Cryptography based on neural networks - analytical results

Mutual learning process between two parity feed-forward networks with discrete and continuous weights is studied analytically, and we find that the number of steps required to achieve full synchronization between the two networks in the case of discrete weights is finite. The synchronization process is shown to be non-self-averaging and the analytical solution is based on random auxiliary variables. The learning time of an attacker that is trying to imitate one of the networks is examined analytically and is found to be much longer than the synchronization time. Analytical results are found to be in agreement with simulations

Synchronization with mismatched synaptic delays: A unique role of elastic neuronal latency

We show that the unavoidable increase in neuronal response latency to ongoing stimulation serves as a nonuniform gradual stretching of neuronal circuit delay loops and emerges as an essential mechanism in the formation of various types of neuronal timers. Synchronization emerges as a transient phenomenon without predefined precise matched synaptic delays. These findings are described in an experimental procedure where conditioned stimulations were enforced on a circuit of neurons embedded within a large-scale network of cortical cells in-vitro, and are corroborated by neuronal simulations. They evidence a new cortical timescale based on tens of microseconds stretching of neuronal circuit delay loops per spike, and with realistic delays of a few milliseconds, synchronization emerges for a finite fraction of neuronal circuit delays.Comment: 12 pages, 4 figures, 13 pages of Supplementary materia

Shannon Meets Carnot: Generalized Second Thermodynamic Law

The classical thermodynamic laws fail to capture the behavior of systems with energy Hamiltonian which is an explicit function of the temperature. Such Hamiltonian arises, for example, in modeling information processing systems, like communication channels, as thermal systems. Here we generalize the second thermodynamic law to encompass systems with temperature-dependent energy levels, $dQ=TdS+dT$, where $$ denotes averaging over the Boltzmann distribution and reveal a new definition to the basic notion of temperature. This generalization enables to express, for instance, the mutual information of the Gaussian channel as a consequence of the fundamental laws of nature - the laws of thermodynamics

The effects of quercetin on liver regeneration after liver resection in rats

The aim of the present study was to assess the influence of quercetine (QE) on liver regeneration after partial hepatectomy (PH) in rats. A total of 24 male Wistar albino rats were divided into three groups: sham-operated (SH), PH and PH+QE; each group contain 8 animals. The rats in QE-treated groups were given QE (15 mg/kg body weight) once a day i.p., for 7 days starting 3 days prior to hepatectomy operation. At 7 days after resection, liver samples were collected. The malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) levels were estimated in liver homogenates. Moreover, histopathological examination, mitotic index (MI), proliferating cell nuclear antigen labelling, proliferation index (PI), transferase-mediated dUTP nick end-labelling assay, apoptotic index (AI) were evaluated at 7 days after hepatectomy. As a result, QE significantly increased MI, PI, and significantly decreased AI in PH rats. Additionally, QE remarkably inhibited the elevation of MDA, restored impaired antioxidant SOD activity and GSH level, and also attenuated hepatic vacuolar degeneration and sinusoidal congestion. These results suggested that QE treatment had a beneficial effect on liver regenerative capacity of the remnant liver tissue after hepatectomy, probably due to its antioxidative, antiapoptotic and proliferative property

Distribution of mast cells in lung tissues of rats exposed to biomass smoke

This study was designed to evaluate the distribution of mast cells in the lung tissues of rats exposed to biomass  smoke. Fifty six female Wistar albino adult rats were used. They were divided into two experimental groups  (control and biomass smoke-treated), each containing 28 animals. Control rats were not exposed to the  biomass smoke at any time during the experiment. Rats in the treatment group were exposed daily (one hour)  to biomass smoke for 3, 6 or 9 months. Lung tissues samples were obtained under deep anesthesia from the  randomly selected 7 animals in both groups. Lung tissues were fixed in Mota’s fixative (BLA) for 24 h and  embedded in paraffin. Sections of 6 μm thickness were cut and stained with 0.5% toluidine blue in 0.5 N  hydrochloric acid at pH 0.5 for 30 min. The numbers of mast cell in lung tissues of the animals exposed to  the biomass for 6 or 9 months were significantly (P<0.05) higher than controls. This study showed that long  term exposure to biomass smoke was associated with the increased number of mast cells in the lung.

