35,915 research outputs found
Evaluation of World Wide Web-based Lessons for a First Year Dental Biochemistry Course
First year dental students at The University of Texas Dental Branch at Houston (Dental Branch) are required to take a basic biochemistry course. To facilitate learning and allow student self-assessment of their progress, WWW-based lessons covering intermediary metabolism were developed as a supplement to traditional lectures. Lesson design combined text, graphics, and animations and included learner control, links to other learning resources, and practice exercises and exams with immediate feedback. Results from an on-line questionnaire completed by students in two different classes showed that they completed 50% of the lessons and spent an average of 4 hrs. on-line. A majority of the students either agreed or strongly agreed that practice exercises were helpful, that the ability to control the pace of the lessons was important, that the lesson structure and presentation was easy to follow, that the illustrations, animations, and hyperlinks were helpful, and that the lessons were effective as a review. The very positive response to the WWW-based lessons indicates the usefulness of this approach as a study aid for dental students
A duality principle for selection games
A dinner table seats k guests and holds n discrete morsels of food. Guests
select morsels in turn until all are consumed. Each guest has a ranking of the
morsels according to how much he would enjoy eating them; these rankings are
commonly known.
A gallant knight always prefers one food division over another if it provides
strictly more enjoyable collections of food to one or more other players
(without giving a less enjoyable collection to any other player) even if it
makes his own collection less enjoyable. A boorish lout always selects the
morsel that gives him the most enjoyment on the current turn, regardless of
future consumption by himself and others.
We show the way the food is divided when all guests are gallant knights is
the same as when all guests are boorish louts but turn order is reversed. This
implies and generalizes a classical result of Kohler and Chandrasekaran (1971)
about two players strategically maximizing their own enjoyments. We also treat
the case that the table contains a mixture of boorish louts and gallant
knights.
Our main result can also be formulated in terms of games in which selections
are made by groups. In this formulation, the surprising fact is that a group
can always find a selection that is simultaneously optimal for each member of
the group.Comment: 8 pages, 2 figure
Comparison of approximate and numerical analyses of nonlinear combustion instability
At the present time, there are three general analytical techniques available to study problems of unsteady motions in rocket motors: linear stability analysis; approximate nonlinear analysis, founded on examining the behavior of coupled normal modes; and numerical calculations based on
the conservation equations for one-dimensional flows. The last two yield the linear results as a limit. It is the main purpose of this paper to check the accuracy of the approximate analysis against the numerical analysis for some special cases. The results provide some justification for using the approximate analysis to study three dimensional problems
Condensation and coexistence in a two-species driven model
Condensation transition in two-species driven systems in a ring geometry is
studied in the case where current-density relation of a domain of particles
exhibits two degenerate maxima. It is found that the two maximal current phases
coexist both in the fluctuating domains of the fluid and in the condensate,
when it exists. This has a profound effect on the steady state properties of
the model. In particular, phase separation becomes more favorable, as compared
with the case of a single maximum in the current-density relation. Moreover, a
selection mechanism imposes equal currents flowing out of the condensate,
resulting in a neutral fluid even when the total number of particles of the two
species are not equal. In this case the particle imbalance shows up only in the
condensate
Stars in the USNO-B1 Catalog with Proper Motions Between 1.0 and 5.0 arcseconds per year
This paper examines a subset of objects from the USNO-B1 catalogue with
listed proper motions between 1.0 and 5.0 arcseconds per year. We look at the
degree of contamination within this range of proper motions, and point out the
major sources of spurious high proper motion objects. Roughly 0.1% of the
objects in the USNO-B1 catalogue with listed motions between 1.0 and 5.0
arcseconds per year are real. Comparison with the revised version of Luyten's
Half Second catalogue indicates that USNO-B1 is only about 47% complete for
stars in this range. Preliminary studies indicate that there may be a dip in
completeness in USNO-B1 for objects with motions near 0.1 arcseconds per year.
We also present two new stars with motions between 1.0 and 5.0 arcseconds per
year, 36 new stars with confirmed motions between 0.1 and 1.0 arcseconds per
year, several new common proper motion pairs, and the recovery of LHS237a
(VBs3).Comment: 42 pages, 16 figures, uses AASTeX v5.2, accepted by A
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