Small Setup Research Articles

From test tube to plate: a simple procedure for the rapid preparation of microcrystallization experiments using the cubic phase method

Crystals of transmembrane proteins for X-ray diffraction experiments may be grown either by employing mixed protein–detergent complexes, or in a matrix of liquid-crystalline membraneous material forming a lipidic cubic phase (in cubo). Widespread use of thein cubomethod has been severely hampered by its tediousness and the large amounts of protein required. Here a simple procedure is presented that by virtue of its simplicity and small setup size substantially reduces the preparation time as well as the amount of protein. Crystallization trials are set up in conventional multi-well plates using a semi-automatic dispenser-driven microsyringe. The microprocedure is amenable to full automation and further miniaturization. Its feasibility is demonstrated by screening for new crystallization conditions for bacteriorhodopsin using volumes ofca200 nl of lipidic cubic phase. New crystallization conditions were identified that avoid the necessity of weighing solid precipitation agents.

Application of MEMS force sensors for in situ mechanical characterization of nano-scale thin films in SEM and TEM

Abstract We present a novel tensile testing technique utilizing MEMS force sensors for in situ mechanical characterization of sub-micron scale freestanding thin films in SEM and TEM. Microfabrication techniques are used to cofabricate the thin film specimens with force sensors to produce the following unique features: (1) small setup size to fit in SEM and TEM for in situ experiments, (2) ability to measure tensile pre-stress in specimen, (3) alignment between specimen and applied loading axes with lithographic precision, (4) no extra gripping mechanism required, and (5) ability to measure creep strain in the material. The technique allows single or multilayers of materials that can be deposited/grown on silicon substrate to be tested. We demonstrate the technique by testing a 100 nm thick, 8.8 μm wide and 275 μm long freestanding aluminum specimen (average grain size about 50 nm) in situ inside an environmental SEM chamber, and present another setup for similar experiment in TEM. Experimental results strongly suggest that at this size scale: (1) elastic modulus does not change, (2) size effects on yield strength are pronounced (63 times the bulk pure aluminum yield stress), and (3) permanent strain hardening effects are absent.

Monitoring Tool for Performance Measurements of Windows Nt-Based Lans

The increasing popularity of the Windows NT operating system has led to many companies and institutions installing Windows NT-based local area networks (LANs). These new Windows-NT based LANs have to be monitored continuously to determine their operating and performance parameters. At present, not many monitoring tools are available for the NT platform. In this article, some of the existing commercially available monitoring tools are discussed. After their drawbacks are identified, a new monitoring tool is developed using virtual device drivers. The developed tool is tested on a small network setup to demonstrate the various advantages.

The effect of setup uncertainty on normal tissue sparing with IMRT for head-and-neck cancer

Purpose: Intensity-modulated radiotherapy (IMRT) is being evaluated in the management of head-and-neck cancers at several institutions, and a Radiation Therapy Oncology Group study of its utility in parotid sparing is under development. There is an inherent risk that the sharper dose gradients generated by IMRT amplify the potentially detrimental impact of setup uncertainty. The International Commission on Radiation Units and Measurements Report 62 (ICRU-62) defined planning organ-at-risk volume (PRV) to account for positional uncertainties for normal tissues. The purpose of this study is to quantify the dosimetric effect of employing PRV for the parotid gland and to evaluate the use of PRV on normal-tissue sparing in the setting of small clinical setup errors. Methods and Materials: The optimized nine-beam IMRT plans for three head-and-neck cancer patients participating in an institutional review board approved parotid-sparing protocol were used as reference plans. A second optimized plan was generated for each patient by adding a PRV of 5 mm for the contralateral parotid gland. The effect of these additions on the quality of the plans was quantified, in terms of both target coverage and normal-tissue sparing. To test the value of PRV in a worst-case scenario, systematic translational setup uncertainties were simulated by shifting the treatment isocenter 5 mm superiorly, inferiorly, left, right, anteriorly, and posteriorly, without altering optimized beam profiles. At each shifted isocenter, dose distributions were recalculated, producing a total of six shifted plans without PRV and six shifted plans with PRV for each patient. The effect of setup uncertainty on parotid sparing and the value of PRV in compensating for the uncertainty were evaluated. Results: The addition of the PRV and reoptimization did not significantly affect the dose to gross tumor volume, spinal cord, or brainstem. In contrast, without any shift, the PRV did increase parotid sparing and reduce coverage of the nodal region adjacent to the parotid gland. As expected, when the plans were shifted, the greatest increase in contralateral parotid irradiation was noted with shifts toward the contralateral parotid gland. With these shifts, the average volume of contralateral parotid receiving greater than 30 Gy was reduced from 22% to 4% when a PRV was used. This correlated with a reduction in the average normal-tissue complication probability (NTCP) from 22% to 7%. Conclusions: The use of PRV may limit the volume of normal tissue structures, such as the parotid gland, exceeding tolerance dose as a result of setup errors. Consequently, it will be important to incorporate the nomenclature of ICRU-62 into the design of future IMRT studies, if the clinical gains of increased normal-tissue sparing are to be realized.

