376 research outputs found
History teaching in Finnish general upper secondary schools: Objectives and practices
In Finland, the trend towards a new kind of history teaching emphasizing the understanding of historical knowledge and historical thinking skills began in the
mid-1990s, when history teaching objectives were defined much more broadly in the curriculum than previously. In this article, we examine how, in over twenty years
since the changes in curriculum objectives were made, general upper secondary school teachers have come to value the curriculum objectives of history teaching
and how these have impacted on their teaching. The data for this article were collected by a semi-structured survey in 2016. Using counts, percentages, means,
standard deviations and medians, a descriptive exploration was made of history teachers’ perceptions of the essential objectives in teaching history and how
often they were put into practice in related student activities. To investigate the balance between the objectives the teachers emphasized as the most essential
and the teaching methods they actually used, we applied the Kruskal–Wallis test and the Friedman test. According to the results, what the teachers considered
essential for teaching history did not correlate with their teaching methods. In addition, according to the results, this state of affairs is still undergoing change; old traditions and new objectives of history teaching are creating tensions. The
results were interpreted in the light of the cultural viewpoints of Finnish teaching, the position of matriculation examinations in Finnish general upper secondary schools and the challenges the curriculum is setting for history teacher
The potential of Landsat time series to characterize historical dynamic and monitor future disturbances in human-modified rainforests of Indonesia
In this study we demonstrated for the first time the potential of using full time series from high spatial resolution (30 m) Landsat satellites, covering a period from 1987-2017, for characterizing historical dynamics in Indonesian humid tropical rainforests. Our special focus was on mapping forest disturbance and post-disturbance regrowth, which in turn can potentially be used to map primary (undisturbed) forests, secondary (disturbed/degraded) forests, and forest land converted to oil palm plantation. We applied the Breaks For Additive Season and Trend (BFAST) Monitor framework for continuous change detection; BFAST is a generic and transparent method, which can be used for near-real-time monitoring. To verify our approach, a preliminary spatial accuracy assessment was carried out for disturbance detection using 418 sample pixels interpreted from very high spatial resolution images acquired through Digital Globe viewing service. Besides, we identified the sources of detection errors and approaches to overcome them. Implementation of the potential map product in existing international and national policies will be discusse
Radial Dependence of the Pattern Speed of M51
The grand-design spiral galaxy M51 has long been a crucial target for
theories of spiral structure. Studies of this iconic spiral can address the
question of whether strong spiral structure is transient (e.g.
interaction-driven) or long-lasting. As a clue to the origin of the structure
in M51, we investigate evidence for radial variation in the spiral pattern
speed using the radial Tremaine-Weinberg (TWR) method. We implement the method
on CO observations tracing the ISM-dominant molecular component. Results from
the method's numerical implementation--combined with regularization, which
smooths intrinsically noisy solutions--indicate two distinct patterns speeds
inside 4 kpc at our derived major axis PA=170 deg., both ending at corotation
and both significantly higher than the conventionally adopted global value.
