Entropically stabilized local dipole formation in lead chalcogenides

We report the observation of local structural dipoles that emerge from an undistorted ground state on warming, in contrast to conventional structural phase transitions in which distortions emerge on cooling. Using experimental and theoretical probes of the local structure, we demonstrate this behavior in binary lead chalcogenides, which were believed to adopt the ideal, undistorted rock-salt structure at all temperatures. The behavior is consistent with a simple thermodynamic model in which the emerging dipoles are stabilized in the disordered state at high temperature due to the extra configurational entropy despite the fact that the undistorted structure has lower internal energy. Our findings shed light on the anomalous electronic and thermoelectric properties of the lead chalcogenides. Similar searches may show that the phenomenon is more widespread.     

Time Consumption and Production Costs of Two Small-Scale Wood Harvesting Systems in Northern Greece

A field-based study was carried out to determine the productivity and production cost of the tree length (TL) and the wood assortment (WA) systems implemented under small-scale forestry conditions in two Scots pine stands in Northern Greece. Tree felling and processing productivity were estimated at 8.64 m³ per productive machine hour (PMH^?1) and 10.21 m³ PMH^?1, respectively. Wood felling and processing times were strongly dependent on dbh and total tree volume. However, when manual debarking was also considered the productivity rates decreased to 1.96 and 1.43 m³ PMH^?1, respectively. Skidding productivity was calculated to be 3.35 m³ PMH^?1 for TL and 7.17 m³ PMH^?1 for WA, respectively. Strong correlations have been found between the net skidding time and (a) the skidding distance and (b) the load per turn in both wood harvesting systems. Production costs varied greatly, from 19.38 € m^?3 up to 44.81 € m^?3 of roundwood depending on the harvesting system and the inclusion of debarking. The findings suggest that the WA system is more efficient in terms of productivity and production cost than TL, and that there is a substantial optimization potential. The optimization potential can be encoded in four suggestions: (a) opening up of more forest roads to reduce high skidding times, (b) replacement of manual debarking by mechanical debarking at the sawmill, (c) replacement of old pieces of equipment with newer ones and (d) training of the existing workforce.     

Comparison of the volatile composition in thyme honeys from several origins in Greece

Thyme honey is the most appreciated unifloral Greek honey in Greece as well as around the world. In an effort to investigate the headspace composition of this type of honey, 28 samples were analyzed by means of solid-phase microextraction coupled to a gas chromatography-mass spectrometry system. The botanical origin of the samples was ascertained by pollen analysis, and samples displayed relative frequencies of thyme pollen between 18 and 41%. A total of 62 compounds were isolated, and phenylacetaldehyde was the most abundant (32.9% of the total peak area). Possible botanical markers are 1-phenyl-2,3-butanedione (13.4%), 3-hydroxy-4-phenyl-2-butanone, 3-hydroxy-1-phenyl-2-butanone (14.7%), phenylacetonitrile (4.8%), and carvacrol (0.9%), since these compounds are found only in thyme honey. Additionally, high proportions of phenylacetaldehyde are also characteristic ( F = 12.282, p < 0.001). The average concentrations of seven compounds were significantly different ( p < 0.05), namely phenylacetaldehyde, acetophenone, octanoic acid, carvacrol, phenylethyl alcohol, nonanal, and hexadecane. Applying principal component analysis to the data, six components were extracted, explaining 85.4% of the total variance. The first component explained 46.2% of the total variance and was positively correlated to phenylacetaldehyde, nonanoic acid, acetophenone, decanoic acid, benzaldehyde, phenylacetonitrile, isophorone, and nonanal. The extracted components were used as variables to the discriminant analysis, which showed good discrimination, especially for samples from Crete. A leave-one-out classification showed 85.7% of cross-validated grouped cases correctly classified. These results are promising to establish a discrimination model for these geographical regions. This is crucial for local beekeeper corporations on their effort to produce honey with geographical origin label.     

Dispersion of Odorous Gaseous Compounds Emitted from Wastewater Treatment Plants

Municipal wastewater treatment plants (WTP) emit odorous compounds that produce nuisance to the workers and nearby residents. Several chemical compounds contribute to odour problems, among them, sulphurous organic compounds, hydrogen sulphide, phenols and indoles, ammonia, volatile amines and volatile fatty acids. In the current study, hydrogen sulphide (H₂S) concentrations were measured during the summer period of 2007 by a portable handheld device at the WTP of Chania City (Greece). Measurements were taken in several places within the facility. The highest hydrogen sulphide levels were measured close to the primary sedimentation tanks and the tanks where the recycled activated sludge is mixed, the sludge from the primary sedimentation tanks reaching 30 ppm. In conjunction with the measurements, the Gaussian dispersion model AERMOD code was modified in order to estimate the maximum odour concentration for very short time steps using peak-to-mean ratios. The probability of detection of H₂S exceeds 50% at 400 m distance from the main emission sources (time interval of 5 s) with a relative high degree of annoyance (3.2 AU) under typical summer period conditions. Furthermore, relations between odour annoyance and odour exposure concentrations have been embedded in the model, in order to express the odour impacts in terms of probability of detection and degree of annoyance of the population near the WTP of Chania.     

