Gelatine sizing and discoloration: A comparative study of optical spectra obtained from ancient and artificially aged modern papers

The role of gelatine sizing in ancient paper discoloration is still subject to debate. In this report we have addressed this issue by comparing the optical reflectance of sized and non-sized artificially aged modern papers with reflectance data obtained from a set of ancient specimens. We have used different ageing procedures and prepared the gelatine following methods set down in ancient recipes. Gelatine-sized aged papers showed an optical response comparable with that of ancient paper specimens, while very small reflectance modifications were observed in pure cellulose unsized samples under the same ageing conditions. In addition, measurements carried out on pure gelatine films confirmed that gelatine plays a major role in paper discoloration. Some differences in discoloration effects induced by artificial and natural ageing on sized paper are discussed and a possible explanation is proposed.     

Large quartic groups on translation planes,II—Even order: Characterization of the Ott‐Schaeffer planes

A general theory of collineation groups generated by quartic groups of even order is considered. Applications are given to collineation groups generated by ‘large’ quartic groups. © 2005 Wiley Periodicals, Inc. J Combin Designs 13: 195–210, 2005.     

Partial miscibility in a nylon‐6/nylon‐66 blend coalesced from their common α‐cyclodextrin inclusion complex

We successfully formed a series of inclusion complexes (ICs) between an α‐cyclodextrin (α‐CD) host and two kinds of guest polymers, nylon‐6 and nylon‐66. An attempt to achieve an intimate blend between nylon‐6 and nylon‐66 through the formation and dissociation of their common α‐CD IC was made. The formation of all nylon ICs was verified with wide‐angle X‐ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) and cross‐polarized/magic‐angle‐spinning ¹³C NMR spectroscopy. The experimental results demonstrated that α‐CD could only host single nylon polymer chains in the IC channels, either nylon‐6 or nylon‐66 in their own complexes, and presumably either nylon in neighboring channels of their common IC. The IC‐coalesced blend of nylon‐6 and nylon‐66 was obtained after the removal of the host cyclodextrin from their common IC with dimethyl sulfoxide. The spectroscopic results (FTIR and ¹³C NMR) illustrated that there was a degree of intimate miscibility existing in the IC‐coalesced blend, but not in the solution‐cast physical blend, although X‐ray diffraction patterns showed that the crystal structure of the IC‐coalesced blend was similar to that of the physical blend. DSC thermal profiles suggested that nylon‐66 first formed crystals during coalescence and that the subsequent crystallization of nylon‐6 was greatly affected by the nylon‐66 crystallites because of the close proximity of the two components in portions of the coalesced blend. DSC observations also demonstrated that the melting of the coalesced blend did not lead to complete phase separation of the nylon‐6 and nylon‐66 components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1369–1378, 2004     

Oscillation of coupled nonlinear discrete systems

The problem of oscillation of a second order nonlinear difference system is considered and conditions for oscillation are derived by means of a complete analysis of nonoscillatory solutions. The case of systems with deviating arguments is also analyzed, and the results are shown to significantly generalize some existing ones.     

Generalized Hermite–Gaussian functions and pulse propagation in optical fiber systems

Chirped Hermite–Gaussian functions shows outstanding potentialities in mathematical models for linear and non linear pulse propagation in optical fibers. We propose three generalized subclasses of Hermite–Gaussian functions as natural extension to the complex domain. We exemplify the properties of these subclasses by analyzing some relevant cases of pulse oscillatory dynamics governed by nonlinear Schrödinger equation with constant or periodic coefficfients.     

High efficiency UV solid state lasers based on Ce:LiCaAlF6 crystals

We report the spectroscopy and laser results of cerium-doped colquiriite LiCaAlF₆ (LiCAF) single crystals. High quality samples have been grown using the Czochralski technique and characterized by means of X-ray Laue diffractometry, absorption and emission spectra. Moreover, we measured the lifetime and deduced the emission cross-sections of the laser transition. Using this crystal we realized two lasers devices: a high-efficiency laser emitting at 289 nm with a repetition rate (RR) of up to 2 kHz and a widely tunable laser (from 280 nm to 317 nm) with an RR of up to 4.3 kHz. The high quality of the crystal made it possible to obtain the highest slope efficiency (49%) ever reported to our knowledge for a Ce:LiCAF laser. PACS 42.55.Rz; 78.55.Hx; 81.10.Fq     

Numerical Modeling of PMD

A procedure for evaluating system performance considering all orders of polarization mode dispersion (PMD) is presented. The method provides engineering rules for computing system penalty introduced by PMD. Computer simulation of PMD induced penalty indicates that for generating a realistic system budget, effect of higher order PMD in presence of chromatic dispersion is essential. Considering all of these penalties, in order to obtain a system-reach of 3200 km at 40 Gb/s, a fiber PMD of less than 0.04 ps/km^1/2 is required when at the signal wavelength chromatic dispersion is 0. In presence of 18 ps/nm chromatic dispersion for the same system reach this PMD value reduces to about 0.02 ps/km^1/2.     

O– centers in LuAG:Ce,Mg ceramics

Electron traps are known to a have great influence on the carriers transport process in Ce based scintillators. On the other hand, the role of hole traps in the scintillation process has been less considered. By means of electron spin resonance (ESR), we detected hole traps in highly Ce‐doped LuAG:Ce,Mg ceramics in the form of σ‐type O^– centers. The g ‐tensor components turn out to be g_⊥ = 2.0103, and g_|| = 2.0023, revealing the axial symmetry of these defects. Mg‐perturbed variants of O^– centers are proposed to exist in LuAG:Ce,Mg. Their occurrence is related to an elongated Mg–O bond as evidenced by DFT calculations. Finally, the multiple role of O^– centers in the scintillation process is discussed.

     

A Polypyrrole Based Sensor for the Electrochemical Detection of OH Radicals

Polypyrrole was used as sensitive material in the development of a new device employed for the indirect detection of OH radicals. The polypyrrole film was electrosynthesized on glassy carbon. The modified electrode was exposed to the OH radicals generated by Fenton reaction. As a result of the overoxidation the conductivity of the polymer diminished very much. The overoxidation (%) was directly proportional to the ^.OH amount that reached the electrode surface. ABTS^.+, superoxide and alkylperoxy radicals did not interfere in the determination. The applicability of the device was demonstrated by estimating the ^.OH scavenging ability of ascorbic acid.