The sorption/desorption behaviour of n-hexane in high molarmass linear polyethylene (PE) and branched PEs with 0.39 and5.09 hexyl branches per 100 main chain C atoms andcrystallinities between 4 and 82% at 298 K has been studied.Crystal core contents determined by Raman spectroscopy werealways lower than those determined by density measurements. Then-hexane solubilities in the copolymers depended in anon-linear manner on the content of penetrable polymercomponent and were lower for homogeneous copolymers than forheterogeneous copolymers at the same contents of penetrablecomponent. The solubility of hexane in the linear PE sampleswas proportional to the volume fraction of the penetrablepolymer and the solubility was low in comparison with that ofthe branched PE of the same crystallinity. TheCohen-Turnbull-Fujita (CTF) free volume theory was capable ofdescribing the desorption process in the PEs studied. Theconcentration dependence of the thermodynamic diffusivitypredicted by the CTF free volume theory was confirmed by thedata obtained by the differential method, and the differencesbetween the results obtained by the integral and differentialmethods were within the margins of experimental error. Thedependence of the fractional free volume of the penetrablephases on the phase composition suggests that mass transporttakes place from the liquid-like component to the interfacialcomponent and that the penetrant molecules are trapped at theinterfacial sites. The linear PE samples showed a physicallyrealistic trend with a decrease in the geometrical impedancefactor (t) with decreasing degree of crystallinity, whereas theopposite trend was obtained for the copolymers. The decrease int with increasing crystallinity in the copolymers may beexplained by the presence of wide crystal lamellae in the lowcrystallinity samples. A novel melt-extrusion method was used to createcircumferential chain orientation in pipes of crosslinked PE.The microstructure of the pipes was characterized usingdifferential scanning calorimetry (DSC), density measurements,X-ray diffraction, infrared dichroism and contractionmeasurements. The mechanical properties were assessed byuniaxial tensile tests. The maximum degree of circumferentialorientation was obtained at the inner wall of the orientedpipe. The oriented pipe material exhibited a 5-15% higherdegree of crystallinity and a greater crystal thickness thanconventionally crosslinked pipe. The circumferential and axialmoduli of the oriented, crosslinked pipe were greater than thecorresponding moduli of the non-oriented crosslinked pipe. Blends of single-site materials of linear PE andethyl-branched PE were prepared using solution- and melt-mixingmethods. The thermal properties of the blends were studied byDSC and results obtained by the two mixing methods werecompared. Data obtained for heats of melting andcrystallization, melting and crystallization peak temperaturesand melting and crystallization temperature profiles wereessentially the same for the samples obtained by the two mixingmethods. The heat associated with the high temperature meltingpeak of the blend samples obtained by both preparation methodsafter crystallization at 398 K was higher than that of thelinear polyethylene included in the blends, suggesting that apart of the branched polyethylene crystallized at 398 K. <b>Key words:</b>n-Hexane diffusion, polyethylene, free volume,solubility, sorption, desorption, mechanical properties,orientation, thermal properties, blend.

