Reflection anisotropy spectroscopy (RAS) is a non-destructive optical technique which can be used to measure the surface properties of sample. We use the technique to detect the optical anisotropy of rubbed polyimide thin film. Atomic force microscopy study of rubbed polyimide showed that rubbing produced microgrooves on the surface of the polyimide thin films, and the surface roughness of the polymer thin films increased slightly with the rubbing strength. Reflection anisotropy signals have been found to be generated on the surface of polyimide thin film on completion of mechanical rubbing, and will increase with an increase in the rubbing strength. We also tried to find out the correlation between RA strength of the polyimide alignment layer and pretilt angle of liquid crystal at the rubbed polyimide films.

Improving the identification ability of surfaced-immobilized nucleic acid probes for small size DNA or RNA targets, utilizing optical or electrochemical methods, has been the goal for the gene chip technology. This study focuses on new probe design for introducing hairpin structural features and locked nucleic acid modification. We use three kinds of probes (DNA-LN, DNA-HP and LNA-HP) to prepare recognition layers via self-assembly processes on a gold substrate, and utilize AFM-based nanolithography technique to produce nanofeatures to observe the stiffness changes of oligonucleotide chains resulting from the formation of rigid double stranded duplexes when target sequence hybridizes to the probe. We also monitor the topographic changes upon exposure to the single mismatched and non-complementary targets as a function of time. The results reveal LNA-HP probes exhibit the highest response to discriminating single-point mutation in the base sequence. In addition, we study the effects of salt concentration, reaction temperature and the small size on the hybridization efficiency.

Optical beam induced current (OBIC) mapping has found wide-spread applications in characterizing semiconductor devices and integrated circuitry. In this study, we have used a two-photon scanning microscope to investigate InGaN light emitting diodes (LED). The defects induced by electrostatic discharge (ESD) can be clearly identified by DC-OBIC images. Additionally, we have combined an E-O modulator and a high frequency phase sensitive lock-in amplifier to conduct time-resolved study on the dynamical properties of the LEDs. The defects also exhibit different delay time when compared with the normal parts.

During hemostatic and inflammatory responses, cell adhesion molecules play a major role in regulating the leukocytes and platelets adhesion to vascular surfaces under the hydrodynamic environment of the circulation. Selectin-ligand interactions (bonds) mediate leukocyte rolling on vascular surfaces. The molecular basis for differential ligand recognition by selectins is poorly understood. Using atomic force microscopy (AFM), the kinetics of three mutants L-selectin interacting with surrogates of PSGL-1 and PNAd, is compared with those of wild-type L-selectin. The interaction between glycoprotein Ib (GPIb) and von Willebrand Factor (VWF) mediates platelet translocation at the vascular vessel damage sites, which plays a critical role in initiating the platelets adhesion and thrombus formation. Translocation of platelets on VWF requires a shear threshold, suggesting a possible catch bond at work there. We characterized the kinetics of GPIbα interacting with VWF A1 domain, confirming the catch bond existed. Two type 2B VWD A1 mutants eliminated the catch bond and gave longer low force lifetimes. The prolonged lifetimes at low force resulted in more agglutination of platelets with A1 coated microspheres in flow. During the process of hemostasis, the size of prothrombotic ULVWF affects the affinity of VWF to platelets bearing GPIbα on the membrane. ADAMTS13 has been identified and characterized as a multi-domain metalloprotease that regulate the size of ULVWF. We studied how force regulated the binding and cleavage of ADAMTS13 on VWF. We found the cleavage effects could only be observed after the catastrophic structural change of A1A2A3. The unfolding exposed the ADAMTS13 cleavage site and favored the cleavage. Two protocols using different stretching molecules (GPIbα and CR1) and A1A2A3 immobilization methods revealed the cleavage effects diminished with increasing stretching force. This study elucidated mechanisms of the binding kinetics of L-selectin with different structure components from PSGL-1 and PNAd by structural variants. It also provided new insights into our current knowledge of the dynamic adhesion and regulation of GPIbα-VWF interaction in vivo. Using single molecule method, the chemical catalytic reaction between enzyme and substrate has been targeted. These results help us understand this important enzyme-substrate interaction involved in the hemostasis.

