[Effects of screen exposure on language skills in children].

Objective: To investigate the association between screen exposure and language skills in children aged 2-5 years. Methods: There were 299 children aged 2-5 years, recruited by convenience sampling from those who visited the Center of Children's Healthcare, Children's Hospital, Capital Institute of Pediatrics for routine physical examination from November 2020 to November 2021. Their development status were evaluated by the children neuropsychological and behavioral scale (revision 2016). A self-designed questionnaire for parents was conducted to collect demographic and socioeconomic information and screen exposure characteristics (time and quality). One-way ANOVA and independent sample t test were applied to compare the differences in language development quotient of children with different screen exposure time and quality. Multiple linear regression was used to analyze the correlation between screen exposure time and quality with language developmental quotient. Multivariate Logistic regression was used to analyze the risk of language underdevelopment in children with different screen exposure time and quality. Results: Among 299 children, 184 (61.5%) were boys and 115 (38.5%) were girls, with the age of (3.9±1.1) years. The number of children with daily screen time <60, 60-120 and>120 min was 163 children (54.5%), 86 children (28.8%) and 50 children (16.7%), respectively, with the language development quotients of 94±13, 90±13, 84±14, respectively, demonstrating a statistically significant difference (F=8.92, P<0.001). Logistic regression analysis revealed that screen exposure time of 60-120 and >120 min per day were both risk factors for children's language developmental quotients (OR=2.28, 95%CI 1.00-5.17, P=0.043; OR=3.96, 95%CI 1.86-9.17, P<0.001), and co-viewing and exposure to educational programs were both protective factors for children's language developmental quotients (OR=0.48, 95%CI 0.25-0.91, P=0.024, OR=0.36, 95%CI 0.19-0.70, P=0.003). Conclusions: Excessive exposure screen time and inappropriate screen exposure habits are associated with children's poorer language development. Screen exposure time should be limited and screen use should be rational to promote children's language skills.

ToTEM: A software for fast TEM image simulation.

ToTEM, a multislice-based image simulation software is developed for transmission electron microscope (TEM). This software implements the following major features: (i) capability of assigning three-dimensional potentials of atom into multiple slices and precise introduction of phase shift caused by the sub-pixel atomic position, (ii) employing CUDA coding and graphical processing units (GPU) with multithreading parallel algorithm based on the powerful batch (inverse) fast Fourier transform (FFT), which is especially beneficial for image simulation of scanning transmission electron microscopy (STEM) or (integrated) differential phase contrast (I)DPC, (iii) design for efficiently generating large batch of data set of high-resolution transmission electron microscopy (HRTEM) images. Image simulation acceleration for STEM has been verified by simulating a large-scale SrTiO3 . Additionally, iDPC image of MFI-type zeolites with xylene molecules encapsulated in straight channels demonstrates the advantage of iDPC in detecting light molecules.

[Psychological and behavioral functioning of children and adolescents during long-term home-schooling].

