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Nanoscale Jun 2023Optical limiters are greatly needed to protect eyes and sensitive optoelectronic devices such as photodetectors and sensors from laser damage, but they are currently...
Optical limiters are greatly needed to protect eyes and sensitive optoelectronic devices such as photodetectors and sensors from laser damage, but they are currently plagued by low efficiency. In this work, we utilized CuVSe nanocrystals (NCs) to enhance laser protection performance, and they exhibit higher saturation intensity and broader nonlinear spectral response extending into the near IR region than the C60 benchmark. A flexible optical limiter goggle prototype based on the NCs significantly attenuated the incident laser beam, with scan and scan measurements demonstrating a giant nonlinear absorption coefficient value of 1.0 × 10 m W, a large optical damage threshold of 3.5 J cm, and a small starting threshold of 0.22 J cm. Transient absorption spectroscopy disclosed that the origin of the excellent nonlinearity was associated with quasi-static dielectric resonance behavior and a large TPA cross-section of 3.3 × 10 GM was measured for CuVSe NCs, suggesting the potential of intermediate bandgap (IB) semiconductors as alternatives to plasmonic noble metals for ultrafast photonics. Hence, optical limiters based on such semiconductors offer new avenues for laser protection in optoelectronic and defense fields.
Topics: Light; Optics and Photonics; Lasers; Nanoparticles
PubMed: 37309836
DOI: 10.1039/d3nr00498h -
Sensors (Basel, Switzerland) Jul 2023Wearable optical fiber sensors have great potential for development in medical monitoring. With the increasing demand for compactness, comfort, accuracy, and other... (Review)
Review
Wearable optical fiber sensors have great potential for development in medical monitoring. With the increasing demand for compactness, comfort, accuracy, and other features in new medical monitoring devices, the development of wearable optical fiber sensors is increasingly meeting these requirements. This paper reviews the latest evolution of wearable optical fiber sensors in the medical field. Three types of wearable optical fiber sensors are analyzed: wearable optical fiber sensors based on Fiber Bragg grating, wearable optical fiber sensors based on light intensity changes, and wearable optical fiber sensors based on Fabry-Perot interferometry. The innovation of wearable optical fiber sensors in respiration and joint monitoring is introduced in detail, and the main principles of three kinds of wearable optical fiber sensors are summarized. In addition, we discuss their advantages, limitations, directions to improve accuracy and the challenges they face. We also look forward to future development prospects, such as the combination of wireless networks which will change how medical services are provided. Wearable optical fiber sensors offer a viable technology for prospective continuous medical surveillance and will change future medical benefits.
Topics: Optical Fibers; Prospective Studies; Light; Interferometry; Wearable Electronic Devices
PubMed: 37571457
DOI: 10.3390/s23156671 -
Reviews on Environmental Health Sep 2023In March 2020, ICNIRP (the International Commission for Non-Ionizing Radiation Protection) published a set of guidelines for limiting exposure to electromagnetic fields... (Review)
Review
In March 2020, ICNIRP (the International Commission for Non-Ionizing Radiation Protection) published a set of guidelines for limiting exposure to electromagnetic fields (100 kHz to 300 GHz). ICNIRP claims this publication's view on EMF and health, a view usually termed "the thermal-only paradigm", is consistent with current scientific understanding. We investigated the literature referenced in ICNIRP 2020 to assess if the variation in authors and research groups behind it meets the fundamental requirement of constituting a broad scientific base and thus a view consistent with current scientific understanding, a requirement that such an important set of guidelines is expected to satisfy. To assess if this requirement has been met, we investigated the span of authors and research groups of the referenced literature of the ICNIRP 2020 Guidelines and annexes. Our analysis shows that ICNIRP 2020 itself, and in practice all its referenced supporting literature stem from a network of co-authors with just 17 researchers at its core, most of them affiliated with ICNIRP and/or the IEEE, and some of them being ICNIRP 2020 authors themselves. Moreover, literature reviews presented by ICNIRP 2020 as being from independent committees, are in fact products of this same informal network of collaborating authors, all committees having ICNIRP 2020 authors as members. This shows that the ICNIRP 2020 Guidelines fail to meet fundamental scientific quality requirements and are therefore not suited as the basis on which to set RF EMF exposure limits for the protection of human health. With its thermal-only view, ICNIRP contrasts with the majority of research findings, and would therefore need a particularly solid scientific foundation. Our analysis demonstrates the contrary to be the case. Hence, the ICNIRP 2020 Guidelines cannot offer a basis for good governance.
