Contraintes écophysiologiques de la distribution d'une espèce : divergence parmi les populations sympatriques de Dreissena polymorpha (Pallas) et de D. bugensis (Andrusov) dans l'estuaire et du fleuve Saint-Laurent

Les différences spatiales existant dans les conditions environnementales peuvent favoriser l’apparition de réponses physiologiques plastiques de la part de plusieurs organismes. Ainsi, des environnements divergents, mais stables temporellement, peuvent mener à la création de différences physiologiques intrinsèques chez un organisme. Le but de cette thèse est de déterminer si les populations contigües chez les adultes des moules zébrée et quagga (Dreissena polymorpha et D. bugensis respectivement) dans un environnement où les contraintes sont distribuées sous forme de mosaïque peuvent favoriser l’apparition de traits divergents. Si tel est le cas, nous déterminerons si les différences enregistrées sont plastiques ou sont des ajustements irréversibles. La comparaison entre des masses d’eau du Saint-Laurent contrastées en terme de physico-chimie de l’eau à permis d’identifier des différences en termes d’indice de condition (contenu en glycogène, ratio ARN/ADN, résistance et masse de la coquille). La réponse enregistrée pour les tissus des moules zébrées et quagga sont similaires, cependant la coquille plus légère (mince) des moules quagga semble lui conférer un avantage lorsque les deux espèces coexistent. Les échantillonnage effectués en milieu naturel et en laboratoire ont démontrés que la distribution en amont des moules zébrés est limitée par l’intrusion saline. Cependant, il semble que les individus retrouvés dans la zone où se retrouve l’intrusion saline sont en meilleur condition (masse des tissus mous vs. la taille de la coquille) que ceux échantillonnés en amont dans la section d’eau douce. Afin de déterminer si les différenciations observées entre les populations locales sont de nature plastique ou sont issues de différenciation physiologique irréversible, nous avons effectué des expériences de transfert réciproque entre les moules en provenance des masses d’eau des Grand Lacs et ceux de l’estuaire moyen. Les résultats indiquent que le taux de croissance de la coquille dépend de l’origine de la population, est indépendante du site de transfert. En comparaison, le ratio ARN/ADN, qui représente une mesure à court terme de la condition et de la croissance, est significativement plus élevé pour les moules en provenance de l’estuaire. Dans le milieu fluvial (eau douce) ou les deux espèces coexistent, les moules quagga croissent plus rapidement que les moules zébrées. Ce résultat va de pair avec l’observation du remplacement des moules zébrées par les moules quagga qui s’opère actuellement dans le système des Grand Lacs –fleuve Saint-Laurent. Il semble cependant que les moules quagga ne performent pas aussi bien que les moules zébrées en milieu estuarien. Ainsi, cela suggère que leur influence risque d’être limité aux régions exclusivement d’eau douce, à moins bien sur qu’elle ne puissent s’ajuster physiologiquement comme le font les moules zébrées. La comparaison de la croissance des coquilles entre les périodes estivales et hivernales indique que la période estivale est plus productive. La moule quagga exhibe un taux de croissance supérieur à celui des moules zébrées pour l’été 2002, hiver 2002 et l’hiver 2003 mais cette observation est inversée pour l’été 2003.Spatial differences in environmental conditions can lead to plastic physiological responses in many organisms. Yet stable but divergent environmental conditions over multiple generations can produce intrinsic local differences in an organism’s physiology. The goal of this research is to determine whether a contiguous population of adult zebra and quagga mussel (Dreissena polymorpha and D. bugensis) in a stable mosaic of environmental constraints has developed divergent traits and if so are they plastic or irreversible adjustments. Comparison among contrasting St. Lawrence River water-masses found population differentiation in condition (tissue glycogen content, RNA/DNA ratio of tissue as well as shell strength and mass. Though the soft tissue responses of zebra and quagga mussels were similar, the lighter shell of the quagga mussels appears to be an advantage where the two species co-occur. Field sampling and laboratory experiments show that the downstream distribution of zebra mussels is constrained by the tidal intrusion of salinity, but counter-intuitively that the animals at this limit were actually in better condition than those upriver. To explore whether the observed population differentiation represents plasticity or alternatively intrinsic local differentiation, reciprocal transplants of adult mussels from the fluvial estuary and the Great Lakes water masses were conducted. Results indicate that shell growth depends on source population, independent of the environment (river source mussels > estuary source mussels). In contrast, RNA/DNA ratio, a short-term measure of tissue condition and growth, was significantly higher for estuary mussels. In the riverine environment where they coexist, quagga mussels grew faster than zebra mussels, supporting observations that they are displacing zebra mussels throughout the Great Lakes – St. Lawrence system. Yet quagga mussels did not perform as well in the estuarine environment suggesting that their influence will be limited to the strictly freshwater unless they can adjust physiologically as zebra mussels did. Comparisons of shell growth between summer and winter transplants indicated that summer is more productive and that quagga mussels grow faster than zebra mussels. Yet the summer growth rates of the two species measured at the same site in consecutive years reversed, indicating both spatial and temporal components to growth and production

