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In this paper, we present a new complete and constructive characterization of all the stabilizing regions in the PID gain space. It is based on D-partition theory and the fact that for a given proportional gain $k_{p}$ the stability boundaries in the plane of integral and derivative gains are all straight lines. Actually, we present the notion of the critical $k_{p}$ point, which is defined in the sense that the topology of the D-partition of $(k_{i},k_{d})$ plane can change when the $k_{p}$ crosses a critical $k_{p}$ point. Moreover, we identify seven types of critical $k_{p}$ points and provide formulas for their computation. With the availability of all critical $k_{p}$ points, the stabilizing $k_{p}$ intervals can be exhaustively and exactly determined. By sweeping the $k_{p}$ parameter over the stabilizing $k_{p}$ intervals, the whole set of stabilizing PID controllers for a given plant is created. In addition, it allows for an efficient test of the existence of a stabilizing PID controller set without sweeping the $k_{p}$ parameter. To validate the newly presented analytical and constructive characterization of stabilizing PID controller sets and demonstrate the existence of seven types of critical $k_{p}$ points, five examples are provided.

The resultant-based frequency-sweeping approach is appealing for creating a stability map to study stability robustness against delay uncertainties. It relies on converting the system’s transcendental characteristic function into a polynomial form such that the crossing frequency set and the corresponding stability switching curves in the delay parameter plane can be exactly and exhaustively determined using only algebraic computations. In the existing literature, the equation conversion has been achieved by using Rekasius substitution, bilinear substitution, or half-angle tangent substitution, and variable eliminations are carried out by using Sylvester resultant or Dixon resultant. In this paper, we first point out that since the computation of Dixon resultant involves a polynomial division, it could be beneficial in a symbolic programming environment. Then, we provide numerical evidence to compare the computational complexity of using different equation conversion methods and the subsequent resultant elimination to obtain the critical crossing frequencies from which the exact crossing frequency set can be determined. Next, based on the resultant theory, we reveal the roles of the critical crossing frequencies that play in the characterization of the delay map. Finally, we provide an efficient procedure for constructing stability charts in the delay parameter plane for linear time-invariant systems with two delays in states. To demonstrate our contributions, explanatory examples are provided along with a complete illustrative example.

This paper is focused on the retrofitting techniques of Zuo-Dou connections in Dieh-Dou timber frames in Far East Asia. The target is to develop appropriate techniques for the reinforcement and maintenance of the wooden cultural heritage. A series of full-scale tests are intended for the evaluation of the rotational and shear characteristics of the various retrofitting techniques for the Zuo-Dou joints. These retrofitting techniques are conceived by this study based on the principles of the conservation of cultural heritage. The reversible materials, invisible layouts, and structurally efficient schemes are taken into account to figure out the reinforcement strategies. Regarding the conservation targets, this study applies the self-tapping screw (STS) and the bamboo nail for reinforcement. Corresponding to the loading circumstances, moment- and shear-constraining schemes are developed. The STS and the bamboo nail are applied by means of moment- or shear-constraining strategies. Then, rotational and shear tests are carried out to estimate the structural efficiency of the conceived retrofitting techniques. With the appropriate schemes, the STS and the bamboo nail contribute to the enhancement of the structural performance of the Zuo-Dou connection. The STS in a moment-constraining profile can ameliorate the Zuo-Dou’s rotational behaviour. As far as post retrofitting and preventing reinforcing are concerned, the STS reveals considerable structural efficiency. The bamboo nail in a shear-constraining scheme can increase the shear capacity of the Zuo-Dou joint. Besides the quantitative outcomes, these retrofitting techniques exhibit ductility and enhance the deformation processes of the connections. With the alternative fasteners, the slump or vibration during the deformation becomes moderate and the severe damages, such as rocking or block shear failure, are alleviated. The techniques and associated materials used in this study exhibit compatibility and feasibility for constraining the rotation, deformation, and crack of the Zuo-Dou connection. These effects are helpful for retaining the joints’ structural behaviour and contribute to the conservation of traditional timber constructions.

