Revisiting the Asian second-generation advantage: response to comment by L.J Zigerell

In his critical comment, Zigerell focuses on three related, yet distinct, claims in our work. First, second-generation Asians are over-credentialed in education to achieve professional parity with whites. Second, second-generation Asians' educational advantage over whites disappears in the labour market where Asians are only as likely as whites to attain a managerial or professional occupation. Third, second-generation Asians might face a bamboo ceiling in the workplace, not unlike the glass ceiling that women face. In this rejoinder, we argue that Zigerell conflates these three distinct claims, and the conflation of these claims underlies his criticism of our work. As a result, his criticism fails to negate the substantive conclusion of our research.     

克隆植物中的劳动分工及其生态学效应

劳动分工是经济进步的发动机,克隆植物也具有与经济学相类似的劳动分工现象。环境异质性、分株专化与合作以及分株潜在的生长独立性是克隆植物劳动分工发生的基本条件。根据发生条件可以把克隆植物劳动分工分为环境诱导型和遗传型两种。克隆植物能够通过利用形态或生理可塑性和生理整合、劳动分工机制实现对生境中异质性资源的有效利用。克隆植物劳动分工的生态学效应在于：提高对局部资源的摄食效率、克服局域资源限制、实现生物量的增益与适合度的提升,上述效应的机理可以用经济学边际成本分析和规模报酬规律来解释。同时,劳动分工还能提高种间竞争力、增强觅食有效性、减弱种内自疏,但同时,克隆植物在不稳定环境下的劳动分工效应也会增加生存风险。随着现代生物学研究手段的不断应用,有关克隆植物劳动分工的研究将会得到更加深入的发展。     

富含脯氨酸小蛋白-2在小鼠子宫中的表达及调节

富含脯氨酸小蛋白(Sprrs)参与构建复层扁平上皮的角化细胞壳（CE）,它们在子宫单层上皮中的作用还不清楚.采用RNA印迹和半定量RT-PCR方法,研究了Sprr2在小鼠动情周期和妊娠子宫中的表达及其激素调控.实验结果发现:Sprr2在动情前期和动情期表达上调,而动情后期和间情期表达下调.在妊娠初期表达迅速下调,直至临产期表达重新受到诱导并在产后达到高峰.鉴于其在不同生殖阶段子宫中独特的表达模式和在复层上皮中保护性的功能,推测Sprr2与子宫对交配和分娩所产生的应激反应有关.     

When does division of labor lead to increased system output?

This paper develops a set of simplified dynamical models with which to explore the conditions under which division of labor leads to optimized system output, as measured by the rate of production of a given product. We consider two models: in the first model, we consider the flow of some resource into a compartment, and the conversion of this resource into some product. In the second model, we consider the growth of autoreplicating systems. In this case, we divide the replication and metabolic tasks among different agents. The general features that emerge from our models is that division of labor is favored when the resource to agent ratio is at intermediate values, and when the time cost associated with transporting intermediate products is small compared to characteristic process times. The results of our model are consistent with the behavior of the cellular slime mold Dictyostelium discodeum, which switches from a single-celled to a multi-celled state when resources become limited. We also argue that division of labor in the context of our replication model suggests an evolutionary basis for the emergence of the stem-cell-based tissue architecture in complex organisms. Finally, the results of this paper may be useful for understanding how, in an economic context, firm productivity is maximized at intermediate firm sizes.     

Perceptual differences in trail-following leaf-cutting ants relate to body size

Leaf-cutting ants of the genus Atta have highly size-polymorphic workers, and size is related to division of labor. We studied trail-following behavior of different-sized workers in a laboratory colony of Atta vollenweideri. For small and large workers, we measured responsiveness and preference to artificial conspecific and heterospecific pheromone trails made from poison gland extracts of A. vollenweideri and A. sexdens. Responsiveness was measured as the probability of trail-following, and preference was measured by testing the discrimination between one conspecific and one heterospecific trail. Minute amounts of the releaser component methyl-4-methylpyrrole-2-carboxylate (0.4pg/1m), present in both, conspecific and heterospecific trails, suffice to elicit trail-following behavior. Workers followed heterospecific trails, and these trails (after normalizing their concentration) were as effective as conspecific trails. Small workers were less likely to follow a trail of a given concentration than large workers. In the discrimination test, small workers preferred the conspecific trail over the heterospecific trail, whereas large workers showed no significant preference. It is suggested that large workers primarily respond to the releaser component present in both trails, whereas small workers focus more on the conspecific traits provided by the blend of components contained in the trail pheromone.     

