231 research outputs found
Does the mode of delivery affect mathematics examination results?
At present most examinations are delivered on paper but there is a growing trend in many subjects to deliver some or part of these examinations by computer. It is therefore important to know whether there are any differences in the results obtained by candidates sitting examinations taken by computer compared with those obtained by candidates sitting conventional examinations using pen and paper. The purpose of this article is to describe the outcome of a pilot study designed to∗ investigate possible causes of any differences in results from the use of different modes of delivery in a mathematics examination. One outcome of this study was that the process of translating examination questions into a format required for use on the computer (but keeping this as a pen and paper test) can have a significant effect on examination results. However, the main conclusion is that changing the medium only has no effect on the results in mathematics examinations
Numerical Study of Competing Spin-Glass and Ferromagnetic Order
Two and three dimensional random Ising models with a Gaussian distribution of
couplings with variance and non-vanishing mean value are studied
using the zero-temperature domain-wall renormalization group (DWRG). The DWRG
trajectories in the () plane after rescaling can be collapsed on two
curves: one for and other for . In the first case
the DWRG flows are toward the ferromagnetic fixed point both in two and three
dimensions while in the second case flows are towards a paramagnetic fixed
point and spin-glass fixed point in two and three dimensions respectively. No
evidence for an extra phase is found.Comment: a bit more data is taken, 5 pages, 4 eps figures included, to appear
in PR
Partial credit in mathematics exams - a comparison of traditional and CAA exams
With the growing trend in many subjects to deliver at least some part of examinations by computer, it is important to know whether there are any differences in the results obtained by candidates sitting examinations taken by computer compared to those obtained by candidates sitting conventional examinations using pen and paper. The purpose of this paper is to describe a pilot project to compare the traditional type of assessment with assessment done by computer in mathematics examinations and in particular to investigate the role of partial credit in these examinations. In paper based examinations full marks are awarded for a completely correct answer. If, however, a student obtains an incorrect answer but gets some parts of the working correct then in mathematics examinations partial credit is normally awarded. In a computer examination an incorrect answer to a question is normally awarded no marks with no consideration of any partial credit. The mechanism for giving partial credit in the computer examinations of this project was to break the question down into Steps. The project compared results of students taking computer tests in three different formats (either no Steps, compulsory Steps or optional Steps) and the partial credit they would have obtained by taking the corresponding examinations on paper. The tests were at the level of Scottish Higher school examinations and were taken by school students who were about to sit their Higher examinations. This level was chosen as it was high enough to test the students on strategy and mathematical working, while the questions were not too long so that a clearer analysis of the results was possible
Immunohistochemical detection improves the prognostic value of lymphatic and blood vessel invasion in primary ductal breast cancer
Background<p></p>
Lymphovascular invasion (LBVI) including lymphatic (LVI) and blood (BVI) vessel invasion is a critical step in cancer metastasis. In breast cancer, the optimal detection method of LBVI remains unclear. This research aimed to compare the prognostic value of different assessments of the LVI and BVI in patients with early breast cancer.<p></p>
Methods<p></p>
The study cohort included 360 patients with a median follow-up of 168 months. LBVI on H&E sections (LBVIH&E) was reviewed centrally and blinded to the pathology report. Immunohistochemical staining for D2-40 and Factor VIII was performed to identify LVID2–40 and BVIFVIII.<p></p>
Results<p></p>
LBVIH&E, LVID2–40 and BVIFVIII were present in 102 (28%), 127 (35%) and 59 (16%) patients respectively. In node-negative patients (206), LBVIH&E, LVID2–40 and BVIFVIII were present in 41 (20%), 53 (26%) and 21 (10%) respectively. In triple-negative patients (120), LBVIH&E, LVID2–40 and BVIFVIII were present in 35 (29%), 46 (38%) and 16 (13%) respectively. LBVIH&E was significantly associated with tumour recurrence in the whole cohort (P < 0.001), node-negative patients (P = 0.001) and triple-negative patients (P = 0.004). LVID2–40 and BVIFVIII were significantly associated with tumour recurrence in whole cohort, node-negative (all P < 0.001) and triple-negative patients (P = 0.002). In multivariate survival analysis, only LVID2–40 and BVIFVIII were independent predictors of cancer specific survival in the whole cohort (P = 0.023 and P < 0.001 respectively), node-negative patients (P = 0.004 and P = 0.001 respectively) and triple-negative patients (P = 0.014 and P = 0.001 respectively).<p></p>
Conclusion<p></p>
Assessment of LVI and BVI by IHC using D2-40 and Factor VIII improves prediction of outcome in patients with node-negative and triple-negative breast cancer
Multiwavelength Studies of Young OB Associations
We discuss how contemporary multiwavelength observations of young
OB-dominated clusters address long-standing astrophysical questions: Do
clusters form rapidly or slowly with an age spread? When do clusters expand and
disperse to constitute the field star population? Do rich clusters form by
amalgamation of smaller subclusters? What is the pattern and duration of
