54 research outputs found

    Anisotropic strange stars in Tolman-Kuchowicz spacetime

    Full text link
    We attempt to study a singularity-free model for the spherically symmetric anisotropic strange stars under Einstein's general theory of relativity by exploiting the Tolman-Kuchowicz metric. Further, we have assumed that the cosmological constant Λ\Lambda is a scalar variable dependent on the spatial coordinate rr. To describe the strange star candidates we have considered that they are made of strange quark matter (SQM) distribution, which is assumed to be governed by the MIT bag equation of state. To obtain unknown constants of the stellar system we match the interior Tolman-Kuchowicz metric to the exterior modified Schwarzschild metric with the cosmological constant, at the surface of the system. Following Deb et al. we have predicted the exact values of the radii for different strange star candidates based on the observed values of the masses of the stellar objects and the chosen parametric values of the Λ\Lambda as well as the bag constant B\mathcal{B}. The set of solutions satisfies all the physical requirements to represent strange stars. Interestingly, our study reveals that as the values of the Λ\Lambda and B\mathcal{B} increase the anisotropic system becomes gradually smaller in size turning the whole system into a more compact ultra-dense stellar object.Comment: 18 pages, 10 figure

    Synthesis and fabrication of self-sustainable triboelectric energy case for powering smart electronic devices

    Get PDF
    In recent times, Triboelectric Nanogenerators (TENG) have attained the focus of the scientific community due to its potential as a medium to harvest mechanical energy from the ambient environment. Human motion has been attributed as a source of mechanical energy to drive electronic devices and sensors through TENG. Based on the principles of single electrode TENG, we have developed a Triboelectricity based Stepping and Tapping Energy Case (TESTEC) which magnifies the prospect to power touch electronic devices by utilizing finger tapping and stepping motion. This novel case was constructed with two single electrode TENG operating through the triboelectric mechanism between human skin and Polyethylene terephthalate (PET) film on the front part and Nitrile Butadiene Rubber (NBR) and PET film on the back part. This cost effective device was further tested by attaching with a cell phone at variable load frequency, airgap and finger combinations where the output response increased with the increased frequencies (60–240 BPM) and air gap (1 cm–5 cm). Maximum output voltages of 14.8 V and 50.8 V were obtained for the front and back parts, respectively. Besides, maximum output powers were observed to be 3.78 W/m2 at 0.46 MΩ and 6.21 W/m2 at 1.02 MΩ, respectively. Also, the device was tested by integrating with conventional electronic components including capacitors, bridge rectifiers and 15 LEDs. Based on the results, a electrical circuit has been proposed to power touch cell phones. The device was further modified using Silver (Ag) nanoparticles in the front part. The modified TESTEC provided higher output response compared to the primary TESTEC. The TESTEC can be a self sustainable way to power touch electronic devices which can reudce the necessity to charge electronics devices in the conventional way

    Polymer Based Triboelectric Nanogenerator for Cost‐Effective Green Energy Generation and Implementation of Surface‐Charge Engineering

    Get PDF
    Performance of triboelectric nanogenerators for harvesting mechanical energy from the ambient environment has been limited by structural complexity, cost-effectiveness, and mechanical weakness of materials. Herein, a cost-effective vertical contact separation mode triboelectric nanogenerator using polyethylene (PE) and polycarbonate (PC) in a regular digital versatile disc is reported. This cost-effective nanogenerator with simplified structures is able to generate an open-circuit voltage of 215.3 V and short-circuit current of 80 μA. The effects of the distance of impact and the air gap between the triboelectric layers have also been tested from 3 to 9 cm, and 0.25 to 1 cm, respectively. It is determined that 0.5 cm is the optimal air gap. The nanogenerator is also tested in different real-life scenarios including stresses produced by a moving car, walking, and a rolling skateboard over the nanogenerator. The surfaces of the triboelectric layers are further modified by surface-charge engineering which induced a 460% increase in the output power. These tests reveal a significant electrical response and mechanical stability under stress. In summary, this study demonstrates that the relatively inexpensive PE and PC triboelectric pair has the potential to be used for highly efficient, mechanically robust triboelectric nanogenerators

    CSR in major European football leagues in the age of COVID-19: financial vulnerability, mental health and domestic violence

