HP Series Research Articles

Effects of Hexagonal Boron Nitride and Mesoporous Silica Nanoparticles on the Morphology, Mechanical Properties and Antimicrobial Activity of Dental Composites

Hexagonal boron nitride (HBN), an artificial material with unique properties, is used in many industries. This article focuses on the extent to which hexagonal boron nitride and silica nanoparticles (MSN) affect the physicochemical and mechanical properties and antimicrobial activity of prepared dental composites. In this study, HBN, and MSN were used as additives in dental composites. 5% and 10% by weight of HBN are added to the structure of the composite materials. FTIR analysis were performed to determine the components of the produced boron nitride powders, hexagonal boron nitride-containing composites, and filling material applications. The structural and microstructural properties of dental composites have been extensively characterized using X-ray diffractometry (XRD). Surface morphology and distributions of nano boron nitride were determined by scanning electron microscopy (SEM)-EDS. In addition, the solubility of dental composites in water and their stability in water and chemical solution (Fenton) were determined by three repetitive experiments. Finally, the antimicrobial activity of dental composites was detected by using Minimum Inhibitory Concentration (MIC) measurement, as well as Minimum Fungicidal Concentration (MFC) method against yeast strain Saccharomyces cerevisiae, and Minimum Bactericidal Concentration (MBC) method against bacteria strains, Staphylococcus aureus and Escherichia coli. Since the HMP series have better antimicrobial activity than the HP series, they are more suitable for preventing dental caries and for long-term use of dental composites. In addition, when HMP and HP series added to the composite are compared, HMP-containing dental composites have better physicochemical and mechanical properties and therefore have a high potential for commercialization.

Application of magnetic analyzers for detecting carburization of pyrolysis furnace tubes

Ethylene pyrolysis furnace is a key equipment in the ethylene production industry with the pyrolysis furnace tube being the core component of the system. The tube operates at high temperature (950°C–1,100°C) and hydrocarbon medium for a long time, and the Cr35Ni45Nb centrifugal casting alloy material is often chosen as the material of the tube. Due to its harsh working conditions, its common failure issues include carburization, high-temperature creep cracking, thermal shock and thermal fatigue, overheating, creep expansion, bending, etc. Among them, carburization is the main cause of furnace tube failure. In this work, based on the characteristics of HP series (ASTM HP grade) furnace tube material, which is transformed from paramagnetic material to ferromagnetic material following carburization, the cracking furnace tube with different carburization layer thickness has been prepared, and the coercivity of furnace tube with different thickness of carburization layer is tested by magnetic analyzer. The relationship curve between carburization layer thickness and coercivity is subsequently studied to find a means to test the carburization layer thickness in engineering. By fitting the experimental data, the fitting rate reached 97%, which in turn verified the validity and accuracy of the method.

Estudio de las propiedades al creep en aceros termorresistentes

Cuando los componentes de una planta industrial se encuentran sometidos a condiciones severas de temperatura y esfuerzos mecánicos, sufren una deformación plástica que continua a lo largo del tiempo. Este proceso, denominado termofluencia (creep), se presenta en industrias petroquímicas, plantas generadoras de energía y refinerías de petróleo, donde sus componentes son utilizados durante largos períodos de tiempo y expuestos a condiciones severas de servicio.El objetivo de esta tesis es estudiar el comportamiento al creep de aceros ferríticos (1Cr 0.5Mo, 2.25 Cr 1 Mo y 5Cr 0.5 Mo), y aleaciones base níquel ((Incoloy 800 (30 Ni – 20 Cr), Inconel 601 (60 Ni – 25 Cr) y aceros de la serie HP (25 Cr – 35 Ni) que poseen, alta resistencia termomecánica asociada a la microestructura interna de la matriz. Se analiza la variación de los parámetros característicos al creep, tales como la energía de activación y el coeficiente de tensión, relacionados con la velocidad de deformación, la tensión aplicada y la temperatura; simultáneamente se caracteriza la evolución microestructural, en las condiciones de temperatura y tiempo similares a los ensayos. En forma experimental, mediante ensayos de creep, se reproducirán condiciones de ensayo en el laboratorio, de características similares a las de operación en servicio. Las curvas experimentales obtenidas de esta forma, nos van a permitir conocer la variación de las propiedades físicas y mecánicas; estudiar los mecanismos responsables del fenómeno y describir parámetros que estén vinculados con la resistencia mecánica del material.

