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Helicobacter pylori neutrophil-activating protein (HP-NAP)-induced production of reactive oxygen species (ROS) by neutrophils and monocytes is regulated by pertussis toxin (PTX)-sensitive G proteins, whereas HP-NAP-induced cytokine secretion by monocytes is mediated by Toll-like receptor 2 (TLR2). However, it is unclear whether TLR2 participates in HP-NAP-induced cytokine secretion by neutrophils. Here, all-trans retinoic acid (ATRA)-induced differentiated HL-60 cells were first employed as a neutrophil model to investigate the molecular mechanisms underlying neutrophil responses to HP-NAP. HP-NAP-induced ROS production in ATRA-induced differentiated HL-60 cells is mediated by the PTX-sensitive heterotrimeric G protein-dependent activation of extracellular signal-regulated kinase 1/2 and p38-mitogen-activated protein kinase, which is consistent with the findings reported for human neutrophils. Next, whether TLR2 participated in HP-NAP-induced secretion of interleukin-8 (IL-8) was investigated in neutrophils and ATRA-induced differentiated HL-60 cells. In both cells, TLR2 participated in HP-NAP-induced IL-8 secretion but not HP-NAP-induced ROS production. Interestingly, PTX-sensitive G proteins also contributed to the HP-NAP-induced secretion of IL-8 from neutrophils and the differentiated HL-60 cells. Our ELISA-based binding assay further revealed the competitive binding of Pam3CSK4, a TLR2 agonist, and HP-NAP to TLR2, which suggests the presence of specific and direct interactions between HP-NAP and TLR2. Thus, HP-NAP directly interacts with and activates TLR2 to induce IL-8 secretion in neutrophils and ATRA-induced differentiated HL-60 cells.

Virus-like particle (VLP) technology is an alternative platform for developing vaccines to combat seasonal and pandemic influenza. Influenza VLPs are non-infectious nanoparticles that can elicit effective vaccine immunogenicity in hosts. B-cell-activating factor (BAFF, or BLyS) and a proliferation-inducing ligand (APRIL) are members of the tumor necrosis factor (TNF) superfamily of cytokines. Both BAFF and APRIL are homotrimers that interact with homotrimeric receptors. Here, we report a method of the production of influenza VLPs by molecular incorporation with BAFF or APRIL homotrimers to interact with their receptors. We engineered the VLPs by direct fusion of BAFF or APRIL to the transmembrane anchored domain of the hemagglutinin (HA) gene. We also describe procedures for the production of BAFF-VLPs containing H5H7 and H1H5H7 for multi-subtype vaccine development.

BACKGROUND The coronavirus disease (COVID-19) pandemic is an important health crisis worldwide. Several strategies were implemented to combat COVID-19, including wearing masks, hand hygiene, and social distancing. The impact of these strategies on COVID-19 and other viral infections remains largely unclear. OBJECTIVE We aim to investigate the impact of implemented infectious control strategies on the incidences of influenza, enterovirus infection, and all-cause pneumonia during the COVID-19 pandemic. METHODS We utilized the electronic database of the Taiwan National Infectious Disease Statistics System and extracted incidences of COVID-19, influenza virus, enterovirus, and all-cause pneumonia. We compared the incidences of these diseases from week 45 of 2016 to week 21 of 2020 and performed linear regression analyses. RESULTS The first case of COVID-19 in Taiwan was reported in late January 2020 (week 4). Infectious control strategies have been promoted since late January. The influenza virus usually peaks in winter and decreases around week 14. However, a significant decrease in influenza was observed after week 6 of 2020. Regression analyses produced the following results: 2017, R2=0.037; 2018, R2=0.021; 2019, R2=0.046; and 2020, R2=0.599. A dramatic decrease in all-cause pneumonia was also reported (R2 values for 2017-2020 were 0.435, 0.098, 0.352, and 0.82, respectively). Enterovirus had increased by week 18 in 2017-2019, but this was not observed in 2020. CONCLUSIONS Using this national epidemiological database, we found a significant decrease in cases of influenza, enterovirus, and all-cause pneumonia during the COVID-19 pandemic. Wearing masks, hand hygiene, and social distancing may contribute not only to the prevention of COVID-19 but also to the decline of other respiratory infectious diseases. Further studies are warranted to elucidate the causal relationship.

