170 research outputs found
THE FIELD TRIP PROJECT: USING ENVIRONMENTAL EDUCATION TO BRIDGE SCIENCE LEARNING ACROSS FORMAL AND INFORMAL KINDERGARTEN SETTINGS
The Field Trip Study was conducted in direct response to the emergence of scientific thinking as it relates to childrenâs cognitive abilities. The purpose of the study was to evaluate the effects of nature-based, experiential activities on childrenâs acquisition of science knowledge. A multiple treatments and controls with pretest research design was utilized to compare science knowledge acquisition between kindergarten children in four instructional conditions: 1) nature-based field trip plus extension activities from an environmental education curriculum, and corresponding book reading and activities, 2) nature-based field trips plus extension activities from an environmental education curriculum, 3) nature-based field trips plus corresponding book reading and book-related activities, and 4) nature-based field trip with business as usual instruction. Study teachers implemented activities from the Growing Up WILD curriculum and National Science Teacher Association childrenâs books. An age-appropriate science assessment and accompanying scoring rubric were created in correspondence with Next Generation Science Standards and piloted prior to use as the pretest and posttest for kindergarten children enrolled in the study. Children were interviewed in small groups to elaborate on assessment responses. Kindergarten teachersâ perceptions of using environmental education curricula as a part of field trip extension activities were assessed during a group interview. Gender, treatment condition, and pretest scores were predictors of childrenâs posttest scores. Children in condition 1 scored significantly higher on posttest mean scores than children in other groups. Teachers enjoyed using the environmental education curriculum and believed it made teaching NGSS accessible
Studies on the biology and ecology of the free swimming larval stages of Lepeophtheirus Salmonis (Kroyer, 1838) and Caligus Elongatus Nordmann, 1832 (Copepoda: Caligidae)
The study investigated biological and ecological parameters controlling and
influencing the production and distribution of the free-swimming larval stages of
Lepeophtheirus salmonis (Kroyer, 1838), and to a lesser extent Caligus elongatus
Nordmann 1832, in the natural environment
The reproductive output of L. salmonis was influenced by seasonal effects. The
number of eggs produced per brood showed an inverse relationship with increasing
temperature. The number of eggs per brood was also influenced by adult female body
size (cephalothorax length), which in itself exhibited an inverse relationship with
increasing temperature. Photoperiod had no significant effect upon the number of eggs
produced or on adult female size. Mean egg size of L. salmonis varied significantly
over the year; larger eggs were produced during the summer months and smaller eggs
over the winter. However, factors controlling the size of the eggs were not elucidated.
The proportion of viable eggs per L. salmonis ovisac remained constant throughout the
year. Large variations in egg number per egg string were found in both L. salmonis and
C elongatus populations sampled at one point in time. These were attributed in part to
phenotypic variation in adult female size and also the number of broods individual
females had produced. Egg viability was not correlated with brood size, but mean egg
size was related to the number of eggs per brood.
Experimental studies indicated that hatching and development of L. salmonis
was highly variable. The percentage of eggs hatched and the time period over which
hatching occurred varied markedly, even when held under constant and optimal
environmental conditions. Temperature did not affect hatching success or viability of
the nauplius I stage, although at higher temperatures the period over which hatching occurred was reduced. Low and medium salinities caused a significant decrease in both
hatching success and nauplius viability. Photoperiod had no effect on initiation of
hatching. Hatching occurred in a manner similar to that observed in free-living
copepods. The nauplii were enclosed by two egg membranes, the outer one bursting
within the ovisac, the inner one after the ovisac membrane has split. Swelling of the
egg and its subsequent hatching was attributed to osmotic effects, with water being
taken up from the external environment.
Development was also highly dependent upon both temperature and salinity.
At 5'C, nauplius 11 stages failed to enter the moult to the copepodid stage. At 7.5'C,
although moulting was initiated, in a large proportion of cases it was not successfully
completed. At I O'C, development to the copepodid stage was successful. Nauplii only
developed successfully to the copepodid stage at salinities of 25%o or greater.
Copepodids raised under optimal conditions then exposed to a range of salinities had a
greater salinity tolerance than nauplii.
