Extreme red shifted SERS nanotags

Surfaced enhanced Raman scattering (SERS) nanotags operating with 1280 nm excitation were constructed from reporter molecules selected from a library of 14 chalcogenopyrylium dyes containing phenyl, 2-thienyl, and 2-selenophenyl substituents and a surface of hollow gold nanoshells (HGNs). These 1280 SERS nanotags are unique as they have multiple chalcogen atoms available which allow them to adsorb strongly onto the gold surface of the HGN thus producing exceptional SERS signals at this long excitation wavelength. Picomolar limits of detection (LOD) were observed and individual reporters of the library were identified by principal component analysis and classified according to their unique structure and SERS spectra.     

Structural and thermal characterization of copper(II) complexes with phenyl-2-pyridylketoxime and deposition of thin films by spin coating

Four copper(II) oxime complexes, [Cu(HPPK)(PPK)X] (HPPK = phenyl-2-pyridylketoxime and X = CI^? (I), CF₃COO^? (II), C₃F₇COO^? (III), and [Cu(PPK)₂]₂ (IV)), were synthesized and characterized by elemental analysis, infrared spectroscopy (IR), and single-crystal X-ray diffraction (XRD). XRD analysis revealed that I–III contain copper(II) coordinated by four nitrogen atoms from two oxime molecules in the basal plane and one monodentate anion X in the apical position of a distorted square pyramid. Complex IV is dimeric and it is formed by two Cu(PPK)₂ units. Bridges between these units are formed by the two oxygen atoms of the deprotonated oxime groups. Thermal stability of I–IV was investigated by thermogravimetric analysis (TGA) in air and in nitrogen atmosphere, respectively. Evolved gaseous decomposition products were characterized by IR. I–IV decompose via multistep processes. Fluorocarbons and CO₂ were observed to be the most abundant gaseous species evolved. Preliminary ammonolysis experiments were performed to examine the possibility of using II and IV as precursors for the synthesis of copper nitride. Moreover, solutions of IV were spin-coated onto silicon substrates. Surface structure and morphology of the resulting films were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and layers with island-like distribution of material were observed.     

Programming With Models: Writing Statistical Algorithms for General Model Structures With NIMBLE

We describe NIMBLE, a system for programming statistical algorithms for general model structures within R. NIMBLE is designed to meet three challenges: flexible model specification, a language for programming algorithms that can use different models, and a balance between high-level programmability and execution efficiency. For model specification, NIMBLE extends the BUGS language and creates model objects, which can manipulate variables, calculate log probability values, generate simulations, and query the relationships among variables. For algorithm programming, NIMBLE provides functions that operate with model objects using two stages of evaluation. The first stage allows specialization of a function to a particular model and/or nodes, such as creating a Metropolis-Hastings sampler for a particular block of nodes. The second stage allows repeated execution of computations using the results of the first stage. To achieve efficient second-stage computation, NIMBLE compiles models and functions via C++, using the Eigen library for linear algebra, and provides the user with an interface to compiled objects. The NIMBLE language represents a compilable domain-specific language (DSL) embedded within R. This article provides an overview of the design and rationale for NIMBLE along with illustrative examples including importance sampling, Markov chain Monte Carlo (MCMC) and Monte Carlo expectation maximization (MCEM). Supplementary materials for this article are available online.     

A flexible synthesis of C-6 and N-1 analogues of a 4-amino-1,3-dihydroimidazo[4,5-c]pyridin-2-one core

A flexible route which enables access to derivatives of 4-amino-1,3-dihydroimidazo[4,5-c]pyridin-2-ones is described. Issues of selectivity, reaction safety, and low yields in original routes are overcome with the key improvements to the route, including a Negishi cross-coupling and use of a carbamate as a protecting group and intrinsic carbonyl source. The new route enables variation of C-6 and N-1 substituents.     