Background Human gut microbiome has an essential role in human health and disease. Although the major dominant microbiota within individuals have been reported, the change of gut microbiome caused by external factors, such as antibiotic use and bowel cleansing, remains unclear. We conducted this study to investigate the change of gut microbiome in overweight male adults after bowel preparation, where none of the participants had been diagnosed with any systemic diseases. Methods A total of 20 overweight, male Taiwanese adults were recruited, and all participants were omnivorous. The participants provided fecal samples and blood samples at three time points: prior to bowel preparation, 7 days after colonoscopy, and 28 days after colonoscopy. The microbiota composition in fecal samples was analyzed using 16S ribosome RNA gene amplicon sequencing. Results Our results demonstrated that the relative abundance of the most dominant bacteria hardly changed from prior to bowel preparation to 28 days after colonoscopy. Using the ratio of Prevotella to the sum of Prevotella and Bacteroides in the fecal samples at baseline, the participants were separated into two groups. The fecal samples of the Type 1 group was Bacteroides-dominant, and that of the Type 2 group was Prevotella-dominant with a noticeable presence Bacteroides. Bulleidia appears more in the Type 1 fecal samples, while Akkermensia appears more in the Type 2 fecal samples. Of each type, the gut microbial diversity differed slightly among the three collection times. Additionally, the Type 2 fecal microbiota was temporarily susceptible to bowel cleansing. Predictive functional analysis of microbial community reveals that their activities for the mineral absorption metabolism and arachidonic acid metabolism differed significantly between the two types. Depending on their fecal type, the variance of triglycerides and C-reactive protein also differed between the two types of participants. Conclusions Depending upon the fecal type, the microbial diversity and the predictive functional modules of microbial community differed significantly after bowel preparation. In addition, blood biochemical markers presented somewhat associated with fecal type. Therefore, our results might provide some insights as to how knowledge of the microbial community could be used to promote health through personalized clinical treatment. Electronic supplementary material The online version of this article (10.1186/s12864-018-5285-6) contains supplementary material, which is available to authorized users.

Human infections with highly pathogenic avian influenza H5N1 viruses persist as a major global health concern. Vaccination remains the primary protective strategy against H5N1 and other novel avian influenza virus infections. We investigated the use of E. coli type IIb heat labile enterotoxin B subunit (LTIIb-B5) as a mucosal adjuvant for intranasal immunizations with recombinant HA proteins against H5N1 avian influenza viruses. Use of LTIIb-B5 adjuvant elicited more potent IgG, IgA, and neutralizing antibody titers in both sera and bronchoalveolar lavage fluids, thus increasing protection against lethal virus challenges. LTIIb-B5 mucosal adjuvanticity was found to trigger stronger Th17 cellular response in spleen lymphocytes and cervical lymph nodes. Studies of anti-IL-17A monoclonal antibody depletion and IL-17A knockout mice also suggest the contribution from Th17 cellular response to anti-H5N1 protective immunity. Our results indicate a link between improved protection against H5N1 live virus challenges and increased Th17 response due to the use of LTIIb-B5 mucosal adjuvant with HA subunit proteins.

Background The coronavirus disease (COVID-19) pandemic is an important health crisis worldwide. Several strategies were implemented to combat COVID-19, including wearing masks, hand hygiene, and social distancing. The impact of these strategies on COVID-19 and other viral infections remains largely unclear. Objective We aim to investigate the impact of implemented infectious control strategies on the incidences of influenza, enterovirus infection, and all-cause pneumonia during the COVID-19 pandemic. Methods We utilized the electronic database of the Taiwan National Infectious Disease Statistics System and extracted incidences of COVID-19, influenza virus, enterovirus, and all-cause pneumonia. We compared the incidences of these diseases from week 45 of 2016 to week 21 of 2020 and performed linear regression analyses. Results The first case of COVID-19 in Taiwan was reported in late January 2020 (week 4). Infectious control strategies have been promoted since late January. The influenza virus usually peaks in winter and decreases around week 14. However, a significant decrease in influenza was observed after week 6 of 2020. Regression analyses produced the following results: 2017, R2=0.037; 2018, R2=0.021; 2019, R2=0.046; and 2020, R2=0.599. A dramatic decrease in all-cause pneumonia was also reported (R2 values for 2017-2020 were 0.435, 0.098, 0.352, and 0.82, respectively). Enterovirus had increased by week 18 in 2017-2019, but this was not observed in 2020. Conclusions Using this national epidemiological database, we found a significant decrease in cases of influenza, enterovirus, and all-cause pneumonia during the COVID-19 pandemic. Wearing masks, hand hygiene, and social distancing may contribute not only to the prevention of COVID-19 but also to the decline of other respiratory infectious diseases. Further studies are warranted to elucidate the causal relationship.