The rapid growth of the microelectronics industry in the last decades made it possible to produce structures in the sub-micrometer scale on silicon chips and to reach an integration scale under 100 nm. Decreasing the size and increasing the complexity of these structures make a control of quality and defects investigation more difficult. During a long time ultrasound devices are being used for nondestructive investigation of materials, like ultrasound microscopes, scanning photo-acoustic microscopes or scanning electron-acoustic microscopes, where acoustic waves are generated by acoustic transducers, focused laser or electron beams, respectively. The aim of this work is to investigate more precisely the acoustic wave generation by pulsed and periodically modulated ion beams in different solid materials depending on the beam parameters and to demonstrate the possibility to apply an intensity modulated focused ion beam (FIB) for acoustic emission and for nondestructive investigation of the internal structure of materials on a microscopic scale. The combination of a FIB and an ultrasound microscope in one device can provide the opportunity of nondestructive investigation, production and modification of micro- and nanostructures simultaneously. The FIB spot size in modern systems is comparable with that of a focused electron beam and the penetration depth of ions with energy of 20-60 keV is lower than 100 nm. This makes it possible to reach a sub-micrometer resolution of a scanning ion acoustic microscope. On the other hand side a FIB with energy of 20-60 keV is a good tool which can be used for the fabrication of nanostructures using ion milling, implantation or ion beam assisted deposition techniques. The bulk ultrasound emission in a solid was investigated using a pulsed high energy ion beam focused on aluminum, copper, iron and silicon samples. Oxygen, silicon and gold ion beams were applied in charge states from 1+ to 4+ with the pulse duration of 0.5 - 4 µs and an energy of 1.5 - 10 MeV. Intensity of the detected acoustic waves shows a linear dependence on the energy of the incident ions, on the ion flux as well as on the pulse duration. No influence of the ion charge and ion mass to the emission of acoustic waves was observed. The ion acoustic effect was applied for a nondestructive material inspection using intensity modulated FIB providing by the IMSA-100 FIB system with an accelerating potential of 30-35 kV. The achieved lateral resolution of this scanning ion acoustic microscope is in the micrometer range depending on the sample material and the beam modulation frequency. The resolution can be improved by increasing the frequency. The maximal modulation frequency which was obtained at IMSA-100 is about 2 MHz corresponding to lateral resolution of 4-5 µm on silicon. Using this microscope, some images of integrated microstructures on a silicon chip were obtained using the lock-in technique for filtering of the signal from the noise and increasing of the total imaging time. The possibility to visualize near sub-surface structure was demonstrated. Due to the strong sputtering effect and the long time of irradiation the imaged structures were significantly damaged. Si2+, Ge2+, Ga+ and Au+ ions were used. All these ions are quite heavy and have high sputtering coefficients. Long-time imaging improves the quality of acoustic images, i. e. the signal-to-noise ratio is reduced with the square root from the pixel time, but leads to significant erosion of the imaged structure.

