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The use of (He-3, BF-3) gas-based thermal neutron detector systems is limited by the cost, size, weight, and power requirements for many of the emerging applications. Therefore, the development of low-cost large-area solid-state neutron detectors for a wide range of civilian and defense applications is desirable. Solar cell type solid-state neutron detector using highly matured silicon technology would provide significant benefits in terms of cost, size, weight, and volume, and allow for wafer level integration with charge preamplifier and readout electronics. We present here the recent efforts on the fabrication of large area 10B filled honey-comb structured solid state thermal neutron detectors and detector modules with detection area up to 16 cm2 that requires only a single pre-amp and shaping amplifier for data acquisition. The average leakage current density of 1 cm2 area device is about 3×10−8 Acm−2 and neutron detection efficiency of ∼29% for 0.0253 eV neutrons. For two stacked 1 cm2 detector, the efficiency is about 46% with gamma efficiency of 0.001% above the discrimination level of 0.5 MeV.

Considerable progress has been achieved recently to enhance the thermal neutron detection efficiency of solid-state neutron detectors that incorporate neutron sensitive materials such as 10B and 6LiF in Si micro-structured p-n junction diode. Here, we describe the design, fabrication process optimization and characterization of an enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction. Boron deposition and diffusion processes were carried out using a low pressure chemical vapor deposition to study the effect of diffusion temperature on current density-voltage characteristics of p+-n diodes. TSUPREM-4 was used to simulate the thickness and surface doping concentration of p+-Si layers. MEDICI was used to simulate the depletion width and the capacitance of the microstructured devices with continuous p+-n junction. Finally, current density-voltage and pulse height distribution of fabricated devices with 2.5×2.5 mm2 size were studied. A very low leakage current density of ~2×10-8 A/cm2 at -1 V (for both planar and honeycomb structured devices) and a bias-independent thermal neutron detection efficiency of ~26% under zero bias voltage were achieved for an enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction.

Aims Heart failure is among the most frequent complications of patients on long-term haemodialysis. The benefits of renin–angiotensin system (RAS) blockade on the outcomes of these patients have yet to be determined. Methods and results We conducted a nationwide observational study using data from the Taiwan National Health Insurance claims database, between 1999 and 2010. We enrolled patients aged ≥35 years with new-onset heart failure [diagnosed by International Classification of Diseases, 9th revision, clinical modification (ICD-9-CM) codes] under treatment with medications. New users of a RAS blocker (RASB; i.e. an ACE inhibitor or an ARB used as monotherapy or dual therapy) were selected to compare with non-RASB users. We used Cox proportional hazards regression with and without propensity score adjustment to compare the risk of 3-year all-cause and cardiovascular mortality. Stratified analyses and RASB therapy duration as a time-dependent covariate were also performed. In all, 4771 were treated with an RASB (n = 3024) or without an RASB (n = 1747). RASB users had a higher prevalence of hypertension and diabetes, and a higher number of hospitalization. Among RASB users, 1148 deaths (38.0%) occurred during 5272 person-years of follow-up compared with 734 deaths (42.0%) among non-RASB users during 2683 person-years of follow-up. Three-year mortality rates were 45.4% and 49.1% for patients receiving and those not receiving an RASB, respectively (log-rank test, P < 0.001). Adjusted hazard analysis revealed that RASB therapeutic effects remained significant on all-cause [hazard ratio (HR) 0.8; 95% confidence interval (CI) 0.72–0.89; P < 0.001] and cardiovascular mortality (HR 0.76; 95% CI 0.64–0.90; P < 0.01). Conclusions RASB therapy reduced all-cause and cardiovascular mortality in heart failure patients on long-term haemodialysis.

In recent years, driving fatigue and cognitive lapses have gained increasing attentions in the fields of public security, especially regarding the safe manipulation of vehicles. Studies have explored the relation between electroencephalogram (EEG) and driving behavior and several of them further proposed effective approaches (e.g., auditory feedback) to arouse subjects from drowsiness. However, these studies were performed under laboratory-oriented configurations using tethered, ponderous EEG equipment. In real environments, the setup of bulky cognitive monitoring equipment with a long-prep time is not feasible. Therefore, this study extends previous laboratory work by developing an on-line Drowsiness Monitoring and Management (DMM) System featuring a mobile wireless dry-sensor EEG headgear and a cell-phone based real-time EEG processing platform. The DMM system can continuously observe EEG dynamics, deliver arousing feedback to users experiencing momentary cognitive lapses, and assess the efficacy of the feedback in near real-time.

