Interesting Candidate For Use Research Articles

A comprehensive study of the phase segregation of a urea-based phase change material tested under thermal cycling conditions

Eutectic mixtures are used as PCMs due to the possibility to tailor the melting temperatures and mainly because the phase transition occurs at a unique temperature. Eutectic mixtures are assumed to be congruent melting and solidification materials. Compositional segregation has rarely been reported, when have been researched for its use as PCM. However, the previous premise does not always match the observed facts. The presented work aims to deepen the knowledge regarding the use of eutectic mixtures as PCMs and to determine the influence of operation parameters in the eutectic PCMs potential phase segregation.The eutectic mixture formed by urea and sodium nitrate can be an interesting candidate for use as a phase change material for thermal energy storage in space heating and domestic hot water applications. Nevertheless, the eutectic mixture showed an unforeseen segregation phenomenon when it was exposed to repeated melting-solidification cycles using volumes in the scale of grams. As a result, the phenomenon was studied to determine the potential causes. An experimental campaign was performed to study the urea and sodium nitrate eutectic mixture under different conditions: consisting of thermal cycling using representative masses, and subsequently, the segregated materials and obtained samples were analyzed by different techniques (including XRD, HTXRD, and DSC); and the production of samples under different cooling conditions that were analyzed using microscopy (PLM and SEM). The results established a relationship between the operation conditions, with the resulting crystal structures, which explain the phase segregation in the eutectic mixture. A mitigation measure was determined consisting of mechanical stirring.

Suitability of pre-digested dairy effluent for mixotrophic cultivation of the hydrogen-producing microalgae Tetraselmis subcordiformis

ABSTRACT The costs associated with microalgal biomass production can be reduced by leveraging alternative and cheap growth media. Digestate from fermentation reactors is a particularly interesting candidate for use in cultivating mixotrophic species. The aim of the present study was to assess whether pre-digested milk-industry effluent can be harnessed to grow Tetraselmis subcordiformis and produce hydrogen. The experimental series with 25% and 50% effluent in the growth medium performed the best, producing more than 2000 mgVS biomass/dm3. The biogas produced in these variants contained over 60% hydrogen. Increasing the effluent in the medium to 75% led to significant deterioration of performance, both in terms of T. subcordiformis biomass growth and biohydrogen production. The highest efficiency of nitrogen and phosphorus removal, respectively 98.1 ± 1.9% and 97.1 ± 1.4%, was observed in the system to which 25% of sewage was introduced. Increasing the share of fermented wastewater directly reduced the efficiency of removing biogenic compounds. A very strong negative correlation was found between initial N-NH4 in the growth medium and T. subcordiformis biomass production rates (R2 = 0.9177).

Long-term assessment of the thermal stability of sodium nitrate-urea eutectic phase change material

The eutectic mixture formed by urea and sodium nitrate can be an interesting candidate for use as a phase change material for thermal energy storage in space heating and domestic hot water applications. It shows a melting point of 85 °C, a melting enthalpy of 172 J/g and a price around 0.9 €/kg. However, the thermal stability of the mixture is a great concern for this application. A preliminary evaluation of the thermal stability was performed and previously reported by the authors. It consisted of an accelerated thermal cycling test with 210 thermal cycles and the material showed a stable behavior. Nevertheless, the long-term stability of urea in the liquid state at temperatures below 100 °C is uncertain and requires a specific study. The main objective of the present work is to evaluate the long-term thermal stability of the mixture when it is exposed to long periods of use under conditions representative of actual applications, by means of analyzing the thermal and compositional behavior of samples remaining at 100 °C for several periods up to one year. A methodology is proposed, which intends to isolate the thermal degradation phenomenon from others, such as phase segregation, supercooling, and polymorphism, that can be introduced by thermal-cycling. It also aims to be more representative of the actual application than the accelerated thermal cycling approach. • Long-term degradation study of the urea-sodium nitrate eutectic mixture as a phase change material. • Experimental tests representative of actual use conditions. • Urea mainly degrades to biuret and cyanuric acid. • Degradation levels stabilize after an initial significant decrease. • Tightness is a key parameter and greatly influences degradation.

Quorum Sensing Controls Both Rhamnolipid and Polyhydroxyalkanoate Production in Burkholderia thailandensis Through ScmR Regulation.

