Symmetry is one of the most generic and useful concepts in science, often leading to conservation laws and selection rules. Here we formulate a general group theory for dynamical symmetries (DSs) in ...time-periodic Floquet systems, and derive their correspondence to observable selection rules. We apply the theory to harmonic generation, deriving closed-form tables linking DSs of the driving laser and medium (gas, liquid, or solid) in (2+1)D and (3+1)D geometries to the allowed and forbidden harmonic orders and their polarizations. We identify symmetries, including time-reversal-based, reflection-based, and elliptical-based DSs, which lead to selection rules that are not explained by currently known conservation laws. We expect the theory to be useful for ultrafast high harmonic symmetry-breaking spectroscopy, as well as in various other systems such as Floquet topological insulators.
The purpose of this study is to explore the possibility of developing a biomarker that can discriminate early-stage Parkinson's disease from healthy brain function using electroencephalography (EEG) ...event-related potentials (ERPs) in combination with Brain Network Analytics (BNA) technology and machine learning (ML) algorithms.
Currently, diagnosis of PD depends mainly on motor signs and symptoms. However, there is need for biomarkers that detect PD at an earlier stage to allow intervention and monitoring of potential disease-modifying therapies. Cognitive impairment may appear before motor symptoms, and it tends to worsen with disease progression. While ERPs obtained during cognitive tasks performance represent processing stages of cognitive brain functions, they have not yet been established as sensitive or specific markers for early-stage PD.
Nineteen PD patients (disease duration of ≤2 years) and 30 healthy controls (HC) underwent EEG recording while performing visual Go/No-Go and auditory Oddball cognitive tasks. ERPs were analyzed by the BNA technology, and a ML algorithm identified a combination of features that distinguish early PD from HC. We used a logistic regression classifier with a 10-fold cross-validation.
The ML algorithm identified a neuromarker comprising 15 BNA features that discriminated early PD patients from HC. The area-under-the-curve of the receiver-operating characteristic curve was 0.79. Sensitivity and specificity were 0.74 and 0.73, respectively. The five most important features could be classified into three cognitive functions: early sensory processing (P50 amplitude, N100 latency), filtering of information (P200 amplitude and topographic similarity), and response-locked activity (P-200 topographic similarity preceding the motor response in the visual Go/No-Go task).
This pilot study found that BNA can identify patients with early PD using an advanced analysis of ERPs. These results need to be validated in a larger PD patient sample and assessed for people with premotor phase of PD.
Light is a very powerful and precise tool, allowing us to control1, shape2,3 and create new phases4 of matter. In such tasks, the magnetic component of a light wave is essential in defining the ...wave’s helicity, but it influences the optical response of matter only weakly. Chiral molecules offer a typical example, in which the weakness of magnetic interactions hampers our ability to control the strength of their chiro-optical response5, limiting it at several orders of magnitude below the full potential. Here, we introduce and theoretically analyse a new type of chiral light: freely propagating, locally and globally chiral electric fields, which interact with chiral matter extremely efficiently. We show that this synthetic chiral light enables full control over the intensity, polarization and propagation direction of the nonlinear enantio-sensitive optical response of randomly oriented chiral molecules. This response can be quenched or enhanced at will in a desired enantiomer, opening up efficient ways to control chiral matter and for ultrafast imaging of chiral dynamics in gases, liquids and solids.
Abstract
High harmonic generation (HHG) is an extremely nonlinear effect generating coherent broadband radiation and pulse durations reaching attosecond timescales. Conventional models of HHG that ...treat the driving and emitted fields classically are usually very successful but inherently cannot capture the quantum-optical nature of the process. Although prior work considered quantum HHG, it remains unknown in what conditions the spectral and statistical properties of the radiation depart considerably from the known phenomenology of HHG. The discovery of such conditions could lead to novel sources of attosecond light having squeezing and entanglement. Here, we present a fully-quantum theory of extreme nonlinear optics, predicting quantum effects that alter both the spectrum and photon statistics of HHG, thus departing from all previous approaches. We predict the emission of shifted frequency combs and identify spectral features arising from the breakdown of the dipole approximation for the emission. Our results show that each frequency component of HHG can be bunched and squeezed and that each emitted photon is a superposition of all frequencies in the spectrum, i.e., each photon is a comb. Our general approach is applicable to a wide range of nonlinear optical processes, paving the way towards novel quantum phenomena in extreme nonlinear optics.
•Molnupiravir is a broad acting, oral antiviral versus SARS-CoV-2, flu, Ebola and others.•Clinical development was greatly accelerated in response to the COVID19 pandemic.•Phase 1 studies showed the ...drug to be safe at therapeutic dose levels.•The drug successfully completed Phase 2 COVID-19 clinical studies and is now in Phase 3.
Despite the availability of vaccines, there remains an urgent need for antiviral drugs with potent activity against SARS-CoV-2, the cause of COVID-19. Millions of people are immune-suppressed and may not be able to mount a fully protective immune response after vaccination. There is also an increasingly critical need for a drug to cover emerging SARS-CoV-2 variants, against which existing vaccines may be less effective. Here, we describe the evolution of molnupiravir (EIDD-2801, MK-4482), a broad-spectrum antiviral agent originally designed for the treatment of Alphavirus infections, into a potential drug for the prevention and treatment of COVID-19. When the pandemic began, molnupiravir was in pre-clinical development for the treatment of seasonal influenza. As COVID-19 spread, the timeline for the development program was moved forward significantly, and focus shifted to treatment of coronavirus infections. Real time consultation with regulatory authorities aided in making the acceleration of the program possible.
Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available ...at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.
Solitons are self-localized wave packets arising from a robust balance between dispersion and nonlinearity. They are a universal phenomenon, exhibiting properties typically associated with particles. ...Thus far, interactions between solitons have been observed only between neighbouring solitons at close proximity. Here, we study interactions between solitons in highly non-local nonlinear media, and demonstrate experimentally attraction between solitons propagating in different samples, where their optical fields never overlap and the interaction is mediated solely by a non-optical wire. This increases the soliton interaction range by orders of magnitude, and breaks the close-proximity and nearest-neighbour limitations on soliton interactions. We also experiment with three-dimensional interactions between solitons that are far apart, where the solitons capture each other into a spiralling motion with a circular orbit, and a tangential velocity that does not depend on the separation between solitons. Our study suggests that these phenomena could be used in the construction of novel model systems for studying the behaviour of complex nonlinear networks. PUBLICATION ABSTRACT
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