Search

AbstractThe Z-type manifold microchannel heat sinks are mostly used by researchers due to the simple structure and considerable heat transfer performance. In this study, a novel Z-type manifold microchannel heat sink with fins arranged at intervals in an arithmetic sequence is proposed to improve the thermo-hydraulic performance of the conventional Z-type manifold microchannel. The novel feature of the proposed design is the channel widths being in an arithmetic sequence with a negative common difference, which contributes to equalize the flow distribution among the channels. Various fin arrangements with different common differences under the same heat transfer area are numerically investigated to determine the thermo-hydraulic performance. The results show that the fins arranged at intervals in an arithmetic sequence have a great potential in mitigating the flow maldistribution. Compared to the conventional manifold microchannel, the proposed manifold microchannel has better thermal performance without a significant increase in pressure drop. [ABSTRACT FROM AUTHOR]

Despite extensive research on received signal strength (RSS)-based visible light positioning (VLP), the receiver (RX) is assumed to stand vertically during the positioning process in most reported system designs. In this work, we propose a positioning strategy using a deep neural network (DNN) trained by synthetic data to address this problem. We further explicitly state the deficiencies in the current RSS-VLP algorithms when handling positioning problems involving RX orientation. Compared with existing RSS-VLP algorithms, our method can achieve high positioning accuracy even when the RX orientation is unknown. The results can further verify the feasibility of the system. In addition to the orientation predictability, the trained DNN can also regulate the algorithm time for each position. [ABSTRACT FROM AUTHOR]

Recent technological innovations in wearable electronics offer possibilities to perform real‐time monitoring of electrophysiological parameters, such as ECG, EMG, and EEG. To achieve accurate and long‐term electrophysiological measurement, great signs of progress have been made in the skin–electrode interfacial problems; nevertheless, the challenges related to sweat have not been fully resolved. Excessive sweat between human skin and the electrode usually fails to achieve a conformal and intact contact, and the nonconductive barriers will lead to a high skin–electrode impedance. Inspired by the structure of liquid directional movement in nature, a Janus gold nanowires/nitrocellulose (AuNWs/NC) electrophysiological electrode with conical micropores is developed to solve interfacial problems caused by sweat. The Janus AuNWs/NC electrodes spontaneously wick sweat from the AuNW side to the NC side, thus keeping intimate skin–electrode contact and low interfacial impedance to ensure a high‐fidelity signal during the long‐term monitoring. By integrating Janus AuNWs/NC electrode with circuit modules and advanced algorithms, a real‐time visualization system is developed for muscle activity intensity. This system is applied to precisely evaluate the muscle controllability and assess the muscle balance ability, which presents great potentials for health monitoring, sports training, and the areas of human–computer interaction. [ABSTRACT FROM AUTHOR]

Influenza A virus (IAV) is a major human pathogen associated with significant morbidity and mortality worldwide. Through serial passage in mice, we generated a recombinant pdmH1N1 2009 IAV, A/Guangdong/GLW/2018 (GLW/18-MA), which encodes an mCherry gene fused to the C-terminal of a polymerase acidic (PA) segment and demonstrated comparable growth kinetics to the wild-type. Nine mutations were identified in the GLW/18-MA genome: PA (I61M, E351G, and G631S), NP (E292G), HA1 (T164I), HA2 (N117S and P160S), NA (W61R), and NEP (K44R). The recombinant IAV reporter expresses mCherry, a red fluorescent protein, at a high level and maintains its genetic integrity after five generations of serial passages in Madin-Darby Canine Kidney cells (MDCK) cells. Moreover, the imaging is noninvasive and permits the monitoring of infection in living mice. Treatment with oseltamivir or baicalin followed by infection with the reporter IAV led to a decrease in fluorescent protein signal in living mice. This result demonstrates that the IAV reporter virus is a powerful tool to study viral pathogenicity and transmission and to develop and evaluate novel anti-viral drugs, inhibitors, and vaccines in the future. [ABSTRACT FROM AUTHOR]

A series of Tb3+- and Eu3+-doped Ca8ZnLu(PO4)7 (CZLP:Tb3+ and CZLP:Eu3+) as well as Ca8ZnTb(PO4)7:Eu3+ (CZTP:Eu3+) phosphors have been prepared via the traditional high-temperature solid-state reaction. X-ray powder diffraction (XRD) patterns of the as-prepared phosphors indicate that the introduction of Tb3+ or Eu3+ affects neither the phase impurity nor the crystal structure of the CZLP host lattice. The concentration dependent photoluminescence (PL) spectra reveal that even if Lu3+ was fully substituted by the dopants, Tb3+ or Eu3+, the phenomenon of concentration quenching would not occur. Color tunable emissions from green to red can be realized by adjusting the type of doping ion (Tb3+ and Eu3+) and their relative concentration. Furthermore, the energy transfer from Tb3+ to Eu3+ was confirmed and the mechanism was determined to be the dipole–quadrupole interaction. In addition, the quantum efficiencies were found to be 0.61, 0.58 and 0.85 for CZTP, CZTP:0.2Eu3+ and CaZnEu(PO4)7 (CZEP), respectively. As a result, a white light emitting diode (WLED) device was fabricated using the optimal CZTP:0.2Eu3+ yellow phosphor, the BaMgAl10O17:Eu2+ (BAM:Eu2+) blue phosphor and a 370 nm near-ultraviolet (n-UV) chip. The obtained device displays a suitable color rendering index (CRI, ∼81.3) and correlated color temperature (CCT, ∼2634 K) value, indicating its potential application in n-UV LEDs. [ABSTRACT FROM AUTHOR]

