Plaigiarise an American? The French would never do that!

May 21, 2008 at 11:07 am | | literature, science community, scientific integrity

I was recently doing a bit of reading and happened to have two papers on the same subject, short pulse amplification, on my desk at the same time. As I was reading the more recent paper I kept having the feeling that I had just read something very similar. Upon comparison I found that almost the entirety of the more recent paper was plaigiarised from the earlier paper. The French authors even stole a figure from the earlier paper, all without referencing. Ironically the figure that they stole happened to be figure 6 in the original and in their paper, so the text that I copied from the two manuscripts even has the same figure numbers in it! Check out the papers yourself to see just how low people can go in science.

This is excerpted from the 1998 paper by Backus et al.

materials due to the Pockels cells and polarizers can add high-order dispersion to an amplifier system, making it more difficult to recompress very short pulses. Nevertheless, regenerative amplifiers have also been used to generate pulses of 30 fs and shorter durations.102–104

A multipass preamplifier configuration differs from the regenerative amplifier in that, as its name suggests, the beam passes through the gain medium multiple times without the use of a cavity, as shown in Fig. 6(b). The particular geometry

This is excerpted from the 2001 paper by Cheriaux and Chambaret

materials due to the Pockels cells and polarizers can add high-order dispersion to an amplifier system, making the recompression more difficult for very short pulses. Nevertheless, regenerative amplifiers have also been used to
generate pulses of 30 fs and shorter duration [36, 37].

A multipass preamplifier configuration (figure 6(b)) differs from the regenerative amplifier in that, as its name suggests, the beam passes through the gain medium multiple times without the use of a cavity. The particular geometry

[UPDATE: I wanted to put in the copied figures. See my addition to David’s post below.

From the first paper:

From the later paper:

And there you have it. -Sam]

Rube Goldberg Science

July 13, 2007 at 8:27 am | | everyday science, grad life, stupid technology

Most people have probably heard of or seen pictures of so called Rube Goldberg Machines. These are extremely complicated apparatuses which do extremely simple tasks. Here is an example from the Rube Goldberg website.


This one could actually be useful for those grad students who have bosses that keep track of time in lab.

There are even Rube Goldberg Machine contests, in which teams try to design a machine that can use the greatest number of steps to complete a simple task.

Now, science is often complicated and it doesn’t need any extra help from us grad students to make it more complicated but I fell into the trap myself and let this be a warning to all those who think they have a really good idea… think again.

The required task is: Do a pump-probe anisotropy measurement using infrared light. Simple enough at face value, but all you visible spectroscopists out there must keep in mind that IR polarizers are ~1000 times worse than visible polarizers and there is no such thing as a broadband IR half wave plate. Tack onto that the fact that IR detectors are much less efficient that visible detectors and you’ve got a passel of stumbling blocks in front of you when you’re trying to do this experiment. I’ve tried a number of different techniques and because the IR polarizers and half wave plates are a little sketchy, transmission always seems to screw things up. So I thought to myself, what if we did everything using reflections! Then it would be achromatic and everything would be hunky dory. Here’s a schematic diagram of what the pump beam is subjected to in this scheme. The actual layout is much more complicated but I didn’t have a digital camera with me.


The periscope serves to change the polarization of the pump beam so that it will be parallel or perpendicular to the probe. The bottom mirror in this periscope is on a computer controlled rotation stage so that it can rotate to spit the beam out in two different directions depending on the polarization you want. In addition to that, since there are now two beam paths we added a computer controlled mirror that could flip in and out of the beam depending on which beam path you were using (which polarization). It was a thing of wonder to watch these things rotate and flip on the click of a mouse button, almost mesmerizing and utterly satisfying as well. Needless to say, it didn’t actually work for the purpose it was designed for. I wasn’t able to align the two beam paths well enough and/or the mechanical devices weren’t repeatable enough to consistently steer the beams in the same direction. Bummer. Like so many things that seem perfect on paper, real life imperfections rear their ugly head when you try to make it work in practice.

Now, this experiment isn’t a simple task by any stretch of the imagination, but making it more complicated is certainly not going to make it work better. It was only after I was humbled by the lack of repeatability of my fancy new system that I remembered Rube Goldberg and kicked myself for falling into his trap.

50/50 Beamsplitter?

March 26, 2007 at 8:06 am | | everyday science, hardware, help me

I guess optics are harder to make in the infrared. You ask for a 50/50 beamsplitter for 3.5 to 6.5 microns and you get something like this. I guess it crosses 50% T a couple of times within the spectral window so I shouldn’t complain.

If anyone knows a good source for IR beamsplitters that have flat spectral responses and also don’t achieve their %Reflectance with multiple little reflections leading to strings of pulses separated in time by a few tens of femtoseconds let me know.

Just another Gedanken experiment

December 13, 2006 at 11:20 am | | literature, nerd

I’m sure most of you who’ve taken physics classes have heard of some of the famous gedankens of history. Maybe you remember some of Einstein’s gedankens, or Schrodinger’s, but did you ever wonder about Gedanken’s gedankens? I didn’t until I was scrolling through the TOC alerts for J. Phys. Chem. and I saw the authors for this article:

MnO Octahedral Nanocrystals and MnO@C Core-Shell Composites: Synthesis,
Characterization, and Electrocatalytic Properties
Sangaraju Shanmugam and Aharon Gedanken

Now, I admit that this is pretty nerdy but the second author’s last name was funny and ironic to me on several levels. First, the paper he’s publishing is a real experiment, not a gedanken experiment, yet everything he does is at least partially a Gedanken experiment so how does he ever achieve anything? Secondly, it’s also ironic that a guy working at a university in Israel should have a last name that means “thought” in German. I leave that to you to wonder about….

Until then, I’ll continue with my gedanken experiments seeing as I haven’t been able to do any real ones for several months.

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