Temperature seeds

To obtain a crystalline product, a solution of the residue in 30 ml. of benzene containing a few drops of triethylamine (Note 4) is placed in a 250-ml. Erlenmeyer flask, heated gently on a steam bath, and diluted with 150 ml. of hexane. Heating is continued for about 5 minutes (Note 5), after which the solution is allowed to cool to room temperature, seeded, and put in a freezer at —15° for at least 5 hours. The resulting solid is collected by suction filtration and washed with cold hexane. After vacuum drying, 5.8 g. (94%) of light cream-colored crystals, m.p. 75-77°, is obtained. 

Solarization effects on weed population was hypothesized to be due to different mechanisms, such as changes in cell metabolism and ultrastructure (Singla et al. 1997), microbial parasitism on seeds weakened by sublethal temperatures, seed dormancy interruption by raising temperatures, and foliar scorching of weeds under the plastic mulch (Egley 1990 Katan and DeVay 1991). Moreover, imbalance of 02 and C02 or release of acetaldehyde, ethylene, and other volatile toxic compounds were also reported as accounting for weed death (Rubin and Benjamin 1984 Gamliel et al. 2000). 

Seed crystals begin to form at temperatures 3 to 10°F lower than the hydrate-forming temperatures discussed later in this chapter.2 Or, at a given temperature, seed crystals start forming at 300 or more psi above hydrate-forming pressure. However, dust or rust particles may act like seed crystals in initiating hydrate formation. 

A total of six parameters—seed level, seeding temperature, seed aging period, initial cool-down period, second cool-down temperature, and third cool-down period—were evaluated. In studying the effect of these six parameters, the best-fitted models (by least squares) of the data are ... 

Start-up methods. In this study, methods of start-up of a continuous cooling crystallizer are considered. Although several start-up methods are possible two typical ones as shown in Figure 2 were chosen. This description is based on the SFC (Sequential Function Chart). The SFC is conq)Osed of step and transition . Step , which is denoted with a box, shows the state of apparatus. Transition with a bold line indicates a condition that makes a move of the step . The items on the side of step are actual operations. The feed solution was charged to the crystallizer from the feed line. The feed was stopped when the liquid level arrived at the set up value, i.e. the hold up was fulfilled, l en, the solution was cooled to the operating temperature. Seed crystals were added when the solution temperature became constant at the set up value. After that, the continuous feeding and discharge were started. In this study, the experimental duration was more than 10 residence times in order to ensure the attainment of steady state. This method of start-up is defined as SU Method 1. 

For enantiotropic systems the temperature range of the crystallization process will be determined by the particular polymorph required. If it is metastable below the transition temperature, crystallization should begin just above transition temperature, where the kinetics are relatively slow. Seeding with the desired polymorph at this point is recommended. If the required polymorph is stable below the transition temperature, seeding should be commenced just below the transition temperature. 

To prevent the desired product from oiling ouf of solufion rafher fhan crystallizing, the reaction mixture must cool slowly. To accomplish this, place the Erlenmeyer flask in a water bath warmed to about 60 °C, and let the bath and flask cool to room temperature. Seeding the solution to effect crystallization may be required and can be performed according to the procedure described in Section 3.2. Once the solution has cooled to room temperature and no more crystallization is apparent, cool the flask in an ice-water bath for a few minutes to complete the process. Then isolate the product by vacuum filtration, and air-dry it. 

A 3-neck flask fitted with a pressure-equalizing addition ftmnel is filled with 50 mL of DMF and cooled to -20 °C. Concentrated sulfuric acid (2.70 mL, 4.97 g, 48.6 mmol) was added over 5 to 10 min at a rate that maintained a temperature between -15 and -20 °C. The flask containing ketol 2 is placed in an oil bath and heated to 95 °C. At approximately 70 °C internal temperature, an 18.8 mL aliquot of the sulfuric acid solution is added as one batch. The reaction mixture is heated for 3 h at 95 °C an additional batch of sulfuric acid solution (7.5 mL) was added after 1 h. After the reaction is judged complete by GLC, the solvent is removed at 0.3 mm pressure to give a brown oil. The residue is dissolved in 375 mL dichloromethane, washed with two portions of sodium chloride saturated 2.0 N aqueous sulfuric acid (190 mL each), two portions of sodium chloride saturated aqueous sodium bicarbonate solution (190 mL each) and finally one 190 mL portion of brine. Each aqueous wash is back extracted twice with the same 190 mL portion of dichloromethane. The combined organic extracts are dried over sodium sulfate, filtered and concentrated in vacuo to yield approximately 39 g of an oily, brown semisolid. The residue is taken up in 78 mL of ethyl acetate and directly loaded onto a silica gel column (78 g) after elution with 600 mL of ethyl acetate, the column fi-actions are concentrated to yield 37.2 to 38.8 g of a tan crystalline solid. The solid is further purified by bulb-to-bulb distillation (120-135 °C, 0.1 mm) and recrystallisation. The approximately 36 g of yellow cream solid are dissolved in refluxing ether (74 mL). After addition of hexanes (19 mL), the resulting turbid suspension is cooled to room temperature, seeded and then placed into a 17 C water ice bath for 30 min. The precipitate is collected on... 

