Noise minimization in RC-active filters using generalized impedance converters

A procedure has been given for minimizing the total output noise of a Generalized Impedance Converter (GIC), subject to constraints dictated by signal handling capability of the Operational Amplifiers and ease of microcircuit fabrication. The noise reduction is achieved only by the adjustment of RC elements of the GIC, and the total output noise after optimization in the example cited is close to the theoretical lower limit. The output noise of a higher-order filter can be reduced by RC-optimizing the individual GIC's of the active realization. Experimental results on a 20–24 kHz channel bank band-pass filter demonstrate the effectiveness of the above procedure.

Geochemistry and petrology of the ferropicrite dikes and associated rocks of Vestfjella, western Dronning Maud Land, Antarctica

This study provides insights into the composition and origin of ferropicrite dikes (FeOtot = 13 17 wt. %; MgO = 13 19 wt. %) and associated meimechite, picrite, picrobasalt, and basalt dikes found at Vestfjella, western Dronning Maud Land, Antarctica. The dikes crosscut Jurassic Karoo continental flood basalts (CFB) that were emplaced during the early stages of the breakup of the Gondwana supercontinent ~180 Ma ago. Selected samples (31 overall from at least eleven dikes) were analyzed for their mineral chemical, major element, trace element, and Sr, Nd, Pb, and Os isotopic compositions. The studied samples can be divided into two geochemically distinct types: (1) The depleted type (24 samples from at least nine dikes) is relatively depleted in the most incompatible elements and exhibits isotopic characteristics (e.g., initial εNd of +4.8 to +8.3 and initial 187Os/188Os of 0.1256 0.1277 at 180 Ma) similar to those of mid-ocean ridge basalts (MORB); (2) The enriched type (7 samples from at least two dikes) exhibits relatively enriched incompatible element and isotopic characteristics (e.g., initial εNd of +1.8 to +3.6 and initial 187Os/188Os of 0.1401 0.1425 at 180 Ma) similar to those of oceanic island basalts. Both magma types have escaped significant contamination by the continental crust. The depleted type is related to the main phase of Karoo magmatism and originated as highly magnesian (MgO up to 25 wt. %) partial melts at high temperatures (mantle potential temperature >1600 °C) and pressures (~5 6 GPa) from a sublithospheric, water-bearing, depleted peridotite mantle source. The enriched type sampled pyroxene-bearing heterogeneities that can be traced down to either recycled oceanic crust or melt-metasomatized portions of the sublithospheric or lithospheric mantle. The source of the depleted type represents a sublithospheric end-member source for many Karoo lavas and has subsequently been sampled by the MORBs of the Indian Ocean. These observations, together with the purported high temperatures, indicate that the Karoo CFBs were formed in an extensive melting episode caused mainly by internal heating of the upper mantle beneath the Gondwana supercontinent. My research supports the view that ferropicritic melts can be generated in several ways: the relative Fe-enrichment of mantle partial melts is most readily achieved by (1) relatively low degree of partial melting, (2) high pressure of partial melting, and (3) melting of enriched source components (e.g., pyroxenite and metasomatized peridotite). Ferropicritic whole-rock compositions could also result from accumulation, secondary alteration, and fractional crystallization, however, and caution is required when addressing the parental magma composition.

Molecular conformation of alamethicin in dimethylsulfoxide solution A two-dimensional n.m.r. study

The solution conformation of alamethicin, a 20-residue antibiotic peptide, has been investigated using two-dimensional n.m.r. spectroscopy. Complete proton resonance assignments of this peptide have been carried out using COSY, SUPERCOSY, RELAY COSY and NOESY two-dimensional spectroscopies. Observation of a large number of nuclear Overhauser effects between sequential backbone amide protons, between backbone amide protons and CβH protons of preceding residues and extensive intramolecular hydrogen bonding patterns of NH protons has established that this polypeptide is in a largely helical conformation. This result is in conformity with earlier reported solid state X-ray results and a recent n.m.r. study in methanol solution (Esposito et al. (1987) Biochemistry26, 1043-1050) but is at variance with an earlier study which favored an extended conformation for the C-terminal half of alamethicin (Bannerjee et al.

Spectral Invariance of SG Pseudo-Differential Operators on L-P(R-n)

We prove the spectral invariance of SG pseudo-differential operators on L-P(R-n), 1 < p < infinity, by using the equivalence of ellipticity and Fredholmness of SG pseudo-differential operators on L-p(R-n), 1 < p < infinity. A key ingredient in the proof is the spectral invariance of SC pseudo-differential operators on L-2(R-n).

