UPS of multilayer nitrogen‐bearing compounds on the Si(100) surface

Ultraviolet photoemission spectra (UPS) are presented for condensed layers of three ethylated amines; mono‐, di‐, and triethylamine (TEA) on the Si(100) surface at 100 K. The photoemission peaks associated with the nitrogen lone pair electrons are identified in the amines and compared with the corresponding spectra for condensed ammonia. Shifts in the lone pair binding energy for the ethyl‐substituted amines are shown to be consistent with conventional chemical paradigms. Also, for comparison purposes spectra for two nonethylated amines, trimethylamine (TMA), and its silicon analog, trisilylamine (TSA), are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Toward a Rational Design of Highly Folded Peptide Cation Conformations. 3D Gas-Phase Ion Structures and Ion Mobility Characterization

Heptapeptide ions containing combinations of polar Lys, Arg, and Asp residues with non-polar Leu, Pro, Ala, and Gly residues were designed to study polar effects on gas-phase ion conformations. Doubly and triply charged ions were studied by ion mobility mass spectrometry and electron structure theory using correlated ab initio and density functional theory methods and found to exhibit tightly folded 3D structures in the gas phase. Manipulation of the basic residue positions in LKGPADR, LRGPADK, KLGPADR, and RLGPADK resulted in only minor changes in the ion collision cross sections in helium. Replacement of the Pro residue with Leu resulted in only marginally larger collision cross sections for the doubly and triply charged ions. Disruption of zwitterionic interactions in doubly charged ions was performed by converting the C-terminal and Asp carboxyl groups to methyl esters. This resulted in very minor changes in the collision cross sections of doubly charged ions and even slightly diminished collision cross sections in most triply charged ions. The experimental collision cross sections were related to those calculated for structures of lowest free energy ion conformers that were obtained by extensive search of the conformational space and fully optimized by density functional theory calculations. The predominant factors that affected ion structures and collision cross sections were due to attractive hydrogen bonding interactions and internal solvation of the charged groups that overcompensated their Coulomb repulsion. Structure features typically assigned to the Pro residue and zwitterionic COO-charged group interactions were only secondary in affecting the structures and collision cross sections of these gas-phase peptide ions.

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One water molecule stabilizes the cationized arginine zwitterion

Singly hydrated clusters of lithiated arginine, sodiated arginine, and lithiated arginine methyl ester are investigated using infrared action spectroscopy and computational chemistry. Whereas unsolvated lithiated arginine is nonzwitterionic, these results provide compelling evidence that attachment of a single water molecule to this ion makes the zwitterionic form of arginine, in which the side chain is protonated, more stable. The experimental spectra of lithiated and sodiated arginine with one water molecule are very similar and contain spectral signatures for protonated side chains, whereas those of lithiated arginine and singly hydrated lithiated arginine methyl ester are different and contain spectral signatures for neutral side chains. Calculations at the B3LYP/6-31++G** level of theory indicate that solvating lithiated arginine with a single water molecule preferentially stabilizes the zwitterionic forms of this ion by 25-32 kJ/mol and two essentially isoenergetic zwitterionic structure are most stable. In these structures, the metal ion either coordinates with the N-terminal amino group and an oxygen atom of the carboxylate group (NO coordinated) or with both oxygen atoms of the carboxylate group (OO coordinated). In contrast, the OO-coordinated zwitterionic structure of sodiated arginine, both with and without a water molecule, is clearly lowest in energy for both ions. Hydration of the metal ion in these clusters weakens the interactions between the metal ion and the amino acid, whereas hydrogen-bond strengths are largely unaffected. Thus, hydration preferentially stabilizes the zwitterionic structures, all of which contain strong hydrogen bonds. Metal ion size strongly affects the relative propensity for these ions to form NO or OO coordinated structures and results in different zwitterionic structures for lithiated and sodiated arginine clusters containing one water molecule.     

The Anti-Inflammatory Effect of a γ-Lactone Isolated from Ostrich Oil of Struthio camelus (Ratite) and Its Formulated Nano-Emulsion in Formalin-Induced Paw Edema

The ostrich oil of Struthio camelus (Ratite) found uses in folk medicine as an anti-inflammatory in eczema and contact dermatitis. The anti-inflammatory effect of a γ-lactone (5-hexyl-3H-furan-2-one) isolated from ostrich oil and its formulated nano-emulsion in formalin-induced paw edema was investigated in this study. Ostrich oil was saponified using a standard procedure; the aqueous residue was fractionated, purified, and characterized as γ-lactone (5-hexyl-3H-furan-2-one) through the interpretation of IR, NMR, and MS analyses. The γ-lactone was formulated as nano-emulsion using methylcellulose (MC) for oral solubilized form. The γ-lactone methylcellulose nanoparticles (γ-lactone-MC-NPs) were characterized for their size, shape, and encapsulation efficiency with a uniform size of 300 nm and 59.9% drug content. The γ-lactone was applied topically, while the formulated nanoparticles (NPs) were administered orally to rats. A non-steroidal anti-inflammatory drug (diclofenac gel) was used as a reference drug for topical use and ibuprofen suspension for oral administration. Edema was measured using the plethysmograph method. Both γ-lactone and γ-lactone-MC-NPs showed reduction of formalin-induced paw edema in rats and proved to be better than the reference drugs; diclofenac gel and ibuprofen emulsion. Histological examination of the skin tissue revealed increased skin thickness with subepidermal edema and mixed inflammatory cellular infiltration, which were significantly reduced by the γ-lactone compared to the positive control (p-value = 0.00013). Diuretic and toxicity studies of oral γ-lactone-MC-NPs were performed. No diuretic activity was observed. However, lethargy, drowsiness, and refusal to feeding observed may limit its oral administration.     

