Assortative Mixing Equilibria in Social Network Games

It is known that individuals in social networks tend to exhibit homophily (a.k.a. assortative mixing) in their social ties, which implies that they prefer bonding with others of their own kind. But what are the reasons for this phenomenon? Is it that such relations are more convenient and easier to maintain? Or are there also some more tangible benefits to be gained from this collective behaviour? The current work takes a game-theoretic perspective on this phenomenon, and studies the conditions under which different assortative mixing strategies lead to equilibrium in an evolving social network. We focus on a biased preferential attachment model where the strategy of each group (e.g., political or social minority) determines the level of bias of its members toward other group members and non-members. Our first result is that if the utility function that the group attempts to maximize is the degree centrality of the group, interpreted as the sum of degrees of the group members in the network, then the only strategy achieving Nash equilibrium is a perfect homophily, which implies that cooperation with other groups is harmful to this utility function. A second, and perhaps more surprising, result is that if a reward for inter-group cooperation is added to the utility function (e.g., externally enforced by an authority as a regulation), then there are only two possible equilibria, namely, perfect homophily or perfect heterophily, and it is possible to characterize their feasibility spaces. Interestingly, these results hold regardless of the minority-majority ratio in the population. We believe that these results, as well as the game-theoretic perspective presented herein, may contribute to a better understanding of the forces that shape the groups and communities of our society

School Dropouts and Conditional Cash Transfers: Evidence from a Randomized Controlled Trial in Rural China’s Junior High Schools.

Recent anecdotal reports suggest that dropout rates may be higher and actually increasing over time in poor rural areas. There are many reasons not to be surprised that there is a dropout problem, given the fact that China has a high level of poverty among the rural population, a highly competitive education system and rapidly increasing wages for unskilled workers. The overall goal of this study is to examine if there is a dropout problem in rural China and to explore the effectiveness that a Conditional Cash Transfer (CCT) program could have on dropouts (and mechanism by which the CCT might affect drop outs). To meet this objective, we conducted a randomized controlled trial (RCT) of a CCT using a sample of 300 junior high school students in a nationally-designated poor county in Northwest China. Using our data, we found that the annual dropout rate in the study county was high, about 7%. We find, however, that a CCT program reduces drop outs by 60%; the dropout rate is 13.3% in the control group and 5.3 % in the treatment group. The program is most effective in the case of girls, younger students and the poorest performing students.

School dropouts and conditional cash transfers: evidence from a randomized controlled trial in rural China's junior high schools.

Recent anecdotal reports suggest that dropout rates may be higher and actually increasing over time in poor rural areas. There are many reasons not to be surprised that there is a dropout problem, given the fact that China has a high level of poverty among the rural population, a highly competitive education system and rapidly increasing wages for unskilled workers. The overall goal of this study is to examine if there is a dropout problem in rural China and to explore the effectiveness that a Conditional Cash Transfer (CCT) program could have on dropouts (and mechanism by which the CCT might affect drop outs). To meet this objective, we conducted a randomized controlled trial (RCT) of a CCT using a sample of 300 junior high school students in a nationally-designated poor county in Northwest China. Using our data, we found that the annual dropout rate in the study county was high, about 7.0%. We find, however, that a CCT program reduces drop outs by 60%; the dropout rate is 13.3% in the control group and 5.3 % in the treatment group. The program is most effective in the case of girls, younger students and the poorest performing students.

Do Poor Students Benefit from China’s Merger Program? Transfer Path and Educational Performance.

Aiming to provide better education facilities and improve the educational attainment of poor rural students, China’s government has been merging remote rural primary schools to centralized village, town, or county schools since the late 1990s. To accompany the policy, boarding facilities have been constructed that allow (mandate) primary school-aged children to live at school rather than at home. More generally, there also have been efforts to improve rural schools, especially those in counties and towns. Unfortunately, little empirical work has been available to evaluate the impact of the new merger and investment programs on the educational performance of students. Drawing on a unique dataset that records both the path by which students navigate their primary school years (i.e., which different types of schools did students attend) as well as math test scores in three poverty-stricken counties, we use descriptive statistics and multivariate analysis (both OLS and covariate matching) to analyze the relationship between different transfer paths and student educational performance. This allows us to examine the costs and benefits of the school merger and investment programs. The results of the analysis show that students who attend county schools perform systematically better than those attend village or town schools. However, completing primary school in town schools seems to have no effect on students’ academic performance. Surprisingly, starting primary education in a teaching point does not hurt rural students; on the contrary, it increases their test scores in some cases. Finally, in terms of the boarding effect, the neutral estimate in OLS and the negative estimate in covariate matching results confirm that boarding at school does not help the students; in some cases it may even reduce their academic performance.

