A biochar from casein and its properties

A biochar was prepared by pyrolysis of casein. A helium and mercury porosimeter were used to measure the true and apparent densities of the chars respectively, elemental and IR analysis were used to characterize the chemical composition of char. A SEM was used to observe the char surfaces in order to verify the presence of porosity. The biochar has 9.02% of nitrogen, content of porosity is 20%. The experimental results show that it is possible to prepare chars with relatively high porosity from casein for the further preparation of activated carbon.     

Optimization of dc SQUID voltmeter and magnetometer circuits

We calculate the signal-to-noise ratio in a dc SQUID system as a function of source impedance, taking into account the effects of current and voltage noise sources in the SQUID. The optimization of both tuned and untuned voltmeters and magnetometers is discussed and typical sensitivities are predicted using calculated noise spectra. The calculations are based on an ideal symmetric dc SQUID with % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaHYoGycqGH9a% qpcaaIYaacbaGaa8htaiaa-LeadaWgaaWcbaacbiGaa4hmaaqabaGc% caGGVaGaeuOPdy0aaSbaaSqaaiaa+bdaaeqaaOGaeyypa0JaaGymaa% aa!3D23!\[\beta = 2LI_0 /\Phi _0 = 1\] and moderate noise rounding % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaaiiGacqWFOaakcq% WFtoWrcqWF9aqpcqWFYaGmcqaHapaCcaWGRbWaaSbaaSqaaiaadkea% aeqaaGqaaOGaa4hvaiaac+cacaGFjbWaaSbaaSqaaerbbjxAHXgaiu% GacaqFWaaabeaakiab-z6agnaaBaaaleaacaqGGaacbiGaaWhmaaqa% baGccqGH9aqpcaaIWaGaaiOlaiaaicdacaaI1aGaaiykaaaa!471A!\[(\Gamma = 2\pi k_B T/I_0 \Phi _{{\rm{ }}0} = 0.05)\], where ₀ is the flux quantum, T is the temperature, L is the SQUID inductance, and I ₀ is the critical current of each junction. The optimum noise temperatures of tuned and untuned voltmeters are found to be 2.8(L/R)T and 8(L/R)T (1 + 1.5² + 0.7⁴)^1/2/² respectively, where /2 is the signal frequency, assumed to be much less than the Josephson frequency, and is the coupling coefficient between the SQUID and its input coil. It is found that tuned and untuned magnetometers can be characterized by optimum effective signal energies given by (16k _B TLE/² R)[1 + (1 + 1.5² + 0.7²)^1/2 + 0.75²] and 2k_B T _iR_iB/² L _p respectively, where B is the bandwidth, R _i is the resistance representing the losses in the tuned circuit at temperature T _i and L _p is the inductance of the pickup coil.This work was supported by the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy, and by the U.S. Office of Naval Research.Guggenheim Fellow.     

The Analysis of Monopole Antennas Located on a Spherical Vehicle: Part 1, Theory

In this paper, a technique for determining the behavior of thin-wire antennas mounted radially on a conducting sphere is formulated. The method of analysis involves the derivation of an integral equation for the antenna current. By a proper choice of boundary conditions, a modified Green's tensor for the sphere can be defined. This limits the range of the integral equation to over the thin wires only, thereby permitting a relatively simple solution for the antenna currents.     

Development and Use of the BLT Equation in the Time Domain as Applied to a Coaxial Cable

This paper discusses the use of the Baum-Liu-Tesche (BLT) equation for calculating transmission-line load responses directly in the time domain. From the frequency-domain BLT equation, its transient counterpart is first derived. For the special case of a coaxial cable, explicit expressions for the transient propagation function, the surge impedance and admittance, and the transient reflection coefficients at each end of the line are derived. These quantities, together with the transient-BLT equation, are used to compute the transient load voltages. The computed results are subsequently compared with transient responses obtained using the frequency-domain BLT equation and Fourier inversion, and the agreement is excellent for highly conducting cables. The benefit of deriving the BLT equation in the time domain is that it may be used, with slight modifications, to treat the case of nonlinear or time-varying loads. This will be described in a future paper     

