Photo-oxidation of polymers—III: Molecular weight changes in the photolysis and photo-oxidation of polystyrene

Changes of molecular weight distribution resulting from vacuum photolysis and photo-oxidation of polystyrene have been determined by gel permeation chromatography. On irradiation at 253.7 nm, crosslinking is predominant in vacuo; in the presence of oxygen, crosslinking and main chain scission occur simultaneously because of light absorption by two or more different chromophores. Main chain scission is more important than crosslinking in the photolysis and photo-oxidation of polystyrene containing cumene hydroperoxide irradiated at 313 nm or containing benzophenone irradiated in the range 320–420 nm. In this last case, main chain scission and crosslinking are both strongly inhibited if the sample contains napthalene which acts as quencher of the excited triplet state of benzophenone. Only moderate inhibition is observed in the presence of 2,6-di-t-butyl-4 methylphenol.     

Mixed Problem with an Integral Condition for the One-Dimensional Biwave Equation

We consider a mixed problem for the one-dimensional biwave equation with boundary conditions and a nonlocal integral condition. We prove the existence and uniqueness of the classical solution of the problem and obtain an analytic representation of the solution.     

New strong convergence theorem of the inertial projection and contraction method for variational inequality problems

Numerical Algorithms - In this paper, we introduce a new algorithm which combines the inertial projection and contraction method and the viscosity method for solving monotone variational inequality...     

Robust and data-driven approaches to call centers

We propose both robust and data-driven approaches to a fluid model of call centers that incorporates random arrival rates with abandonment to determine staff levels and dynamic routing policies. We test the resulting models with real data obtained from the call center of a US bank. Computational results show that the robust fluid model is significantly more tractable as compared to the data-driven one and produces overall better solutions to call centers in most experiments.     

On the role of secondary interactions in the production of bremsstrahlung spectra from a thick target

Bremsstrahlung emission, or radiation loss, is the dominant mechanism of energy dissipation of electrons at relativistic energies greater than a few MeV when it is subjected to acceleration in the field of the nucleus or of the electrons. In this study, the Monte Carlo calculations for bremsstrahlung spectra have been described for the case of a thick tungsten target with incident electron beams from 10 to 50 MeV, where secondary interactions induced by the electrons and photons in the target, such as energy loss, absorption, scattering, and (e ⁺, e ⁻)-pair production effects, were taken into account. The text was submitted by the authors in English.     

New indications of potential rat intestinal α-glucosidase inhibition by Syzygium zeylanicum (L.) and its hypoglycemic effect in mice

Research on Chemical Intermediates - Natural α-glucosidase inhibitors (aGIs) have been considered effective agents for type 2 diabetes management. In this study, Syzygium zeylanicum (L.)...     

Inhibitory Effects of Cucurbitane-Type Triterpenoids from Momordica charantia Fruit on Lipopolysaccharide-Stimulated Pro-Inflammatory Cytokine Production in Bone Marrow-Derived Dendritic Cells

The bitter melon, Momordica charantia L., was once an important food and medicinal herb. Various studies have focused on the potential treatment of stomach disease with M. charantia and on its anti-diabetic properties. However, very little is known about the specific compounds responsible for its anti-inflammatory activities. In addition, the in vitro inhibitory effect of M. charantia on pro-inflammatory cytokine production by lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells (BMDCs) has not been reported. Phytochemical investigation of M. charantia fruit led to the isolation of 15 compounds (1−15). Their chemical structures were elucidated spectroscopically (one- and two-dimensional nuclear magnetic resonance) and with electrospray ionization mass spectrometry. The anti-inflammatory effects of the isolated compounds were evaluated by measuring the production of the pro-inflammatory cytokines interleukin IL-6, IL-12 p40, and tumor necrosis factor α (TNF-α) in LPS-stimulated BMDCs. The cucurbitanes were potent inhibitors of the cytokines TNF-α, IL-6, and IL-12 p40, indicating promising anti-inflammatory effects. Based on these studies and in silico simulations, we determined that the ligand likely docked in the receptors. These results suggest that cucurbitanes from M. charantia are potential candidates for treating inflammatory diseases.     

Molecularly engineering polymeric membranes for H2/CO2 separation at 100–300 °C

Over the last two decades, polymers with superior H₂/CO₂ separation properties at 100–300 °C have gathered significant interest for H₂ purification and CO₂ capture. This timely review presents various strategies adopted to molecularly engineer polymers for this application. We first elucidate the Robeson's upper bound at elevated temperatures for H₂/CO₂ separation and the advantages of high-temperature operation (such as improved solubility selectivity and absence of CO₂ plasticization), compared with conventional membrane gas separations at ~35 °C. Second, we describe commercially relevant membranes for the separation and highlight materials with free volumes tuned to discriminate H₂ and CO₂, including functional polymers (such as polybenzimidazole) and engineered polymers by cross-linking, blending, thermal treatment, thermal rearrangement, and carbonization. Third, we succinctly discuss mixed matrix materials containing size-sieving or H₂-sorptive nanofillers with attractive H₂/CO₂ separation properties.     

Existence of multi-solitary waves with logarithmic relative distances for the NLS equation

We construct 2-solitary wave solutions with logarithmic distance to the nonlinear Schrödinger equation,

$\mathrm{i}{?}_{t}u+\mathrm{\Delta }u+|u{|}^{p?1}u=0,t\in \mathbb{R},x\in {\mathbb{R}}^d,$

in mass-subcritical cases $1<p<1+\frac{4}{d}$ and mass-supercritical cases $1+\frac{4}{d}<p<\frac{d+2}{d?2}$, i.e. solutions $u(t)$ satisfying

${6u(t)?{\mathrm{e}}^{\mathrm{i}\gamma (t)}\sum _{k=1}^{2}Q(??x_k(t))6}_{H^1}\to 0$

and

$|x_1(t)?x_2(t)|～2\log ?t,\text{as}t\to +\infty ,$

where Q is the ground state. The logarithmic distance is related to strong interactions between solitary waves.In the integrable case ($d=1$ and $p=3$), the existence of such solutions is known by inverse scattering (E. Olmedilla, Multiple pole solutions of the nonlinear Schrödinger equation, Physica D 25 (1987) 330–346; T. Zakharov, A.B. Shabat, Exact theory of two-dimensional self-focusing and one-dimensional self-modulation of waves in nonlinear media, Sov. Phys. JETP 34 (1972) 62–69). The mass-critical case $p=1+\frac{4}{d}$ exhibits a specific behavior related to blow-up, previously studied in Y. Martel, P. Raphaël (Strongly interacting blow up bubbles for the mass critical NLS, Ann. Sci. Éc. Norm. Supér. 51 (2018) 701–737).     

On periodic subsolutions to steady second-order systems and applications

Bostan and Namah (Remarks on bounded solutions of steady Hamilton–Jacobi equations, C. R. Acad. Sci. Paris, Ser. I 347(15–16) (2009) 873–878) proved that constant functions are the only bounded solutions to $H(Du)=H(0)$ when H is superlinear and strictly convex. In this short note, we present a proof other than that of Bostan and Namah for equations that can be easily applied to some types of possibly degenerate parabolic systems. Our proof applies for periodic subsolutions instead of bounded solutions like that of Bostan and Namah; however, we need periodic subsolutions, which is quite restrictive. We do not consider Hopf–Lax's formula in our proof, so we can relax some restrictions on H. We also present an application to the large-time behavior of solutions to degenerate parabolic systems.