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Synaptic transmission between rods and horizontal cells (HCs) was studied by simultaneously recording from the pre- and postsynaptic cells in the living retinal slices of the larval tiger salamander. Voltage tails after the termination of a flash were observed in dark-adapted rods and HC somata, but not in cones. These simultaneously recorded voltage tails were used to isolate the rod input from the cone input to the HCs. The rod voltage versus the HC voltage in the response tails yielded the input-output relation of the rod-HC synapse. Two factors, a luminance-dependent signal delay between the rod and HC responses and a voltage-dependent depolarizing current in the HCs, complicate the analysis of the rod-HC synapse. A single input-output relation of the rod-HC synapse was obtained after these two factors had been corrected. The rod-HC synapse was approximately linear near the rod dark potential (-40 mV) with a synaptic gain around 12, but it became progressively nonlinear at more hyperpolarized potentials. The synaptic gain at Vrod = -50 mV was about 0.65.

An optical measurement system has been developed for the simultaneous detection of multiple geometric error components of machine tools. The system is designed based upon laser alignment techniques where laser beams are used as measurement reference datum. The system can measure simultaneously 5 error components for each moving axis of a machine tool or coordinate measuring machine. They are: two straightness error components, pitch, yaw, and roll errors. Through actual calibration and measurement, the accuracy of the current system is estimated to be 2 µm for straightness measurements and better than 0.05 arcsec for angular error measurements with a 0.5 m offset between a reflecting mirror and a receiving photo sensor.

The establishment of the carcinogenic role of aflatoxins has been impeded by the lack of suitable tests to measure individual exposure for long-term studies. It was shown that the use of immuno-concentration followed by high pressure liquid chromatography (HPLC) or immunoassay can regularly detect aflatoxins down to pg/ml in fluids including urine. Aflatoxin M1 (AFM1) in free form was identified as the major metabolite in urine suitable for use as an approximate dosimetric indicator of recent exposure to aflatoxin B1 (AFB1). A panel of monoclonal antibodies of IgG class were developed in the murine system against AFB1 and/or AFM1. Their affinity constants are at the level of 10(8)-10(9) L/mol, and they are suitable for use in either effective immuno-concentration or in high sensitivity immunoassays. It was shown in a high risk area of liver cancer (Qidong of China) that 10% or more of the local inhabitants had a urinary output of AFM1 one or two orders of magnitude higher than that of Beijing people, especially during the wet seasons. The ingestion of AFB1 among these local people was estimated to exceed 1 mg/year. The major source came from contaminated corn and rice, but local alcoholic beverages also contributed. The increased excretion of AFM1 was more pronounced in patients with chronic active hepatitis. This observation of very low AFM1 content in urine of a significant percentage of local people implies their food storage practices may offer a feasible method for such prevention. The value and possible problems in conducting long-term studies on primary prevention are discussed.

A dynamic data system, a discrete time-series method, has been employed to analyze and estimate the stability characteristics of boiling water reactor dynamics. Twelve sets of pressure-perturbed neutron noise data were analyzed; the results have been compared favorably with those obtained from the conventional transfer function approach. However, the dynamic data system technique appears to be more efficient numerically and also provides a statistically adequate characterization of the prediction uncertainty. The method has also been applied to unperturbed neutron noise operation data, and the stability results have been confirmed with other analyses. A conceptual design of an on-line stability analyzer has been investigated.

Signals representing the force and displacement of the table of the M-139 machine gun during firing were analyzed. A constrained ARMA (2,1) model was fitted to the displacement data to explain the reason why the gun was jammed. Force data during and after firing were represented by the 4th and 6th order stochastic differential equation models. These models after decomposing yielded the dynamics of three subsystems; a supporting table, a recoil system and a bolt assembly. (Author)

Drilling is one of the most fundamental and widely used of machining operations. A single-engine fighter aircraft or a missile could need as many as a quarter of a million holes drilled. Yet drilling, for lack of understanding of the operation, is an art rather than a science. Consequently, drilling costs could be unnecessarily high without being noticed.

In cancer prevention work, main efforts had been placed on identifying carcinogens in the hope that they could be removed from the environment. Unfortunately, a complete removal of all causative agents proved to be impossible. Since the beginning of this decade, much attention has transferred to finding factors that can increase resistance in human bodies against cancer. Trace elements represent one such factor.

A six-branched chlorophyll a biosynthetic pathway instead of a four-branched pathway has been proposed as being responsible for the formation of chlorophyll a in green plants. The several biosynthetic routes that make up the pathway have been described as leading to the formation of ten chemically different groups of chlorophyll a species. The latter differ from one another by one or more of the following modifications: (a) by having a vinyl or ethyl group at position 4 of the macrocycle, (b) by the nature of the long-chain fatty alcohols at position 7 of the macrocycle, and (c) by having a 6-membered lactone ring instead of a 5-membered cyclopentanone ring. The chemical structure of several of the metabolic intermediates of that pathway and of some of the chlorophyll a species have now been determined by primary chemical derivatization methods coupled to spectrofluorometric, nuclear magnetic resonance and mass spectral analyses. The formation of highly organized photosynthetic membranes in which some of the chlorophyll alpha molecules are specifically oriented is ascribed to the multiplicity of chlorophyll biosynthetic routes which result in the formation of multiple chlorophyll alpha chemical species. Proper orientation of chlorophyll in the photosynthetic membranes is visualized as being controlled by peripheral group modifications that either modulate the polarity of the Chl chromophore or control the magnitude of the net positive charge on the central Mg atom. Finally it is proposed that in addition to the proper orientation of chlorophyll a, chemical heterogeneity of the chlorophyll chromophores in the photosynthetic reaction centers is mandatory for efficient charge separation, and proper vectorial electron transfer.