Urea is an important nitrogen fertilizer for plant nutrition, but is very susceptible to moisture sorption and caking even at low moisture contents, e.g. 0.25% w/w. When urea particles adsorb moisture followed by drying, crystal bridges form between urea particles. For particles in a bed, this process is called caking. Cakes in stored urea cause a degradation of its quality and value. Investigations of the moisture absorption in beds of manufactured urea particles and adsorption on the external and internal surfaces of urea particles are a necessary step if engineers are to recommend procedures to reduce caking and control inventories. Research on moisture adsorption and cake strength of urea fertilizer has not been sufficiently explored. Only recently have researchers started to devise tests to investigate the crystal bonding between two urea particles. Prior to this research, investigations of the moisture interactions in beds of urea were nearly non-existent. This thesis presents experimental, theoretical and numerical methods to investigate the coupled heat and moisture transfer processes in a bed of urea particles while the bed is exposed to ambient air with changing temperature and humidity.<p> Urea particles are nearly spherical with uniform particle size distribution. The particle size, its internal pore structure and rough crystalline external surface depend on the manufacturing process. In this thesis, two types of urea products are investigated, i.e. prill Georgia urea and granular Terico urea. The rough external surface and internal pore structure of each particle makes the total surface area exposed to water much larger than similar smooth and solid spherical particles. Although Georgia urea has higher external surface area than Terico urea, the latter type has larger total surface area and internal pore volume. For both Terico urea and Georgia, the internal surface area dominates the water sorption process but the external moisture sorption of Georgia urea is more important than that of Terico urea.<p> All the water vapor interaction experiments were carried out with air flow through a test bed because it shortens the duration of each experiment to a few hours in most cases. A series of experiments with step changes in inlet air temperature and humidity for air flow through a urea bed indicated that the measured outlet air temperature and humidity responses, each at a specific air flow rate, reveals a typical exponential or transient time change that can be characterized by a time constant. After formulating the theoretical problem for step changes in the inlet properties, the analytical solutions showed that the time constants of outlet response to whether a temperature step change or a humidity step change are functions of the convection coefficient and air velocity. The predicted outlet air temperature is determined by only one time constant for a temperature step change while it is determined by these two time constants for a humidity step change.<p> A new test cell with sampling test ports was developed to measure the transient moisture uptake of a urea particle bed and its distribution at any time without any interruption of the experiment. A novel particle sampling device, modified from a syringe and pistons, was designed to minimize the particle exposure to ambient air during the moisture content determination using a Karl Fischer titrator. Data from two continuous cyclic step changes in the inlet flow with relative humidities between 4% and 70% at room temperature showed a hysteresis in the isothermal moisture content for only the first cycle. After the second sorption- desorption cycle, the hysteresis disappeared. This implies that the internal pore and particle surface geometry changes are very slow after the first cycle.<p> A new theoretical porous media model was developed for a coupled heat and moisture transport process when humid air flowed uniformly through a large test bed in two coupled computational domains: internal domain (i.e., the particle phase) and the external domain (i.e., the interstitial air space). The moisture migration in two computational domains included: water vapor diffusion inside each particle, and water vapor convection and diffusion in the interstitial air space in the urea particle bed. For energy transport, the temperature was assumed to be uniform inside each particle, but heat convection and conduction between the urea particles and the interstitial air outside particles occurred throughout the bed. Both heat transfer and mass transfer in internal domain and external domain were coupled by the heat and mass convection at the gas-particle interface. The numerical simulation was compared with the data of moisture uptake and showed good agreement implying that the internal moisture diffusion that dominates the moisture uptake process is a very slow process.<p> These above experimental, theoretical and numerical research studies provide a set of information on how urea particles adsorb or desorb moisture from or to ambient air on the external and internal pore surface, which offers a useful suggestion for urea caking prevention and is also a first and necessary step to the study of further caking formation and strength.

