Indirect control

Gobburu, J.V. and Jusko, W.J., Role of dosage regimen in controlling indirect pharmacodynamic responses, Adv. Drug Deliv. Rev., 46, 45-57, 2001. 

Regulation of protein synthesis in the rabbit reticulocyte. The vast majority of the protein synthesized in the rabbit reticulocyte is hemoglobin. The gross rate of protein synthesis in the reticulocyte is controlled indirectly by the concentration of heme. Heme inactivates a kinase that would otherwise inactivate the initiation complex involving eIF-2 and eIF-2B. The kinase phosphorylates the eIF-2 factor, making it impossible for the eIF-2-eIF-2B complex to exchange GDP for GTP. 

In the first case, product purities are controlled indirectly by controlling front positions. In distillation columns the front positions are easily controlled with cheap, reliable and fast online temperature measurements on sensitive trays inside the column [27]. A similar procedure was recently proposed for moving-bed chromatographic processes with UV rather than temperature measurement [37]. However, the performance of such an approach is usually limited. Exact product specifications cannot be guaranteed because of this indirect approach. Furthermore, in combined reaction separation processes the relationship between the measured variable and the variable to be controlled is often non-unique, which may lead to severe operational problems as shown for reactive distillation processes [23], It was concluded that these problems could be overcome if in addition some direct or indirect measure of conversion is taken into account. 

For years, it was assumed that the rate of RNA synthesis was the rate-limiting step that controls indirectly the amount of protein synthesized. However, this simplistic view has been replaced by results clearly showing that mRNA and protein levels do not always correlate fully, and that extensive regulation of mRNA transcript processing and availability for translation occurs. 

The second step is to establish whether the calcites were deposited in isotopic equilibrium with the waters from which they are derived. During slow degassing, the isotopic fractionation between the aqueous and solid phases is controlled indirectly by cave temperature under equilibrium conditions. However, under an evaporative cave regime or rapid crystallisation, the isotopic fractionation is modulated by kinetic effects which inhibit isotopic equilibrium between the calcite and the drip waters (Hendy, 1971). 

Polymerization process control can benefit significantly from using online state estimation techniques. In general, online control of polymer properties such as molecular weight, MWD, copolymer composition, MI, density, etc. is difficult, mainly because of the lack of adequate online or in-process sensors. Therefore, many of these polymer property parameters are controlled indirectly by controlling first-level process variables such as temperature, pressure, and the flow rates of various reactants, solvents, and catalysts. When some deviations in polymer properties are detected through laboratory sample analysis, certain reactor variables need to be adjusted. Extensive plant experience might be required to make such process adjustments, or model-based online state estimator can be used. 

Thwaites, D.T. et al. (2002) H/dipeptide absorption across fhe human intestinal epithelium is controlled indirectly via a functional Na/H exchanger. Gastroenterology, 122 (5), 1322-1333. 

Long time response (2) long time response and increasing complexity (3) V/F control is not desirable in general (4) column bottom level control by steam flow is desirable. (Comments are due toT. Umeda). b Direct M.B. = direct material balance control Indirect M.B. indirect material balance control V/F = vapor to feed ratio control... 

Second, in configuration 3 the benzene product composition is controlled directly by the distillate flow, whereas in configuration 19 it is controlled indirectly by the steam rate. Therefore, the first is more responsive and is retained as better. 

Legal Status tma-2 controlled indirectly as an isomer of (Schedule r) tma... 

An important advantage of fuel cells is the selectivity of the electrochemical reactions. Contrary to combustion processes where the reactions are controlled indirectly through the dependence of the rates on temperature and pressure, the electrochemical reactions are direcdy related to the cell voltage and are highly selective, that is no NO is produced when air is used as the oxidant at the cathode. The fuel cell itself has no moving parts and therefore it produces almost no noise. In some fuel cell systems a low noise level may arise from blowers but generally these systems are comparatively silent. 

Other social controls indirectly influence industrial safety performance, such as laws and norms for corporate governance that cause companies to inform shareholders and potential investors about corporate activities so they can make informed decisions about financial risks. If the activities are hazardous, these sources of financial support may need to be convinced that their financial risks are held to acceptable levels by evidence of effective safety management, which thereby makes it necessary for companies to develop and implement codes of conduct and safety management practices that adhere to industrial standards and comply with government regulations. ... 

Containment tightness control Indirectly, by vent system ( filters), see item 79... 

Steam flow is controlled Indirectly by steam pressure control. 

The price of drugs sold to the NHS is controlled indirectly by the DHSS through the Pharmaceutical Price Regulation Scheme (PPRS) which began in 1957. The scheme has been revised several times and requires that companies present details of costs, sales, exports, capital investment and estimates of future sales and profits. Rather than regulate the price of each individual product, the scheme aims to limit overall the return on capital which a company makes on its business with the NHS. The scheme works mainly by negotiation between the companies and the DHSS but the Secretary of State for Health can if necessary fix prices by order. For example, in 1983 the minister enforced a 2 % cut across the board. Moreover, limitations have been placed on the amount of money to be spent on promotion. It has been reduced to 10% of the sales for 1984 and 9% for 1985. Companies can in effect be fined under the PPRS for exceeding the limits on promotion. 

Indirect Temperature Control Indirect Pressure Control... 

Another way of reducing the efficiency of the condenser is to reduce the effective surface area used for heat transfer. Figure 12.39 shows how, by placing the control valve under the condenser, liquid can accumulate in the condenser. This flooded condenser is less efficient because less heat transfer takes place in the submerged part of the tube bundle. Here sensible heat is removed in subcooling the liquid, in the exposed part of the bundle, heat of vaporisation is removed condensing the vapour. The pressure controller indirectly changes the level of liquid in the condenser. 

In this method, the pore size distribution is controlled indirectly by defining the relative porosity of the so-called meso-porous scale ( m,) as a percentage of total porosity ... 

An alternative arrangement, used especially when the condenser is built into the head of the column, is that of Figure 3.15. Direct measurement and control of reflux are not possible since the flow is internal. Instead it must be controlled indirectly by manipulation of condenser cooling water, which, in turn, may be reset by a vapor-composition controller. This internal reflux arrangement works well if a heat-computation scheme is used for control. A scheme that we have used successfully is discussed in Chapter 11, Section 4. 

With GCs made before the 1990s, carrier flow rate was controlled indirectly by controlling the carrier inlet pressure, or "column head pressure." The actual flow rate was measured at the outlet of the column or the detector with an electronic flow meter, or a bubble flow meter, and could be an involved, time consuming, and frustrating process. The pressure setting was not able to be varied during the run, and thus the flow was essentially constant during the analysis. The relation between flow rate and inlet pressure is calculated with Poiseuille s equation for compressible fluids. 

Systems of this type have been evaluated and both gave excellent results. They work on a needle valve principle, the position of the needle valve being controlled indirectly by electric or pneumatic drive systems mounted directly on the applicator head. 

Vaporizers with controls Indirect fluid electric vaporizer with controls mounted. Very high-pressure heater of corrosive fluid. Fluid side 3175 psi (223 kg/cm or 216 ATM) design pressure. (See Fig. V-12.)... 

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