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An investigation into the weldability of the Al-Li-Cu-Mg-Zr alloy 8090 using a CO2laser indicates that the grain structure and microstructure of the weld zone are sensitive to the post-weld heat treatment. If a slow heating rate of 1Kmin-1to the solution treatment temperature is used the formation of β' dispersoids is promoted which leads to a uniformly small grain size within the fusion zone. If, however, faster heating rates are employed massive grains can form in the fusion zone. This is shown to be associated with a virtual absence of ß' precipitates.

Context. The periodicity of 5.5 years for some observational events occurring in ??Carinae manifests itself across a large wavelength range and has been associated with its binary nature. These events are supposed to occur when the binary components are close to periastron. To detect the previous periastron passage of ??Car in 2003, we started an intensive, ground-based, optical, photometric observing campaign. Aims. We continued observing the object to monitor its photometric behavior and variability across the entire orbital cycle. Methods. Our observation program consisted of daily differential photometry from CCD images, which were acquired using a 0.8?m telescope and a standard BVRI filter set at La Plata Observatory. The photometry includes the central object and the surrounding Homunculus nebula. Results. We present up-to-date results of our observing program, including homogeneous photometric data collected between?2003 and?2008. Our observations demonstrated that ??Car has continued increasing in brightness at a constant rate since 1998. In 2006, it reached its brightest magnitude (V ~ 4.7) since about?1860. The object then suddenly reverted its brightening trend, fading to V = 5.0 at the beginning of 2007, and has maintained a quite steady state since then. We continue the photometric monitoring of ??Car in anticipation of the next ?periastron passage?, predicted to occur at the beginning of 2009.

Context. The physical properties of almost any kind of astronomical object can be derived by fitting synthetic spectra or photometry extracted from theoretical models to observational data.Aims. We want to develop an automatic procedure to perform this kind of fitting to a relatively large sample of members of a stellar association and apply this methodology to the case of Collinder?69.Methods. We combine the multiwavelength data of our sources and follow a work-flow to derive the physical parameters of the sources. The key step of the work-flow is performed by a new VO-tool, VOSA. All the steps in this process are done in a VO environment.Results. We present this new tool, and provide physical parameters such as Teff, gravity, luminosity, etc. for ~170 candidate members of Collinder?69, and an upper-limit for the age of this stellar association.Conclusions. This kind of study of star forming regions, clusters, etc. produces a huge amount of data, very tedious to analyse using the traditional methodology. Thus, they are excellent examples of where to apply the VO techniques.

AbstractThis paper studies the concept of strongly omnipresent operators that was recently introduced by the first two authors. An operator Ton the space H(G)of holomorphic functions on a complex domain Gis called strongly omnipresent whenever the set of T-monsters is residual in H(G), and a T-monster is a function fsuch that Tfexhibits an extremely ?wild? behaviour near the boundary. We obtain sufficient conditions under which an operator is strongly omnipresent, in particular, we show that every onto linear operator is strongly omnipresent. Using these criteria we completely characterize strongly omnipresent composition and multiplication operators.

One of the acceptable sequences of the working stages of the design process contains: (a) specifications, (b) conceptual design, (c) embodiment design, and (d) detailed design as its working stages. Following the principle of deployment as used in quality function deployment, it can be said that specifications deploy customer requirements, conceptual design deploys specifications and embodiment design deploys conceptual design. Based on this deployment principle it is possible to establish three charts namely: (a) specification chart, (b) conceptual design chart, and (c) embodiment design chart to represent the designs at different levels of abstraction. The paper describes how these charts are constructed and used to store designs. It also shows how the charts can be developed to represent the design of a portable belt conveyor at different stages.

The effect of a 15% reduction in maternal nutrition for the first 70 days of gestation on cardiovascular and hypothalamic–pituitary–adrenal (HPA) axis responses to administration of corticotropin releasing hormone (CRH) + arginine vasopressin (AVP) was studied at 128 0.7 days gestation in fetal sheep and postnatally, at 85 4.5 days in young lambs. The effect on the fetal cardiovascular response to acute hypoxaemia was also examined. Under basal conditions, fetal heart rate (FHR) was reduced (P<0.05) and basal femoral artery vascular resistance (FVR) was increased (P<0.05) in fetuses of dietary-restricted (R) ewes compared with controls (C). Fetal mean arterial pressure (MAP) was similar in both groups. Femoral artery vascular resistance was also greater during hypoxaemia in R fetuses compared with C fetuses (P<0.05), suggesting that chemoreflex mechanisms were augmented in the R group. The fetal ACTH response to CRH + AVP was similar in both groups. However, cortisol responses to CRH + AVP were smaller in R fetuses compared with C fetuses (P<0.05). Postnatally, basal MAP (P<0.05), and ACTH (P<0.01) and cortisol (P<0.001) responses were greater in R lambs compared with C lambs. It was concluded that modest maternal undernutrition during pregnancy alters development of the cardiovascular system, producing elevated blood pressure in postnatal life. Development of the HPA axis is also altered, with reduced activity during fetal life, but increased activity postnatally. The data suggest that the HPA axis may play a role in mediating the elevation of MAP in R lambs. Extra keywords: blood pressure, nutrition.

