Pushing for answers: is myosin V directly involved in moving mitochondria?

In budding yeast, the actin-based class V myosin motors, Myo2 and Myo4, transport virtually all organelles from mother to bud during cell division. Until recently, it appeared that mitochondria may be an exception, with studies showing that the Arp2/3 complex is required for their movement. However, several recent studies have proposed that Myo2 has a direct involvement in mitochondria inheritance. In this issue, Altmann et al. (Altmann, K., M. Frank, D. Neumann, S. Jakobs, and B. Westermann. 2008. J. Cell Biol. 181:119–130) provide the strongest support yet that Myo2 and its associated light chain Mlc1 function directly and significantly in both mitochondria–actin interactions and in the movement of mitochondria from mother to bud. The conflicting functions of Arp 2/3 and Myo2 may be reconciled by the existence of multiple pathways involved in mitochondrial transport

Excitonic Effects and Optical Spectra of Single-Walled Carbon Nanotubes

Many-electron effects often dramatically modify the properties of reduced dimensional systems. We report calculations, based on an many-electron Green's function approach, of electron-hole interaction effects on the optical spectra of small-diameter single-walled carbon nanotubes. Excitonic effects qualitatively alter the optical spectra of both semiconducting and metallic tubes. Excitons are bound by ~ 1 eV in the semiconducting (8,0) tube and by ~ 100 meV in the metallic (3,3) tube. These large many-electron effects explain the discrepancies between previous theories and experiments.Comment: 6 pages, 3 figures, 2 table

Artificial Perches as a Technique for Enhancing Tropical Forest Restoration: A Case Study From the Dominican Republic

Recovering secondary forests on degraded agricultural lands represents a promising opportunity to offset global carbon emissions as well as increasing local biodiversity and ecosystem services. In the insular tropical forests of the Caribbean, frugivorous birds are the primary seed dispersers for most native woody plants and have a large influence on regeneration dynamics during forest succession. In 2017, we initiated an experimental forest restoration program incorporating artificial perches on private farms within the Rio Yaque del Norte watershed in La Vega province, Dominican Republic. Five restoration plots (0.15–0.25 ha) were constructed in pastures near deforested streams. In each plot, 6-12 artificial perches, each 5 m in height, were constructed from bamboo poles fitted with crossbars. We remotely monitored perch use by birds using video cameras and evaluated the effects of perches on the establishment of woody plants in seedling quadrats both below perches and in open spaces. During the summer of 2019, we conducted a behavioral experiment using audio broadcasts of bird sound to test the effect of different avian taxa and feeding guilds on attracting seed dispersers. Eleven avian species were recorded visiting perches, with the most common being Northern Mockingbird and Gray Kingbird. Broadcasting bird sounds led to a significantly greater number of avian visits to the plot. We documented 1,171 seeds from 31 distinguishable species collected from seed traps below perches during the study. Most seedling regeneration in our plots was from exotic non-bird-dispersed taxa which grew equally in perches and control quadrats. Native plant seedlings were infrequent (i.e. beneath 4 of 36 perches) but grew exclusively beneath perches. We conclude that artificial perches are an effective method for augmenting the natural seed bank but are likely to be most effective when used in tandem with planting trees that readily grow to produce shade and litter.https://digitalcommons.odu.edu/gradposters2020_sciences/1004/thumbnail.jp

The activation cycle of Rab GTPase Ypt32 reveals structural determinants of effector recruitment and GDI binding

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116366/1/feb2s0014579311007538-sup-m0005.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/116366/2/feb2s0014579311007538.pd

A Modeling Study on the Sensitivities of Atmospheric Charge Separation According to the Relative Diffusional Growth Rate Theory to Nonspherical Hydrometeors and Cloud Microphysics

