Search

As one of the main ingredients in some milk powders, whey powder is sometimes added to pure goat milk products, which can cause health risks, economic fraud, and unfair competition of food industries. This study is the first to explore qualitative and quantitative methods to identify adulteration of bovine whey powder in goat dairy products based on DNA. We extracted DNA from whey powder using a modified DNA extraction method; this exhibited good quality and integrity, with purity of 1.53 to 1.75 and concentration of 122 to 179 ng/μL. Conventional PCR and real-time PCR were compared for qualitative detection of bovine whey powder; real-time PCR demonstrated sensitivity of 0.01 ng/μL, which was higher than the 0.05 ng/μL detected by the conventional PCR method. Furthermore, real-time PCR was conducted for DNA quantitative detection, with good linearity (R

The process and condition of saturable absorption (SA) and reverse saturable absorption (RSA) of ultrafast nonlinear optics in metal nanoparticles are essential for applications including light generation, amplification, modulation, and switching. Here, we first discover and explore the multiple transformations (SA-RSA-SA) of ultrafast nonlinear absorption behavior of metal nanoparticles in femtosecond pulses. Correspondingly, the energy level model and fitting formula of multiple transformations are established to illustrate the process of optical response. The femtosecond transient absorption spectra provide information about their ultrafast dynamics process and vibrational mode, which further reveals the multiple transformation mechanisms of nonlinear absorption in gold nanobipyramids (Au-NBPs). Furthermore, Au-NBPs exhibit a significantly higher SA modulation depth up to 42% in the femtosecond, which is much higher than the reported values of other nanomaterials. Our results indicate that Au-NBPs can be used as broadband ultrafast Q-switching and mode-locking, and the conversion offers new opportunities for metal nanostructures in applications of optical switching.

We present an all-optical scheme for the generation of longitudinal magnetization superoscillation based on the vectorial diffraction theory and the inverse Faraday effect. To achieve this, an azimuthally polarized high-order Laguerre–Gaussian vortex mode is firstly focused by a high numerical aperture (NA) objective and then impinges on an isotropic magneto-optical material. It is found that, by judiciously controlling the intrinsic arguments (radial mode index (p) and truncation parameter (β)) of such a configurable vectorial vortex beam, the longitudinal magnetic domain induced in the focal plane can be switched from a peak sub-wavelength magnetization (> 0.36λ/NA), via the fastest Fourier magnetization component (∼0.36λ/NA), to a super-oscillation magnetization hotspot (< 0.36λ/NA). We further examine the dependence of the transverse size, the side lobe, and the energy conversion efficiency within the focal magnetization domain on both the p and β of the initial vortex modes, confirming that the higher-order structured vortex beams are preferable alternatives to trigger robust longitudinal magnetization superoscillation. In addition, the underlying mechanisms behind the well-defined magnetization phenomena are unveiled. The ultra-small-scale longitudinal magnetization demonstrated here may hold massive potential applications in high-density all-optical magnetic recording/storage, super-resolution magnetic resonance imaging, atom trapping and spintronics.

Four substituted twistacenes decorated with different twisted π-conjugated units are synthesized to investigate their structure–property relationship. To improve the nonlinear optical (NLO) respons...

There is great interest in transition metal-doped InSe because of its high nonlinearity and ultrafast response time at higher light fluence. Herein, Ag-doped InSe nanofilms were precisely manufactured using a direct current-radio frequency sputtering method, and their ultrafast broadband nonlinear optical responses in near-infrared were systematically researched. Ag-doped InSe nanofilm exhibited a broadband nonlinear optical response (800–1100 nm) and ultrafast carrier absorption (

Single crystalline strontium titanate (SrTiO3) submicron cubes have been synthesized based on a molten salt method. The submicron cubes showed superior photocatalytic activity towards both water splitting and carbon dioxide reduction, in which methane (CH4) and hydrogen (H2) were simultaneously produced. The average production rate of methane up to 8 h is 4.39 μmol g−1 h−1 but drops to 0.46 μmol g−1 h−1. However, the average production rate of hydrogen is 14.52 before 8 h but then increases to 120.23 μmol g−1 h−1 after 8 h. The rate change of the two processes confirms the competition between the H2O splitting and CO2 reduction reactions. Band structure and surface characteristics of the SrTiO3 submicron cubes were characterized by diffuse reflective UV-Vis spectroscopy, Mott–Schottky analysis, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The results reveal that the simultaneous and competitive production of methane and hydrogen is due to a thermodynamics factor, as well as the competition between the adsorption of carbon dioxide and water molecules on the surface of the faceted SrTiO3. This work demonstrates that SrTiO3 photocatalysts are efficient in producing sustainable fuels via water splitting and carbon dioxide reduction reactions.

