Showing papers by "University of Crete published in 2006"
TL;DR: Experimental results of the proposed MPPT system indicate near-optimal WG output power, increased by 11%-50% compared to a WG directly connected via a rectifier to the battery bank, and better exploitation of the available wind energy is achieved, especially under low wind speeds.
Abstract: A wind-generator (WG) maximum-power-point-tracking (MPPT) system is presented, consisting of a high-efficiency buck-type dc/dc converter and a microcontroller-based control unit running the MPPT function. The advantages of the proposed MPPT method are that no knowledge of the WG optimal power characteristic or measurement of the wind speed is required and the WG operates at a variable speed. Thus, the system features higher reliability, lower complexity and cost, and less mechanical stress of the WG. Experimental results of the proposed system indicate near-optimal WG output power, increased by 11%-50% compared to a WG directly connected via a rectifier to the battery bank. Thus, better exploitation of the available wind energy is achieved, especially under low wind speeds.
907 citations
TL;DR: The present data suggest that ultrasound-guided catheterisation of the internal jugular vein in critical care patients is superior to the landmark technique and therefore should be the method of choice in these patients.
Abstract: Central venous cannulation is crucial in the management of the critical care patient. This study was designed to evaluate whether real-time ultrasound-guided cannulation of the internal jugular vein is superior to the standard landmark method. In this randomised study, 450 critical care patients who underwent real-time ultrasound-guided cannulation of the internal jugular vein were prospectively compared with 450 critical care patients in whom the landmark technique was used. Randomisation was performed by means of a computer-generated random-numbers table, and patients were stratified with regard to age, gender, and body mass index. There were no significant differences in gender, age, body mass index, or side of cannulation (left or right) or in the presence of risk factors for difficult venous cannulation such as prior catheterisation, limited sites for access attempts, previous difficulties during catheterisation, previous mechanical complication, known vascular abnormality, untreated coagulopathy, skeletal deformity, and cannulation during cardiac arrest between the two groups of patients. Furthermore, the physicians who performed the procedures had comparable experience in the placement of central venous catheters (p = non-significant). Cannulation of the internal jugular vein was achieved in all patients by using ultrasound and in 425 of the patients (94.4%) by using the landmark technique (p < 0.001). Average access time (skin to vein) and number of attempts were significantly reduced in the ultrasound group of patients compared with the landmark group (p < 0.001). In the landmark group, puncture of the carotid artery occurred in 10.6% of patients, haematoma in 8.4%, haemothorax in 1.7%, pneumothorax in 2.4%, and central venous catheter-associated blood stream infection in 16%, which were all significantly increased compared with the ultrasound group (p < 0.001). The present data suggest that ultrasound-guided catheterisation of the internal jugular vein in critical care patients is superior to the landmark technique and therefore should be the method of choice in these patients.
594 citations
TL;DR: Long-term THM exposure was associated with a twofold bladder cancer risk, with an odds ratio of 2.10 (95% confidence interval: 1.09, 4.02) for average household THM levels of >49 versus < or =8 micro g/liter.
Abstract: Bladder cancer has been associated with exposure to chlorination by-products in drinking water, and experimental evidence suggests that exposure also occurs through inhalation and dermal absorption. The authors examined whether bladder cancer risk was associated with exposure to trihalomethanes (THMs) through ingestion of water and through inhalation and dermal absorption during showering, bathing, and swimming in pools. Lifetime personal information on water consumption and water-related habits was collected for 1,219 cases and 1,271 controls in a 1998-2001 case-control study in Spain and was linked with THM levels in geographic study areas. Long-term THM exposure was associated with a twofold bladder cancer risk, with an odds ratio of 2.10 (95% confidence interval: 1.09, 4.02) for average household THM levels of >49 versus 35 micro g/day through ingestion had an odds ratio of 1.35 (95% confidence interval: 0.92, 1.99). The odds ratio for duration of shower or bath weighted by residential THM level was 1.83 (95% confidence interval: 1.17, 2.87) for the highest compared with the lowest quartile. Swimming in pools was associated with an odds ratio of 1.57 (95% confidence interval: 1.18, 2.09). Bladder cancer risk was associated with long-term exposure to THMs in chlorinated water at levels regularly occurring in industrialized countries.
