Repository Replication Using NNTP and SMTP

We present the results of a feasibility study using shared, existing, network-accessible infrastructure for repository replication. We investigate how dissemination of repository contents can be ``piggybacked'' on top of existing email and Usenet traffic. Long-term persistence of the replicated repository may be achieved thanks to current policies and procedures which ensure that mail messages and news posts are retrievable for evidentiary and other legal purposes for many years after the creation date. While the preservation issues of migration and emulation are not addressed with this approach, it does provide a simple method of refreshing content with unknown partners.Comment: This revised version has 24 figures and a more detailed discussion of the experiments conducted by u

Synaptic input from CA3 pyramidal cells to dentate basket cells in rat hippocampus.

1. Excitatory inputs from CA3 pyramidal cells to dentate basket cells were examined using the whole-cell recording technique in neonatal (10-16 days) rat hippocampal slices to characterize this unexpected feedback pathway. 2. Minimal electrical stimulation of the CA3 pyramidal layer evoked in basket cells short latency (5.2 +/- 0.4 ms) glutamate receptor-mediated excitatory postsynaptic currents (EPSCs) with fast rise times (at -70 mV, 0.9 +/- 0.2 ms), fast decay time constants (3.6 +/- 0.6 ms), and small amplitudes (-14 +/- 3.4 pA). Minimal electrical stimulation evoked monosynaptic EPSCs in only 48 +/- 9.2% of the trials suggesting that the CA3 pyramidal cell to basket cell pathway was unreliable. 3. CA3 pyramidal cell layer stimulation did not antidromically or synaptically activate granule cells but did evoke polysynaptic IPSCs in granule cells, suggesting that the net effect of CA3 pyramidal cell firing on the dentate gyrus was granule cell inhibition. 4. Stimulation of the CA3 pyramidal cell layer evoked both monosynaptic and polysynaptic EPSCs in basket cells, which were eliminated by a knife lesion separating CA3 from the dentate gyrus. The latencies of the EPSCs evoked in 0.6 mM extracellular calcium were the same as the earliest latencies of EPSCs in 1.5 mM calcium, suggesting that those EPSCs were monosynaptic. The polysynaptic input was more prominent in the presence of 10 microM bicuculline, implying that inhibitory GABAergic circuits normally limit this feedback from CA3 to basket cells. 5. In recordings from 103 pairs of CA3 pyramidal cells and dentate basket cells from 11 slices, two polysynaptic connections were found that were active only when the presynaptic CA3 pyramidal neuron fired in bursts. No monosynaptic connections between CA3 pyramidal cells and basket cells were identified indicating that connections between the two cell types may be sparse. 6. Raising the external potassium concentration from 3.5 to 8.5 mM, which elicited burst firing in CA3 pyramidal cells, resulted in a barrage of EPSCs and action potentials in basket cells. In contrast, granule cells neither fired action potentials nor exhibited increased EPSC frequency in elevated potassium but instead received a higher frequency of bicuculline-sensitive IPSCs, consistent with interneuron firing. The CA3 pyramidal cell to basket cell monosynaptic pathway exhibited paired-pulse facilitation as manifested by an increased probability of release, which supports the idea that basket cells were better activated by short trains of action potentials than by single inputs

Sensible Privacy: How We Can Protect Domestic Violence Survivors Without Facilitating Misuse

Privacy is a concept with real life ties and implications. Privacy infringement has the potential to lead to serious consequences for the stakeholders involved, hence researchers and organisations have developed various privacy enhancing techniques and tools. However, there is no solution that fits all, and there are instances where privacy solutions could be misused, for example to hide nefarious activities. Therefore, it is important to provide suitable measures and to make necessary design tradeoffs in order to avoid such misuse. This short paper aims to make a case for the need of careful consideration when designing a privacy solution, such that the design effectively addresses the user requirements while at the same time minimises the risk of inadvertently assisting potential offenders. In other words, this paper strives to promote “sensible privacy” design, which deals with the complex challenges in balancing privacy, usability and accountability. We illustrate this idea through a case study involving the design of privacy solutions for domestic violence survivors. This is the main contribution of the paper. The case study presents specific user requirements and operating conditions, which coupled with the attacker model, provide a complex yet interesting scenario to explore. One example of our solutions is described in detail to demonstrate the feasibility of our approach

Immunity and inflammation in status epilepticus and its sequelae: possibilities for therapeutic application.

