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Delicate morphology and defect control are crucial for high-performance optoelectronics. For metal halide perovskites, antisolvent precipitation is the most common process to realize the control and develop the state-of-art devices. However, the solute/solvent/antisolvent interactions and their influence on the film formation process are unclear. Here, we propose a novel solubility parameter δDNto measure the coordinate interaction between solvent and perovskite precursors. A combination of δDNand Hansen’s solubility parameters allows for the first comprehensive analysis of interactions between pure liquids and the perovskite precursors. The relative energy difference (RED) between antisolvent and solvent is used to quantify the supersaturation level during film deposition. Dense morphology films form in the maximum supersaturation region (0.85 < RED < 1.00). Perovskite properties are controlled by the interaction behavior difference in antisolvent/solutes. The photovoltaic performance increases by 53% when RED increases from 0.416 to 0.858. We demonstrate that detailed knowledge of the physicochemical characteristics of the solutions used to form films of perovskites is a valuable tool in the discovery of optimum film formation conditions and consequently in attaining efficient optoelectronic performance.

A major challenge in orthopedics is the repair of large non-union bone fractures. A promising therapy for this indication is the use of biodegradable bioinspired biomaterials that stabilize the fracture site, relieve pain and initiate bone formation and healing. This study uses a multidisciplinary evaluation strategy to assess immunogenicity, allergenicity, bone responses and physicochemical properties of a novel biomaterial scaffold. Two-photon stereolithography generated personalized custom-built scaffolds with a repeating 3D structure of Schwarz Primitive minimal surface unit cell with a specific pore size of ∼400 μm from three different methacrylated poly(d,l-lactide-co--caprolactone) copolymers with lactide to caprolactone monomer ratios of 16 : 4, 18 : 2 and 9 : 1. Using in vitroand in vivoassays for bone responses, immunological reactions and degradation dynamics, we found that copolymer composition influenced the scaffold physicochemical and biological properties. The scaffolds with the fastest degradation rate correlated with adverse cellular effects and mechanical stiffness correlated with in vitroosteoblast mineralization. The physicochemical properties also correlated with in vivobone healing and immune responses. Overall these observations provide compelling support for these scaffolds for bone repair and illustrate the effectiveness of a promising multidisciplinary strategy with great potential for the preclinical evaluation of biomaterials.

Phosphate-based glasses (PBGs) are bioactive and fully degradable materials with tailorable degradation rates. PBGs can be produced as porous microspheres through a single-step process, using changes in their formulation and geometry to produce varying pore sizes and interconnectivity for use in a range of applications, including biomedical use. Calcium phosphate PBGs have recently been proposed as orthobiologics, based on their in vitro cytocompatibility and ion release profile. In this study, porous microspheres made of two PBG formulations either containing TiO2(P40Ti) or without (P40) were implanted in vivo in a large animal model of bone defect. The biocompatibility and osteogenic potential of these porous materials were assessed 13 weeks postimplantation in sheep and compared to empty defects and autologous bone grafts used as negative and positive controls. Histological analysis showed marked differences between the two formulations, as lower trabeculae-like interconnection and higher fatty bone marrow content were observed in the faster degrading P40-implanted defects, while the slower degrading P40Ti material promoted dense interconnected tissue. Autologous bone marrow concentrate (BMC) was also incorporated within the P40 and P40Ti microspheres in some defects; however, no significant differences were observed in comparison to microspheres implanted alone. Both formulations induced the formation of a collagen-enriched matrix, from 20 to 40% for P40 and P40Ti2.5 groups, suggesting commitment toward the bone lineage. With the faster degrading P40 formulation, mineralization of the tissue matrix was observed both with and without BMC. Some lymphocyte-like cells and foreign body multinucleated giant cells were observed with P40Ti2.5, suggesting that this more durable formulation might be linked to an inflammatory response. In conclusion, these first in vivo results indicate that PBG microspheres could be useful candidates for bone repair and regenerative medicine strategies and highlight the role of material degradation in the process of tissue formation and maturation.

