Self‐Assembly Structure Formation during the Digestion of Human Breast Milk

An infant′s complete diet, human breast milk, is the basis for its survival and development. It contains water‐soluble and poorly water‐soluble bioactive components, metabolic messages, and energy, all of which are made bioavailable during the digestion process in the infant′s gastrointestinal tract. Reported is the first discovery of highly geometrically organized structures formed during the digestion of human breast milk under simulated in vivo conditions using small‐angle X‐ray scattering and cryogenic transmission electron microscopy. Time of digestion, pH, and bile salt concentration were found to have symbiotic effects gradually tuning the oil‐based environment inside the breast milk globules to more water‐like structures with high internal surface area. The structure formation is necessarily linked to its function as carriers for poorly water‐soluble molecules in the digestive tract of the infant.     

A grain-boundary model for polycrystals and sintered carbides

Experimental verification is given for the predicted action of a model depicting polycrystalline or sintered-carbide systems under stress as proposed by Drucker. The models employed consisted of a regular array of hexagonal bars of aluminum separated by asphalt “cement” layers of uniform thickness throughout. Construction of the models as well as the methods used to determine the viscoelastic properties of the asphalt are described in detail. The results of a series of creep tests, each at a constant load, are compared with the predicted behavior.     

Speech intelligibility and localization in a multi-source environment.

Natural environments typically contain sound sources other than the source of interest that may interfere with the ability of listeners to extract information about the primary source. Studies of speech intelligibility and localization by normal-hearing listeners in the presence of competing speech are reported on in this work. One, two or three competing sentences [IEEE Trans. Audio Electroacoust. 17(3), 225-246 (1969)] were presented from various locations in the horizontal plane in several spatial configurations relative to a target sentence. Target and competing sentences were spoken by the same male talker and at the same level. All experiments were conducted both in an actual sound field and in a virtual sound field. In the virtual sound field, both binaural and monaural conditions were tested. In the speech intelligibility experiment, there were significant improvements in performance when the target and competing sentences were spatially separated. Performance was similar in the actual sound-field and virtual sound-field binaural listening conditions for speech intelligibility. Although most of these improvements are evident monaurally when using the better ear, binaural listening was necessary for large improvements in some situations. In the localization experiment, target source identification was measured in a seven-alternative absolute identification paradigm with the same competing sentence configurations as for the speech study. Performance in the localization experiment was significantly better in the actual sound-field than in the virtual sound-field binaural listening conditions. Under binaural conditions, localization performance was very good, even in the presence of three competing sentences. Under monaural conditions, performance was much worse. For the localization experiment, there was no significant effect of the number or configuration of the competing sentences tested. For these experiments, the performance in the speech intelligibility experiment was not limited by localization ability.     

Behavior of a Microwave Cavity Discharge over a Wide Range of Pressures and Flow Rates

Experiments are conducted over a wide range of pressures, flow rates, and power levels to demonstrate the versatility of a microwave cavity discharge. The experimental results are justified using a linear, cold plasma theory that accounts for the electron-neutral particle collisional losses in the plasma. The resonant coupling of E. M. energy to a surface wave and the resulting formation of a long, large volume plasma column is demonstrated. The absorbed power characteristics of the microwave cavity discharge are examined for gas pressures up to 500 torr and flow rates up to 2500 cm3/min in the TE011 and TE*111 mode operation of the plasma cavity system. The experimental results show that the absorbed power variation as a function of pressure of this discharge is uniform. The power absorbed by the flowing plasma is shown to increase directly as a function of the flow rate initially and reach a saturation at high flow rates. By simultaneously optimizing the cavity length, discharge pressure, and the gas flow, it is possible to couple as much as 90% of the incident power to the plasma.     

Metabolic products of microorganisms. Structure of cinerubine B

The structural determination of the anthracycline antibiotic Cinerubine B by degradation, spectroscopic studies and an X-ray crystallographic analysis of a degradation product is described.     

Bonded stationary phases for reversed phase liquid chromatography with a water mobile phase: application to subcritical water extraction

Reversed phase high-performance liquid chromatography (RP-HPLC) is demonstrated for hydrophobic analytes such as aromatic hydrocarbons on a chemically bonded stationary phase and a mobile phase consisting of only water. Reversed phase liquid chromatography separations using a water-only mobile phase has been termed WRP-LC for water-only reversed phase LC. Reasonable capacity factors are achieved through the use of a non-porous silica substrate resulting in a chromatographic phase volume ratio much lower than usually found in RP-HPLC. Two types of bonded WRP-LC columns have been developed and applied. A brush phase was synthesized from an organochlorosilane. The other phase, synthesized from an organodichlorosilane, is termed a branch phase and results in a polymeric structure of greater thickness than the brush phase. A baseline separation of a mixture containing benzaldehyde, benzene, toluene, and ethyl benzene in less than 5 min is demonstrated using a water mobile phase with 12 000 plates generated for the unretained benzaldehyde peak. The theoretically predicted minimum reduced plate height is also shown to be approached for the unretained analyte using the brush phase. As an application, subcritical water extraction (SWE) at 200°C is combined with WRP-LC. This combination allows for the extraction of organic compounds from solid matrices immediately followed by liquid chromatographic separation of those extracted compounds all using a solvent of 100% water. We demonstrate SWE/WRP-LC by spiking benzene, ethyl benzene, and naphthalene onto sand then extracting the analytes with SWE followed by chromatographic separation on a WRP column. A sand sample contaminated with gasoline was also analyzed using SWE/WRP-LC. This extraction process also provides kinetic information about the rate of analyte extraction from the sand matrix. Under the conditions employed, analytes were extracted at different rates, providing additional selectivity in addition to the WRP-LC separation.     

Synthesis and characterization of carboxylate complexes of Sn(IV) porphyrin monomers and oligomers

Most of the porphyrin-recognition chemistry we have investigated previously has centred on kinetically labile metal-ligand interactions, such as Z-N and Ru-N. Our interest in the broader scope of molecular recognition required a metal with the ability to specifically recognise non-nitrogen-based ligands, with a significantly different binding interaction to distinguish it from nitrogen-based analogues. In this report we describe interactions of Sn(IV) porphyrins that bind oxygen-based ligands and for which the Sn(IV)bond;O bond is in slow exchange on the NMR timescale. A series of carboxylate complexes is employed to highlight the structural/geometric features of porphyrin monomers and cyclic oligomers. Where more than one porphyrin unit is present in a molecular scaffold, we report the effect of carboxylate binding on the complex when the two porphyrins contain different metals (typically Sn(IV) and Zn(II)). The unexpected spectroscopic and structural properties of the Sn(2)(9-anthroic acid)porphyrin dimer are also reported.     

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