Measurement of Bottom versus Charm as a Function of Transverse Momentum with Electron-Hadron Correlations in p+p Collisions at sqrt(s)=200 GeV

The momentum distribution of electrons from semi-leptonic decays of charm and bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative quantum chromodynamics (pQCD) calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is \sigma_{b\b^bar}= 3.2 ^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.Comment: 432 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Multiplexed suspension array platform for high-throughput protein assays

A multiplexed suspension array platform, based on SU8 disks patterned with machine-readable binary identification codes is presented. Multiple probe molecules, each attached to individual disks with different unique codes, provide multiplexed detection of targets in a small sample volume. The experimental system consists of a microfluidic chamber for arraying the particles in a manner suitable for high throughput imaging using a simple fluorescent microscope, together with custom software for automated code readout and analysis of assay response. The platform is demonstrated with a multiplexed antibody assay targeting 3 different human inflammatory cytokines. The suitability of the platform for other bio-analytical applications is discussed.<br/

The activity of a thermostable lipoyl synthase from Sulfolobus solfataricus with a synthetic octanoyl substrate

The protein lipoyl synthase (LipA) is essential for lipoic acid biosynthesis via sulfur insertions into a protein-bound octanoyl group. We have developed an in vitro assay for LipA using a synthetic tetrapeptide Substrate, containing an N-epsilon-octanoyl lysine residue, corresponding in sequence to the lipoyl binding domain of the E2 subunit of pyruvate dehydrogenase. A putative LipA from the hypothermophilic archaea Sulfolobus solfataricus was expressed in Escherichia coli and purified, and the activity was measured using this novel assay. The optimal temperature for the S. solfataricus LipA-dependent formation of the lipoyl group was found to be 60 degrees C

Bead-based immunoassays using a micro-chip flow cytometer

A microfabricated flow cytometer has been developed for the analysis of micron-sized polymer beads onto which fluorescently labelled proteins have been immobilised. Fluorescence measurements were made on the beads as they flowed through the chip. Binding of antibodies to surface-immobilised antigens was quantitatively assayed using the device. Particles were focused through a detection zone in the centre of the flow channel using negative dielectrophoresis. Impedance measurements of the particles (at 703 kHz) were used to determine particle size and to trigger capture of the fluorescence signal. Antibody binding was measured by fluorescence at single and dual excitation wavelengths (532 nm and 633 nm). Fluorescence compensation techniques were implemented to correct for spectral overspill between optical detection channels. The data from the microfabricated flow cytometer was shown to be comparable to that of a commercial flow cytometer (BD-FACSAria). Graphical abstract image for this article (ID: b707507n

Sensors for chemical detection based on top-down fabricated polycrystalline silicon nanowires

Semiconducting Silicon (Si) nanowires (NWs) have been widely investigated for their potential to function as highly sensitive and selective sensors for both chemical and biological purposes. A key point of this sensing method is to be real-time and label-free. Several interesting sensing assays have been demonstrated such as sensing of ions, proteins, DNA and viruses[1-3]. The available approaches of silicon nanowire fabrication usually use some advanced lithographic techniques i.e., deep-UV, electron-beam or nanoimprint lithography to pattern silicon nanowires on SOI wafers. Recently, spacer nanowires patterned by a conventional anisotropic dry etch were used to form transistors. While this approach has the advantage of CMOS-compatibility, these techniques are extremely expensive and accessible only to large-scale integrated circuit manufacturers. While this approach delivers a cheap route for nanowire definition, nanowire volume control across the wafer remains challenging as the nanowire sidewall region generally receives unwanted etching

Polycrystalline silicon nanowires patterned by top-down lithography for biosensor applications

Recently, Si nanowires are receiving much attention for biosensing because they offer the prospect of realtime, label-free, high sensitivity sensing. The most popular approach to silicon nanowire fabrication uses electron-beam lithography to pattern silicon nanowires on SOI wafers. While this approach has the advantage of CMOS-compatibility, it has the disadvantage of high cost, because both the lithography and the SOI wafers are expensive. Recently, spacer nanowires patterned by a conventional anisotropic dry etch were used to form transistors, which tends to give a triangular shape. In this paper, we demonstrate a low cost, CMOS-compatible fabrication process of polycrystalline silicon nanowires for biosensor applications using a Bosch dry etch process. The nanowires produced in this way have a rectangular shape, which gives good control over the nanowire width -height and electrical characteristics

Low cost nanowire biosensor fabrication using thin film amorphous silicon crystallisation technologies

Recently, Si nanowires are receiving much attention for biosensing because they offer the prospect of real-time, label-free, high sensitivity sensing. The most popular approach to silicon nanowire fabrication uses electron-beam lithography to define silicon nanowires on SOI wafers. While this approach has the advantage of CMOS-compatibility, it has the disadvantage of high cost, because both the lithography and the SOI wafers are expensive. In this paper we demonstrate a low cost, CMOS-compatible fabrication process for silicon nanowire biosensors, which is based on thin film transistor technology. The key steps in the fabrication process are the deposition of an amorphous Si layer over a sharp step in an insulating film and an anisotropic Si etch to create a silicon nanowire on the side of the step. The anisotropic etch was performed on an ICP etcher using the Bosch process, which gives well-defined, rectangular amorphous silicon nanowires with a geometry of 80 x 120 nm, measured by cross-sectional SEM. Metal induced lateral crystallization is then used to crystallize the amorphous silicon at a temperature around 500°C to create polycrystalline silicon nanowires. The approach used for nanowire functionalisation produces a maleimide activated surface that is amenable to the immobilization of biomolecules with a free thiol