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Relationship between spin squeezing and single-particle coherence in two-component Bose-Einstein condensates with Josephson coupling
We investigate spin squeezing of a two-mode boson system with a Josephson
coupling. An exact relation between the squeezing and the single-particle
coherence at the maximal-squeezing time is discovered, which provides a more
direct way to measure the squeezing by readout the coherence in atomic
interference experiments. We prove explicitly that the strongest squeezing is
along the axis, indicating the appearance of atom number-squeezed state.
Power laws of the strongest squeezing and the optimal coupling with particle
number are obtained based upon a wide range of numerical simulations.Comment: 4 figures, revtex4, new refs. are adde
UV Upturn in Elliptical Galaxies: Theory
The UV upturn is the rising flux with decreasing wavelength between the Lyman
limit and 2500\AA found virtually in all bright spheroidal galaxies. It has
been a mystery ever since it was first detected by the OAO-2 space telescope
(Code & Welch 1979) because such old metal-rich populations were not expected
to contain any substantial number of hot stars. It was confirmed by following
space missions, ANS (de Boer 1982), IUE (Bertola et al. 1982) and HUT (Brown et
al. 1997). The positive correlation between the UV-to-optical colour (i.e., the
strength of the UV upturn) and the Mg2 line strength found by Burstein et al.
(1987) through IUE observations has urged theorists to construct novel
scenarios in which metal-rich () old ( a few Gyr)
stars become UV bright (Greggio & Renzini 1990; Horch et al. 1992). Also
interesting was to find using HUT that, regardless of the UV strength, the UV
spectral slopes at 1000--2000\AA in the six UV bright galaxies were nearly
identical suggesting a very small range of temperatures of the UV sources in
these galaxies (Brown et al. 1997), which corresponds to K. This, together with other evidence, effectively ruled out
young stars as the main driver of the UV upturn. A good review on the
observational side of the story is given in the next article by Tom Brown, as
well as in the recent articles of Greggio & Renzini (1999) and O'Connell
(1999).Comment: 6 figures; belated paper from Keele Conferenc
A flexible mandatory access control policy for XML databases
A flexible mandatory access control policy (MAC) for XML
databases is presented in this paper. The label type and label
access policy can be defined according to the requirements of
applications. In order to preserve the integrity of data in XML
databases, a constraint between a read access rule and a write
access rule in label access policy is introduced. Rules for label
assignment and propagation are proposed to alleviate the
workload of label assignment. Also, a solution for resolving
conflicts of label assignments is proposed. At last, operations for
implementation of the MAC policy in a XML database are
illustrated
Corruption and Cross-Border Investment: Firm-Level Evidence
This paper studies the impact of corruption on inward foreign direct investment using a unique firm-level data set. It examines two effects of corruption simultaneously: a reduction in the volume of foreign investment and a shift in the ownership structure. Corruption makes local bureaucracy less transparent and hence acts as a tax on foreign investors. Moreover, corruption affects the decision to take on a local partner. On the one hand, corruption increases the value of using a local partner to cut through the bureaucratic maze. On the other hand, corruption decreases the effective protection of investor’s intangible assets and lowers the probability that disputes between foreign and domestic partners will be adjudicated fairly, which reduces the value of having a local partner. The importance of protecting intangible assets increases with investor’s technological sophistication, which tilts the preference away from joint ventures in a corrupt country. Empirical evidence shows that corruption reduces inward FDI and shifts the ownership structure towards joint ventures. Technologically more advanced firms are found to be less likely to engage in joint ventures.http://deepblue.lib.umich.edu/bitstream/2027.42/39879/3/wp494.pd
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A practical mandatory access control model for XML databases
A practical mandatory access control (MAC) model for XML databases is presented in this paper. The
label type and label access policy can be defined according to the requirements of different applications. In order to
preserve the integrity of data in XML databases, a constraint between a read-access rule and a write-access rule in
label access policy is introduced. Rules for label assignment and propagation are presented to alleviate the workload
of label assignments. Furthermore, a solution for resolving conflicts in label assignments is proposed. Rules for
update-related operations, rules for exceptional privileges of ordinary users and the administrator are also proposed
to preserve the security of operations in XML databases. The MAC model, we proposed in this study, has been
implemented in an XML database. Test results demonstrated that our approach provides rational and scalable
performance
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