Nanomorphology and nanomechanical characteristics of solution-blow-spun PVDF-based fibers filled with carbon nanotubes

Fibers of poly(vinylidene fluoride) (PVDF) filled with multiwalled carbon nanotubes (MWCNTs) were prepared by solution blow spinning (SBS). The influence of the MWCNTs on the surface morphology and mechanical behavior of single fibers was studied. The morphology of the materials prepared and the dispersion of the MWCNTs within the polymer were studied by optical microscopy (OM) and transmission electron microscopy (TEM), while atomic force microscopy (AFM) was used to inspect the topography of single fibers and to perform nanoindentation tests. OM and TEM images indicated a good dispersion of the MWCNTs within the PVDF. AFM images evidenced clear changes in the topography of the blow-spun fibers when the MWCNTs were present in the polymer. A greater amount of MWCNTs in the PVDF led to more heterogeneous fiber surfaces. The nanoindentation force curves revealed that the stiffness was practically constant along the fibers, which indicated that the mechanical response was homogeneous and, in turn, an even distribution of the MWCNTs. The incorporation of the MWCNTs produced a mechanical reinforcement of the PVDF fibers, showing increases of 31% and 49% in the elastic modulus when 1% and 5% by weight of MWCNTs were added to the polymer, respectively. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47115.     

Automatic continuous venovenous hemodiafiltration in cardiosurgical patients

Intermittent substitutive treatments in severely ill patients with acute renal failure are difficult or not suitable because of technical problems and/or hemodynamic instability. Continuous venovenous hemodiafiltration allows an adequate, slow removal of fluid, electrolytes, and waste products by combining diffusive and convective solute transport. Eight patients with acute renal failure, after cardiovascular surgery and cardiogenic shock, were treated by continuous venovenous hemodiafiltration. An automatic system (Equaline System, Amicon Division, USA) was employed. Venous accesses (femoral or subclavian) were used with double lumen catheters. A polysulfone filter (0.4 m2) was used in the study. Blood flow was 30 ml/min and dialysate flow rate 16.6 ml/min. Sterile pyrogen-free hemofiltration substitution fluid was used as dialysate. Mean duration of treatment was 10.3 +/- 3.2 days. After 72 hours blood urea nitrogen levels dropped from 136 +/- 46.13 to 53.5 +/- 12.3 mg/dl and creatinine levels dropped from 6.9 +/- 1.7 to 2.6 +/- 0.9 mg/dl. A controlled steady-state was then maintained. Mean urea clearance was 21 +/- 5.3 ml/min; mean ultrafiltration rate was 20.3 +/- 4.1 L/day. Continuous venovenous hemodiafiltration, with the Equaline System, is effective for the clearance of waste products and is able to maintain perfect fluid balance in catabolic patients with acute renal failure and multiple organ failure.     

Detection of herbicide subclasses by an optical multibiosensor based on an array of photosystem II mutants

Massive use of herbicides in agriculture over the last few decades has become a serious environmental problem. The residual concentration of these compounds frequently exceeds the maximum admissible concentration in drinking water for human consumption and is a real environmental risk for the aquatic ecosystem. Herbicides inhibiting photosynthesis via targeting photosystem II function still represent the basic means of weed control. A multibiosensor was constructed for detecting herbicides using as biosensing elements photosynthetic preparations coupled to an optical fluorescence transduction system (Giardi et al. EU patent EP1134585, 01830148.1-2204); this paper is about its application in the detection of herbicide subclasses in river water. Photosynthetic material was immobilized on a silicio septum inside a series of flow cells, close to diodes so as to activate photosystem II (PSII) fluorescence. The principle of the detection was based on the factthat herbicides selectively modify PSII fluorescence activity. The multibiosensor has the original feature of being able to distinguish the subclasses of the photosynthetic herbicides by using specific immobilized biomediators isolated from mutated organisms. This setup resulted in a reusable, portable multibiosensor for the detection of herbicide subclasses with a half-life of 54 h for spinach thylakoids and limit of detection of 3 x 10(-9) M for herbicides present in river water.     

Aroma compounds and sensory characteristics as biomarkers of quality of differently processed Tunisian virgin olive oils

The influence of the extraction system (continuous vs. discontinuous) and the degree of freshness of olives on the chemical composition and the quality of Chemlali and Chétoui virgin olive oil has been studied. Analytical data mainly concerning the volatile and sensory profiles revealed statistically significant differences in relation to the extraction system. All quality indices and sensory characteristics showed statistically significant differences associated with the degree of freshness of fruits. These results further confirm the general consensus that volatile compounds can be very useful as biomarkers of the quality of virgin olive oil and show correlations with the sensory characteristics.     

Ultrasound-assisted liquefaction of rosemary honey: Influence on rheology and crystal content

Crystallization of honey is a common process of the honey industry. Liquid honey is preferred by most of the consumers and by food companies for ease of handling. A better method compared to expensive and time-consuming heating is desirable to accelerate the liquefaction and retard the crystallization process in honey. In this work, samples of crystallized honey were liquefied by an ultrasonic bath of 40 kHz at temperatures of 40-60 °C for 20, 40 and 60 min. Then, the rheological properties and crystal content were analyzed and compared to only heat-treated samples. Results show that an ultrasound treatment speeds up the liquefaction of honey especially at temperatures below 50 °C. Lower temperatures preserve the honey’s quality and save the energy consumption. In addition, ultrasound-treated samples are clearer and more transparent than only heat-treated honey samples. The amount and size of the crystals were also smallest in the ultrasound treated samples.     

