多变鱼腥藻半稳定状态连续培养的若干特征

分别使用恒化装置和全玻璃发酵罐连续培养多变鱼腥藻。在稳定条件下加以周期性的光照(L∶D=12∶12),经5—6d得到半稳定状态连续培养物。在光照阶段,培养物的生物量增长速度约等于稀释速度D的两倍,叶绿素的增长速度略小于D的两倍,糖原的累积速度几乎高出D~5的一个数量级。细胞内糖原和蛋白质含量变化的时间过程反映出培养物在光-暗条件下的碳氮物质合成与消耗相互联系的代谢特点。半稳定状态连续培养受培养物内在的生理活性支配,生长参数的变化符合方程X=X_(oe)~((μ-D)~t),但不同于恒浊培养和恒化培养。外界因素的强弱变化只改变生长参量变化的强度。本法适用于研究微藻的生态生理。     

Qualitative theory of compartmental systems with lags

Dynamic models of many processes in the biological and physical sciences give systems of ordinary differential equations called compartmental systems. Often, these systems include time lags; in this context, continuous probability density functions (pdfs) of lags are far more important than discrete lags. There is a relatively complete theory of compartmental systems without lags, both linear and non-linear [SIAM Rev. 35 (1993) 43]. The authors extend their previous work on compartmental systems without lags to show that, for discrete lags and for a very large class of pdfs of continuous lags, compartmental systems with lags are equivalent to larger compartmental systems without lags. Consequently, the properties of compartmental systems with lags are the same as those of compartmental systems without lags. For a very large class of compartmental systems with time lags, one can show that the time lags themselves can be generated by compartmental systems without lags. Thus, such systems can be partitioned into a main system, which is the original system without the lags, plus compartmental subsystems without lags that generate the lags. The latter may be linear or non-linear and may be inserted into main systems that are linear or non-linear. The state variables of the compartmental lag subsystems are hidden variables in the formulation with explicit lags.     

Multiscale analysis of collective motion and decision-making in swarms: An advection-diffusion equation with memory approach

We propose a (time) multiscale method for the coarse-grained analysis of collective motion and decision-making in self-propelled particle models of swarms comprising a mixture of ‘naïve’ and ‘informed’ individuals. The method is based on projecting the particle configuration onto a single ‘meta-particle’ that consists of the elongation of the flock together with the mean group velocity and position. We find that the collective states can be associated with the transient and asymptotic transport properties of the random walk followed by the meta-particle, which we assume follows a continuous time random walk (CTRW). These properties can be accurately predicted at the macroscopic level by an advection-diffusion equation with memory (ADEM) whose parameters are obtained from a mean group velocity time series obtained from a single simulation run of the individual-based model.     

Meniscal lesion detection and characterization in adult knee MRI: A deep learning model approach with external validation

PurposeEvaluation of a deep learning approach for the detection of meniscal tears and their characterization (presence/absence of migrated meniscal fragment).MethodsA large annotated adult knee MRI database was built combining medical expertise of radiologists and data scientists’ tools. Coronal and sagittal proton density fat suppressed-weighted images of 11,353 knee MRI examinations (10,401 individual patients) paired with their standardized structured reports were retrospectively collected. After database curation, deep learning models were trained and validated on a subset of 8058 examinations. Algorithm performance was evaluated on a test set of 299 examinations reviewed by 5 musculoskeletal specialists and compared to general radiologists’ reports. External validation was performed using the publicly available MRNet database. Receiver Operating Characteristic (ROC) curves results and Area Under the Curve (AUC) values were obtained on internal and external databases.ResultsA combined architecture of meniscal localization and lesion classification 3D convolutional neural networks reached AUC values of 0.93 (95% CI 0.82, 0.95) for medial and 0.84 (95% CI 0.78, 0.89) for lateral meniscal tear detection, and 0.91 (95% CI 0.87, 0.94) for medial and 0.95 (95% CI 0.92, 0.97) for lateral meniscal tear migration detection. External validation of the combined medial and lateral meniscal tear detection models resulted in an AUC of 0.83 (95% CI 0.75, 0.90) without further training and 0.89 (95% CI 0.82, 0.95) with fine tuning.ConclusionOur deep learning algorithm demonstrated high performance in knee menisci lesion detection and characterization, validated on an external database.     

Human and natural impacts on forests along lower Tana river,Kenya: implications towards conservation and management of endemic primate species and their habitat

Seventy-three forest patches were assessed to determine the effects of human and natural impact on native forests along the Lower Tana River flood plains in Kenya between January and March 2001. Seventeen of these forests were within the Tana River Primate National Reserve (TRPNR) while 56 were outside the protected area. Cultivation and dyke construction had the most devastating human impact, which involved partial or complete forest clearing resulting in further fragmentation of forest patches [Suleman MA, Wahungu GM, Mouria PK, Karere GM, Oguge N, Moinde NN (2001) Tana River primate census and forest evaluation. A report to Kenya Wildlife Services]. Natural impacts were either die back or flooding, which appeared to cause progressive degradation of forest structure and biodiversity. Overall, forest area in the Lower Tana significantly reduced by 34.5% (P < 0.001) over a 21-year period. Forest loss was greater outside the reserve (38%) than inside (29.2%) reiterating the significant role played by this protected area in habitat and species conservation. Continued forest loss increases extinction risks for the endemic primate species the Tana River Red Colobus (Procolobus rufomitratus) and the Crested Mangabey sub-species (Cercocebus galeritus galeritus). Initiation of community conservation programmes outside the reserve and introduction of sustainable micro-economic projects were recommended to enhance sustainable livelihoods and the environment.     

