Dynamics of excited OCS investigated by resonance-enhanced multiphoton ionization

The predissociation decay behavior of molecule carbonyl sulfide (OCS) has been investigated by resonance-enhanced multiphoton ionization spectroscopy using the pump-probe technique of dichroic femtosecond lasers in real time. The lifetime of excited OCS around 74 720 cm(-1) by two-photon absorption of 268 nm, corresponding to upsilon(1)=1 of the Rydberg state [(2)Pi(1/2)]4ppi((1)Sigma(+)), is directly determined to be tau(D)=1071+/-11 fs. This picosecond decay process indicates that the excited state is predissociative. The temporal information of dissociation enriches the knowledge of the potential-energy surface of the associative excited state.

压力探针技术原理及其在植物水分关系研究中的应用

现代压力探针主要分为高等植物细胞压力探针、根压力探针、木质部压力探针和取样压力探针4个变种,并形成了相关的理论体系,广泛应用于植物生理学及其相关领域的研究中。现代压力探针技术不仅可用于高等植物细胞和组织水平水分关系、水和溶质的相互作用关系的研究,还可进行根木质部负压的测定及高等植物活体单细胞内含物的取样研究等。未来更可借助取样压力探针与微量分析技术的结合,将高等植物单细胞内的水分关系和代谢过程定量联系起来;或可试图拓宽木质部压力探针测定的压力范围,进一步研究和验证内聚力-张力学说的理论和机制。

Microchip Micellar Electrokinetic Chromatography Based on One Functionalized Ionic Liquid and Its Excellent Performance on Proteins Separation

Herein, one water-soluble functionalized ionic liquid (IL), 1-butyl-3-methylimidazolium dodecanesulfonate (BAS), was designed, investigated and successfully applied to microchip micellar electrokinetic chromatography (MEKC) construction. It possessed the properties of both IL and surfactant. A fairly stable pH value similar to 7.4, which was fit to pH values of general biological buffers, was nicely placed at the optimum concentration of 20 mM BAS solution. While applying BAS solution as running buffer in poly(dimethylsiloxane) (PDMS) microfluidic systems, significantly enhanced electroosmotic flow (8-fold) and resolutions between analytes were obtained than that using other supporting electrolytes or surfactants.

加氢反应器壁原子氢分布的在线、实时、无损检测新技术

为了在线、实时、无损检测高温高压条件下运行的加氢反应器的多层器壁中原子氢的渗透速率和在任何指定剖面上的体浓度分布，发展了一种新型的检测技术．介绍了检测仪的结构设计及其特征。

记忆年老化与焦虑

It is well established that memory functioning deteriorates with advancing age. However, research indicates that the magnitude of age-related memory deficits varies across different types of memory, and broad individual differences can be observed in the rate and timing of memory aging. The general aim of this study was to investigate the selectivity and variability of memory functioning in relation to anxiety. Firstly, memory effectiveness was assessed in episodic memory tasks with reality monitoring and external source monitoring paradigms, semantic memory tasks referred to general knowledge and word fluency, and perceptual priming task reflected in word completion. According to the scores on trait version of STAI, the high-trait and low-trait anxious subjects were screened respectively from young and old participants matched for educational level. Secondly, based on the results of the first part, concurrent primary and secondary tasks with probe technique assessing spare processing capacity were used to explore the relation between memory efficiency and anxiety. The first main findings were that: (a) there were no age-related differences in semantic memory assessed by general knowledge and PRS, whereas age effects were observed in episodic memory and semantic memory assessed by word fluency with stringent time restraints. (b) Furthermore, comparison of age-related deficits in source and item was not related to the presentation ways and encoding effort for source, but was affected by types of source. Specifically, memory was more sensitive to aging than item memory in external source monitoring processes involved in discriminating two external sources (i.e., female vs. male voices), but not in reality monitoring processes in discriminating between internal and external sources (i.e., acting vs. listening). The second main findings were that: (a) Anxiety had no effects on the effectiveness and efficiency of semantic memory in recall of general knowledge and PRS, but impaired those of semantic memory in word fluency. (b) The effects of anxiety on episodic memory were different between the old and the young. Both the effectiveness and the efficiency of episodic memory of the old were affected adversely by anxiety. More importantly, source recall in external source monitoring processes was observed to be more vulnerable to anxiety than item memory. The effectiveness of episodic memory of the young was relatively unrelated to anxiety, while anxiety might have adverse effect on their memory efficiency. These results indicated that: First, the selectivity of age-related memory deficits existed not only between memory systems, but also within episodic memory system. The tendency to forget the source even when the fact was retained in external source monitoring was suggested to be a specific feature of cognitive aging. Second, anxiety had adverse impact on the individual differences in memory aging, and mediated partial age-related differences in episodic memory performance.

