Estimation of spectral responses and chlorophyll based on growth stage effects explored by machine learning methods

Estimation of leaf chlorophyll content(LCC) by proximal sensing is an important tool for photosynthesis evaluation in high-throughput phenotyping. The temporal variability of crop biochemical properties and canopy structure across different growth stages has great impacts on wheat LCC estimation, known as growth stage effects. It will result in the heterogeneity of crop canopy at different growth stages, which would mask subtle spectral response of biochemistry variations. This study aims to explore spectral responses on the growth stage effects and establish LCC models suited for different growth stages. A total number of 864 pairwise samples of wheat canopy spectra and LCC values with 216 observations of each stage were sampled at the tillering, jointing, booting and heading stages in 2021. Firstly, statistical analysis of LCC and spectral response presented different distribution traits and typical spectral variations peak at 470, 520 and 680 nm. Correlation analysis between LCC and reflectance showed typical red edge shifts. Secondly, the testing model of partial least square(PLS) established by the entire datasets to validate the predictive performance at each stage yielded poor LCC estimation accuracy. The spectral wavelengths of red edge(RE) and blue edge(BE) shifts and the poor estimation capability motivated us to further explore the growth stage effects by establishing LCC models at respective growth periods.Finally, competitive adaptive reweighted sampling PLS(CARS-PLS), decision tree(DT) and random forest(RF) were used to select sensitive bands and establish LCC models at specific stages. Bayes optimisation was used to tune the hyperparameters of DT and RF regression. The modelling results indicated that CARS-PLS and DT did not extract specific wavelengths that could decrease the influences of growth stage effects. From the RF out-of-bag(OOB) evaluation, the sensitive wavelengths displayed consistent spectral shifts from BE to GP and from RE to RV from tillering to heading stages. Compared with CARS-PLS and DT,results of RF modelling yielded an estimation accuracy with deviation to performance(RPD) of 2.11, 2.02,3.21 and 3.02, which can accommodate the growth stage effects. Thus, this study explores spectral response on growth stage effects and provides models for chlorophyll content estimation to satisfy the requirement of high-throughput phenotyping.

Neighborhood diversity structure and neighborhood species richness effects differ across life stages in a subtropical natural secondary forest

Natural secondary forest has a strong capacity to regrow naturally and recover biodiversity rapidly on abandoned lands.However,at the neighborhood scale,which can truly reflect the facilitative or competitive interactions among individual plants,the local diversity spatial structure in secondary forest and the feedback effects of neighborhood diversity on natural regeneration remain unclear,and this may be the key to properly understand the mechanisms of natural secondary forest species diversity recovery.To this end,this study established a dynamic plot in a rehabilitated secondary forest after disturbance and conducted a comprehensive survey of 68,336 individual plants with repeated measurements at 5-year interval to assess the characteristics of neighborhood diversity structure across life history stages and link the neighborhood species richness(NSR)effect translated by species interactions at species diversity structure with individual trees recruitment/mortality in secondary forest regeneration.The results showed that,compared with tropical and temperate natural forests,a higher proportion of diversity accumulators and a lower proportion of repellers in subtropical secondary forests resulted in neighborhood diversity structures characterized by heterospecific or high-diversity patches,which are beneficial to the maintenance or restoration of biodiversity.As an important supplement to the research on the relationship between diversity and productivity,our findings show a positive diversity-survival relationship in subtropical secondary forests.Importantly,we observed that the neighborhood diversity structure exhibited a trend of accumulator-dominated to neutral-dominant changes with life stage from sapling to adult,which,in turn,determined the direction and strength of NSR effects on recruitment/mortality.Specifically,diverse local neighborhoods at a later successional stage characterized with‘neutral’species-species interactions can act as a‘welfare net’by offering favorable microhabitats for the most vulnerable recruitments or saplings,i.e.,the NSR effects that promoted individual recruitment/survival in our study.These results not only enrich our understanding of the biodiversity-productivity-survival relationship but also highlight the importance of retaining latesuccessional species of native trees in intensive forest production or in situ conservation policies.

