Cryogenic operation of FinFETs aiming at analog applications

FinFETs are recognized as promising candidates for the CMOS nanometer era. In this paper the most recent results for cryogenic operation of FinFETs will be demonstrated with special emphasis on analog applications. Threshold voltage, subthreshold slope and carrier mobility will be studied. Also some important figures of merit for analog circuit operation as for readout electronics, such as transconductance, output conductance and intrinsic voltage gain will be covered. It is demonstrated that the threshold voltage of undoped narrow FinFETs is less temperature-dependent than for a planar single-gate device with similar doping concentration. The temperature reduction improves the transconductance over drain current ratio in any operational region. On the other hand, the output conductance is degraded when the temperature is reduced. The combination of these effects shows that the intrinsic gain of a L = 90 nm FinFET is degraded by 2 dB when the temperature reduces from 300 K to 100 K. (C) 2009 Elsevier Ltd. All rights reserved.

Temperature influence on the gate-induced floating body effect parameters in fully depleted SOI nMOSFETs

The temperature influence on the gate-induced floating body effect (GIFBE) in fully depleted (FD) silicon-on-insulator (SOI) nMOSFETs is investigated, based on experimental results and two-dimensional numerical simulations. The GIFBE behavior will be evaluated taking into account the impact of carrier recombination and of the effective electric field mobility degradation on the second peak in the transconductance (gm). This floating body effect is also analyzed as a function of temperature. It is shown that the variation of the studied parameters with temperature results in a ""C"" shape of the threshold voltage corresponding with the second peak in the gm curve. (C) 2008 Elsevier Ltd. All rights reserved.

Vibration-enhanced posture stabilization achieved by tactile supplementation: May blind individuals get extra benefits?

Diminished balance ability poses a serious health risk due to the increased likelihood of falling, and impaired postural stability is significantly associated with blindness and poor vision. Noise stimulation (by improving the detection of sub-threshold somatosensory information) and tactile supplementation (i.e. additional haptic information provided by an external contact surface) have been shown to improve the performance of the postural control system. Moreover, vibratory noise added to the source of tactile supplementation (e.g. applied to a surface that the fingertip touches) has been shown to enhance balance stability more effectively than tactile supplementation alone. In view of the above findings, in addition to the well established consensus that blind subjects show superior abilities in the use of tactile information, we hypothesized that blind subjects may take extra benefits from the vibratory noise added to the tactile supplementation and hence show greater improvements in postural stability than those observed for sighted subjects. If confirmed, this hypothesis may lay the foundation for the development of noise-based assistive devices (e.g. canes, walking sticks) for improving somatosensation and hence prevent falls in blind individuals. (C) 2011 Elsevier Ltd. All rights reserved.

Cryogenic Operation of Junctionless Nanowire Transistors

This letter presents the properties of nMOS junctionless nanowire transistors (JNTs) under cryogenic operation. Experimental results of drain current, subthreshold slope, maximum transconductance at low electric field, and threshold voltage, as well as its variation with temperature, are presented. Unlike in classical devices, the drain current of JNTs decreases when temperature is lowered, although the maximum transconductance increases when the temperature is lowered down to 125 K. An analytical model for the threshold voltage is proposed to explain the influence of nanowire width and doping concentration on its variation with temperature. It is shown that the wider the nanowire or the lower the doping concentration, the higher the threshold voltage variation with temperature.

