Effect of receiver shape and volume on the Alzheimer disease for molecular communication via diffusion

Nano‐devices are featured to communicate via molecular interaction, the so‐called molecular communication (MC). In MC systems, the information is carried by molecules where the amount of molecules constitutes the level of the signal. In this study, an MC‐based system was analysed with different receiver topology and related parameters, such as size, shape, and orientation of receptors on the receiver. Also in the concept of nano‐medicine, the effect of amyloid‐beta (Aβ), which is believed as the main cause of Alzheimer disease, on the successful reception ratio of molecules with the proposed receiver models was investigated. It was demonstrated that the cubic receiver model is superior to sphere one in terms of the correct reception ratio of the molecular signal. A cubic model where its edge (not rotated around the centre) is placed across the transmitter demonstrated a better performance in reducing the effect of Aβ as compared to the sphere model while a cubic model where its corner (rotated around the centre) is placed across the transmitter demonstrated a worse performance than the spherical model. From this expression, it may be concluded that with the adjustment of topological system parameters the probability of successful reception ratio in MC may be possible.Inspec keywords: diseases, molecular biophysics, neurophysiology, probabilityOther keywords: receiver shape, Alzheimer disease, molecular communication, nanodevices, molecular interaction, smart medicine, neuronal communication, MC systems, high signal level, low‐signal level, topological parameters, MC‐based system, nanomedicine, cubic receiver model, correct reception ratio, molecular signal, cubic model, spherical model, topological system parameters     

Passive wake-up radios: From devices to applications

Energy efficiency is one of the most important criteria in the design of a wireless sensor network. Sensor nodes are usually battery-powered and thus have very limited lifetime. In this paper, we introduce a novel passive wake-up radio device named WISP-Mote that uses a passive RFID tag as a wake-up receiver for a traditional sensor node. We characterize the WISP-Mote with field tests in different operating environments and present the wake-up probabilities based on the distance between the wake-up transmitter and receiver. We then perform simulations to compare the performance of a network with WISP-Motes and with duty-cycling of the sensor nodes, using the wake-up probabilities measured in our field tests. Additionally, potential applications that can benefit from WISP-Motes are discussed, and the advantages of using WISP-Motes are identified by simulation results based on these application scenarios. Results show that the wake-up radio sensor networks have great potential over duty-cycling approaches for energy efficiency, while providing similar latency and packet delivery performances.     

Gold nanoparticle modified conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrole-1-l) benzenamine for potential use as a biosensing material

Gold nanoparticle (AuNP) modified conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH₂) was used as the biosensing platform for glucose analysis. Electrochemical measurements were carried out by following the consumed oxygen due to the enzymatic reaction of glucose oxidase (GOx) at −0.7 V vs Ag/AgCl. Optimisation of pH, enzyme loading, stability experiments were carried out. Effect of NP was investigated by monitoring the signal responses at different AuNP sizes and amounts. A linear relation of y = 1.597x + 0.264 (R² = 0.993) was found for glucose concentrations between 0.002 and 5.0 mM. The analytical characteristics of the system were also evaluated for glucose determination in flow injection analysis (FIA) mode. Finally, the system was checked for glucose detection on real samples.     

Amino acid decarboxylase activities and biogenic amine formation abilities of lactic acid bacteria isolated from shalgam

56 lactic acid bacteria were isolated during shalgam fermentation and identified as Lactobacillus spp. (51 isolates), Lactococcus spp. (3 isolates), Streptococcus sp. (one isolate), and Leuconostoc sp. (one isolate). 53 of all isolates decarboxylated both arginine and tyrosine, while others decarboxylated one of arginine or tyrosine. None of the isolates could decarboxylate histidine, ornithine, lysine, phenylalanine, or tryptophan. All isolates produced both agmatine (105.8–867.5 mg L^–1) and tyramine (24.5–649.7 mg L^–1). Although none of the isolates displayed ornithine decarboxylase activity, putrescine was produced (2.1–33.3 mg L^–1) by all isolates, except one Lactobacillus strain. Therefore, lactic acid bacteria seem to be responsible mainly for tyramine and agmatine formation during shalgam fermentation, as well as a small amount of putrescine.     

Sol–Gel/Chitosan/Gold Nanoparticle-Modified Electrode in Mediated Bacterial Biosensor

A mediated whole cell biosensor was designed and characterized using glucose as the substrate. Gluconobacter oxydans cells were immobilized on the graphite electrode via sol–gel (tetraethyl orthosilicate)/chitosan hybrid composite modified with gold nanoparticles (TEOS/CHIT/AuNPs/G. oxydans). A soluble mediator, potassium hexacyanoferrate (III), was used for the amperometric detection of the respiratory activity of the intact bacterial cells. After optimization of preparation conditions of the TEOS/CHIT/AuNPs/G. oxydans biosensor, characterization studies have been carried out. The linear range for glucose was found to be 0.5–2.0 mM with a response time of 80 s. Moreover, repeatability and electrode-to-electrode reproducibility of the system were investigated and relative standard deviations were calculated as 1.7% and 2.2% for 1.0 mM glucose (n = 5). Finally, the proposed system was applied to ethanol and glucose detection in real samples and the results were compared with a reference method.     

