Different patterns of germination inhibition by carvacrol and thymol in Bacillus subtilis spores.

This study aimed to clarify how the phenolic monoterpene carvacrol and its structural isomer thymol both as essential oil components (EOCs) inhibit the germination of Bacillus subtilis spore. Germination was evaluated by the OD600 reduction rate in a growth medium and phosphate buffer containing either l-alanine (l-Ala) system or l-asparagine, d-glucose, d-fructose plus KCl (AGFK) system. The germination of the wild-type spores in the Trypticase Soy broth (TSB) was found to be greatly inhibited by thymol than by carvacrol. Such a difference in the germination inhibition was confirmed by the dipicolinic acid (DPA) release from germinating spores in the AGFK buffer system, but not in the l-Ala system. Similar to the wild-type spores, no difference in the inhibitory activity between the EOCs was also indicated with the gerB, gerK-deletion mutant spores in the l-Ala buffer system and the above substantial difference was also done with the gerA-deleted mutant spores in the AGFK. Fructose was found to release spores from the EOC inhibition and inversely even stimulated. Increased concentrations of glucose and fructose partially suppressed the germination inhibition by carvacrol. The results obtained should contribute to the elucidation of the control effects of these EOCs on bacterial spores in foods.

Colloidal Stability of Emulsifier-free Oil-in-Water Emulsions: Effect of Oil Properties.

This study aims to determine the factors affecting the colloidal stabilization of emulsifier-free (EF) oil-in-water (O/W) emulsions prepared by mixing oil and water with a high-powered bath-type ultrasonicator (HPBath-US; 28 kHz, 300 W) in the absence of emulsifiers such as surfactants. The interrelation between the colloidal stability, oil properties (oil density, interfacial tension between oil and water, solubility parameter of oil, and oil viscosity), and emulsion properties (diameter and zeta-potential of oil droplets) of such EF-O/W emulsions were examined for this purpose. The colloidal stability of EF-vegetable oil-in-water emulsions (EF-VEG/W) was significantly higher than that of EF-hydrocarbon oil-in-water emulsions (EF-HDC/W) and EF-fatty acid-in-water emulsions (EF-FA/W). This can be attributed to the larger density of vegetable oils (VEG) (approximately 0.9 g cm-3), the formation of smaller-sized oil droplets (diameter of approximately 0.2 µm) in the EF-VEG/W emulsions, and the lower solubility parameter of VEG (δ around 1). Furthermore, the formation of smaller-sized oil droplets in the EF-O/W emulsions correlated with the physical properties of the oil.

Colloidal Stability of Emulsifier-free Triolein-in-Water Emulsions: Effects of Temperature.

Herein, we report the colloidal stability of emulsifier-free (EF-) triolein-in-water (TO/W) emulsions prepared by mixing TO and water using a high-powered bath-type ultrasonicator (HPBath-US; 28 kHz, 300 W) in the absence of emulsifiers such as surfactants. In particular, the effect of the temperature (15-60℃) on the colloidal stability of EF-TO/W emulsions was examined because this is important for the practical application of EF-TO/W emulsions, for example, in foods, pharmaceuticals, and cosmetics. We found that the colloidal stability of the EF-TO/W emulsions decreased with increase in the temperature from 15 to 25°C, whereas it increased with increase in temperature from 25 to 40°C, and the high colloidal stability of the EF-TO/W emulsions was maintained above 40°C. The reduction in the colloidal stability of EF-TO/W emulsions between 15 and 25°C is likely a result of the TO droplets formed by thermal motion, as well as enhanced Ostwald ripening at higher temperatures. On the other hand, the increase in the colloidal stability of the EF-TO/W emulsions from 25 to 40°C and their high colloidal stability above 40℃ is attributed to the reduction in the interfacial tension between TO and water at higher temperatures. This decrease in the interfacial tension between TO and water with temperature increase is related to the transformation of short-range ordered domains (clusters) of TO molecules in the liquid state, which increases the colloidal stability of the EF-TO/W emulsions.

Pore-Mouth Structure of Highly Agglomerated Detonation Nanodiamonds.

