Bandgap scaling and negative differential resistance behavior of zigzag phosphorene antidot nanoribbons (ZPANRs).

This work examines the prospect of phosphorene antidot nanoribbons (PANRs) using the density functional based tight binding (DFTB) method. Horizontally perforated PANRs with both armchair (A) and zigzag (Z) configurations were considered for electrical simulations. Our simulation results found that the APANRs cannot be scaled down with nanoribbon width, whereas ZPANRs can be scaled easily. Bandgap scaling in terms of ribbon width, length and antidot number was thoroughly analyzed for ZPANRs. In the end, a two-terminal device was constructed and transmission analysis was performed using the non-equilibrium Green's function (NEGF) methodology. A negative differential resistance (NDR) region appeared in the current-voltage characteristics of the ZPANRs, which paved a pathway for nano-device application.

Role of Interfacial Viscosity and pH in L-Phenylalanine, L-Tryptophan Molecular Rotors.

Protein folding involves the aminoacid sequence to come forth and form an energy minimized structure. Recently molecular crowding leading to increase in viscosity is said to be one of the major concerns affecting protein folding. Many external fluorescent probes are used to detect such increases in viscosity. Since most of the protein sequences contain L-Phe and L-Trp, in this study we have used these aminoacids as probes to detect changes in viscosity. This study will help to advance the knowledge on molecular crowding effects in protein folding.

Nanohydroxyapatite-chitosan-gelatin polyelectrolyte complex with enhanced mechanical and bioactivity.

A wet chemical approach was used to synthesis HAp-chitosan-gelatin nanocomposites at different wt.% of chitosan-gelatin (CG) ratios such as CG-00, CG-40, CG-31, CG-22, CG-13 and CG-04. XRD analysis confirms the formation of HAp on nanocomposite matrix and the decreased crystallite size was found with the decrease in chitosan and increase in gelatin compositions. FTIR study reveals that the presence of characteristic bands of HAp and CG. The decrease in chitosan in CG leads to band shift of organic phase towards a higher wave number side due to the intimate bonding with an inorganic phase. FE-SEM images show that the particles had a short nanorod-like morphology. The bioresorbability and microhardness test indicate that the composites have better resorbability and hardness than pure HAp. It was inferred that particle size, morphology, resorbability and hardness of the composite can be altered by tuning the composition.

Modeling basal ganglia for understanding Parkinsonian reaching movements.

We present a computational model that highlights the role of basal ganglia (BG) in generating simple reaching movements. The model is cast within the reinforcement learning (RL) framework with correspondence between RL components and neuroanatomy as follows: dopamine signal of substantia nigra pars compacta as the temporal difference error, striatum as the substrate for the critic, and the motor cortex as the actor. A key feature of this neurobiological interpretation is our hypothesis that the indirect pathway is the explorer. Chaotic activity, originating from the indirect pathway part of the model, drives the wandering, exploratory movements of the arm. Thus, the direct pathway subserves exploitation, while the indirect pathway subserves exploration. The motor cortex becomes more and more independent of the corrective influence of BG as training progresses. Reaching trajectories show diminishing variability with training. Reaching movements associated with Parkinson's disease (PD) are simulated by reducing dopamine and degrading the complexity of indirect pathway dynamics by switching it from chaotic to periodic behavior. Under the simulated PD conditions, the arm exhibits PD motor symptoms like tremor, bradykinesia and undershooting. The model echoes the notion that PD is a dynamical disease.

Multifractal eigenstates of quantum chaos and the Thue-Morse sequence.

We analyze certain eigenstates of the quantum baker's map and demonstrate, using the Walsh-Hadamard transform, the emergence of the ubiquitous Thue-Morse sequence, a simple sequence that is at the border between quasiperiodicity and chaos, and hence is a good paradigm for quantum chaotic states. We show a family of states that are also simply related to the Thue-Morse sequence and are strongly scarred by short periodic orbits and their homoclinic excursions. We give approximate expressions for these states and provide evidence that these and other generic states are multifractal.