We investigated labor- related plasticity in the circadian clock of the bumblebee Bombus terrestris. Bumblebee workers vary enormously in body size, and we found that size, division of labor, and diurnal rhythms in activity are correlated in B. terrestris colonies. Large workers typically perform foraging activities with strong diurnal rhythms and low activity at night, whereas small bees typically care for ( nurse) brood around the clock with weak or no diurnal rhythms. Under constant laboratory conditions, circadian rhythms in locomotor activity were weaker, less stable, and developed at a later age in small ( nurse- size) bees compared to their larger ( forager- size) sisters. Under a light: dark illumination regime, many small bees, particularly at a young age, were active during the dark phase, fewer small bees developed rhythms, and they did so later compared to large bees. Taken together these findings reveal naturally occurring attenuation or suppression in the circadian clock of small bees that is determined during pre- adult development. This deficiency in clock function, however, does not result in pathology but rather appears to be functionally significant, because it is associated with around- the- clock brood care activity and therefore apparently improves divisions of labor and colony efficiency. This in turn suggests that variation in social biology influences traits of the circadian clock.
Regular annuities provide payment for the duration of an owner's lifetime. Period-Certain annuities provide additional payment after death to a beneficiary provided the insured dies within a certain period after annuitization. It has been argued that the bequest option offered by the latter is dominated by life insurance which provides non-random bequests. This is correct if competitive annuity and life insurance markets have full information about individual longevities. In contrast, this paper shows that when individual longevities are private information, a competitive pooling equilibrium which offers annuities at common prices to all individuals may have positive amounts of both types of annuities in addition to life insurance. In this equilibrium, individuals self-select the types of annuities that they purchase according to their longevity prospects. The break-even price of each type of annuity reflects the average longevity of its buyers. The broad conclusion that emerges from this paper is that adverse-selection due to asymmetric information is reflected not only in the amounts of insurance purchased but, importantly, also in the choice of insurance products suitable for different individual characteristics. This conclusion is supported by recent empirical work about the UK annuity market (Finkelstein and Poterba (2004)).
Regular annuities provide payment for the duration of an owner’s lifetime. Period-Certain annuities provide additional payment after death to a beneficiary provided the insured dies within a certain period after annuitization. It has been argued that the bequest option offered by the latter is dominated by life insurance which provides non-random bequests. This is correct if competitive annuity and life insurance markets have full information about individual longevities. In contrast, this paper shows that when individual longevities are private information, a competitive pooling equilibrium which offers annuities at common prices to all individuals may have positive amounts of both types of annuities in addition to life insurance. In this equilibrium, individuals self-select the types of annuities that they purchase according to their longevity prospects. The break-even price of each type of annuity reflects the average longevity of its buyers. The broad conclusion that emerges from
Regular annuities provide payment for the duration of an owner’s lifetime. Period-Certain annuities provide additional payment after death to a beneficiary provided the insured dies within a certain period after annuitization. It has been argued that the bequest option offered by the latter is dominated by life insurance which provides non-random bequests. This is correct if competitive annuity and life insurance markets have full information about individual longevities. In contrast, this paper shows that when individual longevities are private information, a competitive pooling equilibrium which offers annuities at common prices to all individuals may have positive amounts of both types [...]
Regular annuities provide payment for the duration of an owner’s lifetime. Period-Certain annuities provide additional payment after death to a beneficiary provided the insured dies within a certain period after annuitization. It has been argued that the bequest option offered by the latter is dominated by life insurance which provides non-random bequests. This is correct if competitive annuity and life insurance markets have full information about individual longevities. In contrast, this paper shows that when individual longevities are private information, a competitive pooling equilibrium which offers annuities at common prices to all individuals may have positive amounts of both types of annuities in addition to life insurance. In this equilibrium, individuals self-select the types of annuities that they purchase according to their longevity prospects. The break-even price of each type of annuity reflects the average longevity of its buyers. The broad conclusion that emerges from
Oliver J Miller, Bernath, Kalia , Agresti, Jeremy J, Amitai, Gil , Kelly, Bernard T, Mastrobattista, Enrico , Taly, Valerie , Magdassi, Shlomo , Tawfik, Dan S, ו Griffiths, Andrew D. 2006. “Directed Evolution By In Vitro Compartmentalization.”. Nat. Methodsnature Methods, 3, Pp. 561 - 570. תקציר
The goal of in vitro compartmentalization (IVC) is to divide a large reaction between many microscopic compartments. This technique was first developed to generate "artificial cells" for the directed evolution of proteins. Typically, an aq. soln. of genes and an in vitro transcription-translation system is stirred (or homogenized) into an oil-surfactant mixt. to create a water-in-oil (w/o) emulsion with -1010 aq. droplets per mol of emulsion. The majority of droplets contain no more that a single gene along with all of the mol. machinery needed to express that gene. The expressed proteins and the products of their catalytic activities cannot leave the droplets, and so genotype is coupled to phenotype in vitro, making it possible to select very large libraries of genes (108-1011 genes). We describe the advantages and applications of IVC. A protocol for performing a directed evolution expt. by IVC makes use of one or more w/o emulsions. This procedure involves the generation of a gene library, the performance of a selection, and the subsequent recovery of the selected genes by PCR. We also describe two procedures for converting w/o emulsions to water-in-oil-in-water (w/o/w) emulsions for high-throughput screening using a fluorescence-activated cell sorter (FACS). Finally, we describe two methods for delivering substrates, regulators and other compds. to the preformed aq. droplets of w/o emulsion. [on SciFinder(R)]
