In situ small angle X-ray scattering and benzene adsorption on polymer-based carbon hollow fiber membranes

The structural changes and the mechanism of benzene adsorption on microporous carbon hollow fiber membranes with different surface and pore network properties have been investigated by in situ small-angle X-ray scattering (SAXS) and benzene adsorption. Benzene adsorption measurements have been carried out in situ with SAXS alongside an adsorption/desorption isotherm cycle at 293 K with the aid of a specially constructed adsorption sample cell. In addition low-pressure C₆H₆ and high-pressure CO₂, CH₄ and N₂ adsorption isotherms have been performed. Two carbon hollow fiber membranes, both prepared by controlled pyrolysis procedures of polyimide membrane precursor, were under study. During benzene adsorption the intensity of the SAXS curves changes in a way that depends on how the pores are filled and the contrast fluctuations occur. The SAXS data have been modeled by evaluating the form factor of lamellar micropores upon filling with C₆H₆. The existence of ultra micropores within the surrounding matrix was also taken into account. The results suggest that the arrangement of the ultra micropores on the non-activated membrane is in such a way that the access of benzene to the micropores is restricted, resulting in an incomplete filling. On the other hand, the activation process generates a more accessible pore network where the micropores are completely filled.     

Synthesis of fused dihydropyrido[e]purines via ring closing metathesis

Ring closing metathesis (RCM) of 8,9-diallylpurines or 9-butenyl-8-vinylpurines with the Grubbs 2nd generation catalyst resulted in fused 6,9- or 8,9-dihydropyrido[e]purines, respectively. The 8,9-dialkenylpurines were prepared from 8-bromopurines after 9-alkenylation and subsequent Stille coupling at C-8 with alkenylstannanes in the presence of Pd(PPh₃)₄ or Pd(PPh₃)₂Cl₂.     

An exterior point simplex algorithm for (general) linear programming problems

We present an exterior point simplex type algorithm that possesses a new monotonic property. A dual feasible basic solution is required to start with. Intermediate solutions are neither primal nor dual feasible. Cycling-free pivoting rules and an exponentional example are presented.     

Incorporation of fullerene derivatives into smectite clays: a new family of organic-inorganic nanocomposites

Three fulleropyrrolidine derivatives, characterized by the presence of positive charges, were introduced in the interlayer space of montmorillonite. The composites were characterized by powder X-ray diffraction and differential thermal and thermogravimetric (DTA-TGA) analysis, in conjunction with FTIR, UV-Vis, Raman, and (57)Fe-M?ssbauer spectroscopies. Organophilic derivatives were intercalated into organically modified clays, while water-soluble fulleropyrrolidines were introduced into the clay galleries through ion exchange. The experiments, complemented by computer simulations, show that not all the clay-clay platelets are intercalated by the fullerene derivatives and that a sizable amount of charge transfer takes place between the host and the guests.     

Inhibition of hIAPP amyloid-fibril formation and apoptotic cell death by a designed hIAPP amyloid- core-containing hexapeptide

The pathogenesis of type II diabetes is associated with the aggregation of the 37-residue human islet amyloid polypeptide (hIAPP) into cytotoxic beta sheet aggregates and fibrils. We have recently shown that introduction of two N-methyl rests in the beta sheet- and amyloid-core-containing sequence hIAPP(22-27), or NFGAIL converted this amyloidogenic and cytotoxic sequence into nonamyloidogenic and noncytotoxic NF(N-Me)GA(N-Me)IL. Here, we show that NF(N-Me)GA(N-Me)IL is able to bind with high-affinity full-length hIAPP and to inhibit its fibrillogenesis. NF(N-Me)GA(N-Me)IL also inhibits hIAPP-mediated apoptotic beta cell death. By contrast, unmodified NFGAIL does not inhibit hIAPP amyloidogenesis and cytotoxicity, suggesting that N-methylation conferred on NFGAIL the properties of NF(N-Me)GA(N-Me)IL. These results support the concept that rational N-methylation of hIAPP amyloid-core sequences may be a valuable strategy to design pancreatic-amyloid diagnostics and therapeutics for type II diabetes.     

