Conventional Growth Conditions Research Articles

Improved detection of mycobacteria in CF and tissue samples grown in mycobacteria growth indicator tube incubated at 30°C compared to conventional growth conditions of liquid and solid media.

Our study shows that the addition of mycobacteria growth indicator tube (MGIT) liquid culture incubated at 30°C improves the detection of mycobacteria from CF and tissue samples. MGIT incubated at 30°C recovered significantly more mycobacterial isolates than MGIT incubated at 37°C and significantly more isolates than either Lowenstein Jensen or Stonebrink solid media incubated at either 36°C or 30°C. Of 202 mycobacterial isolates recovered from 1,549 specimens, 170 were recovered from MGIT incubated at 30°C, followed by MGIT incubated at 37°C with 124 isolates and solid media culture conditions that recovered between 95 and 107 mycobacterial isolates. All conventional culture conditions combined without MGIT incubated at 30°C recovered 166 isolates. MGIT incubated at 30°C recovered the highest number of isolates detected exclusively by a single culture condition and recovered mycobacterial isolates of highly relevant mycobacterial species, including Mycobacterium abscessus and Mycobacterium tuberculosis.

The Toxoplasma gondii homolog of ATPase inhibitory factor 1 is critical for mitochondrial cristae maintenance and stress response.

The production of energy in the form of ATP by the mitochondrial ATP synthase must be tightly controlled. One well-conserved form of regulation is mediated via ATPase inhibitory factor 1 (IF1), which governs ATP synthase activity and gene expression patterns through a cytoprotective process known as mitohormesis. In apicomplexans, the processes regulating ATP synthase activity are not fully elucidated. Using the model apicomplexan Toxoplasma gondii, we found that knockout and overexpression of TgIF1, the structural homolog of IF1, significantly affected gene expression. Additionally, TgIF1 overexpression resulted in the formation of a stable TgIF1 oligomer that increased the presence of higher order ATP synthase oligomers. We also show that parasites lacking TgIF1 exhibit reduced mitochondrial cristae density, and that while TgIF1 levels do not affect growth in conventional culture conditions, they are crucial for parasite survival under hypoxia. Interestingly, TgIF1 overexpression enhances recovery from oxidative stress, suggesting a mitohormetic function. In summary, while TgIF1 does not appear to play a role in metabolic regulation under conventional growth conditions, our work highlights its importance for adapting to stressors faced by T. gondii and other apicomplexans throughout their intricate life cycles.

Single-walled carbon nanotube growth from Ni catalyst particles under conventional growth conditions by alcohol catalytic chemical vapor deposition: in situ X-ray absorption fine structure study

In situ X-ray absorption fine structure (XAFS) analysis was performed on Ni catalysts during the growth of single-walled carbon nanotubes (SWCNTs) by alcohol catalytic chemical vapor deposition (ACCVD). Ni catalysts were gradually reduced during the heating process and became metallic at the growth temperature (800 °C). With the addition of ethanol during SWCNT growth, Ni catalysts were slightly carbonized. Such behavior was similar to that observed for Ir catalysts in our previous study, although the Ni catalysts had a carbon composition of ∼5%. The results of this study demonstrated the growth of SWCNTs from almost metallic catalysts under the conventional growth conditions of ACCVD using Ni catalysts. Our result obtained by in situ XAFS analysis was consistent with the result of atomistic computer simulations.

H∞and Asymptotic Stability via delay feedback for hybrid neutral stochastic delay differential equations with Lévy noise

AbstractThis work addresses existence and stabilization problem for a hybrid neutral stochastic delay differential equations with Lévy noise (HNSDDELN). The coefficients of such systems do not satisfy the conventional linear growth conditions, but are subject to high nonlinearity. We first prove the existence and uniqueness of the solution. We then design a delay feedback controller to make an unstable HNSDDELN $H_{\infty }$ and asymptotically stable in ${\mathbb{L}}^{p}$. We end up with a numerical example that corroborates our theoretical findings.

