RESUMO
Herein a series of chiral BTI radical anions bearing different chiral substituents were efficiently prepared by chemical reduction. X-ray crystallography revealed finely-tuned packing and helix assemblies of the radicals by the size of chiral substituents in crystalline state. In accordance with the crystalline-state packing, the powder ESR spectra indicate that 4 a- â CoCp2 + and 4 c- â CoCp2 + π-dimers exhibit thermally excited triplet states arising from strong spin-spin interactions, while discrete 4 b- â CoCp2 + shows a broad doublet-state signal reflecting weak spin-spin interactions. The interplay between the unpaired electron spin and chiral substituents was studied by UV-Vis-NIR spectra, electronic circular dichroism (ECD) and TD DFT calculations. Different NIR absorptions of the radicals attributing to isolated SOMOâLUMO+1 (~889â nm) transitions were recorded. The emergence of Cotton effects (CEs) at the NIR region for 4 c- â CoCp2 + radical enantiomers suggest the interplay between chirality and unpaired electron spin. The origin of the different circularly polarized light absorptions regarding SOMO derived transitions (around 880â nm) was attributed to chiral substitutes regulated electric and magnetic transition dipole moments of the unpaired electron participated transition.
RESUMO
Cry11Aa and Cyt1Aa are two pesticidal toxins produced by Bacillus thuringiensis subsp. israelensis. To improve our understanding of the nature of their oligomers in the toxic actions and synergistic effects, we performed the atomic force microscopy to probe the surfaces of their natively grown crystals, and used the L-weight filter to enhance the structural features. By L-weight filtering, molecular sizes of the Cry11Aa and Cyt1Aa monomers obtained are in excellent agreement with the three-dimensional structures determined by x-ray crystallography. Moreover, our results show that the layered feature of a structural element distinguishes the topographic characteristics of Cry11Aa and Cyt1Aa crystals, suggesting that the Cry11Aa toxin has a better chance than Cyt1Aa for multimerization and therefore cooperativeness of the toxic actions.
Assuntos
Bacillus thuringiensis , Endotoxinas , Endotoxinas/química , Endotoxinas/toxicidade , Toxinas de Bacillus thuringiensis , Proteínas Hemolisinas/química , Proteínas Hemolisinas/toxicidade , Proteínas de Bactérias/química , Bacillus thuringiensis/químicaRESUMO
BACKGROUND: Malaria, transmitted by the bite of infective female Anopheles mosquitoes, remains a global public health problem. The presence of an invasive Anopheles stephensi, capable of transmitting Plasmodium vivax and Plasmodium falciparum parasites was first reported in Ethiopia in 2016. The ecology of An. stephensi is different from that of Anopheles arabiensis, the primary Ethiopian malaria vector, and this suggests that alternative control strategies may be necessary. Larviciding may be an effective alternative strategy, but there is limited information on the susceptibility of Ethiopian An. stephensi to common larvicides. This study aimed to evaluate the efficacy of temephos and Bacillus thuringiensis var. israelensis (Bti) larvicides against larvae of invasive An. stephensi. METHODS: The diagnostic doses of two larvicides, temephos (0.25 ml/l) and Bti (0.05 mg/l) were tested in the laboratory against the immature stages (late third to early fourth stages larvae) of An. stephensi collected from the field and reared in a bio-secure insectary. Larvae were collected from two sites (Haro Adi and Awash Subuh Kilo). For each site, three hundred larvae were tested against each insecticide (as well as an untreated control), in batches of 25. The data from all replicates were pooled and descriptive statistics prepared. RESULTS: The mortality of larvae exposed to temephos was 100% for both sites. Mortality to Bti was 99.7% at Awash and 100% at Haro Adi site. CONCLUSIONS: Larvae of An. stephensi are susceptible to temephos and Bti larvicides suggesting that larviciding with these insecticides through vector control programmes may be effective against An. stephensi in these localities.
