Thermal Effects in the HTBB-3200pg Furnace on Metal-Carbon Eutectic Point Implementation

The general statement that a temperature fixed-point cell will show better melting and freezing plateaux with better temperature uniformity along the dimensions of the fixed point is understood to be valid for metal-carbon (M-C) eutectics as well as for pure metal fixed points. In this article, it is shown that improved temperature uniformity in the central part of the high-temperature blackbody BB3200pg (HTBB), where the M-C fixed point is implemented, results in flatter and longer plateaux. Pyrolitic graphite rings, clamped together by a spring, form the heated cavity of the HTBB. As a first step, the relative electrical resistivity of each pyrolitic graphite ring was measured using a method advised by the furnace manufacturer. Next, the ring positions were optimized, taking into account their relative resistivities, in order to obtain a more homogeneous temperature distribution. Subsequent measurement of the temperature uniformity at the furnace walls confirmed the improvement. Measuring the melting plateaux of the Pt-C eutectic with different arrangements of the rings, and thereby operating the fixed-point cell in different temperature distributions, confirmed the influence of the temperature distribution on the plateau shape, with the best plateau shape corresponding to the most homogeneous temperature distribution.     

Carboxymethyl Cocoyam Starch: Synthesis,Characterisation and Influence of Reaction Parameters

Twenty carboxymethyl starch derivatives of cocoyam starch were synthesized under different reaction conditions. The influences of sodium hydroxide concentration, sodium monochloroacetate concentration, water, type of organic solvent, reaction time and temperature were evaluated for degree of substitution (DS) and reaction efficiency (RE). The optimal ratio of moles of NaOH per mole anhydroglucose unit (AGU), n_NaOH/n_AGU was 1.62. Increases in ratio of moles of monochloroacetate (n_SMCA) to mole of AGU (n_AGU) increased the DS progressively. The ratio of water to solvent (isopropanol, IPA) in the reaction media was optimal at H₂O/IPA 0.16. Both RE and the DS increased with increase in reaction time within the studied time range (1‐4 h). Increases in temperature enhanced both reaction efficiency and DS. Among the solvents studied, an isopropanol – water medium produced the optimal result. The starch paste clarity improved remarkably after carboxymethylation. Wide angle X‐ray diffractometry revealed that starch crystallinity was reduced after carboxymethylation. ¹³C‐NMR showed peaks at δ = 180.42 ppm, 80.35 ppm, 77.77 ppm, and 71.96 ppm, which were assigned to C‐O, substituted C‐2, C‐3 and C‐6, respectively. In addition, three signals appeared at δ = 74.16 ppm, 73.42 ppm and 72.59 ppm and they were assigned to the CH₂ in the carboxylate substituents.     

6‐Aryl and Heterocycle Quinazoline Derivatives as Potent EGFR Inhibitors with Improved Activity toward Gefitinib‐Sensitive and ‐Resistant Tumor Cell Lines

A group of novel anilinoquinazoline derivatives with variable aryl and heterocyclic substituents at position 6 were synthesized and tested for their EGFR‐inhibitory activity. Aryl and heterocyclic rings were attached to the quinazoline scaffold through different linkages such as imine, amide, and thiourea. Most of the aryl and heterocyclic derivatives showed potent inhibition of wild‐type EGFR with IC₅₀ values in the low nanomolar range. Among these, thiourea derivatives 6 a , 6 b and compound 10 b also retained significant activity toward the gefitinib‐insensitive EGFR^T790M/L858R mutant, displaying up to 24‐fold greater potency than gefitinib. In addition, cell growth inhibitory activity was tested against cancer cell lines with wild‐type (KB cells) and mutant EGFR (H1975 cells). Several compounds including 6 a were found to be more potent than the reference compound gefitinib toward both cell lines, as was the case for compound 10 b against H1975 cells. Therefore, compounds 6 a and 10 b in particular may serve as new leads for the development of inhibitors effective against wild‐type EGFR as well as gefitinib‐resistant mutants.     

Identification of the Sex Pheromone of Sesamia cretica Lederer

By using solid phase micro-extraction and gas chromatography–mass spectrometry analyses, a sex pheromone blend for the stem borer, Sesamia cretica Lederer (Lepidoptera, Noctuidae), was identified as consisting of (Z)-9-tetradecen-1-ol (80%), (Z)-9-tetradecen-1-yl acetate (10%), and (Z)-11-hexadecen-1-ol (10%). The first two components had previously been discovered as attractants for S. cretica in field tests, but had not been identified in the female’s sex pheromone gland. A field-trapping trial showed that the three-component blend gave the highest catches of male S. cretica. This blend, in a sticky trap, was used to monitor a population of S. cretica in Iran, allowing the seasonal flight activity of this insect to be compared with that of a sympatric population of S. nonagrioides. The role of pheromones in the reproductive isolation of these species is discussed.     

