Space-qualifying silicon photonic modulators and circuits.

Reducing the form factor while retaining the radiation hardness and performance matrix is the goal of avionics. While a compromise between a transistor's size and its radiation hardness has reached consensus in microelectronics, the size-performance balance for their optical counterparts has not been quested but eventually will limit the spaceborne photonic instruments' capacity to weight ratio. Here, we performed space experiments of photonic integrated circuits (PICs), revealing the critical roles of energetic charged particles. The year-long cosmic radiation exposure does not change carrier mobility but reduces free carrier lifetime, resulting in unchanged electro-optic modulation efficiency and well-expanded optoelectronic bandwidth. The diversity and statistics of the tested PIC modulator indicate the minimal requirement of shielding for PIC transmitters with small footprint modulators and complexed routing waveguides toward lightweight space terminals for terabits communications and intersatellite ranging.

Neural Correlates of Spatial Navigation in Primate Hippocampus.

The hippocampus has been extensively implicated in spatial navigation in rodents and more recently in bats. Numerous studies have revealed that various kinds of spatial information are encoded across hippocampal regions. In contrast, investigations of spatial behavioral correlates in the primate hippocampus are scarce and have been mostly limited to head-restrained subjects during virtual navigation. However, recent advances made in freely-moving primates suggest marked differences in spatial representations from rodents, albeit some similarities. Here, we review empirical studies examining the neural correlates of spatial navigation in the primate (including human) hippocampus at the levels of local field potentials and single units. The lower frequency theta oscillations are often intermittent. Single neuron responses are highly mixed and task-dependent. We also discuss neuronal selectivity in the eye and head coordinates. Finally, we propose that future studies should focus on investigating both intrinsic and extrinsic population activity and examining spatial coding properties in large-scale hippocampal-neocortical networks across tasks.

Structural Phase Transitions between Layered Indium Selenide for Integrated Photonic Memory.

The primary mechanism of optical memoristive devices relies on phase transitions between amorphous and crystalline states. The slow or energy-hungry amorphous-crystalline transitions in optical phase-change materials are detrimental to the scalability and performance of devices. Leveraging an integrated photonic platform, nonvolatile and reversible switching between two layered structures of indium selenide (In2 Se3 ) triggered by a single nanosecond pulse is demonstrated. The high-resolution pair distribution function reveals the detailed atomistic transition pathways between the layered structures. With interlayer "shear glide" and isosymmetric phase transition, switching between the α- and ß-structural states contains low re-configurational entropy, allowing reversible switching between layered structures. Broadband refractive index contrast, optical transparency, and volumetric effect in the crystalline-crystalline phase transition are experimentally characterized in molecular-beam-epitaxy-grown thin films and compared to ab initio calculations. The nonlinear resonator transmission spectra measure of incremental linear loss rate of 3.3 GHz, introduced by a 1.5 µm-long In2 Se3 -covered layer, resulted from the combinations of material absorption and scattering.

High-extinction-ratio low-voltage dual-racetrack modulator for low-power DAC-less PAM-4 modulation.

In a parallel-coupled dual-racetrack modulator, resonant light in two resonators can interfere with each other. In lieu of critical coupling, such interference is capable of producing high extinction ratios (ERs) for high-speed modulation. Experiments demonstrate ERs of over 9 dB at 50 Gb/s and 40-50% modulation depth enhancement compared with a single-resonator modulator at 50-56 Gb/s with a peak-to-peak driving voltage of 2.3 V. Furthermore, joint modulation of two racetracks offers the possibility to combine two separate bits of driving signals to generate four-level pulse-amplitude modulation (PAM-4) without an external digital-to-analog converter (DAC). To tackle the complex multi-variable transfer function of this modulator, a procedure for configuring PAM-4 states is theoretically developed. Finally, we demonstrate 100 Gb/s PAM-4 with an electro-optic modulation power consumption of < 40 fJ/bit for this device.

Spatial modulation of hippocampal activity in freely moving macaques.

The hippocampal formation is linked to spatial navigation, but there is little corroboration from freely moving primates with concurrent monitoring of head and gaze stances. We recorded neural activity across hippocampal regions in rhesus macaques during free foraging in an open environment while tracking their head and eye. Theta activity was intermittently present at movement onset and modulated by saccades. Many neurons were phase-locked to theta, with few showing phase precession. Most neurons encoded a mixture of spatial variables beyond place and grid tuning. Spatial representations were dominated by facing location and allocentric direction, mostly in head, rather than gaze, coordinates. Importantly, eye movements strongly modulated neural activity in all regions. These findings reveal that the macaque hippocampal formation represents three-dimensional (3D) space using a multiplexed code, with head orientation and eye movement properties being dominant during free exploration.

