University of Crete

About: University of Crete is a education organization based out in Rethymno, Greece. It is known for research contribution in the topics: Population & Galaxy. The organization has 8681 authors who have published 21684 publications receiving 709078 citations. The organization is also known as: Panepistimio Kritis.

Local Feedback-Based Mainstream Traffic Flow Control on Motorways Using Variable Speed Limits

Abstract: Recent research has proposed mainstream traffic flow control (MTFC), enabled via variable speed limits (VSLs), as a novel motorway traffic management tool and has demonstrated its efficiency based on sophisticated optimal control methods that may face difficulties in practical field implementations. A simple local MTFC feedback controller is designed in this paper, taking into account a number of practical requirements and restrictions. The MTFC controller relies only on readily available real-time measurements (no online model usage and no demand predictions are needed) and is therefore robust and suitable for field implementations. The controller is evaluated in simulation and compared with optimal control results. Despite its simplicity, the new controller's performance is shown to approach the optimal control results while considering several practical and safety restrictions for a number of investigated scenarios.

A Herschel/PACS Far-infrared line emission survey of local luminous infrared galaxies

Abstract: We present an analysis of, [O I]_(63) [O III]_(88), [N II]_(122), and [C II]_(158) far-infrared (FIR) fine-structure line observations obtained with Herschel/PACS, for ~240 local luminous infrared galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey. We find pronounced declines ("deficits") of line-to-FIR continuum emission for [N II]_(122) , [O I]_(63) and [C II]_(158) as a function of FIR color and infrared luminosity surface density, Σ_(IR). The median electron density of the ionized gas in LIRGs, based on the [N II]_(122)/[N II]_(205) ratio, is n_e = 41 cm^(−3). We find that the dispersion in the [C II]_(158) deficit of LIRGs is attributed to a varying fractional contribution of photodissociation regions (PDRs) to the observed [C II]_(158) emission, f([C II]^(PDR)_(158)) = [C II]^(PDR)_(158)/[C II]_(158), which increases from ~60% to ~95% in the warmest LIRGs. The [O I]_(63)/[C II]^(PDR)_(158) ratio is tightly correlated with the PDR gas kinetic temperature in sources where [O 1]_(63) is not optically thick or self-absorbed. For each galaxy, we derive the average PDR hydrogen density, n_H, and intensity of the interstellar radiation field, G, in units of G_0 and find G/n_H ratios of ~0.1–50 G_0 cm^3, with ULIRGs populating the upper end of the distribution. There is a relation between G/n_H and Σ_(IR), showing a critical break at Σ*_(IR) 5 × 10^(10) L⊙ kpc^(−2). Below Σ*_(IR), G/n_H remains constant, 0.32 G_0 cm^3, and variations in Σ_(IR) are driven by the number density of star-forming regions within a galaxy, with no change in their PDR properties. Above Σ*_(IR), G/n_H increases rapidly with Σ_(IR), signaling a departure from the typical PDR conditions found in normal star-forming galaxies toward more intense/harder radiation fields and compact geometries typical of starbursting sources.

