Measuring very negative water potentials with polymer tensiometers: principles,performance and applications

In recent years, a polymer tensiometer (POT) was developed and tested to directly measure matric potentials in dry soils. By extending the measurement range to wilting point (a 20-fold increase compared to conventional, water-filled tensiometers), a myriad of previously unapproachable research questions are now open to experimental exploration. Furthermore, the instrument may well allow the development of more water-efficient irrigation strategies by recording water potential rather than soil water content. The principle of the sensor is to fill it with a polymer solution instead of water, thereby building up osmotic pressure inside the sensor. A high-quality ceramic allows the exchange of water with the soil while retaining the polymer. The ceramic has pores sufficiently small to remain saturated even under very negative matric potentials. Installing the sensor in an unsaturated soil causes the high pressure of the polymer solution to drop as the water potentials in the soil and in the POT equilibrate. As long as the pressure inside the polymer chamber remains sufficiently large to prevent cavitation, the sensor will function properly. If the osmotic potential in the polymer chamber can produce a pressure of approximately 2.0 MPa when the sensor is placed in water, proper readings down to wilting point are secured. Various tests in disturbed soil, including an experiment with root water uptake, demonstrate the operation and performance of the new polymer tensiometer and illustrate how processes such as root water uptake can be studied in more detail than before. The paper discusses the available data and explores the long term perspectives offered by the instrument.     

The use of low-quality water on the transport and transformation of waste water in irrigation soils

Waste water use for agricultural production in the semi-arid and arid climate areas is increasingly regarded as a solution for water shortage. Still today many questions remain unanswered about the mid- and long-term effect of irrigation by waste water on plant, soil and human health. In this paper the effect of the use of waste water on the soil hydraulic properties, the solute transport and transformation behaviour is being studied conducting steady state and non-steady state waste water application treatments on undisturbed soil columns and a field plot. Detailed spatial and temporal information on the propagation of water and solute is obtained using tensiometers, soil solute extraction and time domain reflectometry probes. The experimental data are processed using the HYDRUS-2D modeling tool. After calibration, the model is used in a predictive way as to simulate the mid- and long-term effects of the use of treated waste water as irrigation water.     

Analysis of the spatial variability in maize root density

In a maize field, one inter-row out of two was compacted two years down to 30-cm depth. This compacted inter-row (CIR) had a low root density down to 85-cm depth, while the soil below the row and the non compacted inter-row (NCIR) was densely rooted. Soil water status was monitored in each of these three compartments using tensiometers, neutron probe and gravimetric measurements. Both years, the rate of water extraction was about one half in the CIR compared with the row and the NCIR. As a consequence, appreciable differences in soil water potential were observed between colonized and sparsely colonized zones of each layer. These horizontal gradients were steeper than the vertical gradient between layers. This calls into question the suitability of one-dimensional models of water extraction for non-regular root systems, which are common in the field.     

塑料大棚渗灌灌水下限对番茄生长和产量的影响

利用土壤水分张力计监测土壤水分吸力的变化,以灌水时30cm土层的土壤水分吸力表示渗灌灌水下限,研究灌水下限为10、16、25、40和63kPa时对塑料大棚番茄生长和产量的影响．结果表明,番茄株高、生物量分别随灌水下限的增大而减小．番茄的产量和水分利用率与灌水下限间的关系曲线为抛物线,而茎粗／株高比与灌水下限间的关系曲线为三次多项式曲线．灌水下限不同,番茄的根／冠比(R／S)动态不同,番茄根系与株冠的生长状况不同．灌水下限在25～33kPa时,番茄植株生长健壮,根冠比例协调,产量大,水分利用率高．此指标作为渗灌灌水下限,灌水时土壤水分的含量比常规灌水低,灌水次数少,有利于提高保护地番茄栽培的水分利用率和劳动生产率．     

A new automated technique for measuring respiration in soil samples

An automated 36 place valve to provide continuous soil respiration measurements was constructed. The valve is fully computer controlled and can sample and purge the soil atmosphere as frequently as every 75 minutes. The concentrations, automatically measured by the valve, are essentially identical to those measured manually by gas chromatography in the concentration range of 0.1 to 1% CO₂, and are kept in this range by adjusting the mass of soil and the sampling frequency. Data are transferred automatically to a computer spreadsheet program for data handling and plotting on either a rate or cumulative basis. The system has proved reliable over many thousands of analyses and has made detailed analysis of microbial activity on a continuous basis possible.     

