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Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and is mainly treated with chemotherapy-based combination therapy. In recent years, the increasing development of single-cell sequencing (SCS) has become one of the most promising technologies in the field of biotechnology. The study of the heterogeneity of TNBC tumor cells using SCS will expand our current knowledge of metastasis, drug resistance mechanisms, mutations, and cloning in these cells; this will further guide clinical chemotherapy, targeted therapy, and immunotherapy. Relevant studies shown that SCS exactly plays an important role in clinical diagnosis and treatment. To highlight the role of SCS in the study of TNBC, we elaborate on the progress of research and the applications of SCS in TNBC.

A new variable exponential discrete-time sliding mode control (DSMC) reaching law is proposed to suppress the chattering phenomenon and accelerate the reaching speed for the switching function. The variable exponential reaching law consists of two-phase different exponential term. The main effect of the first phase exponential reaching law is to reduce reaching steps. The second phase exponential reaching law can decrease the magnitude of quasi-sliding-mode domain (QSMD). Otherwise, the disturbance term is restrained by second order difference function which can also significantly diminish the range of QSMD. The reaching steps of the reaching law to converge to QSMD are derived from this new reaching law. Meanwhile, the dynamic analysis of the DSMC system based on new reaching law is presented. Finally, the mathematical simulations are conducted to preliminarily verify the results of theoretical analysis.

Silicon carbide (SiC) microchannels are attractive for their wide applications in microsensors, MOS devices, UV photodiodes, microcatalytic reactors, and microchannel heat exchangers in harsh environments. However, the machining of SiC microchannels poses many challenges because of the difficulty and cost involved in the material removal process due to the high hardness and brittleness of SiC ceramic. In the present study, we developed a thin diamond wheel grinding process to fabricate SiC microchannels in a conventional vertical milling machine. Microchannels with trapezoidal shapes were successfully processed in SiC substrates by thin diamond wheels. The formation, geometric dimensions, and surface quality of SiC microchannels were studied together with the analysis of material removal mechanism. The effects of grinding processing parameters, i.e., wheel speed, feed speed, grinding depth, and grinding tool parameters including grit size and thickness of diamond grinding wheel, on the geometric dimension and surface morphology were comprehensively explored. The top width of microchannels first increased and then decreased with the increase in wheel speed, whereas a reverse tendency was observed with increasing grinding depth, feed speed, and grit size. The surface roughness decreased continuously with increasing wheel speed, but it tended to increase with the increase in feed speed generally. The variations in geometric dimensions and surface roughness of SiC microchannels can be related to the crack or fracture propagations and material removal mechanism during the thin diamond wheel grinding process. Besides, the influential significance of the above processing and grinding tool parameters were also evaluated by analysis of variance (ANOVA).

XYZ-precision positioning stages are of great significance in micro/nanoscale manipulation applications. This paper presents a novel parallel 3-degree-of-freedom (3-DOF) XYZ precision positioning stage with compact structure. Compared with the existing parallel triaxial positioning stages, the proposed stage features more compact size in the height. A newly developed Z-shaped flexure hinge based mechanism is introduced in the design of stage to generate decoupled motions in both z-axis and y-axis based on the bending deformation of the beams and the differential moving principle, respectively. The input stiffness of the positioning stage is calculated by resorting to matrix-based method, and validated by finite-element analysis. The simulation results are shown to be almost consistent with the results of the derived analytical model with negligible errors. Moreover, the reachable workspace is determined and the maximum stress is also obtained by loading the assumed maximum input displacement on the platform. The preliminary results pave the way for promising applications of the proposed stage in the future.

Microchannel cooling provides an efficient thermal management method for regenerative cooling systems of advanced areo engines. In this study, a prototype combustor with microchannel cooling passages in the walls is experimentally developed. Combustion tests are systematically conducted in a range of air inlet temperature (30–70 °C), equivalence ratios (0.8–1.2) and flow rates of coolant (100–300 kg/m2s) using liquid fuel of ethanol and air mixture. Comparative studies against a combustor without microchannel cooling are also conducted to assess the feasibility of performance enhancement. The introduction of microchannel cooling was found to induce an 80% reduction of the maximum wall temperatures, and a larger than 90% reduction of the streamline wall temperature gradient. The combustor with microchannel cooling also induced a 1%–3.2% increase of the combustion efficiency and a 0.3%–1.7% reduction of the CO emissions in general compared to that without microchannel cooling. The wall temperatures and combustion efficiency of the combustor with microchannel cooling were found to increase with the increase in air inlet temperatures from 30 to 70 °C, whereas they tended to decrease when the equivalence ratio increased from 0.8 to 1.2. Nevertheless, the flow rate of coolant played a negligible role on the combustion performance of the combustor with microchannel cooling.

