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1.
Evidences for the existence of ferromanganese crust boundary were found for the first time during the survey of the “DA YANG YI HAO” Vessel 2003. Some typical characteristics of the boundary are summarized and the significances of the finding of the boundary are included in the genesis discussion. Ore prospecting and assessment of the crust resources are described in this paper. The morphologic and extending characteristics of the crust boundary led to the recognition of two types of crust boundary： interpenetration crust boundary and closed crust boundary. According to the distribution and types of the crust, however, the boundaries are classified into three types： the boundary between ferromanganese crust and detrital sediment, the boundary between tabular crust and seamount nodules, and the boundary between tabular crust and rudaceous crust. This study revealed that the boundary between tabular crust and nodules was not formed under different regional environments but formed under different nucleation potential barriers between different initial growth （nucleation and germination） processes and between solid rocks and loose sediments. The rudaceous crusts are controlled spatially by fracture zones and the crusts＇ boundaries are controlled by the seamount structure and landform. The discovery of the crust boundaries reveals the crust＇s ‘negative growth’ phenomena （especially for some seamount nodules）. The boundary investigation can be helpful in identifying the existence of tabular crust covered by detrital sediments and in calculating the area covered by the crust. The resource calculation error and the resource quality as well as resource exploration degree can be assessed through the survey of crust boundary.  相似文献   

2.
The coexistence of thyroid diseases with primary hyperparathyroidism （PHPT） can present a challenge in the clinical diagnosis and management for these patients. This study aims to determine the frequency of coexisting thyroid gland lesions in a consecutive series patients with PHPT, and to analyze the clinical features, diagnosis and treatment of these patients. Twenty-two cases of a total of 52 PHPT patients who had synchronous thyroid and parathyroid pathology were surgically managed in this study Thirteen patients had ipsilateral thyroid nodules, and 9 patients had thyroid nodules in contralateral or bilateral side. Seven patients underwent direct parathyroidectomy and hemithyroidectomy via a mini-incision （about 3 cm）, while other 15 procedures were converted to Kocher incision. Seventeen nodular goiter （32.7%）, 2 thyroiditis （3.8%）, 2 thyroid adenoma （3.8%） and 1 thyroid carcinoma （1.9%） coexisting with parathyroid adenoma were pathologically diagnosed. The sensitivity of preoperative ultra- sonography （US） and methoxy-isobutyl-isonitrile （MIBI） scintigraphy for parathyroid lesions was 63.6% and 85.7%; and the overall positive predictive values for MIBI and US were 100% and 95.5% respectively. A high incidence of thyroid diseases that coexisted with PHPT in literatures was briefly reviewed. Our study illustrated the need for clinical awareness of concomitant PHPT and thyroid disease. A combination of US, computed tomography （CT） and MIBI scintigraphy would be recommended for preoperative localization of enlarged parathyroid adenoma and for evaluation of thyroid lesions. Synchronous treatment of associated thyroid abnormalities is desirable, and open minimally invasive surgical approach with additional resection of isolated ipsilateral thyroid nodules is possible in some of these patients.  相似文献   

3.
Interaction Between DEHP and Particulate in a Eutrophic Lake   总被引：2，自引：0，他引：2  
Characteristics of interaction between di-2-ethylhexyl phthalate(DEHP) and particulate in a eutrophic lake were studied in this paper. DEHP concentrations ranged from 89.9 to 247 μg/L with an average value of 146 μg/L in subsurface water (SSW) samples, and from 82.0 to 390 μg/L with an average value of 211 μg/L in water surface microlayer (SM) samples. The results indicate that there was only a weak correlation between the DEHP concentrations and suspended particulate material(SPM) concentrations in both SSW and SM,while the significant correlation between DEHP concentrations and chlorophyll a concentrations was found,which suggestes that DEHP was principally bound to phytoplankton in the eutrophic lake. Correlation between DEHP concentrations and total phosphor (TP) concentrations was also found in this investigation. Enrichment factors (EF) of DEHP in SM were in the range of 0.85 to 2.12 with an average value of 1.35..DEHP EFs were significantly related to the enrichment of chlorophyll a in SM. The results suggest that the enrichment of DEHP in SM of this eutrophic lake was mainly due to DEHP accumulation in phytoplankton and was controlled by distribution of phytoplankton between SM and SSW.  相似文献   