Assuntos
Anopheles , Bacillus thuringiensis , Inseticidas , Malária , Animais , Feminino , Humanos , Temefós/farmacologia , Larva , Etiópia , Mosquitos Vetores , Inseticidas/farmacologiaRESUMO
Assays to evaluate the susceptibility of Simulium larvae to temephos and Bacillus thuringiensis var israelensis (Bti) were carried out by setting-up an in vitro laboratory test ('bio assay') and a semi-natural test ('système de goutières') to assess the LC50/LC90 values. Larvae of Simulium species in Cameroon (S. damnosum s.l., S. hargreavesi, S. vorax and S. cervicornutum) and (S. (Odagmia) ornatum and S. latipes) in Germany were identified and tested. In the bio-assay, 50 larvae were exposed for 10 min to concentrations from 0.01 to 10 ppm. For the Simulium from Germany, the LC50 (LC90) values after 3 and 6 h were 3.1 (27.9) and 0.14 (1.26) ppm for temephos and for Bti 7.8 (70.2) and 1.7 (15.3) ppm, respectively. For Cameroonian species, the values of LC50 (LC90) were lower, that is, 0.42 (8.04), 0.14 (2.70) and 0.073 (1.38) ppm, respectively, after 3, 6 and 12 h for temephos. In a semi natural condition, the LC50 of 10 min of application of temephos was 0.84 ppm after 3 h and a working solution (2.6 L) of Bti killed 50% after 6 h. To detect an upcoming of any resistance as it happened in Ivory Coast, a study of the occurrence resistance genes should be implemented.
Assuntos
Bacillus thuringiensis , Inseticidas , Simuliidae , Animais , Temefós , Inseticidas/farmacologia , Larva , Camarões , Alemanha , Controle Biológico de VetoresRESUMO
Bacillus thuringiensis subsp. israelensis produces crystal inclusions composed of three-domain Cry proteins and cytolytic Cyt toxins, which are toxic to different mosquito larvae. A key component is the Cyt toxin, which synergizes the activity of the other Cry toxins, thereby resulting in high toxicity. The precise mechanism of action of Cyt toxins is still debated, and two models have been proposed: the pore formation model and the detergent effect. Here, we performed a systematic structural characterization of the Cyt toxin interaction with different membranes, including in Aedes aegypti larval brush border membrane vesicles, small unilamellar vesicle liposomes, and rabbit erythrocytes. We examined Cyt1Aa insertion into these membranes by analyzing fluorescence quenching in solution and in the membrane-bound state. For this purpose, we constructed several Cyt1Aa variants having substitutions with a single cysteine residue in different secondary structures, enabling Cys labeling with Alexa Fluor 488 for quenching analysis using I-soluble quencher in solution and in the membrane-bound state. We identified the Cyt1Aa residues exposed to the solvent upon membrane insertion, predicting a possible topology of the membrane-inserted toxin in the different membranes. Moreover, toxicity assays with these variants revealed that Cyt1Aa exerts its insecticidal activity and hemolysis through different mechanisms. We found that Cyt1Aa exhibits variable interactions with each membrane system, with deeper insertion into mosquito larva membranes, supporting the pore formation model, whereas in the case of erythrocytes and small unilamellar vesicles, Cyt1Aa's insertion was more superficial, supporting the notion that a detergent effect underlies its hemolytic activity.
