Transcript 3.3M - The University of Sydney

Honours Coursework 2013
2011
SCIENTIFIC LITERATURE
Objectives
Be able to research a scientific topic from primary
sources
Be able to synthesize a coherent and instructive story
based on these findings
Communicate this story in written prose, paying
attention to correct referencing
Honours Coursework 2013
2011
SCIENTIFIC LITERATURE
Your task
You will write a Science Perspectives style article on any
paper published in Science in 2003 (ie 10 years ago) for which
a Perspectives article was not originally written.
•
•
•
•
•
Explain the motivation and the context of the work
Explain the key experiment(s)
Explain the importance
Who else was working on the problem?
What have been the consequences of the work?
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Assessment
20% - literature web, Fri 22nd Feb
10% - first paragraph, Fri 1st March
70% - final report, Fri 22nd March
2500 words maximum
Honours Coursework 2013
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SCIENTIFIC LITERATURE
The Ideal Perspective: Guidelines for Authors
Perspectives in SCIENCE are short overviews of current research findings,
intended for a very broad audience of scientists.
Your task is to tell other readers, especially those outside of your field,
about exciting research developments within your area of expertise.
Perspectives may accompany either a paper in SCIENCE, discuss work
published elsewhere, or describe results presented at a workshop or
conference. In each case, the goal should be interdisciplinary
communication.
Perspectives are not intended to be hypotheses or unsupported
speculation, nor should they be presentations of your own original
research. Perspectives commenting on papers in Science should add a
fresh dimension to the research and not merely summarize the
experiments reported in the paper.
Honours Coursework 2013
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SCIENTIFIC LITERATURE
The Ideal Perspective: Guidelines for Authors
a max
of two figures
• Perspectives are limited to about 2500
1000 words and one
figure
unless the editor has specified otherwise.
Figurescan
should
be incorporated
intosubmitted
the text as
• Figures
be draft
artwork or ideas
aspublication
sketches or quality
written descriptions. Figure files must be in Illustrator, Postscript,
JPEG, TIFF, or EPS format (see “Figure formats” below).
• Permission is required from copyright holders to reprint any
published or Web images.
• Citations to unpublished work and personal communications should
not be used to support the main points of the commentary.
• Because we want this section of the journal to be visually engaging as
well as informative, each Perspective should include one figure.
• Text (including reference list and figure caption) should be no more
than 1000
2500 words.
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Writing your Perspective:
• You should begin with an introductory paragraph that captures the
reader's interest and immediately gets to the point. If you are discussing a
specific scientific paper, be sure to refer to the paper somewhere in the
first paragraph. Your introduction should be general enough to orient the
reader not familiar with the specifics of your field. Here, and throughout
the text, you should avoid jargon and the special terms of your field. If the
language of specialists is necessary, please briefly define it for the general
reader. Please keep the use of acronyms to a minimum.
• The final paragraph should draw the piece to a concise conclusion,
without simply restating the text. Tell the reader about future prospects
and implications. What are the unanswered questions? Where is the field
going?
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Writing your Perspective:
Negotiable
• The references should be as condensed as possible (no
more than<30
15
items), while still citing the essential literature. Perspectives are not
comprehensive reviews, so the reference list cannot be an exhaustive
bibliography. Avoid lengthy notes, details, or asides that interrupt the
flow of the text.
• Include (for the extra up to 1500 words) how the science of your chosen
article has developed over the intervening 10 years:
 what is its impact?
 did the science move in the directions initially anticipated?
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Lecture Schedule
1. Introduction
5. First sentence*
2. Writing a paper
6. First paragraph*
3. Writing a paper
7. Last paragraph*
4. The key paper*
Literature web*
9. Report due
* class-led discussion
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SCIENTIFIC LITERATURE
“In science the credit goes to the man who
convinces the world, not to the man to
whom the idea first occurs.”
Sir Francis Darwin (1848-1925 English Botanist, son of
Charles Darwin)
Essay on Francis Galton 1822-1911 Eugenics Review, April 1914
“I should like to express my appreciation of the honour done
me in asking me to give the first Galton lecture. In many
ways I am a bad choice, since I have had no share in his
science of eugenics, neither has my research-work been
directly connected with evolution.”