<p>A part of the Ph.D. project focused on growth and characterization of metal multilayers is presented in this licentiate thesis. The main interest in carrying out this research is to develop highly reflective normal-incidence condenser mirrors for soft X-ray microscopy studies in the water window (λ=2.4-4.2 nm) wavelength regime.</p><p>Transition metals like Sc, Ti V, etc. have been considered because of the presence of their 2p-absorption edges within the water window. An anomalous dispersion at absorption edges has been utilized to get enhanced reflectance of soft X-rays. Since a single surface exhibits a very poor X-ray reflectivity, Cr/Sc, Cr/Ti, and Ni/V multilayers were grown in order to coherently add many reflections from several interfaces. The selection of Cr and Ni, as spacer layer, was made on the basis of their X-ray optical contrasts with the above-mentioned transition metals. The multilayer design, i.e., the individual layer thicknesses and the total number of bilayers, directly influences the resultant reflectance and careful determination was therefore made with the aid of computer simulations.</p><p>All multilayers were grown on chemically cleaned Si substrates by ion-assisted dual target magnetron sputtering under high vacuum (~10^-7 Torr) conditions. The effect of low and high ion-flux bombardment of low energy (<50 eV) Ar ions, on growing surfaces was studied for all material systems. Furthermore, a two-stage deposition of each individual layer with modulated ion-energies was applied in order to obtain smooth and abrupt interfaces with as small intermixing as possible. Ion-surface interactions were also theoretically considered for estimating an appropriate ion-flux and ion-energy range desired for sufficient ad-atom mobilities.</p><p>X-ray reflectivity and transmission electron microscopy have been the main probes for multilayer characterization in this work. For the Cr/Ti multilayer designed for normal incidence and grown with optimized two-stage ion-energy modulation, a peak reflectance of 2.1% was achieved at the Ti-2p absorption edge (λ=2.74 nm). For a multilayer mirror designed for the Brewster angle a maximum reflectance of 4.3% was accomplished. These measurements were made at the synchrotron radiation source BESSY in Berlin. Specular reflectivity and diffuse scattering scans were utilized for quantitative and qualitative analysis of the vertical and lateral structure of the multilayers. At-wavelength measurements of a series of Cr/Ti multilayers revealed the accumulation of roughness with increasing number of bilayers (N>100) for this material system. Hard X-ray reflectivity and diffractometry were used for quality checks of the multilayers for rapid feedback to the deposition. In-situ annealing using hard X-ray reflectivity was also performed to assess the thermal stability of Cr/Ti multilayers. It was found that probably due to a strong thermal diffusion the degradation of multilayers (with bilayer period of 1.37 nm) in this material system occurs just above the growth temperature (~40°C). The accumulation of a low spatial frequency "waviness" with increasing number of layers in Cr/Ti multilayers was investigated by transmission electron microscopy. The influence of process conditions on multilayer structure with different periodicities was investigated by TEM analyses of a series of three samples for each of the above-mentioned material system. The Cr/Sc multilayers have shown the most flat and abrupt interface structure without any significant roughness evolution when grown with optimum process parameters.</p> / Report code: LiU-TEK-LIC-2005:48. On the day of the defence data the status of article I was: Accepted.

<p>The aim of this diploma work is to improve selectivity and sensitivity in DNA-chips by utilizing fluorescence resonance energy transfer (FRET) between conjugated polyelectrolytes (CPEs) and fluorophores.</p><p>Leclerc and co-workers have presented successful results from studies of super FRET between fluorophore tagged DNA and a CPE during hybridisation of the double strand. Orwar and co-workers have constructed a DNA-chip using standard photo lithography creating a pattern of the hydrophobic photoresist SU-8 and cholesterol tagged DNA (chol-DNA). This diploma work will combine and modify these two ideas to fabricate a improved DNA-chip.</p><p>Immobilizing of DNA onto surface has been done by using soft lithography. Hydrophobic pattern arises from the poly(dimethylsiloxane) (PDMS) stamp. The hydrophobic pattern will attract chol-DNA that is adsorbed to the chip. Different sets of fluorophores are covalently bound to the DNA and adding CPEs to the complex will make FRET occur between CPE and bound fluorophore.</p><p>We will here show that the specificity in DNA hybridization by using PDMS patterning was high. FRET clearly occurred, especially with the CPEs as donor to the fluorophore Cy5. The intensity of FRET was higher when the fluorophore and the CPE were conjugated to the same DNA strand. The largest difference in FRET intensity between double stranded and single stranded complexes was observed with the CPE tPOMT. Super FRET has been observed but not yet fully proved. The FRET efficiency was lower with the fluorophore Alexa350 as donor compared to the Cy5/CPE complex. Most of the energy transferred from Alexa350 was extinguished by quenching.</p>

