Temperate Forms Research Articles

Performance enhancement of Cu/SiO2 catalyst for hydrogenation of dimethyl oxalate to ethylene glycol through zinc incorporation

Abstracts CuO-ZnO/SiO2 catalysts with various Zn/Cu molar ratios were prepared by precipitation and characterized by XRD, H2-TPR, TEM, XAES and catalytic performance for hydrogenation of dimethyl oxalate. Characterizations revealed that suitable zinc incorporation resulted in higher Cu+ content on the surface of catalysts, better dispersion of Cu0 particles and better sintering resistance. Cu0.8Zn0.2/SiO2 exhibited the best activity and sintering resistance with 99.5% DMO conversion and 91.5%selectivity to ethylene glycol, after deactivation treatment (T = 400 °C, H2 atmosphere, 2.0 h), the catalyst maintained its activity with DMO conversion of 99.0%, while selectivity to ethylene glycol increased to 95.2%.

Femtosecond transmission electron microscopy for nanoscale photonics: a numerical study.

Recent developments in ultrafast electron microscopy have shown that spatial and temporal information can be collected simultaneously on very small and fast scales. In the present work, an instrumental design study with application to nanoscale dynamics, we optimize the conditions for a femtosecond transmission electron microscope (fs-TEM). The fs-TEM numerically studied employs a metallic nanotip source, electrostatic acceleration, magnetic lenses, a condenser-objective around the sample and a temporal compressor, and considers space-charge effects during propagation. We find a spatial resolution of the order of 1 nm and a temporal resolution of below 10 fs will be feasible for pulses comprised of on average 20 electrons. The influence of a transverse electric field at the sample plane is modelled, indicating 1 V μm-1 can be resolved, corresponding to a surface charge density of 10e per μm2, comparable to fields generated in light-driven electronics and ultrafast nanoplasmonics. The realisation of such an instrument is anticipated to facilitate unprecedented elucidation of laser-initiated physical, chemical and biological structural dynamics on atomic time- and length-scales.

Assembly of hollow CeO2@Fe-ZSM-5 and SCR performance

The hollow-structured catalysts have raised attention due to the utilization of large specific surface area. In this paper, the catalyst CeO2@Fe-ZSM-5 (composed of a CeO2 core and a Fe-ZSM-5 shell) with hollow structure was prepared. Their catalytic performances for NH3-SCR were studied, and the resistance to H2O and SO2 were enhanced significantly compared with CeO2 and Fe-ZSM-5 catalyst. During the synthesis process of hollow CeO2@Fe-ZSM-5, the preparation conditions were investigated by the effect of crystallization time, the PC dosage and the adsorption of Fe-ZSM-5 seed. The catalysts were characterized by XRD, TEM, and XPS. It was known from the results of TEM and catalytic performance tests that the as-prepared hollow CeO2@Fe-ZSM-5 catalyst showed excellent NH3-SCR activity and N2 selectivity.

Effect of oxidation degree of graphene oxide on the electrochemical performance of CoAl-layered double hydroxide/graphene composites

CoAl-layered double hydroxide (CoAl-LDH) was deposited on the surface of graphene oxide (GO) with various oxidation degree (OD) via hydrothermal method. The synthesized CoAl-layered double hydroxide/graphene (CoAl-LDH/GN) composites have been characterized by XRD, FT-IR, XPS, Raman, SEM, TEM, TGA and electrochemical performance. The results showed that the relative content of GO participated in the fabrication of CoAl-LDH/GN composites, and the residual oxygenous functional groups and defects in the GN of the composites increased with the OD, while the size of the in-plane sp2 domains in the GN of the composites decreased with the OD. The increase of the former ones and the decrease of the latter one lead to a decrease in the electrical conductivity of the composites. Consequently, the CoAl-LDH/GN composite fabricated by optimizing OD of GO exhibited the maximum specific capacitance of 895F/g (1.25A/g) and the best capacitive behavior.

