Tunable photoluminescence from rare earth and transition metal ions activated silicate glasses and glass ceramics

The motivation of this thesis is given in the introduction, followed by the corresponding background. The second chapter gives the results and discussions in the form of publications. Firstly, dual-mode PL of mixed valence Eu3+/Eu2+ doped glass ceramics are investigated. During the crystallization processes, Eu3+ ions are partially incorporated into crystalline phases, and gradually reduced to Eu2+. It is investigated how to control the blue PL of Eu2+ and red PL of Eu3+ in these glass ceramics. Secondly, tunable IVMn2+/VIMn2+ PL of Li2ZnSiO4 glass ceramics are displayed. The Mn2+ ions are octahedrally coordinated in the SLZAKP glass. After crystallization, Mn2+ can be partially incorporated into the crystalline phase. Consequently, the ratio of IVMn2+/VIMn2+ and the emission color can be tailored by annealing temperature. Thirdly, broadband PL of V5+ doped SLZAKP glasses and corresponding Li2ZnSiO4 glass ceramics are studied. The PL from [VO4]3– is centered at 550–590 nm. After crystallization, a tenfold increase in the emission intensity is observed. Fourthly, broadband NIR PL of VINi2+ doped Ba-Al titanate glass ceramics is investigated. Ni2+ ions are tetrahedrally coordinated in precursor glasses, whereas Ni2+-species are incorporated into the crystalline environment in octahedral sites. The broadband NIR PL of VINi2+ spans the spectral range of 1.0–1.6 μm. Decay kinetics of the emission band can be adjusted. Lastly in this chapter, DC of one blue photon to two NIR photons is obtained from the Pr3+/Yb3+ co-doped SLABS glasses and Mn2+/Yb3+ do-doped Zn2GeO4. Pr3+ ions act as sensitizers by absorbing 415–505 nm photons and transferring the absorbed energy to Yb3+ ions in a cooperative down-conversion process. In the Zn2GeO4 lattice, intrinsic defect transitions and Mn2+ ions act as broadband spectral sensitizers by absorbing UV-Vis photons. The absorbed energy is transferred to Yb3+ ions in a cooperative DC process. The third chapter summarizes the thesis

The within-field and between-field dispersal of weedy rice by combine harvesters

International audienceAbstractWeedy rice (Oryza sativa L.) severely decreases the grain yield and profitability of rice is one of the most significant problems in the majority of rice fields worldwide. Few reports focus on the dispersal of weedy rice, especially how it rapidly spreads to large areas and long distances. Here, we quantify for the first time the within- and between-field dispersal of weedy rice associated with combine harvesting operations. We randomly sampled 31 combine harvesters to determine where and how much weedy rice seeds remained on the machines at three locations in Jiangsu Province, China. Based on the sampling results, the field area over which weedy rice seeds were retained on the combine harvester during harvesting was estimated to assess the within-field dispersibility of weedy rice seeds remaining in the harvesters. A tracking experiment was also carried out by tracing the distribution of weedy rice seeds along harvest trails, to estimate the dispersal of weedy rice seeds within the field being harvested. Weedy rice seeds remained in the harvest pocket, on the pedrail, and the metal plate of the combine harvester. On average, more than 5000 weedy rice seeds which were 22.80% of remaining grains could potentially be transported into adjacent fields by the combine after each rice field infested with weedy rice had been harvested. Of the statistical models compared, a double exponential model simulating the variation in seed retention predicted that weedy rice seeds remaining on the metal plate could be dispersed over 6473.91 m2 or 3236.96 m into the next field during the harvesting operation. Within the field, the number of fallen weedy rice seeds and their dispersal distance were positively correlated to weedy rice panicle density with the combine dispersing most of seeds away from their mother plant thus creating new weed patches. Therefore, fields that were severely infested with weedy rice should be harvested cautiously and separately and seed remaining in a harvester should be avoided to prevent intra- and inter-field, and even cross-regional dispersal of weedy rice

Smartphone‐Based Luminescent Thermometry via Temperature‐Sensitive Delayed Fluorescence from Gd0_{0}O2_{2}S:Eu3+^{3+}

Thermal images generated from infrared radiation are useful for monitoring many processes; however, infrared cameras are orders of magnitude more expensive than their visible counterparts. Methods that allow visible cameras to capture thermal images are therefore of interest. In this contribution, thermal images of a surface coated with an inexpensive inorganic micropowder phosphor are generated from the analysis of a video taken with a smartphone camera. The phosphor is designed to have a temperature‐dependent emission lifetime that is long enough to be determined from the analysis of a 30 frames‐per‐second video recording. This proof‐of‐principle work allows temperatures in the 270–320 K range to be accurately determined with a precision better than 2 K, even in the presence of bright background illuminance up to 1500 lm m$^{-2}$. In the broader context, this inspires further development of phosphors to bring time‐resolved sensing techniques into lifetime long enough ranges to allow smartphone‐based detection