Objective: To study the characteristics and risk factors of psychological and behavioral problems of children and adolescents of different ages and genders in long-term home-schooling during the coronavirus disease-2019 pandemic. Further, to provide scientific basis for more targeted psychological intervention and coping strategies in the future. Methods: A cross-sectional survey using an online questionnaire was conducted on students aged 6-16 years old in five representative cities of North (Beijing), East (Shanghai), West (Chongqing), South (Guangzhou) and Middle (Wuhan) in China. In this study, the social behavior and psychological abnormalities which was defined as the positive of any dimension were investigated in multiple dimensions during long-term home-schooling. The influencing factors of psycho-behavioral problems were analyzed by Logistic regression, and the confounding factors were corrected with graded multivariable adjustment. Results: A total of 6 906 valid questionnaires were collected including 3 592 boys and 3 314 girls, of whom 3 626 were children (6-11 years old) and 3 280 were adolescents (12-16 years old). The positive detection rate of psychosocial-behavioral problems were 13.0% (900/6 906) totally, 9.6% (344/3 592) in boys and 16.8% (556/3 314) in girls respectively, and 7.3%(142/1 946) in boys aged 6-11, 14.0%(235/1 680) in girls aged 6-11, 12.3%(202/1 646) in boys aged 12-16, 19.6%(321/1 634) in girls aged 12-16 respectively. There were significant differences between the psychological problems group and the non-psychological problems group in gender, parent-offspring conflict, number of close friends, family income change, sedentary time, homework time, screen exposure time, physical activity, dietary problems (χ²=78.851, 285.264, 52.839, 26.284, 22.778, 11.024, 10.688, 36.814, 70.982, all P<0.01). The most common symptoms in boys aged 6-11 years were compulsive activity, schizoid and depression, in girls aged 6-11 years were schizoid/compulsive activity, hyperactivity and social withdrawal, in boys aged 12-16 years were hyperactivity, compulsive activity and aggressive behavior, and in girls aged 12-16 years were schizoid, anxiety/compulsive activity and depression/withdrawal, respectively. After graded multivariable adjustment, besides the common risk factors, homework time and online study time were the risk factors of 6-11 years old groups [boys OR(95%CI): 1.750 (1.32-2.32), 1.214(1.00-1.47), girls: 1.579(1.25-1.99), 1.222(1.05-1.42), all P<0.05], videogames time were the risk factors of 12-16 years old groups [ boys: 2.237 (1.60-3.13), girls: 1.272 (1.00-1.61), all P<0.05]. Conclusions: Some children and adolescents may have psychological and behavioral problems during long-term home-schooling. The psychological and behavioral manifestations differed in age and gender subgroups, which deserve special attention in each subgroups. Schools, families and specialists should actively provide precise psychological support and comprehensive intervention strategies according to special features and risk factors.

[Research on the status and risk factors of screen exposure in children under three years of age].

Objective: To investigate the time and characteristics of screen exposure, to analyze the risk factors affecting screen exposure in children aged 3 years and younger, and to provide scientific basis for the intervention of screen exposure in children. Methods: The data were collected by convenience sampling from 317 children for routine examination aged 0-36 months who visited the Department of Child Healthcare, Children's Hospital, Capital Institute of Pediatrics from December 2019 to December 2020. Self-designed questionnaires of the screen exposure were completed by the parents. The basic information, home nurture environment and screen exposure conditions were investigated. Children <18 months of age who used electronic devices and 18-36 months of age who spent more than 1 h/d on electronic devices were defined as with screen exposure. The differences between <18 and 18-36 months of age were compared by rank sum test. Chi-square test and multivariate Logistic regression were used to analyze the association between screen exposure and potential influential factors. Results: Among 317 children, 209 were boys and 108 girls, aged (28±10) months. There were 117 patients aged <18 months and 200 patients aged 18-36 months. Screen exposure time was 0.3 (0, 1.0) h/d and 1.2 (0.6, 2.0) h/d in children aged <18 months and aged 18-36 months, respectively (Z=-6.770, P<0.01). The proportion of screen exposure was 25.6% (30/117) and 49.0% (98/200) in two age groups, respectively. Logistic regression analysis disclosed that not being the first child (OR=3.81, 95%CI: 1.13-12.77, P=0.030), caregivers spending >1 h/d on electronic devices in front of their children (OR=7.39, 95%CI: 2.24-24.46, P=0.001), caregivers believing that screen exposure can promote early childhood development (OR=4.14, 95%CI: 1.26-13.52, P=0.019) were risk factors for children's screen exposure in <18 months of age. Caregivers spending >1 h/d on electronic devices in front of their children (OR=3.29, 95%CI: 1.78-6.08, P<0.01) was risk factor for children's screen exposure in 18-36 months of age. Mothers with bachelor's or higher degree (OR=0.19, 95%CI: 0.05-0.66, P=0.009; OR=0.35, 95%CI: 0.19-0.66, P=0.001), no television in living room (OR=0.11, 95%CI: 0.03-0.42, P=0.001; OR=0.45, 95%CI: 0.21-0.98, P=0.045) were protective factors for children's screen exposure in children <18 months and 18-36 months of age. Conclusions: Excessive screen exposure is common among children aged 3 years and younger. The exposure time increases with age, and is affected by several factors.

