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Inspired by the requirements of miniaturization and multifunction of molecular devices, we investigate the quantum transport properties of three unique molecular devices with silicon carbide chains bridging gold electrodes by an ab initio approach.

Background Xanthine dehydrogenase (XDH) is a critical enzyme involved in the oxidative metabolism of purines, pterin and aldehydes and a central component of the innate immune system. However, the prognostic value of XDH in predicting tumor-infiltrating lymphocyte abundance, the immune response, and survival in different cancers, including hepatocellular carcinoma (HCC), is still unclear. Methods XDH expression was analyzed in multiple databases, including Oncomine, the Tumor Immune Estimation Resource (TIMER), the Kaplan–Meier plotter database, the Gene Expression Profiling Interactive Analysis (GEPIA) database, and The Cancer Genome Atlas (TCGA). XDH-associated transcriptional profiles were detected with an mRNA array, and the levels of infiltrating immune cells were validated by immunohistochemistry (IHC) of HCC tissues. A predictive signature containing multiple XDH-associated immune genes was established using the Cox regression model. Results Decreased XDH mRNA expression was detected in human cancers originating from the liver, bladder, breast, colon, bile duct, kidney, and hematolymphoid system. The prognostic potential of XDH mRNA expression was also significant in certain other cancers, including HCC, breast cancer, kidney or bladder carcinoma, gastric cancer, mesothelioma, lung cancer, and ovarian cancer. In HCC, a low XDH mRNA level predicted poorer overall survival, disease-specific survival, disease-free survival, and progression-free survival. The prognostic value of XDH was independent of the clinical features of HCC patients. Indeed, XDH expression in HCC activated several immune-related pathways, including the T cell receptor, PI3K-AKT, and MAPK signaling pathways, which induced a cytotoxic immune response. Importantly, the microenvironment of XDHhigh HCC tumors contained abundant infiltrating CD8 + T cells but not exhausted T cells. A risk prediction signature based on multiple XDH-associated immune genes was revealed as an independent predictor in the TCGA liver cancer cohort. Conclusion These findings suggest that XDH is a valuable prognostic biomarker in HCC and other cancers and indicate that it may function in tumor immunology. Loss of XDH expression may be an immune evasion mechanism for HCC.

The simultaneous ground-state refrigeration of multiple vibrational modes is a prerequisite for observing significant quantum effects of multiple-vibration systems. Here we propose how to realize a large amplification in the net-refrigeration rates based on cavity optomechanics and to largely improve the cooling performance of multivibration modes beyond the resolved-sideband regime. By employing an auxiliary mechanical coupling (AMC) between two mechanical vibrations, the dark mode, which is induced by the coupling of these vibrational modes to a common optical mode and cuts off cooling channels, can be fully removed. We use fully analytical treatments for the effective mechanical susceptibilities and net-cooling rates and find that when the AMC is turned on, the amplification of the net-refrigeration rates by more than six orders of magnitude can be observed. In particular, we reveal that the simultaneous ground-state cooling beyond the resolved-sideband regime arises from the introduced AMC, without which it vanishes. Our work paves the way for quantum control of multiple vibrational modes in the bad-cavity regime., 12 pages, 5 figures

PURPOSE Dynamic susceptibility contrast (DSC)-MRI is a perfusion imaging technique from which useful quantitative imaging biomarkers can be derived. Relative cerebral blood volume (rCBV) is such a biomarker commonly used for evaluating brain tumors. To account for the extravasation of contrast agents in tumors, post-processing leakage correction is often applied to improve rCBV accuracy. Digital reference objects (DRO) are ideal for testing the post-processing software, because the biophysical model used to generate the DRO can be matched to the one that the software uses. This study aims to develop DROs to validate the leakage correction of software using Weisskoff model and to examine the effect of background signal time curves that are required by the model. METHODS Three DROs were generated using the Weisskoff model, each composed of nine foreground lesion objects with combinations of different levels of rCBV and contrast leakage parameter (K2). Three types of background were implemented for these DROs: (1) a multi-compartment brain-like background, (2) a sphere background with a constant signal time curve, and (3) a sphere background with signal time curve identical to that of the brain-like DRO's white matter (WM). The DROs were then analyzed with an FDA-cleared software with and without leakage correction. Leakage correction was tested with and without brain segmentation. RESULTS Accuracy of leakage correction was able to be verified using the brain-like phantom and the sphere phantom with WM background. The sphere with constant background did not perform well with leakage correction with or without brain segmentation. The DROs were able to verify that for the particular software tested, leakage correction with brain segmentation achieved the lowest error. CONCLUSIONS DSC-MRI DROs with biophysical model matched to that of the post-processing software can be well used for the software's validation, provided that the background signals are also properly simulated for generating the reference time curve required by the model. Care needs to be taken to consider the interaction of the design of the DRO with the software's implementation of brain segmentation to extract the reference time curve.

