A microfluidic approach to investigate the effects of bacteria deposition in porous media containing randomly packed microbeads via real-time pressure measurement

We present a real-time microfluidic permeability characterization device for quantifying effects of bacterial deposition on permeability of porous media. Here, we demonstrate a microfluidic approach that allows the effect of bacterial deposition on permeability alteration to be quantified via the measurement of pressure difference, coupled with direct visualization of bacterial distribution. Our experiments reveal three main findings. First, we observe the average percent of cell trapped to be 44.8 ± 9.7%, independent of the average bacterial density at three levels of concentration between 2.05 × 10^7 and 2.85 × 10^8 cells/ml. Second, the deposited bacterial cell count appears to follow an exponential reduction in permeability, where the reduction of permeability approaches a pseudo-steady state when a critical number of bacterial cell deposited is achieved. Last, the experiment discerned that bacterial cells tend to preferentially get deposited in regions with larger voids within the porous medium. A theoretical model is developed to determine the relationship between the spatial distribution of voids in the porous medium and the resultant bacterial cell density distribution. The approach described here shows good potential for better understanding the relationship between the spatial distribution of voids and deposited bacteria. More work can be done to further investigate these interactions, such as strategically designed voids to enhance the deposition of bacterial cells, or quantification of inflow bacterial density required to achieve a desired level of pseudo-steady state permeability reduction under various environmental conditions.Ministry of Education (MOE)Submitted/Accepted versionThis research is supported by the Ministry of Education, Singapore, under its Academic Research Funds Tier 2 MOE2018-T2-2-052 and Academic Research Funds Tier 1 RT04/1

Immunoanalysis Methods for the Detection of Dioxins and Related Chemicals

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Functional Analysis of the Dioxin Response Elements (DREs) of the Murine CYP1A1 Gene Promoter: Beyond the Core DRE Sequence

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates the biological and toxicological effects of halogenated aromatic hydrocarbons, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). When activated by dioxin, the cytosolic AhR protein complex translocates into the nucleus and dimerizes with the ARNT (Ah receptor nuclear translocator) protein. The heteromeric ligand:AhR/Arnt complex then recognizes and binds to its specific DNA recognition site, the dioxin response element (DRE). DREs are located upstream of cytochrome P4501A1 (CYP1A1) and other AhR-responsive genes, and binding of the AhR complex stimulates their transcription. Although CYP1A1 expression has been used as the model system to define the biochemical and molecular mechanism of AhR action, there is still limited knowledge about the roles of each of the seven DREs located in the CYP1A1 promoter. These seven DREs are conserved in mouse, human and rat. Deletion analysis showed that a single DRE at -488 was enough to activate the transcription. Truncation analysis demonstrated that the DRE at site -981 has the highest transcriptional efficiency in response to TCDD. This result was verified by mutation analysis, suggesting that the conserved DRE at site -981 could represent a significant and universal AhR regulatory element for CYP1A1. The reversed substituted intolerant core sequence (5'-GCGTG-3' or 5'-CACGC-3') of seven DREs reduced the transcriptional efficiency, which illustrated that the adjacent sequences of DRE played a vital role in activating transcription. The core DRE sequence (5'-TNGCGTG-3') tends to show a higher transcriptional level than that of the core DRE sequence (5'-CACGCNA-3') triggered by TCDD. Furthermore, in the core DRE (5'-TNGCGTG-3') sequence, when “N” is thymine or cytosine (T or C), the transcription efficiency was stronger compared with that of the other nucleotides. The effects of DRE orientation, DRE adjacent sequences and the nucleotide “N” in the core DRE (5'-TNGCGTG-3') sequence on the AhR-regulated CYP1A1 transcription in response to TCDD were studied systematically, and our study laid a good foundation for further investigation into the AhR-dependent transcriptional regulation triggered by dioxin and dioxin-like compounds

