Potential-flow studies of steady two-dimensional jets, waterfalls, weirs and sprays

Various numerical and analytical calculations of jets, waterfalls, weirs and sprays are discussed. Steady planar potential flows are considered. Boundary-integral-equation methods, series-truncation techniques and slender-body theory are among the methods to be used. The connections between the various results are stressed. Joint work with Professor E. O. Tuck as well as research inspired by him are presented.     

A Unified Structure Theory for Polycyclic Conjugated Hydrocarbons--A Review of What Every Chemist Should Know!

The important concepts of a formula periodic table set, aufbau principle, elementary substructures, excised internal structure/circumscribing algorithm, leapfrog algorithm, and hexagonal-to-pentagonal ring contraction algorithm will be reviewed. These concepts have been instrumental in organizing polyhex/polypent systems from benzenoid hydrocarbons to fullerene carbons. Some recent experimental verification of our prior predictions in this work will be noted.     

Hopf bifurcation on a simple cubic lattice

We study Hopf bifurcation for diff erential equations defined on the space of functions on R3 which are triply periodic with respect to a simple (primitive) cubic lattice. The centre manifold theorem reduces the problem to a system of ordinary diff erential equations (ODEs) on the space (C+C)3 and symmetric under the group (O=Zc2) + T3. We abstract this group as the wreath product group O(2) /S3, and we use a general theory of symmetry - breaking bifurcations for wreath product groups to find (up to conjugacy) all branches of periodic solutions with maximal isotropy. The stability of these solutions is calculated . Branches of periodic solutions with sub-maximal isotropy can also exist. Some possibilities for bifurcations to heteroclinic cycles are explored.     

Trans Fat Supplementation Increases UV-Radiation-Induced Oxidative Damage on Skin of Mice

We evaluated the influence of fish oil (FO, rich in n-3 FA), soybean oil (SO, rich in n-6 FA) and hydrogenated vegetable fat (HVF, rich in trans FA) on the oxidative status and viability of skin cells of mice exposed to ultraviolet radiation (UVR). Mice were supplemented with FO, SO or HVF for three months and exposed to UVR (2.72 mJ/cm²) for 2 days. One day after the last UVR session, the FO group showed higher levels of n-3 fatty acids (FA), while the HVF showed higher incorporation of trans FA (TFA) in dorsal skin. UVR increased lipid peroxidation and protein carbonyl levels of the HVF and to a lesser extent of the control and SO groups. Although all irradiated groups showed increased skin thickness, this increase was slighter in FO mice. UVR exposure reduced skin cell viability of the control, SO and HVF groups, while FO prevented this. Catalase activity was reduced independently of the supplementation and SOD level was increased in C and FO groups after UVR exposure; FO prevented the UVR-induced increase in glutathione levels, which was observed in skin of the control, SO and HVF mice. Our results showed the beneficial effects of FO supplementation, as well as the harmful effects of trans FA, whose intensity can increase vulnerability to skin diseases.     

The Effectiveness of Fish Oil Supplementation in Asthmatic Rats is Limited by an Inefficient Action on ASM Function

Episodes of acute exacerbation are the major clinical feature of asthma and therefore represent an important focus for developing novel therapies for this disease. There are many reports that the n-3 fatty acids found in fish oil exert anti-inflammatory effects, but there are few studies of the action of fish oil on airway smooth muscle (ASM) function. In the present investigation, we evaluated the effect of fish oil supplementation on smooth muscle force of contraction in ovalbumin-induced asthmatic Wistar rats, and its consequences on static lung compliance, mucus production, leukocyte chemotaxis and production of proinflammatory cytokines. Fish oil supplementation suppressed the infiltration of inflammatory cells into the lung in asthmatic animals (2.04 ± 0.19 × 10⁶ cells vs. 3.33 ± 0.43 × 10⁶ cells in the control asthmatic group; P < 0.05). Static lung compliance increased with fish oil supplementation in asthmatic rats (0.640 ± 0.053 mL/cm H₂O vs. 0.399 ± 0.043 mL/cm H₂O; P < 0.05). However, fish oil did not prevent asthma-associated lung eosinophilia and did not affect the concentrations of tumor necrosis factor-α and interleukin-1β in lung tissue or the proportion of the airways obliterated with mucus. Fish oil had no effect on the force of contraction in asthmatic rats in response to acetylcholine (3.026 ± 0.274 mN vs. 2.813 ± 0.364 mN in the control asthmatic group). In conclusion, although fish oil exerts some benefits in this model of asthma, its effectiveness appears to be limited by an inefficient action on airway smooth muscle function.     

Stability of some stationary solutions to the forced KdV equation with one or two bumps

Free-surface flows past submerged obstacles in a channel are considered. The fluid is assumed to be inviscid and incompressible and the flow to be irrotational. The first-order approximation of long nonlinear surface waves over one or two bumps results in a forced Korteweg?Cde Vries (fKdV) equation. Solutions of the stationary fKdV equation are constructed and their stability is studied, either analytically or numerically. These various solutions include solitary waves over a single bump, solitary waves with two humps over a double bump, table-top solutions over a double bump and fronts.     

Liquidus Projection of the B-Fe-U Diagram: The Fe-Rich Corner

The liquidus projection of the Fe-rich corner of the B-Fe-U phase diagram is proposed based on powder X-ray diffraction measurements, differential thermal analysis, and scanning electron microscopy observations complemented by energy dispersive X-ray spectroscopy. The present work demonstrates the existence of 10 ternary reactions together with 18 monovariant lines and establishes their location and approximate temperatures. The ternary compounds existing in this region of the B-Fe-U ternary phase diagram, UFe₃B₂, UFe₄B, and U₂Fe₂₁B₆, were confirmed to form by ternary peritectic reactions, yet UFe₄B and U₂Fe₂₁B₆ have minute primary crystallization fields, indicating a more challenging preparation of single crystals for these compounds when compared with UFe₃B₂.     

Molecular Modeling Studies of Candidate Chromophores

Two 2-dimensional tableaus of heterocyclic molecular systems are shown to have molecular graphs that are pairwise strongly subspectral (having a preponderance of common eigenvalues). Based on this result, the electronic similarity of candidate chromophores are proposed.     

Two experimental methods to determining stress–strain behavior of work-hardened surface layers of metallic components

Two experimental methods to characterize the mechanical behavior of work-hardened surface layers of metallic materials, induced by mechanical surface treatments, are described and discussed. The study was conducted using two steels with different mechanical properties, subjected to a similar shot-peening treatment. To characterize the elastic–plastic behavior of the surface layers affected by shot-peening, the X-ray diffraction assisted four-point bending method (XRDABM) and the normalized hardness variation method (NHVM) were applied. The results were compared and discussed taking into account the advantages and disadvantages of both methods. Similar yield strength values of the treated surfaces were found by both proposed methods. Taking into account their measuring characteristics, these can be considered complementary methods.