Digital Micromirror Device Based Microstereolithography for Micro Structures of Transparent Photopolymer and Nanocomposites

This paper describes a Digital Micromirror Device (DMD) based ultraviolet (UV) microstereolithography (µ-SL) system developed for rapid prototyping and manufacturing of micro 3D structures. Characterization experiments show that the developed the DMD-based imaging system irradiates an entire photopolymer layer at once, providing reasonable curing speed and good resolution at a low cost. 2D and 3D micro parts were fabricated. High frequency ultrasonic vibration (above 20 kHz) was experimented and verified that it can be used to significantly decrease the leveling time of viscous photopolymer. Furthermore, micro parts were also fabricated in nanocomposites, which were obtained by ultrasonic mixing of the transparent photopolymer and nano-sized ceramic particles. High quality micro models fabricated by this novel process could be used for micro scale investment casting, tooling, devices, and medical applications.Mechanical Engineerin

Effect of the Inhomogeneity of Ice Crystals on Retrieving Ice Cloud Optical Thickness and Effective Particle Size

Spherical or spheroidal air bubbles are generally trapped in the formation of rapidly growing ice crystals. In this study the single-scattering properties of inhomogeneous ice crystals containing air bubbles are investigated. Specifically, a computational model based on an improved geometric-optics method (IGOM) has been developed to simulate the scattering of light by randomly oriented hexagonal ice crystals containing spherical or spheroidal air bubbles. A combination of the ray-tracing technique and the Monte Carlo method is used. The effect of the air bubbles within ice crystals is to smooth the phase functions, diminish the 22deg and 46deg halo peaks, and substantially reduce the backscatter relative to bubble-free particles. These features vary with the number, sizes, locations and shapes of the air bubbles within ice crystals. Moreover, the asymmetry factors of inhomogeneous ice crystals decrease as the volume of air bubbles increases. Cloud reflectance lookup tables were generated at wavelengths 0.65 m and 2.13 m with different air-bubble conditions to examine the impact of the bubbles on retrieving ice cloud optical thickness and effective particle size. The reflectances simulated for inhomogeneous ice crystals are slightly larger than those computed for homogenous ice crystals at a wavelength of 0.65 microns. Thus, the retrieved cloud optical thicknesses are reduced by employing inhomogeneous ice cloud models. At a wavelength of 2.13 microns, including air bubbles in ice cloud models may also increase the reflectance. This effect implies that the retrieved effective particle sizes for inhomogeneous ice crystals are larger than those retrieved for homogeneous ice crystals, particularly, in the case of large air bubbles

Optical Properties of Ice Particles in Young Contrails

The single-scattering properties of four types of ice crystals (pure ice crystals, ice crystals with an internal mixture of ice and black carbon, ice crystals coated with black carbon, and soot coated with ice) in young contrails are investigated at wavelengths 0.65 and 2.13 micrometers using Mie codes from coated spheres. The four types of ice crystals have distinct differences in their single-scattering properties because of the embedded black carbon. The bulk scattering properties of young contrails consisting of the four types of ice crystals are further investigated by averaging their single-scattering properties over a typical ice particle size distribution found in young contrails. The effect of the radiative properties of the four types of ice particles on the Stokes parameters I, Q, U, and V is also investigated for different viewing zenith angles and relative azimuth angles with a solar zenith angle of 30 degrees using a vector radiative transfer model based on the adding-doubling technique. The Stokes parameters at a wavelength of 0.65 micrometers show pronounced differences for the four types of ice crystals. Those at a wavelength of 2.13 micrometers show similar variations with the viewing zenith angle and relative azimuth angle, but their values are noticeably different

Synergetic treatment of dye contaminated wastewater using microparticles functionalized with carbon nanotubes/titanium dioxide nanocomposites

