基于Runtime的iOS编程研究与实现

在iOS开发过程中,因为系统自带方法对应的功能不足,使部分业务需求不能有效地实现.为此,首先对Runtime库的主要API接口用途进行了研究,找到可利用的接口;然后对Runtime消息转发机制进行研究,证明函数调用的实质就是消息的传递;最后通过实际案例,证明了应用Runtime可以解决系统方法不足的问题.结果 表明,通...     

The first cleavage of the mouse zygote predicts the blastocyst axis

One of the unanswered questions in mammalian development is how the embryonic-abembryonic axis of the blastocyst is first established. It is possible that the first cleavage division contributes to this process, because in most mouse embryos the progeny of one two-cell blastomere primarily populate the embryonic part of the blastocyst and the progeny of its sister populate the abembryonic part. However, it is not known whether the embryonic-abembryonic axis is set up by the first cleavage itself, by polarity in the oocyte that then sets the first cleavage plane with respect to the animal pole, or indeed whether it can be divorced entirely from the first cleavage and established in relation to the animal pole. Here we test the importance of the orientation of the first cleavage by imposing an elongated shape on the zygote so that the division no longer passes close to the animal pole, marked by the second polar body. Non-invasive lineage tracing shows that even when the first cleavage occurs along the short axis imposed by this experimental treatment, the progeny of the resulting two-cell blastomeres tend to populate the respective embryonic and abembryonic parts of the blastocyst. Thus, the first cleavage contributes to breaking the symmetry of the embryo, generating blastomeres with different developmental characteristics.     

Behavioural ecology: bees associate warmth with floral colour

Floral colour signals are used by pollinators as predictors of nutritional rewards, such as nectar. But as insect pollinators often need to invest energy to maintain their body temperature above the ambient temperature, floral heat might also be perceived as a reward. Here we show that bumblebees (Bombus terrestris) prefer to visit warmer flowers and that they can learn to use colour to predict floral temperature before landing. In what could be a widespread floral adaptation, plants may modulate their temperature to encourage pollinators to visit.     

Human urotensin-II is a potent vasoconstrictor and agonist for the orphan receptor GPR14.

Urotensin-II (U-II) is a vasoactive 'somatostatin-like' cyclic peptide which was originally isolated from fish spinal cords, and which has recently been cloned from man. Here we describe the identification of an orphan human G-protein-coupled receptor homologous to rat GPR14 and expressed predominantly in cardiovascular tissue, which functions as a U-II receptor. Goby and human U-II bind to recombinant human GPR14 with high affinity, and the binding is functionally coupled to calcium mobilization. Human U-II is found within both vascular and cardiac tissue (including coronary atheroma) and effectively constricts isolated arteries from non-human primates. The potency of vasoconstriction of U-II is an order of magnitude greater than that of endothelin-1, making human U-II the most potent mammalian vasoconstrictor identified so far. In vivo, human U-II markedly increases total peripheral resistance in anaesthetized non-human primates, a response associated with profound cardiac contractile dysfunction. Furthermore, as U-II immunoreactivity is also found within central nervous system and endocrine tissues, it may have additional activities.     

Unique sex chromosome mediated behavioral response specificity of hybrid male European corn borer moths

Unlike the narrow response windows exhibited by the parent races, hybrid male European corn borers resulting from crosses of the E and Z races respond to a wide range of sex pheromone blends. The F₁ response profile consists of some individuals that respond to both the Z pheromone and the 6535 E/Z blend produced by F₁ females. Some F₁ males fail to respond to any blend and some do not respond as broadly as others. The hybrid male populations, however, are not tuned optimally to the pheromone blend produced by F₁ females and there is no coupling of F₁ blend production and response.     

Sustainability of three apple production systems

Escalating production costs, heavy reliance on non-renewable resources, reduced biodiversity, water contamination, chemical residues in food, soil degradation and health risks to farm workers handling pesticides all bring into question the sustainability of conventional farming systems. It has been claimed, however, that organic farming systems are less efficient, pose greater health risks and produce half the yields of conventional farming systems. Nevertheless, organic farming became one of the fastest growing segments of US and European agriculture during the 1990s. Integrated farming, using a combination of organic and conventional techniques, has been successfully adopted on a wide scale in Europe. Here we report the sustainability of organic, conventional and integrated apple production systems in Washington State from 1994 to 1999. All three systems gave similar apple yields. The organic and integrated systems had higher soil quality and potentially lower negative environmental impact than the conventional system. When compared with the conventional and integrated systems, the organic system produced sweeter and less tart apples, higher profitability and greater energy efficiency. Our data indicate that the organic system ranked first in environmental and economic sustainability, the integrated system second and the conventional system last.     

Pheromone behavioral responses in unusual male European corn borer hybrid progeny not correlated to electrophysiological phenotypes of their pheromone-specific antennal neurons

In genetic studies on the sex pheromone communication system of two races of European corn borer, which use opposite pheromone blends of the E and Z compounds, it was found that antennal olfactory cell response amplitudes to the two compounds were controlled by an autosomal factor, whereas behavioral responses to the blends were controlled by a sex-linked locus. Because of the difference in genetic controls, it was postulated that some unusual males would be produced in F₂ crosses between these two races. These unusual males would have antennal olfactory cells that respond as the Z-race males, but would respond behaviorally to the E blend. The present studies combined behavioral studies in a flight tunnel and single cell electrophysiological studies to show that these unusual males do indeed exist. These findings show that the spike amplitude of peripheral olfactory cells is not important in regulating species- or race-specific pheromone responses, as compared to some central nervous system factor assesses the spike frequencies from different pheromone-component-specific cells on the antenna. This factor seems to be essential in governing the pheromone-blend specific behavioral responses of male moths.