The contribution of urban green spaces to the improvement of environment in cities: Case study of Chania, Greece

This paper investigates how vegetation, mainly through evapotranspiration, affects the improvement of microclimatic conditions in urban areas and, more specifically, it examines the case for the city of Chania in Crete. The objectives of this study are to examine the bioclimatic role of green areas in urban sites as they affect the thermal comfort of residents, and to study the cross-correlation of factors that participate in this process. To achieve these objectives, we have examined the parameters that contribute to the microclimate of a space and consider how it is influenced by vegetation. In addition, we have analyzed the effect of vegetation with respect to evapotranspiration, and have recorded the existing vegetation of Chania city and the relationship with the geomorphologic and urban characteristics of the city. This has involved calculating the evapotranspiration of various plant species, and collecting measurements at various places in Chania. These studies are designed to determine the cause of the changes of thermal comfort in different parts of the city, and to examine the differentiation of thermal comfort that is observed between different plant species with respect to the evapotranspiration measure that has been calculated for each of them. The intention of this work is to aid efforts to improve the environment of Chania through better planning and the appropriate choice of the species used for planting open spaces. Finally, it is hoped that the results of this work will be of use in planning the environments of spaces in other cities that have similar characteristics

Critical currents in Josephson junctions with macroscopic defects

The critical currents in Josephson junctions of conventional superconductors with macroscopic defects are calculated for different defect critical current densities as a function of the magnetic field. We also study the evolution of the different modes with the defect position, at zero external field. We study the stability of the solutions and derive simple arguments, that could help the defect characterization. In most cases a reentrant behavior is seen, where both a maximum and a minimum current exist.Comment: 17 pages with 16 figures, submitted to Supercond. Sci. Techno

Graphene/Carbon Dot Hybrid Thin Films Prepared by a Modified Langmuir-Schaefer Method

The special electronic, optical, thermal, and mechanical properties of graphene resulting from its 2D nature, as well as the ease of functionalizing it through a simple acid treatment, make graphene an ideal building block for the development of new hybrid nanostructures with well-defined dimensions and behavior. Such hybrids have great potential as active materials in applications such as gas storage, gas/liquid separation, photocatalysis, bioimaging, optoelectronics, and nanosensing. In this study, luminescent carbon dots (C-dots) were sandwiched between oxidized graphene sheets to form novel hybrid multilayer films. Our thin-film preparation approach combines self-assembly with the Langmuir-Schaefer deposition and uses graphene oxide nanosheets as template for grafting C-dots in a bidimensional array. Repeating the cycle results in a facile and low-cost layer-by-layer procedure for the formation of highly ordered hybrid multilayers, which were characterized by photoluminescence, UV-visible, X-ray photoelectron, and Raman spectroscopies, as well as X-ray diffraction and atomic force microscopy.</p