4.
A fast and facile method of fabricating fiber-optic localized surface plasmon resonance sensors based on spherical gold nanoparticles was introduced in this study. The gold nanoparticles with an average diameter of 55 nm were synthesized via the Turkevich method and were then immobilized onto the surface of an uncladded sensor probe using a polydopamine layer. To obtain a sensor probe with high sensitivity to changes in the refractive index, a set of key optimization parameters, including the sensing length, coating time of the polydopamine layer, and coating time of the gold nanoparticles, were investigated. The sensitivity of the optimized sensor probe was 522.80 nm per refractive index unit, and the probe showed distinctive wavelength shifts when the refractive index was changed from 1.328 6 to 1.398,7. When stored in deionized water at 4 ℃, the sensor probe proved to be stable over a period of two weeks. The sensor also exhibited advantages, such as low cost, fast fabrication, and simple optical setup, which indicated its potential application in remote sensing and real-time detection.  相似文献   

5.
Although most courses are offered in the traditional synchronous way where teaching and learning mainly take place in the classroom, the Internet has proven to be an effective tool in learning. The demand of online courses is constantly growing, however, there is a paucity of research of online delivery success factors, especially of accounting courses. The aim of this paper was to investigate＇the factors that contribute to student satisfaction from online teaching and learning of an accounting course. This study was conducted at a university in the United States （U.S.） amongst 80 students enrolled in an online accounting course over a period of two semesters. The quantitative data are based on the students＇ course evaluation forms of the instructor＇s teaching and overall satisfaction with the course. The findings suggest that the students found the asynchronous online teaching and learning interesting and challenging. The factors that mainly contribute to student satisfaction include the instructor＇s preparation for the course and her availability to students, the clear grading criteria, the assignment which they found useful, and the other resources that were available online. They value the least the development of writing skills. Additionally, this study proposes that there is a positive significant correlation between the instructor＇s overall performance and the overall student satisfaction from the course. The instructor＇s performance, availability, and easy to use technology enhance the learning and teaching from online pedagogies.  相似文献   

6.
The construction of the cables is a key step for erecting suspen-dome structures. In practical engineering, it is difficult to ensure that the designed pre-stresses of cables have been exactly introduced into the structures in the site; so it is necessary to evaluate the influence of the variation of the pre-stresses on the structural behavior. In the present work, an orthogonal design method was employed to investigate the pre-stressed cables' sensitivity to the suspen-dome system. The investigation was concentrated on a Kiewitt suspen-dome. Parametric studies were carried out to study the sensitivity of the structure's static behavior, dynamic behavior, and buckling loads when the pre-stresses in the cables varied. The investigation indicated that suspen-dome structures are sensitive to the pre-stresses in all cables; and that the sensitivity depended on the location of the cables and the kind of structural behavior. Useful suggestions are given at the end of the paper.  相似文献   

7.
Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one.  相似文献   

8.
Objective: Malignant middle cerebral artery (MCA) infarction is characterized by mortality rate of up to 80%. The aim of this study was to determine the value of decompressive craniectomy in patients presenting malignant MCA infarction compared with those receiving medical treatment alone. Methods: Patients with malignant MCA infarction treated in our hospital between January 1996 and March 2004 were included in this retrospective analysis. The National Institute of Health Stroke Scale (NIHSS) was used to assess neurological status on admission and at one week after surgery. All patients were followed up for assessment of functional outcome by the Barthel index (BI) and modified Rankin Scale (RS) at 3 months after infarction. Results: Ten out of 24 patients underwent decompressive craniectomy. The mean interval between stroke onset and surgery was 62.10 h. The mortality was 10.0% compared with 64.2% in patients who received medical treatment alone (P<0.001). The mean NIHSS score before surgery was 26.0 and 15.4 after surgery (P<0.001). At follow up, patients who underwent surgery had significantly better outcome with mean BI of 53.3, RS of 3.3 as compared to only 16.0 and 4.60 in medically treated patients. Speech function also improved in patients with dominant hemispherical infarction. Conclusion: Decompressive craniectomy in patients with malignant MCA infarction improves both survival rates and functional outcomes compared with medical treatment alone. A randomized controlled trial is required to substantiate those findings.  相似文献   

9.
Variation in the limit dextrinase activity of barley malt, and the relationships between limit dextrinase activity and malt quality parameters were investigated using eight cultivars grown at seven diverse locations in China for two successive years. Limit dextrinase activity varied with genotype and location, with the levels ranging from 0.245 U/g to 0.980 U/g. The results showed that the variation in limit dextrinase activity was more attributable to the environment （location and year） than to the genotype. The response of limit dextrinase activity to the environment differed markedly among cultivars, and was reflected by large difference in coefficient of variation of cultivars across diverse locations. Regression analysis showed that limit dextrinase activity was negatively correlated with malt viscosity （r=-0.52, P〈0.01）, positively correlated with Kolbach index （r=0.38, P〈0.01） and malt extract （r=0.30, P〈0.05）, but had no significant correlation with malt protein content and diastatic power.  相似文献   

