Investigation of Brønsted acidity in zeolites through adsorbates with diverse proton affinities.

Understanding the adsorption behavior of base probes in aluminosilicates and its relationship to the intrinsic acidity of Brønsted acid sites (BAS) is essential for the catalytic applications of these materials. In this study, we investigated the adsorption properties of base probe molecules with varying proton affinities (acetonitrile, acetone, formamide, and ammonia) within six different aluminosilicate frameworks (FAU, CHA, IFR, MOR, FER, and TON). An important objective was to propose a robust criterion for evaluating the intrinsic BAS acidity (i.

Brønsted acidity in zeolites measured by deprotonation energy.

Acid forms of zeolites have been used in industry for several decades but scaling the strength of their acid centers is still an unresolved and intensely debated issue. In this paper, the Brønsted acidity strength in aluminosilicates measured by their deprotonation energy (DPE) was investigated for FAU, CHA, IFR, MOR, FER, MFI, and TON zeolites by means of periodic and cluster calculations at the density functional theory (DFT) level. The main drawback of the periodic DFT is that it does not provide reliable absolute values due to spurious errors associated with the background charge introduced in anion energy calculations.

Toward accurate ab initio modeling of siliceous zeolite structures.

Structures of purely siliceous materials in the International Zeolite Association database were investigated with four different theoretical methods ranging from the empirical approaches, such as the distance least squares and force fields to the computationally demanding dispersion-corrected density functional theory method employing the generalized gradient approximation-type functional. The structural characteristics were first evaluated for dense silica polymorphs, for which reliable low-temperature experiments are available. Due to the significant errors in experimentally determined atomic positions of siliceous zeolites, lattice parameters and the cell volume were proposed as reliable descriptors for the structural assessment of zeolite frameworks.

Methane adsorption in ADOR zeolites: a combined experimental and DFT/CC study.

Physical adsorption of methane in purely siliceous molecular sieves prepared by a recently discovered synthetic pathway using 2D zeolites as nanoscale building blocks has been investigated by means of combined experimental and theoretical approaches. The DFT/CC-based method has been tested on ADOR zeolites of the UTL family and a few experimentally well-characterized siliceous zeolites. Excellent agreement between theoretical and experimental heats of adsorption has been found for OKO, PCR, MFI, CHA and AEI zeolites.

Food-Allergic Adolescents at Risk for Anaphylaxis: A Randomized Controlled Study of Supervised Injection to Improve Comfort with Epinephrine Self-Injection.

Background: Epinephrine self-injection is a key element in the management of food allergy, yet many adolescents report that they may not be able to use the autoinjector when needed. We hypothesized that supervised self-injection with an empty syringe would increase adolescents' comfort with self-injection.

Objective: The objective of this study was to examine the effect of supervised self-injection on self- and parent-reported comfort and anxiety during and after clinic visits in a food allergy center.

The effect of the zeolite pore size on the Lewis acid strength of extra-framework cations.

The catalytic activity and the adsorption properties of zeolites depend on their topology and composition. For a better understanding of the structure-activity relationship it is advantageous to focus just on one of these parameters. Zeolites synthesized recently by the ADOR protocol offer a new possibility to investigate the effect of the channel diameter on the adsorption and catalytic properties of zeolites: UTL, OKO, and PCR zeolites consist of the same dense 2D layers (IPC-1P) that are connected with different linkers (D4R, S4R, O-atom, respectively) resulting in the channel systems of different sizes (14R × 12R, 12R × 10R, 10R × 8R, respectively).

Accurate ab initio description of adsorption on coordinatively unsaturated Cu(2+) and Fe(3+) sites in MOFs.

The performance of different exchange-correlation functionals was evaluated for the description of the interaction of small molecules with (i) cluster models containing Cu(2+) and Fe(3+) coordinatively unsaturated metal sites and (ii) HKUST-1 metal organic framework (MOF). Adsorbates forming dispersion-bound complexes (CH4), complexes with important dispersion and electrostatic contributions (H2, N2, CO2), and complexes stabilized also by a partial dative bond (CO, H2O, and NH3) were considered. The interaction with coordinatively unsaturated sites was evaluated with respect to the coupled-cluster calculations for Cu(2+) and Fe(3+) centers represented by cluster models.