Assuntos
Aedes/metabolismo , Toxinas de Bacillus thuringiensis/farmacologia , Bacillus thuringiensis/química , Endotoxinas/farmacologia , Membrana Eritrocítica/metabolismo , Proteínas Hemolisinas/farmacologia , Animais , Larva , Lipossomos , CoelhosRESUMO
It is generally believed that Bacillus thuringiensis var. israelensis (Bti) biopesticides are harmless to non-target organisms; however, new research shows controversial results. We exposed acutely and chronicallyLithobates sylvaticusandAnaxyrus americanus tadpoles until metamorphic climax to VectoBac 200G (granules) and VectoBac 1200L (aqueous suspension) at 300-20,000 ITU/L covering field-relevant concentrations and higher. The data show that the exposure parameters tested did not affect significantly the survival, total length, total weight, hepatosomatic index, gonadosomatic index, the expression of genes of interest (i.e., related to xenobiotic exposure, oxidative stress, and metamorphosis), and the intestine tissue layer detachment ofL. sylvaticusandA. americanus in a concentration-response pattern. In contrast, VectoBac 200G significantly increased the median time to metamorphosis ofL. sylvaticus tadpoles by up to 3.5 days and decreased the median by up to 1 day inA. americanus. VectoBac 1200L significantly increased the median time to metamorphosis ofL. sylvaticusandA. americanustadpoles by up to 4.5 days. Also, the exposure to VectoBac 200G and 1200L altered the intestine bacterial community composition inA. americanus at application rates recommended by the manufacturer, which led to an increase in the relative abundance of Verrucomicrobia, Firmicutes, Bacteroidetes, and Actinobacteria. Changes in the intestine microbiota might impact the fitness of individuals, including the susceptibility to parasitic infections. Our results indicate that the effect of Bti commercial products is limited; however, we recommend that Bti-spraying activities in amphibian-rich ecosystems should be kept minimal until there is more conclusive research to assess if the changes in the time to metamorphosis and microbiota can lead to negative outcomes in amphibian populations and, eventually, the functioning of ecosystems.
Assuntos
Bacillus thuringiensis , Microbioma Gastrointestinal , Animais , Agentes de Controle Biológico , Ecossistema , Humanos , Larva , Controle Biológico de VetoresRESUMO
Here a solution for a Microchip Health Monitoring (MHM) system using MTOL (Multi-Temperature Operational Life) reliability testing assessment data is proposed. The module monitors frequency degradation over time compared to lab tested data. Since trends in performance degradation in recently developed devices have transitioned from multiple failure mechanisms to a single dominant failure mechanism, development of the monitor is greatly simplified. The monitor uses a novel circuit customized to deliver optimum accuracy by combining the concepts of ring oscillator (RO) and phase locked loop (PLL) circuits. The modified circuit proposed is a new form of the frequency locked loop (FLL) circuit. We demonstrate that the collection of frequency degradation data from the ring circuits of each test produces Weibull distributions with steep slopes. This implies that the monitor can predict accurate end-of-life (EOL) predictions at early stages of chip degradations. The design of the microchip health monitoring system projected in this work can have great benefit in all systems using FPGA and ASIC devices.
RESUMO
BACKGROUND: Malaria prevention in Africa is mainly through the use of long-lasting insecticide treated nets (LLINs). The objective of the study was to assess the effect of supplementing LLINs with either larviciding with Bacillus thuringiensis israelensis (Bti) or community education and mobilization (CEM), or with both interventions in the context of integrated vector management (IVM). METHODS: The study involved a factorial, cluster-randomized, controlled trial conducted in Malindi and Nyabondo sites in Kenya and Tolay site in Ethiopia, to assess the impact of the following four intervention options on mosquitoes and malaria prevalence: LLINs only (arm 1); LLINs and Bti (arm 2); LLINs and CEM (arm 3); and, LLINs combined with Bti and CEM (arm 4). Between January 2013 and December 2015, CDC light traps were used to sample adult mosquitoes during the second, third and fourth quarter of each year in 10 houses in each of 16 villages at each of the three study sites. Larvae were sampled once a fortnight from potential mosquito-breeding habitats using standard plastic dippers. Cross-sectional malaria parasite prevalence surveys were conducted involving a total of 11,846 primary school children during the 3-year period, including 4800 children in Tolay, 3000 in Malindi and 4046 in Nyabondo study sites. RESULTS: Baseline relative indoor anopheline density was 0.11, 0.05 and 0.02 mosquitoes per house per night in Malindi, Tolay and Nyabondo sites, respectively. Nyabondo had the highest recorded overall average malaria prevalence among school children at 32.4%, followed by Malindi with 5.7% and Tolay 1.7%. There was no significant reduction in adult anopheline density at each of the three sites, which could be attributed to adding of the supplementary interventions to the usage of LLINs. Malaria prevalence was significantly reduced by 50% in Tolay when using LLINs coupled with application of Bti, community education and mobilization. The two other sites did not reveal significant reduction of prevalence as a result of combining LLINs with any of the other supplementary interventions. CONCLUSION: Combining LLINs with larviciding with Bti and CEM further reduced malaria infection in a low prevalence setting in Ethiopia, but not at sites with relatively higher prevalence in Kenya. More research is necessary at the selected sites in Kenya to periodically determine the suite of vector control interventions and broader disease management strategies, which when integrated would further reduce adult anopheline populations and malaria prevalence beyond what is achieved with LLINs.
