Experimental wound dressings of degradable PHA for skin defect repair

The present study reports construction of wound dressing materials from degradable natural polymers such as hydroxy derivatives of carboxylic acids (PHAs) and 3-hydroxybutyrate/4-hydroxybutyrate [P(3HB/4HB)] as copolymer. The developed polymer films and electrospun membranes were evaluated for its wound healing properties with Grafts—elastic nonwoven membranes carrying fibroblast cells derived from adipose tissue multipotent mesenchymal stem cells. The efficacy of nonwoven membranes of P(3HB/4HB) carrying the culture of allogenic fibroblasts was assessed against model skin defects in Wistar rats. The morphological, histological and molecular studies revealed the presence of fibroblasts on dressing materials which facilitated wound healing, vascularization and regeneration. Further it was also observed that cells secreted extracellular matrix proteins which formed a layer on the surface of membranes and promoted the migration of epidermal cells from the neighboring tissues surrounding the wound. The wounds under the P(3HB/4HB) membrane carrying cells healed 1.4 times faster than the wounds under the cell-free membrane and 3.5 times faster than the wounds healing under the eschar (control).The complete wound healing process was achieved at Day 14. Thus the study highlights the importance of nonwoven membranes developed from degradable P(3HB/4HB) polymers in reducing inflammation, enhancing angiogenic properties of skin and facilitating better wound healing process.     

Domino reactions of alkane dithiolates with 2,3-dichloro-1-propene in hydrazine hydrate – KOH medium

2,3-Dichloro-1-propene reacts with alkane dithiolates in hydrazine hydrate – KOH medium to produce derivatives of dithiin, dithiepin, chloropropenyl, and allenyl sulfides depending on conditions and dithiolate structure. The formation of the heterocyclic products is a result of possible domino reactions, including a substitution of an allylic chlorine atom, dehydrochlorination, and intramolecular heterocyclization.     

Evaluation of accuracy of literature gasoline blending models to predict octane numbers of gasoline blends

The gasoline blending prediction models available in the open literature: Linear method, Ethyl method, Stewart method, Zahed method, and Twu method were tested on 25 gasoline blends prepared from 14 components used by LUKOIL Neftohim Burgas (LNB) refinery to produce commercial gasoline grades. The performed tests with these models showed prediction accuracy outside of the acceptable ASTM D 2699 and ASTM D 2700 reproducibility limits. However, the LNB-modified regression model of Zahed method turned out to predict RON and MON of studied gasoline blends with accuracy equivalent to the reproducibility of the standard methods for measurement of RON and MON.     

Balancing control and flexibility in joint risk management: Lessons learned from two construction projects

Joint risk management (JRM) is an approach that highlights the importance of collaboration between the project actors in managing risk that cannot be identified at the outset of the project. Despite the recognition of the concept in the literature, the use of JRM in practice seems to be rare. Based on contingency theory, we investigate how mechanistic (control-oriented) and organic (flexibility-oriented) management systems influence the implementation of JRM in two construction projects. In the first project, the actors managed to achieve a balance between control and flexibility, which paved the way for successful JRM. The extensive use of control in the second project hampered flexibility and constrained the use of JRM. We conclude that JRM requires both control for managing risk that has been identified and flexibility for dealing with unforeseen events. When a mechanistic approach is dominant, risk management remains a formal process carried out individually rather than collaboratively.     

Cybercampuses: design issues and future directions

In recent years, the usage of 3D cyberworlds for educational purposes has increased. The metaphors behind the visual design of such cyberworlds are quite diverse, from replication of real universities, art museums and scientific labs to non-existing fictitious places. In this paper, we focus specifically on “cybercampuses”, i.e. virtual worlds representing real educational institutions such as universities and schools. Based on the results of a case study that we have performed, this paper provides an initial set of requirements for a cybercampus representing an existing university. In this connection, we analyze place metaphors and associated design features of the Virtual Campus of Nanyang Technological University in Singapore, discuss the correspondence between the identified metaphors and associated educational goals, and provide directions for further development. Finally, we outline the major challenges for the future evolution of cybercampuses in the context of organizational, social and technological development.     