The effect of annealing temperatures on surface properties,hydroxyapatite growth and cell behaviors of TiO2 nanotubes

Well‐ordered TiO₂ nanotubes were prepared by the electrochemical anodization of titanium in an ethylene glycol electrolyte containing 1 wt% NH₄F and 10 wt% H₂O at 20 V for 20 min, followed by annealing. The surface morphology and crystal structure of the samples were examined as a function of the annealing temperature by field emission scanning electron microscopy (FE‐SEM) and X‐ray diffraction (XRD), respectively. Crystallization of the nanotubes to the anatase phase occurred at 450 °C, while rutile formation was observed at 600 °C. Disintegration of the nanotubes was observed at 600 °C and the structure vanished completely at 750 °C. Electrochemical corrosion studies showed that the annealed nanotubes exhibited higher corrosion resistance than the as‐formed nanotubes. The growth of hydroxyapatite on the different TiO₂ nanotubes was also investigated by soaking them in simulated body fluid (SBF). The results indicated that the tubes annealed to a mixture of anatase and rutile was clearly more efficient than that in their amorphous or plain anatase state. The in vitro cell response in terms of cell morphology and proliferation was evaluated using osteoblast cells. The highest cell activity was observed on the TiO₂ nanotubes annealed at 600 °C. Copyright © 2010 John Wiley & Sons, Ltd.     

Exact and heuristic methods for cell suppression in multi-dimensional linked tables

The increasing demand for information, coupled with the increasing capability of computer systems, has compelled information providers to reassess their procedures for preventing disclosure of confidential information. This paper considers the problem of protecting an unpublished, sensitive table by suppressing cells in related, published tables. A conventional integer programming technique for two-dimensional tables is extended to find an optimal suppression set for the public tables. This can be used to protect the confidentiality of sensitive data in three- and higher-dimensional tables. More importantly, heuristics that are intimately related to the structure of the problem are also presented to mitigate the computational difficulty of the integer program. An example is drawn from healthcare management. Data tables are randomly generated to assess the computational time/space restrictions of the IP model, and to evaluate the heuristics.     

Applications of nanotechnology in food packaging and food safety: barrier materials, antimicrobials and sensors

In this article, several applications of nanomaterials in food packaging and food safety are reviewed, including: polymer/clay nanocomposites as high barrier packaging materials, silver nanoparticles as potent antimicrobial agents, and nanosensors and nanomaterial-based assays for the detection of food-relevant analytes (gasses, small organic molecules and food-borne pathogens). In addition to covering the technical aspects of these topics, the current commercial status and understanding of health implications of these technologies are also discussed. These applications were chosen because they do not involve direct addition of nanoparticles to consumed foods, and thus are more likely to be marketed to the public in the short term.     

New ternary and quaternary barium nitride halides; synthesis and crystal chemistry

New ternary and quaternary nitride halides, Ba(2)N(X,X') (X = F, Cl, Br; X' = Br, I), have been synthesized from the high temperature reactions of barium subnitride with the respective barium halides under an inert atmosphere. The former include the first fully characterized barium nitride halides for X other than F, and the latter are the first examples of barium nitride mixed halides. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques. The heavier ternary and quaternary nitride halides (X, X' = Cl, Br, I) crystallize in the hexagonal space group R3m, with the anti-α-NaFeO(2) structure. Ba(2)NF forms with both an anti-α-NaFeO(2) structure, in which N(3-) and F(-) are ordered and an anion-disordered simple rock salt structure. The hexagonal polymorph of Ba(2)NF is the only example to date of a nitride fluoride adopting this layered structure. Both the ternary and the quaternary compounds display very weak, temperature independent paramagnetism.     

Probing small molecule binding to amyloid fibrils

Much effort has focussed in recent years on probing the interactions of small molecules with amyloid fibrils and other protein aggregates. Understanding and control of such interactions are important for the development of diagnostic and therapeutic strategies in situations where protein aggregation is associated with disease. In this perspective article we give an overview over the toolbox of biophysical methods for the study of such amyloid-small molecule interactions. We discuss in detail two recently developed techniques within this framework: linear dichroism, a promising extension of the more traditional spectroscopic techniques, and biosensing methods, where surface-bound amyloid fibrils are exposed to solutions of small molecules. Both techniques rely on the measurement of physical properties that are very directly linked to the binding of small molecules to amyloid aggregates and therefore provide an attractive route to probe these important interactions.