Equivalent Substrates Research Articles

Correction of substrate-induced thin-film modulus deviations in nanoindentation measurements

The influence of substrate effects on the accurate measurement of mechanical properties of thin films remains to be clarified. Therefore, in this study, (AlCrNbSiTi)N thin films were deposited on four substrates—Si, SiO2, sapphire (Al2O3), and Ni—with varying thicknesses. Nanoindentation testing was conducted to measure the mechanical properties, revealing variations in the modulus of the thin film depending on the substrate and film thickness. To address these variations, we introduced the concept of two springs connected in series, following Hooke's law, to determine the elastic deformations of the thin film and its underlying substrate. By applying linear regression to four datasets corresponding to equivalent film thicknesses but different substrates, substrate-induced measurement errors were effectively mitigated, and the true modulus of the thin film was determined. Furthermore, we introduced a k value to represent the ratio of the actual force on the substrate to the force exerted by the indenter. Our findings indicate that even when the indenter contact depth is less than 1% of the film thickness, the substrate is still subjected to 7.6% of the applied force. This underscores the non-negligible nature of substrate elastic deformation during the measurement process and importance of correcting for substrate-induced variations in thin-film moduli. The findings can contribute to advancing the understanding of mechanical properties in ceramics and related materials.

The characteristic impedance calculation method of microstrip line and application in embroidered microstrip line

Presently, it is difficult to measure the characteristic impedance of embroidered microstrip line for its conductive anisotropy directly. The published work had proposed to use S-parameters to estimate the port impedance of a balanced dipole antenna, and it cannot be used to calculate the characteristic impedance of microstrip lines with one arm. Thus, it is still a problem on measuring and obtaining 50 Ω characteristic impedance of embroidered microstrip line. Therefore, taking the reflection coefficient as an intermediate variable, this work proposes to use return loss [Formula: see text] to derive the expression of the characteristic impedance of microstrip line. Combined theoretical calculation with experimental testing on characteristic impedance of the fabric-based microstrip line, the expression of the characteristic impedance was verified. Then, the expression of the characteristic impedance of microstrip line was used to calculate the characteristic impedance of embroidered microstrip line and determine its equivalent substrates. The results show that the fabric embroidered with a single-layer conductive strip is a part of its equivalent substrate, and the fabric embroidered with a double-layer conductive strip is not a part of its equivalent substrate.

Catalytic, Z-Selective, Semi-Hydrogenation of Alkynes with a Zinc–Anilide Complex

The reversible activation of dihydrogen with a molecular zinc anilide complex is reported. The mechanism of this reaction has been probed through stoichiometric experiments and density functional theory (DFT) calculations. The combined evidence suggests that H2 activation occurs by addition across the Zn-N bond via a four-membered transition state in which the Zn and N atoms play a dual role of Lewis acid and Lewis base. The zinc hydride complex that results from H2 addition has been shown to be remarkably effective for the hydrozincation of C═C bonds at modest temperatures. The scope of hydrozincation includes alkynes, alkenes, and a 1,3-butadiyne. For alkynes, the hydrozincation step is stereospecific leading exclusively to the syn-isomer. Competition experiments show that the hydrozincation of alkynes is faster than the equivalent alkene substrates. These new discoveries have been used to develop a catalytic system for the semi-hydrogenation of alkynes. The catalytic scope includes both aryl- and alkyl-substituted internal alkynes and proceeds with high alkene: alkane, Z:E ratios, and modest functional group tolerance. This work offers a first example of selective hydrogenation catalysis using zinc complexes.

Electromagnetic Backscattering Mechanisms of Frequency Selective Surfaces for Effective Analysis of Radar Cross Section by the First-Order Approximation of Floquet Modes

Full-wave analysis of finite but electrically large frequency selective surfaces (FSSs) substrates for the radar cross section (RCS) estimation is too time-consuming and unbearable for practical applications. Such FSS substrates can be either absorbing or reflective types and are widely used as radomes of antennas for stealth applications, where the electromagnetic (EM) backscattering is of much concern. This large EM problem is simplified by applying Floquet mode decomposition on the scattering fields, where the Kirchhoff approximation is employed to find the backscattering fields for RCS estimation. The resulted formula allows one to explore the scattering mechanism for RCS enhancement or reduction. Besides, the approximation is used to resemble the FSS radome by equivalent substrates. Thus, the transmission and reflection coefficients of the equivalent dielectric substrates are similar to those from FSS elements under an infinite array assumption. Afterward, the resulting EM problems of antenna radiations and scattering can be easily analyzed using the equivalent substrates of EM materials. Numerical examples of planar FSSs to form radomes demonstrate the feasibility of numerical simulations’ proposed work. The presented work can also be directly applied for fast analysis of EM shielding effectiveness by FSS substrates.