The chemical formulation of phosphate-based glasses (PBGs) can be tailored to fit particular end applications such as bone tissue engineering. While most reports to date have evaluated the effect of PBG chemical formulation on bone cells, this study specifically explored the manufacturing process, the changes in physical and chemical properties of PBG particles after flame spheroidization, and subsequent effects on human mesenchymal stem cells (hMSCs), a prime cell type for regenerative medicine applications. Flame spheroidization involves feeding irregular PBG particles (microparticles, MP) into a hot flame, causing them to melt and mold into solid spherical PBG particles (microspheres, MS). The laser diffraction analysis showed an increase in the volume-weighted mean diameter of particles from 48 to 139 μm after spheroidization and also revealed changes in the chemical composition of smaller MS (< 45 μm in size), whereas MS in other size ranges did not show significantly different chemical composition compared to MP. Additionally, some air bubbles were entrapped inside particles during spheroidization, causing a 2% drop in relative density of MS. However, the packing density of MS was 30% higher than that of MP. Culture of hMSCs on the particles showed significant improvement in cell spreading on MS compared to that on MP and nearly 2 times higher cell metabolic activity after 7 days of culture, suggesting that MS provided a more favorable support and geometry for hMSC attachment and growth for tissue engineering.

Quinternary phosphate-based glasses of up to 2.67 μm, deposited by radio-frequency magnetron sputtering, were degraded in distilled water and phosphate-buffered saline (PBS) to investigate their degradation characteristics. Magnetron-sputtered coatings have been structurally compared to their compositionally equivalent melt-quenched bulk glass counterparts. The coatings were found to have structurally variable surfaces to melt-quenched glass such that the respective bridging oxygen to nonbridging oxygen bonds were 34.2% to 65.8% versus 20.5% to 79.5%, forming metaphosphate (PO3)−(Q2) versus less soluble (P2O7)4–(Q1) and (PO4)3–(Q0), respectively. This factor led to highly soluble coatings, exhibiting a t1/2degradation dependence in the first 2 h in distilled water, followed by a more characteristic linear profile because the subsequent layers were less soluble. Degradation was observed to preferentially occur, forming voids characteristic of pitting corrosion, which was confirmed by the use of a focused ion beam. Coating degradation in PBS precipitated a (PO3)−metaphosphate, an X-ray amorphous layer, which remained adherent to the substrate and seemingly formed a protective diffusion barrier, which inhibited further coating degradation. The implications are that while compositionally similar, sputter-deposited coatings and melt-quenched glasses are structurally dissimilar, most notably, with regard to the surface layer. This factor has been attributed to surface etching of the as-deposited coating layer during deposition and variation in the thermal history between the processes of magnetron sputtering and melt quenching.

Adding redox activity into ionic liquids (ILs) extends their practical roles beyond an inert ionic conductor or electrolyte for applications in electrochemical energy storage. Especially for supercapatteries, redox ILs are desirable because they can contribute to increasing the charge storage capacity by merging the capacitive and Nernstian storage mechanisms without compromising their intrinsic wide potential windows. Several prospects of redox ILs are identified and discussed for optimising performance in supercapatteries.

The anisotropic character of the chemical shift can be measured by experiments that provide shift tensor values and comparing these experimental components, obtained from microcrystalline powders, with 3D nuclear shielding tensor components, calculated with quantum chemistry, yields structural models of the analyzed molecules. The use of a metric tensor for evaluating the mean squared deviations, d2, between two or more tensors provides a statistical way to verify the molecular structure governing the theoretical shielding components. The sensitivity of the method is comparable with diffraction methods for the heavier organic atoms i.e., C, O, N, etc. but considerably better for the positions of H atoms. Thus, the method is especially powerful for Hbond structure, the position of water molecules in biomolecular species, and other proton important structural features, etc. Unfortunately, the traditional Cartesian tensor components appear as reducible metric representations and lack the orthogonality of irreducible icosahedral and irreducible spherical tensors, both of which are also easy to normalize. Metrics give weighting factors that carry important statistical significance in a structure determination. Details of the mathematical analysis are presented and examples given to illustrate the reason nuclear magnetic resonance are rapidly assuming an important synergistic relationship with diffraction methods Xray, neutron scattering, and high energy synchrotron irradiation. © 2009 Wiley Periodicals, Inc.Concepts Magn Reson Part A 34A: 217–237, 2009.

