Self Organized Growth in Thulium Doped Gaas Using MBE

1996 ◽  
Vol 422 ◽  
Author(s):  
M. R. Bennett ◽  
K. E. Singer ◽  
A. C. Wright ◽  
Z. H. Jafri
Keyword(s):  
Quantum Wires ◽  
Strain Relaxation ◽  
Solubility Limit ◽  
Growth Conditions ◽  
Nano Particles ◽  
Uniform Size ◽  
Self Organized ◽  
High Resolution Tem ◽  
Doping Profiles ◽  
First Time

AbstractThe growth of epitaxial GaAs doped with the rare earth thulium (Tm) by MBE is reported for the first time. The nature of the incorporation of Tm has been studied using SIMS, RBS, TEM, PL and DCXRD. Sharp doping profiles have been observed by SIMS from samples doped in a staircase structure. Under standard GaAs growth conditions, TEM has revealed a solubility limit of ∼5×1019cm−3, above which Tm precipitates as spherical nano-particles of uniform size (1.3–1.7nm). High resolution TEM has provided no evidence for strain relaxation around these precipitates. Growth at higher substrate temperatures (≥620°C) or at As:Ga ratios close to stoichiometry, results in the formation of precipitate wires and/or bifurcated structures (“quantum trees”) aligned approximately in the direction of growth. Such behaviour is in common with that of Er in GaAs and suggests that the precipitates result from the self-organised growth of TmAs. Mechanisms for the formation of the quantum wires and trees are suggested. Initial photoluminescence spectra from these samples show two groups of narrow Tm3+ intra 4f transition lines corresponding to the 3H5 – 3H6 (∼1.01eV/1.2μm) and 3H4 – 3H6 (∼ 0.71eV/1.7μm) transitions. The spectra exhibit an excellent correlation with those obtained from samples grown by MOVPE and also those implanted with Tm by other groups.

scholarly journals Peculiarities of Aluminum Anodization in AHAs-Based Electrolytes: Case Study of the Anodization in Glycolic Acid Solution

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5362
Author(s):  
Lidia Zajączkowska ◽  
Małgorzata Norek
Keyword(s):  
Pore Formation ◽  
Anodization Voltage ◽  
Unusual Behavior ◽  
Uniform Size ◽  
Self Organized ◽  
Aluminum Anodization ◽  
Alpha Hydroxy Acids ◽  
First Time ◽  
Density Behavior

The anodization of aluminum (Al) in three alpha-hydroxy acids (AHAs): glycolic (GC), malic (MC), and citric (CC), was analyzed. Highly ordered pores in GC were obtained for the first time. However, the hexagonal cells were characterized by a non-uniform size distribution. Although common features of current density behavior are visible, the anodization in AHAs demonstrates some peculiarities. The electric conductivity (σ) of 0.5 M GC, MC, and CC electrolytes was in the following order: σ(CC) > σ(MC) > σ(GC), in accordance with the acid strength pKa(CC) < pKa(MC) < pKa(GC). However, the anodization voltage, under which a self-organized pore formation in anodic alumina (AAO) was observed (Umax), decreased with increasing pKa: Umax(CC) > Umax(MC) ≥ Umax(GC). This unusual behavior is most probably linked with the facility of acid ions to complex Al and the active participation of the Al complexes in the AAO formation. Depending on the AHA, its tendency and different modes to coordinate Al ions, the contribution of stable Al complexes to the AAO growth is different. It can be concluded that the structure of Al complexes, their molecular mass, and the ability to lose electrons play more important roles in the AAO formation than pKa values of AHAs.

Preparation and Growth of Pb2Sr2Y0.5Ca0.5Cu3O8+δ Thin Film Superconductors

1992 ◽  
Vol 285 ◽  
Author(s):  
S.H.H. Naqvi ◽  
M. Vickers ◽  
S. Tarling ◽  
P. Barnes ◽  
I.W. Boyd
Keyword(s):  
Thin Film ◽  
Pulsed Laser ◽  
Growth Conditions ◽  
Laser Deposition ◽  
Ex Situ ◽  
Dc Resistivity ◽  
Basic Set ◽  
Zero Resistance ◽  
Van Der Pauw ◽  
First Time