A general-purpose spray coating deposition software simulator

In this work the coating thickness from a high kinetic energy spray process is predicted as a function of the gun and object kinematics. The developed simulation package is capable of handling complex parts of arbitrary geometry, in the form of triangulated surfaces. Supported features include object rotation, simultaneous 5 DOF gun movement, uniform and Gaussian radial profile of spray plume intensity, identification of triangles hidden from the plume and adaptive time-stepping methods. Advanced visualization of the results is also provided. The resulting coating thickness for each elementary triangle on the surface of an object is computed from interpolated look-up tables that contain coating parameter information such as the impact angle, stand-off distance and spot surface speed. The accuracy of the simulator is validated by comparing the predicted coating thickness with experimental measurements on equivalent and representative substrates.

The impact of mixtures of xylose and glucose on the microbial diversity and fermentative metabolism of sequencing-batch or continuous enrichment cultures.

Efficient industrial fermentation of lignocellulosic waste containing a large part of glucose and xylose is desirable to implement a circular economy. Mixed culture biotechnologies can aid in realizing this goal. The effect of feeding equivalent substrates to a microbial community, such a xylose and glucose, is not well understood in terms of the number of dominant species and how these species compete for the substrates. We compared the metabolism and microbial community structure in a continuous-flow stirred tank reactor (CSTR) and a sequencing batch reactor (SBR) fed with a mixture of xylose and glucose, inoculated with bovine rumen at pH 8, 30°C and a hydraulic retention time of 8 h. We hypothesised that a CSTR will select for generalist species, taking up both substrates. We used 16S rRNA gene sequencing and fluorescent in situ hybridisation to accurately determine the microbial community structures. Both enrichments were stoichiometrically and kinetically characterised. The CSTR enrichment culture was dominated by Clostridium intestinale (91% ± 2%). The SBR showed an abundance of Enterobacteriaceae (75% ± 8%), dominated by Citrobacter freundii and a minor fraction of Raoultella ornithinolytica. C. freundii ferments xylose and glucose in a non-diauxic fashion. Clearly, a non-diauxic generalist outcompetes specialists and diauxic generalists in SBR environments.

Markov chain approach to anomalous diffusion on Newman–Watts networks

A Markov chain (MC) formalism is used to investigate the mean-square displacement (MSD) of a random walker on Newman–Watts networks. It leads to a precise analysis of the conditions for the emergence of anomalous sub- or super-diffusive regimes in such random media. Whereas results provided by most numerical approaches used so far base their results on the computation of a large number of independent runs over many equivalent substrates, the MC framework is applied only once to each equivalent sample. Starting from the simple cycle graph with 2k nearest neighbor connections, for which exact MSD expressions within the MC formalism can be derived, the randomness and complexity of the substrate is easily controlled by the number x of added links. Results for different values of k, x, and the number N of nodes make it possible to distinguish actual anomalous regimes from transient behavior and finite size effects. Albeit the high computing cost restricts the size of our networks to nodes, our very precise results justify a new and more comprehensive scaling ansatz for the walker dynamics, from which the behavior for very large networks can be derived.

Nonenzymatic release of N7-methylguanine channels repair of abasic sites into an AP endonuclease-independent pathway in Arabidopsis.

Abasic (apurinic/apyrimidinic, AP) sites in DNA arise from spontaneous base loss or by enzymatic removal during base excision repair. It is commonly accepted that both classes of AP site have analogous biochemical properties and are equivalent substrates for AP endonucleases and AP lyases, although the relative roles of these two types of enzymes are not well understood. We provide here genetic and biochemical evidence that, in Arabidopsis, AP sites generated by spontaneous loss of N7-methylguanine (N7-meG) are exclusively repaired through an AP endonuclease-independent pathway initiated by FPG, a bifunctional DNA glycosylase with AP lyase activity. Abasic site incision catalyzed by FPG generates a single-nucleotide gap with a 3'-phosphate terminus that is processed by the DNA 3'-phosphatase ZDP before repair is completed. We further show that the major AP endonuclease in Arabidopsis (ARP) incises AP sites generated by enzymatic N7-meG excision but, unexpectedly, not those resulting from spontaneous N7-meG loss. These findings, which reveal previously undetected differences between products of enzymatic and nonenzymatic base release, may shed light on the evolution and biological roles of AP endonucleases and AP lyases.