An exhaustive experimental study of a novel air-water based thermoelectric cooling unit

In this paper, the cooling feasibility of air flow via a novel air-water based TEC system (as an alternative air cooling unit) is experimentally investigated for different climate conditions. Contrary to previous studies, thermoelectric hot side temperature was adjusted by a low constant water flow rate (and not by an air fan) which significantly increased the cold side performance of TEM. Ten parameters including Ta,inlet, Tw,inlet, Ta,outlet, Tw,outlet, Tc, Ta, ṁa,ṁw and DC voltage and DC current were directly recorded by measurement instruments during the experiments. Six other parameters including qc, qh, COPc, COPmax, COPc/COPmax and qair were evaluated by formulas and correlations using of aforesaid measured data. Five numbers of aforementioned parameters were variant parameters. Indeed, the effect of ṁa,ṁw, DC voltage/current and Ta,inlet (variant parameters) on other impressionable parameters were investigated in present study. Optimum working condition was evaluated from a new point of view. Indeed, in this paper, it was accidently found out that, despite the descending behavior of both COPc and COPmax (due to changing of variants), the ratio of said parameters (COPc/COPmax) creates a peak point (ascending and then descending) in all cases. Said peak point can be considered as an appropriate working condition of thermoelectric units. Findings showed that, the cold side of thermoelectric system can act as an applicable air cooling system especially when the hot side of thermoelectric is cooled by a current liquid such as water.

Structural; magnetic and catalytic properties of nanocrystalline Cu0.5Zn0.5Fe2O4 synthesized by microwave combustion and ball milling methods

Effects of high energy ball-milling on nanosized Cu0.5Zn0.5Fe2O4 powders were studied at 30 and 330 min of milling. The powders were initially synthesized from its stoichiometric metal nitrates and urea mixtures, using a microwave assisted combustion method. Ball-milling induced electromechanical reaction was examined by XRD, TEM, Mössbauer spectroscopy, magnetization, and catalytic performance by exploring potential changes in size, phases and chemical structure. Before Milling, the as-prepared powders were comprised of small grains of poor spinel crystallinity and very small crystallite size, and a minor α-Fe2O3 phase. Progressive milling significantly reduced the grain size, increased chemical disorder, and reduced the hematite phase. These changes are also manifested in the magnetization measurements. The Catalytic activity performance was carried out using dehydrogenation of isopropyl alcohol. The observed activity was correlated to the presence of Cu2+ and Fe3+ catalysts at octahedral sites before and after milling.

Archaeogenetic study of prehistoric rice remains from Thailand and India: evidence of early japonica in South and Southeast Asia

We report a successful extraction and sequencing of ancient DNA from carbonized rice grains (Oryza sativa) from six archaeological sites, including two from India and four from Thailand, ranging in age from ca. 2500 to 1500 BP. In total, 221 archaeological grains were processed by PCR amplification and primary-targeted fragments were sequenced for comparison with modern sequences generated from 112 modern rice populations, including crop and wild varieties. Our results include the genetic sequences from both the chloroplast and the nuclear genomes, based on four markers from the chloroplast and six from the nuclear genome. These markers allow differentiation of indica rice from japonica rice, the two major subspecies of Asian rice (O. sativa) considered to have separate geographical origins. One nuclear marker differentiates tropical and temperate forms of subspecies japonica. Other markers relate to phenotypic variation selected for under domestication, such as non-shattering, grain stickiness (waxy starch) and pericarp colour. Recovery and identification of sequences from nuclear markers was generally poor, whereas recovery of chloroplast sequences was successful, with at least one of four markers recovered in 61 % of archaeological grains. This allowed for successful differentiation of indica or japonica subspecies variety, with japonica identified in all the Thai material and a mixture of indica and japonica chloroplasts in the two Indian assemblages. Rice subspecies was also assessed through conventional archaeobotanical methods relying on grain metrics, based on measurements from 13 modern populations and 499 archaeological grains. Grain metrics also suggest a predominance of japonica-type grains in the Southeast Asian sites and a mixture of japonica and indica in the Indian sites with indica in the minority. The similar results of grain metrics and ancient DNA (aDNA) affirm that grain measurements have some degree of reliability in rice subspecies identification. The study also highlights the great potential of ancient DNA recovery from archaeological rice. The data generated in the present study adds support to the model of rice evolution that includes hybridization between japonica and proto-indica.

