Prediction of knee pain improvement over two years for knee osteoarthritis using a dynamic nomogram based on MRI-derived radiomics: a proof-of-concept study.

OBJECTIVES: To develop and validate a nomogram to detect improved knee pain in osteoarthritis (OA) by integrating magnetic resonance imaging (MRI) radiomics signature of subchondral bone and clinical characteristics. METHODS: Participants were selected from the Vitamin D Effects on Osteoarthritis (VIDEO) study. The primary outcome was 20% improvement of knee pain score over 2 years in participants administrated either vitamin D or placebo. Radiomics features of subchondral bone and clinical characteristics from 216 participants were extracted and analyzed. The participants were randomly split into the training and validation cohorts at a ratio of 8:2. Least absolute shrinkage and selection operator (LASSO) regression was used to select features and generate radiomics signatures. The optimal radiomics signature and clinical indicators were fitted into a nomogram using multivariable logistic regression model. RESULTS: The nomogram showed favorable discrimination performance [AUCtraining, 0.79 (95% CI: 0.72-0.79), AUCvalidation, 0.83 (95% CI: 0.70-0.96)] as well as a good calibration. Additional contributing value of fusion radiomics signature to the nomogram was statistically significant (NRI, 0.23; IDI, 0.14, P < 0.001 in training cohort and NRI, 0.29; IDI, 0.18, P < 0.05 in validating cohort). Decision curve analysis confirmed the clinical usefulness of nomogram. CONCLUSION: The radiomics-based nomogram comprising the MR radiomics signature and clinical variables achieves a favorable predictive efficacy and accuracy in differentiating improvement in knee pain among OA patients. This proof-of-concept study provides a promising way to predict clinically meaningful outcomes.

First-principles study of the structures and superconductivity of H-S-La systems under high pressure.

Recent experimental and theoretical studies have shown that a La-H system displays remarkable superconducting properties, and it is also possible to improve the superconducting state by introducing other elements into this system. In this study, we systematically investigated the crystal structures and physical properties of an H-S-La system by using first-principles calculations combined with the CALYPSO structure exploration technique. We predicted four stable stoichiometries containing H2SLa, H3SLa, H4Sla, and H6SLa. These compounds undergo a series of phase transitions under 50-300 GPa. The bonding characters and electronic properties were calculated. It was found that Cm-H2SLa, C2/c-H2SLa, and Cmcm-H6SLa exhibit good metallic nature, which stimulates us to further study their superconducting properties. The calculated superconducting transition temperatures (Tc) of Cm-H2SLa, C2/c-H2Sla, and Cmcm-H6SLa are 15.0 K at 200 GPa, 6.9 K at 300 GPa, and 23.6 K at 300 GPa, respectively.

[Analysis of conventional echocardiographic features in apical hypertrophic cardiomyopathy patients complicated with left ventricular apical aneurysm].

Objective: To explore the basic characteristics of conventional echocardiography of apical hypertrophic cardiomyopathy (ApHCM) patients complicating with left ventricular apical aneurysm (LVAA). Methods: This is a retrospective study. Patients who underwent echocardiography and cardiac magnetic resonance (CMR) and were diagnosed with ApHCM complicated with LVAA by CMR at Fuwai Hospital, Chinese Academy of Medical Sciences from August 2012 to July 2017 were enrolled. According to whether LVAA was detected by echocardiography, the enrolled patients were divided into two groups: LVAA detected by echocardiography group and LVAA not detected by echocardiography group. Clinical data of the two groups were compared to analyze the causes of missed diagnosis by echocardiography. Results: A total of 21 patients were included, of whom 67.0% (14/21) were males, aged (56.1±16.5) years. Patients with chest discomfort accounted for 81.0% (17/21), palpitation 38.1% (8/21), syncope 14.3% (3/21). ECG showed that 21 (100%) patients had ST-T changes and 18 (85.7%) had deep T-wave invertion. Echocardiography revealed ApHCM in 17 cases (81.0%) and LVAA in 7 cases (33.3%). The mean left ventricular apical aneurysm diameter was 33.0 (18.0, 37.0) mm, and left ventricular ejection fraction was (66.5±6.6) %, and left ventricular apex thickness was (21.0±6.3) mm. Left ventricular outflow tract obstruction was presented in 4 cases and middle left ventricular obstruction in 10 cases. The mean left ventricular apical aneurysm diameter of LVAA detected by echocardiography was greater than that of LVAA not detected by echocardiography (25.0 (18.0, 28.0) mm vs. 16.0 (12.3, 21.0) mm, P=0.006). Conclusions: Conventional echocardiography examination has certain limitations in the diagnosis of ApHCM. Smaller LVAA complicated with ApHCM is likely to be unrecognized by echocardiography. Clinicians should improve their understanding of this disease.