Measurement of monoterpenes including / alpha-pinene, camphene, beta-pinene, d-limonene, gamma-terpinene, linalool, 1-isopulegol, 1-borneol, dl-menthol, alpha-terpineol, dihydrocarveol, citronellol, pulegone, geraniol / and gas phase inorganic pollutants (O3 and NOx) were investigated on Uludag Mountain, which is the highest point in North-west Turkey. The sampling site (1645 m altitude) is surrounded by mainly Uludag fir, which is characteristic to Uludag, while altitudes lower than 1000 m were composed of mixed deciduous trees. Sampling apparatus and sampling strategy for collection of the studied terpenes on Uludag Mountain were developed. Breakthrough Volume experiments were performed for accurate sampling. Samples were collected in a field campaign performed during October 2002 by means of active sampling onto glass coated stainless steel tubes containing Tenax&amp / #61666 / TA (55 mg) and Carbopack&amp / #61652 / B (65 mg). The mass flow rate and duration of sampling were 30 mL/min and 4 hours. Short-Path-Thermal-Desorption/Gas Chromatography-Mass Spectrometer (SPTD/GC-MS) was used for the analysis of monoterpenes during 12-14 October 2002. The cryogenic preconcentration (-40oC) was maintained by liquid CO2. HP-1-MS capillary column provided good resolution of peaks, except for pulegone and citronellol at standard operation procedure. Internal standard calibration was applied by adding carefully measured spikes of fenchone to the samples and standards. The detection limits for each terpene were found to be at sub-ppbv level. Daily intermediate standard measurements and auto-tune provided checking the instrumental capabilities. Selected Ion Monitoring mode was used for analysis of the terpenes. For quantitation of the spectra at least one qualifier ion was expected to be within 80% correlation with target ion. Alpha-pinene, camphene, beta-pinene, and d-limonene were determined. The average concentrations of monoterpenes were found to be 0.385, 0.168, 0.111, and 0.204 ppbv respectively. Simultaneous measurements of O3, NOx, SO2, and meteorological parameters were also performed. The data resolution was 15 min for each pollutant. Ozone displayed strong diurnal variation (around 5-30 ppb), while NOx concentrations were almost constant around 15 ppb. During the sampling campaign terpenes showed similar behaviours with O3, but not with NOx. Terpenes had a direct relation with temperature and relative humidity.

Since the introduction of electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI), there has been an unprecedented growth of biomolecule analysis using mass spectrometry (MS). One of the most popular applications for mass spectrometry is the field of proteomics, which has emerged as the next scientific challenge in the post-genome era. One critical step in proteomic analysis is sample preparation, a major bottleneck that is attributed to many time consuming and labor-intensive steps involved. Microfluidics can play an important role in proteome sample preparation due to its ability to handle small volumes of sample and reagent, and its capability to integrate multiple processes on a single chip with the potential for high-throughput analysis. However, to utilize microfluidic systems for proteome analysis, an efficient interface between microfluidic chip and mass spectrometry is required. This thesis presents several methods for coupling of microfluidic chips with ESI-MS and MALDIMS. III Three microfluidic-ESI interfaces were developed. The first interface involves fabricating a polymer based microchannel at the rectangular corners of the glass substrates using a single photolithography step. The second interface was build upon the previous interface in which a digital microfluidic platform was integrated with the microchannel in a “top-down” format. The integrated microfluidic system was used for inline quantification of amino acids in dried blood spots that have been processed by digital microfluidics. The third interface was formed by sandwiching a pulled glass capillary emitter between two digital microfluidic substrates. This method is a simpler and more direct coupling of digital microfluidics with ESI-MS as compared to the method used for second interface. Finally, a strategy using a removable plastic “skin” was developed to interface digital microfluidics with MALDI-MS for offline sample analysis. We demonstrated the utility of this format by implementing on-chip protein digestion on immobilized enzyme depots.

Since the introduction of electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI), there has been an unprecedented growth of biomolecule analysis using mass spectrometry (MS). One of the most popular applications for mass spectrometry is the field of proteomics, which has emerged as the next scientific challenge in the post-genome era. One critical step in proteomic analysis is sample preparation, a major bottleneck that is attributed to many time consuming and labor-intensive steps involved. Microfluidics can play an important role in proteome sample preparation due to its ability to handle small volumes of sample and reagent, and its capability to integrate multiple processes on a single chip with the potential for high-throughput analysis. However, to utilize microfluidic systems for proteome analysis, an efficient interface between microfluidic chip and mass spectrometry is required. This thesis presents several methods for coupling of microfluidic chips with ESI-MS and MALDIMS. III Three microfluidic-ESI interfaces were developed. The first interface involves fabricating a polymer based microchannel at the rectangular corners of the glass substrates using a single photolithography step. The second interface was build upon the previous interface in which a digital microfluidic platform was integrated with the microchannel in a “top-down” format. The integrated microfluidic system was used for inline quantification of amino acids in dried blood spots that have been processed by digital microfluidics. The third interface was formed by sandwiching a pulled glass capillary emitter between two digital microfluidic substrates. This method is a simpler and more direct coupling of digital microfluidics with ESI-MS as compared to the method used for second interface. Finally, a strategy using a removable plastic “skin” was developed to interface digital microfluidics with MALDI-MS for offline sample analysis. We demonstrated the utility of this format by implementing on-chip protein digestion on immobilized enzyme depots.

