Partial Discharge Signal Pattern Recognition of Composite Insulation Defects in Cross-Linked Polyethylene Cables.

To investigate the pattern recognition of complex defect types in XLPE (cross-linked polyethylene) cable partial discharges and analyze the effectiveness of identifying partial discharge signal patterns, this study employs the variational mode decomposition (VMD) algorithm alongside entropy theories such as power spectrum entropy, fuzzy entropy, and permutation entropy for feature extraction from partial discharge signals of composite insulation defects. The mean power spectrum entropy (PS), mean fuzzy entropy (FU), mean permutation entropy (PE), as well as the permutation entropy values of IMF2 and IMF13 (Pe) are selected as the characteristic quantities for four categories of partial discharge signals associated with composite defects. Six hundred samples are selected from the partial discharge signals of each type of compound defect, amounting to a total of 2400 samples for the four types of compound defects combined. Each sample comprises five feature values, which are compiled into a dataset. A Snake Optimization Algorithm-optimized Support Vector Machine (SO-SVM) model is designed and trained, using the extracted features from cable partial discharge datasets as case examples for recognizing cable partial discharge signals. The identification outcomes from the SO-SVM model are then compared with those from conventional learning models. The results demonstrate that for partial discharge signals of XLPE cable composite insulation defects, the SO-SVM model yields better identification results than traditional learning models. In terms of recognition accuracy, for scratch and water ingress defects, SO-SVM improves by 14.00% over BP (Back Propagation) neural networks, by 5.66% over GA-BP (Genetic Algorithm-Back Propagation), and by 12.50% over SVM (support vector machine). For defects involving metal impurities and scratches, SO-SVM improves by 13.39% over BP, 9.34% over GA-BP, and 12.56% over SVM. For defects with metal impurities and water ingress, SO-SVM shows enhancements of 13.80% over BP, 9.47% over GA-BP, and 13.97% over SVM. Lastly, for defects combining metal impurities, water ingress, and scratches, SO-SVM registers increases of 11.90% over BP, 9.59% over GA-BP, and 12.05% over SVM.

Quality in screening and measuring blood pressure in China's primary health care: a national cross-sectional study using unannounced standardized patients.

Background: This study aims to evaluate primary care providers' adherence to the standard of measuring blood pressure for people aged 35 or above during their initial visit, as per Chinese guidelines, and to identify factors affecting their practices. Methods: We developed 11 standardized patients (SP) cases as tracer conditions to evaluate primary care, and deployed trained SPs for unannounced visits to randomly selected providers in seven provinces of China. The SPs used a checklist based on guidelines to record whether and how blood pressure was measured. Data were analyzed descriptively and regression analysis was performed to examine the association between outcomes and factors such as provider, patient, facility, and clinical case characteristics. Findings: The SPs conducted 1201 visits and found that less than one-third of USPs ≥35 had their blood pressure measured. Only 26.9% of migraine and 15.4% of diabetes cases received blood pressure measurements. Additionally, these measurements did not follow the proper guidelines and recommended steps. On average, 55.6% of the steps were followed with few providers considering influencing factors before measurement and only 6.0% of patients received both-arm measurements. The use of wrist sphygmomanometers was associated with poor blood pressure measurement. Interpretation: In China, primary care hypertension screening practices fall short of guidelines, with infrequent initiation of blood pressure measurements and inadequate adherence to proper measurement steps. To address this, priority should be placed on adopting, implementing, and upholding guidelines for hypertension screening and measurement. Funding: National Natural Science Foundation of China, Swiss Agency for Development and Cooperation, Doctoral Fund Project of Inner Mongolia Medical University, China Postdoctoral Science Foundation.

Effect of Family-Centered Empowerment Model in Home Care of Older Adult Patients After Total Knee Arthroplasty.

PURPOSE: In the present study, we investigated the effect of the family-centered empowerment model (FCEM) in the home care of older adult patients after total knee arthroplasty (TKA). DESIGN: The current study was a randomized controlled study. METHODS: Two hundred eighty older adult patients who underwent TKA in our hospital from December 2020 to December 2022 were selected. They were divided into intervention and control groups using the random number table method, with 140 cases in each group. After follow-up and attrition, 133 patients were assigned to the intervention group and 130 to the control group. The control group received conventional care, and the intervention group received the care provided using the FCEM. The general characteristics of the study subjects were compiled using a general information questionnaire designed by the researcher. The chi-square test and t-test were used to compare the changes in self-care efficacy, knee function, and the occurrence of postoperative complications in the two groups before and after the intervention. FINDINGS: The results suggest that the adoption of FCEM improved patient motivation and self-care efficacy, promoted the recovery of knee function in the short term after surgery, and reduced the likelihood of occurrence of complications. CONCLUSION: The present study highlights the importance of extending the FCEM to multiple domains to fill the gaps in the currently available medical care system for older adults. In addition, the study provides a reference basis for reducing the occurrence of complications and improving patient prognosis. CLINICAL EVIDENCE: The FCEM model is an effective strategy to improve the effectiveness of home nursing for older adults.

