Characterization of two electrode systems for corona-charging of non-woven filter media

The aim of this paper is to provide a better understanding of the corona-charging process of non-woven electret filters for automotive and medical applications. The experiments were performed on polypropylene samples: 500-μm-thick non-woven fabrics (fiber diameter: 24 μm), laid on a grounded plate electrode and subjected to positive or negative corona generated either by a dual wire–cylinder electrode or by a triode-type electrode set. The paper reports the results of current–voltage characteristics measurements, as well as the repartition of the current density at the surface of the grounded electrode.     

Stereospecific Synthesis of D -Glycero- D -ido-oct-2-ulose

 D-Glycero-D-gulo-heptose reacted with 2,2-dimethoxypropane to give its 2,3:6,7-di-O-isopropylidene derivative. Its base-catalyzed addition to formaldehyde resulted in the formation of 2,3:6,7-di-O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo-heptofuranose. After acid hydrolysis of this aldolization product, a new branched-chain aldose, 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose, was obtained, which was stereospecifically rearranged under the catalytic action of molybdic acid to D-glycero-D-ido-oct-2-ulose.     

Analysis of human blood plasma and hen egg white by chiroptical spectroscopic methods (ECD, VCD, ROA)

Chiroptical methods are widely used in structural and conformational analyses of biopolymers. The application of these methods to investigations of biofluids would provide new avenues for the molecular diagnosis of protein-misfolding diseases. In this work, samples of human blood plasma and hen egg white were analyzed using a combination of conventional and chiroptical methods: ultraviolet absorption/electronic circular dichroism (UV/ECD), Fourier transform infrared absorption/vibrational circular dichroism (FTIR/VCD), and Raman scattering/Raman optical activity (Raman/ROA). For comparison, the main components of these substances—human serum albumin (HSA) and ovalbumin (Ova)—were also analyzed by these methods. The ultraviolet region of the ECD spectrum was analyzed using the CDNN CD software package to evaluate the secondary structures of the proteins. The UV/ECD, FTIR/VCD, and Raman/ROA spectra of the substances were quite similar to those of the corresponding major proteins, while some differences were also detected and explained. The conclusions drawn from the FTIR/VCD and Raman/ROA data were in good agreement with the secondary structures calculated from ECD. The results obtained in this work demonstrate that the chiroptical methods used here can be applied to analyze not only pure protein solutions but also more complex systems, such as biological fluids.

Bimetallic Anionic Organic Frameworks with Solid-State Cation Conduction for Charge Storage Applications

A new phosphonate-based anionic bimetallic organic framework, with the general formula of A₄−Zn−DOBDP (wherein A is Li⁺ or Na⁺, and DOBDP⁶⁻ is the 2,5-dioxido-1,4-benzenediphosphate ligand) is prepared and characterized for energy storage applications. With four alkali cations per formula unit, the A₄−Zn−DOBDP MOF is found to be the first example of non-solvated cation conducting MOF with measured conductivities of 5.4×10⁻⁸ S cm⁻¹ and 3.4×10⁻⁸ S cm⁻¹ for Li₄- and Na₄- phases, indicating phase and composition effects of Li⁺ and Na⁺ shuttling through the channels. Three orders of magnitude increase in ionic conductivity is further attained upon solvation with propylene carbonate, placing this system among the best MOF ionic conductors at room temperature. As positive electrode material, Li₄−Zn−DOBDP delivers a specific capacity of 140 mAh g⁻¹ at a high average discharge potential of 3.2 V (vs. Li⁺/Li) with 90 % of capacity retention over 100 cycles. The significance of this research extends from the development of a new family of electroactive phosphonate-based MOFs with inherent ionic conductivity and reversible cation storage, to providing elementary insights into the development of highly sought yet still evasive MOFs with mixed-ion and electron conduction for energy storage applications.     

Closely embedded Kre?n spaces and applications to Dirac operators

Motivated by energy space representation of Dirac operators, in the sense of K. Friedrichs, we recently introduced the notion of closely embedded Kre?n spaces. These spaces are associated to unbounded selfadjoint operators that play the role of kernel operators, in the sense of L. Schwartz, and they are special representations of induced Kre?n spaces. In this article we present a canonical representation of closely embedded Kre?n spaces in terms of a generalization of the notion of operator range and obtain a characterization of uniqueness. When applied to Dirac operators, the results differ according to a mass or a massless particle in a dramatic way: in the case of a particle with a nontrivial mass we obtain a dual of a Sobolev type space and we have uniqueness, while in the case of a massless particle we obtain a dual of a homogenous Sobolev type space and we lose uniqueness.     

A limiting case for the divergence equation

We consider the equation $\text{ div}\,\mathbb{Y }=f$ , with $f$ a zero average function on the torus $\mathbb{T }^d$ . In their seminal paper, Bourgain and Brezis [J Am Math Soc 16(2):393–426, 2003 (electronic)] proved the existence of a solution $\mathbb{Y }\in W^{1,d}\cap L^\infty $ for a datum $f\in L^d$ . We extend their result to the critical Sobolev spaces $W^{s,p}$ with $(s+1)p=d$ and $p\ge 2$ . More generally, we prove a similar result in the scale of Triebel–Lizorkin spaces. We also consider the equation $\text{ div} \,\mathbb{Y }=f$ in a bounded domain $\varOmega $ subject to zero Dirichlet boundary condition.     

Synthesis of Hydroxypyrrolone Carboxamides Employing Selectfluor

Reaction of pyrrole‐2‐carboxamides with Selectfluor in MeCN/water (4:1) affords 2‐hydroxy‐5‐oxopyrrole‐2‐carboxamides in yields of up to 80 %. A variety of sensitive functional groups is tolerated, among them aldehydes and alkynes. The new method also works in the presence of allyl groups and appears to be superior to the use of singlet oxygen. Reaction of the monobrominated dihydropyrrolo[1,2‐a]pyrazinone mukanadin C and its nonbrominated analogue afforded bicyclic hydroxypyrrolones. These compounds are interesting as they constitute a partial structure of the marine natural product oxocyclostylidol.