FQPSK-B viterbi receiver

An FQPSK-B receiver uses a simplified trellis system which uses combinations of FQPSK-B waveforms to correlate against an input signal. This enables reduction of the number of correlators that are used and the number of comparisons that are made by the correlators

Optical studies of carrier and phonon dynamics in Ga_{1-x}Mn_{x}As

We present a time-resolved optical study of the dynamics of carriers and phonons in Ga_{1-x}Mn_{x}As layers for a series of Mn and hole concentrations. While band filling is the dominant effect in transient optical absorption in low-temperature-grown (LT) GaAs, band gap renormalization effects become important with increasing Mn concentration in Ga_{1-x}Mn_{x}As, as inferred from the sign of the absorption change. We also report direct observation on lattice vibrations in Ga1-xMnxAs layers via reflective electro-optic sampling technique. The data show increasingly fast dephasing of LO phonon oscillations for samples with increasing Mn and hole concentration, which can be understood in term of phonon scattering by the holes.Comment: 13 pages, 3 figures replaced Fig.1 after finding a mistake in previous versio

Universal Scaling and Signatures of Nodal Structures in Electron Tunneling from Two-Dimensional Semimetals

We present the theory of out-of-plane electron thermal-field emission from 2D semimetals. We show that the current($\mathcal{J}$)-field($F$)-temperature($T$) characteristic is captured by a universal scaling law applicable for broad classes of 2D semimetals, including monolayer and few-layer graphene, nodal point semimetals, nodal line semimetals and Dirac semimetals at the verge of topological phase transition. The low-temperature scaling takes the universal form, $\log\left( \mathcal{J}/F^\gamma \right) \propto -1/F$ with $\gamma = 1$ for 2D semimetals, which is in stark contrast to the classic Fowler-Nordheim scaling of $\gamma = 2$ for 3D metals. Importantly, the Fermi level dependence of the tunneling currents depends sensitively on the nodal structure through the electronic density of states, thus serving as a probe for detecting the various possible nodal structures of 2D semimetals. Our findings provide a theoretical basis for the understanding of tunneling charge transport phenomena in solid/vacuum and solid/solid interfaces, critical for the development of 2D-material-based vacuum and solid-state electronic devices.Comment: 8 pages, 2 figure

Systematic design of single-mode coupled-resonator optical waveguides in photonic crystals

By establishing a direct relation between the dispersion and the field profile of a coupled-resonator optical waveguide (CROW) and those of its constituent cavities, we present a systematic method for the design of a single-mode CROW and for control of its dispersion. The procedure includes the design of a single-mode cavity and control of its frequency by engineering its structure. Then, by chaining these cavities in the proper direction and at an appropriate distance, we achieve the desired dispersion for the CROW

Vortex solutions of a Maxwell-Chern-Simons field coupled to four-fermion theory

We find the static vortex solutions of the model of Maxwell-Chern-Simons gauge field coupled to a (2+1)-dimensional four-fermion theory. Especially, we introduce two matter currents coupled to the gauge field minimally: the electromagnetic current and a topological current associated with the electromagnetic current. Unlike other Chern-Simons solitons the N-soliton solution of this theory has binding energy and the stability of the solutions is maintained by the charge conservation laws.Comment: 7 pages, harvmac, To be published in Phys. Rev. D5

Organ-Specific Alterations in Fatty Acid De Novo Synthesis and Desaturation in a Rat Model of Programmed Obesity

<p>Abstract</p> <p>Background</p> <p>Small for gestational age (SGA) leads to increased risk of adult obesity and metabolic syndrome. Offspring exposed to 50% maternal food restriction <it>in utero </it>are born smaller than Controls (FR), catch-up in growth by the end of the nursing period, and become obese adults. The objective of the study was to determine stearoyl-CoA desaturase activity (SCD1) and rates of de novo fatty acid synthesis in young FR and Control offspring tissues at the end of the nursing period, as possible contributors to catch-up growth.</p> <p>Methods</p> <p>From gestational day 10 to term, dams fed ad libitum (Control) or were 50% food-restricted to produce small FR pups. Control dams nursed all pups. At postnatal day 1 (p1) and p21, offspring body tissues were analyzed by GC/MS, and desaturation indices of palmitoleate/palmitate and oleate/stearate were calculated. SCD1 gene expression was determined by real-time PCR on adipose and liver. Offspring were enriched with deuterium that was given to dams in drinking water during lactation and de novo synthesis of offspring body tissues was determined at p21. Primary adipocyte cell cultures were established at p21 and exposed to U¹³C-glucose.</p> <p>Results</p> <p>FR offspring exhibited higher desaturation index in p1 and p21 adipose tissue, but decreased desaturation index in liver at p21. SCD1 gene expression at p21 was correspondingly increased in adipose and decreased in liver. FR subcutaneous fat demonstrated increased de novo synthesis at p21. Primary cell cultures exhibited increased de novo synthesis in FR.</p> <p>Conclusions</p> <p>Adipose tissue is the first site to exhibit increased de novo synthesis and desaturase activity in FR. Therefore, abnormal lipogenesis is already present prior to onset of obesity during the period of catch-up growth. These abnormalities may contribute to future obesity development.</p

Incidence of maternal desaturation among patients undergoing elective caesaraen section under regional anaesthesia

This was a prospective observational study to identify the incidence and possible risk factors for maternal desaturation following neuraxial blockade for elective caesarean section (CS). Patients with body mass index (BMI) ≥ 30 kg/m2 at the first antenatal consultation were identified and classified into the obese group. Neuraxial blockade in the form of subarachnoid block (SAB) or combined spinal-epidural (CSE) was performed. Mean arterial pressure (MAP) and oxygen saturation (SpO2) were recorded at baseline and at 5-minute intervals following neuraxial blockade. Desaturation, defined as SpO2 < 94% for more than 30 seconds without artifacts, was managed with oxygen therapy and other appropriate measures. Newborn Apgar score and umbilical cord blood gases were analysed. Among a total of 254 recruited patients, 69 (27.2%) were obese and were associated with significantly higher age, parity, previous CS and pre-existing diabetes mellitus. The incidence of oxygen desaturation was 1.2%, involving three patients in the non obese group. These desaturation episodes were short-lived and associated with intraoperative hypotension. Six patients, two of whom in the obese group, received rescue oxygen therapy following intraoperative events such as deteriorating SpO2 or hypotension. The mean MAP was significantly lower at baseline and at 5 minutes post neuraxial blockade in the non obese group, which could account for the occurrence of desaturation in this group only. There were no significant inter-group differences in terms of neonatal outcome, umbilical cord blood gases and changes in mean SpO2 post neuraxial blockade. In conclusion, the current practice of not routinely giving supplementary oxygen to patient during elective CS at our institution is deemed to be safe, provided continuous SpO2 monitoring is available throughout the surgery. Further randomised clinical trials are indicated to investigate the impact of maternal obesity and of labouring patients presenting for urgent or emergency CS on intraoperative oxygen desaturation