Influence of carbon and nutrient additions on a decomposer food chain and the growth of pine seedlings in microcosms

Because of N deposition plant production is becoming increasingly limited by other nutrients in boreal forests. At the same time more C is suggested to become available for below-ground food webs because of enhanced CO 2 fixation. We studied the effects of carbon and nutrient addition on a fungus–nematode food chain and on the growth of mycorrhizal or nonmycorrhizal pine seedlings ( Pinus sylvestris L.) in microcosms with N-rich mineral soil and a humus layer. The role of the food chain and mycorrhizal fungi for pine growth was tested in a smaller set-up. The total pine biomass was not N-limited at the scale of two experimental growing seasons. In accordance with established knowledge on fertile soils, the mycorrhizal fungi did not affect pine growth. The fungus–nematode food chain reduced both above- and below-ground pine biomass. The abiotic manipulations had strong effects on the total fungal biomass and nematode abundance. Both carbon and nutrient addition increased fungal biomass in the nonmycorrhizal, but not in the mycorrhizal systems. Fertilization reduced fungal biomass in mycorrhizal microcosms, but not in combination with carbon addition. Nematode abundance was higher in the absence of mycorrhizal fungi both in humus and in mineral soil, and increased after C addition in the nonmycorrhizal systems. Although the strong below-ground effects of resource manipulations were not reflected in total pine biomass, C addition reduced the ratio of stem dry mass to stem length significantly. The results illustrate that although decomposers may become redundant for plant growth in nutrient rich soil, carbon enrichment to a redundant decomposer food chain is not necessarily reflected in plant growth. Two hypothesis (changes in fungal biomass quality and allelopathy) are discussed as possible explanations for the resistance of pine biomass to changes in the decomposer food chain. In addition, the results demonstrate that mycorrhizal fungi can regulate below-ground responses to resource additions other than rhizodeposition even when they are redundant in terms of plant growth.

A new method for joint replenishment problems

This paper considers joint replenishment problems (JRP) of n items under deterministic and constant demand. Two new algorithms for JRP are proposed, based on a pair of tighter bounds for optimal cyclic time. The proposed algorithms can be used to determine the optimal cyclic policy and the optimal strict cyclic policy. Both algorithms are qualified for JRP with small major set-up costs, while only one of them can cope with JRP with any type of major set-up costs. Numerical experiments on randomly generated problems show that the new algorithms significantly outperform the existing exact algorithms for almost all of the test problems.

IMPROVING JOB SHOP PERFORMANCE THROUGH PROCESS QUEUE MANAGEMENT UNDER TRANSFER BATCHING

This research investigated the value of protecting the continuity of release batchs in a transfer batching environment, by modifying the SPT rule. A simulation model of a job shop was used to test the modified SPT rule. The performance measures evaluated were mean flow time, flow time variance, and mean lateness. Conditions under which the SPT modification improved results were as follows: large number of transfer batches, small setup time to process time ratio, and large variation in process times from station to station. The results suggest that shop loading is not a significant factor affecting performance of the modified SPT rule.

