Significant improvement of n-contact performance and wall plug efficiency of AlGaN-based deep ultraviolet light-emitting diodes by atomic layer etching.

The reactive ion etching (RIE) process is needed to fabricate deep ultraviolet (DUV) light-emitting diodes (LEDs). However, the n-contact performance deteriorates when the high-Al n-AlGaN surface undergoes RIE, leading to decreased LED performance. In this study, we employed an atomic layer etching (ALE) technology to eliminate surface damage generated during the mesa etching process, thus enhancing the n-Al0.65Ga0.35N ohmic contact. The improved contact performance reduced LED operation voltage and mitigated device heat generation. It was observed that DUV LEDs treated with 200 cycles of ALE showed a reduction in operating voltage from 8.3 to 5.2 V at 10 mA, with a knee voltage of 4.95 V. The peak wall plug efficiency (WPE) was approximately 1.74 times that of reference devices. The x-ray photoelectron spectroscopy (XPS) analysis revealed that ALE removed the surface damage layer induced by plasma etching, eliminating surface nitrogen vacancies and increasing surface electron concentration. Consequently, it facilitated better ohmic contact formation on n-Al0.65Ga0.35N. This study demonstrates that the ALE technology achieves etching with minor surface damage and is suitable for use in III-nitride materials and devices to remove surface defects and contaminations, leading to improved device performance.

Evaluation and comparison of liquid chromatography/high-resolution mass spectrometry platforms for the separation and characterization of ginsenosides from the leaves of Panax ginseng.

The measurement of data repeatability in small-molecule metabolites acquired within and among different liquid chromatography-mass spectrometry (LC-MS) platforms is crucial for data sharing or data transfer in natural products research. This work was designed to investigate and evaluate the separation and detection performance of three commercial high-resolution LC-MS platforms (e.g., Agilent 6550 QTOF, Waters Vion IM-QTOF, and Thermo Scientific Orbitrap Exploris 120) using 68 ginsenoside references and the extract of Panax ginseng leaf. The retention time (tR), measured on these three platforms (under the same chromatography condition), showed good stability in different concentration tests, and within/among different instruments for both intra-day and inter-day precision examinations. Correlation in tR of ginsenosides was also highly determined on these three platforms. In spite of the different mass analyzers involved, these three platforms gave the accurate mass determination ability, especially enhanced resolution gained because of the ion mobility (IM) separation facilitated by IM-quadrupole time-of-flight. The current study has systematically evaluated the separation and MS detection performance enabled by three high-resolution LC-MS platforms taking ginsenosides as the template, and the reported findings can benefit the researchers for the selection of analytical platforms and the purpose of data sharing or data transfer.

Detoxification of tetracycline and synthetic dyes by a newly characterized Lentinula edodes laccase, and safety assessment using proteomic analysis.

Fungal laccase has strong ability in detoxification of many environmental contaminants. A putative laccase gene, LeLac12, from Lentinula edodes was screened by secretome approach. LeLac12 was heterogeneously expressed and purified to characterize its enzymatic properties to evaluate its potential use in bioremediation. This study showed that the extracellular fungal laccase from L. edodes could effectively degrade tetracycline (TET) and the synthetic dye Acid Green 25 (AG). The growth inhibition of Escherichia coli and Bacillus subtilis by TET revealed that the antimicrobial activity was significantly reduced after treatment with the laccase-HBT system. 16 transformation products of TET were identified by UPLC-MS-TOF during the laccase-HBT oxidation process. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that LeLac12 could completely mineralize ring-cleavage products. LeLac12 completely catalyzed 50 mg/L TET within 4 h by adding AG (200 mg/L), while the degradation of AG was above 96% even in the co-contamination system. Proteomic analysis revealed that central carbon metabolism, energy metabolism, and DNA replication/repair were affected by TET treatment and the latter system could contribute to the formation of multidrug-resistant strains. The results demonstrate that LeLac12 is an efficient and environmentally method for the removal of antibiotics and dyes in the complex polluted wastewater.

