Particulate Projectiles Driven by Cavitation Bubbles.

The removal of surface-attached particles with cavitation bubbles is usually attributed to the jetting or shear stresses when bubbles collapse. In this Letter, we report an unexpected phenomenon that millimeter-sized spherical particles made of heavy metals (e.g., stainless steel), when initially resting on a fixed rigid substrate, are suddenly accelerated like projectiles through the production of nearby laser-induced cavitation bubbles of similar sizes. We show experimentally and theoretically that the motion of a particle with radius R_{p} is determined by the maximum bubble radius R_{b,max}, the initial distance from the laser focus to the center of the particle L_{0}, and the initial azimuth angle φ_{0}. We identify two dominant regimes for the particle's sudden acceleration, namely, the unsteady liquid inertia dominated regime and the bubble contact dominated regime, determined by R_{b,max}R_{p}/L_{0}^{2}. We find the nondimensional maximum vertical displacement of the particle follows the fourth power and the square power scaling laws for respective regimes, which is consistent with the experimental results. Our findings can be applied to nonintrusive particle manipulation from solid substrates in a liquid.

Motion of a Free-Settling Spherical Particle Driven by a Laser-Induced Bubble.

We document experimentally four different interactions of a laser-induced bubble and a free-settling particle, with different combinations of the geometric and physical parameters of the system. Our force balance model shows that four nondimensional factors involving the particle radius a, the maximum bubble radius R_{max}, the initial separation distance l_{0} between the particle center and the bubble center, the fluid viscosity µ_{f}, and the particle and fluid densities ρ_{p} and ρ_{f}, respectively, in detail l_{0}/R_{max}, a/R_{max}, ρ_{p}/ρ_{f}, and µ^{*}=µ_{f}T_{c}/ρ_{f}R_{max}^{2}, where T_{c}=0.915R_{max}sqrt[ρ_{f}/(p_{∞}-p_{v})], influence the particle-bubble dynamics, and reasonably predict the maximum particle velocity and the limiting condition when the particle starts to "bounce off" the bubble during bubble growth. In particular, we also discover the high-speed ejection of the particle, and a cavity behind the particle, in cases when initially the particle is in very close proximity to the bubble. These observations offer new insights into the causal mechanism for the enhanced cavitation erosion in silt-laden water.

Morphological analysis of mercury in solid wastes from natural gas processing plants: optimization of a temperature-programmed decomposition and desorption method.

Determination of mercury species over solid waste from natural gas processing plants is a prerequisite for solid waste decontamination and mercury recycling. The temperature-programmed decomposition and desorption method (TPDD) is a promising technique to determine the mercury species over solid waste. Mercury species over solid wastes with complex components and similar desorption temperature, however, cannot always be determined using only the TPDD method. In the present study, the EPA 3200 method was applied to optimize the TPDD process for speciation of the mercury compound over solid wastes collected from a natural gas processing plant, including four spent adsorbents and three sludges. The mercury species with similar desorption temperatures over solid wastes were completely separated by the EPA 3200 method optimized TPDD process. The mercury species over spent adsorbents and sludges could be determined based on the fingerprints of the mercury compounds. The mercury compounds over spent adsorbents were specified to be Hg0 and/or M-Hg amalgam, HgS(black) and HgO(red), of which HgS(black) was the primary mercury compound. However, the mercury species over sludge were analyzed to be Hg0 and/or M-Hg amalgam, HgCl2(minor), HgS(black), HgO(yellow) and HgS(red). The mercury recovery rates of solid wastes ranged from 73% to 120%. With the above results, it was considered that the EPA 3200 method optimized TPDD process was a promising method to specify and semi-quantify the mercury compounds in solid waste.

Construction of Pt/Ni/NiFe2O4/C nanocomposite with one dimensional hollow structure for portable glucose sensing application.