Rhamnolipids are surface-active agents of microbial origin used as alternatives to synthetic surfactants. Burkholderia thailandensis is a non-pathogenic rhamnolipid-producing bacterium that could represent an interesting candidate for use in commercial processes. However, current bioprocesses for rhamnolipid production by this bacterium are not efficient enough, mainly due to low yields. Since regulation of rhamnolipid biosynthesis in B. thailandensis remains poorly understood, identifying new regulatory factors could help increase the production of these valuable metabolites. We performed a random transposon mutagenesis screening to identify genes directing rhamnolipid production in B. thailandensis E264. The most efficient rhamnolipid producer we identified harbored an inactivating transposon insertion in the scmR gene, which was recently described to encode as a secondary metabolite regulator in B. thailandensis. We investigated the impact of scmR loss on rhamnolipid biosynthesis and cell growth. Because biosynthesis of rhamnolipids and polyhydroxyalkanoates (PHAs) could share the same pool of lipid precursors, we also investigate the effect of ScmR on PHA production. We found that production of both rhamnolipids and PHAs are modulated by ScmR during the logarithmic growth phase and demonstrate that ScmR downregulates the production of rhamnolipids by affecting the expression of both rhl biosynthetic operons. Furthermore, our results indicate that PHA biosynthesis is reduced in the scmR- mutant, as ScmR promotes the transcription of the phaC and phaZ genes. By studying the relationship between ScmR and quorum sensing (QS) regulation we reveal that QS acts as an activator of scmR transcription. Finally, we pinpoint the QS-3 system as being involved in the regulation of rhamnolipid and PHA biosynthesis. We conclude that ScmR negatively affects rhamnolipid production, whereas it positively impacts PHAs biosynthesis. This could provide an interesting approach for future strain engineering, leading to improved yields of these valuable metabolites.

An ultra-narrowband all-optical filter based on the resonant cavities in rod-based photonic crystal microstructure

In view of the large scientific and technical interest in the frequency-selective all-optical devices, and some optical filters limitations, we focus on the design and analysis of a novel ultra-narrowband all-optical filter. The proposed structure consists of input/output waveguides and a resonator in a microstructured photonic crystal that encompasses silicon rods. We study the effects of the variations of rod radius, the lattice constant, and the refractive index of the filter on the resonance wavelength, quality factor, transmission, and full width at half maximum (FWHM) by solving Maxwell’s equations using the finite-difference time-domain method. The numerical results show that the proposed filter with a lattice constant of a = 540 nm, central resonant rod radius of 216 nm, and the rod radius of r = 0.2a has a resonant wavelength of λr = 1253 nm, the quality factor of Qf = 3288, FWHM of 0.26 nm and broad free spectral range of FSR = 790 nm while this filter for r = 0.26a has λr = 1552 nm, Qf = 5542, FWHM of 0.28 nm, and FSR = 720 nm. Some promising characteristics, such as its short propagation time and a small area of 102.6 µm2 make this optical filter an interesting candidate for use in photonic integrated chips.

Electrically Small Water-Based Hemispherical Dielectric Resonator Antenna

Recently, water has been proposed as an interesting candidate for use in applications such as tunable microwave metamaterials and dielectric resonator antennas due to its high and temperature-dependent permittivity. In the present work, we considered an electrically small water-based dielectric resonator antenna made of a short monopole encapsulated by a hemispherical water cavity. The fundamental dipole resonances supported by the water cavity were used to match the short monopole to its feed line as well as the surrounding free space. Specifically, a magnetic (electric) dipole resonance was exploited for antenna designs with a total efficiency of 29.5% (15.6%) and a reflection coefficient of −24.1 dB (−10.9 dB) at 300 MHz. The dipole resonances were effectively excited with different monopole lengths and positions as well as different cavity sizes or different frequencies in the same cavity. The overall size of the optimum design was 18 times smaller than the free-space wavelength, representing the smallest water-based antenna to date. A prototype antenna was characterized, with an excellent agreement achieved between the numerical and experimental results. The proposed water-based antennas may serve as cheap and easy-to-fabricate tunable alternatives for use in very high frequency (VHF) and the low end of ultrahigh frequency (UHF) bands for a great variety of applications.

