Reminded me of the book Tuxedo Park by Jennet Conant.
Interesting stat on Marginal Corporate Income Tax Rates
|
Country
|
Marginal Corporate
Income Tax Rate
|
|
United States
|
40%
|
|
Japan
|
38%
|
|
France
|
33.3%
|
|
Australia
|
30%
|
|
Germany
|
29.5%
|
|
China
|
25%
|
|
South Korea
|
24.2%
|
|
United Kingdom
|
23%
|
|
Sweden
|
22%
|
|
Global Average
|
24%
|
Source: KPMG
Thursday, May 2, 2013
Running again
I am hoping to start running more frequently again. The greatest part about signing up for races, is you can publicly shame yourself with lousy running times, which should serve as a motivator for future performance.
One site called Athlinks, accumulates some of your results and can even compare your results to other runners who have ran in the same races as you head to head. This site doesn't have all my results, but you can even submit race results to it. For instance it currently shows that i haven't ran a race since 2010, but there is at least one race from 2011 that should be posted.
Time to sign up for some races, I plan to run a slow 5-k this month.
For results check it out. Athlinks
http://athlinks.com/myresults/73871534/David-Roesener.aspx
And yes those horribly slow marathon results are mine.
One site called Athlinks, accumulates some of your results and can even compare your results to other runners who have ran in the same races as you head to head. This site doesn't have all my results, but you can even submit race results to it. For instance it currently shows that i haven't ran a race since 2010, but there is at least one race from 2011 that should be posted.
Time to sign up for some races, I plan to run a slow 5-k this month.
For results check it out. Athlinks
http://athlinks.com/myresults/73871534/David-Roesener.aspx
And yes those horribly slow marathon results are mine.
Wednesday, May 1, 2013
Notes on VNC screen refresh issues
http://tightvnc.10971.n7.nabble.com/No-screen-refresh-using-TightVNC-client-on-XP-to-Vine-Server-server-on-OS-X-td2397.html
http://tightvnc.10971.n7.nabble.com/No-screen-refresh-using-TightVNC-client-on-XP-to-Vine-Server-server-on-OS-X-td2397.html
http://tightvnc.10971.n7.nabble.com/No-screen-refresh-using-TightVNC-client-on-XP-to-Vine-Server-server-on-OS-X-td2397.html
VNC install for remote viewing
Installing x11vnc on Fedora Core
This is a very short guide how to install x11vnc to your Fedora Core.
x11vnc allows one to view remotely and interact with real X displays (i.e. a display corresponding to a physical monitor, keyboard, and mouse) with any VNC viewer. In this way it plays the role for Unix/X11 that WinVNC plays for Windows.
x11vnc is by far the easiest available vnc server for Linux. Just download, configure/make, and off you go! And it works like a charm over ssh tunnel!
Here's how I installed x11vnc on my FC8:
1) Download .tar.gz from http://www.karlrunge.com/x11vnc/
2) Make sure you have X Software Development packets installed on your FC. To be sure, just open your sytem >> add/remove software, scroll down to development, and make sure you have X on your "x11 development".
3) After downloading http://www.karlrunge.com/x11vnc/x11vnc-0.9.4.tar.gz, just tar zxvf x11vnc-0.9.4.tar.gz, ./configure, make and make install
4) Now you have your x11vnc server ready to be tested... It's propably installed at /usr/bin/x11vnc, and you can test drive it by just typing the command "x11vnc".
x11vnc allows one to view remotely and interact with real X displays (i.e. a display corresponding to a physical monitor, keyboard, and mouse) with any VNC viewer. In this way it plays the role for Unix/X11 that WinVNC plays for Windows.
x11vnc is by far the easiest available vnc server for Linux. Just download, configure/make, and off you go! And it works like a charm over ssh tunnel!
Here's how I installed x11vnc on my FC8:
1) Download .tar.gz from http://www.karlrunge.com/x11vnc/
2) Make sure you have X Software Development packets installed on your FC. To be sure, just open your sytem >> add/remove software, scroll down to development, and make sure you have X on your "x11 development".
3) After downloading http://www.karlrunge.com/x11vnc/x11vnc-0.9.4.tar.gz, just tar zxvf x11vnc-0.9.4.tar.gz, ./configure, make and make install
4) Now you have your x11vnc server ready to be tested... It's propably installed at /usr/bin/x11vnc, and you can test drive it by just typing the command "x11vnc".
Referenced in: Evaluation of multiple image-based modalities for image-guided radiation
The probability of correct target dosage: dose-population histograms for deriving treatment margins in radiotherapy
Abstract
Purpose: To provide an analytical description of the effect of random and systematic geometrical deviations on the target dose in radiotherapy and to derive margin rules.Methods and Materials: The cumulative dose distribution delivered to the clinical target volume (CTV) is expressed analytically. Geometrical deviations are separated into treatment execution (random) and treatment preparation (systematic) variations. The analysis relates each possible preparation (systematic) error to the dose distribution over the CTV and allows computation of the probability distribution of, for instance, the minimum dose delivered to the CTV.
