Construction of an Accessible Ocean-Acidification Simulator to Investigate Physiological Responses of the Green Crab, Carcinus Maenas, to Acidified Conditions

The European green crab Carcinus maenas L, is a major invasive species in North America as well as many other regions around the world, including South Africa, Australia, South America, and Asia. The species poses a significant threat to the diverse ecosystems and the aquaculture industries on the East coast of the United States, with the state of Maine particularly at risk. The shellfish industry is a significant part of Maine’s economy, and is threatened by the foraging behavior of green crabs toward small bivalves (Beal 2015). Climate change likely plays a large role in the rapid population growth of C. maenas over the last 5-10 years by opening up marginal habitats for the crabs to occupy (Beal 2015). Steroid activity is highly dependent on environmental conditions, and changes in temperature have been linked to the ecological success of C. maenas. This project will focus on developing an accessible low-cost ocean-acidification simulator at the University of Maine Aquaculture Research Center to be used to explore physiological responses of C. maenas to acidified conditions and quantify estradiol levels in the animals using an Enzyme-Linked Immunosorbent Assay (ELISA). Animal trials conducted with the system will provide information on parameters related to the effect of acidic stress on the endocrine system of green crabs. Additionally, the outlines for the construction of the simulator can be used as a model for students for an inexpensive holding facility to test effects of acidification. Data obtained from the Accessible Low-Cost Ocean Acidification Simulation Tool (ALCOAST) can also be used by policy makers to evaluate whether climate change can provide information on physiological interactions between C. maenas and its environment. This study stands to fill a significant gap in knowledge that is relevant not only to Maine’s economy and management of invasive species, but also to studies of how invasive species react to climate change

Shifts in carbon and nitrogen stable isotope composition and epicuticular lipids in leaves reflect early water-stress in vineyards

Changes in leaf carbon and nitrogen isotope composition (δ <sup>13</sup> C and δ <sup>15</sup> N values) and the accumulation of epicuticular lipids have been associated with plant responses to water stress. We investigated their potential use as indicators of early plant water deficit in two grapevine (Vitis vinifera L.) cultivars, Chasselas and Pinot noir, that were field-grown under well-watered and water-deficient conditions. We tested the hypothesis that the bulk δ <sup>13</sup> C and δ <sup>15</sup> N values and the concentrations of epicuticular fatty acids may change in leaves of similar age with the soil water availability. For this purpose, leaves were sampled at the same position in the canopy at different times (phenological stages) during the 2014 growing season. Bulk dry matter of young leaves from flowering to veraison had higher δ <sup>13</sup> C values, higher total nitrogen content, and lower δ <sup>15</sup> N values than old leaves. In both cultivars, δ <sup>15</sup> N values were strongly correlated with plant water deficiency, demonstrating their integration of the plant water stress response. δ <sup>13</sup> C values recorded the water deficiency only in those plants that had not received foliar organic fertilization. The soil water deficiency triggered the accumulation of C <sub>>26</sub> fatty acids in the cuticular waxes. The compound-specific isotope analysis (CSIA) of fatty acids from old leaves showed an increase in δ <sup>13</sup> C among the C <sub>16</sub> -C <sub>22</sub> chains, including stress signaling linoleic and linolenic acids. Our results provide evidence for leaf <sup>13</sup> C-enrichment, <sup>15</sup> N-depletion, and enhanced FA-chain elongation and epicuticular accumulation in the grapevine response to water stress. The leaf δ <sup>13</sup> C and δ <sup>15</sup> N values, and the concentration of epicuticular fatty acids can be used as reliable and sensitive indicators of plant water deficit even when the level of water stress is low to moderate. They could also be used, particularly the more cost-efficient δ <sup>13</sup> C and δ <sup>15</sup> N measurements, for periodic biogeochemical mapping of the plant water availability at the vineyard and regional scale

Low noise all-fiber amplification of a coherent supercontinuum at 2 \mu m and its limits imposed by polarization noise

We report the amplification of an all-normal dispersion supercontinuum pulse in a Thulium / Holmium co-doped all-fiber chirped pulse amplification system. With a -20 dB bandwidth of more than 300 nm in the range 1800-2100 nm the system delivers high quality 66 fs pulses with more than 70 kW peak power directly from the output fiber. The coherent seeding of the entire emission bandwidth of the doped fiber and the stability of the supercontinuum generation dynamics in the silicate glass all-normal dispersion photonic crystal fiber result in excellent noise characteristics of the amplified ultrashort pulses

Ultrathin epitaxial Fe films in vicinal GaAs(001): A study by spin-resolved photoelectron spectroscopy

Thin epitaxial Fe films have been grown on vicinal GaAs(001) substrates and their remanent magnetic properties and the degree of substrate atom diffusion investigated using synchrotron-based photoelectron spectroscopy. The vicinal Fe films, though exhibiting greater As diffusion than their singular homologues, displayed better film quality both from the structural and the magnetic points of view. The spin-resolved valence spectra of the vicinal films resemble those for crystalline bulk Fe at lower film thicknesses than for singular films

Ptychographic ultrafast pulse reconstruction

We demonstrate a new ultrafast pulse reconstruction modality which is somewhat reminiscent of frequency resolved optical gating but uses a modified setup and a conceptually different reconstruction algorithm that is derived from ptychography. Even though it is a second order correlation scheme it shows no time ambiguity. Moreover, the number of spectra to record is considerably smaller than in most other related schemes which, together with a robust algorithm, leads to extremely fast convergence of the reconstruction.Comment: 4 pages, 4 figures, 3 references added, new figure 2, matches published versio

Structural characterization of the closed conformation of mouse guanylate kinase

Guanylate kinase (GMPK) is a nucleoside monophosphate kinase that catalyzes the reversible phosphoryl transfer from ATP to GMP to yield ADP and GDP. In addition to phosphorylating GMP, antiviral prodrugs such as acyclovir, ganciclovir, and carbovir and anticancer prodrugs such as the thiopurines are dependent on GMPK for their activation. Hence, structural information on mammalian GMPK could play a role in the design of improved antiviral and antineoplastic agents. Here we present the structure of the mouse enzyme in an abortive complex with the nucleotides ADP and GMP, refined at 2.1 Angstrom resolution with a final crystallographic R factor of 0.19 (R-free = 0.23). Guanylate kinase is a member of the nucleoside monophosphate (NMP) kinase family, a family of enzymes that despite having a low primary structure identity share a similar fold, which consists of three structurally distinct regions termed the CORE, LID, and NMP-binding regions. Previous studies on the yeast enzyme have shown that these parts move as rigid bodies upon substrate binding. It has been proposed that consecutive binding of substrates leads to "closing" of the active site bringing the NMP-binding and LID regions closer to each other and to the CORE region. Our structure, which is the first of any guanylate kinase with both substrates bound, supports this hypothesis. It also reveals the binding site of ATP and implicates arginines 44, 137, and 148 (in addition to the invariant P-loop lysine) as candidates for catalyzing the chemical step of the phosphoryl transfer