The microstructural development of the Al-Li-Cu-Mg-Zr alloy 8090 has been studied after autogenous CO2 laser welding. Sheets ranging in thickness from 1–4 mm were welded at speeds of between 20–120 mm s-1 and powers from 1.5–3.8 kW. Optical microscopy, scanning and transmission electron microscopy were used to study the as-received base metal, the heat-affected zone and the solidified fusion zone. The base metal was supplied in a superplastically formable condition and thus had an unrecrystallized grain structure containing 1–2 µm sized sub-grains with sub-micrometre d' and ß' precipitates in the matrix. In the fusion zone, the as-solidified grain structure was columnar at the interface with the base metal but became equiaxed in the central region of the weld pool. The weld depth and top bead width both increased with decreasing welding speed and increasing beam power within the limits investigated. The fusion zone microstructure was cellular-dendritic. Intermetallic precipitates, which are rich in copper, magnesium, silicon (and presumably lithium), formed in the cell/dendrite boundaries. Very fine-scale d' precipitates were present in the as-solidified a-Al matrix but there was no evidence for the ß', S' and T1 phases. The heat-affected zone was only 100 µm wide and was characterized by regions of partial melting. Radiographs of welds reveal that porosity occurred predominantly along the weld centre-line. In partial penetration welds, two types of pores were observed: near spherical and irregular. However, in fully penetrating welds, only the spherical type of porosity was present. Overall volume fractions of porosity were measured from metallographic sections and were found to vary with welding speed and weld type, i.e. partial or full penetration.

1The maturation of carotid chemoreceptor steady‐state and dynamic responses to CO2in newborn lambs was measured. In total, sixteen fibres (13 lambs) were studied at 3–4 days, nineteen fibres (13 lambs) at 5–9 days and twenty‐one fibres (17 lambs) at 10–24 days after birth.2Steady‐state CO2sensitivity was measured over a range of arterial CO2pressures (Pa,CO2) at four levels of arterial O2pressure (Pa,O2): hyperoxia (Hyp), 115–150 mmHg; normoxia (Nx), 90–105 mmHg; moderate hypoxia (ModHx), 40–60 mmHg; and severe hypoxia (SvHx), 20–35 mmHg.3Steady‐state CO2sensitivity was present at all ages, and a significant effect of age (P< 0.001) and Pa,O2(P< 0.025) (ANOVA) was observed. Older lambs were unable to sustain an increase in chemoreceptor discharge during SvHx as CO2was increased.4Dynamic CO2sensitivity was measured by producing alternations in end‐tidal CO2levels (etCO2) (alternation amplitude, 1.23 ± 0.07% (mean ±s.e.m.); etCO2, 7.56 ± 0.15%) over 2–8 s at two Pa,O2levels only: 80–100 (Nx) and 40–60 mmHg (ModHx). Peak and trough values of the oscillation in chemoreceptor discharge were plotted against maximum and minimum etCO2for the control and CO2‐loaded breaths. Dynamic CO2sensitivity was calculated as the slope between these points.5Dynamic CO2sensitivity was greater than steady‐state sensitivity in Nx (P< 0.05) and ModHx (P< 0.01, Student's paired ttest). Unlike steady‐state CO2sensitivity, there was no significant effect of age or Pa,O2on dynamic sensitivity (P> 0.39 and P> 0.68, respectively, ANOVA).6Our results show that the neonatal lamb possesses a carotid body steady‐state CO2sensitivity within a few days of birth, an age when hypoxia sensitivity is low. This CO2sensitivity increases with age, perhaps due to the increasing interaction between CO2and O2. Dynamic sensitivity of the carotid body to CO2is mature at birth and does not increase with age, as predicted if the response of the carotid body to rapid changes in CO2is independent of the sensitivity to the partial pressure of O2(PO2).

The effect of corrosion by H2R.4 on the values of room temperature thermal diffusivity (?) and the microstructure of API5L-X52 pipeline steel are studied. The samples were exposed for 3, 6, 9, 12 and 15 days in a corrosive solution in an atmosphere with relative humidity of 57.16% in average and at temperature of 23.6 ?C. The ? values were measured by the photoacoustic technique in a heat transmission configuration. Our results show a ? decrease with the corrosion time (t), with a behavior described by an exponentially decreasing curve. Microestructural study on the samples revealed the appearance of irregular surfaces with corroded grain frontiers, porosity and fractures of micrometer size as a consequence of corrosion, as well as a presence of phases mainly composed by tetra hydrated iron and manganese sulphates. The decreasing evolution of ? vs t show the activity-passivity behavior in the corrosion process.

The thermal properties of Sr0,3 Ba0,7Ti1-yZryO3 (BST30Zr) ferroelectric ceramics with different concentrations of Zr are studied by a Photoacoustic (PA) technique and the temperature relaxation method. The results of the measurements shows that the thermal conductivity of the samples increases linearly with the content of Zr, a behavior explained using the Maxwell-model for the dependence of this magnitude from sample?s porosity.

We report a method for determining the specific heat capacity in solids by means of the photoacoustic (PA) technique in a heat transmission configuration. This method involves a modulation frequency range where the samples are thermally thin and a liquid (i.e., distilled water) as a reference sample. It is free of PA cell parameters and was tested in some metals and semiconductors. The results agree very well with literature reported values for these samples.