Effects of Oral Repetition on Learners’ Japanese Word Accentuation

Japanese word accentuation is a problematic area for learnersunfamiliar with a pitch accent system. Since accent locations areunpredictable, learners are typically told to memorize them by rote,which is a time-consuming, tedious, and demanding task. It wouldcertainly be ideal for learners to learn correct accentuation withoutexplicit instruction as they learn new words. This article reports on apreliminary study that examined effects of a computer-based onlineword repetition exercise on the learning of Japanese wordaccentuation. 41 students in their 10th week and 17 students in their12th week in a 2nd-year 1st-semester Japanese course took a pretest,followed by computer-based online word repetition practice on theSpeak Everywhere system, a posttest immediately after the practice,and a delayed posttest after one week (class-and-computer condition).Out of the same group of students now in a 2nd-year 2nd-semestercourse, 22 students took a pretest, followed by two posttests in their 5thweek (class-only condition). A paired t-test (two tailed) performed on13 overlapping subjects found a significant difference between the twoconditions (t=5.58, p<.001, Cohen’s d =1.9309). The online word repetition practice produced a significant gain in accentuation scores without explicit instruction, while classroom instruction alone was not sufficient to produce a significant gain

Modeling peculiar velocities of dark matter halos

We present a simple model that accurately describes various statistical properties of peculiar velocities of dark matter halos. We pay particular attention to the following two effects; first, the evolution of the halo peculiar velocity depends on the local matter density, instead of the global density. Second, dark matter halos are biased tracers of the underlying mass distribution, thus halos tend to be located preferentially at high density regions. For the former, we develop an empirical model calibrated with N-body simulations, while for the latter, we use a conventional halo bias models based on the extended Press-Schechter model combined with an empirical log-normal probability distribution function of the mass density distribution. We find that compared with linear theory, the present model significantly improves the accuracy of predictions of statistical properties of the halo peculiar velocity field including the velocity dispersion, the probability distribution function, and the pairwise velocity dispersion at large separations. Thus our model predictions may be useful in analyzing future observations of the peculiar velocities of galaxy clusters.Comment: This paper was published in MNRAS, 343, 1312 (2003). Owing to an error in numerical computations, some incorrect results were presented there. Erratum is to be published in MNRAS. Conclusions of the original version are unaffected by the correction. This version supersedes the original versio

Boneh-Boyen Signatures and the Strong Diffie-Hellman Problem

The Boneh-Boyen signature scheme is a short signature scheme which is provably secure in the standard model under the q-Strong Diffie-Hellman (SDH) assumption. The primary objective of this thesis is to examine the relationship between the Boneh-Boyen signature scheme and SDH. The secondary objective is to survey surrounding topics such as the generic group model, related signature schemes, intractability assumptions, and the relationship to identity-based encryption (IBE) schemes. Along these lines, we analyze the plausibility of the SDH assumption using the generic bilinear group model. We present the security proofs for the Boneh-Boyen signature scheme, with the addition of a small improvement in one of the probability bounds. Our main contribution is to give the reduction in the reverse direction; that is, to show that if the SDH problem can be solved then the Boneh-Boyen signature scheme can be forged. This contribution represents the first known proof of equivalence between the SDH problem and Boneh-Boyen signatures. We also discuss the algorithm of Cheon for solving the SDH problem. We analyze the implications of Cheon's algorithm for the security of the Boneh-Boyen signature scheme, accompanied by a brief discussion on how to counter the attack

A user study of off-the-record messaging

Instant messaging is a prevalent form of communication across the Internet, yet most instant messaging services provide little security against eavesdroppers or impersonators. There are a variety of systems that exist that aim to solve this problem, but the one that provides the highest level of privacy is Off-the-Record Messaging (OTR), which aims to give instant messaging conversations the level of privacy available in a face-to-face conversation. In the most recent redesign of OTR, as well as adding an added security feature, one of the goals of the designers was to make OTR easier to use without users needing to understand details of computer security such as keys or fingerprints. To determine if this design goal has been met, we conducted a user study of the OTR plugin for the Pidgin instant messaging client using the think aloud method. As a result of this study we have identified a variety of usability flaws remaining in the design of OTR. These flaws that we have discovered have the ability to cause confusion, make the program unusable, and even decrease the level of security to users of OTR. We discuss how these errors can be repaired, as well as identify an area that requires further research to improve its usability

Extracellular Vesicles in Periodontal Medicine : The Candidates Linking Oral Health to General Health

The term, periodontal medicine is used to describe the multitude of systemic diseases which are regarded to link periodontal disease. The concept of periodontal medicine has been widely accepted today, however, the molecular mechanisms which periodontal diseases impact general health in whole body are not elucidated in detail. Extracellular vesicles (EVs) and outer membrane vesicles (OMVs) are the nano-sized particles released from mammalian cells and bacterial cells resectively, which influence the health and various disease by transporting biological factors to the neighbor and distant cells. In this review, we will discuss whether EVs and OMVs produced in periodontal diseases could be implicated in periodontal medicine