Simulation Study of Continuous Solar Adsorption Refrigeration System Driven by Compound Parabolic Concentrator

Solar adsorption refrigeration is promising technology especially in the developing countries and remote areas because the system can be driven by solar energy without involving electricity. Therefore, it is technologically possible and socially feasible in the areas where electricity is not enough but solar energy is rather easy to obtain. The conventional system works intermittently and produces cooling only during night. In this article, a solar adsorption refrigerator is pre- sented that produces cooling continuously using only solar energy. The system consists of two beds with CPC collectors, a condenser and evaporator. The one cycle complete in two days. A simulation model was developed to evaluate the sys- tem performance. The objectives of this study were to investigate the dynamic behaviour of the system, and to compare the system behaviour with the conventional system. The results show that system produces continuous cooling. Cooling rate decreased in the middle of the day because of relatively high ambient temperature. The performance of the system in- creased with high value of heat transfer coefficient between receiver and bed, and decreased by increasing the adsorbent mass. The performance of the continuous system was compared with that of intermittent system. It was found that the evaporator temperature in the intermittent system increased during the day because cooling is not produced during day in that system, while proposed system kept the evaporator at low temperature continuously. This study will facilitate the fu- ture researches in solar adsorption continuous refrigeration technology because achieving continuous cooling only with solar energy is very attractive.

Supported palladium–copper catalysts: Preparation and catalytic behavior in hydrogen-related reactions

Two series of highly dispersed supported Pd–Cu catalysts were prepared using different supports: highly acidic aluminum fluoride HS-AlF3, characterized by high surface area, and active carbon, both prepared by different preparation methods (fluorolytic sol–gel method and co-impregnation). A variety of techniques: chemisorption of hydrogen, XRD, TEM, and catalytic performance in two hydrogen-related probe reactions (in n-pentane hydroisomerization and CCl4 hydrodechlorination) were employed to probe metal dispersion and the extent of interaction between two metal components. A reasonable degree of bimetal intermixing in Pd–Cu/HS-AlF3 catalysts synthesized by fluorolytic co-gelation was recognized by the catalytic behavior in bifunctional hydroisomerization of n-pentane. A significantly decreased, compared to pure palladium, hydrogenation–dehydrogenation potential of Pd–Cu alloys led to a weaker performance of bimetallic catalysts. Similarly, it was found that incipient wetness co-impregnation of active carbon resulted in the formation of catalysts characterized by good metal dispersion and significant extent of Pd–Cu alloying. Although the monometallic 2wt% Cu/carbon catalyst is nearly inactive in CCl4 hydrodechlorination, copper addition to palladium in the co-impregnated catalysts had very pronounced effect, vastly increasing the selectivity toward longer than methane hydrocarbons.

Middle East Transitions: A Long, Hard Road

Since the onset of the Arab Spring, economic uncertainty in Egypt, Jordan, Libya, Morocco, Tunisia, and Yemen (Arab Countries in Transition, ACTs) has slowed already sluggish growth; worsened unemployment, particularly of youth; undermined business confidence, affected tourist arrivals, and depressed domestic and foreign direct investment. Furthermore, political and social tensions have constrained reform efforts. Assessing policy options as presented in the voluminous literature on the Arab Spring and based on cross-country experience, this paper concludes that sustainable and inclusive growth calls for a two pronged approach: short term measures that revive growth momentum and partially allay popular concerns; complemented with efforts to adjust the public’s expectations and prepare the ground for structural reforms that will deliver the desired longer tem performance.