[Characteristics of consonant among children with speech sound disorder].

Objective: To investigate the characteristics of consonant among children with speech sound disorder (SSD) and to provide an empirical basis for the subsequent clinical evaluation and evidence-based intervention. Methods: In this retrospective research a total of 1 395 children diagnosed with SSD from the Language-Speech Clinic of the Department of Children Health Care, Children's Hospital, Capital Institute of Pediatrics from January 2007 to December 2018 were enrolled and underwent the phonological examination on the lexical level with picture naming, according to phoneme development in Chinese mandarin. The Chi-square trend test was applied to analyze the differences and trends of the proportion of consonant error subtypes in children of different age groups. The Chi-square test was conducted to compare the proportion of consonant error subtypes in different gender. Results: The 1 395 children diagnosed with SSD included 1 044 boys and 351 girls, with an age of (5.1±0.8) years. The occurrence of consonant errors in different locations of articulation was the highest for blade-alveolar /l/ (71.8%, 1 002/1 395) and the lowest for labial/b/(9.3%, 130/1 395). The occurrence of consonant errors of labial/p/f/, supra-dental/z/c/s/, blade-alveolar/t/l/, blade-palatal/ch/r/, velar/k/h/, and lingua-palatal/q/decreased with age (all P<0.05). The occurrence of consonant errors of labial/b/m/, supra-dental/z/c/, blade-alveolar/n/l/, blade-palatal/sh/, velar/h/, and lingua-palatal/x/were higher in boys than those in girls (10.3% (108/1 044) vs. 6.3% (22/351), 11.4% (119/1 044) vs. 6.0% (21/351), 64.8% (676/1 044) vs. 51.9% (182/351), 67.8% (708/1 044) vs. 59.8% (210/351), 16.7% (174/1 044) vs. 8.8% (31/351), 73.7% (769/1 044) vs. 66.1% (232/351), 58.0% (606/1 044) vs. 47.6% (167/351), 24.0% (251/1 044) vs. 14.2% (50/351), and 39.9% (417/1 044) vs. 27.6% (97/351); χ²=5.167, 8.533, 16.889, 7.447, 12.863, 7.412, 11.650, 14.900, and 17.099, all P<0.05). The error types of consonant were substitution, omission, and distortion. Omission was the main error type of blade-alveolar/l/(53.3%, 743/1 395), distortion was the main error type of velar/h/(11.8%, 165/1 395), and substitution was the main error type of all other consonants. Substitution with blade-palatal/ch/having the highest occurrence of error (60.2%, 840/1 395). Conclusions: The occurrence of the blade-alveolar/l/error is the highest in children with SSD, with boys demonstrating more serious articulation problems. The main error type of consonant is substitution, with blade-palatal/ch/having the highest occurrence of error. These results suggest the necessity of attending to preschoolers' articulation development. Phonological training targeting blade-alveolar/l/and blade-palatal/ch/should be carried out as early as possible.

[A convolutional neural network based model for assisting pathological diagnoses on thyroid liquid-based cytology].

