Numerical simulations on dissipative-soliton-resonance generation in an all-normal-dispersion fiber ring laser are presented. Situations with monotonic and periodical saturable absorption are both ...considered. The multipulse operation in dissipative soliton laser is found to be caused by the spectral filtering effect that limits the spectral maximum width, and the multipulsing can be fully circumvent by inducing strong peak-power-clamping effect of a sinusoidal saturable absorber in the cavity. When the cavity peak-power-clamping effect is strong enough that the pulse peak power and the pulse spectral width are both confined at a low value, the spectral filtering effect induced multipulse operation is prevented and the dissipative-soliton-resonance is generated. Otherwise, the spectral filtering effect causes pulse breaking before the pulse peak power reaches the saturation point. Further results show that under the dissipative-soliton-resonance, the generated pulse peak power can be directly controlled by the cavity peak-power-clamping effect, which is determined by the saturation power of the saturable absorber.
We report on the optical saturable absorption of few-layer black phosphorus nanoflakes and demonstrate its application for the generation of vector solitons in an erbium-doped fiber laser. By ...incorporating the black phosphorus nanoflakes-based saturable absorber (SA) into an all-fiber erbium-doped fiber laser cavity, we are able to obtain passive mode-locking operation with soliton pulses down to ~670 fs. The properties and dynamics of the as-generated vector solitons are experimentally investigated. Our results show that BP nanoflakes could be developed as an effective SA for ultrashort pulse fiber lasers, particularly for the generation of vector soliton pulses in fiber lasers.
Given the ongoing studies on the adverse effects of organophosphate ester (OPE) flame retardants and plasticizers on human health, there is an increasing scientific interest in the risk of exposure ...to OPEs via dietary intake. Using peer-reviewed literature published up to 2018, this review surveyed and compiled the available and reported data on the concentrations and distributions of 30 OPEs based on their occurrence in various food samples from around the world. Regardless of sampling locations or food categories, 22 OPEs were detectable in at least one of analyzed sample, and there were clear variations in OPE levels among samples from different locations or food categories. For instance, cereals and fats/oils were the most contaminated by OPEs in China and Belgium, whereas fats/oils and desserts were the main polluted products in Sweden. In contrast, vegetables, fruits, fluid dairy products, and cereals were reported as the primary categories of food polluted by OPEs in Australia. Animal-based food categories such as eggs, fish and meat were the least contaminated, whereas the highest median OPE concentrations were found in meat and fish from the United State. The levels and distribution patterns of OPEs in foodstuffs demonstrated a tremendous difference even when collected from the same country and the same food item. Rice from China had the highest tris(2‑chloroethyl) phosphate (TCEP, mean: 29.8 ng/g dw) levels, whereas 2‑ethylhexyl‑diphenyl phosphate (EHDPP, mean: 4.17 ng/g ww), triphenyl phosphate (TPHP, mean: 26.14 ng/g ww), tris(2-chloroisopropyl) phosphate (TCIPP, mean: 0.87 ng/g ww) and tributyl phosphate (TNBP, median: 0.55 ng/g ww) concentrations were the highest in the same food category from Sweden, Belgium, Australia, and the United States, respectively. These discrepancies may be due to a variety of reasons such as differences in OPE physico-chemical properties, extent of usage, uptake, metabolic pathways, industrial food manufacturing processes, OPE level differences as a function of habitat, and accumulation and degradability of OPEs in different species. It is worth noting that, due to its worldwide usage in food packaging materials, EHDPP was more prominently found in processed food compared to non-processed food. Based on reported OPE levels in various foods, this review conducted a preliminary assessment of human exposure to OPEs through dietary intake, which suggested that the OPE estimated daily intake (EDI) for humans was around 880 ng/kg bw/day (95th percentile). This value was well below the corresponding OPE health reference dose given by the U.S. EPA (≥15,000 ng/kg bw/day). Even so, dietary exposure to OPEs via food intake may be not negligible based on some important factors such as dilution effects, cooking processes, and the contribution of as yet unknown means of OPE exposure. Overall, this review highlights several gaps in our understanding of OPEs in foodstuffs: 1) the investigation of contamination levels of OPEs in foodstuffs should be extended to other regions, especially North America and European countries, where OPEs are widely used and frequently detected in environmental samples, and 2) newly identified OPE derivatives/by-products, e.g., OP diesters and hydroxylated metabolites, which have been reported as end-products of OPE enzymatic metabolism or degradation through aqueous hydrolysis, and which may co-exist with parent OPEs, could also be screened with precursor OPEs in foodstuffs in future studies.
