Binary‐offset‐carrier modulation techniques with applications in satellite navigation systems

An important aspect in designing the modulation scheme for various satellite systems, such as the modernized GPS and Galileo, is to obtain good spectral properties and suitable spectral shaping. For example, in the future satellite navigation systems, some of the main goals are: low interference with the existing GPS signals, good root‐mean‐square (RMS) bandwidth, good time resolution (in order to allow the separation between channel paths and to decrease the synchronization errors) etc. Starting from the recently proposed cosine‐ and sine‐BOC modulation families for GPS and Galileo systems, we introduce a new, generalized family, denoted here by double‐BOC (DBOC) modulation. We derive and analyze the properties of the power spectral densities (PSD) and autocorrelation functions (ACF) of the DBOC modulation with various orders, we show its relationship with BPSK, sine‐ and cosine‐BOC modulations, and we illustrate via several examples how to choose optimally the parameters of this new modulation family, according to different optimization criteria. The examples are targeting at applications such as the design of suitable modulations for Galileo open service (OS) and public regulated service (PRS) signals, but the authors believe that the DBOC concept might be useful to other satellite‐based applications, when the available bandwidth is large enough. Copyright © 2006 John Wiley & Sons, Ltd.     

Recognizing a triple bond between main group atoms

The electron pair density, in conjunction with the theory of an atom in a molecule, enables one to unambiguously determine the nature of the bonding between the gallium atoms in bent [HGa-GaH]²⁻. The Ga-Ga bonding in the dianion at the experimental bond length is found to be the result of the sharing of two electron pairs at the Hartree-Fock level of theory, the level consistent with the Lewis model of the electron pair. Received: 27 July 2000 / Accepted: 4 October 2000 / Published online: 19 January 2001     

A System for Measuring Tremor Intensity in Rats

An accurate and physically defined system for measuring tremor in unanesthetized and unrestrained rats is described. The method is based on measuring the vibrations of an ordinary animal cage induced by the tremor of the animal inside it. The vibrations of the animal cage were recorded with a piezoelectric acceleration sensor and analyzed using a microprocessor on-line system. The computer was programmed in assembly language to perform a fast Fourier transform (FFT) spectrum analysis in real time. In those cases in which a frequency distribution curve is too complicated to handle, a mean value of all tremor components belonging to the different frequencies can be used. This mean value is called tremor intensity. Theoretical considerations using the spectral density distribution were employed to find a physically motivated measure of tremor intensity. The measuring system is carefully analyzed, and it is shown that the output of the system can be adjusted to give an estimate of the theoretically motivated measure of the tremor intensity. Measurements of some drug-induced tremor spectra are represented.     

Determination of phosphorus in waste water by EDXRF

Summary In a method developed for the determination of phosphorus in aqueous solutions, phosphorus was changed to the phosphate form, coprecipitated with hydrated iron(III) oxide, bound with activated charcoal and measured by EDXRF. The detection limit was 0.89 mg P/g activated charcoal. The method was used to determine the total phosphorus content of a waste water sample from a paper mill. Investigation of two sample destruction methods, dry ashing/HCl digestion and persulphate oxidation, showed the former to be more suitable for our purpose.     

Finnish research on affect in mathematics: blended theories, mixed methods and some findings

Since the 1990s there has developed a strong cluster of research around the affect in mathematics in Finland. This review highlights some outcome of this work. It is argued that both theoretically and methodologically there has been a tendency to incorporate influences from several sources, which has provided a fertile ground for innovative research. Some of the empirical findings are also reviewed.     

Phase and Element Contents of the cBN Based Composites as Estimated by XPS

X-ray photoelectron spectroscopy (XPS) is used to estimate phase and element contents of the composites based on cubic boron nitride. A composite is a mixture of several compounds and the use of traditional X-ray diffraction for phase analysis in many cases can be difficult. By using XPS, we were able to evaluate the atomic concentration of elements and the content of different compounds of each element. SEM and XPS showed that samples are heterogeneous. The TiB₂ phase, expecting from thermodynamic calculations, was formed in both investigated samples of cBN/Ti₃SiC₂/TiC but in different amount. The Ti₃SiC₂ additive was found more chemically active then TiC.     