Refrigeration systems employing the NH3-H2O absorption cycle provide cooling using a thermal energy input. This cycle relies on the zeotropic nature of the refrigerant - absorbent pair: because of the difference in boiling temperatures between NH3 and H2O, they can be separated through selective boiling in the desorber. Desorbers with counter-current flow of the solution and generated vapor enable efficient heat and mass transfer between the two phases, reducing the absorbent content in the generated vapor. Flow visualization experiments at temperatures, concentrations and pressures representative of operating conditions are necessary to understand the heat and mass transfer processes and flow regime characteristics within the component. In this study, a Flooded Column desorber, which accomplishes desorption of the refrigerant vapor through a combination of falling-film and pool boiling, was fabricated and tested. Refrigerant-rich solution enters the top of the component and fills a column, which is heated by an adjacent heated microchannel array. The vapor generated within the component is removed from the top of the component, while the dilute solution drains from the bottom. Flow visualization experiments showed that the Flooded Column desorber operated most stably in a partially flooded condition, with a pool-boiling region below a falling-film region. It was found that the liquid column level was dependent on operating conditions, and that the pool-boiling region exhibits aggressive mixing between the vapor and solution phases. Heat transfer coefficients were calculated from the data for the pool-boiling region, and were compared with the predictions of several mixture pool-boiling correlations from the literature. The correlations from the literature were in general unable to predict the data from this study adequately. It was found that the Flooded Column desorber yielded higher heat transfer coefficients within the pool-boiling region than those predicted by these correlations. Therefore, modifications to existing mixture boiling correlations are suggested based on the findings of this study. The resulting modified correlation predicts 33 of the 35 data points from this study within ±40%, with an average absolute error of 19%.

Unique physical properties such as small effective mass, high electron drift velocities, high electron mobility and small band gap energy make InN a candidate for applications in high-speed microelectronic and optoelectronic devices. The aim of this research is to understand the surface properties, desorption kinetics and thermal stability of InN epilayers that affect the growth processes and determine film quality as well as device performance and life time. We have investigated the structural properties, the surface desorption kinetics, and the thermal stability using Auger electron spectroscopy (AES), x-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), high resolution electron energy loss spectroscopy (HREELS), and temperature programmed desorption (TPD). Investigations on high pressure chemical vapor deposition (HPCVD)-grown InN samples revealed the presence of tilted crystallites, which were attributed to high group V/III flux ratio and lattice mismatch. A study of the thermal stability of HPCVD-grown InN epilayers revealed that the activation energy for nitrogen desorption was 1.6±0.2 eV, independent of the group V/III flux ratio. Initial investigations on the ternary alloy In0.96Ga0.04N showed single-phase, N-polar epilayers using XRD and HREELS, while a thermal desorption study revealed an activation energy for nitrogen desorption of 1.14 ± 0.06 eV. HREELS investigations of atomic layer epitaxy (ALE)-grown InN revealed vibrational modes assigned to N-N vibrations. The atomic hydrogen cleaned InN surface also exhibited modes assigned to surface N-H without showing In-H species, which indicated N-polar InN. Complete desorption of hydrogen from the InN surface was best described by the first-order desorption kinetics with an activation energy of 0.88 ± 0.06 eV and pre-exponential factor of (1.5 ± 0.5) ×105 s-1. Overall, we have used a number of techniques to characterize the structure, surface bonding configuration, thermal stability and hydrogen desorption kinetics of InN and In0.96Ga0.04N epilayers grown by HPCVD and ALE. High group V/III precursors ratio and lattice mismatch have a crucial influence on the film orientation. The effects of hydrogen on the decomposition add to the wide variation in the activation energy of nitrogen desorption. Presence of surface defects lowers the activation energy for hydrogen desorption from the surface.