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Complete suppression of the resonances from protonated carbons in a slow magic angle spinning experiment can be achieved using five dipolar dephasing (Five-DD) periods distributed in one rotor period. This produces a spectrum containing only the spinning sidebands (SSB) from the nonprotonated carbons. It is shown that the SSB patterns corresponding to the nonprotonated carbons are not distorted over a wide range of dipolar dephasing times. Hence, this method can be used to obtain reliable principal values of the chemical shift tensors for each nonprotonated carbon. The Five-DD method can be readily incorporated into isotropic–anisotropic 2D experiments such as FIREMAT and 2D-PASS to facilitate the measurement of the 13C chemical shift tensors in complex systems.

The ¹³C principal values of the chemical-shift tensor for fluorene, carbazole, dibenzofuran and dibenzothiophene were determined with the FIREMAT and PHORMAT experiments. Theoretical calculations (DFT) of the tensors were used as an aid to spectral assignment of the tensors, particularly in some positions in which the isotropic chemical shifts were accidentally degenerate. The principal values are discussed in terms of the effects of the heterosubstitutions. Copyright © 2001 John Wiley & Sons, Ltd.

It is shown in this paper that a previously reported 90° sample flipping 13C 2D CSA-CSA correlation experiment may be carried out alternatively by employing constant slow sample rotation about the magic angle axis and by synchronizing the read pulse to 13of the rotor cycle. A high-resolution 3D CSA-CSA-CSA correlation experiment based on the magic angle turning technique is reported in which the conventional 90° 2D CSA-CSA powder pattern for each carbon in a system containing a number of inequivalent carbons may be separated according to the isotropic chemical shift value. The technique is demonstrated on 1,2,3-trimethoxybenzene in which all of the overlapping powder patterns that cannot be segregated by the 2D CSA-CSA experiment are resolved successfully by the 3D CSA-CSA-CSA experiment, including even the two methoxy groups (M1and M3) whose isotropic shifts, confirmed by high-speed MAS, are separated by only 1 ppm. A difference of 4 ppm in the principal value component (δ33) between M1and M3is readily obtained.

1H dynamic nuclear polarization (DNP) has been measured in supercritical ethylene in the pressure range 60–300 bar in an external field of 1.4 T. A single-cell sapphire tube was used as a high-pressure cell, and powdered 1,3-bisdiphenylene-2-phenyl allyl (BDPA) free radicals were added and distributed at the wall of the cell. At all pressures the dominant DNP mechanism was a positive Overhauser enhancement, caused by proton–electron contact interactions at the fluid/solid radical interface. The observed enhancements varied from 12 at 60 bar to 17 at 300 bar. Besides the Overhauser enhancement, small solid state and thermal mixing enhancements also were observed, indicating that part of the ethylene was adsorbed at the radical surface for a prolonged time. The impacts of the experimental conditions on the Overhauser enhancement factors are discussed, and enhancements of at least 40–60 are estimated when the EPR saturation factor and the leakage factor become maximal. These data indicate that DNP-enhanced NMR has the potential of extending the impact of NMR in research areas involving supercritical fluids.

