Head only

Note that both the discharge and suction pressures must be on the same base/units. These illustrations are for static head only, while overall (he pump has to work against the static and the pressure heads. (To be discussed.)... 

Contents in (J.S. gallons for one head only. This table is only approximate, but close enough for practical use. By permission, The Permutit Co., Inc., Data Book, 1953. 

LTHW systems are usually under a pressure of static head only, with an open expansion tank, in which case the design operating temperature should not exceed 83°C. Where MTHW systems operating above 110°C are pressurized by means of a head tank, an expansion vessel should be incorporated into the feed and expansion pipe. This vessel should be adequately sized to take the volume of expansion of the whole system so that boiling will not occur in the upper part of the feed pipe. On no account should an open vent be provided for this type of system. MTHW and HTHW systems require pressurization such that the saturation temperature at operating pressure at all points in the circuit exceeds the maximum system flow temperature required. A margin of 17 K (minimum)... 

Introductory page, with links to (main headings only) Alchemical music from Atalanta fugiens Searchable database of alchemical emblems [500 + images] Paintings and other artwork Images from manuscripts and books Images of alchemical apparatus Alchemical symbols for substances, processes and equipment Other material... 

TABLE 1-5 Mortality of Rats Exposed to Aniline via Head-Only or Whole-Body Exposures for 4 h... 

Head-Only Exposures Whole-Body Exposures ... 

A controlled human exposure study provided information regarding non-lethal effects following acute (head-only) exposure to monomethylhydrazine... 

Orifice meters, Venturi meters and flow nozzles measure volumetric flow rate Q or mean velocity u. In contrast the Pitot tube shown in a horizontal pipe in Figure 8.7 measures a point velocity v. Thus Pitot tubes can be used to obtain velocity profiles in either open or closed conduits. At point 2 in Figure 8.7 a small amount of fluid is brought to a standstill. Thus the combined head at point 2 is the pressure head P/( pg) plus the velocity head v2/(2g) if the potential head z at the centre of the horizontal pipe is arbitrarily taken to be zero. Since at point 3 fluid is not brought to a standstill, the head at point 3 is the pressure head only if points 2 and 3 are sufficiently close for them to be considered to have the same potential head... 

Groups of ten male Crl CD rats were exposed to HCN in polymethymethacrylate exposure chambers under flow-through conditions (E.I. du Pont de Nemours 1981). The chamber atmosphere was measured continuously by infrared spectrophotometry measurements were validated by gas chromatography. The experiment was performed in duplicate with one set of animals exposed head-only to the test gas while the other set was allowed free movement inside the exposure chamber. Free-moving rats inhaled concentrations of 273 to 508 ppm for 5 min, 110 to 403 ppm for 15 min, 128 to 306 ppm for 30 min, or 76 to 222 ppm for 60 min. The postexposure observation period was 14 d, during which body weights were monitored. 

Many inhalation exposure techniques, such as the whole-body, nose-only, mouth-only, or head-only technique (Drew and Laskin, 1973 MacFarland, 1976 Leong et al., 1981 Phalen, 1984 Nelson, 1980), the intranasal exposure technique (Elliott and DeYoung, 1970 Smith et ah, 1981), the endotracheal nebulization technique (Leong et ah, 1985, 1988 Schreck et ah, 1986), and the body plethysmographic techniques (Alarie, 1966 Thome and Karol, 1989), have been developed for inhalation toxicity studies. Table 10.2 provides a summary of the advantages and disadvantages of each of the major inhalation exposure methodologies. 

Head only Good for repeated exposure Limited routes of entry into animal More efficient dose delivery Stress to animal Losses can be large Seal around neck Labor in loading/unloading Even distribution Pressure fluctuations Sampling and losses Air temperature, humidity Animal comfort Animal restraint... 

A Guidance Document on Acute Inhalation Toxicity Testing is being developed and presently exists as a draft (OECD 2004b). The document recommends the Acute Toxic Class (ATC) Method with a group size of three animals per sex, if the objective of the test is solely related to hazard classification. Limits for particle-size distribution of aerosolized test substances are suggested. The preferred mode of exposure is the nose-only, head-only, or head/nose-only exposure technique, because this mode of exposure minimizes exposure or uptake by noninhalation routes. 

