Enhanced injection method for synthetically generated turbulence within the flow domain of eddy-resolving simulations

The quality of eddy-resolving turbulence simulations strongly depends on appropriate inflow conditions. In most cases they have to be time-dependent and satisfy certain conditions for the first (mean velocities) and second-order moments (Reynolds stresses) as well as concerning suitable length scales. To mimic a physically realistic incoming flow, synthetically generated turbulent velocity fluctuations superimposed on the mean velocity field are a valuable solution. However, the resolution of the grid near the inlet has to be sufficiently fine to avoid excessive damping of the turbulence intensity. In order to circumvent this problem, the injection of synthetically generated inflow data not at the inlet itself but inside the flow domain near the area of interest, where the grid is typically much finer, is an elegant loophole. In the present study two different injection techniques based on a source-term formulation are analyzed and evaluated. In addition to these techniques the injected data are weighted by a Gaussian distribution defining the influence area. In the recent work the definition of the influence area is enhanced compared to the initial version of Schmidt and Breuer (2017) extending the application range. The case of a rather small influence area in comparison with the grid cell size is now tackled which is often relevant for industrial applications.The flow past a wall-mounted hemisphere is chosen as test case. The bluff body is exposed to a thick turbulent boundary layer at Re $=$ 50,000. The generation of the turbulent velocity fluctuations in the present investigation relies on the digital filter concept, but the injection techniques evaluated are not restricted to this inflow generator. The synthetic turbulent velocity fluctuations are injected about one diameter upstream of the hemisphere. Wall-resolved large-eddy simulations are carried out for two grid resolutions and the corresponding results are analyzed and compared with the reference measurements by Wood et al. (2016). Finally, one injection technique is found to be clearly superior to the other, since it guarantees the correct level of the velocity fluctuations and the reproduction of the autocorrelations.     

Random forest classifier‐based safe and reliable routing for opportunistic IoT networks

Designing a safe and reliable way for communicating the messages among the devices and humans forming the Opportunistic Internet of Things network (OppIoT) has been a challenge since the broadcast mode of message sharing is used. To contribute toward addressing such challenge, this paper proposes a Random Forest Classifier (RFC)‐based safe and reliable routing protocol for OppIoT (called RFCSec) which ensures space efficiency, hash‐based message integrity, and high packet delivery, simultaneously protecting the network against safety threats viz. packet collusion, hypernova, supernova, and wormhole attacks. The proposed RFCSec scheme is composed of two phases. In the first one, the RFC is trained on real data trace, and based on the output of this training, the second phase consists in classifying the encountered nodes of a given node as belonging to one of the output classes of nodes based on their past behavior in the network. This helps in proactively isolating the malicious nodes from participating in the routing process and encourages the participation of the ones with good message forwarding behavior, low packet dropping rate, high buffer availability, and a higher probability of delivering the messages in the past. Simulation results using the ONE simulator show that the proposed RFCSec secure routing scheme is superior to the MLProph, RLProph, and CAML routing protocols, chosen as benchmarks, in terms of legitimate packet delivery, probability of message delivery, count of dropped messages, and latency in packet delivery. The out‐of‐bag error obtained is also minimal     

High Frequency Electronically Tunable Floating Memristor Emulators employing VDGA and Grounded Capacitor

This paper introduces novel electronically tunable floating and grounded memristor emulator circuits using voltage differencing gain amplifier and one capacitor. The decremental and incremental memristor emulators have been suggested for both floating as well as grounded type configurations. Decremental to incremental and incremental to decremental configurations of memristor emulators can be easily obtained. The fingerprint of memristor is the pinched hysteresis loops that are maintained for the significant range of frequencies from 5 kHz to 1 MHz. The proposed memristor emulator sustains its range of frequency for both grounded and floating configurations. The simulations have been done in Eldo simulation tool of Mentor Graphics using TSMC 0.18 µm complementary metal-oxide semiconductor (CMOS) technology parameters. The proposed electronically tunable memristor emulators are used to realize analog filters in view of performance verification.

     

Citrulline malate supplementation does not improve German Volume Training performance or reduce muscle soreness in moderately trained males and females

Background

Use of supplements to aid performance is common practice amongst recreationally active individuals, including those without a sufficient evidence base. This investigation sought to assess whether acute supplementation with 8 g of citrulline malate (CM) (1.11: 1 ratio) would improve anaerobic performance.

Methods

A randomised double blind placebo control trial was employed, using a counterbalanced design. We recruited recreationally active men and women to take part in an isokinetic chair protocol, based on German Volume Training (GVT) whereby participants attempted to perform 10 sets of 10 repetitions against a force representing 70% of their peak concentric force.

Results

The number of repetitions achieved over the course of the GVT was 94.0?±?7.9 and 90.9?±?13.9 for placebo and CM respectively. There was no significant difference between the placebo and CM treatment for number of repetitions (P?=?0.33), isometric (P?=?0.60), concentric (P?=?0.38), or eccentric (P?=?0.65) peak force following the GVT. Total muscle soreness was significantly higher in the CM compared to the placebo treatment following the GVT protocol over 72 h (P?=?0.01); although this was not accompanied by a greater workload/number of repetitions in the CM group.