Extraction of polyphenols from processed black currant (Ribes nigrum L.) residues

The total phenol and anthocyanin contents of black currant pomace and black currant press residue (BPR) extracts, extracted with formic acid in methanol or with methanol/water/acetic acid, were studied. Anthocyanins and other phenols were identified by means of reversed phase HPLC, and differences between the two plant materials were monitored. In all BPR extracts, phenol levels, determined by the Folin-Ciocalteu method, were 8-9 times higher than in the pomace extracts. Acid hydrolysis liberated a much higher concentration of phenols from the pomace than from the black currant press residue. HPLC analysis revealed that delphinidin-3-O-glucoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside, and cyanidin-3-O-rutinoside were the major anthocyanins and constituted the main phenol class ( approximately 90%) in both types of black currant tissues tested. However, anthocyanins were present in considerably lower amounts in the pomace than in the BPR. In accordance with the total phenol content, the antioxidant activity determined by scavenging of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation, the ABTS(*)(+) assay, showed that BPR extracts prepared by solvent extraction exhibited significantly higher (7-10 times) radical scavenging activity than the pomace extracts, and BPR anthocyanins contributed significantly (74 and 77%) to the observed high radical scavenging capacity of the corresponding extracts.     

Reforestation of degraded Kermes oak shrublands with planted pines: effects on vegetation cover, species diversity and community structure

This paper examines the results of plantings of the Mediterranean pine species, Pinus halepensis and Pinus pinea, in a degraded Mediterranean kermes oak (Quercus coccifera) shrubland in Northern Greece, which were accomplished in order to mitigate ecosystem degradation. Plant establishment and the vegetation differences between the degraded ecosystem’s previous state and the new state following reforestation were measured in order to evaluate the effect of reforestation. Monitoring of the seedling survival and growth of the planted species was carried out during the next five years. In the fifth year we conducted botanical inventories in 18 and 15 plots (50 m² in size) from the reforested and control area, respectively. Plant community parameters estimated were: vegetation composition, total plant cover, planted species cover, native woody, herb and grass species cover, plant species richness, Shannon-Weiner index, community structure and dominant plant height. P. halepensis exhibited higher survival and growth than P. pinea. The reforested area exhibited higher plant diversity, higher vegetation cover, taller plants and more complex community structures than the control area, which concludes that plantings of pines can be successfully used in degraded ecosystem reforestation projects, in areas with similar site conditions.     

Status and Job Satisfaction of Greek Forest Workers

The aim of this study was to examine the perception of forestry experts and forest workers on the status of the forest workers in Greece. A postal questionnaire was distributed to 115 experts on forest operations in Greece, and 106 forest workers were interviewed in the context of this study. According to the majority of the study participants, there is lack of interest on behalf of the State and the most pressing problems are income-related. The effectiveness of seminars organized during the last years is under question, since they did not result in fewer or less severe accidents. Despite the mentioned problems, the interviewed forest workers are reluctant to change their jobs, indicating a possible potential for maintaining or even increasing employment in forestry, which would warrant further study. The organization of a forest workers’ training system along with institutional changes can significantly improve the quality and the employment conditions of the Greek forest operations’ sector.     

FT-Raman spectroscopic simultaneous determination of fructose and glucose in honey

A new method for mass percentage determination of fructose and glucose based on FT-Raman spectroscopy is evaluated with a standard HPLC-based method. FT-Raman spectra manipulation is done via the spectrometer software, and a PLS (partial least squares) method is developed with the TQ Analyst software (Ver 1. 1a). The simultaneous quantitative determination uses an input range from 1700 to 700 cm(-1) without correction or baseline factors. The standards used in the PLS method are honey samples previously analyzed by HPLC to obtain their mass percentage concentrations in fructose and glucose. The returned results are statistically tested with those of the HPLC method. Both methods appear to score equally in terms of reproducibility. The honey content of the two sugars in total was found up to 40-74%. The honey samples content in fructose and glucose was determined by HPLC (24.1-42.9% and 16.2-33.1%, respectively) and FT-Raman (24.0-40.8% and 21.1-32.2%, respectively).