Thermolysis of the polyyne C8H2 in hexane and methanol: Experimental and theoretical study

The mean lifetimes of polyyne C₈H₂ in hexane were determined at 50, 60, 80, and 100 °C and in methanol at 60 °C. The reactions are second order at all temperatures: ln k₂ = 20.5 ± 1.5-10303 ± 520T⁻¹ and the corresponding activation energy is 85.7 ± 6.3 kJ mol⁻¹ (7164 cm⁻¹). Extrapolation suggests that solutions at 1 mM concentration are significantly unstable at room temperature. Quantum chemical calculations show that polyynes C_mH₂ + C_nH₂ (m + n = 16) could be products, but these were not detected. Alternatively, C₁₆H₂ isomers could form. IR spectra of the solid residues from hexane and methanol solutions were obtained.     

Improvements in seismic event locations in a deep western U.S. coal mine using tomographic velocity models and an evolutionary search algorithm

Methods of improving seismic event locations were investigated as part of a research study aimed at reducing ground control safety hazards. Seismic event waveforms collected with a 23-station three-dimensional sensor array during longwall coal mining provide the data set used in the analyses. A spatially variable seismic velocity model is constructed using seismic event sources in a passive tomographic method. The resulting three-dimensional velocity model is used to relocate seismic event positions. An evolutionary optimization algorithm is implemented and used in both the velocity model development and in seeking improved event location solutions. Results obtained using the different velocity models are compared. The combination of the tomographic velocity model development and evolutionary search algorithm provides improvement to the event locations.     

Formation and Properties of Chalcogenide Glasses in the GeSe2–As2Se3–CdSe System

The glass-forming region in a GeSe₂–As₂Se₃–CdSe system and the dependence of properties on glass compositions as a formula of 70GeSe₂–(30− x )As₂Se₃– x CdSe ( x =0–25) were investigated. Measurements included density, micro-hardness, differential scanning calorimetry (DSC), X-ray diffraction, and IR transmission spectra. A large glass-forming region was shown while addition of Cd increases the crystallization trend of the system. Besides, the Cd content accommodated by the system to form glass is found to be lower in the As₂Se₃-rich region than in the GeSe₂-rich region. With the introduction of CdSe, density, micro-hardness, and T _g of glasses increase whereas an exothermal peak in the DSC curve appears and thermal stability (Δ T ) decreases. The activation energy of crystallization and the Avrami exponent were also obtained using the modified Ozawa equation.     

Kinetics and mechanism of ?-caprolactone and l,l-lactide polymerization coinitiated with zinc octoate or aluminum acetylacetonate: The next proofs for the general alkoxide mechanism and synthetic applications

Following our previous papers on mechanism of cyclic esters' polymerization coinitiated by tin(II) octoate [tin(II) bis-(2-ethylhexanoate), (Sn(Oct)₂)] in the presence of either the low molar mass coinitiator (an alcohol, hydroxy acid, or H₂O) or a macromolecule fitted with a hydroxy end group (ROH), the present work deals with ?-caprolactone (CL) and l,l-lactide (LA) polymerizations coinitiated with zinc octoate (Zn(Oct)₂) or aluminum acetylacetonate (Al(Acac)₃). A series of kinetic measurements revealed that similarly as in the Sn(Oct)₂ coinitiated process, these polymerizations proceed by simple monomer insertion into the …Mt-OR bond, reversibly formed in the reaction -Mt-L + ROH ? …-Mt-OR + LH (where Mt = Sn, Zn or Al; L = Oct or Acac), taking place throughout the whole polymerization process. MtL_n itself does not play an active role in the polymerization. Applicability of the commercially available Zn(Oct)₂ or Al(Acac)₃ for the aliphatic polyester (10³ ≤ M_n ≤ 4 × 10⁵) synthesis is also discussed.     

What localizes beneath: A metric multisensor localization and mapping system for autonomous underground mining vehicles

Robustly and accurately localizing vehicles in underground mines is particularly challenging due to the unavailability of GPS, variable and often poor lighting conditions, visual aliasing in long tunnels, and airborne dust and water. In this paper, we present a novel, infrastructure‐less, multisensor localization method for robust autonomous operation within underground mines. The proposed method integrates with existing mine site commissioning and operation procedures and includes both an offline map‐building process and an online localization algorithm. The approach combines the strengths of visual‐based place recognition, LIDAR‐based localization, and odometry in a particle filter fusion process. We provide an extensive experimental validation using new large data sets acquired in two operational Australian underground hard‐rock mines (including a 600m‐deep multilevel mine with approximately 33 km of mapping data and 7 km of vehicle localization) by actual mining vehicles during production operations. We demonstrate a significant increase in localization accuracy over prior state‐of‐the‐art SLAM research systems and real‐time operation, with processing times in the order of 10 Hz. We present results showing a mean error of 0.68 m from the Queensland Mine data set and 1.32 m from the New South Wales Mine data set and at least 86% reduction in error compared with prior state of the art. We also analyze the impact of the particle filter parameters with respect to localization accuracy. Together this study represents a new approach to positioning systems for currently deployed autonomous vehicles within underground mine environments.     