    Get PDF
    Purpose COVID-19 pandemic has significantly impacted the lives of people and businesses around the world in different ways. France, Spain, Italy and the UK are among the worst affected countries by this pandemic. The purpose of this paper is to identify and compare different corporate social responsibility (CSR) activities taken by the clubs and player of the major football leagues of these four countries to develop a more comprehensive model of intervention. Design/methodology/approach This paper has analyzed the initiatives taken by these football clubs and players to address financial vulnerabilities, mental health problems and domestic violence among the stakeholders and compared them with the existing CSR and humanitarian models. A case study approach has been used to collect and analyze data related to the CSR activities taken by the players and club management. Official websites of the clubs, newspaper and journal articles were among the major sources used to collect data for the paper. Findings Football clubs and players of the four major leagues have raised funds through different campaigns and delivered foods and essential medical supplies to the communities and hospitals to address financial vulnerabilities, mental health issues and domestic violence within their communities during the COVID-19 pandemic. They have provided guidance to their followers using social and television media to improve their physical and mental health during the pandemic. Online competitions, quizzes or virtual hangouts have also been used by the players to engage the stakeholders on a frequent basis. Football clubs have also initiated campaigns to raise awareness within the community on available medical services for the victims of domestic violence and also provided them with shelter, food, medical, legal and online counseling services. Originality/value Football clubs and players of the major leagues were always at the forefront to help the communities and hospitals to address issues related to mental health problems, financial vulnerabilities and domestic violence during the COVID-19 pandemic. The findings of this paper could help and guide other entities in designing a more comprehensive model of CSR interventions during pandemics or crisis situations to address financial vulnerabilities, mental health problems and domestic violence within their communities.©2022 Emerald Publishing Limited. This manuscript version is made available under the Creative Commons Attribution–NonCommercial 4.0 International (CC BY–NC 4.0) license, https://creativecommons.org/licenses/by-nc/4.0/fi=vertaisarvioitu|en=peerReviewed

    Piezo-Tribo Dual Effect Hybrid Nanogenerators for Health Monitoring

    Get PDF
    Over the years, nanogenerators for health monitoring have become more and more attractive as they provide a cost-effective and continuous way to successfully measure vital signs, physiological status, and environmental changes in/around a person. Using such sensors can positively affect the way healthcare workers diagnose and prevent life-threatening conditions. Recently, the dual piezo-tribological effect of hybrid nanogenerators (HBNGs) have become a subject of investigation, as they can provide a substantial amount of data, which is significant for healthcare. However, real-life exploitation of these HBNGs in health monitoring is still marginal. This review covers piezo-tribo dual-effect HBNGs that are used as sensors to measure the different movements and changes in the human body such as blood circulation, respiration, and muscle contractions. Piezo-Tribo dual-effect HBNGs are applicable within various healthcare settings as a means of powering noninvasive sensors, providing the capability of constant patient monitoring without interfering with the range of motion or comfort of the user. This review also intends to suggest future improvements in HBNGs. These include incorporating surface modification techniques, utilizing nanowires, nanoparticle technologies, and other means of chemical surface modifications. These improvements can contribute significantly in terms of the electrical output of the HBNGs and can enhance their prospects of applications in the field of health monitoring, as well as various in vitro/in vivo biomedical applications. While a promising option, improved HBNGs are still lacking. This review also discusses the technical issue which has prevented so far, the real use of these sensors

    Rickettsial illnesses as important causes of febrile illness in Chittagong, Bangladesh

    Get PDF
    We conducted a yearlong prospective study of febrile patients admitted to a tertiary referral hospital in Chittagong, Bangladesh, to assess the proportion of patients with rickettsial illnesses and identify the causative pathogens, strain genotypes, and associated seasonality patterns. We diagnosed scrub typhus in 16.8% (70/416) and murine typhus in 5.8% (24/416) of patients; 2 patients had infections attributable to undifferentiated Rickettsia spp. and 2 had DNA sequence-confirmed R. felis infection. Orientia tsutsugamushi genotypes included Karp, Gilliam, Kato, and TA763-like strains, with a prominence of Karp-like strains. Scrub typhus admissions peaked in a biphasic pattern before and after the rainy season, whereas murine typhus more frequently occurred before the rainy season. Death occurred in 4% (18/416) of cases; case-fatality rates were 4% each for scrub typhus (3/70) and murine typhus (1/28). Overall, 23.1% (96/416) of patients had evidence of treatable rickettsial illnesses, providing important evidence toward optimizing empirical treatment strategies

    Volatile constituents of essential oils isolated from leaf and rhizome of Zingiber cassumunar Roxb.

    No full text
    The composition of the essential oil of Zingiber cassumunar Roxb. from Bangladesh was examined by gas chromatography mass spectroscopy (GC-MS). Sixty-four components were identified in leaf oil and 32 components were identified in the rhizome oil, accounting for 94.60% and 98.56% of the total yields, respectively. The main component in leaf oil was sabinene (14.99%), b-pinene (14.32%), caryophyllene oxide (13.85%) and caryophyllene (9.47%). On the other hand, rhizome oil contained triquinacene 1,4-bis (methoxy) (26.47%), (Z)-ocimene (21.97%) and terpinen-4-ol (18.45%). The compositions of both oils varied qualitatively and quantitatively
    corecore