531 citations
TL;DR: In this paper, a specific hypothesis was tested: self-efficacy expectations, as a representation of a capable self, and perceived social support, as representation of helpful world, shape optimism which is an outcome expectation.
499 citations
TL;DR: The machinery appears to be highly specialized involving activation of distinct signalling molecules depending on the type of extracellular stimulus, and each step of cyclooxygenease-2 regulation can be used as potential therapeutic target.
462 citations
TL;DR: In this paper, the authors present 5-38 μm mid-infrared spectra at a spectral resolution of R ≈ 65-130 of a large sample of 22 starburst nuclei taken with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope.
Abstract: We present 5-38 μm mid-infrared spectra at a spectral resolution of R ≈ 65-130 of a large sample of 22 starburst nuclei taken with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. The spectra show a vast range of starburst SEDs. The silicate absorption ranges from essentially no absorption to heavily obscured systems with an optical depth of τ_(9.8 μm) ~ 5. The spectral slopes can be used to discriminate between starburst and AGN powered sources. The monochromatic continuum fluxes at 15 and 30 μm enable a remarkably accurate estimate of the total infrared luminosity of the starburst. We find that the PAH equivalent width is independent of the total starburst luminosity L_(IR) as both continuum and PAH feature scale proportionally. However, the luminosity of the 6.2 μm feature scales with L_(IR) and can be used to approximate the total infrared luminosity of the starburst. Although our starburst sample covers about a factor of 10 difference in the [Ne III]/[Ne II] ratio, we found no systematic correlation between the radiation field hardness and the PAH equivalent width or the 7.7 μm/11.3 μm PAH ratio. These results are based on spatially integrated diagnostics over an entire starburst region, and local variations may be "averaged out." It is presumably due to this effect that unresolved starburst nuclei with significantly different global properties appear spectrally as rather similar members of one class of objects.
461 citations
TL;DR: It is shown that a curvature correction to the entropy that is polynomial in the Ricci scalar requires a nonequilibrium treatment.
Abstract: It has previously been shown that the Einstein equation can be derived from the requirement that the Clausius relation dS = �Q/T hold for all local acceleration horizons through each spacetime point, where dS is one quarter the horizon area change in Planck units, andQ and T are the energy flux across the horizon and Unruh temperature seen by an accelerating observer just inside the horizon. Here we show that a curvature correction to the entropy that is polynomial in the Ricci scalar requires a non-equilibrium treatment. The corresponding field equation is derived from the entropy balance relation dS = �Q/T + diS, where diS is a bulk viscosity entropy production term that we determine by imposing energy-momentum conservation. Entropy production can also be included in pure Einstein theory by allowing for shear viscosity of the horizon.
450 citations
TL;DR: Describing the spatial pattern of functional connectivity by computing the "synchronization likelihood" of EEG at rest and during performance of a 2Back working memory task using letters of the alphabet presented on a PC screen in subjects with schizophrenia and healthy controls could be helpful for diagnosis and evaluation of the severity of the disease.
444 citations
Spanish National Research Council1, University of Seville2, Ankara University3, Akdeniz University4, National Clonal Germplasm Repository5, University of Agricultural Sciences, Dharwad6, Hebrew University of Jerusalem7, University of Pennsylvania8, Institut national de la recherche agronomique9, University of Zagreb10, University of Crete11, Academy of Sciences of Albania12, Agharkar Research Institute13, Arts et Métiers ParisTech14, Kuban State Agrarian University15
TL;DR: The results suggest the existence of at least two important origins for the cultivated germplasm, one in the Near East and another in the western Mediterranean region, the latter of which gave rise to many of the current Western European cultivars.
