Permian-Triassic extinction event by Ciro Santilli 35 Updated +Created
As usual, blame the Russians.
Western World by Ciro Santilli 35 Updated +Created
Russia by Ciro Santilli 35 Updated +Created
North America by Ciro Santilli 35 Updated +Created
Pre-sequencing preparation by Ciro Santilli 35 Updated +Created
One cool thing we did in this procedure was to use magnetic separation with magnetic beads to further concentrate the DNA: Figure 1. "GE MagRack 6 pipetting.".
The beads are coated to stick to the DNA, which allows us to easily extract the DNA from the rest of the solution. This is cool, but bio people are borderline obsessed by those beads! Go figure!
Figure 1.
GE MagRack 6 pipetting.
Source.
Figure 2.
GE MagRack 6 eppendorf with magnetic beads mounted.
Source.
Then we prepared the DNA for sequencing with the Oxford Nanopore specific part: Oxford Nanopore SQK-LSK109 Ligation Sequencing Kit.
Here some of the steps required a bit more of vortexing for mixing the reagents, and for this we used the VELP Scientifica WIZARD IR Infrared Vortex Mixer which appears to be quicker to use and not as strong as the Vortex Genie 2 previously used to break up the cells:
Figure 3.
VELP Scientifica WIZARD IR Infrared Vortex Mixer running.
Source.
After all that was done, the DNA of the several 400 ml water bottles and hours of hard purification labour were contained in one single Eppendorf!
PCR verification with gel electrophoresis by Ciro Santilli 35 Updated +Created
Biology experiments are hard, and so they go wrong, a lot.
For this reason, it is wise to verify that certain steps are correct whenever possible.
And so this is the first thing we did on the second day!
Gel electrophoresis separates molecules by their charge-to-mass ratio. It is one of those ultra common lab procedures!
This allows us to determine how long are the DNA fragments present in our solution.
Since we know that we amplified the 16S regions which we know the rough size of (there might be a bit of variability across species, but not that much), we were expecting to see a big band at that size.
And that is exactly what we saw!
First we had to prepare the gel, put the gel comb, and pipette the samples into wells present in the gel:
Figure 1.
Gel electrophoresis insert comb.
Source.
Figure 2.
Gel electrophoresis top view with wells visible.
Source.
Figure 3.
Gel electrophoresis pipette sample into wells.
Source.
To see the DNA, we added ethidium bromide to the samples, which is a substance that that both binds to DNA and is fluorescent.
Because it interacts heavily with DNA, ethidium bromide is a mutagen, and the biology people sure did treat the dedicated electrophoresis bench area with respect! Figure 4. "Gel electrophoresis dedicated bench area to prevent ethidium bromide contamination.".
Figure 4.
Gel electrophoresis dedicated bench area to prevent ethidium bromide contamination.
Source.
Figure 5.
Gel electrophoresis dedicated waste bin for centrifuge tubes and pipette tips contaminated with ethidium bromide.
Source.
The UV transilluminator we used to shoot UV light into the gel was the Fisher Scientific UVP LM-26E Benchtop 2UV Transilluminator. The fluorescent substance then emitted a light we can see.
As barely seen at Figure 8. "Fischer Scientific UVP LM-26E Benchtop 2UV Transilluminator illuminated gel." due to bad photo quality due to lack of light, there is one strong green line, which compared to the ladder matches our expected 16S length. What we saw it with the naked eyes was very clear however.
Figure 6.
Fischer Scientific UVP LM-26E Benchtop 2UV Transilluminator
. Source.
Figure 7.
Fischer Scientific UVP LM-26E Benchtop 2UV Transilluminator loading gel.
Source.
Figure 8.
Fischer Scientific UVP LM-26E Benchtop 2UV Transilluminator illuminated gel.
Source.
Post filtration purification by Ciro Santilli 35 Updated +Created
After filtration, all DNA should present in the filter, so we cut the paper up with scissors and put the pieces into an Eppendorf: Video 1. "Cutting vacuum pump filter and placing it in Eppendorf".
Video 1.
Cutting vacuum pump filter and placing it in Eppendorf
. Source.
Now that we had the DNA in Eppendorfs, we were ready to continue the purification in a simpler and more standardized lab pipeline fashion.
First we added some small specialized beads and chemicals to the water and shook them Eppendorfs hard in a Scientific Industries Inc. Vortex-Genie 2 machine to break the cell and free the DNA.
Once that was done, we added several reagents which split the solution into two phases: one containing the DNA and the other not. We would then pipette the phase with the DNA out to the next Eppendorf, and continue the process.
In one step for example, the DNA was present as a white precipitate at the bottom of the tube, and we threw away the supernatant liquid: Figure 1. "White precipitate formed with Qiagen DNeasy PowerWater Kit".
Figure 1.
White precipitate formed with Qiagen DNeasy PowerWater Kit
. Source.
At various stages, centrifuging was also necessary. Much like the previous vacuum pump step, this adds extra gravity to speed up the separation of phases with different molecular masses.
In our case, we used a VWR Micro Star 17 microcentrifuge for those steps:
Figure 2.
VWR Micro Star 17 microcentrifuge.
Source.
Figure 3.
VWR Micro Star 17 microcentrifuge loading.
