Maximal diversity algebraic space-time codes with low peak-to-mean power ratio

The design requirements for space-time coding typically involves achieving the goals of good performance, high rates, and low decoding complexity. In this paper, we introduce a further constraint on space-time code design in that the code should also lead to low values of the peak-to-mean envelope power ratio (PMEPR) for each antenna. Towards that end, we propose a new class of space-time codes called the "low PMEPR space-time" (LPST) codes. The LPST codes are obtained using the properties of certain cyclotomic number fields. The LPST codes achieve a performance identical to that of the threaded algebraic space-time (TAST) codes but at a much smaller PMEPR. With M antennas and a rate of one symbol per channel use, the LPST codes lead to a decrease in PMEPR by at least a factor of M relative to a Hadamard spread version of the TAST code. For rates beyond one symbol per channel use and up to a guaranteed amount, the LPST codes have provably smaller PMEPR than the corresponding TAST codes. Additionally, with the concept of punctured LPST codes proposed in this paper, significant performance improvement is obtained over the full diversity TAST schemes of comparable complexity. Numerical examples are provided to illustrate the advantage of the proposed codes in terms of PMEPR reduction and performance improvement for very high rate wireless communications.     

Strong cellulose nanofibre–nanosilica composites with controllable pore structure

Flexible nanocellulose composites with silica nanoparticle loading from 5 to 77 wt% and tunable pore size were made and characterised. The pore structure of the new composites can be controlled (100–1000 nm to 10–60 nm) by adjusting the silica nanoparticle content. Composites were prepared by first complexing nanoparticles with a cationic dimethylaminoethyl methacrylate polyacrylamide, followed by retaining this complex in a nanocellulose fibre network. High retention of nanoparticles resulted. The structural changes and pore size distribution of the composites were characterised through scanning electron microscopy (SEM) and mercury porosimetry analysis, respectively. The heavily loaded composites formed packed bed structures of nanoparticles. Film thickness was approximately constant for composites with low loading, indicating that nanoparticles filled gaps created by nanocellulose fibres without altering their structure. Film thickness increased drastically for high loading because of the new packed bed structure. Unexpectedly, within the investigated loading range, the level of the tensile index on nanocellulose mass basis remained constant, showing that the silica nanoparticles did not significantly interfere with the bonding between the cellulose nanofibres. This hierarchically engineered material remains flexible at all loadings, and its unique packing enables use in applications requiring nanocellulose composites with controlled pore structure and high surface area.     

FT‐IR characterization and hydrolysis of PLA‐PEG‐PLA based copolyester hydrogels with short PLA segments and a cytocompatibility study

A series of the biodegradable copolyester hydrogels was prepared using a redox‐initiated polymerization with a constant 1:9 mole ratio of the Boltorn‐based acrylate and diacrylate triblock comacromonomers. The Boltorn® macromonomer was derived from the hyperbranched polyester Boltorn H20, which was functionalized at each terminus with poly(ethylene glycol) acrylate, and the diacrylate triblock macromonomer was poly (lactide‐b‐ethylene glycol‐b‐lactide) diacrylate. The hydrolysis of the copolyesters at pH 7.4 in a phosphate buffered saline solution at 37 °C was studied using ATR‐FTIR spectroscopy. It was found that the presence of the Boltorn, the PEG, and lactide block lengths both play vital roles in determining the structure‐property relationships in these materials. The ATR‐FTIR studies showed that with increasing lactide segment length, the rate of ester hydrolysis increased due to the increased concentration of the hydrolytically sensitive poly(lactic acid) (PLA) ester groups in the network. However, incorporation of Boltorn into the PLA‐PEG‐PLA copolymer did not significantly change the kinetic rate constant for hydrolysis of the PLA segments. The cytocompatibility of a typical one of these materials in the presence of its degradation by‐products was assessed using cultured osteoblasts from the rat. The hydrogel was degraded for 28 days and found to be cytocompatible with osteoblasts over days 23 to 28 of the hydrolysis period. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5163–5176     

Sensitive and rapid high‐performance liquid chromatography tandem mass spectrometry method for estimation of fulvestrant in rabbit plasma

A rapid and sensitive high‐performance liquid chromatography and electrospray tandem mass spectrometry method was developed and validated for estimation of fulvestrant in rabbit plasma using liquid–liquid extraction. The separation and quantification of fulvestrant were achieved by reverse‐phase chromatography on a Sunfire C₁₈ column (50 × 2.1. i.d., 3.5 μm) with isocratic elution at a flow rate of 300 μL/min using norethistrone as an internal standard from 500 μL plasma sample. The method was validated over the concentration range from 0.092 to 16.937 ng/mL with a lower limit of detection of 0.023 ng/mL. The intra‐day and inter‐day accuracy and precision were within 10%. The recovery was 85 and 90% for fulvestrant and norethistrone respectively. The chromatographic run time was only 2.5 min. Copyright © 2009 John Wiley & Sons, Ltd.     