Effect of intervention treatment from different stages on prognosis in children with central coordination disturbance

BACKGROUND： Central coordination disturbance is regarded as the early-stage symptom of brain injury-induced cerebral palsy. This disease manifests itself as motor disorder, abnormal attitudinal reflex and muscular tension. Early intervention may improve its prognosis. OBJECTIVE： To observe the effects of intervention treatment from different stages on the prognosis of central coordination disturbance following brain injury in children patients. DESIGN： A contrast observation experiment SETTING： Department of Neurology and Rehabilitation, Urumqi Children＇s Hospital PARTICIPANTS ： Totally 151 children who were diagnosed as central coordination disturbance from January 2002 to December 2003 in the Department of Neurology and Rehabilitation of Urumqi Children＇s Hospital were recruited. All the children patients, including 101 male and 50 female, aged from 3 months to 1 year old, met the diagnosis criteria of central coordination disturbance from Vojta. They were divided into slight, moderate and severe abnormity according to Vojta attitudinal reflex. All 151 patients were divided into 2 groups according to their age at diagnosis： 3-6 months old group （n=74）, 62 severe, 10 moderate and 2 slight; 7-12 months old group （n=77）, 66 severe, 7 moderate and 4 slight. All the relatives of children patients were informed of the experiment. METHODS： ① Both groups received physical training （PT） as the main treatment; Hand training was given if necessary. All of the patients received additional hyperbaric oxygen therapy, bioelectric therapy, scalp acupuncture, drug treatment and family training. The importance of integration of hospital and family based rehabilitation was stressed. Those who did not catch up with the normal development or had abnormal reflexes continued to receive treatment. ② Around the age of 2 years old, all children did a final evaluation using Bayley Scales of Infant Development （BSID）. Mental development index （MDI） and physical development index （PDI） were taken as evaluative criteria. Children with scores 80 and above on MDI and PDI were considered to have normal motor and mental development; 79 and below were considered delayers. The Diagnostic Criteria of Cerebral Palsy and Infantecondary School Social Adaptation Scale were used in the final evaluation[scores ≤5 was extremely severe （extremely severe cerebral palsy）, 6 was severe（severe cerebral palsy）, 7 was moderate（moderate cerebral palsy）, 8 was slight（slight cerebral palsy）, 9 was borderline（slight cerebral palsy）, 10 was normal, 11 was above average, 12 was excellent and ≥13 was extremely excellent]. ③ Final evaluative results of 2 groups were compared. And u test was used for the comparison of Bayley development index and Chi-square test for the comparison of normalization rate. MAIN OUTCOME MEASURES： BSID MDI and PDI as well as the normalization rate of motor function and mental behavior of children patients at 2 years old. RESULTS： Totally 151 children patients entered the stage of result analysis. ①Two groups of children patients were given integrated rehabilitation therapy , and evaluated at 2 years old . The 3-6 months old group had higher MDI and PDI than the 7-12 months old group （91.81＋19.99 vs 71.93＋18.98;91.55＋23.61 vs 68.95＋23.51, u=6.265,5.894,P 〈 0.01 ）.②After being given integrated rehabilitation therapy, children patients of 3-6 months old group had significantly higher normalization rate of motor function and mental behavior than 7-12 months old group （73% ,27%,X2=29.723 9,P 〈 0.01 ）. ③Six slight and 17 moderate central coordination disturbance children of 2 groups all completely recovered; After intervention treatment, among 128 severe central coordination disturbance children, 52 recovered and 76 were still abnormal, in which, 43 slight cerebral palsy, 18 moderate cerebral palsy, 5 severe cerebral palsy and 10 extremely severe cerebral palsy. CONCLUSION： To perform integrated intervention treatment before 6 months old can better improve and promote mental and physical development levels of children patients with central coordination disturbance after brain injury than 6 months later.

Frequency equation for the submicron CMOS ring oscillator using the first order characterization

By utilizing the first order behavior of the device,an equation for the frequency of operation of the submicron CMOS ring oscillator is presented.A 5-stage ring oscillator is utilized as the initial design,with different Beta ratios,for the computation of the operating frequency.Later on,the circuit simulation is performed from 5-stage till 23-stage,with the range of oscillating frequency being 3.0817 and 0.6705 GHz respectively.It is noted that the output frequency is inversely proportional to the square of the device length,and when the value of Beta ratio is used as 2.3,a difference of 3.64%is observed on an average,in between the computed and the simulated values of frequency.As an outcome,the derived equation can be utilized,with the inclusion of an empirical constant in general,for arriving at the ring oscillator circuit’s output frequency.