INSIGHT TO THE MICROSTRUCTURE CHARACTERIZATION OF A HP AUSTENITIC HEAT RESISTANT STEEL AFTER LONG-TERM SERVICE EXPOSURE

Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used in high temperature structural applications. Their composition include Nb as strong carbide former. Electron Backscatter Diffraction (EBSD) investigations revealed that, in the as-cast condition, alloys exhibit austenitic matrix with intergranular primary carbides such as MC, M23C6 and/or M7C3. During exposure at a high temperature, phase transformations occurred: chromium carbides of M7C3 type transform into the more stable M23C6 type, intergranular M23C6 carbides precipitate, and Lave phase due to increase of Niobium activity with temperature increase, as thermodynamic simulation confirmed. Therefore, combination of EBSD-EDS technique with thermodynamic calculation is one of the novel and most accurate method to investigation of phase transformation, as the precipitations are identified on the basis of their crystal structure, chemical composition and their thermodynamic features.

Microstructural evolution of a modified HP alloy: experimental and complementary computational study

In this work is presented results of the microstructural characterization of austenitic stainless steel (HP series) modified with Nb, aged at temperatures of 750, 800, 850, 900 and 950oC in air at different times. Microstructural changes were analyzed using optical microscopy, scanning electron microscopy (SEM) equipped with (EDS), x-ray diffraction and Vickers hardness. In the as-cast condition, the microstructure consists of an austenitic matrix and eutectic carbides network, Cr, Nb-rich carbides. The Cr-rich carbides are M7C3 type, whereas, those rich in Nb are NbC. During aging, there is a second precipitation in the matrix of very fine needle form of M23C6 carbides, which leads to an increase in hardness. After that, the decreasing in hardness is associated with a coalescence phenomenon of the secondary precipitates. Computational modeling shows that M23C6 is lesser stable than M7C3 carbide.

Non-crystallographic symmetry of liquid metal, flat crystallographic faults and polymorph transformation of the M7C3 carbide.

The fine lamellar fault structure of primary M7C3 carbide particles in the heat-resistant Fe-Cr-Ni-C alloy of the HP series (0.45C-25Cr-35Ni) in the cast condition has been revealed using transmission electron microscopy. The lamellar fault structure is regarded as an inheritance of the initial melt structure. A one-to-one correspondence between the crystal structures of M7C3, M5C2, M3C and M23C6 carbides and constructions of the projective 103 Desargues configuration and its subconfigurations is shown. Mutual mapping between 103 Desargues subconfigurations determines transformations of the ten-vertex equal-edged triangulated clusters appearing as building units of these carbides.

Optimizing Performance of SABC Comminution Circuit of the Wushan Porphyry Copper Mine—A Practical Approach

This research is focused on the Phase I SABC milling circuit of the Wushan porphyry copper mine. Improvements to the existing circuit were targeted without any significant alterations to existing equipment or the SABC circuit. JKSimMet simulations were used to test various operating and design conditions to improve the comminution process. Modifications to the SABC comminution circuit included an increase in the SAG mill ball charge from 8% to 10% v/v; an increase in the mill ball charge from 23% v/v to 27% v/v; an increase in the maximum operating power draw in the ball mill to 5800 kW; the replacement of the HP Series pebble crusher with a TC84 crusher; and the addition of a pebble bin. Following these improvements, an increase in circuit throughput, a reduction in energy consumption, and an increase in profitability were obtained.

Kinetics of the Formation of Intermetallic Phases in HP-Type Heat-Resistant Alloys at Long-Term High-Temperature Exposure

The kinetics of formation and morphology of the intermetallic phases in the structure of heat-resistant as-cast HP40NbTi alloys in the course of long high-temperature exposure have been studied with the help of light and electron microscopy, electron microprobe, and X-ray diffraction. During exposure of 2 to 1000 hours at 1423 K (1150 °C), intermetallic phase with conditional formula Cr7Ni5Si3N3FeNb is formed in the alloy. The analysis of the kinetics of intermetallic phase’s growth for an impact assessment of certain metal substitutional elements (niobium, chromium, silicon) on the size of the formed particles was performed. Formation and growth of the intermetallic phases with high silicon content in the alloy structure on the boundaries between niobium and chromium carbides (NbC and M23C6) and matrix γ-phase provide a diffusion barrier for oxygen in oxidizing environment. This may create partial protection against oxidation of hardening carbide phases in the structure and promote increasing of the serviceability of the HP series alloys under operating conditions in the petrochemical industry.

