Origins of the Rio Capim kaolinites (northern Brazil) revealed by δO and δD analyses

Deuterium (δD) and oxygen (δ¹⁸O) isotope data from the Rio Capim kaolin, northern Brazil, were combined with optical studies in order to better understand the genesis and evolution of the kaolinites. The results show that δ¹⁸O values from a lower soft kaolin unit range from 6.0‰ to 19.2‰ for Ka (size ranging from 1 to 3 μm) and Kb (size ranging from 10 to 30 μm) kaolinites, and from 15.4‰ to 24.9‰ for Kc (size < 200 nm) kaolinites. The δD values range from − 63.1‰ to 79.5‰ for the Ka + Kb kaolinites, and from − 68.8‰ to − 244.35‰ for the Kc kaolinites. An upper semi flint kaolin unit, dominated by Kc kaolinites, displays δ¹⁸O and δD values ranging from 15.1‰ to 21.8‰, and − 71.3‰ to − 87.4‰, respectively. Based on these data, and on the δ¹⁸O and δD values obtained for the surface meteoric water and groundwater, it can be concluded that the kaolinites are not in equilibrium with the modern weathering environment, but they reflect isotopic compositions of the formation time, probably due to the interaction with fossil groundwater. However, mineralogical contaminations derived from replacements of framework grains also had great influence in the isotopic composition of these kaolinites. In addition, the isotope values of the Kc kaolinites from the semi-flint kaolin unit is variable, which is due to the presence of Kc kaolinites of different origins, including kaolinites derived from the underlying soft kaolin unit, kaolinites formed during different phases of paleoweathering, as well as later phases of coarse-grained kaolinites formed along fractures. Due to these complexities, binary diagrams contrasting δ¹⁸O and δD values, worldwide applied for distinguishing supergenic from hypogenic kaolinites, as well as those formed under weathering conditions, can not be applied to interpret the origin of the kaolinites in the Rio Capim Kaolin.     

Synthesis of -leucine nanoparticles via physical vapor deposition at varying saturation conditions

Preparation of L-leucine nanoparticles by a process based on physical vapor deposition has been presented. In an aerosol flow reactor method, aqueous L-leucine droplets were first dried followed by the sublimation of L-leucine to produce vapor that upon vapor deposition resulted in L-leucine nanoparticles with size ranging from 40 to 200 nm. Onset temperature for the sublimation of L-leucine at concentrations from 0.02 to increased from 135 to , respectively. The formation of nanoparticles was initiated in three different ways: (i) via droplet drying, (ii) via heterogeneous nucleation of L-leucine vapor on solid L-leucine particles, and (iii) via homogeneous nucleation of L-leucine vapor to form new-born nanoparticles. Consequently, the saturation conditions of L-leucine vapor in the reactor determined the resulting particle size, size distribution and number concentration, those depending very much on nucleation mode. In general, the both nucleation modes produced narrow size distributions, that is, geometric standard deviation (GSD) was <1.8 although the number concentration increased with the increased amount of L-leucine vapor. Upon desublimation and vapor deposition, L-leucine formed leafy crystals whose size was the largest when produced from the heated section at the vicinity of the onset temperature and the smallest far above the onset temperature. All the particles prepared in the conditions (i)–(iii) were crystalline. However, X-ray diffraction analysis showed preferential direction for crystal growth according to the way of particle formation.     

Polymer-polymer interaction parameters in the ternary system polystyrene/poly(α-methyl styrene)/n-butyl chloride

The polymer-polymer interaction parameter χ′12, for the polystyrene/poly(α-methyl styrene)/n-butyl chloride ternary system, has been determined from activity coefficients of the solution measured using piezoelectric vapour sorption methods in the temperature range 30°–60°C. (These measurements where carried out in the concentration range 0.06 < ψ₀ < 0.26, where ψ is the segment fraction of the solvent). The values of χ¹⁰₁₂ extrapolated to zero solvent concentration over the range 30°–60°C, are large and negative (−0.2 to −0.9) χ¹₁₂ was found to increase with ψ₀. The negative values of χ¹₁₂ in this work are in agreement with the T_g in the polystyrene

Full-size image (1K)

M_w = 9.09 × 10⁴) blends on the point of blend compatibility. The polymer-polymer interaction parameters obtained in this work are discussed by taking into account the high susceptibility of polymers in the glassy state to solution of organic solvents.     

