Synthetic control of defect structure and hierarchical extra-large/small-pore microporosity in aluminosilicate zeolite SWY

R.G.C. thanks the University of St. Andrews and Johnson Matthey for funding. P.A.W. thanks the Royal Society (Industrial Fellowship INF\R2\192052) for support. R.G.C. acknowledges the support of the EPSRC Light Element Analysis Facility grant EP/T019298/1 and the EPSRC Strategic Equipment Resource grant EP/R023751/1 for the use of the Jeol JSM-IT800 electron microscope at the University of St Andrews. A.M. acknowledges the Spanish Ministry of Science (RYC2018-024561-I) and the Gobierno of Aragon (Nanomidas group, code E13_23R).The SWY-type aluminosilicate zeolite, STA-30, has been synthesized via different routes to understand its defect chemistry and solid acidity. The synthetic parameters varied were the gel aging, the Al source, and the organic structure directing agent. All syntheses give crystalline materials with similar Si/Al ratios (6–7) that are stable in the activated K,H-form and closely similar by powder X-ray diffraction. However, they exhibit major differences in the crystal morphology and in their intracrystalline porosity and silanol concentrations. The diDABCO-C82+ (1,1′-(octane-1,8-diyl)bis(1,4-diazabicyclo[2.2.2]octan)-1-ium)-templated STA-30 samples (but not those templated by bisquinuclidinium octane, diQuin-C82+) possess hierarchical microporosity, consisting of noncrystallographic extra-large micropores (13 Å) that connect with the characteristic swy and gme cages of the SWY structure. This results in pore volumes up to 30% greater than those measured in activated diQuin-C8_STA-30 as well as higher concentrations of silanols and fewer Brønsted acid sites (BASs). The hierarchical porosity is demonstrated by isopentane adsorption and the FTIR of adsorbed pyridine, which shows that up to 77% of the BASs are accessible (remarkable for a zeolite that has a small-pore crystal structure). A structural model of single can/d6r column vacancies is proposed for the extra-large micropores, which is revealed unambiguously by high-resolution scanning transmission electron microscopy. STA-30 can therefore be prepared as a hierarchically porous zeolite via direct synthesis. The additional noncrystallographic porosity and, subsequently, the amount of SiOHs in the zeolites can be enhanced or strongly reduced by the choice of crystallization conditions.Publisher PDFPeer reviewe

Detecting RNA base methylations in single cells by in situ hybridization.

Methylated bases in tRNA, rRNA and mRNA control a variety of cellular processes, including protein synthesis, antimicrobial resistance and gene expression. Currently, bulk methods that report the average methylation state of ~104-107 cells are used to detect these modifications, obscuring potentially important biological information. Here, we use in situ hybridization of Molecular Beacons for single-cell detection of three methylations (m62A, m1G and m3U) that destabilize Watson-Crick base pairs. Our method-methylation-sensitive RNA fluorescence in situ hybridization-detects single methylations of rRNA, quantifies antibiotic-resistant bacteria in mixtures of cells and simultaneously detects multiple methylations using multicolor fluorescence imaging

Pyrethroids and Nectar Toxins Have Subtle Effects on the Motor Function, Grooming and Wing Fanning Behaviour of Honeybees (Apis mellifera)

Sodium channels, found ubiquitously in animal muscle cells and neurons, are one of the main target sites of many naturally-occurring, insecticidal plant compounds and agricultural pesticides. Pyrethroids, derived from compounds found only in the Asteraceae, are particularly toxic to insects and have been successfully used as pesticides including on flowering crops that are visited by pollinators. Pyrethrins, from which they were derived, occur naturally in the nectar of some flowering plant species. We know relatively little about how such compounds—i.e., compounds that target sodium channels—influence pollinators at low or sub-lethal doses. Here, we exposed individual adult forager honeybees to several compounds that bind to sodium channels to identify whether these compounds affect motor function. Using an assay previously developed to identify the effect of drugs and toxins on individual bees, we investigated how acute exposure to 10 ng doses (1 ppm) of the pyrethroid insecticides (cyfluthrin, tau-fluvalinate, allethrin and permethrin) and the nectar toxins (aconitine and grayanotoxin I) affected honeybee locomotion, grooming and wing fanning behaviour. Bees exposed to these compounds spent more time upside down and fanning their wings. They also had longer bouts of standing still. Bees exposed to the nectar toxin, aconitine, and the pyrethroid, allethrin, also spent less time grooming their antennae. We also found that the concentration of the nectar toxin, grayanotoxin I (GTX), fed to bees affected the time spent upside down (i.e., failure to perform the righting reflex). Our data show that low doses of pyrethroids and other nectar toxins that target sodium channels mainly influence motor function through their effect on the righting reflex of adult worker honeybees