Ultrastructural study of mouse adipose‐derived stromal cells induced towards osteogenic direction

We investigated the ultrastructural characteristics of mouse adipose‐derived stem/stromal cells (ASCs) induced towards osteogenic lineage. ASCs were isolated from adipose tissue of FVB‐Cg‐Tg(GFPU)5Nagy/J mice and expanded in monolayer culture. Flow cytometry, histochemical staining, and electron microscopy techniques were used to characterize the ASCs with respect to their ability for osteogenic differentiation capacity. Immunophenotypically, ASCs were characterized by high expression of the CD44 and CD90 markers, while the relative content of cells expressing CD45, CD34 and CD117 markers was <2%. In assays of differentiation, the positive response to osteogenic differentiation factors was observed and characterized by deposition of calcium in the extracellular matrix and alkaline phosphatase production. Electron microscopy analysis revealed that undifferentiated ASCs had a rough endoplasmic reticulum with dilated cisterns and elongated mitochondria. At the end of the osteogenic differentiation, the ASCs transformed from their original fibroblast‐like appearance to having a polygonal osteoblast‐like morphology. Ultrastructurally, these cells were characterized by large euchromatic nucleus and numerous cytoplasm containing elongated mitochondria, a very prominent rough endoplasmic reticulum, Golgi apparatus and intermediate filament bundles. Extracellular matrix vesicles of variable size similar to the calcification nodules were observed among collagen fibrils. Our data provide the ultrastructural basis for further studies on the cellular mechanisms involved in osteogenic differentiation of mouse adipose‐derived stem/stromal cells. Microsc. Res. Tech. 79:557–564, 2016. © 2016 Wiley Periodicals, Inc.     

Quantum dots as multimodal photoacoustic and photothermal contrast agents

Quantum dots (QDs) have primarily been developed as fluorescent probes with unique optical properties. We herein demonstrate an extension of these QD utilities to photoacoustic (PA) and photothermal (PT) microscopy, using a nanosecond pulse laser excitation (420-900 nm, 8 ns, 10(-3)-10 J/cm(2)). The laser-induced PA, PT and accompanying bubble formation phenomena were studied with an advanced multifunctional microscope, which integrates fluorescence, PA, PT imaging, and PT thermolens modules. It was demonstrated that QDs, in addition to being excellent fluorescent probes, can be used as PA and PT contrast agents and sensitizers, thereby providing an opportunity for multimodal high resolution (300 nm) PA-PT-fluorescent imaging as well as PT therapy. Further improvements for this technology are suggested by increasing the conversion of laser energy in PT, PA, and bubble phenomena in hybrid multilayer QDs that have optimized absorption, thermal, and acoustic properties.     

Direct observation of the transition point between quasi-spherical and cubic nanoparticles in a two-step seed-mediated growth method

An aqueous seed-mediated growth method is adapted to explore the shape transformation of quasi-spherical Au seeds to nanocubes in a direct and continuous manner. Quenching the growth process at varied reaction-duration times and exploring the intermediate products by high-resolution transmission electron microscopy and UV/vis spectroscopy shows an abrupt cuboctahedral-to-nanocube transition at 25-27 nm without any change in the nanoparticle size. The size of the obtained nanocubes remains constant (25-27 nm) until most (>90%) of the cuboctahedral nanoparticles are transformed to nanocubes. At this point, the (25-27 nm) nanocubes initiate further continuous and homogeneous growth until they reach 50-nm Au cubes. These observations are ascribed to a scenario in which the kinetically controlled growth mode of the nanoparticle is significantly affected by the surface self-diffusion of metal adatoms, especially when the adatom's self-diffusion distance is comparable with the nanoparticle's size.     

The synthesis and properties of highly exfoliated graphites from fluorinated graphite intercalation compounds

A series of new highly exfoliated graphites were synthesized from fluorinated graphite intercalation compounds of compositions C₂F·xR (R = ClF₃, (CH₃)₂CO, CH₃CN, C₆H₆, CCl₄). The exfoliation degree of these materials reaches more than 2000 times, indicating a significantly higher exfoliated state than observed for the conventional expanded graphites derived from graphite bisulphate or nitrate. These exfoliated graphites have increased interlayer distances, specific surface areas as high as 170–370 m²/g, low bulk densities of 0.4–0.7 g/L, and good sorption capacities towards a range of organic and inorganic liquids. The influence of the nature of the intercalated molecules on the properties of the exfoliated graphite is discussed.