Assuntos
Anopheles , Bacillus thuringiensis/química , Educação em Saúde/estatística & dados numéricos , Larva , Malária/prevenção & controle , Controle de Mosquitos/estatística & dados numéricos , Mosquitos Vetores , Animais , Anopheles/crescimento & desenvolvimento , Estudos Transversais , Etiópia , Educação em Saúde/organização & administração , Quênia , Larva/crescimento & desenvolvimentoRESUMO
OBJECTIVES: The annual incidence of dengue has been increasing over the last few years in Sri Lanka with seasonal epidemics. Biological control of the vector has not been part of the integrated vector control implemented by the public health authorities of Sri Lanka so far. This pilot study assessed the effectiveness of using Bacillus thuringiensis israelensis (Bti) spray to control the Aedes mosquito vector population density. METHODS: Prospective controlled effectiveness study in three administrative divisions of Colombo. Study areas were selected from urban, semiurban and rural administrative divisions within the district, and they were compared with two matching controls from the same division. Test areas received three cycles of Bti spraying 1 month apart. Control areas were not sprayed with Bti. Ovitrap and larval indices were calculated at baseline and 2 weeks after each spray cycle. RESULTS: There was a significant improvement in the adult vector population (ovitrap index) in the test areas after three spray cycles, but this effect had disappeared after 8 weeks (no residual effect). There was no consistent positive impact on larval indices (premise, container and Breteau indices) after each spray cycle. CONCLUSION: Bti might have a moderate impact on adult vector populations mediated via transient reductions in larval populations. However, this effect is not sustained probably due to rapid re-infestation. Bti spray, if implemented, can only play a supplementary role to other vector control methods.
Assuntos
Aedes , Bacillus thuringiensis/fisiologia , Dengue/prevenção & controle , Controle de Mosquitos/métodos , Controle Biológico de Vetores/métodos , Animais , Bioensaio , Humanos , Insetos Vetores , Estudos Prospectivos , Sri LankaRESUMO
Short-term impacts of aerial application of Bacillus thuringiensis israelensis (Bti) on Culicidae and Chironomidae were investigated over several years in temporary waters of the Dyje and Morava floodplains in Eastern Austria. The sampling followed a Before-After-Control-Impact (BACI) approach with sampling dates immediately before and shortly after the application and was repeated for 3 years. To test for effects of the Bti treatment on the two Diptera families, linear mixed-effects models were used. Data analysis included the factors Before-After and Control-Impact as fixed effects, while general temporal and spatial variables were random effects. One hundred sixteen taxa of chironomids were identified. Abundance varied between 2 and 1125 larvae per m2, while culicid densities reached values of several 100 ind. per liter. Total culicid abundance significantly decreased after the Bti treatment, whereas no significant effects were found on the abundance of total chironomids and dominant chironomid subfamilies, tribes, and genera, on relative proportions of chironomid feeding guilds, diversity, and species composition. Further studies from this area are needed to extend the investigation over a period of several weeks in order to reveal possible delayed effects of the larvicide application.
Assuntos
Bacillus thuringiensis/metabolismo , Chironomidae/crescimento & desenvolvimento , Culicidae/crescimento & desenvolvimento , Larva/microbiologia , Controle de Mosquitos/métodos , Animais , Áustria , Chironomidae/microbiologia , Culicidae/microbiologia , Monitoramento AmbientalRESUMO
Pilot studies have indicated that peroral endoscopic myotomy (POEM) might be a safe and effective treatment for achalasia. We performed a prospective, international, multicenter study to determine the outcomes of 70 patients who underwent POEM at 5 centers in Europe and North America. Three months after POEM, 97% of patients were in symptom remission (95% confidence interval, 89%-99%); symptom scores were reduced from 7 to 1 (P < .001) and lower esophageal sphincter pressures were reduced from 28 to 9 mm Hg (P < .001). The percentage of patients in symptom remission at 6 and 12 months was 89% and 82%, respectively. POEM was found to be an effective treatment for achalasia after a mean follow-up period of 10 months.