Detonation nanodiamond aggregates contain water that is removed by thermal treatments in vacuo, leaving available pores for the adsorption of target molecules. A hard hydrogel of detonation nanodiamonds was thermally treated at 423 K for 2 h, 10 h, and 52 h in vacuo to determine the intensive water adsorption sites and clarify the hygroscopic nature of nanodiamonds. Nanodiamond aggregates heated for long periods in vacuo agglomerate due to the removal of structural water molecules through the shrinkage and/or collapse of the pores. The agglomerated nanodiamond structure that results from long heating periods decreases the nitrogen adsorption but increases the water adsorption by 40%. Nanodiamonds heated for long times possess ultramicropores <0.4 nm in diameter in which only water molecules can be adsorbed, and the characteristic mouth-shaped mesopores adsorb 60% more water than nitrogen. The pore mouth controls the adsorption in the mesopores. Long-term dehydration partially distorts the pore mouth, decreasing the nitrogen adsorption. Furthermore, the nitrogen adsorbed at the pore mouth suppresses additional nitrogen adsorption. Consequently, the mesopores are not fully accessible to nitrogen molecules because the pore entrances are blocked by polar groups. Thus, mildly oxidized detonation nanodiamond particles can show a unique molecular sieving behavior.

Unimodal sized silica nanocapsules produced through water-in-oil emulsions prepared by sequential irradiation of kilo- and submega-hertz ultrasounds.

This study investigates the regulation of the size of 100 nm hollow-sphere silica particles using surfactant-free water-in-oil (W/O) emulsion. First, water droplets were dispersed in soybean oil via sequential ultrasound irradiation (28 kHz → 200 kHz → 950 kHz). A precursor of hollow silica particles was prepared using hydrolysis and polymerization of methylsilyl trichloride into a stable W/O emulsion. The final structure/morphology of the silica particles was influenced by the volume ratio of water/soybean oil, the cycle number of the sequential ultrasound irradiation, and the amount of organosilane added to the emulsion. The emulsion was stabilized by Ostwald ripening, as the size distribution at 5/103 (water/oil = v/v) was a bimodal split between a water droplet size of a few µm and some with a size of a few tens of nm. The most appropriate cycle number was 3 in this system. Further cycling to 5 resulted in a broad and bimodal size distribution of the final particles due to rapid coalescence of water droplets. Subsequent hydrolysis of methylsilyl trichloride consumed water with diminishing large droplets, forming fine and unimodal (0.12 ± 0.02 µm) hollow silica particles. Very fine and uniform-sized hollow particles (0.08 ± 0.01 µm) were successfully produced by decreasing the volume ratio to 1/103 (water/oil) because of a transparent stable emulsion as a homogeneous template of the hollow structures.

Unusual hygroscopic nature of nanodiamonds in comparison with well-known porous materials.

Nanodiamond aggregates have interparticle pores of 4.5 nm on average, exhibiting porous nature involved in their water storage. This work studies the hygroscopic nature of porous nanodiamond aggregates by water absorption based on liquid water droplets. Nanodiamond aggregates show hydrophobicity from the water vapor adsorption. Surprisingly, porous nanodiamond aggregates quickly absorb water droplets at the bulk scale. The volume of absorbed liquid water is comparable to that of the water-absorbing clay Montmorillonite and higher than those of zeolites ZSM-5 and molecular sieve 5A. This hygroscopic nature of nanodiamonds is ascribed to the micro- and mesoporous structure of their aggregates and the special core-shell structure of each nanodiamond particle (wrapped by graphene-like carbon). The absorption rate of liquid water in the porous nanodiamonds is influenced by the surface wettability, while the hygroscopic capacity depends mainly on the hierarchical porosity.

Inhibitory Effect of Spice Powders on the Development of Heated and Irradiated Bacillus subtilis Spores as Evaluated by Calorimetry.

Inhibitory effects of the powders of paprika, red pepper, black pepper, sage, oregano and thyme in a solid medium after heat treatment and gamma-irradiation on the development from spore of Bacillus subtilis were examined using calorimetry. Based on the f(t) curve (Antoce et al., 1996) from the thermogram obtained, two parameters, the growth rate constant and the growth retardation time, were used to evaluate the inhibitory effect. The inhibitory effects of paprika and red pepper powders were enhanced by the spore pretreatment with heat, but not significantly with irradiation. The inhibitory enhancement by preheating depended upon the kind of spices used. Sage, oregano and thyme powders per se inhibited the development from spores completely even at a low concentration of 0.04 g/ml. Inhibitory effects of paprika and red pepper powders were obviously observed with heat treatment but not with irradiation. With black pepper powder, by contrast, substantial enhancement was neither observed with heat treatment nor gamma-irradiation. The results suggested that the addition of those spice powders might be useful in the thermal inactivation process of solid foods contaminated with Bacillus subtilis spores.

Nanoporosity Change on Elastic Relaxation of Partially Folded Graphene Monoliths.

