Repetitively pulsed, wavelength-selective carbon dioxide laser

Carbon dioxide laser as a simple portable unit generates coherent light pulses at selected infrared wavelengths. The improved laser was designed for the detection of air pollutants but can be applied to optical communications

A significant upper limit for the rate of formation, of OCS from the reaction of OH with CS2

The rate of reaction of OH with CS2 to form OCS by reaction (1) has been measured through observation of O14CS following 254 nm equation image photolysis of mixtures of H2O2 with 14CS2. The OH concentrations have been monitored through simultaneous measurement in the same cell of either (a) the oxidation of CO to CO2, or (b) the removal of a hydrocarbon such as C3H8 or iso-C4H10. The upper limit for the formation of OCS based on (a) corresponds to a rate constant k1 < 0.3 × 10−14 cm³ molecule−1 sec−1. Other chemical reactions in the system have led to the formation of both 14CO and 14CO2, indicating the existence of a complex combination of reactions such that the observed O14CS need not have been formed by (1). The rate of reaction (1) is sufficiently slow that it is neither an important atmospheric sink for CS2 nor an important source for atmospheric OCS. The reaction of OH with OCS has not been measured in these experiments, but by analogy with k1 it is probably not an important atmospheric sink for OCS nor an important source of SO2

Quantum Cascade Laser-Based Photoacoustic Sensor for Trace Detection of Formaldehyde Gas

We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH2O) using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 μm. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm−1 is selected for CH2O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters

Optimizing Molecular Cloning Strategies for Naturally Diverse HIV-1 env

Broadly Neutralizing Antibodies (bNAbs) can bind and neutralize multiple strains of HIV-1 at evolutionarily and structurally conserved sites of the Env surface protein. bNAbs develop in some HIV-infected individuals during infection, and they have been shown to prevent infection upon SHIV challenge in the Macaque model. This makes bNAb elicitation a primary objective in the effort to create a vaccine for HIV-1.The origin of bNAbs during natural infection is a result of co-evolution between the HIV-1 Env population and the broad antibody lineage, and studies of longitudinal donor samples can help us understand how these bNAbs arise. These studies are typically quite time consuming, and, in this thesis, I will explore preliminary investigations into high-throughput strategies for characterizing the co-evolution of HIV env and antibody lineages.By creating libraries of diverse env sequences, a range of high-throughput experiments become available. This thesis describes the efforts to create libraries of diverse env for different projects: we would aim to conduct one project that uses the libraries for transduction of HEK293T cells for cell sorting to determine sequence similarities among envs that bind the bNAb, as well as enriched features. The other project uses libraries to grow virus and observe the ability of the virus to escape certain bNAbs. Both projects require cloning Env libraries from primary samples into large plasmid vectors, and this cloning is the focus of my thesis