Authenticated LSM Trees with Minimal Trust

In the age of user-generated contents, the workloads imposed on information-security infrastructures become increasingly write-intensive. How- ever, existing security protocols, specifically authenticated data structures (ADSs), are historically designed based on update-in-place data structures and incur overhead when serving write-intensive workloads. In this work, we present LPAD (Log-structured Persistent Authenticated Directory), a new ADS protocol designed uniquely based on the log-structured merge trees (LSM trees) which recently gained popularity in the design of modern storage systems. On the write path, LPAD supports streaming, non-interactive updates with constant proof from trusted data owners. On the read path, LPAD supports point queries over the dynamic dataset with polynomial proof. The key to enable this efficiency is a verifiable reorganization operation, called verifiable merge, in LPAD. Verifiable merge is secured by the execution in an enclave of trusted execution environments (TEE). To minimize the trusted computing base (TCB), LPAD places the code related to verifiable merge in enclave, and nothing else. Our implementation of LPAD on Google LevelDB codebase and on Intel SGX shows that the TCB is reduced by 20 times: The enclave size of LPAD is one thousand code lines out of more than twenty thousands code lines of a vanilla LevelDB. Under the YCSB workloads, LPAD improves the performance by an order of magnitude compared with that of existing update-in-place ADSs

Helicobacter pylori infection and circulating ghrelin levels - A systematic review

BACKGROUND: The nature of the association between ghrelin, an orexigenic hormone produced mainly in the stomach, and Helicobacter pylori (H pylori), a bacterium that colonises the stomach, is still controversial. We examined available evidence to determine whether an association exists between the two; and if one exists, in what direction. METHODS: We reviewed original English language studies on humans reporting circulating ghrelin levels in H pylori infected and un-infected participants; and circulating ghrelin levels before and after H pylori eradication. Meta-analyses were conducted for eligible studies by combining study specific estimates using the inverse variance method with weighted average for continuous outcomes in a random effects model. RESULTS: Seventeen out of 27 papers that reported ghrelin levels in H pylori positive and negative subjects found lower circulating ghrelin levels in H pylori positive subjects; while 10 found no difference. A meta-analysis of 19 studies with a total of 1801 participants showed a significantly higher circulating ghrelin concentration in H pylori negative participants than in H pylori positive participants (Effect estimate (95%CI) = -0.48 (-0.60, -0.36)). However, eradicating H pylori did not have any significant effect on circulating ghrelin levels (Effect estimate (95% CI) = 0.08 (-0.33, 0.16); Test for overall effect: Z = 0.67 (P = 0.5)). CONCLUSIONS: We conclude that circulating ghrelin levels are lower in H pylori infected people compared to those not infected; but the relationship between circulating ghrelin and eradication of H pylori is more complex

Randomized competitive algorithms for successful and unsuccessful search

This paper studies the classical dictionary problem using a self-adjusting linear list. We designed and analyzed randomized, on-line algorithms for a sequence of successful and unsuccessful searches which are competitive with off-line algorithms. Our algorithms combined the ps bit technique which speeds up unsuccessful search with the randomized move-to-front scheme of Reingold et al., which they used to speed up successful search.link_to_subscribed_fulltex

Parenting practices and prospective levels of hyperactivity/inattention across early- and middle-childhood

This study examined specific parenting practices as predictors of prospective levels of children’s hyperactivity/inattention across early- and middle-childhood. Participants were a mixed-sex community cohort (N = 976; 52 % boys) aged 4–10 years (M = 6.5, SD = 1.3). Measures of parenting practices, hyperactivity/inattention, conduct problems, and maternal education were collected at baseline, and hyperactivity/inattention re-assessed at 12-month follow-up. Analyses examined predictors of 12-month hyperactivity/inattention while controlling for levels at baseline. High levels of parental involvement were associated with reduced levels of hyperactivity/inattention, but only across early childhood. Conversely, increases in child age were associated with increased levels of hyperactivity/inattention across middle-childhood, but only among children exposed to high levels of inconsistent discipline. Inconsistent discipline and parental involvement appear to be uniquely associated with prospective hyperactivity/inattention across childhood, independent of associated conduct problems. Our results further suggest some developmental specificity with regard to the effects of these distinct dimensions of parenting on hyperactivity/inattention at different points in childhood

Labels of love: How migrants negotiate (or not) the culture of sexual identity

Drawing on in-depth interviews with 10 French lesbians, gays and bisex-uals (LGBs) living in the United States and 13 American LGBs living in France, this article examines how national cultural context shapes the way LGBs understand and frame their sexual identity. The meaning these mostly White middle-class migrants attributed to their sexual identity was revealed-and in some cases changed-through cultural mechanisms provoked by crossing borders. Their journey gave them a unique perspective on the dominant national understandings of sexual identity in both countries. Through interaction, they discovered on the one hand, the French cultural expectations that individuals downplay their differences in the public sphere, and on the other, American cultural expectations that individuals align themselves with a minority category in the public sphere. As theories on the relationship between sexual identity and culture would predict, some respondents expressed feeling more comfortable with the sexual identity model of the country in which they came to embrace their sexuality. Half, however, preferred the model of the new context. These findings suggest that further theorization is necessary to understand why sexual identity appears to be highly contingent on culture for some people but seemingly independent of it for others