Optical and radio behaviour of the BL Lacertae object 0716+714 ⋆

Abstract: Eight optical and four radio observatories have been intensively monitoring the BL Lac object 0716+714 in the last years: 4854 data points have been collected in the UBVRI bands since 1994, while radio light curves extendback to 1978. Many of these data, which all together constitute the widest optical and radio database available on this object, are presented here for the first time. Four major optical outbursts were observed at the beginning of 1995, in late 1997, at the end of 2000, and in fall 2001. In particular, an exceptional brightening of 2.3 mag in 9 days was detected in the R band just before the BeppoSAX pointing of October 30, 2000. A big radio outburst lasted from early 1998 to the end of 1999. The long-term trend shown by the optical light curves seems to vary with a characteristic time scale of about 3.3 years, while a longer period of 5.5-6 years seems to characterize the radio long-term variations. In general, optical colour indices are only weakly correlated with brightness; a clear spectral steepening trend was observed during at least one long-lasting dimming phase. Moreover, the optical spectrum became steeper after JD ∼ 2451 000, the change occurring in the decaying phase of the late-1997 outburst. The radio flux behaviour at different frequencies is similar, but the flux variation amplitude decreases with increasing wavelength. The radio spectral index varies with brightness (harder when brighter), but the radio fluxes seem to be the sum of two different-spectrum contributions: a steady base level and a harder-spectrum variable component. Once the base level is removed, the radio variations appear as essentially achromatic, similarly to the optical behaviour. Flux variations at the higher radio frequencies lead the lower-frequency ones with week-month time scales. The behaviour of the optical and radio light curves is quite different, the broad radio outbursts not corresponding in time to the faster optical ones and the cross-correlation analysis indicating only weak correlation with long time lags. However, minor radio flux enhancements simultaneous with the major optical flares can be recognized, which may imply that the mechanism producing the strong flux increases in the optical band also marginally affects the radio one. On the contrary, the process responsible for the big radio outbursts does not seem to affect the optical emission.

In vitro study of the insulin-mimetic behaviour of vanadium(IV, V) coordination compounds

Abstract: A representative set of vanadium(IV and V) compounds in varying coordination environments has been tested in the concentration range 1 to 10–6 mM, using transformed mice fibroblasts (cell line SV 3T3), with respect to their short-term cell toxicity (up to 36 hours) and their ability to stimulate glucose uptake by cells. These insulin-mimetic tests have also been carried out with non-transformed human fibroblasts (cell line F26). The compounds under investigation comprise established insulin-mimetic species such as vanadate ([H2VO4]–), [VO(acetylacetonate)2], [VO2(dipicolinate)]– and [VO(maltolate)2], and new systems and coordination compounds containing OO, ON, OS, NS and ONS donor atom sets. A vitality test assay, measuring the reduction equivalents released in the mitochondrial respiratory chain by intracellular glucose degradation, is introduced and the results are counter-checked with 3H-labelled glucose. Most compounds are toxic at the 1 mM concentration level, and most compounds are essentially non-toxic and about as effective as or more potent than insulin at concentrations of 0.01 mM and below. VV compounds tend to be less toxic than VIV compounds, and complexes containing thio functional ligands are somewhat more toxic than others. Generally, ON ligation is superior in insulin-mimetic efficacy to OO or O/NS coordination, irrespective of the vanadium oxidation state. There is, however, no striking correlation between the nature of the ligand systems and the insulin-mimetic potency in these cell culture tests, encompassing 41 vanadium compounds, the results on 22 of which are reported in detail here. The syntheses and characteristics of various new compounds are provided together with selected speciation results. The crystal and molecular structures of {[VO(naph-tris)]2} [where naph-tris is the Schiff base formed between o-hydroxynaphthaldehyde and tris(hydroxymethyl)amine] are reported. Electronic supplementary material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00775-001-0311-5

Social influences on false belief access : Specific sibling influences or general apprenticeship ?

Abstract: Some recent studies have found a relation between the number of siblings 3–4-year-old children have and their performance on false belief tasks. 2 experiments reported here examine a variety of factors in children's social environments, including daily contact with peers and adults as well as the numbers of their siblings, on a battery of false belief tests. In Experiment 1, 82 preschoolers were studied in Rethymnon, Crete, in order to obtain a range of extended kin available as a resource for the child. In Experiment 2, 75 Cypriot preschoolers were studied in Nicosia in order to examine the influences of each child's daily social contacts, as measured by maternal questionnaire. Logistic regression revealed that the factors which account for most of the predicted variance on the theory of mind tests were (a) the number of adult kin available (Experiment 1) or adults interacted with daily (Experiment 2), (b) the child's age, (c) the number of older siblings a child has, and (d) the number of older children interacted with daily. The results suggested that theory of mind is not simply passed from one sibling to another in a process of social influence. It seems more likely that a variety of knowledgeable members of her or his culture influence the apprentice theoretician of mind.