Increased gravitational force reveals the mechanical, resonant nature of physiological tremor

Human physiological hand tremor has a resonant component. Proof of this is that its frequency can be modified by adding mass. However, adding mass also increases the load which must be supported. The necessary force requires muscular contraction which will change motor output and is likely to increase limb stiffness. The increased stiffness will partly offset the effect of the increased mass and this can lead to the erroneous conclusion that factors other than resonance are involved in determining tremor frequency. Using a human centrifuge to increase head-to-foot gravitational field strength, we were able to control for the increased effort by increasing force without changing mass. This revealed that the peak frequency of human hand tremor is 99% predictable on the basis of a resonant mechanism. We ask what, if anything, the peak frequency of physiological tremor can reveal about the operation of the nervous system.This work was funded by a BBSRC Industry Interchange Award to J.P.R.S. and R.F.R. C.J.O. was funded by BBSRC grant BB/I00579X/1. C.A.V. was funded by A∗Midex (Aix-Marseille Initiative of Excellence

Analysis of Antimicrobial-Triggered Membrane Depolarization Using Voltage Sensitive Dyes

The bacterial cytoplasmic membrane is a major inhibitory target for antimicrobial compounds. Commonly, although not exclusively, these compounds unfold their antimicrobial activity by disrupting the essential barrier function of the cell membrane. As a consequence, membrane permeability assays are central for mode of action studies analysing membrane-targeting antimicrobial compounds. The most frequently used in vivo methods detect changes in membrane permeability by following internalization of normally membrane impermeable and relatively large fluorescent dyes. Unfortunately, these assays are not sensitive to changes in membrane ion permeability which are sufficient to inhibit and kill bacteria by membrane depolarization. In this manuscript, we provide experimental advice how membrane potential, and its changes triggered by membrane-targeting antimicrobials can be accurately assessed in vivo. Optimized protocols are provided for both qualitative and quantitative kinetic measurements of membrane potential. At last, single cell analyses using voltage-sensitive dyes in combination with fluorescence microscopy are introduced and discussed

Soundness of Unravelings for Conditional Term Rewriting Systems via Ultra-Properties Related to Linearity

Unravelings are transformations from a conditional term rewriting system (CTRS, for short) over an original signature into an unconditional term rewriting systems (TRS, for short) over an extended signature. They are not sound w.r.t. reduction for every CTRS, while they are complete w.r.t. reduction. Here, soundness w.r.t. reduction means that every reduction sequence of the corresponding unraveled TRS, of which the initial and end terms are over the original signature, can be simulated by the reduction of the original CTRS. In this paper, we show that an optimized variant of Ohlebusch's unraveling for a deterministic CTRS is sound w.r.t. reduction if the corresponding unraveled TRS is left-linear or both right-linear and non-erasing. We also show that soundness of the variant implies that of Ohlebusch's unraveling. Finally, we show that soundness of Ohlebusch's unraveling is the weakest in soundness of the other unravelings and a transformation, proposed by Serbanuta and Rosu, for (normal) deterministic CTRSs, i.e., soundness of them respectively implies that of Ohlebusch's unraveling.Comment: 49 pages, 1 table, publication in Special Issue: Selected papers of the "22nd International Conference on Rewriting Techniques and Applications (RTA'11)

LONGITUDINAL FACE CRACK PREDICTION WITH THERMO-MECHANICAL MODELS OF THIN SLABS IN FUNNEL MOULDS

This paper investigates longitudinal depressions and cracks in steel continuous-cast in funnel moulds usinga finite-element model to simulate thermo-mechanical behavior of the solidifying shell in the thin-slab castermould at the Corus Direct Sheet Plant (DSP) in IJmuiden, The Netherlands. The commercial code ABAQUS[1] is used to study the effect of the funnel shape on the stresses developed within a two-dimensional sectionthrough the shell while it moves through the mould. The model first simulates heat transfer, based on heatflux profiles found from extensive plant measurements of mould heat removal and thermocouples embedded inthe mould wall. It incorporates the drop in heat flux due to local gap formation. The temperature solution isinput to the mechanical model which incorporates grade-dependent elastic-viscoplastic constitutive behavior,ferrostatic pressure, taper, mould-wall oscillations, and contact with the profiled mould wall. The results arevalidated with plant measurements, including a breakout shell, and crack statistics. The model is applied tostudy the effects of increasing casting speed and funnel design in order to avoid longitudinal cracks

