Theoretical study of acousto-optical coherence tomography using random phase jumps on ultrasound and light

Acousto-optical coherence tomography (AOCT) is a variant of acousto-optic imaging (also called ultrasonic modulation imaging) that makes it possible to get the z resolution with acoustic and optic continuous wave beams. We describe here theoretically the AOCT effect, and we show that the acousto-optic "tagged photons" remain coherent if they are generated within a specific z region of the sample. We quantify the z selectivity for both the "tagged photon" field and for the Lesaffre et al. [Opt. Express 17, 18211 (2009)] photorefractive signal.     

Synthesis,Properties and Applications of Biodegradable Polymers Derived from Diols and Dicarboxylic Acids: From Polyesters to Poly(ester amide)s

Poly(alkylene dicarboxylate)s constitute a family of biodegradable polymers with increasing interest for both commodity and speciality applications. Most of these polymers can be prepared from biobased diols and dicarboxylic acids such as 1,4-butanediol, succinic acid and carbohydrates. This review provides a current status report concerning synthesis, biodegradation and applications of a series of polymers that cover a wide range of properties, namely, materials from elastomeric to rigid characteristics that are suitable for applications such as hydrogels, soft tissue engineering, drug delivery systems and liquid crystals. Finally, the incorporation of aromatic units and α-amino acids is considered since stiffness of molecular chains and intermolecular interactions can be drastically changed. In fact, poly(ester amide)s derived from naturally occurring amino acids offer great possibilities as biodegradable materials for biomedical applications which are also extensively discussed.     

High-contrast fast Fourier transform acousto-optical tomography of phantom tissues with a frequency-chirp modulation of the ultrasound

We report new results on acousto-optical tomography in phantom tissues using a frequency chirp modulation and a CCD camera. This technique allows quick recording of three-dimensional images of the optical contrast with a two-dimensional scan of the ultrasound source in a plane perpendicular to the ultrasonic path. The entire optical contrast along the ultrasonic path is concurrently obtained from the capture of a film sequence at a rate of 200 Hz. This technique reduces the acquisition time, and it enhances the axial resolution and thus the contrast, which are usually poor owing to the large volume of interaction of the ultrasound perturbation.     

Charge states and optical transitions of vanadium in Bi4Ge3O12 identified by MCD and ODMR

The spectroscopic properties of V-doped Bi₄Ge₃O₁₂ have been investigated in detail via several complementary techniques bringing a series of consistent results. The optical absorption spectrum of annealed samples is strongly modified under UV-illumination and the initial state can be restored optically with visible light. Optical absorption and magnetic circular dichroism (MCD) demonstrate that a diamagnetic defect is partly destroyed during UV-illumination while a paramagnetic one is created. The latter shows a very characteristic S-shaped MCD pattern in the near-IR, which is readily assigned to the ²E→²T₂ internal transition of tetragonal V⁴⁺ centers at the Ge sites. This assignment was further confirmed by optically detected magnetic resonance (ODMR), via the change of the MCD under microwaves at 35 GHz. The g tensor of V⁴⁺ was found to be anisotropic with principal values g_||=1.81±0.03 and g=1.94±0.02. Two additional MCD bands in the visible spectral region could be attributed to V⁴⁺ via ODMR measurements. Ionization thresholds for holes (V⁵⁺) and electrons (V⁴⁺) were determined by optical absorption experiments and the V^4+/5+ donor level was positioned 1.9 eV below the conduction band. The presence of the V^4+/3+ acceptor state in the forbidden band is also suggested.     

In vitro enzymatic biodegradation of amino acid based poly(ester amide)s biomaterials

A systematic in vitro biodegradation study of regular poly(ester amide)s (PEAs) composed of naturally occurring hydrophobic alpha-amino acids, fatty diols and dicarboxylic acids was carried out in the presence of hydrolases like trypsin, alpha-chymotrypsin, and lipase. An automatic potentiometric titration method was used to examine the biodegradation property of the PEAs. Spontaneous immobilization (absorption) of the enzymes onto the PEAs films surfaces was observed. The surface immobilized enzyme not only accelerated the erosion of the PEAs but also was able to catalyze the hydrolysis of both low-molecular-weight (ATEE) and high-molecular-weight (protein) external substrates. It was found that the enzyme surface absorption process is reversible by nature. A kinetic method for a quantitative determination of the enzyme desorbed from the film surface was developed. The enzymes could also be impregnated into the PEAs to make them "self-destructive" at a target rate. A comparison of the PEAs' in vitro biodegradation data with polylactide (PDLLA) showed that PEAs exhibited a far more tendency toward enzyme catalyzed biodegradation than PDLLA.     

A survey of control strategies in chemical pulp plants

A survey of the last development of control strategies in the chemical pulp industry is presented. It does not refer to the small local control loops but only reports the philosophy with which most of the control systems for the different parts of the pulping process are designed: cooking, bleaching, recovery systems. It also outlines the recent studies about control of the whole mill production. Particular attention is paid to the different control schemes, depending especially on the outputs that are chosen, as well as on the control actions. References are also made to the mathematical models of the processes, not only because they are very useful for the design of the control, but also because they are a good indication of the state of the knowledge.