The other main route used for pharmaceutical preparations is inhalation using a head only exposure system. Parenteral administration, although technically possible, is usually avoided because of the local irritant effects that can occur with repeated injection, particularly by the subcutaneous route. Topical administration is an option for materials intended for administration to the skin. 

The toxicity profile after exposure to airborne NMP depends strongly on the ratio of vapor to aerosol and on the area of exposure (i.e., head only or whole body). Because of the higher skin absorption for the aerosol, uptake is higher in animals exposed to aerosol than those exposed to vapor at similar concentrations. Rats exposed head only to 1000 mg showed only minor nasal irritation, but massive mortality occurred with whole body exposure to the same concentration of coarse droplets at high humidity. ... 

The oral LDso for rats was 4.6g/kg, and the rabbit dermal LDso was 4.9g/kg. Three of six rats succumbed to 4 hours of exposure at 4000 ppm. Ten-hour exposure at 670 ppm caused some deaths in mice and guinea pigs but not in rabbits. Mice exposed in a head-only exposure chamber at 1100 ppm for 10 minutes had a 50% decrease in respiratory rate. ... 

Regional node(s) cannot be assessed No regional lymph node metastasis Metastasis in the cystic ducts, pericholedochal lymph nodes, and/or hilar lymph nodes (i.e., in the hepatoduodenal ligament) Metastasis in the peripancreatic (head only), periduodenal, periportal, celiac, superior mesenteric, and/or posterior pancreaticoduodenal lymph nodes... 

The remaining fetuses are submitted to fresh soft tissue examination or preserved for fixed visceral examination (see Note 2). Various techniques are available typically based on Wilson s sections of the head and body or Wilson s sections of the head only with microdissection of the body. The techniques used for the preparation and examination of the fetuses are described in Chapters 16-21. 

Successful results have been achieved using this technique with—rat whole body from fetuses at Day 20 of gestation rat heads only or whole body from fetuses at Day 21 of gestation mouse whole body from fetuses at Day 17, 17.5, and 18 of gestation and rabbit heads only from fetuses at Day 29 of gestation. 

Sprayed acetone solutions Wind tunnel—5 mph individual exposures—head only no motivation—as for study 1 0.03-8.0 35 0.1 0.07... 

Fewer studies were located on death in laboratory animals exposed for intermediate and chronic-durations. One study by Mobay Corporation (1984) determined the toxicity of HDI via inhalation exposures in Sprague-Dawley rats over a 3-week period. Male and female rats were exposed (head-only) to HDI vapors at average concentrations of 0.005, 0.0175, 0.15, or 0.3 ppm for 5 hours a day,... 

In studies of intermediate-duration, groups of 10 male and 10 female rats were exposed (head-only) to HDI vapors at average eoneentrations of 0.005, 0.0175, 0.15, or 0.3 ppm for 5 hours a day, 5 days a week for 3 weeks. Five animals per sex per exposure concentration were saerifieed at the end of the exposure period the remaining animals were allowed a 2-week reeoveiy period and then saerifieed. No signifieant differenees in blood ehemistry and hematology were observed compared to eontrol animals for both male and female rats (Mobay Corporation 1984). Similarly, Fiseher 344 rats were exposed to 0, 0.011, 0.041, or 0.143 ppm HDI in air for 6 hours per day for 66-69 days over a period of approximately 13 weeks. Animals were exposed to HDI in 2-cubic-meter chambers (whole body). All rats were saerifieed at... 

Reaction XVIII. Ring Formation by Elimination of Water from certain Molecules. (B., 41, 3632, A., 311, 178.)—Many important syntheses of ring compounds come under this heading. Only a few can be mentioned. 

First a man is to be made of iron, having two noses on his head, Fig. 89, and onhie crown a mouth which may be opened and again close shut. This if it be to be used for the cone, of metals is to be so inserted into another man made of iron or stone, that the inward head only may come forth of the outward man, but the rest of bis body or belly may remain hidden in the belly of the exterior man. And to each nose of the head glass receivers are to be applied to receive the vapours ascending from the hot stomach. When you use this... 

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