Insect electroantennogram responses to semiochemicals recorded with an inexpensive personal computer

ABSTRACT. . A circuit and accompanying program that allow an inexpensive personal computer to replace an expensive storage oscilloscope in displaying electroantennogram (EAG) recording is described. The maximum amplitude of the EAG is calculated automatically by the computer and appears as an alphanumeric display on the monitor screen. Because the entire EAG trace is stored by the computer, parameters of the EAG trace other than the maximum amplitude are also available for analysis, such as voltages at specified times after antennal stimulation.     

智能化鼠多功能行为训练系统的研究

目的：研制一种微机控制的大鼠多功能行为训练检测系统－梯度电压自动驱动大鼠及微机适时显示,记录和分析实验结果。方法：采用仿windows界面,以TurboC2．0编制,利用TC直接对硬件端口操作,完成信号的采集,处理和对实验仪器的控制。结果：本系统实现了：①梯度电压自动驱动;②声,光,电不同条件刺激;③多路径自动设置;④所没数据建立数据库以SAS软件处理其结果。结论：本系统自动化程度高,操作简便,数据处理科学、准确,尤其是还可用于听觉、视觉等特殊鼠记忆模型的建立。     

Automated whole-cell patch-clamp electrophysiology of neurons in vivo

Whole-cell patch-clamp electrophysiology of neurons is a gold-standard technique for high-fidelity analysis of the biophysical mechanisms of neural computation and pathology, but it requires great skill to perform. We have developed a robot that automatically performs patch clamping in vivo, algorithmically detecting cells by analyzing the temporal sequence of electrode impedance changes. We demonstrate good yield, throughput and quality of automated intracellular recording in mouse cortex and hippocampus.     

A thermoelectric, heat-flux-controlled cooling stage for measuring freezing parameters of small plants

A new cooling system was developed which permits the accurate recording of the freezing temperatures of small samples which contain less than 1 mg of water. The cooling system consists of a thermoelectric cooling stage with automatically controlled heat exchange between sample and coolant and of a sample-temperature recording unit. The heat exchange controller keeps the latent heat dissipation small during freezing, thus it is also possible to record an accurate freezing plateau in small samples like buds, leaves, conifer needles, short apices, and roots as well as small tissue samples like leaf disks, isolated bark, cambium or wood.Construction and performance of the system are discussed. Results of cooling experiments are presented to illustrate the system's performance as well as some of the problems encountered with test material of varying sizes and water contents. Based upon this experience we may recommend the use of this system for various cryobiological investigations.     

学习行为实验控制仪

本文介绍一种可以控制分辨学习、条件反射及交互延缓等行为实验的仪器,它采用脉冲数字电路,具有“自动”和“手控”两种工作方式。它能鉴别受试者所作反应的正确或错误,并发出相应信号供记录之用,本仪器为研究与学习行为有关的中枢神经系统电活动提供了不少方便,不仅可以节省人力还可以使实验结果更为可靠。     

A continuous flow automatically recording respirometer

A respirometer suitable for continuous operation over extended periods of time is described. Oxygen is supplied to the culture by the electrolysis of water. The quantity of oxygen produced by electrolysis within any specified time interval is automatically printed on a tape. This record is combined with a continuous recording of the concentration of dissolved oxygen entering and leaving the reactor to produce a mass balance for oxygen in the system. Details on respirometer construction and operation are presented.     

压脚痛阈测定法的改进和应用

本文介绍一种改进的压脚测痛法。采用电机驱动替代用手挤压橡皮球完成升压过程;通过一个自动的电路切断结构判定抽脚反应,较目视更加客观;用读数保持电路记录压力变化,较直接读取刻度值更加准确,可靠。这些优点,业经电针和吗啡镇痛实验验证。     

An Improved Method of Soil Moisture Control with Observations on Tomato Growth and Water Uptake