ABSTRACTThe lead based superconductor Pb2Sr2Y0.5Ca0.5Cu3O8+δ is a most complex material. If any oxygen is present in the PbO-CuOδ-PbO sandwich layer (i.e. if δ>0) the superconductivity deteriorates. This is also a most difficult material to grow not only because of the large number of cation stoichiometries which have to be precisely balanced but also because of the tendency for multiple phases to form. Pulsed laser deposition (PLD) has been applied to prepare thin films of the 2213-phase on MgO (100) single crystal substrates at low temperature (300°C) in low oxidizing atmospheres. A basic set of ex-situ growth conditions has been determined which produce for the first time good quality films of this material as characterized by DC resistivity using the Van der Pauw method, as well as EDX and XRD. The layers are reasonably c-axis oriented and display a superconducting onset transition temperature of 79K and zero resistance at 65K after subsequent annealing in a nitrogen ambient.

scholarly journals Impact of forest growth conditions on the wood density: the case of Amur Region

2018 ◽  
Vol 60 (4) ◽  
pp. 292-298
Author(s):  
Natalia A. Romanova ◽  
Alexander B. Zhirnov ◽  
Natalia A. Yust ◽  
Xu Fucheng
Keyword(s):  
Wood Density ◽  
Far East ◽  
Growth Conditions ◽  
Amur Region ◽  
Forest Growth ◽  
Far East Of Russia ◽  
Density Determination ◽  
The Far East ◽  
First Time

Abstract The problem of determining the dependence of the chainsaw on the density of wood, substantiation of effective options for the number of chainsaws in the assortment and whiplash method of logging is quite relevant. In the Far East of Russia, in particular, in the Amur region, the forest growth conditions are different from the western ones, and therefore, the properties of the wood differ from the generally accepted ones. The article describes forest growth conditions that influence the properties of the wood in areas of the Amur region. Using the method of density determination, the density of larch, pine and birch were studied for first time in the areas of the region. The dependence of the density on humidity, age, species, season of the year and the area of growth was found out. The results of the research showed that under humidity of 70%, the density of larch was 1088.99 kg/m3, it was 919.8 kg/m3 for pine and it was for birch 915.9 kg/m3.

scholarly journals PHOTOCHEMICAL DEGRADATION OF PHENOL WITH THE PARTICIPATION OF TiO2 NANOPARTICLES AND ETHYL-3,3,5,5-TETRACIANO-2-HYDROXIDE-2-METIL-4,6-DIPHENYL CYCLOHEXANE CARBOXYLATE

2021 ◽  
pp. 101-105
Author(s):  
E.M. Gadirova ◽  
Keyword(s):  
Tio2 Nanoparticles ◽  
Uv Irradiation ◽  
Uv Spectroscopy ◽  
Nano Particles ◽  
Photochemical Degradation ◽  
Cyclohexane Carboxylate ◽  
Photochemical Decomposition ◽  
First Time

The photochemical decomposition of phenol with the participation of TiO2 nano-particles and ethyl-3,3,5,5-tetraciano-2-hydroxide-2-metil-4,6-diphenyl cyclohexane carboxylate by UV spectroscopy was studied for the first time. It has been shown, that UV irradiation of this mixture during 1 hour brings to 52% decomposition of phenol

scholarly journals Effects of Calcium Phosphate Nanoparticles on Ca-PO4 Composite

2007 ◽  
Vol 86 (4) ◽  
pp. 378-383 ◽  
Author(s):  
H.H.K. Xu ◽  
M.D. Weir ◽  
L. Sun ◽  
S. Takagi ◽  
L.C. Chow
Keyword(s):  
Volume Fraction ◽  
High Strength ◽  
Nano Particles ◽  
Nano Silica ◽  
Ion Release ◽  
Mass Fractions ◽  
Calcium Phosphate Nanoparticles ◽  
Filler Mass ◽  
First Time ◽  
Filler Level

