Incubation periods

Plasmodium vivax, responsible for the most prevalent form of malaria (benign tertian), has an incubation period of 8—27 days (14 average). A variety seen in northern and northeastern Europe has an incubation period as long as 8—10 months. The disease can cause splenic mpture and anemia. Relapses (renewed manifestations of erythrocytic infection) can occur with this type of malaria. Overall, P. vivax is stiU susceptible to chloroquine however, resistant strains have been reported from Papua New Guinea and parts of Indonesia. Plasmodium malariae the cause of quartan malaria, has an incubation period of 15—30 days and its asexual cycle is 72 hours. This mildest form of malaria can cause nephritis in addition to the usual symptoms. It is a nonrelapsing type of malaria but the ted blood ceU infection can last for many years. No resistance to chloroquine by this plasmodium has been reported. Plasmodium ovale responsible for ovale tertian malaria, has an incubation period of 9—17 days (15 average). Relapses can occur in people infected with this plasmodium. No chloroquine resistance has been reported for this parasite. 

With the renewed interest in environmentally friendly products, ceUulose esters are being re-evaluated as a natural source of biodegradable thermoplastics. CeUulose acetates are potentiaUy biodegradable (152). Films prepared from a ceUulose acetate with a DS of 2.5 were shown to require only a 10—12 day incubation period for extensive degradation in an in vitro enrichment assay. Similarly, films prepared from a ceUulose acetate with a DS of 1.7 saw 70% degradation in 27 days in a wastewater treatment facUity, whereas films prepared from a ceUulose acetate with a DS of 2.5 required approximately 10 weeks for similar degradation to occur. The results of this work demonstrate that ceUulose acetate fibers and films are potentiaUy environmentally nonpersistant. 

Under certain conditions hydrogen cyanide can polymerize to black soHd compounds, eg, hydrogen cyanide homopolymer [26746-21-4] (1) and hydrogen cyanide tetramer [27027-02-2], C H N (2). There is usually an incubation period before rapid onset of polymer formation. Temperature has an inverse logarithmic effect on the incubation time. Acid stabilizers such as sulfuric and phosphoric acids prevent polymerization. The presence of water reduces the incubation period. 

There is often a period before corrosion starts in a crevice in passivating metals. This so-called incubation period corresponds to the time necessary to establish a crevice environment aggressive enough to dissolve the passive oxide layer. The incubation period is well known in stainless steels exposed to waters containing chloride. After a time period in which crevice corrosion is negligible, attack begins, and the rate of metal loss increases (Fig. 2.8). 

The incubation period varies widely depending on such factors as crack morphology, water chemistry, and temperature. However, experience in a wide variety of cooling water environments has shown that many stainless alloys develop noticeable attack within 6 months of first being exposed to water. It is rare to see attack initiating many years after equipment commissioning unless service conditions change in the interim. 

Figure 2.8 Schematic representation of corrosion rate as a function of time in a crevice in stainless steel exposed to chloride-containing water. The time before corrosion initiation is called the incubation period.

Metal damage due to cavitation can be both rapid (Figs. 12.3A through D) and severe. However, cavitation damage can have a time dependency see Fig. 12.4. An incubation period may be observed... 

The anodically produced acid is neutralized by the alkaline mortar (CaO). Corrosion is then possible only if the supply of alkali at the steel surface is consumed and the steel becomes active. This process is possible only under certain circumstances after a very long incubation period. Apparently in steel-concrete foundations the possible current densities are so small that this case never arises. The possibility of danger has to be verified with thin outer coatings where deliming has been noticed on the steel surface. 

Type 316L-This is the low-carbon (0.03% max.) version of type 316 that should be used where the heat input during fabrication exceeds the incubation period of the 316 (0.08% carbon) grade. For example, it is used for welding plates thicker than 1 cm. 

Fig. 7.13. The conversion of theta- to alpha-phase alumina was found to be strongly affected by shock modification in work of Beauchamp and co-workers [90B01]. Whereas the unshocked powder showed evidence for an incubation period of 60 min, the shock-modified materials show immediate conversion typical of the presence of shock-formed nuclei.

Thermal treatment of shock-modified theta-phase alumina, which initially contained about 30% alpha phase, showed a dramatic change in the rate of transformation to the alpha phase [90B01]. As shown in Fig. 7.13, the shocked sample showed no evidence for an incubation period and displayed a rapid conversion to the alpha phase, in sharp contrast to the unshocked sample. Such behavior clearly indicates that the shock process resulted in formation of larger concentrations of alpha-phase nuclei. 

At the end of the incubation period the fermentation culture mixture is adjusted to pH 2 with concentrated hydrochloric acid, the solid material present is removed by filtration, and the filter cake is washed with water. The washings are combined with the main filtrate, adjusted to pH 7.0, and 15.5 liters of the filtered culture liquid is introduced into a columnar exchanger d /a" i.d.) packed with 380 ml of carboxylic acid resin which has been preliminarily washed in succession with two liters of an aqueous solution of 37.5 grams of sodium hydroxide and with two liters of water. The column containing paromomycin is washed with two hold-up volumes of water and is eluted with 0.5 N hydrochloric acid. 

A spore sand culture containing Gibberella zeae (Gordon) NRRL-2830 was aseptically placed in a sterile tube containing 15 ml of Czapek s-Dox solution and a small amount of agar. This medium was then incubated for about 168 hours at approximately 25°C. At the end of the incubation period, the medium was washed with 5 ml of steriledeionized water and transferred to a sterile tube containing 45 ml of Czapek s-Dox solution. The contents of the tube were then incubated for about 96 hours at about 25°C after which the material was available for use in inoculation of a fermentation medium. 

Any test (several such tests are used) in which time to failure of smooth specimens is determined is an overall measure of the incubation period to initiate a crack, the ability to resist the propagation of a stress corrosion crack and the ability to resist final mechanical fracture. Since this test does not indicate the relative merits of an alloy in each individual aspect of the... 

When corrosion of a chromium-coated metal takes place, the corroding current concentrates its action on fissures in the deposit. There appears to be an incubation period, after which rapid attack occurs in the form of pits, and... 

S.C.C. has received a share of the potentiostatic approach to corrosion. Barnartt and van Rooyen reported that potentiostatically controlled corrosion in a potential range 50-100 mV above the corrosion potential provided an accelerated test for the s.c.c. of stainless steels. The elevation of the potential by means of a potentiostat eliminated the incubation period, and also increased the density of cracks. Booth and Tucker used potentiostatic methods in the s.c.c. of Al-Mg alloys. 

E. coli can easily grow on corn steep liquor with phosphate buffer for an incubation period of 3 days. Lysine is an essential amino acid for the nutrition of humans, which is used as a... 

In the manufacture of baker s yeast, the stock strain is inoculated into a medium that containing molasses and com steep liquor. The pH of the medium is adjusted to be slightly acidic at pH 4-5. The acidic pH may retard the bacterial growth. The inoculated medium is aerated during the incubation period. At the end, the cells are harvested by centrifuging out the fermentation broth, and they are recovered by filter press. A small amount of vegetable oil is added to act as plasticiser, and then the cell mass is moulded into blocks. The process is shown in Figure 1.2. 

Retroviruses Human T-cell leukaemia virus (HTLV-1) Spherical enveloped virus lOOnm in diameter, icosahedral cores contain two copies of linear RNA molecules and reverse transcriptase HTI.V is spread inside infected lymphocytes in blood, semen or breast milk. Most infections remain asymptomatic but after an incubation period of 10-40 years in about 2% of cases, adult T-cell leukaemia can result... 

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