Digital adaptive phase noise reduction in coherent optical links

Coherent optical links enable high-density constellations and, consequently, a higher throughput. However, the phase noise associated with the transmitter and the receiver lasers is a challenging issue in coherent lightwave systems. The authors present an approach that relies on using digital signal processing techniques to compensate for the laser phase-noise effects. The proposed approach exploits the digital processing power to address the problems arising from optical imperfections. The authors present an adaptive filtering scheme that reduces the effect of the laser phase noise and, consequently, relaxes the laser linewidth requirement. The proposed approach shows how the signal processing techniques can be exploited to compensate for the optical impairments by utilizing the continuing scale down in size and power in very large scale integration (VLSI) technology.     

Robust wireless location over fading channels

This paper develops an estimation algorithm for the time and amplitude of arrival of a known transmitted sequence over a single-path fading channel. The algorithm is optimized to enhance robustness to fast channel fading and low signal-to-noise ratio (SNR) conditions, which are common in wireless location applications. The paper also presents a noise and fading bias correction technique for amplitude of arrival estimation that improves the estimation accuracy significantly. The proposed algorithm is then applied to the case of code-division multiple-access (CDMA) wireless location finding for which the paper gives simulation results that demonstrate significant estimation accuracy improvement over known algorithms.     

Technetium-99m-MIBI myocardial SPECT: supine versus right lateral imaging and comparison with coronary arteriography

Myocardial perfusion SPECT using the prone position improves inferior wall counts and decreases motion problems as compared with the usual supine position. Nonetheless, it is not suitable for women. In addition, it is associated with artifactual anteroseptal defects and hot spots. METHODS: The right lateral (RL) position was evaluated instead of the prone position in 72 patients (26 women). RL imaging was performed immediately after the supine imaging during a routine 2-day 99mTc-sestamibi exercise protocol. The SPECT images were scored semiquantitatively by three physicians. Moreover, regional myocardial counts, as well as extent and severity of defects, were assessed by quantitative polar map analysis. RESULTS: All patients tolerated the RL position well and there was no significant patient movement in either position. Higher inferior myocardial counts per pixel were observed in the RL than in supine images. Inferior wall defects (especially mild ones) were more common in the supine than the RL images, whereas defects in other regions were not different. Quantitative analysis confirmed these findings. Analysis of 34 patients with recent coronary arteriography revealed an overall coronary artery disease (CAD) supine- and RL-imaging specificity of 50% and 75%, respectively, and the sensitivities of both were 93%. Right CAD sensitivity, specificity and normalcy rates for the supine position were 100%, 44% and 55%, whereas those of the RL position were 94%, 75% and 90%, respectively. CONCLUSION: The RL position improves CAD diagnostic accuracy, particularly right CAD, without significant artifacts in other myocardial regions. Unlike the prone position, the RL position is well tolerated by both women and men.     

Changes in blocking mechanisms during membrane processing of pomegranate juice

The effect of pressure, velocity, pretreatment, membrane type and pore size on fouling mechanisms were evaluated. Pomegranate juice was treated with polyvinylidene fluoride (PVDF) 0.22 μm and mixed cellulose ester (MCE) 0.1 μm at different pressures. Cake formation which was the dominant mechanism was formed in the first stages of process and, as the filtration proceeded, intermediate, standard, and complete blocking, respectively occurred at higher pressure (5 kPa). At lower pressure (0.5 kPa) the last mechanism did not occur. Results showed that cake formation was the only mechanism in MCE 0.22 μm, however, others occurred with MCE 0.1 μm and PVDF 0.22 μm. Using MCE 0.22 μm prior to MCE 0.025 μm can reduce the role of cake formation in pore blocking. Evaluation of the impact of velocity showed that at the higher velocity (0.53 m s⁻¹) the complete blocking occurred faster than at the lower velocity (0.09 m s⁻¹).     

Dielectric relaxation of monoesters based poly(styrene-co-maleic anhydride) copolymer

A series of alkyl-grafted copolymers based on styrene-maleic anhydride (SMA) copolymers were synthesized by esterification of SMA with several long chain normal aliphatic alcohols. The prepared copolymers were characterized by FT-IR and ¹H NMR and DSC. The dielectric behavior of these copolymers was investigated in the frequency 20–10⁵ Hz and temperature −40 to 180 °C ranges. Two relaxation processes were observed, α, and β-relaxation. The former is associated with the glass-rubber transition and is characterized by the Vogel–Fulcher–Tammann temperature dependence and the latter relaxation is related to the local motion of the ester side groups attached to the polymer backbone. The apparent activation energy for the β-relaxation was found to depend significantly on the alkyl chain length. The dielectric analysis of the β-relaxation process detected is discussed.     

Enzymatic interesterification of structured lipids containing conjugated linoleic acid with palm stearin for possible margarine production

Structured lipids containing conjugated linoleic acid as a functional ingredient were blended with palm stearin in the ratios of 30 : 70, 40 : 60, 50 : 50, 60 : 40 and 70 : 30 (wt/wt). The blends were subjected to enzymatic interesterification by Candida antarctica lipase. After interesterification of the blends, changes in the physical properties of the products, including lower melting points and solid fat contents along with different melting behaviors, were evidenced. Analysis of triacylglycerols (TAG) of the interesterified blends showed a decrease in the concentration of high‐melting TAG. X‐ray diffraction analysis revealed, that all the reacted blends were predominantly in the β' crystal form. The mixture could be used for the formulation of margarines or other, similar products.     

Differences in physicochemical and antigenic properties of chlamydial strains

Antigenic analysis of Chlamydia psittaci, C. trachomatis, and Lymphogranuloma venereum (LGV) revealed basic physicochemical differences among the three chlamydial strains. These were manifested in structural, isoelectric points, absorption spectra, and in the characteristics of the chromophobe-containing proteins. The effective period of sonication for C. psittaci and C. trachomatis is around 60 min during which the linkages most susceptible to external sonication forces were broken, releasing all attainable cellular components. Denaturation studies demonstrated that less than 50% of protein content of C. psittaci was denatured after 1 h of sonication, only 5% in the case of C. trachomatis. The protein and carbohydrate content of the most reactive fractions in macrophage-spreading inhibition test were different for LGV and C. trachomatis. The structural differences appear to determine the antigenic properties observed among the chlamydial strains as well as the specificity and probably the mechanisms (s) of cellular immune reactivity to Chlamydiae. This in turn may explain the failure of chlamydial vaccines, prepared from stock strains, to protect immunized children against 'wild' chlamydial strains.     

Microwave Hall-mobility measurements on vanadium bronze V2O5 (Na0.33V2O5 and Cu0.0083V2O5)

The Hall mobilities of two examples of vanadium-bronze are reported using microwave techniques. The hopping conduction mechanism is confirmed for the copper-vanadium-bronze by comparing the d.c. conductivity and mobility to the microwave conductivity and mobility.