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Is there memory for the memoryless? (Vol. 50, No. 4)
Inertia plays a role on the evolution of Brownian particles. Nevertheless, the interplay of inertial time-scale contributions and an overdamped dynamics with non-Markovian stochastic forces leads to contradictions that make equilibration impossible. This is due to assuming memory correlations for the dissipation, which seems to be inconsistent with the overdamped approximation, where thermal fluctuations adjust instantaneously to the state of the particle. Effectively, by taking the noise correlation time-scale to be zero (no memory) we certainly recover the expected physical behaviour of the problem, e.g., the equilibrium distribution. On the other hand, we can deal with the contradiction by inserting another source of noise, of Markovian type, and with “effective temperature” different from the non-Markovian noise. As a result, the stationary state may be regularized and the equilibrium recovered if both noises have same temperatures, even for finite memory time-scales. The additional white noise brings the system back to equilibrium, no matter how small the new noise intensity is.
E. S. Nascimento and W. A. M. Morgado, Non-Markovian effects on overdamped systems, EPL 126, 10002 (2019)
[Abstract]
Inner electrons behave differently in aromatic hydrocarbons (Vol. 50, No. 4)
When an electron from one of the lower energy levels in an atom is knocked out of the atom, it creates a space which can be filled by one of the higher-energy electrons, also releasing excess energy. This energy is released in an electron called an Auger electron - and produces an effect known as Auger decay. Now, the authors have studied the Auger effect in four hydrocarbon molecules: benzene, cyclohexane, hexatriene and hexadiene. These molecules were chosen because they exhibit different characteristics of aromaticity. They found that molecules containing pi bonds have a lower threshold for Auger decay. Potential applications of this decay effect include a treatment called Auger therapy, which is used to help cancer patients.
G. Zhao, T. Miteva, and N. Sisourat, Inner-valence Auger decay in hydrocarbon molecules, Eur. Phys. J. D 73, 69 (2019)
[Abstract]
Chip-Based Frequency Shift Super-Resolution Imaging (Vol. 50, No. 4)
Current label-free super-resolution methods suffer from either limited resolution improvements, small field-of-views or complex implementations, and a method with high-resolution, high-throughput and easy configuration is desirable for the practical applications in materials, biology and medicine, etc. To break this limitation, the authors propose a Si3N4 waveguide platform design for multi-wavelength illuminated label-free super-resolution microscopy imaging. The deep-subwavelength resolution was enabled by large wave-vector evanescent illumination induced spatial frequency shift effect, which also provides the high throughput for its wide field implementation.
In the method, chip-based waveguide with high refractive index produced evanescent wave illumination on the upper surface, the high tangential wave vector shifted the high spatial frequency components into the passband of the detection system from the perspective of the reciprocal domain. Multi-wavelength illuminated method was employed to cover the complete detection in the frequency domain. This enlarged the detectable broad-band frequency spectrum range, and high-resolution image with high signal-to-noise-ratio could be achieved using reconstruction algorithm. The optimized waveguide design to realize single mode behaviour and low attenuation guaranteed uniform evanescent wave illumination for the low-noise wide-field imaging. The integrated device is cost-effective, mass-producible and can conveniently give super resolvability to conventional microscopy as a compact module.
X. Xu, X. Liu, Ch. Pang, Y. Ma, Ch. Meng, J. Zhang, X. Liu and Q. Yang, Si3N4 waveguide platform for label-free super-resolution imaging: simulation and analysis, J. Phys. D: Appl. Phys. 52, 284002 (2019)
[Abstract]
How red blood cells behave in crowded vessels (Vol. 50, No. 4)
A new model of red blood flowing through narrow capillaries shows that the cells change shape and alignment, allowing plasma to flow down the sides
Blood consists of a suspension of cells and other components in plasma, including red blood cells, which give it its red colour. When blood flows through the narrowest vessels in the body, known as the capillaries, the interactions between the cells become much more important. In a new study published recently, a team of researchers has now developed a mathematical model of how red blood cells flow in narrow, crowded vessels. This could help design more precise methods for intravenous drug delivery, as well as 'microfluidic chips' incorporating artificial capillaries, which could offer faster, simpler and more precise blood-based diagnoses.
G. R. Lázaro, A. Hernandez-Machado and I. Pagonabarraga, Collective behavior of red blood cells in confined channels, Eur. Phys. J. E 42, 46 (2019)
[Abstract]