Measuring Bottleneck Link Speed in Package-Switched Networks

The quality of available network connections can often have a large impact on the performance of distributed applications. For example, document transfer applications such as FTP, Gopher and the World Wide Web suffer increased response times as a result of network congestion. For these applications, the document transfer time is directly related to the available bandwidth of the connection. Available bandwidth depends on two things: 1) the underlying capacity of the path from client to server, which is limited by the bottleneck link; and 2) the amount of other traffic competing for links on the path. If measurements of these quantities were available to the application, the current utilization of connections could be calculated. Network utilization could then be used as a basis for selection from a set of alternative connections or servers, thus providing reduced response time. Such a dynamic server selection scheme would be especially important in a mobile computing environment in which the set of available servers is frequently changing. In order to provide these measurements at the application level, we introduce two tools: bprobe, which provides an estimate of the uncongested bandwidth of a path; and cprobe, which gives an estimate of the current congestion along a path. These two measures may be used in combination to provide the application with an estimate of available bandwidth between server and client thereby enabling application-level congestion avoidance. In this paper we discuss the design and implementation of our probe tools, specifically illustrating the techniques used to achieve accuracy and robustness. We present validation studies for both tools which demonstrate their reliability in the face of actual Internet conditions; and we give results of a survey of available bandwidth to a random set of WWW servers as a sample application of our probe technique. We conclude with descriptions of other applications of our measurement tools, several of which are currently under development.

TEMPORALLY AND SPATIALLY-RESOLVED PLASMA PARAMETERS AND EEDF MEASUREMENTS IN A LOW-FREQUENCY DISCHARGE

A time-resolved Langmuir probe technique is used to measure the dependence of the electron density, electron temperature, plasma potential and electron energy distribution function (EEDF) on the phase of the driving voltage in a RF driven parallel plate discharge. The measurements were made in a low-frequency (100-500 kHz), symmetrically driven, radio frequency discharge operating in H-2, D-2 and Ar at gas pressures of a few hundred millitorr. The EEDFs could not be represented by a single Maxwellian distribution and resembled the time averaged EEDFs reported in 13.56 MHz discharges. The measured parameters showed structure in their spatial and temporal dependence, generally consistent with a simple oscillating sheath model. Electron temperatures of less than 0.1 eV were measured during the phase of the RF cycle when both electrodes are negative with respect to the plasma.

Dissociative electron attachment to C2F5 radicals

Dissociative electron attachment to the reactive C2F5 molecular radical has been investigated with two complimentary experimental methods; a single collision beam experiment and a new flowing afterglow Langmuir probe technique. The beam results show that F- is formed close to zero electron energy in dissociative electron attachment to C2F5. The afterglow measurements also show that F- is formed in collisions between electrons and C2F5 molecules with rate constants of 3.7 × 10-9 cm3 s-1 to 4.7 × 10-9 cm3 s-1 at temperatures of 300–600 K. The rate constant increases slowly with increasing temperature, but the rise observed is smaller than the experimental uncertainty of 35%.