Fabrication of nanographene shows a promising route for production of designed porous carbons, which is indispensable for highly efficient molecular separation and energy storage applications. This process requires a better understanding of the mechanical properties of nanographene in their aggregated structure. We studied the structural and mechanical properties of nanographene monoliths compressed at 43 MPa over different times from 3 to 25 h. While in monoliths compressed over shorter time adsorption isotherms of Ar at 87 K or N2 at 77 K exhibited a prominent hysteresis due to presence of predominant mesopores, compression for long time induces a low pressure hysteresis. On the other hand, compression for 25 h increases the microporosity evaluated by Ar adsorption, not by N2 adsorption, indicating that 25 h compression rearranges the nanographene stacking structure to produce ultramicropores that can be accessible only for Ar. TEM, X-ray diffraction, and Raman spectroscopic studies indicated that the compression for 25 h unfolds double-bent-like structures, relaxing the unstable nanographene stacked structure formed on the initial compression without nanographene sheets collapse. This behavior stems from the highly elastic nature of the nanographenes.

In situ observation of Pt oxides on the low index planes of Pt using surface enhanced Raman spectroscopy.

In situ vibrational spectra of Pt oxides that cannot be measured with IR spectroscopy have been studied on the low index planes of Pt using surface enhanced Raman spectroscopy with bare Au nanoparticles (NPSERS). Two bands appear around 570 and 340 cm-1 at higher potentials in 0.1 M HClO4 saturated with Ar, which are assigned to the stretching vibration of Pt-O(H) and the libration vibration of Pt-O, respectively. NPSERS spectra are measured in O2 saturated solution for the first time. The band intensities of Pt-O(H) and Pt-O in O2 saturated solution are enhanced significantly compared with those in Ar saturated solution. The onset potentials of Pt-O and Pt-O(H) formation are 1.15 V(RHE) on Pt(100) and 1.2 V(RHE) on Pt(111) and Pt(110). The onset potential of Pt-O and Pt-O(H) and band shape differ from the results obtained using shell isolated surface enhanced Raman spectroscopy (SHINERS). The Pt-O and Pt-O(H) band intensities are normalized using COad as an internal standard. The Pt-O(H) band intensity depends on surface structures as Pt(110) < Pt(111) ≪ Pt(100), whereas the Pt-O band gives a different intensity order for Pt(111) and Pt(110) as Pt(111) ≤ Pt(110) ≪ Pt(100) in O2 saturated solution.

Water Adsorption Property of Hierarchically Nanoporous Detonation Nanodiamonds.

The detonation nanodiamonds form the aggregate having interparticle voids, giving a marked hygroscopic property. As the relationship between pore structure and water adsorption of aggregated nanodiamonds is not well understood yet, adsorption isotherms of N2 at 77 K and of water vapor at 298 K of the well-characterized aggregated nanodiamonds were measured. HR-TEM and X-ray diffraction showed that the nanodiamonds were highly crystalline and their average crystallite size was 4.5 nm. The presence of the graphitic layers on the nanodiamond particle surface was confirmed by the EELS examination. The pore size distribution analysis showed that nanodiamonds had a few ultramicropores with predominant mesopores of 4.5 nm in average size. The water vapor adsorption isotherm of IUPAC Type V indicates the hydrophobicity of the nanodiamond aggregates, with the presence of hydrophilic sites. Then the hygroscopic nature of nanodiamonds should be associated with the surface functionalities of the graphitic shell and the ultramicropores on the mesopore walls.

Adsorption-desorption mediated separation of low concentrated D2O from water with hydrophobic activated carbon fiber.

The adsorption and desorption of D2O on hydrophobic activated carbon fiber (ACF) occurs at a smaller pressure than the adsorption and desorption of H2O. The behavior of the critical desorption pressure difference between D2O and H2O in the pressure range of 1.25-1.80kPa is applied to separate low concentrated D2O from water using the hydrophobic ACF, because the desorption branches of D2O and H2O drop almost vertically. The deuterium concentration of all desorbed water in the above pressure range is lower than that of water without adsorption-treatment on ACF. The single adsorption-desorption procedure on ACF at 1.66kPa corresponding to the maximum difference of adsorption amount between D2O and H2O reduced the deuterium concentration of desorbed water to 130.6ppm from 143.0ppm. Thus, the adsorption-desorption procedure of water on ACF is a promising separation and concentration method of low concentrated D2O from water.

Enhanced podocyte vesicle transport in the nephrotic rat.