Background Coronavirus disease 19 (COVID-19) is a global health threat with significant medical, economic, social and political implications. The optimal strategies for combating COVID-19 have not been fully determined and vary across countries. Methods By the end of February 2020 in Taiwan, 2,150 patients received diagnostic COVID-19 testing and 39 confirmed cases were detected. This is a relatively lower rate of infection compared to other Asian countries. In this article, we summarize the epidemiological characteristics of the 39 infected patients as well as public and hospital responses to COVID-19. Results Thirty-nine COVID-19 cases and one death have been confirmed in Taiwan. Seventeen of these patients were infected by family members or in hospital wards, emphasizing how COVID-19 is mostly spread by close contact. We examined how hospital have responded to COVID-19, including their implementation of patient route control, outdoor clinics, hospital visit restrictions and ward and staff modifications. We also studied the public’s use of face masks in response to COVID-19. These strategies may reduce the spread of COVID-19 in other countries. Conclusion The emergence and spread of COVID-19 is a threat to health worldwide. Taiwan has reported lower infected cases and its strategies may contribute to further disease prevention and control.

Human infections with H7N9 avian influenza A virus can result in severe diseases with high mortality. Developing an effective vaccine is urgently needed to prevent its pandemic potential. Vaccine delivery routes via mucosal surfaces are known to elicit mucosal immune responses such as secretory IgA antibodies in mucosal fluids, thus providing first-line protection at infection sites. PEG-b-PLACL (PELC) is a squalene-based oil-in-water emulsion adjuvant system that can enhance antigen penetration and uptake in nasal mucosal layers with enhanced mucin interactions. In this study, intranasal immunizations with recombinant H7 (rH7) proteins with a PELC/CpG adjuvant, as compared to the use of poly (I:C) or bacterial flagellin adjuvant, elicited higher titers of H7-specific IgG, IgA, hemagglutination inhibition, and neutralizing antibodies in sera, and increased numbers of H7-specific IgG- and IgA-antibody secreting cells in the spleen. Both PELC/CpG and poly (I:C) adjuvants at a dose as low as 5 &mu, g HA provided an 80% survival rate against live virus challenges, but a lower degree of PELC/CpG-induced Th17 responses was observed. Therefore, the mucosal delivery of rH7 proteins formulated in a PELC/CpG adjuvant can be used for H7N9 mucosal vaccine development.

Figure S7. Box plots of three inflammation cytokines. (PDF 377â kb)

Figure S2. Principal coordinate analysis (PCoA) based on the UniFrac distance values. (PDF 414â kb)

Figsure S3-S5. Correlation networks for 61 genera at three sample collection times. (PDF 2498â kb)

Table S10. Means of 26 predictive functional modules between the Type 1 and Type 2 fecal samples. (PDF 209â kb)

Figure S1. The differences of microbial diversity between the type 1 and 2 groups. (PDF 331â kb)

Figure S6. Percentage of the number of correlation change between SB and S7; SB and S28. (PDF 232â kb)

Table S3. Descriptive statistics of richness and Shannon diversity index. (PDF 184â kb)