Abstract: The domestication of the Eurasian grape (Vitis vinifera ssp. sativa) from its wild ancestor (Vitis vinifera ssp. sylvestris) has long been claimed to have occurred in Transcaucasia where its greatest genetic diversity is found and where very early archaeological evidence, including grape pips and artefacts of a 'wine culture', have been excavated. Whether from Transcaucasia or the nearby Taurus or Zagros Mountains, it is hypothesized that this wine culture spread southwards and eventually westwards around the Mediterranean basin, together with the transplantation of cultivated grape cuttings. However, the existence of morphological differentiation between cultivars from eastern and western ends of the modern distribution of the Eurasian grape suggests the existence of different genetic contribution from local sylvestris populations or multilocal selection and domestication of sylvestris genotypes. To tackle this issue, we analysed chlorotype variation and distribution in 1201 samples of sylvestris and sativa genotypes from the whole area of the species' distribution and studied their genetic relationships. The results suggest the existence of at least two important origins for the cultivated germplasm, one in the Near East and another in the western Mediterranean region, the latter of which gave rise to many of the current Western European cultivars. Indeed, over 70% of the Iberian Peninsula cultivars display chlorotypes that are only compatible with their having derived from western sylvestris populations.
402 citations
TL;DR: In this article, a theoretical framework is proposed to analyze the conditions under which a farmer facing production uncertainty and incomplete information will adopt a more efficient irrigation technology, and a reduced form of this model is empirically estimated using a sample of 265 farms located in Crete, Greece.
Abstract: We propose a theoretical framework to analyze the conditions under which a farmer facing production uncertainty (due to a possible water shortage) and incomplete information will adopt a more efficient irrigation technology. A reduced form of this model is empirically estimated using a sample of 265 farms located in Crete, Greece. The empirical results suggest that farmers choose to adopt the new technology in order to hedge against production risk. In addition, we show that the farmer's human capital also plays a significant role in the decision to adopt modern, more efficient irrigation equipment.
400 citations
TL;DR: In this paper, the negative index properties of short wire-pair structures were investigated using simulations and microwave experiments, and it was shown unambiguously that the transmittance and the reflectance properties of such structures are negative at the same frequency.
Abstract: Negative refraction is currently achieved by a combination of artificial ``electric atoms'' (metallic wires with negative electrical permittivity $\ensuremath{\epsilon}$) and artificial ``magnetic atoms'' (split-ring resonators with negative magnetic permeability $\ensuremath{\mu}$). Both $\ensuremath{\epsilon}$ and $\ensuremath{\mu}$ must be negative at the same frequency, which is not easy to achieve at higher than THz frequencies. We introduce improved and simplified structures made of periodic arrays of pairs of short metal wires and continuous wires that offer a potentially simpler approach to building negative index materials. Using simulations and microwave experiments, we have investigated the negative index $n$ properties of short wire-pair structures. We have measured experimentally both the transmittance and the reflectance properties and found unambiguously that $nl0$. The same is true for $\ensuremath{\epsilon}$ and $\ensuremath{\mu}$. Our results show that short wire-pair arrays can be used very effectively in producing materials with negative refractive indices.
TL;DR: The hypothesis that the salinity-generated ROS signal induces α-G DH subunit expression, and the anionic iso-GDHs assimilate ammonia, acting as antistress enzymes in ammonia detoxification and production of Glu for Pro synthesis, is supported.