Improving eye care quality through brief verbal intervention on optometry service provider by using unannounced standardized patient with refractive error: study protocol for a randomized controlled trial.

BACKGROUND: Improper refractive correction can be harmful to eye health, aggravating the burden of vision impairment. During most optometry clinical consultations, practitioner-patient interactions play a key role. Maybe it is feasible for patients themselves to do something to get high-quality optometry. But the present empirical research on the quality improvement of eye care needs to be strengthened. The study aims to test the effect of the brief verbal intervention (BVI) through patients on the quality of optometry service. METHODS: This study will take unannounced standardized patient (USP) with refractive error as the core research tool, both in measurement and intervention. The USP case and the checklist will be developed through a standard protocol and assessed for validity and reliability before its full use. USP will be trained to provide standardized responses during optical visits and receive baseline refraction by the skilled study optometrist who will be recruited within each site. A multi-arm parallel-group randomized trial will be used, with one common control and three intervention groups. The study will be performed in four cities, Guangzhou and three cities in Inner Mongolia, China. A total of 480 optometry service providers (OSPs) will be stratified and randomly selected and divided into four groups. The common control group will receive USP usual visits (without intervention), and three intervention groups will separately receive USP visits with three kinds of BVI on the patient side. A detailed outcome evaluation will include the optometry accuracy, optometry process, patient satisfaction, cost information and service time. Descriptive analysis will be performed for the survey results, and the difference in outcomes between interventions and control providers will be compared and statistically tested using generalized linear models (GLMs). DISCUSSION: This research will help policymakers understand the current situation and influencing factors of refractive error care quality, and then implement precise policies; at the same time, explore short and easy interventions for patients to improve the quality of optometry service. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2200062819. Registered on August 19, 2022.

The Agreement Between Virtual Patient and Unannounced Standardized Patient Assessments in Evaluating Primary Health Care Quality: Multicenter, Cross-sectional Pilot Study in 7 Provinces of China.

BACKGROUND: The unannounced standardized patient (USP) is the gold standard for primary health care (PHC) quality assessment but has many restrictions associated with high human and resource costs. Virtual patient (VP) is a valid, low-cost software option for simulating clinical scenarios and is widely used in medical education. It is unclear whether VP can be used to assess the quality of PHC. OBJECTIVE: This study aimed to examine the agreement between VP and USP assessments of PHC quality and to identify factors influencing the VP-USP agreement. METHODS: Eleven matched VP and USP case designs were developed based on clinical guidelines and were implemented in a convenience sample of urban PHC facilities in the capital cities of the 7 study provinces. A total of 720 USP visits were conducted, during which on-duty PHC providers who met the inclusion criteria were randomly selected by the USPs. The same providers underwent a VP assessment using the same case condition at least a week later. The VP-USP agreement was measured by the concordance correlation coefficient (CCC) for continuity scores and the weighted κ for diagnoses. Multiple linear regression was used to identify factors influencing the VP-USP agreement. RESULTS: Only 146 VP scores were matched with the corresponding USP scores. The CCC for medical history was 0.37 (95% CI 0.24-0.49); for physical examination, 0.27 (95% CI 0.12-0.42); for laboratory and imaging tests, -0.03 (95% CI -0.20 to 0.14); and for treatment, 0.22 (95% CI 0.07-0.37). The weighted κ for diagnosis was 0.32 (95% CI 0.13-0.52). The multiple linear regression model indicated that the VP tests were significantly influenced by the different case conditions and the city where the test took place. CONCLUSIONS: There was low agreement between VPs and USPs in PHC quality assessment. This may reflect the "know-do" gap. VP test results were also influenced by different case conditions, interactive design, and usability. Modifications to VPs and the reasons for the low VP-USP agreement require further study.