Retroperitoneal laparoscopic partial nephrectomy for unilateral synchronous multifocal renal carcinoma with different pathological types: A case report.

BACKGROUND: The majority of renal cell carcinomas are single lesions; unilateral synchronous multifocal renal carcinoma (USMRC) is rarely reported and poses a treatment challenge for urological oncologists. CASE SUMMARY: A 56-year-old man was hospitalized for pain and discomfort in the right kidney area for 6 d. Contrast-enhanced computed tomography demonstrated cT1a renal tumors at the lower pole of the right kidney and a cT1b renal tumor at the middle dorsal portion of the right kidney. The patient underwent retroperitoneal laparoscopic partial nephrectomy (RLPN). There were no complications peri-operatively. Histopathology revealed a low-grade, pathologic stage T1a (pT1a), clear cell renal cell carcinoma at the lower pole of the right kidney and a pT1b, chromophobe renal cell carcinoma at the middle dorsal portion of the right kidney. No tumor bed recurrence or metastasis was observed on imaging and his renal function remained stable during the 12-mo follow-up period. CONCLUSION: RLPN is a safe, effective, and feasible for the management of USMRC, which can obtain equivalent oncological results with optimal renal function preservation.

Device architectures for low voltage and ultrafast graphene integrated phase modulators.

The atomic layer thin geometry and semi-metallic band diagram of graphene can be utilized for significantly improving the performance matrix of integrated photonic devices. Its semiconductor-like behavior of Fermi-level tunability allows graphene to serve as an active layer for electro-optic modulation. As a low loss metal layer, graphene can be placed much closer to active layer for low voltage operation. In this work, we investigate hybrid device architectures utilizing semiconductor and metallic properties of the graphene for ultrafast and energy efficient electro-optic phase modulators on semiconductor and dielectric platforms. (1) Directly contacted graphene-silicon heterojunctions. Without oxide layer, the carrier density of graphene can be modulated by the directly contact to silicon layer, while silicon intrinsic region stays mostly depleted. With doped silicon as electrodes, carrier can be quickly injected and depleted from the active region in graphene. The ultrafast carrier transit time and small RC constant promise ultrafast modulation speed (3dB bandwidth of 67 GHz) with an estimated Vπ·L of 1.19 V·mm. (2) Graphene integrated lithium niobite modulator. As a transparent electrode, graphene can be placed close to integrated lithium niobate waveguide for improving coupling coefficient between optical mode profile and electric field with minimal additional loss (4.6 dB/cm). Numerical simulation indicates 2.5× improvement of electro-optic field overlap coefficient, with estimated V π of 0.2 V.

Hydrogen Plasma Exposure of Monolayer MoS2 Field-Effect Transistors and Prevention of Desulfurization by Monolayer Graphene.

Atomic vacancies related to structural disorder and doping variation influence carrier transport in monolayer transition-metal dichalcogenide devices. Here, we investigate the effect of hydrogen plasma exposure (HPE) on monolayer MoS2 field-effect transistors (FETs). We observe that a 1% increase in sulfur vacancy after HPE results in incremental 0.06 eV of the Schottky barrier. Short-range scattering from the sulfur vacancies reduces the carrier mobility of monolayer MoS2 by 2 orders of magnitude. Despite the defects and grain boundaries formed during the chemical vapor deposition and transferring process, the surface desulfurization induced by the proton exposure and thermally accelerated oxidation can be blocked by monolayer graphene cladding with a van der Waals contact distance of 2.5 Å. The material-level study indicates a promising route for a low-cost and robust fabrication of smart sensor circuits on a monolithic MoS2 wafer, where the bare MoS2 FETs can serve as proton sensors, with their electronic readout processed by a logic circuit of graphene-protected pristine FETs with a high on/off ratio.

Vision and Locomotion Combine to Drive Path Integration Sequences in Mouse Retrosplenial Cortex.

The retrosplenial cortex (RSC) is involved in a broad range of cognitive functions, integrating rich sensory, motor, and spatial signals from multiple brain areas, including the hippocampal system. RSC neurons show hippocampus-dependent activity reminiscent of place cell sequences. Using cellular calcium imaging in a virtual reality (VR)-based locomotion task, we investigate how the integration of visual and locomotor inputs may give rise to such activity in RSC. A substantial population shows neural sequences that track position in the VR environment. This activity is driven by the conjunction of visual stimuli sequences and active movement, which is suggestive of path integration. The activity is anchored to a reference point and predominantly follows the VR upon manipulations of optic flow against locomotion. Thus, locomotion-gated optic flow, combined with the presence of contextual cues at the start of each trial, is sufficient to drive the sequential activity. A subpopulation shows landmark-related visual responses that are modulated by animal's position in the VR. Thus, rather than fragmenting the spatial representation into equivalent locomotion-based ensemble versus optic-flow-based ensemble, in RSC, optic flow appears to override locomotion signals coherently in the population, when the gain between the two signals is altered.