[Clinical efficacy evaluation of minimally invasive cardiac surgery coronary artery bypass grafting in patients with multivessel coronary artery disease].

Objective: To investigate the clinical efficacy of minimally invasive cardiac surgery coronary artery bypass grafting (MICS CABG) in the treatment of patients with multivessel coronary artery disease. Methods: A total of 147 patients with multi-vessel coronary artery disease and coronary heart disease who underwent surgical treatment in Henan Provincial People's Hospital from March 2016 to March 2019 were retrospectively selected. Of which, 69 patients were treated by MICS CABG (minimally invasive group) and 78 patients were treated using the traditional thoracotomy (traditional group). The perioperative indexes, serum myocardial enzyme indexes and renal function indexes of patients before and after operation were compared between the two groups; Two groups of patients were followed up for 2 years; the incidence of adverse cardiovascular events (MACE) was recorded, and survival analysis was performed. Results: The age of the patients in the minimally invasive group and the traditional group were (66.9±5.8) and (68.2±7.0) years old, respectively, and the proportions of males were 60.9% (42 cases) and 51.3% (40 cases) (all P>0.05). All patients in the two groups successfully completed the operation, and no patients in the minimally invasive group were converted to thoracotomy. Before surgery, there was no significant difference in serum cTnI, CK-MB, BUN, Scr, and creatinine clearance between the minimally invasive group and the traditional group (all P>0.05). After re-examination 48 hours after operation, the serum cTnI in the minimally invasive group was (3.109±0.664) µg/L, and the CK-MB was (18.03±3.27) U/L, which were lower than those in the traditional group (3.438±0.715) µg/L, (20.63±4.28) U/L; the difference was statistically significant (all P<0.05). During the 2-year follow-up, there was no statiscally significant difference in the incidence of recurrent myocardial infarction, postoperative atrial fibrillation, postoperative stroke, arrhythmia, heart failure, thrombosis, cardiac death, and MACE events between the minimally invasive group and the traditional group. Statistical significance (all P>0.05). The survival curve analysis showed that the cumulative rates of MACE events in the minimally invasive and traditional groups were 17.39% and 26.92%, respectively (P=0.171). Conclusions: The effect of MICS CABG in the treatment of patients with multivessel coronary artery disease and coronary heart disease is not much different from that of traditional open thoracotomy, but the former is less traumatic, quicker after surgery, and has clinical significance for the recovery of patients' myocardial function.

[The role of nitric oxide in the inhibitory effects of exogenous hydrogen sulfide on rat colonic smooth muscle contraction].

Objective: To investigate the role of nitric oxide (NO) in hydrogen sulfide (H(2)S)-induced inhibition upon colonic smooth muscle contraction. Methods: Immunohistochemistry was applied to observe the distribution of H(2)S-producing enzymes CBS and CSE in adult male Wistar rats. Organ bath system was used to observe the spontaneous contraction of colonic smooth muscle. Patch clamp technique was applied to record currents of L-type calcium channel (I(Ca,L)) in smooth muscle cells. Results: Specific immunoreactivity for CSE and CBS was observed in mucosa, smooth muscle and enteric plexus of rat proximal colon. NaHS elicited relaxation in a concentration-dependent manner upon muscle contraction in the presence of tetrodotoxin. The NaHS IC(50) of LM was 917.6 µmol/L (95% CI: 776.3-1 085 µmol/L, n=6) and the NaHS IC(50) of CM was 730.4 µmol/L (95% CI: 592.2-900.8 µmol/L, n=6). The SNP-induced relaxation in muscle strips was partially reversed by NaHS (P<0.05). Instead, the relaxation caused by NaHS was decreased by the sGC inhibitor ODQ but affected neither by NO precursor L-arginine, the NO inhibitor L-NNA nor the competitive cGMP antagonist PET-cGMP. NaHS (100 µmol/L) increased I(Ca,L) while NaHS (300 µmol/L) decreased the peak I(Ca,L) with modifying the ion channel characteristics (P<0.05). Conclusions: Exogenous hydrogen sulfide might have a dual effect on colonic motility and its inhibitory effect might be independent of NO signaling system. L-type calcium channel may play an important role during the process of H(2)S modulating colonic contraction.