The spectral editing approach of Zilm and coworkers utilizes polarization, polarization inversion, and spin depolarization methods for enhancing or suppressing NMR spectral lines in solids. The proposed pulse sequences allow nonprotonated C, CH, CH2, and CH3types of carbon resonances to be separated from one another and identified accordingly. The former method tentatively separates the nonprotonated C and CH3peaks with a cutoff shift of 35 ppm. This shift is a reasonable demarcation shift for a preponderance of organic molecules, but exceptions do exist that could constitute a serious drawback in a few instances. The new approach separates the nonprotonated C and CH3carbon peaks unequivocally using modified pulse sequences similar to those of Zilm. Further, both the CH only and CH2only spectra, respectively, can be acquired directly from combining so called (+) and (−) sequences using different spectral delay periods and pulse parameters. The (+) and the (−) pulse sequences produce signals for the nonprotonated and methyl carbons that have essentially the same amplitude but opposite phases. These spectra, combined with the previously reported CH3and nonprontonated C only spectra, offer a complete spectral editing technique for solid samples. Examples of these spectral editing methods are provided for 3-methylglutaric acid, fumaric acid monoethyl ester, and two complex natural products: methyl o-methylpodocarpate and 10-deacetylbaccatin III.

Many solid-state spectra have been shown to have problems related to the poor proton decoupling of carbon nuclei in methylene groups under conditions of slow magic-angle turning. Two-pulse phase-modulation (TPPM) decoupling during the 2D PHORMAT chemical shift separation experiment is shown to be more effective in comparison to that obtainable at much higher spin rates using conventional CW decoupling. TPPM decoupling can also alleviate similar inadequacies when observing the15N nucleus, particularly with NH2groups. This is demonstrated in the15N resonances of fully labeledl-arginine hydrochloride, where a line narrowing of about a factor of two was observed at moderate rotation rates. This significant advantage was also obtained at turning frequencies as low as 500 Hz.

Complete carbon-13 chemical-shift tensors are measured in single crystals of the monosaccharides β-D-fructopyranose [57-48-7], α-L-sorbopyranose [87-79-6], and α-D-xylopyranose [58-86-6] using the two-dimensional chemical-shift correlation technique with a multiple-axis sample-reorientation mechanism. Symmetry-constrained fitting of the experimental data extracts the tensors for the four equivalent molecules in theP212121unit cells and the directions of the three twofold axes in the orthorhombic crystals. The standard deviations of the symmetry fits to the data are 0.30, 0.40, and 0.29 ppm for the three monosaccharide molecules, respectively. Gauge-invariant atomic orbital (GIAO) computations using the D-95 double-zeta basis set are then used to assign the experimental tensors to the carbons in the molecules and to the molecules in the unit cell. All assignment permutations and combinations are explored, and that which minimizes the RMS deviation between the experimental and computed tensors is accepted as the best assignment. The GIAO results also identify the experimental twofold axes with the crystallographic axes. Because the hydroxymethyl hydroxyl group in sorbose jumps between two positions, it is necessary to compute the tensors for both molecular configurations and then to take a weighted average of the results for comparison with the experimental data. The D-95 GIAO results have RMS deviations from the experimental tensors of 1.90 ppm for fructose, 2.61 ppm for sorbose, and 2.66 ppm for xylose. Similar computations confirm a previous assignment of the carbon-13 tensors in sucrose and yield a 2.85 ppm RMS deviation.

A very simple and general procedure that extracts constant-evolution-frequency data from a truncated multidimensional (2D, 3D, 4D, etc.) FID is described, generalized, analyzed, and illustrated. The method replaces Fourier transformation of the evolution dimension with a linear model created from a separate, high-quality 1D FID. The equivalent of high resolution in the evolution dimension can be achieved without obtaining an extensive multidimensional FID. The analysis of the 1D FID can also be used to predict the signal to noise ratio of the extracted slices that will result from various evolution dimension sampling protocols, making it possible to developa priorian optimal sampling strategy for the multidimensional FID. The evolution dimension need not be sampled periodically. The procedure has a potential signal-to-noise ratio advantage because it extracts usable information from a multidimensional FID at short evolution times before the magnetization has decayed significantly.