Topics: Humans; Radiation Protection; Radio Waves; Authorship; Electromagnetic Fields
PubMed: 35751553
DOI: 10.1515/reveh-2022-0037 -
Ying Yong Sheng Tai Xue Bao = the... Jul 2023Light response curve of photosynthesis (- curve) is a useful modeling tool to investigate how photosynthesis reacts with different abiotic factors, which would help... (Review)
Review
Light response curve of photosynthesis (- curve) is a useful modeling tool to investigate how photosynthesis reacts with different abiotic factors, which would help quantify the response of photosynthetic rate to photosynthetically active radiation. Based on the mathematical characteristics of photosynthesis - models, we reviewed the advantages of using these model in practice and the potential caveats. We proposed the development of new mechanistic photosynthesis - models based on the primary light response and discussed its advantages in the field of plant ecology and physiology. Photosynthesis has three main steps, including the primary reaction, the assimilatory power forms, and the carbon assimilation. Changes in each step could directly affect the photochemical efficiency and carbon assimilation in photosynthesis. The primary reaction consists of a series of physical processes that are related to light energy absorption and utilization, including the absorption of light energy, the change of quantum state, and the transfer and de-excitation of exciton resonance of light-trapping pigment molecules. How-ever, the empirical photosynthesis - models can not explain some scenarios. For example, the non-photochemical quenching in plants increases with increasing light intensity in a non-linear manner. Further, the life-time of singlet chlorophyll molecules can be extended when plant light-harvesting pigment molecules absorb excessive light energy but would not be immediately used for the photochemical reaction. Meanwhile, the parameters obtained by fitting the mechanistic - curve model can not only reflect the primary photochemical reaction characteristics of plants, but also describe the physical characteristics of plant light harvesting pigment molecules, such as the number of light harvesting pigment molecules in the excited state () and effective light energy absorption cross-section ('). This can be used to further investigate the physical characteristics of light harvesting pigment molecules, including the light-response of and ' and the average life time of light harvesting pigment molecules in the lowest exciting state (). In addition, it would be necessary to determine how to incorporate abiotic factors, such as temperature and CO concentration, into the mechanistic - curve model, as well as to determine the association between the abiotic factors and light harvesting pigment molecules, such as , ', and .
Topics: Photosynthesis; Chlorophyll; Light; Carbon; Ecology
PubMed: 37694485
DOI: 10.13287/j.1001-9332.202307.003 -
Journal of Magnetic Resonance (San... Nov 2023Flexible coils offer improved patient comfort and better imaging quality. However, rigid and bulky baluns in RF coils limit flexibility and manufacturing. A miniaturized...
Flexible coils offer improved patient comfort and better imaging quality. However, rigid and bulky baluns in RF coils limit flexibility and manufacturing. A miniaturized and flexible balun design was proposed to address this issue. It replaced rigid components with an ultra-flexible rubber tube and a flexible coaxial capacitor. Simulations validated the concept, and bench tests confirmed its performance, including a measured common-mode rejection ratio of -15.8 dB. The flexible balun was integrated into a 4-channel coil array, evaluating impedance changes caused by the "hand effect." Compared to coils without the balun, the flexible coil with the proposed balun showed improved robustness in impedance matching and inter-element couplings. Transmit efficiency of the flexible coil with the balun was compared to coils without a balun and with a rigid, shielded cable trap. Results demonstrated that the proposed balun circuit maintained high transmit efficiency. Overall, the flexible balun design offers a promising solution for improving the flexibility and performance of RF coil arrays in MRI applications.
Topics: Humans; Phantoms, Imaging; Magnetic Resonance Imaging; Radio Waves; Equipment Design
PubMed: 37897924
DOI: 10.1016/j.jmr.2023.107577 -
Magma (New York, N.Y.) Jul 2023To simulate the magnetic and electric fields produced by RF coil geometries commonly used at low field. Based on these simulations, the specific absorption rate (SAR)... (Review)
Review
OBJECTIVE
To simulate the magnetic and electric fields produced by RF coil geometries commonly used at low field. Based on these simulations, the specific absorption rate (SAR) efficiency can be derived to ensure safe operation even when using short RF pulses and high duty cycles.
METHODS
Electromagnetic simulations were performed at four different field strengths between 0.05 and 0.1 T, corresponding to the lower and upper limits of current point-of-care (POC) neuroimaging systems. Transmit magnetic and electric fields, as well as transmit efficiency and SAR efficiency were simulated. The effects of a close-fitting shield on the EM fields were also assessed. SAR calculations were performed as a function of RF pulse length in turbo-spin echo (TSE) sequences.