Remarkable Reactivity Differences between Glucosides with Identical Leaving Groups.

Two isomeric aryl 2-deoxy-2-fluoro-β-glucosides react with a β-glucosidase at rates differing by 106-fold, despite the fact that they release the same aromatic aglycone. In contrast, the equivalent glucoside substrates react with essentially identical rate constants. Insight into the source of these surprising rate differences was obtained through a comprehensive study of the nonenzymatic (spontaneous) hydrolysis of these same substrates, wherein an approximate 105-fold difference in rates was measured, clarifying that the differences were inherent rather than being due to specific interactions with the enzyme. The possibility that an alternate nucleophilic aryl substitution mechanism was responsible for the rapid reaction of the faster substrate was excluded through 18O-labeling studies. Further exploration of the origins of these rate differences involved analysis of X-ray crystal structures as well as quantum chemical calculations, which surprisingly revealed that ground state destabilization and transition state stabilizing effects contribute almost equally to the observed reactivity differences. These studies highlight the dangers of using simple reference equilibria such as pKa values as measures of leaving group ability.

Synthesis and hyperpolarisation of eNOS substrates for quantification of NO production by 1H NMR spectroscopy

Hyperpolarization enhances the intensity of the NMR signals of a molecule, whose in vivo metabolic fate can be monitored by MRI with higher sensitivity. SABRE is a hyperpolarization technique that could potentially be used to image nitric oxide (NO) production in vivo. This would be very important, because NO dysregulation is involved in several pathologies, including cardiovascular ones. The nitric oxide synthase (NOS) pathway leads to NO production via conversion of l-arginine into l-citrulline. NO is a free radical gas with a short half-life in vivo (≈5s), therefore direct NO quantification is challenging. An indirect method – based on quantifying conversion of an l-Arg- to l-Cit-derivative by 1H NMR spectroscopy – is herein proposed. A small library of pyridyl containing l-Arg derivatives was designed and synthesised. In vitro tests showed that compounds 4a–j and 11a–c were better or equivalent substrates for the eNOS enzyme (NO2− production=19–46μM) than native l-Arg (NO2− production=25μM). Enzymatic conversion of l-Arg to l-Cit derivatives could be monitored by 1H NMR. The maximum hyperpolarization achieved by SABRE reached 870-fold NMR signal enhancement, which opens up exciting future perspectives of using these molecules as hyperpolarized MRI tracers in vivo.

Substrate concentration dependence of voltage and power production characteristics in two-chambered mediator-less microbial fuel cells with acetate and peptone substrates.

Power production characteristics and substrate concentration dependence of voltage have been investigated together with the determination of kinetic constants in two-chambered mediator-less microbial fuel cells (MFC) for acetate and peptone substrates. At 500 mg DOC l-1 (dissolved organic carbon), power densities normalized to the anode surface of 112 mW m-2 with acetate and 114 mW m-2 with peptone as electron donor were attained by applying cathodes with a Pt catalyst layer. Related anode surface specific substrate removal rate was 44 g DOC m-2 h-1 for acetate and 52gDOCm-2h-1 for peptone. Substrate concentration dependency of the voltage suggests Monod-like kinetics with extremely low, <1 mg DOC l-1, half saturation constants and with final DOC concentrations of 6-10 mg l-1. Acetate and peptone are equivalent substrates for the exoelectrogenic bacteria both from the point of view of biodegradation kinetics and power production characteristics.

Studying the role of surface chemistry on polyelectrolyte adsorption using gold-thiol self-assembled monolayer with optical reflectivity.

Self-assembled monolayers of thiols on gold are employed to study the role of surface chemistry on adsorption of polyelectrolytes to solid substrates. The suitability of these substrates is demonstrated in optical reflectivity, which combines high sensitivity to the possibility to precisely control the hydrodynamic conditions at the solid/water interface. Therefore, this system allows the determination of both the adsorbed amount and the kinetics of adsorption. The behavior of two representative strong polyelectrolytes of opposite charge is discussed as a function of pH and of concentration of a monovalent electrolyte in aqueous solutions. The application of equivalent substrates with varying surface chemistry sheds light on the role of different energetic contributions driving polyelectrolyte adsorption.