Middle East Transitions: A Long, Hard Road

Since the onset of the Arab Spring, economic uncertainty in Egypt, Jordan, Libya, Morocco, Tunisia, and Yemen (Arab Countries in Transition, ACTs) has slowed already sluggish growth; worsened unemployment, particularly of youth; undermined business confidence, affected tourist arrivals, and depressed domestic and foreign direct investment. Furthermore, political and social tensions have constrained reform efforts. Assessing policy options as presented in the voluminous literature on the Arab Spring and based on cross-country experience, this paper concludes that sustainable and inclusive growth calls for a two pronged approach: short term measures that revive growth momentum and partially allay popular concerns; complemented with efforts to adjust the public’s expectations and prepare the ground for structural reforms that will deliver the desired longer tem performance.

Origination of a separate form of Neoechinorhynchus salmonis Ching, 1984 (Acanthocephales: Neoechinorhynchidae) in severe environment of the Asian Arctic

Previous morphological research has shown that the species Neoechinorhynchus salmonis, first described from Canada, is also widespread in the northern Asia, in different climatic zones. Analysis of data from samples collected in various parts of its area of distribution leads to a conclusion about the existing two life forms of this species, namely temperate and polar ones. The specimens of the latter at the adult stage develop at far greater rate and reach maturity being smaller in size. It results in morphological difference: in the temperate form, the maximal body length of males is 7.8mm; of females-15.0mm, while in the polar form corresponding values are 4.5 and 7.8mm (irrespective of host species). In the temperate form, in the course of maturing and growth of the adult worms, no seasonality was found which means a continuous replenishment of infection in the definitive hosts throughout a year. In the polar form, seasonal behavior of the intermediate hosts, the ostracods Cypria kolymensis, secures a heavy infection of the definitive hosts at the very beginning of the warm period (late June). In late August, the majority of parasites reach maturity and there are solid grounds to believe that adult worms are eliminated during the nearing wintering. In our opinion, the traits of the polar form are an adaptation to severe climatic conditions.

The Forms of the Culex pipiens Complex in East Asia, with Ecological Thoughts on Their Origin and Interrelation

In East Asia, 4 forms of the Culex pipiens complex have been confirmed. A form pipiens s. s. (anautogeous pipiens) has been confirmed only in westernmost China. A temperate form pallens and a subtropical and tropical form quinquefasciatus are connected with intermediates in morphology and many aspects of ecology, but their difference is rather clear in climatic adaptation traits. The distribution of a form molestus overlaps with pallens and, in Taiwan, quinquefasciatus, and, in East Asia, this form requires artificial underground habitats for its persistence. The origin and interrelation of 3 forms other than pipiens s. s. are considered from ecological aspects, especially climatic adaptation. A hypothesis is presented that molestus was originally a form having adapted to the Mediterranean climate in the western Palaearctic, secondarily colonized artificial underground habitats, and reached East Asia in the early 20th century by ships from North America. At present, it is difficult to assign pallens with certainty to either the old or new groups of the Manchurian mosquito fauna. Three hypotheses about the interrelation between pallens and quinquefasciatus are compared, and the strengths and problems of each hypothesis are indicated. Finally, a map to show the distribution of the forms of the Culex pipiens complex before it was extensively changed by humans is presented as an initial trial. The Culex pipiens problems now troubling humans are largely human-made problems.

Weight-length relationship of 63 demersal fishes on the shallow coast of Paraná, Brazil

