981 research outputs found
Exploring the relationship between the Engineering and Physical Sciences and the Health and Life Sciences by advanced bibliometric methods
We investigate the extent to which advances in the health and life sciences
(HLS) are dependent on research in the engineering and physical sciences (EPS),
particularly physics, chemistry, mathematics, and engineering. The analysis
combines two different bibliometric approaches. The first approach to analyze
the 'EPS-HLS interface' is based on term map visualizations of HLS research
fields. We consider 16 clinical fields and five life science fields. On the
basis of expert judgment, EPS research in these fields is studied by
identifying EPS-related terms in the term maps. In the second approach, a
large-scale citation-based network analysis is applied to publications from all
fields of science. We work with about 22,000 clusters of publications, each
representing a topic in the scientific literature. Citation relations are used
to identify topics at the EPS-HLS interface. The two approaches complement each
other. The advantages of working with textual data compensate for the
limitations of working with citation relations and the other way around. An
important advantage of working with textual data is in the in-depth qualitative
insights it provides. Working with citation relations, on the other hand,
yields many relevant quantitative statistics. We find that EPS research
contributes to HLS developments mainly in the following five ways: new
materials and their properties; chemical methods for analysis and molecular
synthesis; imaging of parts of the body as well as of biomaterial surfaces;
medical engineering mainly related to imaging, radiation therapy, signal
processing technology, and other medical instrumentation; mathematical and
statistical methods for data analysis. In our analysis, about 10% of all EPS
and HLS publications are classified as being at the EPS-HLS interface. This
percentage has remained more or less constant during the past decade
Universality of citation distributions revisited
Radicchi, Fortunato, and Castellano [arXiv:0806.0974, PNAS 105(45), 17268]
claim that, apart from a scaling factor, all fields of science are
characterized by the same citation distribution. We present a large-scale
validation study of this universality-of-citation-distributions claim. Our
analysis shows that claiming citation distributions to be universal for all
fields of science is not warranted. Although many fields indeed seem to have
fairly similar citation distributions, there are quite some exceptions as well.
We also briefly discuss the consequences of our findings for the measurement of
scientific impact using citation-based bibliometric indicators
Electron tunnel sensor technology
Researchers designed and constructed a novel electron tunnel sensor which takes advantage of the mechanical properties of micro-machined silicon. For the first time, electrostatic forces are used to control the tunnel electrode separation, thereby avoiding the thermal drift and noise problems associated with piezoelectric actuators. The entire structure is composed of micro-machined silicon single crystals, including a folded cantilever spring and a tip. The application of this sensor to the development of a sensitive accelerometer is described
Astronomy using basic Mark 2 very long baseline interferometry
Two experiments were performed in April and September 1976 to determine precise positions of radio sources using conventional Mark 2 VLBI techniques. Four stations in the continental United States observed at a wavelength of 18 cm. The recording bandwidth was 2 MHz. The preliminary results using analyses of fringe rate and delay are discussed and the source positions compared with the results of other measurements
A Review of Research on the Kentucky River Ecosystem: Biota and Human Impacts
This report provides information about the water conditions in the Kentucky River Basin, through collection of previous studies
Citation analysis may severely underestimate the impact of clinical research as compared to basic research
Background: Citation analysis has become an important tool for research
performance assessment in the medical sciences. However, different areas of
medical research may have considerably different citation practices, even
within the same medical field. Because of this, it is unclear to what extent
citation-based bibliometric indicators allow for valid comparisons between
research units active in different areas of medical research.
Methodology: A visualization methodology is introduced that reveals
differences in citation practices between medical research areas. The
methodology extracts terms from the titles and abstracts of a large collection
of publications and uses these terms to visualize the structure of a medical
field and to indicate how research areas within this field differ from each
other in their average citation impact.
Results: Visualizations are provided for 32 medical fields, defined based on
journal subject categories in the Web of Science database. The analysis focuses
on three fields. In each of these fields, there turn out to be large
differences in citation practices between research areas. Low-impact research
areas tend to focus on clinical intervention research, while high-impact
research areas are often more oriented on basic and diagnostic research.
Conclusions: Popular bibliometric indicators, such as the h-index and the
impact factor, do not correct for differences in citation practices between
medical fields. These indicators therefore cannot be used to make accurate
between-field comparisons. More sophisticated bibliometric indicators do
correct for field differences but still fail to take into account within-field
heterogeneity in citation practices. As a consequence, the citation impact of
clinical intervention research may be substantially underestimated in
comparison with basic and diagnostic research
Excess sub-millimetre emission from GRS 1915+105
We present the first detections of the black hole X-ray binary GRS 1915+105
at sub-millimetre wavelengths. We clearly detect the source at 350 GHz on two
epochs, with significant variability over the 24 hr between epochs.
Quasi-simultaneous radio monitoring indicates an approximately flat spectrum
from 2 - 350 GHz, although there is marginal evidence for a minimum in the
spectrum between 15 - 350 GHz. The flat spectrum and correlated variability
imply that the sub-mm emission arises from the same synchrotron source as the
radio emission. This source is likely to be a quasi-steady partially
self-absorbed jet, in which case these sub-mm observations probe significantly
closer to the base of the jet than do radio observations and may be used in
future as a valuable diagnostic of the disc:jet connection in this source.Comment: 5 pages, 3 figures, accepted for publication in MNRA
Comparison of VLBI, TV and traveling clock techniques for time transfer
A three part experiment was conducted to develop and compare time transfer techniques. The experiment consisted of (1) a very long baseline interferometer (VLBI), (2) a high precision portable clock time transfer system between the two sites, and (3) a television time transfer. A comparison of the VLBI and traveling clock shows each technique can perform satisfactorily at the five nsec level. There was a systematic offset of 59 nsec between the two methods, which we attributed to a difference in epochs between VLBI formatter and station clock. The VLBI method had an internal random error of one nsec at the three sigma level for a two day period. Thus, the Mark II system performed well, and VLBI shows promise of being an accurate method of time transfer. The TV system, which had technical problems during the experiment, transferred time with a random error of about 50 nsec
Rivals for the crown: Reply to Opthof and Leydesdorff
We reply to the criticism of Opthof and Leydesdorff [arXiv:1002.2769] on the
way in which our institute applies journal and field normalizations to citation
counts. We point out why we believe most of the criticism is unjustified, but
we also indicate where we think Opthof and Leydesdorff raise a valid point
Plans for phase coherent long baseline interferometry for geophysical applications using the Anik-B communications satellite
A pilot project to establish an operational phase stable very long baseline interferometer (VLBI) for geophysical studies is described. Methods for implementation as well as practical applications are presented
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