Honours Coursework 2013
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SCIENTIFIC LITERATURE
“If you can't explain what you're doing and
why you're doing it to any intelligent
layman, that really means that you don't
understand it yourself.”
Allan Bromley, former President of the American Physical
Society.
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Presentation Objectives
Importance of
Scientific Writing
Key Principles
audience
occasion
purpose
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SCIENTIFIC LITERATURE
Impact of Career
How well you communicate affects your career
• Successful scientist spent 25% of work week writing
(Davis 1997)
• Professional scientists found writing their most useful
subject (University of Wisconsin)
• MSU CANR Alumni need most work on their writing
(Suvedi, 2001)
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SCIENTIFIC LITERATURE
Impact on Others
Explosion was caused by failure of
O-rings in the solid rocket
boosters
Engineers knew of O-ring problems
well before fatal launch
Space Shuttle
Challenger
(January 28, 1986)
Engineers failed to communicate
seriousness of problem
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SCIENTIFIC LITERATURE
Communication Needs
Conferences
Lectures
Meetings
Posters
Reports
Articles
Proposals
Web Pages
specific
technical
audiences
general
technical
audiences
non-technical
audiences
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SCIENTIFIC LITERATURE
In the Beginning
Begin by analyzing your constraints
• Audience
•
•
•
•
Who they are
What they know
Why they will read
How they will read
• Occasion
•
•
•
•
Format
Formality
Politics and ethics
Process and deadline
• Purpose
• To inform
• To persuade
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Let’s have a look at a 2002 Science Paper
Constraints on Melt Movement Beneath the East Pacific Rise
From 230Th-238U Disequilibrium
Haibo Zou, Alan Zindler, Yaoling Niu
ABSTRACT
We report 230Th-238U disequilibrium data on mid-ocean ridge basalts
recovered 5 to 40 kilometers off the ridge axis near 9°30′N of the
East Pacific Rise. These data indicate near-symmetrical eruptions of
normal mid-ocean ridge basalts (NMORBs) and incompatible
element–enriched mid-ocean ridge basalts (EMORBs) as far as 20
kilometers off axis. Our results suggest large-scale subsurface lateral
transport of NMORB melt at 19 to 21 centimeters per year and also
provide constraints on the petrogenesis of EMORBs of off-axis origin.
Science 4 January 2002:
Vol. 295 no. 5552 pp. 107-110
DOI: 10.1126/science.1064295
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Lavas that erupt on the seafloor away from the axis of mid-ocean ridges (MORs) contain information about
melting, melt movement, and crustal accretion processes associated with MOR spreading centers (1–3). For
off-axis basalts to be used to develop a better understanding of the process of melt movement, they must be
demonstrably distinguished from those originally erupted at the ridge axis.230Th-238U disequilibrium can
provide temporal information crucial to identifying basalts of off-axis origin and has been used to study
basalts as far as 4 km away from the ridge axis (4). To span a scale of melt movement beneath MORs that
may be greater than 4 km, and to avoid large axial eruptions that send lava flows as far as 3.5 km away from
the axis (5), we measured the 230Th-238U disequilibrium of basalts from 5 to 40 km off-axis.
Our samples were collected during the Phoenix-02 cruise (research vessel Melville) by dredging out to 40 to
50 km from the East Pacific Rise (EPR) on both the Cocos and Pacific plates near 9°30′N. In the vicinity of
9°30′N, the EPR spreads almost symmetrically at 11.1 cm year−1 (6). Therefore, basalt sampled at
distances of 40 to 50 km from the ridge axis corresponds to a spreading age of about 800 thousand years
ago (ka). Samples were analyzed by secondary ion mass spectrometry for Th isotopes and thermal
ionization mass spectrometry for U and Pb isotopes (7). Pb isotopic compositions exhibited small variations
in 208Pb/204Pb (37.60 to 38.05),207Pb/204Pb (15.47 to 15.57), and206Pb/204Pb (18.18 to 18.56) ratios (Table 1).