Nano-particles of dicalcium phosphate anhydrous (DCPA) were synthesized for the first time. The objectives of this study were to incorporate DCPA nano-particles into resin for Ca-PO4 release to combat dental caries, and to investigate the filler level effects. Nano-DCPA and nano-silica-fused silicon nitride whiskers at a 1:1 ratio were used at filler mass fractions of 0–75%. The flexural strengths in MPa (mean ± SD; n = 6) of DCPA-whisker composites ranged from (106 ± 39) at 0% fillers to (114 ± 23) at 75% fillers, similar to (112 ± 22) of a non-releasing composite (TPH) (p > 0.1). The composite with 75% fillers in a NaCl solution (133 mmol/L, pH = 7.4, 37°C) yielded a Ca concentration of (0.65 ± 0.02) mmol/L and PO4 of (2.29 ± 0.07) mmol/L. Relationships were established between ion-release and DCPA volume fraction VDCPA: Ca = 4.46 VDCPA1.6, and = 66.9 VDCPA2.6. Nano-DCPA-whisker PO4 composites had high strength and released high levels of Ca-PO4 requisite for remineralization. These new nano-composites could provide the needed combination of stress-bearing and caries-inhibiting capabilities.

Fabrication of Semiconductor Nano-particles in the Protein Cage of Apoferritin

2005 ◽  
Vol 873 ◽  
Author(s):  
Kenji Iwahori ◽  
Keiko Yoshizawa ◽  
Masahiro Muraoka ◽  
Ichiro Yamashita
Keyword(s):  
Chemical Reaction ◽  
Reaction System ◽  
Nano Particles ◽  
Internal Cavity ◽  
Reaction Parameters ◽  
Synthesis System ◽  
X Ray ◽  
Protein Cage ◽  
High Resolution Tem ◽  
Chemical Reaction System

AbstractWe specially designed a slow chemical reaction system to synthesize the zinc selenide nanoparticles (ZnSe NPs), in the cavity of the cage-shaped protein, apoferritin. The newly designed chemical synthesis system for ZnSe NPs makes the chemical reaction of compound semiconductor element ions dramatically slow, resulting in that ZnSe NPs can be synthesized in the internal cavity of the apoferritin. The ZnSe NPs synthesized by the optimized reaction parameters are efficiently produced in the aqueous solution. The UVVis spectrum analysis of synthesized ZnSe-ferritin suggests that the formation of ZnSe nuclei in the apoferritin cavity takes about 6 hours by using our slow chemical reaction system. The synthesized ZnSe NPs were characterized by high resolution TEM, X-ray powder diffraction (XRD) and Energy Dispersive Spectrometory (EDS) and it was revealed that the synthesized NPs are a collection of cubic ZnSe crystals.

The expression, lamin-dependent localization and RNAi depletion phenotype for emerin inC. elegans

2002 ◽  
Vol 115 (5) ◽  
pp. 923-929 ◽  
Author(s):  
Yosef Gruenbaum ◽  
Kenneth K. Lee ◽  
Jun Liu ◽  
Merav Cohen ◽  
Katherine L. Wilson
Keyword(s):  
Nuclear Envelope ◽  
Molecular Mechanisms ◽  
Cell Types ◽  
Growth Conditions ◽  
Rnai Phenotype ◽  
Lamin B ◽  
C Elegans ◽  
Nuclear Lamins ◽  
First Time

Emerin belongs to the LEM-domain family of nuclear membrane proteins, which are conserved in metazoans from C. elegans to humans. Loss of emerin in humans causes the X-linked form of Emery-Dreifuss muscular dystrophy(EDMD), but the disease mechanism is not understood. We have begun to address the function of emerin in C. elegans, a genetically tractable nematode. The emerin gene (emr-1) is conserved in C. elegans. We detect Ce-emerin protein in the nuclear envelopes of all cell types except sperm, and find that Ce-emerin co-immunoprecipitates with Ce-lamin from embryo lysates. We show for the first time in any organism that nuclear lamins are essential for the nuclear envelope localization of emerin during early development. We further show that four other types of nuclear envelope proteins, including fellow LEM-domain protein Ce-MAN1, as well as Ce-lamin, UNC-84 and nucleoporins do not depend on Ce-emerin for their localization. This result suggests that emerin is not essential to organize or localize the only lamin (B-type) expressed in C. elegans. We also analyzed the RNAi phenotype resulting from the loss of emerin function in C. elegans under laboratory growth conditions, and found no detectable phenotype throughout development. We propose that C. elegans is an appropriate system in which to study the molecular mechanisms of emerin function in vivo.

scholarly journals Two Different Quinohemoprotein Amine Dehydrogenases Initiate Anaerobic Degradation of Aromatic Amines inAromatoleum aromaticumEbN1