Ischemic stroke is one of the main causes of mortality and disability worldwide. However, efficient therapeutic strategies are still lacking. Stem/progenitor cell-based therapy, with its vigorous advantages, has emerged as a promising tool for the treatment of ischemic stroke. The mechanisms involve new neural cells and neuronal circuitry formation, antioxidation, inflammation alleviation, angiogenesis, and neurogenesis promotion. In the past decades, in-depth studies have suggested that cell therapy could promote vascular stabilization and decrease blood-brain barrier (BBB) leakage after ischemic stroke. However, the effects and underlying mechanisms on BBB integrity induced by the engrafted cells in ischemic stroke have not been reviewed yet. Herein, we will update the progress in research on the effects of cell therapy on BBB integrity after ischemic stroke and review the underlying mechanisms. First, we will present an overview of BBB dysfunction under the ischemic condition and cells engraftment for ischemic treatment. Then, we will summarize and discuss the current knowledge about the effects and underlying mechanisms of cell therapy on BBB integrity after ischemic stroke. In particular, we will review the most recent studies in regard to the relationship between cell therapy and BBB in tissue plasminogen activator (t-PA)-mediated therapy and diabetic stroke.

The deformation behavior involved in Nb/NiTi composite for biomedical applications within a large macroscopic strain range was investigated by tensile loading–unloading test and in situ synchrotron X-ray diffraction (SXRD). Experimental results show that during loading, the Nb/NiTi composite experiences the elastic elongation of B2-NiTi austenitic, B19′-NiTi martensitic and β-Nb phases, B2 → B19′ stress-induced martensitic (SIM) transformation and tensile plastic deformation of β-Nb phase. During unloading, the deformation behavior involved in Nb/NiTi composite includes the elastic recovery of B2-NiTi austenitic, B19′-NiTi martensitic and β-Nb phases, reverse phase transformation B19′ → B2 and compressive deformation of β-Nb phase. The martensitic transformation in this composite is almost reversible and occurs in a localized manner. These results might contribute to a comprehensive understanding of the deformation mechanism involved in Nb/NiTi composite and shed some light on design and development of novel composites with a combination of good biocompatibility and excellent superelasticity for biomedical applications.

Permanganate (Mn(VII)) is a widely used oxidant in water treatment, which can oxidize trace organic contaminants (TrOCs) and Mn(II). Interestingly, this study found that presence of Mn(II) could accelerate the abatement of bisphenol A by Mn(VII) only under oxic condition. Herein, the effects of Mn(II) and dissolved oxygen (DO) on the abatement of TrOCs by Mn(VII) oxidation and the related mechanism were investigated. Results indicate that DO was involved in the Mn(VII)/Mn(II) reaction, with the reaction stoichiometry of Δ[Mn(VII)]:Δ[Mn(II)] determined to be 1:2 and 1:1.5 in the presence and absence of DO, respectively. Quenching and electron paramagnetic resonance tests verified that both superoxide radicals (O

Background and Purpose: Sirt5 (Sirtuin 5) desuccinylates multiple metabolic enzymes and plays an important role in maintaining energy homeostasis. The goal of this study was to determine whether Sirt5-mediated desuccinylation restores the energy metabolism and protects brain against subarachnoid hemorrhage (SAH). Methods: Male C57BL/6 or Sirt5 −/− mice were used. The endovascular perforation SAH model was applied. Protein lysine succinylation in the brain cortex was examined using liquid chromatography-tandem mass spectrometry analysis. The brain metabolism was evaluated by measurement of brain pH as well as ATP and reactive oxygen species level. Neuronal cell death and neurobehavioral deficits were assessed 24 hours after SAH. The expression and desuccinylation activity of Sirt5, lysine succinylation of citrate synthase and ATP synthase subunits were investigated by Western blot, immunohistochemistry, and ELISA in SAH mice and patients. Furthermore, the benefits of resveratrol-mediated Sirt5 activation were investigated. Results: A total of 211 lysine succinylation sites were differentially expressed on 170 proteins in mice brain after SAH. Thirty-nine percent of these succinylated proteins were localized in mitochondria and they are related to energy metabolism. SAH caused a decrease of Sirt5 expression and succinylated citrate synthase as well as the subunits of ATP synthase, subsequently lowered brain pH, reduced ATP and increased reactive oxygen species production, leading to neuronal cell death, and neurological deficits. Knockdown of Sirt5 aggravated SAH-induced effects, mentioned above. Administration of resveratrol resulted in activation of Sirt5. The activation was accompanied both with restoration of the mitochondrial metabolism and alleviation of early brain injury as well as with desuccinylating citrate synthase and ATP synthase. Conclusions: Protein lysine succinylation is a biochemical hallmark of metabolic crisis after SAH, and disruption of lysine succinylation through activation of Sirt5 might be a promising therapeutic strategy for the treatment of SAH.