cluster formation in massive star forming regions (MSFRs)? Past observational
difficulties in obtaining good stellar censuses of MSFRs have been alleviated
in recent studies that combine X-ray and infrared surveys to obtain rich,
though still incomplete, censuses of young stars in MSFRs. We describe here one
of these efforts, the MYStIX project, that produced a catalog of 31,784
probable members of 20 MSFRs. We find that age spread within clusters are real
in the sense that the stars in the core formed after the cluster halo. Cluster
expansion is seen in the ensemble of (sub)clusters, and older dispersing
populations are found across MSFRs. Direct evidence for subcluster merging is
still unconvincing. Long-lived, asynchronous star formation is pervasive across
MSFRs.Comment: 22 pages, 9 figures. To appear in "The Origin of Stellar Clusters",
edited by Steven Stahler, Springer, 2017, in pres
The Eigenvalue Analysis of the Density Matrix of 4D Spin Glasses Supports Replica Symmetry Breaking
We present a general and powerful numerical method useful to study the
density matrix of spin models. We apply the method to finite dimensional spin
glasses, and we analyze in detail the four dimensional Edwards-Anderson model
with Gaussian quenched random couplings. Our results clearly support the
existence of replica symmetry breaking in the thermodynamical limit.Comment: 8 pages, 13 postscript figure
Ultrametricity in 3D Edwards-Anderson spin glasses
We perform an accurate test of Ultrametricity in the aging dynamics of the
three dimensional Edwards-Anderson spin glass. Our method consists in
considering the evolution in parallel of two identical systems constrained to
have fixed overlap. This turns out to be a particularly efficient way to study
the geometrical relations between configurations at distant large times. Our
findings strongly hint towards dynamical ultrametricity in spin glasses, while
this is absent in simpler aging systems with domain growth dynamics. A recently
developed theory of linear response in glassy systems allows to infer that
dynamical ultrametricity implies the same property at the level of equilibrium
states.Comment: 4 pages, 5 figure
Influence of Carbon Concentration on the Superconductivity in MgCxNi3
The influence of carbon concentration on the superconductivity (SC) in
MgCNi has been investigated by measuring the low temperature specific
heat combined with first principles electronic structure calculation. It is
found that the specific heat coefficient of the
superconducting sample () in normal state is twice that of the
non-superconducting one (). The comparison of measured
and the calculated electronic density of states (DOS) shows that the
effective mass renormalization changes remarkably as the carbon concentration
changes. The large mass renormalization for the superconducting sample and the
low (7K) indicate that more than one kind of boson mediated
electron-electron interactions exist in MgCNi.Comment: 4 pages, 4 figure
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Transpacific Transport of Ozone Pollution and the Effect of Recent Asian Emission Increases on Air Quality in North America: An Integrated Analysis Using Satellite, Aircraft, Ozonesonde, and Surface Observations
We use an ensemble of aircraft, satellite, sonde, and surface observations for April–May 2006 (NASA/INTEX-B aircraft campaign) to better understand the mechanisms for transpacific ozone pollution and its implications for North American air quality. The observations are interpreted with a global 3-D chemical transport model (GEOS-Chem). OMI NO2 satellite observations constrain Asian anthropogenic NOx emissions and indicate a factor of 2 increase from 2000 to 2006 in China. Satellite observations of CO from AIRS and TES indicate two major events of Asian transpacific pollution during INTEX-B. Correlation between TES CO and ozone observations shows evidence for transpacific ozone pollution. The semi-permanent Pacific High and Aleutian Low cause splitting of transpacific pollution plumes over the Northeast Pacific. The northern branch circulates around the Aleutian Low and has little impact on North America. The southern branch circulates around the Pacific High and some of that air impacts western North America. Both aircraft measurements and model results show sustained ozone production driven by peroxyacetylnitrate (PAN) decomposition in the southern branch, roughly doubling the transpacific influence from ozone produced in the Asian boundary layer. Model simulation of ozone observations at Mt. Bachelor Observatory in Oregon (2.7 km altitude) indicates a mean Asian ozone pollution contribution of 9±3 ppbv to the mean observed concentration of 54 ppbv, reflecting mostly an enhancement in background ozone rather than episodic Asian plumes. Asian pollution enhanced surface ozone concentrations by 5–7 ppbv over western North America in spring 2006. The 2000–2006 rise in Asian anthropogenic emissions increased this influence by 1–2 ppbv.Earth and Planetary SciencesEngineering and Applied Science
Coulomb gap in a model with finite charge transfer energy
The Coulomb gap in a donor-acceptor model with finite charge transfer energy
describing the electronic system on the dielectric side of the
metal-insulator transition is investigated by means of computer simulations on
two- and three-dimensional finite samples with a random distribution of equal
amounts of donor and acceptor sites. Rigorous relations reflecting the symmetry
of the model presented with respect to the exchange of donors and acceptors are
derived. In the immediate neighborhood of the Fermi energy the the
density of one-electron excitations is determined solely by
finite size effects and further away from is described by
an asymmetric power law with a non-universal exponent, depending on the
parameter .Comment: 10 pages, 6 figures, submitted to Phys. Rev.
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