Improving Data Surveillance Resilience Beyond COVID-19: Experiences of Primary heAlth Care quAlity Cohort In ChinA (ACACIA) Using Unannounced Standardized Patients.

We analyzed COVID-19 influences on the design, implementation, and validity of assessing the quality of primary health care using unannounced standardized patients (USPs) in China. Because of the pandemic, we crowdsourced our funding, removed tuberculosis from the USP case roster, adjusted common cold and asthma cases, used hybrid online-offline training for USPs, shared USPs across provinces, and strengthened ethical considerations. With those changes, we were able to conduct fieldwork despite frequent COVID-19 interruptions. Furthermore, the USP assessment tool maintained high validity in the quality checklist (criteria), USP role fidelity, checklist completion, and physician detection of USPs. Our experiences suggest that the pandemic created not only barriers but also opportunities to innovate ways to build a resilient data collection system. To build data system reliance, we recommend harnessing the power of technology for a hybrid model of remote and in-person work, learning from the sharing economy to pool strengths and optimize resources, and dedicating individual and group leadership to problem-solving and results. (Am J Public Health. 2022;112(6):913-922. https://doi.org/10.2105/AJPH.2022.306779).

Women's cesarean section preferences and influencing factors in relation to China's two-child policy: a cross-sectional study.

OBJECTIVE: This study explored women's preference for cesarean section (CS) and the preference for cesarean sections' influencing factors, particularly nonmedical factors. METHODS: A cross-sectional study was conducted in four tertiary hospitals in Hohhot. We recruited 1,169 pregnant women at ≥ 28 gestational weeks and classified subjects into three groups by delivery mode preference: vaginal birth (VB), CS, and "no clear preference". We identified the influencing factors of women's choices by multinomial logistic regression. The adjusted relative-risk ratios (aRRRs) for the factors affecting the preference for CS and "no clear preference" categories and their 95% CIs were computed, using the preference for VB as the reference group. RESULTS: VB was preferred by 80.3% of the subjects, 8.8% preferred CS, and 10.9% had not decided yet. In the multinomial logistic regression, pregnant women intending to have more than one child were less likely to prefer CS (aRRR: 0.37; 95% CI: 0.22-0.61); choosing a lucky day for baby birth was the strongest factor for CS preference (aRRR: 12.36; 95% CI: 6.62-23.08), and other factors for CS preference were being aged 40 years and above (aRRR: 4.21; 95% CI: 1.43-12.40), being ethnic minority (aRRR: 2.00; 95% CI: 1.17, 3.41), feeling difficulty in getting pregnant (aRRR: 2.23; 95% CI: 1.20, 4.13), and having husband's preference for CS (aRRR: 7.62; 95% CI: 4.00-14.54). The top reasons for preferring CS were the belief that CS was safer (51.5%), associated with less pain (40.8%), and better for baby's and woman's health (24.3% and 22.3%, respectively). CONCLUSION: Less than one-tenth of the study subjects preferred CS. The cultural beliefs had the strongest influence on the decision of delivery mode. Those intending to have two or more children following the two-child policy were less likely to choose CS.

Arbuscular mycorrhiza fungi facilitate rapid adaptation of Elsholtzia splendens to copper.

Closely associated microbes have been shown to drive local adaptation of plants. However, few studies provide direct evidence, disclosing the role of arbuscular mycorrhiza fungi (AMF) in their rapid adaptation of plants toward heavy metal tolerance. Elsholtzia splendens is a Cu-tolerant plant that was used as a model plant to study seed morphological traits as well as traits related to seed germination and seedling growth. This was achieved after acclimation for two generations with 1000mg/kg CuSO4 in either absence or presence of AMF. In the absence of AMF, acclimation to Cu for two generations significantly decreased surface area, perimeter length, and perimeter width of E. splendens seeds, as well as seedling survival rate and fresh weight of the radicle of seedlings. However, in the presence of AMF, both the germination rate and the germination index of E. splendens seeds as well as the fresh weights of hypocotyl and radicle significantly increased. These results revealed that after Cu acclimation treatment, seeds and seedlings that had been inoculated with AMF outperformed those without AMF inoculation under Cu addition, indicating that AMF can facilitate rapid adaptation of E. splendens to Cu stress. In addition, two generations of Cu acclimation under AMF absence significantly increased radicle length, while amplitude increased under AMF presence, indicating that the direct adaptive plasticity response of radicle length to Cu stress helps with the Cu stress adaptation of E. splendens.