Assuntos
Acalasia Esofágica/cirurgia , Esofagoscopia/métodos , Adulto , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Cirurgia Endoscópica por Orifício Natural , Estudos Prospectivos , Resultado do TratamentoRESUMO
OBJECTIVE: To evaluate combinations of larvicides and fish which are predators of larvae of Aedes aegypti, namely Betta splendens, Trichogaster trichopterus and Poecilia reticulata. METHODS: We used 15 water tanks with a capacity of 250 litres of water. In 10 tanks, larvicide - Temephos, Bti and Novaluron - was added, the other five contained only one specimen of fish and unchlorinated water. The fish were monitored for a week without changing the water, and their survival recorded on a form. An estimate of the Kaplan-Meier survival was performed to determine the significance of the tests. RESULTS: Betta splendens showed the lowest mortality range of larvicides tested. CONCLUSION: Combined use of larvivorous fish and larvicides in large water tanks is feasible.
Assuntos
Aedes , Dengue/prevenção & controle , Peixes , Inseticidas , Larva , Controle de Mosquitos , Controle Biológico de Vetores , Animais , Humanos , Insetos Vetores , Estimativa de Kaplan-Meier , Água , Abastecimento de ÁguaRESUMO
Given the current maturity of printed technologies, Organic Thin-Film Transistors (OTFT) still show high initial variability, which can be beneficial for its exploitation in security applications. In this work, the process-related variability and aging of commercial OTFTs have been characterized to evaluate the feasibility of OTFTs-based Physical Unclonable Functions (PUFs) implementation. For our devices, ID-based PUFs show good uniformity and uniqueness. However, PUFs' reliability could be compromised because of the observed transient and aging effects in the OTFTs, which could hinder the reproducibility of the generated fingerprints. A systematic study of the aging of OTFTs has been performed to evaluate the PUFs' reliability. Our results suggest that the observed transient and aging effects could be mitigated so that the OTFTs-based PUFs' reliability could be improved.
RESUMO
The gate-all-around (GAA) nanosheet (NS) field-effect-transistor (FET) is poised to replace FinFET in the 3 nm CMOS technology node and beyond, marking the second seminal shift in device architecture across the extensive 60-plus-year history of MOSFET. The introduction of a new device structure, coupled with aggressive pitch scaling, can give rise to reliability challenges. In this article, we present a review of the key reliability mechanisms in GAA NS FET, including bias temperature instability (BTI), hot carrier injection (HCI), gate oxide (Gox) time-dependent dielectric breakdown (TDDB), and middle-of-line (MOL) TDDB. We aim to not only underscore the unique reliability attributes inherent to NS architecture but also provide a holistic view of the status and prospects of NS reliability, taking into account the challenges posed by future scaling.