Strip-Width and Slot-Gap Dependent Equivalent Isotropic Substrate and Dispersion Characteristics of Asymmetric Coplanar Waveguide, Symmetric Coplanar Waveguide and Micro-Coplanar Strip Line on Anisotropic Substrates

In this paper, we reformulate the quasi-static spectral-domain approach, using the partial capacitance method (PCM), to compute the W/h and S/h dependent equivalent isotropic substrates corresponding to the anisotropic substrate asymmetric coplanar waveguide (ACPW), coplanar waveguide (CPW), micro-coplanar strip line (MCS), and microstrip line. We have used the closed-form dispersion relations over equivalent substrates to obtain the dispersion in these line structures. For this purpose, the ACPW and MCS structures are converted to the equivalent symmetrical CPW and the available closed-form dispersion model for the CPW is adapted to the ACPW and MCS structures. The dispersion results for these lines are compared against the results of the HFSS with average deviations in the range of 1%-4%. We get nearly the same range of deviations in the results of HFSS against the experimental results on the isotropic substrates.

Tuning tRNA Sequences for Optimal Translation

The approximately 50 different bacterial tRNAs are structurally quite diverse despite acting as fairly equivalent substrates of the ribosome. We hypothesize that much of this structural diversity has evolved to compensate for the differing physical properties of the esterified amino acid and the codon‐anticodon interaction such that each tRNA can function with similar rate and accuracy. Interestingly, the sequences of tRNAs possessing the same anticodon are also highly diverse among different bacteria suggesting that multiple evolutionary “solutions” are available to optimize tRNA function. Our progress in understanding how the sequences of tRNAs are “tuned” in translation will focus on their interaction with EF‐Tu on and off the ribosome and their ability to efficiently decode the correct codon while avoiding incorporation at incorrect codons.

ChemInform Abstract: Synthesis of Allylic and Homoallylic Alcohols from Unsaturated Cyclic Ethers Using a Mild and Selective C—O Reduction Approach.

Unsaturated cyclic ethers can be mildly and selectively reduced with catalytic amounts of B(C6F5)3 in the presence of an alkylsilane. The allylic position is preferentially reduced with minimal or no scrambling of olefin geometry. For electronically equivalent substrates, steric factors guide the reducing agent to the least substituted site.

Synthesis of allylic and homoallylic alcohols from unsaturated cyclic ethers using a mild and selective C–O reduction approach

Unsaturated cyclic ethers can be mildly and selectively reduced with catalytic amounts of B(C(6)F(5))(3) in the presence of an alkylsilane. The allylic position is preferentially reduced with minimal or no scrambling of olefin geometry. For electronically equivalent substrates, steric factors guide the reducing agent to the least substituted site.

Substrate-Specific Kinetics of Dicer-Catalyzed RNA Processing

The specialized ribonuclease Dicer plays a central role in eukaryotic gene expression by producing small regulatory RNAs—microRNAs (miRNAs) and short interfering RNAs (siRNAs)—from larger double-stranded RNA (dsRNA) substrates. Although Dicer will cleave both imperfectly base-paired hairpin structures (pre-miRNAs) and perfect duplexes (pre-siRNAs) in vitro, it has not been clear whether these are mechanistically equivalent substrates and how dsRNA binding proteins such as trans-activation response (TAR) RNA binding protein (TRBP) influence substrate selection and RNA processing efficiency. We show here that human Dicer is much faster at processing a pre-miRNA substrate compared to a pre-siRNA substrate under both single and multiple turnover conditions. Maximal cleavage rates ( V max) calculated by Michaelis–Menten analysis differed by more than 100-fold under multiple turnover conditions. TRBP was found to enhance dicing of both substrates to similar extents, and this stimulation required the two N-terminal dsRNA binding domains of TRBP. These results demonstrate that multiple factors influence dicing kinetics. While TRBP stimulates dicing by enhancing the stability of Dicer–substrate complexes, Dicer itself generates product RNAs at rates determined at least in part by the structural properties of the substrate.

Invasion by native tree species prevents biotic homogenization in novel forests of Puerto Rico