Collisional charge transfer between graupel and ice crystals in the presence of cloud droplets is considered the dominant mechanism for charge separation in thunderclouds. According to the relative diffusional growth rate (RDGR) theory, the hydrometeor with the faster diffusional radius growth is charged positively in such collisions. We explore sensitivities of the RDGR theory to nonspherical hydrometeors and six parameters (pressure, temperature, liquid water content, sizes of ice crystals, graupel, and cloud droplets). Idealized simulations of a thundercloud with two‐moment cloud microphysics provide a realistic sampling of the parameter space. Nonsphericity and anisotropic diffusional growth strongly control the extent of positive graupel charging. We suggest a tuning parameter to account for anisotropic effects not represented in bulk microphysics schemes. In a susceptibility analysis that uses automated differentiation, we identify ice crystal size as most important RDGR parameter, followed by graupel size. Simulated average ice crystal size varies with temperature due to ice multiplication and heterogeneous freezing of droplets. Cloud microphysics and ice crystal size thus indirectly determine the structure of charge reversal lines in the traditional temperature‐water‐content representation. Accounting for the variability of ice crystal size and potentially habit with temperature may help to explain laboratory results and seems crucial for RDGR parameterizations in numerical models. We find that the contribution of local water vapor from evaporating rime droplets to diffusional graupel growth is only important for high effective water content. In this regime, droplet size and pressure are the dominant RDGR parameters. Otherwise, the effect of local graupel growth is masked by small ice crystal sizes that result from ice multiplication

Method for separating single-wall carbon nanotubes and compositions thereof

The invention relates to a process for sorting and separating a mixture of (n, m) type single-wall carbon nanotubes according to (n, m) type. A mixture of (n, m) type single-wall carbon nanotubes is suspended such that the single-wall carbon nanotubes are individually dispersed. The nanotube suspension can be done in a surfactant-water solution and the surfactant surrounding the nanotubes keeps the nanotube isolated and from aggregating with other nanotubes. The nanotube suspension is acidified to protonate a fraction of the nanotubes. An electric field is applied and the protonated nanotubes migrate in the electric fields at different rates dependent on their (n, m) type. Fractions of nanotubes are collected at different fractionation times. The process of protonation, applying an electric field, and fractionation is repeated at increasingly higher pH to separated the (n, m) nanotube mixture into individual (n, m) nanotube fractions. The separation enables new electronic devices requiring selected (n, m) nanotube types

Ultrafast Optical Spectroscopy of Micelle-Suspended Single-Walled Carbon Nanotubes

We present results of wavelength-dependent ultrafast pump-probe experiments on micelle-suspended single-walled carbon nanotubes. The linear absorption and photoluminescence spectra of the samples show a number of chirality-dependent peaks, and consequently, the pump-probe results sensitively depend on the wavelength. In the wavelength range corresponding to the second van Hove singularities (VHSs), we observe sub-picosecond decays, as has been seen in previous pump-probe studies. We ascribe these ultrafast decays to intraband carrier relaxation. On the other hand, in the wavelength range corresponding to the first VHSs, we observe two distinct regimes in ultrafast carrier relaxation: fast (0.3-1.2 ps) and slow (5-20 ps). The slow component, which has not been observed previously, is resonantly enhanced whenever the pump photon energy resonates with an interband absorption peak, and we attribute it to radiative carrier recombination. Finally, the slow component is dependent on the pH of the solution, which suggests an important role played by H$^+$ ions surrounding the nanotubes.Comment: 6 pages, 8 figures, changed title, revised, to be published in Applied Physics

Nonsteroidal Antiinflammatory Drug Use and Association With Incident Hypertension in Ankylosing Spondylitis.

ObjectiveNonsteroidal antiinflammatory drugs (NSAIDs) increase blood pressure and potentially cardiovascular burden, which may limit their use in ankylosing spondylitis (AS). Our objective was to determine the association of NSAID use with incident hypertension in a longitudinal AS cohort.MethodsAdults with AS were enrolled in a prospective cohort study of patient outcomes and examined every 4-6 months. Hypertension was defined by patient-reported hypertension; antihypertensive medication use; or, on 2 consecutive visits, systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg. Continuous NSAID use was dichotomized based on the validated NSAID index. We assessed the association of NSAID use as a time-varying exposure with the incidence of hypertension using Cox proportional hazards models.ResultsOf the 1,282 patients in the cohort, 628 patients without baseline hypertension had at least 1 year of follow-up and were included in the analysis. Of these, 72% were male, the mean age at baseline was 39 ± 13 years, and 200 patients used NSAIDs continuously. On follow-up, 129 developed incident hypertension. After controlling for other variables, continuous NSAID use was associated with a hazard ratio of 1.12 for incident hypertension (95% confidence interval 1.04-1.20), compared to noncontinuous or no use. The association did not differ in subgroups defined by age, body mass index, biologic use, or disease activity.ConclusionIn our prospective, longitudinal AS cohort, continuous NSAID use was associated with a 12% increased risk for the development of incident hypertension, as compared to noncontinuous or no NSAID use