In this work, the up-conversion luminescence of Yb 3 + /Er 3 + doped Gd2O3 phosphors for optical temperature sensing in green and red regions are investigated. The intense green (522 and 562 nm) and red emissions (660 and 682 nm) radiated from Er 3 + /Yb 3 + tri-doped Gd2O3 phosphors are successfully realized via tuning the doping proportion of Er 3 + and Yb 3 + . To evaluate their potential ability of optical thermometry in green light range and the first biological window, the temperature-dependent green and red emissions are investigated. Based on the florescence intensity ratio (FIR) of 522 and 562 nm, the absolute sensing sensitivities of Gd2O3: 1 mol% Er 3 + /4 mol% Yb 3 + and Gd2O3: 1 mol% Er 3 + /6 mol% Yb 3 + phosphors reach 1.16 and 1.2% K−1 (523 K), respectively. In addition, the temperature sensing sensitivities based on the FIR of 660 and 682 nm reach 0.8 and 0.6% K−1 (300 K), respectively. Moreover, the changes of FIR ( Δ R) are smaller than 3% within the cycling heat and cool processes. These results reveal that Gd2O3:1mol%Er/4(6)mol%Yb phosphors are promising for FIR-based temperature sensing in high temperature via green emissions and room temperature via red emissions.

Machine learning models developed from real-world data can inherit potential, preexisting bias in the dataset. When these models are used to inform decisions involving human beings, fairness concerns inevitably arise. Imposing certain fairness constraints in the training of models can be effective only if appropriate criteria are applied. However, a fairness criterion can be defined/assessed only when the interaction between the decisions and the underlying population is well understood. We introduce two feedback models describing how people react when receiving machine-aided decisions and illustrate that some commonly used fairness criteria can end with undesirable consequences while reinforcing discrimination.

Future traffic information through vehicular communication allows connected and automated vehicles to optimize their speed trajectories and drive more safely and efficiently through predictive controllers. Sharing accurate information about the vehicle allows such controllers to perform best, but may raise privacy concerns. To improve privacy guarantee over the shared information while preserving its utility for predictive controllers, this article proposes a novel information perturbation mechanism, as opposed to the baseline of independently perturbing the data in each broadcast. Specifically, the mechanism is applied to the transmitted vehicle speed, and this perturbed data is used in an optimal speed planner to design a fuel and emissions efficient speed trajectory. Results show a deterioration of the controller performance when privacy is taken into consideration under the baseline method. With the proposed method, the controller performance is improved while providing the same privacy guarantee. It is shown that controller design is also affected by the choice of perturbation mechanism.

The Er3+/Tm3+/Yb3+ tri-doped Y7O6F9 phosphor is synthesized by a typical hydrothermal method. The Y7O6F9: 0.6%Er3+/0.2%Tm3+/15%Yb3+ phosphor is selected for the study. The up-conversion characteristics and temperature sensing performances of the phosphor are investigated under the excitation of 980 nm laser. The temperature sensing performances are investigated in the temperature range of 306–546 K based on thermal and non-thermal coupled levels by using fluorescence intensity ratio technology. The maximum sensitivity is 54.3 × 10−3 K−1 at 546 K, which is based on 3F2,3 (red emission at 695 nm of Tm3+) and 4S3/2 (green emission at 545 nm of Er3+) levels. After comparison, it is found that the sensing sensitivity of Y7O6F9: 0.6%Er3+/0.2%Tm3+/15%Yb3+ phosphor is relatively high. The excellent temperature sensing performances of the phosphor are verified. What's more, the white luminescent emission of the phosphor is achieved by adjusting excitation power and sample temperature during the experiment. And the luminescent emission color of the phosphor can be modulated widely. The above experimental results not only enable us to have a deeper understanding of tunable upconversion luminescent emission and optical temperature sensing, but also provide a significant step for high sensitivity thermometry, white light illuminating and color displaying.