[Effects of hydroxyl acetylated curcumin induced sonodynamic therapy on viability, apoptosis and necrosis of THP-1 macrophages].

OBJECTIVE: We aim to investigate the sonodynamic effect induced by hydroxyl acetylated curcumin (HAC) on THP-1 macrophages. METHODS: THP-1 derived macrophages (1 x 10(5) per milliliter) were cultured with HAC at a concentration of 5 µg/mL for 4 h and then exposed to pulse ultrasound treatment (0.5 W/cm2) for 5 min. Six hours later, cell viability analysis was performed with CCK-8 assay, apoptosis and necrosis analysis were detected with Annexin V/PI staining by flow cytometery. RESULTS: The cell viability of THP-1 macrophage decreased significantly in the group treated with the combination of HAC and ultrasound (P < 0.01), and HAC-SDT induced both apoptosis and necrosis in THP-1 macrophages, the apoptotic rate was higher than the necrotic rate with appropriate conditions, the maximum apoptosis/necrosis ratio was detected in sonodynamic therapy (SDT) group (P < 0.01). CONCLUSION: hAC-SDT was effective to induce THP-1 macrophages apoptosis.

[Automatic Classification of Epileptic Electroencephalogram Signal Based on Improved Multivariate Multiscale Entropy].

Traditional sample entropy fails to quantify inherent long-range dependencies among real data. Multiscale sample entropy (MSE) can detect intrinsic correlations in data, but it is usually used in univariate data. To generalize this method for multichannel data, we introduced multivariate multiscale entropy into multiscale signals as a reflection of the nonlinear dynamic correlation. But traditional multivariate multiscale entropy has a large quantity of computation and costs a large period of time and space for more channel system, so that it can not reflect the correlation between variables timely and accurately. In this paper, therefore, an improved multivariate multiscale entropy embeds on all variables at the same time, instead of embedding on a single variable as in the traditional methods, to solve the memory overflow while the number of channels rise, and it is more suitable for the actual multivariate signal analysis. The method was tested in simulation data and Bonn epilepsy dataset. The simulation results showed that the proposed method had a good performance to distinguish correlation data. Bonn epilepsy dataset experiment also showed that the method had a better classification accuracy among the five data set, especially with an accuracy of 100% for data collection of Z and S.

Isolation and identification of a new ent-kaurane diterpenoid from the leaves of Isodon japonica.

A new ent-kaurane diterpenoid, 3α, 14ß, 16α-trihydroxy-ent-kaurane (1), together with seven known diterpenoids (2-8), was isolated from the leaves of Isodon japonica. Their structures were elucidated by spectroscopic methods, including 1D and 2D NMR experiments, IR, HR-ESI-MS and X-ray crystallographic analysis.

Isolation, structural elucidation, and cytotoxicity of three new ent-kaurane diterpenoids from Isodon japonica var. glaucocalyx.

Three new ENT-kaurane diterpenoids, glaucocalyxin H ( 1), glaucocalyxin I ( 2), and glaucocalyxin J ( 3), together with four known diterpenoids ( 4- 7), were isolated from the leaves of Isodon japonica Hara var. glaucocalyx. Their structures were elucidated by spectroscopic analysis, and the structures of compounds 2 and 3 were further confirmed by X-ray crystallographic analysis. Compounds 1, 4, and 5 were evaluated for their cytotoxicity IN VITRO against CE-1, U87, A-549, MCF-7, Hela, K-562, and HepG-2 human tumor cell lines. Compound 1 showed potent inhibitory activities against six tumor cell lines with IC (50) values ranging from 1.86-10.95 µM, and compounds 4 and 5 exhibited significant selective cytotoxicity on seven tumor cell lines.

3ß,11α-Dihy-droxy-12-ursen-3-yl palmitate.

In the title compound, C(46)H(80)O(3), a natural ursane-type triperpenoid, four of the five six-membered rings adopt chair conformations; the fifth, which has a C=C double bond, adopts an approximate half-boat conformation. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, forming chains along [010].

Using 915 nm laser excited Tm³+/Er³+/Ho³+- doped NaYbF4 upconversion nanoparticles for in vitro and deeper in vivo bioimaging without overheating irradiation.