Seeding, maturation and propagation of amyloid ß-peptide aggregates in Alzheimer's disease.

Alzheimer's disease is neuropathologically characterized by the deposition of the amyloid ß-peptide (Aß) as amyloid plaques. Aß plaque pathology starts in the neocortex before it propagates into further brain regions. Moreover, Aß aggregates undergo maturation indicated by the occurrence of post-translational modifications. Here, we show that propagation of Aß plaques is led by presumably non-modified Aß followed by Aß aggregate maturation. This sequence was seen neuropathologically in human brains and in amyloid precursor protein transgenic mice receiving intracerebral injections of human brain homogenates from cases varying in Aß phase, Aß load and Aß maturation stage. The speed of propagation after seeding in mice was best related to the Aß phase of the donor, the progression speed of maturation to the stage of Aß aggregate maturation. Thus, different forms of Aß can trigger propagation/maturation of Aß aggregates, which may explain the lack of success when therapeutically targeting only specific forms of Aß.

An efficient approach addressing the chemical complexity of Jiawei Fangji Huangqi decoction by integrating ultra-high-performance liquid chromatography/ion mobility-quadrupole time-of-flight mass spectrometry and intelligent data processing workflows.

A challenge in the quality control of traditional Chinese medicine is the systematic multicomponent characterization of the compound formulae. Jiawei Fangji Huangqi, a modified form of Fangji Huangqi, is a prescription comprising seven herbal medicines. To address the chemical complexity of the Jiawei Fangji Huangqi decoction, we integrated ion mobility-quadrupole time-of-flight high-definition MSE coupled to ultra-high-performance liquid chromatography and intelligent data processing workflows available in the UNIFI software package. Good chromatographic separation was achieved on CORTECS UPLC T3 column within 52 min, and high-accuracy MS2 data were acquired using high-definition MSE in the negative and positive modes. A chemical library of 1250 compounds was created and incorporated into the UNIFI software to enable automatic peak annotation of the high-definition MSE data. We identified or tentatively characterize 430 compounds in the Jiawei Fangji Huangqi decoction. The potential superiority of high-definition MSE over conventional MS data acquisition approaches was revealed in its spectral quality (MS2 ), differentiation of isomers, separation of coeluting compounds, and target mass coverage. The multiple components of the Jiawei Fangji Huangqi decoction were elucidated, offering insight into its improved pharmacological action compared with that of the Fangji Huangqi formula.

Collision Cross Section Prediction Based on Machine Learning.

Ion mobility-mass spectrometry (IM-MS) is a powerful separation technique providing an additional dimension of separation to support the enhanced separation and characterization of complex components from the tissue metabolome and medicinal herbs. The integration of machine learning (ML) with IM-MS can overcome the barrier to the lack of reference standards, promoting the creation of a large number of proprietary collision cross section (CCS) databases, which help to achieve the rapid, comprehensive, and accurate characterization of the contained chemical components. In this review, advances in CCS prediction using ML in the past 2 decades are summarized. The advantages of ion mobility-mass spectrometers and the commercially available ion mobility technologies with different principles (e.g., time dispersive, confinement and selective release, and space dispersive) are introduced and compared. The general procedures involved in CCS prediction based on ML (acquisition and optimization of the independent and dependent variables, model construction and evaluation, etc.) are highlighted. In addition, quantum chemistry, molecular dynamics, and CCS theoretical calculations are also described. Finally, the applications of CCS prediction in metabolomics, natural products, foods, and the other research fields are reflected.

Reflective metalens with an enhanced off-axis focusing performance.