Continuous Models for Cell Migration in Tissues and Applications to Cell Sorting via Differential Chemotaxis

Chemotaxis, the guided migration of cells in response to chemical gradients, is vital to a wide variety of biological processes, including patterning of the slime mold Dictyostelium, embryonic morphogenesis, wound healing, and tumor invasion. Continuous models of chemotaxis have been developed to describe many such systems, yet few have considered the movements within a heterogeneous tissue composed of multiple subpopulations. In this paper, a partial differential equation (PDE) model is developed to describe a tissue formed from two distinct chemotactic populations. For a “crowded” (negligible extracellular space) tissue, it is demonstrated that the model reduces to a simpler one-species system while for an “uncrowded” tissue, it captures both movement of the entire tissue (via cells attaching to/migrating within an extracellular substrate) and the within-tissue rearrangements of the separate cellular subpopulations. The model is applied to explore the sorting of a heterogeneous tissue, where it is shown that differential-chemotaxis not only generates classical sorting patterns previously seen via differential-adhesion, but also demonstrates new classes of behavior. These new phenomena include temporal dynamics consisting of a traveling wave composed of spatially sorted subpopulations reminiscent of Dictyostelium slugs.     

A Double-Needle Gold-Silver Electrodes Continuous Glucose Monitoring Device

ObjectivesDiabetes is a serious, long-term disease and the use of continuous glucose monitoring sensors can reduce reliance on other painful invasive blood testing methods such as the finger blood glucose test. According to our work, a low-cost continuous glucose sensor has been developed based on electrochemical measurement techniques.MaterialsThe sensor is based on a two needles system; a gold and a silver electrode are integrated into a circular shaped electronic printed circuit board (PCB). The sensing part is based on biological electrochemical measurements. Glucose oxidase (Gox) was used as the active sensing element and ferrocene (Fc) as a mediator. Simple and low-cost coating methods were used; these methods are self-assembled monolayers and deep coating. This will reduce the final cost of the sensor as no expensive technique was used. The electrical subsystem contains a low-noise and low-power trans-impedance front-end as well as a single-chip low-power Bluetooth microcontroller with a 12-bit Analog-to-Digital Converter (ADC).ResultsThe sensor was tested in various concentrations of glucose. As a result of initial in vitro experiments, detailed analytical performance metrics are presented. The device has consistently shown a sensitivity of 3.059 mV/(mg/dl) reading with a linear range of 0-400 mg/dl.ConclusionThe proposed study shows promising results for glucose detection. Thus, this type of sensor can be used for different analyzes targeting biological applications after further investigations and analysis.     

Preliminary survey of the distribution and population of chimpanzees in the Republic of Guinea

An investigation of the distribution and population of chimpanzees in the Republic of Guinea was carried out with the help of the Government authorities on the basis of a questionnaire. As a result, at least 20 out of the 36 prefectures in the country were confirmed to be inhabited by chimpanzees, and the estimated total number of animals in the present population amounted to 6,625. This number represented an approximately 50% reduction from the 13,940 estimated by the same informants on the same questionnaire based on assumptions for the past (20–60 years ago). On comparing these data with our observations in some localities, the present number of chimpanzees as estimated from the questionnaire appeared to be overestimated. Among the 16 other prefectures without any reply, at least 7 have chimpanzees according to our own and our colleagues' observations. On our modest estimate, the number of chimpanzees at present could be only about 1,420 for 30 prefectures rather than 6,625 for 20 prefectures. The true population size in the whole country may lie between the two estimates, 1,420–6,625, even including other prefectures with no information. The reduction in population size during the last 20–60 years must be half or even more. The reason for this drastic reduction of the chimpanzee population is thought to be mainly the destruction of its habitat and poaching in some prefectures adjacent to Sierra Leone and Liberia. These findings emphasize that urgent efforts need to be directed towards the conservation of the chimpanzees and their habitat, especially through international cooperative programmes.     

Conservation biology of the succulent shrub,Euphorbia barnardii,a serpentine endemic of the Northern Province,South Africa

Euphorbia barnardii White, Dyer & Sloane is a relatively small, succulent shrub found in the Northern Province of South Africa. In 1994 it was listed as endangered by the Transvaal Threatened Plants Programme, because only three populations, totalling 1150 plants, were found. However, our study found five populations totalling 10 783 plants (9503 were reproductive). One population, found 50 km from the others, in the Bewaarkloof district, differs in terms of habitat type and morphology and may therefore be a different taxon. The other populations occur in Sekhukhuneland. Soil analyses showed that E. barnardii is restricted to ultramafic (serpentine) substrates. A sample of 2015 plants was examined in 1995 for size, stage, new growth, dead branches, reproduction (indices of vigour), damage and disease. Analysis of the results of 10 years’ demographic monitoring (1985–1995) on two of the Sekhukhuneland populations showed that one population, which was vigorous in 1995, showed little change in population size and structure, while the other, which had low vigour in 1995, showed a precipitous decline to local extinction in the monitoring plot. Aerial photographs taken in 1957 (1963 for Bewaarkloof) and 1986 showed large increases in human population density within 1.5 km of the E. barnardii populations except at Bewaarkloof, where it decreased. An increase in human habitation is associated with an increase in livestock (mostly cattle and goats) which trample plants. Trampling damages the terminal segments, which may lead to lowered reproductive output and increase susceptibility to opportunistic bacterial wilt pathogens. Bacterial wilts were prevalent on all populations but were particularly high at Bewaarkloof and on the population that showed a steep decline in numbers. Disease incidence was associated with the level of plant damage. The impact on plants further up the slopes and on the crest of hills (quite far from human settlements) was to a far lesser degree but further increases in human population density could change this situation. While this study has shown that the population size of E. barnardii is much greater than previously thought, the species is still threatened by several different processes and should be listed as ‘Vulnerable (A1a + c, B1, B2b + e, C1, D2)’ according to World Conservation Union categories.