Designing portable electrochemical sensors combined with highly efficient glucose oxidation electrodes offers a significant opportunity for convenient glucose detection. In this report, we present the design and preparation of platinum deposited Ni/NiFe2O4/Carbon composite (Pt/Ni/NiFe2O4/C) derived from Ni/Fe metal-organic frameworks (MOFs) followed by Pt deposition. Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electron microscopy (EM) were utilized to analyze the crystal structure, morphology, and chemical composition of the resulting materials. The glucose sensing capabilities of the optimal Pt/Ni/NiFe2O4/C-3 were assessed using amperometry methods on a smartphone-based portable device. Acting as a nonenzymatic glucose sensor, the Pt/Ni/NiFe2O4/C-3 electrode demonstrated notable sensitivity and a low limit of detection for glucose. The portable sensor exhibits high sensitivities of 131.88 µM mM cm-2 at low glucose concentration (3-500 µM) and 29.52 µA mM cm-2 at high glucose concentration (700-4000 µM), achieving a low detection limit of 1.1 µM (S/N = 3). The sensor also demonstrates enhanced selectivity and stability for detecting glucose. Furthermore, the portable sensor exhibits a clear step-ampere response in the detection of serum samples with satisfactory recovery ranging from 99.30 to 101.32%. This suggests the significant potential of portable glucose sensing applications.

Electrochemical sensors based on platinum-coated MOF-derived nickel-/N-doped carbon nanotubes (Pt/Ni/NCNTs) for sensitive nitrite detection.

As excess nitrite has a serious threat to the human health and environment, constructing novel electrochemical sensors for sensitive nitrite detection is of great importance. In this report, platinum nanoparticles were deposited on nickel-/N-doped carbon nanotubes, which were obtained through a self-catalytically grown process with Ni-MOF as precursors. The as-prepared Pt/Ni/NCNTs were applied as amperometric sensors and presented superior sensing properties for nitrite detection. Benefiting from the synergy of Pt and Ni/NCNTs, Pt/Ni/NCNTs displayed much wider detection ranges (0.5-40 mM and 40-110 mM) for nitrite sensing. The sensitivity is 276.92 µA mM-1 cm-2 and 224.39 µA mM-1 cm-2, respectively. The detection limit is 0.17 µM. The Pt/Ni/NCNTs sensors also showed good feasibility for nitrite sensing in real samples (milk and peach juice) analysis. The active Pt/Ni/NCNTs composites and facile fabrication technique may provide useful strategies to develop other sensitive nitrite sensors.

PMS activation by magnetic cobalt-N-doped carbon composite for ultra-efficient degradation of refractory organic pollutant: Mechanisms and identification of intermediates.

Refractory organic pollutant effluent has led to severe water pollution. In this study, magnetic Co-N-doped carbon hybrid catalysts (Co-NC-x) were fabricated using a facile cation exchange combined pyrolysis and self-reduction technique to activate peroxymonosulfate (PMS) for rehabilitation of the water environment. Factors affecting the catalytic activity of the Co-NC-850 were comprehensively examined. 100% of RhB degradation efficiency within 20 min was achieved in the Co-NC-850/PMS system at the optimum conditions (C0 = 80 mg L-1, catalyst loading 0.025 g L-1, PMS concentration 0.8 mM, native pH and 25 °C). The electron paramagnetic resonance measurements and competitive quenching tests demonstrated that a sulfate radical (SO4•-) and singlet oxygen (1O2) account for RhB degradation in the Co-NC-850/PMS system, and 1O2 contributed ~86.2% to RhB removal. The synergistic effect of Co0 nanoparticles (NPs) and NC on Co-NC-850 might induce a predominant non-radical route to trigger PMS activation for RhB degradation. Direct oxidation of O2•- by a hydroxyl radical (•OH) might be the crucial process for forming 1O2. Magnetic response and successive cycles verified that Co-NC-850 has superior separable performance and reusability. This innovative magnetic Co-NC-850 hybrid catalyst for PMS activation delivered vast potential for disintegration of refractory organic contaminants.

Magnetic Fe3O4-N-doped carbon sphere composite for tetracycline degradation by enhancing catalytic activity for peroxymonosulfate: A dominant non-radical mechanism.

