The seed shadow of oak ( Quercus liaotungensis Koidz.) was investigated in a broad_leaved deciduous forest in Dongling Mountain in 1997. The seed rain patterns under oak tree crown for three out of four oak trees fit...The seed shadow of oak ( Quercus liaotungensis Koidz.) was investigated in a broad_leaved deciduous forest in Dongling Mountain in 1997. The seed rain patterns under oak tree crown for three out of four oak trees fit quadratic distribution, with high coefficients of determination. For each of the four trees selected in this study the seed rain size estimated from the viable acorns collected from the traps deployed under the crown was low, ranging from 26 to 259. For each of the four oak trees, the average density of the seed rain under oak tree crown ranged from 0.76 to 7.26 seeds/m 2. The average seed rain density estimated from the acorns in the traps deployed randomly in the field was 1.57 seeds/m 2. After all viable acorns fell, the acorn ground density estimated from the acorns in the quadrats was 0.13 seeds/m 2, but no viable acorns were found on the ground under the tree crown of the four oak trees, although the area under the crown was over 5 folds than the area of the combined quadrats. These results indicated that a large number of acorns was removed or predated by vertebrates once the acorns fell on the ground and acorns predation was more intensive in the sites directly under the parent trees than the sites away from the parent trees; this supports the distance_dependent hypothesis. Of the total acorns of all four oak trees, the viable acorns only accounted for 18.1%, and 17.8% for acorns infected by insect larvae, 12.1% for immature acorns, 3.6% for decayed acorns, and the acorns predated by rodent directly in the crown was the highest, accounting for 48.4%. The proportion of acorns predated by animals including vertebrates and invertebrates amounts up to 78.3%, indicating that acorn predation by animals is a limiting factor affecting acorn survival before seed dispersal. The sustained time of viable acorn fall ranged from September 8 to October 3 for the four oak trees, with the peak between 16th and 26th September. The number of acorns was not significantly different among the four directions around the trunk base.展开更多
In order to overcome the shortcomings that the reconstructed spectral reflectance may be negative when using the classic principal component analysis （PCA）to reduce the dimensions of the multi-spectral data, a nonne...In order to overcome the shortcomings that the reconstructed spectral reflectance may be negative when using the classic principal component analysis （PCA）to reduce the dimensions of the multi-spectral data, a nonnegative constrained principal component analysis method is proposed to construct a low-dimensional multi-spectral space and accomplish the conversion between the new constructed space and the multispectral space. First, the reason behind the negative data is analyzed and a nonnegative constraint is imposed on the classic PCA. Then a set of nonnegative linear independence weight vectors of principal components is obtained, by which a lowdimensional space is constructed. Finally, a nonlinear optimization technique is used to determine the projection vectors of the high-dimensional multi-spectral data in the constructed space. Experimental results show that the proposed method can keep the reconstructed spectral data in [ 0, 1 ]. The precision of the space created by the proposed method is equivalent to or even higher than that by the PCA.展开更多
The differential equations of motion of a comtlaint system with parameters and variable mass, of a system with variable mass and servo constraints and those for the control problem on the forced motion of constraint s...The differential equations of motion of a comtlaint system with parameters and variable mass, of a system with variable mass and servo constraints and those for the control problem on the forced motion of constraint systems with variable mass are given respectively. Finally, an example is presented.展开更多
Let G=(V, E) be a simple graph without an isolate. A subset T of V is a total dominating set of G if for any there exists at least one vertex such that .The total domination number γ1(G) of G is the minimum order of...Let G=(V, E) be a simple graph without an isolate. A subset T of V is a total dominating set of G if for any there exists at least one vertex such that .The total domination number γ1(G) of G is the minimum order of a total dominating set of G. This paper proves that if G is a connected graph with n≥3 vertices and minimum degree at least two.展开更多
