DAC-Less amplifier-less generation and transmission of QAM signals using sub-volt silicon-organic hybrid modulators

We demonstrate generation and transmission of optical signals by directly interfacing highly efficient silicon-organic hybrid (SOH) modulators to binary output ports of a field-programmable gate array. Using an SOH Mach-Zehnder modulator (MZM) and an SOH IQ modulator we generate ON-OFF- keying and binary phase-shift keying signals as well as quadrature phase-shift keying and 16-state quadrature amplitude modulation (16QAM) formats. Peak-to-peak voltages amount to only 0.27 V-pp for driving the MZM and 0.41 V-pp for the IQ modulator. Neither digital-to-analog converters nor drive amplifiers are required, and the RF energy consumption in the modulator amounts to record-low 18 fJ/bit for 16QAM signaling

Grueneberg ganglion olfactory subsystem employs a cGMP signaling pathway

The mammalian olfactory sense employs several olfactory subsystems situated at characteristic locations in the nasal cavity to detect and report on different classes of odors. These olfactory subsystems use different neuronal signal transduction pathways, receptor expression repertoires, and axonal projection targets. The Grueneberg ganglion (GG) is a newly appreciated olfactory subsystem with receptor neurons located just inside of the nostrils that project axons to a unique domain of interconnected glomeruli in the caudal olfactory bulb. It is not well understood how the GG relates to other olfactory subsystems in contributing to the olfactory sense. Furthermore, the range of chemoreceptors and the signal transduction cascade utilized by the GG have remained mysterious. To resolve these unknowns, we explored the molecular relationship between the GG and the GC-D neurons, another olfactory subsystem that innervates similarly interconnected glomeruli in the same bulbar region. We found that mouse GG neurons express the cGMP-associated signaling proteins phosphodiesterase 2a, cGMP-dependent kinase II, and cyclic nucleotide gated channel subunit A3 coupled to a chemoreceptor repertoire of cilia-localized particulate guanylyl cyclases (pGC-G and pGC-A). The primary cGMP signaling pathway of the GG is shared with the GC-D neurons, unifying their target glomeruli as a unique center of olfactory cGMP signal transduction. However, the distinct chemoreceptor repertoire in the GG suggests that the GG is an independent olfactory subsystem. This subsystem is well suited to detect a unique set of odors and to mediate behaviors that remained intact in previous olfactory perturbations. J. Comp. Neurol. 516:36-48, 2009. © 2009 Wiley-Liss, Inc

Maternal oxytocin response predicts mother-to-infant gaze

The neuropeptide oxytocin is importantly implicated in the emergence and maintenance of maternal behavior that forms the basis of the mother-infant bond. However, no research has yet examined the specific association between maternal oxytocin and maternal gaze, a key modality through which the mother makes social contact and engages with her infant. Furthermore, prior oxytocin studies have assessed maternal engagement primarily during episodes free of infant distress, while maternal engagement during infant distress is considered to be uniquely relevant to the formation of secure mother-infant attachment. Two patterns of maternal gaze, maternal gaze toward and gaze shifts away from the infant, were micro-coded while 50 mothers interacted with their 7-month-old infants during a modified still-face procedure. Maternal oxytocin response was defined as a change in the mother's plasma oxytocin level following interaction with her infant as compared to baseline. The mother's oxytocin response was positively associated with the duration of time her gaze was directed toward her infant, while negatively associated with the frequency with which her gaze shifted away from her infant. Importantly, mothers who showed low/average oxytocin response demonstrated a significant decrease in their gaze toward their infants during periods of infant distress, while such change was not observed in mothers with high oxytocin response. The findings underscore the involvement of oxytocin in regulating the mother's responsive engagement with her infant, particularly in times when the infant's need for access to the mother is greatest

Diet breadth of fish communities in Vamanapuram river, Kerala, South India

An understanding of the feeding habits of fish species in natural environment gives clues for selecting the species for aquaculture. It helps in formulating artificial feeds for culturing species under artificial conditions for small scale or large scale aquaculture. The main objective of the present study was to find the food preferences of fish species in different ecological niches such as low land streams, riverine and estuary. Stomachs were cut, food items removed and stored in 4% formalin. Diet breadth was calculated as per the standard methods widely recommended. The diet breadth calculated for the fish assemblages in Vamanapuram River showed that Puntius amphibius has the highest breadth of 6.64. The surface feeding fishes had low diet breadth which ranged from 1.13-1.83. Their main food has been observed to be terrestrial insects. The generalists like Rasbora daniconius and Puntius filamentosus have diet breadth of 3.27 and 4.15, respectively. Whereas fish species found in estuarine habitats showed diet breadth range from 1.00 to 2.82. The fishes present in the upper regions of the river habitat were observed to have low diet breadth than lowland streams. In general, high diet breadth values were observed during February to May. The breadth of Barilius bakeri showed minor variations among the three seasons (1.00 to 1.20). Based on the diet breadth, the majority of the fishes in Vamanapuram River generalists