Successful further development of superhigh-constrast upconversion (UC) bioimaging requires addressing the existing paradox: 980 nm laser light is used to excite upconversion nanoparticles (UCNPs), while 980 nm light has strong optical absorption of water and biological specimens. The overheating caused by 980 nm excitation laser light in UC bioimaging is computationally and experimentally investigated for the first time. A new promising excitation approach for better near-infrared to near-infrared (NIR-to-NIR) UC photoluminescence in vitro or in vivo imaging is proposed employing a cost-effective 915 nm laser. This novel laser excitation method provides drastically less heating of the biological specimen and larger imaging depth in the animals or tissues due to quite low water absorption. Experimentally obtained thermal-graphic maps of the mouse in response to the laser heating are investigated to demonstrate the less heating advantage of the 915 nm laser. Our tissue phantom experiments and simulations verified that the 915 nm laser is superior to the 980 nm laser for deep tissue imaging. A novel and facile strategy for surface functionalization is utilized to render UCNPs hydrophilic, stable, and cell targeting. These as-prepared UCNPs were characterized by TEM, emission spectroscopy, XRD, FTIR, and zeta potential. Specifically targeting UCNPs excited with a 915 nm laser have shown very high contrast UC bioimaging. Highly stable DSPE-mPEG-5000-encapsulated UCNPs were injected into mice to perform in vivo imaging. Imaging and spectroscopy analysis of UC photoluminescence demonstrated that a 915 nm laser can serve as a new promising excitation light for UC animal imaging.

Detection and photodynamic therapy of inflamed atherosclerotic plaques in the carotid artery of rabbits.

Photodynamic therapy (PDT) has been applied in the treatment of artery restenosis following balloon injury. This study aimed to detect the accumulation of 5-aminolevulinic acid (ALA)-derived protoporphyrin IX (PpIX) in inflamed atherosclerotic plaque in rabbit model and evaluate the efficacy of PDT. The inflamed atherosclerotic plaque in the common carotid artery was produced by combination of balloon denudation injury and high cholesterol diet. After intravenous administration of ALA, the fluorescence of PpIX in plaque was detected. At the peak time, the correlation between the fluorescence intensity of PpIX and the macrophage infiltration extent in plaque was analyzed. Subsequently, PDT (635nm at 50J/cm(2)) on the atherosclerotic plaques (n=48) was performed and its effect was evaluated by histopathology and immunohistochemistry. The fluorescence intensity of PpIX in the plaque reached the peak 2h after injection and was 12 times stronger than that of adjacent normal vessel segment, and has a positive correlation with the macrophage content (r=0.794, P<0.001). Compared with the control group, the plaque area was reduced by 59% (P<0.001) at 4week after PDT, the plaque macrophage content decreased by 56% at 1week and 64% at 4week respectively, the smooth muscle cells (SMCs) was depleted by 24% at 1week (P<0.05) and collagen content increased by 44% at 4week (P<0.05). It should be pointed out that the SMC content increased by 18% after PDT at 4week compared with that at 1week (P<0.05). Our study demonstrated that the ALA-derived PpIX can be detected to reflect the macrophage content in the plaque. ALA mediated PDT could reduce macrophage content and inhibit plaque progression, indicating a promising approach to treat inflamed atherosclerotic plaques.

Hematoporphyrin monomethyl ether-mediated photodynamic effects on THP-1 cell-derived macrophages.

Photodynamic therapy (PDT) has been shown to attenuate atherosclerotic plaque progression and decrease macrophage-infiltration. The effectiveness of PDT depends strongly on the type of photosensitizers. Hematoporphyrin monomethyl ether (HMME) is a promising second-generation porphyrin-related photosensitizer for PDT. This study is designed to characterize effects of HMME-based PDT on THP-1 cell-derived macrophages and define the cell-death pathway. HMME was identified to accumulate in the macrophages by fluorescence microscopy and confocal scanning laser microscope. Our data demonstrated that the intensity of laser-induced HMME fluorescence in macrophages steadily increased with the increasing incubation concentration of HMME. The survival rate of macrophages determined by MTT assay decreased with the increasing HMME concentration and irradiation time. HMME-based PDT induced macrophage apoptosis via caspase-9 and caspase-3 activation pathway detected by caspase fluorescent assay kit and flow cytometer. The PDT increased the number of apoptotic macrophages by 14-fold at 12 h post irradiation by 9 J/cm(2) 635 nm diode laser. These results imply that photodynamic therapy with HMME may therefore be a useful clinical treatment for unstable atherosclerotic plaques.

Apoptosis of vascular smooth muscle cells induced by photodynamic therapy with protoporphyrin IX.

