1,851 research outputs found
Leeway for the loyal: a model of employee discretion
This article examines the factors underlying task discretion from an economist's perspective. It argues that the key axis for understanding discretion is the trade-off between the positive effects of discretion on potential output per employee and the negative effects of greater leeway on work effort. In empirical analysis using matched employer-employee data, it is shown that discretion is strongly affected by the level of employee commitment. In addition, discretion is generally greater in high-skilled jobs, although not without exceptions, and lower where employees are under-skilled. Homeworking and flexitime policies raise employee discretion. The impact of teamworking is mixed. In about half of cases team members do not jointly decide about work matters, and the net effect of teams on task discretion in these cases is negative. In other cases, where team members do decide matters jointly, the impact is found to be neutral according to employees' perceptions, or positive according to managers' perceptions. There are also significant and substantial unobserved establishment-level factors which affect task discretion
The chaotic behavior of the black hole system GRS 1915+105
A modified non-linear time series analysis technique, which computes the
correlation dimension , is used to analyze the X-ray light curves of the
black hole system GRS 1915+105 in all twelve temporal classes. For four of
these temporal classes saturates to which indicates that
the underlying dynamical mechanism is a low dimensional chaotic system. Of the
other eight classes, three show stochastic behavior while five show deviation
from randomness. The light curves for four classes which depict chaotic
behavior have the smallest ratio of the expected Poisson noise to the
variability () while those for the three classes which depict
stochastic behavior is the highest (). This suggests that the temporal
behavior of the black hole system is governed by a low dimensional chaotic
system, whose nature is detectable only when the Poisson fluctuations are much
smaller than the variability.Comment: Accepted for publication in Astrophysical Journa
Scientific knowledge acquisition during the extension of GSA: An expert system for generic safety analysis
This paper describes an extension of GSA, a knowledge based expert system designed to help nonexperts perform generic safety analysis. GSA is implemented on the EMYCIN expert system shell, consists of approximately 150 safety related rules, and runs on a VAX 11-750 computer. As originally implemented, GSA organized several generic safety problems within a well-structured tree and focused on problems within interface biomechanics. GSA also emphasized the application of theoretical principles instead of empirical data. To extend GSA, a specialized empirical knowledge base was developed that described the available slip resistance found for various combinations of surfaces, shoes, and contaminants. During knowledge acquisition, it became apparent that fundamental problems were present in much of the past research regarding to available slip resistance. We therefore chose to directly collect data during a large controlled experiment. The collected data was initially organized by applying statistical methods. After the statistical results were classified into conceptually meaningful categories, a set of rules was easily described and added to the system. The conclusion was that GSA describes an extendable framework that can organize and selectively apply very specialized safety ergonomics research.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26511/1/0000049.pd
The association between bacterial infections and the risk of coronary heart disease in type 1 diabetes
Background Diabetes increases the risk of infections as well as coronary heart disease (CHD). Whether infections increase the risk of CHD and how this applies to individuals with diabetes is unclear. Objectives To investigate the association between bacterial infections and the risk of CHD in type 1 diabetes. Methods Individuals with type 1 diabetes (n = 3781) were recruited from the Finnish Diabetic Nephropathy Study (FinnDiane), a prospective follow-up study. CHD was defined as incident events: fatal or non-fatal myocardial infarction, coronary artery bypass surgery or percutaneous coronary intervention, identified through national hospital discharge register data. Infections were identified through national register data on all antibiotic purchases from outpatient care. Register data were available from 1.1.1995-31.12.2015. Bacterial lipopolysaccharide (LPS) activity was measured from serum samples at baseline. Data on traditional risk factors for CHD were collected during baseline and consecutive visits. Results Individuals with an incident CHD event (n = 370) had a higher mean number of antibiotic purchases per follow-up year compared to those without incident CHD (1.34 [95% CI: 1.16-1.52], versus 0.79 [0.76-0.82],P <0.001), as well as higher levels of LPS activity (0.64 [0.60-0.67], versus 0.58 EU mL(-1)[0.57-0.59],P <0.001). In multivariable-adjusted Cox proportional hazards models, the mean number of antibiotic purchases per follow-up year was an independent risk factor for incident CHD (HR 1.21, 95% CI: 1.14-1.29,P <0.0001). High LPS activity was a risk factor for incident CHD (HR 1.93 [1.34-2.78],P <0.001) after adjusting for static confounders. Conclusion Bacterial infections are associated with an increased risk of incident CHD in individuals with type 1 diabetes.Peer reviewe
Teichm\"uller's problem in space
Quasiconformal homeomorphisms of the whole space Rn, onto itself normalized
at one or two points are studied. In particular, the stability theory, the case
when the maximal dilatation tends to 1, is in the focus. Our main result
provides a spatial analogue of a classical result due to Teichm\"uller. Unlike
Teichm\"uller's result, our bounds are explicit. Explicit bounds are based on
two sharp well-known distortion results: the quasiconformal Schwarz lemma and
the bound for linear dilatation. Moreover, Bernoulli type inequalities and
asymptotically sharp bounds for special functions involving complete elliptic
integrals are applied to simplify the computations. Finally, we discuss the
behavior of the quasihyperbolic metric under quasiconformal maps and prove a
sharp result for quasiconformal maps of R^n \ {0} onto itself.Comment: 25 pages, 2 figure
Photometric Variability in the Ultracool Dwarf BRI 0021-0214: Possible Evidence for Dust Clouds
We report CCD photometric monitoring of the nonemission ultracool dwarf BRI
0021-0214 (M9.5) obtained during 10 nights in 1995 November and 4 nights in
1996 August, with CCD cameras at 1 m class telescopes on the observatories of
the Canary Islands. We present differential photometry of BRI 0021-0214, and we
report significant variability in the I-band light curve obtained in 1995. A
periodogram analysis finds a strong peak at a period of 0.84 day. This
modulation appears to be transient because it is present in the 1995 data but
not in the 1996 data. We also find a possible period of 0.20 day, which appears
to be present in both the 1995 and 1996 datasets. However, we do not find any
periodicity close to the rotation period expected from the spectroscopic
rotational broadening (< 0.14 day). BRI 0021-0214 is a very inactive object,
with extremely low levels of Halpha and X-ray emission. Thus, it is unlikely
that magnetically induced cool spots can account for the photometric
variability. The photometric variability of BRI 0021-0214 could be explained by
the presence of an active meteorology that leads to inhomogeneous clouds on the
surface. The lack of photometric modulation at the expected rotational period
suggests that the pattern of surface features may be more complicated than
previously anticipated.Comment: Accepted for publication in ApJ. 26 pages, 13 figures include
Testing black hole no-hair theorem with OJ287
We examine the ability to test the black hole no-hair theorem at the 10%
level in this decade using the binary black hole in OJ287. In the test we
constrain the value of the dimensionless parameter q that relates the scaled
quadrupole moment and spin of the primary black hole: q2 = -q 2 . At the
present we can say that q = 1 \pm 0.3 (one), in agreement with General
Relativity and the no-hair theorems. We demonstrate that this result can be
improved if more observational data is found in historical plate archives for
the 1959 and 1971 outbursts. We also show that the predicted 2015 and 2019
outbursts will be crucial in improving the accuracy of the test. Space-based
photometry is required in 2019 July due the proximity of OJ287 to the Sun at
the time of the outburst. The best situation would be to carry out the
photometry far from the Earth, from quite a different vantage point, in order
to avoid the influence of the nearby Sun. We have considered in particular the
STEREO space mission which would be ideal if it has a continuation in 2019 or
LORRI on board the New Horizons mission to Pluto.Comment: 14 pages, 14 figure
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