Economics of payment cards: a status report

This article surveys the recent theoretical literature on payment cards (focusing on debit and credit cards) and studies this research's possible implications for the current public policy debate over payment card networks and the pricing of their services for both consumers and merchants.Payment systems ; Credit cards

The Inactivation of a New Peptidoglycan Hydrolase Pmp23 Leads to Abnormal Septum Formation in Streptococcus pneumoniae

The bacterial peptidoglycan is the major component of the cell wall which integrity is essential to cell survival. In a previous work, we identified, in the positive-Gram pathogen Streptococcus pneumoniae , a unique protein containing a new putative peptidoglycan hydrolytic domain named PECACE (PEptidoglycan CArbohydrate Cleavage Enzyme). In this study, we characterise the physiological function of this protein called Pmp23 (Pneumococcal Membrane Protein of 23 kDa). A cell wall hydrolytic activity is observed with the recombinant protein. Inactivation of the pmp23 gene in the pneumococcus led to a decreased flocculation, an increased sensitivity to β-lactam antibiotics and morphological alterations affecting the formation and localisation of the division septa. Taken together these observations indicate that Pmp23 is a hydrolase whose function is linked to peptidoglycan metabolism at the septum site

Unusual two-dimensional behavior of iron-based superconductors with low anisotropy

© 2017 American Physical Society. We study angular-dependent magnetoresistance in iron-based superconductors Ba1-xNaxFe2As2 and FeTe1-xSex. Both superconductors have relatively small anisotropies γ∼2 and exhibit a three-dimensional (3D) behavior at low temperatures. However, we observe that they start to exhibit a profound two-dimensional behavior at elevated temperatures and in applied magnetic field parallel to the surface. We conclude that the unexpected two-dimensional (2D) behavior of the studied low-anisotropic superconductors is not related to layeredness of the materials, but is caused by appearance of surface superconductivity when magnetic field exceeds the upper critical field Hc2(T) for destruction of bulk superconductivity. We argue that the corresponding 3D-2D bulk-to-surface dimensional transition can be used for accurate determination of the upper critical field

Orientation-independent room temperature optical C-13 hyperpolarization in powdered diamond

Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of nuclear magnetic resonance beyond the traditional limits imposed by magnetic field strength and temperature. Among the various alternative implementations, the use of nitrogen vacancy (NV) centers in diamond—a paramagnetic point defect whose spin can be optically polarized at room temperature—has attracted widespread attention, but applications have been hampered by the need to align the NV axis with the external magnetic field. We overcome this hurdle through the combined use of continuous optical illumination and a microwave sweep over a broad frequency range. As a proof of principle, we demonstrate our approach using powdered diamond with which we attain bulk 13C spin polarization in excess of 0.25% under ambient conditions. Remarkably, our technique acts efficiently on diamond crystals of all orientations and polarizes nuclear spins with a sign that depends exclusively on the direction of the microwave sweep. Our work paves the way toward the use of hyperpolarized diamond particles as imaging contrast agents for biosensing and, ultimately, for the hyperpolarization of nuclear spins in arbitrary liquids brought in contact with their surface

Valorization and Potential Antimicrobial Use of Olive Mill Wastewater (OMW) from Italian Olive Oil Production

The production of olive oil generates olive mill wastewater (OMW) which essentially derives from the processing, treatment and pressing of olives in mills. Traditional milling processes require a quantity of water varying between 40 and 120 L per quintal of pressed olives, generating a considerable amount of wastewater. It is thus necessary to reduce process water and enhance its use to implement the concept of a circular economy. To this end, our preliminary work was dedicated to water purification by means of suitable and efficient filtration systems. The microfiltered OMW was firstly concentrated through reverse osmosis. Then, an additional concentration step was carried out via vacuum membrane distillation using hydrophobic hollow fiber membranes. The application of the membrane-based processes allowed the recovery of a purified water and the concentration of valuable polyphenols in a smaller volume. The different fractions obtained from the purification have been tested for the determination of the antioxidant power (DPPH assay) and dosage of polyphenols (Folin–Ciocalteu assay) and were characterized using IR spectroscopy. All samples showed relevant antioxidant activity (percentage range: 10–80%) and total phenolic content in the 1.5–15 g GAE/L range. The obtained fractions were tested for their antimicrobial effect on numerous clinical isolates of Gram-positive and Gram-negative species, resistant and multi-resistant to current antibiotic drugs. OMW samples showed widespread activity against the considered (phyto)pathogens (MIC range 8–16 mg/mL) thus supporting the value of this waste material in the (phyto)pharmaceutical field

Low-field microwave-mediated optical hyperpolarization in optically pumped diamond.

The emergence of a new class of optically polarizable electronic spins in diamond, nitrogen vacancy (NV) defect centers, has opened interesting new avenues for dynamic nuclear polarization. Here we review methods for the room-temperature hyperpolarization of lattice 13C nuclei using optically pumped NV centers, focusing particular attention to a polarization transfer via rotating-frame level anti-crossings. We describe special features of this optical DNP mechanism at low-field, in particular, its deployability to randomly oriented diamond nanoparticles. In addition, we detail methods for indirectly obtaining high-resolution NV ESR spectra via hyperpolarization readout. These mechanistic features provide perspectives for interesting new applications exploiting the optically generated 13C hyperpolarization

Unusual two-dimensional behavior of iron-based superconductors with low anisotropy

© 2017 American Physical Society. We study angular-dependent magnetoresistance in iron-based superconductors Ba1-xNaxFe2As2 and FeTe1-xSex. Both superconductors have relatively small anisotropies γ∼2 and exhibit a three-dimensional (3D) behavior at low temperatures. However, we observe that they start to exhibit a profound two-dimensional behavior at elevated temperatures and in applied magnetic field parallel to the surface. We conclude that the unexpected two-dimensional (2D) behavior of the studied low-anisotropic superconductors is not related to layeredness of the materials, but is caused by appearance of surface superconductivity when magnetic field exceeds the upper critical field Hc2(T) for destruction of bulk superconductivity. We argue that the corresponding 3D-2D bulk-to-surface dimensional transition can be used for accurate determination of the upper critical field