Status epilepticus (SE) is a life-threatening neurological emergency often refractory to available treatment options. It is a very heterogeneous condition in terms of clinical presentation and causes, which besides genetic, vascular and other structural causes also include CNS or severe systemic infections, sudden withdrawal from benzodiazepines or anticonvulsants and rare autoimmune etiologies. Treatment of SE is essentially based on expert opinions and antiepileptic drug treatment per se seems to have no major impact on prognosis. There is, therefore, urgent need of novel therapies that rely upon a better understanding of the basic mechanisms underlying this clinical condition. Accumulating evidence in animal models highlights that inflammation ensuing in the brain during SE may play a determinant role in ongoing seizures and their long-term detrimental consequences, independent of an infection or auto-immune cause; this evidence encourages reconsideration of the treatment flow in SE patients

Possible mechanisms of enkephalin action on hippocampal CA1 pyramidal neurons

(1) Intracellular and extracellular recordings were made from CA1 pyramidal neurons in an in vitro rat hippocampal slice preparation, while [D-Ala2, D-Leu5]enkephalin (DADL) was applied by perfusion at a known concentration (1 to 5 X 10-7 M), in a small droplet, or by iontophoresis into the cellular and dendritic layers of the slice. The effects of DADL on synaptic potentials and membrane properties were studied in an effort to determine the mechanisms underlying its epileptogenic action in the hippocampus. (2) DADL increased the size and often the duration of excitatory postsynaptic potentials (EPSPs) generated on either the apical or basal dendrites; this resulted in an increased discharge probability for a constant orthodromic stimulus. Extracellular field potential recordings showed a larger population spike for a given size field EPSP. These effects of DADL could be reversed substantially by perfusion with naloxone (1 to 5 X 10-7 M) and appeared qualitatively different from the epileptiform actions of penicillin. (3) DADL did not appear to increase the intrinsic excitability of the soma membrane, since membrane potential, input resistance, spike threshold, and antidromic field potentials all were unchanged. In addition, the shape of the membrane charging curve during hyperpolarizing current injection was not changed noticeably by DADL. (4) At the concentrations tested, DADL did not attenuate recurrent inhibition in the CA1 region, as evaluated by comparing in the absence and presence of DADL: (a) antidromically evoked recurrent inhibitory postsynaptic potentials (IPSPs) and their dependence of membrane potential, (b) the reduction of a synaptically driven population spike by a prior antidromic volley, (c) iontophoretic GABA (gamma-aminobutyric acid) responses. Similarly, IPSPs evoked by orthodromic stimulation appeared either unaffected or occasionally enhanced by DADL. (5) By iontophoretic mapping, it was shown that the DADL-sensitive sites are limited to stratum oriens and stratum pyramidale. Local application of DADL into stratum radiatum was relatively ineffective in enhancing the efficacy of synapses located in this region. (6) The dendritic input-output relationship between the presynaptic fiber volley and the field EPSP was not changed by DADL. This finding and the results of the iontophoretic mapping experiments suggest that increased excitatory transmitter release was not involved. (7) The data are consistent with the proposal that DADL selectively attenuates a dendritic IPSP which is virtually invisible to the soma, although the possibility cannot be ruled out that DADL may, in addition, act to enhance the responsiveness of pyramidal dendritic membrane to excitatory synaptic activation

Unlinkable content playbacks in a multiparty DRM system

We present a solution to the problem of privacy invasion in a multiparty digital rights management scheme. (Roaming) users buy content licenses from a content provider and execute it at any nearby content distributor. Our approach, which does not need any trusted third party--in contrast to most related work on privacy-preserving DRM--is based on a re-encryption scheme that runs on any mobile Android device. Only a minor security-critical part needs to be performed on the device's smartcard which could, for instance, be a SIM card

An Empirical Study of the I2P Anonymity Network and its Censorship Resistance

Tor and I2P are well-known anonymity networks used by many individuals to protect their online privacy and anonymity. Tor's centralized directory services facilitate the understanding of the Tor network, as well as the measurement and visualization of its structure through the Tor Metrics project. In contrast, I2P does not rely on centralized directory servers, and thus obtaining a complete view of the network is challenging. In this work, we conduct an empirical study of the I2P network, in which we measure properties including population, churn rate, router type, and the geographic distribution of I2P peers. We find that there are currently around 32K active I2P peers in the network on a daily basis. Of these peers, 14K are located behind NAT or firewalls. Using the collected network data, we examine the blocking resistance of I2P against a censor that wants to prevent access to I2P using address-based blocking techniques. Despite the decentralized characteristics of I2P, we discover that a censor can block more than 95% of peer IP addresses known by a stable I2P client by operating only 10 routers in the network. This amounts to severe network impairment: a blocking rate of more than 70% is enough to cause significant latency in web browsing activities, while blocking more than 90% of peer IP addresses can make the network unusable. Finally, we discuss the security consequences of the network being blocked, and directions for potential approaches to make I2P more resistant to blocking.Comment: 14 pages, To appear in the 2018 Internet Measurement Conference (IMC'18

