RESUMEN

The current increase in antibiotic resistance worldwide and the emergence of microbial strains that are resistant to all known antibiotics have stimulated research into novel strategies such as aPDI that are thought to be unlikely to lead to the development of resistance. Although many studies have reported in vitro aPDI killing of microorganisms by a range of different photosensitizers, there are still limitations to the effectiveness of aPDI, and recurrence of bacterial growth may occur in animal studies after completion of the illumination. In this chapter we cover a novel and relatively simple method to improve the efficacy of aPDI against Gram-positive Staphylococcus aureus, Gram-negative Escherichia coli, and fungal yeast Candida albicans by the addition of potassium iodide, a nontoxic inorganic salt. Under some circumstances up to six-logs additional killing can be obtained.

Asunto(s)

RESUMEN

Carboxylated cellulose nanocrystals prepared by TEMPO-mediated oxidation exhibit a distinct ability to form nematic order, however, their ability to form chiral nematic films remains relatively unexplored. In this study, bleached cotton pulp hydrolyzed with hydrochloric acid and oxidized by TEMPO-mediated oxidation produce carboxylated cellulose nanocrystals with different aspect ratios 33.1, 32.8, 30.9, 29.0 and 28.9, and surface charge densities 0.16, 0.56, 1.00, 1.25, and 1.42 e·nm-2. By tuning the aspect ratio and surface charge density, the optimal carboxylated cellulose nanocrystals producing left-handed chiral nematic films by evaporation-induced self-assembly are obtained. The left-handed chiral nematic films enable selective reflection of left-handed circularly polarized light with the peak wavelength tunable from the visible to the near-infrared regime by modifying the characteristics of nanorods and suspensions. Such carboxylated cellulose nanocrystal films transform spontaneous luminescence to right-handed circularly polarized luminescence with the peak luminescence dissymmetry factor of -0.51.

Asunto(s)

RESUMEN

Sodium (Na) metal batteries are promising as next-generation energy storage systems due to the high specific capacity of the Na metal anode as well as rich natural abundance and low cost of Na resources. Nevertheless, uncontrolled growth of dendritic/mossy Na arising from the unstable solid-electrolyte interphase (SEI) leads to rapid electrode degradation and severe safety issues. In this work, we introduce cetyltrimethylammonium bromide (CTAB) as an electrolyte additive that enables a synergistic effect from both the CTA+ cation and Br- anion in stabilizing the Na metal anode. Notably, cryogenic transmission electron microscopy is utilized to investigate the effect of the additive, revealing the critical morphology and structure of the SEIs and Na electrodes at the nano/atomic scale. Benefiting fromthe additive, a stable Na anode can be realized at an ultrahigh capacity of 30 mAh cm-2 at 10 mA cm-2 over 400 h.

RESUMEN

Cellulose and TEMPO-oxidized cellulose fibers (TOCF) from the wheat straw were prepared with ultrasonic and chemical treatments to investigate structure and functionalities. Sol-gel transition of TOCF suspensions has been investigated using rheology to unveil the roles of ultrasonic pretreatment and temperature at various concentration. It was found that TOCF extracted with or without ultrasonic pretreatment exhibit similar functional groups in FTIR. However, different crystal structures and thermal stabilities were revealed in XRD and TGA, respectively. The gelation was independent of the ultrasonic pretreatment, while the rheological properties were highly infuenced by the concentration and temperature of the TOCF suspensions. TOCF suspensions presented a strain thinning behavior in large amplitude oscillatory shear tests. Lissajous curves showed that the elastoplastic behavior was predominantly modulated by the fiber concentration and strain amplitude other than the ultrasonic pretreatment. These results could improve the understanding of the relationships between TOCF structure and rheological properties.

RESUMEN

One-pot fabrication of sacchachitin (SC) for mass-production was developed and optimized by selecting KOH as alkaline agent in depigmentation step and utilizing NaClO2 as bleaching agent in subsequent step in the same pot. Overall yield of one-pot-fabricated SC was up to 35 %w/w of initial weight with a fibrous texture soft enough for mechanical disintegration into SC nanofibers (SCNFs) and better dispersion for producing TEMPO-oxidized SCNFs (T033SC). Both SCNFs and T033SC could form a 3D gelatinous scaffold into which MC3T3-E1 cells were attracted. Higher calcium-trapping ability of T033SC resulting from a greater extent of carboxylate groups provided an excellent bone regeneration environment that resulted in better outcomes of bone regeneration in a femur defect rat model compared to those with SCNFs possessed fewer carboxylate groups. In conclusion, biomaterial scaffolds based on TEMPO-oxidized SCNFs produced from one-pot fabricated SC showed great potential for bone regeneration due to unique physical and chemical properties.