Mental Health Screening Outcomes in a Pediatric Specialty Care Setting.

Objective: To evaluate whether a psychosocial screening program that included free and flexible access to mental health (MH) consultation resulted in increased rate of consultations.

Study Design: This is a post hoc review of a clinical screening program in a pediatric food allergy clinic in New York City. Screening was limited to 2 days per week, providing an opportunity to compare screened and nonscreened cohorts.

Allocation of food allergy responsibilities and its correlates for children and adolescents.

This study examined the degree to which children and adolescents with food allergy accept responsibility for their own care, and the extent to which greater self-management is associated with past history of a life-threatening allergic reaction or anxiety. For children (n = 190), caregiver and patient report of self-management was consistent, but agreement was poor for adolescent dyads (n = 59). History of a life-threatening allergic reaction was associated with greater self-management for children only, while among adolescents, it was associated with greater anxiety.

The importance of mental health monitoring during transfer to adult care settings as examined among paediatric transplant recipients.

Aim: Although the transfer out of paediatrics is established as a dangerous time for transplant recipients, the reasons for this are not well understood. One possible explanation is that in general, young adulthood is a period of vulnerability to psychological distress, which could impact self-management. The purpose of the present study was to investigate whether psychological distress is associated with medication non-adherence after transfer.

Computational investigation of the Lewis acidity in three-dimensional and corresponding two-dimensional zeolites: UTL vs IPC-1P.

The adsorption and catalytic properties of three-dimensional zeolite UTL were investigated computationally along with properties of its two-dimensional analogue IPC-1P that can be obtained from UTL by a removal of D4R units. Adsorption properties and Lewis acidity of extra-framework Li(+) sites were investigated for both two- and three-dimensional forms of UTL using the carbon monoxide as a probe molecule. The CO adsorption enthalpies, calculated with various dispersion-corrected DFT methods, including DFT/CC, DFT-D2, and vdW-DF2, and the CO stretching frequencies obtained with the νCO/rCO correlation method are compared for corresponding Li(+) sites in 3D and 2D UTL zeolite.

Theoretical investigation of layered zeolites with MWW topology: MCM-22P vs. MCM-56.

The inter-layer interactions and the possible arrangements of MWW-type layers were investigated computationally at the non-local density functional theory level. Powder XRD patterns were simulated for structures obtained computationally and compared with experimental data. The MCM-22P material corresponds to the layers bound with relatively strong hydrogen bonds between surface silanol groups that is an energetically preferred structure in the presence of a structure directing agent (hexamethyleneimine).

Measuring the Brønsted acid strength of zeolites--does it correlate with the O-H frequency shift probed by a weak base?

Brønsted-acid zeolites are currently being used as catalysts in a wide range of technological processes, spanning from the petrochemical industry to biomass upgrade, methanol to olefin conversion and the production of fine chemicals. For most of the involved chemical processes, acid strength is a key factor determining catalytic performance, and hence there is a need to evaluate it correctly. Based on simplicity, the magnitude of the red shift of the O-H stretching frequency, Δν(OH), when the Brønsted-acid hydroxyl group of protonic zeolites interacts with an adsorbed weak base (such as carbon monoxide or dinitrogen) is frequently used for ranking acid strength.

Child and parental reports of bullying in a consecutive sample of children with food allergy.

Objective: The social vulnerability that is associated with food allergy (FA) might predispose children with FA to bullying and harassment. This study sought to quantify the extent, methods, and correlates of bullying in a cohort of food-allergic children.

Methods: Patient and parent (83.

Combined theoretical and experimental investigation of CO adsorption on coordinatively unsaturated sites in CuBTC MOF.