Production of hydrogen by unmixed steam reforming of methane

Unmixed steam reforming is an alternative method of catalytic steam reforming that uses separate air and fuel–steam feeds, producing a reformate high in H₂ content using a single reactor and a variety of fuels. It claims insensitivity to carbon formation and can operate autothermally. The high H₂ content is achieved by in situ N₂ separation from the air using an oxygen transfer material (OTM), and by CO₂ capture using a solid sorbent. The OTM and CO₂ sorbent are regenerated during the fuel–steam feed and the air feed, respectively, within the same reactor. This paper describes the steps taken to choose a suitable CO₂-sorbent material for this process when using methane fuel with the help of microreactor tests, and the study of the carbonation efficiency and regeneration ability of the materials tested. Elemental balances from bench scale experiments using the best OTM in the absence of the CO₂ sorbent allow identifying the sequence of the chemical reaction mechanism. The effect of reactor temperature between 600 and on the process outputs is investigated. Temperatures of 600 and under the fuel–steam feed were each found to offer a different set of desirable outputs. Two stages during the fuel–steam feed were characterised by a different set of global reactions, an initial stage where the OTM is reduced directly by methane, and indirectly by hydrogen produced by methane thermal decomposition, in the second stage, steam reforming takes over once sufficient OTM has been reduced. The implications of these stages on the process desirable outputs such as efficiency of reactants conversion, reformate gas quality, and transient effects are discussed.     

Modelling and simulation of a gas–solids dispersion flow in a high-flux circulating fluidized bed (HFCFB) riser

Radial solids velocity profiles were computed on seven axial levels in the riser of a high-flux circulating fluidized bed (HFCFB) using a two-phase 3-D computational fluid dynamics model. The computed solids velocities were compared with experimental data on a riser with an internal diameter of 76 mm and a height of 10 m, at a high solids flux of 300 kg m⁻² s⁻¹ and a superficial velocity of 8 m s⁻¹. Several hundreds of experimental and numerical studies on CFBs have been carried out at low fluxes of less than 200 kg m⁻² s⁻¹, whereas only a few limited useful studies have dealt with high solids flux. The k– two-phase turbulence model was used to describe the gas–solids flow in an HFCFB. The model predicts a core–annulus flow in the dilute and developed flow regions similar to that found experimentally, but in the region of highest solids concentration it is somewhat overpredicted at the level close to the inlet.     

Synthesis of polymers and copolymers of c-(N-AcrLys-Sar) and their interaction with small molecules in solution

An acrylamide derivative having a mono-N-methylated cyclic dipeptide as a substituent, c-(N^εAcrLys-Sar), was synthesized and polymerized by radical polymerization, giving homopolymers and copolymers with styrene, 4-vinylpyridine, and N-dodecylacrylamide. The relative reactivities of these monomers in the radical polymerization decreased in the following order: styrene > 4-vinylpyridine > N-dodecylacrylamidec-(N^ε-AcrLys-Sar). Poly[c-(N^ε-AcrLys-Sar)] was soluble in water and the usual organic solvents except diethylether and n-hexane. In mixed solvent, poly[c-(N^ε-AcrLys-Sar)] interacted most strongly with Ba²⁺ among alkali and alkaline-earth metal cations. A cyclic dipeptide, which is equivalent to the side chain of poly[c-(N^ε-AcrLys-Sar)], did not interact with these cations, indicating that the side chain ligand groups of poly[c-(N^ε-AcrLys-Sar)] interacts specifically with Ba²⁺ by intramolecular cooperation. However, the copolymer of c-(N^ε-AcrLys-Sar) with styrene interacts more strongly with larger alkali cations, and equally well with Ba²⁺ and Ca²⁺. These results indicate that the styrene units in the copolymer influence its solubility and regulate the intramolecular cooperation of the cyclic dipeptide ligand groups as spacer groups. The copolymer of c-(N^ε-AcrLys-Sar) with 4-vinylpyridine interacted very strongly with Ba²⁺ as a result of the intramolecular cooperation of a pyridyl group and a cyclic dipeptide group. The formation constant of the ternary complex was determined to be 10⁹ M⁻³, which is larger by 10² fold than that by a polymer carrying benzo-15-crown-5 in the side chain. The copolymer of c-(N^ε-AcrLys-Sar) with N-dodecylacrylamide was found to bind methyl orange in aqueous solution by hydrophobic interaction. The copolymer of c-(N^ε-AcrLys-Sar) with styrene was found to extract phenylalanine from an aqueous solution to a n-octanol phase. However, the extraction was not enantiomer-selective.     