Owing to few thermal populations or spectral absence at extreme low temperature, fluorescence intensity ratio (FIR) technique based on thermal coupling levels is sometimes unpractical for low temperature sensing. Herein, using bandwidth as a sensing parameter, the low temperature sensing performances of YOF:Yb3+/Tm3+ phosphor are reported. The YOF:10%Yb3+/0.2%Tm3+ phosphor is prepared by hydrothermal and calcined methods. Under 980 nm excitation, the temperature dependent upconversion spectra are recorded in the range of 12–300 K, and the temperature sensing behaviors are investigated in detail. The phosphor exhibits a single-band near-infrared (NIR) luminescence composed of multiple narrow peaks. Thereinto, the ultranarrow bandwidths of 12,485 cm−1 (800.9 nm) and 12,580 cm−1 (794.9 nm) emission bands are only 14 cm−1 (0.9 nm) and 12 cm−1 (0.75 nm) at 12 K, respectively. Based on temperature dependent bandwidth, the maximum relative sensitivities are found to be 0.60% K−1 (12–190 K) and 0.84% K−1 (190–300 K), which enable the YOF:10%Yb3+/0.2%Tm3+ phosphor to be a promising thermometer for low temperature sensing.

Rubus chingii Hu (Fu-Pen-Zi), a perennial woody plant in the Rosaceae family, is a characteristic traditional Chinese medicinal plant because of its unique pharmacological effects. There are abundant hydrolyzable tannin (HT) components in R. chingii that provide health benefits. Here, an R. chingii chromosome-scale genome and related functional analysis provide insights into the biosynthetic pathway of HTs. In total, sequence data of 231.21 Mb (155 scaffolds with an N50 of 8.2 Mb) were assembled into seven chromosomes with an average length of 31.4 Mb, and 33 130 protein-coding genes were predicted, 89.28% of which were functionally annotated. Evolutionary analysis showed that R. chingii was most closely related to Rubus occidentalis, from which it was predicted to have diverged 22.46 million years ago (Table S8). Comparative genomic analysis showed that there was a tandem gene cluster of UGT, carboxylesterase (CXE) and SCPL genes on chromosome 02 of R. chingii, including 11 CXE, eight UGT, and six SCPL genes, which may be critical for the synthesis of HTs. In vitro enzyme assays indicated that the proteins encoded by the CXE (LG02.4273) and UGT (LG02.4102) genes have tannin hydrolase and gallic acid glycosyltransferase functions, respectively. The genomic sequence of R. chingii will be a valuable resource for comparative genomic analysis within the Rosaceae family and will be useful for understanding the biosynthesis of HTs.

Efficient separation of photogenerated electron-hole pairs is a crucial factor for high-performance photocatalysts. Effective electron-hole separation and migration could be achieved by heterojunctions with suitable band structures. Herein, a porous SrTiO

Algorithmic fairness in decision-making has been studied extensively in static settings where one-shot decisions are made on tasks such as classification. However, in practice most decision-making processes are of a sequential nature, where decisions made in the past may have an impact on future data. This is particularly the case when decisions affect the individuals or users generating the data used for future decisions. In this survey, we review existing literature on the fairness of data-driven sequential decision-making. We will focus on two types of sequential decisions: (1) past decisions have no impact on the underlying user population and thus no impact on future data; (2) past decisions have an impact on the underlying user population, and therefore the future data, which can then impact future decisions. In each case the impact of various fairness interventions on the underlying population is examined.

Fractals have emerged as a promising platform for realizing broadband absorption metasurfaces. In this paper, we propose an ultra-broadband absorber with high absorption operational in the long-wave infrared regime by means of a second-order Peano fractal curve (PFC) metasurface with a four-layer insulator–metal–insulator–metal (Ge/Cr/Ge/Cr) waveguide structure. The unique space-filling shape of the PFC enables the generation of multiple gap plasmon resonance modes, which expands the bandwidth of the absorber. In addition, the hybridization of these modes with cavity mode resonances and localized surface plasmon resonances enhances the average absorption of the device in the spectrum of operation, with an average absorption of 94.3% obtained for TM-polarized light with wavelengths between 12.3 µm and 32 µm in our simulations. A second-order quasi-PFC is designed for polarization-insensitive broadband absorption. Our findings establish general and systematic strategies for guiding the design of metamaterial absorbers with excellent broadband absorption.

