The Effect of Mineral Admixtures and Fine Aggregates on the Characteristics of High-Strength Fiber-Reinforced Concrete.

INTRODUCTION: the article discusses the effect of the complex of active mineral additives consisting of silica and fly ash, and a fine aggregate, including finely ground natural-white quartz sand for partial replacement of river sand, on the mechanical properties of high-strength concrete containing steel fiber. MATERIALS AND METHODS: high-strength concrete containing Dramix®3D 65/35 steel fiber in the amount of 100 kg per 1 m3 of concrete mixture was suggested where 22% to 100% of river sand was replaced by finely ground white natural sand of the particle size of 5 to 1800 µm and containing the complex of active mineral additives for partial replacement of cement as part of a multicomponent binder, consisting of low-calcium fly ash of thermal power plants and silica and containing, respectively, 20, 30, 40% fly ash and from 5 to 15% silica by weight of the binder. RESULTS: research results have shown that 100% replacement of river sand with finely ground natural white sand, in concrete containing 20% of the mass as part of a multicomponent binder, fly ash and from 5 to 15% by weight of silica, contributes to the increase of its strength properties: the values of concrete compressive strength after 28 days were in the range from 118.5 to 128 MPa, tensile strength during bending and splitting, respectively, from 18.8 to 25.4 MPa and from 10.2 to 11.9 MPa, which is higher than the strength of concrete samples containing river sand. CONCLUSIONS: the achieved results have demonstrated the efficiency of using finely ground natural white sand as an alternative to river sand for producing high-strength concrete, thus helping to save the river sand resources in Vietnam. The use of fly ash and micro silicon, which are power and metallurgy wastes, as part of a multicomponent binder in order to partially replace cement reduces the carbon footprint in the production of binders and will also have a beneficial effect on environmental protection against industrial waste pollution.

Deposition of zinc cobaltite nanoparticles onto bismuth vanadate for enhanced photoelectrochemical water splitting.

During the past few decades, photoelectrochemical (PEC) water splitting has attracted significant attention because of the reduced production cost of hydrogen obtained by utilizing solar energy. Significant efforts have been invested by the scientific community to produce stable ternary metal oxide semiconductors, which can enhance the stability and increase the overall production of oxygen. Herein, we present the ternary metal oxide deposition of ZnCo2O4 as a route to obtain a novel photocatalyst layer on BiVO4 to form BiVO4/ZnCo2O4 a novel composite photoanode for PEC water splitting. The structural, topographical, and optical analyses were performed using field emission scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy, and UV-Vis spectroscopy to confirm the structure of the ZnCo2O4 grafted over BiVO4. A remarkable 4.4-fold enhancement of the photocurrent was observed for the BiVO4/ZnCo2O4 composite compared with bare BiVO4 under visible illumination. The optimum loading of ZnCo2O4 over BiVO4 yields unprecedented stable photocurrent density with an apparent cathodic shift of 0.46 V under 1.5 AM simulated light illumination. This is also evidenced by the flat-band potential change through Mott-Schottky analysis, which reveals the formation of p-ZnCo2O4 on n-BiVO4. The improvement in the PEC performance of the composite with respect to bare BiVO4 is ascribed to the formation of thin passivating layer of p-ZnCo2O4 on n-BiVO4 which improves the kinetics of interfacial charge transfer. Based on our study, we have gained an in-depth understanding of the BiVO4/ZnCo2O4 composite as high potential in efficient PEC water splitting devices.

Anion exchange and successive ionic layer adsorption and reaction-assisted coating of BiVO4 with Bi2S3 to produce nanostructured photoanode for enhanced photoelectrochemical water splitting.