Biochemical analysis of the eggs of L. salmonis revealed that lipids constituted
a large proportion of their dry weight. Naupliar stages contained a discrete area
containing lipid which decreased in size over time, suggesting that the free-swimming
larval stages utilised this as an energy reserve. Rate of depletion was faster in nauplii
held at higher temperatures. Longevity, activity and infectivity of the infective stage
decreased with age. However, both spontaneous and stimulus dependent activity
ceased many hours before death and both activity and longevity were affected by
temperature. Infectivity of I day old L. salmonis copepodids was higher than 7 day old
larvae, and was considered to be related to the size of the energy reserves. The settlement and distribution pattern of copepodids did not change with age of copepodid,
the majority being recorded from the fins.
All three L. salmonis free-swimming larval stages demonstrated a "hop and
sink" swimming pattern. The velocity and duration of both passive sinking and active
swimming was recorded for both nauplii and copepodids. Although greater periods of
time were spent passively sinking, the speeds obtained during both upward spontaneous
and stimulated swimming meant that a net upward movement of larvae in the water
column occurred. At higher temperatures spontaneous swimming activity increased,
whilst low salinities caused a cessation of such ability. L. salmonis larvae were
positively phototactic and negatively geotactic. As well as their positive responses to
light intensity, the nauplius 11 and copepodid stages reacted positively to blue-green
spectral wavelengths. Moulting times were relatively short, although the larvae were
not able to swim during such periods. No relationship was found between the level of
lipid reserves and the overall buoyancy of the larvae.
Naupliar stages of both L. salmonis and C. elongalus were obtained from the
water column as a result of a plankton sampling programme at a commercial Atlantic
salmon farm. No copepodid stages of either species were found. There was no
difference in the vertical distribution of the two L. salmonis naupliar stages. Live
larvae tended to aggregate between 0 and 5m in depth, with no diurnal vertical
migration. Dead nauplii, and those with low lipid reserves, were found deeper in the
water column. Naupliar stages, and in particular the first larval stage, were
concentrated in number within cages indicating that the cages have a retentive
characteristic. A novel control method in the form of a commercially available light
lure was tested. Though increasing the numbers of free-living copepods captured, it had no effect on
the numbers of L. salmonis naupliar or copepodid stages obtained in plankton samples.
The present study has therefore provided valuable data concerning the biology
and ecology of the free-swimming larval stages of sea lice, in what was a comparatively
poorly understood area
First lipase catalysed resolution of epoxy enol esters.
We report the first enzyme-catalysed kinetic resolution of epoxy enol esters. The lipase-promoted hydrolysis of these compounds provided α-hydroxyketones or α-hydroxyaldehydes (arising from the spontaneous rearrangement of the epoxy enols) and the residual esters with moderate to good enantioselectivity (E up to 100)
Ab initio calculations for bromine adlayers on the Ag(100) and Au(100) surfaces: the c(2x2) structure
Ab initio total-energy density-functional methods with supercell models have
been employed to calculate the c(2x2) structure of the Br-adsorbed Ag(100) and
Au(100) surfaces. The atomic geometries of the surfaces and the preferred
bonding sites of the bromine have been determined. The bonding character of
bromine with the substrates has also been studied by analyzing the electronic
density of states and the charge transfer. The calculations show that while the
four-fold hollow-site configuration is more stable than the two-fold
bridge-site topology on the Ag(100) surface, bromine prefers the bridge site on
the Au(100) surface. The one-fold on-top configuration is the least stable
configuration on both surfaces. It is also observed that the second layer of
the Ag substrate undergoes a small buckling as a consequence of the adsorption
of Br. Our results provide a theoretical explanation for the experimental
observations that the adsorption of bromine on the Ag(100) and Au(100) surfaces
results in different bonding configurations.Comment: 10 pages, 4 figure, 5 tables, Phys. Rev. B, in pres
Roughening of close-packed singular surfaces
An upper bound to the roughening temperature of a close-packed singular
surface, fcc Al (111), is obtained via free energy calculations based on
thermodynamic integration using the embedded-atom interaction model. Roughening