Abstract: Glutamate dehydrogenase (GDH) may be a stress-responsive enzyme, as GDH exhibits considerable thermal stability, and de novo synthesis of the α-GDH subunit is induced by exogenous ammonium and senescence. NaCl treatment induces reactive oxygen species (ROS), intracellular ammonia, expression of tobacco (Nicotiana tabacum cv Xanthi) gdh-NAD;A1 encoding the α-subunit of GDH, increase in immunoreactive α-polypeptide, assembly of the anionic isoenzymes, and in vitro GDH aminating activity in tissues from hypergeous plant organs. In vivo aminating GDH activity was confirmed by gas chromatorgraphy–mass spectrometry monitoring of 15N-Glu, 15N-Gln, and 15N-Pro in the presence of methionine sulfoximine and amino oxyacetic acid, inhibitors of Gln synthetase and transaminases, respectively. Along with upregulation of α-GDH by NaCl, isocitrate dehydrogenase genes, which provide 2-oxoglutarate, are also induced. Treatment with menadione also elicits a severalfold increase in ROS and immunoreactive α-polypeptide and GDH activity. This suggests that ROS participate in the signaling pathway for GDH expression and protease activation, which contribute to intracellular hyperammonia. Ammonium ions also mimic the effects of salinity in induction of gdh-NAD;A1 expression. These results, confirmed in tobacco and grape (Vitis vinifera cv Sultanina) tissues, support the hypothesis that the salinity-generated ROS signal induces α-GDH subunit expression, and the anionic iso-GDHs assimilate ammonia, acting as antistress enzymes in ammonia detoxification and production of Glu for Pro synthesis.
TL;DR: The phenotypes generated in experimental mouse models for apoA-I, ABCA1, LCAT, SR-BI, and other proteins of the HDL pathway may facilitate early diagnosis of similar phenotypes in the human population and provide guidance for proper treatment.
Abstract: The concentration, composition, shape, and size of plasma high-density lipoprotein (HDL) are determined by numerous proteins that influence its biogenesis, remodeling, and catabolism. The discoveries of the HDL receptor (scavenger receptor class B type I, SR-BI) and the ABCA1 (ATP-binding cassette transporter A1) lipid transporter provided two missing links that were necessary to understand the biogenesis and some of the functions of HDL. Existing data indicate that functional interactions between apoA-I and ABCA1 are necessary for the initial lipidation of apoA-I. Through a series of intermediate steps, lipidated apoA-I proceeds to form discoidal HDL particles that can be converted to spherical particles by the action of lecithin:cholesterol acyltransferase (LCAT). Discoidal and spherical HDL can interact functionally with SR-BI and these interactions lead to selective lipid uptake and net efflux of cholesterol and thus remodel HDL. Defective apoA-I/ABCA1 interactions prevent lipidation of apoA-I that is necessary for the formation of HDL particles. In the same way, specific mutations in apoA-I or LCAT prevent the conversion of discoidal to spherical HDL particles. The interactions of lipid-bound apoA-I with SR-BI are affected in vitro by specific mutations in apoA-I or SR-BI. Furthermore, deficiency of SR-BI affects the lipid and apolipoprotein composition of HDL and is associated with increased susceptibility to atherosclerosis. Here we review the current status of the pathway of HDL biogenesis and mutations in apoA-I, ABCA1, and SR-BI that disrupt different steps of the pathway and may lead to dyslipidemia and atherosclerosis in mouse models. The phenotypes generated in experimental mouse models for apoA-I, ABCA1, LCAT, SR-BI, and other proteins of the HDL pathway may facilitate early diagnosis of similar phenotypes in the human population and provide guidance for proper treatment.
TL;DR: In this paper, the authors show that equivalent circuits offer a qualitative and even quantitative simple explanation for the behavior of various types of left-handed (or negative-index) metamaterials and apply this unifying circuit approach in accounting for the features and in optimizing the structure employing parallel metallic bars on the two sides of a dielectric film.
Abstract: We show that equivalent circuits offer a qualitative and even quantitative simple explanation for the behavior of various types of left-handed (or negative-index) metamaterials. This allows us to optimize design features and parameters while avoiding trial and error simulations or fabrications. In particular, we apply this unifying circuit approach in accounting for the features and in optimizing the structure employing parallel metallic bars on the two sides of a dielectric film.
TL;DR: The results verify in both theoretical levels that SiCNTs seem to be more suitable materials for hydrogen storage than pure CNTs.