RESULTS
Simulations of RF coil characteristics and B transmit efficiencies agreed well with corresponding experimentally determined parameters. Overall, the SAR efficiency was, as expected, higher at the lower frequencies studied, and many orders of magnitude greater than at conventional clinical field strengths. The tight-fitting transmit coil results in the highest SAR in the nose and skull, which are not thermally sensitive tissues. The calculated SAR efficiencies showed that only when 180° refocusing pulses of duration ~ 10 ms are used for TSE sequences does SAR need to be carefully considered.
CONCLUSION
This work presents a comprehensive overview of the transmit and SAR efficiencies for RF coils used for POC MRI neuroimaging. While SAR is not a problem for conventional sequences, the values derived here should be useful for RF intensive sequences such as T, and also demonstrate that if very short RF pulses are required then SAR calculations should be performed.
Topics: Phantoms, Imaging; Magnetic Resonance Imaging; Neuroimaging; Head; Radio Waves
PubMed: 36933091
DOI: 10.1007/s10334-023-01073-3 -
Medical Physics May 2024X-ray multi-contrast imaging with gratings provides a practical method to detect differential phase and dark-field contrast images in addition to the x-ray absorption...
BACKGROUND
X-ray multi-contrast imaging with gratings provides a practical method to detect differential phase and dark-field contrast images in addition to the x-ray absorption image traditionally obtained in laboratory or hospital environments. Systems have been developed for preclinical applications in areas including breast imaging, lung imaging, rheumatoid arthritis hand imaging and kidney stone imaging.
PURPOSE
Prevailing x-ray interferometers for multi-contrast imaging include Talbot-Lau interferometers and universal moiré effect-based phase-grating interferometers. Talbot-Lau interferometers suffer from conflict between high interferometer sensitivity and large field of view (FOV) of the object being imaged. A small period analyzer grating is necessary to simultaneously achieve high sensitivity and large FOV within a compact imaging system but is technically challenging to produce for high x-ray energies. Phase-grating interferometers suffer from an intrinsic fringe period ranging from a few micrometers to several hundred micrometers that can hardly be resolved by large area flat panel x-ray detectors. The purpose of this work is to introduce a four-grating x-ray interferometer that simultaneously allows high sensitivity and large FOV, without the need for a small period analyzer grating.
METHODS
The four-grating interferometer consists of a source grating placed downstream of and close to the x-ray source, a pair of phase gratings separated by a fixed distance placed downstream of the source grating, and an analyzer grating placed upstream of and close to the x-ray detector. The object to be imaged is placed upstream of and close to the phase-grating pair. The distance between the source grating and the phase-grating pair is designed to be far larger than that between the phase-grating pair and the analyzer grating to promote simultaneously high sensitivity and large FOV. The method was evaluated by constructing a four-grating interferometer with an 8 µm period source grating, a pair of phase gratings of 2.4 µm period, and an 8 µm period analyzer grating.
RESULTS
The fringe visibility of the four-grating interferometer was measured to be ≈24% at 40 kV and ≈18% at 50 kV x-ray tube operating voltage. A quartz bead of 6 mm diameter was imaged to compare the theoretical and experimental phase contrast signal with good agreement. Kidney stone specimens were imaged to demonstrate the potential of such a system for classification of kidney stones.
CONCLUSIONS
The proposed four-grating interferometer geometry enables a compact x-ray multi-contrast imaging system with simultaneously high sensitivity and large FOV. Relaxation of the requirement for a small period analyzer grating makes it particularly suitable for high x-ray energy applications such as abdomen and chest imaging.
Topics: Interferometry; X-Rays; Equipment Design
PubMed: 38558430
DOI: 10.1002/mp.17052 -
Functional & Integrative Genomics Sep 2023In the field of biodosimetry, the current accepted method for evaluating radiation dose fails to meet the need of rapid, large-scale screening, and most RNA...