Spatiotemporal Ozone Level Variation in Urban Forests in Shenzhen, China

This study is among the first to investigate ozone levels in urban forests in China. It establishes that urban forest air quality in Yuanshan Forest Park (Shenzhen) is suitable for recreational activities and identifies spatial, seasonal, and diurnal O3 patterns and relationships with micrometeorological parameters, suggesting the possibility of manipulating relevant forest characteristics to reduce Surface ozone (O3) levels. An understanding of O3 levels of urban forest environments is needed to assess potential effects on human health and recreational activities. Such studies in China are scarce. This study investigated urban forest O3 levels to improve understanding and support residents engaging in forest recreational activities. We monitored O3 levels in 2015–2016 for three urban forests representing common habitats (foothill, valley, and ridge) in Yuanshan Forest Park and for an adjacent square. The overall mean daily and daily maximum 8 h mean (MDA8) O3 concentrations were highest for the ridge forest and lowest for the valley forest. Each forest’s O3 concentrations were highest in summer. Diurnally, forest O3 concentrations peaked between 13:00 and 17:00 and reached a minimum between 03:00 and 09:00. The correlation between forest O3 concentrations and air temperature (AT) was strongly positive in summer and autumn but negative in spring. In each season, O3 concentration was negatively correlated with relative humidity (RH). No MDA8 or hourly O3 concentrations in the forests exceeded National Ambient Air Quality Standard Grade I thresholds (100 and 160 μg m−3, respectively). O3 accumulation is present in ridge urban forest in all seasons. Foothill and valley urban forests have better air quality than ridge forestation. Urban forest air quality is better in spring and autumn than in summer and is better from night-time to early morning than from noon to afternoon

The complete chloroplast genome sequence of Hemerocallis minor (Asphodelaceae)

Hemerocallis minor is a kind of wild plant with high ornamental value. In this study, we sequenced the complete chloroplast genome of H. minor by using Illumina sequencing techniques. The whole chloroplast genome was 156,063 bp in size, consisting of a large single-copy (LSC) region of 84,820 bp, a small single-copy (SSC) region of 18,505 bp, and a pair of inverted repeats (IRa and IRb) regions of 26,369 bp. The chloroplast genome contained 134 genes in total, including 88 protein-coding genes, 38 tRNA genes, and eight rRNA genes. The overall GC content was 37.34%. Phylogenetic analysis showed that H. minor was closely related to Hemerocallis citrina of the same genus

Graphene quantum dots coated VO2 arrays for highly durable electrodes for Li and Na Ion batteries

Nanoscale surface engineering is playing important role in enhancing the performance of battery electrode. VO2 is one of high-capacity but less-stable materials and has been used mostly in the form of powders for Li-ion battery cathode with mediocre performance. In this work, we design a new type of binder-free cathode by bottom-up growth of biface VO2 arrays directly on a graphene network for both high-performance Li-ion and Na-ion battery cathodes. More importantly, graphene quantum dots (GQDs) are coated onto the VO2 surfaces as a highly efficient surface “sensitizer” and protection to further boost the electrochemical properties. The integrated electrodes deliver a Na storage capacity of 306 mAh/g at 100 mA/g, and a capacity of more than 110 mAh/g after 1500 cycles at 18 A/g. Our result on Na-ion battery may pave the way to next generation postlithium batteries.ASTAR (Agency for Sci., Tech. and Research, S’pore)Accepted versio

Locus coeruleus and substantia nigra neuromelanin magnetic resonance imaging differentiates Parkinson’s disease and essential tremor

Background: Differential diagnosis of essential tremor (ET) and Parkinson’s disease (PD) can still be a challenge in clinical practice. These two tremor disorders may have different pathogenesis related to the substantia nigra (SN) and locus coeruleus (LC). Characterizing neuromelanin (NM) in these structures may help improve the differential diagnosis. Methods: Forty-three subjects with tremor-dominant PD (PDTD), 31 subjects with ET, and 30 age- and sex-matched healthy controls were included. All subjects were scanned with NM magnetic resonance imaging (NM-MRI). NM volume and contrast measures for the SN and contrast for the LC were evaluated. Logistic regression was used to calculate predicted probabilities by using the combination of SN and LC NM measures. The discriminative power of the NM measures in detecting subjects with PDTD from ET was assessed with a receiver operative characteristic curve, and the area under the curve (AUC) was calculated. Results: The NM contrast-to-noise ratio (CNR) of the LC, the NM volume, and CNR of the SN on the right and left sides were significantly lower in PDTD subjects than in ET subjects or healthy controls (all P < 0.05). Furthermore, when combining the best model constructed from the NM measures, the AUC reached 0.92 in differentiating PDTD from ET. Conclusion: The NM volume and contrast measures of the SN and contrast for the LC provided a new perspective on the differential diagnosis of PDTD and ET, and the investigation of the underlying pathophysiology

