Colorimetric detection of nucleic acid signature of shiga toxin producing Escherichia coli using gold nanoparticles

Enterohemorrhagic E. coil (EHEC) serotype O157:H7 is one of the major pathogens, responsible for the severe disease outbreaks. EHEC causes diseases in humans through production of shiga-like toxin leading to bloody diarrhea. The toxin is encoded by stx2 gene in E. coli. The current methodology for detection of EHEC relies on fluorogenic-substrate based culture media or nucleic acid amplification based Real-Time Polymerase Chain Reaction assays that are either time consuming or need expensive instrumentation. In this study, the optical properties of gold nanoparticles (GNPs) have been exploited for detection of nucleic acid of Escherichia coli O157:H7. The stx2 gene representing EHEC signature has been targeted using the gold nanoparticle probes. Gold nanoparticles (GNPs) of 20 +/- 0.2 nm were synthesised by citrate reduction method and characterised by spectroscopy and transmission electron microscopy. The GNPs were functionalised with 19 and 22 bp of thiolated single stranded DNA complementary to target highly conserved 149 bp region of stx2 gene. Transmission Electron Microscopy revealed the hybridization, aggregation and reduction in the interparticle distances of the GNP probes in the presence of target DNA. The aggregation and the spectral shift in the plasmon band observed with 10(6) copies of target DNA indicates feasibility of a simple and quick colorimetric 'spot and read' test in contrast to amplification based detection methods.     

Vibration analysis of a poroelastic composite hollow sphere

Vibrations in a poroelastic composite hollow sphere are investigated employing Biot’s theory of wave propagation in poroelastic media. A composite hollow poroelastic sphere consists of two concentric poroelastic spherical layers both of which are made of different poroelastic materials with each poroelastic material being homogeneous and isotropic. The boundaries of the composite hollow poroelastic sphere are free from stress. The frequency equations of both radial and rotatory vibrations are obtained each for pervious and impervious surfaces. The frequency equation of vibrations of a poroelastic composite hollow sphere with rigid core is derived as a particular case. The non-dimensional frequency for propagating modes is computed as a function of ratio of thickness to inner radius of core. The results are presented graphically for two types of poroelastic composite spheres and then discussed.     

Fuzzy set based cost model of additive manufacturing with specific example of selective laser sintering

A fuzzy set based cost model for additive manufacturing is proposed. The model is illustrated through an example of selective laser sintering (SLS), a commonly used additive manufacturing (AM) process. Initially, a deterministic cost model is developed. It is then converted to a fuzzy set based model by considering uncertainty in build time estimation and cost components. For the specific case of SLS, a build time estimation procedure is developed as a part of the cost model. A method to evaluate the reliability of the cost estimate in AM and its significance is also introduced. The cost model is illustrated through two examples of products manufactured by SLS.

     

Contamination of surface and potable water in South Asia by Salmonellae: Culture-independent quantification with molecular beacon real-time PCR

Low numbers (15-100 CFU) of Salmonella in food or water may pose a public health risk. The management of infections caused by Salmonella spp. during outbreaks or forecasting of contamination of aquatic resources largely depends on rapid, sensitive and accurate diagnostic in few hours. In this study, a real-time PCR assay in Molecular-Beacon format was developed and culture-independent quantitative enumeration of Salmonella spp. in surface and potable water is being reported for the first time from northern part of India. Molecular Beacon was designed in highly conserved region of invA gene (present in wide range of Salmonella serotypes including all subspecies) encoding an essential component of the invasion associated specialized type Ø protein secretion apparatus for detection of Salmonella spp. in water. The assay could detect directly 10 and 1 genomic equivalent of Salmonella typhimurium ATCC 14028 per PCR with detection probability of 100 and 20%, respectively. Further, the assay could detect 10 CFU/PCR or more of reference strain (S. typhimurium ATCC 14028) without any enrichment in the presence of 10⁸ CFU ml^− 1 of non-pathogenic E. coli (E. coli DH5α) with 100% detection probability. The assay could enumerate Salmonella spp. in surface (n = 40) and potable waters (n = 10) directly (without enrichment). Results indicate that northern India is at high risk of developing Salmonella borne infections. Further, real-time PCR assay in Molecular Beacon format can be used for identification of critical contamination points in natural water resources and potable water distribution systems, necessary to implement vaccination plan timely for prevention of waterborne outbreaks caused by Salmonella spp.     

A set partitioning based heuristic procedure for incremental cell formation with routing flexibility

One of the important issues regarding the implementation of cellular manufacturing relates to deciding whether to convert an existing job shop into a cellular manufacturing system comprehensively in a single go, or to convert in stages incrementally wherein the cells are formed one after the other taking the advantage of experiences of implementation. In this paper, a heuristic method based on iterative set partitioning is proposed for incremental cell formation where part operations can be processed on alternative machines. The objective is to minimize cycle time for a given number of workstations. The proposed method is numerically compared with the existing branch and bound technique and another heuristic algorithm based on multistage programming. It is found that the proposed method requires significantly less computational efforts to yield the optimal solution.     

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and The Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.     

Intentional forgetting as a facilitator for recalling new product attributes.

When market changes alter what product attributes are deemed important, consumers may intentionally try to forget old product information in an attempt to remember new product information. In Experiment 1, the authors demonstrated that intentional forgetting of this nature temporarily inhibits retrieval of old product information and leads to a benefit to memory for new product information. The results show that, after a short delay, benefits continue in the absence of costs, which is supportive of a multiple-process account of intentional forgetting. Experiment 2 extends these effects using an advertising message to stimulate forgetting. Across both experiments, results also show that brand preference is based on learning of new attribute information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigation of Ba<Subscript>2-x</Subscript>Sr<Subscript>x</Subscript>TiO<Subscript>4</Subscript>: Structural aspects and dielectric properties

Investigation of solid solution of barium-strontium orthotitanates of the type, Ba_2-x Sr _x TiO₄ (0 ≤x≤ 2), show that pure phases exist only for the end members, Ba₂TiO₄ and Sr₂TiO₄, crystallizing in the β-K₂SO₄ and K₂NiF₄ structures, respectively. The intermediate compositions (till≥ 1) lead to a biphasic mixture of two Ba₂TiO₄-type phases (probably through a spinodal decomposition) with decreasing lattice parameters, indicating Sr-substitution in both the phases. Forx > 1, Sr₂TiO₄ along with a secondary phase is obtained. The dielectric constant and dielectric loss were found to decrease with Sr substitution till the nominal composition ofx = 1. However, pure Sr₂TiO₄ shows higher dielectric constant compared to the solid solution composition. Sr₂TiO₄ shows very high temperature stability of the dielectric constant.