The design of sustainable, effective and recyclable hybrid catalysts for advanced oxidation processes is highly significant for remediation of the water environment. In this study, we synthesized magnetic Fe3O4-N-doped carbon sphere composite catalysts (Fe3O4-NCS-x) for efficient removal of tetracycline by activating peroxymonosulfate (PMS). The Fe3O4-NCS-x composite was obtained by facile hydrothermal treatment of chitosan-iron complexes followed by pyrolysis. The unique structure of N-doped carbon spheres embedded in Fe3O4 nanoparticles intensified the electron transport, consequently improving the catalytic activity via a synergistic effect. Factors influencing the catalytic activity of the Fe3O4-NCS-2 were systematically investigated. High degradation efficiency of TC-97.1% within 1 h-was achieved in this Fe3O4-NCS-2/PMS system under the optimum conditions (C0 = 20 mg L-1, catalyst dosage 0.2 g L-1, PMS concentration 2.4 mM, native pH and 25 °C). The inhibitory effect of anions in the water matrix decreased in the order Cl- > NO3- > SO42- > CH3COO- > HCO3-. The obtained results from the competitive quenching tests and electron paramagnetic resonance measurements demonstrated that singlet oxygen (1O2), a non-radical species, plays a major role in TC degradation. It is estimated that 1O2 and hydroxyl radicals (·OH) contributed ∼65.2% and ∼24.2% to TC degradation in the Fe3O4-NCS-2/PMS system, respectively. The M-H hysteresis loop of Fe3O4-NCS-2 revealed that its saturation moment is 56 emu g-1. Magnetic responsive behavior and consecutive runs confirmed that Fe3O4-NCS-2 possesses remarkable separation performance and desirable reusability. This novel magnetic Fe3O4-NCS-2 composite activator for PMS promises great potential in TC degradation.

ZnCl2 enabled synthesis of activated carbons from ion-exchange resin for efficient removal of Cu2+ ions from water via capacitive deionization.

Capacitive deionization (CDI) is a promising method to remove metal contaminants in water. Herein, we report on the preparation of activated carbon from cation-exchange resin by introducing ZnCl2 via ion exchange followed by heat treatment and CO2 activation, which is evaluated for removal of Cu2+ in water via CDI technology. The results have shown that both the heat treatment and the CO2 activation are helpful to tune the pore structure of the activated carbons in terms of ions adsorption and transportation. The activated carbon prepared by heat treatment at 600 °C and CO2 activation at 750 °C, named as AC-600-750, has the highest specific surface area of 1162 m2 g-1 and a specific capacitance of 247.4 F g-1 at 50 mV-1, with a Cu2+ adsorption capacity of 77.8 mg g-1 at 1.2 V in 50 mg L-1 CuCl2 solution that is much higher than that of the commercial activated carbon. The electrosorption of Cu2+ ions over activated carbon follows a monolayer adsorption scheme, of which the kinetic can be well explained by pseudo-first-order kinetic model. The resin-based activated carbons are of potential as an electrode material for efficient removal of heavy metal from contaminated water by CDI process.

Study on the Influence of Calcined Underground Ant Nest Powder on the Durability of Concrete.

Ants have strict requirements on the building materials of the nest, such as the size, weight, luster and color of soil particles. The soil of underground ant nests is composed of clay particles cemented together to form a hard brick-like material. The ant nest powder shows pozzolanic activity after calcination, which can meet the requirements for active admixture of concrete. Under the standard curing condition, the influence of calcined ant nest clay powder (CANCP) on the durability of concrete is evaluated by chloride penetration resistance, carbonization resistance and freeze-thaw resistance, and the influence of the powder content is investigated. The results show that when the content of CANCP is less than 10%, the chloride penetration resistance of concrete increases with content of CANCP. In the early stage of carbonation, the greater the content of CANCP, the higher the carbonization rate of concrete. In the middle and later stage of carbonation, the carbonation rate of CANCP concrete is significantly lower than that in the early stage, and the carbonation depth is linearly related to the carbonation time. When the content of CANCP is less than 20%, the freeze-thaw resistance of CANCP concrete is better than that of the reference concrete.

