Influence of the Presence of Choline Chloride on the Classical Mechanism of “Gelatinization” of Starch

The aim of this research is to contribute to a better understanding the destructuration of three native starches and a wheat flour in mixtures of water and choline chloride. Model systems have thus been defined to allow a better approach to hydrothermic transformations related to the interactions between choline chloride and starch. We have observed that choline chloride has an impact on the gelatinization of starch which corresponds to the stabilizing salts phenomenon. The depolymerization and dissolution of the starch have also been demonstrated and can there dominate the gelatinization. However, the results obtained in X-ray diffraction by heating cell have shown that the exotherm which appeared was not only related to the depolymerization of the starch, but that a stage of crystalline rearrangement of the starch coexisted with this phenomenon.

IntraMolecular Diels–Alder Reactions of Vinylarenes and Alkynyl Arenes (the IMDAV Reaction)

This comprehensive review summarizes the published literature data concerning the intramolecular Diels–Alder reactions of vinylarenes (the IMDAV reaction) and alkynyl arenes from 1970 to 2019, and covers mainly intramolecular [4+2] cycloaddition reactions of vinyl- or acetylene-substituted furans, thiophenes, pyrroles, indoles, imidazoles, benzenes, and naphthalenes, in which the unsaturated substituent is linked directly to an arene moiety. The selected area of the Diels–Alder reaction differs from other forms of [4+2] cycloadditions due to the uniqueness of the diene fragment, which, along with an exocyclic multiple bond, includes the double bond of an aromatic or heteroaromatic nucleus in its system. Thus, during the formation of the [4+2] cycloaddition intermediate, the aromaticity of furan, thiophene and even benzene rings is broken, leading, as a rule, to the formation of heterocyclic structures rarely accessible by other methods, in contrast to the majority of intermolecular Diels–Alder reactions, with the highest degree of chemo-, regio-, and diastereoselectivity. Therefore, the IMDAV approach is often used for the synthesis of naturally occurring and bioactive molecules, which are also discussed in this review alongside other applications of this reaction. Whenever possible, we have tried to avoid examples of radical, photochemical, oxidative, precious-metal-complex-catalyzed cyclizations and other types of formal [4+2] cycloadditions, focusing on thermal Diels–Alder reactions in the first step, according to the classical mechanism. The second stage of the process, aromatization, is unique for many initial substrates, and hence considerable attention in this overview is given to the detailed description of the reaction mechanisms.1 Introduction2 IMDAV Reactions of Vinylfurans2.1 Alkenes as Internal Dienophiles2.2 Alkynes and Allenes as Internal Dienophiles3 IMDAV Reactions of Vinylthiophenes3.1 Alkenes as Internal Dienophiles3.2 Alkynes as Internal Dienophiles4 IMDAV Reactions of Vinylbenzothiophenes5 IMDAV Reactions of Vinylpyrroles6 IMDAV Reactions of Vinylindoles6.1 Alkenes as Internal Dienophiles6.2 Alkynes as Internal Dienophiles7 IMDAV Reactions of Styrenes and Vinylnaphthalenes7.1 Alkenes as Internal Dienophiles7.2 Alkynes as Internal Dienophiles7.3 Alkynes as Internal Dienophiles in Aryl Acetylenes (the Intramolecular Dehydro Diels–Alder Reaction)8 IMDAV Reactions of Vinylimidazoles, Vinylisoxazoles and Vinylpyridines9 Conclusion10 Abbreviations

Kinematic Analysis and Design of a Six-Degrees of Freedom 3-RRPS Mechanism for Bone Reduction Surgery

Robot-assisted bone reduction surgery consists in using robots to reposition the bone fragments into their original place prior to fracture healing. This study presents the application of a 3-RRPS augmented tripod mechanism with six degrees-of-freedom for longitudinal bone reduction surgery. First, the inverse and forward kinematic models of the mechanism are investigated. Particularly, the forward kinematic is solved by applying Sylvester's dialytic method. Second, the velocity model is studied and its singular configurations are identified. The workspace of the 3-RRPS mechanism is then outlined and compared with the Stewart platform, which is a classical mechanism for the targeted application. The results show that this mechanism provides a larger workspace, especially its rotation angle about the vertical axis, which is an important aspect in the bone reduction. A series of simulations on the numerical and graphic software is performed to verify the entire analysis of the parallel mechanism. A physiguide and mscadams software are used to carry out a simulation of a real case of femur fracture reduction using the proposed mechanism to validate its suitability. Finally, a robotic prototype based on the mechanism is manufactured and experimented using an artificial bone model to evaluate the feasibility of the mechanism.

Nonclassical nucleation of protein mesocrystals via oriented attachment

Self-assembly of proteins holds great promise for the bottom-up design and production of synthetic biomaterials. In conventional approaches, designer proteins are pre-programmed with specific recognition sites that drive the association process towards a desired organized state. Although proven effective, this approach poses restrictions on the complexity and material properties of the end-state. An alternative, hierarchical approach that has found wide adoption for inorganic systems, relies on the production of crystalline nanoparticles which in turn become the building blocks of a next-level assembly process driven by oriented attachment (OA). As it stands, OA has not been observed for proteins. Here we employ cryoEM in the high nucleation rate limit of protein crystals and map the self-assembly route at molecular resolution. We observe the initial formation of facetted nanocrystals that merge lattices by means of OA alignment well before contact is made, satisfying non-trivial symmetry rules in the process. The OA mechanism yields crystal morphologies that are not attainable through conventional crystallization routes. Based on these insights we revisit a system of protein crystallization that has long been classified as non-classical, but our data is in direct conflict with that conclusion supporting a classical mechanism that implicates OA. These observations raise further questions about past conclusions for other proteins and illustrate the importance of maturation stages after primary nucleation has taken place.

