Comparison of S, Pt, and Hf adsorption on NiAl(1 1 0)

First-principles periodic slab density-functional theory (DFT) calculations with a plane-wave basis are used to predict the properties of S, Pt, and Hf adsorption on NiAl(1 1 0). Stable adsorption sites are identified, and adsorbate binding energies and structures are predicted. We find that while S adsorbs in a threefold site, the metals prefer to adsorb in the Ni-Ni twofold bridge site. The latter finding is consistent with scanning tunneling microscopy experiments for adsorption of various transition metals on NiAl(1 1 0) by Ho and coworkers. S is predicted to easily diffuse between threefold sites. We find that Pt and Hf both induce significant changes in the local surface structure, changing twofold bridge sites into fourfold coordination sites by drawing next-nearest-neighbor atoms nearly equidistant with the nearest-neighbor atoms. We find Pt favors interaction with Al slightly more than Ni, while Hf shows a particularly strong affinity for Ni compared to Al. We also predict that Hf may diffuse one-dimensionally along Ni rows with a barrier of ≈0.6 eV.     

Self-compression of ultrashort pulses through ionization-induced spatiotemporal reshaping

We present the first demonstration of a new mechanism for temporal compression of ultrashort light pulses that operates at high (i.e., ionizing) intensities. By propagating pulses inside a hollow waveguide filled with low-pressure argon gas, we demonstrate a self-compression from 30 to 13 fs, without the need for any external dispersion compensation. Theoretical models show that 3D spatiotemporal reshaping of the pulse due to a combination of ionization-induced spectral broadening, plasma-induced refraction, and guiding in the hollow waveguide are necessary to explain the compression mechanism.     

Detection of spectrally complex signals in comodulated maskers: effect of temporal fringe

This study tested the hypothesis that masking release for a complex signal under conditions where signal energy is present in all frequency regions occupied by the masker is attributable to an across-frequency-channel comodulation masking release (CMR) process. The approach was to identify a signature CMR trait, and to then determine if that trait was associated with the detection advantage for complex signals. The selected trait was the decline of CMR in the presence of a random temporal fringe. In experiment 1, a masking release was observed for a four-component harmonic signal presented in a comodulated masker, and this masking release was diminished by the random temporal fringe. A similar effect was observed in experiment 2 for a four-component inharmonic signal. These results support the hypothesis that a CMR can be measured for a complex signal even when there is substantial spectral overlap between the signal and its comodulated masker. This finding has consequences for CMR models since it demonstrates that the presence of "signal-free" cue bands is not a prerequisite for CMR, and that the presence of comodulation during the signal window is not sufficient to result in CMR.     

Use of bis-(chiral alpha-methylbenzyl)glycine esters for synthesis of enantiopure beta-hydroxyamino esters

[reaction: see text] Aldol reactions using bis-(chiral alpha-methylbenzyl)glycine esters with aldehydes gave excellent diastereoselectivity. Thus, an enantiopure ribosylglycine was prepared for the synthesis of analogues of the natural antibiotics muraymycin. This method was extended for formation of beta-hydroxyamino esters.     

Tandem Diels-Alder/fragmentation approach to the synthesis of eleutherobin

[reaction: see text] A synthesis of 28, the carbon framework of the eleutherobin aglycone, is reported in a 15-step sequence from readily available starting materials. The tandem Diels-Alder reaction of 6 and 7 to produce 18, in which three new rings and six new stereocenters are formed, is a key step in the reaction sequence.     

The masking level difference for signals placed in masker envelope minima and maxima

Previous data on the masking level difference (MLD) have suggested that NoSpi detection for a long-duration signal is dominated by signal energy occurring in masker envelope minima. This finding was expanded upon using a brief 500-Hz tonal signal that coincided with either the envelope maximum or minimum of a narrow-band Gaussian noise masker centered at 500 Hz, and data were collected at a range of masker levels. Experiment 1 employed a typical MLD stimulus, consisting of a 30-ms signal and a 50-Hz-wide masker with abrupt spectral edges, and experiment 2 used stimuli generated to eliminate possible spectral cues. Results were quite similar for the two types of stimuli. At the highest masker level the MLD for signals coinciding with masker envelope minima was substantially larger than that for signals coinciding with envelope maxima, a result that was primarily due to decreased NoSpi thresholds in masker minima. For most observers this effect was greatly reduced or eliminated at the lowest masker level. These level effects are broadly consistent with the presence of physiological background noise and with a level-dependent binaural temporal window. Comparison of these results with predictions of a published model suggest that basilar-membrane compression alone does not account for this level effect.     

