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We present a study of the maximum stress supported by elastics bands of nitrile as a function of the natural length and the load time. The maximum tension of rupture and the corresponding variation in length were found by measuring the elongation of an elastic band when a mass is suspended from its free end until it reaches the breaking point. The work done by non-conservative forces was calculated by means of mechanical hysteresis cycles. Measurement of the hysteresis cycle was performed by the controlled addition and subtraction of masses to produce the band's stretching and contraction processes. It was found that the tension of rupture of an elastic band is independent of its natural length and that it decreases linearly with increasing load time. The mechanical work lost in the hysteresis cycle increases linearly with the natural length of the elastic band. An analysis using a state equation of the thermodynamics of rubber bands was performed obtaining good agreement with the experimental results. Also shown is the dependence on the work done by non-conservative forces in repetitive processes of cyclic hysteresis. This experiment is suitable to be implemented in experimental physics courses as an example of showing the characteristics of elastic materials; furthermore it can be done with inexpensive equipment. (Contains 13 figures.)

The aim of this work is to analyse the influence of spring length on the simple harmonic motion of a spring-mass system. In particular, we study the effect of changing the spring length on the elastic constant "[kappa]", the angular frequency "[omega]" and the damping factor "[gamma]" of the oscillations. To characterize the behaviour of these variables we worked with a series of springs of seven different lengths, in which the elastic constant was found by means of the spring-elongation measurement and "[omega]" was obtained from the measurement of the oscillation period "T" of a suspended mass. The oscillatory movement was recorded using a force sensor and the "[gamma]" value was determined by the fit of the envelope oscillations. Graphical analysis of the results shows that "[kappa]", "[omega]" and "[gamma]" decrease when the natural spring length increases. This experiment can be performed with equipment normally found in undergraduate physics laboratories. In addition, through graphical analysis students can deduce some relationships between variables that determine the simple harmonic motion behaviour. (Contains 10 figures and 1 table.)

Optical absorption in oxygen-deficient and Li+-ion inserted titanium oxide films was studied in the framework of small-polaron hopping. Non-stoichiometric TiOy films with 1.68 ≤ y ≤ 2.00 were deposited by reactive DC magnetron sputtering and were subjected to electrochemical intercalation of Li+-ions and charge-balancing electrons to obtain LixTiOy films with 0.12 ≤ x ≤ 0.34. Dispersion analysis was applied to calculate the complex dielectric function ϵ(ħω)≡ϵ1(ħω)+iϵ2(ħω) from numerical inversion of optical transmittance and reflectance spectra; a superposition of Tauc-Lorentz and Lorentz oscillator models was used for this purpose. Data on ϵ2(ħω) were employed to calculate the optical conductivity and fit this property to a smallpolaron model for disordered systems with strong electron-phonon interaction and involving transitions near the Fermi level. The introduction of oxygen vacancies and/or Li+ insertion yielded band gap widening by ~0.20–0.35 eV, and both processes induced similar low-energy optical absorption. The small-polaron-based analysis indicated increases in the Fermi level by ~0.15–0.3 eV for sub-stoichiometric and/or Li+-inserted films. This suggests the existence of polaronic Ti3+ states in the lower part of the conduction band arising from transfer of electrons from oxygen vacancies and/or inserted Li+ species. The present article is a sequel to an earlier paper on oxygen-deficient and/or Li+-inserted amorphous WOy thin films and forms part of a comprehensive investigation of optical absorption in amorphous transition metal oxides with different valence states of the metallic ions. [ABSTRACT FROM AUTHOR]

Thin films of LixWO3-z with 0 ≤ x ≤ 0.27 and 0 ≤ z ≤ 0.27 were prepared by sputter deposition followed by electrochemical lithiation. Kramers-Kronig-consistent complex dielectric functions were obtained for these films by numerical inversion of experimental spectra of optical transmittance and reflectance by using a superposition of Tauc-Lorentz and Lorentz oscillator models. Low-energy optical absorption bands were induced by oxygen vacancies and/or by electrochemical intercalation of Li+ species together with charge compensating electrons. The experimental optical conductivity was fitted to a small-polaron model for disordered systems with strong electron-phonon interaction, taking into account transitions near the Fermi level. The optical absorption is due to small-polaron hopping and associated with the formation of W5+ states due to transfer of electrons from oxygen vacancies and/or insertion of Li+ species. The results also show increases in the Fermi level, caused by oxygen deficiency or Li+ insertion, which occur along with a band gap shift towards higher energies for the Li+ intercalated films. [ABSTRACT FROM AUTHOR]

