Biomimetic studies on polyenes

The crispatenes and SNF4435 C&D are complex polypropionate derived natural products. The core structures of these compounds along with a complex unnatural structure can be easily prepared from a common polyene precursor simply by variation of the reaction conditions. The reaction pathways provide insight into the biosynthesis of these complex natural products.     

Valence instabilities, phase transitions, and abrupt lattice expansion at 5 K in the YbGaGe system

The powder synchrotron X-ray diffraction technique was used to study the thermal expansion behavior of the mixed valence layered compound, YbGa1.05Ge0.95 in the temperature range 3-1123 K. A surprising abrupt isosymmetric phase transition, accompanied by a dramatic volume increase (negative thermal expansion), was found at 5 K induced by a sudden Yb valence transition from +(2 + epsilon) toward +2. At high temperatures, the material undergoes a transformation to a highly disordered structure until it eventually collapses at 1123 K to a structure with isovalent Yb ions and flat Ga/Ge planes (AlB2 type).     

Gold nanoparticles stabilized by modified halloysite nanotubes for catalytic applications

A highly sustainable prototype of a flow system based on gold nanoparticles (4.2 nm) supported on thiol‐functionalized halloysite nanotubes (HNTs) was developed for catalytic applications. The catalytic performances were evaluated using the reduction of 4‐nitrophenol to 4‐aminophenol as a model system. Under the best experimental conditions (0.0001 mol%, 1.97 × 10^?8 mg of Au nanoparticles), an impressive apparent turnover frequency value up to 2 204 530 h^?1 was achieved and the halloysite‐based catalyst showed full recyclability even after ten cycles. The high catalytic activity confirms the importance of the use of HNTs as support for Au nanoparticles that can exert a synergistic effect both as medium for transfer of electrons from borohydride ions to 4‐nitrophenol and by modulating interfacial electron transfer dynamics. With the application of flow technology, the obtained heterogeneous HNT@Au catalyst was fully recovered and reused for at least one month.     

Variational Problems with Symmetries: A Pfaffian System Approach

Reduction methods for completely integrable Pfaffian Systems with symmetry are applied to variational problems, providing analogues of the Arnold?CLiouville Theorem and Marsden?CWeinstein reduction in the Lagrangian setting. A?generalization of the Mishchenko?CFomenko Theorem for non Abelian integrability is given in terms of solvable structures.     

7-Isopentenyloxycoumarin: What Is New across the Last Decade

7-Isopentenyloxycoumarin is among the most widespread naturally occurring prenyloxy umbelliferone derivatives. This secondary metabolite of mixed biosynthetic origin has been typically isolated from plants belonging to several genera of the Rutaceae and Apiaceae families, comprising widely used medicinal plants and in general plants with beneficial effects on human welfare, as well as edible fruits and vegetables. Although known for quite a long time (more than 50 years), only in the last two decades has this natural compound been revealed to exert powerful and promising pharmacological properties, such as active cancer chemopreventive, antibacterial, antiprotozoal, antifungal, anti-inflammatory, neuroprotective, and antioxidant properties, among the activities best outlined in the recent literature. The aim of this comprehensive miniature review article is to detail the novel natural sources and the effects described during the last decade for 7-isopentenyloxycoumarin and what has been reported on the mechanisms of action underlying the observed biological activities of this oxyprenylated secondary metabolite. In view of the herein described data, suggestions on how to address future research on the abovementioned natural product and structurally related derivatives in the best ways according to the authors will be also provided.     

Cellulose-based fiber spinning processes using ionic liquids

Cellulose - Cellulose, a natural, renewable, and environment friendly biopolymer, has been considered as a sustainable feedstock in the near future. However, only 0.3% of cellulose is today...     

Autologous Materials in Regenerative Dentistry: Harvested Bone,Platelet Concentrates and Dentin Derivates

The jawbone is a peculiar type of bone tissue, unique for its histological, anatomical and physiological characteristics. Therefore, a defect in the maxilla or in the mandible, because of pathological sequelae is difficult to prevent and to restore. Several biomaterials have been and are currently being developed to respond to the demands of regenerative medicine. A specific group of biomaterials used in regenerative dentistry is represented by the autologous materials. Platelet concentrates harvested bone and dentin derivates are indeed used in an attempt to minimise the alveolar resorption or in vertical ridge augmentation procedures or in sinus lift interventions. The aim of this review is to examine the properties of the above-listed materials, to compare them and to indicate eventual clinical applications.