Neoarchean sanukitoid series in the Karelian Province, Finland

Sanukitoid series intrusions can be found throughout the Archean Karelian Province of the Fennoscandian shield. All sanukitoids share the same controversial elemental characteristics: they have high content of incompatible elements such as K, Ba, and Sr as well as high content of the compatible elements Mg, Cr, and Ni, and high Mg#. This composition is explained by an enriched mantle wedge origin in a Neoarchean subduction setting. This study concentrates on sanukitoid intrusions and tonalite-trondhjemite-granodiorite series (TTGs) from Finnish part of the Karelian Province. The collected rock samples have been studied in the field and under microscope as well as for their whole-rock (including isotopes) and mineral compositions. The new data together with previously published analyses help us to better understand the petrogenesis, tectonic setting and reworking of the Archean rock units. TTGs from the Karelian Province form a voluminous series of granitoids and reworked migmatites. This study divides TTG series into two subgroups based on their elemental composition: low-HREE (heavy rare earth element) TTGs and high-HREE TTGs indicating pressure differences in their source. Sanukitoid series is a minor, divergent group of intrusions. These intrusions are variable sized, and the texture varies from even-grained to K-feldspar porphyritic. The elemental composition differentiates sanukitoids from more voluminous TTG groups, the SiO2 in sanukitoids varies to include series of gabbro, diorite, and granodiorite. U Pb age determinations from sanukitoid series show temporally limited emplacement between ~ 2745 2715 Ma after the main crust forming period in the area. Hafnium, neodymium, common lead, and oxygene isotopes indicate well homogenized characteristics. Recycled crust has made a variable, yet minor, contribution to sanukitoids, as evidenced by oxygene isotopes and inherited zircon cores. A proposed tectonic setting for the formation of the sanukitoid series is slab breakoff of oceanic lithosphere in subduction setting, with sanukitoids deriving from an enriched mantle wedge. The proposed setting explains some of the peculiar features of sanukitoids, such as their temporally limited occurrence and controversial elemental composition. Sanukitoids would occur after cessation of the regional growth of Archean crust, and they could be derived from mantle wedge previously enriched by melts and fluids from oceanic crust and sediments. A subsequent event during the Paleoproterozoic Svecofennian orogeny at ~1.9 Ga affected the appearance and microstructures of the rocks as well as caused redistribution of lead between minerals and whole rock. However, the deformation was not able to obliterate the original geochemical characteristics of these sanukitoids.

Correlation of helicopter rotor aeroelastic response with HART-II wind tunnel test data

Purpose - This paper aims to validate a comprehensive aeroelastic analysis for a helicopter rotor with the higher harmonic control aeroacoustic rotor test (HART-II) wind tunnel test data. Design/methodology/approach - Aeroelastic analysis of helicopter rotor with elastic blades based on finite element method in space and time and capable of considering higher harmonic control inputs is carried out. Moderate deflection and coriolis nonlinearities are included in the analysis. The rotor aerodynamics are represented using free wake and unsteady aerodynamic models. Findings - Good correlation between analysis and HART-II wind tunnel test data is obtained for blade natural frequencies across a range of rotating speeds. The basic physics of the blade mode shapes are also well captured. In particular, the fundamental flap, lag and torsion modes compare very well. The blade response compares well with HART-II result and other high-fidelity aeroelastic code predictions for flap and torsion mode. For the lead-lag response, the present analysis prediction is somewhat better than other aeroelastic analyses. Research limitations/implications - Predicted blade response trend with higher harmonic pitch control agreed well with the wind tunnel test data, but usually contained a constant offset in the mean values of lead-lag and elastic torsion response. Improvements in the modeling of the aerodynamic environment around the rotor can help reduce this gap between the experimental and numerical results. Practical implications - Correlation of predicted aeroelastic response with wind tunnel test data is a vital step towards validating any helicopter aeroelastic analysis. Such efforts lend confidence in using the numerical analysis to understand the actual physical behavior of the helicopter system. Also, validated numerical analyses can take the place of time-consuming and expensive wind tunnel tests during the initial stage of the design process. Originality/value - While the basic physics appears to be well captured by the aeroelastic analysis, there is need for improvement in the aerodynamic modeling which appears to be the source of the gap between numerical predictions and HART-II wind tunnel experiments.