Photodynamic therapy (PDT) had been shown effective in the treatment of intimal hyperplasia, which contributes to restenosis, by eradicating cells in the vessel wall. This study is designed to evaluate the effects of PDT with protoporphyrin IX (PpIX) on the viability of vascular smooth muscle cells (SMCs) and to define the cell-death pathway. Fluorescence microscopy and laser-induced fluorescence spectroscopic detection showed that SMCs selectively uptake PpIX, and the intracellular PpIX concentration increases with the amount of PpIX in the incubation solution. PDT with PpIX impaired cellular viability from 93+/-3.4% to 36+/-3.9% when the light intensity increases from 2 to 9J/cm(2) and intracellular PpIX concentration increases from 0.5 to 20 microg/ml. Although PDT induced both apoptosis and necrosis, the ratio of apoptotic cells increased with light dosage or intracellular PpIX concentration. The loss of mitochondrial membrane potential coincided with the apoptotic ratio. Our results indicated that the induction of apoptosis of SMCs may be one of the mechanisms by which PDT inhibits restenosis in vivo.

Autofluorescence-free in vivo multicolor imaging using upconversion fluoride nanocrystals.

Non-invasive fluorescence imaging is an important technique in biology. However, detection of traditional biomarker emissions is accompanied by a high background signal. In this study we examined whether upconversion sodium yttrium fluoride (NaYF(4)) nanocrystals were suitable for autofluorescence-free multicolor fluorescence imaging in a living animal. Tissue autofluorescence was induced with a 405 nm light source, then rats were subjected to injection of fluorescein isothiocyanate (FITC), cadmium selenide/zinc sulfide (CdSe/ZnS) quantum dots (QDs), or NaYF(4):ytterbium/thulium (Yb(3+)/Tm(3+)), NaYF(4):Yb(3+)/holmium (Ho(3+)), and NaYF(4):Yb(3+)/Ho(3+)/cerium (Ce(3+)) nanocrystals. Imaging with NaYF(4) nanocrystals (974 nm laser) completely removed the high tissue autofluorescence, in marked contrast to imaging with FITC and QDs (405 nm light). Optical imaging experiments demonstrated that multiple biological targets and organs could be imaged at the same time using multicolor NaYF(4) upconversion nanocrystals under a single excitation wavelength (974 nm). These data demonstrated the proof-of-principle that autofluorescence-free multicolor imaging using near-infrared to visible upconversion of NaYF(4) nanocrystals excited by laser can be performed in a living animal.

Near vacuum ultraviolet luminescence of Gd3+ and Er3+ ions generated by super saturation upconversion processes.

Near vacuum ultraviolet (UV) upconversion (UC) emissions with a spectral resolution of 1 nm, from the (6)G(J), (6)D(J), (6)I(J), (6)P(J) levels of Gd(3+) and the (2)L(17/2), (4)D(7/2), (2)H(2)(9/2), (2)D(5/2), (4)G(7/2), (2)K(13/2), (2)P(3/2) levels of Er(3+), were observed under 974 nm laser excitation. Mechanism analyses illustrate that successive energy transfers (ETs) from Yb(3+) to Er(3+) generate UV UC radiations in Er(3+), while two resonant ETs from Er(3+) to Gd(3+) lead to UV UC radiations in Gd(3+). Power dependence analyses indicate that the expected inefficient four- and five-photon processes have been switched into efficient two-photon processes due to a super saturation UC phenomenon that employs consecutive saturations at the intermediate states.

Upconversion emission tuning from green to red in Yb3+/Ho3+-codoped NaYF4 nanocrystals by tridoping with Ce3+ ions.

Upconversion (UC) emission tuning from green to red in monodisperse NaYF(4):Yb(3+)/Ho(3+) nanocrystals was successfully achieved by tridoping with Ce(3+) ions under diode laser excitation of 970 nm. It is proposed that two efficient cross-relaxation processes, 5S2/5F4(Ho) + 2F(5/2)(Ce) --> 5F5(Ho) + 2F(7/2)(Ce) and 5I6(Ho) + 2F(5/2)(Ce) --> 5I7(Ho) + 2F(7/2)(Ce)between Ho(3+) and Ce(3+) ions, have been employed to select UC pathways to tune the UC radiation. Theoretical investigations based on steady-state equations demonstrate the proposed UC mechanisms and explain well the observed linear increase of the UC red-to-green intensity ratio with the increment of Ce(3+) ion concentrations.