Liquid seal for compact micropiston actuation at the capillary tip

Actuators at the tip of a submillimetric catheter could facilitate in vivo interventional procedures at cellular scales by enabling tissue biopsy and manipulation or supporting active micro-optics. However, the dominance of frictional forces at this scale makes classical mechanism problematic. Here, we report the design of a microscale piston, with a maximum dimension of 150 μm, fabricated with two-photon lithography onto the tip of 140-μm-diameter capillaries. An oil drop method is used to create a seal between the piston and the cylinder that prevents any leakage below 185-mbar pressure difference while providing lubricated friction between moving parts. This piston generates forces that increase linearly with pressure up to 130 μN without breaking the liquid seal. The practical value of the design is demonstrated with its integration with a microgripper that can grasp, move, and release 50-μm microspheres. Such a mechanism opens the way to micrometer-size catheter actuation.

Analysis of the 2D motion of a monolith platform mechanism

This paper summarises the results of motion analysis of a platform mechanism with a monolith design. A four-link planar mechanism was engineered in which the platform positioning is effected via one passive link and two eccentric links actuated by stepper motors. The prototype of the device was fabricated following a computation procedure based on the classical mechanism and machine theory and FEM calculations. Testing performed on the model and on the real device revealed the presence of two points on the platform for which the resultant of two independent perpendicular displacements implemented by two stages can be obtained for small values of angular displacement.

Kinematic analysis and evaluation of a hybrid mechanism for computer assisted bone reduction surgery

In severe fracture cases, a bone can be separated into two fragments and it is mandatory to reposition the bone fragments together. This type of surgery is called “bone reduction surgery”. Originally, the operation consisted in manipulating the bones fragments by hand in open surgery. The most advanced technique relies on robotic manipulators providing higher precision and stability. A new mechanical architecture is proposed based on a 3-RPS tripod parallel mechanism combined with a Double Triangular Planar parallel mechanism. Its kinematic and velocity models are calculated and the parasitic motion generated by the tripod mechanism is considered in the final result. The workspace it can generate is compared to the Stewart manipulator, which is a classical mechanism for the targeted application. The use of a robotic manipulator is due to be part of an entire surgical procedure involving a pre-operative simulation software dedicated to pre-planning reduction surgery, namely PhysiGuide. It is used to measure the kinematic associated with bone fragments manipulation and transfer it to the robot during the intra-operative phase. Simulations are then performed based on a real patient's fracture images showing the suitability of the present mechanism with bone reduction surgery.

Carbonate characteristics of the Gulf of Anadyr waters

The first field data describing the dynamics of the carbonate system, aragonite saturation state, and CO2 fluxes between the ocean and the atmosphere in the Gulf of Anadyr in the late autumn season are presented. It was established that during this period the gulf waters absorbed carbon dioxide from the atmosphere at a rate of -22,5 mmol m‑2 day‑1, which determined the “classical” mechanism of seawater acidification due to uptake of excess atmospheric CO2. In general, surface waters of the gulf were supersaturated with respect to aragonite. The exception was the highly dynamic region of Anadyr Strait, where the vertical distribution of the investigated parameters was homogeneous, the surface waters were close to equilibrium with respect to aragonite, and CO2 flux was directed to the atmosphere. Bottom waters of the gulf, in contrast, were characterized by significant seasonal corrosivity with respect to aragonite due primarily to remineralization of organic matter to CO2. It was shown that during the late fall relatively salty and acidic, quasi-equilibrium with respect to aragonite, and oxygen-depleted waters with high concentrations of nutrients and CO2 have been entered the Chirkov Basin and further the Arctic Ocean with the Navarin current.

Axisymmetric Balance Dynamics of Tropical Cyclone Intensification and Its Breakdown Revisited

This paper revisits the evolution of an idealized tropical cyclone–like vortex forced by a prescribed distribution of diabatic heating in the context of both inviscid and frictional axisymmetric balance dynamics. Prognostic solutions are presented for a range of heating distributions, which, in most cases, are allowed to contract as the vortex contracts and intensifies. Interest is focused on the kinematic structure and evolution of the secondary circulation in physical space and on the development of regions of symmetric and static instability. The solutions are prolonged beyond the onset of unstable regions by regularizing the Sawyer–Eliassen equation in these regions, but for reasons discussed, the model ultimately breaks down. The intensification rate of the vortex is essentially constant up to the time when regions of instability ensue. This result is in contrast to previous suggestions that the rate should increase as the vortex intensifies because the heating becomes progressively more “efficient” when the local inertial stability increases. The solutions provide a context for reexamining the classical axisymmetric paradigm for tropical cyclone intensification in the light of another widely invoked intensification paradigm by Emanuel, which postulates that the air in the eyewall flows upward and outward along sloping absolute angular momentum (M) surfaces after it exits the frictional boundary layer. The conundrum is that the classical mechanism for spinup requires the air above the boundary layer to move inward while materially conserving M. Insight provided by the balance solutions helps to refine ideas for resolving this conundrum.