In situ XAFS study of the chemical state of a Co catalyst during single-walled carbon nanotube growth under conventional growth conditions using alcohol catalytic chemical vapor deposition

In situ X-ray absorption fine structure spectroscopy (XAFS) analysis was performed on cobalt (Co) catalysts during single-walled carbon nanotube (SWCNT) growth by alcohol catalytic chemical vapor deposition. Co K-edge XAFS analysis showed that Co catalysts prepared from Co acetates were composed of both Co oxides and carbides, which were reduced as the temperature increased to 800 °C. Upon addition of ethanol, the Co catalysts gradually changed to carbides. Our results show that Co catalysts are mainly composed of carbides formed during SWCNT growth under conventional growth conditions in alcohol catalytic chemical vapor deposition (ACCVD).

Epitaxial growth of β -Ga2O3 on (110) substrate by plasma-assisted molecular beam epitaxy

Epitaxial growth of β-Ga2O3 films on (110) substrates has been performed via plasma-assisted molecular beam epitaxy (PAMBE). The atomic force microscopy scan shows a very low root mean square roughness of 0.08 nm for the surface of the as-received (110) substrates. High-resolution x-ray diffraction measurements reveal a 2.5 nm/min growth rate of β-Ga2O3 films on (110) substrates for conventional PAMBE growth conditions (∼700 °C), which is comparable to that on (010) substrates. The surface morphology of β-Ga2O3 epitaxial films is smooth and has a similar dependence on Ga flux to (010) growth. However, the (110) plane does not have a tendency to show a well-defined step–terrace structure in spite of the appearance of (110) facets in the growth of (010) β-Ga2O3. Indium catalyzed growth was also demonstrated to improve the growth rate up to 4.5 nm/min and increase the maximum growth temperature up to 900 °C of (110) β-Ga2O3.

Large-scale production of an abalone probiotic, Vibrio midae, isolated from a South African abalone, Halitotis midae for use in aquaculture

Abstract The South African abalone industry is under severe pressure due to illegal harvesting and poaching of this seafood delicacy. These abalone are harvested excessively and consequently, these animals do not have a chance to replace themselves, ensuing in a drastic decrease in natural abalone stocks. Abalone, has an extremely slow growth rate, and takes approximately four years to reach a size that is marketable. Probiotics offer a viable treatment solution to improve the growth, health and vigour of these animals. Two microorganisms, a yeast isolate Debaryomyces hansenii and a bacterial isolate Vibrio midae, from the gut of the South African abalone were characterised for their probiotic abilities. This work resulted in an internationally competitive concept technology that was patented. Thereafter research was focussed on developing a suitable bioprocess to enable commercial production of one the isolates, V. midae. During this development, production parameters such as temperature and pH, as well as alternative medium additives, such as the use of corn steep liquor (CSL) and high test molasses (HTM) was assessed. Once a high efficiency production process was developed at laboratory scale, this up- and downstream production technology was scaled up to manufacturing scale, which resulted in a final market ready probiotic product. The optimization of the key variables resulted in a 180% increase in cell concentration and a 5716-fold increase in cell productivity, in comparison to conventional growth conditions and parameters used at the beginning of the study.

Investigation of the changes in bran mineral content according to the years and growth conditions in bread wheat genotypes

Bran is not only the raw material of animal feed or functional products; it has also become a natural additive used in the other industrial fields. For this reason, in this study, it has been aimed to reveal to what extent the minerals (K, P, S, Mg, Ca, Zn, Fe, Mn, Cu, and Na) are affected by genotypes, growth seasons (years) and growth conditions and their interactions, rather than how much and what kind of minerals the wheat bran contains. For this purpose, in the study, in the growth seasons of 2013-2014 and 2014-2015, five bread wheat genotypes were carried out as three replicated under organic and conventional growth conditions according to the trial design of split plots in random blocks. At the end of the study, all minerals except Cu were affected by at least one of the variation sources; in other words, although it varies according to minerals, wheat bran minerals were significantly affected by wheat genotypes, growth years and growth conditions and their interactions. In addition, with this study, significant correlations were found between some minerals in organic and conventional conditions.

Stabilisation of highly non‐linear continuous‐time hybrid stochastic differential delay equations by discrete‐time feedback control

In this study, the authors consider how to use discrete-time state feedback to stabilise hybrid stochastic differential delay equations. The coefficients of these stochastic differential delay equations do not satisfy the conventional linear growth conditions, but are highly non-linear. Using the Lyapunov functional method, they show that a discrete feedback controller, which depends on the states of the discrete-time observations, can be designed to make the solutions of such controlled hybrid stochastic differential delay equations asymptotically stable and exponentially stable. The upper bound of the discrete observation interval is also given in this study. Finally, a numerical example is given to illustrate the proposed theory.