Timbo´ ⁄ SC, BrasilSummaryThis work presents the weight–length relationship of 63 speciesof fish belonging to 24 families. Data were collected monthlyalong the Parana´state coast (Brazil) from August 2004 to July2005 on five transects between 6 and 15 m. Several of thesespecies had no previously published weight–length relation-ships.IntroductionWeight–length relationships are used by researchers to esti-mate weight from a given length (Froese, 2006). The objectiveof the present study was to establish the weight–lengthrelationships for 63 fish species from the shallow continentalshelf of the Parana´ state coast (Brazil).The continental shelf of the Parana´ state coast is character-ized, for the most part, by a covering of sand, mud and clay(Matsuura, 1986). According to Figueiredo (1981), the Parana´state coast contains the southern boundaries of tropical speciesdistribution, the northern boundaries of temperate forms and aseries of endemic species.Materials and methodsFour 15-min bottom trawls on five transects were carried outmonthly parallel to the coast at depths of 6, 9, 12 and 15 m(25 20¢⁄48 07¢;2546¢⁄48 30¢). Sampling was conducted usingtwo commercial trawl nets.Fish from each sample were packed in labeled plastic bagsand taken to the fish biology laboratory of the Centro deEstudos do Mar – UFPR for analysis. They were identified tothe species level according to Figueiredo (1977), Figueiredoand Menezes (1978, 1980, 2000), Menezes and Figueiredo(1980, 1985) and Menezes et al. (2003). The species in thisstudy were reviewed as regards the taxonomic classificationand the nomenclature based on FishBase. Total length (cm)(from the tip of the snout to the end of the caudal fin),standard length (cm) (from the tip of the snout to the end ofthe vertebral column) and weight (g) data were obtained fromeach specimen (sample chosen randomly and up to a maximumof 30 samples per species).The presence of outliers for each species that presented nineor more captured fish (66 species) was verified using totallength (TL) and weight (W) data (log-transformed and plottedgraphically) (Giacalone et al., 2010). Species in which thenumber of captured fish was fewer than nine after theexclusion of the outliers were excluded from the analyses,with 63 species distributed in 24 families remaining. Theadopted model was: (log W = log a + b*log TL), where W isthe weight in grams, TL the total length in centimeters, a theconstant and b the allometric coefficient (King, 1995; Froese,2006). These last two values were estimated using a linearregression analysis (program Excel, 2007) (Giacalone et al.,2010).Results and discussionA total of 23 654 fish was analyzed (Table 1). They belongedto 63 species, nine of which (Anchoa spinifer, Aspistorluniscutis, Narcine brasiliensis, Oligoplites saliens, Ophioscionpunctatissimus, Rypticus randalli, Rhinobatos percellens, Tri-nects microphthalmus and Zapteryx brevirostris) had noweight-length data recorded in FishBase or in the literature.The extreme b-values may be caused by narrow length-ranges(CitharichthysspilopterusandAnchoalyolepis),orwherethere were only juveniles (Cynoscion leiarchus and Selenesetapinnis). Comparing the obtained b-values with publishedvalues (3.135 ± 0.050 for C. spilopterus, 3.101 ± 0.121 forA. lyolepis, 2.872 ± 0.019 for C. leiarchus and 2.796 ± 0.016for S. setapinnis; Joyeux et al., 2009; Muto et al., 2000), it isimportant to emphasize that these LWR estimates in particularshould not be used outside the length range given.AcknowledgementsThe authors thank H.A. Pichler, S.B. Stoiev, C. Bernardo,L.O. Santos, G.M.L.N. Queiroz and C. Santos for assistancein field collections and laboratory analyses. A.C. Passos andR. Schwarz Jr. acknowledge financial support by the CAPES.References

Quantitative analysis of image contrast in phase contrast STEM for low dose imaging

This work quantitatively evaluates the contrast in phase contrast images of thin vermiculite crystals recorded by TEM and aberration-corrected bright-field STEM. Specimen movement induced by electron irradiation remains a major problem limiting the phase contrast in TEM images of radiation-sensitive specimens. While spot scanning improves the contrast, it does not eliminate the problem. One possibility is to utilise aberration-corrected scanning transmission electron microscopy (STEM) with an Ångstrom-sized probe to illuminate the sample, and thus further reduce irradiation-induced specimen movement. Vermiculite is relatively radiation insensitive in TEM to electron fluences below 100,000 e −/Å 2 and this is likely to be similar for STEM although different damage mechanisms could occur. We compare the performance of a TEM with a thermally assisted field emission electron gun (FEG) and charge coupled device (CCD) image capture to the performance of STEMs with spherical aberration correction, cold field emission electron sources and photomultiplier tube image capture at a range of electron fluences and similar illumination areas. We show that the absolute contrast of the phase contrast images obtained by aberration-corrected STEM is better than that obtained by TEM. Although the STEM contrast is higher, the efficiency of collection of electrons in bright field STEM is still much less than that in bright field TEM (where for thin samples virtually all the electrons contribute to the image), and the SNR of equivalent STEM images is three times lower. This is better than expected, probably due to the absence of a frequency dependent modulation transfer function in the STEM detection system. With optimisation of the STEM bright field collection angles, the efficiency may approach that of bright field TEM, and if reductions in beam-induced specimen movement are found, STEM could surpass the overall performance of TEM.