Training a perceptron in a discrete weight space

On-line and batch learning of a perceptron in a discrete weight space, where each weight can take $2 L+1$ different values, are examined analytically and numerically. The learning algorithm is based on the training of the continuous perceptron and prediction following the clipped weights. The learning is described by a new set of order parameters, composed of the overlaps between the teacher and the continuous/clipped students. Different scenarios are examined among them on-line learning with discrete/continuous transfer functions and off-line Hebb learning. The generalization error of the clipped weights decays asymptotically as $exp(-K \alpha^2)$/$exp(-e^{|\lambda| \alpha})$ in the case of on-line learning with binary/continuous activation functions, respectively, where $\alpha$ is the number of examples divided by N, the size of the input vector and $K$ is a positive constant that decays linearly with 1/L. For finite $N$ and $L$, a perfect agreement between the discrete student and the teacher is obtained for $\alpha \propto \sqrt{L \ln(NL)}$. A crossover to the generalization error $\propto 1/\alpha$, characterized continuous weights with binary output, is obtained for synaptic depth $L > O(\sqrt{N})$.Comment: 10 pages, 5 figs., submitted to PR

Gaps and opportunities in nitrogen pollution policies around the world

Nitrogen pollution is an important environmental issue gaining traction in policy circles. However, there is little understanding of current nitrogen policies around the world: whether they account for nitrogen’s unique ability to exacerbate multiple environmental impacts or balance nitrogen’s dual role as an essential agricultural input and major pollutant. Here we assemble and analyse the first database of nitrogen policies generated by national and regional legislatures and government agencies, a collection of 2,726 policies across 186 countries derived from the ECOLEX database. The database covers all major environmental sinks (such as air, water and climate), economic sectors (including agriculture, wastewater and industry) and policy instruments (from market mechanisms to regulatory standards). We find that sink-centred policies are focused predominantly on water, mirroring the distribution of nitrogen’s global environmental and human health costs. However, policy integration across sinks is severely lacking, which heightens the risk of substituting one form of nitrogen pollution for another. Moreover, two-thirds of agricultural policies (ranging from broad sectoral programmes to nitrogen-specific measures) incentivize nitrogen use or manage its commerce, demonstrating the primacy of food production over environmental concerns

Effects of Dual-Chamber Pacing for Pediatric Patients With Hypertrophic Obstructive Cardiomyopathy

AbstractObjectives. The effects of both temporary and permanent dual-chamber pacing (DCP) were evaluated in symptomatic pediatric patients with hypertrophic obstructive cardiomyopathy (HOCM) unresponsive to medications.Background. Permanent DCP pacing can reduce left ventricular outflow tract (LVOT) gradient and relieve symptoms in adult patients with HOCM.Methods. Ten patients (mean [±SD] age 11.1 ± 6 years, range 1 to 17.5) with HOCM and a Doppler LVOT gradient ≥40 mm Hg were studied. The seven patients showing hemodynamic improvement during temporary pacing at cardiac catheterization underwent surgical implantation of a permanent DCP system. The effects of permanent pacing were evaluated using a questionnaire, Doppler evaluation, treadmill testing and repeat cardiac catheterization.Results. At initial cardiac catheterization, three patients failed to respond to temporary pacing (inadequate pace capture in two; congenital mitral valve abnormality in one). The remaining seven patients (70%, 95% confidence interval 38.0% to 91.7%; mean age 13 ± years, range 4 to 17.5) showed a significant reduction (p < 0.05) in LVOT gradient, left ventricular systolic pressure and pulmonary capillary wedge pressure. After pacemaker implantation, these seven patients reported a significant reduction in dyspnea on exertion and exercise intolerance. Serial Doppler evaluation showed a significant reduction in LVOT gradient. Follow-up catheterization at 23 ± 4 months in six patients (one patient declined restudy) showed a persistent decrease in LVOT gradient (53 ± 13 vs. 16 ± 11 mm Hg), left ventricular systolic pressure (149 ± 16 vs. 108 ± 14 mm Hg) and pulmonary capillary wedge pressure (18 ± 2 vs. 12 ± 4 mm Hg) versus preimplantation values.Conclusions. Permanent DCP is an effective therapy for selected pediatric patients with HOCM. Rapid atrial rates and intrinsic atrioventricular conduction, as well as congenital mitral valve abnormalities, may preclude effective pacing in certain patients.(J Am Coll Cardiol 1997;29:734–40