Stability of the antimicrobial activity of acetogenins from avocado seed,under common food processing conditions,against Clostridium sporogenes vegetative cell growth and endospore germination

Anticlostridial activity of acetogenins from avocado seed was further characterised, and their stability and effectiveness under food processing conditions, and in a model food system, studied for the first time. Isolated AcO‐avocadenyne (1) and AcO‐avocadene (2) showed anticlostridial potential, particularly the latter molecule. Enriched acetogenins extracts, obtained at laboratory scale (EAE) and semi‐commercially (Avosafe^®), presented similar MIC values (3.9–9.8 ppm) and a bacteriostatic effect. Extracts bioactivity showed resistance to heat (≤120 °C), high hydrostatic pressure (HHP; 300–600 MPa, 3–6 min, 25 °C) and salt (≤3% w/v). In addition, the extract was most stable at pH ≥ 7.0 and potency against endospores increased after HHP treatment and exposure to pH 9.5, suggesting a positive effect on solubility or structure of particular acetogenins. In a model food system processed by HHP, acetogenins were retained; however, initial quantities gradually declined by 63% and 32% at 25 and 4 °C, respectively, at the end of the storage period (42 days). Most stable molecules (persediene (4) > persenones > AcO‐avocadene (2)) possess a keto or trans‐enone group at C‐4 in the aliphatic chain, which could support hydrogen donation to surrounding carbon atoms and confer antioxidant activity. Active endospores were completely inhibited by 5000 ppm Avosafe^® in the model food system (37 °C, 72 h) and lower concentrations (500–1000 ppm) resulted in 1–2 log reduction of a 3 log inoculum target. Efficacy information generated in the present work is considered crucial to improve scientific knowledge on spore inhibition properties of avocado acetogenins.     

Investigation of the morphotropic region in the Sr-doped lead hafnate-titanate solid solution Pb0.94Sr0.06Hf1-TixO3

Sr-doped lead hafnate titanate (PHT) oxides were synthesized by solid-state reaction and carefully studied in order to identify the reaction mechanisms. The reaction sequences in the formation of Sr-doped PbHfO₃, Sr-doped PbTiO}_{3 and Sr-doped PbHf_{1 - x}Ti_xO₃ were investigated using X-ray powder diffraction and differential thermal analysis. The Sr-doped PbHfO₃ oxide is mainly elaborated from the reaction between PbO and HfO₂, while Sr-doped PbTiO₃ oxide is formed from the reaction between Pb₃O₄ and TiO₂. The Sr-doped PbHf_1-xTi_xO₃ oxide is obtained from a solid-state reaction between Sr-doped PbHfO₃ and Sr-doped PbTiO₃ solid solutions. For x close to 0.5, tetragonal and rhombohedral ferroelectric phases coexist in a region commonly called the morphotropic region which presents the best dielectric and electromechanical properties. By means of X-ray powder diffraction, the boundaries of the morphotropic region in the (Pb_0.94Sr_0.06)Hf_1-xTi_xO₃ system have been determined for x ranging between 0.42 and 0.58. Finally, electrical and piezoelectric characterizations have been performed on Sr-doped PHT ceramics crystallizing in the morphotropic region. The compositional dependence of the electromechanical coupling factor (k_P), piezoelectric coefficients (d_{33 and g₃₃) and relative permittivity (_r) has been studied. An optimum composition has been determined as x equal to 0.51. © 2001 Kluwer Academic Publishers     

Tungsten Lamps as an Affordable Light Source for Testing of Photovoltaic Cells

An improved Tungsten light source system for photovoltaic cell testing made from low-cost, commercially available materials is presented as an alternative to standard expensive testing equipment. In this work, spectral correction of the Tungsten light source is achieved by increasing the color temperature to ??5200 K using inexpensive commercially available filters. Spectral measurements of the enhanced light source reveal that a better spectrum match towards the solar spectrum is achieved than what has been previously demonstrated. Specifically, the improved solar spectrum match is achieved by substantial filtering of the infrared range. The proposed setup is used to evaluate the performance of both silicon and organic based photovoltaic cells.     

Liquid phase sintering and oxidation resistance of WC–Ni–Co–Cr cemented carbides

Fully dense WC–Ni–Co–Cr alloys have been consolidated via sinter HIP processing. Dilatometric tests show that shrinkage undergoes several accelerations and decelerations during heating, a phenomenon likely associated to the heterogeneous distribution of Cr in the binder phase. WC grain growth follows trends similar to those described for WC–Co hardmetals, increasing with the C activity and the amount of liquid phase of the cermets. Finally, the oxidation resistance of WC–Ni–Co–Cr cemented carbides is observed to improve as the metal content increases and the C content decreases. In both cases, the oxide layers present a higher proportion of (Co, Ni)WO₄ tungstates. The oxide scales formed on compositions with low metal content contain a higher amount of WO₃ oxide.     