Locality preserving projection （LPP） is a typical and popular dimensionality reduction （DR） method,and it can potentially find discriminative projection directions by preserving the local geometric structure in da...Locality preserving projection （LPP） is a typical and popular dimensionality reduction （DR） method,and it can potentially find discriminative projection directions by preserving the local geometric structure in data. However,LPP is based on the neighborhood graph artificially constructed from the original data,and the performance of LPP relies on how well the nearest neighbor criterion work in the original space. To address this issue,a novel DR algorithm,called the self-dependent LPP （sdLPP） is proposed. And it is based on the fact that the nearest neighbor criterion usually achieves better performance in LPP transformed space than that in the original space. Firstly,LPP is performed based on the typical neighborhood graph; then,a new neighborhood graph is constructed in LPP transformed space and repeats LPP. Furthermore,a new criterion,called the improved Laplacian score,is developed as an empirical reference for the discriminative power and the iterative termination. Finally,the feasibility and the effectiveness of the method are verified by several publicly available UCI and face data sets with promising results.展开更多
An optimal dimension-down iterative algorithm （DDIA） is proposed for solving a mixed （continuous/ discrete） transportation network design problem （MNDP）, which is generally expressed as a mathematical programmin...An optimal dimension-down iterative algorithm （DDIA） is proposed for solving a mixed （continuous/ discrete） transportation network design problem （MNDP）, which is generally expressed as a mathematical programming with equilibrium constraints （MPEC）. The upper level of the MNDP aims to optimize the network performance via both the expansion of existing links and the addition of new candidate links, whereas the lower level is a traditional Wardrop user equilibrium （UE） model. The idea of the proposed DDIA is to reduce the dimensions of the problem. A group of variables （discrete/continuous） are fixed to altemately optimize another group of variables （continuous/discrete）. Some continuous network design problems （CNDPs） and discrete network design problems （DNDPs） are solved repeatedly until the optimal solution is obtained. A numerical example is given to demonstrate the efficiency of the proposed algorithm.展开更多
For an in-depth study on the integration problem of the constrained mechanical systems the method of integration for the Birkhoffian system with constraints is discussed and the method of variation of parameters for s...For an in-depth study on the integration problem of the constrained mechanical systems the method of integration for the Birkhoffian system with constraints is discussed and the method of variation of parameters for solving the dynamical equations of the constrained Birkhoffian system is provided.First the differential equations of motion for the constrained Birkhoffian system as well as for the corresponding free Birkhoffian system are established.Secondly a system of auxiliary equations is constructed and the general solution of the equations is found.Finally by varying the parameters and utilizing the properties of the generalized canonical transformation of the Birkhoffian system the solution of the problem can be obtained.The proposed method reveals the inherent relationship between the solution of a free Birkhoffian system and that of a constrained Birkhoffian system. The research results are of universal significance which can be further used in a variety of constrained mechanical systems such as non-conservative systems and nonholonomic systems etc.展开更多
Objective:This study aimed to examine the psychometric properties of the Conditions for Workplace Effectiveness Questionnaire-Ⅱ-Arabic Version(CWEQ-Ⅱ-AV),which measures structural empowerment among nurses.To enhance...Objective:This study aimed to examine the psychometric properties of the Conditions for Workplace Effectiveness Questionnaire-Ⅱ-Arabic Version(CWEQ-Ⅱ-AV),which measures structural empowerment among nurses.To enhance the usability and credibility of the CWEQ-Ⅱ among researchers within Arabicspeaking countries,a valid and reliable Arabic version of the measure is necessary.Methods:A cross-sectional research design was used.From December 2018 to June 2019,275 nurses working in 4 hospitals participated in the study.Reliability was assessed by examining internal consistency and split-half reliability.A confirmatory factor analysis was performed to evaluate the factor structure of the CWEQ-Ⅱ-AV.Results:The psychometric properties of the CWEQ-Ⅱ-AV were excellent regarding the six-factor model(opportunity,information,resources,support,formal power,and informal power).The results showed the following fit indices meet the criteria set a priori:comparative fit index(CFI)=0.96,root mean square of error approximation(RMSEA)=0.06,andХ^(2)/df=2.08.Cronbach's a coefficient was 0.95 for the total questionnaire and ranged between 0.83 and 0.89 for the individual subscales.The split-half reliability was 0.91 for the total questionnaire and ranged from 0.83 to 0.87 for individual subscales.Conclusion:This study provides evidence that CWEQ-Ⅱ-AV is both a reliable and valid measure of structural empowerment among Arab nurses.展开更多
