The Pt‐Organometallic Version of Perigraniline: Going Blue

Four conjugated push–pull organometallic polymers ( [Pt]‐AQ )_n ( [Pt] = trans‐bis(phenylacetylene)bis(tributylphosphine)platinum(II); AQ = 2‐bromo‐, 2,6‐dibromo‐, 2,6‐diamino‐, and unsubstituted anthraquinone diimine) were prepared and characterized by UV–vis spectroscopy and electrochemistry. A low‐energy charge transfer, CT, band ( [Pt] *→ AQ ; confirmed by density functional theory calculations), was found in the 445–500 nm window rather than the expected red‐shifted range above 630 nm. X‐ray structures of four model compounds reveal that steric hindrance induces large dihedral angles between the C₆H₄ and NCC₂ planes, rendering π‐orbital overlap difficult between the [Pt] and AQ units. The position of the CT band is mainly driven the reduction potential of the anthraquinone diimine unit.     

Relative intensity noise and frequency noise of a compact Brillouin laser made of As38Se62 suspended-core chalcogenide fiber

Relative intensity noise and frequency noise have been measured for the first time for a single-frequency Brillouin chalcogenide As38Se62 fiber laser. This is also the first demonstration of a compact suspended-core fiber Brillouin laser, which exhibits a low threshold power of 22 mW and a slope efficiency of 26% for nonresonant pumping.     

Vocal warm-up produces acoustic change in singers' vibrato rate

Vibrato rate and vibrato extent were acoustically assessed in 12 classically trained female singers before and after 25 minutes of vocal warm-up exercises. Vocal warm-up produced three notable changes in vibrato rate: (1)?more regularity in the cyclic undulations comprising the vibrato rate of a note, (2) more stability in mean vibrato rates from one sustained note to the next, and (3) a moderating of excessively fast and excessively slow mean vibrato rates. No significant change was found for vibrato extent. The findings indicate that vocal warm-up may regulate vibrato rate. Thus tone quality, which is strongly linked to vibrato characteristics, may undergo positive change as a result of vocal warm-up.     

In situ Raman spectroscopic monitoring of hydroxyapatite as human mesenchymal stem cells differentiate into osteoblasts

The differentiation of stem cells into specific cell types is playing an essential role in the development of stem cell therapy, tissue engineering, and regenerative medicine. In this research, Raman microspectroscopy was applied to monitor the development of hydroxyapatite [HA, Ca₅ (PO₄)₃ (OH)], which is associated with the differentiation of the human mesenchymal stem cells (hMSCs) into osteoblasts. Raman spectra exhibited dramatic changes in the HA region, 950–970 cm⁻¹, over the period of 7–21 days after the start of differentiation. This work demonstrates the successful application of Raman spectroscopy for monitoring and quantitatively evaluating hMSC differentiation into osteoblasts. Copyright © 2008 John Wiley & Sons, Ltd.     

Acoustic and Perceptual Appraisal of Vocal Gestures in the Female Classical Voice

Long-term average spectra (LTAS) have identified features in the sounds of singers and have compared different vocal qualities based on energy changes that occur during different vocal tasks. In this study, we compared the perceptual ratings of vocal quality of expert pedagogues with acoustic measures performed on LTAS. Fifteen expert judges rated 24 samples with six repeats of six advanced singing students under two conditions: "optimal" (O), which represented the application of the maximal open throat technique; and "suboptimal" (SO), which represented the application of the reduced open throat technique. LTAS were performed on each singing sample, and two conventional assessments of peak energy height [singing power ratio (SPR)] and peak area [energy ratio (ER)] were calculated on each LTAS. Perceptual scores, SPR, and ER were rank ordered. We then compared perceptual rankings with rankings of acoustic measures (SPR and ER) to assess whether these acoustic measurements matched the perceptual judgments of vocal quality. Although we found the expected significant relationship between SPR and ER, there was no relationship between perceptual ratings of vocal samples or singers based on SPR or ER. These findings suggest that because LTAS measures are not consistent with perceptual ratings of vocal quality, such measurements cannot define a voice of quality. Future research with LTAS to assess vocal quality should consider alternative measures that are more sensitive to subtle differences in vocal parameters.     