Methane-producing archaea and methylotrophic bacteria use tetrahydromethanopterin (H4MPT) and/or tetrahydrofolate (H4F) as coenzymes in one-carbon (C1) transfer pathways. The α-proteobacterium Methylobacterium extorquens AM1 contains a dihydromethanopterin reductase (DmrA) and two annotated dihydrofolate reductases (DfrA and DfrB). DmrA has been shown to catalyze the final step of H4MPT biosynthesis; however, the functions of DfrA and DfrB have not been examined biochemically. Moreover, sequence alignment (BLAST) searches have recognized scores of proteins that share up to 99% identity with DmrA but are annotated as diacylglycerol kinases (DAGK). In this work, we used bioinformatics and enzyme assays to provide insight into the phylogeny and substrate specificity of selected Dfr and DmrA homologs. In a phylogenetic tree, DmrA and homologs annotated as DAGKs grouped together in one clade. Purified histidine-tagged versions of the annotated DAGKs from Hyphomicrobium nitrativorans and M. nodulans (respectively, sharing 69 and 84% identity with DmrA) showed only low activity in phosphorylating 1,2-dihexanoyl-sn-glycerol when compared with a commercial DAGK from Escherichia coli. However, the annotated DAGKs successfully reduced a dihydromethanopterin analog (dihydrosarcinapterin, H2SPT) with kinetic values similar to those determined for M. extorquens AM1 DmrA. DfrA and DfrB showed little or no ability to reduce H2SPT under the conditions studied; however, both catalyzed the NADPH-dependent reduction of dihydrofolate. These results provide the first evidence that DfrA and DfrB function as authentic dihydrofolate reductases, while DAGKs with greater than 69% identity to DmrA may be misannotated and are likely to function in H4MPT biosynthesis.

In this paper, we propose a recessed-gate tunneling field-effect transistor (TFET) to improve the on current of TFETs by increasing the tunnel area with line tunneling. We investigate the effects of the recessed-body thickness and the doping level on the device performance. For optimal device structures, our proposedn-TFET reaches 1.44 x 10-6 A/µm of on current and 3.22 x 109 ON/OFF current ratio. A minimum subthreshold swing SSmin = 28.3 mV/dec and an average swing SSavg = 59.8 mV/dec over seven orders of drain current are achieved. In addition, complementary TFET inverters showgood noisemargins of NMH = 65 mV (38.5 % VDD) and NML = 77 mV (32.5 % VDD) and also a high voltage gain even at VDD = 0.2 V. [ABSTRACT FROM AUTHOR]

In this study, solid-liquid equilibria of dicarboxylic acids for binary mixtures, hexanedioic acid (1) + octanedioic acid (2) (eutectic temperature T E = 390.54 K, eutectic composition x 1E = 0.419); hexanedioic acid (1) + nonanedioic acid (2) (T E = 372.52 K, x 1E = 0.269); hexanedioic acid (1) + decanedioic acid (2) (T E = 387.43 K, x 1E = 0.514); heptanedioic acid (1) + octanedioic acid (2) (T E = 365.81 K, x 1E = 0.782); heptanedioic acid (1) + nonanedioic acid (2) (T E = 352.50 K, x 1E = 0.558); heptanedioic acid (1) + decanedioic acid (2) (T E = 367.07 K, x 1E = 0.753); octanedioic acid (1) + decanedioic acid (2) (T E = 387.97 K, x 1E = 0.465); nonanedioic acid (1) + octanedioic acid (2) (T E = 367.62 K, x 1E = 0.712); and nonanedioic acid (1) + decanedioic acid (2) (T E = 370.49 K, x 1E = 0.687), are measured using differential scanning calorimetry and correlated using Clarke-Glew equation. An observation here is simple eutectic phase diagrams for these systems. It can be noted that experiment results, correlated with Wilson and nonrandom two-liquid activity coefficient models, are highly satisfactory. [ABSTRACT FROM AUTHOR]

This research focuses on measuring the solubility of three antioxidants--ethylenediaminetetraacetic acid disodium salt hydrate, ethylenediaminetetraacetic acid calcium disodium salt hydrate, and L-cysteine hydrochloride--in supercritical carbon dioxide. Using a semiflow apparatus, the experiment takes data at 308.15, 313.15, and 318.15 K with pressure ranging from 10 to 22 MPa (for ethylenediaminetetraacetic acid disodium salt dihydrate) or from 12 to 24 MPa (for ethylenediaminetetraacetic acid calcium disodium salt hydrate and L-cysteine hydrochloride). Two semiempirical equations--one proposed by Chrastil, the other Mendez-Santiago and Teja--are applied to find the correlated relationship of the experimental data. With the choice of fitted parameters, the correlation derived from the two equations are satisfactory: the average absolute relative deviation is under 5.1%. [ABSTRACT FROM AUTHOR]

