Polymers are usually considered thermal insulators, because the amorphous arrangement of the molecular chains reduces the mean free path of heat-conducting phonons. The most common method to increase thermal conductivity is to draw polymeric fibres, which increases chain alignment and crystallinity, but creates a material that currently has limited thermal applications. Here we show that pure polythiophene nanofibres can have a thermal conductivity up to ∼ 4.4 W m(-1) K(-1) (more than 20 times higher than the bulk polymer value) while remaining amorphous. This enhancement results from significant molecular chain orientation along the fibre axis that is obtained during electropolymerization using nanoscale templates. Thermal conductivity data suggest that, unlike in drawn crystalline fibres, in our fibres the dominant phonon-scattering process at room temperature is still related to structural disorder. Using vertically aligned arrays of nanofibres, we demonstrate effective heat transfer at critical contacts in electronic devices operating under high-power conditions at 200 °C over numerous cycles.
We derived a new method for direct calculation of the modal contributions to thermal conductivity, which is termed Green-Kubo modal analysis (GKMA). The GKMA method combines the lattice dynamics formalism with the Green-Kubo formula for thermal conductivity, such that the thermal conductivity becomes a direct summation of modal contributions, where one need not define the phonon velocity. As a result, the GKMA method can be applied to any material/group of atoms, where the atoms vibrate around stable equilibrium positions, which includes non-stoichiometric compounds, random alloys, amorphous materials and even rigid molecules. By using molecular dynamics simulations to obtain the time history of each mode's contribution to the heat current, one naturally includes anharmonicity to full order and can obtain insight into the interactions between different modes through the cross-correlations. As an example, we applied the GMKA method to crystalline and amorphous silicon. The modal contributions at each frequency result from the analysis and thereby allow one to apply a quantum correction to the mode heat capacity to determine the temperature dependence of thermal conductivity. The predicted temperature dependent thermal conductivity for amorphous silicon shows the best agreement with experiments to date. The GKMA method provides new insight into the nature of phonon transport, as it casts the problem in terms of mode-mode correlation instead of scattering, and provides a general unified formalism that can be used to understand phonon-phonon interactions in essentially any class of materials or structures where the atoms vibrate around stable equilibrium sites.
Optimal treatment for resectable esophageal squamous cell carcinoma (ESCC) is controversial, especially in the context of potential benefit of combining PD‐1 blockade with neoadjuvant therapy. This phase 2 study aimed to assess neoadjuvant camrelizumab plus chemotherapy in this population. Patients (clinical stage II‐IVA) received two cycles of neoadjuvant chemoimmunotherapy (NIC) with camrelizumab (200 mg on day 1) plus nab‐paclitaxel (260 mg/m2 in total on day 1 and day 8) and cisplatin (75 mg/m2 in total on days 1‐3) of each 21‐day cycle. Surgery was performed approximately 6 weeks after completion of NIC. Primary endpoint was complete pathologic response (CPR) rate in primary tumor. Secondary endpoints were objective response rate (ORR) per RECIST v1.1, 2‐year progression‐free survival (PFS) rate after surgery, PFS, overall survival (OS) and safety during NIC and perioperative period. Between 17 January 2020 and 8 December 2020, 56 patients were enrolled, and 51 received esophagectomy. Data cutoff date was 25 August 2021. The CPR rate was 35.3% (95% CI, 21.7%‐48.9%). NIC had an ORR of 66.7% (95% CI, 40.0%‐70.4%) and treatment‐related adverse events (TRAEs) of low severity (grade 1‐2, 75.0%; grade 3, 10.7%; grade 4‐5, no). No perioperative mortality occurred. Three (5.9%) patients had tumor recurrence and one (2.0%) patient died. The 2‐year PFS rate, median PFS and median OS had not been reached yet. Camrelizumab plus neoadjuvant chemotherapy in resectable ESCC demonstrates promising efficacy with acceptable toxicity, providing a feasible and effective option. Study is ongoing for long‐term survival analyses.
Current understanding of phonons treats them as plane waves/quasi-particles of atomic vibration that propagate and scatter. The problem is that conceptually, when any level of disorder is introduced, whether compositional or structural, the character of vibrational modes in solids changes, yet nearly all theoretical treatments continue to assume phonons are still waves. For example, the phonon contributions to alloy thermal conductivity (TC) rely on this assumption and are most often computed from the virtual crystal approximation (VCA). Good agreement is obtained in some cases, but there are many instances where it fails-both quantitatively and qualitatively. Here, we show that the conventional theory and understanding of phonons requires revision, because the critical assumption that all phonons/normal modes resemble plane waves with well-defined velocities is no longer valid when disorder is introduced. Here we show, surprisingly, that the character of phonons changes dramatically within the first few percent of impurity concentration, beyond which phonons more closely resemble the modes found in amorphous materials. We then utilize a different theory that can treat modes with any character and experimentally confirm its new insights.
The first synthesis of the tamoxifen metabolite norendoxifen is reported. This included syntheses of (E)-norendoxifen, (Z)-norendoxifen, and (E,Z)-norendoxifen isomers. (Z)-Norendoxifen displayed affinity for aromatase (Ki 442 nM), estrogen receptor-α (EC50 17 nM), and estrogen receptor-β (EC50 27.5 nM), while the corresponding values for (E)-norendoxifen were aromatase (Ki 48 nM), estrogen receptor-α (EC50 58.7 nM), and estrogen receptor-β (EC50 78.5 nM). Docking and energy minimization studies were performed with (E)-norendoxifen on aromatase, and the results provide a foundation for structure-based drug design. The oral pharmacokinetic parameters for (E,Z)-norendoxifen were determined in mice, and (Z)-norendoxifen was found to result in significantly higher plasma concentrations and exposures (AUC values) than (E)-norendoxifen. The affinities of both isomers for aromatase and the estrogen receptors, as well as the pharmacokinetic results, support the further development of norendoxifen and its analogues for breast cancer treatment.
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