Photoelectrochemical water splitting is an environmentally benign way to store solar energy. Properties such as fast charge recombination and poor charge transport rate severely restrict the use of BiVO4 as a photoanode for photoelectrochemical water splitting and many attempts were made to improve the current performance limit of the photoanode. To address these disadvantages, a highly efficient BiVO4/Bi2S3 heterojunction was fabricated applying facial anion-exchange (AE) and successive ionic layer adsorption and reaction (SILAR). The deposition of Bi2S3 on BiVO4 nanoworms by both AE and SILAR was confirmed through morphological, structural, and optical analyses. The morphological analysis indicated that Bi2S3 grown through SILAR has relatively more crystalline-amorphous phase boundaries than Bi2S3 generated using the anion-exchange method. The highest photocurrent density was observed for the SILAR-coated Bi2S3 on BiVO4, which is three times the value of the pristine BiVO4 measured under 1 sun illumination (100 mW cm-2 with Air mass (AM) 1.5 filter) in a 0.5 M Na2SO4 electrolyte at 1.6 V vs. RHE. In addition, the deposition of Bi2S3 through AE results in a twofold higher photocurrent density compared to uncoated BiVO4. The comparison of the two cost-effective AE and SILAR methods to deposit Bi2S3 on BiVO4 showed a negative shift in the flat band Mott-Schottky values, which coincides with the drifted onset potential values of the current density-voltage (J-V) curve. Furthermore, photoelectrochemical impedance spectroscopy (PEIS) analyses and band alignment studies revealed that SILAR-grown Bi2S3 creates an effective heterojunction with BiVO4, which leads to an efficient charge transfer.

Hypertension, blood pressure control and diabetic retinopathy in a large population-based study.

BACKGROUND: Clinical trials have shown beneficial effects of blood pressure (BP) control in reducing the risk of diabetic retinopathy (DR). However, association between BP control and DR in population-based studies is not clear. We aimed to examine the association of hypertension and BP control with DR. METHODS: We analysed data from a population-based cross-sectional study of Chinese, Malay and Indians adults with diabetes and hypertension (2004-2011, n = 2189, aged 40-80 years) in Singapore. DR severity was assessed from retinal photographs and graded for any- and vision-threatening DR (VTDR) using the modified Airlie House classification. Hypertension status was classified into (1) good control: on treatment (SBP < 130 and DBP < 80 mm Hg), (2) moderate control: on treatment, with BP levels other than group 1 and 3, (3) poor control: on treatment (SBP ≥140 and DBP ≥ 90 mm Hg), (4) untreated hypertension, any BP level. SBP, DBP and pulse pressure (PP) were analyzed as categories and as continuous variables. The association between BP and DR was assessed using multivariable logistic regression models. RESULTS: The prevalence of any-DR and VTDR in the study population was 33.8% and 9.0% respectively. Both poorly controlled and untreated hypertension were significantly associated with any-DR with odds ratio (OR) (95% confidence interval [CI]) of 1.97 (1.39-2.83), and 2.01 [1.34-3.05]. Among BP components, SBP and PP were associated with both any-DR and VTDR with OR (95% CI) of 1.45 (1.28-1.65) and 1.61 (1.41-1.84) for any-DR, and 1.44 (1.19-1.76) and 1.67 (1.37-2.06) for VTDR. CONCLUSION: In a population-based sample of Asian adults with diabetes and hypertension, treated but poorly controlled as well as untreated hypertension were significantly associated with any-DR. Among the BP components, higher SBP and PP levels were associated with both any-DR and VTDR. Further longitudinal studies are necessary to confirm our findings.

One year structural and functional glaucoma progression after trabeculectomy.

We evaluated the changes in visual field mean deviation (VF MD) and retinal nerve fibre layer (RNFL) thickness in glaucoma patients undergoing trabeculectomy. One hundred patients were examined with VF and spectral-domain optical coherence tomography (OCT) before trabeculectomy and 4 follow-up visits over one year. Linear mixed models were used to investigate factors associated with VF and RNFL. VF improved during the first 3 months of follow-up (2.55 ± 1.06 dB/year) and worsened at later visits (-1.14 ± 0.29 dB/year). RNFL thickness reduced by -4.21 ± 0.25 µm/year from 1st month of follow-up. Eyes with an absence of initial VF improvement (ß = 0.64; 0.30-0.98), RNFL thinning (ß = 0.15; 0.08-0.23), increasing intraocular pressure (IOP; ß = -0.11; -0.18 to -0.03) and severe glaucoma (ß = -10.82; -13.61 to -8.02) were associated with VF deterioration. Eyes with VF deterioration (ß = 0.19; 0.08-0.29), increasing IOP (ß = -0.09; -0.17 to -0.01), and moderate (ß = -6.33; -12.17 to -0.49) or severe glaucoma (ß = -19.58; -24.63 to -14.52) were associated with RNFL thinning. Changes in RNFL structure and function occur over a 1-year follow-up period after trabeculectomy. Early VF improvement is more likely to occur in patients with mild/moderate glaucoma, whereas those with severe glaucoma show greater decline over one year. Our findings indicate that progression is observable using OCT, even in late-stage glaucoma.

