Roughness and surface material effects on nucleate boiling heat transfer from cylindrical surfaces to refrigerants R-134a and R-123

This paper presents results of an experimental investigation carried out to determine the effects of the surface roughness of different materials on nucleate boiling heat transfer of refrigerants R-134a and R-123. Experiments have been performed over cylindrical surfaces of copper, brass and stainless steel. Surfaces have been treated by different methods in order to obtain an average roughness, Ra, varying from 0.03 mu m to 10.5 mu m. Boiling curves at different reduced pressures have been raised as part of the investigation. The obtained results have shown significant effects of the surface material, with brass being the best performing and stainless steel the worst. Polished surfaces seem to present slightly better performance than the sand paper roughened. Boiling on very rough surfaces presents a peculiar behavior characterized by good thermal performance at low heat fluxes, the performance deteriorating at high heat fluxes with respect to smoother surfaces. (C) 2008 Elsevier Inc. All rights reserved.

A geometrical approach of 3-D FEA for educational purposes applied to electrostatic fields

A geometrical approach of the finite-element analysis applied to electrostatic fields is presented. This approach is particularly well adapted to teaching Finite Elements in Electrical Engineering courses at undergraduate level. The procedure leads to the same system of algebraic equations as that derived by classical approaches, such as variational principle or weighted residuals for nodal elements with plane symmetry. It is shown that the extension of the original procedure to three dimensions is straightforward, provided the domain be meshed in first-order tetrahedral elements. The element matrices are derived by applying Maxwell`s equations in integral form to suitably chosen surfaces in the finite-element mesh.

Evidences of the evolution from solid solution to surface segregation in Ni-doped SnO(2) nanoparticles using Raman spectroscopy

Ni-doped SnO(2) nanoparticles, promising for gas-sensing applications, have been synthesized by a polymer precursor method. X-ray diffraction (XRD) and transmission electron microscopy (TEM) data analyses indicate the exclusive formation of nanosized particles with rutile-type phase (tetragonal SnO(2)) for Ni contents below 10 mol%. The mean crystallite size shows a progressive reduction with the Ni content. Room-temperature Raman spectra of Ni-doped SnO(2) nanoparticles show the presence of Raman active modes and modes activated by size effects. From the evolution of the A(1g) mode with the Ni content, a solubility limit at similar to 2 mol% was estimated. Below that content, Raman results are consistent with the occurrence of solid solution (ss) and surface segregation (seg.) of Ni ions. Above similar to 2 mol% Ni, the redshift of A(1g) mode suggests that the surface segregation of Ni ions takes place. Disorder-activated bands were determined and their integrated intensity evolution with the Ni content suggest that the solid-solution regime favors the increase of disorder; meanwhile, that disorder becomes weaker as the Ni content is increased. Copyright (C) 2010 John Wiley & Sons, Ltd.

Chaotic Synchronization in Discrete-Time Systems Connected by Bandlimited Channels

Due to the broadband characteristic of chaotic signals, many of the methods that have been proposed for synchronizing chaotic systems do not usually present a satisfactory performance when applied to bandlimited communication channels. Here, the effects of bandwidth limitations imposed by the channel on the synchronous solution of a discrete-time chaotic master-slave network are investigated. The discrete-time system considered in this study is the Henon map. It is analytically shown that synchronism can be achieved in such a network by introducing a digital filter in the feedback loop responsible for generating the chaotic signal that will be sent to the slave node. Numerical simulations relating the filter parameters, such as its order and cut-off frequency, to the maximum Lyapunov exponent of the master node, which determines if the transmitted signal is chaotic or not, are also presented. These results can be useful for practical communication schemes based on chaos.