X-ray interferometry of surfaces with Fresnel mirrors

With a small double-mirror setup, we used grazing-x-ray interferometry to study nanometric steps. These one-dimensional steps were microfabricated upon the surface of one of the two mirrors; the other mirror provided the reference wave. Two geometries were studied. In the longitudinal case in which the x rays are parallel to the step edges, it is straightforward to determine the step size. In the transverse case, one deals with Fourier holography, and a reconstruction process for a phase object had been demonstrated for the case of a single step.

Modeling of Drop Disintegration in Liquid Pulsed Sieve-Tray Extractors with Regard to Viscosity

This paper describes a physical model for a stable drop size in liquid pulsed extractors. It is based on the physical phenomena of drop disintegration which were experimentally investigated in a small test setup. The aim was to derive a relatively simple model on the basis of meaningful simplifications and assumptions, however, including the drop phase viscosity and other important influences. A comparison of the calculated and measured drop sizes shows that the new equation given in this paper is able to calculate the diameter of stable drops in the technical range of drop phase viscosities, pulsation intensities and sieve tray parameters.

Are push and pull systems really so different?

A distinction is frequently made between push and pull production planning and control systems. Many people believe that pull systems are inherently better at reducing stocks because they try to eliminate queues, not provide for them, whereas push systems encourage queues to cushion operations and to increase work station utilisation but at higher cost. However, the definitions of push and pull are inconsistent between different researchers. Worse, arguments about performance are sometimes circular. Thus, if the performance of a pull system is poor then it may be suggested that this is because the fundamentals of JIT are not being observed, whereas, if the performance of a push system is poor, then that is a consequence of it being a push system. After defining push and pull systems, this paper examines, by means of simulation, the effect that push and pull information flows have on system performance, under a variety of conditions. In particular, the performance of both push and pull information flow systems are considered in conjunction with high-quality levels, small set-ups and small batches, i.e. the conditions normally associated with JIT continuous improvement programmes. Similarly, the performance of both push and pull information flow systems are investigated in the presence of conditions such as large set-up times, which are frequently eliminated as part of a continuous improvement programme. The question investigated in this study is how system performance is affected by the flow of control information. The investigation uses models of the material and information flows of push and pull systems to examine the conditions which affect performance. A production sequence is chosen which consists of ordering materials, making parts and assembling products which are then despatched to customers. A set of decision rules is used to operate the systems using different demand and inventory level data.

Regional Blocs and Foreign Direct Investment

This paper examines the impact of the emergence of regional blocs (customs unions) on the patterns of inter-bloc and intra-bloc trade when firms have the option to engage in direct investment (FDI). The consequences of bloc formation for exogenously given external tariffs is examined first. When two regional blocs co-exist and firms have the option to engage in FDI, all inter-bloc trade may cease--complete trade diversion that is replaced by inter-bloc FDI--investment creation. In such an event the volume of world trade declines, but this is more than offset by the increase in world output due to direct investment. Hence, total world output is the same as under free trade. Second, I investigate the optimal tariff that a trading bloc levies on imports from non-member countries. The equilibrium tariffs resulting from a non-cooperative game played by the trading blocs is restricted by the option to circumvent the tariff via two-way direct investment. Small set-up cost associated with FDI leads to low tariffs, and the outcome is almost free trade. Moderate set-up costs restrain the regional blocs from mutually harming one another through an escalation in the tariff war. Finally, the formation of two regional blocs enhances the welfare of all countries.