Particle detection at cryogenic temperatures with undoped CsI

Scintillators are widely used as particle detectors in particle physics. Scintillation at cryogenic temperatures can give rise to detectors with particle discrimination for rare-event searches such as dark matter detection. We present time-resolved scintillation studies of Cesium Iodide (CsI) under excitation of both α and γ particles over a long acquisition window of 1 ms to fully capture the scintillation decay between room temperature and 4 K. This allows a measurement of the light yield independent of any shaping time of the pulse. We find the light yield of CsI to increase up to two orders of magnitude from that of room temperature at cryogenic temperatures, and the ratio of α to γ excitation to vary significantly, exceeding 1 over a range of temperatures between 10 and 100 K. This property could be useful in separating α backgrounds from the low energy nuclear recoil signal region. We also find the time structure of the emitted light to follow similar exponential decay time constants between α and γ excitation, with the temperature behavior consistent with a model of self-trapped exciton de-excitation. Based on these properties, undoped CsI is an interesting candidate for use in cryogenic particle detectors.

Liposome-Coated Iron Fumarate Metal-Organic Framework Nanoparticles for Combination Therapy.

One of the main problems for effective treatment of cancer is resistances, which often require combination therapy—for effective treatment. While there are already some potential drug carriers—e.g., liposomes, available for treatment—the effective loading and retention of the desired drug ratio can be challenging. To address this challenge, we propose a new type of drug carrier: liposome-coated metal-organic framework (MOF) nanoparticles. They combine the advantages of liposomes with an easy and efficient loading process. In this work, we present the successful synthesis of liposome-coated MOF nanoparticles via the fusion method. The resulting particles, once loaded, show no premature leakage and an efficient release. Their successful loading with both single and multiple drugs at the same time makes them an interesting candidate for use in combination therapy.

Linalool, a Piper aduncum essential oil component, has selective activity against Trypanosoma cruzi trypomastigote forms at 4°C.

BACKGROUND Recent studies showed that essential oils from different pepper species (Piper spp.) have promising leishmanicidal and trypanocidal activities.OBJECTIVES In search for natural compounds against Trypanosoma cruzi, different forms of the parasite were incubated for 24 h at 28ºC or 4ºC with Piper aduncum essential oil (PaEO) or its main constituents linalool and nerolidol.METHODS PaEO chemical composition was obtained by GC-MS. Drug activity assays were based on cell counting, MTT data or infection index values. The effect of PaEO on the T. cruzi cell cycle and mitochondrial membrane potential was evaluated by flow cytometry.FINDINGS PaEO was effective against cell-derived (IC50/24 h: 2.8 μg/mL) and metacyclic (IC50/24 h: 12.1 μg/mL) trypomastigotes, as well as intracellular amastigotes (IC50/24 h: 9 μg/mL). At 4ºC - the temperature of red blood cells (RBCs) storage in blood banks - cell-derived trypomastigotes were more sensitive to PaEO (IC50/24 h = 3.8 μg/mL) than to gentian violet (IC50/24 h = 24.7 mg/mL). Cytotoxicity assays using Vero cells (37ºC) and RBCs (4ºC) showed that PaEO has increased selectivity for cell-derived trypomastigotes. Flow cytometry analysis showed that PaEO does not affect the cell cycle of T. cruzi epimastigotes, but decreases their mitochondrial membrane potential. GC-MS data identified nerolidol and linalool as major components of PaEO, and linalool had trypanocidal effect (IC50/24 h: 306 ng/mL) at 4ºC.MAIN CONCLUSION The trypanocidal effect of PaEO is likely due to the presence of linalool, which may represent an interesting candidate for use in the treatment of potentially contaminated RBCs bags at low temperature.

Melatonin: plant growth regulator and/or biostimulator during stress?

Melatonin regulates the growth of roots, shoots, and explants, to activate seed germination and rhizogenesis and to delay induced leaf senescence. The antioxidant properties of melatonin would seem to explain, at least partially, its ability to fortify plants subjected to abiotic stress. In this Review we examine recent data on the gene-regulation capacity of melatonin that point to many interesting features, such as the upregulation of anti-stress genes and recent aspects of the auxin-independent effects of melatonin as a plant growth regulator. This, together with the recent data on endogenous melatonin biosynthesis induction by environmental factors, makes melatonin an interesting candidate for use as a natural biostimulating treatment for field crops.