Asunto(s)

RESUMEN

TEMPO-oxidization and mechanical disintegration were utilized to develop sacchachitin nanofibers (SCNF) with a 3D gel structure for being an ideal scaffold. Mechanically disintegrated SCNF (MDSCNF) with NanoLyzer® at 20,000 psi for 5 cycles and TEMPO-oxidized SCNF (TOSCNF) produced with 5.0 and 10.0 mmole NaClO/g SC was designated as SCN5, T050SC, and T100SC, respectively. All 2% MDSCNF suspensions were demonstrated to be in gel form, while all except T100SC of 2% TOSCNF suspensions showed to be wet fiber-like hydrogel. In diabetic wound healing study, both SCN5 and T050SC incorporated in AMPS (2-acrylamide-2-methyl-propane sulfonate)-based wound dressing were showed to accelerate diabetic wound healing forming nearly the same as normal tissues. T050SC/H further provided the healed wound with growth of sweat glands and hair follicles indicating the wound had healed as functional tissue. Conclusively, TEMPO-oxidized SCNF-based hydrogel scaffolds showed greater potentials in tissue regeneration due to its unique physical and chemical properties.

Asunto(s)

RESUMEN

A theoretical study of the time-dependent vibrational echo spectroscopy of sodium bromide solutions in deuterated water at two different concentrations of 0.5 and 5.0 M and at temperatures of 300 and 350 K is presented using the method of ab initio molecular dynamics simulations. The instantaneous fluctuations in frequencies of local OD stretch modes are calculated using time-series analysis of the simulated trajectories. The third-order polarization and intensities of three pulse photon-echo are calculated from ab initio simulations. The timescales of vibrational spectral diffusion are determined from the frequency time correlation functions (FTCF) and short-time slope of three pulse photon echo (S3PE) calculated within the second-order cumulant and Condon approximations. It is found that under ambient conditions, the rate of vibrational spectral diffusion becomes slower with increase in ionic concentration. Decay of S3PE calculated for different systems give timescales, which are in close agreement with those of FTCF and also with the results of experimental time-dependent vibrational spectroscopic experiments. © 2019 Wiley Periodicals, Inc.

RESUMEN

Long-term storage of common beans leads to loss of cooking quality and an ill-defined solution, appropriate storage, is recommended. Therefore, the polymer science theory of glasses that hypothesizes stability of a system below its glass transition temperature (Tg) was applied to determine bean stability during storage in relation to cooking behavior. Since composition influences Tg, powders of cotyledons and seed coats in addition to whole beans were equilibrated above different saturated salt solutions in order to generate materials with different moisture contents. A thermal mechanical compression test which measures compressibility changes in a system upon reaching its glass-rubber transition temperature region was conducted to obtain the Tg. A Tg-moisture relation was established, whose relevance was confirmed by storage and cooking experiments which showed development of hard-to-cook in beans stored above Tg but not below it. Therefore, this relation constitutes a stability map for storage of common beans.

Asunto(s)

RESUMEN

3-(1,1,1-Tri-methyl-hydrazin-1-ium-2-yl)propano-ate (C6H14N2O2, M, more commonly known under its commercial names Meldonium or Mildronate) co-crystalizes with sodium bromide and sodium iodide forming polymeric hydrates poly[[tetra-µ-aqua-di-aqua-bis-[3-(1,1,1-tri-methyl-hydrazin-1-ium-2-yl)propano-ate]disodium] dibromide tetra-hydrate], [Na2(C6H14N2O2)2(H2O)6]Br2·4H2O, and poly[[di-µ-aqua-di-aqua-[µ-3-(1,1,1-tri-methyl-hydrazin-1-ium-2-yl)propano-ate]disodium] diiodide], [Na2(C6H14N2O2)2(H2O)4]I2. The coordination numbers of the sodium ions are 6; the coordination polyhedra can be described as distorted octa-hedra. Metal ions and M zwitterions are assembled into infinite layers via electrostatic inter-actions and hydrogen-bonded networks. These layers are connected via electrostatic attraction between halogenide ions and positive tri-methyl-hydrazinium groups into a three-dimensional structure.

