941 research outputs found
Dynamics of neural cryptography
Synchronization of neural networks has been used for novel public channel
protocols in cryptography. In the case of tree parity machines the dynamics of
both bidirectional synchronization and unidirectional learning is driven by
attractive and repulsive stochastic forces. Thus it can be described well by a
random walk model for the overlap between participating neural networks. For
that purpose transition probabilities and scaling laws for the step sizes are
derived analytically. Both these calculations as well as numerical simulations
show that bidirectional interaction leads to full synchronization on average.
In contrast, successful learning is only possible by means of fluctuations.
Consequently, synchronization is much faster than learning, which is essential
for the security of the neural key-exchange protocol. However, this qualitative
difference between bidirectional and unidirectional interaction vanishes if
tree parity machines with more than three hidden units are used, so that those
neural networks are not suitable for neural cryptography. In addition, the
effective number of keys which can be generated by the neural key-exchange
protocol is calculated using the entropy of the weight distribution. As this
quantity increases exponentially with the system size, brute-force attacks on
neural cryptography can easily be made unfeasible.Comment: 9 pages, 15 figures; typos correcte
Genetic attack on neural cryptography
Different scaling properties for the complexity of bidirectional
synchronization and unidirectional learning are essential for the security of
neural cryptography. Incrementing the synaptic depth of the networks increases
the synchronization time only polynomially, but the success of the geometric
attack is reduced exponentially and it clearly fails in the limit of infinite
synaptic depth. This method is improved by adding a genetic algorithm, which
selects the fittest neural networks. The probability of a successful genetic
attack is calculated for different model parameters using numerical
simulations. The results show that scaling laws observed in the case of other
attacks hold for the improved algorithm, too. The number of networks needed for
an effective attack grows exponentially with increasing synaptic depth. In
addition, finite-size effects caused by Hebbian and anti-Hebbian learning are
analyzed. These learning rules converge to the random walk rule if the synaptic
depth is small compared to the square root of the system size.Comment: 8 pages, 12 figures; section 5 amended, typos correcte
An empirical (re)exploration of leadership in a nonprofit: Understanding leadership as a perspective and a practice
Leadership is a complex concept to define, understand and put into practice. This study first problematizes the concept of leadership as a trait or possession. The project then explores leadership as a dynamic communication process that is co-created through meaningful patterns of interaction. To this end, two conceptual themes about leadership as communication emerged through a synthesis of the literature: leadership as influence and leadership as cultural empowerment. Through qualitative methods, the research aims to investigate these themes as possible leadership symbolic interaction patterns at a nonprofit organization in the Pacific Northwest. This study found that there were three key aspects to conceptualizing where organizational communication starts and leadership communication begins: setting the stage, belief in the system, and how to go on together. The significance of these findings emerges in the nuance of how important routine organizing processes are in constructing inclusive cultural assumptions that then lend to constituting leadership as collective agency or collective ability to act, act for, and act with others toward a purpose. This thesis also illustrates how it is possible for leadership to be understood as both a perspective and a process
The 89,000-Mr murine cytomegalovirus immediate-early protein activates gene transcription
To study trans-activation of gene expression by murine cytomegalovirus (MCMV) immediate-early (IE) proteins, the IE coding region 1 (ie1), which encodes the 89,000-Mr IE phosphoprotein (pp89), was stably introduced into L cells. A cell line was selected and characterized that efficiently expressed the authentic viral protein. The pp89 that was constitutively expressed in L cells stimulated the expression of transfected recombinant constructs containing the bacterial chloramphenicol acetyltransferase (CAT) gene under the control of viral promoters. The regulatory function of the ie1 product was confirmed by transient expression assays in which MCMV IE genes were cotransfected into L cells together with recombinant constructs of the CAT gene. For CAT activation by the ie1 product, a promoter region was required, but there was no preferential activation of a herpes simplex virus type 1 delayed-early promoter. All plasmid constructs that contained the intact coding sequences for pp89 induced gene expression in trans. The MCMV enhancer region was not essential for the expression of a functional IE gene product, and testing of the cis-regulatory activity of the MCMV enhancer revealed a low activity in L cells. Another region transcribed at IE times of infection, IE coding region 2, was unable to induce CAT expression and also did not augment the functional activity of ie1 after cotransfection
Glycerol confined in zeolitic imidazolate frameworks: The temperature-dependent cooperativity length scale of glassy freezing
In the present work, we employ broadband dielectric spectroscopy to study the
molecular dynamics of the prototypical glass former glycerol confined in two
microporous zeolitic imidazolate frameworks (ZIF-8 and ZIF-11) with
well-defined pore diameters of 1.16 and 1.46 nm, respectively. The spectra
reveal information on the modified alpha relaxation of the confined supercooled
liquid, whose temperature dependence exhibits clear deviations from the typical
super-Arrhenius temperature dependence of the bulk material, depending on
temperature and pore size. This allows assigning well-defined cooperativity
length scales of molecular motion to certain temperatures above the glass
transition. We relate these and previous results on glycerol confined in other
host systems to the temperature-dependent length scale deduced from nonlinear
dielectric measurements. The combined experimental data can be consistently
described by a critical divergence of this correlation length as expected
within theoretical approaches assuming that the glass transition is due to an
underlying phase transition.Comment: 14 pages, 5 figures + Supplemental Material (4 pages, 6 figures).