Ecological speciation in sympatric palms: 1. Gene expression, selection and pleiotropy.

Ecological speciation requires divergent selection, reproductive isolation and a genetic mechanism to link the two. We examined the role of gene expression and coding sequence evolution in this process using two species of Howea palms that have diverged sympatrically on Lord Howe Island, Australia. These palms are associated with distinct soil types and have displaced flowering times, representing an ideal candidate for ecological speciation. We generated large amounts of RNA-Seq data from multiple individuals and tissue types collected on the island from each of the two species. We found that differentially expressed loci as well as those with divergent coding sequences between Howea species were associated with known ecological and phenotypic differences, including response to salinity, drought, pH and flowering time. From these loci, we identified potential 'ecological speciation genes' and further validate their effect on flowering time by knocking out orthologous loci in a model plant species. Finally, we put forward six plausible ecological speciation loci, providing support for the hypothesis that pleiotropy could help to overcome the antagonism between selection and recombination during speciation with gene flow.

Rare Seagull Cooing Murmur from Acute Aortic Dissection.

Acute aortic dissection is a rare but potentially fatal disease. The early recognition of this disease is important for timely treatment. Some signs and symptoms, such as past history of hypertension, tearing pain and pulselessness, can provide valuable clues to the diagnosis of this disease. In this case study, the mechanism of a seagull murmur from aortic dissection is first described. This information is potentially useful for the differential diagnosis of dissection.

[Multi-phase CT synthesis-assisted segmentation of abdominal organs].

OBJECTIVE: To propose a method for abdominal multi-organ segmentation assisted by multi-phase CT synthesis. METHODS: Multi-phase CT synthesis for synthesizing high-quality CT images was used to increase the information details for image segmentation. A transformer block was introduced to help to capture long-range semantic information in cooperation with perceptual loss to minimize the differences between the real image and synthesized image. RESULTS: The model was trained using multi-phase CT dataset of 526 total cases from Nanfang Hospital. The mean maximum absolute error (MAE) of the synthesized non-contrast CT, venous phase contrast- enhanced CT (CECT), and delay phase CECT images from arterial phase CECT was 19.192±3.381, 20.140±2.676 and 22.538±2.874, respectively, which were better than those of images synthesized using other methods. Validation of the multi-phase CT synthesis-assisted abdominal multi-organ segmentation method showed an average dice coefficient of 0.847 for the internal validation set and 0.823 for the external validation set. CONCLUSION: The propose method is capable of synthesizing high-quality multi-phase CT images to effectively reduce the errors in registration between different phase CT images and improve the performance for segmentation of 13 abdominal organs.

Propofol and memory: a study using a process dissociation procedure and functional magnetic resonance imaging.

Thirty volunteers randomly received either mild or deep propofol sedation, to assess its effect on explicit and implicit memory. Blood oxygen level-dependent functional magnetic resonance during sedation examined brain activation by auditory word stimulus and a process dissociation procedure was performed 4 h after scanning. Explicit memory formation did not occur in either group. Implicit memories were formed during mild but not deep sedation (p = 0.04). Mild propofol sedation inhibited superior temporal gyrus activation (Z value 4.37, voxel 167). Deep propofol sedation inhibited superior temporal gyrus (Z value 4.25, voxel 351), middle temporal gyrus (Z value 4.39, voxel 351) and inferior parietal lobule (Z value 5.06, voxel 239) activation. Propofol only abolishes implicit memory during deep sedation. The superior temporal gyrus is associated with explicit memory processing, while the formation of both implicit and explicit memories is associated with superior and middle temporal gyri and inferior parietal lobule activation.

Effect of midazolam on memory: a study of process dissociation procedure and functional magnetic resonance imaging.