Four chalcogenophene-fused acenes containing O, S, Se, or Te, respectively, were presented, and the chalcogenophene effect on linear and nonlinear optics was systematically investigated. Their excited-state absorption performance and two-photon absorption (TPA) capacity could be modulated by the incorporating chalcogen atoms. The experimental results showed that the heavy chalcogen facilitated the intersystem crossing resulting in the presence of the triplet state absorption for PyPSe and PyPTe, and the TPA capacity gradually increased with the atomic size of the chalcogens. The theoretical calculation inferred that their nonlinear optical performance was closely related to the contributions of the chalcogenophene component to heterotwistacenes in the final excited state. In addition, PyPTe was able to work under various laser pulses from femtoseconds to nanoseconds.

Single crystalline strontium titanate (SrTiO

Objective To clarify the efficacy of functional magnetic stimulation (FMS) in improving hemiplegic upper extremity function in patients with sub-acute stroke. Methods In this randomized controlled trial, 40 sub-acute stroke patients with hemiplegia were recruited from inpatient wards in the Department of Rehabilitation and randomly assigned to two groups. In the FMS group, magnetic stimulation was applied to extensor muscle groups of the affected upper extremity. In the low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) group, stimulation was applied to the contralesional primary motor cortex. All patients received occupational therapy. Hand and upper extremity motor function was evaluated using the Fugl–Meyer Assessment for upper extremity (FMA-UE), and the Barthel Index (BI) evaluated daily living abilities. Results The FMA-UE and BI scores were significantly increased in both groups following stimulation. Furthermore, a significant between-group difference was observed in both FMA-UE and BI scores after 2 weeks of therapy. In the FMS group, 6 of 19 patients regained wrist and finger extension abilities, but only 2 patients regained equivalent motor skills in the LF-rTMS group Conclusions FMS improves paretic upper extremity function and leads to better recovery of motor activity than LF-rTMS. FMS may be a novel modality to improve motor function.

Cyanobacteria blooms are crucial environmental issues by threatening both aquatic ecosystem and human health. A biomass by-product with antimicrobial activity, pyroligneous acid (PA) was tested for its suitability for removal of the cyanobacteria Microcystis aeruginosa (M. aeruginosa) in this work. Results show that the removal efficiency could reach up to 90% in the presence of 0.45% of PA and the inhibition to M. aeruginosa growth could extend to at least 40 days. The removal mechanism was studied. Both organic acids and phenols are functional content in M. aeruginosa removal and acetic acid is the most important one. Zeta potential analysis and morphology study show that the damage of cells dominates the flocculation and sedimentation of M. aeruginosa under low PA concentration (0.7%), and increasing PA (≥0.7%) resulted in a trend of zeta potential to zero, thus removing any "shield" and triggering flocculation. Finally, study on the phenols residual after M. aeruginosa treatment shows that it could be close to 0 in 70 h. Therefore, this work proposes a possible method for world-wide treatment of cyanobacteria bloom and a new way for further utilization of PA.

We first present the all-optical realization of a scalable super-resolved magnetic vortex core (MVC) by tightly focusing two modulated counter-propagating radially polarized doughnut Gaussian beams based on the vectoial diffraction theory and the inverse Faraday effect. It is shown that by imposing spiral phase plates (SPPs) on the incident vectorial beams, single three-dimensional (3D) super-resolved (λ3/22) MVC can be achieved in the 4π focusing setup, which is radically different from that produced with a single lens focusing. Furthermore, the light-induced MVC texture turns to be richer and more complex when the radially polarized beams are tailored by the SPPs and judiciously designed multi-ring filters all together. In this case, we are able to garner not only transverse super-resolved (0.447λ) MVC needle with an uniformly extended area (40λ) in the single lens focusing system, but also the multiple uniform 3D super-resolved (λ3/24) chain-like MVC cells in the 4π focusing system, thus giving rise to the tunable and scalable super-resolved MVC extension. The related physical mechanisms to trigger such peculiar magnetization polarization topologies are unraveled as well. These resultant achievements would pave the way for the integrated transfer and storage of optomagnetic information, atomic trapping, and beyond.