Inspection of the rotation curve suggests that the pattern speed interior to 2
kpc lacks an ILR, consistent with the leading structure seen in HST near-IR
observations. We also find tentative evidence for a lower pattern speed between
4 and 5.3 kpc measured by extending the regularized zone. As with the original
TW method, uncertainty in major axis position angle (PA) is the largest source
of error in the calculation; in this study, where \delta PA=+/-5 deg. a ~20%
error is introduced to the parameters of the speeds at PA=170 deg. Accessory to
this standard uncertainty, solutions with PA=175 deg. (also admitted by the
data) exhibit only one pattern speed inside 4 kpc, and we consider this
circumstance under the semblance of a radially varying PA.Comment: 14 pages in emulateapj format, 12 figures, accepted for publication
in Ap
Double Bars, Inner Disks, and Nuclear Rings in Early-Type Disk Galaxies
We present results from an imaging survey of an unbiased sample of
thirty-eight early-type (S0--Sa), low-inclination, optically barred galaxies in
the field. Our goal was to find and characterize central stellar and gaseous
structures: secondary bars, inner disks, and nuclear rings. Bars inside bars
are surprisingly common: at least one quarter of the sample galaxies (possibly
as many as 40%) are double-barred, with no preference for Hubble type or the
strength of the primary bar. A typical secondary bar is ~12% of the size of its
primary bar and 240--750 pc in radius. We see no significant effect of
secondary bars on nuclear activity. We also find kiloparsec-scale inner disks
in at least 20% of our sample, almost exclusively in S0 galaxies. These disks
are on average 20% the size of their host bar, and show a wider range of
relative sizes than do secondary bars. Nuclear rings are present in about a
third of our sample. Most are dusty, sites of current or recent star formation,
or both; such rings are preferentially found in Sa galaxies. Three S0 galaxies
(15% of the S0's) appear to have purely stellar nuclear rings, with no evidence
for dust or recent star formation. The fact that these central stellar
structures are so common indicates that the inner regions of early-type barred
galaxies typically contain dynamically cool and disklike structures. This is
especially true for S0 galaxies, where secondary bars, inner disks, and/or
stellar nuclear rings are present at least two thirds of the time. (abridged)Comment: LaTeX, 15 pages, 7 EPS figures; to appear in The Astronomical Journal
(July 2002
Development of a Sandwich ELISA to Measure Exposure to Occupational Cow Hair Allergens
Background: Cow hair and dander are important inducers of occupational allergies in cattle-exposed farmers. To estimate allergen exposure in farming environments, a sensitive enzyme immunoassay was developed to measure cow hair allergens. Methods: A sandwich ELISA was developed using polyclonal rabbit antibodies against a mixture of hair extracts from different cattle breeds. To assess the specificity of the assay, extracts from other mammalian epithelia, mites, molds and grains were tested. To validate the new assay, cow hair allergens were measured in passive airborne dust samples from the stables and homes of farmers. Dust was collected with electrostatic dust fall collectors (EDCs). Results: The sandwich ELISA was found to be very sensitive (detection limit: 0.1 ng/ml) and highly reproducible, demonstrating intra-and interassay coefficients of variation of 4 and 10%, respectively. The assay showed no reactivity with mites, molds and grains, but some cross-reactivity with other mammalian epithelia, with the strongest reaction with goat. Using EDCs for dust sampling, high concentrations of bovine allergens were measured in cow stables (4,760-559,400 mu g/m(2)). In addition, bovine allergens were detected in all areas of cattle farmer dwellings. A large variation was found between individual samples (0.3-900 mu g/m(2)) and significantly higher values were discovered in changing rooms. Conclusion: The ELISA developed for the detection of cow hair proteins is a useful tool for allergen quantification in occupational and home environments. Based on its low detection limit, this test is sensitive enough to detect allergens in passive airborne dust. Copyright (C) 2011 S. Karger AG, Base
Predictors for occupational injuries and diseases among commercial fishers in Finland 1996–2015
Fishing is a hazardous occupation worldwide. Commercial fishers in Finland are an aging and diminishing population with a high injury rate. Insurance claims data for self-employed Finnish commercial fishers during the years 1996 through 2015 (n = 1951) were analysed to assess predictors for occupational injuries and diseases. Out of the available variables, fishery location, career length, and participation in the voluntary occupational health service programme were not significant predictors. Male gender (OR 2.02; 95% CI 1.37–2.99), Finnish mother tongue vs. Swedish (OR 1.98, 95% CI 1.53–2.55), and higher income levels from fishing (four income categories, OR range: 1.71–3.53) were associated with higher odds for a compensated occupational injury or disease claim among commercial fishers in the final multivariate model. The identified risk groups could be targeted for interventions, and the content of the occupational health service programme should be developed to gain protective effect