Vowel Effect on Glottal Parameters and the Magnitude of Jaw Opening

This study investigated the relationship among the magnitude of jaw opening, intrinsic fundamental frequency (F0), and glottal parameters in natural speech. Acoustic, jaw opening, and electroglottographic (EGG) signals were simultaneously recorded. The subjects were 10 healthy men with New Zealand English as their native language. Subjects were asked to repeat a standard nonemphasized sentence in which one of the target vowels (/a/, /e/, /i/, /o/, and /u/) was embedded in various contexts. The glottal parameters F0, open quotient (OQ), and speed quotient (SQ) were measured from the EGG signal. Results of a series of one-way repeated-measures analyses of variance (ANOVA) showed a significant vowel effect on the magnitude of jaw opening [F(4, 24) = 25.512, P < .001], F0 [F(4, 28) = 45.415, P < .001] and speed quotient [F(4, 28) = 5.233, P = .003], but not on the open quotient [F(4, 28) = 0.501, P = .735]. The magnitude of jaw opening was found to be inversely related with F0 (r = -0.624, n = 25, P = .0009). These findings showed that the magnitude of jaw opening was related to F0 and that jaw opening might be a control signal for simulation of long-term F0 variation to achieve a higher degree of naturalness in artificial voice.     

Correlation of molecular and morphologic effects of thermoembolization in a swine model using mass spectrometry imaging

Hepatocellular carcinoma is a growing worldwide problem with a high mortality rate. This malignancy does not respond well to chemotherapy, and most patients present late in their disease at which time surgery is no longer an option. Over the past three decades, minimally invasive methods have evolved to treat unresectable disease and prolong survival. Intra‐arterial embolization techniques are used for large or multiple tumors but have distressingly high levels of local recurrence and can be costly to implement. A new method called thermoembolization was recently reported, which destroys target tissue by combining reactive exothermic chemistry with an extreme local change in pH and ischemia. Described herein are experiments performed using this technique in vivo in a swine model. A microcatheter was advanced under fluoroscopic guidance into a branch of the hepatic artery to deliver a targeted dose of dichloroacetyl chloride dissolved in ethiodized oil into the liver. The following day, the animals were imaged by computed tomography and euthanized. Assessing the reaction product distribution and establishing a correlation with the effects are important for understanding the effects. This presented a significant challenge, however, as the reagent used does not contain a chromophore and is not otherwise readily detectable. Mass spectrometry imaging was employed to determine spatial distribution in treated samples. Additional insights on the biology were obtained by correlating the results with histology, immunohistochemistry, and immunofluorescence. The results are encouraging and may lead to a therapy with less local recurrence and improved overall survival for patients with this disease.     

On the Products of Cholesterol Autoxidation in Phospholipid Bilayers and the Formation of Secosterols Derived Therefrom

In homogenous solution, cholesterol autoxidation leads to a mixture of epimers of 5 primary products, whose concentrations vary in the presence/absence of antioxidants, such as vitamin E. Two of the products (5α‐OOH and 6β‐OOH) undergo Hock fragmentation to yield electrophilic secosterols implicated in disease. Herein, we show that the product distribution is similar in phospholipid bilayers, in that the 7‐OOHs are the major products, but the presence/absence of vitamin E has no effect on the distribution. Cholesterol 7α‐OOH, but not 7β‐OOH, undergoes Hock fragmentation to yield a mixture of unprecedented A‐ring cleavage products and 6,7‐epoxides. When subjected to typical derivatization conditions, 7α‐OOH yields products with essentially indistinguishable chromatographic and spectroscopic features from the previously identified secosterols, casting further doubt on their controversial origin from endogenous O₃.