Private valuation of carbon sequestration in forest plantations

Approval of the Clean Development Mechanism, provided for in the Kyoto Protocol, enables countries with afforested land to trade in carbon emissions reduction certificates related to carbon dioxide equivalent quantities (CO(2-e)) stored within a certain forest area. Potential CO(2-e) above base line sequestration was determined for two forest sites on commercial eucalyptus plantations in northern Brazil (Bahia). Compensation values for silvicultural regimes involving rotation lengths greater than economically optimal were computed using the Faustmann formula. Mean values obtained were US$8.16 (MgCO(2-e))(-1) and US $7.19 (MgCO(2-e))(-1) for average and high site indexes, respectively. Results show that carbon supply is more cost-efficient in highly productive sites. Annuities of US$18.8 Mg C(-1) and US$35.1 Mg C(-1) and yearly payments of US$4.4 m(-3) and US$8.2 m(-3) due for each marginal cubic meter produced were computed for high and average sites, respectively. The estimated value of the tonne of carbon defines minimum values to be paid to forest owners, in order to induce a change in silvicultural management regimes. A reduction of carbon supply could be expected as a result of an increase in wood prices, although it would not respond in a regular manner. For both sites, price elasticity of supply was found to be inelastic and increased as rotation length moved further away from economically optimal: 0.24 and 0.27 for age 11 years in average- and high-productivity sites, respectively. This would be due to biomass production potential as a limiting factor; beyond a certain threshold value. an increase in price does not sustain a proportional change in carbon storage supply. The environmental service valuation model proposed might be adequate for assessing potential supply in plantation forestry, from a private landowner perspective, with an economic opportunity cost. The model is not applicable to low commercial value forest plantations. (C) 2009 Elsevier B.V. All rights reserved.

How rare is too rare to harvest? Management challenges posed by timber species occurring at low densities in the Brazilian Amazon

Tropical forests are characterized by diverse assemblages of plant and animal species compared to temperate forests. Corollary to this general rule is that most tree species, whether valued for timber or not, occur at low densities (<1 adult tree ha(-1)) or may be locally rare. In the Brazilian Amazon, many of the most highly valued timber species occur at extremely low densities yet are intensively harvested with little regard for impacts on population structures and dynamics. These include big-leaf mahogany (Swietenia macrophylla), ipe (Tabebuia serratifolia and Tabebuia impetiginosa), jatoba (Hymenaea courbaril), and freijo cinza (Cordia goeldiana). Brazilian forest regulations prohibit harvests of species that meet the legal definition of rare - fewer than three trees per 100 ha - but treat all species populations exceeding this density threshold equally. In this paper we simulate logging impacts on a group of timber species occurring at low densities that are widely distributed across eastern and southern Amazonia, based on field data collected at four research sites since 1997, asking: under current Brazilian forest legislation, what are the prospects for second harvests on 30-year cutting cycles given observed population structures, growth, and mortality rates? Ecologically `rare` species constitute majorities in commercial species assemblages in all but one of the seven large-scale inventories we analyzed from sites spanning the Amazon (range 49-100% of total commercial species). Although densities of only six of 37 study species populations met the Brazilian legal definition of a rare species, timber stocks of five of the six timber species declined substantially at all sites between first and second harvests in simulations based on legally allowable harvest intensities. Reducing species-level harvest intensity by increasing minimum felling diameters or increasing seed tree retention levels improved prospects for second harvests of those populations with a relatively high proportion of submerchantable stems, but did not dramatically improve projections for populations with relatively flat diameter distributions. We argue that restrictions on logging very low-density timber tree populations, such as the current Brazilian standard, provide inadequate minimum protection for vulnerable species. Population declines, even if reduced-impact logging (RIL) is eventually adopted uniformly, can be anticipated for a large pool of high-value timber species unless harvest intensities are adapted to timber species population ecology, and silvicultural treatments are adopted to remedy poor natural stocking in logged stands. (C) 2008 Elsevier B.V. All rights reserved.

Lepidopteran larva consumption of soybean foliage: basis for developing multiple-species economic thresholds for pest management decisions

BACKGROUND: Defoliation by Anticarsia gemmatalis (Hubner), Pseudoplusia includens (Walker), Spodoptera eridania (Cramer), S. cosmioides (Walker) and S. frugiperda (JE Smith) (Lepidoptera: Noctuidae) was evaluated in four soybean genotypes. A multiple-species economic threshold (ET), based upon the species` feeding capacity, is proposed with the aim of improving growers` management decisions on when to initiate control measures for the species complex. RESULTS: Consumption by A. gemmatalis, S. cosmioides or S. eridania on different genotypes was similar. The highest consumption of P. includens was 92.7 cm(2) on Codetec 219RR; that of S. frugiperda was 118 cm(2) on Codetec 219RR and 115.1 cm(2) on MSoy 8787RR. The insect injury equivalent for S. cosmoides, calculated on the basis of insect consumption, was double the standard consumption by A. gemmatalis, and statistically different from the other species tested, which were similar to each other. CONCLUSIONS: As S. cosmioides always defoliated nearly twice the leaf area of the other species, the injury equivalent would be 2 for this lepidopteran species and 1 for the other species. The recommended multiple-species ET to trigger the beginning of insect control would then be 20 insect equivalents per linear metre. (C) 2010 Society of Chemical Industry

