A gas chromatography-quartz crystal microbalance for speciation of sulfur compounds in landfill gas.
A new method, based on separation with gas chromatography and detection with a quartz crystal microbalance, was used for the quantification of ethane-1-thiol, propane-1-thiol, ethyl methyl sulfide, propane-2-thiol, butane-2-thiol and butane-1-thiol. The analytical error, the analysis time and the general analytical performance are identical for gas chromatography-mass spectrometry (GC-MS) and gas chromatography-quartz crystal microbalance (GC-QCM). However, the GC-QCM method constitutes a low cost alternative to GC-MS for monitoring individual sulfur compounds in landfill gas. It is an easily assembled apparatus made with an injection device, a furnace, a column, a crystal cell and a quartz crystal.
Physisorption and Chemisorption of Alkanethiols and Alkyl Sulfides on Au(111)
The energetics and kinetics of the adsorption of a variety of sulfur-containing hydrocarbons onto Au(111) have been explored using helium beam reflectivity and temperature-programmed desorption (TPD) techniques. Simple alkanethiols as well as dialkyl sulfides, dialkyl disulfides, and other sulfur-containing organics were found to adsorb with a low coverage physisorption enthalpy about 20% greater than the heat of vaporization in the bulk. In contrast to the dialkyl sulfides that only physisorb, alkanethiols and dialkyl disulfides also interact chemically with the gold with a chemisorption enthalpy of 126 kJ/mol that is independent of alkyl chain length. The presence of sterically hindering substituent groups on the carbon atom adjacent to the sulfur atom produces, however, a reduction in the chemisorption enthalpy of up to 15%. Temperature-programmed desorption of nonequilibrated, high exposure layers of alkanethiols with eight carbon atoms or longer displayed a second, higher energy, chemisorption peak a...
An intelligent control system for ventilators.
This study reports on a ventilator system that consists of several intelligent modules for controlling ventilator operation. These modules are software programs in two controllers. One controller is a personal computer used for diagnoses, determining settings and checking the effects of settings. The other controller is a single-chip microprocessor in a ventilator that controls the ventilator's settings in accordance with the computer settings. After setting up the system, an artificial lung model simulating a patient's lung is used to test the system. The result of test run indicated that it always responds to a patient's lung condition in a stable manner. Thus, the proposed system with its intelligent modules may assist clinicians in caring for patients and managing ventilator operation.