Gentoo 10.0 to 13.0 profiles upgrade & server profiles going away

We've generated a new set of profiles for Gentoo installation. These are now called 13.0 instead of 10.0, e.g., "default/linux/amd64/10.0/desktop" becomes "default/linux/amd64/13.0/desktop".
Everyone should upgrade as soon as possible. This brings (nearly) no user-visible changes. Some new files have been added to the profile directories that make it possible for the developers to do more fine-grained use flag masking (see PMS-5 for the details), and this formally requires a new profile tree with EAPI=5 (and a recent portage version, but anything since sys-apps/portage-2.1.11.31 should work and anything since sys-apps/portage-2.1.11.50 should be perfect).
Since the 10.0 profiles will be deprecated immediately and removed in a year, emerge will suggest a replacement on every run. I strongly suggest you just follow that recommendation.
One additional change has been added to the package: the "server" profiles will be removed; they do not exist in the 13.0 tree anymore. If you have used a server profile so far, you should migrate to its parent, i.e. from "default/linux/amd64/10.0/server" to "default/linux/amd64/13.0". This may change the default value of some use-flags (the setting in "server" was USE="-perl -python snmp truetype xml"), so you may want to check the setting of these flags after switching profile, but otherwise nothing happens.

KDE 4.10.0 plasma-desktop crashes and qt frustrations

While on my machine KDE 4.10.0 runs perfectly fine, unfortunately a lot of Gentoo users see immediate crashes of plasma-desktop - which makes the graphical desktop environment completely unuseable. We know more or less what happened in the meantime, just not how to properly fix it...
The problem:

• plasma-desktop uses a new code path in 4.10, which triggers a Qt bug leading to immediate SIGSEGV. 
• The Qt bug only becomes fatal for some compiler options, and only on 64bit systems (amd64).
• The Qt bug may be a fundamental architectural problem that needs proper thought.

The links:

• Gentoo bug 450818: "x11-libs/qt-core-4.8.4: QDeclarativeVMEMetaObject::metaCall SIGSEGV when called from QMetaObject::metaCall"
• KDE bug 311751: "QML system tray crashes plasma-desktop on startup"
• Qt bug 29082: "QDeclarativeVMEMetaObject::metaCall SIGSEGV when called from QMetaObject::metaCall"
• Qt code review 46228: "Avoid calling metacall directly from the property animation code"

The bugfixing situation:

• Reverting the commit to plasma-workspace that introduced the problem makes the crash go away, but plasma-desktop starts hogging 100% CPU after a while. (This is done in plasma-workspace-4.10.0-r1 as a stopgap measure.) Kinda makes sense since the commit was there to fix a problem - now we hit the original problem.
• The bug seems not to occur if Qt is compiled with CFLAGS="-Os". Cause unknown. 
• David E. Narváez aka dmaggot wrote a patch for Qt that fixes this particular codepath but likely does not solve the global problem.
• So far comments from Qt upstream indicate that this is in their opinion not the right way to fix the problem.
• Our Gentoo Qt team understandably only wants to apply a patch if it has been accepted upstream.

Right now, the only option we (as Gentoo KDE team) have is wait for someone to pick up the phone. Either from KDE (to properly use the old codepath or provide some alternative), or from Qt (to fix the bug or apply a workaround)...

Sorry & stay tuned.

PhD position available: A carbon nanotube as a moving weak link

The combination of localized states within carbon nanotubes and superconducting contact materials leads to a manifold of fascinating physical phenomena and is a very active area of current research. An additional bonus is that the carbon nanotube can be suspended, i.e. the quantum dot between the contacts forms a nanomechanical system. In this research field a PhD position is immediately available; the working title of the project is "A carbon nanotube as a moving weak link".

You will develop and fabricate chip structures combining various superconductor contact materials with ultra-clean, as-grown carbon nanotubes. Together with your colleagues, you will optimize material, chip geometry, nanotube growth process, and measurement electronics. Measurements will take place in one of our ultra-low temperature setups.

Good knowledge of superconductivity is required. Certainly helpful is knowledge of semiconductor nanostructures and low temperature physics, as well as basic familiarity with Linux. The starting salary is 1/2 TV-L E13.

Interested? Contact Andreas K. Hüttel (e-mail: andreas.huettel@ur.de, web: http://www.physik.uni-r.de/forschung/huettel/ ) for more information!

PhD position available: Gigahertz nanomechanics with carbon nanotubes

We are currently working on integrating carbon nanotube nanomechanical systems into superconducting radio-frequency electronics. Overall objective is the detection and control of nanomechanical motion towards its quantum limit. In this project, we've got a PhD position with project working title "Gigahertz nanomechanics with carbon nanotubes" available immediately.

You will design and fabricate superconducting on-chip structures suitable as both carbon nanotube contact electrodes and gigahertz circuit elements. In addition, you will build up and use - together with your colleagues - two ultra-low temperature measurement setups to conduct cutting-edge measurements.

Good knowledge of electrodynamics and possibly superconductivity are required. Certainly helpful is low temperature physics, some sort of programming experience, as well as basic familiarity with Linux. The starting salary is 1/2 TV-L E13.

Interested? Contact Andreas K. Hüttel (e-mail: andreas.huettel@ur.de, web: http://www.physik.uni-r.de/forschung/huettel/ ) for more information!