Formation and structural characterization of novel polynuclear palladium selenolato complexes [Pd3Se(SePh)3(PPh3)3]Cl and [Pd6Cl2Se4(SePh)2(PPh3)6]

In addition to well-known dinuclear phenylselenolato palladium complexes, the reaction of [PdCl₂(PPh₃)₂] and NaSePh affords small amounts of novel trinuclear and hexanuclear complexes [Pd₃Se(SePh)₃(PPh₃)₃]Cl (1) and [Pd₆Cl₂Se₄(SePh)₂(PPh₃)₆] (2). Complex 1 is triclinic, P1?, a=13.6310(2), b=16.2596(2), c=16.9899(3) Å, α=83.1738(5), β=78.9882(5), γ=78.7635(5)°. Complex 2 is monoclinic, C2/c, a=25.7165(9), b=17.6426(8), c=27.9151(14) Å, β=110.513(2)°. There are no structural forerunners for 1, but the hexanuclear complex 2 is isostructural with [Pd₆Cl₂Te₄(TeR)₂(PPh₃)₆] (R=Ph, C₄H₃S) that have been observed as one of the products in the oxidative addition of R₂Te₂ to [Pd(PPh₃)₄]. Mononuclear palladium complexes may play a significant role as building blocks in the formation of the polynuclear complexes.     

A matrix infrared study of association of formamide

The association of formamide has been studied in argon. In the spectral region from 800 to 200 cm⁻¹ several characteristic bands due to association were found and assigned to the out-of-plane bending modes of the NH group. The widths of these low-frequency bands are of the same order of magnitude as those of the fundamental bands of the monomer. By comparing the spectra of self-associated species with spectra of heteroassociated species between formamide and N,N-dimethyl formamide, it was possible to assign association bands to the open dimers as well as to the cyclic dimers. A band appearing upon warming at about 230 cm⁻¹ has been assigned to a H-bond stretching mode. The results indicate that dimers trapped from the gas phase are predominantly open, and that both open and cyclic structures are formed upon diffusion-controlled association in the matrix.     

Synthesis,spectroscopic, magnetic properties and MMX force field study of two imidazolate-bridged dinuclear copper(II) complexes

Two new imidazolate-bridged dinuclear Cu^II complexes, Na[Cu₂(L¹)₂(im)] and K[Cu₂(L²)₂(im)] (where H₂L¹=6-amino-1,3-dimethyl-5(2-carboxyphenyl)azouracil and H₂L²=1,3-dimethyl-5(2-carboxyphenyl)azobarbituric acid) have been prepared and characterized by magnetic susceptibility and spectroscopic measurements. Both compounds exhibit the expected antiferromagnetic behaviour with 2J=−54.8 and −30.4 cm⁻¹, respectively. Because of the lack of suitable crystals for single crystal X-ray analysis, we have calculated the lowest energy structures using a program based on the MMX force field. On the basis of the results, the magnitude of the magnetic interaction is discussed. TMC 2623     

SYNTHESIS OF TRIFLUOROMETHYL-IMINES BY SOLID ACID/SUPERACID CATALYZED MICROWAVE ASSISTED APPROACH

A new solid acid/superacid catalyzed microwave assisted synthesis of trifluoromethyl-imines is described. Various α,α,α-trifluoromethylketones react readily with primary amines to produce the corresponding imines. Two different strategies have been employed; one is the application of microwave irradiation coupled with solvent-free solid acid catalysis. The other method, for highly deactivated substrates includes the use of a pressure vessel at 175 °C temperature, with solid superacid catalysis. Using the solid acid K-10 montmorillonite or the superacidic perfluorinated resinsulfonic acid Nafion-H, a wide variety of trifluoromethylated imines have been synthesized using the above methods. The products have been isolated in good to excellent yields and high selectivities. This new environmentally friendly synthetic methodology provides significantly higher yields than traditional methods during relatively short reaction times for the preparation of the target compounds.