Aims: SUMOylation is a posttranslational modification related to multiple human diseases. SUMOylation can be reversed by classes of proteases known as the sentrin/SUMO‐specific proteases (SENPs). In the present study, we investigate the potential role of SENP1 in pericytes in the brain ischemia. Methods: Pericyte‐specific deletion of senp1 mice (Cspg4‐Cre; senp1f/f) were used for brain function and neuronal damage evaluation following brain ischemia. The cerebral blood vessels of diameter, velocity, and flux were performed in living mice by two‐photon laser scanning microscopy (TPLSM). Biochemical analysis and immunohistochemistry methods were used to address the role and mechanism of pericyte‐specific SENP1 in the pathological process of brain ischemia. A coculture model of HBVPs and HBMECs mimicked the BBB in vitro and was used to evaluate BBB integrity after glucose deprivation. Results: Our results showed that senp1‐specific deletion in pericytes did not affect the motor function and cognitive function of mice. However, the pericyte‐specific deletion of senp1 aggravated the infarct size and motor deficit following focal brain ischemia. Consistently, the TPLSM data demonstrated that SENP1 deletion in pericytes accelerated thrombosis formation in brain microvessels. We also found that pericyte‐specific deletion of senp1 exaggerated the neuronal damage significantly following brain ischemia in mice. Moreover, SENP1 knockdown in pericytes could activate the apoptosis signaling and disrupt the barrier integrity in vitro coculture model. Conclusions: Our findings revealed that targeting SENP1 in pericytes may represent a novel therapeutic strategy for neurovascular protection in stroke. [ABSTRACT FROM AUTHOR]

A focused ultrasound field is set up in a heat transfer cavity with an elliptical cross section. A sound source and a heat source are designed at the two focus points where the sound intensity is reinforced based on the interference and standing wave criteria. The sound intensities and heat transfer coefficients of the cavity with a focused ultrasonic field and an ordinary cavity with a rectangular cross section are measured under the natural convection heat transfer regime. The distribution of the heat transfer coefficient matches the distribution of the sound intensity. The heat transfer performance is then enhanced in the cavity with a focused ultrasonic field. The cavitations and acoustic streaming characteristics in the cavity with a focused ultrasonic field and the ordinary cavity are also studied. The velocity of acoustic streaming is larger in the cavity with a focused ultrasonic field than in the ordinary cavity, and no cavitation is observed in the ordinary cavity. Although the cavitation cloud around the heat source is unfavorable for the heat transfer in the cavity with a focused ultrasonic field, the cavitations collapse and the resulting high temperature, higher pressure, and microjet effects still contribute substantially to heat transfer. [ABSTRACT FROM AUTHOR]

Abstract This paper is aiming to improve the ultrasonic heat transfer enhancement by controlling the sound intensity distribution and constructing an acoustic focusing field, which can reduce energy dissipation and dramatically enhance the local sound intensity of heat transfer surface. Two design criteria are proposed to construct the acoustic focusing field by utilizing acoustic interference and acoustic resonance. Correspondingly, an elliptical acoustic focusing tank is designed and fabricated. Two-dimensional simulation and experimental tests of sound intensity distribution in the elliptical acoustic focusing tank are performed to verify the theoretical conception and design. In addition, the heat transfer coefficients are measured at different locations in the elliptical tank under natural convection, using a square tank as a control. The experimental results show that the elliptical acoustic focusing tank can promote the intensity of the whole sound field, especially the focus region compared with the square tank. The heat transfer coefficient and heat transfer enhancement rate anywhere in the elliptical tank is higher than that in the square tank. The maximum heat transfer enhancement rate of the elliptical tank is 55.3% in natural convection, which is 47.1% higher than that of the square tank under the same condition. [ABSTRACT FROM AUTHOR]

