On sets of subspaces with two intersection dimensions and a geometrical junta bound

Designs, Codes and Cryptography - In this article, constant dimension subspace codes whose codewords have subspace distance in a prescribed set of integers, are considered. The easiest example of...     

Ternary blends of poly(ethylene oxide) and acrylate-based copolymers: Crystallinity, miscibility, interactions and proton conductivity

In the present work, blends of poly(ethylene oxide) (PEO), poly(acrylonitrile-co-methyl acrylate) (PANMA) and poly(4-vinylphenol-co-2-hydroxyethyl methacrylate) (PVPh-HEM) were studied by DSC, FTIR and electrochemical impedance spectroscopy (EIS). PEO/PANMA blends were found to be immiscible, while PEO/PVPh-HEM blends are miscible and PVPh-HEM/PANMA exhibits partial miscibility behaviour. The ternary PEO/PANMA/PVPh-HEM blends exhibited miscible compositions for PVPh-HEM and PEO-rich systems. The miscibility observed is a direct consequence of the hydrogen bond interactions among the polymer chains, in which the phenol groups in PVPh-HEM interact with both PEO and PANMA chains. The proton conductivity of a selected membrane based on the ternary blend containing 60% PEO and doped with H₃PO₄ aqueous solution reached 8 × 10⁻³ Ω⁻¹ cm⁻¹ at room temperature and 3 × 10⁻² Ω⁻¹ cm⁻¹ at 80 °C.     

Analysis of phytosterols in extra-virgin olive oil by nano-liquid chromatography

In this work the applicability of nano-liquid chromatography (nano-LC) was evaluated for the determination of phytosterols in extra-virgin olive oil samples. These compounds represent a minor part of lipids in vegetable oils, but their quantification can be useful to establish oil origin and to reveal intentional adulterations. The analysis of five main sterols, specifically brassicasterol, stigmasterol, campesterol, cholesterol and β-sitosterol, was performed in a laboratory-assembled nano-LC system coupled with a UV detector. The separation of all compounds was obtained in about 20 min, employing a capillary column packed with a C18-RP (sub-2 μm particles) stationary phase for 15 cm. Methanol only was used as mobile phase. The simple method developed and optimized was validated in terms of repeatability, linearity, limit of detection and limit of quantification (0.78 and 1.56 μg/mL, respectively) achieving good results. After this, it was applied to the determination of phytosterols in extra-virgin olive oil samples. Isolation of phytosterols was obtained by solid-phase extraction, after saponification and liquid–liquid extraction of the unsaponified fraction with diethyl ether. Recovery tests were performed and values between 90% and 103%, with RSDs within 5%, were obtained. Moreover the nano-LC system was coupled with a mass spectrometer for an accurate identification of phytosterols.     

On a generalization of cyclic semifields

A new construction is given of cyclic semifields of orders q ²ⁿ , n odd, with kernel (left nucleus) and right and middle nuclei isomorphic to , and the isotopism classes are determined. Furthermore, this construction is generalized to produce potentially new semifields of the same general type that are not isotopic to cyclic semifields. In particular, a new semifield plane of order 4⁵ and new semifield planes of order 16⁵ are constructed by this method.     

Infinite families of new semifields

We construct six new infinite families of finite semifields, all of which are two-dimensional over their left nuclei. We give constructions for both even and odd characteristics when the left nucleus has odd dimension over the center. The characteristic is odd in the one family in which the left nucleus has even dimension over the center. Spread sets of linear maps are used in all the constructions.     

Use of SPME-GC-MS in the study of time evolution of the constituents of saffron aroma: modifications of the composition during storage

