Nonequilibrium transport through a quantum dot weakly coupled to Luttinger liquids

We study the nonequlibrium transport through a quantum dot weakly coupled to Luttinger liquids (LL). A general current expression is derived by using nonequilibrium Green function method. Then a special case of the dot with only a single energy level is discussed. As a function of the dot's energy level, we find that the current as well as differential conductance is strongly renormalized by the interaction in the LL leads. In comparison with the system with Fermi liquid (FL) leads, the current is suppressed, consistent with the suppression of the electron tunneling density of states of the LL; and the outset of the resonant tunneling is shifted to higher bias voltages. Besides, the linear conductance obtained by Furusaki using master equation can be reproduced from our result.Comment: 8 pages, 3 figures, Late

THE DISCOVERY AND STUDY OF FLUVIRUCIN B1 POLYKETIDE SYNTHASE

Rapidly decreasing numbers of viable therapeutic leads in the pharmaceutical pipeline demand new, sustainable methods for improved drug discovery and development. Despite vast improvements in de novo drug design and target recognition, Nature remains the richest source of small molecule therapeutics. Among many natural products, polyketides are not only the most promising ones for developing new antibiotic leads, but also exhibit unusually high therapeutic value ranging from clinical use as anticancer, antiviral, and immunosuppressant drugs. Modular polyketide synthases (PKSs) are dedicated nano-machinery that can be manipulated to produce a structurally diverse library for drug discovery programs. The ability to manipulate these natural systems to produce novel metabolites rests largely on increased mechanistic understanding of how these molecules are generated and how these processes can be manipulated. As impressive as their pharmaceutical properties are, the biosynthetic engineering potential of these compounds continues to draw widespread attention from the research community. Although some success has been realized in terms of polyketide structure diversification, severe limitations in engineered product output continue to impede efforts toward practical combinatorial biosynthesis. This thesis is focused on understanding and exploiting a new biosynthetic enzyme assembly and overcoming the engineering hurdles for making novel polyketide metabolites. Fluvirucin B1, produced by Actinomadura vulgaris, is a 14-membered macrolactam active against a variety of infectious fungi as well as influenza A. Despite considerable interest from the synthetic community, very little information is available regarding the biosynthetic origins of the fluvirucins. Herein, we report the identification and initial characterization of the fluvirucin B1 polyketide synthase and related enzymes. The cluster consists of five extender modules flanked by an N-terminal acyl carrier protein and C-terminal thioesterases domain. All but one of the synthase modules contain the full complement of tailoring domains (ketoreductase, dehydratase, and enoyl reductase) as determined by sequence homology with known polyketide synthases. Active site analyses of several key components of the cluster are performed to further verify that this gene cluster is associated with production of fluvirucin B1. This work will both open doors toward a better understanding of macrolactam formation and provide an avenue to genetics based diversification of fluvirucin structure

A Novel Model Considered Mass and Energy Conservation for Both Liquid and Vapor in Adsorption Refrigeration System.

In this paper, we proposed a dynamic model for a two-bed adsorption refrigeration system. Different from most existing researches which assume saturation vaper pressure in each device, the proposed method models the pressure in each device by considering both the liquid and vaper content in the device. Therefore, it can be more accurate in describing the system response and more suitable for studying the system instrumentation. The components included in this system model are: adsorption bed, evaporator, condenser, expansion valve, and etc. Each device is modeled based on the energy and mass conservation. Furthermore, the adsorption phenomenon is modeled by the “Freundlich equation,†and “linear driving force model.†The phase change of the refrigerant in evaporator and condenser is modeled by Hertz-Knudsen theory. In a case study, the pressure of the adsorption bed during the adsorption process is estimated to be 0.7kPa by the proposed model, while it was 1.6kPa by conventional method which assuming saturated vapor pressure. The coefficient-of-performance of the adsorption system is estimated to be 0.246 by this model, 0.36 by conventional method, and 0.28 by experimental data. The proposed model can estimate system performance more accurate than the conventional method. Moreover, the proposed model also inspire a new instrumentation strategy for the adsorption system, in which the system efficiency is improved and the pressure surge is avoided

Ultrasonication-Assisted Spray Ionization Mass Spectrometry for the Analysis of Biomolecules in Solution

In this paper, we describe a novel technique—ultrasonication-assisted spray ionization (UASI)—for the generation of singly charged and multiply charged gas-phase ions of biomolecules (e.g., amino acids, peptides, and proteins) from solution; this method employs a low-frequency ultrasonicator (ca. 40 kHz) in place of the high electric field required for electrospray ionization. When a capillary inlet is immersed into a sample solution within a vial subjected to ultrasonication, the solution is continually directed to the capillary outlet as a result of ultrasonication-assisted capillary action; an ultrasonic spray of the sample solution is emitted at the outlet of the tapered capillary, leading to the ready generation of gas-phase ions. Using an ion trap mass spectrometer, we found that singly charged amino acid and multiply charged peptides/proteins ions were generated through this single-step operation, which is both straightforward and extremely simple to perform. The setup is uncomplicated: only a low-frequency ultrasonicator and a tapered capillary are required to perform UASI. The mass spectra of the multiply charged peptides and proteins obtained from sample solutions subjected to UASI resemble those observed in ESI mass spectra

Rapid identification of allergenic and pathogenic molds in environmental air by an oligonucleotide array

<p>Abstract</p> <p>Background</p> <p>Airborne fungi play an important role in causing allergy and infections in susceptible people. Identification of these fungi, based on morphological characteristics, is time-consuming, expertise-demanding, and could be inaccurate.</p> <p>Methods</p> <p>We developed an oligonucleotide array that could accurately identify 21 important airborne fungi (13 genera) that may cause adverse health problems. The method consisted of PCR amplification of the internal transcribed spacer (ITS) regions, hybridization of the PCR products to a panel of oligonucleotide probes immobilized on a nylon membrane, and detection of the hybridization signals with alkaline phosphatase-conjugated antibodies.</p> <p>Results</p> <p>A collection of 72 target and 66 nontarget reference strains were analyzed by the array. Both the sensitivity and specificity of the array were 100%, and the detection limit was 10 pg of genomic DNA per assay. Furthermore, 70 fungal isolates recovered from air samples were identified by the array and the identification results were confirmed by sequencing of the ITS and D1/D2 domain of the large-subunit RNA gene. The sensitivity and specificity of the array for identification of the air isolates was 100% (26/26) and 97.7% (43/44), respectively.</p> <p>Conclusions</p> <p>Identification of airborne fungi by the array was cheap and accurate. The current array may contribute to decipher the relationship between airborne fungi and adverse health effect.</p