Diet-dependent life history, feeding preference and thermal requirements of the predatory mite Neoseiulus baraki (Acari: Phytoseiidae)

Neoseiulus baraki Athias-Henriot (Acari: Phytoseiidae) has been reported from the Americas, Africa and Asia, often in association with Aceria guerreronis Keifer (Acari: Eriophyidae), one of the most important pests of coconut (Cocos nucifera L.) in diVerent parts of the world. That phytoseiid has been considered one of the most common predators associated with A. guerreronis in Brazil. The objective of this study was to evaluate the feeding preference and the eVect of food items commonly present on coconut fruits and several temperature regimes on the life history of a Brazilian population of N. baraki. Completion of immature development was possible when N. baraki was fed A. guerreronis, Steneotarsonemus concavuscutum Lofego and Gondim Jr., and Tyrophagus putrescentiae (Schrank). Fecundity was highest on T. putrescentiae (39.4 eggs), followed by A. guerreronis (24.8 eggs). In choice tests, irrespective of the food on which N. baraki was reared, a larger number of adults of this predator chose leaf discs containing A. guerreronis than discs containing other food items, demonstrating a preference of the former for the latter as food. Egg to adult thermal developmental time was calculated as 84.2 degree-days, above a threshold of 15.8 degrees C. This lower developmental threshold is higher than previously published for phytoseiid species from higher latitudes. Neoseiulus baraki was shown to have higher biotic potential at 30 degrees C (r(m) 0.29). The results suggest N. baraki to be a promising biological control agent of A. guerreronis, well adapted to survive and develop in areas with relatively high temperatures, where that pest prevails.

Biological characteristics and thermal requirements of a Brazilian strain of the parasitoid Trichogramma pretiosum reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis

A new strain of the parasitoid Trichogramma pretiosum, was collected in Rio Verde County, State of Goias, Central Brazil, and designated as T. pretiosum RV. This strain was then found to be the most effective one among several different strains of T. pretiosum tested in a parasitoid selection assay. Therefore, its biological characteristics and thermal requirements were studied, aiming at allowing its multiplication under controlled environmental conditions in the laboratory. The parasitoid was reared on eggs of Pseudoplusia includens and Anticarsia gemmatalis at different constant temperatures within an 18-32 degrees C temperature range. The number of annual generations of the parasitoid was also estimated at those temperatures. Results have shown that T. pretiosum RV developmental time, from egg to adult, was influenced by all temperatures tested within the range, varying from 6.8 to 20.3 days and 6.0 to 17.0 days on eggs of P. includens and A. gemmatalis, respectively. The emergence of T. pretiosum RV from eggs of A. gemmatalis was higher than 94% at all temperatures tested. When this variable was evaluated on eggs of P. includens, however, the figures were higher than that within the 18-30 degrees C range (more than 98%), and were also statistically higher than the emergence observed at 32 degrees C (90.2%). The sex ratio of the parasitoids emerged from eggs of A. gemmatalis decreased from 0.55 to 0.29 at 18-32 degrees C, respectively. However, for those emerged from eggs of P. includens, the sex ratio was similar (0.73, 0.72 and 0.71) at 20, 28 and 32 degrees C, respectively. The lower temperature threshold (Tb) and thermal constant (K) were 10.65 degrees C and 151.25 degree-days when the parasitoid was reared on eggs of P. includens; and 11.64 degrees C and 127.60 degree-days when reared on eggs of A. gemmatalis. The number of generations per month increased from 1.45 to 4.23 and from 1.49 to 4.79 when the parasitoid was reared on eggs of P. includens and A. gemmatalis, respectively, following the increases in the temperature. (C) 2009 Elsevier Inc. All rights reserved.