TIME SERIES ANALYSIS OF RAINFALL DATA OF NESTORIO – KASTORIA – GAUGE STATION USING A RECURRENT NEURAL NETWORK MODEL

Στην  παρούσα  εργασία,  εφαρμόζεται  ένα  μοντέλο  προσομοίωσης  χρονοσειράς βασισμένο σε  δομές Τεχνητών Νευρωνικών  δικτύων (ΤΝΔ). Τα ΤΝΔ,  τα οποία  είναι μοντέλα «μαύρου κουτιού», χρησιμοποιούνται αφενός επειδή μπορούν να εφαρμοστούν σε  συστήματα  οι  διεργασίες  των  οποίων  χαρακτηρίζονται  από  υψηλό  βαθμό πολυπλοκότητας και αφετέρου λόγω της σημαντικής απλότητας που τα χαρακτηρίζει. Η χρονοσειρά στην οποία εφαρμόζονται, προέρχεται από τα δεδομένα 41 ετών μηνιαίων παρατηρήσεων (1962 – 2003)  των  βροχοπτώσεων  του  βροχομετρικού  σταθμού Νεστορίου – Καστοριάς. Το τελικό προτεινόμενο μοντέλο που διαμορφώνεται είναι ένα (12,5,3,1) επανατροφοδοτούμενο δίκτυο (recurrent network) το οποίο αποτελείται από 12  κόμβους  εισόδου (βροχόπτωση  κατά  τους 12  προηγούμενους  μήνες),  δύο  κρυφά επίπεδα  5  και  3  κόμβων  αντίστοιχα  και  1  κόμβο  εξόδου (βροχόπτωση  του  μήνα αναφοράς). Το μοντέλο εμφανίζει καλή προσαρμογή στα δεδομένα λόγω της σύγκλισης των  τιμών  σφάλματος  των  δεδομένων  εκπαίδευσης  και  των  δεδομένων  δοκιμής.  Το τελικό  εκτιμώμενο  σφάλμα (RMSE)  είναι  ίσο  με 0,94,  είναι  της  τάξης  του  ενός χιλιοστού  βροχής  και  κρίνεται  πολύ  ικανοποιητικό.  Η  πλατφόρμα  λογισμικού  που χρησιμοποιήθηκε για την ανάπτυξη του  μοντέλου ήταν το Neurosolution της εταιρείας Neurodimension (http://www.nd.com).In the present study, a time series model is applied based on Artificial Neural Network algorithms. Neural Networks are applied because, as “black box” models, they can simulate systems which are characterized  by very complicated natural processes and moreover it is easy to be applied. The time  series in which the Neural Network is applied, is the monthly rainfall data of Nestorio – Kastoria – rainfall gauge for a period of 41 years (1962 – 2003). The final proposed model that is formulated, is a (12,5,3,1) recurrent network, which consists of 12 nodes of the input layer, two hidden layers of 5 and 3 nodes respectively and 1 node of the output layer. The model reveal good fitting in the raw data because of the convergence between the training and validation errors. The final RMSE value is equal to 0,94 and is correspond to one mm of rainfall, so the method obtain very satisfactory results. The software package which has been used for the development of the model is Neurosolution of Neurodimension Company (http://www.nd.com)

Effects of Space Charge, Dopants, and Strain Fields on Surfaces and Grain Boundaries in YBCO Compounds

Statistical thermodynamical and kinetically-limited models are applied to study the origin and evolution of space charges and band-bending effects at low angle [001] tilt grain boundaries in YBa$_2$Cu$_3$O$_7$ and the effects of Ca doping upon them. Atomistic simulations, using shell models of interatomic forces, are used to calculate the energetics of various relevant point defects. The intrinsic space charge profiles at ideal surfaces are calculated for two limits of oxygen contents, i.e. YBa$_2$Cu$_3$O$_6$ and YBa$_2$Cu$_3$O$_7$. At one limit, O$_6$, the system is an insulator, while at O$_7$, a metal. This is analogous to the intrinsic and doping cases of semiconductors. The site selections for doping calcium and creating holes are also investigated by calculating the heat of solution. In a continuum treatment, the volume of formation of doping calcium at Y-sites is computed. It is then applied to study the segregation of calcium ions to grain boundaries in the Y-123 compound. The influences of the segregation of calcium ions on space charge profiles are finally studied to provide one guide for understanding the improvement of transport properties by doping calcium at grain boundaries in Y-123 compound.Comment: 13 pages, 5 figure

A Structural View on the Stereospecificity of Plant Borneol‐Type Dehydrogenases

The development of sustainable processes for the valorization of byproducts and other waste streams remains an ongoing challenge in the field of catalysis. Racemic borneol, isoborneol and camphor are currently produced from alpha-pinene, a side product from the production of cellulose. The pure enantiomers of these monoterpenoids have numerous applications in cosmetics and act as reagents for asymmetric synthesis, making an enzymatic route for their separation into optically pure enantiomers a desirable goal. Known short-chain borneol-type dehydrogenases (BDHs) from plants and bacteria lack the required specificity, stability or activity for industrial utilization. Prompted by reports on the presence of pure (-)-borneol and (-)-camphor in essential oils from rosemary, we set out to investigate dehydrogenases from the genus Salvia and discovered a dehydrogenase with high specificity (E>120) and high specific activity (>0.02 U mg(-1)) for borneol and isoborneol. Compared to other specific dehydrogenases, the one reported here shows remarkably higher stability, which was exploited to obtain the first three-dimensional structure of an enantiospecific borneol-type short-chain dehydrogenase. This, together with docking studies, led to the identification of a hydrophobic pocket in the enzyme that plays a crucial role in the stereo discrimination of bornane-type monoterpenoids. The kinetic resolution of borneol and isoborneol can be easily integrated into the existing synthetic route from alpha-pinene to camphor thereby allowing the facile synthesis of optically pure monoterpenols from an abundant renewable source