On-chip wavefront shaping with dielectric metasurface.

Metasurfaces can be programmed for a spatial transformation of the wavefront, thus allowing parallel optical signal processing on-chip within an ultracompact dimension. On-chip metasurfaces have been implemented with two-dimensional periodic structures, however, their inherent scattering loss limits their large-scale implementation. The scattering can be minimized in single layer high-contrast transmitarray (HCTA) metasurface. Here we demonstrate a one-dimensional HCTA based lens defined on a standard silicon-on-insulator substrate, with its high transmission (<1 dB loss) maintained over a 200 nm bandwidth. Three layers of the HCTAs are cascaded for demonstrating meta-system functionalities of Fourier transformation and differentiation. The meta-system design holds potential for realizing on-chip transformation optics, mathematical operations and spectrometers, with applications in areas of imaging, sensing and quantum information processing.

Hippocampus-dependent emergence of spatial sequence coding in retrosplenial cortex.

Retrosplenial cortex (RSC) is involved in visuospatial integration and spatial learning, and RSC neurons exhibit discrete, place cell-like sequential activity that resembles the population code of space in hippocampus. To investigate the origins and population dynamics of this activity, we combined longitudinal cellular calcium imaging of dysgranular RSC neurons in mice with excitotoxic hippocampal lesions. We tracked the emergence and stability of RSC spatial activity over consecutive imaging sessions. Overall, spatial activity in RSC was experience-dependent, emerging gradually over time, but, as seen in the hippocampus, the spatial code changed dynamically across days. Bilateral but not unilateral hippocampal lesions impeded the development of spatial activity in RSC. Thus, the emergence of spatial activity in RSC, a major recipient of hippocampal information, depends critically on an intact hippocampus; the indirect connections between the dysgranular RSC and the hippocampus further indicate that hippocampus may exert such influences polysynaptically within neocortex.

Qualitative and Quantitative Detection of PrPSc Based on the Controlled Release Property of Magnetic Microspheres Using Surface Plasmon Resonance (SPR).

Prion protein (PrPSc) has drawn widespread attention due to its pathological potential to prion diseases. In this work, we constructed a novel surface plasmon resonance (SPR) detection assay involving magnetic microspheres (MMs) and its controlled release property, for selective capture, embedding, concentration, and SPR detection of PrPSc with high sensitivity and specificity. Aptamer-modified magnetic particles (AMNPs) were used to specifically capture PrPSc. Amphiphilic copolymer was used to embed the labeled PrPSc and form magnetic microspheres to isolate PrPSc from the external environment. Static magnetic and alternating magnetic fields were used to concentrate and control release the embedded PrPSc, respectively. Finally, the released AMNPs-labeled PrPSc was detected by SPR which was equipped with a bare gold sensing film. A good linear relationship was obtained between SPR responses and the logarithm of PrPSc concentrations over a range of 0.01-1000 ng/mL. The detection sensitivity for PrPSc was improved by 10 fold compared with SPR direct detection format. The specificity of the present biosensor was also determined by PrPC and other reagents as controls. This proposed approach could also be used to isolate and detect other highly pathogenic biomolecules with similar structural characteristics by altering the corresponding aptamer in the AMNPs conjugates.

Sparse orthogonal population representation of spatial context in the retrosplenial cortex.

Sparse orthogonal coding is a key feature of hippocampal neural activity, which is believed to increase episodic memory capacity and to assist in navigation. Some retrosplenial cortex (RSC) neurons convey distributed spatial and navigational signals, but place-field representations such as observed in the hippocampus have not been reported. Combining cellular Ca2+ imaging in RSC of mice with a head-fixed locomotion assay, we identified a population of RSC neurons, located predominantly in superficial layers, whose ensemble activity closely resembles that of hippocampal CA1 place cells during the same task. Like CA1 place cells, these RSC neurons fire in sequences during movement, and show narrowly tuned firing fields that form a sparse, orthogonal code correlated with location. RSC 'place' cell activity is robust to environmental manipulations, showing partial remapping similar to that observed in CA1. This population code for spatial context may assist the RSC in its role in memory and/or navigation.Neurons in the retrosplenial cortex (RSC) encode spatial and navigational signals. Here the authors use calcium imaging to show that, similar to the hippocampus, RSC neurons also encode place cell-like activity in a sparse orthogonal representation, partially anchored to the allocentric cues on the linear track.