The control of soil moisture depended on the arrangement ofnumerous auto-irrigation cells radially around the plant, allowingrelatively unrestricted spread of the root system, the cellsbeing so placed that no point in the soil was more than about1 in from a water-supplying surface. Water for the cells wassupplied from barostat reservoirs fixed at the levels requiredto give the target hydrostatic pressures of –27, –84,–149, –266 mb at the centre of the cells. The degree of soil moisture control achieved was assessed bysoil moisture tensiometers. Three months after sowing mean matricpotentials were reduced below target levels to minimum valuesof only –33, –104, –178, and –329 mb.At this time some of the tomato plants had leaf areas in excessof 2000 cm² per plant and water uptakes of 200 ml per day perplant in the –27 mb and of 150 ml in the –266 mbtreatment. Leaf area per plant decreased with decrease in matric potential;leaf dry weight decreased with matric potentials less than –84mb; root growth, observed in glass panels, was depressed atboth the largest and smallest matric potentials. The reductionin water uptake with decreasing matric potential was more thancould be accounted for by a smaller leaf area alone.     

A root observation chamber for replicated use in a natural plant community

Summary A relatively small, low cost root observation chamber of steel construction has been designed for replicated use in a natural plant community. An undisturbed soil profile, suitable for detailed study can be obtained by avoiding conventional backfilling methods and despite such factors as the recognized need for teh chamber roof to be below ground level. Installation procedure emphasizes preparation of the observation face in established woody plant communities. The technique incorporates microscopic study of roots and simultaneous recording of major soil climatic factors.     

Abscission: quantitative measurement with a recording abscissor

The construction, operation, and effectiveness of an abscission measuring instrument called an abscissor is described. The device measured the force required for a spring-opposed plunger to shear abscission zone explants and was capable of automatically recording break strength data. Examples of data obtained with the abscissor are presented to demonstrate its capability of rapidly measuring significant changes in explant break strength.     

Short-term BOD (BODst) as a parameter for on-line monitoring of biological treatment process; Part II: instrumentation of integrated flow injection analysis (FIA) system for BODst estimation

An instrument with integrated flow injection analysis (FIA) system has been developed for on-line monitoring a process for conversion of biomass under field condition. The instrument consists of a newly designed biosensor for easy renewal of the bio-receptor without disassembling the sensor, a FIA controller for controlling the analysis operations, and a computer-based data acquisition system for data recording and processing. The instrument performed a sequence operations automatically including preparation of sample in the desired concentration, sample loading, sample injection, signal recording, data processing, and self-cleaning of the system. This makes the instrument being an interesting and promising device for on-line process monitoring.     

A self-adapting approach for the detection of bursts and network bursts in neuronal cultures

Dissociated networks of neurons typically exhibit bursting behavior, whose features are strongly influenced by the age of the culture, by chemical/electrical stimulation or by environmental conditions. To help the experimenter in identifying the changes possibly induced by specific protocols, we developed a self-adapting method for detecting both bursts and network bursts from electrophysiological activity recorded by means of micro-electrode arrays. The algorithm is based on the computation of the logarithmic inter-spike interval histogram and automatically detects the best threshold to distinguish between inter- and intra-burst inter-spike intervals for each recording channel of the array. An analogous procedure is followed for the detection of network bursts, looking for sequences of closely spaced single-channel bursts. We tested our algorithm on recordings of spontaneous as well as chemically stimulated activity, comparing its performance to other methods available in the literature.     

Non-invasive devices and methods for large animal monitoring using automated video processing

ObjectivesIt is now standard for polysomnographical equipment to include video recording, although this modality is generally underexploited, since there is no automated processing associated with the latter. In the present report, we investigated the set of features that can be automatically extracted from a video recording, in the context of monitoring of freely moving, non-sedated, newborn lambs.Material and methodsOur database contained seven lambs and a total of 11 recordings, using two different cameras allowing a top view and a side view. Using appropriate methodologies, we show that it is possible to estimate the lamb's movements, its posture (standing or lying) as well as its covered trajectory.ResultsResults are discussed as a function of the camera and show that side view recording is well suited for accurate scoring of the lamb's posture, whereas trajectory is best estimated using the top view camera. On the other hand, both cameras provide qualitatively similar results for the estimation of movement of the animals.ConclusionThe data gained from automated video processing, as reported herein, may have multiple applications, especially for animal studies, but may also be extended to human sleep monitoring.