The role of Na surface species on oxygen charge transfer in the Pt/YSZ system

The role of sodium surface species in the modification of a platinum (Pt) catalyst film supported on 8 mol% yttria-stabilised-zirconia (YSZ) was investigated under a flow of 20 kPa oxygen at 400 °C. Cyclic and linear sweep voltammetry were used to investigate the kinetics of the oxygen charge transfer reaction. The Pt/YSZ systems of both ‘clean’ and variable-coverage sodium-modified catalyst surfaces were also characterised using SEM, XPS and work function measurements using the Kelvin probe technique.

Samples with sodium coverage from 0.5 to 100% were used. It was found that sodium addition modifies the binding energy of oxygen onto the catalyst surface. Cyclic voltammetry experiments showed that higher overpotentials were required for oxygen reduction with increasing sodium coverage. In addition, sodium was found to modify oxygen storage and/or adsorption and diffusion increasing current densities at higher cathodic overpotential. Ex situ XPS measurements showed the presence of sodium hydroxide, carbonate and/or oxide species on the catalyst surface, while the Kelvin probe technique showed a decrease of approximately 250 meV in the work function of samples with more than 50% sodium coverage (compared to a nominally ‘clean’ sample).

MPGDs based radiation imaging devices and applications

Este trabalho descreve o desenvolvimento e aplicação de sistemas baseados em detetores gasosos microestruturados, para imagiologia de fluorescência de raios-X por dispersão em energia (EDXRF). A técnica de imagiologia por fluorescência de raios-X assume-se como uma técnica poderosa, não-destrutiva, em análises da distribuição espacial de elementos em materiais. Os sistemas para imagiologia de EDXRF desenvolvidos são constituídos por: um tubo de raios-X, usado para excitar os elementos da amostra; um detetor gasoso microestruturado; e uma lente pinhole que foca a radiação de fluorescência no plano do detetor formando assim a imagem e permitindo a sua ampliação. Por outro lado é estudada a influência do diâmetro da abertura do pinhole bem como do fator de ampliação obtido para a imagem, na resolução em posição do sistema. Foram usados dois conceitos diferentes de detetores gasosos microestruturados. O primeiro, baseado na microestrutura designada por 2D-Micro-Hole & Strip Plate (2D-MHSP) com uma área ativa de 3 3 cm2, enquanto que o segundo, baseado na estrutura 2D-Thick-COBRA (2D-THCOBRA) apresenta uma área ativa de deteção de 10 10 cm2. Estes detetores de raios-X de baixo custo têm a particularidade de funcionar em regime de fotão único permitindo a determinação da energia e posição de interação de cada fotão que chega ao detetor. Deste modo permitem detetar a energia dos fotões X de fluorescência, bem como obter imagens 2D da distribuição desses fotões X para o intervalo de energias desejado. São por isso adequados a aplicações de imagiologia de EDXRF. Os detetores desenvolvidos mostraram resoluções em energia de 17% e 22% para fotões incidentes com uma energia de 5.9 keV, respectivamente para o detetor 2D-MHSP e 2D-THCOBRA e resoluções em posição adequadas para um vasto número de aplicações. Ao longo deste trabalho é detalhado o desenvolvimento, o estudo das características e do desempenho de cada um dos detetores, e sua influência na performance final de cada sistema proposto. Numa fase mais avançada apresentam-se os resultados correspondentes à aplicação dos dois sistemas a diversas amostras, incluindo algumas do nosso património cultural e também uma amostra biológica.

Therapeutics bioconjugates: evaluation of iminoboronates as payload delivery system for cancer

