A new busy signal-based MAC protocol supporting QoS for ad-hoc networks with hidden nodes

This article presents three versions of a novel MAC protocol for IEEE 802.11 ad-hoc networks called Busy Signal-based Mechanism turned On (BusySiMOn) (This is an extended version of our conference paper: [15]). The key idea of the proposed solution is based on an intelligent two-step reservation procedure combined with the advantages of EDCA service differentiation. The former alleviates the hidden node problem while the latter ensures compatibility with the IEEE 802.11 standard. Simulation results obtained for saturated and non-saturated network conditions emphasize the advantages of the new protocol over the currently used four-way handshake mechanism in terms of fairness, throughput, and average frame delay.     

Novel N-Substituted 3-Aryl-4-(diethoxyphosphoryl)azetidin-2-ones as Antibiotic Enhancers and Antiviral Agents in Search for a Successful Treatment of Complex Infections

A novel series of N-substituted cis- and trans-3-aryl-4-(diethoxyphosphoryl)azetidin-2-ones were synthesized by the Kinugasa reaction of N-methyl- or N-benzyl-(diethyoxyphosphoryl)nitrone and selected aryl alkynes. Stereochemistry of diastereoisomeric adducts was established based on vicinal H3–H4 coupling constants in azetidin-2-one ring. All the obtained azetidin-2-ones were evaluated for the antiviral activity against a broad range of DNA and RNA viruses. Azetidin-2-one trans-11f showed moderate inhibitory activity against human coronavirus (229E) with EC₅₀ = 45 µM. The other isomer cis-11f was active against influenza A virus H1N1 subtype (EC₅₀ = 12 µM by visual CPE score; EC₅₀ = 8.3 µM by TMS score; MCC > 100 µM, CC₅₀ = 39.9 µM). Several azetidin-2-ones 10 and 11 were tested for their cytostatic activity toward nine cancerous cell lines and several of them appeared slightly active for Capan-1, Hap1 and HCT-116 cells values of IC₅₀ in the range 14.5–97.9 µM. Compound trans-11f was identified as adjuvant of oxacillin with significant ability to enhance the efficacy of this antibiotic toward the highly resistant S. aureus strain HEMSA 5. Docking and molecular dynamics simulations showed that enantiomer (3R,4S)-11f can be responsible for the promising activity due to the potency in displacing oxacillin at β-lactamase, thus protecting the antibiotic from undesirable biotransformation.     

Mechanical and Infrared Thermography Analysis of Shape Memory Polyurethane

Multifunctional new material—polyurethane shape memory polymer (PU-SMP)—was subjected to tension carried out at room temperature at various strain rates. The influence of effects of thermomechanical couplings on the SMP mechanical properties was studied, based on the sample temperature changes, measured by a fast and sensitive infrared camera. It was found that the polymer deformation process strongly depends on the strain rate applied. The initial reversible strain is accompanied by a small drop in temperature, called thermoelastic effect. Its maximal value is related to the SMP yield point and increases upon increase of the strain rate. At higher strains, the stress and temperature significantly increase, caused by reorientation of the polymer molecular chains, followed by the stress drop and its subsequent increase accompanying the sample rupture. The higher strain rate, the higher stress, and temperature changes were obtained, since the deformation process was more dynamic and has occurred in almost adiabatic conditions. The constitutive model of SMP valid in finite strain regime was developed. In the proposed approach, SMP is described as a two-phase material composed of hyperelastic rubbery phase and elastic-viscoplastic glassy phase, while the volume content of phases is specified by the current temperature.     