Structural insights into the coordination and extraction of Pb(II) by disulfonamide ligands derived from o-phenylenediamine

The o-phenylenediamine-derived disulfonamide ligands 1 and 2 complex and efficiently extract Pb(II) from water into 1,2-dichloroethane via ion-exchange, in combination with 2,2'-bipyridine (97.5% and 95.0%, respectively, for 1:1 ligand-to-Pb ratios). The corresponding Pb(II)-sulfonamido binary complexes of ligands 1 and 2 (3 and 4, respectively), and ternary complexes with 2,2'-bipyridine (5 and 6, respectively), were isolated and characterized. (1)H NMR spectra of the organic phases after extraction show the formation of ternary Pb-sulfonamido-bipy complexes. X-ray characterization of 3, 4, and the ternary complex 5 consistently demonstrates four primary coordination sites and a stereochemically active lone pair on Pb. The X-ray structure of 3 shows a pseudo trigonal bipyramidal configuration on Pb, with the lone pair occupying one of the equatorial sites, and the formation of an unusual "hemidirected" coordination polymer via axial S=O-Pb coordination. The same axial S=O-Pb coordination pattern with two DMSO molecules is observed in the structure of 4.[2(CH(3))(2)SO)], thus rationalizing the high solubility of the binary complexes in strongly coordinating solvents. In contrast, the X-ray structure of the ternary complex 5 reveals a distorted four-coordinate configuration with only weak S=O-Pb coordination leading to dimer formation, thus explaining its higher solubility in weakly coordinating solvents. FT-IR spectroscopy confirms the X-ray data, since the ligand nu(S)(=)(O) stretching frequencies shift to lower values in the binary Pb(II)-sulfonamido complexes and are again altered upon formation of the ternary Pb(II)-sulfonamido-bipy complexes, as would be expected for 2,2'-bipy complexation and hindered S=O-Pb coordination.     

Superstrong and other large cardinals are never Laver indestructible

Superstrong cardinals are never Laver indestructible. Similarly, almost huge cardinals, huge cardinals, superhuge cardinals, rank-into-rank cardinals, extendible cardinals, 1-extendible cardinals, 0-extendible cardinals, weakly superstrong cardinals, uplifting cardinals, pseudo-uplifting cardinals, superstrongly unfoldable cardinals, Σ_n-reflecting cardinals, Σ_n-correct cardinals and Σ_n-extendible cardinals (all for n ≥  3) are never Laver indestructible. In fact, all these large cardinal properties are superdestructible: if κ exhibits any of them, with corresponding target θ, then in any forcing extension arising from nontrivial strategically <κ-closed forcing \({\mathbb{Q} \in V_\theta}\), the cardinal κ will exhibit none of the large cardinal properties with target θ or larger.     

A spatiotemporal Data Envelopment Analysis (S-T DEA) approach: the need to assess evolving units

We consider a two-stage supply chain with one supplier and one manufacturer. The manufacturer faces a Poisson demand process where the arrival rate depends on the selling price, the announced delivery time, and the delivery reliability defined as the probability of satisfying the announced delivery time. Such a demand model generalizes the works in the literature by simultaneously considering the above three demand sensitivity factors. The main purpose of this paper is to study the equilibrium decisions in the supply chain with an all-unit quantity discount contract. We consider four scenarios regarding whether the leadtime standard, the delivery reliability standard, and the manufacturer’s capacity are endogenous, and whether the manufacturer’s production cost is its private information. We find that an all-unit quantity discount scheme can coordinate the supply chain for most cases. Managerial insights are observed regarding the impact of the three demand sensitivity factors. For example, the breakpoint in an optimal quantity discount contract always increases with the delivery reliability sensitivity under an exogenous delivery reliability, but may decrease under an endogenous delivery reliability; with asymmetric information, a higher variance of the manufacturer’s unit production costs leads to a lower unit wholesale price for the low-cost manufacturer.