The present invention provides an in vitro system for compartmentalization of large mol. libraries and provides methods for selection and isolation of mols. having desired activities from such libraries. The present invention provides novel and inventive applications of IVC for the selection of mols. being capable of modulating a particular activity of a known biol. active moiety, including, but not limited to an enzyme. The inventors of the present invention utilize a micelle delivery system that enables the transport of various solutes, including metal ions, into the emulsion droplets thereby inducing a desired activity of the known biol. active moiety or of the gene product. The present invention is based ion part on the unexpected finding that an IVC system can be used for directed evolution of nuclease inhibitors. In vitro compartmentalization (IVC) uses water-in-oil emulsions to create artificial cell-like compartments in which genes can be individually transcribed and translated. Here, the inventors present a new application of IVC for the selection of DNA-nuclease inhibitors. They developed a nano-droplets delivery system that allows the transport of various solutes, including metal ions, into the emulsion droplets. This transport mechanism was used to regulate the activity of colicin nucleases that were co-compartmentalized with the genes, so that the nucleases were activated by nickel or cobalt ions only after the potential inhibitor genes have been translated. They demonstrated its utility by selecting libraries of the gene encoding the cognate inhibitor of colicin E9 (immunity protein 9, or Im9) for inhibition of another colicin (ColE7). The in vitro evolved inhibitors show significant inhibition of ColE7 both in vitro and in vivo. These Im9 variants carry mutations into residues that det. the selectivity of the natural counterpart (Im7) while completely retaining the residues that are conserved throughout the family of immunity protein inhibitors. [on SciFinder(R)]
Gold-tipped CdSe rods (nanodumbbells) were solubilized in an aqueous phase and self-assembled in a head-to-tail manner using biotin disulfide and avidin. The disulfide end of the biotin molecule attaches to the gold tip of the nanodumbbell, and the biotin end of the molecule is able to conjugate to an avidin protein. The avidin can strongly conjugate up to four biotin molecules. Changing the ratios of biotin to nanodumbbells leads to the formation of dimers, trimers, and flowerlike structures. To further improve the distribution of chain lengths, a separation method based upon weight was applied using a concentration gradient. The gold tips provide effective anchor points for constructing complex nanorod structures by self-assembly.
Scholars have always found it tough to define what constitutes early modernity due to lack of exacting terms of reference and the awareness of the role of point of view when attempting to characterize the Middle Ages and modernity. An attempt is made to suggest plausible reasons why the term ’early modernity’ replaced the traditional terms ’Renaissance and Reformation’ and to point out different temporal boundaries between early modernity and the Middle Ages in historiography over the last forty years.
A class of integer-valued allocation games – "General Lotto games" – is introduced and solved. The results are then applied to analyze the classical discrete "Colonel Blotto games"; in particular, optimal strategies are obtained for all symmetric Colonel Blotto games.
Pure magnetite nanoparticles (Fe3O4) have been synthesized in water by copptn. using two different approaches (from ferrous sulfate and a mixt. of ferrous and ferric chlorides). All materials aggregated in aq. suspension, but their subsequent dispersion on treatment with a variety of agents was obsd. to be different. Magnetite produced using ferrous sulfate could not be disaggregated, whereas magnetite produced from a mixt. of ferrous and ferric chlorides could be disaggregated to a quasi-monodispersed form. The dispersing agents were tetra-Me ammonium hydroxide, Disperbyk 190 and polyacrylic acid. The finding has potentially important implications for the surface activation of superparamagnetic magnetite nanoparticles and their ability to be used in bio/life science applications. [on SciFinder(R)]
Proposals to cede Arab localities from Israeli to Palestinian sovereignty, presented as "populated land exchanges", involve forcibly revoking the citizenship of tens of thousands of Arabs. Since the October 2000 events these proposals penetrated the heart of public discourse. The Arab leadership and public vehemently oppose these proposals. This study examines the Jewish discourse supporting the idea alongside Arab opposition to it in Israel and the territories as well as its implications on the character of the State of Israel. It examines Israeli and international legal perspectives and demographic and territorial implications. The study emphasizes the danger and folly of this idea and recommends discussing the idea as part of the Arab-Jewish discourse and as part of the status of the Arab minority in a democratic Jewish state.
This study examines the impact of two concurrent processes on the Israeli-Palestinian conflict: the changing leadership and governmental reshuffle on the one hand and the Israeli disengagement on the other hand. The relationship between the Palestinian Authority and its residents are also examined as are the means used to present the Oslo Accords to them, and other functioning characteristics underlying the political stalemate. The Palestinian reactions to disengagement are considered, the power struggle developing among the various foci of power and the impacts on the inter-organizational relationship. The researcher attempts to point out possible directions of development in the Israeli-Palestinian relationship after the stabilization of the Palestinian government and the implementation of the disengagement program.