Attachment and proliferation of human osteoblast-like cells (MG-63) on laser-ablated titanium implant material

Demand is increasing for shortening the long (3–6 months) osseointegration period to rehabilitate patients' damaged chewing apparatus in as short a time as possible. For dental implants, as for biomaterials in general, the bio- and osseointegration processes can be controlled at molecular and cellular levels by modification of the implant surface. One of the most promising of such surface modifications is laser ablation, as demonstrated by our previous results [46]. Commercially pure (CP4) sand-blasted, acid-etched titanium disks (Denti® System Ltd., Hungary) were irradiated with a KrF excimer laser (248 nm, fluence 0.4 J/cm², FWHM 18 ns, 2000 pulses), or with a Nd:YAG laser (532 nm, 1.3 J/cm², 10 ns, 200 pulses) then examined by SEM, AFM, and XPS. In vitro attachment (24 h) and proliferation (72 h) of MG-63 osteoblast cells were investigated via dimethylthiazol-diphenyl tetrazolium bromide (MTT), alamarBlue (AB) assays alkaline phosphatase quantification (ALP) and SEM. SEM and AFM revealed significant changes in morphology and roughness. XPS confirmed the presence of TiO₂ on each sample; after Nd:YAG treatment a reduced state of Ti (Ti^3 +) was also observed. MTT, AB and ALP measurements detected an increase in the number of cells between the 24- and 72 hour observations; however, laser treatment did not affect cell attachment and proliferation significantly.     

Chemo-enzymatic Synthesis of Novel β-Hydroxy-β-methylbutryric Acid (HMB)–Medium Chain Triacylglycerol (MCT) Complexes

β-Hydroxy-β-methylbutyrate (HMB) is reported to have ergogenic benefits such as reducing muscle wasting, promoting exercise performance and skeletal muscle hypertrophy. When used as a dietary feed, it has been found to improve colostral milk fat and the growth of piglets. Medium chain triacylglycerols (MCT) are a good energy source as they can be subjected to β-oxidation in the liver without being stored as fats. When used as animal feed, HMB–MCT complexes are reported to stimulate growth and produce leaner meat product. A high yield two-steps chemo-enzymatic pathway for synthesis of HMB–MCT complexes has been developed. Ethyl HMB ester was first synthesized using a chemical catalyst. Following that, it was transesterified with MCT by using a biocatalyst. Approximately 85 wt% of HMB–MCT complexes can be achieved using this two-step synthetic pathway. The reaction mechanism and some of the reaction parameters were also briefly elucidated.     

Removal of Copper(II) from Chloride Solutions using Hydrophobic Pyridyl Ketone Oximes

Abstract: The model oximes of 1‐(2‐pyridyl)undecane‐1‐one (2PC10), 1‐(2‐pyridyl)tridecane‐1‐one (2PC12) and 1‐(4‐pyridyl)tridecane‐1‐one (4PC12) were synthesized and used for copper(II) extraction from chloride solutions. The behavior of these ligands towards copper(II) extraction was investigated for different experimental conditions with a particular emphasis on the influence of the concentrations of copper ions, chloride ions, and ligand. The obtained results indicated the ability of pyridylketoximes to extract copper(II) from chloride solutions. 2‐Pyridyl ketone oximes are stronger extractants of copper than 4‐pyridyl ketone oximes. Copper can be effectively stripped by water or diluted sulfuric acid.     

Application of MALDI-TOFMS Combined with Partial Least Square Regression for the Determination of Mercury and Copper in Canned Tuna,Using Dithizone as the Complexing Agent and Ag(I) as Internal Standard