Source.
Then, when we had finally finished all the purification steps, we measured the quantity of DNA with a Biochrom SimpliNano spectrophotometer to check that the purification went well:
Figure 4.
Biochrom SimpliNano spectrophotometer loading sample.
Source.
Figure 5.
Biochrom SimpliNano spectrophotometer result readout.
Source.
And because the readings were good, we put it in our -20 C fridge to preserve it until the second day of the workshop and called it a day:
Figure 6.
Minus 20 fridge storing samples.
Source.
Asia by Ciro Santilli 35 Updated +Created
Stereochemistry by Ciro Santilli 35 Updated +Created
Molecules that are the same if you just look at "what atom is linked to what atom", they are only different if you consider the relative spacial positions of atoms.
Geologic time scale hierarchy by Ciro Santilli 35 Updated +Created
DF_1_PIE by Ciro Santilli 35 Updated +Created
Determines if an executable is a position independent executable (PIE).
Seems to be informational only, since not used by Linux kernel 5.0 or glibc 2.29.
Pangaea by Ciro Santilli 35 Updated +Created
Ubuntu 21.10 does not wake up from suspend by Ciro Santilli 35 Updated +Created
Does not happen every time, only some times. Can't figure out why. Usually happens when has suspended for a longer time.
bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-470/+bug/1946303 sounds like a likely report, Nvidia driver version 470, but can't find those error messages anywhere. The last line of:
journalctl -o short-precise -k -b -1
once was:
PM: suspend entry (deep)
which is when sleep starts.
This suggests that it is not a video bug then, seems that it is not waking up at all? Gotta try to SSH into it. OK. I did SSH into it, and that was fine, so it is just the video that won't start.
PM: suspend exit
bugs.launchpad.net/ubuntu/+source/linux/+bug/1949977 is another possible bug, based on kernel version. I'm running 5.13, which is one of the failing versions on the report. Can't find any interesting dmesg though.
In another crash:
journalctl -o short-precise -k -b -1
had the following interesting lines:
nvidia-modeset: WARNING: GPU:0: Lost display notification (0:0x00000000); continuing.
[24307.640014] NVRM: GPU at PCI:0000:01:00: GPU-18af74bb-7c72-ff70-e447-87d48378ea20
[24307.640018] NVRM: Xid (PCI:0000:01:00): 79, pid=8828, GPU has fallen off the bus.
[24307.640021] NVRM: GPU 0000:01:00.0: GPU has fallen off the bus.
[24328.054022] nvidia-modeset: ERROR: GPU:0: The requested configuration of display devices (LGD (DP-4)) is not supported on this GPU.
[repeats several more times]
[24328.056767] nvidia-modeset: ERROR: GPU:0: The requested configuration of display devices (LGD (DP-4)) is not supported on this GPU.
[24328.056951] nvidia-modeset: ERROR: GPU:0: Failed to query display engine channel state: 0x0000927c:0:0:0x0000000f
[24328.056955] nvidia-modeset: ERROR: GPU:0: Failed to query display engine channel state: 0x0000927c:1:0:0x0000000f
[24328.056959] nvidia-modeset: ERROR: GPU:0: Failed to query display engine channel state: 0x0000927c:2:0:0x0000000f
[24328.056962] nvidia-modeset: ERROR: GPU:0: Failed to query display engine channel state: 0x0000927c:3:0:0x0000000f
[24328.056983] nvidia-modeset: ERROR: GPU:0: DP-4: Failed to disable DisplayPort audio stream-0
[24328.056992] nvidia-modeset: ERROR: GPU:0: Failed to query display engine channel state: 0x0000947d:0:0:0x0000000f
and there was a corresponding /var/crash/_usr_sbin_gdm3.0.crash.
Sequelize example by Ciro Santilli 35 Updated +Created
To run examples on a specific database:
  • ./index.js or ./index.js l: SQLite
  • ./index.js p: PostgreSQL. You must manually create a database called tmp and ensure that peer authentication works for it
All examples can be tested on all databases with:
cd sequelize
./test
Overview of the examples:
Raspberry Pi Pico W UART by Ciro Santilli 35 Updated +Created
You can connect form an Ubuntu 22.04 host as:
screen /dev/ttyACM0 115200
When in screen, you can Ctrl + C to kill main.py, and then execution stops and you are left in a Python shell. From there:
  • Ctrl + D: reboots
  • Ctrl + A K: kills the GNU screen window. Execution continues normally
but be aware of: Raspberry Pi Pico W freezes a few seconds after after screen disconnects from UART.
Superconducting qubits are regarded as promising because superconductivity is a macroscopic quantum phenomena of Bose Einstein condensation, and so as a macroscopic phenomena, it is easier to control and observe.
This is mentioned e.g. in this relatively early: physicsworld.com/a/superconducting-quantum-bits/. While most quantum phenomena is observed at the atomic scale, superconducting qubits are micrometer scale, which is huge!
Physicists are comfortable with the use of quantum mechanics to describe atomic and subatomic particles. However, in recent years we have discovered that micron-sized objects that have been produced using standard semiconductor-fabrication techniques – objects that are small on everyday scales but large compared with atoms – can also behave as quantum particles.

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