Results: The probability distributions of the cumulative dose over a population of patients are called dose-population histograms in short. Large execution (random) variations lead to CTV underdosage for a large number of patients, while the same level of preparation (systematic) errors leads to a much larger underdosage for some of the patients. A single point on the histogram gives a simple “margin recipe.” For example, to ensure a minimum dose to the CTV of 95% for 90% of the patients, a margin between CTV and planning target volume (PTV) is required of 2.5 times the total standard deviation (SD) of preparation (systematic) errors (Σ) plus 1.64 times the total SD of execution (random) errors (σ′) combined with the penumbra width, minus 1.64 times the SD describing the penumbra width (σp). For a σp of 3.2 mm, this recipe can be simplified to 2.5 Σ + 0.7 σ′. Because this margin excludes rotational errors and shape deviations, it must be considered as a lower limit for safe radiotherapy.
Conclusion: Dose-population histograms provide insight into the effects of geometrical deviations on a population of patients. Using a dose-probability based approach, simple algorithms for choosing margins were derived.
Monday, April 29, 2013
Thursday, April 25, 2013
Thyratron replacement tonight
Thyratron is a switching tube and is essentially a gas filled triode. When the grid is charged positively, the electrons flow from the cathode to the anode. The gas within the tube ionizes and conducts larger currents than do other switching devices. At the end of the pulse, the grid voltage is removed, preventing further current flow while the pulse forming network recharges. This cycle is repeated between 50 and 500 times per second.
Notes: 4252013 Sh, WI Siemens Primus
Virtual source position for electrons
Today the concept of virtual source position for electrons came up.
I looked it up on my blog and had posted from an unknown reference a few years ago and never included the information.
8.1.3. Inverse square law (virtual source position)
In contrast to a photon beam, which has a distinct focus located at the
accelerator X ray target, an electron beam appears to originate from a point in
space that does not coincide with the scattering foil or the accelerator exit
window. The term ‘virtual source position’ was introduced to indicate the
virtual location of the electron source.
The effective source to surface distance (SSD) for electron beams
(SSDeff) is defined as the distance from the virtual source position to the point
of the nominal SSD (usually the isocentre of the linac). The inverse square law
may be used for small SSD differences from the nominal SSD to make
corrections to the absorbed dose for variations in air gaps between the patient
surface and the applicator.
There are various methods to determine the SSDeff. One commonly used
method consists of measuring the dose at various distances from the electron
applicator by varying the gap between the phantom surface and the applicator
(with gaps ranging from 0 to 15 cm). In this method, doses are measured in a
phantom at the depth of maximum dose zmax, with the phantom first in contact
with the applicator (zero gap) and then at various distances g from the
applicator. Suppose I0 is the dose with zero gap (g = 0) and Ig is the dose with
gap distance g. It follows then from the inverse square law that:
I looked it up on my blog and had posted from an unknown reference a few years ago and never included the information.
8.1.3. Inverse square law (virtual source position)
In contrast to a photon beam, which has a distinct focus located at the
accelerator X ray target, an electron beam appears to originate from a point in
space that does not coincide with the scattering foil or the accelerator exit
window. The term ‘virtual source position’ was introduced to indicate the
virtual location of the electron source.
The effective source to surface distance (SSD) for electron beams
(SSDeff) is defined as the distance from the virtual source position to the point
of the nominal SSD (usually the isocentre of the linac). The inverse square law
may be used for small SSD differences from the nominal SSD to make
corrections to the absorbed dose for variations in air gaps between the patient
surface and the applicator.
There are various methods to determine the SSDeff. One commonly used
method consists of measuring the dose at various distances from the electron
applicator by varying the gap between the phantom surface and the applicator
(with gaps ranging from 0 to 15 cm). In this method, doses are measured in a
phantom at the depth of maximum dose zmax, with the phantom first in contact
with the applicator (zero gap) and then at various distances g from the
applicator. Suppose I0 is the dose with zero gap (g = 0) and Ig is the dose with
gap distance g. It follows then from the inverse square law that:
Swiss Society of Radiobiology and Medical Physics
Swiss Society of Radiobiology and Medical Physics Member of the European Federation of Organisations for Medical Physics (EFOMP) and the International Organization for Medical Physics (IOMP) Quality Control of Medical Electron Accelerators
http://www.sgsmp.ch/r11qca-e.pdf
http://www.sgsmp.ch/r11qca-e.pdf
Book in the works
I haven't posted much to this blog in a few years, it was originally hosted at medicalphysicsinfo.blogspot.com I have recently migrated it to my personal blog.
Last year I discussed with the friend the idea of writing an interesting book related to my career and some of the pioneers responsible for the equipment. It is in the research stage, but I hope to publish some excerpts from it as they become available. I am still very busy clinically so work on this project, is accomplished sporadically. While much of this blog may discuss my career, it is certain to also feature my other interests including music and exercise. As you can see I already posted one of my favorite training methods for running your best mile.
Last year I discussed with the friend the idea of writing an interesting book related to my career and some of the pioneers responsible for the equipment. It is in the research stage, but I hope to publish some excerpts from it as they become available. I am still very busy clinically so work on this project, is accomplished sporadically. While much of this blog may discuss my career, it is certain to also feature my other interests including music and exercise. As you can see I already posted one of my favorite training methods for running your best mile.
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