The light–matter interaction in noble metal nanoparticles is intrinsically determined by the surface plasmon resonance (SPR) and bandgap. To determine the process of electronic transition and the limitation of energy bands on nonlinearity at different excitation wavelengths, we investigate the broadband nanosecond nonlinear absorption of gold nanobipyramids from 532 nm to 850 nm. The experimental results indicate that with the increase of the incident light intensity, gold nanobipyramids have the characteristic of transforming from saturable absorption (SA) to reverse saturable absorption (RSA) at 532 nm to 690 nm, and exhibit a single SA after 690 nm until 850 nm. Based on the wavelength-dependent response, the SA is attributed to the intraband transition of sp-band, whereas sequential two-photon absorption leads to RSA. Unlike other metal nanoparticles, gold nanobipyramids exhibited a significantly higher modulation depth up to 47%. Lastly, building on the excellent SA characteristic, we achieve pulse width compression of nanosecond laser pulses at multi-wavelengths.

NaLuF4: Yb3+/Er3+ phosphors are synthesized via a hydrothermal method. The photoluminescence properties of the phosphors are researched at a temperature range from 296 to 461 K under 1064 nm excitation. Fluorescence intensity ratio I/I0 shows a linear relationship with increasing the temperature from 296 to 420 K. The maximum sensitivity is obtained to be 0.0194 K-1 using non-contact ratiometric thermometer through multi-phonon assisted excitation.

Lanthanide-doped up-converting nano-particles reveal significant promise for data storage, biological imaging, and temperature sensing, but have not been extensively used due to their low emission intensity. Here, we investigate the up-conversion emissions of Gd2(MoO4)3:Er/Yb thin films that are sandwiched by Gd2(MoO4)3:Yb thin films. Our results show that the sandwiched thin films possess significant enhancement of emission intensities. The enhancement factors of the green and red emissions, radiated from Gd2(MoO4)3:Er/Yb films, reach 9.5 and 5, respectively. Moreover, the ability of sandwich structured thin films in multi-photon up-conversion enhancement is more excellent than that of laser power, attributed to the suppression of undesired radiative/non-radiative recombination of the intermediate states. In addition, the intensity-based temperature absolutely sensitivity of sandwich structured Gd2(MoO4)3:Er3+/Yb3+ reaches 0.013 K−1 at 498 K, which indicate this sandwich structured thin films have larger potential in thermal sensors. This sandwich structure might extend the applications of Ln3+-doped materials in super-resolution imaging and temperature sensing.

The topology regimes of the electromagnetic modes of metal–dielectric multilayered nanostructures have been proven to be dependent on the frequencies and ratios of layer thicknesses indicated by the effective media approximation. Here, we put forward a mechanism by taking the individual layer thickness into consideration. Based on the exact transfer-matrix method with periodic boundary condition, the numerical results reveal that the modes can be modulated dramatically through individual layer thickness, which can not only change dispersion significantly of the modes in the topology regimes predicted by the effective media approximation, but also make modes in the different topology regimes possible. In practice, beam refraction of a TM-polarized Gauss incident light input into a metal–dielectric multilayered structure is also discussed.

Monoclinic phase Gd2(MoO4)3: Yb3+/Er3+ phosphor is synthesized via a simple sol-gel method. The XRD result reveals that the phosphor possesses monoclinic structure with space group C2/c(15). Under the excitation of a 980 nm laser, its emission spectra shows remarkably intense green and negligible red emissions, which are all two-photon process. By investigating effect of temperature on green emission of the sample, the competition between the thermal agitation and non-radiative relaxation of 2H11/2 level can be found, which is verified by the measurement of lifetime. In addition, the sensitivity of optical thermometry is studied based on the fluorescence intensity ratio technique through infrared excited green upconversion. The maximum sensitivity is found to be about 0.02574 K−1 at 510.2 K, suggesting that the phosphor can be used as an excellent material for optical temperature sensing.

The nearly pure green and red emissions of Ho3+/Yb3+ co-doped Gd2(MoO4)3 were realized by tri-doping Eu3+ and Ce3+, respectively. The Ho3+/Yb3+ co-doped Gd2(MoO4)3 powder, radiating intense green and red emissions, was prepared by a typical sol-gel method. Under the excitation of 980 nm laser, the red-to-green ratio was tuned from 0.2 to 4 as the concentration of Eu3+ changed from 6 to 0 mol%, attributed to the energy transfer processes between Ho3+ and Eu3+. Meanwhile, the red-to-green ratio altered from 4 to 20 as the concentration of Ce3+ changed from 0 to 20 mol% via the cross relaxing processes between Ho3+ and Ce3+. The prepared phosphors, possessing large tuning range of red-to-green ratio and resisting high temperature, can be potentially applied to colorful display and solid-state lighting.