The use of laser desorption as a sample introduction method for solid phase microextraction (SPME) has been investigated in this research project. Three different types of analytical instruments, mass spectrometry (MS), ion mobility spectrometry (IMS) and gas chromatography (GC) were employed as detectors. The coupling of laser desorption SPME to these three instruments was constructed and described in here. <br /><br /> Solid phase microextraction/surface enhanced laser desorption ionization fibers (SPME/SELDI) were developed and have been coupled to two IMS devices. SPME/SELDI combines sampling, sample preparation and sample introduction with the ionization and desorption of the analytes. Other than being the extraction phase for the SPME fiber, the electro-conductive polymer coatings can facilitate the ionization process without the involvement of a matrix assisted laser desorption/ionization (MALDI) matrix. The performance of the SPME coatings and the experimental parameters for laser desorption SPME were investigated with the SPME/SELDI IMS devices. The new SPME/SELDI-IMS 400B device has a faster data acquisition system and a more powerful data analysis program. The optimum laser operation parameters were 250 <em>&mu;J</em> laser energy and 20 <em>Hz</em> repetition rate. Three new SPME coatings, polypyrrole (PPY), polythiophene (PTH) and polyaniline (PAN) were developed and evaluated by an IMS and a GC. The PPY coating was found to have the best performance and was used in most of the experiments. The characteristics of the PPY and the PTH SPME/SELDI fiber were then assessed with both IMS and MS. Good linearity could be observed between the fiber surface area and the signal intensity, and between the concentration and the signal intensities. <br /><br /> The ionization mechanism of poly(ethylene glycol) 400 (PEG) was studied with the SPME/SELDI-IMS 400B device. It was found that the potassiated ions and sodiated ions were both present in the ion mobility spectra. The results obtained with quadrupole time-of-flight (QTOF) MS confirmed the presence of both potassiated and sodiated ions. This result suggested that cationization is the main ionization process when polymers are directly ionized from the PPY coated silica surface. Four PEGs with different average molecular weights and poly(propylene glycol) 400 were also tested with this SPME/SELDI device. The differences between the ion mobility spectra of these polymers could be used for the fast identification of synthetic polymers. <br /><br /> The SPME/SELDI fibers were then coupled to QTOF MS and hybrid quadrupole linear ion trap (QqLIT) MS, respectively. Improved sensitivity could be achieved with QqLIT MS, as the modified AP MALDI source facilitated the ion transmission. The application of method for analysis of urine sample and the bovine serum albumin (BSA) digest were demonstrated with both PPY and PTH fibers. The LOD for leucine enkephalin in urine was determined to be 40 <em>fmol &mu;L^-1</em> with PTH coated fiber; and the LOD for the BSA digest was 2 <em>fmol &mu;L^-1</em> obtained with both PTH and PPY fibers. <br /><br /> A new multiplexed SPME/AP MALDI plate was designed and evaluated on the same QqLIT MS to improve the throughput, and the performance of this technique. The experimental parameters were optimized to obtain a significant improvement in performance. The incorporation of diluted matrix to the extraction solution improved the absolute signal and S/N ratio by 104X and 32X, respectively. The incorporation of reflection geometry for the laser illumination improved the S/N ratio by more than two orders of magnitude. The fully optimized high throughput SPME/AP MALDI configuration generated detection limit improvements on the order of 1000-7500X those achieved prior to these modifications. This system presents a possible alternative for qualitative proteomics and drug screening. <br /><br /> Laser desorption SPME as a sample introduction method for the fast analysis of non-volatile synthetic polymers was also demonstrated here. The coupling of laser desorption SPME to GC/FID and GC/MS was performed, and the advantage of laser desorption over traditional thermal desorption was demonstrated in this research. Laser desorption PEG 400 was observed more effcient than thermal desorption. Good separation was obtained even with a 1-m or 2-m column. These results demonstrate the potential of laser desorption SPME as a sample introduction method for the fast GC analysis of non-volatile compounds such as synthetic polymers.