Influence of Temperature‐Dependent Substrate Decomposition on Graphene for Separable GaN Growth

AbstractGraphene has been adopted in III−V material growth since it can reduce the threading dislocations and the III−V epilayer can easily be separated from the substrate due to the weak chemical bond. However, depending on the substrate supporting the graphene, some substrates decompose in the III−V material growth environment, which results in the problem that no graphene remains. In this study, the influence of temperature‐dependent substrate decomposition on graphene through an annealing process that resembles conventional growth conditions in metal–organic chemical vapor deposition (MOCVD) is investigated. It is also confirmed that trimethylgallium, hydrogen, and ammonia gases do not directly affect the graphene loss through gallium nitride (GaN) growth on a graphene/sapphire. In addition, GaN grown on graphene/sapphire could separate, but GaN grown on a graphene/GaN template could not be separated due to GaN template decomposition and related graphene damage. Through further investigation for graphene/gallium arsenide, it is deduced that the gallium generated by substrate decomposition does not play a major role in damage to the graphene but instead the nitrogen generated by substrate decomposition is closely related to it. These results suggest that it is very important to adopt a decomposition‐free substrate that do not damage graphene during GaN growth in MOCVD.

Effects of temperatures and high pressures on the growth and survivability of methanogens and stable carbon isotope fractionation: implications for deep subsurface life on Mars

AbstractIn order to examine the potential survivability of life in the Martian deep subsurface, we have investigated the effects of temperature (45°C, 55°C and 65°C) and pressure (1, 400, 800 and 1200 atm) on the growth, carbon isotopic data and morphology of chemolithoautotrophic anaerobic methanogenic archaea, Methanothermobacter wolfeii. The growth and survivability of this methanogen were determined by measuring the methane concentration in headspace gas samples after the cells were returned to their conventional growth conditions. Interestingly, this methanogen survived at all the temperatures and pressures tested. M. wolfeii demonstrated the highest methane concentration following exposure to pressure of 800 atm and a temperature of 65°C. We found that the stable carbon isotopic fractionation of methane, δ13C(CH4), was slightly more enriched in 12C at 1 atm and 55°C than the carbon isotopic data obtained in other temperature and pressure conditions. A comparison of the images of the cells before and after the exposure to different temperatures and pressures did not show any obvious alteration in the morphology of M. wolfeii. The research reported here suggests that at least one methanogen, M. wolfeii, may be able to survive under hypothetical Martian subsurface conditions with respect to temperature and pressure.

Selective growth of ZnTe on sapphire substrates using a SiO2 mask

ZnTe/sapphire heterostructures have attracted attention for their suitable properties as a terahertz wave detector material. In this study, we focused on the selective growth of ZnTe on SiO2‐masked sapphire substrates by molecular beam epitaxy (MBE). When ZnTe was grown at a high temperature (=350 °C), low growth rate (≦ 0.3 μm h−1), and low JTe/JZn flux ratio (≦ 0.83) compared with the conventional film growth conditions, the formation of ZnTe nuclei on the SiO2 mask was avoided. The Te flux intensity significantly affected the selectivity of ZnTe growth. The selective growth of ZnTe on sapphire was revealed to be limited by the desorption of Te adatoms from the SiO2.

Modified textured surface MOCVD-ZnO:B transparent conductive layers for thin-film solar cells

Modified textured surface boron-doped ZnO (ZnO:B) transparent conductive layers for thin-film solar cells were fabricated by low-pressure metal organic chemical vapor deposition (LP-MOCVD) on glass substrates. These modified textured surface ZnO:B thin films included two layers. The first ZnO:B layer, which has a pyramid-shaped texture, was deposited under conventional growth conditions, and the second layer, which has a sphere-like structure, at a relatively lower growth temperature. Typical bi-layer ZnO:B thin films exhibit a high electron mobility of 27.6 cm2/(V·s) due to improved grain boundary states. For bi-layer ZnO:B, the haze value increases and the total transmittance decreases with the increasing film thickness of the second modification layer. When applied in hydrogenated microcrystalline silicon (μc-Si:H) thin-film solar cells, the modified textured surface ZnO:B layers present relatively higher conversion efficiency than conventional ZnO:B films.