Strategies of survival and resource exploitation in the Antarctic fellfield ecosystem

Antarctic fellfields present organisms with a heterogeneous habitat characterised by a wide variety of environmental stresses. These include low temperatures, limited moisture availability, frequent and often rapid freeze-thaw and hydration-dehydration cycles, exposure to high photosynthetic photon flux density and ultraviolet (uv) irradiance, seasonal snow cover, high winds, cryoturbation and, depending on location south of the Antarctic Circle, considerable daylight in summer. Most of these factors vary both predictably and unpredictably in spatial and temporal planes. In response to this adverse environment, fellfield organisms have developed a variety of strategies to overcome physiological stress and to exploit the limited resources available during the short austral growing season. A high degree of synchronisation exists, so that investment in non-essential activity and adaptations is minimised. Here, we review the combined suites of co-adapted traits used by different fellfield taxa to achieve energy acquisition, growth and reproduction under adverse levels of two principal limiting factors: low temperatures and the scarcity of water. To this end, a detailed characterisation of the Antarctic fellfield microenvironment is followed by a synthesis of available data on the morphology, physiology, life history and behaviour of successful Antarctic flora and fauna. Tolerance of low temperatures by fellfield organisms is achieved by elevation of standard metabolism, production and accumulation of cryoprotectants, supercooling, melanic pigmentation, behavioural avoidance, compact growth forms and synchronised reproduction and extended life cycles. Low moisture conditions are overcome by dehydration resistance, anhydrobiosis, development of resting stages and by behavioural avoidance of desiccating conditions. Occupancy of the Antarctic fellfield habitat is considered to require the ability to respond rapidly to ephemeral resources and to tolerate severe environmental stresses. During summer, organisms rely on opportunism to maintain a positive energy balance. During winter, resistance adaptations are used to withstand the potentially lethal climate, especially in habitats not protected by snow cover. This deterministic framework has led to the selection of species that are genetically and physiologically pre-adapted for resource acquisition yet sufficiently robust to withstand cold and desiccation stresses. Non-adapted taxa fail to become established. Despite the environmental selection pressures, available evidence suggests that colonisation of the fellfield habitat has not required the evolution of any adaptations, only the refinement of those already possessed to an extent by some temperate forms. This has led to the convergence of survival strategies. It is hypothesised that, in the short term, the majority of Antarctic fellfield biota are able to absorb the predicted effects of a changing climate by their high levels of physiological tolerance and life-cycle flexibility.

Shallow-water asteroids, echinoids, and holothuroids at 6 sites across the tropical west Pacific, 1988-1989

Species richness of asteroids, echinoids, and holothuroids was surveyed on shallow reefs at 6 sites across the tropical west Pacific: Seto, on the west coast of the Kii Peninsula, Honshu Island; Okinawa, Ryukyus Islands; Madang, Papua New Guinea; Palm Islands, Queensland, Australia; ‘Upolu, Western Samoa; and Moorea, French Polynesia. A total of 113 nominal species were recorded. No species was unambiguously found at all 6 sites, only 17 (15%) were found at 4 or more sites, and 63 (56%) were found at only one site. Single-site finds represented 48% of the species at Seto, 21-32% of the species at 4 other sites, and only 4% (1 species) at ‘Upolu. Madang had the most species (74), followed by Okinawa (54), Moorea (34), Samoa (25), Seto (23), and the Palm Islands (15). Although Seto had a diverse echinoid fauna (17 species), including several temperate forms, there was a dearth of asteroids (4) and holothuroids (2). In contrast, all 3 classes were well represented on the reefs of Okinawa (11 asteroids, 16 echinoids, and 27 holothuroids) and Madang (22 asteroids, 17 echinoids, 35 holothuroids), both of which had a rich diversity of widespread tropical oceanic species. Substantially fewer species were found farther to the east, at Samoa and Moorea, consistent with the pattern seen in other taxa. Species richness was surprisingly low around the Palm Islands on the inner portion of the Great Barrier Reef, perhaps because of human disturbance causing run-off from the land and siltation.