L'étude des processus intervenant dans la réalisation d'auto-assemblages moléculaires est au centre de nombreuses recherches en physique, chimie ou biologie. Dans ce cadre les organisations de surface formant des structures mono-couche constituent des systèmes particulièrement attractifs autant pour leur utilisation potentielle, que pour la simplification apparente des processus d'organisation liés à la réduction de la dimensionnalité. En outre, ces systèmes peuvent être étudiés directement à l'échelle de la molécule unique à partir de microscopes en champ proche. Ces techniques permettent également d'investiguer en temps réel les processus dynamiques intervenant au cours des processus d'assemblages. Les résultats de microscopie à effet tunnel rapportés dans cette thèse décrivent tout d'abord, et dans le détail, les mécanismes régulant l'organisation d'une famille de molécules modèles sur une surface de graphite HOPG. Dans ce cadre, nous verrons de manière quantitative les contributions respectives des interactions (ici non-covalentes\ de type Van der Waals) intervenant entre molécules et entre molécules et substrat. Cette étape constituera la base d'une étude dédiée à l'observation et la compréhension des mécanismes dynamiques intervenant à la surface de l'échantillon, au cours, et après l'organisation des molécules sur la surface de graphite. Ces deux chapitres nous permettrons de tirer les enseignements nécessaires à la réalisation en surface d'auto-assemblages nano-poreux aux propriétés originales. Ceux-ci se révèlerons en effet, suffisamment stables pour exister à température ambiante et permettre le piégeages de molécules hôtes au sein de leurs pores, tout en présentant des propriétés dynamiques particulières permettant un contrôle circonstancié et originale du déplacement en surface de ces hôtes de cavités en cavités. Nous montrerons que ces assemblages sont assimilables à des tamis moléculaires de surface dont nous décrirons le fonctionnement et les propriétés en détails. Des résultats, rapportant l'influence d'un champ optique incident sur ces monocouches de molécules, concluent cette thèse. Ils constituent une première étape en vue d'un contrôle externe et local de la dynamique des molécules en surface

Reproduction de : Thèse de docteur-ingénieur : informatique : Grenoble, INPG : 1985. / Titre provenant de l'écran-titre.

Sets of natural opening-mode fractures in sedimentary rocks may show a variety of types of aperture-size distributions. A frequently documented size distribution type, in the literature and in data presented here, is the power law. The emergence of power-law distributions of fracture aperture and length sizes has been simulated using various quasi-mechanical fracture-growth routines but models based on linear-elastic fracture mechanics rarely produce such patterns. I collected a fracture-size dataset of unprecedented size and resolution using core and field methods and scanning electron microscope-based cathodoluminescence (SEM-CL) images. This dataset confirms the prevalence of power laws with a narrow range of power-law exponents among fractures that contain synkinematic cement. Organized microfractures are ubiquitous in sandstones. A fracture-growth simulation I devised reproduces observed size-scaling patterns by distributing fracture-opening increments among actively growing fractures. The simulated opening increments have a uniform size, which can be specified; uniform opening size is consistent with observations of narrow ranges of micron-scale widths of opening increments within crack-seal texture in natural fractures. Thus power-law size scaling of natural fractures can be explained using non-power-law (uniform-sized) opening increments, arranged using rules designed to simulate the effects of cement precipitation during fracture opening. A fundamental shortcoming of previous models of fracture-set evolution is the absence of a test because only natural fracture end states, not growth histories, could be measured. Using a technique to constrain fracture timing based on fluid inclusion microthermometry and thermal history modeling, I tested growth models by reconstructing the opening history of a set of natural fractures in the Triassic El Alamar Formation in northeast Mexico. The natural-fracture data show that, consistent with simulations, new microscopic fractures are continually introduced during natural fracture pattern evolution. As well, larger fractures represent sites of concentrated reactivation, although smaller fractures may be reactivated after long periods of quiescence. The pattern likely arises through feedback between fracture growth and the mechanically adhesive effects of contemporaneous fracture cement deposition. The narrow range in power-law exponents documented among fractures can help improve estimates of meter-scale large-fracture spacing where limited fracture samples are available. / text