Biochemical, histopathological and ultrastructural changes in rat liver induced by r-( + )-pulegone, a monoterpene ketone

Biochemical, histopathological and ultrastructural changes occurring at different time points after intraperitoneal administration of a single dose of pulegone (300 mg/kg) were studied. Significant decreases in the level of liver microsomal cytochrome P-450 (67%), heme (37%), aminopyrine N-demethylase (60%) and glucose-6-phosphatase (58%), were noticed 24 hr after pulegone treatment. Alanine amino transferase (ALT) levels increased in a time dependent manner, following exposure of rats to pulegone. Light microscopic studies of liver tissues showed dilation of central veins and distention of sinusoidal spaces 6 hr after pulegone treatment. Initial centrilobular necrosis was noticed at 12 hr. Centrilobular necrosis became severe at 18 hr and nuclear changes included karyorrhexis and karyolysis. Midzonal and periportal degenerative changes in addition to centrilobular necrosis was observed 24 hr after pulegone administration. Electron microscopic changes showed severe degeneration of endoplasmic reticulum, swelling of mitochondria and nuclear changes, 24 hr after administration of pulegone. The time course profile of the hepatocytes after treatment with pulegone indicates that endoplasmic reticulum is the organelle most affected, following which other degenerative changes occur ultimately leading to cell death.

Crystal Chemistry of the Noncentrosymmetric Eulytites: A(3)Bi(XO4)(3) (X = V, A = Pb; X = P, A = Ca, Cd, Sr, Pb)

Eulytite compounds, A(3)Bi(XO4)(3) (X = P, A = Ca, Cd, Sr, Pb), belong to the noncentrosymmetric space group l (4) over bar 3d (No. 220) as determined by single-crystal X-ray diffraction studies. The crystals were grown from the melt-cool technique with considerable difficulty as the compounds melt incongruently at their melting temperature, except for the compound Pb3Bi(PO4)(3). The unit cell parameter a is 9.984(5), 9.8611(3), 10.2035(3), and 10.3722(2) angstrom for Ca3Bi(PO4)(3), Cd3Bi(PO4)(3), Sr3Bi(PO4)(3), and Pb3Bi(PO4)(3) respectively, and there are four formula units in the unit cell. The structure of Pb3Bi(VO4)(3), a unique eulytite with vanadium substitution, is compared with all these phosphorus substituted eulytites. The A(2+) and Bi3+ cations occupy the special position (16c) while the O anions occupy the general Wyckoff position (48e) in the crystal structure. Only one O position has been identified for Pb3Bi(PO4)(3) and Pb3Bi(VO4)(3), whereas two O atom sites were identified for Ca3Bi(PO4)(3), Cd3Bi(PO4)(3), and Sr3Bi(PO4)(3). The UV-vis diffuse reflectance spectra indicate large band gaps for all the phosphate eulytites while a lower band gap is observed for the vanadate eulytite. The feasibility of the use of these compounds in optoelectronic devices has been tested by measuring the second-harmonic generation (SHG) values which have been found to be of a magnitude equivalent to the commercially used KDP (KH2PO4).

Inelastic dynamic response of R.C. beam column joints by using B.E.M.

A BEM formulation to obtain the inelastic response of R.C. Beam-Column joints subjected to sinusoidal loading along the boundary is presented. The equations of motion are written along with kinematical and constitutive equations. The dynamic reciprocal theorem is presented and the temporal dependence is removed by assuming steady state response.

Playing Games on Sets and Models

The most prominent objective of the thesis is the development of the generalized descriptive set theory, as we call it. There, we study the space of all functions from a fixed uncountable cardinal to itself, or to a finite set of size two. These correspond to generalized notions of the universal Baire space (functions from natural numbers to themselves with the product topology) and the Cantor space (functions from natural numbers to the {0,1}-set) respectively. We generalize the notion of Borel sets in three different ways and study the corresponding Borel structures with the aims of generalizing classical theorems of descriptive set theory or providing counter examples. In particular we are interested in equivalence relations on these spaces and their Borel reducibility to each other. The last chapter shows, using game-theoretic techniques, that the order of Borel equivalence relations under Borel reduciblity has very high complexity. The techniques in the above described set theoretical side of the thesis include forcing, general topological notions such as meager sets and combinatorial games of infinite length. By coding uncountable models to functions, we are able to apply the understanding of the generalized descriptive set theory to the model theory of uncountable models. The links between the theorems of model theory (including Shelah's classification theory) and the theorems in pure set theory are provided using game theoretic techniques from Ehrenfeucht-Fraïssé games in model theory to cub-games in set theory. The bottom line of the research declairs that the descriptive (set theoretic) complexity of an isomorphism relation of a first-order definable model class goes in synch with the stability theoretical complexity of the corresponding first-order theory. The first chapter of the thesis has slightly different focus and is purely concerned with a certain modification of the well known Ehrenfeucht-Fraïssé games. There we (me and my supervisor Tapani Hyttinen) answer some natural questions about that game mainly concerning determinacy and its relation to the standard EF-game