Length Dependent Thermal Conductivity Measurements Yield Phonon Mean Free Path Spectra in Nanostructures

Thermal conductivity measurements over variable lengths on nanostructures such as nanowires provide important information about the mean free paths (MFPs) of the phonons responsible for heat conduction. However, nearly all of these measurements have been interpreted using an average MFP even though phonons in many crystals possess a broad MFP spectrum. Here, we present a reconstruction method to obtain MFP spectra of nanostructures from variable-length thermal conductivity measurements. Using this method, we investigate recently reported length-dependent thermal conductivity measurements on SiGe alloy nanowires and suspended graphene ribbons. We find that the recent measurements on graphene imply that 70 % of the heat in graphene is carried by phonons with MFPs longer than 1 micron

Quasiballistic Thermal Transport from Nanoscale Heaters and the Role of the Spatial Frequency

Quasiballistic heat conduction from nanoscale heat sources of size comparable to phonon mean free paths has recently become of intense interest both scientifically and for its applications. Prior work has established that, in the quasiballistic regime, the apparent thermal properties of materials depend both on intrinsic mechanisms and the characteristics of the applied thermal gradient. However, many aspects of this regime remain poorly understood. Here, we experimentally study the thermal response of crystals to large thermal gradients generated by optical heating of nanoline arrays. Our experiments reveal the key role of the spatial frequencies and Fourier series amplitudes of the heating profile for thermal transport in the quasiballistic regime, in contrast to the conventional picture that focuses on the geometric dimensions of the individual heaters. Our work provides the insight needed to rationally mitigate local hot spots in modern applications by manipulating the spatial frequencies of the heater patterns

With Brexit, inward investment will fall in the UK

Supply chains cross borders many times before components go into a final product in any EU country, write David Bailey, Nigel Driffield and Michail Karoglo

Progressive Research in the Molecular Mechanisms of Chronic Fluorosis

Long-term excessive intake of fluoride (F) leads to chronic fluorosis, resulting in dental fluorosis and skeletal fluorosis. Chronic exposure to high doses of fluoride can also cause damage to soft tissues, especially when it passes through the blood-brain, blood-testis, and blood-placenta barrier, causing damage to the corresponding tissues. Fluorosis has become a public health problem in some countries or regions around the world. Understanding the pathogenesis of fluorosis is very important. Although the exact mechanism of fluorosis has not been fully elucidated, various mechanisms of fluoride-induced toxicity have been proposed. In this chapter, we will introduce the research progress of the mechanism of fluorosis, focusing on dental fluorosis, skeletal fluorosis, nervous and reproductive system toxicity, and influential factors related to fluoride toxicity (i.e., genetic background, co-exposure with other element). In addition, the application of proteomics and metabolomics in the study of the pathogenesis of fluorosis is also introduced. Currently, there is still no specific treatment for fluorosis. However, since fluorosis is caused by excessive intake of fluoride, avoiding excessive fluoride intake is the critical measure to prevent the disease. In endemic regions, health education and supplement diet with vitamins C, D and E, and calcium and antioxidant compounds are important

Mechanism of circular RNA hsa_circ_0012779 expression in nasopharyngeal carcinoma and its influence on cell biological behavior

Background and purpose: Circular RNA (circRNA) plays an important regulatory role in the development of a variety of tumors. However, the abnormal expression and biological function of circRNA in nasopharyngeal carcinoma remain unclear. This study aimed to explore the effect of hsa_circ_0012779 on the biological behavior of nasopharyngeal carcinoma cells and its molecular mechanism. Methods: The expression of hsa_circ_0012779 in human immortalized nasopharyngeal epithelial cell line NP69 and nasopharyngeal carcinoma cell lines CNE2, 5-8F, HNE1 and SUNE1 was detected by real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR). Cell counting kit-8 (CCK-8) assay and transwell invasion assay were used to detect the effect of hsa_circ_0012779 on the proliferation and invasion ability of nasopharyngeal carcinoma cells. The protein level of ELAV like protein 1 (ELAVL1) in NPC cells with hsa_circ_0012779 knockdown was detected by Western blot. The binding of hsa_circ_0012779 and ELAVL1 was verified by RNA pull-down assay. Results: hsa_circ_0012779 was highly expressed in nasopharyngeal carcinoma tissues and cells. Knockdown hsa_circ_0012779 could inhibit the proliferation and invasion of nasopharyngeal carcinoma cells. hsa_circ_0012779 bound to RNA-binding protein ELAVL1 to promote its expression and colocalization in cytoplasm. In the meanwhile, the effect of knockdown hsa_circ_0012779 on nasopharyngeal carcinoma cells could be reversed by the overexpression of ELAVL1. Conclusion: hsa_circ_0012779 promote the expression of ELAVL1 and thus promote the proliferation and invasion of nasopharyngeal carcinoma, and influence the occurrence and development of nasopharyngeal carcinoma

Locate and Beamform: Two-dimensional Locating All-neural Beamformer for Multi-channel Speech Separation

Recently, stunning improvements on multi-channel speech separation have been achieved by neural beamformers when direction information is available. However, most of them neglect to utilize speaker's 2-dimensional (2D) location cues contained in mixture signal, which limits the performance when two sources come from close directions. In this paper, we propose an end-to-end beamforming network for 2D location guided speech separation merely given mixture signal. It first estimates discriminable direction and 2D location cues, which imply directions the sources come from in multi views of microphones and their 2D coordinates. These cues are then integrated into location-aware neural beamformer, thus allowing accurate reconstruction of two sources' speech signals. Experiments show that our proposed model not only achieves a comprehensive decent improvement compared to baseline systems, but avoids inferior performance on spatial overlapping cases.Comment: Accepted by Interspeech 2023. arXiv admin note: substantial text overlap with arXiv:2212.0340