RESUMEN

In this study, the processing derived contaminants 2- and 3-monochloropropanediol (2- and 3-MCPD) esters and glycidyl esters (GEs) were analysed in 84 oil samples by GC-MS/MS for the discrimination of processing grades of olive oils as a potential authentication tool. Concentrations of 2- and 3-MCPD esters and GEs varied in the ranges 0-6 mg/kg, 0-1.5 mg/kg, and 0-1 mg/kg oil, respectively. The concentrations of the three compounds in lower grade olive oils were significantly higher (P < .001) than that in EVOO. A similar difference was observed for other refined and cold-pressed vegetable oils. The limit of fraud detection of lower grade oils in EVOO was 2% when using 3-MCPD esters, 5% for 2-MCPD esters, and 13-14% for GEs based on calculations of virtual mixtures of the current sample set. Especially the MCPD esters appear very specific and promising for the detection of lower processing grade oils in EVOO.

Asunto(s)

RESUMEN

In this study we demonstrate that lignin monomers formed as byproducts of pulping or bioprocessing of lignocellulosic biomass is an effective enhancer to oxidize cellulose surfaces with ozone for the production of cellulose nanofibers (CNF). Never dried softwood pulp with minimum mercerization was enzymatically treated leading to a homogeneous pulp slurry with a higher reactivity. The slurry was oxidized by ozone gas in the presence of syringic acid, a lignin degradation model compound, as an oxidation enhancer at room temperature and pH 11. Transmission electron microscopy (TEM) observations showed that stable CNF bundles with 3-10nm widths and lengths >100nm were obtained after ultrasonication of the oxidized product in water. Extensive characterization of the new CNF films revealed the nanofibers had carboxylate content similar to conventional carboxylated cellulose prepared by TEMPO-mediated oxidation. Based on NMR spectra, chemical conversion of the syringic acid during oxidation is proposed.

RESUMEN

Monitoring nitrous oxide (N2O) emissions from wastewater treatment plants has attracted much attention in recent years demanding accurate and rapid quantification methods. In the present study a salt-assisted methodology is proposed by which N2O is chemically stripped out from wastewater and quantified by gas chromatography (GC-TCD) subsequently. Eight different inorganic salts have been evaluated for this purpose, likewise the application of ultrasound. By addition of sodium bromide (NaBr) the best recovery rate of about 98% (=1.14±0.05kg·m-3) N2O from a saturated stock solution (1.16kg·m-3, 295.85K and 1atm) was achieved. The application of ultrasound led to considerable smaller N2O recoveries of 37% (=0.43±0.01kg·m-3) after a 60min treatment. Practical applicability of the method has been demonstrated by applying NaBr to grab samples from a municipal wastewater treatment plant. The highest N2O concentration was found in the secondary clarifier with 10.99±0.20g·m-3. Besides, N2O could be quantified in the activated sludge process with up to 9.87±0.50g·m-3 yielding 7.75gN2O·PE-1·a-1 specifically for the investigated wastewater treatment plant. Hence, the proposed method proved suitable as a routine quantification method for N2O.

RESUMEN

Simultaneous with a 12 channel ECG, body composition was analysed by segmental multi-frequency impedance analysis in 101 healthy subjects and in 118 patients with chronic heart failure (CHF, n= 40), chronic renal failure with haemodialysis (HD, n= 20), and miscellaneous internal diseases (n= 58). Whole body DXA and sodium bromide dilution were used as reference methods for total body water (TBW), extracellular fluid (ECF), appendicular muscle mass (AppMM) and fat mass (FM). Empirical prediction equations were developed in a randomized evaluation sample and then evaluated in unknowns. TBW, ECF, AppMM and FM could be predicted with regression coefficients of 0.96, 0.90, 0.95 and 0.93, respectively, all with p< 0.001. Only segmental impedances and height, but not age, sex, weight and BMI contributed to the prediction of water compartments. About half the patients with CHF and half of those on HD showed increased ECF/ICF ratio in relation to % FM at the legs but not at the thorax. The predicted AppMM was additionally corrected for increased ECF to determine "dry AppMM", which is markedly lower than the misleading reference DXA. This methodology shows promise as a combination of routine ECG with measurement of body composition, assessment of sarcopenia and detection of overhydration.

Asunto(s)

RESUMEN

Nickel-tungsten (Ni­W) coatings were fabricated by electrodeposition method with varying quantities of sodium dodecyl sulphate and sodium bromide to examine the effects of the aforesaid additives on the coatings. The obtained nanocoatings were studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and hardness tester. The hardness, tungsten content and grain size attained a maximum value at current density of 0.15 A/cm²,0.1 A/cm² and 0.1 A/cm², respectively. There was a pronounced impact of both the additives on the microstructure and morphology of the coatings. According to results, there are considerable difference in terms of the impact caused by the additives to the tungsten content, hardness and grain size of the coatings. The obtained results suggest that hardness of coatings is mainly contributed by W content in the deposits.

