272 research outputs found
Incorporating revocation of certification into a PKI model
Public key infrastructures (PKIs) are complex distributed systems that are responsible for giving users enough information to make reasonable trust judgments about one another. PKI is a prerequisite for security in distributed systems and for electronic commerce. The validation of public keys is hence of paramount importance. This is achieved by public-key certificates. Several researches have done to evaluate the confidence afforded; one of them is Maurer's model. The problem of assigning and evaluating confidence values numerically (Maurer model) is non-trivial, in particular when certification paths intersect. A restriction in this model is that certificate revocation is not included, but usually revocation happens. While Maurer consider only positive evidence, in this paper has been considered negative evidence as well as revocation. Moreover a few of authors incorporate negative values in inference rules on deterministic part. In this paper we have used a tailored form of that and consider revocation on inference rules. After that negative evidence to exert in probabilistic part, with to take in to a suitable value for this evidence omits the path of trust include the revoked certification
Orexin A presynaptically decreases inhibitory synaptic transmission in rat locus coeruleus neurons
Locus coeruleus nucleus (LC) is a major noradrenergic nucleus in the brain. It receives dense orexinergic projections from lateral hypothalamus. Whilst it is known that orexin A increases firing rate of LC neurons, its effect on spontaneous and evoked inhibitory postsynaptic currents (sIPSCs and eIPSCs, respectively) has not been yet identified. In this research, we investigated the effect of orexin A on eIPSCs and sIPSCs in LC neurons. Whole-cell recordings revealed that orexin A suppresses eIPSCs amplitude in which this effect was blocked by an orexin type-1 receptors antagonist (SB-334867) and cannabinoid type-1 (CB1) receptors antagonist (AM251). Moreover, exposure of neurons to BAPTA (Ca2+ chelator) and U73122 (phospholipase C inhibitor) prevented orexin A-induced eIPSCs depression. On the other hand, orexin A increased pair pulse ratio and sIPSCs frequency but had no effect on sIPSCs amplitude. Our results revealed that eIPSCs suppression in the LC is mediated by CB1 receptor through a presynaptic mechanism
Risk-Averse Matchings over Uncertain Graph Databases
A large number of applications such as querying sensor networks, and
analyzing protein-protein interaction (PPI) networks, rely on mining uncertain
graph and hypergraph databases. In this work we study the following problem:
given an uncertain, weighted (hyper)graph, how can we efficiently find a
(hyper)matching with high expected reward, and low risk?
This problem naturally arises in the context of several important
applications, such as online dating, kidney exchanges, and team formation. We
introduce a novel formulation for finding matchings with maximum expected
reward and bounded risk under a general model of uncertain weighted
(hyper)graphs that we introduce in this work. Our model generalizes
probabilistic models used in prior work, and captures both continuous and
discrete probability distributions, thus allowing to handle privacy related
applications that inject appropriately distributed noise to (hyper)edge
weights. Given that our optimization problem is NP-hard, we turn our attention
to designing efficient approximation algorithms. For the case of uncertain
weighted graphs, we provide a -approximation algorithm, and a
-approximation algorithm with near optimal run time. For the case
of uncertain weighted hypergraphs, we provide a
-approximation algorithm, where is the rank of the
hypergraph (i.e., any hyperedge includes at most nodes), that runs in
almost (modulo log factors) linear time.