Real time analysis of lead-containing atmospheric particles in Guangzhou during wintertime using single particle aerosol mass spectrometry

The toxic effects of lead on human health and the environment have long been a focus of research. To explore sources of lead in Guangzhou, China, we investigated atmospheric lead-containing particles (LCPs) during wintertime using a single particle aerosol mass spectrometer (SPAMS). Based on mass spectral features, LCPs were classified into eight major particle types, including Pb-Cl and Pb-Cl-Li (coal combustion and waste incineration), Pb-Cl-EC and Pb-Cl-OC (diesel trucks and coal combustion), Pb-Cl-Fe (iron and steel industry), Pb-Cl-AlSi (dust), Pb-Sec (secondary formation), and Pb-Cl-Zn (industrial process); these sources (in parentheses) were identified by comparing atmospheric LCP mass spectra with authentic Pb emission source mass spectra. Sampling periods with LCP number fractions (NFs) more than three times the average LCP NF (APF = 4.35%) and below the APF were defined as high LCP NF periods (HLFPs: H1, H3, and H5) and low LCP NF APF periods (LLFPs: L2 and L4), respectively. Diurnal patterns and high Pb-Sec content during LLFPs indicate that photochemical activity and heterogeneous reactions may have controlled Pb-Sec particle formation. The inverse Pb-Cl and Pb-Sec particle diurnal trends during LLFPs suggest the replacement of Cl by sulfate and nitrate. On average over the five periods, similar to 76% of the LCPs likely arose from coal combustion and/or waste incineration, which were dominant sources during all five periods, followed by diesel trucks during LLFPs and iron- and steel-related sources during HLFPs; HLFP LCPs arose mainly from primary emissions. These results can be used to more efficiently control Pb emission sources and prevent harm to human and environmental health from Pb toxicity

Programmed cell death ligand 1 expression in osteosarcoma

Programmed cell death ligand 1 (PDL1, also known as B7H1) is a cell-surface protein that suppresses the cytotoxic CD8(+) T-cell-mediated immune response. PDL1 expression and its clinical relevance in sarcomas are not well understood. Therefore, we sought to measure RNA expression levels for PDL1 in 38 clinically annotated osteosarcoma tumor samples and aimed to determine if PDL1 expression correlates with clinical features and tumor-infiltrating lymphocytes (TIL). Quantitative real-time RT-PCR for PDL1 was optimized in 18 cell lines, of which 5 were osteosarcoma derived. qRT-PCR results were validated via flow cytometry and immunohistochemistry (IHC) in select cell lines. Total RNA was isolated from 38 human osteosarcoma samples for qRT-PCR analysis. Clinical data were sorted, and significance was determined by the Student t test. TILs were examined in patient samples by tissue microarray hematoxylin-eosin staining. We confirmed the constitutive PDL1 mRNA expression in cell lines by qRT-PCR, flow cytometry, and IHC. Across human osteosarcoma samples, PDL1 mRNA gene expression ranged over 4 log (>5,000-fold difference). Relative expression levels were evaluated against clinical factors such as age/gender, metastasis, recurrence, chemotherapy, percentage of necrosis, and survival; no significant associations were identified. The presence of TILs was associated with high PDL1 expression (R(2) = 0.37; P = 0.01). In summary, we developed an RNA-based assay to determine PDL1 expression levels, and we show, for the first time, that high levels of PDL1 are expressed in a subset of osteosarcoma, and PDL1 expression is positively correlated with TILs. Multiple agents targeting PD1/PDL1 are in clinical development, and this may be a novel immunotherapeutic strategy for osteosarcoma clinical trials