RESUMO
The conservation and management of riparian ecosystems rely on understanding the ecological consequences of anthropogenic stressors that impact natural communities. In this context, studies investigating the effects of anthropogenic stressors require reliable methods capable of mapping the relationships between taxa occurrence or abundance and environmental predictors within a spatio-temporal framework. Here, we present an integrative approach using DNA metabarcoding and Hierarchical Modelling of Species Communities (HMSC) to unravel the intricate dynamics and resilience of chironomid communities exposed to Bacillus thuringiensis var. israelensis (Bti). Chironomid emergence was sampled from a total of 12 floodplain pond mesocosms, half of which received Bti treatment, during a 16-week period spanning spring and summer of 2020. Subsequently, we determined the community compositions of chironomids and examined their genus-specific responses to the Bti treatment, considering their phylogenetic affiliations and ecological traits of the larvae. Additionally, we investigated the impact of the Bti treatment on the body size distribution of emerging chironomids. Our study revealed consistent responses to Bti among different chironomid genera, indicating that neither phylogenetic affiliations nor larval feeding strategies significantly contributed to the observed patterns. Both taxonomic and genetic diversity were positively correlated with the number of emerged individuals. Furthermore, our findings demonstrated Bti-related effects on chironomid body size distribution, which could have relevant implications for size-selective terrestrial predators. Hence, our study highlights the value of employing a combination of DNA metabarcoding and HMSC to unravel the complex dynamics of Bti-related non-target effects on chironomid communities. The insights gained from this integrated framework contribute to our understanding of the ecological consequences of anthropogenic stressors and provide a foundation for informed decision-making regarding the conservation and management of riparian ecosystems.
Assuntos
Bacillus thuringiensis , Chironomidae , Culicidae , Humanos , Animais , Ecossistema , Chironomidae/fisiologia , Controle de Mosquitos/métodos , Código de Barras de DNA Taxonômico , Filogenia , Larva , Controle Biológico de VetoresRESUMO
BACKGROUND: Toxins of Bacillus thuringiensis subsp. israelensis (Bti) are safer alternatives for controlling dipteran pests such as black flies and mosquitoes. The biting midge Culicoides sonorensis (Diptera: Ceratopogonidae) is an important pest of livestock in much of the United States and larval midges utilize semi-aquatic habitats which are permissive for Bti product application. Reports suggest that Bti products are ineffective at killing biting midges despite their taxonomic relation to black flies and mosquitoes. Here, we investigate the toxicity of a Bti-based commercial insecticide and its active ingredient in larval Culicoides sonorensis. A suspected mechanism of Bti tolerance is an acidic larval gut, and we used a pH indicator dye to examine larval Culicoides sonorensis gut pH after exposure to Bti. RESULTS: The lethal concentration to kill 90% (LC90) of larvae of the commercial product (386 mg/L) was determined to be almost 10 000 times more than that of some mosquito species, and no concentration of active ingredient tested achieved 50% larval mortality. The larval gut was found to be more acidic after exposure to Bti which inhibits Bti toxin activity. By comparison, 100% mortality was achieved in larval Aedes aegypti at the product's label rate for this species and mosquito larvae had alkaline guts regardless of treatment. Altering the larval rearing water to alkaline conditions enhanced Bti efficacy when using the active ingredient. CONCLUSION: We conclude that Bti is not practical for larval Culicoides sonorensis control at the same rates as mosquitos but show that alterations or additives to the environment could make the products more effective. © 2024 Society of Chemical Industry.
Assuntos
Ceratopogonidae , Trato Gastrointestinal , Larva , Animais , Ceratopogonidae/efeitos dos fármacos , Ceratopogonidae/fisiologia , Concentração de Íons de Hidrogênio , Larva/crescimento & desenvolvimento , Larva/efeitos dos fármacos , Trato Gastrointestinal/efeitos dos fármacos , Bacillus thuringiensis/química , Inseticidas/farmacologia , Toxinas de Bacillus thuringiensisRESUMO
With the technological scaling of metal-oxide-semiconductor field-effect transistors (MOSFETs) and the scarcity of circuit design margins, the characteristics of device reliability have garnered widespread attention. Traditional single-mode reliability mechanisms and modeling are less sufficient to meet the demands of resilient circuit designs. Mixed-mode reliability mechanisms and modeling have become a focal point of future designs for reliability. This paper reviews the mechanisms and compact aging models of mixed-mode reliability. The mechanism and modeling method of mixed-mode reliability are discussed, including hot carrier degradation (HCD) with self-heating effect, mixed-mode aging of HCD and Bias Temperature Instability (BTI), off-state degradation (OSD), on-state time-dependent dielectric breakdown (TDDB), and metal electromigration (EM). The impact of alternating HCD-BTI stress conditions is also discussed. The results indicate that single-mode reliability analysis is insufficient for predicting the lifetime of advanced technology and circuits and provides guidance for future mixed-mode reliability analysis and modeling.