Patientenverfügungen und Advance Care Planning bei Demenz und anderen kognitiven Beeinträchtigungen

Definition of the problem

Advance directives for later states of grave cognitive impairment that are typical for late stages of dementia meet with more far-reaching reservations than advance directives for other states of reduced competence. One of the reasons seems to lie in the ethical and psychological conflicts arising from advance directives demanding nontreatment of additional diseases or the abstention from artificial nutrition in situations in which patients show no signs of suffering from their condition.

Arguments

In this article, it is argued that a “mixed” ethical strategy be used for these cases.

Conclusion

Advance directives in the legally defined sense, especially if drawn up in a process of advance care planning, should be followed in order to avoid that advance directives as an instrument of patient autonomy are rendered futile to a degree incompatible with confidence that wishes for terminating medical treatment will be followed. In contrast, the authority of “care directives” without recognized legal status should be restricted to cases in which there is concordance between the patient’s will as expressed in the directive and the patient’s “natural” will in the relevant situation.

     

Kinetic analysis of cellular internalization and expulsion of unstructured D-chirality cell penetrating peptides

Most cell penetrating peptides (CPPs) are unstructured and susceptible to proteolytic degradation. One alternative is to incorporate D-chirality amino acids into unstructured CPPs to allow for enhanced uptake and intracellular stability. This work investigates CPP internalization using a series of time, concentration, temperature, and energy dependent studies, resulting in a three-fold increase in uptake and 50-fold increase in stability of D-chirality peptides over L-chirality counterparts. CPP internalization occurred via a combination of direct penetration and endocytosis, with a percentage of internalized CPP expelling from cells in a time-dependent manner. Mechanistic studies identified that cells exported the intact internalized D-chirality CPPs via an exocytosis independent pathway, analogous to a direct penetration method out of the cells. These findings highlight the potential of a D-chirality CPP as bio-vector in therapeutic and biosensing applications, but also identify a new expulsion method suggesting a relationship between uptake kinetics, intracellular stability, and export kinetics.     

Modeling drop breakage using the full energy spectrum and a specific realization of turbulence anisotropy

The assumption of homogeneous isotropic turbulence when modeling drop breakage in industrially relevant geometries is questionable. We describe the development of an anisotropic breakage model, where the anisotropy is introduced via the inclusion of a perturbed turbulence spectrum. The selection of the perturbed spectrum is itself motivated by our previous large-eddy simulations of high-pressure homogenizers. The model redistributes energy from small to large scales, and assumes that the anisotropic part of the Reynolds stresses is confined to the energy-containing range. The second-order structure function arising from the perturbed spectrum is used in the standard framework of Coulaloglou and Tavlarides to calculate breakage frequency. While the base model exhibits non-monotonic behavior (by predicting a maximum value for a certain drop size), the effect of anisotropy is shown to increase breakage frequency in length scales larger than this peak, thereby reducing non-monotonicity. This effect is more pronounced for small turbulence Reynolds numbers.     

Host Plant Constancy in Ovipositing Manduca sexta

Journal of Chemical Ecology - Many pollinating insects exhibit flower constancy, i.e. they target flower species they have already experienced and fed from. While the insects might profit from...     

The mechanical milling of Al/TiO2 composite powders

The processing of Al/TiO₂ composite powders produced by high-energy mechanical milling leads to production of a range of valuable, titanium-based materials. They include Ti(Al,O)/Al₂O₃ and Ti_xAl_y(O)/Al₂O₃ composite powders, bulk composites and Ti₃Al/TiAl alloy powders, and corresponding bulk materials. The strength of the Ti(Al,O)/Al₂O₃ and Ti_xAl_y(O)/Al₂O₃ composites is moderate, but their high-temperature oxidation resistance is exceptionally high, making the titanium-based composite powders favorable feedstock materials for protective coatings. The hardness of the Ti(Al,O)/Al₂O₃ and Ti₃Al(O)/Al₂O₃ composites is also very high (10–16 GPa). For more information, contact D.L. Zhang, University of Waikato, Waikato Centre for Advanced Materials, Department of Materials and Process Engineering, Private Bag 3105, Hamilton, New Zealand; 011-64-7-838-4783; fax 011-64-7-838-4835; e-mail d.zhang@waikato.ac.nz.