Conclusions

We conclude that an acute dose of CM does not significantly affect anaerobic performance using an isokinetic chair in recreational active participants. Practical implications include precaution in recommending CM supplementation. Coaches and athletes should be aware of the disparity between the chemical analyses of the products reviewed in the present investigation versus the manufacturers’ claims.

     

New grounded and floating memristor emulators using OTA and CDBA

In this paper, grounded and floating decremental/incremental memristor emulators have been proposed by using an operational transconductance amplifier (OTA), current differencing buffered amplifier (CDBA), and a grounded capacitor. The proposed memristor emulators are simpler in design over most of the realizations of memristor emulators available in the literature. The proposed configurations of grounded and floating decremental memristor emulators can be easily converted into grounded and floating incremental memristor emulators. The pinched hysteresis loops obtained from proposed memristor emulators are maintained up to 1-MHz frequency in both decremental and incremental configurations. Simulation results have been obtained using a Mentor Graphics Eldo simulation tool in 0.18-μm complementary metal-oxide semiconductor (CMOS) technology parameters. Analog filters have also been designed to verify the performance of proposed grounded and floating memristor emulators.     

Ant and Mite Diversity Drives Toxin Variation in the Little Devil Poison Frog

Poison frogs sequester chemical defenses from arthropod prey, although the details of how arthropod diversity contributes to variation in poison frog toxins remains unclear. We characterized skin alkaloid profiles in the Little Devil poison frog, Oophaga sylvatica (Dendrobatidae), across three populations in northwestern Ecuador. Using gas chromatography/mass spectrometry, we identified histrionicotoxins, 3,5- and 5,8-disubstituted indolizidines, decahydroquinolines, and lehmizidines as the primary alkaloid toxins in these O. sylvatica populations. Frog skin alkaloid composition varied along a geographical gradient following population distribution in a principal component analysis. We also characterized diversity in arthropods isolated from frog stomach contents and confirmed that O. sylvatica specialize on ants and mites. To test the hypothesis that poison frog toxin variability reflects species and chemical diversity in arthropod prey, we (1) used sequencing of cytochrome oxidase 1 to identify individual prey specimens, and (2) used liquid chromatography/mass spectrometry to chemically profile consumed ants and mites. We identified 45 ants and 9 mites in frog stomachs, including several undescribed species. We also showed that chemical profiles of consumed ants and mites cluster by frog population, suggesting different frog populations have access to chemically distinct prey. Finally, by comparing chemical profiles of frog skin and isolated prey items, we traced the arthropod source of four poison frog alkaloids, including 3,5- and 5,8-disubstituted indolizidines and a lehmizidine alkaloid. Together, the data show that toxin variability in O. sylvatica reflects chemical diversity in arthropod prey.     

Biosorption of Cr(VI) by immobilized biomass of two indigenous strains of cyanobacteria isolated from metal contaminated soil

Biosorption of Cr(VI) using native strains of cyanobacteria from metal contaminated soil in the premises of textile mill has been reported in this paper. Biosorption was studied as a function of pH (1-5), contact time (5-180 min) and initial chromium ion concentration (5-20mg/l) to find out the maximum biosorption capacity of alginate immobilized Nostoc calcicola HH-12 and Chroococcus sp. HH-11. The optimum conditions for Cr(VI) biosorption are almost same for the two strains (pH 3-4, contact time 30 min and initial chromium concentration of 20mg/l) however, the biomass of Chroococcus sp. HH-11 was found to be more suitable for the development of an efficient biosorbent for the removal of Cr(VI) from wastewater, as it showed higher values of q(m) and K(f), the Langmuir and Freundlich isotherm parameters. Both the isotherm models were suitable for describing the biosorption of Cr(VI) by the cyanobacterial biosorbents.     

Taste,Smell and Sound On the Street in Chinatown and Little Italy

Like magnets, Chinatown and Little Italy, in Manhattan, attract New Yorkers and tourists alike, who come to eat and browse. The sale of food from street vendors, restaurants, cafés and specialist shops encourages a dynamic street life. Despite the commercial success and headlining in guide books of these districts, city officials the world over regard street vendors as disruptive and unsanitary. Nisha Fernando argues on their behalf, evoking the distinctive sensory experiences they afford.     

Melatonin Modulates Plant Tolerance to Heavy Metal Stress: Morphological Responses to Molecular Mechanisms

Heavy metal toxicity is one of the most devastating abiotic stresses. Heavy metals cause serious damage to plant growth and productivity, which is a major problem for sustainable agriculture. It adversely affects plant molecular physiology and biochemistry by generating osmotic stress, ionic imbalance, oxidative stress, membrane disorganization, cellular toxicity, and metabolic homeostasis. To improve and stimulate plant tolerance to heavy metal stress, the application of biostimulants can be an effective approach without threatening the ecosystem. Melatonin (N-acetyl-5-methoxytryptamine), a biostimulator, plant growth regulator, and antioxidant, promotes plant tolerance to heavy metal stress by improving redox and nutrient homeostasis, osmotic balance, and primary and secondary metabolism. It is important to perceive the complete and detailed regulatory mechanisms of exogenous and endogenous melatonin-mediated heavy metal-toxicity mitigation in plants to identify potential research gaps that should be addressed in the future. This review provides a novel insight to understand the multifunctional role of melatonin in reducing heavy metal stress and the underlying molecular mechanisms.