Simple, robust and on-demand generation of single and correlated photons

We propose two different setups to generate single photons on demand using an atom in front of a mirror, along with either a beam-splitter or a tunable coupling. We show that photon generation efficiency ~99% is straightforward to achieve. The proposed schemes are simple and easily tunable in frequency. The operation is relatively insensitive to dephasing and can be easily extended to generate correlated pairs of photons. They can also in principle be used to generate any photonic qubit of the form $\mu |0 \rangle + \nu |1\rangle$ in arbitrary wave-packets, making them very attractive for quantum communication applications.Comment: 10 pages, Added appendi

Differing Effects of Glycerin on Anaerobic Co-digestion of Mixed Substrates in Bench-Scale Assays and Sub Pilot-Scale Reactors

Bench-scale methods such as Biochemical Methane Potential (BMP) assays and Anaerobic Toxicity Assays (ATAs) are useful tools in evaluating potential feedstocks for anaerobic digestion. The BMP method provides a preliminary indication of substrate biodegradability and methane production, while the ATAs provide an indication of substrate toxicity to anaerobic microbial consortia. Previous research using small (\u3c20 \u3eL) reactors indicated that co-digestion of manures with small amounts of glycerin (ca. 1 – 2 %) can double methane production, but toxicity can result if glycerin exceeds 2% (volumetric basis). This paper investigated the relationship between bench-scale methods (BMPs and ATAs) and sub pilot-scale digester results, using glycerin as a test substrate mixed with a baseline feedstock (beef manure, corn processing wastewater, lagoon liquid, and short-fiber cardboard). The batch-fed, stirred ATAs indicated that glycerin was toxic to methane production at all inclusion levels. The batch-fed, stirred BMPs indicated no significant difference between methane production in the 0.0%to 4.0% addition levels; however at 8.0% addition, methane production tripled. The continuously fed, non-stirred, plug-flow sub pilot-scale reactors indicated toxicity effects in the 2.0% and 4.0% glycerin mixtures and no difference from the control in the 1.0% glycerin mixture. These results demonstrate the variations in scale performance of glycerin as a co-substrate and identify some serious challenges in extrapolating bench-scale assays to large-scale performance of mixed-waste anaerobic digestion systems

Comparison of Methane Production from Bench- and Sub Pilot-Scale Anaerobic Digesters

Design and construction of full-scale anaerobic digesters that co-digest manure with other substrates, such as food processing wastes, is challenging because of the large number of potential mixtures that can be fed to the digester. In this work we examine the relationship between results from bench-scale methods such as biochemical methane potential assays (BMPs) and sub pilot-scale reactors. The baseline feedstock for this study was beef manure from concrete feedlot pens (open and covered) in eastern Iowa. Additional co-digestion substrates tested were short-fiber cardboard, corn processing wastewater, enzyme processing wastewater and lagoon liquid. Substrates were characterized for total solids (TS), volatile solids (VS), chemical oxygen demand (COD), pH, alkalinity, and ammonia, after which BMPs were conducted on all substrates. Based on the BMP and anaerobic toxicity assay (ATA) results, a mixture was created and evaluated using BMPs and tested in 100-L sub pilot-scale reactors. This study showed that results from BMPs of feedstock co-digestion mixtures accurately estimated the range of methane produced from three 100-L, plug flow reactors

Approaches for Selecting Anaerobic Digestion Co-Substrates for a Full-Scale Beef Manure Digester Using Biochemical Methane Potentials and Anaerobic Texicity Assays