Albumin endocytosis is enhanced in the podocytes of minimal change nephrotic syndrome. We investigated that the endocytic vesicle transport in the podocyte using three-dimensional observation in a rat model of puromycin aminonucleoside (PAN)-induced nephrotic syndrome. At day 7, Evans Blue-labeled albumin was intravenously injected in PAN rats, and one kidney was fixed for a morphological analysis; the other was used for the isolation of glomeruli through sieving and protein analyses. Evans Blue-labeled albumin was found to accumulate in an increased number of vesicles in the podocytes of PAN rat. Continuous sections and its three-dimensional observation demonstrated that vesicles may be transported from the cytoplasm to the apical membrane of the podocytes. The increased protein bands in the gel electrophoresis of the sieved glomeruli of nephrotic rats were analyzed by mass spectrometry in comparison to the control rats. The major proteins increased in the nephrotic rats were cytoplasmic dynein 1 heavy chain, myosin IX, and myosin VIIb. In conclusion, the podocyte endocytic vesicles carrying albumin increased with glomerular cytoplasmic dynein and myosin in minimal change nephrotic rats.

Isolation and Characterization of a Variant Manganese Resistant Strain of Saccharomyces cerevisiae.

　Manganese contamination in water is one of the most serious problems in Southeast Asian countries, including Vietnam. Bioremediation using microorganisms, especially from the brewing yeast Saccharomyces cerevisiae, is expected to be a useful technique to remove manganese from contaminated water. Yeast strain S. cerevisiae BY4741 as the wild-type strain and some manganese-accumulating mutants bred from BY4741 were examined for cell growth and manganese accumulation in YPD liquid medium containing various concentrations of Mn2+.　Variants accumulating larger concentrations of manganese were isolated by the repeated screening of survivors in YPD media containing10mM Mn2+. Manganese was accumulated by the yeast cells during growth, but the growth of BY4741 was retarded with increasing Mn2+ concentrations and almost inhibited at 15mM Mn2+. One variant isolate, named IM3, showed no retardation of growth up to 15 mM Mn2+ and could absorb over 4-fold more manganese than the BY4741 strain. Effects of culture temperature and pH on the growth and manganese accumulation were analyzed for IM3. Maximum accumulation was shown at 30℃, pH 6.0 while the optimal growth was shown at 37℃, pH 5.0 - 7.0. Interestingly, IM3 could grow a little at pH 9.0 when manganese was added to the culture media, while it could not grow without the addition of manganese.

Essential Role of Viscosity of SWCNT Inks in Homogeneous Conducting Film Formation.

Newly developed inorganic single-wall carbon nanotube (SWCNT) inks of the Zn/Al complex and colloidal silica give a quite homogeneous SWCNT film on the polyethylene terephthalate (PET) substrate by the bar-coating method, whereas the surfactant-based SWCNT inks of sodium dodecyl sulfonate (SDS) and sodium dodecyl benzene sulfonate (SDBS) cannot give a homogeneous film. The key properties of SWCNT inks were studied for the production of homogeneous SWCNT films. The contact angle and surface tension of the inorganic dispersant-based SWCNT inks were 70° and 72 mN m(-1), respectively, being close to those of water (71.5° and 71 mN m(-1)). The viscosity was significantly higher than that of water (0.90 mPa·s), consequently, providing sufficient wettability, spreadability, and slow drying of the ink on the substrate, leading to homogeneous film formation. On the other hand, the surfactant dispersant-aided SWCNT inks have the contact angle and surface tension twice lower than the inorganic dispersant-based SWCNT inks, guaranteeing better wettability and spreadability than the inorganic dispersant-based inks. However, the small viscosity close to that of water induces a heterogeneous flow of SWCNT ink on rapid drying, leading to inhomogeneous film formation.

Hydrogen-assisted fabrication of spherical gold nanoparticles through sonochemical reduction of tetrachloride gold(III) ions in water.

Spherical gold nanoparticles (AuNPs) were selectively synthesized through sonochemical reduction of tetrachloride gold(III) ions ([AuCl4](-)) in an aqueous solution of hydrogen tetrachloroaurate(III) tetrahydrate (HAuCl4 · 4H2O) with the aid of hydrogen (H2) gas in the absence of any additional capping agents. On the other hand, various shaped-AuNPs such as spherical nanoparticles, triangular and hexagonal plates were formed from sonochemical reduction of [AuCl4](-) in argon (Ar)-, nitrogen (N2)- or oxygen (O2)-purged aqueous [AuCl4](-) solutions. The selective fabrication of spherical AuNPs assisted by H2 gas is most likely attributed to the generation of hydrogen radicals (H) promoted by the reaction of H2 introduced and hydrogen oxide radicals (OH) produced by sonolysis of water.

Titania/CnTAB Nanoskeleton as adsorbent and photocatalyst for removal of alkylphenols dissolved in water.