Metalenses are one of the most promising metasurface applications. However, all-dielectric reflective metalenses are rarely studied, especially regarding their off-axis focusing performance. After experimentally studying the material optical properties in this work, we propose reflective metalens based on titanium dioxide (TiO2) and silicon dioxide (SiO2), which operate at a visible wavelength of 0.633 µm. Unlike conventional reflective metalenses based on metallic mirrors, the proposed device was designed based on a modified parabolic phase profile and was integrated onto a dielectric distributed Bragg reflector periodic structure to achieve high reflectivity with five dielectric pairs. The focusing efficiency characteristics of the metalens were experimentally studied for beam angles of incidence between 0∘ and 30∘. The results reveal that the focusing efficiency for the modified metalens design remains higher than 54%, which is higher than 50%, making it promising for photonic miniaturization and integration.

Effect of the AlN strain compensation layer on InGaN quantum well red-light-emitting diodes beyond epitaxy.

An atomically thick AlN layer is typically used as the strain compensation layer (SCL) for InGaN-based-red light-emitting diodes (LEDs). However, its impacts beyond strain control have not been reported, despite its drastically different electronic properties. In this Letter, we describe the fabrication and characterization of InGaN-based red LEDs with a wavelength of 628 nm. A 1-nm AlN layer was inserted between the InGaN quantum well (QW) and the GaN quantum barrier (QB) as the SCL. The output power of the fabricated red LED is greater than 1 mW at 100 mA current, and its peak on-wafer wall plug efficiency (WPE) is approximately 0.3%. Based on the fabricated device, we then used numerical simulation to systematically study the effect of the AlN SCL on the LED emission wavelength and operating voltage. The results show that the AlN SCL enhances the quantum confinement and modulates the polarization charges, modifying the device band bending and the subband energy level in the InGaN QW. Thus, the insertion of the SCL considerably affects the emission wavelength, and the effect on the emission wavelength varies with the SCL thickness and the Ga content introduced into the SCL. In addition, the AlN SCL in this work reduces the LED operating voltage by modulating the polarization electric field and energy band, facilitating carrier transport. This implies that heterojunction polarization and band engineering is an approach that can be extended to optimize the LED operating voltage. We believe our study better identifies the role of the AlN SCL in InGaN-based red LEDs, promoting their development and commercialization.

Localized surface plasmon resonance-enhanced solar-blind Al0.4Ga0.6N MSM photodetectors exhibiting high-temperature robustness.

The appealing properties of tunable direct wide bandgap, high-temperature robustness and chemical hardness, make AlxGa1-xN a promising candidate for fabricating robust solar-blind photodetectors (PDs). In this work, we have utilized the optical phenomenon of localized surface plasmon resonance (LSPR) in metal nanoparticles (NPs) to significantly enhance the performance of solar-blind Al0.4Ga0.6N metal-semiconductor-metal PDs that exhibit high-temperature robustness. We demonstrate that the presence of palladium (Pd) NPs leads to a remarkable enhancement by nearly 600, 300, and 462%, respectively, in the photo-to-dark current ratio (PDCR), responsivity, and specific detectivity of the Al0.4Ga0.6N PD at the wavelength of 280 nm. Using the optical power density of only 32µW cm-2at -10 V, maximum values of ∼3 × 103, 2.7 AW-1, and 2.4 × 1013Jones are found for the PDCR, responsivity and specific detectivity, respectively. The experimental observations are supported by finite difference time domain simulations, which clearly indicate the presence of LSPR in Pd NPs decorated on the surface of Al0.4Ga0.6N. The mechanism behind the enhancement is investigated in detail, and is ascribed to the LSPR induced effects, namely, improved optical absorption, enhanced local electric field and LSPR sensitization effect. Moreover, the PD exhibits a stable operation up to 400 K, thereby exhibiting the high-temperature robustness desirable for commercial applications.

Application of collagen triple helix repeat containing-1 and mitotic spindle apparatus antibody in small cell lung cancer diagnosis.