Objective: To develop a convolutional neural network based model for assisting pathological diagnoses on thyroid liquid-based cytology specimens. Methods: Seven-hundred thyroid TCT slides were collected, scanned for whole slide imaging (WSI), and divided into training and test sets after labeling the correct diagnosis (benign versus malignant). The extracted regions of interest after noise filtering were cropped into pieces of 512 × 512 patch on 10 × and 40 × magnifications, respectively. A classification model was constructed using deeply learning algorithms, and applied to the training set, then automatically tuned in the test set. After data enhancement and parameters optimization, accuracy, sensitivity, specificity, positive predictive value and negative predictive value of the model were calculated. Results The training set with 560 WSI contained 4 926 cell clusters (11 164 patches), while the test set with 140 WSI contained 977 cell clusters (1 402 patches). YOLO network was selected to establish a detection model, and ResNet50 was used as a classification model. With 40 epochs training, results from 10× magnifications showed an accuracy of 90.01%, sensitivity of 89.31%, specificity of 92.51%, positive predictive value of 97.70% and negative predictive value of 70.82%. The area under curve was 0.97. The average diagnostic time was less than 1 second. Although the model for data of 40× magnifications was very sensitive (98.72%), but its specificity was poor, suggesting that the model was more reliable at 10× magnification. Conclusions: The performance of a deep-learning based model is equivalent to pathologists' diagnostic performance, but its efficiency is far beyond. The model can greatly improve consistency and efficiency, and reduce the missed diagnosis rate. In the future, larger studies should have more morphology diversity, improve model's accuracy and eventually develop a model for direct clinical use.

[Analysis of functional speech sound disorder and related erroneous consonants in children].

Objective: To investigate the features and trends of functional speech sound disorder and related erroneous consonants in children, so as to provide evidence for clinical evaluation and rational intervention. Methods: Clinical data of 1 562 children diagnosed with functional speech sound disorder in the language-speech clinic of the Department of Child Health Care, Children's Hospital, Capital Institute of Pediatrics from January 2007 to December 2018 were analyzed retrospectively. By using the mandarin phonetic test table, the picture-naming method was adopted to test the word-level pronunciation. The Chi-square test was conducted to analyze the incidence of consonant errors in different age groups, gender and different places of articulation. The trend in incidence of the consonant errors in different age groups and during the last 12 years were analyzed by chi-square trend test. Results: A total of 1 562 cases were diagnosed with functional speech sound disorder, including 1 171 males and 391 females, the age was 4-17 years. The incidence of consonant errors in different places of articulation was 43.0% (672/1 562) for labial, 47.0% (734/1 562) for lingua-palatal, 63.7% (995/1 562) for velar, 77.7% (1 213/1 562) for linguo-alveolar, 78.9% (1 233/1 562) for apico-dental and 81.6% (1 274/1 562) for palatal. The incidence of consonant errors in males on labial, lingua-palatal, linguo-alveolar and palatal was higher than that in females (44.7% (523/1 171) vs. 38.1% (149/391), 49.1% (575/1 171) vs. 40.7% (159/391), 80.1% (938/1 171) vs. 70.3% (275/391), 82.8% (970/1 171) vs. 77.7% (304/391), χ²=5.138, 8.379, 16.126 and 5.042,all P<0.05). The incidence of consonant errors on labial, lingua-palatal, velar, linguo-alveolar, apico-dental and palatal decreased with age (χ²=27.023, 13.230, 20.579, 29.718, 26.390, and 17.887, all P<0.01). The incidence of consonant errors on labial, linguo-alveolar, apico-dental increased with years (χ²=9.030, 51.894 and 18.507, all P<0.01). Conclusions: The incidence of palatal errors is the highest in children with functional speech sound disorder. As part of the palatal errors could not be completely self-healing with growing, the phonological therapy for palatal errors should be carried out as early as possible. The incidence of consonant errors on labial, linguo-alveolar, and apico-dental presents an upward tendency with years, more attention should be paid to the factors related to the acquisition of these consonants.

CalAtom: A software for quantitatively analysing atomic columns in a transmission electron microscope image.

We developed a software tool named CalAtom in MATLAB™ for quantitative analyses of atomic columns in (scanning) transmission electron microscopy, (S)TEM, images. This software provides three algorithms to determine the position of an atomic column with high precision: the moment method, the model-based method and the multiple-ellipse fitting method. Based on the measured positions, the software offers several options for further analyses, such as in-plane scale local environments of the atomic columns, local elementary composition and real-space averaging of image motifs. As an example, we use the CalAtom software to determine atomic positions and local elemental composition of the MoS2(1-x)Se2x alloy monolayers.