The adsorption of CO in metal-organic framework CuBTC material is investigated by a combination of theoretical and experimental approaches. The adsorption enthalpy of CO on CuBTC determined experimentally to be -29 kJ mol(-1) at the zero-coverage limit is in very good agreement with the adsorption enthalpy calculated at the combined DFT-ab initio level with the periodic model. Calculations show that polycarbonyl complexes cannot be formed on regular coordinatively unsaturated sites in CuBTC.

Self-organization of 1-methylnaphthalene on the surface of artificial snow grains: a combined experimental-computational approach.

A combined experimental-computational approach was used to study the self-organization and microenvironment of 1-methylnaphthalene (1MN) deposited on the surface of artificial snow grains from vapors at 238 K. The specific surface area of this snow (1.1 × 10(4) cm(2) g(-1)), produced by spraying very fine droplets of pure water from a nebulizer into liquid nitrogen, was determined using valerophenone photochemistry to estimate the surface coverage by 1MN.

Accurate description of argon and water adsorption on surfaces of graphene-based carbon allotropes.

Accurate interaction energies of nonpolar (argon) and polar (water) adsorbates with graphene-based carbon allotropes were calculated by means of a combined density functional theory (DFT)-ab initio computational scheme. The calculated interaction energy of argon with graphite (-9.7 kJ mol(-1)) is in excellent agreement with the available experimental data.

VERDANDI is a direct target of the MADS domain ovule identity complex and affects embryo sac differentiation in Arabidopsis.

In Arabidopsis thaliana, the three MADS box genes SEEDSTICK (STK), SHATTERPROOF1 (SHP1), and SHP2 redundantly regulate ovule development. Protein interaction studies have shown that a multimeric complex composed of the ovule identity proteins together with the SEPALLATA MADS domain proteins is necessary to determine ovule identity. Despite the extensive knowledge that has become available about these MADS domain transcription factors, little is known regarding the genes that they regulate.

Experimental and theoretical determination of adsorption heats of CO(2) over alkali metal exchanged ferrierites with different Si/Al ratio.

The adsorption of CO(2) in Li-, Na-, and K-FER was investigated by a combination of volumetric adsorption experiments, FTIR spectroscopy, and density functional theory. Experimental isosteric heats of CO(2), Q(st), depend significantly on the cation size, cation concentration, and on the amount of adsorbed CO(2). The differences observed in experimentally determined isosteric heats were interpreted at the molecular level based on good agreement between experimental and calculated characteristics.

Ab initio vibrational dynamics of molecular hydrogen on graphene: An effective interaction potential.

The interaction potential confining the stretching and translational motions of a molecular hydrogen physisorbed on the graphene surface has been calculated by means of the DFT/CC approach. Using a simple adiabatic separation of the stretching and translational motions, a set of effective stretching potentials is generated by performing a "finite box" integrating over the translational degrees of freedom. The resulting potentials, forming energetically narrow bands, are used to evaluate the corresponding average stretching energies, which are in turn compared to their experimental counterparts.

DFT/CC investigation of physical adsorption on a graphite (0001) surface.

The physical adsorption of molecules (C(2)H(2), C(2)H(4), C(2)H(6), C(6)H(6), CH(4), H(2), H(2)O, N(2), NH(3), CO, CO(2), Ar) on a graphite substrate has been investigated at the DFT/CC level of theory. The calculated DFT/CC interaction energies were compared with the available experimental data at the zero coverage limit. The differences between the DFT/CC results and experiment are within a few tenths of kJ mol(-1) for the most accurate experimental estimates (Ar, H(2), N(2), CH(4)) and within 1-2 kJ mol(-1) for the other systems (C(2)H(2), C(2)H(4), C(2)H(6), C(6)H(6), CO, CO(2)).

DFT/CCSD(T) investigation of the interaction of molecular hydrogen with carbon nanostructures.

The interaction of molecular hydrogen with carbon nanostructures is investigated within the DFT/CC correction scheme. The DFT/CC results are compared with the benchmark calculations at the CCSD(T) level of theory for benzene and naphthalene, and at the MP2 level for the more extended systems. The DFT/CC method offers a reliable alternative to the highly correlated ab initio calculations at a cost comparable to the standard DFT method.