The origin of Dendrosenecio within the Senecioneae (Asteraceae) based on chloroplastDNA EVIDENCE

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141916/1/ajb213859.pd

A limit on the detectability of the energy scale of inflation

We show that the polarization of the cosmic microwave background can be used to detect gravity waves from inflation if the energy scale of inflation is above 3.2 times 10^15 GeV. These gravity waves generate polarization patterns with a curl, whereas (to first order in perturbation theory) density perturbations do not. The limiting ``noise'' arises from the second--order generation of curl from density perturbations, or rather residuals from its subtraction. We calculate optimal sky coverage and detectability limits as a function of detector sensitivity and observing time.Comment: 4 pages, 3 figures, submitted to PR

On superconducting and magnetic properties of iron-oxypnictides

Pairing symmetry in oxypnictides, a new family of multiband high-Tc superconductors, is partially imposed by the positions of multiple Fermi pockets, which itself can give rise to new order parameters, such as s+,- states or the state of dx^2-y^2 symmetry. Other pairing states may appear on small pockets for long range interactions, but they are expected to be sensitive to defects. We identify the competing antiferromagnetic order with the triplet exciton transition in the semi- metallic background and discuss whether its coexistence with superconductivity explains the doping dependence of Tc.Comment: Fig1b replace

Light-stable rhodopsin. I. A rhodopsin analog reconstituted with a nonisomerizable 11-cis retinal derivative

With the aim of preparing a light-stable rhodopsin-like pigment, an analog, II, of 11-cis retinal was synthesized in which isomerization of the C11-C12 cis-double bond is blocked by a cyclohexene ring built around the C10 to C13-methyl. The analog II formed a rhodopsin-like pigment (rhodopsin-II) with opsin expressed in COS-1 cells and with opsin from rod outer segments. The rate of rhodopsin-II formation from II and opsin was ~10 times slower than that of rhodopsin from 11-cis retinal and opsin. After solubilization in dodecyl maltoside and immunoaffinity purification, rhodopsin-II displayed an absorbance ratio (A280nm/A512nm) of 1.6, virtually identical with that of rhodopsin. Acid denaturation of rhodopsin-II formed a chromophore with λmax, 452 nm, characteristic of protonated retinyl Schiff base. The ground state properties of rhodopsin-II were similar to those of rhodopsin in extinction coefficient (41,200 M-1 cm-1) and opsin-shift (2600 cm-1). Rhodopsin-II was stable to hydroxylamine in the dark, while light-dependent bleaching by hydroxylamine was slowed by ~2 orders of magnitude relative to rhodopsin. Illumination of rhodopsin-II for 10 s caused ~3 nm blue-shift and 3% loss of visible absorbance. Prolonged illumination caused a maximal blue-shift up to ~20 nm and ~40% loss of visible absorbance. An apparent photochemical steady state was reached after 12 min of illumination. Subsequent acid denaturation indicated that the retinyl Schiff base linkage was intact. A red-shift (~12 nm) in λmax and a 45% recovery of visible absorbance was observed after returning the 12-min illuminated pigment to darkness. Rhodopsin-II showed marginal light-dependent transducin activation and phosphorylation by rhodopsin kinase

Lineage dynamics of murine pancreatic development at single-cell resolution.

Organogenesis requires the complex interactions of multiple cell lineages that coordinate their expansion, differentiation, and maturation over time. Here, we profile the cell types within the epithelial and mesenchymal compartments of the murine pancreas across developmental time using a combination of single-cell RNA sequencing, immunofluorescence, in situ hybridization, and genetic lineage tracing. We identify previously underappreciated cellular heterogeneity of the developing mesenchyme and reconstruct potential lineage relationships among the pancreatic mesothelium and mesenchymal cell types. Within the epithelium, we find a previously undescribed endocrine progenitor population, as well as an analogous population in both human fetal tissue and human embryonic stem cells differentiating toward a pancreatic beta cell fate. Further, we identify candidate transcriptional regulators along the differentiation trajectory of this population toward the alpha or beta cell lineages. This work establishes a roadmap of pancreatic development and demonstrates the broad utility of this approach for understanding lineage dynamics in developing organs

Bostonia. Volume 12

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Quantitative analysis of regulatory flexibility under changing environmental conditions

The circadian clock controls 24-h rhythms in many biological processes, allowing appropriate timing of biological rhythms relative to dawn and dusk. Known clock circuits include multiple, interlocked feedback loops. Theory suggested that multiple loops contribute the flexibility for molecular rhythms to track multiple phases of the external cycle. Clear dawn- and dusk-tracking rhythms illustrate the flexibility of timing in Ipomoea nil. Molecular clock components in Arabidopsis thaliana showed complex, photoperiod-dependent regulation, which was analysed by comparison with three contrasting models. A simple, quantitative measure, Dusk Sensitivity, was introduced to compare the behaviour of clock models with varying loop complexity. Evening-expressed clock genes showed photoperiod-dependent dusk sensitivity, as predicted by the three-loop model, whereas the one- and two-loop models tracked dawn and dusk, respectively. Output genes for starch degradation achieved dusk-tracking expression through light regulation, rather than a dusk-tracking rhythm. Model analysis predicted which biochemical processes could be manipulated to extend dusk tracking. Our results reveal how an operating principle of biological regulators applies specifically to the plant circadian clock

Selection Rules for One- and Two-Photon Absorption by Excitons in Carbon Nanotubes

Recent optical absorption/emission experiments showed that the lower energy optical transitions in carbon nanotubes are excitonic in nature, as predicted by theory. These experiments were based on the symmetry aspects of free electron-hole states and bound excitonic states. The present work shows, however, that group theory does not predict the selection rules needed to explain the two photon experiments. We obtain the symmetries and selection rules for the optical transitions of excitons in single-wall carbon nanotubes within the approach of the group of the wavevector, thus providing important information for the interpretation of theoretical and experimental optical spectra of these materials.Comment: 4 pages, 1 figure, 1 tabl

Exploring Large-scale Structure with Billions of Galaxies

We consider cosmological applications of galaxy number density correlations to be inferred from future deep and wide multi-band optical surveys. We mostly focus on very large scales as a probe of possible features in the primordial power spectrum. We find the proposed survey of the Large Synoptic Survey Telescope may be competitive with future all-sky CMB experiments over a broad range of scales. On very large scales the inferred power spectrum is robust to photometric redshift errors, and, given a sufficient number density of galaxies, to angular variations in dust extinction and photometric calibration errors. We also consider other applications, such as constraining dark energy with the two CMB-calibrated standard rulers in the matter power spectrum, and controlling the effect of photometric redshift errors to facilitate the interpretation of cosmic shear data. We find that deep photometric surveys over wide area can provide constraints that are competitive with spectroscopic surveys in small volumes.Comment: 11 pages, 7 figures, ApJ accepted, references added, expanded discussion in Sec. 3.