To meet the demand of designing piezoelectric actuators with long working stroke and high resolution, a new parasitic motion principle (PMP) linear actuator based on the symmetrical Z-shaped compliant mechanism was proposed in this paper. The mechanism design and the operation principle of the proposed linear actuator were elaborated. The theoretical model of the symmetrical Z shaped compliant mechanism deformation was established, and was verified by the simulation analysis. Experimental studies were conducted on a manufactured prototype to investigate the performances of the proposed linear actuator. The results indicate that a linear actuator with bi-directional motion can be achieved, which has a resolution of 106 nm in the forward direction and 84 nm in the reverse direction. Under the locking force of 0.8 N, the maximum speed of 270 µm s−1 was reached, when the amplitude and the frequency of the driving voltage were set to 60 V and 650 Hz. It is also noted that the proposed linear actuator can work with a loading capacity of 25 g. This study has provided an alternative way for the development of a PMP linear actuator with bi-directional motion.

Trifluoroacetic acid (TFA) is a very persistent, very mobile substance (vPvM) with potential toxicity, and causes increasing environmental concerns worldwide. Conventional wastewater treatment strategies are inefficient for selective TFA removal in the presence of inorganic anions. Here we show that surface defunctionalized activated carbon felt (DeACF) carrying anion exchange sites exhibits an outstanding adsorption efficiency towards TFA thanks to introduced electrostatic attraction and enhanced interactions between hydrophobic carbon surface and CF

Silicon carbide (SiC) microchannels show their promising merits in the applications of microchannel heat sink cooling systems, microsensor MOS devices, and UV photodiodes. The fabrication of SiC microchannels is critical for their wide applications. In this study, a laser micromilling method is utilized to process SiC microchannels. A series of SiC microchannels are fabricated using a pulsed fiber laser. Based on the SEM observations and 3D confocal microscope measurements, the formation of microchannels is analyzed. The effects of laser processing parameters, such as laser output power, scanning speed, and scanning times as well as the predetermined microchannel width, on the geometric dimension and surface morphology are systematically assessed. The common recast layer deposited around the laser-scanned areas in the laser micromilling of metallic structures was not found for the SiC microchannels. A transition between triangular and trapezoidal shapes occurred for the laser-micromilled microchannels depending on the processing parameters and predetermined width. The microchannel depth increased monotonically with the laser output power and laser scanning time but decreased with increasing scanning speed. On the contrary, the bottom width of microchannels presented an inverse trend. The surface roughness was dependent on the laser scanning speed, scanning time, as well as predetermined width.

A new high precision ultra-compact decoupled XYZ θ motion stage based on flexure hinges is designed and analyzed. The stage mainly consists of three components including serial–parallel dual-stage amplifier, Z-shape motion steering mechanism and motion decoupled mechanism. Compared with the existing stages, the proposed high precision motion stage has many advantages such as extremely compact structure, large output decoupling motion and XYZ θ four axes output displacement. The function of serial–parallel dual-stage amplifier is to amplify the travel range of nano positioning piezo actuator (PZT) by connecting two parallel bridge type mechanism. The Z-shape mechanism can change the direction of motion transmission to make the stage more compact and form movement in XYZ θ four directions. The decouple mechanism can reduce the implicative movement of different piezo actuators. Then, kinetostatic analysis of this new XYZ θ stage is conducted to analyze the stage. Finally, the finite-element analysis (FEA) and prototype experiments are implemented to verify the design objectives.

This study developed a type of composite porous vapor chambers (CPVCs) with uniform radial grooves in the evaporator, providing radial multi-artery channels for the fast liquid backflow with low hydraulic resistance. The separated porous powder parts between adjacent radial grooves were in intimate contact with the condenser porous wick to strengthen the structures of vapor chambers. These CPVCs can be fabricated without solid supporting columns with low cost. A series of CPVCs were fabricated by sintering two types of copper powder with spherical and irregular shapes, and five different particle sizes of