Rare earth doped materials with dual-mode luminescence have broad application potential. Among them, the dual-mode luminescence ink has been widely concerned in the field of anti-counterfeiting technology. In this work, the Y2O3: Eu@SiO2 nanomaterials were prepared with Y2O3: Eu as the core nanocrystals, SiO2 as the shell layer. Then, the Y2O3: Er(Tm/Yb) nanocrystals are adsorbed on the surface of the SiO2 layer to form Y2O3: Eu@SiO2/Y2O3: Er(Tm/Yb) composite nanomaterials. The Y2O3: Eu@SiO2/Y2O3: Er(Tm/Yb) composite nanomaterials can simultaneously achieve the dual-mode (up-conversion and down-shifting) luminescence. The Y2O3: Eu@SiO2/Y2O3: Er composite nanomaterials can emit different color luminescence emission under the 405 nm excitation, 980 nm excitation and 980/405 nm co-excitation, respectively. The up-conversion luminescence color under 980 nm excitation is regulated by doping different rare earth ions in the absorption layer. The dual-mode luminescence characteristics of composite nanomaterials make it possible to extract information only when two excitation sources exist at the same time, which increases the illegal forgery difficulty. Moreover, the composite nanomaterials can emit more variable color emission via adjusting the power intensity of 980 nm laser under 980/405 nm co-excitation, which improves the color resolution of multicolor emission. These results indicate that the Y2O3: Eu@SiO2/Y2O3: Er(Tm/Yb) composite nanomaterials are expected to be applied in the fields of color displaying and fluorescence encryption anti-counterfeiting.

It is very meaningful to implement a tunable transparency window device with a simple metasurface structure in the mid-infrared band. In this paper, we propose a symmetric metasurface structure that consists of thin layers of graphene and a split anti-ring (SAR). This structure can achieve a tunable lattice-induced transparency-like (LIT-like) spectral response in the wide frequency range of 20–40 THz. Our simulation results show that the realization of the LIT-like phenomenon is due to the strong coupling between the lattice diffraction resonance mode (LDRM) and the wide plasmon resonance mode produced by SAR. The LIT-like response can be dynamically shifted by adjusting the incident pitch angle, the single and double LIT-like can also be switched by adjusting the azimuth angle, which provides convenient post-fabrication tunability. The coupling mechanism of the single LIT-like phenomenon is explained via a dual-oscillator model, which agrees well with the simulation results. In addition, the effects of spacer layer thickness, spacer layer refractive index, ambient refractive index on the position and size of the transparency window are analyzed. Lastly, a tunable delay bandwidth product between 0.46 and 0.86 will be produced due to the addition of graphene. Our finding manifests a novel design of the mid-infrared dynamically tuned slow-light device.

In order to evaluate the freeze stress of the winter wheat, field and pot experiments were conducted. The crop variables including plant height, above ground dry biomass (AGDB), chlorophyll content (CHLC), peroxidase (POD), superoxide dismutase (SOD), malondialdehyde (MDA), photosynthetic indexes, and canopy spectra were selected and assessed. Statistical methods of correlation analysis, principal component analysis (PCA), partial least squares (PLS), importance of variables analysis, and multiple linear regression (MLR) were implemented to establish freeze injury comprehensive evaluation index (FICEI), extract sensitive bands, and build the freeze injury predictive model. The results demonstrated that FICEI can be used to evaluate the damage degree. The major spectral regions were selected with the B-coefficient, variable importance in projection (VIP), and the frequencies of selection (FS) parameters derived from the PLS analysis. The combination of all three approaches can be utilized to reduce invalid spectral regions. According to the importance of variables analysis, the seven sensitive bands were extracted, which were 574 nm, 702 nm, 1093 nm, 1111 nm, 1210 nm, 1302 nm, and 1333 nm, respectively. The calibrated MLR model based on the selected bands demonstrated an excellent performance as the R 2 and RMSE were 0.924, 0.279 for FICEI. The model also illustrated an accurate and robust performance by using the pot validation data set since the higher value of coefficient of the determination and lower root mean squared error in validation model were confirmed. Our findings show that the estimation model for FICEI of winter wheat is reliable.