To alleviate the heavy load of massive alarm on operators, alarm threshold in chemical processes was optimized with principal component analysis(PCA) weight and Johnson transformation in this paper. First, few variabl...To alleviate the heavy load of massive alarm on operators, alarm threshold in chemical processes was optimized with principal component analysis(PCA) weight and Johnson transformation in this paper. First, few variables that have high PCA weight factors are chosen as key variables. Given a total alarm frequency to these variables initially, the allowed alarm number for each variable is determined according to their sampling time and weight factors. Their alarm threshold and then control limit percentage are determined successively. The control limit percentage of non-key variables is determined with 3σ method alternatively. Second, raw data are transformed into normal distribution data with Johnson function for all variables before updating their alarm thresholds via inverse transformation of obtained control limit percentage. Alarm thresholds are optimized by iterating this process until the calculated alarm frequency reaches standard level(normally one alarm per minute). Finally,variables and their alarm thresholds are visualized in parallel coordinate to depict their variation trends concisely and clearly. Case studies on a simulated industrial atmospheric-vacuum crude distillation demonstrate that the proposed alarm threshold optimization strategy can effectively reduce false alarm rate in chemical processes.展开更多
A 2D analytical electrostatics analysis for the cross-section of a FinFET (or tri-gate MOSFET) is performed to calculate the threshold voltage.The analysis results in a modified gate capacitance with a coefficient H i...A 2D analytical electrostatics analysis for the cross-section of a FinFET (or tri-gate MOSFET) is performed to calculate the threshold voltage.The analysis results in a modified gate capacitance with a coefficient H introduced to model the effect of tri-gates and its asymptotic behavior in 2D is that for double-gate MOSFET.The potential profile obtained analytically at the cross-section agrees well with numerical simulations.A compact threshold voltage model for FinFET,comprising quantum mechanical effects,is then proposed.It is concluded that both gate capacitance and threshold voltage will increase with a decreased height,or a decreased gate-oxide thickness of the top gate,which is a trend in FinFET design.展开更多
AIM： To investigate the endoscopic ampullectomy practices of expert biliary endoscopists. METHODS： An anonymous expert biliary endoscopists practices. survey was mailed to 79 to assess ampullectomy RESULTS： Forty s...AIM： To investigate the endoscopic ampullectomy practices of expert biliary endoscopists. METHODS： An anonymous expert biliary endoscopists practices. survey was mailed to 79 to assess ampullectomy RESULTS： Forty six （58%） biliary endoscopists returned the questionnaire. Of these, 63% were in academia and in practice for an average of 16.4 years （± 8.6）. Endoscopists performed an average of 1.1 （± 0.8） ampullectomies per month. Prior to ampullectomy, endoscopic ultrasound was ＂always＂ utilized by 67% of respondents vs ＂sometimes＂ in 31% of respondents. Empiric biliary sphincterotomy was not utilized uniformly, only 26% ＂always＂ and 37% ＂sometimes＂ performed it prior to resection. Fifty three percent reported ＂never＂ performing empiric pancreatic sphincterotomy prior to ampullectomy. Practitioners with high endoscopic retrograde cholangiopancreatography volumes were the most likely to perform a pancreatic sphincterotomy （OR = 10.9; P = 0.09）. Participants overwhelmingly favored ＂always＂ placing a prophylactic pancreatic stent, with 86% placing it after ampullectomy rather than prior to resection （23%）. Argon plasma coagulation was the favored adjunct modality （83%） for removal of residual adenomatous tissue. Practitioners uniformly （100%） preferred follow-up examination to be within 6 mo postmpullectomy.CONCLUSION： Among biliary experts, there is less variation in ampultectomy practices than is reflected in the literature.展开更多