In the field of biodosimetry, the current accepted method for evaluating radiation dose fails to meet the need of rapid, large-scale screening, and most RNA marker-related studies of biodosimetry are concentrating on a single type of ray, while some other potential factors, such as trauma and burns, have not been covered. Microarray datasets that contain the data of human peripheral blood samples exposed to X-ray, neutron, and γ-ray radiation were obtained from the GEO database. Totally, 33 multi-type ray co-induced genes were obtained at first from the differentially expressed genes (DEGs) and key genes identified by weighted gene co-expression network analysis (WGCNA), and these genes were mainly enriched in DNA damage, cellular apoptosis, and p53 signaling pathway. Following transcriptome sequencing of blood samples from 11 healthy volunteers, 13 patients with severe burns, and 37 patients with severe trauma, 6635 trauma-related DEGs and 7703 burn-related DEGs were obtained. Through the exclusion method, a total of 12 radiation-specific genes independent of trauma and burns were identified. ROC curve analysis revealed that the DDB2 gene performed the best in diagnosis of all three types of ray radiation, while correlation analysis showed that the MDM2 gene was the best in assessment of radiation dose. The results of multiple-linear regression analysis indicated that such analysis could improve the accuracy in assessment of radiation dose. Moreover, the DDB2 and MDM2 genes remained effective in radiation diagnosis and assessment of radiation dose in an external dataset. In general, the study brings new insights into radiation biodosimetry.
Topics: Humans; Burns; Gamma Rays; Apoptosis; DNA Damage; Radiation Dosage; DNA-Binding Proteins; Proto-Oncogene Proteins c-mdm2
PubMed: 37688632
DOI: 10.1007/s10142-023-01222-w -
Nanoscale Sep 2023Identification of non-amplified DNA sequences and single-base mutations is essential for molecular biology and genetic diagnostics. This paper reports a novel sensor...
Identification of non-amplified DNA sequences and single-base mutations is essential for molecular biology and genetic diagnostics. This paper reports a novel sensor consisting of electrochemically-gated graphene coplanar waveguides coupled with a microfluidic channel. Upon exposure to analytes, propagation of electromagnetic waves in the waveguides is modified as a result of interactions with the fringing field and modulation of graphene dynamic conductivity resulting from electrostatic gating. Probe DNA sequences are immobilised on the graphene surface, and the sensor is exposed to DNA sequences which either perfectly match the probe, contain a single-base mismatch or are unrelated. By monitoring the scattering parameters at frequencies between 50 MHz and 50 GHz, unambiguous and reproducible discrimination of the different strands is achieved at concentrations as low as one attomole per litre (1 aM). By controlling and synchronising frequency sweeps, electrochemical gating, and liquid flow in the microfluidic channel, the sensor generates multidimensional datasets. Advanced data analysis techniques are utilised to take full advantage of the richness of the dataset. A classification accuracy >97% between all three sequences is achieved using different Machine Learning models, even in the presence of simulated noise and low signal-to-noise ratios. The sensor exceeds state-of-the-art sensitivity of field-effect transistors and microwave sensors for the identification of single-base mismatches.
Topics: Graphite; Microwaves; Biosensing Techniques; DNA Probes; Signal-To-Noise Ratio
PubMed: 37682040
DOI: 10.1039/d3nr01239e -
Applied Radiation and Isotopes :... Aug 2023Gamma detector detection technology based on NaI(Tl) scintillation crystal has become a popular research topic and has been applied in the field of marine radioactive...
Gamma detector detection technology based on NaI(Tl) scintillation crystal has become a popular research topic and has been applied in the field of marine radioactive environment automatic monitoring because of its advantages of low power consumption, low cost and strong environmental adaptability. However, insufficient energy resolution of the NaI(Tl) detector and great Compton scattering in the low-energy region caused by the abundance of natural radionuclides in seawater hinder the automatic analysis of radionuclides in seawater. This study adopts the combination of theoretical derivation, simulation experiment, water tank test and seawater field test, establishing an effective and feasible spectrum reconstruction method. The measured spectrum in seawater is regarded as the output signal formed by the convolution of the incident spectrum and the detector response function. The acceleration factor p is introduced to construct the Boosted-WNNLS deconvolution algorithm, which is used to iteratively reconstruct the spectrum. The analysis results of the simulation test, water tank test and field test meet the radionuclide analysis speed and accuracy requirements for the in-situ automatic monitoring of seawater radioactivity. The spectrum reconstruction method in this study converts the physical problem of insufficient detection accuracy of spectrometer in the practical application into a mathematical problem of deconvolution solution, restores the original radiation information in seawater, and improves the resolution of the seawater gamma spectrum.
Topics: Radiation Monitoring; Spectrometry, Gamma; Radioactivity; Monte Carlo Method; Seawater; Radioisotopes; Water; Gamma Rays
PubMed: 37216724
DOI: 10.1016/j.apradiso.2023.110853