The nonreciprocal photon transmission between two optical modes which are nonlinearly coupled in a cross-Kerr type is investigated by using a damped auxiliary optical mode as their common engineered reservoir. The optical nonreciprocity is created by quantum interference between the nonlinear coupling induced by the cross-Kerr nonlinearity and the dissipative coupling mediated by the adiabatic elimination of the auxiliary optical mode. The photon transmission probabilities in forward and backward directions for the relative phase $\ensuremath{\varphi}$ between the two couplings are symmetric about the resonance with the probabilities for the phase $\ensuremath{\pi}\ensuremath{-}\ensuremath{\varphi}$, and are exchange symmetric with those in the case of the phase $2\ensuremath{\pi}\ensuremath{-}\ensuremath{\varphi}$. By tuning the dissipative coupling, in addition to the photon nonreciprocity being improved, the nonreciprocal photon amplification is produced. Meanwhile, it is found that not only can the cross-Kerr nonlinearity lead to a broadband optical nonreciprocity, but also it effectively produces the optical squeezing in the present scheme. The combination of the photon nonreciprocity with the optical squeezing will be useful in the realization of the quantum information processing with noise reduction.

We propose how to achieve significantly enhanced quantum refrigeration and entanglement by coupling a pumped auxiliary cavity to an optomechanical cavity. We obtain both analytical and numerical results, and find optimal-refrigeration and -entanglement conditions under the auxiliary-cavity-assisted (ACA) mechanism. Our method leads to a giant amplification in the net refrigeration rate, and reveals that the ACA entanglement has a much stronger noise-tolerant ability in comparison with the unassisted case. By appropriately designing the ACA mechanism, an effective mechanical susceptibility can be well adjusted, and a genuine tripartite entanglement of cooling-cavity photons, auxiliary-cavity photons, and phonons could be generated. Specifically, we show that both optomechanical refrigeration and entanglement can be greatly enhanced for the blue-detuned driving of the auxiliary cavity but suppressed for the red-detuned case. Our work paves a way towards further quantum control of macroscopic mechanical systems and the enhancement and protection of fragile quantum resources., Comment: Physical Review A, accepted, 16 pages, 10 figures

We study tunable optomechanically induced transparency by controlling the dark-mode effect induced by two mechanical modes coupled to a common cavity field. This is realized by introducing a phase-dependent phonon-exchange interaction, which is used to form a loop-coupled configuration. Combining this phase-dependent coupling with the optomechanical interactions, the dark-mode effect can be controlled by the quantum interference effect. In particular, the dark-mode effect in this two-mechanical-mode optomechanical system can lead to a double-amplified optomechanically induced transparency (OMIT) window and a higher efficiency of the second-order sideband in comparison with the standard optomechanical system. This is because the effective mechanical decay rate related to the linewidth of the OMIT window becomes a twofold increase in the weak-coupling limit. When the dark-mode effect is broken, controllable double transparency windows appear and the second-order sideband, as well as the light delay or advance, is significantly enhanced. For an N-mechanical-mode optomechanical system, we find that in the presence of the dark-mode effect, the amplification multiple of the linewidth of the OMIT window is nearly proportional to the number of mechanical modes, and that the OMIT with a single window becomes the one with N tunable windows by breaking the dark-mode effect. The study will be useful in optical information storage within a large-frequency bandwidth and multichannel optical communication based on optomechanical systems., 14 pages, 7 figures

In this study, laboratory-scale magnetic flocculation systems were set up and the optimal coagulant and flocculent dosage, magnetic seed immersion, pH, stirring intensity, and precipitation time were all evaluated. A total of 729 expansion reaction conditions were generated, and 700 of the expansion reaction conditions were used to train a back-propagation neural network (BPNN) and general regression neural network (GRNN). The other 29 conditions were used to verify the networks’ regression ability. The optimum coagulant was poly-aluminum chloride at a dosage of 100 mg/L; the optimum flocculent was anionic polyacrylamide at a dosage of 4 mg/L; the optimum size of the magnetic seed was 200 mesh at a dosage of 1 g/L; and the optimum stirring intensities were 300 r/min for the coagulation tank, 200 r/min for the mixing tank, and 100 r/min for the flocculation tank. Comparing BPNN and GRNN, the GRNN’s regression performance better matched the relationship between the reaction conditions and results.