Experimental observation and crystallographic description of M7C3 carbide transformation in Fe–Cr–Ni–C HP type alloy

Abstract The microstructure and phase composition of the heat resistant Fe–Cr–Ni–C alloy of the HP series (0.45С–25Cr–35Ni) in the as cast condition and after holding at 1150 °C during 2–100 h have been studied with the help of light and electron microscopy, electron microprobe and X-ray diffraction. The fragmentation of the initial single crystal М7С3 carbide particles into subdomains of ∼500 nm size and a subsequent gradual transition of certain subdomains into the М23С6 carbide have been detected after 2 h holding at 1150 °C. After 100 h holding at 1150 °C, complete transition of the hexagonal eutectic carbide М7С3 into the М23С6 carbide with face-centered cubic lattice occurred as ‘in situ’ transformation process. The mechanism of the in situ transformation from М7С3 to М23С6 carbides by increasing of the metal atoms number in the carbon coordination polyhedron from six to eight has been explained within the framework of the recent combinatory model for polymorph transformations in metals (Talis and Kraposhin, 2014).

Biosynthesis of the regulatory oxysterol, 5-cholesten-3β,25-diol 3-sulfate, in hepatocytes

Cellular cholesterol homeostasis is maintained through coordinated regulation of cholesterol synthesis, degradation, and secretion. Nuclear receptors for oxygenated cholesterol derivatives (oxysterols) are known to play key roles in the regulation of cholesterol homeostasis. We recently identified a sulfated oxysterol, 5-cholesten-3beta,25-diol 3-sulfate (25HC3S), that is localized to liver nuclei. The present study reports a biosynthetic pathway for 25HC3S in hepatocytes. Assays using mitochondria isolated from rats and sterol 27-hydroxylase (Cyp27A1) gene knockout mice indicated that 25-hydroxycholesterol (25HC) is synthesized by CYP27A1. Incubation of cholesterol or 25HC with mitochondrial and cytosolic fractions in the presence of 3'-phosphoadenosyl 5'-phosphosulfate resulted in the synthesis of 25HC3S. Real-time RT-PCR and Western blot analysis showed the presence of insulin-regulated hydroxycholesterol sulfotransferase 2B1b (SULT2B1b) in hepatocytes. 25HC3S, but not 25HC, decreased SULT2B1b mRNA and protein levels. Specific small interfering RNA decreased SULT2B1b mRNA, protein, and activity levels. These findings demonstrate that mitochondria synthesize 25HC, which is subsequently 3beta-sulfated to form 25HC3S.

EBSD Phase Identification and Modeling of Precipitate Formation in HP Alloys

Heat-resistant steels of HP series (Fe-25Cr-35Ni) are used as reformer tubes in petrochemical industries. Their composition includes Nb and Ti as strong carbide formers. In the ascast condition, alloys exhibit an austenite matrix with intergranular MC, M23C6 and/or M7C3 eutectic carbides. During exposure at high temperature, phase transformations occur: chromium carbides of M7C3 type transform into the more stable M23C6 type, intragranular M23C6 carbides precipitate, and a silicide, the G-phase (Ni16Nb6Si7), forms due to the instability of MC carbides (NbC). Thermodynamic simulation is of great help for understanding precipitate formation and transformations. Thermo-Calc and Dictra are used to simulate the precipitation of carbides in the austenite matrix during service. However, from an experimental point of view, M23C6 and M7C3 are not easy to distinguish in bulk alloys. Indeed, backscattered scanning electron microscopy does not bring any contrast between the two phases, and energy dispersive spectroscopy (EDS) analysis does not lead to carbon content and consequently to the distinction between M23C6 and M7C3. With transmission electron microscopy (TEM), sample preparation is difficult and the observed area is extremely small. In the present work, HP alloys are investigated by electron backscatter diffraction (EBSD) coupled to EDS. Carbides are identified on the basis of crystal structure, in the bulk, within their microstructural context, and the experimental procedure is both simpler and cheaper than TEM. Precipitates (M23C6, M7C3) could be identified by orientation mapping and single spot analysis.

Structure and phase stability in a cast modified-HP austenite after long-term ageing

Phase transformations in a cast HP series alloy after long-term ageing were determined by analytical electron microscopy (AEM). Beyond the chromium and niobium carbides normally expected for the as-cast material, an eta phase enriched in Nb and Si is present, indicating phase instability at high temperatures (∼1000 °C).

