Effects of information transmission delay and channel blocking on synchronization in scale-free Hodgkin-Huxley neuronal networks

In this paper,we investigate the evolution of spatiotemporal patterns and synchronization transitions in dependence on the information transmission delay and ion channel blocking in scale-free neuronal networks.As the underlying model of neuronal dynamics,we use the Hodgkin-Huxley equations incorporating channel blocking and intrinsic noise.It is shown that delays play a significant yet subtle role in shaping the dynamics of neuronal networks.In particular,regions of irregular and regular propagating excitatory fronts related to the synchronization transitions appear intermittently as the delay increases.Moreover,the fraction of working sodium and potassium ion channels can also have a significant impact on the spatiotemporal dynamics of neuronal networks.As the fraction of blocked sodium channels increases,the frequency of excitatory events decreases,which in turn manifests as an increase in the neuronal synchrony that,however,is dysfunctional due to the virtual absence of large-amplitude excitations.Expectedly,we also show that larger coupling strengths improve synchronization irrespective of the information transmission delay and channel blocking.The presented results are also robust against the variation of the network size,thus providing insights that could facilitate understanding of the joint impact of ion channel blocking and information transmission delay on the spatiotemporal dynamics of neuronal networks.

A CODE DESIGN CRITERIA FOR NOT FULLY CONNECTED CHANNEL

There are parallel channels which are not fully connected in practice, such as Frequency Division Multiplex (FDM or Orthogonal FDM) systems. Conventional space-time codes can be used for such parallel channels but not the optimal. Based on the derivation of PEP expression for codes transmitted on parallel block fading channels, criteria of codes design for not fully connected channels are proposed and are compared with Tarokh's criteria for fully connected channel. New codes for such channels are provided by systematical and exhaustive search. Simulation results show that these codes offer better performance on parallel FDM channels than other known codes.

Pharmacological evaluation of smooth muscle relaxant and cardiac-modulation potential of Phyla nodiflora in ex-vivo and in-vivo experiments

Objective: To investigate the pharmacological basis of its uses of Phyla nodiflora(P. nodiflora) for the treatment of anomalies predominantly by smooth muscle containing tissues such as gastrointestinal/vascular/broncho spasm and cardiovascular modulation.Methods: The crude hydroalcoholic extract of P. nodiflora(Pn.Cr) and its fractions were evaluated on isolated rabbit jejunum, rat trachea, aorta and atrium. To access the contractile or relaxant effects of testing materials, the tissues were mounted in isolated organ bath and responses were recorded with transducers coupled with data acquisition system.BALB/c mice were challenged with castor oil for the assessment of in-vivo antidiarrheal activity. Normotensive rats were used for in-vivo hypotensive study.Results: Hydroalcoholic extract of Pn.Cr at variable concentrations inhibited the natural spontaneous rhythm and 80 mmol/L K^+ mediated contractions in isolated segment of jejunum with EC_(50) values of 3.18 and 1.91 mg/mL respectively. Verapamil, a Ca^(2+) channel blocker, demonstrated akin pattern in jejunum and therefore possibly suggesting calcium blocking activity. On isolated rat tracheal tissue, Pn.Cr showed relaxation of high-K^+and carbachol mediated contractions(EC_(50) values: 1.24 and 2.42 mg/mL). Pn.Cr treatment relaxed the rat aortic ring in a cumulative doses with high-K^+ and phenylephrine-induced contractions(EC_(50) values 0.25 and 0.92 mg/mL). Activity based fractionation of Pn.Cr showed that dichloromethane fraction was more potent for relaxing the tissues spasm compared to aqueous fraction. In-vivo experiments, significant protection by Pn.Cr(P < 0.05) was observed in castor oil-induced diarrhea(50–500 mg/kg)whereas hypotensive effect in anesthetized rats was seen at the dose range of 1–10 mg/kg of Pn.Cr(P < 0.05).Conclusion: This study suggests the blockage of calcium channel in the smooth muscles as a pharmacological application to make usage of P. nodiflora in the management of diarrhea, asthma and hypotensive effect.