This journal is © The Royal Society of Chemistry. The highly efficient treatment of azo dye contaminated wastewater from the textile industry is an important but challenging problem. Herein, polydimethylsiloxane (PDMS) microparticles, incorporating multiple-walled carbon nanotubes/titanium dioxide (MWCNTs/TiO2) nanocomposites, were successfully synthesized to treat wastewater containing Rhodamine B (RhB) dyes in a synergetic approach, by combining sorption and photocatalytic degradation. The surfactant wrapping sol-gel method was applied to synthesize MWCNTs/TiO2 nanocomposites with TiO2 nanoparticles evenly distributed on the surface of the MWCNTs. The PDMS microparticles were fabricated with an oil-in-water (O/W) single emulsion template, using needle-based microfluidic devices. MWCNTs/TiO2 nanocomposites (at a weight ratio of 1%, and 2%, respectively) were mixed with the PDMS precursor as the dispersed phase, and an aqueous solution of polyvinyl alcohol (PVA) was used as the continuous phase. Highly monodispersed microparticles, with average diameters of 692.7 μm (Coefficient of Variation, CV = 0.74%) and 678.3 μm (CV = 1.04%), were formed at an applied flow rate of the dispersed and continuous phase of 30 and 200 μL min-1, respectively. The fabricated hybrid microparticles were employed for the treatment of RhB, involving a dark equilibrium for 5 hours and UV irradiation for 3 hours. The experimental conditions of applied PDMS type, mass loading amount, treatment duration, photodegradation kinetics, initial concentration of pollutants and environmental pH values were investigated in this work. The PDMS microparticles with 2 wt% MWCNTs/TiO2 nanocomposites can exhibit a removal efficiency of 85%. Remarkably, an efficiency of 70% can be retained after the microparticles have been recycled and reused for 3 cycles. The PDMS-MWCNTs/TiO2 microparticles possess a superior performance over conventional treatment approaches for dye contaminated wastewater, especially in recyclability and the prevention of secondary pollution. This work provides a feasible and eco-friendly route for developing an efficient and low-cost microfluidic method for treating complicated water environmental systems

Assessment of Evolving TRMM-Based Real-Time Precipitation Estimation Methods and Their Impacts on Hydrologic Prediction in a High-Latitude Basin

The real-time availability of satellite-derived precipitation estimates provides hydrologists an opportunity to improve current hydrologic prediction capability for medium to large river basins. Due to the availability of new satellite data and upgrades to the precipitation algorithms, the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis real-time estimates (TMPA-RT) have been undergoing several important revisions over the past ten years. In this study, the changes of the relative accuracy and hydrologic potential of TMPA-RT estimates over its three major evolving periods were evaluated and inter-compared at daily, monthly and seasonal scales in the high-latitude Laohahe basin in China. Assessment results show that the performance of TMPA-RT in terms of precipitation estimation and streamflow simulation was significantly improved after 3 February 2005. Overestimation during winter months was noteworthy and consistent, which is suggested to be a consequence from interference of snow cover to the passive microwave retrievals. Rainfall estimated by the new version 6 of TMPA-RT starting from 1 October 2008 to present has higher correlations with independent gauge observations and tends to perform better in detecting rain compared to the prior periods, although it suffers larger mean error and relative bias. After a simple bias correction, this latest dataset of TMPA-RT exhibited the best capability in capturing hydrologic response among the three tested periods. In summary, this study demonstrated that there is an increasing potential in the use of TMPA-RT in hydrologic streamflow simulations over its three algorithm upgrade periods, but still with significant challenges during the winter snowing events

First Evaluation of the Climatological Calibration Algorithm in the Real-time TMPA Precipitation Estimates over Two Basins at High and Low Latitudes

The TRMM Multi-satellite Precipitation Analysis (TMPA) system underwent a crucial upgrade in early 2009 to include a climatological calibration algorithm (CCA) to its realtime product 3B42RT, and this algorithm will continue to be applied in the future Global Precipitation Measurement era constellation precipitation products. In this study, efforts are focused on the comparison and validation of the Version 6 3B42RT estimates before and after the climatological calibration is applied. The evaluation is accomplished using independent rain gauge networks located within the high-latitude Laohahe basin and the low-latitude Mishui basin, both in China. The analyses indicate the CCA can effectively reduce the systematic errors over the low-latitude Mishui basin but misrepresent the intensity distribution pattern of medium-high rain rates. This behavior could adversely affect TMPA's hydrological applications, especially for extreme events (e.g., floods and landslides). Results also show that the CCA tends to perform slightly worse, in particular, during summer and winter, over the high-latitude Laohahe basin. This is possibly due to the simplified calibration-processing scheme in the CCA that directly applies the climatological calibrators developed within 40 degrees latitude to the latitude belts of 40 degrees N-50 degrees N. Caution should therefore be exercised when using the calibrated 3B42RT for heavy rainfall-related flood forecasting (or landslide warning) over high-latitude regions, as the employment of the smooth-fill scheme in the CCA bias correction could homogenize the varying rainstorm characteristics. Finally, this study highlights that accurate detection and estimation of snow at high latitudes is still a challenging task for the future development of satellite precipitation retrievals

Structural Analysis of Alkaline β-Mannanase from Alkaliphilic Bacillus sp. N16-5: Implications for Adaptation to Alkaline Conditions