Intra-session repeatability of quantitative metrics using widefield optical coherence tomography angiography (OCTA) in elderly subjects.

PURPOSE: To assess the repeatability of retinal vascular metrics using different postprocessing methods as obtained from the swept-source optical coherence tomography angiography (SS-OCTA). METHODS: Thirty-two participants (63% males; mean [SD] age, 70 [7] years) underwent SS-OCTA imaging (PLEX® Elite 9000, Carl Zeiss Meditec, Inc., Dublin, USA). Each participant underwent 2 repeated scans of 2 scan protocols: a macular-centred 3 × 3-mm2 and a widefield 12 × 12-mm2 for a total of 4 acquisitions. Images of superficial vascular plexuses (SVP) and deep vascular plexuses (DVP) were processed using different filters to generate the perfusion density (PD) and vessel density (VD). Vessel enhancement filters ranged from vessel targeted (Hessian and Gabor filters), classical denoising (Gaussian filter), to a scale-selective adaption (modified Bayesian residual transform [MBRT]). Intra-session repeatability of the different filters and their correlation with the original data set were calculated with the intraclass correlation coefficient (ICC) and Pearson's r. RESULTS: Of the 32 eyes, 17 and 15 were right and left eyes, respectively. For 3 × 3-mm2 scans, both MBRT and Gabor filters yielded very good repeatable PD and VD (both ICCs > 0.87) values. Gabor filter was the most correlated with the original data set for the OCTA metrics (r = 0.95-0.97). For 12 × 12-mm2 scans, MBRT filter produced good-to-moderate ICC values for SVP (ICC>0.89) and DVP (ICC>0.73) metrics. Both the MBRT and Gabor filters were highly correlated with the original 12 × 12-mm2 scan data set (r = 0.96-0.98). The ICCs for the agreement between 3 × 3-mm2 and cropped 12 × 12-mm2 were high only for the PD values at the SVP layer and were poor for the VD at SVP and DVP measurements (ICC < 0.50). CONCLUSION: Our findings show that with the proper choice of postimaging processing methods, SS-OCTA metrics can be obtained with high repeatability, which supports its use in various clinical settings.

A Separated Receptor/Transducer Scheme as Strategy to Enhance the Gas Sensing Performance Using Hematite-Carbon Nanotube Composite.

Nanocomposite structures, where the Fe, Fe2O3, or Ni2O3 nanoparticles with thin carbon layers are distributed among a single-wall carbon nanotube (SWCNT) network, are architectured using the co-arc discharge method. A synergistic effect between the nanoparticles and SWCNT is achieved with the composite structures, leading to the enhanced sensing response in ammonia detection. Thorough studies about the correlation between the electric properties and sensing performance confirm the independent operation of the receptor and transducer in the sensor structure by nanoparticles and SWCNT, respectively. Nanoparticles with a large specific surface area provide adsorption sites for the NH3 gas molecules, whereas hole carriers are supplied by the SWCNT to complete the chemisorption process. A new chemo-resistive sensor concept and its operating mechanism is proposed in our work. Furthermore, the separated receptor and transducer sensor scheme allows us more freedom in the design of sensor materials and structures, thereby enabling the design of high-performance gas sensors.

NO gas sensing kinetics at room temperature under UV light irradiation of In2O3 nanostructures.

In2O3 nanostructure sensors were fabricated by arc-discharging a source composed of a graphite tube containing indium. The NO gas sensing properties, as well as the morphology, structure, and electrical properties, were examined at room temperature under UV light illumination. In particular, the response and recovery kinetics of the sensor at room temperature under various UV light intensities were studied. The maximum response signal was observed at an intermediate UV light intensity, which could be corroborated by a nano-size effect based on the conduction model of a resistive chemical nano sensor. The mechanism for the enhanced adsorption/desorption kinetics for NO in an air environment under UV light irradiation is discussed in detail. Furthermore, the general requirements of the sensor, including the stability, repeatability, and selectivity, are discussed.

Biological control of Xanthomonas Oryzae pv. Oryzae causing rice bacterial blight disease by Streptomyces toxytricini VN08-A-12, isolated from soil and leaf-litter samples in Vietnam.