The effect of storage on the composition of saffron aroma is studied. Six samples of saffron from different areas of Italy are analyzed by solid-phase microextraction-gas chromatography-mass spectrometry. Samples 1, 2, and 3 are derived from cultivations of Crocus sativus in the zone of Salerno (Southern Italy) from 2000 to 2002. Samples 4, 5, and 6 are derived from cultivations in Sardinia, Italy (from 1998, 2000, and 2001, respectively). In all samples, 3,5,5-trimethyl-2-cyclohexen-1-one; 3,5,5-trimethyl-2-cyclohexen-1,4-dione; safranal; and 2,4,4-3,5,5-trimethyl-2-cyclohexen-1,4-dione; safranal; and 2,4,4-trimethyl-6-hydroxy-3-carboxaldehyde-2,5-cyclohexadien-1-one are found. 5,5-Dimethyl-2-methylene-1-carboxaldehyde-3-cyclohexene; 3,5,5-trimethyl-1,4-cyclohexandione; and beta-ionone are found with nonanal, dihydro-beta-ionone, and 2,6-di-t-butylphenol. Safranal is the main component in all of the samples. The most important changes are in the presence of alcohols and aldehydes and oxidation products of the major terpenoids components. Furthermore, the presence of safranal--the most important constituent of the flavor--changes during the time, increasing during 3 years, then decreasing after 5 years.     

Solid phase microextraction and gas chromatography mass spectrometry analysis of Zingiber officinale and Curcuma longa

SPME analysis of Zingiber officinale Roscoe and Curcuma longa L. were performed by using a DVB/CARB/PDMS fiber. The SPME analysis of Zingiber officinale showed that the main components found were camphene (7.27%), geranial (8.37%), α-zingiberene (14.50%), α-farnesene (9.14%), β-bisabolene (6.52%), and β-sesquiphellandrene (9.92%). The SPME analysis of Curcuma longa showed that main components were p-cymene (12.96%) and ar-turmerone (12.08%). Other components were β-phellandrene (7.86%), terpinolene (6.97%), ar-curcumene (8.53%), α-zingiberene (8.46%), and β-sesquiphellandrene (7.37%).     

Thermal behaviour of g-zirconium phosphate intercalation compounds with template surfactants

Long chain alkylammonium cations can be exchanged into a preswelled phase of g-zirconium phosphate, a layered inorganic ion-exchanger. The derived materials are used as templates to give organic-inorganic composite materials. The cationic exchange occurs very quickly. These intercalation compounds behave in a very similar way. They are still layered and exhibit an interlayer distance d notably greater than that of its precursor whose behavior depends on the chain length. By thermal and microanalyser characterizations it can be observed that the surfactant is lost in two stages, the second one as a result of the fragmentation of the chain. The layered structure with the expanded interlayer distance is maintained up to ~350°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

A new time-domain frequency-selective quantification algorithm

In this paper a new time-domain frequency-selective quantification algorithm is presented. Frequency-selective quantification refers to a method that analyzes spectral components in a selected frequency region, ignoring all the other components outside. The algorithm, referred to as MeFreS (Metropolis Frequency-Selective), is based on rank minimization of an opportune Hankel matrix. The minimization procedure is satisfied by the down-hill simplex method, implemented with the simulated annealing method. MeFreS does not use any preprocessing step or filter to suppress nuisance peaks, but the signal model function is directly fitted. In this manner, neither inherent signal distortions nor estimation biases to be corrected occur. The algorithm was tested with Monte Carlo simulations. A comparison with VARPRO and AMARESw algorithms was carried out. Finally, two samples of known content from NMR data were quantified.     

A subspace time-domain algorithm for automated NMR spectral normalization

Recently, two methods have been proposed for quantitatively comparing NMR spectra of control and treated samples, in order to examine the possible occurring variations in cell metabolism and/or structure in response to numerous physical, chemical, and biological agents. These methods are the maximum superposition normalization algorithm (MaSNAl) and the minimum rank normalization algorithm (MiRaNAl). In this paper a new subspace-based time-domain normalization algorithm, denoted by SuTdNAl (subspace time-domain normalization algorithm), is presented. By the determination of the intersection of the column spaces of two Hankel matrices, the common signal poles and further on the components having proportionally varying amplitudes are detected. The method has the advantage that it is computationally less intensive than the MaSNAl and the MiRaNAl. Furthermore, no approximate estimate of the normalization factor is required. The algorithm was tested by Monte Carlo simulations on a set of simulation signals. It was shown that the SuTdNAl has a statistical performance similar to that of the MiRaNAl, which itself is an improvement over the MaSNAl. Furthermore, two samples of known contents are compared with the MiRaNAl, the SuTdNAl, and an older method using a standard. Finally, the SuTdNAl is tested on a realistic simulation example derived from an in vitro measurement on cells.