Growth, Characterizations, and Applications of Patterned Nanostructured Thin Film

A unique microreactor-assisted nanomaterial synthesis and printing process was studied for the fabrication of patterned metal oxide nanostructured thin films. The process uses a continuous flow microreactor to control and generate a reactive chemical flux that was transported to a patterned microfluidic channel. The microreactor-assisted nanomaterial synthesis process can generate reactive building blocks, ranging from molecules, clusters to nanoparticles with constant concentration and compositions. The reactive solution was then delivered to the substrate surface, guided by a patterned microchannel. The growth kinetics of the nanostructured ZnO on silicon wafers were studied by measuring the thickness of the film using the stylus profiler and scanning electron microscope under various growth conditions controlled by using the microreactor and the microchannel made of Polydimethylsiloxane. The process contains three zones, a mixing zone, a reactant generation zone, and a deposition zone. This process allows a separation of the homogeneous reaction in the solution and the heterogeneous reaction on the substrate surface, resulting in a well-controlled growth of the ZnO nanostructures on the substrate surface so that the growth mechanisms and kinetics can be studied. Different growth parameters, including flow rate, residence time, the temperature of the chemical solution and temperature of the substrate, are varied to study the growth kinetics. A key process parameter is the flow rate; a higher flow rate can result in faster growth of ZnO nanostructures. A lower flow rate will result in a longer residence time of the chemical solution within zone 2, which can lead to the homogenous formation of solid nanoparticles, thus reduce the concentration of reactive Zn(OH)₂ (aq). This finding is further supported by growth experiments carried out using reactors with two different reaction channel lengths within zone 2. Besides, the thickness of rectangular patterned ZnO nanostructured films show a saddle-shaped profile, which is thinner near the center. This thickness profile is a result of combined heat and mass transfer of the reactive solution within the patterned channel, as qualitatively supported by COMSOL simulations. By measuring the growth rates as a function of substrate temperatures, the activation energy of the rate constant is obtained at 22.65kJ/mol. This process not only provides better control to fabricate patterned metal oxide nanostructures but also offers the unique capability to study the growth mechanisms. The improved understandings were applied to demonstrate a novel, scalable process to fabricate ZnO nanostructures with multiscale 3D geometric shapes. In particular, the precursor solutions were firstly mixed and heated in a microreactor to control solution temperature and to generate reactive species. The reacting solution was then delivered to the substrate surface guided by a patterned PDMS channel with different designs, including the spiral pattern, the parallel pattern, and the split-and-recombine pattern. ZnO nanostructures with multiscale 3D geometric shapes were formed guided by the patterned channel. It is found that geometry is controlled by the channel geometry, flow rate, and substrate temperature. The stylus profiler measures film thickness, and the result shows that the unique characteristics of each pattern type. With the aid of the Comsol simulation, the parameters that control the growth are studied: in the spiral pattern, the consumption of the reactant can result in a thinner film as the solution flows through the channel. In the parallel-design pattern, the film thickness is determined by the flow rate of the solution in each channel in parallel. With the channel narrowed and the flow rate reduced, a thinner ZnO nanostructured film is obtained. In the split-and-recombine design pattern, the film growth rate is halved as the channel split and doubled as the channels re-combined. The temperature profile within the channel is another critical parameter of controlling the growth of ZnO nanostructures in all dimensions. This scalable process, aided with new understandings, will provide a unique capability to fabricate metal oxide nanostructures of controlled multiscale 3D geometric shapes. Besides ZnO, the microreactor-assisted nanomaterial synthesis and printing process was used to deposit patterned CuO and Cu₂(OH)₃NO₃ nanostructures on surface, including dense nanocrystalline CuO film, CuO nanorods, Cu₂(OH)₃NO₃ nanorods, and Cu₂(OH)₃NO₃ nanoplates using the same reactants, Cu(NO3)2 and Hexamethylenetetramine. The critical process parameter that controls the formation of different products is the concentration of the OH- in the solution, which can be controlled by the ratio of the reactants and the temperature of the microreactor. The high concentration of OH- leads to the formation of Cu(OH)₂, which is then converted to CuO on the heated substrate surface. In contrast, the low concentration of OH- leads to the formation of Cu₂(OH)₃NO₃. These results show the applicability of the microreactor-assisted nanomaterial synthesis and printing process to deposit metal oxide nanostructures with controlled structure and composition. The utility of microreactor-assisted nanomaterial synthesis and printing process was demonstrated via the fabrication of heterojunction ZnO/CuO bi-layer film. The bilayer film was built by depositing a patterned nanocrystalline CuO film on a gold-coated glass surface using the microreactor-assisted nanomaterial synthesis and printing process, followed by the deposition of ZnO nanostructured film with a smaller-size pattern using the same process. The heterojunction ZnO/CuO bi-layer film shows rectifying behavior; it allows currents to flow when forward biased and passes only low leakage currents with reverse bias; the p-n diode has a rectification ratio around 10⁴, which is comparable to the values among the best solution-processed p-n junction diodes. The results of this study demonstrate the capability of our microreactor-assisted nanomaterial synthesis and printing process to fabricate structured thin films for functional devices