Highly selective photochemical synthesis of perfluoroalkyl bromides and iodides

Highly fluorinated alkyl iodides are conveniently synthesized by telomerization of a fluoroalkyl-iodide, RI, with, e.g., C 2F 4. Normally, the reaction, often carried out in the liquid phase with a radical initiator, gives products with a broad distribution of molecular weights. In this work, we report a method that obtains selectively products of a desired molecular weight: this method is a photochemically induced reaction in the gas phase; the gas is circulated through a trap or a rectification still which continuously removes the heavier products, whereas the more volatile molecules return to the photoreactor. An analysis by rate equations shows which control parameters are important, and by a suitable choice of these parameters, we obtained a better selectivity for, e.g., C 8F 17I than previously. This method also works with BrC 2F 4Br instead of an iodide. In this case, we demonstrated in a small laboratory setup with simple low-pressure Hg lamps (5 × 30 W), a productivity of more than 0.5 kg/day. In the telomerization of CF 3Br or HC 2F 4Br with C 2F 4 we found, however, a few percent of dibromide side products which are sometimes difficult to separate because of similar boiling points. For this case, it is better to synthesize the iodides instead, and then exchange the I for Br, if desired.

A simple low-temperature ultrahigh-vacuum scanning tunneling microscope capable of atomic manipulation

The design of a low-temperature scanning tunneling microscope is described. The microscope can be operated in ultrahigh vacuum in the temperature range between 15 and 300 K. The main features are a scanner which is based on the Besocke ‘‘beetle’’ design principle combined with a spring suspension of the microscope and complete surrounding of the whole microscope by a 4 K radiation shield. The microscope can be extended to work as a force microscope using the optical lever detection technique for force measurement. It is demonstrated that this comparatively small and reliable setup is well suited to study the adsorption of single atoms and molecules at low temperatures. Moreover, examples of lateral and vertical manipulation of atoms and molecules are shown to demonstrate the performance of the system.

High resolution end group determination of low molecular weight polymers by matrix-assisted laser desorption ionization on an external ion source fourier transform ion cyclotron resonance mass spectrometer

Matrix-assisted laser desorption ionization was performed on an external ion source Fourier transform ion cyclotron resonance mass spectrometer equipped with a 7-T superconducting magnet to analyze end groups of synthetic polymers in the mass range from 500 to 5000 u. Native, perdeutero methylated, propylated, and acetylated polyethylene glycol and polyvinyl pyrrolidone with unknown end-group elemental composition were investigated in the mass range up to 5000 u by using a 2,5-dihydroxybenzoic acid matrix. A small electrospray setup was used for the deposition of the samples. Two methods to process data were evaluated for the determination of end groups from the measured masses of the component molecules in the molecular weight ranges: a regression method and an averaging method. The averaging method is demonstrated to allow end-group mass determinations with an accuracy within 3 mu for the molecular weight range from 500 to 1400 and within 20 mu for the molecular weight range from 3400 to 5000. This is sufficient to identify the elemental composition of end groups in unknown polymer samples.

Planning and Control in Multi‐Cell Manufacturing

This research compares Material Requirements Planning (MRP), Kanban, and Period Batch Control (PBC) as alternative approaches to the planning and control of multi‐cell manufacturing involving flow cells and assembly. Since previous research on performance of these systems in cellular manufacturing has been primarily conceptual, the experiments reported here provide new insights into their comparative performance.The results show that the production environment is a major factor in system choice. Three operating factors—Master Production Schedule (MPS) volume variation, MPS mix variation, and setup time/lot size—clearly affect system choice. All systems performed well under Justin‐Time (JIT) conditions; there was no advantage to Kanban. Under the mixed conditions of high MPS variation, but small setup time/lot sizes, PBC produced superior performance compared to Kanban and MRP. Under non‐JIT conditions, MRP was seen as clearly more effective. Finally, the results indicate that when conditions permit very small lot sizes relative to requirements, Kanban may perform best, even when MPS variation is high.