Noninvasive, in utero imaging of mouse embryonic heart development with 40-MHz echocardiography

BACKGROUND: The increasing number of transgenic and targeted mutant mice with embryonic cardiac defects has resulted in the need for noninvasive techniques to examine cardiac structure and function in early mouse embryos. We report the first use of a novel 40-MHz ultrasound imaging system in the study of mouse cardiac development in utero. METHODS AND RESULTS: Transabdominal scans of mouse embryos staged between 8.5 and 13.5 days of gestation (E8.5 to E13.5) were obtained in anesthetized mice. Atrial and ventricular contractions could be discerned from E9.5, and changes in cardiac morphology were observed from E9.5 to E13.5. Hyperechoic streaming patterns delineated flow through the umbilical, vitelline, and other major blood vessels. Diastolic and systolic ventricular areas were determined by planimetry of the epicardial borders, and fractional area change was measured as an index of contractile function. Significant increases in ventricular size were documented at each stage between E10.5 and E13.5, and the ability to perform serial imaging studies over 3 days of embryonic development is described. Finally, the detection of vascular cell adhesion molecule 1 (VCAM-1) homozygous null mutant embryos demonstrates the first example of noninvasive, in utero analysis of cardiac structure and function in a targeted mouse mutant. CONCLUSIONS: We used 40-MHz echocardiography to identify key elements of the early mouse embryonic cardiovascular system and for noninvasive dimensional analysis of developing cardiac ventricles. The ability to perform serial measurements and to detect mutant embryos with cardiac defects highlights the usefulness of the technique for investigating normal and abnormal cardiovascular development.     

Radical irradiation with the split-course technique in carcinoma of the lung

The possible advantages of a split-course of irradiation in the treatment of patients with locally advanced and/or inoperable carcinoma of the lung were explored in over 200 cases. The patients were separated into two groups with different prognostic factors: Group A, patients with well-differentiated tumors confined to the lung and mediastinum; and Group B, cases with anaplastic tumors and/or supraclavicular metastases, bone erosion, or superior venal caval syndrome. The treatment consisted of 5500-6000 rads tumor dose in 20 to 24 fractions over a period of 7 to 8 weeks with a rest interval of 2 to 4 weeks in the middle. The 3- and 5-year survival figures, 19% and 16%, respectively, in Group A cases, along with the excellent tolerance, suggest that the split-course approach has definite advantages.     

Comprehensive numerical modelling of the hot isostatic pressing of Ti-6Al-4V powder: From filling to consolidation

Hot Isostatic Pressing (HIP) is a manufacturing process for production of near-net-shape components, where models based on Finite Element Method (FEM) are generally used for reducing the expensive experimental trials for canister design. Researches up to date implement in the simulation a uniform powder relative density distribution prior HIPping. However, it has been experimentally observed that the powder distribution is inhomogeneous after filling, leading to a non-uniform tool shrinkage. In this study a comprehensive numerical model for HIPping of Ti-6Al-4V powder is developed to improve model prediction by simulating powder filling and pre-consolidation by means of a two-dimensional Discrete Element Method (DEM). Particles’ dimension has been scaled up in order to reduce the computational cost of the analysis. An analytical model has been developed to calculate the relative density distribution from powder particle distribution provided by DEM, which is then passed in information to a three-dimensional FEM implementing the Abouaf and co-workers model for simulating powder densification during HIPping. Results obtained implementing the initial relative density distribution calculated from DEM are compared with those obtained considering a uniform relative density distribution over the powder domain (classic approach) at the beginning of the analysis. Experimental work has been carried out for validating the DEM (filling) and FEM (HIP) model. Comparison between experimental and numerical results shows the ability of the DEM model to represent the powder flow during filling and pre-consolidation, providing also a reliable values of the relative density distribution. It also highlights that taking into account the non-uniform powder distribution inside the canister prior HIP is vital to improve numerical results and produce near-net-shape components.     

A method for computing minimum voltage stability margins of power systems

A new and fast method for computing the minimum voltage stability margin (VSM) of power systems is presented. The computation of the VSM is required for power systems planning and operation. Usually, it is assumed that loads increase along a predefined direction (e.g. with constant power factor, followed by a proportional MW generation increase) up to the system's maximum loading point is reached. Situations may occur where variations from the predefined load increase direction, for example an unexpected load increase at some bus or area may result in smaller VSM, taking the system to an insecure state. The computation of the minimum VSM (mVSM) allows forecasting the load increase worst scenario. The information regarding the mVSM and the corresponding load increase direction for which it occurs, along with the usual VSM, allows operators to take measures like preventive control actions to move the system to securer operating points. Simulation results for IEEE test systems and for realistic systems are shown. Also, the proposed method is compared with other methods found in the literature.     

Fundamental phenomena affecting low temperature combustion and HCCI engines,high load limits and strategies for extending these limits

Low temperature combustion (LTC) engines are an emerging engine technology that offers an alternative to spark-ignited and diesel engines. One type of LTC engine, the homogeneous charge compression ignition (HCCI) engine, uses a well-mixed fuel–air charge like spark-ignited engines and relies on compression ignition like diesel engines. Similar to diesel engines, the use of high compression ratios and removal of the throttling valve in HCCI allow for high efficiency operation, thereby allowing lower CO₂ emissions per unit of work delivered by the engine. The use of a highly diluted well-mixed fuel–air charge allows for low emissions of nitrogen oxides, soot and particulate matters, and the use of oxidation catalysts can allow low emissions of unburned hydrocarbons and carbon monoxide. As a result, HCCI offers the ability to achieve high efficiencies comparable with diesel while also allowing clean emissions while using relatively inexpensive aftertreatment technologies.