Piezooptical effects in the tellurite glasses doped by europium and gold

We present the temperature dependence of piezooptical coefficients for three samples of TeO(2)-GeO(2)-PbO glasses doped with 0.5% of Eu(2)O(3), 0.5% and 1% of Au(2)O(3), after different thermoannealing times. We have established that there exist two temperatures singularities - minima in the range 655-695 K and maxima - at 850 K. It is crucial that for the glasses annealed during 61 h, at temperatures about 850 K, the anomaly of piezooptical coefficient disappears. Simultaneously the minima within the range 655-695 K changed depending on the duration of the thermoannealing which leads to low temperature shift of the minima. Towards lower temperature the piezooptical maxima occurs around 850 K and disappears after the increase of the annealing time. It is also crucial that the values of the piezooptical coefficients decrease with the enhancement of the thermoannealing. The observed temperature dependence with the piezooptical coefficients has a good correlation with the temperature dependences of the DSC. We have found that the pure glasses and glasses doped only by Au(2)O(3) and Eu(2)O(3) possess the piezooptical coefficients one order less with respect to the samples possessing simultaneously Au(2)O(3) and Eu(2)O(3). (C) 2008 Elsevier B.V. All rights reserved.

KI effects on the reversible electrodeposition of silver on poly(ethylene oxide) for application in electrochromic devices

A new approach to electrochromics, based on the reversible coating-dissolution of an oxide from an inorganic electrochromic electrolyte consisting of a silver-amine complex in a polymer electrolyte (PEO), has proven successful. The reversible electrodeposition of silver onto indium-tin oxide coated glass (ITO) was investigated and the influence of HClO(4) and KI was evaluated. Several characteristics of the electrolyte Ag-PEO make it suitable for use in electrochromic reversible silver electrodeposition devices, such as visible absorption spectrum with an absorbance variation of 60%, an electrochromic efficiency of 5.2 cm(2) C(-1) and an ionic conductivity 4.4 x 10(-4) S cm(-1). The addition of perchloric acid improved the transparency of Ag-PEO, and potassium iodide (KI) was fundamental in setting up the process of reversible silver electrodeposition in the PEO polymeric matrix. A description of the electrochemical processes implied is presented. A number of approaches focusing on the improvement of system performance are tested. (C) 2009 Elsevier Ltd. All rights reserved.

Effects of sewage sludge amendment on the properties of two Brazilian oxisols and their humic acids

The effect of sewage sludge (SS) amendment on the general properties of the top layers of a sandy and a clayey oxisols and on the nature of their humic acid (HA) fractions was evaluated by chemical and physico-chemical techniques. The amended soils, especially the sandy soil, benefited of SS amendment by increasing their pH to above neutrality and enhancing the contents of C, N, P, and Ca and cation exchange capacity. The SS-HA-like sample showed larger H and N contents and a greater aliphatic character and humification degree than the HAs isolated from non-amerided soils. The composition and structure of amended soil HAs were affected by SS application as a function of soil type and layer. In particular, N-containing groups and aliphatic structures of SS-HA-like sample appears to be partially incorporated in the amended soil HAs, and these effects were more evident in the HAs from the sandy oxisol. (C) 2007 Elsevier Ltd. All rights reserved.

Assessing the effects of early silvicultural management on long-term site productivity of fast-growing eucalypt plantations: the Brazilian experience

Eucalyptus is the dominant and most productive planted forest in Brazil, covering around 3.4 million ha for the production of charcoal, pulp, sawtimber, timber plates, wood foils, plywood and for building purposes. At the early establishment of the forest plantations, during the second half of the 1960s, the eucalypt yield was 10 m(3) ha(-1) y(-1). Now, as a result of investments in research and technology, the average productivity is 38 m3 ha(-1) y(-1). The productivity restrictions are related to the following environmental factors, in order of importance: water deficits > nutrient deficiency > soil depth and strength. The clonal forests have been fundamental in sites with larger water and nutrient restrictions, where they out-perform those established from traditional seed-based planting stock. When the environmental limitations are small the productivities of plantations based on clones or seeds appear to be similar. In the long term there are risks to sustainability, because of the low fertility and low reserves of primary minerals in the soils, which are, commonly, loamy and clayey oxisols and ultisols. Usually, a decline of soil quality is caused by management that does not conserve soil and site resources, damages soil physical and chemical characteristics, and insufficient or unbalanced fertiliser management. The problem is more serious when fast-growing genotypes are planted, which have a high nutrient demand and uptake capacity, and therefore high nutrient output through harvesting. The need to mobilise less soil by providing more cover and protection, reduce the nutrient and organic matter losses, preserve crucial physical properties as permeability ( root growth, infiltration and aeration), improve weed control and reduce costs has led to a progressive increase in the use of minimum cultivation practices during the last 20 years, which has been accepted as a good alternative to keep or increase site quality in the long term. In this paper we provide a synthesis and critical appraisal of the research results and practical implications of early silvicultural management on long-term site productivity of fast-growing eucalypt plantations arising from the Brazilian context.