10.
A micro-sized tube heat exchanger(MTHE) was fabricated, and its performance in heat transfer and pressure drop was experimentally studied. The single-phase forced convection heat transfer correlation on the sides of the MTHE tubes was proposed and compared with previous experimental data in the Reynolds number range of 500—1 800. The average deviation of the correlation in calculating the Nusselt number was about 6.59%. The entrance effect in the thermal entrance region was discussed. In the same range of Reynolds number, the pressure drop and friction coefficient were found to be considerably higher than those predicted by the conventional correlations. The product of friction factor and Reynolds number was also a constant, but much higher than the conventional.  相似文献   

11.
The root development of Actinidia chinensis plantlets was studied in exposure to environmental stress of mechanical vibration at respectively 1 Hz, 2 Hz, 3 Hz, 4 Hz and 5 Hz. The plantlets exposed to vibration stimuli at all those frequencies have a larger total number and a larger total length of roots and a smaller permeability of root plasma-membrane, compared with those cultivated in an environment without vibration stress. Vibration at respectively 1 Hz, 2 Hz, 3 Hz and 4 Hz enhances root activity and the 3 Hz vibration is the most favorable. There is an obvious negative correlation between root activity and permeability of root plasma-membrane. The effects may be explained by the likelihood that mechanical vibration at an appropriate frequency facilitates roots’ absorbing water and minerals which are indispensable to inducing and synthesizing in roots some active substances favorable to growth. Nevertheless, overstress damages the integrity of root plasm-membrane, increases the permeability, and results in the disability of protecting root cells.  相似文献   

12.
Due to the globalization and the spread of the Internet, distance learning （D-learning） has gained extraordinary impulse in recent years by classes broadcasted by Websites and assignments fulfilled by students in their own computers. D-learning facilitates the access to education to those people who are working or have low buying power due to its reduced cost and time convenience. Although D-learning has existed in the world for over 150 years, only in the last decades, it has become the focus of academic studies and researches in a systematic way. In this context, the objective of this research is to evaluate the impact of computer literacy on the academic performance of the D-learning students of Faculdade lnterativa COC--EAD （COC--D-learning Interactive College）, P61o Lafaiete （Lafaiete Branch）, Ribeirao Preto. The research consisted of a questionnaire with 21 qualitative dichotomous questions, concerning the level of knowledge and mastery of information techdologies, besides the gender and academic performance （weighted average and marks of the last module）. The data were tabulated, being considered two main variables： （a） academic performance, represented by the marks of the last module; and （b） computer literacy, represented by the sum of the questions concerning this matter. The data were analyzed statistically, and the correlation between the two variables considered was analyzed by Pearson＇s Correlation Test. The interviews of the 54 interviewees （24 males （44.45%） and 30 females （55.55%）） taking the business administration course were analyzed. The correlation coefficient r = 0.303 indicates that there is a meaningful correlation between the students＇ academic performance （marks） and their computer literacy, that is, the greater the computer literacy, the better the marks obtained by these students in the D-learning course. D-learning has computing as its main tool, theretbre, the students with less computer literacy find barriers in D-learning, which o ref  相似文献   

13.
A kind of image distortion in Optical Coherence Tomography (OCT) resulted from average refractive index changes between structures of bio-tissue is discussed for the first time. Analysis is given on following situations:1) Exact refraction index changes between mierostruetures;2)The gradient of average refractive index change between different tissue layers is parallel to the probe beam;3) The gradient of average refractive index change is vertical to the probe beam. The results show that the image distortion of situation 1) is usually negligible ;in situation 2) there is a spread or shrink effect without relative location error; however, in situation 3)there is a significant image error inducing relative location displacement between different structures. Preliminary design to eliminate the distortion is presented, the method of which mainly based on the image classification and pixel array re-arrangement.  相似文献   

14.
In this study, the authors analyzed data from a nationally representative survey of youth to study happiness amongst Canadian adolescents aged 12-17. Testing for differences in the level of happiness between female and male adolescents was conducted. Following this, multivariate analysis was employed to determine which factors were associated with adolescent happiness. The authors determined that the level of happiness appeared to vary between the genders, as the males reported a higher level of happiness than the females. However, the difference between the genders in terms of reported happiness was modest. The authors detected some gender differences in regards to determinants of happiness. The study＇s theoretical and practical implications are also considered.  相似文献   