This study explores electroencephalographic (EEG) dynamics and behavioral changes in response to arousing auditory signals presented to individuals experiencing momentary cognitive lapses. Arousing auditory feedback was delivered to the subjects in half of the non-responded lane-deviation events during a sustained-attention driving task, which immediately agitated subject's responses to the events. The improved behavioral performance was accompanied by concurrent power suppression in the theta- and alpha-bands in the lateral occipital cortices. This study further explores the feasibility of estimating the efficacy of arousing feedback presented to the drowsy subjects by monitoring the changes in EEG power spectra.

In this study, a system with force feedback assistance was adopted to improve human's motor learning. Subjects tried to perform a trajectory tracking task of visuo-motor coordination by using a joystick which involved force feedback assistance. Force feedback was proportionally generated (maximal output 9N) by the joystick and warned subjects of the deviation of the tracking task. In the experiments, motor behavior performances of assistance group and non-assistance group were taken into comparison. The results demonstrated that a joystick with force feedback assistance brought significant influence. Motor performance was improved in the motion of flexion and extension while adding the force feedback assistance. This study provided important new light on the force feedback assistance. It could be an advanced function to improve and deepen people's motor learning capabilities.

This study investigates brain dynamics and behavioral changes in response to arousing auditory signals presented to individuals experiencing momentary cognitive lapses during a sustained-attention task. Electroencephalographic (EEG) and behavioral data were simultaneously collected during virtual-reality (VR) based driving experiments, in which subjects were instructed to maintain their cruising position and compensate for randomly induced lane deviations using the steering wheel. 30-channel EEG data were analyzed by independent component analysis and the short-time Fourier transform. Across subjects and sessions, intermittent performance during drowsiness was accompanied by characteristic spectral augmentation or suppression in the alpha- and theta-band spectra of a bilateral occipital component, corresponding to brief periods of normal (wakeful) and hypnagogic (sleeping) awareness and behavior. Arousing auditory feedback was delivered to the subjects in half of the non-responded lane-deviation events, which immediately agitated subject's responses to the events. The improved behavioral performance was accompanied by concurrent spectral suppression in the theta- and alpha-bands of the bilateral occipital component. The effects of auditory feedback on spectral changes lasted 30s or longer. The results of this study demonstrate the amount of cognitive state information that can be extracted from noninvasively recorded EEG data and the feasibility of online assessment and rectification of brain networks exhibiting characteristic dynamic patterns in response to momentary cognitive challenges.

This study reports the synthesis of morphology-controlled BaTiO(3) nanostructures such as spherical, cube-shaped and rod-shaped BaTiO(3) using a molten-salt synthesis method. This method synthesized products from a reaction of BaO/BaCO(3) and TiO(2) with a eutectic mixture of NaCl-KCl flux at 700 degrees C for 1 h. The experiment used powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy to investigate the structure and morphology of the products. Moreover, the current work also provides a proposed synthetic mechanism of BaTiO(3) in the molten salt to illustrate the in situ transformation mechanism of BaTiO(3) nanostructures in the reaction. The results of the study revealed that the initial shape of the titania and the dissolution rate of the initial precursors critically determine the shapes of the final products.

Objective. This study explores the neurophysiological changes, measured using an electroencephalogram (EEG), in response to an arousing warning signal delivered to drowsy drivers, and predicts the efficacy of the feedback based on changes in the EEG. Approach. Eleven healthy subjects participated in sustained-attention driving experiments. The driving task required participants to maintain their cruising position and compensate for randomly induced lane deviations using the steering wheel, while their EEG and driving performance were continuously monitored. The arousing warning signal was delivered to participants who experienced momentary behavioral lapses, failing to respond rapidly to lane-departure events (specifically the reaction time exceeded three times the alert reaction time). Main results. The results of our previous studies revealed that arousing feedback immediately reversed deteriorating driving performance, which was accompanied by concurrent EEG theta- and alpha-power suppression in the bilateral occipital areas. This study further proposes a feedback efficacy assessment system to accurately estimate the efficacy of arousing warning signals delivered to drowsy participants by monitoring the changes in their EEG power spectra immediately thereafter. The classification accuracy was up 77.8% for determining the need for triggering additional warning signals. Significance. The findings of this study, in conjunction with previous studies on EEG correlates of behavioral lapses, might lead to a practical closed-loop system to predict, monitor and rectify behavioral lapses of human operators in attention-critical settings.

