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Temperature coefficient
About: Temperature coefficient is a research topic. Over the lifetime, 14126 publications have been published within this topic receiving 202714 citations.
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TL;DR: It is concluded that a combined use of both temperature coefficients and exchange rates produces a far morereliable indicator of hydrogen bonding than either alone.
Abstract: Temperature coefficients have been measured by 2D NMR methods forthe amide and CαH proton chemical shifts in two globularproteins, bovine pancreatic trypsin inhibitor and hen egg-white lysozyme.The temperature-dependent changes in chemical shift are generally linear upto about 15° below the global denaturation temperature, and the derivedcoefficients span a range of roughly −16 to +2 ppb/K for amide protonsand −4 to +3 ppb/K for CαH. The temperaturecoefficients can be rationalized by the assumption that heating causesincreases in thermal motion in the protein. Precise calculations oftemperature coefficients derived from protein coordinates are not possible,since chemical shifts are sensitive to small changes in atomic coordinates.Amide temperature coefficients correlate well with the location of hydrogenbonds as determined by crystallography. It is concluded that a combined useof both temperature coefficients and exchange rates produces a far morereliable indicator of hydrogen bonding than either alone. If an amide protonexchanges slowly and has a temperature coefficient more positive than−4.5 ppb/K, it is hydrogen bonded, while if it exchanges rapidly andhas a temperature coefficient more negative than −4.5 ppb/K, it is nothydrogen bonded. The previously observed unreliability of temperaturecoefficients as measures of hydrogen bonding in peptides may arise fromlosses of peptide secondary structure on heating.
477 citations
TL;DR: In this paper, a first-order one-component model and a parallel firstorder twocomponent model were fitted to the CO2-C evolution data in each experiment using a least-squares procedure.
Abstract: The literature was reviewed regarding laboratory incubation studies where C mineralization was measured. Experiments were selected in which the same substrate was incubated at least at two different temperatures and where time-series were available with at least four measurements for each substrate and temperature. A first-order one-component model and a parallel first-order two-component model were fitted to the CO2–C evolution data in each experiment using a least-squares procedure. After normalising for a reference temperature, the temperature coefficient (Q10) function and three other temperature response functions were fitted to the estimated rate constants. The two-component model could describe the dynamics of the 25 experiments much more adequately than the one-component model (higher R2, adjusted for the number of parameters), even when the rate constants for both were assumed to be equally affected by temperature. The goodness-of-fit did not differ between the temperature response models, but was affected by the choice of the reference temperature. For the whole data set, a Q10 of 2 was found to be adequate for describing the temperature dependence of decomposition in the intermediate temperature range (about 5–35 °C). However, for individual experiments, Q10 values deviated greatly from 2. At least at temperatures below 5 °C, functions not based on Q10 are probably more adequate. However, due to the paucity of data from low-temperature incubations, this conclusion is only tentative, and more experimental work is called for.
465 citations
TL;DR: In this article, the microwave characteristics of two dielectric resonator materials were investigated and the relationship between the micro-structures of these materials and dielectrics loss was determined.
Abstract: The microwave characteristics of two dielectric resonator materials were investigated. This research included (Zr, Sn)TiO4, a material having the characteristics of a dielectric constant K= 38, Q= 7000 at 7 GHz, and temperature coefficient of resonant frequency τf, = 0 ppm/°C. The investigation determined the relations between the dielectric loss and micro-structures of this ceramic. Analysis by X-ray microanalyzer made it clear that the addition of Fe2O3 increased the dielectric loss of this ceramic because the Fe ions diffused into the grain. The other material investigated was BaO-PbO-Nd2O3-TiO2, a ceramic having a dielectric constant of K= 88, Q= 5000 at 1 GHz, and τf= 0 ppm/°C. As this ceramic has a very high dielectric constant, it is useful for applications at frequencies <1 GHz.
464 citations
TL;DR: In this paper, the authors reviewed the application of NTCR thermistors from an industrial perspective and outlined some of the common applications of such thermistors and future challenges, as well as their potential applications in a wide range of applications.
Abstract: Monitoring and control of temperature is of paramount importance in every part of our daily life. Temperature sensors are ubiquitous not only in domestic and industrial activities but also in laboratory and medical procedures. An assortment of temperature sensors is commercially available for such purposes. They range from metallic thermocouples to resistive temperature detectors and semiconductive ceramics, showing a negative temperature coefficient of resistance (NTCR). NTCR ceramic sensors occupy a respected market position, because they afford the best sensitivity and accuracy at the lowest price. Despite the enormous commercial success of NTCR thermistors, this area of advanced functional ceramics has not been recently reviewed. Nearly 100 years elapsed between the first report of NTCR behavior and the fabrication of NTCR devices. The manufacture of the first NTCR ceramic thermistors was problematic, as often the devices suffered from poor stability and nonreproducibility. Before NTCR ceramics could be seriously considered for mass production of thermistors, it was necessary to devote a large amount of R&D effort to study the nature of their semiconductivity and understand the influence of impurities/dopants and heat treatments on their electrical characteristics, particularly in their time dependence resistivity (aging). Simultaneously, from a technological viewpoint it was important to develop methods enabling reliable and permanent electrical contacts, and design suitable housing for ceramics, in order to preserve their electrical properties under conditions of variable oxygen partial pressure and humidity. These topics are reviewed in this article from an industrial perspective. Examples of common applications of NTCR thermistors and future challenges are also outlined.
454 citations
TL;DR: In this paper, a thin-film bulk acoustic resonator (TFBAR) with fundamental resonance at 3.6 GHz has been fabricated to assess resonator properties, and the material parameters derived from the thickness resonance were a coupling factor k=0.23 and a sound velocity vs.
Abstract: Aluminum nitride thin films have been grown by reactive magnetron sputter technique using a pulsed power supply. The highly (002)-textured columnar films deposited on platinized silicon substrates exhibited quasi-single-crystal piezoelectric properties. The effective d33 was measured as 3.4 pm/V, the effective e31 as 1.0 C/m2. The pyroelectric coefficient turned out to be positive (4.8 μC m−2 K−1) due to a dominating piezoelectric contribution. Thin-film bulk acoustic resonators (TFBAR) with fundamental resonance at 3.6 GHz have been fabricated to assess resonator properties. The material parameters derived from the thickness resonance were a coupling factor k=0.23 and a sound velocity vs=11 400 m/s. With a quality factor Q of 300, the TFBARs proved to be apt for filter applications. The temperature coefficient of the frequency could be tuned to practically 0 ppm/K.
415 citations