Presynaptic inhibitory effect of acetylcholine in the hippocampus

(1) In order to investigate the effects of acetylcholine (ACh) on synaptic transmission in the rat hippocampus, extracellular and intracellular recordings were made from pyramidal neurons in an in vitro slice preparation while synaptic inputs to the cell population were stimulated. ACh was applied ionophoretically into somatic and dendritic layers of the slice. (2) ACh applied into the apical dendritic layer of the CA1 region reduced the size of the locally evoked field excitatory postsynaptic potential (EPSP) without altering the size of the afferent fiber volley. Likewise, dendritically applied ACh reduced the size of intracellularly recorded EPSPs. This effect of ACh appeared to be muscarinic since it was not affected by hexamethonium (up to 3 X 10-5 M) but was antagonized by atropine in a dose-dependent manner. (3) The distribution of Ach-sensitive sites matched closely the spatial distribution of activated synapses on the pyramidal cell dendrites as shown by ionophoretic mapping experiments. (4) In contrast to the effects of dendritic applications of ACh, ionophoresis of ACh into the cell layer resulted in an increase and prolongation of EPSPs and a transient decrease in the size of recurrent somatic inhibitory postsynaptic potentials (IPSPs). These effects on synaptic potentials could not be explained by the observed changes in membrane potential and input resistance following somatic application of ACh. (5) Short dendritic applications of ACh had no consistent effect on the membrane potential or slope conductance of pyramidal neurons and did not attenuate the depolarization evoked by brief dendritic applications of glutamate. In addition, the time course of ACh-reduced EPSPs was not different from control. (6) We conclude that ACh exerts a presynaptic inhibitory effect on both excitatory and inhibitory afferents to hippocampal pyramidal neurons. This effect of ACh is widespread, occurring in all regions of Ammon's horn tested as well as in stratum moleculare of fascia dentata

Cholinergic cells in the nucleus basalis of mice express the N-methyl-D-aspartate-receptor subunit NR2C and its replacement by the NR2B subunit enhances frontal and amygdaloid acetylcholine levels

It is known that glutamatergic and cholinergic systems interact functionally at the level of the cholinergic basal forebrain. The N-methyl-D-aspartate receptor (NMDA-R) is a multiprotein complex composed of NR1, NR2 and/or NR3 subunits. The subunit composition of NMDA-R of cholinergic cells in the nucleus basalis has not yet been investigated. Here, by means of choline acetyl transferase and NR2B or NR2C double staining, we demonstrate that mice express both the NR2C and NR2B subunits in nucleus basalis cholinergic cells.We generated NR2C-2B mutant mice in which an insertion of NR2B cDNA into the gene locus of the NR2C gene replaced NR2C by NR2B expression throughout the brain. This NR2C-2B mutant was used to examine whether a subunit exchange in cholinergic neurons would affect acetylcholine (ACh) content in several brain structures. We found increased ACh levels in the frontal cortex and amygdala in the brains of NR2C-2B mutant mice. Brain ACh has been implicated in neuroplasticity, novelty-induced arousal and encoding of novel stimuli. We therefore assessed behavioral habituation to novel environments and objects as well as object recognition in NR2C-2B subunit exchange mice. The behavioral analysis did not indicate any gross behavioral alteration in the mutant mice compared with the wildtype mice. Our results show that the NR2C by NR2B subunit exchange in mice affects ACh content in two target areas of the nucleus basalis.

Measuring the Deployment Hiccups of DNSSEC

On May 5, 2010 the last step of the DNSSEC deployment on the 13 root servers was completed. DNSSEC is a set of security extensions on the traditional DNS protocol, that aim in preventing attacks based on the authenticity and integrity of the messages. Although the transition was completed without major faults, it is not clear whether problems of smaller scale occurred. In this paper we try to quantify the effects of that transition, using as many vantage points as possible. In order to achieve that, we deployed a distributed DNS monitoring infrastructure over the PlanetLab and gathered periodic DNS lookups, performed from each of the roughly 300 nodes, during the DNSSEC deployment on the last root name server. In addition, in order to broaden our view, we also collected data using the Tor anonymity network. After analyzing all the gathered data, we observed that around 4% of the monitored networks had an interesting DNS query failure pattern, which, to the best of our knowledge, was due to the transition