BACKGROUND: The clinical significance of serum collagen triple helix repeat protein-1 (CTHRC1) and mitotic spindle apparatus antibody (MSA) in the diagnosis of small cell lung cancer (SCLC). METHODS: Of the 229 lung tumor patients selected, 62 patients were divided into SCLC, 94 patients with non-small cell lung cancer (NSCLC), and 73 patients with benign lung disease (BLD). The health controls (HC) had a span of 66 cases with normal physical condition. The serum extracted from each participator and enzyme-linked immunosorbent assay was adopted for measuring the serum CTHRC1 and MSA; in the meantime, automatic electrochemiluminescence immunoassay was used for the quantitative determination of serum NSA and CEA. And then, the differences in serum CTHRC1, MSA, NSE, and CEA were compared among involved groups. RESULTS: ① Compared with other groups, the concentrations of CTHRC1, MSA, and NSE showed a marked increase in the group of SCLC (all p < 0.01). Especially for SCLC patients with lymph node metastasis, CTHRC1 provided a notably higher level than those without metastasis. ② CTHRC1 and MSA established a diagnostic criterion with the specificity of 90.99% and 86.27% for SCLC, respectively. ③ In series, the specificity of CTHRC1 and NSE was the highest (99.30%), while MSA and NSE had the highest sensitivity (96.72%) in parallel. ④ Both CTHRC1 and MSA were hazardous factors interconnected with SCLC. CONCLUSION: Serum CTHRC1 and MSA had a more exciting prospect of application. When used in conjunction with NSE and CEA, they could optimize the clinical diagnosis value of SCLC.

Tumor necrosis factor-alpha stimulated gene-6: A biomarker reflecting disease activity in rheumatoid arthritis.

BACKGROUND: To explore the serum tumor necrosis factor-alpha stimulated gene-6 (TSG-6) level and its association with disease activity in rheumatoid arthritis (RA) patients. METHODS: We recruited 176 RA patients, 178 non-RA patients (lupus erythematosus, osteoarthritis, ulcerative colitis, ankylosing spondylitis and psoriasis) and 71 healthy subjects. Serum TSG-6 levels were detected by enzyme-linked immunosorbent assay (ELISA). RA patients were divided into inactive RA and active RA groups by disease activity score of 28 joints based on C-reactive protein (DAS28-CRP). The receiver operating characteristic (ROC) curve and Spearman's rank correlation test analyzed the correlation between TSG-6 concentration and RA disease activity. RESULTS: Tumor necrosis factor-alpha stimulated gene-6 levels in the RA group were increased (p < 0.01). TSG-6 concentrations indicated an upward tendency with increased disease activity; The area under the curve (AUC) of TSG-6 for diagnosing RA and assessing the severity of RA were 0.78 and 0.80, respectively; The combination of TSG-6 and anti-mutated citrullinated vimentin antibodies (anti-MCV) (sensitivity:98.4%)improved the diagnostic accuracy of RA. Binary logistic regression analysis showed that TSG-6 was an independent risk factor related to the severity of RA, and OR (95% CI) was 1.2 (1.003-1.453). CONCLUSION: The TSG-6 levels in RA patients were elevated and related to disease activity. Therefore, TSG-6 may serve as a new potential biomarker for evaluating RA disease activity.

Cadmium exposure causes mitochondrial fission and fusion disorder in the pig hypothalamus via the PI3K/AKT pathway.

Cadmium (Cd) is the main environmental pollutant causing endocrine and nervous system dysfunction in animals. High doses of Cd cause cytotoxicity, including programmed necrosis and apoptosis, which has aroused widespread concern. Mitochondrial dynamics plays a key role in programmed necrosis and apoptosis of endocrine organs. Nevertheless, there is a lack of information on the relationship between Cd-induced programmed necrosis/apoptosis of the hypothalamus and the mitochondrial fusion-fission balance. Therefore, a hypothalamic injury model of Cd exposure was established by adding 20 mg/kg CdCl2 to the basic pig diet for 40 days. Analysis of the Cd toxicity mechanism was conducted by inductively coupled plasma mass spectrometry, hematoxylin and eosin staining, the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, and quantitative reverse transcription-polymerase chain reaction, as well as western blot analyses. The results suggested that exposure to Cd inhibited the expression of PI3K and AKT, interfered with the balance of mitochondrial fusion and division, downregulated the expression of Mfn2, Mfn1, and OPA1, and upregulated the expression of Drp1 and Mff, which led to cell apoptosis and programmed necrosis in the pig hypothalamus. This study finds that cadmium exposure leads to mitochondrial fission and fusion dysfunction in porcine hypothalamus via the PI3K/AKT pathway.