A series of manganese oxide catalysts loaded on thermally modified Dolomite-palygorskite clay (MnOx/M-DPC) were synthesized by adopting impregnation, precipitation and citric acid methods and investigated for the selective catalytic reduction of NOx by NH3 (NH3-SCR) at low temperature. The results showed that the precipitated sample was more active (with 83% NOx conversion at 120 °C) by comparing it with the other MnOx/M-DPC samples prepared by impregnation and citric acid methods. Almost all NOx were completely removed by using this sample in the studied temperature range between 180 °C and 300 °C. In addition, all samples offered high N2 selectivity (> 94%) in the whole temperature range, and their SCR performance were affected by H2O introduction and NO oxidation to NO2 in the absence of NH3, but dependent on reaction temperature. The studied samples were characterized by specific surface area, pore size distribution, X-ray diffraction (XRD), Scanning electron microscope (SEM), electron diffraction spectra (EDS) and X-ray photoelectron spectroscopy (XPS). The results of specific surface area and pore size distribution suggested that the surface area and pore structure of catalysts obtained from various preparation methods were different, resulting in great difference in the catalytic performance. The irregular multi-modal mesoporous structure played a crucial role in the high catalytic activity over the precipitated MnOx/M-DPC sample. In addition, the results from XRD, SEM, EDS and XPS analyses indicated that Mn3O4 phase, good dispersion of manganese oxide, higher concentration of Mn as well as higher surface Mn4 + species, high lattice oxygen content on the surface were also beneficial to the superior catalytic efficiency of the precipitated sample.

In this study, the oxidation kinetics, mechanisms, effects and products of metalaxyl (MTL) by two different S(IV)-based processes (i.e., Mn(VII)/S(IV) and Cr(VI)/S(IV)) were systematically investigated and compared. The results showed that the concentration of S(IV) was primarily responsible for driving Mn(VII) and Cr(VI) consumption with a measured second order rate constant (k), and the k of Mn(VII) was less dependent on pH than that of Cr(VI), ranging from 104.7 M−1 s−1 to 104.9 M−1 s−1 and 10−0.4 M−1 s−1 to 101.6 M−1 s−1, respectively. Moreover, the reaction stoichiometry of [Cr(VI)]0:[S(IV)]0 was estimated to about 1:30–1:40 in the presence of O2, which was significantly different from the molar ratio of [Mn(VII)]0 to [S(IV]0 (1:5–1:10). Sulfur radical (SO4 −) was determined to be a major active oxidant in both the systems based on the chemical probes and radical scavenging experiments. Besides, carbonate and chloride have greater inhibitory effects than other coexisting solutes (e.g., nitrate and organic matter) because of the higher reactivity with radical species. In addition, the proposed degradation of MTL mainly proceeded through hydroxylation, demethylation, and carboxylation reactions. All these results indicated that Mn(VII) outperforms Cr(VI) in the activation of S(IV) auto-oxidation for the degradation of MTL. An extremely fast degradation rate, high mineralization and strong adaptation to the water matrices were observed in the process, which were attributed to ultra-fast production of high concentrations of radical species such as SO4 −, HO and high valent manganese intermediates (e.g., Mn(III) and Mn(V)).

We propose a domino-cooling method to realize simultaneous ground-state cooling of a coupled mechanical-resonator chain through an optomechanical cavity working in the unresolved-sideband regime. This domino-effect cooling is realized by combining the cold-damping feedback on the first mechanical resonator with nearest-neighbor couplings between other neighboring mechanical resonators. We obtain analytical results for the effective susceptibilities, noise spectra, final mean phonon numbers, and cooling rates of these mechanical resonators, and find the optimal-cooling condition for these resonators. Particularly, we analyze a two-mechanical-resonator case and find that by appropriately engineering either the laser power or the feedback, a flexible switch between symmetric and asymmetric ground-state cooling can be achieved. This could be used for preparing symmetric quantum states in mechanical systems. We also simulate the cooling performance of a coupled $N$-mechanical-resonator chain and confirm that these resonators can be simultaneously cooled to their quantum ground states in the unresolved-sideband regime. Under proper parameter conditions, the cooling of the mechanical-resonator chain shows a temperature gradient along the chain. This study opens a route to quantum manipulation of multiple mechanical resonators in the bad-cavity regime., Comment: 12 pages, 7 figures

The simultaneous ground-state cooling of multiple degenerate or near-degenerate mechanical modes coupled to a common cavity-field mode has become an outstanding challenge in cavity optomechanics. This is because the dark modes formed by these mechanical modes decouple from the cavity mode and prevent extracting energy from the dark modes through the cooling channel of the cavity mode. Here we propose a universal and reliable dark-mode-breaking method to realize the simultaneous ground-state cooling of two degenerate or nondegenerate mechanical modes by introducing a phasedependent phonon-exchange interaction, which is used to form a loop-coupled configuration. We find an asymmetrical cooling performance for the two mechanical modes and expound this phenomenon based on the nonreciprocal energy transfer mechanism, which leads to the directional flow of phonons between the two mechanical modes. We also generalize this method to cool multiple mechanical modes. The physical mechanism in this cooling scheme has general validity and this method can be extended to break other dark-mode and dark-state effects in physics., Comment: 42 pages, 21 figures

The absorption of single-cavity and double-cavity optomechanical systems and periodic optomechanical lattices has previously been investigated extensively. In this paper, we present the absorption of a nonperiodic cavity chain, where the absorption value on the resonance point shows switchable dips or peaks, according to whether the optomechanical interaction is at an odd or even-numbered position in the chain. Meanwhile, the value of absorption due to the optomechanical interaction varies with the number of the bare cavities. The calculated results may have some novel applications, such as detecting the position of the movable mirror in a long cavity chain, which would be useful in quantum information processing based on optomechanical systems.