Phytomelatonin: Discovery, Content, and Role in Plants

Melatonin (N-acetyl-5-methoxytryptamine) is an indolic compound derived from tryptophan. Usually identified as a neurotransmitter or animal hormone, this compound was detected in plants in 1995. Interest in knowing the melatonin content of plants and its possible role therein is growing, as indicated by the increasing number of related publications. Melatonin is present in all plant species studied, with large variations in its level depending on the plant organ or tissue. It seems to be more abundant in aromatic plants and in leaves than in seeds. Regarding its physiological function in plants, melatonin shows auxin activity and is an excellent antioxidant, regulating the growth of roots, shoots, and explants, activating seed germination and rhizogenesis (lateral- and adventitious-roots), and delaying induced leaf senescence. Its ability to strengthen plants subjected to abiotic stress such as drought, cold, heat, salinity, chemical pollutants, herbicides, and UV radiation makes melatonin an interesting candidate for use as a natural biostimulating substance for treating field crops.

High Conversion Efficiency of Dye-Sensitized Solar Cells Based on Coral-like TiO2 Nanostructured Films: Synthesis and Physical Characterization

Coral-like TiO2 nanostructured films were chemically synthesized through the sol–gel method for fabrication of dye-sensitized solar cell (DSSC). The influence of experimental parameters such as precursor hydrolysis rate, reaction time, type and concentration of acid, and annealing temperature was studied through analysis of the surface structure of the films. The coral-like TiO2 film has excellent light scattering property and a mesoporous structure with fairly large specific surface area of 164 m2 g–1. The resulting DSSC, which consists of a dense, coral-like TiO2 nanostructured film and the dye N719 in an electrolyte, shows a better performance as compared to a fabricated DSSC by using commonly used TiO2. A photocurrent value of approximately 16.1 mA cm–2, a fill factor of 77.6%, and a conversion efficiency of 9.4% were obtained. The low cost and the possibility of controlling the morphology of the prepared film make this method an interesting candidate for use in fabricating photovoltaic devices.

Crystalline Sb–Cu alloy films as anode materials for Li-ion rechargeable batteries

A crystalline Sb–Cu alloy is investigated for use in Li-ion rechargeable batteries, and its structural, electrochemical and thermal properties are characterized. A pulse electrodeposition method is used to prepare Sb–Cu alloy film on Cu foil as a negative electrode. The structure of the alloy film electrode is characterized using XRD, FE-SEM and EDX. The electrochemical behavior of the Sb–Cu alloy film is investigated at the current rate of 0.1C to the cut-off potential range of 1.8 and 0.01 V vs. Li/Li+. Our experimental results demonstrate that the initial discharge capacity is 850 mAh g−1 and that the discharge capacity increases to 1034 mAh g−1 at the end of the 30th cycle with a stable cycle life. The Coulombic efficiency is approximately 83.5% with good cyclability. Moreover, the crystalline Sb–Cu alloy film has relatively low exothermic properties, and it may be an interesting candidate for use in the negative electrodes of Li-ion batteries.

Morphology effect of sulfonated triblock copolymers for water retention and proton conductivity at high temperature

Control of ion transfer paths in ion conducting polymers is an important factor in increasing efficiency in a variety of applications such as the use of ion exchange resins, sensors, secondary batteries, and fuel cells. 1 In particular, the fuel cell has recently gained attention as a promising candidate in generating environmental-friendly energy because of its direct energy conversion by electrochemical reactions. 2 For this application, many researchers have tried to increase efficiency by designing catalysts, electrodes, proton exchange membranes (PEMs), etc. Among these components in the fuel cell, the PEM has a direct relationship with the increase of proton conductivity because the ionic channel formed in the PEM matrix creates a proton migration path from the anode to the cathode. 3 The most famous PEM, Nafion ® , a perfluorosulfonic acid polymer, has been known to give sufficient proton conductivity, as well as good chemical and mechanical stability under 80 o C. However, it suffers from a decrease of proton conductivity and mechanical stability at high temperature, probably due to dehydration in the ionic channel. 4 Among various alternative proton conducting polymers such as polyarylene, polyimide, polyphosphazene, polystyrene-based copolymer, etc., a block copolymer is an interesting candidate for use in overcoming such problems at high temperatures, 5 because the hydrophilic domain (ionic channel) and hydrophobic domain (non ionic matrix) can be controlled by the self assembly of the block copolymer. This is achieved through the control of the molecular weights of the hydrophilic and hydrophobic block segments. 6