of Al (111) is predicted to occur at around 890 K, well below bulk melting (933
K), and it should therefore be observable, save for possible kinetic hindering.Comment: RevTeX 4 pages, embedded figure
Illuminating the planktonic stages of salmon lice: A unique fluorescence signal for rapid identification of a rare copepod in zooplankton assemblages
Monitoring of planktonic salmon louse (Lepeophtheirus salmonis salmonis) abundance and parameterization of key lifeâhistory traits has been hindered by labourâintensive and errorâprone quantification using traditional light microscopy. Fluorescence illumination has been proposed as a means of improving visualization, but prior to this study adequate investigation of the relevant fluorescence profiles and measurement conditions has not been undertaken. We investigated the fluorescence profiles of L. salmonis and nonâtarget copepod spp. with excitation and emission matrices (200â600 nm) and identified unique fluorescence signals. Fluorescence microscopy using excitation wavelengths of 470 ± 40 nm, and emission wavelengths of 525 ± 50 nm, showed that after 90 days of formalin storage salmon lice have a mean fluorescence intensity that is 2.4 times greater than nonâtarget copepods (copepodid and adult stages). A 7âday heat treatment of 42°C in formalin increased the difference between salmon louse copepodids and nonâtarget copepods to a factor of 3.6, eliminating the need for prolonged storage. Differences in the fluorescence signal and endogenous fluorophores were investigated with respect to variation in sea lice species, age, stage and host fish origin. Under the conditions outlined in this paper, the fluorescence signal was found to be a reliable means of visualizing and differentiating salmon lice from nonâtarget zooplankters. Adaptation of the fluorescence signal would greatly expedite traditional methods of enumerating salmon louse larvae in plankton samples and could provide a means of automated detection
Inactivation of palladium-based oxygen scavenger system by volatile sulphur compounds present in the headspace of packaged food
An oxygen scavenger based on a catalytic system with palladium (CSP) was recently developed to remove oxygen in food packagings. Although the CSP worked with various types of food, with some foods, an inhibition of the CSP was observed. Because such catalytic systems are susceptible to poisoning by sulfurcontaining compounds, the aim of this study was to understand the inactivation of palladium-based catalysts in presence of foods containing volatile sulfur compounds (VSCs). To achieve this, the oxygen scavenging activity (OSA) of the CSP was evaluated in presence of selected food products. Afterwards, VSCs mainly present in these foods were exposed to the CSP, and the influence on the OSA was evaluated. Finally, headspace analysis was performed with the diluted VSCs and with the packaged food products using proton transfer reaction time-of-flight mass spectrometry. It was found that the catalytic activity of the CSP was inhibited when VSCs were present in the headspace in concentrations ranging between 10.8â36.0 ppbv (dimethyl sulfide, DMS), 1.2â7.2 ppbv (dimethyl disulfide), 0.7â0.9 ppbv (dimethyl trisulfide), 2.1â5.8 ppbv methional) and 4.6â24.5 ppbv (furfuryl thiol). It was concluded that in packaged roast beef and cheese, DMS may be the compound mainly responsible for the inactivation of the CSP. In packagings containing ham, the key compounds were hydrogen sulfide and methanethiol; in peanuts, it was methanethiol; and in par-baked buns, an accumulation of methional, DMS, butanethiol and methionol. When potato chips were packaged, it was demonstrated that when VSCs are present in low concentrations, oxygen can still be scavenged at a reduced OSA
Structural and Electronic Decoupling of C_(60) from Epitaxial Graphene on SiC
We have investigated the initial stages of growth and the electronic structure of C_(60) molecules on graphene grown epitaxially on SiC(0001) at the single-molecule level using cryogenic ultrahigh vacuum scanning tunneling microscopy and spectroscopy. We observe that the first layer of C_(60) molecules self-assembles into a well-ordered, close-packed arrangement on graphene upon molecular deposition at room temperature while exhibiting a subtle C_(60) superlattice. We measure a highest occupied molecular orbitalâlowest unoccupied molecular orbital gap of ~ 3.5 eV for the C_(60) molecules on graphene in submonolayer regime, indicating a significantly smaller amount of charge transfer from the graphene to C_(60) and substrate-induced screening as compared to C_(60) adsorbed on metallic substrates. Our results have important implications for the use of graphene for future device applications that require electronic decoupling between functional molecular adsorbates and substrates
- âŠ