Kinematics of the outer pseudorings and the spiral structure of the Galaxy
The kinematics of the outer rings and pseudorings is determined by two
processes: the resonance tuning and the gas outflow. The resonance kinematics
is clearly observed in the pure rings, while the kinematics of the gas outflow
is manifested itself in the pseudorings. The direction of systematical motions
in the pure rings depends on the position angle of a point with respect to the
bar major axis and on the class of the outer ring. The direction of the radial
and azimuthal components of the residual velocities of young stars in the
Perseus, Carina, and Sagittarius regions can be explained by the presence of
the outer pseudoring of class R1R2' in the Galaxy. We present models, which
reproduce the directions and values of the residual velocities of
OB-associations in the Perseus and Sagittarius regions, and also model
reproducing the directions of the residual velocities in the Perseus,
Sagittarius, and Carina regions. The kinematics of the Sagittarius region
accurately defines the solar position angle with respect to the bar elongation,
theta_b=45 (+/-5) deg.Comment: 16 pages, 10 figures, accepted for publication in Astronomy Letter
Towards the Secondary Bar: Gas Morphology and Dynamics in NGC 4303
The bulk of the molecular line emission in the double barred galaxy NGC4303
as observed in its CO(1-0) line with the OVRO mm-interferometer comes from two
straight gas lanes which run north-south along the leading sides of the
large-scale primary bar. Inside a radius of ~ 400 pc the molecular gas forms a
spiral pattern which, for the northern arm, can be traced to the nucleus.
Comparison of the OVRO and archival HST data with dynamical models of gas flow
in the inner kiloparsec of single- and double-barred galaxies shows that the
observed global properties of the molecular gas are in agreement with models
for the gas flow in a strong, large-scale bar, and the two-arm spiral structure
seen in CO in the inner kiloparsec can already be explained by a density wave
initiated by the potential of that bar. Only a weak correlation between the
molecular gas distribution and the extinction seen in the HST V-H map is found
in the inner 400 pc of NGC4303: The innermost part of one arm of the nuclear CO
spiral correlates with a weak dust filament in the color map, while the overall
dust distribution follows a ring or single-arm spiral pattern well correlated
with the UV continuum. This complicated nuclear geometry of the stellar and
gaseous components allows for two scenarios: (A) A self-gravitating m=1 mode is
present forming the spiral structure seen in the UV continuum. In this case the
gas kinematics would be unaffected by the small (~ 4'') inner bar. (B) The UV
continuum traces a complete ring which is heavily extincted north of the
nucleus. Such a ring forms in hydrodynamic models of double bars, but the
models cannot account for the UV emission observed on the leading side of the
inner bar. (abridged)Comment: 47 pages, 14 figures, accepted for publication in Ap
On the Link Between Central Black Holes, Bar Dynamics, and Dark Matter Halos in Spiral Galaxies
The discovery of a relationship between supermassive black hole (SMBH) mass
and spiral arm pitch angle (P) is evidence that SMBHs are tied to the overall
secular evolution of a galaxy. The discovery of SMBHs in late-type galaxies
with little or no bulge suggests that an underlying correlation between the
dark matter halo concentration and SMBH mass (MBH) exists, rather than between
the bulge mass and MBH. In this paper we measure P using a two-dimensional fast
fourier transform and estimate the bar pattern speeds of 40 barred spiral
galaxies from the Carnegie-Irvine Galaxy Survey. The pattern speeds were
derived by estimating the gravitational potentials of our galaxies from Ks-band
images and using them to produce dynamical simulation models. The pattern
speeds allow us to identify those galaxies with low central dark halo
densities, or fast rotating bars, while P provides an estimate of MBH. We find
that a wide range of MBH exists in galaxies with low central dark matter halo
densities, which appears to support other theoretical results. We also find
that galaxies with low central dark halo densities appear to follow more
predictable trends in P versus de Vaucouleurs morphological type (T) and bar
strength versus T than barred galaxies in general. The empirical relationship
between MBH and total gravitational mass of a galaxy (Mtot) allows us to
predict the minimum Mtot that will be observationally measured of our fast bar
galaxies. These predictions will be investigated in a subsequent paper.Comment: 17 pages, 1 table, 11 figures, accepted for publication in MNRA
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