Assessment of perfusion of free flaps used in head and neck reconstruction using pulsatility index.

OBJECTIVE: To detect venous or arterial obstruction in the pedicle of a free flap we can monitor resistance in the flap bed which is reflected in Pulsatility Index (PI) Therefore if we detect change in the values of the PI in these flaps then we can detect complications in flap due to vascular insufficiency early. MATERIALS AND METHODS: Seven patients of Free Fibular Flap Reconstruction and ten patients of Free Radial Forearm Flap reconstruction were evaluated over a period of 18 months. In the pre op we recorded PI of Radial and Peroneal artery using colour doppler study. In the Post Operative Period 2 readings of PI at the anastomotic site were taken on Day 1 and Day 7. RESULTS: Both Free Radial Forearm and Free Fibula flaps which were healthy (n = 15) showed a significant decrease in PI values on first Post Op day as compared to Pre Op. Also there was a significant fall in PI on Post Op Day 7 as compared to post op Day 1 (P < 0.05) in these flaps. The flaps developing complications (n = 2) had significantly higher Day 1 Post op PI readings as compared to healthy flaps (P < 0.05). CONCLUSION: PI is an objective index which can indicate changes in perfusion of free flaps used in Head and Neck reconstruction based on which we can predict if a flap is susceptible to circulatory compromise.

Optical modeling of a cylindrical-hemispherical receiver for parabolic dish concentrator.

Among all sub-systems of a solar thermal energy system, the receiver plays a significant role when it gets heat energy from the concentrator. The reliability of such systems depends on the amount of solar energy that the receiver collects and other optical parameters like focal length, aperture diameter, surface absorptivity, and slope error. The present paper discusses the optical analysis of a cylindrical-hemispherical receiver coupled with a parabolic dish concentrator having 3-m diameter. The study has been carried out using the SolTrace software by varying the parameters like receiver aperture diameter (Da) ranging from 0.125 to 0.162 m, surface error of the concentrator varying from 1.7453 to 34.907 mrad, and also surface absorptivity (α) changing from 75 to 95% for different receiver distances (H) ranging from 1.7 to 1.95 m. The simulation results show that the optical efficiency is maximum when the receiver with 0.150-m aperture diameter is placed at a distance of 1.85 m from the concentrator. An increase in slope errors from 1.7453 to 17.453 mrad decreases the average optical efficiency by almost 50% for all receiver diameters. It is also noticed that uniform heat flux distribution can be achieved when the receiver's position is maintained at H = 1.85 m from the concentrator for 0.150-m receiver diameter and 95% absorptivity of the receiver surface. The simulated results of heat flux intensity on the receiver surface are then compared and validated by the experimental results available in the literature. The simulated optical efficiency of the present receiver is found to be 8% higher when compared with a conventional cylindrical receiver with similar dimensions.

Solar parabolic dish collector for concentrated solar thermal systems: a review and recommendations.

Energy demand in the present scenario is rising to meet the increasing demands of energy usage. On the other hand, the use for renewable energy sources now becomes essential to mitigate the climate change as well as to reduce gradual depletion of fossil fuels. Among these renewable energy sources, solar energy particularly solar thermal systems have phenomenal scope in present and future research. In solar thermal systems, concentrators are used to extract the energy from solar irradiation and convert it into useful form. Among different types of solar concentrators, the parabolic dish solar concentrator is preferred as it has high efficiency, high power density, low maintenance, and potential for long durability. In this paper, a detailed review has been carried out on the design parameters like focal length, concentration ratio, and rim angle of the parabolic dish solar concentrator system for achieving higher overall efficiency. The effects of different geometrical shapes of receivers on the overall heat transfer rates are discussed in this paper. Conical shaped receiver is having high overall optical and thermal efficiency comparing with other shapes of receivers. This study also shows that how the thermal performance of the receiver gets enhanced by 10-13% using nanofluids in place of general heat transfer fluids. The paper highlights different models using ray-tracing method for estimation and evaluation of the solar irradiation distribution on the receiver surface. The empirical relations for the design of parabolic dish solar concentrator system are derived for estimating overall concentrator efficiency and heat available at the receiver are given in this review. From the literature, the thermal performance of the receiver affecting the overall performance of the system is observed. Thermal losses due to geometrical properties and ordination of the receiver are explained in the observation section.

A machine learning-based approach to determine infection status in recipients of BBV152 (Covaxin) whole-virion inactivated SARS-CoV-2 vaccine for serological surveys.

Data science has been an invaluable part of the COVID-19 pandemic response with multiple applications, ranging from tracking viral evolution to understanding the vaccine effectiveness. Asymptomatic breakthrough infections have been a major problem in assessing vaccine effectiveness in populations globally. Serological discrimination of vaccine response from infection has so far been limited to Spike protein vaccines since whole virion vaccines generate antibodies against all the viral proteins. Here, we show how a statistical and machine learning (ML) based approach can be used to discriminate between SARS-CoV-2 infection and immune response to an inactivated whole virion vaccine (BBV152, Covaxin). For this, we assessed serial data on antibodies against Spike and Nucleocapsid antigens, along with age, sex, number of doses taken, and days since last dose, for 1823 Covaxin recipients. An ensemble ML model, incorporating a consensus clustering approach alongside the support vector machine model, was built on 1063 samples where reliable qualifying data existed, and then applied to the entire dataset. Of 1448 self-reported negative subjects, our ensemble ML model classified 724 to be infected. For method validation, we determined the relative ability of a random subset of samples to neutralize Delta versus wild-type strain using a surrogate neutralization assay. We worked on the premise that antibodies generated by a whole virion vaccine would neutralize wild type more efficiently than delta strain. In 100 of 156 samples, where ML prediction differed from self-reported uninfected status, neutralization against Delta strain was more effective, indicating infection. We found 71.8% subjects predicted to be infected during the surge, which is concordant with the percentage of sequences classified as Delta (75.6%-80.2%) over the same period. Our approach will help in real-world vaccine effectiveness assessments where whole virion vaccines are commonly used.