Design and construction of full-scale anaerobic digesters that co-digest manure with various materials requires analysis of each substrate. Substrate combinations should be analyzed through a scale up procedure in which substrates are characterized, and then evaluated using biochemical methane potential assays (BMPs) and anaerobic toxicity assays (ATAs). The BMPs provide a preliminary indication of the biodegradability of a substrate and of its potential to produce methane via anaerobic digestion, while ATAs determine the degree to which a particular substrate inhibits methane production. Mixture combinations that perform well in BMPs and ATAs should be tested in laboratory-scale anaerobic digesters. Once proven in lab-scale reactors for at least three hydraulic retention times, the best mixture should be tested in a pilot-scale reactor. This paper focuses on the first steps in this process using BMPs and ATAs results to select mixtures for laboratory-scale digester testing. The baseline feedstock was beef manure obtained from concrete feedlot pens (open and covered) in eastern Iowa. Various bedding materials were available, including oat hulls, corn stover, and wood shavings. To provide additional energy production, industrial byproducts from cardboard manufacturing, enzyme production, and corn and soybean processing were also potential substrates. Substrates were characterized for TS, VS, COD, pH, alkalinity, and ammonia. Then BMPs were completed on all substrates and ATAs were performed as needed. The results reported here were used to develop mixtures for use in laboratory-scale anaerobic digester testing

Quantitative Analysis of Mechatronics and Student Motivation in a First-Year Applied Engineering Course: Preliminary Results

Summary: Limited empirical evidence has been found in current literature to support the use of mechatronics in first-year engineering and technology courses to motivate students. In response, this study lays a quantitative evidence base for the use of mechatronic projects in first-year courses and how they impact student motivation, albeit to different degrees for different students

Simultaneous computation of dynamical and equilibrium information using a weighted ensemble of trajectories

Equilibrium formally can be represented as an ensemble of uncoupled systems undergoing unbiased dynamics in which detailed balance is maintained. Many non-equilibrium processes can be described by suitable subsets of the equilibrium ensemble. Here, we employ the "weighted ensemble" (WE) simulation protocol [Huber and Kim, Biophys. J., 1996] to generate equilibrium trajectory ensembles and extract non-equilibrium subsets for computing kinetic quantities. States do not need to be chosen in advance. The procedure formally allows estimation of kinetic rates between arbitrary states chosen after the simulation, along with their equilibrium populations. We also describe a related history-dependent matrix procedure for estimating equilibrium and non-equilibrium observables when phase space has been divided into arbitrary non-Markovian regions, whether in WE or ordinary simulation. In this proof-of-principle study, these methods are successfully applied and validated on two molecular systems: explicitly solvated methane association and the implicitly solvated Ala4 peptide. We comment on challenges remaining in WE calculations

MR Spectroscopic Imaging of Peripheral Zone in Prostate Cancer Using a 3T MRI Scanner: Endorectal versus External Phased Array Coils.

Magnetic resonance spectroscopic imaging (MRSI) detects alterations in major prostate metabolites, such as citrate (Cit), creatine (Cr), and choline (Ch). We evaluated the sensitivity and accuracy of three-dimensional MRSI of prostate using an endorectal compared to an external phased array "receive" coil on a 3T MRI scanner. Eighteen patients with prostate cancer (PCa) who underwent endorectal MR imaging and proton (1H) MRSI were included in this study. Immediately after the endorectal MRSI scan, the PCa patients were scanned with the external phased array coil. The endorectal coil-detected metabolite ratio [(Ch+Cr)/Cit] was significantly higher in cancer locations (1.667 ± 0.663) compared to non-cancer locations (0.978 ± 0.420) (P < 0.001). Similarly, for the external phased array, the ratio was significantly higher in cancer locations (1.070 ± 0.525) compared to non-cancer locations (0.521 ± 0.310) (P < 0.001). The sensitivity and accuracy of cancer detection were 81% and 78% using the endorectal 'receive' coil, and 69% and 75%, respectively using the external phased array 'receive' coil

Phase conjugate fluorozirconate fibre laser operating at 800nm

We report phase-conjugate feedback into a fluorozirconate optical fiber amplifier at infrared wavelengths. By using a semiconductor laser diode at 807 nm, a grating is established in photorefractive BaTiO3 that, in the ring configuration, provides feedback into the amplifier necessary for laser action. Once written, the grating is self-sustaining, and lasing is observed even after the laser diode is removed