•We reviewed the OPE concentrations in foodstuffs in literature published up to 2018.•Twenty-two OPEs were detectable in at lease of analyzed foodstuff samples.•A tremendous difference exists on OPE levels among locations or food categories.•EHDPP was more prominently found in processed food rather than non-processed food.•Newly identified OPE derivatives/by-products could also be screened in future studies.
Soft wearable electronics for underwater applications are of interest, but depend on the development of a waterproof, long-term sustainable power source. In this work, we report a bionic stretchable ...nanogenerator for underwater energy harvesting that mimics the structure of ion channels on the cytomembrane of electrocyte in an electric eel. Combining the effects of triboelectrification caused by flowing liquid and principles of electrostatic induction, the bionic stretchable nanogenerator can harvest mechanical energy from human motion underwater and output an open-circuit voltage over 10 V. Underwater applications of a bionic stretchable nanogenerator have also been demonstrated, such as human body multi-position motion monitoring and an undersea rescue system. The advantages of excellent flexibility, stretchability, outstanding tensile fatigue resistance (over 50,000 times) and underwater performance make the bionic stretchable nanogenerator a promising sustainable power source for the soft wearable electronics used underwater.
Implantable medical devices provide an effective therapeutic approach for neurological and cardiovascular diseases. With the development of transient electronics, a new power source with ...biocompatibility, controllability, and bioabsorbability becomes an urgent demand for medical sciences. Here, various fully bioabsorbable natural‐materials‐based triboelectric nanogenerators (BN‐TENGs), in vivo, are developed. The “triboelectric series” of five natural materials is first ranked, it provides a basic knowledge for materials selection and device design of the TENGs and other energy harvesters. Various triboelectric outputs of these natural materials are achieved by a single material and their pairwise combinations. The maximum voltage, current, and power density reach up to 55 V, 0.6 µA, and 21.6 mW m−2, respectively. The modification of silk fibroin encapsulation film makes the operation time of the BN‐TENG tunable from days to weeks. After completing its function, the BN‐TENG can be fully degraded and resorbed in Sprague–Dawley rats, which avoids a second operation and other side effects. Using the proposed BN‐TENG as a voltage source, the beating rates of dysfunctional cardiomyocyte clusters are accelerated and the consistency of cell contraction is improved. This provides a new and valid solution to treat some heart diseases such as bradycardia and arrhythmia.
Fully bioabsorbable triboelectric nanogenerators based on natural materials (BN‐TENGs) are developed with a wide material source. After completing their function, the BN‐TENGs can be fully degraded and resorbed in Sprague–Dawley rats. Using the proposed BN‐TENG as a voltage source, the beating rates of dysfunctional cardiomyocyte clusters are accelerated and the consistency of cell contraction is improved.
Cardiovascular diseases are the leading cause of death globally; fortunately, 90% of cardiovascular diseases are preventable by long‐term monitoring of physiological signals. Stable, ultralow power ...consumption, and high‐sensitivity sensors are significant for miniaturized wearable physiological signal monitoring systems. Here, this study proposes a flexible self‐powered ultrasensitive pulse sensor (SUPS) based on triboelectric active sensor with excellent output performance (1.52 V), high peak signal‐noise ratio (45 dB), long‐term performance (107 cycles), and low cost price. Attributed to the crucial features of acquiring easy‐processed pulse waveform, which is consistent with second derivative of signal from conventional pulse sensor, SUPS can be integrated with a bluetooth chip to provide accurate, wireless, and real‐time monitoring of pulse signals of cardiovascular system on a smart phone/PC. Antidiastole of coronary heart disease, atrial septal defect, and atrial fibrillation are made, and the arrhythmia (atrial fibrillation) is indicative diagnosed from health, by characteristic exponent analysis of pulse signals accessed from volunteer patients. This SUPS is expected to be applied in self‐powered, wearable intelligent mobile diagnosis of cardiovascular disease in the future.
A flexible self‐powered ultrasensitive pulse sensor (SUPS) based on a triboelectric active sensor is proposed. SUPS can provide accurate, wireless, and real‐time monitoring of pulse signals of a cardiovascular system on a smart phone/PC. Different types of cardiovascular patients are indicatively diagnosed from health. This SUPS is expected to be applied in intelligent mobile diagnosis of cardiovascular disease in the future.
