Electric Field Measurement of Femtosecond Time-Resolved Four-Wave Mixing Signals in Molecules

We report an experiment to measure the femtosecond electric field of the signal emitted from an optical third-order nonlinear interaction in carbon dioxide molecules. Using degenerate four-wave mixing with femtosecond near infrared laser pulses in combination with the ultra-weak femtosecond pulse measurement technique of TADPOLE, we measure the nonlinear signal electric field in the time domain at different time delays between the interacting pulses. The chirp extracted from the temporal phase of the emitted nonlinear signal is found to sensitively depend on the electronic and rotational contributions to the nonlinear response. While the rotational contribution results in a nonlinear signal chirp close to the chirp of the input pulses, the electronic contribution results in a significantly higher chirp which changes with time delay. Our work demonstrates that electric field-resolved nonlinear spectroscopy offers detailed information on nonlinear interactions at ultrafast time scales.Comment: 8 pages, 4 figures, and supplemental documen

Attosecond Entangled Photons from Two-Photon Decay of Metastable Atoms: A Source for Attosecond Experiments and Beyond

We propose the generation of attosecond entangled bi-photons in the extreme-ultraviolet regime by two-photon decay of a metastable atomic state as a source similar to spontaneous parametric down-conversion photons. The 1s2s $^1S_0$ metastable state in helium decays to the ground state by emission of two energy-time entangled photons with a photon bandwidth equal to the total energy spacing of 20.62 eV. This results in a pair correlation time in the attosecond regime making these entangled photons a highly suitable source for attosecond pump-probe experiments. The bi-photon generation rate from a direct four photon excitation of helium at 240 nm is calculated and used to assess some feasible schemes to generate these bi-photons. Possible applications of entangled bi-photons in attosecond time scale experiments, and a discussion of their potential to reach the zeptosecond regime are presented.Comment: 6 pages, 3 figures, and supplementary materia

Neuromatch Academy: a 3-week, online summer school in computational neuroscience

Neuromatch Academy (https://academy.neuromatch.io; (van Viegen et al., 2021)) was designed as an online summer school to cover the basics of computational neuroscience in three weeks. The materials cover dominant and emerging computational neuroscience tools, how they complement one another, and specifically focus on how they can help us to better understand how the brain functions. An original component of the materials is its focus on modeling choices, i.e. how do we choose the right approach, how do we build models, and how can we evaluate models to determine if they provide real (meaningful) insight. This meta-modeling component of the instructional materials asks what questions can be answered by different techniques, and how to apply them meaningfully to get insight about brain function

High Accuracy Electrodynamic Calculations using Hermite Finite Elements

We show that the present approaches for the solution of Maxwell's equations have limitations that can be overcome through the use of C1-continuous Hermite interpolation polynomials. Our approach yields better accuracy by several orders of magnitude than comparable applications of edge-based vector finite element method (VFEM). We reexamine the issue of removing spurious unphysical zero-frequency solutions. (i) We investigate the group theory of fields in an empty cubic metallic cavity to explain the accidental degeneracy. (ii) We show that the inclusion of a smaller dielectric cube within the cubic cavity leads to the removal of accidental degeneracy. The method delineated here should be effective in solving scalar-vector coupled field problems, such as modeling quantum cavity well lasers

Post-Covid Era: Predictive Aspect of Psychological Condition Due to Sudden Pandemic

Covid-19 has impacted the lives of people in various aspects positive as well as negative. It has an impact on different areas of life, including the economy, industries, global markets, agriculture, human health, etc. The virus caused disruptions to daily life and restrictions on activities in many communities during its multiple outbreaks. Hope for a potential end to the pandemic emerged with the stepping up of vaccination campaigns. However, the continual appearance of mutant strains and vaccine hesitancy has been problems both nationally and internationally. People's normal activities, routines, and livelihoods have been disrupted by self-isolation and quarantine, potentially leading to an increase in loneliness, anxiety, depression, insomnia, excessive alcohol and drug use, and self-harm or suicidal activity. The psychological aspects of the post-covid-19 era are the effect of covid-19 on CNS, and physiological and psychological diseases caused due to covid-19. The article explains Post Trauma Stress Disorder as a psychological scar, Social evils arising due to covid-19, and predictive reasons for the increase in mental illness Keywords- Covid-19, Pandemic, Mental Health, Post Trauma Stress Disorder,  Depression, Anxiet

Evaluating WriteMyNote’s Product and Business Model to Determine the Effectiveness in Different Market Segments

Handwritten notes have been proven to be more impactful than other methods of communication such as email and text messages. Therefore, it is desirable to automate the process of writing notes to save time, especially for businesses and organizations. WriteMyNote is a venture that aims to solve this problem. The goal of this IQP was to evaluate WriteMyNote’s products and business model to determine their potential success in different market segments. In order to accomplish this, the team researched WriteMyNote’s competitors, evaluated different revenue models, and finally looked at different market segments in terms of structure, revenue growth and geographical spread

Inheritance and tagging of <em>Tomato leaf curl virus </em>(ToLCV) disease resistance genes in exotic tomato genotypes

357-363In the present investigation resistance genes have been introgressed into cultivated tomato from wild relatives, Solanum hirsutum accession (EC-520061) and an introgression cultivar of Solanum chilense (EC-538408) which showed a high level of resistance against tomato leaf curl Gujarat virus (Varanasi strain). Genetic studies revealed that one tomato leaf curl virus (ToLCV) disease resistance gene is present in EC-520061 and EC-538408 that segregated independently in their progenies. Furthermore, it has been identified that simple sequence repeats (SSR) markers SSR-306 was associated with the (ToLCV) disease resistance genes in tomato cultivar EC-538408 (derived from S. chilense), and SSR-218 was associated with a ToLCV disease resistance gene of EC-520061 (S. hirsutum). Both ToLCV resistance linked SSR markers were highly reproducible and effective in the identification of ToLCV disease resistance genes in the segregating populations and thus it is concluded that these two SSR markers could be used effectively in marker assisted selection for ToLCV disease resistance breeding program