Because these Pb isotopic compositions represent long-term source U/Pb and Th/Pb ratios, the small range
in Pb isotopic compositions for these basalts suggests a long-term, relatively homogeneous, U/Pb and Th/Pb
source. (234U/238U) ratios (where parentheses indicate an activity ratio) of all samples are close to 1.0,
indicating that the Th-U systematics has not been perturbed by post-eruption alteration. The (230Th/238U)
ratios of the off-axis basalts are therefore controlled by their initial (at the time of eruption) (230Th/238U) ratios
and by the time elapsed since the eruption. The initial (230Th/238U) ratios are determined by the mineralogy of
the source of the melt (such as the relative amount of garnet and clinopyroxene) and the melting processes
(such as the rate of melting and the porosity of the melting zone) (8–11). The initial (230Th/238U) ratios are
independent of the source (230Th/238U) ratios because the source, before melting, is assumed to have
reached secular equilibrium, or (230Th/238U) = 1…
Honours Coursework 2013
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SCIENTIFIC LITERATURE
I cheated…
Science 4 January 2002:
Vol. 295 no. 5552 pp. 55-57
DOI: 10.1126/science.1066318
PERSPECTIVE
GEOPHYSICS
Caught Offside
Tim Elliott
Eighty percent of global volcanism occurs out of sight,
at submarine volcanoes along the 56,000 km of midocean spreading centers that straddle Earth. This
volcanic activity is confined to very narrow (~1 km)
zones between two separating tectonic plates. This
concentration of volcanic activity is particularly
remarkable when the volume of the rock producing the
magmatism is considered: a triangular melting region,
with a base at least 60 km deep, extends 60 km on
either side of the ridge axis (see the first figure).
Off-axis volcanism.
Melt focusing (yellow curves)
as a result of mantle flow
(arrowed
blue
curves)
beneath ridges leads to a
narrow zone of mid-ocean
ridge volcanism. Goldstein et
al. (7) have found “near” offaxis volcanism (thin arrowed
yellow line). Zou et al. (6)
identify
extreme
off-axis
eruptions,
which
they
attribute to dyking from the
ridge axis (sub-horizontal
dashed line) and melting of
enriched
mantle
blebs
(vertical dashed line).
Several fluid dynamic models have been developed to account for this strong focusing of melts
Honours
Coursework
2013
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beneath ridges (1-3). Yet it has also been noticed that the
upper oceanic
crust, which consists
the solidified remains of the erupted melts, continues to
thicken away fromLITERATURE
the ridge axis (4, 5).
SCIENTIFIC
Is the architecture of oceanic crust governed by growth at the ridge crests alone, or is it
embellished by off-axis additions?
To answer this fundamental question about the nature of oceanic crust, we require accurate
chronometers that can tell us whether all off-axis lavas are older than their ridge crest
counterparts, as in a classical plate-spreading model, or whether there are aberrant youngsters.
This problem is beyond the resolution of commonly used isotopic dating systems, but is
addressed in dramatic fashion by Zou et al. on page 107 of this issue.
The authors use high-precision uranium isotope series measurements to provide a new
perspective on this problem. Melting is commonly believed to induce disequilibrium in the shortlived nuclide chains between U and Pb. After eruption, secular equilibrium (in which the decay
rates of all intermediate nuclides are equal) is restored on the geologically short time scales of
the half-lives of the intermediate nuclides; for example, 230Th has a half-life of 75,000 years. For
a fast-spreading ridge, with plates diverging at a rate of 10 cm/year, any melt-produced
disequilibrium still present in lavas more than 20 km from the ridge clearly identifies off-axis
volcanism.
A finer chronology is possible if the initial disequilibrium is known. Assuming that this has
remained constant, Goldstein et al. (7) have inferred off-axis volcanism 1 to 4 km from the ridge
crest. Zou et al. now show striking disequilibrium more than 20 km off axis. At these distances,
few would have anticipated recent volcanism except at well-defined “seamounts.” Yet the
samples analyzed by Zou et al. are from normal oceanic crust on the flanks of the East Pacific
Rise (8, 9).
Zou et al.'s data contain further remarkable features. 230Th-238U disequilibrium at mid-ocean
Honours
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ridges is almost always characterized by 230Th excesses.
Indeed, most
of Zou et al.'s samples
show 230Th excesses, including two samples with unexpectedly
large 230Th
excesses 14 and
SCIENTIFIC
LITERATURE
21 km off axis. Very few samples with 238U excesses have been reported. It has been argued
that these are consistent with melting beneath the deepest (~5 km) parts of the ridge system
(10) and reflect the smaller, shallower underlying melting region at these locations (11). Yet
Zou et al. document 238U excesses for off-axis lavas from a normal ridge segment less than 3
km deep. Furthermore, the off-axis 230Th and 238U excesses appear to alternate nearly
symmetrically on either side of the ridge. Symmetrical features about a ridge are readily
explained by sea-floor spreading but are not expected for off-axis magmas.