Porous copper surfaces show their great merits in the applications of chemical reaction, sound absorption and heat transfer. In this study, a laser micromilling method is proposed to fabricate porous surfaces with homogeneous micro-holes and cavities of the size about 1–15 μm on pure copper plates in a one-step process. The laser micromilling was performed by a pulsed fiber laser via the multiple–pass reciprocating scanning strategy. Based on the measurement of scanning electron microscope (SEM) and 3D laser scanning confocal microscope, the formation of surface structures was investigated together with the laser ablation mechanisms. The effects of laser processing parameters, i.e., laser fluence, scanning speed, number of scanning cycles and scanning interval, on the formation and surface morphology of porous surfaces were systematically assessed. Furthermore, the wettability of the porous copper surfaces was also evaluated by measuring the static contact angle of water. The results showed that the laser fluence played the most significant role on the formation of porous copper surfaces. The average depth and surface roughness of porous copper surfaces increased with increasing the laser fluence and number of scanning cycles while decreased with the increase in scanning interval. The scanning speed played little influence on the formation of porous copper surfaces. These results can be closely related to the variation of energy density and re-melting process during the laser micromilling process. Moreover, all the copper porous surfaces were found to be hydrophobic. The contact angle of porous copper surfaces was significantly dependent on laser fluence, but weakly affected by the scanning speed and number of scanning cycles.

Interconnected reentrant microchannels (IRM) were developed to explore the feasibility of flow boiling enhancement and applications in high heat flux dissipations. They consisted of 14 parallel semi-closed Ω-shaped microchannels and 8 transverse ones each with a hydraulic diameter of 781 μm. These microchannels were fabricated in copper by wire electrical discharge machining process. One-to-one comparative studies between the IRM and parallel reentrant microchannels (PRM) with the same reentrant configurations were conduced in flow boiling experiments. Two coolants tests of deionized water and ethanol were performed at inlet subcoolings of 10 and 40 °C and mass fluxes of 125–300 kg/m2 s. Significant flow boiling heat transfer augmentation, i.e., an enhancement ratio of 40–280% in water tests, and 28–61% in ethanol tests, were achieved for the interconnected reentrant microchannels. This can be attributed to that the addition of transverse microchannels provided more flow passages, diminished the confinement effects for vapor flow and introduced intense disruption and re-initializations of the liquid thin film. Moreover, the two-phase flow instabilities were mitigated considerably, and the stream-wise temperature uniformity was also improved for the IRM. All these features of interconnected reentrant microchannels indicate that they could be a promising option for the application in high heat flux dissipations.

Pool boiling heat transfer in a porous coating with reentrant channels was experimentally studied together with the comparison of a solid sample with the same reentrant configurations. The porous coating was totally constructed by sintered copper powder, and featured 12 parallel Ω-shaped reentrant channels. Pool boiling tests were conducted using two coolants (deionized water and ethanol) in different liquid subcoolings at atmospheric pressure. The boiling heat transfer performance was systematically examined and compared together with the high-speed visualization observations. Experimental results revealed that the porous coating introduced a great decrease in wall superheat at the onset of nucleate boiling (ONB), and a significant enhancement in boiling heat transfer at low to moderate heat fluxes compared to its solid counterpart. The porous coating promoted the boiling nucleation significantly by increasing the nucleation sites and hindering early condensation of vapor embryos. Liquid replenishment through the horizontal reentrant channels and efficient surface rewetting were maintained even at high heat fluxes. Moreover, the effects of liquid subcooling on the boiling heat transfer performance of both porous and solid sample were also assessed.

Microchannel heat sinks have been widely utilized in micro fuel cells, micro medical equipment, high power cooling systems and so on. Fabrication of porous structures on the micorchannel surfaces provides an efficient method to enhance heat transfer, as it enlarges the heat transfer areas considerably. In the study, a laser micro-milling method is used to fabricate porous structures with micro-holes and micro-cavities on the microchannel wall surfaces. Three different shapes of micro-channels, i.e., U-shaped, V-shaped and rectangular ones, were utilized to process the porous structures, which demonstrated that porous structures can be formed on all the microchannels. Besides, the effect of laser fluence on the formation of porous structures on the rectangular microchannels was also explored. It was found that laser fluence played a vital role on the formation of porous structures. With the increase in laser fluence, the cross-sectional shape of the rectangular microchannels changed from rectangular to trapezoidal one. The channel depth and surface roughness of porous copper surfaces increased, whereas the channel bottom width decreased with increasing the laser fluence.

