A multi-type branching process model for epidemics with application to COVID-19.

In this paper we model an infectious disease epidemic using Multi-type Branching Process where the number of offsprings of different types follow non-identical Poisson distributions whose parameters may vary over time. We allow for variation in parameters due to the behavior of citizens, government interventions in the form of lockdown, testing and contact tracing and the infectiousness of the variant of the virus in circulation at a time-point in a location. The model can be used to estimate several unknown quantities of interest in an epidemic such as the number of undetected cases and number of people quarantined following contact tracing. The model is fitted to the publicly available COVID-19 caseload data of India, South Korea, UK and US and is seen to provide good fit. It also provides good short-term forecast of the caseload for these countries. This model can be useful for health policy planners in assessing the impact of various intervention strategies such as testing, contact tracing, quarantine etc.

Exceptional-point-induced asymmetric mode conversion in a dual-core optical fiber segment.

The engineering of exceptional points (EPs) in open optical systems has lately attracted much attention for developing future all-optical devices. However, investigation of the fascinating features of EPs in fiber geometries is lacking. We design a fabrication feasible dual-core optical fiber segment, where non-Hermiticity in terms of a symmetric customized gain-loss profile is introduced to modulate the interaction between two corresponding coupled modes toward hosting a dynamical EP encirclement scheme in the gain-loss parameter space. An asymmetric conversion process between two supported modes is reported by exploiting the chirality of the encountered EP. The proposed scheme can lead to an advanced platform to design mode-manipulative all-optical components in communication and all-fiber photonic devices.

Consumer behaviour and climate action: insights from a Randomised Control Trial experiment in India's residential cooling sector.

Air-conditioning is expected to be the largest consumer of residential energy in India in the future. Good consumer practices related to servicing air-conditioners (ACs) are critical for maintaining high operational efficiency of ACs and reducing leakages of high global warming potential (GWP) refrigerant gases. Little information, however, is available about the knowledge and practices of Indian AC consumers in terms of their operational practices. The Government of India's 'India Cooling Action Plan (ICAP)' recommends a massive consumer awareness program to inform and change AC user behaviour. Within this context of the ICAP that aims to provide access to sustainable cooling to its masses while minimising its environmental impacts, we undertake a survey and a Randomised Control Trial (RCT) experiment including Indian consumers. The survey and experiment together aim to understand the AC servicing behaviour of Indian consumers and experiment with alternative interventions to influence their behaviour and glean insights for India's energy and climate policies. The behavioural experiment is a unique and novel methodological contribution to India's cooling and climate debate. This research is a first-of-its-kind RCT study of Indian consumers' AC servicing practices. We find that the AC users' knowledge of the importance of preventive servicing is much lower than required. The interventions were successful in enhancing general awareness related to the importance of servicing practices, but not in enhancing technical knowledge related to specific good servicing practices. Our analysis shows that consumers who know about the economic benefit of servicing are more likely to undertake preventive servicing. Our findings highlight the presence of information asymmetry in the Indian residential cooling market and argue that this needs to be addressed for achieving the desired behavioural change and actions to mitigate climate change.

Chirality breakdown in the presence of multiple exceptional points and specific mode excitation.

The dynamical parametric encirclement around a second-order exceptional point (EP) enables the time-asymmetric nonadiabatic evolution of light, which follows the chirality of the underlying system. Such light dynamics in the presence of multiple EPs and the corresponding chiral aspect is yet to be explored. In this Letter, we report a gain-loss assisted four-mode-supported optical waveguide that hosts a parameter space to dynamically encircle multiple EPs. In the presence of multiple EPs, we establish a unique nonadiabatic behavior of light, where beyond the chiral aspect of the system, light is switched to a particular mode, irrespective of the choice of the input mode. Proposed scheme certainly opens a step-forward approach in light manipulation to facilitate next-generation integrated photonic systems.

Suppression of excess noise of longer-lived high-quality states in nonuniformly pumped optical microcavities.

We study the formation of longer-lived states via internal coupling near a special avoided resonance crossing between the interacting states in an open optical system. Away from the parity-time symmetry limit, we discuss unconventional cavity resonance states created by a spatially varying gain/loss profile. Now, via S-matrix formalism, we have numerically demonstrated that with suitably chosen system openness and coupling strengths, the excess noise generation among the interacting nonorthogonal states (calculated as Petermann factor K) can be suppressed close to the ideal value of one with a simultaneous order of magnitude enhancement in the quality-factor of the longer-lived state.

Comparison of treatments in a cataract surgery with circular response.

Circular data are a natural outcome in many biomedical studies, e.g. some measurements in ophthalmologic studies, degrees of rotation of hand or waist, etc. With reference to a real data set on astigmatism induced in two types of cataract surgeries we carry out some two-sample testing problems with the possibility of common or different concentration parameters in the circular set up. Detailed simulation study and the analysis of the data set, including redesigning the cataract surgery data, are carried out.

Response-Adaptive Allocation for Circular Data.

Response-adaptive designs are used in phase III clinical trials to allocate a larger proportion of patients to the better treatment. Circular data is a natural outcome in many clinical trial setup, e.g., some measurements in opthalmologic studies, degrees of rotation of hand or waist, etc. There is no available work on response-adaptive designs for circular data. With reference to a dataset on cataract surgery we provide some response-adaptive designs where the responses are of circular nature and propose some test statistics for treatment comparison under adaptive data allocation procedure. Detailed simulation study and the analysis of the dataset, including redesigning the cataract surgery data, are carried out.