Gastric cancer (GC) is the second most frequent cause of cancer-related deaths worldwide. MicroRNAs are single-stranded RNA molecules of 21–23 nucleotides that regulate target gene expression through specific base-pairing interactions between miRNA and untranslated regions of targeted mRNAs. In this study, we generated a multistep approach for the integrated analysis of miRNA and mRNA expression. First, both miRNA and mRNA expression profiling datasets in gastric cancer from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) identified 79 and 1042 differentially expressed miRNAs and mRNAs, respectively, in gastric cancer. Second, inverse correlations between miRNA and mRNA expression levels identified 3206 miRNA–mRNA pairs combined with 79 dysregulated miRNAs and their 774 target mRNAs predicted by three prediction tools, miRanda, PITA, and RNAhybrid. Additionally, miR-204, which was found to be down-regulated in gastric cancer, was ectopically over-expressed in the AGS gastric cancer cell line and all down-regulated targets were identified by RNA sequencing (RNA-seq) analysis. Over-expression of miR-204 reduced the gastric cancer cell proliferation and suppressed the expression of three targets which were validated by qRT-PCR and luciferase assays. For the first time, we identified that CKS1B, CXCL1, and GPRC5A are putative targets of miR-204 and elucidated that miR-204 acted as potential tumor suppressor and, therefore, are useful as a promising therapeutic target for gastric cancer.

Amoxicillin is a commonly prescribed drug for anti- bacterial infection. In this study, we are interested in the effect of the drug on the cellular DNA integrity. Amoxicillin was added to the human or hamster cells in culture, and the DNA lesions induced by the drug were assessed by a comet assay with nuclear extract incubation (Wang et al., 2005 Anal Biochem 337: 70–75). Amoxicillin at 5 mM rapidly induced DNA lesions in human AGS cells. The level of DNA lesions attained a maximum at about 1 h, and then declined steadily and reached almost the basal level at 6 h following the drug treatment. Similar induction pattern of DNA lesions was found with amoxicillin-related antibiotics such as ampicillin but not with the unrelated antibiotics such as kanamycin. For studying the repair kinetics, the cells were treated with amoxicillin for only 1 h and continued culture in the absence of the drug for a certain period of time before subsequent analysis. Repair of the amoxicillin-induced DNA lesions was essentially completed within 4 h. Such repair may not involve nucleotide excision repair (NER) pathway because the repair was completed with similar kinetics in both NER proficient Chinese hamster CHO-K1 cells and its isogenic NER deficient UV24 cells. Instead, the repair may involve base excision repair (BER) pathway because immunodepletion of OGG1/2, glycosylases involved in BER rendered the nuclear extract unable to excise DNA lesions induced by amoxicillin in the modified comet assay. Furthermore, amoxicillin induced intracellular reactive oxygen species (ROS) at the tempo similar to that of DNA lesions induction. Thus, we hypothesize that amoxicillin causes oxidative DNA damage in mammalian cells via ROS.

The success of neuronal implantable microsystems relies on the quality of the interface with neuronal cells. Depending on the application, specifically engineered surfaces may either prevent or enhance cell/tissue growth with an appropriate host response. The surface chemistry and topography have major effects on the cell adherence and the interaction between the tissue and devices. We report on a simple technique to precisely explant cortical neurons in a serum-free medium on 2D electrode arrays and investigated the pad size effect on neuron cell culture and immobilization. We produced gold patterns on glass substrates using microfabrication processes. 11-Amino-1-undecanethiol self-assembled monolayer was coated only on the gold surface. Cortical neurons were cultured on the arrays to examine the dependence of neuron growth and cells distribution on pad size. We found that the terminal functional groups of the highly oriented 11-amino-1-undecanethiol thin film are essential for generating cell-adhesive areas for the rat cortical neurons. A 50 microm x 50 microm SAM pad size was found to be suitable for single cortical neuron immobilization, while the larger pads provide excellent neuron coverage. This technology may enable precise and localized neuron stimulation and surveillance for both biological research and medical applications.