2019 ◽  
Vol 201 (16) ◽  
Author(s):  
Georg Schmitt ◽  
Martin Saft ◽  
Fabian Arndt ◽  
Jörg Kahnt ◽  
Johann Heider
Keyword(s):  
Aromatic Amines ◽  
Catalytic Efficiency ◽  
Growth Conditions ◽  
Complete Replacement ◽  
Content Type ◽  
Enzyme Family ◽  
First Time ◽  
Α Subunits ◽  
Substrate Spectrum

ABSTRACTAromatic amines like 2-phenylethylamine (2-PEA) and benzylamine (BAm) have been identified as novel growth substrates of the betaproteobacteriumAromatoleum aromaticumEbN1, which degrades a wide variety of aromatic compounds in the absence of oxygen under denitrifying growth conditions. The catabolic pathway of these amines was identified, starting with their oxidative deamination to the corresponding aldehydes, which are then further degraded via the enzymes of the phenylalanine or benzyl alcohol metabolic pathways. Two different periplasmic quinohemoprotein amine dehydrogenases involved in 2-PEA or BAm metabolism were identified and characterized. Both enzymes consist of three subunits, contain two hemeccofactors in their α-subunits, and exhibit extensive processing of their γ-subunits, generating four intramolecular thioether bonds and a cysteine tryptophylquinone (CTQ) cofactor. One of the enzymes was present in cells grown with 2-PEA or other substrates, showed an α2β2γ2composition, and had a rather broad substrate spectrum, which included 2-PEA, BAm, tyramine, and 1-butylamine. In contrast, the other enzyme was specifically induced in BAm-grown cells, showing an αβγ composition and activity only with BAm and 2-PEA. Since the former enzyme showed the highest catalytic efficiency with 2-PEA and the latter with BAm, they were designated 2-PEADH and benzylamine dehydrogenase (BAmDH). The catalytic properties and inhibition patterns of 2-PEADH and BAmDH showed considerable differences and were compared to previously characterized quinohemoproteins of the same enzyme family.IMPORTANCEThe known substrate spectrum ofA. aromaticumEbN1 is expanded toward aromatic amines, which are metabolized as sole substrates coupled to denitrification. The characterization of the two quinohemoprotein isoenzymes involved in degrading either 2-PEA or BAm expands the knowledge of this enzyme family and establishes for the first time that the necessary maturation of their quinoid CTQ cofactors does not require the presence of molecular oxygen. Moreover, the study revealed a highly interesting regulatory phenomenon, suggesting that growth with BAm leads to a complete replacement of 2-PEADH by BAmDH, which has considerably different catalytic and inhibition properties.

Fiber nanogratings induced by femtosecond pulse laser direct writing for in-line polarizer

Nanoscale ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 908-914 ◽  
Author(s):  
Jiafeng Lu ◽  
Ye Dai ◽  
Qin Li ◽  
Yali Zhang ◽  
Chunhua Wang ◽  
...  
Keyword(s):  
Pulse Laser ◽  
Femtosecond Pulse ◽  
Direct Writing ◽  
Laser Direct Writing ◽  
Femtosecond Pulse Laser ◽  
Self Organized ◽  
Silica Fibers ◽  
First Time

Self-organized fiber nanogratings (FNGs) induced by femtosecond pulse laser direct writing are demonstrated in optical silica fibers for the first time.

Near-infrared light-controlled circularly polarized luminescence of self-organized emissive helical superstructures assisted by upconversion nanoparticles

2020 ◽  
Vol 56 (88) ◽  
pp. 13649-13652 ◽  
Author(s):  
Ao Juan ◽  
Hao Sun ◽  
Jinghui Qiao ◽  
Jinbao Guo
Keyword(s):  
Near Infrared ◽  
Infrared Light ◽  
Upconversion Nanoparticles ◽  
Near Infrared Light ◽  
Excitation Light ◽  
Circularly Polarized ◽  
Self Organized ◽  
Circularly Polarized Luminescence ◽  
Polarized Luminescence ◽  
First Time

The reversible switching of circularly polarized luminescence in a self-organized emissive helical superstructure using 980 nm NIR excitation light with different power intensities is reported for the first time.

Sign in / Sign up

Export Citation Format

Share Document