Titanium-coated mesh versus standard polypropylene mesh in laparoscopic inguinal hernia repair: a prospective, randomized, controlled clinical trial.

OBJECTIVE: We aimed to compare the clinical outcome of titanium-coated mesh and polypropylene mesh in laparoscopic inguinal hernia repair. METHODS: A total of 102 patients who received laparoscopic inguinal hernia repair in January-June 2016 in Beijing Chao-Yang Hospital were enrolled in this study. Patients were randomly divided into two groups, receiving either titanium-coated mesh (n = 50) or standard polypropylene mesh (n = 52). Multiple clinical parameters were collected and analyzed, including clinical manifestations, operative time, intraoperative blood loss, hospital stay, hospital cost, recovery time, and postoperative complications. RESULTS: All procedures were completed. A statistical difference between two groups was not identified in regards to operative time, intraoperative blood loss, hospital stay, and recovery time (P > 0.05). Three cases with seroma and 15 with foreign body sensation were reported in the titanium-coated mesh group; 9 cases with seroma and 17 with foreign body sensation were reported in the standard polypropylene mesh group. There was no significant difference in the incidence of seroma and/or foreign body sensation. A lower hospital cost but longer recovery period was documented in the standard polypropylene mesh group (P < 0.05). No recurrence, infection or chronic pain was observed during 1-year follow-up in both groups. CONCLUSION: Titanium-coated mesh possesses comparable clinical qualities as the standard polypropylene mesh but with a shorter recovery period. Therefore, this mesh is promising for clinical practice though the cost is higher than the standard polypropylene mesh.

[A multicenter study of reference intervals for 15 laboratory parameters in Chinese children].

Objective: To establish comprehensive laboratory reference intervals for Chinese children. Methods: This was a cross-sectional multicenter study. From June 2013 to December 2014, eligible healthy children aged from 6-month to 17-year were enrolled from 20 medical centers with informed consent. They were assessed by physical examination, questionnaire survey and abdominal ultrasound for eligibility. Fasting blood samples were collected and delivered to central laboratory. Measurements of 15 clinical laboratory parameters were performed, including estradiol (E2), testosterone(T), luteinizing hormone(LH), follicle-stimulating hormone(FSH), alanine transaminase(ALT), serum creatinine(Scr), cystatin C, immunoglobulin A(IgA), immunoglobulin G(IgG), immunoglobulin M(IgM), complement (C3, C4), alkaline phosphatase(ALP), uric acid(UA) and creatine kinase(CK). Reference intervals were established according to central 95% confidence intervals for reference population, stratified by age and sex. Results: In total, 2 259 children were enrolled. Finally, 1 648 children were eligible for this study, including 830 boys and 818 girls, at a mean age of 7.4 years. Age- and sex- specific reference intervals have been established for the parameters. Reference intervals of sex hormones increased gradually with age. Concentrations of ALT, cystatin C, ALP and CK were higher in children under 2 years old. Serum levels of sex hormones, creatinine, immunoglobin, CK, ALP and urea increased rapidly in adolescence, with significant sex difference. In addition, reference intervals were variable depending on assay methods. Concentrations of ALT detected by reagents with pyridoxal 5'-phosphate(PLP) were higher than those detected by reagents without PLP. Compared with enzymatic method, Jaffe assay always got higher results of serum creatinine, especially in children younger than 9 years old. Conclusion: This study established age- and sex- specific reference intervals, for 15 clinical laboratory parameters based on defined healthy children.

Exit-wave phase retrieval from a single high-resolution transmission electron microscopy image of a weak-phase object.