We report the continuous p-n junction formation in honeycomb structured Si diode by in situ boron deposition and diffusion process using low pressure chemical vapor deposition for solid-state thermal neutron detection applications. Optimized diffusion temperature of 800 °C was obtained by current density-voltage characteristics for fabricated p+-n diodes. A very low leakage current density of ∼2 × 10−8 A/cm2 at −1 V was measured for enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction. The neutron detection efficiency for a Maxwellian spectrum incident on the face of the detector was measured under zero bias voltage to be ∼26%. These results are very encouraging for fabrication of large area solid-state neutron detector that could be a viable alternative to 3He tube based technology.

A multiple deposition and etching process has been developed to enable high fill factor boron deposition in high aspect ratio holes fabricated in a (100) silicon substrate. The boron deposition was carried out using low-pressure chemical vapor deposition and the etching was done by inductively coupled plasma reactive ion etching technique. The boron deposition processes were carried out under different conditions in order to find a baseline process condition. The boron etching processes done under different conditions with the photoresist as the mask are also discussed. Finally, the fabricated neutron detector with the highest fill factor was characterized for the thermal neutron detection efficiency.

We report on the design, fabrication, and performance of solid-state neutron detector based on three-dimensional honeycomb-like silicon micro-structures. The fabricated detectors use boron filled deep holes with aspect ratio of over 12 and showed a very low leakage current density of ∼7 × 10−7 A/cm2 at −1 V for device sizes varying from 2 × 2 to 5 × 5 mm2. A thermal neutron detection efficiency of 4.5% ± 0.5% with discrimination setting of 500 keV and gamma to neutron sensitivity of (1.1 ± 0.1) × 10−5 for single layer was measured without external bias for these devices. Monte-Carlo simulation predicts a maximum efficiency of 45% for such devices filled with 95% enriched 10boron.

Variety of applications of fast neutron detection utilize thermal neutron detectors and moderators. Examples include homeland security applications such as portal monitors and nuclear safeguards which employ passive systems for detection of fissile materials. These applications mostly rely on gas filled detectors such as 3 He, BF3 or plastic scintillators and require high voltage for operation. Recently there was considerable progress in the development of solid-state neutron detectors. These operate by detection of charged particles emitted from neutron interactions with a converter material. In order to increase neutron detection efficiency to a usable level, the thickness of the converter material must exceed the range of the charged particles in the converter, which limits the efficiency of planar detectors to several percent. To overcome this limitation three di- mensional structured solid-state devices are considered where the converter can be thicker but still allow the charged particles to escape into the semiconductor. In the research described here this was accomplished by a semiconductor device that resembles a honeycomb with hexagonal holes and thin silicon walls filled with the converter material. Such design can theoretically achieve about 45% thermal neutron detection efficiency, experimentally about 21% was observed with a partially filled detector. Such detectors can be fabricated in variety of sizes enabling designs of directional fast neutron detectors. Other converter materials that allow direct detection of fast neutrons were also considered by both simulation and experiments. Because the semiconductor thickness is less than a few hundred microns, the efficiency of these detectors to g-ray(s) is very low. With further developments these new solid-state neutron detectors can replace gas ionization based detectors in most applications.

We demonstrate the multi-sectional diffractive elements integrated vertically on photonic crystal surface emitting laser featuring the naturally formed periodic ITO cladding layer. The corresponding output beam steering mechanism is investigated in depth.

We demonstrate the beam steering capability of photonic crystal surface emitting laser via direct integration of diffractive structure. Large deflection angle and high transmittance y of laser beam can be achieved by optimization of surface meta-grating.