A novel nanostructured leady oxides comprising porous carbon skeleton has been synthesized by thermal decomposition of lead citrate precursor, recovered from spent lead-acid battery paste. The influences of O 2 percentage in the calcination atmosphere (O 2 /N 2 mixture) and the temperature on leady oxide product characteristics are studied by chemical analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The major crystalline phases of the products are identified as lead oxides, metallic Pb, and carbon. Porous carbon is observed as skeletons within the leady oxide (PbO containing some Pb metal) particles. Mass percentage of Pb metal in the leady oxide increases with increasing the proportion of oxygen in the calcination atmosphere. However, the amount of carbon decreases from approximately 8.0 to 0.3 wt%, and the porous carbon skeleton structure is gradually damaged with oxygen concentration increasing. A model about the thermal decomposition of lead citrate precursor is firstly proposed to elucidate these observations. The nanostructured leady oxides combined with porous carbon can be directly used as precursor of active materials in a new lead acid battery.

A new strategy was proposed to estimate the initial rates of reactions catalyzed by Michaelis–Menten enzymes via integrating the classical initial rate method for low activities with an improved integrated method for high activities. Between these two individual methods, this integration strategy required: (a) the consistent linear response slopes, acquired with an optimized preset substrate concentration (PSC) to derive the initial rates from the maximal reaction rates estimated by the improved integrated method; (b) an overlapped region of the initial rates measurable with consistent results, realized with an optimized reaction duration to record reaction curves for analyses by the improved integrated method; (c) a switch cutoff, preset as the instantaneous substrate concentration slightly above that after a given lag time when the enzyme activity was just below the upper limit for the linear response of the classical initial rates. By simulation with uricases at a given initial substrate concentration ( S 0 ), the optimized PSC was 93% S 0 , the optimized reaction duration at S 0 from 0.35-fold to 11.0-fold Michaelis–Menten constant ( K m ) was within 6.0 min and the switch cutoff was available at the given S 0 after 30-s lag time, all of which were combined to produce 300-fold linear ranges. By experimentation with one uricase of K m at 6.6 μM and the other uricase of K m at 220 μM under optimized conditions, this integration strategy with S 0 at 75 μM produced 100-fold linear ranges. Thus, this integration strategy exhibited much expanded linear ranges and practical efficiency over wide ratios between S 0 and K m .

Two-phase boiling in advanced microchannel heat sinks offers an efficient and attractive solution for heat dissipation of high-heat-flux devices. In this study, a type of reentrant copper microchannels was developed for heat sink cooling systems. It consisted of 14 parallel Ω-shaped reentrant copper microchannels with a hydraulic diameter of 781μm. Two-phase pressure drop characteristics were comprehensively accessed via flow boiling tests. Both deionized water and ethanol tests were conducted at inlet subcooling of 10°C and 40°C, mass fluxes of 125–300kg/m2·s, and a wide range of heat fluxes and vapor qualities. The effects of heat flux, mass flux, inlet subcoolings and coolants on the two-phase pressure drop were systematically explored. The results show that the two-phase pressure drop of reentrant copper microchannels generally increased with increasing heat fluxes and vapor qualities. The role of mass flux and inlet temperatures was dependent on the test coolant. The water tests presented smaller pressure drop than the ethanol ones. These results provide critical experimental information for the development of microchannel heat sink cooling systems, and are of considerable practical relevance.Copyright © 2016 by ASME

A spectrometric method was investigated to measure the activities of recombinant human cyclic nucleotide phosphodiesterase 4 (PDE4), based on the use of malachite green (MLG) to quantify phosphate released from adenosine-5'-monophosphate (AMP) by the action of calf intestinal alkaline phosphatase (CIAP). Glycerol at 2% stabilized the complex between MLG and phosphomolybdate, whose absorbance at 630nm was proportional to phosphate concentrations with resistance to common substances in PDE4 reaction mixtures except papaverine. CIAP had the Michaelis-Menten constant (K(m)) of (12.0+/-2.1)microM (n=3) for AMP at pH 7.4, and was resistant to EDTA below 0.20mM. By the coupled end-point assay at 30.0UL(-1) CIAP with reaction durations within 30min, the rates to release phosphate in PDE4 reaction mixtures containing 10.0mM MgCl(2) and 0.10mM EDTA linearly responded to the amounts of PDE4 over wide ranges. Meanwhile, K(m) of PDE4 was (8.8+/-0.2)microM (n=2), zinc ion inhibited PDE4 and rolipram had the inhibition constant about 10nM. These results supported that by the coupled end-point assay, this method was promising to screen of PDE inhibitors that had no interference with the MLG assay of phosphate.