Evidence for compositionally distinct upper mantle plumelets since the early history of the Tristan-Gough hotspot.

Recent studies indicate that mantle plumes, which transfer material and heat from the earth's interior to its surface, represent multifaceted upwellings. The Tristan-Gough hotspot track (South Atlantic), which formed above a mantle plume, documents spatial geochemical zonation in two distinct sub-tracks since ~70 Ma. The origin and the sudden appearance of two distinct geochemical flavors is enigmatic, but could provide insights into the structural evolution of mantle plumes. Sr-Nd-Pb-Hf isotope data from the Late Cretaceous Rio Grande Rise and adjacent Jean Charcot Seamount Chain (South American Plate), which represent the counterpart of the older Tristan-Gough volcanic track (African Plate), extends the bilateral-zonation to ~100 Ma. Our results support recent numerical models, demonstrating that mantle plumes can split into distinct upper mantle conduits, and provide evidence that these plumelets formed at the plume head-to-plume tail transition. We attribute the plume zonation to sampling the geochemically-graded margin of the African Large Low-Shear-Velocity Province.

Acoustically Induced Vocal Training for Individuals With Impaired Hearing.

OBJECTIVES/HYPOTHESIS: Articulation, phonation, and resonance disorders in the speech of hearing-impaired-speakers reduces intelligibility. The study focusses on (1) whether nonacoustic feedback may facilitate the adjustment of the vocal tract, leading to increased vocal tract resonance, and (2) whether training with the feedback would be helpful for the subsequent formation of vowels. STUDY DESIGN: Prospective. METHODS: Seven profoundly hearing-impaired participants used acoustic sound waves in the frequency range of the first two vocal tract resonances applied in front of the open mouth at intensities above 1 Pa. They were asked to amplify the sound via adjusting the vocal tract. The sound waves corresponded to the first and second resonance frequencies of the vowels [u], [o], and [a]. The self-assessment of the participants and a software-based/auditory analysis was reported. RESULTS: The participants were able to enhance the acoustic signal by adjusting the vocal tract shape. The self-perception of the participants, the auditory voice analysis, and the acoustic analysis of vowels were consistent with each other. While the maximum sound pressure levels were constant, the mean sound pressure levels increased. Breathiness and hoarseness declined during the exercises. Resonance/harmonic-to-noise ratio increased, especially for the vowels [u], [o], [a]. Furthermore, the positively connoted feedback from the participants indicated easier sound production. CONCLUSION: Nonauditory feedback, based on acoustic waves, could be suitable for improving the formation of vowels. The findings are in accordance with a reduction of acoustic losses within the vocal tract.

Vocal Tract and Subglottal Impedance in High Performance Singing: A Case Study.

OBJECTIVES/HYPOTHESIS: The respiratory process is important in vocal training and in professional singing, the airflow is highly important. It is hypothesized that subglottal resonances are important to the singing voice in high performance singing. STUDY DESIGN: Single subject, prospective. METHOD: A professional soprano singer shaped her vocal tract to form the vowels [a], [e], [i], [o], and [u] at the pitch d4. We measured phonated vowels and the vocal tract impedance spectra with a deterministic noise supplied by an iPhone buzzer in the range of 200 to 4,000 Hz at closed glottis, during exhalation and during inhalation while maintaining the shape of the vocal tract. RESULTS: Measurements of the phonated vowels before and after the different glottal adjustments were highly reproducible. Vocal tract resonances and the ones resulting during respiration are reported. The impedance spectra show vowel dependent resonances with closed and open glottis. The formants of the vocal spectra are explained by including both, the vocal tract, and the subglottal resonances. CONCLUSION: The findings indicate that subglottal resonances influence the first formant as well as the singers's formant cluster in high-performance singing. The instrumental setup used for the impedance measurement allows a simple and lightweight procedure for a measurement of vocal tract and subglottal resonances.

Adjustment of Vocal Tract Shape via Biofeedback: Influence on Vowels.

The study assessed 30 nonprofessional singers to evaluate the effects of vocal tract shape adjustment via increased resonance toward an externally applied sinusoidal frequency of 900 Hz without phonation. The amplification of the sound wave was used as biofeedback signal and the intensity and the formant position of the basic vowels /a/, /e/, /i/, /o/, and /u/ were compared before and after a vocal tract adjustment period. After the adjustment period, the intensities for all vowels increased and the measured changes correlated with the participants' self-perception.The diferences between the second formant position of the vowels and the applied frequency influences the changes in amplitude and in formant frequencies. The most significant changes in formant frequency occurred with vowels that did not include a formant frequency of 900 Hz, while the increase in amplitude was the strongest for vowels with a formant frequency of about 900 Hz.

