2,512 research outputs found
Friction of a slider on a granular layer: Non-monotonic thickness dependence and effect of boundary conditions
We investigate the effective friction encountered by a mass sliding on a
granular layer as a function of bed thickness and boundary roughness
conditions. The observed friction has minima for a small number of layers
before it increases and saturates to a value which depends on the roughness of
the sliding surface. We use an index-matched interstitial liquid to probe the
internal motion of the grains with fluorescence imaging in a regime where the
liquid has no significant effect on the measured friction. The shear profiles
obtained as a function of depth show decrease in slip near the sliding surface
as the layer thickness is increased. We propose that the friction depends on
the degree of grain confinement relative to the sliding surfaces.Comment: 4 pages, 6 figure
The “broken escalator” phenomenon: Vestibular dizziness interferes with locomotor adaptation
BACKGROUND: Although vestibular lesions degrade postural control we do not know the relative contributions of the magnitude of the vestibular loss and subjective vestibular symptoms to locomotor adaptation. OBJECTIVE: To study how dizzy symptoms interfere with adaptive locomotor learning. METHODS: We examined patients with contrasting peripheral vestibular deficits, vestibular neuritis in the chronic stable phase (n = 20) and strongly symptomatic unilateral Meniere’s disease (n = 15), compared to age-matched healthy controls (n = 15). We measured locomotor adaptive learning using the “broken escalator” aftereffect, simulated on a motorised moving sled. RESULTS: Patients with Meniere’s disease had an enhanced “broken escalator” postural aftereffect. More generally, the size of the locomotor aftereffect was related to how symptomatic patients were across both groups. Contrastingly, the degree of peripheral vestibular loss was not correlated with symptom load or locomotor aftereffect size. During the MOVING trials, both patient groups had larger levels of instability (trunk sway) and reduced adaptation than normal controls. CONCLUSION: Dizziness symptoms influence locomotor adaptation and its subsequent expression through motor aftereffects. Given that the unsteadiness experienced during the “broken escalator” paradigm is internally driven, the enhanced aftereffect found represents a new type of self-generated postural challenge for vestibular/unsteady patients
Mlh2 is an accessory factor for DNA mismatch repair in Saccharomyces cerevisiae.
In Saccharomyces cerevisiae, the essential mismatch repair (MMR) endonuclease Mlh1-Pms1 forms foci promoted by Msh2-Msh6 or Msh2-Msh3 in response to mispaired bases. Here we analyzed the Mlh1-Mlh2 complex, whose role in MMR has been unclear. Mlh1-Mlh2 formed foci that often colocalized with and had a longer lifetime than Mlh1-Pms1 foci. Mlh1-Mlh2 foci were similar to Mlh1-Pms1 foci: they required mispair recognition by Msh2-Msh6, increased in response to increased mispairs or downstream defects in MMR, and formed after induction of DNA damage by phleomycin but not double-stranded breaks by I-SceI. Mlh1-Mlh2 could be recruited to mispair-containing DNA in vitro by either Msh2-Msh6 or Msh2-Msh3. Deletion of MLH2 caused a synergistic increase in mutation rate in combination with deletion of MSH6 or reduced expression of Pms1. Phylogenetic analysis demonstrated that the S. cerevisiae Mlh2 protein and the mammalian PMS1 protein are homologs. These results support a hypothesis that Mlh1-Mlh2 is a non-essential accessory factor that acts to enhance the activity of Mlh1-Pms1
N-(4-Hydroxyphenyl)-2-(1,1,3-trioxo-2,3-dihydro-1,2-benzothiazol-2-yl)acetamide
In the title compound, C15H12N2O5S, the benzisothiazole group is approximately planar (r.m.s. deviation excluding H atoms and the two O atoms bonded to S = 0.023 Å). The dihedral angle between the benzisothiazole ring and the terminal phenol ring is 84.9 (1)°. In the crystal, molecules are joined by N—H⋯O and O—H⋯O hydrogen bonds, and π-stacking interactions are observed between alternating phenol and benzisothiazole rings [centroid–centroid distances = 3.929 (3) and 3.943 (3) Å]
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