Significant progress has been made in isolating novel alkaline β-mannanases, however, there is a paucity of information concerning the structural basis for alkaline tolerance displayed by these β-mannanases. We report the catalytic domain structure of an industrially important β-mannanase from the alkaliphilic Bacillus sp. N16-5 (BSP165 MAN) at a resolution of 1.6 Å. This enzyme, classified into subfamily 8 in glycosyl hydrolase family 5 (GH5), has a pH optimum of enzymatic activity at pH 9.5 and folds into a classic (β/α)8-barrel. In order to gain insight into molecular features for alkaline adaptation, we compared BSP165 MAN with previously reported GH5 β-mannanases. It was revealed that BSP165 MAN and other subfamily 8 β-mannanases have significantly increased hydrophobic and Arg residues content and decreased polar residues, comparing to β-mannanases of subfamily 7 or 10 in GH5 which display optimum activities at lower pH. Further, extensive structural comparisons show alkaline β-mannanases possess a set of distinctive features. Position and length of some helices, strands and loops of the TIM barrel structures are changed, which contributes, to a certain degree, to the distinctly different shaped (β/α)8-barrels, thus affecting the catalytic environment of these enzymes. The number of negatively charged residues is increased on the molecular surface, and fewer polar residues are exposed to the solvent. Two amino acid substitutions in the vicinity of the acid/base catalyst were proposed to be possibly responsible for the variation in pH optimum of these homologous enzymes in subfamily 8 of GH5, identified by sequence homology analysis and pKa calculations of the active site residues. Mutational analysis has proved that Gln91 and Glu226 are important for BSP165 MAN to function at high pH. These findings are proposed to be possible factors implicated in the alkaline adaptation of GH5 β-mannanases and will help to further understanding of alkaline adaptation mechanism

Microfluidic formation of highly monodispersed multiple cored droplets using needle-based system in parallel mode

© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Scale-up in droplet microfluidics achieved by increasing the number of devices running in parallel or increasing the droplet makers in the same device can compromise the narrow droplet-size distribution, or requires high fabrication cost, when glass- or polymer-based microdevices are used. This paper reports a novel way using parallelization of needle-based microfluidic systems to form highly monodispersed droplets with enhanced production rates yet in cost-effective way, even when forming higher order emulsions with complex inner structure. Parallelization of multiple needle-based devices could be realized by applying commercially available two-way connecters and 3D-printed four-way connectors. The production rates of droplets could be enhanced around fourfold (over 660 droplets/min) to eightfold (over 1300 droplets/min) by two-way connecters and four-way connectors, respectively, for the production of the same kind of droplets than a single droplet maker (160 droplets/min). Additionally, parallelization of four-needle sets with each needle specification ranging from 34G to 20G allows for simultaneous generation of four groups of PDMS microdroplets with each group having distinct size yet high monodispersity (CV < 3%). Up to six cores can be encapsulated in double emulsion using two parallelly connected devices via tuning the capillary number of middle phase in a range of 1.31 × 10−4 to 4.64 × 10−4. This study leads to enhanced production yields of droplets and enables the formation of groups of droplets simultaneously to meet extensive needs of biomedical and environmental applications, such as microcapsules with variable dosages for drug delivery or drug screening, or microcapsules with wide range of absorbent loadings for water treatment

Histone deacetylase activity mediates acquired resistance towards structurally diverse HSP90 inhibitors

Heat shock protein 90 (HSP90) regulates multiple signalling pathways critical for tumour growth. As such, HSP90 inhibitors have been shown to act as effective anticancer agents in preclinical studies but, for a number of reasons, the same effect has not been observed in the clinical trials to date. One potential reason for this may be the presence of de novo or acquired resistance within the tumours. To investigate mechanisms of resistance, we generated resistant cell lines through gradual dose escalation of the HSP90 inhibitor 17‐allylamino‐17‐demethoxygeldanamycin (17‐AAG). The resultant resistant cell lines maintained their respective levels of resistance (7–240×) in the absence of 17‐AAG and were also cross‐resistant with other benzoquinone ansamycin HSP90 inhibitors. Expression of members of the histone deacetylase family (HDAC 1, 5, 6) was altered in the resistant cells. To determine whether HDAC activity contributed to resistance, pan‐HDAC inhibitors (TSA and LBH589) and the class II HDAC‐specific inhibitor SNDX275 were found to resensitize resistant cells towards 17‐AAG and 17‐dimethylaminoethylamino‐17‐demethoxygeldanamycin. Most significantly, resistant cells were also identified as cross‐resistant towards structurally distinct HSP90 inhibitors such as radicicol and the second‐generation HSP90 inhibitors CCT018159, VER50589 and AUY922. HDAC inhibition also resensitized resistant cells towards these classes of HSP90 inhibitors. In conclusion, we report that prolonged 17‐AAG treatment results in acquired resistance of cancer cells towards not just 17‐AAG but also to a spectrum of structurally distinct HSP90 inhibitors. This acquired resistance can be inhibited using clinically relevant HDAC inhibitors. This work supports the potential benefit of using HSP90 and HDAC inhibitors in combination within the clinical setting