Environmental entrainment

As described above the changes in the environment entrain the matura-tional development and care is required to ensure that the captive environment provides the full ambient cycle of proximal factors to entrain particularly gametogenesis and spawning. This environmental entrainment ensures the seasonality in the spawning of many if not most fish species. 

The gasification plant is equipped with two Texaco gasifiers, each capable of producing all of the synthesis gas required for operation of the complex. Eastman chose an entrained-bed gasification process for the Chemicals from Coal project because of three attractive features. The product gas composition using locally available coal is particularly suitable for production of the desired chemicals. Also, the process has excellent environmental performance and generates no Hquids or tars. EinaHy, the process can be operated at the elevated pressure required for the downstream chemical plants. 

Practical separation techniques for hquid particles in gases are discussed. Since gas-borne particulates include both hquid and sohd particles, many devices used for dry-dust collection (discussed in Sec. 17 under Gas-Sohds Separation ) can be adapted to liquid-particle separation. Also, the basic subject of particle mechanics is covered in Sec. 6. Separation of liquid particulates is frequently desirable in chemical processes such as in countercurrent-stage contacting because hquid entrainment with the gas partially reduces true countercurrency. Separation before entering another process step may be needed to prevent corrosion, to prevent yield loss, or to prevent equipment damage or malfunc tion. Separation before the atmospheric release of gases may be necessaiy to prevent environmental problems and for regula-toiy compliance. 

Generally, maximum flow velocities for brass are between 3 and 5 ft/s (0.9 and 1.5 m/s) depending on environmental conditions. In this case, sand and silt entrained in the river water contributed to the erosiveness of the fluid. 

Solvent extraction carried out in conventional contactors like mixer-settlers and columns has certain limitations, including (a) controlling optimum dispersion and coalescence, (b) purifying both phases to ensure that stable emulsions are avoided (c) temperature control within a narrow band (d) high entrained solvent losses and related environmental and process economic effects and (e) large equipment dimensions and energy requirements when the density differential or selectivity is low. 

Some consideration should be given at this point to the need to prevent loss of the organic phase in the aqueous raffinate. This loss can arise by either solubility in the aqueous phase or by entrainment of droplets not fully settled. The solvent lost in this way can offer a finite environmental hazard and be an economic cost on the process. 

Replacement of hexavalent chromium with trivalent chromium offers important environmental advantages. Trivalent chromium is considerably less toxic than hexavalent. Trivalent systems use chromium concentrations that are typically two orders of magnitude less than in hexavalent systems. Thus, far less chromium enters the waste stream. Trivalent systems also generate few toxic air emissions, while hexavalent systems involve a reaction that produces hydrogen bubbles which entrain chromium compounds and carry them out of the baths. Trivalent chromium is readily precipitated from wastewater, while hexavalent chromium solutions must go through an additional step in a treatment system in which the chromium is reduced to its trivalent form before precipitation. It has been shown that trivalent chromium systems can successfully replace hexavalent ones for decorative chrome applications. Trivalent chromium systems are not suitable for hard chrome applications. More information regarding trivalent chromium plating can be obtained from Roy (1984), Robison (1978), Chementator (1982), and Smart (1983). 

Concrete may use plasticizers (e.g., sulphonated melamine and naphthalene formaldehyde condensates), air-entraining agents (aIkyI/aryl sulfonate surfactants), retarders (hydroxy carboxylic acids such as polyethylene glycol mono-p-nonylphenyl ether) and surface washes (benzalkonium chloride) (RAIA 1997). Little has been published on air emissions from concrete additives, their leaching into surface waters appearing to be of greater environmental concern (Ruckstuhl, 2001). 

Alternatively, it is possible that maternal depressive symptoms contribute to the severity of their infant s sleep disturbance. For example, infants of depressed mothers may sleep poorly because they are distressed, not sufficiently active during the day, or receive insufficient environmental cues to entrain their circadian rhythms (115). In addition, the observed increase in sleep disturbance in infants of depressed mothers may simply reflect a reporting bias in that postpartum women with current or past MDD are awake during the night more than women without MDD (31) and might, therefore, be more aware of, and more likely to report, infant sleep disturbances than nondepressed mothers. 

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