In this research, the solubility of sodium l-ascorbate and that of sodium erythorbate monohydrate, both being antioxidants, in supercritical carbon dioxide are measured. Using semiflow type equipment, this experiment gathers the data of solubility for antioxidnats at (308.15, 313.15, and 318.15) K, over a range of pressures from (12 to 24) MPa. The data gleaned from the experiment are forward numerically processed, with the use of the semiempirical equations presented by Chrastil and by Mendez-Santiago and Teja, to make clear the correlation among various characteristics. The final results are satisfactory: when parameters with optimal fitting are picked to examine the correlation, the average absolute relative deviation (AARD) is under 4%. [ABSTRACT FROM AUTHOR]

Solid−liquid equilibria for three organic binary mixtures of hexanedioic acid (1) + benzoic acid (2) (eutectic temperature TE= 378.17 K, eutectic composition x1E= 0.249), benzoic acid (1) + pentanedioic acid (2) (TE= 343.50 K, x1E= 0.402), and hexanedioic acid (1) + pentanedioic acid (2) (TE= 355.87 K, x1E= 0.205) were measured using differential scanning calorimetry (DSC). Simple eutectic behaviors for these systems were observed. The experimental results were correlated using the Wilson and nonrandom two-liquid (NRTL) activity coefficient models with satisfactory results. [ABSTRACT FROM AUTHOR]

Most RNA viruses encode their own RNA polymerases for genome replication, and increasing numbers of them appear to be capable of undergoing RNA recombination. Here, we provide the first report of intergenotypic recombination in hepatitis delta virus (HDV), the only animal RNA virus that requires host RNA polymerase(s) for viral replication. In vivo, we analyzed RNA species derived from the serum of a patient with mixed genotype I and genotype IIb HDV infection by using multiple restriction fragment length polymorphism (RFLP) assays and sequence analysis of cloned reverse transcription (RT)-PCR products. Six HDV recombinants were isolated from 101 tested clones, and HDV recombination in this patient was further confirmed by RT-PCR with genotype-specific primer pairs. Analysis of the recombination junctions suggested that the HDV genome rearrangement occurred through faithful homologous recombination. We then used an RNA cotransfection cell culture system to investigate HDV RNA recombination in vitro. We found that HDV recombinants could indeed be detected in the transfected cells; some of these possessed recombination junctions identical to those identified in vivo. Furthermore, using a PCR-independent RNase protection assay, we were able to readily identify the recombined HDV RNA species in cultured cells. Taken together, our results demonstrate that HDV RNA recombination occurs in both natural HDV infections and cultured cells, thereby presenting a novel mechanism for HDV evolution. [ABSTRACT FROM AUTHOR]

Dihydromethanopterin reductase (Dmr) is a redox enzyme that plays a key role in generating tetrahydromethanopterin (H4MPT) for use in one-carbon metabolism by archaea and some bacteria. DmrB is a bacterial enzyme understood to reduce dihydromethanopterin (H2MPT) to H4MPT using flavins as the source of reducing equivalents, but the mechanistic details have not been elucidated previously. Here we report the crystal structure of DmrB from Burkholderia xenovorans at a resolution of 1.9 Å. Unexpectedly, the biological unit is a 24-mer composed of eight homotrimers located at the corners of a cubic cage-like structure. Within a homotrimer, each monomer-monomer interface exhibits an active site with two adjacently bound flavin mononucleotide (FMN) ligands, one deeply buried and tightly bound and one more peripheral, for a total of 48 ligands in the biological unit. Computational docking suggested that the peripheral site could bind either the observed FMN (the electron donor for the overall reaction) or the pterin, H2MPT (the electron acceptor for the overall reaction), in configurations ideal for electron transfer to and from the tightly bound FMN. On this basis, we propose that DmrB uses a ping-pong mechanism to transfer reducing equivalents from FMN to the pterin substrate. Sequence comparisons suggested that the catalytic mechanism is conserved among the bacterial homologs of DmrB and partially conserved in archaeal homologs, where an alternate electron donor is likely used. In addition to the mechanistic revelations, the structure of DmrB could help guide the development of anti-obesity drugs based on modification of the ecology of the human gut. [ABSTRACT FROM AUTHOR]