The carbon-13 chemical-shift tensors of α-L-rhamnose (6-deoxy-L-mannose) monohydrate (C6H12O5·H2O [10030-85-0]) are measured using two-dimensional chemical-shift correlation spectroscopy. The tensors and the orientation of the twofold axis along thebcrystallographic axis in the sample frame are obtained by symmetry-constrained fitting of the data.Ab initiogauge invariant atomic orbital computations of the chemical shielding are then used to assign the tensors to the carbons in the rhamnose molecule and to the two molecules in the unit cell. These computations are also used to find the direction of thebcrystallographic axis along the twofold axis and to make initial estimates of theaandccrystallographic axes in the sample. The finalaandccrystallographic axes are then determined with a 2D dipolar spectrum. A second independent method, 1D spectra taken with the applied field along directions perpendicular to the (011), the (110), and the (100) crystallographic planes, is used to confirm the result.

Equations describing the magnetization recovery rate of the three identical spins one-half system are presented. The equations are tailored for nuclear spin relaxation studies performed in anisotropic fluids. The ramifications of these expressions are briefly discussed.

The solid state 13C NMR spectra of bicyclo[1.1.0]butane and [1.1.1]propellane have been measured at low temperature. The orientation of the principal axes of the chemical shielding tensor have been determined with ab initio calculations based on the IGLO (Individual Gauge for Localized Orbitals) method when they are not determined by symmetry. Excellent agreement is obtained between the calculated and experimental principal values of the shielding tensor when basis sets containing polarization functions are used. In most cases the agreement is such that the calculated values are within the experimental error.

Abstract:Using data from the 1990 Public Use Microdata Samples (PUMS) and other U.S. census documents, this paper demonstrates how three rather dramatic shifts in the migration behavior of blacks, which took shape during the 1970s, continued to contribute to the geographical redistribution of the black population down the urban hierarchy during the 1980s. Analyses of black migration flows into six metropolitan areas suggest that liberal welfare benefits play, at best, a minor role in contemporary black population redistribution trends. Kinship ties (i.e., location-specific capital), the search for affordable housing, and employment in the hospitality services industry appear to be the dominant forces influencing black migration into the case-study communities.

The Pople model for chemical shielding is applied to calculate the in-plane components of the 13C shielding tensors of condensed aromatic hydrocarbons. The wave functions are evaluated using the MNDO method and the calculated results are supported by the very good agreement with the experimental results in the few cases in which experimental information is available.

Principal values of the ¹³C chemical shift tensor were obtained for the 15 carbons of solid caryophyllene oxide using an improved PHORMAT NMR analysis. The improvements include TIGER processing and improved proton decoupling. TIGER is an alternative to Fourier methods and shortens 2D data collection by incorporating information from a high-resolution isotropic 1D FID to allow accurate processing of even severely truncated 2D evolution FIDs. In caryophyllene oxide, data collection required less than 1 day, giving significant time savings over comparable 2D Fourier methods. Experimental principal values were assigned with high statistical confidence to specific carbons by comparing them with corresponding calculated values. Correctly assigned values were used to evaluate five different tensor calculation methods. For caryophyllene oxide, the B3PW91 method gave the best correlation with experimental principal values with an RMS error of 2.3 ppm. Refinement of x-ray positions for hydrogens was shown to improve the calculated RMS error by a factor of >2. Calculated tensors can be used to provide principal value orientations in the three methyl groups of caryophyllene oxide. One of the perpendicular component, δ⊥, is found to exhibit the largest shift variation and dominates the methyl shifts. Sterically unfavorable non-bonded interactions between proximate hydrogens are shown to correlate with this large upfield shift in the δ⊥ component. © 1998 John Wiley & Sons, Ltd.

Recent advances in the theory of dipolar relaxation in multispin systems are applied to studies of methyl rotators in isotropic fluids. A simple methodology is outlined which is very attractive for the investigation of anisotropic methyl group reorientation. It is demonstrated that this approach does not suffer from many of the inherent limitations of conventional applications of dipolar relaxation to such studies. Analogous extensions of the propounded method become temptingly obvious.