Scattered EM Field Responses of Canonical Scatterers Illuminated by an Impulse-Radiating Antenna (IRA)

This paper investigates the possibility of using the impulse-radiating antenna (IRA) as both a transmitter and receiver of electromagnetic energy for the purpose of target identification. Of specific interest is estimating the induced open-circuit voltage at the IRA's source terminals, when it is illuminated by the scattered EM field from simple conducting bodies excited by an incident field from the same IRA acting as a transmitter. In this study, several different canonical scatters are considered, including thin wires, spheres, conducting boxes, and an infinite conducting plate. For a 7 kV pulse excitation of the IRA, received peak transient voltages at the antenna ranged from a few volts to about 400 volts, depending on the scatterer.     

Hexairidium carbonyl clusters in the micropores of faujasite zeolites: evidence from transmission electron microscopy

[Ir₆(CO)₁₆] was formed in the pores of zeolite NaY by adsorption of [Ir(CO)₂(acac)] followed by treatment in CO + H₂. [Ir₆(CO)₁₅]²⁻ in zeolite NaX was prepared similarly. Each sample was characterized by high‐resolution transmission electron microscopy. The images indicate the presence of the iridium clusters in the zeolite micropores, with almost no scattering centers indicating iridium outside these pores. The supported [Ir₆(CO)₁₆] and [Ir₆(CO)₁₅]²⁻, which have previously been characterized by infrared and extended X‐ray absorption fine structure spectroscopies, are among the most uniform and structurally best defined supported metal clusters. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electron holography of thin amorphous carbon films: measurement of the mean inner potential and a thickness-independent phase shift

The phase shift induced by thin amorphous carbon films with thicknesses between 1 and 16 nm was measured by electron holography in a transmission electron microscope. Large phase shifts Delta phi are observed as the thickness of the amorphous C films decreases which cannot be described by the well-known equation Delta phi = CE V0t (V0: mean inner Coulomb potential of the material, t: sample thickness). Data plotted in a Delta phi vs. t diagram can be well-fitted by a modified equation Delta phi=CE V0t + phi add. The mean inner Coulomb potential of the amorphous carbon with a density of 1.75 g/cm3 was determined to be 9.09 V which is consistent with previous experimental data for amorphous carbon with a higher density. The thickness-independent phase offset phi(add) of 0.497 rad is large for amorphous carbon under the given experimental conditions. We suggest that a surface-related electrostatic potential is responsible for the thickness-independent contribution phi add.     

dc SQUID: Current noise

The computer model used by Tesche and Clarke to calculate the voltage noise across the dc SQUID is extended to calculate the circulating current noise around the SQUID loop, and the correlation between the circulating current noise and the voltage noise across the SQUID. The parameters chosen are % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaHYoGycqGH9a% qpcaaIYaacbaGaa8htaiaa-LeadaWgaaWcbaacbiGaa4hmaaqabaGc% caGGVaacciGae0NPdy0aaSbaaSqaaiab9bcaGiab9bdaWaqabaGccq% GH9aqpcaaIXaGaaiilaiaabccacqqFtoWrcqqF9aqpcqqFYaGmcqaH% apaCcaWGRbWaaSbaaSqaaiaadkeaaeqaaOGaa8hvaiaa-9cacaWFjb% WaaSbaaSqaaiaa+bcacaGFWaaabeaakiab9z6agnaaBaaaleaacqqF% GaaicqqFWaamaeqaaOGaeyypa0JaaeiiaiaabcdacaqGUaGaaeimai% aabwdaaaa!51F9!\[\beta = 2LI_0 /\Phi _{ 0} = 1,{\rm{ }}\Gamma = 2\pi k_B T/I_{ 0} \Phi _{ 0} = {\rm{ 0}}{\rm{.05}}\], and an applied flux of ₀/4 (L is the SQUID inductance, I ₀ is the critical current per junction, T is the temperature, and ₀ is the flux quantum). At frequencies well below the Josephson frequency and at the optimum current bias, the voltage power spectral density is approximately 16 kBTR, the current power spectral density is approximately 11k_B T/R and the voltage-current correlation spectral density is approximately 12k _B T, where R is the resistance per junction.This work was supported by the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy.Guggenheim Fellow.