Accounting for all of Zou et al.'s observations within existing paradigms is not easy. The
authors attribute off-axis magmas with 230Th excesses to subsurface dikes perpendicular to
the dominant direction of fracture propagation at ridges. The source of these lavas is thus the
same as at the ridge itself. In contrast, 238U excesses are suggested to result from a distinct
magma source that is enriched by material from recycled oceanic crust. This helps to explain
the compositions of the lavas with the most extreme 238U excesses, but other samples with
238U excesses do not have such signatures (see the second figure). Moreover, it is not clear
why such an enriched source would occur nearly symmetrically on either side of the ridge and
show no clear signature of a different source (such as distinct Pb isotope ratios).
It has recently been predicted that the two-dimensional effects of melt transport resulting from
(symmetrical) plate spreading can cause systematic variations in melt composition
perpendicular to the ridge (12). Geochemical variations close to the East Pacific ridge at
12°N seem to be consistent with such a model (13). The approach could possibly be
extended to account for the off-axis samples in Zou et al.'s data set. However, the sense of
the variation in their data is opposite to that in (13), with anomalously enriched rather than
depleted samples found off axis.
U-series disequilibrium measurements are technically
2011
demanding, especially at the low concentrations of Honours Coursework 2013
these nuclides in mid-ocean ridge basalts. The SCIENTIFIC LITERATURE
problem is compounded by Mn coatings on sea-floor
lavas, which sequester short-lived nuclides from
seawater. Leaching techniques have been shown to
remove potential contamination from these coatings
for on axis samples (14). The further off axis, the
greater the possible influence of Mn coatings on
surfaces and cracks. However, neither insufficient nor
overzealous leaching would be expected to preserve
near-equilibrium 234U/238U ratios (as documented by
Zou et al.) or to produce 238U excesses as an artifact
of sample preparation, let alone to do so
Not treading a fine line?
symmetrically on either side of the ridge.
Off-axis samples of Zou et al. (circles) (6) are
A couple of problems remain. The off-axis eruptions compared with on- and near-axis samples of
identified by Zou et al. do not have obviously thinner Goldstein et al. (crosses) (7). Samples in isotopic
Mn coatings. The nonquantitative nature of Mn equilibrium plot on a line with a gradient of 1 (the
equiline); those with 230Th excesses plot to the left,
thickness chronology makes U-series dating a crucial and those with 238U excesses to the right. The solid
new contribution, but the qualitative dichotomy for this line indicates the range of compositions for on-axis
data set is noteworthy. It is also troubling that one samples. Off-axis samples of different ages would be
expected to plot along the red lines. Many of Zou et
sample of Zou et al. shows 230Th/232Th and 238U/232Th al.'s samples plot where anticipated, but two samples
ratios much greater than any on-axis sample (see the fall on the zero-age line despite being 14 and 21 km
off axis. Four samples lie to the right of the equiline.
second figure).
Two of the latter show enriched trace element
signatures (pink symbols). One sample is too
extreme to fit within the plot.
Honours Coursework 2013
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SCIENTIFIC LITERATURE
The remarkable features of Zou et al.'s data set will doubtless lead to reanalysis of these
and other samples. The results are quite reasonably interpreted in terms of eruptions of
“normal” and “enriched” lavas some 20 km off axis. The assistant referee's flag is definitely
raised.
References
15 references…
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Go to Web of Science and see how this paper has fared:
22 cites by end of Feb 2013
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Impact Factor of Science is 31.377…
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Try more
Scopus is sometimes better than WoS. But Scopus does not have
complete citation information for articles published before 1996.
+ 7 web citations… Even worse…
Honours Coursework 2013
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SCIENTIFIC LITERATURE
How has this work fared?
Honours Coursework 2013
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SCIENTIFIC LITERATURE
Maybe this was not the “key” paper?
Experimental technique
Idea itself
Off axis Volcanism
Model
Honours Coursework 2013
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SCIENTIFIC LITERATURE
57.96 citations per year
Honours Coursework 2013
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SCIENTIFIC LITERATURE