The advent of bioconjugation impacted deeply the world of sciences and technology. New biomolecules were found, biological processes were understood, and novel methodologies were formed due to the fast expansion of this area. The possibility of creating new effective therapies for diseases like cancer is one of big applications of this now big area of study. Off target toxicity was always the problem of potent small molecules with high activity towards specific tumour targets. However, chemotherapy is now selective due to powerful linkers that connect targeting molecules with affinity to interesting biological receptors and cytotoxic drugs. This linkers must have very specific properties, such as high stability in plasma, no toxicity, no interference with ligand affinity nor drug potency, and at the same time, be able to lyse once inside the target molecule to release the therapeutic warhead. Bipolar environments between tumour intracellular and extracellular medias are usually exploited by this linkers in order to complete this goal. The work done in this thesis explores a new model for that same task, specific cancer drug delivery. Iminoboronates were studied due to its remarkable selective stability towards a wide pH range and endogenous molecules. A fluorescence probe was design to validate this model by creating an Off/On system and determine the payload release location in situ. A process was optimized to synthetize the probe 8-(1-aminoethyl)-7-hydroxy-coumarin (1) through a reductive amination reaction in a microwave reactor with 61 % yield. A method to conjugate this probe to ABBA was also optimized, obtaining the iminoboronate in good yields in mild conditions. The iminoboronate model was studied regarding its stability in several simulated biological environments and each half-life time was determined, showing the conjugate is stable most of the cases except in tumour intracellular systems. The construction of folate-ABBA-coumarin bioconjugate have been made to complete this evaluation. The ability to be uptaken by a cancer cell through endocytosis process and the conjugation delivery of coumarin fluorescence payload are two features to hope for in this construct.

Pulsed laser deposition of YBa2Cu3O7-[delta]/PrBa2Cu3O7-[delta] /

The process of depositing thin films by the use of pulsed laser deposition (PLD) has become a more widely used technique for the growth of substances in a thin film form. Pulsed laser deposition allows for the stoichiometric film growth of the target which is of great significance in the deposition of High Temperature Superconducting materials. We will describe a system designed using an excimer laser and vaccum chamber in which thin films and superlattices of YBa2Cuj07_i, PrBa2Cu307_i, and YBajCujOr-j/ PrBajCusOr-^ were deposited on SrTiOs. Results of resistivity measurements using the four probe technique will be shown.

Effets des nanoparticules d'argent sur les processus enzymatiques des sols

Les nanomatériaux sont de plus en plus présents dans les produits consommables du quotidien. L’argent est le métal le plus utilisé en nanotechnologie pour ses propriétés antimicrobiennes. Par différentes voies d’entrée, les nanoparticules d’argent (nAg) se retrouvent dans l’environnement en quantité significative, notamment dans les sols suite à la valorisation agricole des biosolides municipaux. Il est prévu qu’une interaction négative sur la communauté microbienne terrestre ait des répercussions sur la fertilité du sol et les processus biogéochimiques. Les mesures de l’activité enzymatique ont déjà montré leur efficacité et leur sensibilité dans la détection d’une perturbation physique et chimique du sol. Les effets potentiels des nAg sur l’écosystème terrestre ont été évalués en mesurant l’activité des enzymes β-D-glucosidase (EC 3.2.1.21), leucine-aminopeptidase (EC 3.4.11.1), phosphomonoesterase (EC 3.1.3) et arylsulfatase (EC 3.1.6.1) intervenant dans les cycles des éléments essentiels C, N, P et S, respectivement. L’activité enzymatique est mesurée à l’aide d’une technique basée sur la fluorescence qui requière des substrats synthétiques liés à un fluorophore. Un sol de type sableux a été échantillonné au Campus Macdonald de l’Université McGill (Sainte-Anne-de-Bellevue, Qc) puis exposé aux nAg (taille ~20 nm) ou à la forme ionique Ag+ (Ag-acetate) à des concentrations nominales de 1,25 × 10-3, 1,25 × 10-2, 0,125, 1,25, 6,25 et 31,25 mg Ag kg-1 sol. De plus, le rôle de la matière organique (MO) a été évalué en effectuant un amendement du sol avec un compost de feuilles. Pour mieux comprendre les effets observés, des analyses de spéciation de l’Ag ont été réalisées. Les concentrations en Ag dissous ont été déterminées après filtration à travers des membranes de 0,45 µm ou de 3 kDa (~1 nm, ultrafiltration) pour séparer la phase particulaire des ions dissous. De façon générale, une inhibition de l’activité enzymatique a été observée pour les 4 enzymes en fonction de l’augmentation de la concentration en Ag (totale et dissoute) mais elle est significativement moins importante avec l’ajout de la MO. Les résultats suggèrent que l’inhibition de l’activité des enzymes aux faibles expositions aux nAg est due aux nanoparticules puisqu’une très faible fraction des nAg est réellement dissoute et aucun effet significatif n’a été observé pour les sols traités à des concentrations similaires en Ag+. Par contre, les effets mesurés aux concentrations plus élevées en nAg sont semblables aux expositions à l’Ag+ et suggèrent un rôle de l’Ag colloïdale dans l’inhibition du processus enzymatique des sols.