Substantially enhancing enzymatic regioselective acylation of 1-β-d-arabinofuranosylcytosine with vinyl caprylate by using a co-solvent mixture of hexane and pyridine

Novozym 435-catalyzed regioselective acylation of 1-β-d-arabinofuranosylcytosine (ara-C) with vinyl caprylate for the preparation of its 5′-O-acyl derivative has been performed in six co-solvent mixtures and three pure polar solvents for the first time. Novozym 435 displayed low activity towards 1-β-d-arabinofuranosylcytosine in pure polar solvents, although those solvents can dissolve the nucleosides well. When a hexane–pyridine co-solvent system was adopted, both the initial rate and the substrate conversion were enhanced markedly. The most suitable co-solvent, initial water activity, reaction temperature and the molar ratio of vinyl caprylate to ara-C were hexane/pyridine (28/72, v/v), 0.03, 40 °C and 15, respectively. Under these conditions, the initial rate, the substrate conversion and the regioselectivity were as high as 99.0 mmol h⁻¹, 98% and >99%, respectively. The product of the Novozym 435-catalyzed reaction was characterized by ¹³C NMR and confirmed to be 5′-O-octanoyl 1-β-d-arabinofuranosylcytosine.     

A novel route to α,ω-telechelic poly(-caprolactone) diols, precursors of biodegradable polyurethanes, using catalysis by decamolybdate anion

A new convenient route for the synthesis of poly(-caprolactone) (PCL) with α,ω-telechelic diols' end-groups is presented. Synthesis of α,ω-telechelic PCL diols (HOPCLOH) was achieved by ring-opening polymerization (ROP) of -caprolactone (CL) catalyzed with ammonium decamolybdate (NH₄)₈[Mo₁₀O₃₄] and using diethylene glycol (DEG) as initiator. Obtained HOPCLOH was characterized by ¹H and ¹³C NMR, FT-IR, GPC and MALDI-TOF. Comparative studies demonstrate that ammonium decamolybdate (NH₄)₈[Mo₁₀O₃₄] is better catalyst than Sn-octanoate (SnOct₂) toward CL polymerization in presence of DEG, under the conditions tested. A biodegradable poly(ester-urethane-urea) derivative was efficiently prepared from synthesized HOPCLOH. Obtained polymer shows minor differences with respect to the properties recorded for a poly(ester-urethane-urea) obtained from commercial HOPCLOH.     

Isomerization of α-pinene over dealuminated ferrierite-type zeolites

Isomerization of α-pinene was performed on a series of dealuminated ferrierite (FER)-type zeolites in liquid phase at 363 K using a batch reactor. The course of zeolite dealumination was followed in detail using ²⁹Si, ²⁷Al, ¹H MAS NMR, XRD, FTIR, and sorption of nitrogen. The ammonium form of FER was dealuminated with aqueous solutions of HCl. While retaining the crystallinity of the zeolite particles, the treatments removed up to 53% of the tetrahedrally coordinated aluminum atoms from the FER framework. According to ²⁹Si MAS NMR studies, the framework aluminum atoms located at the 10-membered rings in the main channels of FER (T_B sites) were depleted preferentially from their positions. Even relatively mild dealumination of FER led to an active catalyst containing both Brønsted and Lewis centers, yielding up to 97% conversion of α-pinene at 363 K, in contrast to the 72% observed for the parent hydrogen form. Such catalytic behavior was discussed in terms of the conversion of a reactant inside micropores of the zeolite catalyst, on Brønsted acid centers with enhanced strength located probably in the vicinity of Lewis sites. The selectivity toward camphene and limonene changed smoothly with the dealumination level; thus, a higher selectivity toward limonene was observed at the expense of camphene formation with increasing the n_Si/n_Al ratio of the catalysts. The selectivity toward camphene and limonene was close to 85% for all of the materials studied. The initial rates of α-pinene transformations over FER-type materials exceeded those observed for other catalytic systems, heteropoly acid/SiO₂ and H₂SO₄/ZrO₂. This study demonstrates the successful application of a medium-pore zeolite for the catalytic transformation of α-pinene in liquid phase.     