Estimation of Soil Organic Carbon Content in the Ebinur Lake Wetland, Xinjiang, China, Based on Multisource Remote Sensing Data and Ensemble Learning Algorithms.

Soil organic carbon (SOC), as the largest carbon pool on the land surface, plays an important role in soil quality, ecological security and the global carbon cycle. Multisource remote sensing data-driven modeling strategies are not well understood for accurately mapping soil organic carbon. Here, we hypothesized that the Sentinel-2 Multispectral Sensor Instrument (MSI) data-driven modeling strategy produced superior outcomes compared to modeling based on Landsat 8 Operational Land Imager (OLI) data due to the finer spatial and spectral resolutions of the Sentinel-2A MSI data. To test this hypothesis, the Ebinur Lake wetland in Xinjiang was selected as the study area. In this study, SOC estimation was carried out using Sentinel-2A and Landsat 8 data, combining climatic variables, topographic factors, index variables and Sentinel-1A data to construct a common variable model for Sentinel-2A data and Landsat 8 data, and a full variable model for Sentinel-2A data, respectively. We utilized ensemble learning algorithms to assess the prediction performance of modeling strategies, including random forest (RF), gradient boosted decision tree (GBDT) and extreme gradient boosting (XGBoost) algorithms. The results show that: (1) The Sentinel-2A model outperformed the Landsat 8 model in the prediction of SOC contents, and the Sentinel-2A full variable model under the XGBoost algorithm achieved the best results R2 = 0.804, RMSE = 1.771, RPIQ = 2.687). (2) The full variable model of Sentinel-2A with the addition of the red-edge band and red-edge index improved R2 by 6% and 3.2% over the common variable Landsat 8 and Sentinel-2A models, respectively. (3) In the SOC mapping of the Ebinur Lake wetland, the areas with higher SOC content were mainly concentrated in the oasis, while the mountainous and lakeside areas had lower SOC contents. Our results provide a program to monitor the sustainability of terrestrial ecosystems through a satellite perspective.

Multicomponent Characterization of the Flower Bud of Panax notoginseng and Its Metabolites in Rat Plasma by Ultra-High Performance Liquid Chromatography/Ion Mobility Quadrupole Time-of-Flight Mass Spectrometry.

The flower bud of Panax notoginseng (PNF) consumed as a tonic shows potential in the prevention and treatment of cardiovascular diseases. To identify the contained multi-components and, in particular, to clarify which components can be absorbed and what metabolites are transformed, unveiling the effective substances of PNF is of vital significance. A unique ultrahigh-performance liquid chromatography/ion mobility quadrupole time-of-flight mass spectrometry (UHPLC/IM-QTOF-MS) profiling approach and efficient data processing by the UNIFITM bioinformatics platform were employed to comprehensively identify the multi-components of PNF and the related metabolites in the plasma of rats after oral administration (at a dose of 3.6 g/kg). Two MS2 data acquisition modes operating in the negative electrospray ionization mode, involving high-definition MSE (HDMSE) and data-dependent acquisition (DDA), were utilized aimed to extend the coverage and simultaneously ensure the quality of the MS2 spectra. As a result, 219 components from PNF were identified or tentatively characterized, and 40 thereof could be absorbed. Moreover, 11 metabolites were characterized from the rat plasma. The metabolic pathways mainly included the phase I (deglycosylation and oxidation). To the best of our knowledge, this is the first report that systematically studies the in vivo metabolites of PNF, which can assist in better understanding its tonifying effects and benefit its further development.

