Ghrelin and Obestatin Levels as a Novel Marker in Iraqi Obese Children

Obesity is an escalating health problem in developing countries. One to ten children worldwide are overweight in a report showed by the International Obesity Task Force. Ghrelin, orexigenic peptide, has 28 amino acids, it is considered the greatest remarkable promotion in the last two decades for understanding the physiological changes of action regu­lating food intake and hunger. Obestatin is a 23-amino acid peptide nearly connected to ghrelin that secures from substitution splicing the alike resort molecule, pre-proghrelin. The study is designed to assess the level of ghrelin and obestatin in Iraqi obese children and its relation with other biochemical parameters. Ghrelin and obeststin levels were measured in sixty obese children; the range of their age was (5-16) years, and this group was compared to 30 children in a healthy state as a control. Serum FBS, PPBS, and also lipid profiles (TG, TC, HDL-c, and LDL-c) were determined in the studied groups. Calculation of insulin resistance was done by using (HOMA-IR) a Homeostasis Model assessment of insulin resistance. Ghrelin levels were lower in a significant way in subjects who have obesity in comparison with control group.  Significantly, there was a high increase in obestatin in obese patients when compared with control. This study demonstrates that obestatin raises and ghrelin is low in obesity, these hormones are related to the resistance of insulin, and there is an association between ghrelin and oxidative stress. The scales between obestatin and ghrelin are likely disturbed in obesity

Quantized Constant Envelope Precoding With PSK and QAM Signaling

Coarsely quantized massive multiple-input multiple-output (MIMO) systems are gaining more interest due to their power efficiency. We present a new precoding technique to mitigate the multi-user interference and the quantization distortions in a downlink multi-user MIMO system with coarsely quantized constant envelope (QCE) signals at the transmitter. The transmit signal vector is optimized for every desired received vector taking into account a relaxed version of the QCE constraint. The optimization is based on maximizing the safety margin to the decision thresholds of the receiver constellation modulation. Due to the linear property of the objective function and the constraints, the optimization problem is formulated as a linear programming problem. The simulation results show a significant gain in terms of the uncoded bit error rate compared to the existing precoding techniques

Precoding under instantaneous per-antenna peak power constraint

We consider a multi-user (MU) multiple-input-single-output (MISO) downlink system with M single-antenna users and N transmit antennas with a nonlinear power amplifier (PA) at each antenna. Instead of emitting constant envelope (CE) signals from the antennas to have highly power efficient PAs, we relax the CE constraint and allow the transmit signals to have instantaneous power less than or equal to the available power at each PA. The PA power efficiency decreases but simulation results show that the same performance in terms of bit-error-ratio (BER) can be achieved with less transmitted power and less PA power consumption. We propose a linear and a nonlinear precoder design to mitigate the multi-user interference (MUI) under the constraint of a maximal instantaneous per-antenna peak power

Massive MIMO downlink 1-bit precoding with linear programming for PSK signaling

Quantized massive multiple-input-multiple-output (MIMO) systems are gaining more interest due to their power efficiency. We present a new precoding technique to mitigate the multi-user interference and the quantization distortions in a downlink multi-user (MU) multiple-input-single-output (MISO) system with 1-bit quantization at the transmitter. This work is restricted to PSK modulation schemes. The transmit signal vector is optimized for every desired received vector taking into account the 1-bit quantization. The optimization is based on maximizing the safety margin to the decision thresholds of the PSK modulation. Simulation results show a significant gain in terms of the uncoded bit-error-ratio (BER) compared to the existing linear precoding techniques