Evaluation of xenogenic extracellular matrices as adjuvant scaffolds for the treatment of stress urinary incontinence

Tissue-engineered biomaterials have shown recent promise as adjuvant scaffolds for treating stress urinary incontinence (SUI). The objective of the present study was to compare their mechanical and regenerative properties with synthetic biomaterials in this urogynaecological setting. The biomechanical properties of polypropylene (Serasis®; n = 12), four-ply urinary bladder matrix (UBM; n = 12) and four-ply small intestinal submucosa (SIS; n = 12) were determined with uni-axial tensile testing protocols and compared with stress-strain curves. Subsequently, human dermal fibroblasts (2.5 × 10(4)cells/cm(2)) were cultured onto each biomaterial under conventional laboratory growth conditions for 12 consecutive days. Attachment, viability, and proliferative activity of fibroblasts were evaluated and compared using quantitative viability indicators and scanning electron microscopy. There were no significant differences in the biomechanical properties of each biomaterial assessed. Incremental stiffness at 0-10 % strain measured 5.73 ± 0.36 MPa for polypropylene compared with 8.23 ± 0.92 MPa and 6.81 ± 0.83 MPa for SIS and UBM respectively (p > 0.05). Viability and proliferative activity of fibroblasts differed significantly on all three biomaterials with the luminal and abluminal surfaces of the UBM demonstrating significantly greater rates of fibroblast proliferation compared with polypropylene and SIS (p < 0.01). This is the first comparative study on porcine UBM, porcine SIS, and synthetic polypropylene as adjuvant scaffolds for the treatment of SUI. Our results demonstrate that porcine UBM may provide an attractive alternative owing to its superior remodelling potential.

Ab initio-based approach to elemental growth process on the InAs wetting layer grown on GaAs substrate

The surface reconstructions and migration behavior on InAs(001) and InAs(111)A wetting layer on GaAs substrate are systematically investigated by our ab initio-based approach and Monte Carlo simulations. The ab initio-based approach incorporates the chemical potentials of In atom and As4 molecule in the gas phase as functions of temperature T and beam equivalent pressure pAs4. The calculated surface phase diagrams imply that the respective stable surface structures of InAs(001) and InAs(111)A are the (2×4)α2 and the In-vacancy surfaces at conventional growth conditions at T∼700–750K and pAs4∼10−7–10−6Torr. On these surfaces, adsorption–desorption boundary for In atom appears below the growth temperatures. Therefore, In adatoms tend to desorb from the InAs(001) and the InAs(111)A surfaces at equilibrium. Kinetic behavior of In adatoms obtained by the Monte Carlo simulations reveal that life time τ and diffusion length L of In adatoms are small such as τ=1.59×10−3s and L=618nm on the InAs(001) and τ=4.35×10−14s and L=0.204nm on the InAs(111)A. On the basis of these results, the growth process on the InAs(111)A is discussed in terms of self-surfactant effect where simultaneous As adsorption makes In atom adsorb on the surface.

TEM-study of free-standing self-assembled InSb quantum dots grown on InAs surface

We have investigated the morphology of free-standing self-assembled InSb quantum dots (QDs) grown by liquid-phase epitaxy (LPE) under conventional growth conditions on InAs(001) substrate. Two growth modes, Volmer–Weber for low-density (5×108cm−2) large QDs with 10–12nm in a height and Stranski–Krastanow for high-density (1×1010cm−2) small QDs with a height of 3–4nm, were identified in dependence on a critical growth temperature of InSb QDs formation. Characterization of the sample surface was performed using transmission electron microscopy (TEM) that allowed us to observe some features of the InSb QD shape which transforms from a full dome to truncated one with increasing QD lateral size from 15 to 40nm, respectively. Using pseudo-moiré pattern appearing in plan-view diffraction TEM image the critical size of the InSb QD for plastic deformation was evaluated.