We report here on the removal of alkylphenols (phenol, 4-n-propylphenol, 4-n-heptylphenol and 4-nonylphenol) dissolved in water using the composite particles of nanocrystalline titania and alkyltrimethylammonium bromide (CnH2n+1N(CH3)3Br, CnTAB; n=12, 14, 16 and 18) (named as TiO2/CnTAB Nanoskeleton) as adsorbents and photocatalysts. In particular, the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton in water was investigated in terms of hydrophobic interaction between alkylphenols and CnTAB, surface area, pore structure and crystal size of TiO2/CnTAB Nanoskeleton. We revealed that CnTAB incorporated in the TiO2/CnTAB Nanoskeleton promotes the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton due to the hydrophobic interaction between alkylphenols and CnTAB. On the other hand, the surface area, pore structure and crystal size of TiO2/CnTAB Nanoskeleton did not affect the adsorption of alkylphenols onto TiO2/CnTAB Nanoskeleton. We also found that the alkylphenols dissolved in water were completely removed by the combination of adsorption and photocatalytic degradation by the TiO2/CnTAB Nanoskeleton under UV irradiation. These results prove that the TiO2/CnTAB Nanoskeleton acts as in tandem an adsorbent and a photocatalyst for removal of alkylphenols dissolved in water.

Block copolymer-mediated synthesis of gold nanoparticles in aqueous solutions: segment effect on gold ion reduction, stabilization, and particle morphology.

We report here on the segment effects of poly(ethylene oxide)-containing block copolymers (PEO-BCP) on the reduction activity for tetrachloride gold(III) ([AuCl(4)](-)), interfacial activity for gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions. In particular, the effects of poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), polyethylene (PE) segments and amino group (NH(2)) on the rate of [AuCl(4)](-) reduction, adsorption of PEO-BCP onto gold surface, colloidal stability, and morphology of gold nanoparticles formed in aqueous solutions were examined using a poly(ethylene oxide)-poly(propylene oxide) triblock copolymer (PEO-PPO-PEO, Pluronic L44), an amino-terminated poly(ethylene oxide)-poly(propylene oxide) block copolymer (PEO-PPO-NH(2), SURFONAMINE® L-207), a poly(ethylene oxide) homopolymer (PEO, poly(ethylene glycol)2000), and a polyethylene-poly(ethylene oxide) block copolymer (PE-PEO). We found that the reduction activity of PEO-BCP for [AuCl(4)](-) became higher with the order of PEO-PPO-NH(2)

Stable surfactant-free toluene-polyethylene-in-water emulsion prepared by ultrasonication at high temperature.

A toluene-polyethylene (PE) mixture, only partially miscible at room temperature (RT), was ultrasonically dispersed in hot water, followed by immediate cooling to give a highly stable surfactant-free oil-in-water (O/W) emulsion. This temperature effect was correlated with physical gelation of the bulk mixture. Prolonged stabilization was achieved only through dispersion at a temperature (T(d)) above the gelation temperature (T(gel)) of the toluene-low-density PE (LDPE) mixture and subsequent rapid cooling. These stabilized emulsions exhibited characteristics such as a small droplet size with a narrow size distribution, low ζ-potential, and round-shaped droplets, which were not observed for the emulsions prepared at T(d) < T(gel) or those at T(d) > T(gel) that had been subjected to slow cooling. From these results, physical gelation through crystallization and modification of the droplet surface by PE were concluded to be essential for the prolonged stability of a surfactant-free toluene emulsion.

Translocation of intratracheally instilled multiwall carbon nanotubes to lung-associated lymph nodes in rats.

In order to assess the extrapulmonary effects of multiwall carbon nanotubes (MWCNT), deposition of MWCNT and histopathologic changes in lung-associated lymph nodes (LALN) were examined in MWCNT-administered rats. At the age of 13 wk, male F344 rats were intratracheally instilled with MWCNT at a dose of 0 (vehicle), 40 or 160 µg/rat. The rats were sacrificed on Day 1, 7, 28 or 91 after instillation and light microscopic examinations were performed on LALN tissues. MWCNT was translocated to right and left posterior mediastinal lymph nodes and parathymic lymph nodes. Deposition of MWCNT was greater in the posterior mediastinal lymph node than in the parathymic lymph node, and the amount of MWCNT deposited in these two lymph nodes increased gradually and dose-dependently with time. MWCNT was phagocytosed by nodal macrophages, and some of the MWCNT-laden macrophages were aggregated. Transmission electron microscopic (TEM) observation confirmed the presence of MWCNT fibers with a characteristic multi-walled cylindrical structure.