The methods of modulating emitting color are greatly important for up-conversion phosphors to broaden their applications, ranging from information storage to surface display. In this paper, the Ho3+/Tm3+/Yb3+ tri-doped Gd2(MoO4)3 phosphors are synthesized by typical sol-gel method. It is found that the phosphors can radiate intense blue (475 nm), green (542 nm) and red (660 nm) up-conversion luminescence under 980 nm or 915 nm laser excitation. Especially, the emission color of the phosphors can be tuned from red to lavender by adjusting the excitation power of 980 nm or 915 nm continuous lasers. In addition, the up-conversion luminescence is also investigated under the excitation of 980 nm pulse laser. The emission color varies from green to blue and green to yellow by altering the pulse width and frequency, respectively. Combining the above methods, multi-color and white light are realized, indicating the potential application in dynamic colorful display.

The Y2O3: Tm/Yb, Y2O3: Tm/Yb@Y2O3: Yb and Y2O3: Tm/Yb@Y2O3: Yb@Y2O3: Er/Yb thin films are successfully prepared via spin-coating method. The surface grain size of the thin films is changed by multiple calcinations. The up-conversion luminescence emission of the thin films under 980 nm excitation is improved through two methods, including the increase of surface grain size and the structure of Y2O3: Tm/Yb@Y2O3: Yb bilayer. When the emission intensity of the Y2O3: Tm/Yb@Y2O3: Yb thin films are maximized by adjusting the Yb3+ concentration of the coating layer, the bilayer thin film continually undergoes multiple calcinations, thus further increasing the enhancement effect of each band emission. Besides, the Y2O3: Tm/Yb@Y2O3: Yb@Y2O3: Er/Yb multilayer thin films are designed to realize the modulation of up-conversion emission color, meaning that its luminescence emission color can change from blue to white and finally to orange by adjusting the thickness of the top Y2O3: Er/Yb luminescence layer and the number of calcination. With the capabilities of up-conversion emission enhancement and multicolor luminescence modulation, this multilayer thin film can promote the application of rare earth doped materials in the fields of fluorescence detection and color displaying.

A strategy to improve the sensitivity of NaLuF 4 :Yb 3+ /Er 3+ is elaborated via incorporation Mn 2+ ions, which results a closed energy transfer between Er 3+ and Mn 2+ ions ( 4 S 3/2 (Er 3+ ) → 4 T 1 (Mn 2+ ) → 4 F 9/2 (Er 3+ )). The NaLuF 4 :Yb 3+ /Er 3+ and NaLuF 4 :Yb 3+ /Er 3+ /Mn 2+ phosphors are prepared by a hydrothermal method. Notably, incorporation Mn 2+ for NaLuF 4 :Yb 3+ /Er 3+ phosphor rusults in enhancing the red to green intensity ratio, which acts as a bridge for energy transfer between 4 S 3/2 and 4 F 9/2 levels of Er 3+ . The temperature sensing behaviors of two phosphors are investigated in the 295–595 K range using a ratiometric technique under 980 nm excitation. Based on thermally ( 2 H 11/2 and 4 S 3/2 ) and non-thermally ( 4 F 9/2 and 4 S 3/2 ) coupled levels of Er 3+ , the influences of this energy transfer are discussed in detail. The sensitivity of NaLuF 4 :Yb 3+ /Er 3+ doping with Mn 2+ ions based on non-thermally coupled levels is much higher than that without Mn 2+ ions based on both thermally and non-thermally coupled levels in the 295–525 K range. The maximum sensitivity is 10.99 × 10 −3 K −1 at 295 K for NaLuF 4 :Yb 3+ /Er 3+ /Mn 3+ phosphor. These meaning results indicate that incorporation Mn 2+ ions in NaLuF 4 :Yb 3+ /Er 3+ phosphor is an effective method for enhancing sensitivity in the 295–525 K range.