There is concern that secondary forests dominated by introduced species, known as novel forests, increase taxonomical similarity between localities and lead to biotic homogenization in human-dominated landscapes. In Puerto Rico, agricultural abandonment has given way to novel forests dominated by the introduced African tulip tree Spathodea campanulata Beauv. (Bignoniaceae). In this study, I characterized the tree species composition of S. campanulata forests in Puerto Rico as means to evaluate if biotic homogenization is occurring. Non-metric multidimensional scaling was used to examine what variables were related to the large (≥10 cm diameter at breast height [DBH]), small (≥2.5 to <10 cm DBH), and juvenile (<2.5 cm DBH) tree species composition of 20 sites. Species composition was strongly related to substrate properties, less related to land use history, and unrelated to spatial attributes. The introduced species component was low (mean = 17%, S.E. = 1.8) and compositional differences were mostly due to native tree species of secondary to old growth forests on equivalent substrates. Animals appear to disperse most species (86%) into these forests yet because of this some introduced species will persist. Although uncommon species were largely absent, recent species establishment is shaped by substrate properties making biotic homogenization in these forests unlikely. The S. campanulata forests of Puerto Rico facilitate native tree species establishment in lands where poor management practices extirpated the original forest. These results highlight the importance of remnant old growth forests or trees that act as seed dispersal sources and facilitate native species recovery in novel forests.

Physical Properties of Ground Parboiled Fresh Rice Hulls Used as a Horticultural Root Substrate

Fresh parboiled rice hulls ground in a hammer mill and screened through a 1.18-mm screen and collected on a 0.18-mm screen (RH3) and particles with a specific diameter of 0.5 to 1.0 mm had total pore space (TPS), air-filled pore space (AFP), and water-holding capacity (WHC) similar to that of Canadian sphagnum peat (peat). However, RH3 had more available water, a higher bulk density (BD), and a higher particle density (PD) than peat. When blended with 20% to 40% perlite or 1 cm aged pine bark, RH3-based substrates had lower TPS, similar AFP, and lower WHC than equivalent peat-based substrates. The RH3-containing substrates had higher BD and average PD than equivalent peat-based substrates. When blended with parboiled rice hulls (PBH), RH3-based substrates had lower TPS than equivalent peat-based substrates. When blended with 20% to 40% PBH, RH3-based substrates had lower AFP than equivalent peat-based substrates. RH3-based substrates containing up to 20% PBH had lower WHC than equivalent peat-based substrates. RH3-based substrates containing 40% PBH had a higher WHC than equivalent peat-based substrates. When blended with PBH, all RH3-based substrates had higher BD and average PD than equivalent peat-based substrates. The addition of 40% RH3 to a peat-based substrate containing 20% perlite decreased substrate TPS, whereas the addition of 10% to 40% decreased AFP. The addition of 10% to 30% RH3 increased WHC. The addition of 30% RH3 to a peat-based substrate containing 20% 1 cm aged pine bark decreased substrate TPS and the addition of 20% to 40% RH3 decreased AFP. The addition of 10% RH3 increased WHC, but the addition of 20% or more RH3 did not affect WHC. The addition of 30% RH3 increased the BD, but the addition of RH3 had no effect on average PD. The addition of 20% or more and 30% or more RH3 to a peat-based substrate containing 20% PBH decreased substrate TPS and AFP, respectively. The addition 20% RH3 decreased WHC. The addition of 10% to 40% RH3 increased BD. Overall, RH3 was the ground rice hull product that had physical properties most similar to peat. Peat-based substrates in which up to 40% of the peat was replaced with RH3 had physical properties that, although different from peat controls, were within commonly recommended ranges for substrates used to grow greenhouse crops.

Structure and species composition of novel forests dominated by an introduced species in northcentral Puerto Rico

The African tulip tree, Spathodea campanulata Beauv., is an introduced species forming novel forest types in Puerto Rico. These forests develop naturally after deforestation, agricultural use and land abandonment, and there are many questions as to their ecological characteristics. We sampled structure and species composition of large, small, and juvenile trees (≥10, ≥2.5 to <10, and <2.5 cm diameter at breast height, respectively) in nine secondary forests dominated by S. campanulata on alluvial, karst, and volcanic substrates in northcentral Puerto Rico. No differences were found in S. campanulata forest structure between substrates. Of a total of 79 species found, 17 were introduced. Forests on karst and alluvium had the highest and lowest global species richness, respectively. Species richness increased from large to small to juvenile trees in most sites, but more so on karst. The percentage of introduced species was inversely related to species richness of tree size classes on all substrate types. The dominance of S. campanulata in the large tree size class was highest and lowest in alluvial and volcanic sites, respectively, and decreased from large to small to juvenile trees on all substrate types. Species richness of S. campanulata forests is lower than that of native forests on equivalent substrates. Although land use history affects composition, the juvenile tree species established in S. campanulata forests seems to correspond to the geological substrate were sites are found. This study shows S. campanulata restores forest structure and native tree species on abandoned agriculture and grazing lands in Puerto Rico. Management of these novel forests should consider them as resources were natural processes have the potential of making them more diverse.