The forward biased,Abrupt p-n junction

The abrupt, forward biased pn-junction is solved very accurately for its terminal characteristics and injection efficiency for all values of forward bias. This is accomplished by using a three-region approach and formulating the transport problem in terms of the local pn-product. Analytic solutions are derived for low, medium and high injection conditions.The low injection regime is characterized by negligible majority carrier density increases. However, in this injection region bulk width modulations due to decreasing transition layer widths modify the standard diffusion model results.The medium injection condition prevails if majority carrier density changes due to injection are significant on the lightly doped side of the junction. This as well as an inreasing bulk voltage drop are taken into account to establish new relationships for injection efficiency, which is decreasing with injection, and the terminal characteristics.The high injection regime involves significant majority carrier modulation in both bulk regions. The injection efficiency becomes a constant which is determined by mobility differences since diffusion currents are negligible. The transition region vanishes in width and its total voltage drop goes to zero. The current through the device is governed by a power law because it is a conductivity modulated resistor.     

Partial characterization of polyphenoloxidase from a hybridized wheat (Triticum aestivum L.)

Polyphenol oxidase was extracted and partially purified from wheat leaves by a procedure that included ammonium sulfate fractionation followed by dialysis and gel filtration chromatography. These procedures led to 35.21-fold purification with 17.65% recovery. Optimum pH, temperature, and ionic strength were determined with six substrates. Some kinetic properties of the enzyme such as V _max, K _M, and k _cat were calculated for the substrates. The k _cat/K _M values of the PPO for catechol, catechin, pyrogallol, l-dopa, dopamine, and 4-methyl catechol were 31408, 31167, 28404, 15378, 4865, and 4967 mM/min, respectively. The best substrate of wheat PPO was found to be catechol. The native molecular weight of the PPO was estimated to be 243 kDa based on its mobility in gel filtration column. The inhibitory effects of glutathione, sodium azide, ascorbic acid, oxalic acid, l-cysteine, and thiourea on the reaction catalyzed by the enzyme were tested, and I ₅₀ values were estimated to be 8.0 mM, 10.12 mM, 11.18 mM, 77.33 mM, 183 mM, and 413 mM, and K _i constants were also calculated as 0.416 ± 0.244 mM, 0.317 ± 0.208 mM, 0.820 ± 0.111 mM, 13.80 ± 1.179 mM, 14.10 ± 5.069 mM, and 130 ± 62.45 mM, respectively, by means of Lineweaver–Burk graphs. The most effective inhibitor was glutathione. Glutathione, sodium azide, oxalic acid, and thiourea were competitive inhibitors, whereas ascorbic acid and l-cysteine were also noncompetitive inhibitors.     

Integrated cross-coupled chaos oscillator applied to random number generation

A new cross-coupled LC chaos oscillator suitable for IC realisation is presented. The proposed circuit was fabricated using a 0.35 mm CMOS process and test results showing its feasibility are given. As a possible application, a method for using the proposed oscillator as the core of a random number generator is described. Experimental binary data obtained according to the proposed method pass the four tests of FIPS- 140-2, the full NIST-800-22 and DIEHARD random number test suites.     

Transition region behavior in abrupt,forward-biased pn-junctions

The transition region for abrupt p-n junctions, symmetric and asymmetric, is analyzed in terms of carrier densities at the neutral bulk-space charge region boundaries and the location of these boundaries with respect to the metallurgical junction. The non-equilibrium semiconductor problem is simplified by defining an effective intrinsic carrier concentration and an effective Fermi energy.The relation between the split in the quasi-Fermi levels and applied junction voltage is obtained. Also, density relationships are derived in terms of externally applied junction voltages. A low, high and very high injection formulation results. The transition region width is determined by solving Poisson's equation for a double region problem approximately. MOS concepts such as inversion and depletion are shown to apply to the forward biased junction.     

Energy and delay optimized contention for wireless sensor networks

In wireless sensor network (WSN) studies, the main objective is minimizing the energy consumption so that the lifetime is maximized under the limited battery capacity constraints. Additionally, in most event-driven WSN applications, the end-to-end delay, and hence, the medium access delay should be minimized. Majority of the WSN MAC protocols are contention-based wherein contention window size setting involves an important trade-off between the collision probability and idle listening durations in contentions where both are aimed to be lowered for efficient network operation. In this paper, the energy optimizing and the delay optimizing contention window sizes are derived as a function of the number of contending nodes. For this purpose, we present separate analyses for the contention delay and for the energy consumed which are verified with detailed simulations. In order to obtain close to optimal performance values in a distributed manner, we propose a method for estimating the number of contending nodes since the individual wireless sensor nodes do not have this information readily. Simulations of an event-driven WSN application verify that the proposed method successfully improve both delay and energy efficiency of the contention-based medium access. The end-to-end network performance is also investigated by employing a geographical routing protocol. Results show that using the heuristic method proposed that use the optimum contention window size analyses presented, the overall network performance can be improved without incurring any overhead to the system.