REALFAG – Science and Mathematics

Research - Department of Teacher Education

REALFAG – Science and Mathematics

REALFAG (from the norwegian word realfag, which encompasses science, technology, engineering and mathematics) is a research group focusing on current knowledge and advanced fundamental research in the scientific disciplines classically known as mathematics, physics, chemistry, biology and geology. These disciplines are in constant development, and they are the backbone of today’s and tomorrow’s STEM education at all school levels.

Some of the research lines in the group are:

  • Thermally induced spectrum perturbations and the thermodynamics of small systems. Contact: Rodrigo de Miguel.
  • Electrophysiological properties of neurons of the hippocampus and the entorhinal cortex in brains affected by Alzheimer’s disease. Contact: Pål Kvello.
  • Sensation of CO2 and processing of CO2 - information in the insect nervous system. Contact: Pål Kvello.
  • Quantitative analysis of the collagen structure in cartilage by SHG and P-SHG imaging. Contact: Elisabeth Romijn.
  • Man and nature. Vegetational changes following trampling, burning or scything in protected nature. Contact: Trond Arnesen.
  • Compressed sensing and Bayesian theory. Contact: Solomon Tesfamicael.

Seminars

  • Tuesday, May 14th, 2019, 12:00, Room LY42. Pål Kvello: «Research on the nervous system of mammals and insects.»
  • Tuesday, June 11th, 2019, 11:00, Room LY41. Elizabeth I. Romijn: «Spectroscopic methods to analyze the collagen structure in cartilage.»
  • Tuesday, December 3rd, 2019, 11:00, Room LY41. Rodrigo de Miguel: «Strong coupling and negative themophoresis.»

Seminar REALFAG

On Tuesday, 3 December 2019, REALFAG-group arranges its 3rd seminar. All are welcome.

Time: 11:00-12:00. Room: LY42 (4th floor Lysholm building, Kalvskinnet).

Speaker: Rodrigo de Miguel

Strong coupling and negative thermophoresis

Abstract:

Thermal gradients may induce mass migration, even in the absence of concentration gradients. Usually, the force induced by the thermal gradient drags the particles in the direction of the heat flow, i.e. from hot to cold. This is known as positive thermophoresis, and it is commonly understood as the result of more momentum transfer from solvent particles on the hot side than on the cold side. However, various particles such as colloids, polymers, charged nanoparticles, magnetic particles, fullerenes, proteins and vesicles have been observed to migrate from cold to hot. These observations suggest that there is more to thermophoresis than plain momentum transfer resulting from collisions between hard particles.

Indeed, negative thermophoresis (drift from cold to hot) is a somewhat counterintuitive phenomenon which has thus far eluded a simple thermostatistical description. A better understanding of the mechanism behind negative thermophoresis can be important for the design and operation of advanced nanosystem properties. For example, in applications such as drug delivery, where local heating is easier than local cooling, it is desirable to guide self-propelled particles towards locally heated targets. The thermophilic motion of nanoparticles may also be used to detect and capture DNA and other biological indicators in serum, allowing for the detection of quantities otherwise unachievable in a thermally homogeneous sample. Thermophilic drift is also believed to be a key mechanism in the self-assembly of the nucleic acids and protocells which lead to the origin of life.

In this talk I present a thermodynamic framework based on the formulation of a Hamiltonian of mean force which has the descriptive ability to capture the interesting and elusive phenomenon of negative thermophoresis in an unusually elegant and straightforward fashion. When a system is strongly coupled to the heat bath, the system’s eigenenergies become effectively temperature dependent. This adjustment of the energy levels allows the system to take heat from the environment and return it as work. This effect can make the temperature dependence of the effective energy profile nonmonotonic. As a result, particles may experience a force in either direction depending on the temperature.

This work has recently been published in Physical Review Letters 123, 200602 (2019).
 

tekst REALFAG

Recent publications

Heggland, Ingrid; Kvello, Pål; Witter, Menno. (2019) Electrophysiological Characterization of Networks and Single Cells in the Hippocampal Region of a Transgenic Rat Model of Alzheimer’s Disease. eNeuro. vol. 6 (1).

de Miguel, Rodrigo; Rubí, J. Miguel. Negative thermophoretic force in the strong coupling regime. Physical Review Letters. vol. 123 (200602).

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