To assess the effects of midazolam on explicit and implicit memories, 12 volunteers were randomly divided into the two groups: one with an Observer's Assessment of Alertness/Sedation score of 3 (mild sedation) and one with a score of 1 (deep sedation). Blood oxygen-level-dependent functional magnetic resonance imaging was measured before and during an auditory stimulus, then with midazolam sedation, and then during a second auditory stimulus with continuous midazolam sedation. After 4 h, explicit and implicit memories were assessed. There was no evidence of explicit memory at the two levels of midazolam sedation. Implicit memory was retained at a mild level of midazolam sedation but absent at a deep level of midazolam sedation. At a mild level of midazolam sedation, activation of all brain areas by auditory stimulus (as measured by functional magnetic resonance imaging) was uninhibited. However, a deep level of midazolam sedation depressed activation of the superior temporal gyrus by auditory stimulus. We conclude that midazolam does not abolish implicit memory at a mild sedation level, but can abolish both explicit and implicit memories at a deep sedation level. The superior temporal gyrus may be one of the target areas.

Occurrence of aliphatic hydrocarbons in water, suspended particulate matter and sediments of Daliao River system, China.

In August of 2005 a study was carried out to evaluate contamination of aliphatic hydrocarbons(AHc) in water, suspended particulate matter (SPM) and sediments from Daliao River system composed of the Hun River, Taizi River, and Daliao River in a heavy industrial area of northeast of China. The content of AHc ranged from 13.39 to 283.62 microg L(-1) in surface water, from 22.68 to 5,725.36 microg g(-1) in dry SPM, and from 61.37 to 229.42 microg g(-1) in dry sediments. High hydrocarbon levels were generally found in the areas associated with high anthropogenic impact and port activities. The calculated hydrocarbon indexes suggest that the stations with petrogenic sources and biogenic origin predominance would constitute aliphatic hydrocarbons for the river system. Hierarchical cluster analysis (HCA) of aliphatic hydrocarbons is correspondence with hydrocarbons indexes results.

Differential MicroRNA Expressions in Human Peripheral Blood Mononuclear Cells Are Predictive of Renal Allograft Function.

BACKGROUND: The present diagnostic methods for detecting graft damage after kidney transplantation are either invasive or not available early enough. The microRNAs (miRNAs) in peripheral blood mononuclear cells (PBMCs) have been suggested as promising biomarkers. METHODS: Using quantitative real-time polymerase chain reaction, we identified 9 miRNAs (miR-142-5p, miR-142-3p, miR-223, miR-211, miR-486, miR-155, miR-10b, miR-30a, and let-7c) related to the human renal allograft status in PBMCs from 104 kidney transplant recipients. RESULTS: The miR-142-5p, miR-142-3p, and miR-223 were significantly upregulated and miR-10b was significantly downregulated in recipients with abnormal levels of serum creatinine 3 to 4 weeks after initial sample collection. Moreover, the miR-142-5p and miR-142-3p were also found to be significantly upregulated in recipients with abnormal levels of cystatin C. Through a combination of the validated miRNAs, receiver operating characteristic analyses yielded the highest area under the curve value of 0.7913 and 0.7063 in predicting the levels of serum creatinine and cystatin C, respectively. In the testing stage, the developed models correctly predicted allograft function in 16 to 17 of 22 recipients (false rate, 22.7%-27.2%). CONCLUSIONS: miRNAs in PBMCs of recipients hold great promise to be used as predictive and noninvasive biomarkers after transplantation.

Microwave assisted catalytic oxidation of p-nitrophenol in aqueous solution using carbon-supported copper catalyst.

Carbon-supported copper (Cu/GAC) catalyst was prepared by conventional impregnation method and characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The sizes of Cu particles dispersing on the surface of GAC were 0.3-1.5 microm, which could be penetrated by microwave so that Cu/GAC catalyst could absorb microwave energy effectively. The catalysis of Cu/GAC in microwave assisted catalytic oxidation of p-nitrophenol (PNP) in aqueous solution was investigated through a fixed bed reactor under ambient pressure and continuous flow mode. PNP removal reached 91.8% under optimized conditions, corresponding to 88% of TOC removal. It showed a higher PNP degradation and total organic carbon (TOC) removal for Cu/GAC catalyst than GAC alone, and Cu/GAC catalyst kept on a high catalysis and a good stability for a long time run, which indicated that GAC structure and catalytic capacity were improved by the load of Cu.