In this work, a procedure for the determination of mercury and copper in canned tuna samples is presented, based on the extraction of their respective dithizone complexes and quantification by conventional MALDI-TOFMS with the aid of partial least square regression (PLS2). Methanolic dithizone solution (1 ml, 0.01% m/v) containing Ag(I) as internal standard was added to the calibration solutions and to the acid-digested samples (5 ml, pH 3); copper, mercury, and silver complexes were extracted to cyclohexane (1.5 ml), and after evaporation, the residues were re-constituted in acetone (100 μl). The samples were prepared by dried droplet crystallization with α-cyano-4-hydroxycinnamic acid. The experimental and MALDI-TOFMS instrument operating conditions were set up under criteria of as high as possible detectability and repeatability. When univariate calibration was carried out using the most intense ion of Cu or Hg complex normalized by internal standard, determination seemed feasible yet precision of the results was poor. Taking baseline-corrected spectra in m/z range 560–725, PLS2 model was constructed for the prediction of two elements with the method quantification limits 63 μg kg^?1 for Cu and 75 μg kg^?1 for Hg, respectively. For different brands of canned tuna, the results obtained by MALDI-TOFMS combined with PLS2 and by ICP-MS were in good agreement. The proposed procedure is an attractive alternative for the determination of trace metals in foods because of the procedural simplicity, micro-scale dimension, high speed of data acquisition/processing, and the cost of instrument operation lower as compared to any atomic spectrometry technique.     

A Comparative Analysis of Colour Measurements of the Seed Coat and Endosperm of Wheat Kernels Performed by Various Techniques

The results of this present studies show that the colour of the seed coat of wheat kernels can be determined by digital image analysis (DIA) instead of spectrophotometry. High linear correlations (p < 0.05) were found between colour measurements of the seed coat performed by these techniques. The colour on the cross-sections of wheat kernels was related to the colour of their seed coat. A high correlation was also observed between the colour of the seed coat and the colour of the endosperm of wheat kernels. In all measurements colour was described by the RGB, XYZ, and L*a*b* models. Colour indices, i.e. hue (h⁰) and saturation (S*) were also calculated.     

The Impact of Graphite Oxide Nanocomposites on the Antibacterial Activity of Serum

Nanoparticles can interact with the complement system and modulate the inflammatory response. The effect of these interactions on the complement activity strongly depends on physicochemical properties of nanoparticles. The interactions of silver nanoparticles with serum proteins (particularly with the complement system components) have the potential to significantly affect the antibacterial activity of serum, with serious implications for human health. The aim of the study was to assess the influence of graphite oxide (GO) nanocomposites (GO, GO-PcZr(Lys)₂-Ag, GO-Ag, GO-PcZr(Lys)₂) on the antibacterial activity of normal human serum (NHS), serum activity against bacteria isolated from alveoli treated with nanocomposites, and nanocomposite sensitivity of bacteria exposed to serum in vitro (using normal human serum). Additionally, the in vivo cytotoxic effect of the GO compounds was determined with application of a Galleria mellonella larvae model. GO-PcZr(Lys)₂, without IR irradiation enhance the antimicrobial efficacy of the human serum. IR irradiation enhances bactericidal activity of serum in the case of the GO-PcZr(Lys)₂-Ag sample. Bacteria exposed to nanocomposites become more sensitive to the action of serum. Bacteria exposed to serum become more sensitive to the GO-Ag sample. None of the tested GO nanocomposites displayed a cytotoxicity towards larvae.     

Effects of Brain Size on Adult Neurogenesis in Shrews

Shrews are small animals found in many different habitats. Like other mammals, adult neurogenesis occurs in the subventricular zone of the lateral ventricle (SVZ) and the dentate gyrus (DG) of the hippocampal formation. We asked whether the number of new generated cells in shrews depends on their brain size. We examined Crocidura russula and Neomys fodiens, weighing 10–22 g, and Crocidura olivieri and Suncus murinus that weigh three times more. We found that the density of proliferated cells in the SVZ was approximately at the same level in all species. These cells migrated from the SVZ through the rostral migratory stream to the olfactory bulb (OB). In this pathway, a low level of neurogenesis occurred in C. olivieri compared to three other species of shrews. In the DG, the rate of adult neurogenesis was regulated differently. Specifically, the lowest density of newly generated neurons was observed in C. russula, which had a substantial number of new neurons in the OB compared with C. olivieri. We suggest that the number of newly generated neurons in an adult shrew’s brain is independent of the brain size, and molecular mechanisms of neurogenesis appeared to be different in two neurogenic structures.