An analysis on strip vibration coupled with torsional vibration of main drive system of rolling mill

According to the movement mechanism of strip and rollers during the continuous rolling process, the main drive system of each stand was simplified to a single degree of freedom discrete model, and the strip was simplified to an axially moving Euler beam. Then, a nonlinear continuous-discrete coupled vibration model between transverse and longitudinal vibrations of strip and torsional vibration of main drive system was established. According to Hamilton’s principle, the nonlinear differential equations were established. Moreover, modified iteration method and Kantorovich averaging method were used to solve the differential equations. Depending on numerical calculation, the amplitude-frequency responses of strip vibration coupled with torsional vibration of main drive system were obtained. Finally, the influences of the axial velocity, the strip tension, the torsional stiffness, and the rotational inertia on the vibration characteristics were discussed. The results would provide a theoretical reference for control and analysis of rolling mill vibration in engineering practice

Ratiometric Luminescent Thermometry with Excellent Sensitivity over a Broad Temperature Range Utilizing Thermally‐Assisted and Multiphoton Upconversion in Triply‐Doped La₂O₃:Yb³⁺/Er³⁺/Nd³⁺

A ratiometric optical thermometer based on triply‐doped La$_{2}$O$_{3}$:Yb$^{3+}$/Er$^{3+}$/Nd$^{3+}$ microcrystals is reported with a relative sensitivity above 1% K$^{-1}$ in the entire range from 300–700 K, and is between 1.8–0.7% K$^{-1}$ over the range 290–833 K. The 825 nm upconversion (UC) emission from the Nd$^{3+ 4}$F$_{5/2}$ level relies on thermally‐assisted energy transfer from Yb$^{3+}$; thus, unusually, the near‐infrared emission increases with increasing temperature in the relevant range. More typically, the two‐photon 660 nm UC from Er$^{3+ 4}$F$_{9/2}$ level decreases in intensity with increasing temperature due to increasing non‐radiative rates. The variation of fluorescent intensity ratio between these emissions is amplified by their opposite responses to temperature change leading to excellent sensitivity. Concurrently, the different pathways for the temperature response in the two emitting ions enable the high sensitivity to be maintained over an atypically broad temperature range. The wide separation in wavelength means that a standard silicon‐based monochrome camera with broad (inexpensive) band pass filters is sufficient to use this phosphor for thermography. The concept of combining thermally‐activated UC with classical Stokes‐shifted emission is demonstrated to provide combined features of excellent and broad‐range sensitivity plus excellent repeatability. Materials based on this concept are very promising for optical thermometry

A variant at a potentially functional microRNA-binding site in BRIP1 was associated with risk of squamous cell carcinoma of the head and neck

DNA double-strand breaks (DSBs) are one of the most serious forms of DNA damage to the cell, causing genomic instability and ultimately carcinogenesis. In this study, we hypothesized that single nucleotide polymorphisms (SNPs) at the micro RNA (miRNA)-binding sites of DSB repair genes may influence cancer risk by dysregulating target gene expression. To test our hypothesis, we firstly performed functional prediction for common SNPs in DSB genes and found 12 potentially functional SNPs located at the miRNA-binding sites. We then investigated their associations with risk of squamous cell carcinoma of the head and neck (SCCHN) in 1087 patients and 1090 cancer-free controls in a non-Hispanic white population. As a result, SNP rs7213430 in BRIP1 was found to be significantly associated with cancer risk (Ptrend = 0.021). Compared with the AA homozygotes, the G allele carriers had an increased risk of SCCHN (adjusted OR 1.16, 95 % CI 1.02–1.31). Marginal significance was found for another SNP rs15869 in BRCA2 (P = 0.053). Further, functional analyses showed that SNP rs7213430 is within the miR-101 seed-binding region, and the variant G allele could lead to significantly lower luciferase activity and BRIP1 mRNA expression, compared to the A allele with the presence of miR-101. Our results suggested that SNP rs7213430 in the 3′-UTR of BRIP1 might contribute to SCCHN susceptibility by affecting the binding activity of miR-101 and resulting in a decreased BRIP1 expression. Additional larger population and functional studies are warranted to confirm our findings