Induction of apoptosis and inhibition of telomerase activity in human lung carcinoma cells by the water extract of Cordyceps militaris

Cordyceps militaris is well known as a traditional medicinal mushroom and is a potentially interesting candidate for use in cancer treatment. In this study, the potential of the water extract of C. militaris (WECM) to induce apoptosis in human lung carcinoma A549 cells and its effects on telomerase activity were investigated. The growth inhibition and apoptosis induction by WECM treatment in A549 cells was associated with the induction of Fas, catalytic activation of caspase-8, and Bid cleavage. Activation of caspases, downregulation of anti-apoptotic Bcl-2 expression, and upregulation of pro-apoptotic Bax protein were also observed in WECM-treated cells. However, the cytotoxic effects and apoptotic characteristics induced by WECM were significantly inhibited by z-DEVD-fmk, a caspase-3 inhibitor, which demonstrates the important role that caspase-3 plays in the process. In addition, WECM exerted a dose-dependent inhibition of telomerase activity via downregulation of human telomerase reverse transcriptase (hTERT), c-myc and Sp1 expression. Taken together, the data from this study indicate that WECM induces the apoptosis of A549 cells through a signaling cascade of death receptor-mediated extrinsic and mitochondria-mediated intrinsic caspase pathways. It was also conclude that apoptotic events due to WECM were mediated with diminished telomerase activity through the inhibition of hTERT transcriptional activity.

Efficacy of the amino-acetonitrile derivative, monepantel, against experimental and natural adult stage gastro-intestinal nematode infections in sheep

Multiple drug resistance by nematodes, against anthelmintics has become an important economic problem in sheep farming worldwide. Here we describe the efficacy of monepantel, a developmental molecule from the recently discovered anthelmintic class, the amino-acetonitrile derivatives (AADs). Efficacy was tested against adult stage gastro-intestinal nematodes (GINs) in experimentally and naturally infected sheep at a dose of 2.5 mg/kg body weight when administered as an oral solution. Some of the isolates used in experimental infection studies were known to be resistant to the benzimidazoles or levamisole anthelmintics; strains resistant to the macrocyclic lactones were not available for these tests. Worm count-based efficacies of >98% were determined in these studies. As an exception, Oesophagostomum venulosum was only reduced by 88% in one study, albeit with a low worm burden in the untreated controls (geometric mean 15.4 worms). Similar efficacies for monepantel were also confirmed in naturally infected sheep. While the efficacy against most species was >99%, the least susceptible species was identified as Nematodirus spathiger, and although efficacy was 92.4% in one study it was generally >99%. Several animals were infected with Trichuris ovis, which was not eliminated after the treatment. Monepantel demonstrated high activity against a broad range of the important GINs of sheep, which makes this molecule an interesting candidate for use in this species, particularly in regions with problems of anthelmintic resistance. Monepantel was well tolerated by the treated sheep, with no treatment related adverse events documented.

Biomonitoring of biosurfactant production by green fluorescent protein‐marked Bacillus subtilis W1012

AbstractBACKGROUND: Biosurfactant production was investigated using two strains of Bacillus subtilis, one being a reference strain (B. subtilis 1012) and the other a recombinant of this (B. subtilis W1012) made able to produce the green fluorescent protein (GFP).RESULTS: Batch cultivations carried out at different initial levels of glucose (G0) in the presence of 10 g L−1 casein demonstrated that the reference strain was able to release higher levels of biosurfactants in the medium at 5.0≤G0≤10 g L−1 (Bmax = 104–110 mg L−1). The recombinant strain exhibited slightly lower levels of biosurfactants (Bmax = 90–104 mg L−1) but only at higher glucose concentrations (G0 ≥ 20 g L−1). Under these nutritional conditions, the fluorescence intensity linked to the production of GFP was shown to be associated with the cell concentration even after achievement of the stationary phase.CONCLUSION: The ability of the genetically‐modified strain to simultaneously overproduce biosurfactant and GFP even at low biomass concentration makes it an interesting candidate for use as a biological indicator to monitor indirectly the biosurfactant production in bioremediation treatments. Copyright © 2008 Society of Chemical Industry

