Frontiers of Physics

Neuronal avalanches: Sandpiles of self-organized criticality or critical dynamics of brain waves?
Galinsky VL and Frank LR
Analytical expressions for scaling of brain wave spectra derived from the general nonlinear wave Hamiltonian form show excellent agreement with experimental "neuronal avalanche" data. The theory of the weakly evanescent nonlinear brain wave dynamics [ 2, 023061 (2020); 32, 2178 (2020)] reveals the underlying collective processes hidden behind the phenomenological statistical description of the neuronal avalanches and connects together the whole range of brain activity states, from oscillatory wave-like modes, to neuronal avalanches, to incoherent spiking, showing that the neuronal avalanches are just the manifestation of the different nonlinear side of wave processes abundant in cortical tissue. In a more broad way these results show that a system of wave modes interacting through all possible combinations of the third order nonlinear terms described by a general wave Hamiltonian necessarily produces anharmonic wave modes with temporal and spatial scaling properties that follow scale free power laws. To the best of our knowledge this has never been reported in the physical literature and may be applicable to many physical systems that involve wave processes and not just to neuronal avalanches.
Understanding the physics of DNA using nanoscale single-molecule manipulation
Frey EW, Gooding AA, Wijeratne S and Kiang CH
Processes for decoding the genetic information in cells, including transcription, replication, recombination and repair, involve the deformation of DNA from its equilibrium structures such as bending, stretching, twisting, and unzipping of the double helix. Single-molecule manipulation techniques have made it possible to control DNA conformation and simultaneously detect the induced changes, revealing a rich variety of mechanically-induced conformational changes and thermodynamic states. These single-molecule techniques helped us to reveal the physics of DNA and the processes involved in the passing on of the genetic code.
Detecting nanoparticles by "listening"
Chang H and Zhang J
In the macroscopic world, we can obtain some important information through the vibration of objects, that is, listening to the sound. Likewise, we can also get some information of the nanoparticles that we want to know by the means of "listening" in the microscopic world. In this review, we will introduce two sensing methods (cavity optomechanical sensing and surface-enhanced Raman scattering sensing) which can be used to detect the nanoparticles. The cavity optomechanical systems are mainly used to detect sub-gigahertz nanoparticle or cavity vibrations, while surface-enhanced Raman scattering is a well-known technique to detect molecular vibrations whose frequency generally exceeds terahertz. Therefore, the vibrational information of nanoparticles from low-frequency to high-frequency could be obtained by these two methods. The size of the viruses is at the nanoscale and we can regard it as a kind of nanoparticles. Rapid and ultrasensitive detection of the viruses is the key strategies to break the spread of the viruses in the community. Cavity optomechanical sensing enables rapid, ultrasensitive detection of nanoparticles through the interaction of light and mechanical oscillators and surface-enhanced Raman scattering is an attractive qualitatively analytical technique for chemical sensing and biomedical applications, which has been used to detect the SARS-CoV-2 infected. Hence, investigation in these two fields is of vital importance in preventing the spread of the virus from affecting human's life and health.
Overcoming Debye length limitations: Three-dimensional wrinkled graphene field-effect transistor for ultra-sensitive adenosine triphosphate detection
Ding Y, Li C, Tian M, Wang J, Wang Z, Lin X, Liu G, Cui W, Qi X, Li S, Yue W and Xu S
Adenosine triphosphate (ATP) is closely related to the pathogenesis of certain diseases, so the detection of trace ATP is of great significance to disease diagnosis and drug development. Graphene field-effect transistors (GFETs) have been proven to be a promising platform for the rapid and accurate detection of small molecules, while the Debye shielding limits the sensitive detection in real samples. Here, a three-dimensional wrinkled graphene field-effect transistor (3D WG-FET) biosensor for ultra-sensitive detection of ATP is demonstrated. The lowest detection limit of 3D WG-FET for analyzing ATP is down to 3.01 aM, which is much lower than the reported results. In addition, the 3D WG-FET biosensor shows a good linear electrical response to ATP concentrations in a broad range of detection from 10 aM to 10 pM. Meanwhile, we achieved ultra-sensitive (LOD: 10 aM) and quantitative (range from 10 aM to 100 fM) measurements of ATP in human serum. The 3D WG-FET also exhibits high specificity. This work may provide a novel approach to improve the sensitivity for the detection of ATP in complex biological matrix, showing a broad application value for early clinical diagnosis and food health monitoring.