Selective depletion of macrophages reveals distinct, opposing roles during liver injury and repair.

Macrophages perform both injury-inducing and repair-promoting tasks in different models of inflammation, leading to a model of macrophage function in which distinct patterns of activation have been proposed. We investigated macrophage function mechanistically in a reversible model of liver injury in which the injury and recovery phases are distinct. Carbon tetrachloride---induced liver fibrosis revealed scar-associated macrophages that persisted throughout recovery. A transgenic mouse (CD11b-DTR) was generated in which macrophages could be selectively depleted. Macrophage depletion when liver fibrosis was advanced resulted in reduced scarring and fewer myofibroblasts. Macrophage depletion during recovery, by contrast, led to a failure of matrix degradation. These data provide the first clear evidence that functionally distinct subpopulations of macrophages exist in the same tissue and that these macrophages play critical roles in both the injury and recovery phases of inflammatory scarring.

Sustainable nitrogen-rich hierarchical porous carbon nest for supercapacitor application.

Chitosan has high synthetic flexibility, making it a promising nitrogenous bioresource for industrial applications. Nitrogen-rich hierarchically porous carbon (NHPC) was successfully synthesized by hydrothermal carbonization and self-activation of a chitosan-transition metal ion (Zn2+) complex. The N2 adsorption-desorption isotherm revealed that the as-made NHPC had large specific surface area (1067 m2 g-1) and a unique hierarchical pore structure (0.6-6.4 nm). Scanning electron microscopy (SEM) indicated a 3D finely interconnected nest architecture for NHPC. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the nitrogen atoms in the chitosan were protected by coordination with zinc ions, and most of them were still retained in the carbon matrix (6.36 at%) after high temperature activation. Electrochemical measurements exhibited that NHPC delivers a high specific capacitance (228.7 Fg-1 at 1 A g-1), impressive rate capability (the specific capacitance at 20 A g-1 was 174 Fg-1, maintaining 74.6% of the initial capacitance at 0.5 A g-1), and outstanding long-term cycling stability (98.3% retention after 5000 cycles), together with excellent energy density of 25.7 Wh kg-1 at the power density of 500 W kg-1. This study offers a novel strategy for synthesizing NHPC as one of the desirable electrode material candidates for energy storage.

Chitin based heteroatom-doped porous carbon as electrode materials for supercapacitors.

Chitin biomass has received much attention as an amino-functional polysaccharide precursor for synthesis of carbon materials. Rich nitrogen and oxygen dual-doped porous carbon derived from cicada slough (CS), a renewable biomass mainly composed of chitin, was synthesized and employed as electrode materials for electrochemical capacitors, for the first time ever. The cicada slough-derived carbon (CSC) was prepared by a facile process via pre-carbonization in air, followed by KOH activation. The weight ratio of KOH and char plays an important role in fabricating the microporous structure and tuning the surface chemistry of CSC. The obtained CSC had a large specific surface area (1243-2217m2g-1), fairly high oxygen content (28.95-33.78 at%) and moderate nitrogen content (1.47-4.35 at%). The electrochemical performance of the CS char and CSC as electrodes for capacitors was evaluated in a three-electrode cell configuration with 6M KOH as the electrolyte. Electrochemical studies showed that the as-prepared CSC activated at the KOH-to-char weight ratio of 2 exhibited the highest specific capacitance (266.5Fg-1 at a current density of 0.5Ag-1) and excellent rate capability (196.2Fg-1 remained at 20Ag-1) and cycle durability. In addition, the CSC-2-based symmetrical device possessed the desirable energy density and power density of about 15.97Whkg-1 and 5000Wkg-1 at 5Ag-1, respectively.

Fuel properties and combustion kinetics of hydrochar prepared by hydrothermal carbonization of bamboo.