The occurrence of antibiotics in the environment has recently raised serious concern regarding their potential threat to aquatic ecosystem and human health. In this study, the magnetic ion exchange (MIEX) resin was applied for removing three commonly-used antibiotics, sulfamethoxazole (SMX), tetracycline (TCN) and amoxicillin (AMX) from water. The results of batch experiments show that the maximum adsorption capacities on the MIEX resin for SMX, TCN and AMX were 789.32, 443.18 and 155.15μg/mL at 25°C, respectively, which were 2-7 times that for the powdered activated carbon. The adsorption kinetics of antibiotics on the MIEX resin could be simulated by the pseudo-second-order model (R2=0.99), and the adsorption isotherm data were well described by the Langmuir model (R2=0.97). Solution pH exhibited a remarkable impact on the adsorption process and the absorbed concentrations of the tested antibiotics were obtained around the neutral pH. The MIEX resin could be easily regenerated by 2mol/L NaCl solution and maintained high adsorption removal for the tested antibiotics after regeneration. Anion exchange mechanism mainly controlled the adsorption of antibiotic and the formation of hydrogen binding between the antibiotic and resin can also result in the increase of adsorption capacity. The high adsorption capacity, fast adsorption rate and prominent reusability make the MIEX resin a potential adsorbent in the application for removing antibiotics from water.

Vacuum ultraviolet (VUV) and ultraviolet (UV)/chlorine processes are regarded as two of many advanced oxidation processes (AOPs). Because of the similar cost of VUV/UV and UV lamps, a combination of VUV and UV/chlorine (i.e., VUV/UV/chlorine) may enhance the removal of organic pollutants in water but without any additional power input. In this paper, a mini-fluidic VUV/UV photoreaction system (MVPS) was developed for bench-scale experiments, which could emit both VUV (185 nm) and UV (254 nm) or solely UV beams with a nearly identical UV photon fluence. The photon fluence rates of UV and VUV output by the MVPS were determined to be 8.88 × 10(-4) and 4.93 × 10(-5) einstein m(-2) s(-1), respectively. The VUV/UV/chlorine process exhibited a strong enhancement concerning the degradation of methylene blue (MB, a model organic pollutant) as compared to the total performance of the VUV/UV and UV/chlorine processes, although the photon fluence of the VUV only accounted for 5.6% of that of the UV. An acidic pH favored MB degradation by the VUV/UV/chlorine process. The synergistic mechanism of the VUV/UV/chlorine process was mainly ascribed to the effective use of (•)OH for pollutant removal through formation of longer-lived secondary radicals (e.g., (•)OCl). This study demonstrates that the new VUV/UV/chlorine process, as an enhanced AOP, can be applied as a highly effective and energy-saving technology for small-scale water and wastewater treatment.

In this study, the performance of catalytic ozonation in the treatment of bio-treated coking wastewater (BCW) using pilot- and full-scale systems was investigated. Additionally, the removal efficiency of organic pollutants from BCW, the deactivation mechanism of MnxCe1-xO2/γ-Al2O3, and backflushing optimization for in-situ catalyst regeneration, which have not been previously investigated, were analysed. Results of the 12-month pilot scale experiments showed that catalytic ozonation resulted in the effective removal of organic pollutants when backflushing was applied as an in-situ catalyst regeneration strategy. The effluent chemical oxygen demand (COD) content decreased from 150 to 78 mg L−1, and remained below a discharge limitation of 80 mg L−1, and the stable COD removal efficiencies (from 56.0% to 47.9%) indicated that catalyst deactivation, which primarily resulted from the deposition of inorganic salts on the surface of the catalyst that limited interaction between ozone and active sites and/or prevented electrons transfer, was primarily inhibited by backflushing. The catalyst regeneration via in-situ air- and water-backflushing was attributed to the scrubbing, collision, and/or the loosing effect. Additionally, in the full-scale experiment, the catalytic ozonation process with in-situ alternative backflushing exhibited a stable COD removal efficiency (above 45.6%) for 885 days when water- and air-flushing strengths of 10 L m−2 s−1 and 15 L m−2 s−1, respectively, were applied with a 7-day regeneration interval. Therefore, the results of this study provide new insights into catalytic ozonation and support its engineering application in BCW treatment.