Pleistocene fish otoliths from the Mediterranean Basin: a synthesis

An overview of upper pPliocene and pleistocene otolith assemblages is compiled on the basis of both literature data and newly collected material from several sections located mainly in southern Italy. One hundred and five taxa are listed. Additional comments are provided for taxa subject to discussion. The composition and affinities of the Mediterranean Pleistocene otolith associations (consisting mainly of deep sea fishes) is checked against the available data for Pre-Messinian, Pliocene, and Recent Mediterranean fishes. This analysis is based on the recorded nominal species, but some taxa that could be identified at the generic level only are also included when they are relevant from a biogeographic point of view. Some new data on Piacenzian (middle Pliocene) and Gelasian (upper Pliocene) otoliths are also provided because this time interval still constitutes a major gap in the knowledge of the stratigraphic range of Plio-Pleistocene fish taxa. The Pleistocene deepwater fish fauna of the Mediterranean shows a markedly more oceanic character than the present-day one, a tendency that was all ready observed from early Oligocene till Pliocene times. Starting from the late Piacenzian, an increasing number of Atlantic taxa progressively invaded the Mediterranean including several subpolar and temperate forms. This invasion became stronger in the Gelasian. From this period up to the middle and late Pleistocene, the Mediterranean deepwater fish fauna (mesopelagic and benthopelagic) is enriched by taxa which today are typical for the north Atlantic cold deep water. This faunal shift seems to be correlated with the evolution of the Plio-Pleistocene Mediterranean paleoceanographic setting as well as with the global climatic deterioration.

Preparation of carbon-coated Sn powders and their loading onto graphite flakes for lithium ion secondary battery

Carbon-coated Sn powders were prepared from the powder mixtures of thermoplastic precursor PVA, SnO 2 and MgO. The characterization of composite powders synthesized was carried out by XRD, TG, TEM, SEM and anodic performance measurement. SnO 2 was reduced to metallic Sn by heating with PVA, and its particle size in carbon shell was around 30–100 nm. MgO existence hindered the agglomeration of molten metallic Sn and made the dispersion of metallic Sn as fine particles possible. They showed high anodic performance in lithium ion batteries; high charge capacity as 500 mAh g −1 even after tenth cycle and stable cyclic performance. The spaces left in carbon shell by MgO after its dissolution were supposed to absorb a large volume expansion of Sn metal particle by Li alloying during discharging. When carbon-coated Sn loaded onto graphite flakes, metallic tin contributed to the increase in capacity.

A Model of Adaptation in Collaborative Multi-Agent Systems

Adaptation is an essential requirement for autonomous agent systems functioning in uncertain dynamic environments. Adaptation allows agents to change their behavior in order to improve the overall sys tem performance. We describe a general mechanism for adaptation in multi-agent systems in which agents modify their behavior in response to changes in the environment or actions of other agents. The agents estimate the global state of the system from local observations and adjust their actions accordingly. We derive a mathematical model that describes the collective behavior of such adaptive systems. The model, consisting of coupled rate equations, governs how the collective behavior changes in time. We apply the model to study collaboration in a group of mobile robots. The system we study is an adaptive version of the collaborative stick pulling in a group of robots examined in detail in earlier works (Ijspeert, Martinoli, Billard, & Gambardela, 2001; Lerman, Galstyan, Martinoli, & Ijspeert, 2001). In adaptive stick pulling, robots estimate the number of robots and sticks in the system and adjust their individual behavior so as to improve collective performance. We solve the mathematical model and show that adaptation improves collective performance for all parameter values.