Growth and Characterisation of Radio Frequency Magnetron Sputttered Indium Tin Oxide Thin Films

The increasing interest in the interaction of light with electricity and electronically active materials made the materials and techniques for producing semitransparent electrically conducting films particularly attractive. Transparent conductors have found major applications in a number of electronic and optoelectronic devices including resistors, transparent heating elements, antistatic and electromagnetic shield coatings, transparent electrode for solar cells, antireflection coatings, heat reflecting mirrors in glass windows and many other. Tin doped indium oxide (indium tin oxide or ITO) is one of the most commonly used transparent conducting oxides. At present and likely well into the future this material offers best available performance in terms of conductivity and transmittivity combined with excellent environmental stability, reproducibility and good surface morphology. Although partial transparency, with a reduction in conductivity, can be obtained for very thin metallic films, high transparency and simultaneously high conductivity cannot be attained in intrinsic stoichiometric materials. The only way this can be achieved is by creating electron degeneracy in a wide bandgap (Eg > 3eV or more for visible radiation) material by controllably introducing non-stoichiometry and/or appropriate dopants. These conditions can be conveniently met for ITO as well as a number of other materials like Zinc oxide, Cadmium oxide etc. ITO shows interesting and technologically important combination of properties viz high luminous transmittance, high IR reflectance, good electrical conductivity, excellent substrate adherence and chemical inertness. ITO is a key part of solar cells, window coatings, energy efficient buildings, and flat panel displays. In solar cells, ITO can be the transparent, conducting top layer that lets light into the cell to shine the junction and lets electricity flow out. Improving the ITO layer can help improve the solar cell efficiency. A transparent ii conducting oxide is a material with high transparency in a derived part of the spectrum and high electrical conductivity. Beyond these key properties of transparent conducting oxides (TCOs), ITO has a number of other key characteristics. The structure of ITO can be amorphous, crystalline, or mixed, depending on the deposition temperature and atmosphere. The electro-optical properties are a function of the crystallinity of the material. In general, ITO deposited at room temperature is amorphous, and ITO deposited at higher temperatures is crystalline. Depositing at high temperatures is more expensive than at room temperature, and this method may not be compatible with the underlying devices. The main objective of this thesis work is to optimise the growth conditions of Indium tin oxide thin films at low processing temperatures. The films are prepared by radio frequency magnetron sputtering under various deposition conditions. The films are also deposited on to flexible substrates by employing bias sputtering technique. The films thus grown were characterised using different tools. A powder x-ray diffractometer was used to analyse the crystalline nature of the films. The energy dispersive x-ray analysis (EDX) and scanning electron microscopy (SEM) were used for evaluating the composition and morphology of the films. Optical properties were investigated using the UVVIS- NIR spectrophotometer by recording the transmission/absorption spectra. The electrical properties were studied using vander Pauw four probe technique. The plasma generated during the sputtering of the ITO target was analysed using Langmuir probe and optical emission spectral studies.

Anomalous variation of thermal lens signal with concentration from rhodamine B in methanol solution

Thermal lens signals in solutions of rhodamine B laser dye in methanol are measured using the dual beam pump-probe technique. The nature of variations of signal strength with concentration is found to be different for 514 and 488 nm Ar + laser excitations. However, both the pump wavelengths produce an oscillatory type variation of thermal lens signal amplitude with the concentration of the dye solution. Probable reasons for this peculiar behaviour (which is absent in the case of fluorescent intensity) are mentioned.