Enhanced harmonic generation from Ar+ aligned with M =1

We investigate harmonic generation (HG) from ground-state Ar+ aligned with M=1 at a laser wavelength of 390-nm and intensity of 4x10(14) Wcm-2. Using time-dependent R-matrix theory, we find that an initial state with magnetic quantum number M=1 provides a 4-fold increase in harmonic yield over M=0. HG arises primarily from channels associated with the (3)Pe threshold of Ar2+, in contrast with M=0 for which channels associated with the excited, (1)De threshold dominate HG. Multichannel and multielectron interferences lead to a more marked suppression of HG for M=1 than M=0.Comment: 5 pages, 3 figures. Accepted by Phys. Rev.

The Neural Basis of Predicting the Outcomes of Imagined Actions

A key feature of human intelligence is the ability to predict the outcomes of one’s own actions prior to executing them. Action values are thought to be represented in part in the dorsal and ventral medial prefrontal cortex (mPFC), yet current studies have focused on the value of executed actions rather than the anticipated value of a planned action. Thus, little is known about the neural basis of how individuals think (or fail to think) about their actions and the potential consequences before they act. We scanned individuals with fMRI while they thought about performing actions that they knew would likely be rewarded or unrewarded. Here we show that merely imagining an unrewarded action, as opposed to imagining a rewarded action, increases activity in the dorsal anterior cingulate cortex, independently of subsequent actions. This activity overlaps with regions that respond to actual unrewarded actions. The findings show a distinct network that signals the prospective outcomes of one’s possible actions. A number of clinical disorders such as schizophrenia and drug abuse involve a failure to take the potential consequences of an action into account prior to acting. Our results thus suggest how dysfunctions of the mPFC may contribute to such failures

Errors in statistical analysis and questionable randomization lead to unreliable conclusions

Dear Editor,We read with interest the paper, “The effect of food service system modifications on staff body mass index in an industrial organization”[1]. We noticed several substantial issues with data and calculations, calling into question the randomized nature of the study and validity of analyses.The distribution of baseline weight was significantly differentbetween groups (p-value = “0.00”). We replicated the test using reported means and standard deviations (SDs) andobtained a p-value of approximately 1.9*10-17. It is extraordinarily unlikely that any variable would be that different between two groups if allocation was truly random. Even it was truly random, the stated method of “the samples were randomly divided into two groups”[1] does not describe the “method used to generate the random allocation sequence” and the “type of randomization; details of any restriction (such as blocking and block size)” details specified by Consolidated Standards of Reporting Trials (CONSORT)[2].Given the large difference in baseline weights, it is unusual that the difference in baseline body mass index (BMI) between groups is not more significant (p=0.032), raising the question of what the groups’ distributions of height were. Both groups have 30 males (58.8%), so sex differences are unlikely to explain this discrepancy. Height was not explicitly reported, but it was possible to estimate height utilizing geometric means from body weight and BMI[3,4]. We calculated the baseline control group geometric mean as 2.04 cm taller than the test group. These calculations also suggest the control group shrunk by 1.26 cm while the test group grew by 1.52 cm over the study. Neither change is explained by rounding error nor seems plausible for adult subjects over 40 days.Because there were no SDs of the change scores reported, we were unable to replicate the reported p-value (0.318) for the between-group test of weight change exactly. However, we were able to consider the pre and post-intervention SDs and calculate possible SDs of within-group change scores for a range of pre-post correlations. The largest p-value possible was 0.1282, calculated when each group had perfect negative pre-post correlation (correlation=-1), which is unlikely. If there was no or a positive correlation, the p-value would be much smaller (p=0.0449 when correlation=0 for each group) and plausibly indicates a significant difference between groups. Therefore, although the published results are impossible the correct analysis could make the intervention appear more effective than reported.The results section describes an initial sample size of 116 with 14 dropping out (p. 115). The tables report the remaining sample size to be 102, but the body of the text reports 101 subjects remained until study completion. It is unclear which values were correct; this lack of clarity also fails CONSORT guidelines[2].Considering that the reported findings are essentially impossible given the stated study design, we encourage the authors to explain the treatment allocationand make the raw data available, or the journal to act according to the Committee on Publication Ethics[5] in situations where findings are unreliabl

Heterocyst placement strategies to maximize growth of cyanobacterial filaments

Under conditions of limited fixed-nitrogen, some filamentous cyanobacteria develop a regular pattern of heterocyst cells that fix nitrogen for the remaining vegetative cells. We examine three different heterocyst placement strategies by quantitatively modelling filament growth while varying both external fixed-nitrogen and leakage from the filament. We find that there is an optimum heterocyst frequency which maximizes the growth rate of the filament; the optimum frequency decreases as the external fixed-nitrogen concentration increases but increases as the leakage increases. In the presence of leakage, filaments implementing a local heterocyst placement strategy grow significantly faster than filaments implementing random heterocyst placement strategies. With no extracellular fixed-nitrogen, consistent with recent experimental studies of Anabaena sp. PCC 7120, the modelled heterocyst spacing distribution using our local heterocyst placement strategy is qualitatively similar to experimentally observed patterns. As external fixed-nitrogen is increased, the spacing distribution for our local placement strategy retains the same shape while the average spacing between heterocysts continuously increases.Comment: This is an author-created, un-copyedited version of an article accepted for publication in Physical Biology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher-authenticated version will be available onlin

Circulating emm types of Streptococcus pyogenes in Scotland: 2011-2015

No abstract available