ENDOLYN SORTING AND FUNCTION DURING KIDNEY DEVELOPMENT

The polarity of epithelial cells is critical for proper function. Maintenance of polarity requires sustained proper sorting of proteins and lipids to either apical or basolateral membranes using distinct sorting signals. Compared to basolateral sorting signals, apical signals are not well characterized and can be present within the lumenal, transmembrane, or cytosolic regions of the protein. N-glycosylation has been identified as one of the apical sorting signals. The sialomucin endolyn (CD164) is a transmembrane protein that contains an apical sorting signal (N-glycans) in the lumenal domain and a lysosomal/basolateral targeting signal (YXXØ motif) in its cytoplasmic tail. It cycles between the apical surface and lysosomes of renal epithelial cells and is expressed in embryonic and adult kidney. The first objective of this research was to dissect the specific determinant on N-glycosylation for endolyn apical sorting using a lipofectamine-mediated RNAi approach. The results demonstrated that sialylation but not branching of N-glycans is required for endolyn proper delivery. Futher, knockdown of galectin-9 (but not galectins 3, 4 or 8) selectively disrupted endolyn polarity suggesting that interaction between endolyn and galectin-9 is critical for endolyn apical delivery. Next, the function of endolyn in pronephric kidney was investigated during development using zebrafish as a model system. Knockdown of zebrafish endolyn using a translational inhibiting morpholino resulted in pericardial edema, hydrocephaly, and body curvature, suggesting a possible osmoregulation defect. Although the pronephric kidney appeared normal morphologically, clearance of fluorescent dextran was delayed, indicating an imbalance in water regulation in morphant embryos. Rescue experiments using rat endolyn mRNA revealed that both apical sorting and endocytic/lysosomal targeting are required for endolyn function during development of the zebrafish pronephric kidney. This work broadens our understanding of apical sorting mechanisms in polarized cells as well as its significance on kidney function and development

Shoshonitic enclaves in the high Sr/Y Nyemo pluton, southern Tibet: Implications for Oligocene magma mixing and the onset of extension of the southern Lhasa terrane

Post-collisional potassic and high Sr/Y magmatism in the Lhasa terrane provides critical constraints on the timing and mechanism of subduction of Indian lithosphere and its role in the uplift of the Tibetan Plateau. Here, we report whole-rock geochemistry, mineral geochemistry, zircon U Pb ages, and in situ zircon Hf isotope ratios for the Nyemo pluton, a representative example of such magmatism. The Nyemo pluton is composed of high Sr/Y host rocks and coeval shoshonitic mafic microgranular enclaves (MMEs). Whole-rock compositions of the host rocks and MMEs form linear trends in Harker diagrams, consistent with modification of both end-members by magma mixing. Although the main high Sr/Y phase of the pluton formed by partial melting of the lower crust of the thickened Lhasa terrane, the MMEs display abnormally enriched light rare earth elements, low whole-rock ε_(Nd)(t) and low zircon ε_(Hf)(t) that suggest derivation from low degree melting of hydrous and enriched mantle. Based on the occurrence of shoshonitic magma and high La/Yb and high Sr/Y with adakitic affinity host rocks around 30 Ma, the Nyemo pluton is best explained as a record of onset of extension that resulted from convective removal of the mantle lithosphere beneath Tibet in the Oligocene

New Developments in Aromatic Halogenation, Borylation, and Cyanation

Several green procedures have been developed for synthesizing functionalized aromatics: i) AuCl3-catalyzed halogenation of aromatic compounds, including aryl boronates; ii) Fe2O3-catalyzed direct aromatic C–H bond borylation; iii) Pd-catalyzed direct cyanation of indoles; iv) direct conversion of arylamines to pinacol boronates