Velocity distribution characteristics and parametric sensitivity analysis of liquid nitrogen jet

Liquid nitrogen is expected to be used as a jet medium in petroleum engineering because of its cryogenic and non-polluting characteristics. To identify the velocity distribution characteristics of liquid nitrogen jet, a computational fluid dynamics model was built by coupling the equations for nitrogen properties. The velocity and pressure distributions of liquid nitrogen jet were analyzed by comparing them with water jet ones. Meanwhile, the influences of relevant parameters on the centerline velocity distributions of liquid nitrogen jet were researched as well. The simulation results showed that the liquid nitrogen jet not only displayed higher velocity but also presented fewer kinetic energy losses than the water jet during jetting process. The nozzle outlet velocity of liquid nitrogen jet was increased by increasing the nozzle pressure drop, and was slightly influenced by confining pressure and nozzle diameter. In the external space of the nozzle, the attenuation amplitude of centerline velocity was decreased with the growth of nozzle diameter, and was slightly influenced by nozzle pressure drop and confining pressure. This study is expected to provide a theoretical guide for parametric design of liquid nitrogen jet

Study on the epidemiological burden of acute gastroenteritis in Heilongjiang Province

Objective The objective is to reveal the epidemiological burden and predictors of acute gastroenteritis in Heilongjiang Province. Methods A multi-stage stratified random sampling method was used to collect the incidence of acute gastroenteritis in the past 4 weeks. Results A total of 19 171 people were investigated. The monthly prevalence of acute gastroenteritis was 3.51% [95% confidence interval (95% CI): 3.25%-3.77%], the annual incidence rate was 37.24%, and the incidence rate was 0.466 times per person-year. The weighted monthly prevalence rate was 3.61%, the weighted annual incidence rate was 38.07%, and the weighted incidence rate was 0.479 times per person-year. It was estimated that the average annual incidence of acute gastroenteritis in this province was 14.423 million people per year, with a total of 18.147 million cases. Multivariate Logistic regression analysis showed that the nature of the residence, season, age, whether they had left their residence due to business or trips in the past 2 weeks, and the annual per capita income of the family were the influencing factors.58.66% of acute gastroenteritis cases were attributed to contaminated food. Conclusion Acute gastroenteritis in Heilongjiang Province had a heavy epidemiological burden and a high proportion of foodborne diseases, which should be paid more attention to

Velocity distribution characteristics and parametric sensitivity analysis of liquid nitrogen jet

