Explosion of white dwarfs harboring hybrid CONe cores

Recently, it has been found that off-centre carbon burning in a subset of intermediate-mass stars does not propagate all the way to the center, resulting in a class of hybrid CONe cores. Here, we consider the possibility that stars hosting these hybrid CONe cores might belong to a close binary system and, eventually, become white dwarfs accreting from a non-degenerate companion at rates leading to a supernova explosion. We have computed the hydrodynamical phase of the explosion of Chandrasekhar-mass white dwarfs harboring hybrid cores, assuming that the explosion starts at the center, either as a detonation (as may be expected in some degenerate merging scenarios) or as a deflagration (that afterwards transitions into a delayed detonation). We assume these hybrid cores are made of a central CO volume, of mass M(CO), surrounded by an ONe shell. We show that, in case of a pure detonation, a medium-sized CO-rich region, M(CO)<0.4 Msun, results in the ejection of a small fraction of the mantle while leaving a massive bound remnant. Part of this remnant is made of the products of the detonation, Fe-group nuclei, but they are buried in its inner regions, unless convection is activated during the ensuing cooling and shrinking phase of the remnant. In contrast, and somehow paradoxically, delayed detonations do not leave remnants but for the minimum M(CO) we have explored, M(CO)=0.2 Msun, and even in this case the remnant is as small as 0.13 Msun. The ejecta produced by these delayed detonations are characterized by slightly smaller masses of 56Ni and substantially smaller kinetic energies than obtained for a delayed detonation of a 'normal' CO white dwarf. The optical emission expected from these explosions would hardly match the observational properties of typical Type Ia supernovae, although they make interesting candidates for the subluminous class of SN2002cx-like or SNIax.Comment: Accepted for Astronomy and Astrophysics, 11 pages, 4 figure

Photoassisted tunneling from free-standing GaAs thin films into metallic surfaces

The tunnel photocurrent between a gold surface and a free-standing semiconducting thin film excited from the rear by above bandgap light has been measured as a function of applied bias, tunnel distance and excitation light power. The results are compared with the predictions of a model which includes the bias dependence of the tunnel barrier height and the bias-induced decrease of surface recombination velocity. It is found that i) the tunnel photocurrent from the conduction band dominates that from surface states. ii) At large tunnel distance the exponential bias dependence of the current is explained by that of the tunnel barrier height, while at small distance the change of surface recombination velocity is dominant

Innovating in the textile industry: An uncoordinated dance between firms and their territory?

Considering the process of innovati on development, this paper aimed to examine the eff ect of diff erent dimensions of proximity and the level of coordinati on that exists in a texti le cluster. This study employed a qualitati ve method, based on indepth interviews that were conducted with two leading fi rms in a texti le cluster in Valencia, Spain, which is subject to intense competi ti on from producers in Asia. Firms were selected according to the criteria of innovati on development and opportunity. This is a pilot study that precedes a more ambiti ous one. The results suggested that fi rms' innovati ons are developed in an isolated, disconti nuous, marginal, and uncoordinated way, and clustering has a marginal eff ect. Furthermore, despite high geographical and cogniti ve proximity, low social proximity is maintained by the low level of trust between the fi rms. These fi ndings may be of signifi cant practi cal value for practi ti oners and insti tuti ons. Firms can gain a bett er understanding of the importance of being located in a cluster, as this is a key factor for their survival under intense competi ti on. However, geographical proximity is not suffi cient, and fi rms need to cooperate with each other and share their ideas and experiences. In additi on, insti tuti ons should interact more with companies, speak their language, meet their needs, and devise strong cluster initi ati ves. This study provides a more comprehensive understanding of how insti tuti ons and fi rms interact within a cluster in the process of innovati on development and elaborate upon diff erent dimensions of proximity among fi rm

HS 0139+0559, HS 0229+8016, HS 0506+7725, and HS 0642+5049 : four new long-period cataclysmic variables

We present time-resolved optical spectroscopy and photometry of four relatively bright (V ∼ 14.0−15.5) long-period cataclysmic variables(CVs) discovered in the Hamburg Quasar Survey: HS 0139+0559, HS 0229+8016, HS 0506+7725, and HS 0642+5049. Their respective orbital periods, 243.69 ± 0.49 min, 232.550 ± 0.049 min, 212.7 ± 0.2 min, and 225.90 ± 0.23 min are determined from radial velocity and photometric variability studies. HS 0506+7725 is characterised by strong Balmer and He emission lines, short-period (∼10−20 min) flickering, and weak X-ray emission in the ROSAT All Sky Survey. The detection of a deep low state (B 18.5) identifies HS 0506+7725 as a member of the VY Scl stars. HS 0139+0559, HS 0229+8016, and HS 0642+5049 display thick-disc like spectra and no or only weak flickering activity. HS 0139+0559 and HS 0229+8016 exhibit clean quasi-sinusoidal radial velocity variations of their emission lines but no or very little orbital photometricvariability. In contrast, we detect no radial velocity variation in HS 0642+5049 but a noticeable orbital brightness variation. We identify all three systems either as UX UMa-type novalike variables or as Z Cam-type dwarf novae. Our identification of these four new systems underlines that the currently known sample of CVs is rather incomplete even for bright objects. The four new systems add to the clustering of orbital periods in the 3−4 h range found in the sample of HQS selected CVs, and we discuss the large incidence of magnetic CVs and VY Scl/SW Sex stars found in this period range among the known population of CVs

A further experimental step in the analysis of hierarchical responding

This study is a step forward in the difficult task of analyzing the transformation of functions via hierarchical relations. Eight participants underwent a computer task with five phases. During Phase 1, four stimuli were trained to become the following relational cues: INCLUDES, BELONGS TO, SAME, and DIFFERENT. In Phase 2, three equivalence classes were trained and tested (A1-B1-C1-D1; A2-B2-C2-D2; A3-B3-C3-D3). During Phase 3, inclusion relations were first established, by using the INCLUDES and BELONGS TO relational cues, between the to-be lower levels of the hierarchy, namely A1/B1, A2/B2, and A3/B3; and stimuli X.1, X.2, and Y.1, respectively. Then, the INCLUDES relational cue was used to establish inclusion relations between X.1/X.2 and X, and between Y.1 and Y, so that X and Y would become the most inclusive levels of two separate hierarchical networks. In Phase 4, X.1 was established as cold, D2 as heavy, and C3 as sweet. Lastly, in Phase 5 (Critical Test), seven stimuli from both hierarchical networks were tested for the transformation of functions. Five of the six participants who made it to this test responded correctly. Implications, limitations, and further research are discussed