Platycodin D induces apoptosis and decreases telomerase activity in human leukemia cells

Platycodin D (PD) is a major constituent of triterpene saponins found in the root of Platycodon grandiflorum. Recent studies have demonstrated that PD is a potentially interesting candidate for use in cancer chemotherapy. However, the molecular mechanisms responsible for PD-induced telomerase inhibition remain to be poorly known. In this study, we examined the effects of PD treatment on telomerase activity in different human leukemia cell lines. At concentrations between 10 and 20 μM, PD exerted a dose-dependent direct cytotoxic effect and inhibition of telomerase activity via downregulation of hTERT expression. Because c-Myc and Sp1 are known to directly regulate transcription of hTERT, we also evaluated the expression and DNA binding activity of these proteins. PD treatment reduced c-Myc and Sp1 protein levels and DNA binding activities in a dose-dependent manner. We also observed that PD treatment downregulates the activation of Akt, thereby reducing the phosphorylation and nuclear translocation of hTERT. We conclude that PD has direct cytotoxic effect on human leukemia cells and suppresses telomerase activity through transcriptional and posttranslational suppression of hTERT.

Effects of short- and long-term recombinant equine growth hormone and short-term hydrocortisone administration on tissue sensitivity to insulin in horses

To determine the effects of short-term IV administration of hydrocortisone or equine growth hormone (eGH) or long-term IM administration of eGH to horses on tissue sensitivity to exogenous insulin. 5 Standardbreds and 4 Dutch Warmblood horses. The euglycemic-hyperinsulinemic clamp technique was used to examine sensitivity of peripheral tissues to exogenous insulin 24 hours after administration of a single dose of hydrocortisone (0.06 mg/kg), eGH (20 microg/kg), or saline (0.9% NaCl) solution and after long-term administration (11 to 15 days) of eGH to horses. The amounts of metabolized glucose (M) and plasma insulin concentration (I) were determined. Values for M and the M-to-I ratio were significantly higher 24 hours after administration of a single dose of hydrocortisone than after single-dose administration of eGH or saline solution. After long-term administration of eGH, basal I concentration was increased and the mean M-to-I ratio was 22% lower, compared with values for horses treated with saline solution. Increases in M and the M-to-I ratio after a single dose of hydrocortisone imply that short-term hydrocortisone treatment increases glucose use by, and insulin sensitivity of, peripheral tissues. Assuming a single dose of hydrocortisone improves sensitivity of peripheral tissues to insulin, it may be an interesting candidate for use in reducing insulin resistance in peripheral tissues of horses with several disease states. In contrast, long-term administration of eGH decreased tissue sensitivity to exogenous insulin associated with hyperinsulinemia. Therefore, increased concentrations of growth hormone may contribute to insulin resistance in horses with various disease states.

Methanolic extract of Verbascum macrurum as a source of natural preservatives against oxidative rancidity.

The antioxidant properties of various fractions of a methanolic extract obtained from the aerial parts of Verbascum macrurum have been determined by monitoring their capacity to scavenge the stable free-radical DPPH. They were also evaluated as natural preservatives against oxidative rancidity using the accelerated Rancimat method. Their activities expressed as protection factor (PF(r)) indicated that the fractions rich with phenylpropanoid glycosides were more potent compared to alpha-tocopherol and of the same magnitude as BHT, which were used as reference standards. Ten natural compounds were identified as components of this methanolic extract and were isolated by medium-pressure liquid chromatography (MPLC). Assessment of their antioxidant activities established that acteoside, a polyhydroxylated phenylpropanoid glycoside derivative, is the most potent free radical scavenger and showed the highest protection factor (PF(r)) against sunflower-oil-induced oxidative rancidity. Its activity is comparable to the synthetic antioxidant BHT and clearly superior to natural alpha-tocopherol. This compound therefore represents a very interesting candidate for use in food preservation as natural protecting agent against oxidative rancidity.