Anal fistula is among the most common illnesses affecting man.Medical literature dating back to 400 BC has discussed this problem.Various causative factors have been proposed throughout the centuries,but it appears th...Anal fistula is among the most common illnesses affecting man.Medical literature dating back to 400 BC has discussed this problem.Various causative factors have been proposed throughout the centuries,but it appears that the majority of fistulas unrelated to specific causes (e.g.Tuberculosis,Crohn’s disease) result from infection (abscess) in anal glands extending from the intersphincteric plane to various anorectal spaces.The tubular structure of an anal fistula easily yields itself to division or unroofing (fistulotomy) or excision (fistulectomy) in most cases.The problem with this single,yet effective,treatment plan is that depending on the thickness of sphincter muscle the fistula transgresses,the patient will have varying degrees of fecal incontinence from minor to total.In an attempt to preserve continence,various procedures have been proposed to deal with the fistulas.These include: (1) simple drainage (Seton);(2) closure of fistula tract using fibrin sealant or anal fistula plug;(3) closure of primary opening using endorectal or dermal flaps,and more recently;and (4) ligation of intersphincteric fistula tract (LIFT).In most complex cases (i.e.Crohn’s disease),a proximal fecal diversion offers a measure of symptom-atic relief.The fact remains that an "ideal" procedure for anal fistula remains elusive.The failure of each sphincter-preserving procedure (30%-50% recurrence) often results in multiple operations.In essence,the price of preservation of continence at all cost is multiple and often different operations,prolonged disability and disappointment for the patient and the surgeon.Nevertheless,the surgeon treating anal fistulas on an occasional basis should never hesitate in referring the patient to a specialist.Conversely,an expert colorectal surgeon must be familiar with many different operations in order to selectively tailor an operation to the individual patient.展开更多
On the basis of the data obtained from a field survey, the relationship between land use and soil nutrients was evaluated in Qingzhou County, Shandong Province, China, through a statistical analysis of differences in ...On the basis of the data obtained from a field survey, the relationship between land use and soil nutrients was evaluated in Qingzhou County, Shandong Province, China, through a statistical analysis of differences in 17 nutrients in five types of cultivated land. The results showed significant effects (P < 0.05 or P < 0.01) of land-use type on soil organic matter and concentration of macronutrients, secondary nutrients, and micronutrients, as well as total salt and soil pH. In vegetable land, because of the large amounts of fertilizer applied to vegetable crops, the concentrations of most soil nutrients, with exception of available Si and micronutrients, were higher than those in grain cropland. Grain cropland had a significantly lower total salt content (P < 0.01) and tended to have a higher soil pH than vegetable land. Within subtypes of land use, dry land, irrigable land, and open-air vegetable land had the highest coefficient of variation (CV) for available P, whereas protected vegetable land had the highest CV for total N and available S. In general, land-use types had greater impact on macronutrients than on secondary nutrients and micronutrients.展开更多
文摘The seed shadow of oak ( Quercus liaotungensis Koidz.) was investigated in a broad_leaved deciduous forest in Dongling Mountain in 1997. The seed rain patterns under oak tree crown for three out of four oak trees fit quadratic distribution, with high coefficients of determination. For each of the four trees selected in this study the seed rain size estimated from the viable acorns collected from the traps deployed under the crown was low, ranging from 26 to 259. For each of the four oak trees, the average density of the seed rain under oak tree crown ranged from 0.76 to 7.26 seeds/m 2. The average seed rain density estimated from the acorns in the traps deployed randomly in the field was 1.57 seeds/m 2. After all viable acorns fell, the acorn ground density estimated from the acorns in the quadrats was 0.13 seeds/m 2, but no viable acorns were found on the ground under the tree crown of the four oak trees, although the area under the crown was over 5 folds than the area of the combined quadrats. These results indicated that a large number of acorns was removed or predated by vertebrates once the acorns fell on the ground and acorns predation was more intensive in the sites directly under the parent trees than the sites away from the parent trees; this supports the distance_dependent hypothesis. Of the total acorns of all four oak trees, the viable acorns only accounted for 18.1%, and 17.8% for acorns infected by insect larvae, 12.1% for immature acorns, 3.6% for decayed acorns, and the acorns predated by rodent directly in the crown was the highest, accounting for 48.4%. The proportion of acorns predated by animals including vertebrates and invertebrates amounts up to 78.3%, indicating that acorn predation by animals is a limiting factor affecting acorn survival before seed dispersal. The sustained time of viable acorn fall ranged from September 8 to October 3 for the four oak trees, with the peak between 16th and 26th September. The number of acorns was not significantly different among the four directions around the trunk base.