A parametric study of the large scale production of multi-walled carbon nanotubes by fluidized bed catalytic chemical vapor deposition

A parametric study investigating the impact of temperature, run duration, total pressure, and composition of the gaseous phase on the catalytic growth of multi-walled carbon nanotubes (MWCNT) has been performed. MWCNTs have been produced very selectively on the multi-gram scale by catalytic chemical vapor deposition from ethylene in a fluidized bed reactor. The kinetics of MWCNTs growth is fast and, with the catalyst used, no induction period has been observed. The kinetic law is of positive order in ethylene concentration and the process is limited by internal diffusion in the porosity of the catalyst. The formation of MWCNTs in the macroporosity of the catalyst induces an explosion of the catalyst grains. Such a process, thanks to the absence of temperature gradient and to the efficient mixing of the grains allows a uniform and selective treatment of the catalyst powder leading to very high selectivity towards MWCNTs formation. High purity MWCNTs have been obtained after catalyst dissolution. Depending on the temperature of production, the specific surface area of this material ranged between 95 and 455 m²/g.     

Reactivity of NO/NO2–NH3 SCR system for diesel exhaust aftertreatment: Identification of the reaction network as a function of temperature and NO2 feed content

We present a systematic study of the NH₃-SCR reactivity over a commercial V₂O₅–WO₃/TiO₂ catalyst in a wide range of temperatures and NO/NO₂ feed ratios, which cover (and exceed) those of interest for industrial applications to the aftertreatment of exhaust gases from diesel vehicles. The experiments confirm that the best deNO_x efficiency is achieved with a 1/1 NO/NO₂ feed ratio. The main reactions prevailing at the different operating conditions have been identified, and an overall reaction scheme is herein proposed.

Particular attention has been paid to the role of ammonium nitrate, which forms rapidly at low temperatures and with excess NO₂, determining a lower N₂ selectivity of the deNO_x process. Data are presented which show that the chemistry of the NO/NO₂–NH₃ reacting system can be fully interpreted according to a mechanism which involves: (i) dimerization/disproportion of NO₂ and reaction with NH₃ and water to give ammonium nitrite and ammonium nitrate; (ii) reduction of ammonium nitrate by NO to ammonium nitrite; (iii) decomposition of ammonium nitrite to nitrogen. Such a scheme explains the peculiar deNO_x reactivity at low temperature in the presence of NO₂, the optimal stoichiometry (NO/NO₂ = 1/1), and the observed selectivities to all the major N-containing products (N₂, NH₄NO₃, HNO₃, N₂O). It also provides the basis for the development of a mechanistic kinetic model of the NO/NO₂–NH₃ SCR reacting system.     

Efficacy of bilateral prophylactic mastectomy in women with a family history of breast cancer

BACKGROUND: Options for women at high risk for breast cancer include surveillance, chemoprevention, and prophylactic mastectomy. The data on the outcomes for surveillance and prophylactic mastectomy are incomplete. METHODS: We conducted a retrospective study of all women with a family history of breast cancer who underwent bilateral prophylactic mastectomy at the Mayo Clinic between 1960 and 1993. The women were divided into two groups - high risk and moderate risk - on the basis of family history. A control study of the sisters of the high-risk probands and the Gail model were used to predict the number of breast cancers expected in these two groups in the absence of prophylactic mastectomy. RESULTS: We identified 639 women with a family history of breast cancer who had undergone bilateral prophylactic mastectomy: 214 at high risk and 425 at moderate risk. The median length of follow-up was 14 years. The median age at prophylactic mastectomy was 42 years. According to the Gall model, 37.4 breast cancers were expected in the moderate-risk group; 4 breast cancers occurred (reduction in risk, 89.5 percent; P<0.001). We compared the numbers of breast cancers among the 214 high-risk probands with the numbers among their 403 sisters who had not undergone prophylactic mastectomy. Of these sisters, 38.7 percent (156) had been given a diagnosis of breast cancer (115 cases were diagnosed before the respective proband's prophylactic mastectomy, 38 were diagnosed afterward, and the time of the diagnosis was unknown in 3 cases). By contrast, breast cancer was diagnosed in 1.4 percent (3 of 214) of the probands. Thus, prophylactic mastectomy was associated with a reduction in the incidence of breast cancer of at least 90 percent. CONCLUSIONS: In women with a high risk of breast cancer on the basis of family history, prophylactic mastectomy can significantly reduce the incidence of breast cancer.     

Additive group contributions to density and glass transition temperature in polyurethanes

The method of additive properties was applied to the density and glass transition temperature, T_g, of linear amorphous polyurethanes. This method assumes that certain polymer properties result from the additive effects of unique constituent group properties and that these group properties are independent of their environment. To determine the component properties, 14 model polyurethanes were synthesized. The polymers contained only the following four groups: urethane, phenylene, methylene, and ether oxygen. The densities and T_g's of these polymers were measured. Using these measured values, the known composition of each polymer, and an appropriate additive from, the molar component properties were calculated using a matrix least-squares simultaneous fit algorithm. An error analysis confirmed that the component values were determined with greater accuracy than literature results. The densities ranged from 1.0 to 1.2 g/cm³ and measured versus predicted densities agreed to within 0.3% on the average. T_g's ranged from ?70°C to 70°C and measured versus predicted T_g's agreed to within 1.3% on the average.