Macrosonics in industry: Ultrasonic soldering

Ultrasonic soldering is one of several uses of power ultrasonics that have been known for many years. Although it was discovered nearly 40 years ago, and has the unique capability of joining materials which are difficult to solder such as aluminium, ultrasonic soldering has never enjoyed widespread industrial use. There is a current resurgence of interest in the process, motivated mainly by the application of soldering all-aluminium heat exchangers. This and other new uses in the electronics field may yet permit ultrasonic soldering to achieve the status of a major use of power ultrasound.     

The infinite dimensional Lagrange multiplier rule for convex optimization problems

In this paper an infinite dimensional generalized Lagrange multipliers rule for convex optimization problems is presented and necessary and sufficient optimality conditions are given in order to guarantee the strong duality. Furthermore, an application is presented, in particular the existence of Lagrange multipliers associated to the bi-obstacle problem is obtained.     

DFT study of the fragmentation mechanism of uracil RNA base

The fragmentation process of the uracil RNA base has been investigated via DFT calculations in order to assign fragments to the ionisation mass spectrum obtained after dissociation induced by collision experiments. The analysis of the electronic distribution and geometry parameters of the cation allows selection of several bonds that may be cleaved and lead to the formation of various fragments. Differences are observed in the electronic behaviour of the bond breaking as well as the energy required for the cleavage. It is reported that N(3)-C(4) and N(1)-C(2) bonds are more easily cleaved than the C(5)-C(6) bond, since the corresponding energy barriers amount to ΔG = +1.627, +1.710, +5.459 eV, respectively, which makes the C(5)-C(6) bond cleavage almost prohibited. Among all possible formed fragments, the formation of the OCN(+) fragment for the peak at m/z = 42 Da is excluded because of an intermediate that was not observed experimentally and too a large free energy barrier. Based on the required free energy, it is observed that two fragment derivatives: C(2)H(4)N(+) and C(2)H(2)O˙(+) may be formed, with a small preference for C(2)H(4)N(+). This latter product is not formed through a retro Diels Alder reaction in contrast to C(2)H(2)O˙(+). The following sequence is proposed for the peak at 42 Da: C(2)H(4)N(+) (from N(1)-C(2), C(4)-C(5) cleavages) > C(2)H(2)O˙(+) (from N(3)-C(4), N(1)-C(2) and C(5)-C(6) cleavages) > C(2)H(4)N(+) (from N(1)-C(2), N(3)-C(4) and C(4)-C(5)) > C(2)H(2)O˙(+) (from C(5)-C(6), N(1)-C(2) and N(3)-C(4) cleavages) > NCO(+) (from N(1)-C(2), C(4)-C(5) and N(3)-C(4) cleavages). Finally the peak at 28 Da is assigned to CNH(2)(+) derivatives that can be formed through two different paths, the easiest one requiring 5.4 eV.     

Combinatorial scheme of finding minimal number of periodic points for smooth self-maps of simply connected manifolds

Let M be a closed smooth connected and simply connected manifold of dimension m at least 3, and let r be a fixed natural number. The topological invariant ${{D^m_r} [f]}$ , defined by the authors in [Forum Math. 21 (2009), 491–509], is equal to the minimal number of r-periodic points in the smooth homotopy class of f, a given self-map of M. In this paper, we present a general combinatorial scheme of computing ${{D^m_r} [f]}$ for arbitrary dimension m ≥ 4. Using this approach we calculate the invariant in case r is a product of different odd primes. We also obtain an estimate for ${{D^m_r} [f]}$ from below and above for some other natural numbers r.     

A Multicolor Photoinitiator for Cationic Polymerization and Interpenetrated Polymer Network Synthesis: 2,7‐Di‐tert‐butyldimethyldihydropyrene

For polymer synthesis upon visible light, actual photoinitiator operates in a restricted part of the spectrum. As a consequence, several photoinitiators are necessary to harvest all of the emitted visible photons. Herein, 2,7‐di‐tert‐butyldimethyldihydropyrene is used for the first time as a multicolor photoinitiator for the cationic polymerization of epoxides. Upon addition of diphenyliodonium hexafluorophosphate and optionally N‐vinylcarbazole, the originality of this approach is to allow efficient monomer conversions under various excitation light sources in the 360–650 nm wavelength range: halogen lamps, and light‐emitting and laser diodes. The synthesis of an interpenetrated polymer network from an epoxide/acrylate blend using a red light at 635 nm is also feasible. The formed polymer material exhibits a photochromic character.

     

Combination Therapy Using Verteporfin and Ranibizumab; Optimizing the Timing in the CAM Model

Combining photodynamic therapy (PDT) using verteporfin (Visudyne^®) with ranibizumab (Lucentis^®) can optimize the overall treatment outcome by providing more efficacy in vessel closure, and thus reduce the need for retreatment in patients with wet age-related macular degeneration. In this preclinical study in the chorioallantoic membrane (CAM) of the chicken embryo, we compare the vascular occlusion effects of verteporfin and ranibizumab as monotherapies with those observed in the combined therapy. In order to optimize the combination therapy, we varied the timing and sequence of the PDT and antivascular endothelial growth factor modalities. We observed that 1 day after PDT, the smaller blood vessels (∅ < 70 μm) of the CAM were selectively occluded, but as early as 2 days after PDT, both significant reperfusion and regrowth of new vessels were observed. Both these phenomena could be significantly delayed by application of ranibizumab. Ranibizumab itself did not induce any vascular occlusion. Under the applied conditions of combination therapy, the occlusion of the targeted blood vessels could be significantly extended to 3 days in this model compared with 1 day in the case of verteporfin monotherapy. Thus, in the present preclinical study, we demonstrate that for the applied conditions, the optimal time to administer ranibizumab is 24 h after PDT.     

Selective extraction of triazine herbicides from food samples based on a combination of a liquid membrane and molecularly imprinted polymers

A selective extraction technique based on the combination of liquid membrane (microporous membrane liquid–liquid extraction) and molecularly imprinted polymers (MIP) was applied to triazines herbicides in food samples. Simazine, atrazine and propazine were extracted from aqueous food samples through the hydrophobic porous membrane that was impregnated with toluene, which also formed part of the acceptor phase. In the acceptor phase, the compounds were re-extracted onto MIP particles. The extraction technique was optimised for the amount of molecularly imprinted polymers particles in the organic acceptor phase, extraction time, and type of organic acceptor solvent and desorption solvent. An extraction time of 90 min and 50 mg of MIP were found to be optimum parameters. Toluene as the acceptor phase was found to give higher triazines binding onto MIP particles compared to hexane and combinations of diethyl ether and hexane. 90% methanol in water was found to be the best desorption solvent compared to acetonitrile, methanol and water. The selectivity of the technique was demonstrated by extracting spiked lettuce and apple extracts where clean chromatograms were obtained compared to liquid membrane extraction alone or to the microporous membrane liquid–liquid extraction – non-imprinted polymer combination. The MIP showed a certain degree of group specificity and the extraction efficiency in lettuce extract was 79% (0.72) for simazine, 98% (1.55) for atrazine and 86% (3.08) for propazine.