Empowering statistical methods for cellular and molecular biologists.

We provide guidelines for using statistical methods to analyze the types of experiments reported in cellular and molecular biology journals such as Molecular Biology of the Cell. Our aim is to help experimentalists use these methods skillfully, avoid mistakes, and extract the maximum amount of information from their laboratory work. We focus on comparing the average values of control and experimental samples. A Supplemental Tutorial provides examples of how to analyze experimental data using R software

Now the wars are over: The past, present and future of Scottish battlefields

Battlefield archaeology has provided a new way of appreciating historic battlefields. This paper provides a summary of the long history of warfare and conflict in Scotland which has given rise to a large number of battlefield sites. Recent moves to highlight the archaeological importance of these sites, in the form of Historic Scotland’s Battlefields Inventory are discussed, along with some of the problems associated with the preservation and management of these important cultural sites

Experience with duplex bearings in narrow angle oscillating applications

Duplex ball bearings are matched pairs on which the abutting faces of the rings have been accurately ground so that when the rings are clamped together, a controlled amount of interference (preload) exists across the balls. These bearings are vulnerable to radial temperature gradients, blocking in oscillation and increased sensitivity to contamination. These conditions decrease the service life of these bearings. It was decided that an accelerated thermal vacuum life test should be conducted. The test apparatus and results are described and the rationale is presented for reducing a multiyear life test on oil lubricated bearings to less than a year

Baby-Step Giant-Step Algorithms for the Symmetric Group

We study discrete logarithms in the setting of group actions. Suppose that $G$ is a group that acts on a set $S$. When $r,s \in S$, a solution $g \in G$ to $r^g = s$ can be thought of as a kind of logarithm. In this paper, we study the case where $G = S_n$, and develop analogs to the Shanks baby-step / giant-step procedure for ordinary discrete logarithms. Specifically, we compute two sets $A, B \subseteq S_n$ such that every permutation of $S_n$ can be written as a product $ab$ of elements $a \in A$ and $b \in B$. Our deterministic procedure is optimal up to constant factors, in the sense that $A$ and $B$ can be computed in optimal asymptotic complexity, and $|A|$ and $|B|$ are a small constant from $\sqrt{n!}$ in size. We also analyze randomized "collision" algorithms for the same problem

Testing for sexually transmitted infections among students: a discrete choice experiment of service preferences

Objectives To assess preferences among students for sexually transmitted infection (STI) testing services, with a view to establishing strength of preference for different service attributes. Design Online discrete choice experiment (DCE) questionnaire. Setting South East of England. Participants A convenience sample of 233 students from two universities. Outcomes Adjusted ORs in relation to service characteristics. Results The study yielded 233 responses. Respondents’ ages ranged from 16 to 34 years with a mean age of 22 years. Among this sample, the respondents demonstrated strong preferences for a testing service which provided tests for all STIs including syphilis, herpes and HIV (OR 4.1; 95% CI 3.36 to 4.90) and centres staffed by a doctor or nurse with specialist knowledge of STIs (OR 2.1; 95% CI 1.78 to 2.37). Receiving all test results, whether positive or negative, was also significantly preferable to not being notified when tests were all negative (‘no news is good news’; OR 1.3; 95% CI 1.16 to 1.5). The length of time waiting for an appointment and the method by which results are received were not significant service characteristics in terms of preferences. Patient level characteristics such as age, sex and previous testing experience did not predict the likelihood of testing. Conclusions This study demonstrates that of the examined attributes, university students expressed the strongest preference for a comprehensive testing service. The next strongest preferences were for being tested by specialist STI staff and receiving negative as well as positive test results. However, it remains unclear how strong these preferences are in relation to characteristics which were not part of the study design and whether or not they are cost-effective

Robust estimation of stationary continuous-time ARMA models via indirect inference

In this paper we present a robust estimator for the parameters of a continuous-time ARMA(p,q) (CARMA(p,q)) process sampled equidistantly which is not necessarily Gaussian. Therefore, an indirect estimation procedure is used. It is an indirect estimation because we first estimate the parameters of the auxiliary AR(r) representation ($r\geq 2p-1$) of the sampled CARMA process using a generalized M- (GM-)estimator. Since the map which maps the parameters of the auxiliary AR(r) representation to the parameters of the CARMA process is not given explicitly, a separate simulation part is necessary where the parameters of the AR(r) representation are estimated from simulated CARMA processes. Then, the parameter which takes the minimum distance between the estimated AR parameters and the simulated AR parameters gives an estimator for the CARMA parameters. First, we show that under some standard assumptions the GM-estimator for the AR(r) parameters is consistent and asymptotically normally distributed. Next, we prove that the indirect estimator is consistent and asymptotically normally distributed as well using in the simulation part the asymptotically normally distributed LS-estimator. The indirect estimator satisfies several important robustness properties such as weak resistance, $\pi_{d_n}$-robustness and it has a bounded influence functional. The practical applicability of our method is demonstrated through a simulation study with replacement outliers and compared to the non-robust quasi-maximum-likelihood estimation method

Preliminary investigation of pressure influence on multiphase heat transfer report no. ii

Pressure and surface condition in multiphase boiling heat transfe