Construction and Evaluation of Urinary Bladder Bioreactor for Urologic Tissue-engineering Purposes

To design and construct a urinary bladder bioreactor for urologic tissue-engineering purposes and to compare the viability and proliferative activity of cell-seeded extracellular matrix scaffolds cultured in the bioreactor with conventional static growth conditions. A urinary bladder bioreactor was designed and constructed to replicate physiologic bladder dynamics. The bioreactor mimicked the filling pressures of the human bladder by way of a cyclical low-delivery pressure regulator. In addition, cell growth was evaluated by culturing human urothelial cells (UCs) on porcine extracellular matrix scaffolds in the bioreactor and in static growth conditions for 5 consecutive days. The attachment, viability, and proliferative potential were assessed and compared with quantitative viability indicators and by fluorescent markers for intracellular esterase activity and plasma membrane integrity. Scaffold integrity was characterized with scanning electron microscopy and 4',6-diamidino-2-phenylindole staining. No significant difference in cell viability was identified between both experimental groups after 3 days of culture (P = .06). By day 4, the number of viable UCs was significantly greater in the bioreactor compared with the number cultured under static conditions (P = .009). A significant difference in UC viability was also present after 5 days of culture between the bioreactor and static group (P = .006). Viability/cytotoxicity assays performed on day 5 also confirmed the viability of UCs in both experimental groups. Significantly greater UC growth occurred on the extracellular matrix scaffolds cultured in the bioreactor compared with conventional static laboratory conditions after 3 days of culture. Our initial bioreactor prototype might be helpful for permitting additional advances in urinary bladder bioreactor technology.

Circular polarization of photoluminescence of GaAs/AlGaAs quantum wells as a function of their growth conditions

The degree of circular polarization of the photoluminescence of samples with GaAs/AlGaAs quantum wells grown with growth interruption at both interfaces and under conventional growth conditions has been investigated. It has been revealed that, at a low measurement temperature (4.2 K), the values of the circular polarization measured at different detection energies within the spectral profile of the luminescence band differ substantially for the sample grown with the growth interruption, whereas this effect is not observed for the sample grown without growth interruption. An increase in the sample temperature to 77 K leads to the disappearance of the effect under consideration. The observed behavior has been explained in terms of the model that accounts for a significantly different degree of localization of charge carriers in the growth islands (formed at the interfaces of the structure) with the spatial sizes determined by the specific growth conditions of the sample.

Ab initio-based approach to adsorption–desorption behavior on the InAs(1 1 1)A heteroepitaxially grown on GaAs substrate

The surface reconstructions and adsorption–desorption behavior on InAs(111)A heteroepitaxially grown on GaAs(111) substrate are systematically investigated using our ab initio-based approach incorporating the chemical potentials of In atom and As molecules in the gas phase as functions of temperature and beam equivalent pressure. This approach is also applied to qualitatively clarify the dependence of the surface-related properties on the film thickness of InAs considering various models, such as the InAs fully relaxed and coherently grown without/with GaAs interface. The calculated results imply that the most stable surface structure of the InAs(111)A is the In-vacancy surface at high temperatures including conventional growth conditions, whereas the As-trimer surface appears at low temperatures. In addition to these surface structures, As-adatom structure is newly found as a stable phase only in one atomic double-layer of InAs coherently grown on GaAs. This is because the charge redistribution due to the As adsorption strengthens the interatomic bonds with the surface In atom to stabilize the As-adatom surface. Distinctive features in the In adsorption are shown depending on the film thickness with respect to the computational models. Furthermore, the In adsorption on the In-vacancy surface does not occur without simultaneous As adsorption under conventional growth conditions. This reveals that the self-surfactant effect is crucial for the growth processes of InAs similarly to the GaAs growth.

Formation of InAs quantum dots at ultrahigh growth rates

We fabricated quantum dot (QD) structures at ultrahigh growth rates. Smaller fluctuations in QD size were observed when they were grown at a rate of 1.0 ML/s under conventional growth conditions (growth temperature of 500 °C and As 4 flux of 9×10 −6 Torr). For QDs grown at high rates, growth interruption played an important role in the fabrication of QD structures; this was confirmed by carrying out reflection high-energy electron diffraction. Photoluminescence for QDs grown at high and low growth rates, with growth interruption and with low-temperature capping was observed at around 1250 nm at room temperature, indicating that high-quality QDs can be fabricated by employing high growth rates.