JAP accepted: Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips

Right at the start the new year 2013 brings the pleasant news that our manuscript "Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips" has found its way into Journal of Applied Physics. The background of this work is - once again - spin injection and spin-dependent transport in carbon nanotubes. (To be more precise, the manuscript resulted from our ongoing SFB 689 project.) Control of the contact magnetization is the first step for all the experiments. Some time ago we picked Pd_0.3Ni_0.7 as contact material since the palladium generates only a low resistance between nanotube and its leads. The behaviour of the contact strips fabricated from this alloy turned out to be rather complex, though, and this manuscript summarizes our results on their magnetic properties.
Three methods are used to obtain data - SQUID magnetization measurements of a large ensemble of lithographically identical strips, anisotropic magnetoresistance measurements of single strips, and magnetic force microscopy of the resulting domain pattern. All measurements are consistent with the rather non-intuitive result that the magnetically easy axis is perpendicular to the geometrically long strip axis. We can explain this by maneto-elastic coupling, i.e., stress imprinted during fabrication of the strips leads to preferential alignment of the magnetic moments orthogonal to the strip direction.

"Transversal Magnetic Anisotropy in Nanoscale PdNi-Strips"
D. Steininger, A. K. Hüttel, M. Ziola, M. Kiessling, M. Sperl, G. Bayreuther, and Ch. Strunk
Journal of Applied Physics 113, 034303 (2013); arXiv:1208.2163 (PDF[*])
[*] Copyright American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

My personal KDEPIM upgrade (again): laptop

One year after my last blog post on this topic I encountered some minor difficulties with combining KDEPIM-4.4 (i.e. kmail1) and the KDE 4.10 betas. These difficulties are fixed now, and the combination seems to work fine again. Anyway, I became curious about the level of stability of Akonadi-based kmail2 once more. After all, I've been running it continuously over the year on my office desktop with a constant-on fast internet connection, and that works quite well. So, I gave it a fresh try on my laptop too. I deleted my Akonadi configuration and cache, switched to Akonadi mysql backend, updated kmail and the rest of KDEPIM without migrating to 4.9.4, and re-added my IMAP account from scratch (with "Enable offline mode"). The overall use case description is "laptop with large amount of cached files from IMAP account, fluctuating internet connectivity". Now, here are my impressions...

• Reaction time is occasionally sluggish, but overall OK.
• The progress indicator behaves a bit odd, it checks the mail folders in seemingly random order and only knows 0% and 100% completion.
• Random warning messages. It seems that kmail2 uses some features that "my" IMAP server does not understand. So, I'm getting frequent warning notifications that don't tell me anything and that I cannot do anything about. SET ANNOTATION, UID, ... Please either handle the errors, inform the user what exactly goes wrong, or ignore them in case they are irrelevant. Filed as a wish, bug 311265.
• Network activity stops working sometime. This sounds worse than it actually is, since in 99% of all cases Akonadi now detects fine that the connection to the server is broken (e.g., after suspend/resume, after switching to a different WLAN, or after enabling a VPN tunnel) and reconnects immediately. In the few remaining cases, re-starting the Akonadi server does the trick. You just have to know what to kick.
• More problematic is, while you're in online mode, any problems with connectivity will make kmail "hang". Clicking on a message leads to an attempt to retrieve it, which requires some response from the network. As it seems to me, all such requests are queued up for Akonadi to handle, and if that does not get a reply, pending requests are stuck in the queue... OK, you might say that this is a typical use case for offline mode, but then I would have to be able to predict when exactly my train enters the tunnel... Compare this to kmail1 disconnected IMAP accounts, where regular syncing would be delayed, but local work remained unaffected.
• Offline mode is a nice concept, and half a solution for the last problem, but unfortunately it does not work as expected. For mysterious reasons, a considerable part of the messages is not cached locally. I switch my account to offline mode, click on a message, and obtain an error message "Cannot fetch this in offline mode". Well, bummer. Bug 285935.
• This may just be my personal taste, but once something goes wrong (e.g., non-kde related crash, battery empty, ...) and the cache becomes corrupted somehow, I'd like to be able to do something from kmail2 without having to fiddle with akonadiconsole. A nice addition would be "Invalidate cache" in the context menu of a mail folder, or some sort of maintenance menu with semi-safe options.
• Finally... something is definitely going wrong with PGP signatures; the signatures do not always verify on other mail clients. Tracking this down, it seems that CRLF is not preserved in messages, see bug 306005.

On the whole, for the laptop use case the "new" KDEPIM is now (4.9.4) more mature than the last time I tried. I'll keep it now and not downgrade again, but there are still some significant rough edges. The good thing is, the KDEPIM developers are aware of the above issues and debugging is going on, as you can see for example from this blog post by Alex Fiestas (whose use case pretty much mirrors my own).

The difference between Ubuntu and Gentoo ;)

This gem comes from the xda developers forums; thanks barry99705!

"Using/installing Ubuntu is like buying a car. It may have a few features you'll never need or use, and might need to have a couple features added as aftermarket parts.

Using/installing Gentoo is like buying a pile of sheet metal, a few rubber trees, small pile of copper, a pile of sand, and an oil well. Then you have to cut and fabricate the car's body from the sheet metal, extract the rubber from the trees, then use that to make the tires and all the seals on the car. Use the pile of copper to make all the wires, and use the leftover rubber(you did save the scraps didn't you) to make the insulation. Melt down the pile of glass to make the windshield, side and back windows, also the headlights and lights themselves. Then you need to extract the crude oil from the well to refine your own engine oil and gas. In the end, you have a car created to your exact specifications (if you know what the hell you're doing) that may or may not be any better than just buying a car off the lot."

Of course I should additionally mention that Gentoo provides awesome documentation for all the steps and most of the actual assembly work is done single-handedly by portage!