Liquid nitrogen is expected to be used as a jet medium in petroleum engineering because of its cryogenic and non-polluting characteristics. To identify the velocity distribution characteristics of liquid nitrogen jet, a computational fluid dynamics model was built by coupling the equations for nitrogen properties. The velocity and pressure distributions of liquid nitrogen jet were analyzed by comparing them with water jet ones. Meanwhile, the influences of relevant parameters on the centerline velocity distributions of liquid nitrogen jet were researched as well. The simulation results showed that the liquid nitrogen jet not only displayed higher velocity but also presented fewer kinetic energy losses than the water jet during jetting process. The nozzle outlet velocity of liquid nitrogen jet was increased by increasing the nozzle pressure drop, and was slightly influenced by confining pressure and nozzle diameter. In the external space of the nozzle, the attenuation amplitude of centerline velocity was decreased with the growth of nozzle diameter, and was slightly influenced by nozzle pressure drop and confining pressure. This study is expected to provide a theoretical guide for parametric design of liquid nitrogen jet

Effects of unsaturated flow on Hillslope recession characteristics

Recession flow analysis is usually conducted to infer hydraulic parameters of hillslope aquifers. Various Boussinesq equation-based models, both linear and nonlinear, have been used to analyze the recession curves for sloping aquifers, with a focus on the long-time recession behavior. Based on a modified Boussinesq equation with capillarity incorporated, we demonstrate the significant effect of unsaturated flow on the recession curve, which result in three (instead of two) power law regimes with two transition points (instead of one) corresponding to the formation of a fully unsaturated zone at the adjacent area of the upslope boundary and across the whole domain, respectively. The results show that the power of the second and third recession regime is variable, depending on the slope angles, soil types, and hillslope geometries. The unsaturated flow effects also lead to the absence of drastic drop of (Formula presented.) at the transition between the first and second regime, which was predicted by previous numerical models but has not been observed in the field or laboratory experiments. These findings have important implications for recession flow analysis in studies of hillslope aquifers

Recombinant Sialyltransferase Infusion Mitigates Infection-Driven Acute Lung Inflammation

Inappropriate inflammation exacerbates a vast array of chronic and acute conditions with severe health risks. In certain situations, such as acute sepsis, traditional therapies may be inadequate in preventing severe organ damage or death. We have previously shown cell surface glycan modification by the circulating sialyltransferase ST6Gal-1 regulates de novo inflammatory cell production via a novel extrinsic glycosylation pathway. Here, we show that therapeutic administration of recombinant, bioactive ST6Gal-1 (rST6G) mitigates acute inflammation in a murine model mimicking acute exacerbations experienced by patients with chronic obstructive pulmonary disease (COPD). In addition to suppressing proximal neutrophil recruitment at onset of infection-mediated inflammation, rST6G also muted local cytokine production. Histologically, exposure with NTHI, a bacterium associated with COPD exacerbations, in rST6G-treated animals revealed consistent and pronounced reduction of pulmonary inflammation, characterized by smaller inflammatory cuffs around bronchovascular bundles, and fewer inflammatory cells within alveolar walls, alveolar spaces, and on pleural surfaces. Taken together, the data advance the idea that manipulating circulatory ST6Gal-1 levels has potential in managing inflammatory conditions by leveraging the combined approaches of controlling new inflammatory cell production and dampening the inflammation mediator cascade

PAK1IP1, a ribosomal stress-induced nucleolar protein, regulates cell proliferation via the p53–MDM2 loop

Cell growth and proliferation are tightly controlled via the regulation of the p53–MDM2 feedback loop in response to various cellular stresses. In this study, we identified a nucleolar protein called PAK1IP1 as another regulator of this loop. PAK1IP1 was induced when cells were treated with chemicals that disturb ribosome biogenesis. Overexpression of PAK1IP1 inhibited cell proliferation by inducing p53-dependent G1 cell-cycle arrest. PAK1IP1 bound to MDM2 and inhibited its ability to ubiquitinate and to degrade p53, consequently leading to the accumulation of p53 levels. Interestingly, knockdown of PAK1IP1 in cells also inhibited cell proliferation and induced p53-dependent G1 arrest. Deficiency of PAK1IP1 increased free ribosomal protein L5 and L11 which were required for PAK1IP1 depletion-induced p53 activation. Taken together, our results reveal that PAK1IP1 is a new nucleolar protein that is crucial for rRNA processing and plays a regulatory role in cell proliferation via the p53–MDM2 loop