RESUMO
Attractive toxic sugar baits (ATSBs) are an underexploited method for mosquito control. For ATSBs to be more widely accepted, demonstrably effective ingredients need to be verified. We investigated erythritol as a toxic additive in sugar meals against Aedes aegypti (L.) for potential future use in ATSBs. Erythritol is a sugar alcohol that is commonly used as a sugar substitute, while also being toxic to mosquitoes. Our studies tested formulations of erythritol, sucrose, and blends of both. Secondary investigations included combinations with the active ingredients Bacillus thuringiensis israelensis, spinosyn, and boric acid. Adult Ae. aegypti were separated into test groups and provided various combinations. Formulations containing erythritol, with or without another toxicant, exhibited 90% mortality within 72 h of observation (P = 0.03192). Additionally, erythritol appeared more effective when combined with sucrose in a 1:1 ratio (5% concentration each). This combination showed a 24% and 85% increase in mortality when combined with boric acid and Bti, respectively, at 48 h compared with equivalent groups containing only 10% sucrose. Erythritol appears to kill adult mosquitoes, even in relatively low concentrations, without another toxicant being required. However, erythritol also effectively enhances kill of main ingredient toxicants such as boric acid and Bti, showing a supporting role. The low concentration of erythritol needed to provide significant kill, its ability to fill in as both a sugar base and toxicant, and its ability to be safely handled by humans makes erythritol a strong candidate for use as a supporting ingredient in future bait formulations.
Assuntos
Aedes , Inseticidas , Humanos , Animais , Açúcares , Eritritol , Controle de Mosquitos/métodos , SacaroseRESUMO
The bias temperature instability (BTI) effect of p-GaN gate high-electron-mobility transistors (HEMTs) is a serious problem for reliability. To uncover the essential cause of this effect, in this paper, we precisely monitored the shifting process of the threshold voltage (VTH) of HEMTs under BTI stress by fast sweeping characterizations. The HEMTs without time-dependent gate breakdown (TDGB) stress featured a high VTH shift of 0.62 V. In contrast, the HEMT that underwent 424 s of TDGB stress clearly saw a limited VTH shift of 0.16 V. The mechanism is that the TDGB stress can induce a Schottky barrier lowering effect on the metal/p-GaN junction, thus boosting the hole injection from the gate metal to the p-GaN layer. This hole injection eventually improves the VTH stability by replenishing the holes lost under BTI stress. It is the first time that we experimentally proved that the BTI effect of p-GaN gate HEMTs was directly dominated by the gate Schottky barrier that impeded the hole supply to the p-GaN layer.
RESUMO
Most of the latest generation of integrated circuits use FinFET transistors for their performance, but what about their reliability? Does the architectural evolution from planar MOSFET to FinFET transistor have any effect on the integrated circuit reliability? In this article, we present a test bench we have developed to age and measure the degradation of 5103 ring oscillators (ROs) implemented in nine FPGAs with 16nm FinFET under different temperature and voltage conditions (Vnom≤Vstress≤1.3Vnom and 25°C≤Tstress≤115°C) close to operational conditions in order to predict reliability regarding degradation mechanisms at the transistor scale (BTI, HCI and TDDB) as realistically as possible. By comparing our initial RO measurements and the data extracted from Vivado, we will show that the performance of the nine FPGAs is between 50% and 70% of the best performance expected by Vivado. After 8000 h of ageing, we will see that the relative degradations of the RO are a maximum of 1%, which is a first indicator proving the FPGAs' good reliability. By comparing our results with similar studies on 28 nm MOSFET FPGAs, we will reveal that 16 nm FinFET FPGAs are more reliable. To be implemented in an FPGA, an RO uses logic resources (LUT) and routing resources. We will show that degradation in the two types of resources is different. For this reason, we will present a method for separating degradations in logical and routing resources based on RO degradation measures. Finally, we will model rising and falling edge propagation time degradations in an FPGA as a function of time, temperature, voltage, signal duty cycle and resources used in the FPGA.