Use of ETAAS,FAAS and ICP-OES for production and post-certification monitoring of a multielemental certified reference material according to national regulation limits for elements in drinking water

Accreditation and Quality Assurance - This paper describes the development of a certified reference material (CRM), produced in the National Institute of Quality from Peru (INACAL) in order to...     

Chemical investigation of three plutonium–beryllium neutron sources

Thorough physical and chemical characterization of plutonium–beryllium (PuBe) neutron sources is an important capability with applications ranging from material accountancy to nuclear forensics. Characterization of PuBe sources is not trivial owing to range of existing source designs and the need for adequate infrastructure to deal with radiation and protect the analyst. This study demonstrates a method for characterization of three PuBe sources that includes physical inspection and imaging followed by controlled disassembly and destructive analysis.     

Noise in miniature microphones

The internal noise spectrum in miniature electret microphones of the type used in the manufacture of hearing aids is measured. An analogous circuit model of the microphone is empirically fit to the measured data and used to determine the important sources of noise within the microphone. The dominant noise source is found to depend on the frequency. Below 40 Hz and above 9 kHz, the dominant source is electrical noise from the amplifier circuit needed to buffer the electrical signal from the microphone diaphragm. Between approximately 40 Hz and 1 kHz, the dominant source is thermal noise originating in the acoustic flow resistance of the small hole pierced in the diaphragm to equalize barometric pressure. Between approximately 1 kHz and 9 kHz, the noise originates in the acoustic flow resistances of sound entering the microphone and propagating to the diaphragm. To further reduce the microphone internal noise in the audio band requires attacking these sources. A prototype microphone having reduced acoustical noise is measured and discussed.     

On separating a fixed point from zero by invariants

Assume a fixed point v∈V^G can be separated from zero by a homogeneous invariant f∈𝕜[V]^G of degree p^rd, where p>0 is the characteristic of the ground field 𝕜 and p,d are coprime. We show that then v can also be separated from zero by an invariant of degree p^r, which we obtain explicitly from f. It follows that the minimal degree of a homogeneous invariant separating v from zero is a p-power.     

Hyperfine interactions in amorphous Tm-Cu Alloys

Hyperfine interactions in sputtered amorphous Tm_xCu_1?x, with x=0.70, 0.50, and 0.33, have been measured over a temperature range from 1.7 K to room temperature using the Mössbauer effect in¹⁶⁹Tm. At low temperatures each spectrum shows a well resolved six-line hyperfine pattern indicative of magnetic order and a superimposed quadrupole doublet. The relative spectral weight of the magnetic component increases with increasing Tm concentration and decreases with increasing temperature. The magnetic component persists at unexpectedly high, temperatures with no decrease in overall splitting and no evidence of electronic relaxation. For all three concentrations, the magnetic splitting is the same as that of Tm metal at low temperatures, nearly the free-ion limit. The electric quadrupole shift of the magnetic component is the same for the three samples, but is significantly less than that of Tm metal (hexagonal) and much larger than that of crystalline TmCu (cubic). The non-magnetic doublets have quadrupole splittings that are very nearly the same for the three concentrations and show considerable asymmetry, a typical effect of electronic relaxation, which persists at temperatures above where the magnetic component disappears.     

Possible application of memristors in ESD protection

Memristors as fundamental two-terminal electric circuit elements can be miniaturised to extreme extents. However like other electronic devices memristors can have application in the field of electrical engineering as well, e.g. in the fields of over-current protection, over-voltage protection and EMC. This paper proposes an application opportunity of memristors in ESD protection. Based on their purely dissipative character, these devices can usefully co-operate with ceramic capacitors having no ability to dissipate the energy of ESD surges. A type of structure of memristors for ESD protection purposes and a SPICE model are proposed.     

Transmission of terahertz radiation using a microstructured polymer optical fiber

A hollow-core microstructured polymer optical fiber was analyzed in the terahertz (THz) region. Spectral analysis of time domain data shows propagation of THz waves in both the hollow-core and the microstructured cladding with a time delay of approximately 20 ps. The frequency range and shift of the transmission bands between different sized waveguides suggested photonic bandgap or resonant guidance. Finite-difference time domain calculations agree relatively well to the experimental transmission results. Propagation losses were estimated to be as low as 0.9 dB/cm.     

Structure of chlorotris(1,3,5-triaza-7-phosphaadamantane)platinum(II) chloride hydrate methanolate, [Pt(PTA)3Cl] [Cl]·H2O·CH3OH

The title compound chlorotris(PTA)platinum(II) chloride hydrate methanolate (PTA=1,3,5-triaza-7-phosphaadamantane), [C₁₉H₄₂Cl₂N₉O₂P₃Pt] is monoclinic, witha=10.832(1),b=21.306(7),c=12.702(3)Å,=100.42(5)°,V=2883(2)ų,Z=4,D _x=1.814 g cm^–3,=53.0 cm^–1,F(000)=1568,T=298K in space groupP2₁/c. The structure was solved by heavy atom and Fourier methods and refined toR=0.051 for 4319 unique observed reflections. The complex exhibits approximately square-planar geometry about the Pt atom and a significant trans effect, with bond lengths Pt-Cl1=2.3371(2), Pt-C12 (ionic)=4.463(4), Pt-P _{trans(to cl)}=2.233(2), Pt-P _cis,ave=2.323(3)Å and bond angles Cl-Pt-P _cisave 83.60(3), P _trans -Pt-P _cis,ave 96.49(6)°. The H₂O is apparently hydrogen bonded to two N atoms on different cations, and the methanol OH group to the chloride anion.