When A Blue Service Star Turns To Gold

https://digitalcommons.library.umaine.edu/mmb-vp/4565/thumbnail.jp

Inspecting Gradual and Abrupt Changes in Emotion Dynamics With the Time-Varying Change Point Autoregressive Model

Recent studies have shown that emotion dynamics such as inertia (i.e., autocorrelation) can change over time. Importantly, current methods can only detect either gradual or abrupt changes in inertia. This means that researchers have to choose a priori whether they expect the change in inertia to be gradual or abrupt. This will leave researchers in the dark regarding when and how the change in inertia occurred. Therefore in this article, we use a new model: the time-varying change point autoregressive (TVCP-AR) model. The TVCP-AR model can detect both gradual and abrupt changes in emotion dynamics. More specifically, we show that the inertia of positive affect and negative affect measured in one individual differs qualitatively in how it changes over time. Whereas the inertia of positive affect increased only gradually over time, negative affect changed both in a gradual and abrupt fashion over time. This illustrates the necessity of being able to model both gradual and abrupt changes in order to detect meaningful quantitative and qualitative differences in temporal emotion dynamics

The Nature Conservancy's Emiquon Nature Preserve Fish and Aquatic Vegetation Monitoring Annual Report

Key Ecological Attributes (KEA’s) for thefish and aquatic vegetation communities are used toevaluate theprogressof the restoration efforts at Thompson and Flag lakes of The Nature Conservancy’s Emiquon Nature Preserve.A total of 19 KEA criteria were monitored monthlybetween 4/21/2015-10/23/2015. Of thosecriteria set by the Emiquon Science Advisory Council, 15were met in 2015. The 2015water transparency values were within the desired range (Secchi depths no less than half the maximum water depth when a site is ≤1.5 m deep). However, when 2015results are compared to 2014, we see that the mean monthly transparencies for April-May were lowerthan the same period in 2014. In contrast,transparencies between June-Octoberwere higherthan the corresponding in 2014. Thus,while KEA criteria are being met, there is still room for improvement.The aquatic vegetation community in 2015 continued to be dominated by native aquatic plant species.Despite the dominance by natives, twoinvasive aquatic plants-Eurasian watermilfoilandcurly-leaf pondweedwere among the species collected in 2015.Eurasian watermilfoil and curly-leaf pondweed, while still not dominant,were found at moresites and at a higherdensity than in 2014.An invasive submersed aquatic vegetation species known as Egeria was collected for the first time in 2014 since restoration but was not observed or collectedin 2015.If this increase in densityof these non-natives is an on-going trend, then consideration may need to be given on how to manage theseinvasive plants.The fish community in 2015continuedto be dominated byan increasing number of native species. Despite this, the KEA goal of collecting ≥25 native fish species was not met.Bluegilldominated our catches in 2015whilecatchesof other desirable native fishes including freshwater drum, grass pickerel, and longnose gar were presentbut lowin numbers. Despite the low numbers of thesenative fishes, these were still the highest catches for these species ever observed at the Emiquon Preserve.Of the 21fish species collectedin 2015,only one non-native speciesconsisting of the common carpwas collected. Total common carp catchwas lower than 2014catches and wasthe lowest catch of this species since restoration.The Nature Conservancyunpublishednot peer reviewe

Human chorionic gonadotropin administration is associated with high pregnancy rates during ovarian stimulation and timed intercourse or intrauterine insemination

Abstract Background There are different factors that influence treatment outcome after ovarian stimulation and timed-intercourse or intrauterine insemination (IUI). After patient age, it has been suggested that timing of insemination in relation to ovulation is probably the most important variable affecting the success of treatment. The objective of this study is to study the value of human chorionic gonadotropin (hCG) administration and occurrence of luteinizing hormone (LH) surge in timing insemination on the treatment outcome after follicular monitoring with timed-intercourse or intrauterine insemination, with or without ovarian stimulation. Methods Retrospective analysis of 2000 consecutive completed treatment cycles (637 timed-intercourse and 1363 intrauterine insemination cycles). Stimulation protocols included clomiphene alone or with FSH injection, letrozole (an aromatase inhibitor) alone or with FSH, and FSH alone. LH-surge was defined as an increase in LH level ≥200% over mean of preceding two days. When given, hCG was administered at a dose of 10,000 IU. The main outcome was clinical pregnancy rate per cycle. Results Higher pregnancy rates occurred in cycles in which hCG was given. Occurrence of an LH-surge was associated with a higher pregnancy rate with clomiphene treatment, but a lower pregnancy rate with FSH treatment. Conclusions hCG administration is associated with a favorable outcome during ovarian stimulation. Awaiting occurrence of LH-surge is associated with a better outcome with CC but not with FSH treatment