We complement our theoretical results by testing our approximation algorithms
on a wide variety of synthetic experiments, where we observe in a controlled
setting interesting findings on the trade-off between reward, and risk. We also
provide an application of our formulation for providing recommendations of
teams that are likely to collaborate, and have high impact.Comment: 25 page
Optical and Acoustic Phonons in Turbostratic and Cubic Boron Nitride Thin Films on Diamond Substrates
We report an investigation of the bulk optical, bulk acoustic, and surface
acoustic phonons in thin films of turbostratic boron nitride (t-BN) and cubic
boron nitride (c-BN) grown on B-doped polycrystalline and single-crystalline
diamond (001) and (111) substrates. The characteristics of different types of
phonons were determined using Raman and Brillouin-Mandelstam light scattering
spectroscopies. The atomic structure of the films was determined using
high-resolution transmission electron microscopy (HRTEM) and correlated with
the Raman and Brillouin-Mandelstam spectroscopy data. The HRTEM analysis
revealed that the cubic boron nitride thin films consisted of a mixture of c-BN
and t-BN phases, with c-BN being the dominant phase. It was found that while
visible Raman spectroscopy provided information for characterizing the t-BN
phase, it faced challenges in differentiating the c-BN phase either due to the
presence of high-density defects or the overlapping of the Raman features with
those from the B-doped diamond substrates. In contrast, Brillouin-Mandelstam
spectroscopy clearly distinguishes the bulk longitudinal and surface acoustic
phonons of the c-BN thin films grown on diamond substrates. Additionally, the
angle-dependent surface Brillouin-Mandelstam scattering data show the peaks
associated with the Rayleigh surface acoustic waves, which have higher phase
velocities in c-BN films on diamond (111) substrates. These findings provide
valuable insights into the phonon characteristics of the c-BN and diamond
interfaces and have important implications for the thermal management of
electronic devices based on ultra-wide-band-gap materials.Comment: 27 pages; 4 figure
Successful new product development by optimizing development process effectiveness in highly regulated sectors: the case of the Spanish medical devices sector
Rapid development and commercialization of new products is of vital importance for small and medium sized enterprises (SME) in regulated sectors. Due to strict regulations, competitive advantage can hardly be achieved through the effectiveness of product concepts only. If an SME in a highly regulated sector wants to excell in new product development (NPD) performance, the company should focus on the flexibility, speed, and productivity of its NPD function: i.e. the development process effectiveness. Our main research goals are first to explore if SMEs should focus on their their development process effectiveness rather than on their product concept effectiveness to achieve high NPD performance; and second, to explore whether a shared pattern in the organization of the NPD function can be recognized to affect NPD performance positively. The medical devices sector in Spain is used as an example of a\ud
highly regulated sector. A structured survey among 11 SMEs, of which 2 were studied also as in in-depth case studies, led to the following results. First of all, indeed the companies in the dataset which focused on the effectiveness of their development process, stood out in NPD performance. Further, the higher performing companies did have a number of commonalities in the organisation of their NPD function: 1) The majority of the higher performing firms had an NPD strategy characterized by a predominantly incremental project portfolio.\ud
2) a) Successful firms with an incremental project portfolio combined this with a functional team structure b) Successful firms with a radical project portfolio combined this with a heavyweight or autonomous team structure.\ud
3) A negative reciprocal relationship exists between formalization of the NPD processes and the climate of the NPD function, in that a formalized NPD process and an innovative climate do not seem to reinforce each other. Innovative climate combined with an informal NPD process does however contribute positively to NPD performance. This effect was stronger in combination with a radical project portfolio. The highest NPD performance was measured for companies focusing mainly on incremental innovation. It is argued that in highly regulated sectors, companies with an incremental product portfolio would benefit from employing a functional structure. Those companies who choose for a more radical project portfolio in highly regulated sectors should be aware\ud
that they are likely to excell only in the longer term by focusing on strategic flexibility. In their NPD organization, they might be well advised to combine informal innovation processes with an innovative climate
Specifics of the Elemental Excitations in "True One-Dimensional" MoI van der Waals Nanowires
We report on the temperature evolution of the polarization-dependent Raman
spectrum of exfoliated MoI, a van der Waals material with a "true
one-dimensional" crystal structure that can be exfoliated to individual atomic
chains. The temperature evolution of several Raman features reveals anomalous
behavior suggesting a phase transition of a magnetic origin. Theoretical
considerations indicate that MoI is an easy-plane antiferromagnet with
alternating spins along the dimerized chains and with inter-chain helical spin
ordering. The calculated frequencies of the phonons and magnons are consistent
with the interpretation of the experimental Raman data. The obtained results
shed light on the specifics of the phononic and magnonic states in MoI and
provide a strong motivation for future study of this unique material with
potential for spintronic device applications.Comment: 28 page
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