Confirmation of Potential Herbicidal Agents in Hulls of Rice, <Emphasis Type="Italic">Oryza sativa</Emphasis>

An ethyl acetate extract of Oryza sativa (rice) hulls yielded seven compounds: hentriacontane, 1-tetratriacontanol, β-sitosterol, momilactone A, momilactone B, tricin (a flavonoid), and β-sitosterol-3-O-β-d-glucoside. The structures of these compounds were elucidated with 500 MHz nuclear magnetic resonance (NMR), using 1D and 2D spectral methods, aided by electron ionization mass spectrometry (EI–MS), fast atom bombardment mass spectrometry (FAB–MS), infrared (IR), and ultraviolet (UV) spectrophotometry. The complete ¹H NMR assignments for momilactone A and B and ¹³C NMR assignments for tricin are discussed. To the best of our knowledge, hentriacontane, 1-tetratriacontanol, and β-sitosterol-3-O-β-d-glucoside were identified for the first time in rice hulls. In biological activity tests using these identified compounds, momilactone A and B showed potent inhibitory activity against duckweed (Lemna paucicostata). 1-Tetratriacontanol and β-sitosterol-3-O-β-d-glucoside also showed about 13–20% inhibitory activity based on chlorophyll reduction. Hentriacontane and β-sitosterol did not show any herbicidal activity. In a germination assay of three weed species (Leptochloa chinenesis L., Amaranthus retroflexus L., and Cyperus difformis L.) in culture tubes both momilactones A and B had high inhibitory effects. Momilactone B completely inhibited germination of all three weed species at 20 ppm. Germination of L. chinensis L. was completely inhibited by a 4 ppm solution of momilactone B.Electronic supplementary material Supplementary material to this paper is available in electronic form at     

Deposition and characterisation of TiO2 coatings on various supports for structured (photo)catalytic reactors

Different types of aqueous TiO₂–P25 suspensions were prepared and their properties, including rheological behaviour and zeta potential, were studied. Then, TiO₂ suspensions were used to elaborate TiO₂ coatings on various substrates (cordierite monolith, stainless steel plates and -SiC foam) using a dip-coating method. The relationship between the suspension stability and the coating adhesion has been considered. The structural and morphological characterisation of TiO₂ coatings has been performed using scanning electron microscopy, X-ray diffraction and other methods. Finally, the photocatalytic properties of the materials have been determined by studying the photooxidation of aqueous ammonia.     

Chemotherapeutic engineering: Vitamin E TPGS-emulsified nanoparticles of biodegradable polymers realized sustainable paclitaxel chemotherapy for 168 h in vivo

A full spectrum of proof-of-concept research from nanoparticle preparation and characterization, in vitro drug release, cellular uptake and cytotoxicity, to in vivo pharmacokinetics and xenograft tumor model is developed in this paper to demonstrate how nanoparticles of biodegradable polymers can be applied to formulate anticancer drugs to avoid use of toxic adjuvant and to enable sustained and controlled chemotherapy. Paclitaxel-loaded poly(lactic-co-glycolic acid) nanoparticles were prepared by solvent extraction/evaporation with vitamin E TPGS as the emulsifier, which has much higher emulsification effects and better biocompatibility than other chemical emulsifiers such as polyvinyl alcohol (PVA), resulting in a high drug encapsulation efficiency, high uptake of nanoparticles by cancer cells, and sustainable pharmacokinetics. In vitro C6 cell mortality experiments demonstrated that the nanoparticle formulation was five times more effective than Taxol^®. In vivo pharmacokinetics measurements showed that the nanoparticle formulation had a comparable value of the area-under-the-curve (AUC) with that of Taxol^®, but never exceeded the maximum tolerance level, and hence should greatly reduce the side effects compared with Taxol^®. Moreover, the nanoparticle formulation realized a sustainable therapeutic time of 168 h in comparison with 22 h for Taxol^® at a same dose of 10 mg/kg and achieved four times greater drug tolerance than Taxol^®.     