Distribution of persistent organochlorine residues in sediments from the Songhuajiang River, Northeast China.

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in surface sediments from 10 sampling sites of the Songhuajiang River were analyzed to evaluate their potential pollution and hazards. Gas chromatography equipped with a 63Ni electron capture detector (GC-ECD) and gas chromatography/mass spectrometer (GC/MS) methods were used, respectively. The total concentrations of 13 OCPs varied from 4.26 to 18.45 ng g(-1). Sigma HCH (alpha-HCH, beta-HCH, delta-HCH, gamma-HCH), sigma DDT (p, p'-DDE, p, p'-DDD, o,p'-DDT, p, p'-DDT) and sigma Cyclodiene (Heptachlor, Aldrin, Heptachlor epoxide, Dieldrin, Endrin) ranged from 2.42 to 7.95, 0.14 to 5.12, 0.55 to 6.01 ng g(-1), respectively. The most dominant pollutant among the OCPs was gamma-HCH with the concentration of 3.4 (0.77 to 7.21) ng g(-1). Total PCB concentrations ranged between 0.59 and 15.93 ng g(-1). Low chlorinated biphenyls (tri- and tetra-) dominated in total PCBs. Positive correlations were observed between the EDDT, sigma Cyclodiene, sigma OCP or sigma PCB and TOC of the sediments (P < 0.05, n = 10). No obvious correlation was observed between the sigma HCH and the TOC of the sediments.

miR-198 regulated the tumorigenesis of gastric cancer by targeting Toll-like receptor 4 (TLR4).

OBJECTIVE: To investigate the role of miR-198 and its target gene Toll-like receptor 4 (TLR4) of tumorigenesis of gastric cancer (GC). MATERIALS AND METHODS: The expression of miR-198 in GC cells was detected by quantitative polymerase chain reaction (qPCR). The proliferation, apoptosis, migration, and invasion of GC cells were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), flow cytometry, transwell chamber, and wound scratch assay. Bioinformatics analysis for the results of protein chip was performed to identify the target genes of miR-198. TLR4 was further confirmed to be the target gene of miR-198 by TLR4 luciferase reporter assay. RESULTS: miR-198 expression level in GC SGC-7901 cells significantly decreased compared with the normal cells. When the miR-198 was overexpressed, the proliferation, migration, and invasion of GC cells were significantly decreased, while the apoptosis was increased. The expression of TLR4 in SGC-7901 cells was significantly higher, while the expression of TLR4 in SGC-7901 cells transfected with miR-198 significantly lowered, which was consistent with the Western blot for TLR4. The luciferase reporter assay confirmed that TLR4 was the target genes of miR-198 in GC SGC7901 cells. CONCLUSIONS: miR-198 could induce apoptosis and inhibit the proliferation, migration, and invasion of GC cells through downregulating TLR4 expression.

[Radiographic and masticatory physiologic evaluation after conservative treatment of condylar fractures in children and adolescents].

OBJECTIVE: To evaluate the developmental and functional outcome of condylar fractures in children and adolescents after conservative treatment. METHODS: Eight children and adolescents with unilateral condylar fracture, aged 5-13 were included. A removable occlusal splint, the thickness of which was determined according to the age, the developmental stage of the dentition, the level of the fracture and the degree of dislocation, worn for 1-3 months, and the patients were asked to perform functional exercises. The patients were followed up by clinical observation, panoramic radiograph, temporomandibular joint(TMJ ) cone beam computed tomography(CBCT), and surface electromyography(sEMG) of masticatory muscles (superficial masseter, anterior temporalis, and anterior digastric muscles). Ramus height and body length of mandible were measured on panoramic radiograph. The patients were asked to return for follow-up visits at 1, 3, and 6 months after treatment, and then once a year. The patients underwent clinical examination at each follow-up visit, and radiological examinations at 6 months and then annually. RESULTS: All the patients showed clinically satisfactory results. CBCT showed smooth and continuous cortex. Panoramic X-ray revealed that the ramus height was shorter in the fractured side than in the contralateral side, while body length was longer. The mean asymmetry index(AI,x±s) for ramus height and body length were (3.29±2.68)% and (4.01 ± 2.54)%. sEMG showed either hypertension or hypotension in the masticatory muscles of the fractured side and asymmetries were obvious. The mean AI for sEMG activity of the anterior temporalis, masseter, and anterior digastric muscle were masseter: (15.0 ± 16.9)%; anterior temporalis: (21.5 ± 15.9)%; anterior digastric muscles: (11.9 ± 10.7)%. CONCLUSIONS: Conservative treatment of condylar fracture in children and adolescents had clinically satisfactory results, while mandibular development was slightly interrupted. Asymmetries of EMG activities of masticatory muscles were obvious. EMG could objectively reveal the functional recovery of condylar fracture in children.