Searching for hexagonal analogues of the half-metallic half-Heusler XYZ compounds

The XYZ half-Heusler crystal structure can conveniently be described as a tetrahedral zinc blende YZ structure which is stuffed by a slightly ionic X species. This description is well suited to understand the electronic structure of semiconducting 8-electron compounds such as LiAlSi (formulated Li$^+$[AlSi]$^-$) or semiconducting 18-electron compounds such as TiCoSb (formulated Ti$^{4+}$[CoSb]$^{4-}$). The basis for this is that [AlSi]$^-$ (with the same electron count as Si$_2$) and [CoSb]$^{4-}$ (the same electron count as GaSb), are both structurally and electronically, zinc-blende semiconductors. The electronic structure of half-metallic ferromagnets in this structure type can then be described as semiconductors with stuffing magnetic ions which have a local moment: For example, 22 electron MnNiSb can be written Mn$^{3+}$[NiSb]$^{3-}$. The tendency in the 18 electron compound for a semiconducting gap -- believed to arise from strong covalency -- is carried over in MnNiSb to a tendency for a gap in one spin direction. Here we similarly propose the systematic examination of 18-electron hexagonal compounds for semiconducting gaps; these would be the "stuffed wurtzite" analogues of the "stuffed zinc blende" half-Heusler compounds. These semiconductors could then serve as the basis for possibly new families of half-metallic compounds, attained through appropriate replacement of non-magnetic ions by magnetic ones. These semiconductors and semimetals with tunable charge carrier concentrations could also be interesting in the context of magnetoresistive and thermoelectric materials.Comment: 11 pages, 6 figures, of which 4 are colou

Optimizing propagating spin wave spectroscopy

The frequency difference between two oppositely propagating spin waves can be used to probe several interesting magnetic properties, such as the Dzyaloshinkii-Moriya interaction (DMI). Propagating spin wave spectroscopy is a technique that is very sensitive to this frequency difference. Here we show several elements that are important to optimize devices for such a measurement. We demonstrate that for wide magnetic strips there is a need for de-embedding. Additionally, for these wide strips there is a large parasitic antenna-antenna coupling that obfuscates any spin wave transmission signal, which is remedied by moving to smaller strips. The conventional antenna design excites spin waves with two different wave vectors. As the magnetic layers become thinner, the resulting resonances move closer together and become very difficult to disentangle. In the last part we therefore propose and verify a new antenna design that excites spin waves with only one wave vector. We suggest to use this antenna design to measure the DMI in thin magnetic layers.Comment: 12 pages, 4 figure

Half-metallic ferromagnetism with high magnetic moment and high Curie temperature in Co2_2FeSi

Co$_2$FeSi crystallizes in the ordered L2$_1$ structure as proved by X-ray diffraction and M\"o\ss bauer spectroscopy. The magnetic moment of Co$_2$FeSi was measured to be about $6\mu_B$ at 5K. Magnetic circular dichroism spectra excited by soft X-rays (XMCD) were taken to determine the element specific magnetic moments of Co and Fe. The Curie temperature was measured with different methods to be ($1100\pm20$)K. Co$_2$FeSi was found to be the Heusler compound as well as the half-metallic ferromagnet with the highest magnetic moment and Curie temperature.Comment: conference contribution, MMM200

The role of aromatase inhibitors in ameliorating deleterious effects of ovarian stimulation on outcome of infertility treatment

Clinical utilization of ovulation stimulation to facilitate the ability of a couple to conceive has not only provided a valuable therapeutic approach, but has also yielded extensive information on the physiology of ovarian follicular recruitment, endometrial receptivity and early embryo competency. One of the consequences of the use of fertility enhancing agents for ovarian stimulation has been the creation of a hyperestrogenic state, which may influence each of these parameters. Use of aromatase inhibitors reduces hyperestrogenism inevitably attained during ovarian stimulation. In addition, the adjunct use of aromatase inhibitors during ovarian stimulation reduces amount of gonadotropins required for optimum stimulation. The unique approach of reducing hyperestrogenism, as well as lowering amount of gonadotropins without affecting the number of mature ovarian follicles is an exciting strategy that could result in improvement in the treatment outcome by ameliorating the deleterious effects of the ovarian stimulation on follicular development, endometrial receptivity, as well as oocyte and embryo quality