Invited commentary

Invited commentary

Lead Tetraacetate Mediated One-Pot Multistage Transformations: Theoretical Studies on the Diverging Behavior in the Hajos−Parrish and Wieland−Miescher Series

A computational approach to the proposed mechanistic rationale of the lead tetraacetate mediated oxidative cleavage of selected unsaturated diols in the hydrindenediol (derived from the Hajos-Parrish ketone, abbreviated as HP) and octalindiol (derived from the Wieland-Miescher ketone, abbreviated as WM) series is presented. These two unexpected cascade-type transformations have been found to yield structurally different products despite the similarities in the starting compounds 1-HP and 1-WM, which differ only by the number of carbon atoms in the cycloalkane rings. The final product in the HP series is the complex ring-expanded molecule iii-6, while the final product in the WM series is the ring-expanded bisacetoxy diacetal 7. Calculations carried out at the B3LYP/6-31G level have revealed the fact that the transformations of i-6 to ii-6 and of i-7 to ii-7 are endothermic by 19.93 and 4.20 kcal/mol, respectively. The isomerization of compounds i to ii is more endothermic in the case of the HP series. Furthermore, calculations have shown the transformation of i to ii to be kinetically less favored in the HP series than in its analogue WM series. The activation barrier for the transformation of i-6 to ii-6 is calculated to be 22.09 kcal/mol, whereas the corresponding barrier in the WM series is 13.77 kcal/mol. The thermodynamic features of the reactions support the experimental findings as well: 7 is calculated to be more stable than iii-7, and iii-6 is more stable than 6, as expected. The diverging behavior in the mechanism of the interconversion of i to ii has been attributed to the stabilization of the positive charge by a carbonyl oxygen in ii-7 due to the flexibility of the seven-membered ring in contrast to the rigidity of the six-membered ring.

Vagal and cardiac reactivity to psychological stressors in trained and untrained men.

The aim of this study was to determine whether higher aerobic fitness is associated with enhanced vagal influences on the myocardium, resulting in moderation of chronotropic cardiac activity during psychological stress and recovery. Heart period (HP) and respiratory sinus arrhythmia (RSA) were obtained from 10 aerobically trained (AT) and 10 untrained (UT) college-aged men at rest and during three contiguous psychological challenges and 3 min of recovery. Ratings of perceived stress were obtained at the end of the rest period, at the midpoint of each stressor, and at 30 s into recovery. Time series methods were used to quantify RSA from the beat-to-beat HP series. Responsivity was assessed both in terms of absolute levels of activity and phasic changes in activity (task or recovery minus baseline). Both groups reported similar levels of subjective stress throughout the experiment. The AT exhibited longer HP at rest and during psychological stress and recovery than did the UT. However, the groups did not differ on RSA at rest or during psychological stress and recovery, nor did they differ on phasic changes in RSA or HP during stress or recovery. Additionally, aerobic capacity was not correlated with absolute levels or phasic changes in RSA during psychological challenge for either group and, except in Min 2 for the UT, similar results were obtained for recovery. The results supported the hypothesis that, among young men, higher aerobic fitness is associated with longer HP at rest and during psychological stress and recovery. However, the lower cardiac chronotropic activation observed among the AT relative to the UT was not paralleled by a group difference in the amplitude of RSA. These results suggest that the group difference in HP was not mediated directly by the vagal mechanisms manifested in the amplitude of RSA.

RESPIRATORY SINUS ARRHYTHMIA DURING PSYCHOLOGICAL STRESS AND RECOVERY IN AEROBICALLY TRAINED AND UNTRAINED YOUNG MEN

1434 The aim of this study was to determine if higher aerobic fitness is associated with enhanced vagal influences on the myocardium, resulting in moderation of chronotropic cardiac activity, during psychological stress and recovery. Heart period (HP, in ms) and respiratory sinus arrhythmia (RSA) were obtained from 10 aerobically trained (AT) and 10 untrained (UT) young men ( = 23 yrs) at rest and during three contiguous psychological challenges and subsequent recovery. Time series methods were used to quantify RSA from HP series; RSA (ln ms2) could range from 0 to approximately 10. Both absolute levels and changes from baseline (i.e., difference scores) were examined. The AT exhibited longer HPs at rest and during psychological stress and recovery (overall = 1008.1, SEM = 23.6) than did the UT ( = 822.2, SEM = 17.2). However, the groups did not differ on RSA (AT: overall = 6.57, SEM = 0.16; UT: = 6.54, SEM = 0.12), nor did they differ on phasic changes in RSA (AT: overall = −0.08, SEM = 0.18; UT: = −0.45, SEM = 0.12) or phasic changes in HP (AT: overall = −145.8, SEM = 19.6; UT: = −91.8, SEM = 13.7) during stress or recovery. Therefore, among young men, higher aerobic fitness was associated with lower cardiac chronotropic activation at rest and during psychological stress and recovery but not with an alteration in the vagal influences on the myocardium; nor was higher aerobic fitness associated with smaller phasic RSA and HP responses to the psychological challenges or with faster RSA and HP recovery.