We propose a novel algorithm to numerically retrieve the phase of the exit-wave function from a high-resolution transmission electron microscopy (HRTEM) image of a weak-phase object material, e.g., graphene and hexagonal boron nitride monolayers. It theoretically only requires a single HRTEM image to retrieve the phase under the assumption of a weak-phase object. In addition, it can remove the effects of geometrical aberrations up to fifth order, and also improve the degraded information due to the finite temporal and spatial coherence. We further present its applications and successfully demonstrate the identification of the lattice atoms and line defects in single HRTEM image of graphene.

Multiple-ellipse fitting method to precisely measure the positions of atomic columns in a transmission electron microscope image.

In this paper, we propose a multiple-ellipse fitting method to accurately determine the atomic column positions in transmission electron microscopy (TEM) images. The column is enclosed by a series of ellipses fitted from contour lines at equidistant intensity levels, and each atomic column is shaped by an averaged elliptical shape to obtain its positions. In particular, the intensity profile of the atomic column can be obtained by an elliptically rotational average based on its shape; therefore, the intensities of the neighbouring atomic column can be subtracted for each atomic column during subsequent position refinement. This method can achieve precision in the picometre range, and we quantitatively measure this precision by analysing an image containing two Gaussian-shaped atoms and some simulated high-resolution transmission electron microscopy (HRTEM) images of SrTiO3.

Effects of environmental factors on sperm motility and fertilization rate of Phascolosoma esculenta.

The study investigated the effects of environmental factors (salinity, pH, ions and activation media) on sperm motility (activation rate, duration of quick movement, and lifespan) and fertilization rate of Phascolosoma esculenta. The results showed that spermatozoa in the coelom and nephridium are able to move quickly. The optimal salinity was 14.64 to 43.35 and the optimal pH was 6.46 to 9.53 for sperm activation and motility, whereas the ranges for fertilization were narrower (18.56 to 30.3 for salinity and 6.46 to 8.61 for pH). Of the ions studied, Na+ was indispensable for sperm motility and fertilization, and Ca2+ and Mg2+ were necessary for fertilization. P. esculenta sperm could not fertilize eggs and have short lifespans in 200 to 600 mmol/L NaCl and KCl solutions. Furthermore, they could not be activated or move in 200 to 600 mmol/L CaCl2, MgSO4, and sucrose solutions.

Identification and assessment of differentially expressed genes involved in growth regulation in Apostichopus japonicus.

Rapid and efficient growth is a major consideration and challenge for global mariculture. The differential growth rate of the sea cucumber, Apostichopus japonicus, has significantly hampered the total production of the industry. In the present study, forward and reverse suppression subtractive hybridization libraries were constructed and sequenced from a fast-growth group and a slow-growth group of the sea cucumber. A total of 142 differentially expressed sequence tags (ESTs) with insertions longer than 150 bp were identified and further analyzed. Fifty-seven of these ESTs (approximately 40%) were functionally annotated for cell structure, energy metabolism, immunity response, and growth factor categories. Six candidate genes, arginine kinase, cytochrome c oxidase subunit I, HSP70, ß-actin, ferritin, and the ADP-ribosylation factor, were further validated by quantitative PCR. Significant differences were found between the fast- and slow-growth groups (P < 0.05) for the expression levels of arginine kinase, cytochrome c oxidase, HSP70, the ADP-ribosylation factor, and ß-actin. However, no significant difference was observed for ferritin. Our results provide promising candidate gene markers for practical size screening, and also further promote marker-assisted selective breeding of this species.

Factors affecting the clearance of high-risk human papillomavirus infection and the progression of cervical intraepithelial neoplasia.