Abstract: A multiscale theoretical approach is used for the investigation of hydrogen storage in silicon-carbon nanotubes (SiCNTs). First, ab initio calculations at the density functional level of theory (DFT) showed an increase of 20% in the binding energy of H2 in SiCNTs compared with pure carbon nanotubes (CNTs). This is explained by the alternative charges that exist in the SiCNT walls. Second, classical Monte Carlo simulation of nanotube bundles showed an even larger increase of the storage capacity in SiCNTs, especially in low temperature and high-pressure conditions. Our results verify in both theoretical levels that SiCNTs seem to be more suitable materials for hydrogen storage than pure CNTs.
TL;DR: These studies indicate that ADHD is more common in boys than girls, in younger than older children and adolescents, in one-setting rather than two-setting screening studies, in studies based on DSM-IV rather than DSM-III-R criteria.
Abstract: Attention deficit hyperactivity disorder (ADHD) is among the most common, intensely investigated, and yet diagnostically controversial neurobehavioral conditions of childhood. The prevalence of ADHD has been reported with great variations among different studies, ranging from 2.2% to 17.8%. The aim of this review was to investigate the variables that influence the prevalence of ADHD and to derive a best estimate for the prevalence of the disorder. We reviewed all the 39 studies on ADHD prevalence appearing in the Pubmed and published since 1992. These studies indicate that ADHD is more common in boys than girls, in younger than older children and adolescents, in one-setting rather than two-setting screening studies, in studies based on DSM-IV rather than DSM-III-R criteria. Additional factors that may well influence prevalence rates include source of information and assessment of clinical impairment. In conclusion, our findings suggest that population characteristics, methodology features, ethnic and cultural differences and diagnostic criteria involved in studies affect the prevalence of ADHD. Standardized designs may lead to firm conclusions on the true prevalence of ADHD, the estimation of which seems impossible to be achieved by reviewing the already existing literature.
TL;DR: In this paper, the authors showed that the surface properties of ZnO transparent thin films are strongly influenced by surface morphology, and correlating the optical and electrical film properties with surface parameters (i.e. RMS and grain radius) can lead to an enhancement of the material's potential for gas sensing applications.
TL;DR: The results establish the fact that the carbon nanofiber is the best matrix so far described for the development of biosensors, far superior to carbon nanotubes or graphite powder.
Abstract: The use of highly activated carbon nanofibers for the design of catalytic electrochemical biosensors is demonstrated. The direct immobilization of enzymes onto the surface of carbon nanofibers is shown to be a highly efficient method for the development of a new class of very sensitive, stable, and reproducible electrochemical biosensors. These results establish the fact that the carbon nanofiber is the best matrix so far described for the development of biosensors, far superior to carbon nanotubes or graphite powder.
17 Jun 2006
TL;DR: A new exemplar-based framework unifying image completion, texture synthesis and image inpainting is presented, which carries two very important extensions over standard belief propagation (BP): "prioritybased message scheduling" and "dynamic label pruning".
Abstract: A new exemplar-based framework unifying image completion, texture synthesis and image inpainting is presented in this work. Contrary to existing greedy techniques, these tasks are posed in the form of a discrete global optimization problem with a well defined objective function. For solving this problem a novel optimization scheme, called Priority- BP, is proposed which carries two very important extensions over standard belief propagation (BP): "prioritybased message scheduling" and "dynamic label pruning". These two extensions work in cooperation to deal with the intolerable computational cost of BP caused by the huge number of existing labels. Moreover, both extensions are generic and can therefore be applied to any MRF energy function as well. The effectiveness of our method is demonstrated on a wide variety of image completion examples.
TL;DR: The evolution of the Ion imaging technique is traced, some of the more important breakthroughs with regards to improving image resolution and in image processing and analysis methods are highlighted, and the many applications to which the technique is now being applied are illustrated.
Abstract: Ion imaging methods are making ever greater impact on studies of gas phase molecular reaction dynamics. This article traces the evolution of the technique, highlights some of the more important breakthroughs with regards to improving image resolution and in image processing and analysis methods, and then proceeds to illustrate some of the many applications to which the technique is now being applied—most notably in studies of molecular photodissociation and of bimolecular reaction dynamics.