Background Helicobacter pylori neutrophil-activating protein (HP-NAP) is involved in H. pylori-induced gastric inflammation. Due to its immunogenic and immunomodulatory properties, HP-NAP has been used for developing vaccines against H. pylori infection and new drugs for cancer therapy. Results Here, we provide a simple process for high-yield production of HP-NAP by applying one-step negative chromatography to purify recombinant HP-NAP expressed in Escherichia coli (E. coli). In our E. coli expression system, recombinant HP-NAP constitutes nearly 70% of the total protein. Overexpressed recombinant HP-NAP is almost completely soluble upon cell lysis at pH 9.5. Under the optimal condition at pH 8.0, recombinant HP-NAP with purity higher than 95% can be obtained from E. coli by collecting the unbound fraction using diethylaminoethyl (DEAE) Sephadex resin in batch mode. The overall yield of HP-NAP from a 50-ml E. coli culture is ~19 mg. The purified HP-NAP folds into a multimer with a secondary structure of α-helix and is able to trigger the production of reactive oxygen species by neutrophils. Conclusions Purification of recombinant HP-NAP overexpressed in E. coli using DEAE Sephadex negative mode batch chromatography is an efficient method for high-yield production of highly pure HP-NAP in its native state. The purified HP-NAP is useful for various clinical applications including vaccine development, diagnosis, and new drug development.

We present a high-speed microfluidic cell sorter employing embedded heaters and nozzles to generate deflecting jets to change the movement of the cells. We simulated the transient flow fields to validate the concept and optimize the sorter design. The simulation demonstrates spatial switching windows corresponding to 1.1, 1.5, and 2.4 times the switching chamber length for push, pull, and combined operation modes, respectively. A single-jet sorter with one actuator and one nozzle is also demonstrated for binary sorting. Experimental verification was obtained using micromachined devices characterized by stroboscopic measurements. With a 4.9 μs working period for the 20 μm × 20 μm heaters that generate the deflecting jets, the sorter can potentially attain a working frequency of 50 kHz or higher. We built a scattered-light based optical system to detect moving particles and successfully performed sorting of 20 μm microspheres. This type of sorter is promising for micromanipulation of a variety of biological cells and inorganic particles.

In this paper, we describe high-precision experimental and numerical characterization of the positioning forces acting on Drosophila embryos that have self-assembled onto 2-D arrays of hydrophobic sites on a silicon substrate in water. The forces measured using a surface micromachined optical-encoder force sensor operating in reflection, are in good agreement with numerical simulations based on an extended surface energy model for the oil-based fluidic system. The positioning forces of ellipsoidal embryos on flat sites show a linear-spring-like relationship between the force and displacement on rectangular as well as cross-shaped sites. An average detachment force of 8.9 /spl mu/N/spl plusmn/1.3 /spl mu/N was found for the immobilized embryos on 250 /spl mu/m/spl times/100 /spl mu/m sites. The cross-shaped site has only 19.85% of the area of the rectangular site, but provides a comparable positioning force with a significant reduction in embryo clustering. In contrast, the positioning forces of flat silicon chips, similar in size to the embryos, are linear in the displacement only over a limited range (0/spl sim/40 /spl mu/m), and are then constant up to the detachment force (25.0 /spl mu/N/spl plusmn/3.5 /spl mu/N). Our measurements also show significant hysteresis in the force vs. displacement, indicating that variations in the surface properties play an important role in the self-assembly process.

We describe high precision experimental and numerical characterization of the positioning forces acting on Drosophila embryos that have self-assembled onto two-dimensional arrays of hydrophobic sites on a silicon substrate in water. The forces measured using a surface micromachined optical-encoder force sensor operating in reflection, are in good agreement with numerical simulations based on an extended surface energy model for the oil-based fluidic system. The positioning forces of ellipsoidal embryos on flat pads show a linear-spring-like relationship between the force and displacement on rectangular as well as cross-shaped pads. In contrast, the positioning forces of flat silicon chips, similar in size to the embryos, are linear in the displacement only over a limited range, and are then constant up to the detachment force. The optical force characterization method and the associated surface energy model for the self-assembly process can potentially be used for design optimization of fluidic self-assembly for a wide range of applications in biology.

This paper reports a novel method for fabricating a monolithic inkjet chip by combination of thick resist photolithography and electroforming technologies. It integrates two-step photolithography process by two kinds of thick photoresists, SU-8 and JSR, and one-step nickel electroplating process to form the channels, chambers and nozzles of monolithic inkjet chip. The nickel nozzle plate can be replaced by SU8 material as second thick SU8 resist is used. The first thick resist of SU8 for both kinds of nozzle plates, nickel and SU8, is used for the structure formation of ink channel and chamber. Followed the nickel or SU8 nozzle plates are fabricated on SU8 chambers. The nickel nozzle plate is performed by second thick resist JSR and electroforming process while the SU8 nozzle plate is only by second thick SU8 resist process. A light-absorbing polymer layer is coated between two thick resist layers for protecting the first SU8 layer from overheating during the metal seed layer deposition or over-exposure during the second thick resist lithography process. A prototype of monolithic inkjet chip with a 300 dpi resolution has been successfully demonstrated.