An Efficient Photomixer Based Slot Fed Terahertz Dielectric Resonator Antenna.

A slot fed terahertz dielectric resonator antenna driven by an optimized photomixer is proposed, and the interaction of the laser and photomixer is studied. It is demonstrated that in a continuous wave terahertz photomixing scheme, the generated THz power is proportional to the 4th power of the surface electric field of photocondutive layer. Consequently, the optical to THz conversion efficiency of the proposed photomixer has an enhancement factor of 487. This is due to the fact that the surface electric field of the proposed photomixer with a 2D-Photonic Crystal (PhC) superstrate has been improved from 2.1 to 9.9 V/m, which represents a substantial improvement. Moreover, the electrically thick Gallium-Arsenide (GaAs) supporting substrate of the device has been truncated to create a dielectric resonator antenna (DRA) that offers a typical radiation efficiency of more than 90%. By employing a traditional coplanar strip (CPS) biasing network, the matching efficiency has been improved to 24.4%. Therefore, the total efficiency has been considerably improved due to the enhancements in the laser-to-THz conversion, as well as radiation and matching efficiencies. Further, the antenna gain has been improved to 9dBi at the presence of GaAs superstrate. Numerical comparisons show that the proposed antenna can achieve a high gain with relatively smaller dimensions compared with traditional THz antenna with Si lens.

Sequence of proteome profiles in preclinical and symptomatic Alzheimer's disease.

Proteome profile changes in Alzheimer's disease (AD) brains have been reported. However, it is unclear whether they represent a continuous process, or whether there is a sequential involvement of distinct proteins. To address this question, we used mass spectrometry. We analyzed soluble, dispersible, sodium dodecyl sulfate, and formic acid fractions of neocortex homogenates (mainly Brodmann area 17-19) from 18 pathologically diagnosed preclinical AD, 17 symptomatic AD, and 18 cases without signs of neurodegeneration. By doing so, we identified four groups of AD-related proteins being changed in levels in preclinical and symptomatic AD cases: early-responding, late-responding, gradually-changing, and fraction-shifting proteins. Gene ontology analysis of these proteins and all known AD-risk/causative genes identified vesicle endocytosis and the secretory pathway-related processes as an early-involved AD component. In conclusion, our findings suggest that subtle changes involving the secretory pathway and endocytosis precede severe proteome changes in symptomatic AD as part of the preclinical phase of AD. The respective early-responding proteins may also contribute to synaptic vesicle cycle alterations in symptomatic AD.

Inverse design of plasmonic metasurfaces by convolutional neural network.

Artificial neural networks have shown effectiveness in the inverse design of nanophotonic structures; however, the numerical accuracy and algorithm efficiency are not analyzed adequately in previous reports. In this Letter, we demonstrate the convolutional neural network as an inverse design tool to achieve high numerical accuracy in plasmonic metasurfaces. A comparison of the convolutional neural networks and the fully connected neural networks show that convolutional neural networks have higher generalization capabilities. We share practical guidelines for optimizing the neural network and analyzed the hierarchy of accuracy in the multi-parameter inverse design of plasmonic metasurfaces. A high inverse design accuracy of $\pm 8\;{\rm nm}$±8nm for the critical geometrical parameters is demonstrated.

Treatment of recurrent renal transplant lithiasis: analysis of our experience and review of the relevant literature.