Hydrothermal carbonization, an environmental friendly treatment method was employed to pretreat bamboo for hydrochar preparation in the present study. Hydrothermal carbonization could elevate the fuel properties and combustion behavior of bamboo. The combustion kinetic parameters of raw bamboo and hydrochars were calculated by a simple Arrhenius equation based on the thermogravimetric curves. Two distinct zones were observed for raw bamboo and hydrochars. The activation energies of raw bamboo in zone 1 and zone 2 were 109.5kJ/mol and 46.6kJ/mol, respectively, in the heating rate of 20°C/min. The activation energy of hydrochar in zone 1 increased at the hydrothermal carbonization temperature under 220°C and then decreased at higher hydrothermal carbonization temperature, due to the decomposition of relative reactive compounds in bamboo, and destruction of cellulose and hemicellulose structures, respectively. The activation energies of hydrochars in zone 2 were among 52.3-57.5kJ/mol, lower than that of lignin extracted from bamboo.

Furfural-induced hydrothermal synthesis of ZnO@C gemel hexagonal microrods with enhanced photocatalytic activity and stability.

Here we report the synthesis of ZnO@C coaxial gemel hexagonal microrods with a thin hydrothermal carbon (HTC) layer on their surface by a facile one-step hydrothermal method with furfural as the carbon precursor. The furfural has a unique dual role, which not only induces the nucleation of ZnO in the initial stage of hydrothermal process, but also forms a thin HTC layer deposited on the ZnO surface. The thickness of the surface HTC layer increases with the hydrothermal time until 16 h under the conditions adopted in the present study. It has been found that the HTC layer has resulted in a significant improvement in the photocatalytic activities and photostabilities of the ZnO@C microrods for the UV-irradiated photodegradation of methylene blue solution. The mechanism involved in the process is proposed and discussed in terms of the photodegradation scheme and the properties of the ZnO@C microrods.

Conditional macrophage ablation demonstrates that resident macrophages initiate acute peritoneal inflammation.

The role played by resident macrophages (Mphi) in the initiation of peritoneal inflammation is currently unclear. We have used a conditional Mphi ablation strategy to determine the role of resident peritoneal Mphi in the regulation of neutrophil (PMN) recruitment in experimental peritonitis. We developed a novel conditional Mphi ablation transgenic mouse (designated CD11bDTR) based upon CD11b promoter-mediated expression of the human diphtheria toxin (DT) receptor. The murine DT receptor binds DT poorly such that expression of the human receptor confers toxin sensitivity. Intraperitoneal injection of minute (nanogram) doses of DT results in rapid and marked ablation of F4/80-positive Mphi populations in the peritoneum as well as the kidney, and ovary. In experimental peritonitis, resident Mphi ablation resulted in a dramatic attenuation of PMN infiltration that was rescued by the adoptive transfer of resident nontransgenic Mphi. Attenuation of PMN infiltration was associated with diminished CXC chemokine production at 1 h. These studies indicate a key role for resident peritoneal Mphi in sensing perturbation to the peritoneal microenvironment and regulating PMN infiltration.

In vivo depletion of CD11c+ dendritic cells abrogates priming of CD8+ T cells by exogenous cell-associated antigens.

Cytotoxic T lymphocytes (CTL) respond to antigenic peptides presented on MHC class I molecules. On most cells, these peptides are exclusively of endogenous, cytosolic origin. Bone marrow-derived antigen-presenting cells, however, harbor a unique pathway for MHC I presentation of exogenous antigens. This mechanism permits cross-presentation of pathogen-infected cells and the priming of CTL responses against intracellular microbial infections. Here, we report a novel diphtheria toxin-based system that allows the inducible, short-term ablation of dendritic cells (DC) in vivo. We show that in vivo DC are required to cross-prime CTL precursors. Our results thus define a unique in vivo role of DC, i.e., the sensitization of the immune system for cell-associated antigens. DC-depleted mice fail to mount CTL responses to infection with the intracellular bacterium Listeria monocytogenes and the rodent malaria parasite Plasmodium yoelii.