• Standing wave field in focused ultrasonic cavities ensures better ultrasonic heat transfer enhancement. • A compromise between the standing wave coefficient and the time-averaged sound pressure exists. • Cavitation collapse can disperse bubble cloud in the sub-cooled boiling heat transfer. The ultrasonic heat transfer enhancement has a strong dependence on the sound intensity. The higher the local sound intensity is, the better the heat transfer enhancement achieves. Therefore, a focused ultrasonic field is proposed in cavities with elliptical cross-section based on interference criterion and standing wave criterion. To design a cavity with focused ultrasonic field, sound source and heat source are purposely located at the two focus points where sound intensity could be reinforced. There is a compromise between the value of the standing wave coefficient and the time-averaged sound pressure. The profile of heat transfer coefficient is found to be spatially consistent with the simulated time-averaged sound pressure distribution. The cavities with focused ultrasonic field always present larger heat transfer coefficient of natural convection heat transfer than the ordinary ones and the cavity with standing wave coefficient k 2 = 8 presents better natural convection heat transfer performance than the cavity with standing wave coefficient k 2 = 6. For the sub-cooled boiling heat transfer, bubble plays an important role on the ultrasonic heat transfer enhancement effect. At larger heat flux or smaller sub-cooled temperature, bubbles gather together to form bubble cloud that presents large thermal resistance. The cavitation collapse can disperse the bubble cloud. [ABSTRACT FROM AUTHOR]

Dynamic performance is one of the most important characteristics of a variable focus lens. However, there are few studies investigating the dynamic response of a membrane-based variable focus lens. In this paper, we present a mathematical model to describe spring-damping phenomena in theory. The first order natural frequencies with different scales were confirmed via finite element analysis. We also built a dynamic response experiment platform with changeable optical apertures, which was driven by a high-speed piezo stack actuator. A photodiode module was placed behind the lens to measure the variation of light luminance as the lens changed, and a laser displacement sensor was used to measure the deformation of the membrane. A series of data was collected with different optical apertures (20 mm, 30 mm, 50 mm) and different pre-stretching ratios (200%, 300%) under different driving frequencies (from 5 Hz to 25 Hz in every 5 Hz step). The experimental results were consistent with the mathematical model, which showed that the first order natural frequency increased as the aperture decreased or the membrane stiffness increased. This frequency-dependent characteristic of the variable focus lens provides a basis for further research on its dynamic performance.

A low-cost flexible spectroscopic refractive index matching (SRIM) material with bandpass filtering properties without incidence angle and polarization dependence by randomly dispersing inorganic C a F 2 particles in organic polydimethylsiloxane (PDMS) materials was proposed in our previous study. Since the micron size of the dispersed particles is much larger than the visible wavelength, the calculation based on the commonly used finite-difference time-domain (FDTD) method to simulate light propagation through the SRIM material is too bulky; however, on the other hand, the light tracing method based on Monte Carlo theory in our previous study cannot adequately explain the process. Therefore, a novel approximate calculation model, to the best of our knowledge, based on phase wavefront perturbation is proposed that can well explain the propagation of light through this SRIM sample material and can also be used to approximate the soft scattering of light through composite materials with small refractive index differences, such as translucent ceramics. The model simplifies the complex superposition of wavefront phase disturbances and the calculation of scattered light propagation in space. The scattered and nonscattered light ratios; the light intensity distribution after transmission through the spectroscopic material; and the influence of absorption attenuation of the PDMS organic material on the spectroscopic performance are also considered. The simulation results based on the model are in great agreement with the experimental results. This work is important to further improve the performance of SRIM materials.

A series of Tb 3+ - and Eu 3+ -doped Ca 8 ZnLu(PO 4 ) 7 (CZLP:Tb 3+ and CZLP:Eu 3+ ) as well as Ca 8 ZnTb(PO 4 ) 7 :Eu 3+ (CZTP:Eu 3+ ) phosphors have been prepared via the traditional high-temperature solid-state reaction. X-ray powder diffraction (XRD) patterns of the as-prepared phosphors indicate that the introduction of Tb 3+ or Eu 3+ affects neither the phase impurity nor the crystal structure of the CZLP host lattice. The concentration dependent photoluminescence (PL) spectra reveal that even if Lu 3+ was fully substituted by the dopants, Tb 3+ or Eu 3+ , the phenomenon of concentration quenching would not occur. Color tunable emissions from green to red can be realized by adjusting the type of doping ion (Tb 3+ and Eu 3+ ) and their relative concentration. Furthermore, the energy transfer from Tb 3+ to Eu 3+ was confirmed and the mechanism was determined to be the dipole-quadrupole interaction. In addition, the quantum efficiencies were found to be 0.61, 0.58 and 0.85 for CZTP, CZTP:0.2Eu 3+ and CaZnEu(PO 4 ) 7 (CZEP), respectively. As a result, a white light emitting diode (WLED) device was fabricated using the optimal CZTP:0.2Eu 3+ yellow phosphor, the BaMgAl 10 O 17 :Eu 2+ (BAM:Eu 2+ ) blue phosphor and a 370 nm near-ultraviolet (n-UV) chip. The obtained device displays a suitable color rendering index (CRI, ∼81.3) and correlated color temperature (CCT, ∼2634 K) value, indicating its potential application in n-UV LEDs.