The Effects of Host, Geographic Origin, and Gender on the Thermal Requirements of Diaphorina citri (Hemiptera: Psyllidae)

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the vector of the bacteria that causes citrus greening and is considered one of the world`s most important citrus diseases. We examined how host, geographic region, and gender affect the thermal requirements of D. citri. The insects were reared in climatic chambers at constant temperatures of 18, 20, 22, 25, 28, 30, and 32 1 degrees C, 70 +/- 10% RH, and a 14 h photophase. Host plants for D. citri included orange (Citrus sinensis [Rutaceae]) varieties Pera and Natal, the rootstock, Rungpur lime (C. limonia [Rutaceae]) and the natural host, Orange jessamine (Murraya paniculata [Rutaceae]). To study the influence of geographic origin on thermal requirements, we studied D. citri populations from Piracicaba, SP (warmer region) and Itapetininga, SP (cooler region). The duration and survival of the development stages and the duration of the total development (egg-adult) did not differ significantly on the different hosts, but it did vary with temperature. Nymphs of D. citri created on the different hosts have the same thermal requirements. The thermal requirements for this species collected from the two climate regions were identical; males and females also had the same thermal requirements.

Effects of soybean proteinase inhibitors on development of the soil mite Scheloribates praeincisus (Acari : Oribatida)

Proteinase inhibitors (PI) are present in plant tissues, especially in seeds, and act as a defense mechanism against herbivores and pathogens. Serine PI from soybean such as Bowman-Birk (BBPI) and Kunitz have been used to enhance resistance of sugarcane varieties to the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), the major pest of this crop. The use of these genetically-modified plants (GM) expressing PI requires knowledge of its sustainability and environmental safety, determining the stability of the introduced characteristic and its effects on non-target organisms. The objective of this study was to evaluate direct effects of ingestion of semi-purified and purified soybean PI and GM sugarcane plants on the soil-dwelling mite Scheloribates praeincisus (Berlese) (Acari: Oribatida). This mite is abundant in agricultural soils and participates in the process of organic matter decomposition; for this reason it will be exposed to PI by feeding on GM plant debris. Eggs of S. praeincisus were isolated and after larvae emerged, immatures were fed milled sugarcane leaves added to semi-purified or purified PI (Kunitz and BBPI) or immatures were fed GM sugarcane varieties expressing Kunitz and BBPI type PI or the untransformed near isogenic parental line variety as a control. Developmental time (larva-adult) and survival of S. praeincisus was evaluated. Neither Kunitz nor BBPI affected S. praeincisus survival. On the other hand, ingestion of semi-purified and purified Kunitz inhibitor diminished duration of S. praeincisus immature stages. Ingestion of GM senescent leaves did not have an effect on S. praeincisus immature developmental time and survival, compared to ingestion of leaves from the isogenic parental plants. These results indicate that cultivation of these transgenic sugarcane plants is safe for the non-target species S. praeincisus.