TL;DR: In this article, a Spitzer-based mid-infrared (MIR) study of a large sample of blue compact dwarfs (BCDs) using the InfraredSpectrograph (IRS), including the firstMIRspectrumof IZw18,thearchetypefortheBCDclass and among the most metal-poor galaxies known.
Abstract: We present a Spitzer-based mid-infrared (MIR) study of a large sample of blue compact dwarfs (BCDs) using the InfraredSpectrograph(IRS),includingthefirstMIRspectrumof IZw18,thearchetypefortheBCDclassandamong the most metal-poor galaxies known. We show the spectra of polycyclic aromatic hydrocarbon (PAH) emission in a low-metallicity environment. We find that the equivalent widths (EWs) of PAHs at 6.2, 7.7, 8.6, and 11.2 � ma re generally weaker in BCDs than in typical starburst galaxies and that the fine-structure line ratio, [Ne iii]/[Ne ii], has a weak anticorrelation with the PAH EW. A much stronger anticorrelation is shown between the PAH EW and the product of the [Ne iii]/[Ne ii] ratio and the UV luminosity density divided by the metallicity. We conclude that the PAH EWin metal-poor high-excitation environments is determined by a combination of PAH formation and destruction effects. Subject headings: dust, extinction — galaxies: abundances — galaxies: dwarf — galaxies: starburst — infrared: galaxies
TL;DR: Wittrock et al. as mentioned in this paper presented the first global simultaneous observations of glyoxal (CHOCHO) and formaldehyde (HCHO) columns retrieved from measurements by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) satellite instrument.
Abstract: [1] The first global simultaneous observations of glyoxal (CHOCHO) and formaldehyde (HCHO) columns retrieved from measurements by the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) satellite instrument are presented and compared to model calculations. The global pattern of the distribution of CHOCHO is similar to that of HCHO. High values are observed over areas with large biogenic isoprene emissions (Central Africa, parts of South America, and Indonesia). Also regions with biomass burning and anthropogenic pollution exhibit elevated levels of CHOCHO. The ratio of the columns of CHOCHO to HCHO is generally of the order of 0.05 in regions having biogenic emissions, which is in reasonable agreement with the current understanding of the oxidation of hydrocarbons emitted by the biosphere. However and in contrast to our model, high values of both HCHO and CHOCHO are also observed over areas of the tropical oceans. This is tentatively attributed to outflow from the continents and local oceanic biogenic sources of the precursors of HCHO and CHOCHO. Citation: Wittrock, F., A. Richter, H. Oetjen, J. P. Burrows, M. Kanakidou, S. Myriokefalitakis, R. Volkamer, S. Beirle, U. Platt, and T. Wagner (2006), Simultaneous global observations of glyoxal and formaldehyde from space, Geophys. Res. Lett., 33, L16804, doi:10.1029/2006GL026310.
TL;DR: This work records EEG signals to study neuronal interactions during one WM test in individuals who had few years of formal education (LE) as compared to individuals with university degrees (UE), which suggests that the connections between brain areas of well-educated subjects engaged in WM tasks are not as well-organized in the sense of SWN.
TL;DR: In this paper, the authors report on the wettability properties of silicon surfaces, simultaneously structured on the micrometer-scale and the nanometre-scale by femtosecond (fs) laser irradiation to render silicon hydrophobic.
Abstract: We report on the wettability properties of silicon surfaces, simultaneously structured on the micrometre-scale and the nanometre-scale by femtosecond (fs) laser irradiation to render silicon hydrophobic. By varying the laser fluence, it was possible to control the wetting properties of a silicon surface through a systematic and reproducible variation of the surface roughness. In particular, the silicon–water contact angle could be increased from 66° to more than 130°. Such behaviour is described by incomplete liquid penetration within the silicon features, still leaving partially trapped air inside. We also show how controllable design and tailoring of the surface microstructures by wettability gradients can drive the motion of the drop's centre of mass towards a desired direction (even upwards).