Urea is an important nitrogen fertilizer for plant nutrition, but is very susceptible to moisture sorption and caking even at low moisture contents, e.g. 0.25% w/w. When urea particles adsorb moisture followed by drying, crystal bridges form between urea particles. For particles in a bed, this process is called caking. Cakes in stored urea cause a degradation of its quality and value. Investigations of the moisture absorption in beds of manufactured urea particles and adsorption on the external and internal surfaces of urea particles are a necessary step if engineers are to recommend procedures to reduce caking and control inventories. Research on moisture adsorption and cake strength of urea fertilizer has not been sufficiently explored. Only recently have researchers started to devise tests to investigate the crystal bonding between two urea particles. Prior to this research, investigations of the moisture interactions in beds of urea were nearly non-existent. This thesis presents experimental, theoretical and numerical methods to investigate the coupled heat and moisture transfer processes in a bed of urea particles while the bed is exposed to ambient air with changing temperature and humidity.<p> Urea particles are nearly spherical with uniform particle size distribution. The particle size, its internal pore structure and rough crystalline external surface depend on the manufacturing process. In this thesis, two types of urea products are investigated, i.e. prill Georgia urea and granular Terico urea. The rough external surface and internal pore structure of each particle makes the total surface area exposed to water much larger than similar smooth and solid spherical particles. Although Georgia urea has higher external surface area than Terico urea, the latter type has larger total surface area and internal pore volume. For both Terico urea and Georgia, the internal surface area dominates the water sorption process but the external moisture sorption of Georgia urea is more important than that of Terico urea.<p> All the water vapor interaction experiments were carried out with air flow through a test bed because it shortens the duration of each experiment to a few hours in most cases. A series of experiments with step changes in inlet air temperature and humidity for air flow through a urea bed indicated that the measured outlet air temperature and humidity responses, each at a specific air flow rate, reveals a typical exponential or transient time change that can be characterized by a time constant. After formulating the theoretical problem for step changes in the inlet properties, the analytical solutions showed that the time constants of outlet response to whether a temperature step change or a humidity step change are functions of the convection coefficient and air velocity. The predicted outlet air temperature is determined by only one time constant for a temperature step change while it is determined by these two time constants for a humidity step change.<p> A new test cell with sampling test ports was developed to measure the transient moisture uptake of a urea particle bed and its distribution at any time without any interruption of the experiment. A novel particle sampling device, modified from a syringe and pistons, was designed to minimize the particle exposure to ambient air during the moisture content determination using a Karl Fischer titrator. Data from two continuous cyclic step changes in the inlet flow with relative humidities between 4% and 70% at room temperature showed a hysteresis in the isothermal moisture content for only the first cycle. After the second sorption- desorption cycle, the hysteresis disappeared. This implies that the internal pore and particle surface geometry changes are very slow after the first cycle.<p> A new theoretical porous media model was developed for a coupled heat and moisture transport process when humid air flowed uniformly through a large test bed in two coupled computational domains: internal domain (i.e., the particle phase) and the external domain (i.e., the interstitial air space). The moisture migration in two computational domains included: water vapor diffusion inside each particle, and water vapor convection and diffusion in the interstitial air space in the urea particle bed. For energy transport, the temperature was assumed to be uniform inside each particle, but heat convection and conduction between the urea particles and the interstitial air outside particles occurred throughout the bed. Both heat transfer and mass transfer in internal domain and external domain were coupled by the heat and mass convection at the gas-particle interface. The numerical simulation was compared with the data of moisture uptake and showed good agreement implying that the internal moisture diffusion that dominates the moisture uptake process is a very slow process.<p> These above experimental, theoretical and numerical research studies provide a set of information on how urea particles adsorb or desorb moisture from or to ambient air on the external and internal pore surface, which offers a useful suggestion for urea caking prevention and is also a first and necessary step to the study of further caking formation and strength.

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