Criterion Validity and Applicability of Motor Screening Instruments in Children Aged 5-6 Years:A Systematic Review

The detection of motor developmental problems, especially developmental coordination disorder, at age 5–6 contributes to early interventions. Here, we summarize evidence on (1) criterion validity of screening instruments for motor developmental problems at age 5–6, and (2) their applicability. We systematically searched seven databases for studies assessing criterion validity of these screening instruments using the M-ABC as reference standard. We applied COSMIN criteria for systematic reviews of screening instruments to describe the correlation between the tests and the M-ABC. We extracted information on correlation coefficients or area under the receiver operating curve, sensitivity and specificity, and applicability in practice. We included eleven studies, assessing eight instruments: three performance-based tests (MAND, MOT 4–6, BFMT) and five questionnaires (DCD-Q, PQ, ASQ-3, MOQ-T-FI, M-ABC-2-C). The quality of seven studies was fair, one was good, and three were excellent. Seven studies reported low correlation coefficients or AUC (<0.70), four did not report these. Sensitivities ranged from 21–87% and specificities from 50–96%, with the MOT4–6 having the highest sensitivity and specificity. The DCD-Q, PQ, ASQ-3, MOQ-T-FI, and M-ABC-2-C scored highest on applicability. In conclusion, none of the instruments were sufficiently valid for motor screening at age 5–6. More research is needed on screening instruments of motor delay at age 5–6

The bdbDC operon of Bacillus subtilis encodes thiol-disulfide oxidoreductases required for competence development

The development of genetic competence in the Gram-positive eubacterium Bacillus subtilis is a complex postexponential process. Here we describe a new bicistronic operon, bdbDC, required for competence development, which was identified by the B. subtilis Systematic Gene Function Analysis program. Inactivation of either the bdbC or bdbD genes of this operon results in the loss of transformability without affecting recombination or the synthesis of ComK, the competence transcription factor. BdbC and BdbD are orthologs of enzymes known to be involved in extracytoplasmic disulfide bond formation. Consistent with this, BdbC and BdbD are needed for the secretion of theEscherichia coli disulfide bond-containing alkaline phosphatase, PhoA, by B. subtilis. Similarly, the amount of the disulfide bond-containing competence protein ComGC is severely reduced in bdbC or bdbD mutants. In contrast, the amounts of the competence proteins ComGA and ComEA remain unaffected by bdbDC mutations. Taken together, these observations imply that in the absence of either BdbC or BdbD, ComGC is unstable and that BdbC and BdbD catalyze the formation of disulfide bonds that are essential for the DNA binding and uptake machinery

Distinct Roles of ComK1 and ComK2 in Gene Regulation in Bacillus cereus

The B. subtilis transcriptional factor ComK regulates a set of genes coding for DNA uptake from the environment and for its integration into the genome. In previous work we showed that Bacillus cereus expressing the B. subtilis ComK protein is able to take up DNA and integrate it into its own genome. To extend our knowledge on the effect of B. subtilis ComK overexpression in B. cereus we first determined which genes are significantly altered. Transcriptome analysis showed that only part of the competence gene cluster is significantly upregulated. Two ComK homologues can be identified in B. cereus that differ in their respective homologies to other ComK proteins. ComK1 is most similar, while ComK2 lacks the C-terminal region previously shown to be important for transcription activation by B. subtilis ComK. comK1 and comK2 overexpression and deletion studies using transcriptomics techniques showed that ComK1 enhances and ComK2 decreases expression of the comG operon, when B. subtilis ComK was overexpressed simultaneously