Optical nonreciprocity in a three-mode optomechanical system within a common optical reservoir is considered. It is found that optomechanically induced nonreciprocity is generated by the interference between the incoherent coupling induced by the common reservoir and the optomechanical coupling mediated by the interactions of two optical modes with a mechanical mode. There exist two symmetric nonreciprocal regimes that respectively correspond to the forward and backward photon transmissions, and the optical nonreciprocity for the relative phase φ between the optomechanical couplings is in opposite direction to that for the phase 2 π − φ . Additionally, it is shown that the optimal nonreciprocity as well as the nonreciprocal amplification can be achieved only by adjusting the optomechanical couplings. To compare nonreciprocity induced by incoherent coupling with that in the case of coherent coupling, we consider the optomechanically induced nonreciprocity created by interference between the optomechanical and direct couplings between the two optical modes. The nonreciprocal behaviors and their differences in these two cases are explained by using analytic findings.

Quantum manipulation of coupled mechanical resonators has become an important research topic in optomechanics because these systems can be used to study the quantum coherence effects involving multiple mechanical modes. A prerequisite for observing macroscopic mechanical coherence is to cool the mechanical resonators to their ground state. Here we propose a theoretical scheme to cool two coupled mechanical resonators by introducing an optomechanical interface. The final mean phonon numbers in the two mechanical resonators are calculated exactly and the results show that the ground-state cooling is achievable in the resolved-sideband regime and under the optimal driving. By adiabatically eliminating the cavity field in the large-decay regime, we obtain analytical results of the cooling limits, which show the smallest achievable phonon numbers and the parameter conditions under which the optimal cooling is achieved. Finally, the scheme is extended to the cooling of a chain of coupled mechanical resonators., 14 pages, 8 figures

The design of the isolated propeller duct for multi-rotor aircraft has been investigated by using numerical simulation. The paper is intended to discuss the influences of three factors, i.e., the profile of the duct, the angle of incidence in the duct’s profile, and the spacing between the propeller tip and the duct’s inner wall, on the static performance of the ducted propeller system. Simulation results show that the pull of one propeller in a duct system is smaller than that of an isolated propeller, but the overall pull of the system is greater than that of the isolated propeller. When the airfoil with a large lift-to-drag (L/D) ratio is adopted as the profile of the duct, and the duct’s inner wall is set in the expansion type, the overall pull is substantially increased with the other conditions unchanged. If the airfoil with a large L/D ratio is adopted as the profile of the duct, and its designed angle of incidence is set at 0 degree, the ducted propeller system have the largest pull coefficient, and so on. By exploring the optimal design and pattern of the propeller duct, some propositions have been made in an attempt to improve the design method.

The environmental risk controllability assessment system and its method of controlling volatile organic compounds (VOCs) during remediation of contaminated sites are established in this article based on soil vapor extraction (SVE) technology. According to the properties of VOCs and the technical and operational characteristics of the site remediation process, the environmental risk controllability index system includes environmental risk identification, risk source analysis, and risk assessment. Environmental risk management during site remediation was focused on technical control methods and engineering control technologies. Specifically, acceptance based on risk management was suitable for low-risk levels such as RRI3 and RRI4. Furthermore, control methods for high-level risk (RRI1 or RRI2) could be developed along with transformation and control, combined with the necessary emergency risk plan.

In order to obtain a high adsorption capacity for perchlorate, the epoxide-forming quaternary ammonium (EQA) compounds were chemically bonded onto granular activated carbon (GAC) surface by cationic reaction. The optimum preparation condition of the cationic GAC was achieved while applying softwood-based Gran C as the parent GAC, dosing EQA first at a pH of 12, preparation time of 48 h, preparation temperature of 50 °C, and mole ratio of EQA/oxygen groups of 2.5. The most favorable cationic GAC that had the QUAB360 pre-anchored exhibited the highest perchlorate adsorption capacity of 24.7 mg/g, and presented the longest bed volumes (3000 BV) to 2 ppb breakthrough during rapid small scale column tests (RSSCTs), which was 150 times higher than that for the pristine Gran C. This was attributed to its higher nitrogen amount (1.53 At%) and higher positive surface charge (0.036 mmol/g) at pH 7.5. Also, there was no leaching of the quaternary ammonium detected in the effluent of the RSSCTs, indicating there was no secondary pollution occurring during the perchlorate removal process. Overall, this study provides an effective and environmental-friendly technology for improving GAC perchlorate adsorption capacity for groundwater treatment.

We consider the probe absorption properties in a mechanically coupled optomechanical system in which the two coupled nanomechanical oscillators are driven by the time-dependent forces, respectively. It is found that the mechanical interaction splits the transparency window for a usual single-mode optomechanical system into two parts and then leads to appearance of the double optomechanically induced transparency. The distance between the two transparency positions (the frequency for the maximal transparency) is determined by the mechanical interaction amplitude. This can be explained by using optomechanical dressed-mode picture which is analogue to the interacting dark resonances in coherent atoms. When the mechanical resonators are driven by the external forces, the transparencies in the double-transparency spectrum can be increased into amplifications or be suppressed by tuning the amplitude of the forces. Additionally, it is shown that the double transparencies or the amplifications oscillate with the initial phases of the forces with a period of 2π. These investigations will be useful for more flexible controllability of multi-channel optical communication based on the optomechanical systems.