Odour gradients and patterns in volatile emission of different plant parts and developing fruits of grapefruit (Citrus paradisi L.)

The volatiles spontaneously emitted in vivo by different plant parts of grapefruit (Citrus paradisi Macf., Rutaceae) were collected by solid phase micro-extraction (SPME) during the whole vegetative cycle of the plant and characterised by GC–MS to verify their involvement in entomophilous pollination, a controversial topic in the biology of this species. Furthermore, the essential oils obtained by expression of the pericarp from unripe and ripe fruits were studied. Altogether 127 compounds were identified, accounting from 82.1% to 99.9% of the whole volatiles. The main constituents detected were mono- and sesquiterpenes, with limonene (0.5–95.2%), linalool (0.2–52.5%), sabinene (0.5–42.5%), myrcene (0.2–15.4%), and β-caryophyllene (0.3–41.0%) as the most represented ones.     

Synuclein Analysis in Adult Xenopus laevis

The α-, β- and γ-synucleins are small soluble proteins expressed in the nervous system of mammals and evolutionary conserved in vertebrates. After being discovered in the cartilaginous fish Torpedo californica, synucleins have been sequenced in all vertebrates, showing differences in the number of genes and splicing isoforms in different taxa. Although α-, β- and γ-synucleins share high homology in the N-terminal sequence, suggesting their evolution from a common ancestor, the three isoforms also differ in molecular characteristics, expression levels and tissue distribution. Moreover, their functions have yet to be fully understood. Great scientific interest on synucleins mainly derives from the involvement of α-synuclein in human neurodegenerative diseases, collectively named synucleinopathies, which involve the accumulation of amyloidogenic α-synuclein inclusions in neurons and glia cells. Studies on synucleinopathies can take advantage of the development of new vertebrate models other than mammals. Moreover, synuclein expression in non-mammalian vertebrates contribute to clarify the physiological role of these proteins in the evolutionary perspective. In this paper, gene expression levels of α-, β- and γ-synucleins have been analysed in the main organs of adult Xenopus laevis by qRT-PCR. Moreover, recombinant α-, β- and γ-synucleins were produced to test the specificity of commercial antibodies against α-synuclein used in Western blot and immunohistochemistry. Finally, the secondary structure of Xenopus synucleins was evaluated by circular dichroism analysis. Results indicate Xenopus as a good model for studying synucleinopathies, and provide a useful background for future studies on synuclein functions and their evolution in vertebrates.     

A Novel Mitigation Scheme for JTIDS Impulsive Interference on LDACS System Based on Sensing and Symbol Retransmission

Future digital air/ground communication systems (LDACS) will operate on the L-Band where the coexistence with existing legacy systems shall be guaranteed. This paper proposes a scheme to detect and mitigate the JTIDS impulsive interference on LDACS-1 system. The novel idea advised here is the transmission of two copies of the symbols received with interference that are suitably combined at the receiver after a blanking operation of the corrupted samples. In particular two alternatives are presented that differ for the adopted retransmission policy, namely full combining scheme, where all the symbols are transmitted twice, and partial combining scheme, which foresees the retransmission of only those symbols where interference has been detected. Both these methods permit to efficiently remove the interference without affecting the useful information and exploiting profitably the diversity gain against noise through the soft combining approach. The numerical results provided in the paper highlight a good behavior of the proposed methods and significant advantages in comparison with the traditional blanking method, either in terms of Bit Error Rate and throughput.     

Random access schemes for satellite networks,from VSAT to M2M: a survey

In this survey paper, we review the random access (RA) techniques with particular emphasis on the issues and the possible solutions applicable to satellite networks. RA dates back to the 1970s when the ALOHA protocol was developed to solve the problem of interconnecting university computers located in different Hawaiian islands. Since then, several evolutions of the ALOHA protocol have been developed. In particular, solutions were devised to mitigate the problem of packet collisions severely degrading the RA protocols performance. The approach followed for many years has been to avoid the occurrence of collisions rather than solving them. More recently, techniques tackling the RA packet collision problem have appeared triggered by the need of improving RA performance in satellite and terrestrial wireless networks. In particular, satellite networks large propagation delay does not allow the adoption of enhanced terrestrial RA techniques based on channel sensing. Adopting conventional demand assignment multiple access protocols is not suitable for supporting a large number of sensors or devices transmitting small‐size low duty cycle packets as required for machine‐to‐machine communications. This provided the stimulus to exploit successive interference cancelation schemes to solve packet collision issues. The use of successive interference cancelation in RA is relatively new and has opened up a promising research area. We provide an extensive review of recent high‐performance RA techniques achieving more than three orders of magnitude throughput increase compared with the original ALOHA at low packet loss rate. In this survey, we cover both slotted and unslotted techniques. Finally, we review the use of RA in satellite systems and related standards including recent proposals for machine‐to‐machine applications. Copyright © 2016 John Wiley & Sons, Ltd.