2-vinyloxy ethyl phthalimide polymerization initiated by 1-(isobutoxy) ethyl acetate in the presence of ethyl aluminum dichloride and either ethyl acetate or ethyl benzoate

2-Vinyloxy ethyl phthalimide (ImVE) was polymerized using 1-(isobutoxy) ethyl acetate as the initiator in the presence of ethyl aluminum dichloride and either ethyl acetate or ethyl benzoate. The resulting polymers have a narrow molecular weight distribution, and their molecular weight can be controlled within a narrow range by varying the monomer and initiator concentrations. Diblock copolymers with n-butyl vinyl ether can also be formed. The behavior of the polymerization is consistent with a living cationic mechanism. A brief comparison of the title system with other initiating systems is also presented. © 1996 John Wiley & Sons, Inc.     

Blind adaptive noncoherent multiuser detection for nonlinear modulation

Noncoherent multiuser detection for nonlinear modulation was previously studied and the idea of phase-independent noncoherent decorrelation was introduced and three post-decorrelative detectors were obtained and analyzed. However, their implementation requires the knowledge of the signature waveforms of all the users, which may be available only for centralized implementation. In this paper, we obtain a blind adaptive noncoherent decorrelative detector for nonlinear modulation that is suitable for distributed implementation with the knowledge of only the normalized signals of the desired user and the additive noise variance. This detector is based on the stochastic approximation method and does not require the overhead of any kind of "training." Two adaptive algorithms are developed, one guided by every signal in the desired user's signal set individually, and the other by the user's entire signal space. While this paper focuses on the particular problem of blind adaptive noncoherent decorrelative detection, it addresses a more general adaptation issue, namely, that of improving the convergence properties of an adaptive scheme by effectively using all the information that is known, and adapting only to the part of the desired solution that is truly unknown. Convergence is shown in the mean squared error sense for both the fixed step-size and time-varying step-size versions of the two algorithms.     

Infrared absorption by acetylene in the 12–14 μm region at low temperatures

Spectral transmittance measurements have been performed on N₂-broadened lines of ¹²C₂H₂ and ¹²C¹³CH₂ in the 13.7 μm region at 153,200, and 296 K. From line-by-line comparison of observed and computed spectral transmittance, line strengths, half-widths, and their dependence on temperature have been deduced for conditions relevant to the atmospheres of Jupiter, Saturn, Titan, and Earth.     

Spectral transmission measurements in the v6-fundamental of 12CH3D at 8.65 μm

Spectral transmission measurements have been performed at 300°K in the v₆-fundamental band of ¹²CH₃D. Using the measured wave numbers and the calculated relative intensities of Pinkley et al, for all of the important transitions between 1100 and 1180 cm^-1, a constant hydrogen-broadened line width of 0.075 cm^-1 -atm^-1, and S_v = 63.6 cm^-2 -atm^-1, we have obtained excellent agreement between calculated and observed spectral transmission data.     

Measurements of intensities and nitrogen-broadened linewidths in the CO fundamental at low temperatures

Intensities and nitrogen-broadened half-widths of lines R(0), R(8) and R(16) in the fundamental band of ¹²C¹⁶O have been measured at 83°K, 100°K, 150°K, 200°K and 298°K. The intensities of several other lines in the P- and R-branches of the band have also been measured at 298°K. The absolute intensity derived from the line intensity data using the Herman-Wallis formula is S^°_v = 273 ± 10 cm^-2atm^-1 at S.T.P. A separate measurement employing the Wilson-Wells-Penner-Weber method has yielded S^°_v = 277 ± 4 cm^-2 atm^-1 at S.T.P. Both of these values are within 6 per cent of most of the previously published direct measurements of this parameter. The values for the line intensities reported earlier by other authors are lower by nearly 16 per cent.