We present measurements and simulation of fluid flow and sphere motion in a pressure-driven microfluidic sorter designed for Drosophila embryos. We simulate the flow fields for different channel layouts and study the effect of control pressure, chamber length and entrance length on switching time to find geometries and conditions for optimized embryo movement. We validate the sorter design with fluid experiments in devices fabricated from silicon and Pyrex wafers. The experimental and simulated results are compared both qualitatively and quantitatively by examining the concentration distribution of fluids. This type of microfluidic sorter is promising for micromanipulation of a variety of biological cells, and provides automated operations for higher throughput and accuracy.

We present a micrograting-based force sensor integrated with a surface micromachined silicon-nitride probe for penetration and injection into Drosophila embryos. The probe is supported by springs of a known spring constant, and the penetration force is determined from displacement measurements using a high-resolution, miniaturized optical encoder that is designed to only be sensitive to axial deflections of the probe. The optical-encoder force sensor exhibits configurable sensitivity and dynamic range, allowing monitoring over a wide range of forces. The periodicity of the encoder response can be used for calibration of the injector displacement and to obtain information about the localized elastic properties of the target. We used an force sensor with a measured spring constant of 1.85 N/m for penetration experiments on Drosophila embryos, and found a penetration force of 52.5 μN (±13.2%) and a membrane displacement of 58 μm (±5.2%).

Laser Doppler velocimetry (LDV) measurements are presented of turbulent flow in a two-pass square-sectioned smooth duct simulating the coolant passages employed in gas turbine blades under rotating and nonrotating conditions. For all cases studied, the Reynolds number characterized by duct hydraulic diameter and bulk mean velocity was fixed at 1×104. The rotation number Ro was varied from 0 to 0.2. It is found that as Ro is increased, both the skewness (SK) of streamwise mean velocity and magnitude of secondary-flow velocity increase linearly, SK=2.3 Ro and U2+V2¯/Uh=2.3 Ro+0.4, and the magnitude of turbulence intensity level increases exponentially. As Ro is increased, the curvature induced symmetric Dean vortices in the turn for Ro=0 is gradually dominated by a single vortex most of which impinges directly on the outer part of leading wall. The high turbulent kinetic energy is closely related to the dominant vortex prevailing inside the 180-deg sharp turn. The size of separation bubble immediately after the turn is found to diminish to null as Ro is increased from 0 to 0.2. A simple correlation is developed between the bubble size and Ro. A critical range of Ro responsible for the switch of faster moving flow from near the outer wall to the inner wall is identified. For both rotating and nonrotating cases, the direction and strength of the secondary flow with respect to the wall are the most important fluid dynamic factors affecting local the heat transfer distributions inside a 180-deg sharp turn. The role of the turbulent kinetic energy in the overall enhancement of heat transfer is well addressed.

Heat transfer measurements using a transient liquid crystal thermometry (TLCT) are presented to study the eAect of rotation on the local heat transfer distributions around a sharp 180∞ turn of a two-pass smooth square duct for the first time in open literature. The duct has a dimensionless divider wall thickness of 0.25. Detailed local Nusselt number distributions on the leading and trailing walls are given for rotation numbers ranging from Roa 0 to 0.20 at a Reynolds number of 1:0 10 4 . The results show informative spanwise variations of heat transfer enhancement or abatement resulting from rotation. A critical range of Ro is identified, below which the regional averaged Nusselt number ratios of the regions after the 180∞ sharp turn in a rotating two-pass cooling passage are rather insensitive to the rotation eAect. Laser‐Doppler velocimetry (LDV) measurements within the turn are further performed to explain the local heat transfer distributions. Under rotating conditions, the curvature induced symmetric Dean vortices in the turn for the stationary case change greatly and are dominated by a single vortex most of which impinges directly on the leading wall’s outer part, resulting in a high heat transfer enhancement on the leading wall in the turn. ” 2001 Elsevier Science Ltd. All rights reserved.