RESUMEN

In this study, TEMPO-oxidized bamboo cellulose nanofibers (TO-CNF) with anionic carboxylate groups on the surfaces were in-situ incorporated into poly(N-isopropylacrylamide) (PNIPAm) matrix to improve its thermo-responsive and mechanical properties during the polymerization. The microstructure, swelling behaviors, and compressive strength of resultant PNIPAm composite hydrogels with varying contents of TO-CNFs (0-10wt%) were then examined, respectively. Modified hydrogels exhibited the similar light transparency to pure PNIPAm one due to the formation of semi-IPN structure between PNIPAm and TO-CNF. FT-IR spectra demonstrated that the presence of TO-CNF did not alter the position of characteristic peaks associated with PNIPAm. SEM observation suggested that the pore size of PNIPAm hydrogels was markedly increased after the incorporation of TO-CNF. Also, the composite hydrogels showed superior swelling behavior and much improved compression properties with respect to pure PNIPAm one. Thus, TO-CNF appeared to be a "green" nanofiller that can simultaneously improve swelling and mechanical properties of PNIPAm hydrogel.

Asunto(s)

RESUMEN

Antimicrobial photocatalysis involves the UVA excitation of titanium dioxide (TiO2) nanoparticles (particularly the anatase form) to produce reactive oxygen species (ROS) that kill microbial cells. For the first time we report that the addition of sodium bromide to photoactivated TiO2 (P25) potentiates the killing of Gram-positive, Gram-negative bacteria and fungi by up to three logs. The potentiation increased with increasing bromide concentration in the range of 0-10mM. The mechanism of potentiation is probably due to generation of both short and long-lived oxidized bromine species including hypobromite as shown by the following observations. There is some antimicrobial activity remaining in solution after switching off the light, that lasts for 30min but not 2h, and oxidizes 3,3',5,5'-tetramethylbenzidine. N-acetyl tyrosine ethyl ester was brominated in a light dose-dependent manner, however no bromine or tribromide ion could be detected by spectrophotometry or LC-MS. The mechanism appears to have elements in common with the antimicrobial system (myeloperoxidase+hydrogen peroxide+bromide).

Asunto(s)

RESUMEN

Metal nanowire (NW) networks have the highest performance of any solution-coatable alternative to ITO, but there is as yet no published process for producing NW films with optoelectronic performance that exceeds that of ITO. Here, we demonstrate a process for the synthesis and purification of Ag NWs that, when coated from an ink to create a transparent conducting film, exhibit properties that exceed that of ITO. The diameter, and thus optoelectronic performance, of Ag NWs produced by a polyol synthesis can be controlled by adjusting the concentration of bromide. Ag NWs with diameters of 20 nm and aspect ratios up to 2000 were obtained by adding 2.2 mM NaBr to a Ag NW synthesis, but these NWs were contaminated by nanoparticles. Selective precipitation was used to purify the NWs, resulting in a transmittance improvement as large as 4%. At 130.0 Ω sq(-1), the transmittance of the purified Ag NW film was 99.1%.

RESUMEN

Bioelectrical impedance spectroscopy (BIS) is an inexpensive and non-invasive technique to measure total body water (TBW), extracellular water (ECW), and intracellular water (ICW). The purpose of this study was to validate TBW, ECW and ICW assessed by BIS, using dilution techniques as the reference method (REF) in elite judo athletes. Thirty-two Portuguese elite male judo athletes were evaluated during a period of weight stability. TBW, ECW and ICW were assessed by BIS (Xitron 4000). Deuterium and bromide dilution techniques were used as the criterion method for measuring TBW and ECW, while ICW was calculated as the difference between the two. BIS explained 96%, 77% and 94% of the total variability from REFs for TBW, ECW and ICW, respectively. BIS also demonstrated high precision (ρ ≥ 0.88) and accuracy (Cb = 0.98), with a minimum concordance coefficient correlation of 0.87 for ECW. The mean bias demonstrated that BIS slightly overestimated the REF in 1.1 kg (2.3%), 0.3 kg (1.6%) and 0.8 kg (2.7%) for TBW, ECW and ICW, respectively. The 95% limits of agreement ranged from -1.2 to 3.3 kg in TBW, from -1.8 to 2.4 kg in ECW and from -1.0 to 2.6 kg in ICW. A non-significant trend was found between the difference and the mean of reference and alternative methods. These findings highlight the efficacy of BIS as a valid non-biased tool for the assessment of TBW and its compartments in elite male judo athletes, during a period of weight stability.

Asunto(s)