IFF has been studied both experimentally and mathematically in three categories of no-dopant IFF, dopant-IFP, and inhibitor-IFP. The two main emphases of IFP studies are to produce better GRINs and to produce a predictive tool (i.e., a mathematical model) to determine the ideal conditions to use to produce a desired material [11, 6, 30-32]. Experimental and mathematical work have been conducted from two aspects of the problem (i) product-driven to produce better optical products and (ii) studies to better understand the underlying kinetics as well as the effects that the change in parameters (i.e., initiator concentration, cure temperature, seed composition, amount of small or large molecular weight inhibitor, and dopant type and concentration) have. 

As a general rule flasks and similar vessels should be heated in an air bath (compare Fig. II, 5, 3). A glycerol bath may be employed for temperatures up to 140° the glycerol is subsequently removed from the outside of the vessel by washing with water. Medicinal liquid paraffin may be used for temperatures up to about 220° hard hydrogenated cotton seed oil, Silicone fluids or fusible metal may be employed when higher temperatures are required. Small test-tubes and centrifuge tubes... 

When considering how the evolution of life could have come about, the seeding of terrestrial life by extraterrestrial bacterial spores traveling through space (panspermia) deserves mention. Much is said about the possibility of some form of life on other planets, including Mars or more distant celestial bodies. Is it possible for some remnants of bacterial life, enclosed in a protective coat of rock dust, to have traveled enormous distances, staying dormant at the extremely low temperature of space and even surviving deadly radiation The spore may be neither alive nor completely dead, and even after billions of years it could have an infinitesimal chance to reach a planet where liquid water could restart its life. Is this science fiction or a real possibility We don t know. Around the turn of the twentieth century Svante Arrhenius (Nobel Prize in chemistry 1903) developed this theory in more detail. There was much recent excitement about claimed fossil bacterial remains in a Martian meteorite recovered from Antarctica (not since... 

On the high-pressure side of the nozzle molecules may be seeded into the jet of helium or argon and are also cooled by the many collisions that take place. However, in discussing temperature in molecules, we must distinguish between translational, rotational and vibrational temperatures. The translational temperature is the same as that of the helium or argon carrier gas and may be less than 1 K. 

Many seed oils, especially sunflower and linseed, contain waxes which serve as a protective coating for the seed. These waxes soHdify at colder temperatures and impart turbidity to the oil and interfere with subsequent processing. They are commonly removed from the cmde oil by refrigeration followed by filtration, a process commonly known as winterization. 

Lupine seed, though used primarily in animal feeds (see Feeds AND FEED ADDITIVES), does have potential for use in human appHcations as a replacement for soy flour, and is reported to contain both trypsin inhibitors and hemagglutenins (17). The former are heat labile at 90°C for 8 minutes the latter seem much more stable to normal cooking temperatures. Various tropical root crops, including yam, cassava, and taro, are also known to contain both trypsin and chymotrypsin inhibitors, and certain varieties of sweet potatoes may also be impHcated (18). 

When the closed vessel is heated to 390°C bottom and 330°C top, the resulting pressure is 170 MPa (25,000 psi) and a single fluid fills the vessel. It dissolves nutrient at the bottom and flows by convection, controlled by a baffle, to the upper region, where growth occurs at the lower temperature. A typical 4 cm x 152 cm x 1 mm thick seed plate grows to a 5-cm thickness in about 3 weeks in a 3-m long production vessel. 

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