Two-photon luminescence imaging of Bacillus spores using peptide-functionalized gold nanorods

Bacillus subtilis spores (a simulant of Bacillus anthracis) have been imaged by two-photon luminescence (TPL) microscopy, using gold nanorods (GNRs) functionalized with a cysteine-terminated homing peptide. Control experiments using a peptide with a scrambled amino acid sequence confirmed that the GNR targeting was highly selective for the spore surfaces. The high sensitivity of TPL combined with the high affinity of the peptide labels enables spores to be detected with high fidelity using GNRs at femtomolar concentrations. It was also determined that GNRs are capable of significant TPL output even when irradiated at near infrared (NIR) wavelengths far from their longitudinal plasmon resonance (LPR), permitting considerable flexibility in the choice of GNR aspect ratio or excitation wavelength for TPL imaging.      

Water absorption, mechanical, and thermal properties of halloysite nanotube reinforced vinyl-ester nanocomposites

Halloysite nanotube (HNT) addition to vinyl-ester resin (VER) is a field yet to contain an in-depth repository of information. This work represents the first study on the development and characterisation of HNT-reinforced VER nanocomposites, and presents findings on their water absorption, mechanical, and thermal properties. VER composites reinforced with HNTs (1, 3, and 5 wt%) were fabricated using high speed mechanical stirring. Weight gain and FTIR spectrum analysis indicated that the addition of 5 wt% HNTs gave perceptible reduction in the water absorption behavior of the samples. Results showed that elastic modulus increased with increasing HNT content. Strength and toughness were also found to steadily increase with increasing HNT content. Favorable strength can be attributable to the large aspect ratio of HNTs, favorable adhesion and dispersion, and the suitable extent of inter-tubular interaction while enhancements to toughness can be attributable to crack bridging, deflection, and plastic deformation mechanisms. Thermal stability of nanocomposites was found remarkably enhanced by the incorporation of HNTs. The thermal stability enhancement and decrease in flammability are attributable to HNT’s barriers for heat and mass transport, presence of iron, and hollow tubular structure.     

Multi-scale hybrid eco-nanocomposites: synthesis and characterization of nano-SiC-reinforced vinyl-ester eco-composites

Polymer eco-nanocomposites based on vinyl-ester, recycled cellulose fibre and nano-silicon carbide (n-SiC) have been synthesized and characterized in terms of porosity, water-absorption behaviour, thermal and mechanical properties. The addition of n-SiC led to reduced porosity and water uptake because of enhanced fibre–matrix adhesion which permitted efficient load transfer and thus strength improvement. However, n-SiC addition reduced the prevalence of fibre debonding and pull-outs, thus causing sample brittleness and inferior fracture toughness. In terms of thermal properties, n-SiC addition facilitated improved mass transport and heat barriers, thus improving thermal stability and fire resistance.     

Fracture characterisation of short bamboo fibre reinforced polyester composites

In the study, fracture behaviour of short bamboo fibre reinforced polyester composites is investigated. The matrix is reinforced with fibres ranging from 10 to 50, 30 to 50 and 30 to 60 vol.% at increments of 10 vol.% for bamboo fibres at 4, 7 and 10 mm lengths respectively. The results reveal that at 4 mm of fibre length, the increment in fibre content deteriorates the fracture toughness. As for 7 and 10 mm fibre lengths, positive effect of fibre reinforcement is observed. The optimum fibre content is found to be at 40 vol.% for 7 mm fibre and 50 vol.% for 10 mm fibre. The highest fracture toughness is achieved at 10 mm/50 vol.% fibre reinforced composite, with 340% of improvement compared to neat polyester. Fractured surfaces investigated through the Scanning Electron Microscopy (SEM) describing different failure mechanisms are also reported.     

Metabolic fingerprinting of biofluids by infrared spectroscopy: modeling and optimization of flow rates for laminar fluid diffusion interface sample preconditioning

The laminar fluid diffusion interface (LFDI) is a microfluidic tool that manipulates the composition of liquid mixtures by exploiting differences among diffusion coefficients of the dissolved components. One application is the preprocessing of (bio)fluids prior to spectroscopic characterization. For example, in the case of infrared (IR) spectroscopy, the technique can improve sensitivity to low-concentration serum metabolites. The practical benefit is "metabolic fingerprinting" measurements that are more sensitive to low-concentration metabolites than are the counterpart measurements for the original serum sample. Optimal use of the LFDI technique has proven elusive, since the composition of the product of interest is very sensitive to the choice of flow rates for the liquid streams entering and emerging from the LFDI channel. To provide the basis for optimal use, this study had the objective of developing a simulation package that predicts the composition of the LFDI product, given the LFDI structural and operating parameters. To demonstrate the utility of the simulations, composition of the LFDI products predicted for two illustrative sets of trials were compared with experimental data. The flow rates thus derived provided a LFDI product that is relatively rich in serum metabolites, while largely depleted of protein, and very well suited for subsequent IR spectroscopic characterization.     