递增负荷运动对不同海拔高原人群通气量与心率变化的影响*

目的: 分析不同海拔高原人群在递增负荷运动情况下的通气量与心率的变化特征,探讨其作为高原体力劳动强度分级评价指标的可行性。方法: 选取高原习服男性青年军人88名,平均年龄21.7±1.6。其中3 000 m 30人,3 700 m 30人,4 300 m 28人,进行递增负荷踏车运动,运动负荷从30 W开始,每5 min增加30 W,直到不能坚持则停止运动。采用COSMED K5运动肺功能仪测量每一运动负荷的肺通气量,POLAR V800心率表测量每一运动负荷的运动心率。结果: 不同海拔递增负荷运动中完成最大负荷的人数具有显著差异(P＜0.05),海拔越高,完成人数越少。同一海拔,不同负荷之间,随着负荷的增加,通气量与心率明显增大(P＜0.05),且无上限值;同一负荷,随海拔增加,通气量与心率也明显增大(P＜0.05)。结论: 通气量与心率具有作为高原体力劳动强度分级评价指标的可行性。     

The effects of methyl palmitate,a putative regulator from perivascular fat,on the contractility of pregnant human myometrium

Aims

Methyl palmitate is thought to cause relaxation in vascular smooth muscle by opening voltage-activated potassium channels. We have tested the hypothesis that methyl palmitate, a putative regulator from perivascular fat, is an inhibitor of the contractility of human pregnant myometrium and that its effects might partially explain the higher incidence of dysfunctional labor in obese women compared to those with normal body mass indices.

Main methods

Strips of myometrium obtained with informed consent from women undergoing elective cesarean section at term were mounted in organ baths. Strips stimulated with oxytocin (1 nM) or KCl (30 mM) were exposed to cumulatively increasing concentrations of methyl palmitate up to 10 μM. Similar strips were exposed to cumulative addition of the potassium channel blockers 4-aminopyridine and tetraethylammonium. The contractility of the strips was monitored and analyzed using conventional methods.

Key findings

Methyl palmitate failed to inhibit oxytocin- or KCl-induced contractions over the concentration range tested. In fact, it exerted a slight excitatory effect in the presence of KCl, though not in the presence of oxytocin. The contractility of naïve strips was unaltered by exposure to 1 μM methyl palmitate. Both 4-aminopyridine and tetraethylammonium produced concentration-dependent contractions of human pregnant myometrium providing pharmacological evidence for the presence of voltage-activated potassium channels in this preparation.

Significance

Our findings do not support the hypothesis that methyl palmitate is an inhibitor of human pregnant myometrial contractility. Alternate hypotheses must be pursued to explain the higher incidence of dysfunctional labor in obese women.     

Fine Individual Specialization and Elitism among Workers of the Ant Ectatomma tuberculatum for a Highly Specific Task: Intruder Removal

Insect societies are characterized by a relatively sophisticated division of labor; they form tightly knit groups that must effectively exclude non‐members from the colony. However, the Neotropical predatory ant Ectatomma tuberculatum can harbor several specific myrmecophiles and, in particular, various eucharitid parasitoid wasp species. Adult wasps eclose in the host nests and are removed by worker ants without harm. Previous observations suggest that only a few workers perform this task. To test this hypothesis, we introduced different types of intruders, live and dead, pentane‐washed broad‐nosed grain weevil individuals (Caulophilus oryzae) and dead, pentane‐washed eucharitids (Dilocantha lachaudii), into laboratory colonies containing individually marked workers. We recorded all encounters and behaviors until the intruders were removed. Certain workers removed intruders more frequently than expected by chance. The number of encounters with an intruder was positively correlated with the number of removals performed by the workers. For each nest, a small group of workers was identified as specialized in intruder removal. A subset of very committed workers in the specialists group that performed up to 57% of removals qualified as hyperspecialists or elite workers. The behavioral sequences differed based on the type and condition of the intruder: the sequence was more complex and included numerous aggressive behaviors (mandibular strikes and attempts at stinging) when workers encountered a live weevil. In contrast, the behavioral sequences with dead, pentane‐washed insects were characterized by numerous detections through contact that did not lead to rejection and by the intruders simply being seized and removed from the nest. Overall, the data show that the ants discriminated between live and pentane‐washed intruders and adjusted their behavior accordingly. This is the first demonstration in ants of both behavioral specialization and hyperspecialization in intruder removal.     

The Organization of Male and Female Labor in Foraging Societies: Implications for Early Paleoindian Archaeology

I use cross-cultural ethnographic data to explore the relationship between male and female subsistence labor among hunter-gatherer populations by examining data regarding resource procurement, time allocation, and task differentiation between the sexes relative to dependence on hunted foods. The findings indicate that female foragers generally perform a variety of nonsubsistence collection activities and preferentially procure high-return resources in hunting-based economies. I develop ideas about predictable relationships concerning the amount of time female foragers expend on subsistence and technological tasks relative to the dietary contribution of meat. I then use ethnographic trends to evaluate archaeological assumptions regarding the sexual division of labor in prehistoric foraging contexts, focusing on the dichotomous views of Clovis labor organization. I argue that archaeological interpretations of prehistoric labor roles in hunting-based foraging societies are commonly polarized between stereotypical views of male and female subsistence behaviors. I develop an interpretation of Early Paleoindian labor organization, emphasizing female labor in the production of material goods and the procurement of low-risk plant and animal resources based on global economic trends among foragers.