The atomic structure of large-angle grain boundaries Σ5\Sigma 5 and Σ13\Sigma 13 in YBa2Cu3O7−δ{\rm YBa_2Cu_3O_{7-\delta}} and their transport properties

We present the results of a computer simulation of the atomic structures of large-angle symmetrical tilt grain boundaries (GBs) $\Sigma 5$ (misorientation angles \q{36.87}{^{\circ}} and \q{53.13}{^{\circ}}), $\Sigma 13$ (misorientation angles \q{22.62}{^{\circ}} and \q{67.38}{^{\circ}}). The critical strain level $\epsilon_{crit}$ criterion (phenomenological criterion) of Chisholm and Pennycook is applied to the computer simulation data to estimate the thickness of the nonsuperconducting layer ${\rm h_n}$ enveloping the grain boundaries. The ${\rm h_n}$ is estimated also by a bond-valence-sum analysis. We propose that the phenomenological criterion is caused by the change of the bond lengths and valence of atoms in the GB structure on the atomic level. The macro- and micro- approaches become consistent if the $\epsilon_{crit}$ is greater than in earlier papers. It is predicted that the symmetrical tilt GB $\Sigma5$ \theta = \q{53.13}{^{\circ}} should demonstrate a largest critical current across the boundary.Comment: 10 pages, 2 figure

Strong interconversion of non-polar phonons and Josephson plasma oscillations induced by equilibrium Josephson currents in high T_c superconductors

We analyze consequences of dynamical modulations of Josephson current by non-polar lattice mode in the Josephson junction barrier. In the high $T_c$ junctions, the effect of such modulations can be anomalously strong due to the proximity of the insulating barrier to the superconducting state. Accordingly, the interconversion of sound (as well as other non-polar phonons) and the Josephson plasma oscillations mediated by stationary Josephson currents, which may be present in the junction due to various reasons, becomes possible. We suggest that this effect can be employed for imaging of the stationary Josephson currents. Estimates of the effect are given.Comment: 11 RevTeX pages, no figure

Influence of vortex-vortex interaction on critical currents across low-angle grain boundaries in YBa2Cu3O7-delta thin films

Low-angle grain boundaries with misorientation angles theta < 5 degrees in optimally doped thin films of YBCO are investigated by magnetooptical imaging. By using a numerical inversion scheme of Biot-Savart's law the critical current density across the grain boundary can be determined with a spatial resolution of about 5 micrometers. Detailed investigation of the spatially resolved flux density and current density data shows that the current density across the boundary varies with varying local flux density. Combining the corresponding flux and current pattern it is found that there exists a universal dependency of the grain boundary current on the local flux density. A change in the local flux density means a variation in the flux line-flux line distance. With this knowledge a model is developped that explains the flux-current relation by means of magnetic vortex-vortex interaction.Comment: 7 pages, 14 figure

CryoEM analysis of small plant biocatalysts at sub 2 resolution

Enzyme catalysis has emerged as a key technology for developing efficient, sustainable processes in the chemical, biotechnological and pharmaceutical industries. Plants provide large and diverse pools of biosynthetic enzymes that facilitate complex reactions, such as the formation of intricate terpene carbon skeletons, with exquisite specificity. High resolution structural analysis of these enzymes is crucial in order to understand their mechanisms and modulate their properties by targeted engineering. Although cryo electron microscopy cryoEM has revolutionized structural biology, its applicability to high resolution structural analysis of comparatively small enzymes has so far been largely unexplored. Here, it is shown that cryoEM can reveal the structures of plant borneol dehydrogenases of amp; 8764;120 kDa at or below 2 resolution, paving the way for the rapid development of new biocatalysts that can provide access to bioactive terpenes and terpenoid