OBJECTIVE: This study aimed to identify factors that predict clearance of high-risk human papillomavirus (HPV) infection and progression to cervical intraepithelial neoplasia (CIN) 2 or higher, in women with normal cervical histology or CIN 1. METHODS: A retrospective analysis was performed on 817 high-risk HPV-infected women with histologically verified CIN 1 or normal cervical histology. Patients were followed-up for a maximum of 24 months. Cervical HPV DNA tests were performed at every visit. RESULTS: At the end of followup, 648/817 (79.3%) patients were free from HPV infection and 66/817 patients (8.1%) progressed to CIN 2 or higher. Age, parity, cytology and viral load at diagnosis were significantly and inversely associated with HPV clearance. Cytology, viral load and presence of CIN 1 lesions were significantly associated with lesion progression. CONCLUSIONS: Cytology and high-risk HPV viral load may be useful markers for the likelihood of high-risk HPV clearance and lesion progression. Histological status, parity and marital status may also be useful factors to consider when predicting progression.

Dynamics of movie competition and popularity spreading in recommender systems.

We introduce a simple model to study movie competition in recommender systems. Movies of heterogeneous quality compete against each other through viewers' reviews and generate interesting dynamics at the box office. By assuming mean-field interactions between the competing movies, we show that the runaway effect of popularity spreading is triggered by defeating the average review score, leading to box-office hits: Popularity rises and peaks before fade-out. The average review score thus characterizes the critical movie quality necessary for transition from box-office bombs to blockbusters. The major factors affecting the critical review score are examined. By iterating the mean-field dynamical equations, we obtain qualitative agreements with simulations and real systems in the dynamical box-office forms, revealing the significant role of competition in understanding box-office dynamics.

Observation of curative efficacy and prognosis following combination chemotherapy with celecoxib in the treatment of advanced colorectal cancer.

This study investigated the antitumour and chemosensitizing effects of celecoxib in the treatment of advanced colorectal cancer. A total of 90 patients were randomly divided into two groups: group CF was treated with a combination of celecoxib and the folinic acid-fluorouracil-oxaliplatin (FOLFOX4) regimen; and group F was treated with the FOLFOX4 regimen alone. Immunohisto chemical analysis of tumour tissues for cyclooxygenase-2 (COX-2) protein was performed. With regard to short-term efficacy, the response and disease control rates were significantly greater in group CF than group F. A log-rank test showed that the 3-year survival rate was significantly greater in group CF than group F. It was concluded that the addition of celecoxib to the FOLFOX4 regimen increased the short-term efficacy and the 3-year survival rate, and improved the quality of life of patients with advanced colorectal cancer. The antitumour and chemo sensitizing effects of celecoxib appeared to be independent of COX-2.

Quantitative fitting of nonlinear current-voltage curves and parameter retrieval of semiconducting nanowire, nanotube and nanoribbon devices.

A quantitative metal-semiconductor-metal (MSM) model and a Matlab based program have been developed and used to obtain parameters that are important for characterizing semiconductor nanowires (NWs), nanotubes (NTs) or nanoribbons (NRs). The use of the MSM model for quantitative analysis of nonlinear current-voltage curves of one-dimensional semiconducting nanostructures is illustrated by working through two examples, i.e., an amorphous carbon NT and a ZnO NW, and the obtained parameters include the carrier density, mobility, resistance of the NT(NW), and the heights of the two Schottky barriers formed at the interfaces between metal electrodes and semiconducting NT(NW).

Quantitative analysis of electron field-emission characteristics of individual carbon nanotubes: the importance of the tip structure.

Electron field-emission measurements on individual carbon nanotubes (CNTs) were performed inside the transmission electron microscope (TEM). The field-emission characteristics of CNTs with different tip structures were compared, and their field conversion factor and emission area were studied systematically. It was found that the field-emission characteristics of a CNT depend sensitively on its tip structure, and in particular an opened CNT was shown to be superior to a capped CNT. High-resolution TEM observations revealed that the tip of an opened CNT may, in general, be regarded as being composed of irregular shaped graphitic sheets, and these graphitic sheets have been found to improve dramatically the field-emission characteristics, but the sharp edge may result in larger error in the calculated emission area. The influence of uncertainty in the work function of the CNTs on the field conversion factor and emission area calculation was also investigated.