Predation and reproductive output of the ladybird beetle Stethorus tridens preying on tomato red spider mite Tetranychus evansi

Predatory behaviour and reproductive output of the ladybird beetle Stethorus tridens Gordon as function of the tomato red spider mite (TRSM), Tetranychus evansi Baker & Pritchard, densities was investigated in the laboratory. Adult female of S. tridens were isolated in cylindrical plastic arenas, containing a leaf disc of Solanum americanum Mill. with 5, 20, 40, 60, 80 or 100 T. evansi nymphs. The number of prey consumed and eggs laid were evaluated daily for ten consecutive days, starting at the oviposition. Oviposition of S. tridens was positively correlated with prey consumption and lower threshold prey consumption for S. tridens laying eggs was 16.3 mites per day. The instantaneous rate of attack (ca. discovery area) and the handling time were 0.0062 h(-1) and 0.83 h, and 0.00254 h(-1) and 0.78 h, respectively, for predators at the 1st- and 10th-oviposition day. The predator exhibited a type II functional response at 1st- and 10th-oviposition day with a maximum consumption per predator of 33 T. evansi nymphs per day at the highest prey density. The ladybird beetle S. tridens is often collected associated with red spider mite colonies on solanaceous wild plants and the results suggest the potential of this ladybird beetle to control T. evansi in tomatoes crops.

Spatial portability of numerical models of leaf wetness duration based on empirical approaches

Leaf wetness duration (LWD) models based on empirical approaches offer practical advantages over physically based models in agricultural applications, but their spatial portability is questionable because they may be biased to the climatic conditions under which they were developed. In our study, spatial portability of three LWD models with empirical characteristics - a RH threshold model, a decision tree model with wind speed correction, and a fuzzy logic model - was evaluated using weather data collected in Brazil, Canada, Costa Rica, Italy and the USA. The fuzzy logic model was more accurate than the other models in estimating LWD measured by painted leaf wetness sensors. The fraction of correct estimates for the fuzzy logic model was greater (0.87) than for the other models (0.85-0.86) across 28 sites where painted sensors were installed, and the degree of agreement k statistic between the model and painted sensors was greater for the fuzzy logic model (0.71) than that for the other models (0.64-0.66). Values of the k statistic for the fuzzy logic model were also less variable across sites than those of the other models. When model estimates were compared with measurements from unpainted leaf wetness sensors, the fuzzy logic model had less mean absolute error (2.5 h day(-1)) than other models (2.6-2.7 h day(-1)) after the model was calibrated for the unpainted sensors. The results suggest that the fuzzy logic model has greater spatial portability than the other models evaluated and merits further validation in comparison with physical models under a wider range of climate conditions. (C) 2010 Elsevier B.V. All rights reserved.

Suitability of relative humidity as an estimator of leaf wetness duration

Leaf wetness duration (LWD) is a key parameter in agricultural meteorology since it is related to epidemiology of many important crops, controlling pathogen infection and development rates. Because LWD is not widely measured, several methods have been developed to estimate it from weather data. Among the models used to estimate LWD, those that use physical principles of dew formation and dew and/or rain evaporation have shown good portability and sufficiently accurate results, but their complexity is a disadvantage for operational use. Alternatively, empirical models have been used despite their limitations. The simplest empirical models use only relative humidity data. The objective of this study was to evaluate the performance of three RH-based empirical models to estimate LWD in four regions around the world that have different climate conditions. Hourly LWD, air temperature, and relative humidity data were obtained from Ames, IA (USA), Elora, Ontario (Canada), Florence, Toscany (Italy), and Piracicaba, Sao Paulo State (Brazil). These data were used to evaluate the performance of the following empirical LWD estimation models: constant RH threshold (RH >= 90%); dew point depression (DPD); and extended RH threshold (EXT_RH). Different performance of the models was observed in the four locations. In Ames, Elora and Piracicaba, the RH >= 90% and DPD models underestimated LWD, whereas in Florence these methods overestimated LWD, especially for shorter wet periods. When the EXT_RH model was used, LWD was overestimated for all locations, with a significant increase in the errors. In general, the RH >= 90% model performed best, presenting the highest general fraction of correct estimates (F(C)), between 0.87 and 0.92, and the lowest false alarm ratio (F(AR)), between 0.02 and 0.31. The use of specific thresholds for each location improved accuracy of the RH model substantially, even when independent data were used; MAE ranged from 1.23 to 1.89 h, which is very similar to errors obtained with published physical models for LWD estimation. Based on these results, we concluded that, if calibrated locally, LWD can be estimated with acceptable accuracy by RH above a specific threshold, and that the EXT_RH method was unsuitable for estimating LWD at the locations used in this study. (C) 2007 Elsevier B.V. All rights reserved.