The study on the conductivity of styrene-maleic anhydride copolymer electrolytes based on poly(ethylene glycol)400 and LiClO4

Polyelectrolytes, in this study were synthesized from styrene-maleic anhydride (SMA) copolymer, poly(ethylene glycol)400 (PEG400), and lithium perchlorate (LiClO₄). Fourier transform infrared spectroscopy (FTIR), and magic angle spinning (MAS) solid-state NMR were used to monitor the interaction between Li⁺ ions and polymer. The results of FTIR and MAS solid-state NMR indicate the Li⁺ ions are preferentially coordinated to the ether oxygen of PEG. The T_g of the PEG segments in polyelectrolyte increases with LiClO₄ concentration, as determined by differential scanning calorimetry (DSC), indicating that solubility of the Li⁺ ions in the host polymer increases with the PEG content. Impedance spectroscopy (IS) shows that the bulk conductivity of polyelectrolytes and the conductivity behavior obeys the Vogel-Tamman-Fulcher (VTF) equation.     

A mechanism study of chloride and sulfate effects on Hg reduction in sulfite solution

This paper studied the effects of sulfate and chloride ions on bivalent mercury (Hg²⁺) absorption and reduction behaviors in a simulated WFGD system. The aqueous mercuric ion-sulfite system reduction behaviors were monitored and investigated using a UV-visible spectrum. Thereafter, the mechanism of Hg²⁺ reduction in the presence of sulfate and chloride ions was proposed. Experimental results revealed that both sulfate and chloride ions had inhibition effects on aqueous Hg²⁺ reduction to Hg⁰. The inhibition was assumed due to the formation of (in the presence of ) and / (in the presence of Cl⁻). And it was found that complex was more stable than in excess of Cl⁻. The formation of the above-mentioned complexes in the presence of and Cl⁻ would damp the formation of HgSO₃, whose decomposition was assumed to be the key step of Hg²⁺ reduction.     

Novel coated graphite electrode for the selective determination of Gd(III) in rocks and waste water samples

A novel gadolinium selective coated graphite electrode based on 2,6-bis-[1-{N-cyanopropyl,N-(2-methylpridyl)}aminoethyl]pyridine [P] is described. The best performance was exhibited by the electrode having membrane composition P:NaTPB:PVC:NPOE as 8:4:30:58 (%, w/w). The electrode demonstrates excellent potentiometric characteristics towards gadolinium ion over several interfering ions. The electrode exhibited a Nernstian response to Gd³⁺ ion over a wide concentration range 2.8 × 10⁻⁷ to 5.0 × 10⁻² M with a detection limit (6.3 ± 0.1) × 10⁻⁸ M and slope 19.6 ± 0.1 mV decade⁻¹ of a_Gd³⁺. Furthermore, it showed a fast response time (12 s) and can be used for 2.5 months without significant divergence in its characteristics. Noticeably, the electrode can tolerate the concentration of different surfactants up to 1.0 × 10⁻⁴ M and can be used successfully in 30% (v/v) ethanol media and 10% (v/v) methanol and acetonitrile water mixture. The useful pH range of this sensor is 2.0 to 8.0. It is sufficiently selective and can be used for the determination of Gd³⁺ ions in waste water and rock samples. It also serves as a good indicator in the potentiometric titration of GdCl₃ with EDTA.     

Role of PGC-1α in the Mitochondrial NAD+ Pool in Metabolic Diseases

Mitochondria play vital roles, including ATP generation, regulation of cellular metabolism, and cell survival. Mitochondria contain the majority of cellular nicotinamide adenine dinucleotide (NAD⁺), which an essential cofactor that regulates metabolic function. A decrease in both mitochondria biogenesis and NAD⁺ is a characteristic of metabolic diseases, and peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) orchestrates mitochondrial biogenesis and is involved in mitochondrial NAD⁺ pool. Here we discuss how PGC-1α is involved in the NAD⁺ synthesis pathway and metabolism, as well as the strategy for increasing the NAD⁺ pool in the metabolic disease state.     

The effect of specific surface area on the activity of nano-scale ceria catalysts for methanol decomposition with and without steam at SOFC operating temperatures