Vacuum-UV and Low-Energy Electron-Induced DNA Strand Breaks – Influence of the DNA Sequence and Substrate

DNA is effectively damaged by radiation, which can on the one hand lead to cancer and is on the other hand directly exploited in the treatment of tumor tissue. DNA strand breaks are already induced by photons having an energy below the ionization energy of DNA. At high photon energies, most of the DNA strand breaks are induced by low-energy secondary electrons. In the present study we quantified photon and electron induced DNA strand breaks in four different 12mer oligonucleotides. They are irradiated directly with 8.44 eV vacuum ultraviolet (VUV) photons and 8.8 eV low energy electrons (LEE). By using Si instead of VUV transparent CaF₂ as a substrate the VUV exposure leads to an additional release of LEEs, which have a maximum energy of 3.6 eV and can significantly enhance strand break cross sections. Atomic force microscopy is used to visualize strand breaks on DNA origami platforms and to determine absolute values for the strand break cross sections. Upon irradiation with 8.44 eV photons all the investigated sequences show very similar strand break cross sections in the range of 1.7–2.3×10⁻¹⁶ cm². The strand break cross sections for LEE irradiation at 8.8 eV are one to two orders of magnitude larger than the ones for VUV photons, and a slight sequence dependence is observed. The sequence dependence is even more pronounced for LEEs with energies <3.6 eV. The present results help to assess DNA damage by photons and electrons close to the ionization threshold.     

PLA Electrospun Fibers Reinforced with Organic and Inorganic Nanoparticles: A Comparative Study

In this work, different poly (lactic acid) (PLA)-based nanocomposite electrospun fibers, reinforced with both organic and inorganic nanoparticles, were obtained. As organic fibers, cellulose nanocrystals, CNC, both neat and functionalized by “grafting from” reaction, chitosan and graphene were used; meanwhile, hydroxyapatite and silver nanoparticles were used as inorganic fibers. All of the nanoparticles were added at 1 wt% with respect to the PLA matrix in order to be able to compare their effect. The main aim of this work was to study the morphological, thermal and mechanical properties of the different systems, looking for differences between the effects of the addition of organic or inorganic nanoparticles. No differences were found in either the glass transition temperature or the melting temperature between the different electrospun systems. However, systems reinforced with both neat and functionalized CNC exhibited an enhanced degree of crystallinity of the electrospun fibers, by up to 12.3%. From a mechanical point of view, both organic and inorganic nanoparticles exhibited a decreased elastic modulus and tensile strength in comparison to neat electrospun PLA fibers, improving their elongation at break. Furthermore, all of the organic and inorganic reinforced systems disintegrated under composting conditions after 35 days.     

Dynamic arbitrary waveform shaping in a continuous fiber

We present a low-loss dynamic waveform shaping technique for high-repetition-rate signals by independent phase and amplitude control of spectral lines in a continuous fiber. Our system employs uniform fiber Bragg gratings to separate the spectral lines and provides independent amplitude and phase control for each line via an in-line polarization controller and an in-line fiber stretcher, respectively. Several distinct waveforms are experimentally demonstrated by manipulating five spectral lines with a spectral resolution of 0.12 nm and a temporal resolution of 17 ps. Better temporal resolution can be achieved by increasing the bandwidth through additional spectral lines.     

TADF-based NIR-II semiconducting polymer dots for in vivo 3D bone imaging

Intraoperative fluorescence imaging in the second near-infrared (NIR-II) region heralds a new era in image-guided surgery since the success in the first-in-human liver-tumor surgery guided by NIR-II fluorescence. Limited by the conventional small organic NIR dyes such as FDA-approved indocyanine green with suboptimal NIR-II fluorescence and non-targeting ability, the resulting shallow penetration depth and high false positive diagnostic values have been challenging. Described here is the design of NIR-II emissive semiconducting polymer dots (Pdots) incorporated with thermally activated delayed fluorescence (TADF) moieties to exhibit emission maxima of 1064–1100 nm and fluorescence quantum yields of 0.40–1.58% in aqueous solutions. To further understand how the TADF units affect the molecular packing and the resulting optical properties of Pdots, in-depth and thorough density-functional theory calculations were carried out to better understand the underlying mechanisms. We then applied these Pdots for in vivo 3D bone imaging in mice. This work provides a direction for future designs of NIR-II Pdots and holds promising applications for bone-related diseases.

A series of NIR-II fluorescent TADF-incorporated polymer dots were successfully synthesized. The function of the TADF moiety was fully studied and the bio-applications of these polymer dots including bone imaging were also demonstrated.     

Effect of polymer chain stiffness on initial stages of crystallization of polyetherimides: Coarse‐grained computer simulation

We use dissipative particle dynamics simulation to study the role of the intramolecular stiffness in the crystallization process of aromatic polyetherimides. We have developed and parameterized a coarse‐grained model for polyimides R‐BAPB and R‐BAPS, which have similar chemical structures but different macroscopic properties. The former one is known as semicrystalline, while the latter one is amorphous. In our model, the only difference between these two polyimides is the intramolecular stiffness. We show that this model can reasonably reproduce the structure formation in polyimide melts. We observe initial stages of crystallization of polyimide R–BAPB while R‐BAPS stays amorphous. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1254–1265