BACKGROUND: Renal transplant lithiasis is a rather unusual disease, and the recurrence of lithiasis presents a challenging situation. METHODS: We retrospectively analyzed the medical history of one patient who suffered renal transplant lithiasis twice, reviewed the relevant literature, and summarized the characteristics of this disease. RESULTS: We retrieved 29 relevant studies with an incidence of 0.34 to 3.26% for renal transplant lithiasis. The summarized incidence was 0.52%, and the recurrence rate was 0.082%. The mean interval after transplantation was 33.43 ± 56.70 mo. Most of the patients (28.90%) were asymptomatic. The management included percutaneous nephrolithotripsy (PCNL, 22.10%), ureteroscope (URS, 22.65%), extracorporeal shockwave lithotripsy (ESWL, 18.60%) and conservative treatment (17.13%). In our case, the patient suffered from renal transplant lithiasis at 6 years posttransplantation, and the lithiasis recurred 16 months later. He presented oliguria, infection or acute renal failure (ARF) during the two attacks but without pain. PCNL along with URS and holmium laser lithotripsy were performed. The patient recovered well after surgery, except for a 3 mm residual stone in the calyx after the second surgery. He had normal renal function without any symptoms and was discharged with oral anticalculus drugs and strict follow-up at the clinic. Fortunately, the calculus passed spontaneously about 1 month later. CONCLUSIONS: Due to the lack of specific symptoms in the early stage, patients with renal transplant lithiasis may have delayed diagnosis and present ARF. Minimally invasive treatment is optimal, and the combined usage of two or more procedures is beneficial for patients. After surgery, taking anticalculus drugs, correcting metabolic disorders and avoiding UIT are key measures to prevent the recurrence of lithiasis.

Ultraviolet polarized light emitting and detecting dual-functioning device based on nonpolar n-ZnO/i-ZnO/p-AlGaN heterojunction.

We report on the demonstration of a 386 nm light emission and detection dual-functioning device based on nonpolar a-plane n-ZnO/i-ZnO/p-Al0.1Ga0.9N heterojunction under both forward and reverse bias. The electroluminescence intensity under reverse bias is significantly stronger than that under forward bias, facilitated by carrier tunneling when the valence band of p-AlGaN aligns with the conduction band of i-ZnO under reverse bias. Also amid reverse bias, the photodetection was observed and applied in a duplex optical communication device. Optical polarization of the light emission is studied for potential polarization-sensitive device applications. The proposed device provides an important pathway for the multifunctional devices operating in a UV spectrum.

Outcomes of long-term follow-up of asymptomatic renal stones and prediction of stone-related events.

OBJECTIVES: To evaluate the long-term outcomes of patients undergoing observation of asymptomatic renal calculi and identify factors associated with stone-related events. PATIENTS AND METHODS: Patients with asymptomatic renal calculi electing active surveillance of their stones were retrospectively reviewed. Patients underwent annual ultrasonography and clinical visits with standardised questions regarding the development of symptoms or complications from calculi. Spontaneous stone passage, stone growth, development of stone-related symptoms, and requirement for intervention during follow-up were deemed as stone-related events. RESULTS: Between 2007 and 2017, 293 patients were reviewed to evaluate the natural history of asymptomatic renal calculi. The mean follow-up was 4.2 years. Overall incidences of spontaneous passage, stone growth, development of stone-related symptoms, and requirement of intervention were 32.1%, 16.7%, 28.3% and 12.3%, respectively. Stones >5 mm and lower pole stones were significantly less likely to pass spontaneously. Patients with diabetes mellitus (DM), hyperuricaemia or non-lower calyceal stone were more likely to experience stone growth. Stones >5 mm or non-lower pole stones were more likely to become symptomatic. Significant predictors of surgical intervention were stone size (>5 mm) and patients' age (>60 years). Primary therapy was extracorporeal shockwave lithotripsy in 33 patients and flexible ureteroscopy in three. CONCLUSION: The natural history of asymptomatic renal stones rarely requires intervention, although they do have a slightly higher rate of symptomatic events and growth over the intermediate term. In particular, patients with stones >5 mm, DM, hyperuricaemia, or non-lower calyceal stones are at higher risk of developing stone-related events, and should therefore be recommended for regular follow-up.