Click Chemistry for the Assembly of Gold Nanorods and Silver Nanoparticles

The synthesis of compact nanostructures with highly integratedfunctionalities through the controlled assembly ofnanoparticles (NPs) is potentially of broad interest in researchfields such as drug delivery, multimodal imaging, andelectronic devices. This concept seems to be particularlyimportant in view of the emerging concept of theranostic,according to which both therapeutic and diagnostic capabilitiescan be present in two nanostructures. A key step, however,is how to combine individual nanostructures withoutloosing the original properties

Fractional smoothness and applications in finance

This overview article concerns the notion of fractional smoothness of random variables of the form $g(X_T)$, where $X=(X_t)_{t\in [0,T]}$ is a certain diffusion process. We review the connection to the real interpolation theory, give examples and applications of this concept. The applications in stochastic finance mainly concern the analysis of discrete time hedging errors. We close the review by indicating some further developments.Comment: Chapter of AMAMEF book. 20 pages

A Hedged Monte Carlo Approach to Real Option Pricing

In this work we are concerned with valuing optionalities associated to invest or to delay investment in a project when the available information provided to the manager comes from simulated data of cash flows under historical (or subjective) measure in a possibly incomplete market. Our approach is suitable also to incorporating subjective views from management or market experts and to stochastic investment costs. It is based on the Hedged Monte Carlo strategy proposed by Potters et al (2001) where options are priced simultaneously with the determination of the corresponding hedging. The approach is particularly well-suited to the evaluation of commodity related projects whereby the availability of pricing formulae is very rare, the scenario simulations are usually available only in the historical measure, and the cash flows can be highly nonlinear functions of the prices.Comment: 25 pages, 14 figure

In Vivo Assessment of Cold Adaptation in Insect Larvae by Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy

Background Temperatures below the freezing point of water and the ensuing ice crystal formation pose serious challenges to cell structure and function. Consequently, species living in seasonally cold environments have evolved a multitude of strategies to reorganize their cellular architecture and metabolism, and the underlying mechanisms are crucial to our understanding of life. In multicellular organisms, and poikilotherm animals in particular, our knowledge about these processes is almost exclusively due to invasive studies, thereby limiting the range of conclusions that can be drawn about intact living systems. Methodology Given that non-destructive techniques like 1H Magnetic Resonance (MR) imaging and spectroscopy have proven useful for in vivo investigations of a wide range of biological systems, we aimed at evaluating their potential to observe cold adaptations in living insect larvae. Specifically, we chose two cold-hardy insect species that frequently serve as cryobiological model systems–the freeze-avoiding gall moth Epiblema scudderiana and the freeze-tolerant gall fly Eurosta solidaginis. Results In vivo MR images were acquired from autumn-collected larvae at temperatures between 0°C and about -70°C and at spatial resolutions down to 27 µm. These images revealed three-dimensional (3D) larval anatomy at a level of detail currently not in reach of other in vivo techniques. Furthermore, they allowed visualization of the 3D distribution of the remaining liquid water and of the endogenous cryoprotectants at subzero temperatures, and temperature-weighted images of these distributions could be derived. Finally, individual fat body cells and their nuclei could be identified in intact frozen Eurosta larvae. Conclusions These findings suggest that high resolution MR techniques provide for interesting methodological options in comparative cryobiological investigations, especially in vivo

Comparison of the optoacoustic signal generation efficiency of different nanoparticular contrast agents

Optoacoustic imaging represents a new modality that allows noninvasive in vivo molecular imaging with optical contrast and acoustical resolution. Whereas structural or functional imaging applications such as imaging of vasculature do not require contrast enhancing agents, nanoprobes with defined biochemical binding behavior are needed for molecular imaging tasks. Since the contrast of this modality is based on the local optical absorption coefficient, all particle or molecule types that show significant absorption cross sections in the spectral range of the laser wavelength used for signal generation are suitable contrast agents. Currently, several particle types such as gold nanospheres, nanoshells, nanorods, or polymer particles are used as optoacoustic contrast agents. These particles have specific advantages with respect to their absorption properties, or in terms of biologically relevant features (biodegradability, binding to molecular markers). In the present study, a comparative analysis of the signal generation efficiency of gold nanorods, polymeric particles, and magnetite particles using a 1064 nm Nd:YAG laser for signal generation is described

Developing a high-resolution photoacoustic microscopy platform

Existing optical imaging modalities including confocal microscopy, two-photon microscopy and optical coherence tomography do not image optical absorption directly. Photoacoustic imaging (also called optoacoustic imaging) is a new promising modality in biomedical imaging integrating the benefits of optics and acoustics. When biological tissue is irradiated with ultrashort laserpulses with durations of a few nanoseconds the light is absorbed according to the local absorption properties and is converted successively into heat and pressure by means of the thermoelastic effect. The motivation for photoacoustic imaging is to combine ultrasonic resolution with high contrast due to light absorption depending on the physiology of the examined biological tissue. The resolution of conventional photoacoustic imaging systems is not sufficient for in-vitro measurements of small tissue samples or individual cells. In this work, we present a high-resolution photoacoustic microscopy pla tform based on the SASAM acoustic microscope (Kibero GmbH, Germany) that allows high resolution imaging on living cells. The system based on an inverted optical microscope consists of a laser source for optical multi wavelength excitation (diode- or solidstate- laser) which emits nanosecond laser pulses with a wavelength in the near infrared spectrum (optical window). We use different ultrasound transducers in the frequency range up to 300 MHz for detection of the pressure transients. Read out electronics combined with reconstruction algorithms for photoacoustic imaging allows converting the recorded signals into a spatial representation of the absorbed energy. Furthermore, the possibility of using nanoscaled contrast agents for photoacoustic contrast enhancement is presented. In addition to the photoacoustic imaging mode all common optical modalities are implemented. Pure acoustic imaging and optical transmission mode are used for reference imaging

Visualization of apoptotic cells using scanning acoustic microscopy and high frequency ultrasound

The goal of this project is to investigate changes in the acoustical properties of cells undergoing cell death for the development of a method for tissue apoptosis detection using high frequency ultrasound (10-60 MHz). A scanning acoustic microscope (SAM) was used for visualization of individual cells undergoing apoptosis (SASAM, Fraunhofer IBMT, Germany). The use of the SAM offers high resolution (1 m spot size) and therefore enables the exploration of acoustical properties of the cell nucleus. Cells were labeled with H33342 and DIOC 3(5) for visualizing condensed chromatin and membranes in fluorescence microscopy. In addition the same cell lines interrogated microscopically were investigated using high frequency ultrasound Recorded radio frequency (rf) data were analyzed using ultrasound spectroscopy. Integrated backscatter coefficients and attenuation values were computed for two cell lines: HeLa and MDCK. Both cell lines responded to the applied chemotherapeutic age nt by apoptosis, assessed by fluorescence microscopy. Acoustical and optical microscopy using the SASAM system clearly enabled a differentiation between apoptotic cells and cells not responding to the treatment. Apoptotic cells displayed a higher contrast in the acoustic images and were less regular in shape. Optical images of the same cells showed nuclear condensation and membrane disruption. Spectral parameters estimated from rf ultrasound showed a 100% increase in the integrated backscatter coefficients for HeLa and MDCK. Attenuation values were increased by 50% to 70% for both cell lines as a function of treatment time. The results of this investigation provide a better understanding of changes in the acoustical properties of cells with cell death and thus to the development of a non-invasive method for measuring the treatment response of tumors using acoustic waves