15.
The affinity heptapeptide(HWWWPAS)for insulin,selected from phage display library,was coupled to EAH Sepharose 4B gel and packed to a 1-mL column.The column was used for the affinity purification of insulin from protein mixture and commercial insulin preparation.It was observed that the minor impurity in the commercial insulin was removed by the affinity chromatography.Nearly 40 mg of insulin could be purified with the 1-mL affinity column.The results revealed the high specificity and capacity of the affinity column for insulin purification.Moreover,based on the analysis of the amino acids in the peptide sequence,shorter peptides were designed and synthesized for insulin chromatography.As a result,HWWPS was found to be a good alternative to HWWWPAS,while the other two peptides with three or four amino acids showed weak affinity for insulin.The results indicated that the peptide sequence of HWWWPAS was quite conservative for specific binding of insulin.  相似文献   

16.
The preparation approach and calibration result of an improved type of ion selective electrode （ISE）, which is used to measure the total dissolved S^2-, are introduced in this paper. The improved Ag/Ag2S electrode uses silver wire as the substrate, which is surrounded by electric polymer containing superfine silver powder. After the stabilization of the epoxy-resin, Ag2S layer was formed by chemical reaction with 0.2 mol/L （NH4）2S solution for 5 min. With Ag/AgC1 as reference electrode, the Ag/Ag2S electrode can be used to measure dissolved S^2-. The correlation between the measured potentials and the logarithm of dissolved S^2- is found to be linear, within range of the concentration of dissolved S^2- from 10^-2-10-7 mol/L. The slope of the regression line between measured potential and logarithm of dissolved S^2- is about -27.7, which agrees well with the theoretical Nernst value -29.6. Furthermore, the performance of the improved Ag/Ag2S electrode, such as the response time, sensitivity and stability, greatly outweighs the conventional Ag/Ag2S electrode.  相似文献   

17.
张君  董丹 《海外英语》2013,(6X):37-39
This paper examines language use inside and out of classroom of Uyghur students from the middle schools for both Han and ethnic minorities in Urumqi, Xinjiang, China. A total of 341 Uyghur students between 12 and 15 years of age, attending 3 middle schools for both Han and ethnic minorities in Urumqi, responded to questionnaires requesting information about their language backgrounds, their use of language at school (inside and out of classroom) and in the wider community, their self-perceptions about their linguistic competence in Uyghur and in Chinese and their attitudes towards Uyghur, Chinese and towards bilingualism. The results, in general, demonstrated a positive attitude towards bilingualism, and there was a trend towards favoring the use of Chinese both inside and outside classroom. The implications of the findings for language policy and planning in education are discussed.  相似文献   

18.
Objective: To observe the accuracy of femoral preparation and the position of the cementless prosthesis in femoral cavity, and to compare the results between the computer-assisted surgical group (CASPAR) and the conventional group. Methods: Ten femoral components were implanted either manually or by CASPAR in cadaver femurs. The specimens were cut to 3 mm thick slices. Microradiograms of every slice were sent to a computer for analysis with special software (IDL). The gaps and the medullary cavities between component and bone, the direct bone contact area of the implant surface, the gap width and the percentage of gap and bone contact area were measured in every slice. Results: In the proximal implant coated with HA of the CASPAR group, the average percentage of bone contact reached 93.2% (ranging from 87.6% to 99.7%); the average gap percentage was 2.9% (ranging from 0.3% to 7.8%); the maximum gap width was 0.81 mm and the average gap width was only 0.20 mm. While in the conventional group, the average  相似文献   

19.
This study compares the life events perceived as ＂rites of passage＂ from adolescence to adulthood by respondents between the ages of 14 and 23 in 3 countries and discusses the possible influences of culture and globalization on these perceptions. Participants include： （1） 250 adolescents from the US （125 males and 125 females）; （2） 191 adolescents from southeastern Brazil （70 males and 121 females）; and （3） 163 adolescents from Malaysia （76 males and 87 females）. These adolescents ranked a variety of life events which may be perceived as indicative of adult status by completing a questionnaire about perceived rites of passage. Although there were similarities among the 3 groups, several differences also emerged. The most commonly noted indicator of adult status for Malaysian youth was physical maturity, followed by completing one＇s education. Participants from the US cited financial independence as the major indicator of adult status, while those from Brazil cited the ability to make important decisions independently from family and to take responsibility for others, such as children, aging parents or a spouse. Brazilian youth were significantly more likely to cite a love affair and voting in major elections as rites of passage than were participants from the other 2 countries. Participants from the US were significantly more likely to cite military service, and Malaysian youth were significantly more likely to consider completion of education and achieving physical maturity as rites of passage. Gender and age differences within groups were evident on some items, but these were not consistent across groups. Possible explanations for the differences between countries and implications for educators working with adolescents in rapidly changing societies are discussed.  相似文献   

20.
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