Isolation and functional characterization of a circadian-regulated CONSTANS homolog (GbCO) from Ginkgo biloba.

KEY MESSAGE: This is the first report to clone and functionally characterize a flowering time gene GbCO in perennial gymnosperm Ginkgo biloba. GbCO complements the co mutant of Arabidopsis, restoring normal early flowering. CONSTANS (CO) is a central regulator of photoperiod pathway, which channels inputs from light, day length, and circadian clock to promote the floral transition. In order to understand the role of CO in gymnosperm Ginkgo biloba, which has a long juvenile phase (15-20 years), a CO homolog (GbCO) was isolated and characterized from G. biloba. GbCO encodes a 1741-bp gene with a predicted protein of 400 amino acids with two zinc finger domains (B-box I and B-box II) and a CCT domain. Phylogenic analysis classified GbCO into the group 1a clade of CO families in accordance with the grouping scheme for Arabidopsis CO (AtCO). Southern blot analysis indicated that GbCO belongs to a multigene family in G. biloba. Real-time PCR analysis showed that GbCO was expressed in aerial parts of Ginkgo, with the highest transcript level of GbCO being observed in shoot apexes. GbCO transcript level exhibited a strong diurnal rhythm under flowering-inductive long days and peaked during early morning, suggesting that GbCO is tightly coupled to the floral inductive long-day signal. In addition, an increasing trend of GbCO transcript level was observed both in shoot tips and leaves as the shoot growth under long-day condition, whereas GbCO transcript level decreased in both tissues under short-day condition prior to growth cessation of shoot in G. biloba. GbCO complemented the Arabidopsis co-2 mutant, restoring normal early flowering. All the evidence being taken together, our findings suggested that GbCO served as a potential inducer of flowering in G. biloba.

Closed-loop control of epilepsy by transcranial electrical stimulation.

Many neurological and psychiatric diseases are associated with clinically detectable, altered brain dynamics. The aberrant brain activity, in principle, can be restored through electrical stimulation. In epilepsies, abnormal patterns emerge intermittently, and therefore, a closed-loop feedback brain control that leaves other aspects of brain functions unaffected is desirable. Here, we demonstrate that seizure-triggered, feedback transcranial electrical stimulation (TES) can dramatically reduce spike-and-wave episodes in a rodent model of generalized epilepsy. Closed-loop TES can be an effective clinical tool to reduce pathological brain patterns in drug-resistant patients.

Large-scale recording of neurons by movable silicon probes in behaving rodents.

A major challenge in neuroscience is linking behavior to the collective activity of neural assemblies. Understanding of input-output relationships of neurons and circuits requires methods with the spatial selectivity and temporal resolution appropriate for mechanistic analysis of neural ensembles in the behaving animal, i.e. recording of representatively large samples of isolated single neurons. Ensemble monitoring of neuronal activity has progressed remarkably in the past decade in both small and large-brained animals, including human subjects. Multiple-site recording with silicon-based devices are particularly effective because of their scalability, small volume and geometric design. Here, we describe methods for recording multiple single neurons and local field potential in behaving rodents, using commercially available micro-machined silicon probes with custom-made accessory components. There are two basic options for interfacing silicon probes to preamplifiers: printed circuit boards and flexible cables. Probe supplying companies (http://www.neuronexustech.com/; http://www.sbmicrosystems.com/; http://www.acreo.se/) usually provide the bonding service and deliver probes bonded to printed circuit boards or flexible cables. Here, we describe the implantation of a 4-shank, 32-site probe attached to flexible polyimide cable, and mounted on a movable microdrive. Each step of the probe preparation, microdrive construction and surgery is illustrated so that the end user can easily replicate the process.

[Therapeutic effects for the treatment of senile hip fractures].

OBJECTIVE: To explore the surgical methods and therapeutic effects for the treatment of senile hip fractures. METHODS: From 2001 to 2006, 136 senility patients (over 75-years-old) were reviewed in the study. Among the patients, 37 patients were male and 99 patients were female, ranging in age from 75 to 97 years, with an average of 78.9 years (6 patients over 90 years, and the highest age was 97 years). All the patients were combined with chronicity internal medicine diseases. Thirty-four patients were treated with non-operative method and other 102 patients were treated with operative method. RESULTS: All the patients were followed up for an average of 12 months. In operation group, 9 patients were dead within 1 year, and the mortality was 8.82%. And in non-operation group, 23 patients were dead within 1 year, and the mortality was 67.65%. CONCLUSION: Operation treatment for senile hip fractures was effective to reduce complications, lower mortality. If the patients can pull through the perioperative period successfully, the quality of life will be enhanced remarkably.