Reclaimed wastewater: Effects on citrus nutrition

The effects of irrigation with reclaimed wastewater (RWW) were compared with well water (WW) on citrus (Citrus paradisi Macfad. X Citrus aurantium L) nutrition. The deviation from the optimum percentage (DOP) index of macro- and micro-nutrients were used to evaluate the nutritional status: optimal (DOP = 0), deficiency (DOP < 0) or excess (DOP > 0). After 11 years of RWW irrigation the influence on nutrient concentration in plants decreased in the order: B > Zn > Mn = Ca > Cu > Mg > P > K. Reclaimed wastewater irritation positively affected citrus nutrition as it rendered the concentration of macronutrients, i.e. P, Ca, and K. closer to their optimum levels (Sigma DOP(macro) = 7). However micro-nutrients tended to be excessive in plants (EDOP(micro) = 753) due to imbalanced supply of these elements in the RWW, particularly, for B and Cu. Citrus groves with long-term RWW irrigation may exercised caution in monitoring concentrations of B and Cu to avoid plant toxicity and soil quality degradation. (C) 2011 Elsevier B.V. All rights reserved.

Effects of dietary supplementation of rumen-protected conjugated linoleic acid to grazing cows in early lactation

Conjugated linoleic acids (CLA) are potent anticarcinogens in animal and in vitro models as well as inhibitors of fatty acid synthesis in mammary gland, liver, and adipose tissue. Our objective was to evaluate long-term CLA supplementation of lactating dairy cows in tropical pasture on milk production and composition and residual effects posttreatment. Thirty crossbred cows grazing stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) were blocked by parity and received 150 g/d of a dietary fat supplement of either Ca-salts of palm oil fatty acids (control) or a mixture of Ca-salts of CLA (CLA treatment). Supplements of fatty acids were mixed with 4 kg/d of concentrate. Grazing plus supplements were estimated to provide 115% of the estimated metabolizable protein requirements from 28 to 84 d in milk (treatment period). The CLA supplement provided 15 g/d of cis-9, trans-11 and 22 g of cis-10, trans-12. Residual effects were evaluated from 85 to 112 d in milk (residual period) when cows were fed an 18% crude protein concentrate without added fat. The CLA treatment increased milk production but reduced milk fat concentration from 2.90 to 2.14% and fat production from 437 to 348 g/d. Milk protein concentration increased by 11.5% (2.79 to 3.11%) and production by 19% (422 to 504 g/d) in the cows fed CLA. The CLA treatment decreased milk energy concentration and increased milk volume, resulting in unchanged energy output. Milk production and protein concentration and production were also greater during the residual period for the CLA-treated cows. The CLA treatment reduced production of fatty acids (FA) of all chain lengths, but the larger effect was on short-chain FA, causing a shift toward a greater content of longer chain FA. The CLA treatment increased total milk CLA content by 30% and content of the trans-10, cis-12 CLA isomer by 88%. The CLA treatment tended to decrease the number of days open, suggesting a possible effect on reproduction. Under tropical grazing conditions, in a nutritionally challenging environment, CLA-treated cows decreased milk fat content and secreted the same amount of milk energy by increasing milk volume and milk protein production.

Winter-feeding systems for gestating sheep II. Effects on feedlot performance, glucose tolerance, and carcass composition of lamb progeny

