Modification of the BAX System PCR assay for detecting Salmonella in beef, produce, and soy protein isolate. Performance Tested Method 100201

The BAX System PCR assay for Salmonella detection in foods was previously validated as AOAC Research Institute (RI) Performance Tested Method (PTM) 100201. New studies were conducted on beef and produce using the same media and protocol currently approved for the BAX System PCR assay for E. coli O157:H7 multiplex (MP). Additionally, soy protein isolate was tested for matrix extension using the U.S. Food and Drug Administration-Bacteriological Analytical Manual (FDA-BAM) enrichment protocols. The studies compared the BAX System method to the U.S. Department of Agriculture culture method for detecting Salmonella in beef and the FDA-BAM culture method for detecting Salmonella in produce and soy protein isolate. Method comparison studies on low-level inoculates showed that the BAX System assay for Salmonella performed as well as or better than the reference method for detecting Salmonella in beef and produce in 8-24 h enrichment when the BAX System E. coli O157:H7 MP media was used, and soy protein isolate in 20 h enrichment with lactose broth followed by 3 h regrowth in brain heart infusion broth. An inclusivity panel of 104 Salmonella strains with diverse serotypes was tested by the BAX System using the proprietary BAX System media and returned all positive results. Ruggedness factors involved in the enrichment phase were also evaluated by testing outside the specified parameters, and none of the factors examined affected the performance of the assay.     

Synthesis, structure, and electronic study of some group VII furoyl substituted complexes

The reaction of fulvene 1 with TlOEt in THF affords [Tl{1,2-C₅H₃(COC₄H₃O)₂}] (2) in 60% yield. Treatment of 2 with [MBr(CO)₅] (M = Mn, Re) in benzene reflux gave [Mn{η⁵-1,2-C₅H₃(COC₄H₃O)₂}(CO)₃] (3A) and [Re{η⁵-1,2-C₅H₃(COC₄H₃O)₂}(CO)₃] (3B) in 61% and 66% yields, respectively. Diacyl complexes 3A and 3B were ring-closed to the pyridazine by treating with hydrazine hydrate in methanol at room temperature. Fulvene 1 and diacyl complexes 3A and 3B have been structurally characterized by X-ray crystallography. Additionally, the electronic structure of complexes 3A and 3B and their relaxed structures have been characterized with density functional calculations. Calculated vibrational frequencies are compared with the experimental characterizations.     

Increasing the rate of sample vaporization in an open air desorption ionization source by using a heated metal screen as a sample holder

Rapid vaporization of sample into the ionizing gas exiting a direct analysis in real time (DART®) source has been enabled by directing a high electrical current through a metal wire screen to which sample has been applied. This direct heating of the screen enables rapid vaporization of sample as the wire temperature rises from room temperature to greater than 400°C in less than 20 s. Positioning the screen between the DART source and atmospheric pressure inlet of the mass spectrometer ensures that the ionizing gas is in close proximity to the sample molecules, resulting in efficient ionization while significantly reducing the time required for mass spectrometric analysis. The capability to modulate the electrical current flow through the wires facilitates either rapid desorption for the determination of single component samples or slower desorption where analysis of mixtures might be desired. The technology also enables deployment of strategies for the determination of chemicals present as powders that might otherwise require dissolution prior to analysis. Results from the use of this thermally assisted DART (‘TA‐DART’) system for the analysis of pure compounds, simple mixtures, solids and low vapor pressure samples are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

Design considerations for electrostatic microvalves with applications in poly(dimethylsiloxane)-based microfluidics

Microvalves are critical in the operation of integrated microfluidic chips for a wide range of applications. In this paper, we present an analytical model to guide the design of electrostatic microvalves that can be integrated into microfluidic chips using standard fabrication processes and can reliably operate at low actuation potentials (<250 V). Based on the analytical model, we identify design guidelines and operational considerations for elastomeric electrostatic microvalves and formulate strategies to minimize their actuation potentials, while maintaining the feasibility of fabrication and integration. We specifically explore the application of the model to design microfluidic microvalves fabricated in poly(dimethylsiloxane), using only soft-lithographic techniques. We discuss the electrostatic actuation in terms of several microscale phenomena, including squeeze-film damping and adhesion-driven microvalve collapse. The actuation potentials predicted by the model are in good agreement with experimental data obtained with a microfabricated array of electrostatic microvalves actuated in air and oil. The model can also be extended to the design of peristaltic pumps for microfluidics and to the prediction of actuation potentials of microvalves in viscous liquid environments. Additionally, due to the compact ancillaries required to generate low potentials, these electrostatic microvalves can potentially be used in portable microfluidic chips.     

