Elastic Light Tunable Tissue Adhesive Dendrimers

Development of bioadhesive formulations for tissue fixation remains a challenge. The major drawbacks of available bioadhesives are low adhesion strength, toxic byproducts, and complexity of application onto affected tissues. In order to address these problems, this study has developed a hydrogel bioadhesive system based on poly amido amine (PAMAM) dendrimer, grafted (conjugated) with UV‐sensitive, 4‐[3‐(trifluoromethyl)‐3H‐diazirin‐3‐yl] benzyl bromide (PAMAM‐g‐diazirine). This particular diazirine molecule can be grafted to the surface amine groups of PAMAM in a one‐pot synthesis. Diazirine functionalities are carbene precursors that form covalent crosslinks with hydrated tissues after low‐power UV activation without necessity of free‐radical initiators. The rheological properties and adhesion strength to ex vivo tissues are highly controllable depending on diazirine grafting, hydrogel concentration, and UV dose intensity fitting variety types of tissues. Covalent bonds at the tissue/bioadhesive interface provide robust adhesive and mechanical strength in a highly hydrated environment. The free flowing hydrogel conversion to elastic adhesive after UV activation allows intimate contact with the ex vivo swine tissue surfaces with low in vitro cytotoxicity observed, making it a promising bioadhesive formulation toward clinical applications.

     

Existence and Uniqueness of Invariant Measures for Stochastic Reaction–Diffusion Equations in Unbounded Domains

In this paper, we investigate the long-time behavior of stochastic reaction–diffusion equations of the type \(\text {d}u = (Au + f(u))\text {d}t + \sigma (u) \text {d}W(t)\), where \(A\) is an elliptic operator, \(f\) and \(\sigma \) are nonlinear maps and \(W\) is an infinite-dimensional nuclear Wiener process. The emphasis is on unbounded domains. Under the assumption that the nonlinear function \(f\) possesses certain dissipative properties, this equation is known to have a solution with an expectation value which is uniformly bounded in time. Together with some compactness property, the existence of such a solution implies the existence of an invariant measure, which is an important step in establishing the ergodic behavior of the underlying physical system. In this paper, we expand the existing classes of nonlinear functions \(f\) and \(\sigma \) and elliptic operators \(A\) for which the invariant measure exists, in particular in unbounded domains. We also show the uniqueness of the invariant measure for an equation defined on the upper half space if \(A\) is the Shrödinger-type operator \(A = \frac{1}{\rho }(\text {div} \rho \nabla u)\) where \(\rho = \text {e}^{-|x|^2}\) is the Gaussian weight.     

JRQ and JPA irradiated and annealed reactor pressure vessel steels studied by positron annihilation

The paper is focused on a comprehensive study of JRQ and JPA reactor pressure vessel steels from the positron annihilation lifetime spectroscopy (PALS) point of view. Based on our more than 20 years’ experience with characterization of irradiated reactor steels, we confirmed that defects after irradiation start to grow and/or merge into bigger clusters. Experimental results shown that JPA steel is more sensitive to the creation of irradiation-induced defects than JRQ steel. It is most probably due to high copper content (0.29?wt.% in JPA) and copper precipitation has a major impact on neutron-induced defect creation at the beginning of the irradiation. Based on current PALS results, no large vacancy clusters were formed during irradiation, which could cause dangerous embrittlement concerning operation safety of nuclear power plant. The combined PALS, small angle neutron scattering and atomic probe tomography studies support the model for JRQ and JPA steels describing the structure of irradiation-induced clusters as agglomerations of vacancy clusters (consisting of 2–6 vacancies each) and are separated from each other by a distribution of atoms.     

Isomerization of free base porphyrin. Theoretical study

The photoinduced isomerization reaction of free base porphyrin molecule has been calculated using the DFT-B3LYP method combined with the 6-31G(d,p) basis set. To prove the accuracy of results, the 6-311G+(2p,2d) basis set was used. Two types of isomerization mechanisms were studied. It was found that the stepwise pathway of isomerization is the most appropriate. The geometric parameters of isomers and the transition structures of different multiplets are discussed. Zero-point energy and vibrational frequencies analysis are given.     

Projective functors for algebraic groups

We investigate the regular subquotient category introduced by Soergel in [W. Soergel, On the relation between intersection cohomology and representation theory in positive characteristic, J. Pure Appl. Algebra 152 (1–3) (2000) 311–335]. A detailed study of projective functors enables one to relate those categories for semi-simple algebraic group G and its subgroup schemata G_rT. As an application we derive some information about the characters of tilting modules for G.     

