The Influence of Casing-Sand Adhesion on Cementing Bond Strength.

In the petroleum industry, one of the most serious problems encountered during cementing is the failure at the bonding interface. Many measures including casing-sand adhesion have been developed to improve cementing bond strength. However, due to the lack of detailed study of the technique, many questions remain. The primary goal of this study is to investigate the influence of casing-sand adhesion on cementing bond strength, and to optimize parameters. An orthogonal experiment and a supplementary experiment were conducted. The results indicated that casing-sand adhesion can improve the cementing bond strength. The priority orders of key factors are: sand grain size, sand coverage, adhesive curing temperature and adhesive curing time. The optimal parameters recommended for application are: 1.6mm~1.9mm sand grain size, 60%~70% sand coverage, 30°C curing temperature and 60 hours curing time.

Action orientation overcomes the ego depletion effect.

It has been consistently demonstrated that initial exertion of self-control had negative influence on people's performance on subsequent self-control tasks. This phenomenon is referred to as the ego depletion effect. Based on action control theory, the current research investigated whether the ego depletion effect could be moderated by individuals' action versus state orientation. Our results showed that only state-oriented individuals exhibited ego depletion. For individuals with action orientation, however, their performance was not influenced by initial exertion of self-control. The beneficial effect of action orientation against ego depletion in our experiment results from its facilitation for adapting to the depleting task.

Adapting to an initial self-regulatory task cancels the ego depletion effect.

The resource-based model of self-regulation provides a pessimistic view of self-regulation that people are destined to lose their self-control after having engaged in any act of self-regulation because these acts deplete the limited resource that people need for successful self-regulation. The cognitive control theory, however, offers an alternative explanation and suggests that the depletion effect reflects switch costs between different cognitive control processes recruited to deal with demanding tasks. This account implies that the depletion effect will not occur once people have had the opportunity to adapt to the self-regulatory task initially engaged in. Consistent with this idea, the present study showed that engaging in a demanding task led to performance deficits on a subsequent self-regulatory task (i.e. the depletion effect) only when the initial demanding task was relatively short but not when it was long enough for participants to adapt. Our results were unrelated to self-efficacy, mood, and motivation.

[Arbitrary primed polymerase chain reaction for the genotypic identification of Streptococcus sanguis group].

OBJECTIVE: To find out an ideal method used in identification of Streptococcus sanguis group (SSG) strains by arbitrary primed polymerase chain reaction (AP-PCR). METHODS: AP-PCR was used to distinguish SSG strains by designing 25 bp arbitrary primer 5' AAG AGA GGA GCT AGC TCT TCT TGG A 3'. RESULTS: There were great differences in the main band of DNA polymorphism among SSG species. The similar band can be obtained from the different DNA extractions in the same species. CONCLUSION: AP-PCR may be useful in the identification and classification of SSG species.