The role of cholesterol metabolism and various steroid abnormalities in autism spectrum disorders : A hypothesis paper

© 2017 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research.Peer reviewedPublisher PD

Performance evaluation of CO-OFDM systems based on electrical constant-envelope signals

The influence of the electrical phase modulation index h in the performance of constant-envelope orthogonal frequency division multiplexing (CE-OFDM) in coherent detection optical systems is treated analytically and its range of validity examined by simulations. A compromise between h and subcarrier mapping is identified according to differences in sensitivity related to non-linearities inserted by the optical modulator. It is shown that the proposed scheme outperforms conventional coherent detection OFDM systems, which is strongly dependent on both phase and optical modulation indexes

Closed-form expression for BER of CE-OFDM in optical intensity-modulated direct-detection systems

A closed-form expression for the bit-error-rate (BER) of constant envelope orthogonal frequency division multiplexing (CE-OFDM) in intensity-modulated direct-detection optical systems is provided in this letter. To the best of our knowledge, this letter is the first that provides an expression of the BER that considers the impact of electrical phase modulation index, signal bandwidth, optical modulation index, and Mach-Zehnder modulator bias point. Simulation and experimental results are included to validate the accuracy of the expression, subject to an analysis of the impact of electrical phase modulation index and the level of subcarrier mapping. With the analytical expression, we are able to reduce the computation time in design and parameter optimization of optical systems based in the CE-OFDM

Electrical constant envelope signals for nonlinearity mitigation in coherent-detection orthogonal frequency-division multiplexing systems

A theoretical analysis and a numerical investigation of 3-dB peak-to-average power ratio electrical constant envelope over orthogonal frequency-division multiplexing (OFDM) signals in coherent-detection optical (CO) systems are proposed. A 100 - Gb / s optical system is studied to increase the nonlinear tolerance (NLT) to both Mach–Zehnder modulation and optical propagation impairments. Simulation results show that, with 16- and 64-QAM subcarrier modulations, the proposed system outperforms a conventional CO-OFDM system, if an optical modulation index OMI = 2.5 and an electrical phase modulation index 2 π h = 3 are simultaneously adopted. The achieved NLT denoted by a performance gain of 24 dB is attractive after propagation through 1200 km of dispersion-uncompensated standard single-mode fiber, especially for 10-dBm fiber input power and despite the intrinsic bandwidth enlargement of PMs

Impact of the phase modulation index in the performance of CO-OFDM systems based on electrical domain constant-envelope signals

The impact of the electrical phase modulation index 2πh in the performance of coherent detection optical OFDM systems based on electrical constant-envelope signals is analytically and numerically evaluated in this paper. A compromise between 2πh and system performance, that considers the effect of nonlinearities inserted by Mach-Zehnder optical modulators, is established. Moreover, it is shown that this type of peak-to-average power ratio (PAPR) reduction technique reduces the impact of the optical modulation index in the performance

Increasing the spectral efficiency of DDO-CE-OFDM systems by multi-objective optimization

\u3cp\u3eA multi-objective optimization was implemented to increase the spectral efficiency of direct-detection optical orthogonal frequency division multiplexing (OFDM) systems with constant-envelope (CE) signals. Based on a genetic algorithm, the optimization procedure evaluates the impact of fiber injection power in the reduction of the guard band between the optical carrier and the CE-OFDM signals, optimizing important parameters such as electrical phase modulation and optical modulation indices of the denominated DDO-CE-OFDM system. Simulation results show that a guard-band reduction around 40% was achieved in a 4 Gbps optimized DDO-CE-OFDM system with 16-QAM subcarrier mapping and -7 dBm fiber input power. Results obtained in an experimental proof-of-concept conducted to validate the optimization procedure show that this reduction can reach 66\% according to a power penalty of 2 dB demanded by the inherent spectral broadening of CE-OFDM signals, after propagation over 40 km of standard single-mode fiber.\u3c/p\u3

When Good Turns Bad: Regulation of Invasion and Metastasis by ErbB2 Receptor Tyrosine Kinase

Overexpression and activation of ErbB2 receptor tyrosine kinase in breast cancer is strongly linked to an aggressive disease with high potential for invasion and metastasis. In addition to inducing very aggressive, metastatic cancer, ErbB2 activation mediates processes such as increased cancer cell proliferation and survival and is needed for normal physiological activities, such as heart function and development of the nervous system. How does ErbB2 activation make cancer cells invasive and when? Comprehensive understanding of the cellular mechanisms leading to ErbB2-induced malignant processes is necessary for answering these questions. Here we present current knowledge about the invasion-promoting function of ErbB2 and the mechanisms involved in it. Obtaining detailed information about the “bad” behavior of ErbB2 can facilitate development of novel treatments against ErbB2-positive cancers