Analysis Approach to Durability Based on Material Initial Fatigue Quality and S-N Curve

Based on probabilistic fracture mechanics approach, a new concept of material initial fatigue quality （MIFQ） is developed. Then, the relation between S-N curve and crack propagation curve is studied. From the study, a new durability analysis method is presented. In this method, S-N curve is used to determine crack growth rate under constant amplitude loading and evaluate the effects of different factors on durability and then the structural durability is analyzed. The tests and analyses indicate that this method has lower dependence on testing, and higher accuracy, reliability and generality and is convenient for application.

Chronic kidney disease prediction is an inexact science: The concept of “progressors” and “nonprogressors”

In 2002,the National Kidney Foundation Kidney Disease Outcomes Quality Initiative(NKF KDOQI)instituted new guidelines that established a novel chronic kidney disease(CKD)staging paradigm.This set of guidelines,since updated,is now very widely accepted around the world.Nevertheless,the authoritative United States Preventative Task Force had in August 2012acknowledged that we know surprisingly little about whether screening adults with no signs or symptoms of CKD improve health outcomes and that we deserve better information on CKD.More recently,the American Society of Nephrology and the American College of Physicians,two very well respected United States professional physician organizations were strongly at odds coming out with exactly opposite recommendations regarding the need or otherwise for"CKD screening"among the asymptomatic population.In this review,we revisit the various angles and perspectives of these conflicting arguments,raise unanswered questionsregarding the validity and veracity of the NKF KDOQI CKD staging model,and raise even more questions about the soundness of its evidence-base.We show clinical evidence,from a Mayo Clinic Health System Renal Unit in Northwestern Wisconsin,United States,of the pitfalls of the current CKD staging model,show the inexactitude and unpredictable vagaries of current CKD prediction models and call for a more cautious and guarded application of CKD staging paradigms in clinical practice.The impacts of acute kidney injury on CKD initiation and CKD propagation and progression,the effects of such phenomenon as the syndrome of late onset renal failure from angiotensin blockade and the syndrome of rapid onset end stage renal disease on CKD initiation,CKD propagation and CKD progression to end stage renal disease all demand further study and analysis.Yet more research on CKD staging,CKD prognostication and CKD predictions are warranted.Finally and most importantly,cognizant of the very serious limitations and drawbacks of the NKF K/DOQI CKD staging model,the need to individualize CKD care,both in terms of patient care and prognostication,cannot be overemphasized.

Cumulative cellulolytic enzyme activities and initial litter quality in prediction of cellulose degradation in an alpine meadow of the eastern Tibetan Plateau

Aims Plant litter decomposition is a key ecosystem process that determines carbon and nutrient cycling in terrestrial ecosystems.As a main component of litter,cellulose is a vital energy source for the microbes associated with litter decomposition.The important role of cellulolytic enzymes in litter cellulose degradation is well understood,but seasonal patterns of cellulose degradation and whether cumulative enzyme activities and litter quality forecast cellulose degradation in an alpine meadow remain elusive,which limits our understanding of cellulose degradation in herbaceous plant litter.Methods A two-year field litterbag experiment involving three dominant species(Ajuga ovalifolia,Festuca wallichanica,and Pedicularis roylei)was conducted in an alpine meadow of the eastern Tibetan Plateau to explore the seasonal patterns of cellulose degradation and how cumulative cellulolytic enzyme activities and initial litter quality impact cellulose degradation.Important findings Our study demonstrates that cellulose degraded rapidly and exceeded 50%during the first year,which mainly occurred in the first growing season(31.9%–43.3%).At two years of decomposition,cellulose degradation was driven by cumulative endoglucanase(R^(2)=0.70),cumulative cellobiohydrolase(R^(2)=0.59)and cumulative 1,4-β-glucosidase(R^(2)=0.57).In addition,the concentrations of cellulose,dissolved organic carbon,total phenol,lignin and lignin/N accounted for 52%–78%of the variation in cellulose degradation during the two years of decomposition.The best model for predicting cellulose degradation was the initial cellulose concentration(R^(2)=0.78).The enzymatic efficiencies and the allocation of cellulolytic enzyme activities were different among species.The cellulolytic enzyme efficiencies were higher in the litter of F.wallichanica with relatively lower quality.For the complete cellulose degradation of the leaf litter,A.ovalifolia and F.wallichanica required 4-fold and 6.7-fold more endoglucanase activity,3-fold and 4.5-fold more cellobiohydrolase activity and 1.2-fold and 1.4-fold more 1,4-β-glucosidase activity,respectively,than those required by P.roylei.Our results demonstrated that although microbial activity and litter quality both have significant impacts on cellulose degradation in an alpine meadow,using cellulose concentration to predict cellulose degradation is a good way to simplify the model of cellulose degradation and C cycling during litter decomposition.

Root-order-associated variations in fine-root decomposition and their effects on soil in a subtropical evergreen forest

Background:Despite the importance of root decomposition in predicting ecosystem responses to future climate change,the effects of branch order on root decomposition and the feedback to soil still remains poorly understood.Here we separated root samples taken from two tree species(Castanopsis fargesii and Schima superba in subtropical forests along the coastal area in eastern China)into four-order classes(1st–2nd order,3rd order,4th order,and 5th order)and conducted a 540-day litterbag incubation experiment in laboratory to examine root mass loss,nutrient release,and the influence on soil during decomposition.Results:C.fargesii roots of 1st–2nd and 3rd order decayed more slowly than those of 4th and 5th order,but this pattern was not significant for S.superba.Of all the measured root traits,the decomposition rates correlated best with root C/N ratio,diameter and specific root length(SRL)based on the structural equation modeling.Both tree species and root order exhibited significantly effects on root initial traits.Overall,C.fargesii roots decay faster than S.superba,and this appears to be associated with root initial C quality and N concentration.In addition,root order positively affected root decomposition rates mainly through root diameter and SRL.However,no significant difference was found in C and N content between soils below the litterbag with different-order roots.Conclusions:Our findings suggest the effects of branch order on root decomposition are dependent on tree species.Moreover,root morphological properties might also be the controlling factor in root decay besides root chemistry fractions.Overall,the integrative effects should be considered to improve our understanding of the fate of fine-root litter and their contribution to soil C and N pool.