基金The Pre-Research Foundation of National Ministries andCommissions (No9140A16050109DZ01)the Scientific Research Program of the Education Department of Shanxi Province (No09JK701)
文摘In order to overcome the shortcomings that the reconstructed spectral reflectance may be negative when using the classic principal component analysis （PCA）to reduce the dimensions of the multi-spectral data, a nonnegative constrained principal component analysis method is proposed to construct a low-dimensional multi-spectral space and accomplish the conversion between the new constructed space and the multispectral space. First, the reason behind the negative data is analyzed and a nonnegative constraint is imposed on the classic PCA. Then a set of nonnegative linear independence weight vectors of principal components is obtained, by which a lowdimensional space is constructed. Finally, a nonlinear optimization technique is used to determine the projection vectors of the high-dimensional multi-spectral data in the constructed space. Experimental results show that the proposed method can keep the reconstructed spectral data in [ 0, 1 ]. The precision of the space created by the proposed method is equivalent to or even higher than that by the PCA.
文摘The differential equations of motion of a comtlaint system with parameters and variable mass, of a system with variable mass and servo constraints and those for the control problem on the forced motion of constraint systems with variable mass are given respectively. Finally, an example is presented.
文摘Let G=(V, E) be a simple graph without an isolate. A subset T of V is a total dominating set of G if for any there exists at least one vertex such that .The total domination number γ1(G) of G is the minimum order of a total dominating set of G. This paper proves that if G is a connected graph with n≥3 vertices and minimum degree at least two.
基金Supported by the National Natural Science Foundation of China (60973097)the Scientific Research Foundation of Liaocheng University(X0810029)~~
文摘Locality preserving projection （LPP） is a typical and popular dimensionality reduction （DR） method,and it can potentially find discriminative projection directions by preserving the local geometric structure in data. However,LPP is based on the neighborhood graph artificially constructed from the original data,and the performance of LPP relies on how well the nearest neighbor criterion work in the original space. To address this issue,a novel DR algorithm,called the self-dependent LPP （sdLPP） is proposed. And it is based on the fact that the nearest neighbor criterion usually achieves better performance in LPP transformed space than that in the original space. Firstly,LPP is performed based on the typical neighborhood graph; then,a new neighborhood graph is constructed in LPP transformed space and repeats LPP. Furthermore,a new criterion,called the improved Laplacian score,is developed as an empirical reference for the discriminative power and the iterative termination. Finally,the feasibility and the effectiveness of the method are verified by several publicly available UCI and face data sets with promising results.
基金The National Natural Science Foundation of China(No. 50908235 )China Postdoctoral Science Foundation (No.201003520)
文摘An optimal dimension-down iterative algorithm （DDIA） is proposed for solving a mixed （continuous/ discrete） transportation network design problem （MNDP）, which is generally expressed as a mathematical programming with equilibrium constraints （MPEC）. The upper level of the MNDP aims to optimize the network performance via both the expansion of existing links and the addition of new candidate links, whereas the lower level is a traditional Wardrop user equilibrium （UE） model. The idea of the proposed DDIA is to reduce the dimensions of the problem. A group of variables （discrete/continuous） are fixed to altemately optimize another group of variables （continuous/discrete）. Some continuous network design problems （CNDPs） and discrete network design problems （DNDPs） are solved repeatedly until the optimal solution is obtained. A numerical example is given to demonstrate the efficiency of the proposed algorithm.