Currently the world is facing global warming, one of the causes of which is greenhouse gas (GHG) emissions. For these reasons, the disclosure of GHG emission information is one of the interesting research areas. However, previous research generally focused on developed countries with inconsistent findings. In this sense, this study aims to contribute to GHG disclosure by analyzing the characteristics of firms as determinants of GHG emission disclosure in a developing country, Indonesia. This study also analyzed the role of corporate governance consisting of the structure of the board of commissioners and the effectiveness of the audit committee in moderating the effect of corporate characteristics on GHG emission disclosure. The sample consisted of 69 firms-years companies listed on the Indonesia Stock Exchange (IDX). The results of testing with Partial Least Squares-Structural Equation Modeling (PLS-SEM) showed that the structure of the board of commissioners; consisting of indicators of independence, women representation, and the number of members of the board of commissioners; strengthened the leverage effect on GHG emission disclosure. The results of the moderation test also showed that the effectiveness of the audit committee can encourage firms with high leverage and poor performance to reveal more GHG emissions.

Dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) is one of the major causes of hospitalization and death in people living in southeast Asia. Until recently, the incidence of DHF/DSS and dengue fever in the Americas has been limited. In 1981, there was an epidemic of dengue hemorrhagic fever in Cuba, with 344,203 reported cases, with 10,312 severe illnesses and 158 deaths. The clinical, virological and epidemiological findings from 124 cases of DHF/DSS in children and 104 cases in adults, including 57 deaths of children and 26 of adults are reported. The dengue virus, serotype 2, was isolated from affected individuals and from Aedes aegypti mosquitoes, which are the insect vector of the virus. Clinical symptoms of children included fever, rash (hemorrhagic manifestations), gastrointestinal illness, petechiae (minute areas of hemorrhage in the skin), stomach pain, enlarged liver, and shock occurring after sudden onset of fever and vomiting. The mean age of the children who were hospitalized was four years old. In areas where the disease is endemic, adults do not generally develop dengue fever, as they are usually infected as children and thus develop immunity to the virus. Therefore, this is the first time clinical data has been reported in adults. In adults, the disease was characterized by fever, gastrointestinal symptoms, purpura, upper gastrointestinal bleeding, swelling of the liver, abdominal pain, and shock. Risk factors included the existence of antibodies to dengue virus, and preexisting chronic diseases including asthma, sickle cell anemia and diabetes mellitus. Children, adult women, and whites were at greatest risk. The epidemic was brought under control, thanks to the rapid diagnosis and early treatment of the disease and to the eradication of the mosquito vector. The economic cost of the epidemic was estimated to be about $103 million. It is felt that other epidemics of DHF/DSS in this region may occur, because there are at least three subtypes of the dengue virus circulating to which individuals are not immune, and because the mosquito vector is abundant in other areas outside of Cuba. (Consumer Summary produced by Reliance Medical Information, Inc.), Introduction Although circulation of dengue virus has been widely documented in the Region of the Americas, reports of dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS) have been sporadic--in contrast to the [...]

The Solar Activity Magnetic Monitor (SAMM) Network (SAMNet) is a future UK-led international network of ground-based solar telescope stations. SAMNet, at its full capacity, will continuously monitor the Sun’s intensity, magnetic, and Doppler velocity fields at multiple heights in the solar atmosphere (from photosphere to upper chromosphere). Each SAMM sentinel will be equipped with a cluster of identical telescopes each with a different magneto-optical filter (MOFs) to take observations in K I, Na D, and Ca I spectral bands. A subset of SAMM stations will have white-light coronagraphs and emission line coronal spectropolarimeters. The objectives of SAMNet are to provide observational data for space weather research and forecast. The goal is to achieve an operationally sufficient lead time of e.g., flare warning of 2–8 h and provide many sought-after continuous synoptic maps (e.g., LoS magnetic and velocity fields, intensity) of the lower solar atmosphere with a spatial resolution limited only by seeing or diffraction limit, and with a cadence of 10 min. The individual SAMM sentinels will be connected to their master HQ hub where data received from all the slave stations will be automatically processed and flare warning issued up to 26 h in advance.