An IEEE 802.3 Compatible Real Time Medium Access Control with Length-based Priority

A new medium access control method is proposed over the predominant Ethernet broadcast channel. Taking advantages of intrinsic variable length characteristic of standard Ethemet frame, message-oriented dynamic priority mechanism is established. Prioritized medium access control operates under a so-called block mode in event of collisions. High priority messages have a chance to preempt block status incurred by low priority ones. By this means, the new MAC provides a conditional detrministic real time performance beyond a statistical one. Experiments effectiveness and attractiveness of the proposed scheme.Moreover,this new MAC is completely compatible with IEEE802.3 .

Effects of channel blocks on the spiking regularity in clustered neuronal networks

In this paper,we discuss the influences of channel blocks on the spiking regularity in a clustered neuronal network by applying stochastic Hodgkin-Huxley neuronal models as the building blocks.With the aid of simulation results,we reveal that the spiking regularity of the clustered neuronal network could be resonantly enhanced via fine-tuning of the non-blocked potassium channel fraction xK.While the non-blocked sodium channel fraction xNa can enhance the spiking regularity of the clustered neuronal network in most cases.These results indicate that not only sodium channel blocks but also potassium channel blocks could have great influences on the regularity of spike timings in the clustered neuronal networks.Considering the importance of spike timings in neuronal information transforming processes,our results may give some implications for understanding the nonnegligible role of randomness in ion channels in neuronal systems.

Robustness, Death of Spiral Wave in the Network of Neurons under Partial Ion Channel Block

The development of spiral wave in a two-dimensional square array due to partial ion channel block （Potas- sium, Sodium） is investigated, the dynamics of the node is described by Hodgkin-Huxley neuron and these neurons are coupled with nearest neig1 bor connection. The parameter ratio xNa （and xK）, which defines the ratio of working ion channel number of sodium （potassium） to the total ion channel number of sodium （and potassium）, is used to measure the shift conductance induced by channel block. The distribution of statistical variable R in the two-parameter phase space （parameter ratio vs. poisoning area） is extensively calculated to mark the parameter region for transition of spiral wave induced by partial ion channel block, the area with smaller factors of synchronization R is associated the parameter region that spiral wave keeps Mive and robust to the channel poisoning. SpirM wave keeps alive when the poisoned area （potassium or sodium） and degree of intoxication are small, distinct transition （death, several spiral waves coexist or multi-axm spiral wave emergence） occurs under moderate ratio XNa （and XK） when the size of blocked area exceeds certain thresholds. Breakup of spiral wave occurs and multi-axm of spiral waves are observed when the channel noise is considered.

Emergence of target waves in neuronal networks due to diverse forcing currents

The electric activities of neurons could be changed when ion channel block occurs in the neurons.External forcing currents with diversity are imposed on the regular network of Hodgkin-Huxley(HH) neuron,and target waves are induced to occupy the network.The forcing current I1 is imposed on neurons in a local region with m 0 ×m 0 nodes in the network,neurons in other nodes are imposed with another forcing current I2.Target wave could be developed to occupy the network when the gradient forcing current(I1-I2) exceeds certain threshold,and the formation of target wave is independent of the selection of boundary condition.It is also found that the developed target wave can decrease the negative effect of ion channel block and suppress the spiral wave,and thus channel noise is also considered.The potential mechanism of formation of target wave could be that the gradient forcing current(I1-I2) generates quasi-periodical signal in local area,and the propagation of quasi-periodical signal induces target-like wave due to mutual coupling among neurons in the network.

A radiation-hardened SOl-based FPGA

A radiation-hardened SRAM-based field programmable gate array VS1000 is designed and fabricated with a 0.5μm partial-depletion silicon-on-insulator logic process at the CETC 58th Institute.The new logic cell （LC）,with a multi-mode based on 3-input look-up-table（LUT）,increases logic density about 12%compared to a traditional 4-input LUT.The logic block（LB）,consisting of 2 LCs,can be used in two functional modes：LUT mode and distributed read access memory mode.The hierarchical routing channel block and switch block can significantly improve the flexibility and routability of the routing resource.The VS1000 uses a CQFP208 package and contains 392 reconfigurable LCs,112 reconfigurable user I/Os and IEEE 1149.1 compatible with boundary-scan logic for testing and programming.The function test results indicate that the hardware and software cooperate successfully and the VS1000 works correctly.Moreover,the radiation test results indicate that the VS1000 chip has total dose tolerance of 100 krad（Si）,a dose rate survivability of 1.5×10^（11）rad（Si）/s and a neutron fluence immunity of 1×10^（14） n/cm^2.