Flow visualization using a transient liquid crystal method is presented to study the effect of divider thickness on the local heat transfer distributions around a sharp 180-deg turn of a two-pass smooth square duct. Detailed local Nusselt number distributions on the bottom, blade-tip, and side walls are given for three divider thicknesses, W ∗ d =0.10 , 0.25, and 0.50, at a Reynolds number of 1.2×104. Complementary pressure loss measurements are presented in terms of variation of friction factor with W ∗ d . The thermal performance investigation shows that W ∗ d =0.25 provides the highest total averaged Nusselt number ratios, both at constant flow rate and at constant pumping power conditions, and a moderate friction factor. Near-wall laser-Doppler velocimetry measurements are further performed to explain the liquid crystal measured surface heat transfer distributions. The results show that the direction and strength of the secondary flow with respect to the wall are most important fluid dynamic factors affecting the heat transfer distributions, followed by the convective mean velocity, and then the turbulent kinetic energy.

The effect of divider thickness on fluid flows in a two-pass smooth square duct with a 180 deg straight-corner turn is an important issue to the turbine blade internal cooling but has not been explored in the past. Laser-Doppler velocimetry measurements are thus presented for such a study at a Reynolds number of 1.2 × 104 and dimensionless divider thicknesses (Wd*) of 0.10, 0.25, 0.50. Results are presented in terms of various mean velocity components in two orthogonal streamwise planes and three cross-sectional planes, the local and regional averaged turbulent kinetic energy and resultant mean velocity distributions, and complemented by the liquid crystal measured heat transfer coefficient contours. The measured velocity data are able to reasonably explain published and present measured heat transfer results. Wd* is found to have profound effects on the flow features inside and immediately after the turn. The turbulence level and uniformity in the region immediately after the turn respectively decrease and increase with increasing Wd*.

Measurements are presented of the distributions of heat transfer coefficients along the leading and trailing walls of a rotating two-pass rectangular channel with through flow. The channel has a 180° rectangular turn and a cross-sectional aspect ratio of 1.25. The Reynolds number and rotational number were varied from 5.0×103 to 5.0×104 and 0 to 0.44, respectively. Complementary flow visualization and laser-Dopper velocimetry measurements were also performed to facilitate interpretation of the measured heat transfer distributions. The results show that the secondary flow induced by the curvature and turbulence enhancement associated with unsteadiness of separation bubble downstream of the sharp turn are responsible for the significant heat transfer augmentation attained in the first part of the second pass. Moreover, the quantitative effects of the Coriolis force on the skewness of streamwise mean velocity profiles and in turn different local and average heat transfer features in the radially outward and inward flows are demonstrated and addressed.

A random screening of human blood samples from 24 individuals of nonsmoker was conducted to examine the correlation between the oxidative DNA damage level of lymphocytes and the antioxidant capacity of serum or the base excision repair (BER) activity of lymphocytes. The oxidative DNA damage level was measured with comet assay containing Fpg/Endo III cleavage, and the BER activity was estimated with a modified comet assay including nuclear extract of lymphocytes for enzymatic cleavage. Antioxidant capacity was determined with trolox equivalent antioxidant capacity assay. We found that though the endogenous DNA oxidation levels varied among the individuals, each individual level appeared to be steady for at least 1 month. Our results indicate that the oxidative DNA damage level is insignificantly or weakly correlated with antioxidant capacity or BER activity, respectively. However, lymphocytes from carriers ofHelicobacter pylori(HP) orHepatitis B virus(HBV) tend to give higher levels of oxidative DNA damage (P<0.05). Though sera of this group of individuals show no particular tendency with reduced antioxidant capacity, the respective BER activities of lymphocytes are lower in average (P<0.05). Thus, reduction of repair activity may be associated with the genotoxic effect of HP or HBV infection.

