Design and implementation of a low cost, modular, adaptable and open-source XYZ positioning system for neurophysiology

Design and implementation of a versatile magnetic field mapper for 3D volumes

Magnetic field mapping is an essential step in research, manufacturing, and maintenance. It helps one find out what's under the surface of any object and identify areas of high-flux density. Our magnetic field mapper is easy-to-use and has a user-friendly interface. It comprises a triple axis Hall effect-based magnetometer, meaning that it can measure the strength of magnetic fields in 3D. It is made up of three Hall sensors which are mounted on a triple-slot sensor probe which in turn is attached to translation stages allowing motion in three dimensions. The translation in X and Y motion (independent) is from - 50 to + 50  mm while in Z is from - 150 to + 150  mm with a nominal resolution of 0.1  mm. The height of the magnetometer is 1000 mm and it's originally designed for mapping the magnetic field of permanent magnet assemblies for low-field and mobile magnetic resonance scanners. Sometimes, you need to find out how strong the magnetic field in a particular region is or you may want to measure all the three components of the magnetic flux density to find out the homogeneity or isotropy of the field. In high resonant NMR spectroscopy, the magnetic field needs to be highly uniform and homogeneous and to assess such a field, we need a device which can measure the magnetic field, precisely, accurately and reproducibly. The proposed field mapper is useful in all of these situations. It is low cost and easy to manufacture. The maximum measurable magnetic field is ± 2 T. Furthermore, all the material required for building this device is easily accessible.

Miau, a microbalance autosampler

Powder weighing is an essential but tedious activity in many branches of science. Here I describe a MIcrobalance AUtosampler (miau) that transfers solids in the sub-mg range to a microbalance. Miau is a pick-and-place machine which moves a gripper with dual function: 1) move tin capsules; 2) deliver powder from a container to tin capsules. In our laboratory we routinely use miau to prepare working standards for quality control of elemental and isotopic analyses. In a test, miau produced standards between 0.3 and 1.1 mg, which is a useful range in our laboratory. Failure to produce a weighed standard happened in 5% of the cases. A comparison with manual measurements demonstrated that obtained amounts for automated samples were as accurate and precise as manually prepared ones. Setup for daily use is simple, and the microbalance can be easily used alternately with or without miau. Miau is a low-cost device that can work with microbalances from many manufacturers, and can be readily adopted by many laboratories.

Ender3 3D printer kit transformed into open, programmable syringe pump set

A cheap, open source 3D printer (Creality Ender 3) is transformed into an Open Hardware, programmable syringe pump set. Only 3 parts need to be purchased outside of the printer kit. All other parts are either in the Ender 3 kit, or can be 3D printed. No prior knowledge in electronics or programming languages is required. The pumps are controlled by the 3D printer firmware and motherboard and programmed in simple G-code text files. The total cost of a three pumps setup is ∼€170. The pumps are capable of reaching stable flows down to 5 µL/min using cheap, disposable 10 mL syringes. Higher flow speeds are also achievable, in the order of mL/min.

Electrophysiological characterisation of atrial volume receptors using ex vivo models of isolated rat cardiac atria

NEW FINDINGS

What is the central question of this study? What ex vivo preparation of the rat's cavoatrial junction is efficient for characterising atrial mechanoreceptors? What is the main finding and its importance? Of four different ex vivo preparations, static pressure, flow, open and euthermic, the optimal preparation was the euthermic one and involved direct recording from the right cardiac vagal branch with a Langendorff style perfusion at 37°C. Type A receptors were most common, and appeared insensitive to stretch and sensitive to atrial contraction. Type B and intermediate receptors were not isolated at 20°C but were observed closer to 37°C. The findings may suggest that type A and B receptors utilise different molecular transduction mechanisms.

ABSTRACT

Atrial volume receptors are a family of afferent neurons whose mechanically sensitive endings terminate in the atria, particularly at the cavoatrial junctions. These mechanosensors form the afferent limb of an atrial volume receptor reflex that regulates plasma volume. The prevailing functional classification of atrial receptors arose as a result of in vivo recordings in the cat and dog and were classified as type A, B or intermediate according to the timing of peak discharge during the cardiac cycle. In contrast, there have been far fewer studies of the common small laboratory mammals such as the rat. Using several ex vivo rat cavoatrial preparations, a total of 30 successful single cavoatrial mechanosensory recordings were obtained. These experiments show that the rat possesses type A, B and intermediate atrial mechanoreceptors as described for larger mammals. Recording these cavoatrial receptors proved challenging from the main vagus, but direct recording from the cardiac vagal branch greatly increased the yield of mechanically sensitive single units. In contrast to type A units, type B atrial mechanoreceptor activity was never observed at room temperature but required elevation of temperature to a more physiological range in order to be detected. The adequate stimulus for these receptors remains unclear; however, type A atrial receptors appear insensitive to direct atrial stretch when applied using a programmable positioner. The findings may suggest that type A and type B atrial receptors utilise different molecular transduction mechanisms.

Portable open-source autosampler for shallow waters

Automated water sampling can be very useful, but open-source choices are limited. Here I present an autosampler which consists of a gantry robot that delivers water from a syringe pump to 24 capped 40 ml vials. The autosampler is controlled using an Android tablet automatized using Macrodroid. Three rinsing cycles ensure negligible carryover between consecutive samples. Hourly sampling from a creek under rainy conditions suggested that total organic carbon in water was diluted by the rain. Some important limitations: 1) the autosampler must be on a steady, flat, horizontal surface; 2) unattended sampling can only last as long as the batteries powering the tablet and the motors; 3) distance from the syringe pump to water cannot exceed ~2 m in height and ~4 m in length for 3 mm tubing; 4) sampling frequency does not exceed one sample every eleven minutes. However, because of its open design, the autosampler can be modified and improved to not only overcome these limitations, but also potentially expand its scope to more demanding sampling if necessary.