The problems of accurate and precise drill point grinding are closely related to the performance of the drills. Over a long period of time, the drill grinding machines available today have evolved based on empirical knowledge and by trial and error. The lack of a precise way of describing the drill point is even evidenced in national and international standards where only the conventional quantities like the chisel edge angle, point angle, clearance angle, and web thickness are used to describe the point geometry. It is not difficult to show that this system is not unique, that is, many different point geometries can be described by an identical set of the above-mentioned parameters. On the other hand, it is common knowledge that even minor variations in point geometry may lead to dramatic changes in drill performance.

The Continuous System Simulation Language (CSSL) computer programs are developed in conjunction with the derivation of the mathematical models and optimum algorithm to study the effect of various orifice control laws on the optimal control for the M-37 recoil mechanism. The optimal control greatly decreases the average rod pull peak force and causes the force to level out to a nearly constant value following the peak. Based on the analysis of the acceleration signals of the recoil mechanism, a microprocessor based digital controller is designed to control the orifice area controller. (Author)

Solid carbide drill wear can be correlated to measurable machining parameters when drilling graphite composite work material. The thrust force is found to be the leading indicator of wear with feed and speed having minor influence. Industrial drill wear limits are governed by the quality of the hole produced. The total depth of material removed is a convenient means of expressing the degree of drill wear permissible. An on-line monitoring system has been developed utilizing the computational power and low cost of the microcomputer. Development of sensors to retrofit existing equipment makes the system industrially feasible.

Industrial robots have been used for welding, painting, assembling, and material handling where the required accuracy is usually not very crucial. For drilling processes in the aerospace industry where individual part accuracy and hole quality are important, today’s industrial robots have limitations. There are several difficulties in applying the robot to the drilling process. First, no available drilling machine is suitable for use by a robot. Second, the accuracy or rigidity of present industrial robots is not good enough for hole positioning and is not able to cope with the dynamics of the drilling process. Third, the cutting tool, i.e., drill bit, is subject to tool wear and breakage. At present, a commercially available drilling tool was fitted with the robot, but those existing drill tools were designed for use in manual operation and did not yield satisfactory results. Much effort was put into modifying and augmenting these drilling tools to improve their performance with robots. The knowledge gained in the modification of these manual drills has led us to conclude that a special end effector exclusively designed for robot application is necessary to meet all the needs of robot-controlled drilling.

An adequate mathematical representation to describe the drill point configuration is needed for the analysis and design of drill geometry. Based on the mathematical models, a drill point grinding machine can then be built to produce various desired drill geometries accurately with high repeatability.

Despite the well-established theories and considerable experimental research, the identification of the complex mode shapes of a real machine tool structure with general damping still remains a formidable task. Moreover, the existence of closely coupled modes with heavy damping introduces additional difficulties. This paper presents a detailed procedure for experimental complex modal analysis of a machine tool structure by the Dynamic Data System method. The accuracy and efficiency are first illustrated by numerical examples through simulation studies. It has been shown that closely coupled modes and modes with heavy damping can be successfully identified from both simulated and actual experimental data from a machine tool. Complex mode shapes were also obtained without adding any complexity or losing accuracy as compared to normal mode analysis. The experimental results obtained by the proposed method were compared with those based on the FFT algorithm.

A set of pressure data recorded from the primary coolant system of a pressurized water reactor under normal operation is examined. For pressure sensors under study, it is found that the range of sampling intervals adequate to abstract pressure dynamics is about 0.2 to 0.8 ms. The estimated time constant of the pressure sensor for operating data is 1.83 ms.

A new statistical modeling approach is used to fit models to 200 years of sunspot data and the adequate models for yearly, monthly, and daily sunspot numbers are employed to obtain the minimum mean squared error forecasts. The analysis of new models revealed a long-term 76-year period, a short-term 27-year period, and a 2.5-year period due to stratospheric winds in addition to a commonly known 11-year periodicity of the sunspots. The forecasting charts are developed in a format that can be easily read to obtain the long-term (yearly average) and short-term (daily average) predictions of sunspot numbers.

The second order autoregressive model (AR(2)) is examined to cast light on its physical interpretation and to facilitate its use. A number of AR(2) series are simulated and charts are presented which relate the characteristics of these series to the parameters of the model and their roots and the associated correlation, partial correlation and forecast functions. Charts are also developed for the estimation of the parameters of the model and the construction of confidence regions for the estimates. An example is given to demonstrate the use of the charts.

The Average Run Length of a Cusum chart for controlling a normal mean is calculated by solving the systems of linear equations which approximate the integral equations for the required quantities. The accuracy of approximation by this method is numerically evaluated and the results are compared with those obtained by other approximate methods. The construction and use of a new nomogram based on the contours of Average Run Lengths La . and Lr drawn in the h√n/σ—|μ – k|√n/σ plane is discussed. Numerical examples are given to illustrate the flexibility and convenience provided by this nomogram in the design of Cusum charts.