Skeletal and dental changes following functional regulator therapy on class II patients

Craniofacial growth in 100 patients treated with the functional regulator of Frankel for about 24 months was compared with craniofacial growth seen in a matched group of untreated persons with Class II malocclusion. Both conventional and geometric cephalometric analyses were used to evaluate the skeletal and dental adaptations. This study shows several clear effects of treatment in either of two age ranges considered. The principal skeletal effect was advancement of the mandible along the direction of the facial axis. This advancement resulted in increases in mandibular length and in vertical facial dimensions. There was little effect of treatment upon maxillary skeletal structures with the exception of point A, which moved slightly posteriorly. Dentoalveolar adaptations due to treatment included a decrease in the normal forward movement of the upper molar and an increase in the normal vertical movement of the lower molar. There was a 2-mm posterior movement of the tip of the upper incisor but minimal anterior tipping of the lower incisor.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25601/1/0000148.pd

MULTICHANNEL QUANTUM-DEFECT THEORY SIMULATION OF THE ZERO-KINETIC-ENERGY PHOTOELECTRON-SPECTRUM OF H-2

The multichannel quantum defect theory (MQDT) is applied to the simulation of the v+=2 band of the zero-kinetic-energy (ZEKE) photoelectron spectrum of molecular hydrogen and also to the photoionization spectrum involving autoionizing Rydberg states in the region between the v+=1 and v+=2 thresholds. The results of the calculations are compared with previously reported experimental results [J. Chem. Phys. 96, 4149 (1992)]. The calculations are in very good agreement with experiment and provide quantitative confirmation of the previously proposed mechanisms for intensity perturbation. © 1994 American Institute of Physics

INFRARED PREDISSOCIATION SPECTRUM OF THE CH+ ION

A high-resolution infrared spectrum of the CH+ ion has been recorded in the range 875-1095 cm-1 using a laser/ion beam spectrometer. Eighty-seven transitions were detected by monitoring increased production of C+ fragment ions at resonance arising from predissociation of the upper states. Frequencies, linewidths, doublet splittings, relative intensities and upper state excess energies are reported for the transitions. A prediction of the spectrum, based on data from previous ab initio calculations and spectroscopic studies, was performed by using rotationally adiabatic potentials. Good qualitative agreement between the reported features of the observed spectrum and the prediction is found; the agreement suggests that the majority of the resonances are vibration-rotation transitions within the a 3Π state involving J = 20 to 40 and v = 7 to 12. The doublet splittings (16-672 MHz) are accounted for in terms of the proton nuclear hyperfine Fermi conctact interaction within this state. © 1986

INFRARED PREDISSOCIATION SPECTRUM OF THE CH+ ION

A high-resolution infrared spectrum of the CH+ ion has been recorded in the range 875-1095 cm-1 using a laser/ion beam spectrometer. Eighty-seven transitions were detected by monitoring increased production of C+ fragment ions at resonance arising from predissociation of the upper states. Frequencies, linewidths, doublet splittings, relative intensities and upper state excess energies are reported for the transitions. A prediction of the spectrum, based on data from previous ab initio calculations and spectroscopic studies, was performed by using rotationally adiabatic potentials. Good qualitative agreement between the reported features of the observed spectrum and the prediction is found; the agreement suggests that the majority of the resonances are vibration-rotation transitions within the a 3Π state involving J = 20 to 40 and v = 7 to 12. The doublet splittings (16-672 MHz) are accounted for in terms of the proton nuclear hyperfine Fermi conctact interaction within this state. © 1986

INFRARED PREDISSOCIATION SPECTRUM OF HENE+

One hundred and seven transitions of the HeNe+ ion have been observed using the technique of infrared predissociation spectroscopy. Seventy-eight of the lines have been assigned to rotational components of the A22Π 1 2 -X2Σ+ system. Our analysis leads to a modification of the assignment of the B2Σ+ -X2Σ+ bands of the optical emission spectrum. The predissociation mechanism is unusual in that there are no potential curve crossings between the predissociating state and the perturbing states. Predissociation lifetimes have been calculated for the individual levels and are compared with those obtained from the obserbed spectroscope linewidths. © 1985