基金The National Natural Science Foundation of China(No.10972151,11272227)
文摘For an in-depth study on the integration problem of the constrained mechanical systems the method of integration for the Birkhoffian system with constraints is discussed and the method of variation of parameters for solving the dynamical equations of the constrained Birkhoffian system is provided.First the differential equations of motion for the constrained Birkhoffian system as well as for the corresponding free Birkhoffian system are established.Secondly a system of auxiliary equations is constructed and the general solution of the equations is found.Finally by varying the parameters and utilizing the properties of the generalized canonical transformation of the Birkhoffian system the solution of the problem can be obtained.The proposed method reveals the inherent relationship between the solution of a free Birkhoffian system and that of a constrained Birkhoffian system. The research results are of universal significance which can be further used in a variety of constrained mechanical systems such as non-conservative systems and nonholonomic systems etc.
文摘Objective:This study aimed to examine the psychometric properties of the Conditions for Workplace Effectiveness Questionnaire-Ⅱ-Arabic Version(CWEQ-Ⅱ-AV),which measures structural empowerment among nurses.To enhance the usability and credibility of the CWEQ-Ⅱ among researchers within Arabicspeaking countries,a valid and reliable Arabic version of the measure is necessary.Methods:A cross-sectional research design was used.From December 2018 to June 2019,275 nurses working in 4 hospitals participated in the study.Reliability was assessed by examining internal consistency and split-half reliability.A confirmatory factor analysis was performed to evaluate the factor structure of the CWEQ-Ⅱ-AV.Results:The psychometric properties of the CWEQ-Ⅱ-AV were excellent regarding the six-factor model(opportunity,information,resources,support,formal power,and informal power).The results showed the following fit indices meet the criteria set a priori:comparative fit index(CFI)=0.96,root mean square of error approximation(RMSEA)=0.06,andХ^(2)/df=2.08.Cronbach's a coefficient was 0.95 for the total questionnaire and ranged between 0.83 and 0.89 for the individual subscales.The split-half reliability was 0.91 for the total questionnaire and ranged from 0.83 to 0.87 for individual subscales.Conclusion:This study provides evidence that CWEQ-Ⅱ-AV is both a reliable and valid measure of structural empowerment among Arab nurses.
基金Supported by the National Natural Science Foundation of China(21576143)
文摘To alleviate the heavy load of massive alarm on operators, alarm threshold in chemical processes was optimized with principal component analysis(PCA) weight and Johnson transformation in this paper. First, few variables that have high PCA weight factors are chosen as key variables. Given a total alarm frequency to these variables initially, the allowed alarm number for each variable is determined according to their sampling time and weight factors. Their alarm threshold and then control limit percentage are determined successively. The control limit percentage of non-key variables is determined with 3σ method alternatively. Second, raw data are transformed into normal distribution data with Johnson function for all variables before updating their alarm thresholds via inverse transformation of obtained control limit percentage. Alarm thresholds are optimized by iterating this process until the calculated alarm frequency reaches standard level(normally one alarm per minute). Finally,variables and their alarm thresholds are visualized in parallel coordinate to depict their variation trends concisely and clearly. Case studies on a simulated industrial atmospheric-vacuum crude distillation demonstrate that the proposed alarm threshold optimization strategy can effectively reduce false alarm rate in chemical processes.
文摘A 2D analytical electrostatics analysis for the cross-section of a FinFET (or tri-gate MOSFET) is performed to calculate the threshold voltage.The analysis results in a modified gate capacitance with a coefficient H introduced to model the effect of tri-gates and its asymptotic behavior in 2D is that for double-gate MOSFET.The potential profile obtained analytically at the cross-section agrees well with numerical simulations.A compact threshold voltage model for FinFET,comprising quantum mechanical effects,is then proposed.It is concluded that both gate capacitance and threshold voltage will increase with a decreased height,or a decreased gate-oxide thickness of the top gate,which is a trend in FinFET design.