Control method for a combined active filter system employing a current source converter and a high pass filter

This paper describes a control method with a combined filter system which senses load current, source current, and line voltage to create reference signals for an active filter. The transfer function of the active filter is identified and is used for the control system design. It is shown that the source current feedback is most effective in suppressing the harmonic-enlarging effects due to parallel resonance and the harmonic current generated by source harmonic voltages. A small setup controlled by a DSP was built, and the validity of the proposed method was demonstrated by experimental results. >

Cross-flow microfiltration of kaolinite-in-water dispersions

The convective model of cross-flow microfiltration of suspensions with non-Newtonian viscosity (see E.F. Leonard and C.S. Vassilieff, Chem. Eng. Commun., 30 (1984) 209) predicts different qualitative behaviour depending on the mode of operation (i.e. constant inlet feed or constant inlet pressure). Experiments aimed at testing this prediction are performed with stable kaolinite-in-water dispersions (pH 10) in a small laboratory microfiltration set-up. The observed filtration behaviour follows the pattern predicted by the convective model. The shear-enhanced diffusion model fails to rationalize the experimental observations.

A direct computer control concept for mammalian cell fermentation processes

In the last 10 years, new assignments and the special demands of mammalian cells to the culture conditions caused the development of complex small scale fermentation setups. The use of continuous fermentation and cell retention devices requires appropriate process control systems. An arrangement for control and data-acquisition of complex laboratory-scale bioreactors is presented. The fundamental idea was the usage of a standard personal computer, which is connected to pumps, valves and sensors via ADA-transformation. The possibility of free programming allowed the development of user-oriented software, especially designed for the far-reaching requirements of a university laboratory in the field of animal cell culture. Control of aeration, pumps, data-acquisition and data-storage are combined within one program, which allows the automation of standard operations like measurement of kLa- or OTR-values. Pump control algorithms for all common fermentation strategies (batch, fed batch, chemostat, perfusion) are included and can be selected any time during cultivation. Oxygen partial pressure and pH are controlled via direct digital control (ddc), providing simple adaption of control parameters and set points to current fermentation conditions.

Reduced production rates in the economic lot scheduling problem

The economic lot scheduling problem were the item's production rates can be reduced from the current or nominal production rates is considered. Management may be interested in reducing production rates to avoid a rapid accumulation of inventories. The instances of the problem where reducing the production rates leads to a decrease in a sharp lower bound of the average cost are characterized. These instances include problems where the independent solution ( strictly) satisfies the capacity constraint. The independent solution is likely to satisfy the capacity constraint in facilities with nominal production rates that are high relative to the demand rates, or in facilities with small setup times. It is shown that, in minimizing a sharp lower bound on the average cost, it is optimal to reduce the rate of at most one item. A simple test identifies the item, typically the slowest, with potential for production rate reduction. If a reduction is warranted a line search, on the dual variable of the capacity cons...

Control Method and Compensation Characteristics of the Active Filter System using a Current Source PWM Converter and a High-Pass-Filter.

Nonlinear loads using power semiconductor devices produce harmonic currents and reactive power in AC power lines. As they are popular in many fields, the elimination of harmonic currents and reactive power is one of the important research projects.This paper describes a control method and compensation characteristics of the combined filter system of a current source active filter and a high-pass-filter. The system senses three signals, load currents, source currents and line voltages, to create the reference signals of the active filter. The goal of this paper is to solve the problems:(1) A harmonic-enlarging effect due to the parallel resonance, (2) Filtering of the harmonic currents produced by source-side harmonic voltages, and(3) Drawbacks of analog control such as being sensitive to noises, etc.The transfer function of the current source converter is identified, and is used for designing the control system of the active filter. Digital control based on a DSP is adopted to remove the drawbacks stemming from analog counterpart, but it is found that it introduces a new problem, a computational delay in the output, that results in serious deterioration of the fiter performance. It is shown that the addition of the source current feedback can solve not only the delay problem but ones due to the parallel resonance and source-side harmonic voltages.Finally a small setup controlled by a DSP was built, and the validity of the proposed method was demonstrated by experimental results.