Improvements in glass capillary gas chromatographic polychlorobiphenyl analysis

Separation of a 1:1:1:1 calibration mixture of Aroclors 1221, 1016, 1254, and 1260 on soda glass capillaries coated with Apolane (C-87) or Apiezon L is described. Polychlorobiphenyl congener structures are assigned to 112 separated and partially separated zones. The quantitative composition of Aroclor 1221 is reported. The performance of the two stationary phases on different lengths of laboratory and commercially prepared capillaries is compared and found to be very similar. Aroclors 1221, 1016, 1254, and 1260 are employed (1:1:1:1) for the primary calibration mixture because they contain all components of the commercial materials which pollute the environment; they are also easily obtained from the U.S. EPA Repository so that the method can be used in any laboratory by employing the calibration data given here.     

Magnetic structure of low-dimensional LiCu2O2 multiferroic according to 63,65Cu and 7Li NMR studies

The complex NMR study of the magnetic structure of LiCu₂O₂ multiferroic has been performed. It has been shown that the spin spirals in LiCu₂O₂ are beyond the ab, bc, and ac crystallographic planes. The external magnetic field applied along the c axis of the crystal does not change the spatial orientation of spirals in Cu²⁺ chains. A magnetic field of H ₀ = 94 kOe applied along the a and b axes rotates the planes of spin spirals in chains, tending to orient the normal n of spirals along the external magnetic field. The rotation angle of the planes of the magnetic moments are maximal at H ₀ ?? b.     

Magnetic and dielectric response of cobalt-chromium spinel CoCr<Subscript>2</Subscript>O<Subscript>4</Subscript> in the terahertz frequency range

The nature of the phonon and magnon modes in the CoCr₂O₄ multiferroic with a cubic spinel structure has been studied using submillimeter spectroscopy and infrared Fourier spectroscopy. This paper reports on the first measurement of the evolution with temperature of the exchange optical magnon in the ferrimagnetic (T _C = 94 K) and two low-symmetry (T _S ≈ 26 K, T _lock-in = 14.5 K) phases of CoCr₂O₄ down to T = 5 K in zero magnetic field. It has been shown that the detected magnon is not a ferrimagnetic order parameter and originates, most probably, from spin precession in the cobalt sublattices. At the points of the magnetic phase transitions, the oscillator parameters of the two lowest-frequency phonon modes reveal an anomalous temperature behavior, thus evidencing the presence of significant interaction between the magnetic and phonon subsystems. The increase by 25% of the damping parameter of the phonon mode originating from vibrations of the CoO₄ tetrahedra during the transition of CoCr₂O₄ to the multiferroic state (T < T _S ) suggests structural changes in the lattice involving loss of spatial central symmetry of the medium.     

Lead zirconate titanate-nickel zink ferrite thick-film composites: obtaining by the screen printing technique and magnetoelectric properties

Layered thick-film composites containing one lead zirconate titanate (PZT) layer, one nickel zinc ferrite (NZF) layer, two PZT-NZF layers, or three PZT-NZF-PZT layers each 40–50 μm thick are prepared. The layers are applied by screen printing on a ceramic aluminum oxide substrate with a preformed contact (conducting) layer. The dielectric properties of the composites are studied in the temperature interval 80–900 K and the frequency interval 25 Hz-1 MHz. Polarized samples exhibit piezoelectric, pyroelectric, and magnetoelectric effects. In tangentially magnetized two- and three-layer composites, the magnetoelectric conversion factor equals 57 kV/(m T) at low frequencies and reaches 2000 kV/(m T) at the mechanical resonance frequency.     

Electrodynamic Characteristics of Solid Solutions Pb(Fe1 – xScx)2/3W1/3O3 in a Broad Spectral Range

Physics of the Solid State - The methods of broadband dielectric spectroscopy are used to study the effect of substitution of Fe3+ by Sc3+ in Pb(Fe1&nbsp;–&nbsp;xScx)2/3W1/3O3 solid...     

Moving toward shared realities through empathy in mathematical modeling: An ecological systems theory approach

The mathematics education community has routinely called for mathematics tasks to be connected to the real world. However, accomplishing this in ways that are relevant to students’ lived experiences can be challenging. Meanwhile, mathematical modeling has gained traction as a way for students to learn mathematics through real-world connections. In an open problem to the mathematics education community, this paper explores connections between the mathematical modeling and the nature of what is considered relevant to students. The role of empathy is discussed as a proposed component for consideration within mathematical modeling so that students can further relate to real-world contexts as examined through the lens of Ecological Systems Theory. This is contextualized through a classroom-tested example entitled “Tiny Homes as a Solution to Homelessness” followed by implications and conclusions as they relate to mathematics education.