Probable consequences of the mitigation of citrus canker eradication methodology in Sao Paulo state

Probable consequences of the mitigation of citrus canker eradication methodology in Sao Paulo state Recently the Sao Paulo state government mitigated its citrus canker eradication methodology adopted since 1999. In April 2009 at least 99.8% of commercial sweet orange orchards were free of citrus canker in Sao Paulo state. Consequently the mitigation of the eradication methodology reduced the high level of safety and the competitiveness of the citrus production sector in Sao Paulo state, Brazil. Therefore we suggest the re-adoption of the same eradication methodology of citrus canker adopted in Sao Paulo from 1999 to 2009, or the adoption of a new methodology, effective for citrus canker suppression, because in new sample surveys citrus canker was detected in >0.36% of affected orchards. This incidence threshold was calculated by using the Duncan test (P <= 0.05) to compare the yearly sample surveys conducted in Sao Paulo state to estimate citrus canker incidence between 1999 and 2009. The calculated minimum significant level was 0.28% among sample surveys and the lowest citrus canker incidence in Sao Paulo state was 0.08%, occurring in 2001. Thus, as an alternative, we suggest the adoption of a new eradication methodology for citrus canker suppression when a new sample survey detected >0.36% of affected orchards in Sao Paulo state, Brazil.

Short communication: Evaluation of an on-farm test to estimate somatic cell count

The objective of this study was to compare the results of an on-farm test, named Somaticell, with results of electronic cell counting and for milk somatic cell count (SCC) among readers. The Somaticell test correctly determined the SCC in fresh quarter milk samples. Correlation between Somaticell and electronic enumeration of somatic cells was 0.92 and. coefficient 0.82. Using a threshold of 205,000 cells/mL, the sensitivity and specificity for determination of intramammary infections were 91.3 and 96.0%, respectively. The SCC was greater for milk samples from which major mastitis pathogens were recovered. Minor variation among readers was observed and most likely associated with the mixing procedure. However, the final analysis indicated that this variation was not significant and did not affect the amount of samples classified as having subclinical mastitis. The on-farm test evaluated in this study showed adequate capacity of determining SCC on quarter milk samples and may be considered as an alternative for on-farm detection of subclinical mastitis.

Spatial heterogeneity of leaf wetness duration in apple trees and its influence on performance of a warning system for sooty blotch and flyspeck

To determine the effect of sensor placement on the performance of a disease-warning system for sooty blotch and flyspeck (SBFS), we measured leaf wetness duration (LWD) at 12 canopy positions in apple trees, then simulated operation of the disease-warning system using LWD measurements from different parts of the canopy. LWD sensors were placed in four trees within one Iowa orchard during two growing seasons, and in one tree in each of four orchards during a single growing season. The LWD measurements revealed substantial heterogeneity among sensor locations. In all data sets, the upper, eastern portion of the canopy had the longest mean daily LWD, and was the first site to form dew and the last to dry. The lower, western portion of the canopy averaged about 3 It less LWD per day than the top of the canopy, and was the last zone where dew formed and the first to dry off. On about 25% of nights when dew occurred in the top of the canopy, no dew formed in the lower, western canopy. Intracanopy variability of LWD was more pronounced when dew was the sole source of wetness than on days when rainfall occurred. Daily LWD in the upper, eastern portion of the canopy was slightly less than reference measurements made at a 0.7-m height over turfgrass located near the orchard. When LWD measurements from several canopy positions were input to the SBFS warning system, timing of occurrence of a fungicide-spray threshold varied by as much as 30 days among canopy positions. Under Iowa conditions, placement of an LWD sensor at an unobstructed site over turfgrass was a fairly accurate surrogate for the wettest part of the canopy. Therefore, such an extra-canopy LWD sensor might be substituted for a within-canopy sensor to enhance operational reliability of the SBFS warning system.