Mature pregnant crossbred ewes (n = 90) were used in a randomized complete block design experiment and were assigned to 1 of 3 winter-feeding systems differing in primary feed source: haylage (HL), limit-fed corn (CN), or limit-fed dried distillers grains (DDGS). Effects of these winter-feeding strategies on postweaning progeny performance were determined. Lamb progeny (n = 96) were weaned at 61 +/- 4 d of age and fed a common high-concentrate diet. Lambs were assigned to feedlot pen (n = 18) based on dam mid-gestation pen. Growth rate, DMI, and ADG were determined for the first 40 d of the finishing period. At 96 +/- 4 d of age, 1 wether lamb was randomly selected from each pen (n = 18) for a glucose tolerance test. The experiment was terminated, and lambs were slaughtered individually when they were determined to have achieved 0.6-cm 12th-rib fat thickness. After a 24-h chill, carcass data were collected and a 2.54-cm chop was removed from each lamb from the LM posterior to the 12th rib for ether extract analysis. Additional carcass measurements of bone, muscle, and fat from the shoulder, rack, loin, and leg were collected on 35 carcasses. At weaning, lamb BW was not different among treatments, whereas final BW tended to be greater (P = 0.09) for lambs from ewes fed DDGS and CN during gestation than from those fed HL. Overall lamb growth rate from birth to slaughter was not different among treatments. Lambs from ewes fed DDGS vs. CN or HL tended to have a greater initial insulin response (P = 0.09). Dressing percent was less (P = 0.04) in lambs from ewes fed DDGS, but no difference (P = 0.16) was detected in HCW among treatments. As expected, 12th rib fat thickness was similar among treatments, whereas LM area was largest to smallest (P = 0.05) in lambs from ewes fed CN, HL, and DDGS, respectively. Proportion of internal fat tended to be greatest to smallest (P = 0.06) in lambs from ewes fed DDGS, CN, and HL, respectively. Calculated boneless trimmed retail cuts percentage was less (P = 0.04) in lambs from ewes fed DDGS than CN or HL. Loin muscle weight as a percentage of wholesale cut tended (P = 0.10) to be greater in lambs from ewes fed CN and HL than DDGS, whereas other muscle, bone, and fat weights and proportions were similar (P > 0.24) among treatments. Prepartum diet during mid to late gestation of ewes altered postnatal fat and muscle deposition and may be associated with alterations in insulin sensitivity of progeny.

Adapting the CROPGRO perennial forage model to predict growth of Brachiaria brizantha

Warm-season grasses are economically important for cattle production in tropical regions, and tools to aid in management and research of these forages would be highly beneficial. Crop simulation models synthesize numerous physiological processes and are important research tools for evaluating production of warm-season grasses. This research was conducted to adapt the perennial CROPGRO Forage model to simulate growth of the tropical species palisadegrass [Brachiaria brizantha (A. Rich.) Stapf. cv. Xaraes] and to describe model adaptation for this species. In order to develop the CROPGRO parameters for this species, we began with values and relationships reported in the literature. Some parameters and relationships were calibrated by comparison with observed growth, development, dry matter accumulation and partitioning during a 2-year experiment with Xaraes palisadegrass in Piracicaba, SP, Brazil. Starting with parameters for the bahiagrass (Paspalum notatum Flugge) perennial forage model, dormancy effects had to be minimized, and partitioning to storage tissue/root decreased, and partitioning to leaf and stem increased to provide for more leaf and stem growth and less root. Parameters affecting specific leaf area (SLA) and senescence of plant tissues were improved. After these changes were made to the model, biomass accumulation was better simulated, mean predicted herbage yield per cycle was 3573 kg ha(-1), with a RMSE of 538 kg DM ha(-1) (D-Stat = 0.838, simulated/observed ratio = 1.028). The results of the adaptation suggest that the CROPGRO model is an efficient tool to integrate physiological aspects of palisadegrass and can be used to simulate growth. (C) 2010 Elsevier B.V. All rights reserved.

Determination of volatiles produced during radiation processing in Laurus cinnamomum

In order to protect food from pathogenic microorganisms as well as increase its shelf-life, while keeping sensorial properties (e.g., odor and taste), which are important properties required by spice buyers, it is necessary to analyze volatile formation from irradiation of medicinal and food herbs. Possible changes in the odor of these herbs are evaluated by characterizing different radiation doses and effects on sensorial properties, in order to allow better application of the irradiation technology. The aim of the present study was to analyze volatile formation on cinnamon (Laurus cinnamomum) samples after gamma irradiation. These samples were irradiated into plastic packages using a (60)Co facility. Radiation doses applied were 0, 5, 10, 15, 20 and 25 kGy. For the analysis of the samples, solid-phase microextraction (SPME) was applied, while for the analysis of volatile compounds, CG/MS. Spice irradiation showed the highest decrease in volatile compounds. For L. cinnamomum, the irradiation decreased volatile compounds by nearly 56% and 89.5%, respectively, comparing to volatile from a sample which had not been previously irradiated. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.