A total of 2690 actinomycete strains were screened as potential biological control agents in controlling rice bacterial blight (BB) in Vietnam. From these microorganisms, seventeen actinomycete strains were found to be capable of inhibiting all 10 major Xoo races isolated from Xoo-infected rice leaves. One strain, namely VN08-A-12, contained effective characteristics in selectively inhibiting all 10 races in vitro, but did not inhibit most of the other tested microorganisms. Therefore, VN08-A-12 was subsequently selected for rice field trials for two seasons on two rice cultivars SS1 and KD18. Results showed VN08-A-12 was not only able to reduce Xoo lesion lengths in the two rice cultivars (lesion length reduction of up to 38.3%), but it also significantly reduced Xoo-related yield loss in infected rice cultivars from the field (yield loss reduction of up to 43.2%). Interestingly, the culture of this strain also increased the rice yield in healthy rice cultivars (from 2.66% to 16.98% for SS1 and from 3.11% to 5.94% for KD18 cultivar). The strain VN08-A-12 was shown to be identical to Streptomyces toxytricini. To our knowledge, this is the first study reporting S. toxytricini as a beneficial biological agent for the control of BB in rice.

Polymorphism at the apical membrane antigen 1 gene (AMA1) of the malaria parasite Plasmodium falciparum in a Vietnamese population.

The patterns of molecular evolution of the most diverse region of the apical membrane antigen 1 (AMA1) gene in Plasmodium falciparum from a Vietnamese subpopulation (Bao Loc) were investigated. Within the Bao Loc population, the sequenced gene region showed relatively high allelic and nucleotide diversity (0.985 and 0.02694, respectively). Further, the level of population recombination was substantial, resulting in a significant decay of linkage disequilibrium along the gene region. The results suggest that AMA1 is a useful genetic marker for studying the relationships between adaptation of parasite populations (to the human host immune system) and malaria epidemiology.

Persistence of white spot syndrome virus in shrimp ponds and surrounding areas after an outbreak.

White Spot Syndrome Virus (WSSV) is the major and most serious pathogen in shrimp aquaculture industries. By using a sensitive PCR-based detection technique followed by sequencing multiple PCR products for confirmation, we address to the question of whether WSSV can persist in shrimp ponds and surrounding areas after an outbreak. The seawater samples were taken from two shrimp ponds and surrounding canals in a coastal area in northern Vietnam, Quang Ninh Province where the shrimps cultured in the two ponds had been killed due to a WSSV outbreak in April 2001 and the ponds were thereafter abandoned. A total of 480 seawater samples (30 samples each for July and December of 2001 and 2002) were subjected to WSSV genome detection. Although the detection rates of WSSV genome were generally gradually declined in seawater environments of both diseased shrimp ponds and surrounding canals, WSSV was still detected with rates of more than 10% in the diseased ponds and lower in surrounding canals in December 2002, 20 months after the WSSV outbreak.

Phylogeographic structure and late Quaternary population history of the Japanese oak Quercus mongolica var. crispula and related species revealed by chloroplast DNA variation.

Generally, oaks dominate the broadleaf deciduous forests in Japan. The genetic variation in 6 cpDNA regions (trnT-trnL, trnL-trnF, atpB-rbcL, and trnH-psbA speacers, trnL intron, and matK gene) with regard to the Japanese oak (Quercus mongolica var. crispula) and 3 related species in the section Prinus (Q. serrata, Q. dentata and Q. aliena) was investigated in 598 trees belonging to 44 populations distributed throughout the Japanese archipelago. Additional samples were collected from Korea, China, and Russia (Sakhalin). Thirteen haplotypes (I to XIII) were identified on the bases of 15 nucleotide substitutions and 3 indels. Haplotypes I and II were discovered in northeastern Japan, whereas haplotypes III to IX were distributed in southwestern Japan. The boundary distinguishing these 2 groups was located in central Japan coincident with the Itoigawa-Shzuoka tectonic line. Haplotype I was also found in Sakhalin, whereas haplotypes VI, VII, VIII, X, XI, XII, and XIII were found in Korea and China. Four oak species in the same location shared identical haplotypes, suggesting cpDNA introgression by occasional hybridization. Both the values of total haplotype diversity (HT) and haplotype diversity within populations (HS) in Q. mongolica var. crispula were higher in the southwestern populations than in the northeastern populations. A haplotype network indicated that haplotype VI is the ancestral haplotype. The presence of identical haplotypes in Korea, China, and Japan suggested that the haplotypes diversified on the Eurasian continent before the last glacial period. The difference in genetic structure between the northeastern and southwestern regions indicates a difference in the history of migration and recolonization in Japan during the last glacial period.