The attachment of cells onto solid supports is fundamental in the development of advanced biosensors or biochips. In this work, we characterize cortical neuron adhesion, growth, and distribution of an adhesive layer, depending on the molecular structure and composition . Neuronal networks are successfully grown on amino-terminated alkanethiol self-assembled monolayer (SAM) on a gold substrate without adhesion protein interfaces. Neuron adhesion efficiency was studied for amino-terminated, carboxy-terminated, and 1:1 mixed alkanethiol SAMs deposited on gold substrates. Atomic force microscopy and X-ray photoelectron spectroscopy were used to measure the roughness of gold substrate and thickness of SAM monolayers. Conformational ordering and ionic content of SAMs were characterized by vibrational sum frequency generation (VSFG) spectroscopy. Only pure amino-terminated SAMs provide efficient neuronal cell attachment. Ordering of the terminal amino groups does not affect efficiency of neuron adhesion. VSFG analysis shows that ordering of the terminal groups improves with decreasing surface roughness; however the number of gauche defects in alkane chains is independent of surface roughness. We monitor partial dissociation of carboxy groups in mixed SAMs that implies formation of NH3+ neighbors and appearance of catanionic structure. Such catanionic environment proved inefficient for neuron adhesion. Surface roughness of metal within the 0.7-2 nm range has little effect on the efficiency of neuron adhesion. This approach can be used to create new methods that help map structure-property relationships of biohybrid systems.

A method for assembling Drosophila embryos in a microfluidic device was developed for studies of thermal perturbation of early embryonic development. Environmental perturbation is a complimentary method to injection of membrane-impermeable macromolecules for assaying genetic function and investigating robustness in complex biochemical networks. The development of a high throughput method for perturbing embryos would facilitate the isolation and mapping of signaling pathways. We immobilize Drosophila embryos inside a microfluidic device on minimal potential-energy wells created through surface modification, and thermally perturb these embryos using binary laminar flows of warm and cold solutions. We self-assemble embryos onto oil adhesive pads with an alcohol surfactant carrier fluid (detachment: 0.1 mL/min), and when the surfactant is removed, the embryo-oil adhesion increases to approximately 25 mL/min flow rates, which allows for high velocities required for sharp gradients of thermal binary flows. The microfluidic thermal profile was numerically characterized by simulation and experimentally characterized by fluorescence thermometry. The effects of thermal perturbation were observed to induce abnormal morphogenetic movements in live embryos by using time-lapse differential interference contrast (DIC) microscopy.

We present a high-speed microfluidic cell sorter employing embedded heaters and nozzles to generate deflecting jets to change the movement of the cells. We simulated the transient flow fields to validate the concept and optimize the sorter design. The simulation demonstrates a spatial switching window corresponding to 1.1 times the switching chamber length. Experimental verification was obtained using micromachined devices characterized by stroboscopic measurements. With a 4.9 /spl mu/s working period for the 20/spl times/20 /spl mu/m/sup 2/ heaters that generate the deflecting jets, the sorter can potentially attain a working frequency of 50 kHz or higher. We built a scattered-light based optical system to detect moving particles and successfully performed sorting of 20 /spl mu/m microspheres. This type of sorter is promising for micromanipulation of a variety of biological cells and inorganic particles.

We present measurements and simulation of fluid flow and sphere motion in a pressure-driven microfluidic sorter designed for Drosophila embryos. We simulated the flow fields for different channel layouts and flow parameters to find geometries and conditions for optimised embryo movement. The microfluidic switch has a designed switching time of 360 /spl mu/s. We validated the sorter design with fluid experiments in devices fabricated from silicon and Pyrex wafers. The experimental and simulated results are compared both qualitatively and quantitatively by examining the concentration distribution of fluids. This type of microfluidic sorter is promising for micromanipulation of a variety of biological cells, and provides automated operations for higher throughput and accuracy.

We present a micrograting-based injection force sensor integrated with a surface micromachined silicon-nitride injector. The injector is supported by springs of known spring constant, and the injection force is determined from displacement measurements using a high-resolution, miniaturized optical encoder. The sensor exhibits configurable sensitivity and dynamic range, allowing monitoring over a wide range of forces. The periodicity of the encoder response can be used for calibration and to obtain information about the deformation of the target. We used an injector with a measured spring constant of 1.85 N/m for penetration experiments on Drosophila embryos, and found a penetration force of 52.5/spl plusmn/13.2% /spl mu/N and a membrane displacement of 58/spl plusmn/5.2% /spl mu/m.