Correlation of serum PCSK9 in CHD patients with the severity of coronary arterial lesions.

OBJECTIVE: The present study aims to investigate the correlation between serum level of proprotein convertase subtilisin/kexin type 9 (PCSK9) and the severity of coronary arterial lesion in patients with coronary heart disease (CHD). PATIENTS AND METHODS: Between August 2010 and January 2015, 126 CHD patients and 70 patients with coronary arterial stenosis < 50% (controls) were included in the present study. Serum PCSK9 level was determined using ELISA. Demographic characteristics, relevant clinical data and biochemical data were collected from all patients, and their relationship with PCSK9 was analyzed to evaluate the correlation of PCSK9 expression with the severity of coronary artery disease (CAD). RESULTS: Concentrations of total cholesterol (TC) and fasting blood sugar (FBS) were significantly higher in CHD patients than in controls (p < 0.05). No significant differences were observed in gender, age, body mass index (BMI), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), family history, smoking history and history of hypertension between groups (p > 0.05). Serum PCSK9 levels in the CHD group were significantly higher than those in the control group [(96.4 ± 33.2) ng/mL vs. (81.8 ± 27.6) ng/mL, p < 0.05]. Compared with those of patients with single-vessel or double-vessel disease, PCSK9 levels were significantly elevated in patients with multi-vessel disease (p < 0.05). The Gensini score of the CHD group was significantly lower than that of the control group (11.4 ± 10.5 vs. 37.3 ± 10.3, p < 0.05). The Gensini score of patients with multi-vessel disease was significantly higher compared with patients of single-vessel  or double-vessel disease (p < 0.05). Correlation analysis revealed that PCSK9 was positively correlated with many clinical parameters, including age, BMI, TC, TG, systolic blood pressure, FBS, Gensini score and LDL-C (p < 0.05). However, PCSK9 was not correlated with either gender ratio or diastolic blood pressure (p > 0.05). CONCLUSIONS: Serum PCSK9 level is significantly elevated in CHD patients and its variation is correlated with the severity of CAD.

Interactions between fibroin and sericin proteins from Antheraea pernyi and Bombyx mori silk fibers.

Silkworm silk fibers are core-shell composites of fibroin and sericin proteins. Studying the interactions between fibroin and sericin is essential for understanding the properties of these composites. It is observed that compared to the domestic silk cocoon Bombyx mori (B. mori), the adhesion between fibroin and sericin from the wild silk cocoon, Antheraea pernyi (A. pernyi), is significantly stronger with a higher degree of heterogeneity. The adsorption of A. pernyi sericin on its fibroin is almost twice the value for B. mori sericin on fibroin, both showing a monolayer Langmuir adsorption. (1)H NMR and FTIR studies demonstrate on a molecular level the stronger interactions and the more intensive complex formation between A. pernyi fibroin and sericin, facilitated by the hydrogen bonding between glycine and serine. The findings of this study may help the design of composites with superior interfacial adhesion between different components.

Charge and charging compensation on oxides and hydroxides in oxygen environmental SEM.

Oxygen environment was applied to the scanning electron microscopy (SEM) analysis of insulating samples. In the high vacuum SEM, a local oxygen pressure was provided, and in the environmental SEM, oxygen atmosphere was used instead of water, the commercial mode. The charging effects in the SEM observation and component characterization of samples such as Al(2)O(3), Al(OH)(3), Mg(OH)(2) and others can be eliminated or significantly reduced. The oxygen environment does not only provide a new approach to releasing the charging difficulty in the analyses using electron beam as a probe, but also provide an insightful hint to the understanding of the charging processes in general.