Highly strained metastable structures and selective area epitaxy of Ge-rich Ge1−xSix/Si(100) materials using nanoscale building blocks

Low-temperature heteroepitaxy (330 ^°C–430 ^°C) of Si_0.5Ge_0.5 and Si_0.25Ge_0.75 on Si(100) using single-source silyl-germanes [ SiH₃GeH₃,HSi(GeH₃)₃] produces monocrystalline structures, smooth and continuous surface morphologies and low defect densities. The metastable compressive strain in these films is dramatically enhanced relative to alternative growth methods. At such low temperatures the material grows seamlessly, conformally, and selectively in the “source/drain” regions of prototypical transistors. These results suggest that films grown via silyl-germanes could have applications in optoelectronics and as stressors for mobility enhancement in Si devices.     

Synthesis, characterization and crystal structures of boron-containing intermediates in the reductive amination of ferrocenecarboxaldehyde to a bis(ferrocenylmethyl) amine

Reaction of ferrocenecarboxaldehyde with aqueous methylamine leads to [(methylimino)methyl]ferrocene, which is reduced to N-(ferrocenylmethyl)-N-methylamine by NaBH₄. This amine reacts with ferrocenecarboxaldehyde and NaCNBH₃ to give the tertiary ammonium salt, di(N-(ferrocenylmethyl))-N-methylammonium cyanoborohydride. Hydrolysis of the NaCNBH₃ reaction mixture produces the free amine, di(N-(ferrocenylmethyl))-N-methylamine. Thermolysis of di(N-(ferrocenylmethyl))-N-methylammonium cyanoborohydride in refluxing tetrahydrofuran converts it to the cyanoborane adduct, di(N-ferrocenylmethyl)-N-methylamine-cyanoborane, with elimination of H₂. The new compounds are fully characterized by using spectroscopic and physical methods, including X-ray crystal structure determinations of di(N-(ferrocenylmethyl))-N-methylammonium cyanoborohydride, di(N-(ferrocenylmethyl))-N-methylamine, and di(N-(ferrocenylmethyl))-N-methylamine-cyanoborane.     

Synthesis of herbicidal 3‐substituted‐4(3H)‐pyrimidinones under high pressure

The reaction of an N‐monosubstituted amidine with a β‐ketoester to afford a pyrimidinone is sluggish at best under normal conditions. We now report that this reaction can be effected in moderate yield under high pressure. Thus, 2,6‐dichloro‐4‐pyridyl‐(N‐prop‐2‐ynyl)carboxamidine (4b) was reacted with three α‐substituted‐β‐ketoesters (2b‐d) at 10–16 kbar to afford herbicidal 2‐(2,6‐dichloro‐4‐pyridyl)‐3‐(prop‐2‐ynyl)‐4(3H)‐pyrimidinones 5b and 5c in 15 ‐ 43% yield. This result expands the scope of reactions promoted by application of high pressure.     

Synthesis and Characterization of Some Thallium Cyclopentadienide Fused Ring Pyridazines

Thallium cyclopentadiene (Cp) salts are important precursors for the synthesis of a variety of compounds having materials and commercial applications. The synthesis of 5,6-fused ring thallium Cp pyridazines 2a–d from previously reported 5,6-fused ring pyridazines is described herein. This route was quite general, and features an efficient and convenient two-step synthesis of a series of TlCp salts in a THF solution of thallium ethoxide. Full characterization of newly formed TlCp salts 3a–d are reported.