Modelling the leaching of Pb, Cd, As, and Cr from cementitious waste using PHREEQC

A leaching model was developed using the United States Geological Survey public domain PHREEQC geochemical package to simulate the leaching of Pb, Cd, As, and Cr from cementitious wastes. The model utilises both kinetic terms and equilibrium thermodynamics of key compounds and provides information on leachate and precipitate speciation. The model was able to predict the leaching of Pb, Cd, As, and Cr from cement in the presence of both simple (0.1 and 0.6M acetic acid) and complex municipal landfill leachates. Heavy metal complexation by the municipal landfill leachate was accounted for by the introduction of a monoprotic organic species into the model. The model indicated Pb and As were predominantly incorporated within the calcium silicate hydrate matrix while a greater portion of Cd was seen to exist as discrete particles in the cement pores and Cr (VI) existed mostly as free CrO4(2-) ions. Precipitation was found to be the dominant mechanism controlling heavy metal solubility with carbonate and silicate species governing the solubility of Pb and carbonate, silicate and hydroxide species governing the solubility of Cd. In the presence of acetic acid, at low pH values Pb and Cd acetate complexes were predominant whereas, at high pH values, hydroxide species dominated. At high pH values, the concentration of As in the leachate was governed by the solubility of Ca3(AsO4)2 with the presence of carbonate alkalinity competing with arsenate for Ca ions. In the presence of municipal landfill leachate, Pb and Cd organic complexes dominated the heavy metal species in solution. The reduction of As and Cr in municipal landfill leachate was crucial for determining aqueous speciation, with typical municipal landfill conditions providing the reduced forms of As and Cr.     

Liquid-Metal Synthesized Ultrathin SnS Layers for High-Performance Broadband Photodetectors

Atomically thin materials face an ongoing challenge of scalability, hampering practical deployment despite their fascinating properties. Tin monosulfide (SnS), a low-cost, naturally abundant layered material with a tunable bandgap, displays properties of superior carrier mobility and large absorption coefficient at atomic thicknesses, making it attractive for electronics and optoelectronics. However, the lack of successful synthesis techniques to prepare large-area and stoichiometric atomically thin SnS layers (mainly due to the strong interlayer interactions) has prevented exploration of these properties for versatile applications. Here, SnS layers are printed with thicknesses varying from a single unit cell (0.8 nm) to multiple stacked unit cells (≈1.8 nm) synthesized from metallic liquid tin, with lateral dimensions on the millimeter scale. It is reveal that these large-area SnS layers exhibit a broadband spectral response ranging from deep-ultraviolet (UV) to near-infrared (NIR) wavelengths (i.e., 280–850 nm) with fast photodetection capabilities. For single-unit-cell-thick layered SnS, the photodetectors show upto three orders of magnitude higher responsivity (927 A W⁻¹) than commercial photodetectors at a room-temperature operating wavelength of 660 nm. This study opens a new pathway to synthesize reproduceable nanosheets of large lateral sizes for broadband, high-performance photodetectors. It also provides important technological implications for scalable applications in integrated optoelectronic circuits, sensing, and biomedical imaging.     

Combinational system of a truncated ball lens and a hyperbolic lens for collimating a highly divergent source

We propose the use of a truncated ball lens in a collimating system to transform a spherical wave from a highly divergent source into a plane wave. The proposed scheme, which incorporates a hyperbolic lens, is discussed, and the overall system is found to have a large acceptance angle and to be free of spherical aberration. Diffraction and polarization effects are neglected, as well as skew rays.     

Abrasive Blasting of Metal Matrix Composites

This paper investigates the feasibility of dry erosion by blasting alumina erodent on aluminum composite reinforced with silicon carbide particles. The erosion rate is dependent on the erodent velocity and the matrix hardness. Two different material removal mechanisms are observed due to different attack angles. Blasting between 30-60° is recommended for optimum erosion rate and surface quality. Material removal mechanisms and surface quality of blasted and ground composites are compared. Although its erosion rate is two orders of magnitude less than that for rough grinding, dry blasting is suitable as a finishing process of composites with irregular contours.     

Adjuvant chemotherapy for patients with resected Dukes' C and high-risk B2 colon cancer with fluorouracil and levamisole

Carcinoma of the large bowel is the second leading cause of cancer mortality in Singapore. Although the great majority of patients are discovered at a stage where resection with curative intent is possible, almost half of the patients afflicted will die of it. The combination of 5-fluorouracil + levamisole used in patients with curatively resected high risk Dukes B2 and all Dukes' C colon cancers has been shown to reduce cancer recurrence rate and improve overall survival. Since 1990 adjuvant chemotherapy has been recommended for this group of patients. This report describes patients treated in Singapore, their toxicities and their outcome. A total of 341 patients were treated between 1990 and 1996. Treatment compliance was 71.8%. Toxicity was moderate with mainly grade 1-2 nausea and vomiting, diarrhoea, stomatitis, alopecia, and neutropenia. There was 1 treatment-related death. Median recurrence-free interval was 81 months and median survival was not reached at 90 months. This regimen is tolerable. Until further randomised reports comparing 5-fluorouracil + levamisole to other combinations are available, this combination chemotherapy is recommended to patients after surgical resection of the high risk Dukes' B2 and Dukes' C colon cancer to reduce cancer recurrence and improve overall survival.