Monitoring various medical information distributed throughout the body is of great importance in early clinic diagnosis and treatment of disease. To discover abnormal medical signals and find their ...causes in good time, the human body should be monitored continuously and accurately. To meet the requirements, various battery‐less and self‐powered information acquisition techniques are invented. In this review, the recent advances in self‐powered medical information sensors (SMIS) with different functions, structure design, and electric performance are summarized and discussed. The SMIS mainly involves triboelectric nanogenerator (TENG), piezoelectric nanogenerator (PENG), pyroelectric nanogenerator (PyNG)/ thermoelectric generator (TEG) and solar cell. Additionally, this review also analyzed the remaining challenges and prospected the development direction of SMIS in future.
The monitoring of physiological signals is of important significance for the early detection and timely treatment of diseases. Self‐powered medical sensors (SPMS) provide a new effective technique to obtain various physiological signals from body without battery. This review highlights the recent advance of SPMS in sensor types, device structure, electric performance and application scenarios. Viewpoints on present challenges and future development trends are also discussed.
Despite of the ubiquity of organophosphate esters (OPEs) in various environmental matrices, information regarding the dietary intakes of OPEs is currently limited. To better understand dietary ...exposure and intake, the present study investigated 11 OPE flame retardants (FRs) in 105 composite food samples divided into 9 food categories, collected in 2018 and based on the contents of a typical Chinese food market basket. Nine OPEs, including triethyl phosphate (TEP), tributyl phosphate (TNBP), tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP), triphenyl phosphate (TPHP), 2-ethylhexyl-diphenyl phosphate (EHDPP), tris(2-butoxyethyl) phosphate (TBOEP), tris(2-ethylhexyl) phosphate (TEHP) and tris(methyl-phenyl) phosphate (TMPP), were measurable above the method limits of quantifications (MLOQs) in at least one of the analyzed samples. Among the 9 food categories, sweets were contaminated most severely with a mean sum (Σ) OPE concentration of 10.34 ng/g wet weight (ww). Regardless the food categories, EHDPP and TEP were the predominant OPEs with mean concentrations of 1.12 and 0.95 ng/g ww, respectively. In addition, the levels of OPEs in “processed foods” were significantly (unpaired t-test, p < 0.01) higher than those in “non-processed foods”. Based on the measured OPE concentrations, we estimated daily per capita dietary intakes of ΣOPEs for Chinese adult population to be 44.3 ng/kg bw/day, that was mainly contributed by TCEP (14.3 ng/kg bw/day), TEP (12.7 ng/kg bw/day) and EHDPP (8.4 ng/kg bw/day). In addition to these 9 detected OPEs, further suspect screening in the combined extracts of foodstuffs by use of high-resolution spectrometry revealed a novel OP-FR, triphenyl phosphine oxide (TPPO). The highlight findings in this study were: 1) the amount of OPE via dietary intakes for the Chinese population is generally in the same order of magnitude as for other countries, i.e. the Swedish, Belgian and Australian adult population, and far less than the reference dosage value of each OPE (hazard index ≪ 1); 2) the total dietary intakes of OPEs were dominated by cereals, approximately accounting for 52.2%; and 3) the first reported detection of the novel OP-FR, TPPO, in foodstuff samples.
•Organophosphate esters (OPEs) were examined based on Chinese food market basket.•OPE concentrations were measured in n = 105 composite food samples.•Dietary intakes of OPE in China is comparable with those reported for other countries.•Total dietary intakes of OPEs were dominated (52.2%) by cereals.•First report on detection of the novel OP-FR, TPPO, in foodstuff samples
We demonstrate what is believed to be the first dissipative-soliton-resonance mode-locking of a holmium-doped fiber (HDF) laser. A telecommunication band fiber source was used to pump a piece of ...thulium-doped fiber, resulting in 1.9-μm band lasing, which was subsequently used to intra-cavity-pump another piece of HDF, resulting in lasing beyond 2 μm. A nonlinear optical-loop mirror incorporating two pieces of high nonlinear fiber (HNLF) was employed as an artificial saturable absorber, and, meanwhile, to enhance the cavity nonlinearity. By varying the pump power from ~2.1 to ~4 W, the produced pulse could be tuned from ~4.85 to ~20.8 ns in duration while maintaining a nearly constant peak power, i.e., peak power clamping (PPC) effect. By further incorporating different lengths of HNLF, it was found that the longer the HNLF, the larger the pulse duration and the lower the pulse peak power, due to the expected stronger PPC effect. Meanwhile, spectral blue-shifting effect has occurred due to the increased fiber attenuation loss. Based on our preliminary experiments using the HDF laser as a test bed, a higher pulse energy at a longer wavelength could be expected with further enhanced pumping and gain-tailoring designs.
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