Gd2(MoO4)3:Er3+/Yb3+ phosphor with respective functions of optical temperature sensing and optical heater are investigated in detail. The Gd2(MoO4)3:Er3+/Yb3+ film (~200 nm) and powder are successfully prepared, respectively. The crystalline structure is characterized by XRD and the relevant morphologies are analyzed by SEM and AFM, respectively. Based on fluorescence intensity ratio (FIR) technique, photo-thermal behaviors of Gd2(MoO4)3:Er3+/Yb3+ powder are illustrated. Under 980 nm excitation, the temperature induced by laser is calculated, which varies from 323 to 617 K as exciting power increased from 0.03 to 3.78 W. Additionally, the temperature sensing behaviors of Gd2(MoO4)3:Er3+/Yb3+ film are investigated. Highly accurate temperature sensing can be realized due to the negligible photo-thermal effect. This thermal sensor exhibited a high sensitivity in the range of 295–660 K, and the maximum value of relative sensitivity was determined as 13.4×10−3 K−1 at 295 K. These results demonstrate that Gd2(MoO4)3:Er3+/Yb3+ phosphor can be applied in terms of temperature sensing and optical heater.

Up-conversion phosphor is a potential candidate as non-contact temperature sensor because of its unjammable and unique detection abilities. In this work, we investigate the influence of Yb 3+ concentration on the emission color, thermal sensing and optical heater behavior of Er 3+ doped Y 6 O 5 F 8 phosphor. Our results show that the emission color of Er 3+ and Yb 3+ co-doped Y 6 O 5 F 8 powder changes from green to yellow with the Yb 3+ concentration increasing. Importantly, the temperature sensing sensitivities of Er 3+ and Yb 3+ co-doped Y 6 O 5 F 8 powder reach 0.008, 0.009, 0.010 and 0.011 K −1 as the sample doped with 2%, 5%, 8% and 11% Yb 3+ at 476 K, respectively. Moreover, the temperature of high Yb 3+ concentration sample shows preferable optical heating behavior, whose temperature is ascended by a large value of 94 K when the excitation pump power density changes from 1.0 to 13.1 W cm −2 . These results suggest Er 3+ and Yb 3+ co-doped Y 6 O 5 F 8 powder has great potential in colorful display, temperature sensing and optical heating.

As an important part of the regional environment, the wet-dry climate condition is determined by precipitation and potential evapotranspiration (expressed as ET o). Based on weather station data, this study first calculated ET o by using the FAO56 Penman-Monteith model. Then, the dryness index K (ratio of ET o to precipitation) was used to study the spatio-temporal variation of the wet-dry condition in China from 1961 to 2015; moreover, dominant climatic factors of the wet-dry condition change were discussed. The annual precipitation and ET o of the Qinling-Huaihe line were close to a balance ( K ≈1.0). The annual precipitation in most areas exceeded the ET o in the south of this line and the east of Hengduan Mountains ( K ET o ( K ≥4.0). The overall annual K of China fluctuated around the 55-year mean and its linear trend was not significant. However, a relatively wet period of about 10 yr (1987–1996) was recorded. The overall annual K of China showed strong cyclicality on the time scale of 3, 7–8, 11 and 26–28 yr , and regional differences of the annual K trends and cyclicality were large. The degrees of wetness in the Northwest China and western Qinghai-Tibet Plateau were substantially increased, whereas the degrees of dryness in the Yunnan-Guizhou Plateau, Sichuan Basin, and Loess Plateau were markedly increased. The linear trend of the annual K in most regions of China was not significant, and the annual K of most areas in China showed strong cyclicality on the 8–14 yr time scale. Precipitation was the dominant factor of wet-dry condition change in most areas, especially in North China, where the annual K change was highly correlated with precipitation.

The temperature-dependent up-conversion luminescence of the Yb3+-Er3+ doped NaYF4:Er3+/Yb3+ nanorods, which can emit green, red and blue emissions, was investigated under 980 nm laser excitation. Our results showed that the natural log of I 520/I 550, I 654/I 550, I 520/I 407 and I 654/I 407 had well linear relationship with the reciprocal of temperature, suggesting their potential application in temperature measurement. At 471 K, the maximal sensing sensitivities of the above thermometry methods reached 0.007, 0.032, 0.6, 2.7 K−1, respectively. Moreover, the luminescence color shifted from green to yellow with the temperature increasing from 296 to 471 K. The calculated CIE coordinates varied linearly with the temperature, which also can be used in thermometry. These excellent properties make NaYF4:Er3+/Yb3+ nanorods an excellent candidate as a temperature sensor.