文摘AIM： To investigate the endoscopic ampullectomy practices of expert biliary endoscopists. METHODS： An anonymous expert biliary endoscopists practices. survey was mailed to 79 to assess ampullectomy RESULTS： Forty six （58%） biliary endoscopists returned the questionnaire. Of these, 63% were in academia and in practice for an average of 16.4 years （± 8.6）. Endoscopists performed an average of 1.1 （± 0.8） ampullectomies per month. Prior to ampullectomy, endoscopic ultrasound was ＂always＂ utilized by 67% of respondents vs ＂sometimes＂ in 31% of respondents. Empiric biliary sphincterotomy was not utilized uniformly, only 26% ＂always＂ and 37% ＂sometimes＂ performed it prior to resection. Fifty three percent reported ＂never＂ performing empiric pancreatic sphincterotomy prior to ampullectomy. Practitioners with high endoscopic retrograde cholangiopancreatography volumes were the most likely to perform a pancreatic sphincterotomy （OR = 10.9; P = 0.09）. Participants overwhelmingly favored ＂always＂ placing a prophylactic pancreatic stent, with 86% placing it after ampullectomy rather than prior to resection （23%）. Argon plasma coagulation was the favored adjunct modality （83%） for removal of residual adenomatous tissue. Practitioners uniformly （100%） preferred follow-up examination to be within 6 mo postmpullectomy.CONCLUSION： Among biliary experts, there is less variation in ampultectomy practices than is reflected in the literature.
文摘Anal fistula is among the most common illnesses affecting man.Medical literature dating back to 400 BC has discussed this problem.Various causative factors have been proposed throughout the centuries,but it appears that the majority of fistulas unrelated to specific causes (e.g.Tuberculosis,Crohn’s disease) result from infection (abscess) in anal glands extending from the intersphincteric plane to various anorectal spaces.The tubular structure of an anal fistula easily yields itself to division or unroofing (fistulotomy) or excision (fistulectomy) in most cases.The problem with this single,yet effective,treatment plan is that depending on the thickness of sphincter muscle the fistula transgresses,the patient will have varying degrees of fecal incontinence from minor to total.In an attempt to preserve continence,various procedures have been proposed to deal with the fistulas.These include: (1) simple drainage (Seton);(2) closure of fistula tract using fibrin sealant or anal fistula plug;(3) closure of primary opening using endorectal or dermal flaps,and more recently;and (4) ligation of intersphincteric fistula tract (LIFT).In most complex cases (i.e.Crohn’s disease),a proximal fecal diversion offers a measure of symptom-atic relief.The fact remains that an "ideal" procedure for anal fistula remains elusive.The failure of each sphincter-preserving procedure (30%-50% recurrence) often results in multiple operations.In essence,the price of preservation of continence at all cost is multiple and often different operations,prolonged disability and disappointment for the patient and the surgeon.Nevertheless,the surgeon treating anal fistulas on an occasional basis should never hesitate in referring the patient to a specialist.Conversely,an expert colorectal surgeon must be familiar with many different operations in order to selectively tailor an operation to the individual patient.
基金Project supported by the National Natural Science Foundation of China (No. 40571160)the Experimental Program of Cultivated Land Fertility Investigation and Quality Evaluation of the Agricultural Department of China (No. 2002-23).
文摘On the basis of the data obtained from a field survey, the relationship between land use and soil nutrients was evaluated in Qingzhou County, Shandong Province, China, through a statistical analysis of differences in 17 nutrients in five types of cultivated land. The results showed significant effects (P < 0.05 or P < 0.01) of land-use type on soil organic matter and concentration of macronutrients, secondary nutrients, and micronutrients, as well as total salt and soil pH. In vegetable land, because of the large amounts of fertilizer applied to vegetable crops, the concentrations of most soil nutrients, with exception of available Si and micronutrients, were higher than those in grain cropland. Grain cropland had a significantly lower total salt content (P < 0.01) and tended to have a higher soil pH than vegetable land. Within subtypes of land use, dry land, irrigable land, and open-air vegetable land had the highest coefficient of variation (CV) for available P, whereas protected vegetable land had the highest CV for total N and available S. In general, land-use types had greater impact on macronutrients than on secondary nutrients and micronutrients.