Effect of the structure of cyclic <Emphasis Type="Italic">N</Emphasis>-nitramines on the rate and mechanism of their thermolysis

Manometry together IR spectroscopy, mass spectrometry, and chromatography were used to study thermolysis of six-membered cyclic N-nitramines containing one, two, or three nitramine fragments, as well as oxo, gem-dinitro, azide, nitroimino, amino, and tetrazolyl functions. An effect of the conformation and functional groups on the rate, mechanism, and activation parameters of the limiting stage of themolysis was revealed.     

A challenging synthesis of new 1,3,4‐thiadiazole derivatives starting from 2‐acylamino‐3,3‐dichloroacrylonitriles

Available 2‐acylamino‐3,3‐dichloroacrylonitriles, when treated with hydrazine hydrate, provide 2‐alkyl‐ or 2‐aryl‐5‐hydrazino‐1,3‐oxazole‐4‐carbonitriles that readily add alkyl or aryl isothiocyanates and the adducts formed recyclize on heating. Finally, the synthesis results in 5‐alkyl(aryl)amino‐1,3,4‐thiadiazol‐2‐yl(acylamino)acetonitriles or the products of their further cyclization, 2‐(5‐amino‐1,3‐ oxazol‐2‐yl)‐1,3,4‐thiadiazole derivatives. The structures of the novel substituted 1,3,4‐thiadiazoles are corroborated spectroscopically as well as by X‐ray diffraction method. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:454–458, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20041     

Insights into Modeling Approaches in Chemistry: Assessing Ligand-Protein Binding Thermodynamics Based on Rigid-Flexible Model Molecules

In the field of chemistry, model compounds find extensive use for investigating complex objects. One prime example of such object is the protein-ligand supramolecular interaction. Prediction the enthalpic and entropic contribution to the free energy associated with this process, as well as the structural and dynamic characteristics of protein-ligand complexes poses considerable challenges. This review exemplifies modeling approaches used to study protein-ligand binding (PLB) thermodynamics by employing pairs of conformationally constrained/flexible model molecules. Strategically designing the model molecules can reduce the number of variables that influence thermodynamic parameters. This enables scientists to gain deeper insights into the enthalpy and entropy of PLB, which is relevant for medicinal chemistry and drug design. The model studies reviewed here demonstrate that rigidifying ligands may induce compensating changes in the enthalpy and entropy of binding. Some “rules of thumb” have started to emerge on how to minimize entropy-enthalpy compensation and design efficient rigidified or flexible ligands.     

Chemical interaction in the B-BN system at high pressures and temperatures.: Synthesis of novel boron subnitrides

Chemical interaction and phase transformations in the B-BN system have been in situ studied by X-ray diffraction with synchrotron radiation at pressures up to 5.3 GPa and temperatures up to 2800 K using multianvil press. New rhombohedral boron subnitride B₁₃N₂ has been synthesized by crystallization from the B-BN melt at 5 GPa. The structure of B₁₃N₂ belongs to the R-3m space group (a=5.4455(2) Å, c=12.2649(9) Å) and represents a new structural type. The subnitride is an individual compound and not a solid solution, in contrast to boron carbide. Besides, the formation of two other boron-rich B-N phases denoted as “B₆N” and “B₅₀N₂” has been observed. Their structures seem to be much more sophisticated and have not been even resolved to present time.     

Synthesis,Anticancer, and QSAR Studies of 2‐Alkyl(aryl,hetaryl)quinazolin‐4(3H)‐thione's and [1,2,4]Triazolo[1,5‐c]quinazoline‐2‐thione's Thioderivatives

Considering the frightening high level of mortality from cancer, studies of anticancer agents are vital nowadays. The 24 thioderivatives of 2‐alkyl(aryl)‐quinazolin‐4(3H)‐thiones and 20 thioderivatives of [1,2,4]triazolo[1,5‐c]quinazoline‐2‐thiones were synthesized and evaluated for preliminary in vitro anticancer activity with subsequent in silico QSAR analysis. The substance 18 had the best results inhibiting growth of eight cancer cell lines: CCRF‐CEM of leukemia; SF‐539, SNB‐75, and U251 of CNS cancer; 786, RXF393, and UO‐31 of renal cancer; and MDA‐MB‐231/ATCC of breast cancer (?31.50 – 47.41% of cell growth) with low procancer effect. Calculated QSAR‐models for CCRF‐CEM of leukemia, T‐47D and HS 578T of breast cancer, and mean cell growth demonstrated good rate of anticancer activity prediction (r² = 0.7 – 0.8,  = 0.5 – 0.7).