A novel method has been developed for immobilizing (tailoring) polypyrrole (PPy) into activated carbon (AC) in a manner that facilitates the removal of sulfate, and then electrochemically regenerating the tailored activated carbon. This tailoring was achieved by sorbing pyrrole into AC pores, then oxidizing the pyrrole by means of either a FeCl 3 oxidant or electrochemical oxidation. The resultant oxidized PPy hosted a positive charge that sorbed sulfate from acid mine drainage (AMD) water. Next, the spent AC/PPy was electrochemically reduced such that the nitrogen functionality became neutrally charged, and released the sorbed sulfate. This AC/PPy was then electrochemically oxidized such that it regained a positive charge, and again sorbed sulfate. When processing rapid small scale column tests (RSSCTs) with AMD water that contained 773 mg/L SO 4 2− the media processed 23 bed volumes before breakthrough occurred. Subsequent to these RSSCTs, electrochemical reduction at −2.0 V (vs Ag/AgCl) released 95% of this sorbed sulfate, and subsequent oxidation at 0.4 V yielded a media that had restored 61.5% of its initial sulfate-sorption capacity.

Positively charged nitrogen functional groups were introduced onto the surface of granular activated carbon (GAC), and these increased perchlorate anion removal from drinking water sources. Nitrogen functionalization involved three treatment steps: (1) introducing oxygen groups onto the GAC, (2) incorporating nitrogen groups by thermal treatment in ammonia flow to replace O with N, and (3) quaternerizing pyridine-like groups to create positively charged pyridinium-like groups. Functionalized bituminous GAC provided 6 times more perchlorate removal than its predecessor, pristine bituminous GAC. The conversion of pyridine-like groups (after step 2) to pyridinium-like groups by quaternization (step 3) was confirmed by analysis of the XPS N 1s signals and surface charge analysis. Redox peaks, observed during cyclic voltammetry analysis of the functionalized GAC, evidenced that these nitrogen functional groups were electrochemically active, so that they sorbed perchlorate when they were oxidized, and then desorbed perchlorate when reduced. Moreover, after sorbing perchlorate onto pyridinium-GAC in RSSCTs, the GAC media could be regenerated by electrochemical reduction, and its capacity for perchlorate adsorption was mostly restored. This tailored functionality and redox regeneration of a relatively inexpensive media such as activated carbon could offer novel opportunity to the adsorption industry.

A novel method of removing sulfate from acid mine drainage (AMD) water was developed by depositing polypyrrole into the pores of wood-based activated carbon (RGC) using in situ chemical oxidative polarization. This polypyrrole-tailored activated carbon hosted positively charged polypyrrole functionality that offered sorption capacity for sulfate. Specifically, in batch tests, the polypyrrole-grafted RGC achieved a sulfate loading of 48 mg/g, this being 8 times higher than for pristine RGC. Rapid Small Scale Column Tests appraised the polypyrrole-tailored RGC for removing 773 mg/L sulfate from AMD water. The more favorably tailored carbon removed sulfate to half-breakthrough at 24 bed volumes (BV). This compared to 1.5 BV for pristine activated carbon. Per mass and charge balance, 9% of the nitrogen in the polypyrrole functionality was active for capturing sulfate. On this tailored carbon, the nitrogen content was 12.9%, as characterized by X-ray photoelectron spectroscopy. With this polypyrrole tailoring, the carbon’s pore volume distributions diminished to one-third, as characterized by argon adsorption.

The squeezing transfer from a squeezed vacuum injected in one cavity to the output spectrum of the other cavity in an optomechanical system is investigated. By calculating the noise spectrum of the output field, it is found that two squeezing dips appear symmetrically located about the resonant point. Besides the contribution from the destructive interference between the noise fluctuation of the input field and its optomechanically modified one, the major part of the squeezing is transferred from the squeezed vacuum injected in the cavity. Additionally, it is shown that the adverse effects of the environment temperature on the output spectrum can be strongly suppressed by the injected squeezed field. This study can be useful in quantum communications via the optomechanical interface.

A novel method has been developed for anchoring quaternary ammonium/epoxide-forming compounds (QAEs) within bituminous based granular activated carbons (GACs). This modified GAC was then used to remove perchlorate from groundwater. The effect of the preparation temperature (T), solution pH (pH) and the dry mass ratio of QAE-to-GAC (R) over the perchlorate adsorption capacity (Qe) were studied by the Response Surface Methodology. The combined effects of these variables were fitted to a quadratic model to determine the more favorable preparation protocol for perchlorate removal. Statistical analysis revealed that: (1) the interaction of T and pH incurred the most effect on Qe; and (2) two of the more favorable preparation protocols became apparent: one was at 75 °C, pH 11 and R of 1.73 g QAE/g GAC (U17), the other was at 35 °C, pH 14 and R of 4.00 g QAE/g GAC (U2). Rapid small scale column tests were further employed to evaluate the performance of the QAE-anchored GACs for perchlorate removal. U17 and U2 exhibited 18–20 times longer bed life (BV) to 6 ppb breakthrough than did the Pristine GAC (900 BV), when processing groundwater that had been spiked with 30–35 ppb perchlorate. This indicated the statistical method enhanced GAC’s perchlorate removal efficiency.