TL;DR: In this article, the embedding of the SM hypercharge into an orientifold gauge group is studied, and possible embeddings are classified, and a systematic construction of bottom-up configurations and top-down orientiferold vacua is achieved, solving the tadpole conditions in the context of Gepner orientifolds.
TL;DR: In this paper, a detailed analysis of anomalous U(1)s and their effective couplings is performed both in field theory and string theory, motivated by the possible relevance of such couplings in particle physics, as a potential signal distinguishing string theory from other UV options.
Abstract: A detailed analysis of anomalous U(1)'s and their effective couplings is performed both in field theory and string theory. It is motivated by the possible relevance of such couplings in particle physics, as well as a potential signal distinguishing string theory from other UV options. The most general anomaly related effective action is analyzed and parameterized. It contains Stuckelberg, axionic and Chern-Simons-like couplings. It is shown that such couplings are generically non-trivial in orientifold string vacua and are not in general fixed by anomalies. A similar analysis in quantum field theories provides similar couplings. The trilinear gauge boson couplings are also calculated and their phenomenological relevance is advocated. We do not find qualitative differences between string and field theory in this sector.
TL;DR: The overall conclusion is that the complicated interactions between variables and the lack of data induce difficulties in setting common or uniform environmental quality standards for benthic effects of fish farming and these should take into account the existing considerable differences between geographic regions, depth zones and sediment types.
TL;DR: In this article, a subset of a finite Abelian group, which tiles the group by translation, and such that its tiling complements do not have a common spectrum (orthogonal basis for their L-2 space consisting of group characters).
Abstract: We exhibit a subset of a finite Abelian group, which tiles the group by translation, and such that its tiling complements do not have a common spectrum (orthogonal basis for their L-2 space consisting of group characters). This disproves the Universal Spectrum Conjecture of Lagarias and Wang [7]. Further, we construct a set in some finite Abelian group, which tiles the group but has no spectrum. We extend this last example to the groups Z(d) and R-d (for d >= 5) thus disproving one direction of the Spectral Set Conjecture of Fuglede [1]. The other direction was recently disproved by Tao [12].
TL;DR: A lot of recent interest has been focused on the so-called left-handed materials (LHMs) or negative-index materials, which exhibit highly unusual electromagnetic properties and hold promise for new device applications.
Abstract: A lot of recent interest has been focused on a new class of materials, the so-called left-handed materials (LHMs) or negative-index materials, which exhibit highly unusual electromagnetic properties and hold promise for new device applications. These materials do not exist in nature and can only be fabricated artificially; for this reason, they are called metamaterials. Their unique properties are not determined by the fundamental physical properties of their constituents, but rather by the shape and distribution of the specific patterns included in them. Metamaterials can be designed to exhibit both electric and magnetic resonances that can be separately tuned to occur in frequency bands from megahertz to terahertz frequencies, and hopefully to the visible region of the electromagnetic spectrum. This article presents a short history of the field, describes the underlying physics, and reviews the experimental and theoretical status of the field at present. Many interesting questions on how to fabricate more isotropic LHMs, on how to push the operational frequency to optical wavelengths, how to reduce the losses, and how to incorporate active or nonlinear materials in LHMs remain to be explored further.
TL;DR: The results point to differential links of insecure attachment styles with perceived support in different life-stages and to related cognitive, emotional and social processes.
Abstract: The present study examined the link between attachment, social support and well-being in young and older adults. The results from multi-group path analyses showed significant between-group differences in the links between attachment, perceived support and well-being. Anxious attachment and well-being were inversely associated and this was stronger for the younger group than it was for the older group. Avoidant attachment was negatively related to perceived support satisfaction in the older age group only, and perceived support mediated the effects of avoidant attachment on mental health and loneliness in the older group. Generally, perceived satisfaction with support was more strongly related with well-being in older adults. The results point to differential links of insecure attachment styles with perceived support in different life-stages and to related cognitive, emotional and social processes.