Noncomplement Fixing, IgG4 Autoantibodies Predominate in Patients With Anti-Epiligrin Cicatricial Pemphigoid

This study characterized the specific reactivity, IgG subclass, and complement fixing ability of anti-laminin-5 IgG from 12 patients with anti-epiligrin cicatricial pemphigoid. Circulating IgG from all patients bound the dermal side of 1 M NaCl split skin, immunoprecipitated laminin-5 produced by biosynthetically radiolabeled human keratinocytes, and (in 10 of 12 cases) immunoblotted the laminin-alpha3 subunit. Analysis of the distribution of IgG subclasses in these patients' circulating anti-laminin-5 autoantibodies by semiquantitative indirect immunofluorescence microscopy using the HP series of subclass-specific monoclonal antibodies revealed: (i) IgG4 predominant autoantibodies in seven of 11 sera; (ii) IgG1 and IgG2 at substantially lower levels in a smaller number of sera; and (iii) no specific IgG3 anti-laminin-5 autoantibodies in any patients. The same IgG4-dominant profile of anti-laminin-5 autoantibodies was found in enzyme-linked immunosorbent assay studies of purified human laminin 5. Direct immunofluorescence microscopy of six skin biopsies from three patients found that IgG4 was also the predominant subclass of IgG in epidermal basement membranes in situ. Consistent with these findings, sera from 11 of 11 patients with anti-laminin-5 IgG autoantibodies did not fix C3 to epidermal basement membranes in vitro. These immunochemical studies suggest that complement activation does not play a major role in the pathophysiology of this disease and that subepidermal blisters in these patients may develop via a direct effect of anti-laminin-5 IgG itself.

A PARALLEL BLOCK LANCZOS ALGORITHM FOR DISTRIBUTED MEMORY ARCHITECTURES

Abstract In this paper we propose a block Lanczos algorithm suitable for MIMD distributed memory message passing architectures. It is based on an efficient parallelizaiion of basic linear algebra operations, such as matrix-matrix, sparse matrix-matrix, and dense QR factorization. We assume an unidirectional ring as connection topology and a block column wrap-around matrices distribution. We have chosen this approach to improve load-balancing, to eliminate the intersection of messages and to decrease communication The parallel Lanczos algorithm has been tested on a Convex Meta Series, a cluster of HP Series 9000 workstations running the PVM communication system. Results of the performance evaluation based on some classical parameters are shown.

Storage performance-metrics and benchmarks

The metrics and benchmarks used in storage performance evaluation are discussed. The technology trends taking place in storage systems, such as disk and tape evolution, disk arrays, and solid-state disks, are highlighted. The current popular I/O benchmarks are then described, reviewed, and run on three systems: a DECstation 5000/200 running the Sprite Operating System, a SPARCstation 1+ running SunOS, and an HP Series 700 (Model 730) running HP-UX. Two approaches to storage benchmarks-LADDIS and a self-scaling benchmark with predicted performance-are also described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

AN EXPERIMENTAL STUDY OF POST-CHF HEAT TRANSFER IN A 3x3 ROD BUNDLE

This chapter describes post-critical heat flux (CHF) heat transfer experiments in a 3×3 rod bundle. The objective of these experiments was to obtain measurements of thermodynamic nonequilibrium in the post-CHF regime and to characterize its effects on two-phase heat transfer. In boiling heat transfer systems a maximum value of heat flux called critical heat flux occurs when the heated surface can no longer support continuous liquid contact. A two-phase heat transfer loop was designed and built specifically for convective boiling heat transfer studies using steam-water mixtures. Each fuel rod simulator was equipped with 12 thermocouples such that two thermocouples were in the lower extension, one thermocouple in the upper extension and the remaining nine were in the test length. The data acquisition system consisted of a HP series 200, 9816A computer, HP 3497A Data Acquisition/Control unit and an HP34S6A Digital Voltmeter with all the devices on a single HP-IB interface bus, and a Bascom-Turner fast multichannel data recorder.