Final version as accepted for publicatio
Π‘ΠΈΡΡΠ΅ΠΌΡ Π°Π²ΡΠΎΠΌΠ°ΡΠΈΠ·ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ ΠΏΡΠΎΠΈΠ·Π½ΠΎΡΠ΅Π½ΠΈΡ Π² ΡΠ΅ΡΠ²ΠΈΡΠ°Ρ ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΡΠΌ ΡΠ·ΡΠΊΠ°ΠΌ
Π Π΄Π°Π½Π½ΠΎΠΉ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠΈ Π±ΡΠ» ΠΏΡΠΎΠ²Π΅Π΄Π΅Π½ Π°Π½Π°Π»ΠΈΠ· Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΠΈ ΡΠ»ΡΡΡΠ΅Π½ΠΈΡ ΠΏΡΠΎΠΈΠ·Π½ΠΎΡΠ΅Π½ΠΈΡ ΠΈΠ½ΠΎΡΡΡΠ°Π½Π½ΠΎΠ³ΠΎ ΡΠ·ΡΠΊΠ° Ρ ΠΏΠΎΠΌΠΎΡΡΡ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ ΡΠΈΡΡΠ΅ΠΌ Π°Π²ΡΠΎΠΌΠ°ΡΠΈΠ·ΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ ΠΏΡΠΎΠΈΠ·Π½ΠΎΡΠ΅Π½ΠΈΡ. Π ΡΠ°Π±ΠΎΡΠ΅ ΠΏΠΎΠΊΠ°Π·Π°Π½Ρ ΡΡΡΠ΅ΡΡΠ²ΡΡΡΠΈΠ΅ ΡΠΈΡΡΠ΅ΠΌΡ ΠΎΠ±ΡΡΠ΅Π½ΠΈΡ ΠΏΡΠΎΠΈΠ·Π½ΠΎΡΠ΅Π½ΠΈΡ, ΠΎΠΏΠΈΡΠ°Π½Ρ ΠΊΠ°ΡΠ΅Π³ΠΎΡΠΈΠΈ ΡΡΠΈΡ
ΡΠΈΡΡΠ΅ΠΌ, Π²ΡΠ΄Π΅Π»Π΅Π½Ρ ΠΏΠ»ΡΡΡ ΠΈ ΠΌΠΈΠ½ΡΡΡ, Π° ΡΠ°ΠΊΠΆΠ΅, ΠΏΠΎΠΊΠ°Π·Π°Π½Ρ ΠΏΠ΅ΡΡΠΏΠ΅ΠΊΡΠΈΠ²Ρ ΡΠ°Π·Π²ΠΈΡΠΈΡ ΠΏΠΎΠ΄ΠΎΠ±Π½ΡΡ
ΡΠΈΡΡΠ΅ΠΌ
Orientation dependence of the sticking probability of NO at Ni(100)
Fecher GH, Volkmer M, Pawlitzky B, BΓΆwering N, Heinzmann U. Orientation dependence of the sticking probability of NO at Ni(100). Vacuum. 1990;41(1-3):265-268
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