Silicon Photonics for Coherent Terahertz Generation and Detection

Silicon-plasmonic internal photoemission devices can act as photomixers for generating terahertz frequency carriers (T-waves) for transmitters (Tx), or they function as receivers (Rx) for coherently downconverting Twave signals to the baseband. In a first demonstration, we monolithically integrate a Tx and a Rx on a silicon chip and operate them in a carrier frequency range up to 1THz . With a co-integrated transmission line both components can be connected

Ultra-short silicon-organic hybrid (SOH) modulator for bidirectional polarization-independent operation

We propose a bidirectional, polarization-independent, recirculating IQ-modulator scheme based on the silicon-organic hybrid (SOH) platform. We demonstrate the viability of the concept by using an SOH Mach-Zehnder modulator, operated at 10 GBd BPSK and 2ASK-2PSK

Optical coherence tomography system mass-producible on a silicon photonic chip

Miniaturized integrated optical coherence tomography (OCT) systems have the potential to unlock a wide range of both medical and industrial applications. This applies in particular to multi-channel OCT schemes, where scalability and low cost per channel are important, to endoscopic implementations with stringent size demands, and to mechanically robust units for industrial applications. We demonstrate that fully integrated OCT systems can be realized using the state-of-the-art silicon photonic device portfolio. We present two different implementations integrated on a silicon-on-insulator (SOI) photonic chip, one with an integrated reference path (OCTint) for imaging objects in distances of 5 mm to 10 mm from the chip edge, and another one with an external reference path (OCText) for use with conventional scan heads. Both OCT systems use integrated photodiodes and an external swept-frequency source. In our proof-of-concept experiments, we achieve a sensitivity of −64 dB (−53 dB for OCTint) and a dynamic range of 60 dB (53 dB for OCTint). The viability of the concept is demonstrated by imaging of biological and technical objects

Resonances in rotationally inelastic scattering of OH(X2ΠX^2\Pi) with helium and neon

We present detailed calculations on resonances in rotationally and spin-orbit inelastic scattering of OH (X\,^2\Pi, j=3/2, F_1, f) radicals with He and Ne atoms. We calculate new \emph{ab initio} potential energy surfaces for OH-He, and the cross sections derived from these surfaces compare favorably with the recent crossed beam scattering experiment of Kirste \emph{et al.} [Phys. Rev. A \textbf{82}, 042717 (2010)]. We identify both shape and Feshbach resonances in the integral and differential state-to-state scattering cross sections, and we discuss the prospects for experimentally observing scattering resonances using Stark decelerated beams of OH radicals.Comment: 14 pages, 15 Figure

Structure and Emergence of Specific Olfactory Glomeruli in the Mouse

Olfactory sensory neurons (OSNs) expressing a given odorant receptor (OR) gene project their axons to a few specific glomeruli that reside at recognizable locations in the olfactory bulb. Connecting ∼1000 populations of OSNs to the ∼1800 glomeruli of the mouse bulb poses a formidable wiring problem. Additional progress in understanding the mechanisms of neuronal connectivity is dependent on knowing how these axonal pathways are organized and how they form during development. Here we have applied a genetic approach to this problem. We have constructed by gene targeting novel strains of mice in which either all OSNs or those that express a specific OR gene, M72 or M71, also produce green fluorescent protein (GFP) or a fusion of tau with GFP. We visualized OSNs and their axons in whole mounts with two-photon laser scanning microscopy. The main conclusion we draw from the three-dimensional reconstructions is the high degree of morphological variability of mature glomeruli receiving axonal input from OR-expressing OSNs and of the pathways taken by the axons to those glomeruli. We also observe that axons of OR-expressing OSNs do not innervate nearby glomeruli in mature mice. Postnatally, a tangle of axons from M72-expressing OSNs occupies a large surface area of the bulb and coalesces abruptly into a protoglomerulus at a reproducible stage of development. These results differ in several aspects from those reported for the development of glomeruli receiving input from OSNs expressing the P2 OR, suggesting the need for a more systematic examination of OR-specific glomeruli