Adjustment of the Vocal Tract Shape via Biofeedback: A Case Study.

In this study, an adjustment of the vocal tract shape toward selected sound waves in the frequency range of the first and second formants without phonation is discussed. The sound waves of a loudspeaker in front of the open mouth and amplified by the vocal tract are used as biofeedback signals. It is shown that the resonance amplification of the vocal tract complies with the concept of forced oscillation, with the driver being the sound source and the resonator being the vocal tract. An adjustment toward increased amplification via vocal tract resonance can be related to smaller bandwidths and lower damping. Furthermore, the applied adjustment frequencies are preserved as vocal tract resonances during exhalation and even phonation. This novel form of biofeedback might enrich standard voice training procedures by exercises without phonation.

Influence of structure geometry on THz emission from Black Silicon surfaces fabricated by reactive ion etching.

The influence of structure geometry on THz emission from Black Silicon (BS) surfaces fabricated by reactive ion etching (RIE) has been investigated by a comprehensive study including optical simulations, optical-pump THz probe and THz emission studies. A strong enhancement of THz emission is observed with increasing structure depth, which is mainly related to the increased number of carriers created within the silicon needles and not due to the overall absorption enhancement as previously claimed for silicon nanowires.

Breaking the diffraction limit of light-sheet fluorescence microscopy by RESOLFT.

We present a plane-scanning RESOLFT [reversible saturable/switchable optical (fluorescence) transitions] light-sheet (LS) nanoscope, which fundamentally overcomes the diffraction barrier in the axial direction via confinement of the fluorescent molecular state to a sheet of subdiffraction thickness around the focal plane. To this end, reversibly switchable fluorophores located right above and below the focal plane are transferred to a nonfluorescent state at each scanning step. LS-RESOLFT nanoscopy offers wide-field 3D imaging of living biological specimens with low light dose and axial resolution far beyond the diffraction barrier. We demonstrate optical sections that are thinner by 5-12-fold compared with their conventional diffraction-limited LS analogs.

STED nanoscopy with fluorescent quantum dots.

The widely popular class of quantum-dot molecular labels could so far not be utilized as standard fluorescent probes in STED (stimulated emission depletion) nanoscopy. This is because broad quantum-dot excitation spectra extend deeply into the spectral bands used for STED, thus compromising the transient fluorescence silencing required for attaining super-resolution. Here we report the discovery that STED nanoscopy of several red-emitting commercially available quantum dots is in fact successfully realized by the increasingly popular 775 nm STED laser light. A resolution of presently ∼ 50 nm is demonstrated for single quantum dots, and sub-diffraction resolution is further shown for imaging of quantum-dot-labelled vimentin filaments in fibroblasts. The high quantum-dot photostability enables repeated STED recordings with >1,000 frames. In addition, we have evidence that the tendency of quantum-dot labels to blink is largely suppressed by combined action of excitation and STED beams. Quantum-dot STED significantly expands the realm of application of STED nanoscopy, and, given the high stability of these probes, holds promise for extended time-lapse imaging.

Molecular orientation affects localization accuracy in superresolution far-field fluorescence microscopy.

We investigate the cooperative effect of molecular tilt and defocus on fluorophore localization by centroid calculation in far-field superresolution microscopy based on stochastic single molecule switching. If tilt angle and defocus are unknown, the localization contains systematic errors up to about ±125 nm. When imaging rotation-impaired fluorophores of unknown random orientation, the average localization accuracy in three-dimensional samples is typically limited to about ±32 nm, restricting the attainable resolution accordingly.

Quantum dot blueing and blinking enables fluorescence nanoscopy.

We demonstrate superresolution fluorescence imaging of cells using bioconjugated CdSe/ZnS quantum dot markers. Fluorescence blueing of quantum dot cores facilitates separation of blinking markers residing closer than the diffraction barrier. The high number of successively emitted photons enables ground state depletion microscopy followed by individual marker return with a resolving power of the size of a single dot (∼12 nm). Nanoscale imaging is feasible with a simple webcam.