Two cascaded SOAs used as intensity modulators for adaptively modulated optical OFDM signals in optical access networks.

Detailed theoretical and numerical investigations of the transmission performance of adaptively modulated optical orthogonal frequency division multiplexed (AMOOFDM) signals are undertaken, for the first time, in optical amplification and chromatic dispersion (CD) compensation free single mode fiber (SMF) intensity-modulated and direct-detection (IMDD) systems using two cascaded semiconductor optical amplifiers in a counterpropagating configuration as an intensity modulator (TC-SOA-CC-IM). A theoretical model describing the characteristics of this configuration is developed. Extensive performance comparisons are also made between the TC-SOA-CC and the single SOA intensity modulators. It is shown that, the TC-SOA-CC reaches its strongly saturated region using a lower input optical power much faster than the single SOA resulting in significantly reduced effective carrier lifetime and thus wide TC-SOA-CC bandwidths. It is shown that at low input optical power, we can increase the signal line rate almost 115% which will be more than twice the transmission performance offered by single SOA. In addition, the TC-SOA-CC-IM is capable of supporting signal line rates higher than corresponding to the SOA-IM by using 10dB lower input optical powers. For long transmission distance, the TC-SOA-CC-IM has much stronger CD compensation capability compared to the SOA-IM. In addition the use of TC-SOA-CC-IM is more effective regarding the capability to benefit from the CD compensation for shorter distances starting at 60km SMF, whilst for the SOA-IM starting at 90km.

Prediction of risk for cesarean delivery in term nulliparas: a comparison of neural network and multiple logistic regression models.

OBJECTIVE: We sought to develop a neural network (NN) to predict the risk for cesarean delivery (CD) in term nulliparas. STUDY DESIGN: Using software (BrainMaker for Windows, Version 3.0; California Scientific Software, Nevada City, CA), we trained an NN with 225 patients obtained by chart review and included for nulliparity, singleton vertex > 36 weeks' gestation, and reassuring fetal heart rate on admission. Training inputs included several maternal and fetal clinical variables. Two logistic regression (LR) models using 225 and 600 patients (LR225 and LR600, respectively) were developed. The NN and LR models were tested for prediction of CD in a set of 100 patients not used for development. RESULTS: The NN, LR225, and LR600 correctly predicted 53%, 26%, and 32% of the patients with CD and 88%, 95%, and 95% of the patients with vaginal delivery, respectively. CONCLUSION: Compared with LRs, the NN was slightly better in predicting CD and was similar for predicting vaginal delivery in nulliparas with term singletons.

Upregulation of beta-catenin levels in superior frontal cortex of chronic alcoholics.

BACKGROUND: Chronic and excessive alcohol misuse results in neuroadaptive changes in the brain. The complex nature of behavioral, psychological, emotional, and neuropathological characteristics associated with alcoholism is likely a reflection of the network of proteins that are affected by alcohol-induced gene expression patterns in specific brain regions. At the molecular level, however, knowledge remains limited regarding alterations in protein expression levels affected by chronic alcohol abuse. Thus, novel techniques that allow a comprehensive assessment of this complexity will enable the simultaneous assessment of changes across a group of proteins in the relevant neural circuitry. METHODS: A proteomics analysis was performed using antibody microarrays to determine differential protein levels in superior frontal cortices between chronic alcoholics and age- and gender-matched control subjects. Seventeen proteins related to the catenin signaling pathway were analyzed, including alpha-, beta-, and delta-catenins, their upstream activators cadherin-3 (type I cadherin) and cadherin-5 (type II cadherin), and 5 cytoplasmic regulators c-Src, CK1 epsilon, GSK-3beta, PP2A-C alpha, and APC, as well as the nuclear complex partner of beta-catenin CBP and 2 downstream genes Myc and cyclin D1. ILK, G(alpha1), G(beta1), and G(beta2), which are activity regulators of GSK-3beta, were also analyzed. RESULTS: Both alpha- and beta-catenin showed significantly increased levels, while delta-catenin did not change significantly, in chronic alcoholics. In addition, the level of the beta-catenin downstream gene product Myc was significantly increased. Average levels of the catenin regulators c-Src, CK1 epsilon, and APC were also increased in chronic alcoholics, but the changes were not statistically significant. CONCLUSION: Chronic and excessive alcohol consumption leads to an upregulation of alpha- and beta-catenin levels, which in turn increase downstream gene expressions such as Myc that is controlled by beta-catenin signaling. This study showed that the beta-catenin signal transduction pathway was upregulated by chronic alcohol abuse, and prompts further investigation of mechanisms underlying the upregulation of alpha- and beta-catenins in alcoholism, which may have considerable pathogenic and therapeutic relevance.