A novel method has been developed for anchoring quaternary ammonium/epoxide-forming compounds (QAE) within bituminous and wood based granular activated carbons (GACs). This QAE-anchored GAC was then used to enhance perchlorate removal from perchlorate-spiked natural groundwater. Specifically, for the bituminous based carbon, while processing natural groundwater that had been spiked with 30–35 ppb perchlorate, and passing this water through rapid small scale column tests, the bed volumes (BV) to 2 ppb perchlorate breakthrough increased from 870 BV for pristine GAC up to 21,000 BV for the corresponding GAC that had been pre-anchored with QUAB360 (360 Da). However, the wood based GAC that had been anchored with this QUAB360 achieved only 3000 BV. None of the QAE leached out of these GACs during the column tests. The bituminous GAC that had been pre-anchored with QAE hosted more positive surface charge at pH 7.5 than did the wood based QAE–GAC. Per X-ray photoelectron spectroscopy, the QAE anchored into the GACs increased their N-content by 1–1.3%. By means of multiple analyses, the authors surmised that the active quaternary ammonium sites within the tailored bituminous-based GAC were more exposed and thus more accessible for perchlorate adsorption than those within wood based GAC.

Polypyrrole modified activated carbon was used to remove sulfate from acid mine drainage water. The polypyrrole modified activated carbon created positively charged functionality that offered elevated sorption capacity for sulfate. The effects of the activated carbon type, approach of polymerization, preparation temperature, solvent, and concentration of oxidant solution over the sulfate adsorption capacity were studied at an array of initial sulfate concentrations. A hardwood based activated carbon was the more favorable activated carbon template, and this offered better sulfate removal than when using bituminous based activated carbon or oak wood activated carbon as the template. The hardwood-based activated carbon modified with polypyrrole removed 44.7 mg/g sulfate, and this was five times higher than for the pristine hardwood-based activated carbon. Various protocols for depositing the polypyrrole onto the activated carbon were investigated. When ferric chloride was used as an oxidant, the deposition protocol that achieved the most N+ atomic percent (3.35%) while also maintaining the least oxygen atomic percent (6.22%) offered the most favorable sulfate removal. For the rapid small scale column tests, when processing the AMD water, hardwood-based activated carbon modified with poly pyrrole exhibited 33 bed volume compared to the 5 bed volume of pristine activated carbons.

We consider the optomechanically induced transparency in the double quadratically coupled optomechanical cavities within a common reservoir, in which the two cavities are driven by the coupling fields. It is shown that the probe transparency is improved by increasing the coupling field (the left coupling field) applied on the probing cavity, but the transparency position (the probe frequency of the maximal transparency) is shifted to high frequency. The coupling field (the right coupling field) applied on the other quadratically coupled cavity can lead to a low-frequency shift for the transparency position, which can be used to fix the transparency position by adjusting the right coupling field. We get the quantitative findings that the transparency position is exactly determined by the intensity difference between the two coupling fields. On the other hand, it is found that when the two coupled optomechanical cavities interact with their common reservoir, the cross decay induced by the common reservoir can improve the probe transparency and widen the transparency window. Finally, the effects of the environment's temperature on the transparency are investigated. This will be useful in cooling the membrane, squeezing and entangling the output fields.

In this paper, the effects of the squeezed vacuum (SV) on the transient response in a ∨-type three-level atomic medium are investigated. We find that the properties of transient process can be greatly affected by the SV whether the vacuum-induced coherence (VIC) exists or not. The combined influence of the SV and the VIC can dramatically modify the transient absorption and gain. Especially, the transient gain can be almost eliminated in the absence of VIC. And the response time from the transient to the steady situation is dependent on the SV. When including the VIC, the transient and steady optical properties display a reverse variation with the SV. Besides, it is shown that the considerable steady state population without inversion can be always induced by the SV.

The flow behavior and associated structural changes of an Inconel 600 superalloy were analyzed by using hot compression tests in the temperature and strain rate ranges of 850–1200 °C and 0.001 to 10 s–1, respectively. The stress–strain curves exhibited the trend typical of materials in which deformation is recovery-controlled at high strain rates and low temperatures, while at low strain rates and high temperatures, the flow curves exhibited a softening typical of recrystallization phenomena. Constitutive analysis was carried out to investigate the hot deformation mechanism using the hyperbolic sine law.