Influence of Different Salts on the G-Quadruplex Structure Formed from the Reversed Human Telomeric DNA Sequence

G-rich telomeric DNA plays a major role in the stabilization of chromosomes and can fold into a plethora of different G-quadruplex structures in the presence of mono- and divalent cations. The reversed human telomeric DNA sequence (5′-(GGG ATT)₄; RevHumTel) was previously shown to have interesting properties that can be exploited for chemical sensing and as a chemical switch in DNA nanotechnology. Here, we analyze the specific G-quadruplex structures formed by RevHumTel in the presence of K⁺, Na⁺, Mg²⁺ and Ca²⁺ cations using circular dichroism spectroscopy (CDS) and Förster resonance energy transfer (FRET) based on fluorescence lifetimes. CDS is able to reveal strand and loop orientations, whereas FRET gives information about the distances between the 5′-end and the 3′-end, and also, the number of G-quadruplex species formed. Based on this combined information we derived specific G-quadruplex structures formed from RevHumTel, i.e., a chair-type and a hybrid-type G-quadruplex structure formed in presence of K⁺, whereas Na⁺ induces the formation of up to three different G-quadruplexes (a basket-type, a propeller-type and a hybrid-type structure). In the presence of Mg²⁺ and Ca²⁺ two different parallel G-quadruplexes are formed (one of which is a propeller-type structure). This study will support the fundamental understanding of the G-quadruplex formation in different environments and a rational design of G-quadruplex-based applications in sensing and nanotechnology.     

Problems in managing patients with long QT syndrome and implantable cardioverter defibrillators: a report of two cases

Implantable cardioverter-defibrillators (ICDs) have been a successful adjunct to the management of arrhythmias in patients with Long QT syndrome (LQTS). In two patients, interactions between LQTS and the ICD were diagnosed and corrected. Oversensing of T waves was confirmed in the first, while in the second, the arrhythmia disappeared when T wave abnormalities improved after cessation of H2 blocker therapy. In patients with LQTS and an ICD, T wave oversensing should be considered. Interventions that may have an adverse effect on repolarization should be avoided.     

Cure modelling of polyester thermosets in a glass mould

The curing of unsaturated polyester was studied experimentally and using a model of the process. The kinetic parameters were calculated from the heat flow–time curves obtained by differential scanning calorimetry (Mettler Toledo DSC 823), operating in a non-isothermal mode. The temperature–time histories were studied in a cylindrical glass mould. A potential use of glass as a mould for polymer curing is found in the production of optical sensors. Here, glass was selected as a mould material because it is UV transparent, chemically inert and easy to clean. The thermal properties of glass moulds coupled with the intrinsic curing kinetics are of a significant interest in such investigations. Taking into account the heat transferred by the convection from the air to the mould surface and the conduction through the mould wall and resin, as well as the kinetics of the heat generated in the cure reaction, a numerical model has been constructed. The contributions to the rise in temperature from the heat conduction and chemical reaction are different in different parts of the composite, which can explain the temperature–time histories. The introduction of a carbonate based filler reduced the amount of heat released in the composite and, as a result, lowered the temperatures through the resin. A good agreement between experimental data and the predicted mathematical model of the curing process in the mould has been observed.     

Storage and permeation of hydrogen molecule,atom and ions (H+ and H−) through silicon carbide nanotube; a DFT approach

The barriers for the encapsulation and decapsulation of hydrogen ions (cationic hydrogen and hydride), atom, and molecule through silicon carbide nanotube are thoroughly studied. DFT method is selected to measure the kinetic barriers for the passage of hydrogen atom, ions and molecule through nanotube via scanning potential energy surface. The kinetic barriers for the passage (encapsulation and decapsulation) of hydrogen are very important to understand the mechanism of hydrogen storage and release. The barriers for the permeation of H, H⁺ and H^? across SiC nanosheet are lower compared to hydrogen molecule (H₂). The exohedral and endohedral adsorption of hydrogen ions (cation and anion), atom and exohedral hydrogen molecule on silicon carbide are exothermic in nature. Whereas the encapsulation of hydrogen molecule in silicon carbide is endothermic. Electronic properties are analyzed through measurement of energy gap between highest occupied and lowest unoccupied molecular orbitals gap (G_H-L) and the density of state (DOS) spectra. The G_H-L analysis reveals that endohedral complexes have more pronounced effect on electronic properties compared to exohedral complexes. The SiC nanotube has highly favorable properties for storage and release of hydrogen ions, and atom.     

2D Electrets of Ultrathin MoO2 with Apparent Piezoelectricity

Since graphene, a variety of 2D materials have been fabricated in a quest for a tantalizing combination of properties and desired physiochemical behavior. 2D materials that are piezoelectric, i.e., that allow for a facile conversion of electrical energy into mechanical and vice versa, offer applications for sensors, actuators, energy harvesting, stretchable and flexible electronics, and energy storage, among others. Unfortunately, materials must satisfy stringent symmetry requirements to be classified as piezoelectric. Here, 2D ultrathin single-crystal molybdenum oxide (MoO₂) flakes that exhibit unexpected piezoelectric-like response are fabricated, as MoO₂ is centrosymmetric and should not exhibit intrinsic piezoelectricity. However, it is demonstrated that the apparent piezoelectricity in 2D MoO₂ emerges from an electret-like behavior induced by the trapping and stabilization of charges around defects in the material. Arguably, the material represents the first 2D electret material and suggests a route to artificially engineer piezoelectricity in 2D crystals. Specifically, it is found that the maximum out-of-plane piezoresponse is 0.56 pm V⁻¹, which is as strong as that observed in conventional 2D piezoelectric materials. The charges are found to be highly stable at room temperature with a trapping energy barrier of ≈2 eV.     

Impact damage resistance of CFRP with nanoclay-filled epoxy matrix

The influence of nanoclay on the impact damage resistance of carbon fibre–epoxy composites has been investigated using the low-velocity impact and compression after impact (CAI) tests. The load–energy vs. time relations were analyzed to gain insight into the damage behaviours of the materials. The CFRPs containing organoclay brought about significant improvement in impact damage resistance and damage tolerance in the form of smaller damage area, higher residual strength and higher threshold energy level. The presence of nanoclay in the epoxy matrix induced the transition of failure mechanisms of CFRP laminates during the CAI test, from the brittle buckling mode to more ductile, multi-layer delamination mode. Addition of 3 wt% clay was shown to be an optimal content for the highest damage resistance.