Nano-particulate high surface area CeO₂ was found to have a useful methanol decomposition activity producing H₂, CO, CO₂, and a small amount of CH₄ without the presence of steam being required under solid oxide fuel cell temperatures, 700-1000 °C. The catalyst provides high resistance toward carbon deposition even when no steam is present in the feed. It was observed that the conversion of methanol was close to 100% at 850 °C, and no carbon deposition was detected from the temperature programmed oxidation measurement.The reactivity toward methanol decomposition for CeO₂ is due to the redox property of this material. During the decomposition process, the gas-solid reactions between the gaseous components, which are homogeneously generated from the methanol decomposition (i.e., CH₄, CO₂, CO, H₂O, and H₂), and the lattice oxygen on ceria surface take place. The reactions of adsorbed surface hydrocarbons with the lattice oxygen ( can produce synthesis gas (CO and H₂) and also prevent the formation of carbon species from hydrocarbons decomposition reaction (C_nH_m⇔nC+m/2H₂). V_O^·· denotes an oxygen vacancy with an effective charge 2⁺. Moreover, the formation of carbon via Boudouard reaction (2CO⇔CO₂+C) is also reduced by the gas-solid reaction of carbon monoxide with the lattice oxygen .At steady state, the rate of methanol decomposition over high surface area CeO₂ was considerably higher than that over low surface area CeO₂ due to the significantly higher oxygen storage capacity of high surface area CeO₂, which also results in the high resistance toward carbon deposition for this material. In particular, it was observed that the methanol decomposition rate is proportional to the methanol partial pressure but independent of the steam partial pressure at 700-800 °C. The addition of hydrogen to the inlet stream was found to have a significant inhibitory effect on the rate of methanol decomposition.     

Systematics of salt precipitation in complexes of polyethylene oxide and alkali metal iodides

Conductivity measurements in PEO₃₀MI polymer electrolytes with M=Li, Na, K, Rb, or Cs over the temperature range from about 65 to 200 °C show an increasing tendency for salt precipitation with increasing cation size. The salt precipitation in these complexes upon heating is revealed by the decrease of the dc conductivity starting at a critical temperature T_c. Whereas LiI and NaI complexes do not show precipitation effects, T_c monotonically decreases from about 140 to 65 °C when changing the salt component from KI via RbI to CsI. For the PEO-RbI system, precipitation is further investigated by nuclear magnetic resonance (NMR) and tracer diffusion experiments. NMR analysis unambiguously demonstrates the onset of RbI salt precipitation and the increase of the precipitate fraction with increasing temperature. In diffusion experiments on PEO₃₀RbI with the radiotracers and , the precipitation effect is manifested by anomalous features in the penetration profiles, however, without noticeable changes in their depth range. Combining the resulting tracer diffusion coefficients with the dc conductivity data enables us to assess crucial parameters characterizing ionic transport in PEO₃₀RbI.     

Analysis of the milling rate of pharmaceutical powders using the Distinct Element Method (DEM)

The milling behaviour of microcrystalline cellulose (MCC) and α-lactose monohydrate (αLM) in an oscillatory single ball mill has been analysed by using the Distinct Element Method (DEM). The experimental results suggest that the milling behaviour of αLM is more strongly influenced by the milling frequency as compared to MCC. A similar conclusion is also drawn from the DEM results. The milling behaviour of MCC and αLM is described by a first order rate process, and its rate constant, K_p, is found to correlate very well with the milling power, P_n, determined by the DEM simulation, except for the milling behaviour of αLM at 18 Hz. For the latter, there appears to be an incubation time after which the milling rate increases substantially. The results presented here provide a basis for predicting the milling behaviour of a material systematically based on the fundamental material properties and the machine dynamics without the need for extensive experiment and use of large quantities of materials.     

Highly oriented diamond growth on SixGe1−x (100) thin films

Highly oriented (100) diamond films have been successfully grown on Si_xGe_1−x (100) thin films by bias enhanced nucleation (BEN) in microwave plasma chemical vapor deposition (MPCVD) system. Raman spectra show the 1332 cm⁻¹ peak which proves the formation of diamond. Diamond nucleation density on Si_xGe_1−x substrate estimated by scanning electron microscopy is higher than 10⁹ cm⁻². The interface between diamond and Si_xGe_1−x substrate was characterized by transmission electron microscopy (TEM). About 20 nm decrease in thickness of the Si_xGe_1−x film was observed after bias enhanced nucleation step. TEM shows the existence of silicon carbide and heteroepitaxial diamond grains grown on Si_xGe_1−x substrate. Characterization from high-resolution TEM on the specimen of short time deposition reveals that a number of epitaxial diamond grains were directly nucleated on Si_xGe_1−x with {111} interplanar spacing ratio of diamond and Si_xGe_1−x of 2:3. The diamond nucleation is found to be preferred on the ridge position of the rough substrate surface. Diamond {100} facets were quickly developed in the early stage of growth.