Error bounds for a numerical solution for dynamic economic models

AbstractIn this paper, we analyze a discretized version of the dynamic programming algorithm for a parameterized family of infinite-horizon economic models, and derive error bounds for the approximate value and policy functions. If h is the mesh size of the discretization, then the approximation error for the value function is bounded by Mh2, and the approximation error for the policy function is bounded by Nh, where the constants M and N can be estimated from primitive data of the model

Perceptions of Principal Effectiveness and Teacher Morale: A Study of Public Secondary School Teachers on Guam

For more than a decade, the public schools on Guam have suffered from low student test scores, high turnover rates and low levels of teacher morale. Although there may be many explanations for this persistent problem, an important part of any solution is improving the overall level of teacher morale, which of course, can be influenced in many ways by the actions of the principal. In an effort to determine both the level of teacher morale among secondary school teachers on Guam as well as the factors that may help explain it, including the perceived level of principal effectiveness, this study collected data from 250 secondary school teachers on Guam using the Teacher Outlook and Perceptions Survey and the Audit of Principal Effectiveness. Results of the hierarchical multiple regression analysis suggests that both demographic factors and the perceptions of the principal\u27s effectiveness were important determinants of teachers\u27 morale levels. Specifically, teachers at year-round schools and those with emergency or special contracts had higher levels of morale, as did those with principals that were perceived as effective. However, Caucasian teachers had lower morale than non-Caucasians, and middle school teachers had lower morale than high school teachers. Overall morale levels were slightly less than 5 on a 1–7 scale. Recommendations for future research include further investigation into the determinants of teacher morale, with a specific focus on the importance of the teachers\u27 certification status and ethnic heritage. In addition, a qualitative approach may be necessary to help understand some of the more nuanced reasons why teacher morale levels on Guam have consistently failed to improve

Preliminary study on the potential use of RPA images to quantify the influence of the defoliation after coffee harvesting to its yield

Received: January 24th, 2023 ; Accepted: May 22nd, 2023 ; Published: September 18th, 2023 ; Correspondence: [email protected] is an agricultural commodity with global commercial importance capable of impacting the production chain. The quantification of defoliation at harvest is important for monitoring crop yield because defoliation is one of the main types of damage caused by this agricultural operation in coffee crops. Thus, the objective of this study was to evaluate the relationship between yield and defoliation obtained in the field and obtained through remotely piloted aircraft (RPA) images. The experiment was conducted in a coffee plantation belonging to the Federal University of Lavras (UFLA), Lavras, Minas Gerais state, Brazil. An RPA with a rotary wing containing a multispectral camera was used in autonomous flight mode with a height of 30 m, an image overlap of 80%, and a speed of 3 m s-1 . The images were collected before and after the 2020 and 2021 harvest, defoliation data obtained in the field were measured in 2020 and 2021, and the yield was measured from 2019 to 2021. Image processing was performed in the software PhotoScan, postimage processing was performed in QGIS, and statistical analyses were performed using the software R. With the processing of the images in 2020, the crop showed reductions of 17.3% and 18.4% in leaf area and volume, respectively, after harvest. In 2021, the crop showed reductions of 12.8% and 9.8% in leaf area and volume, respectively, after harvest. The leaf area and leaf volume of the coffee plantation after harvest could be quantified by means of images obtained by RPA, which allowed the observation of the loss of area and volume of the coffee plantation. Furthermore, it was possible to analyse the interactions between field data and the yield of the same harvest year, which were directly proportional, and the interaction of image data from one year with the previous yield, which were inversely proportional. In the year 2020, there was a reduction of 17.3% in leaf area after harvest, and a reduction of 18.4% in leaf volume after harvest in the plots under study.In the processing carried out in 2021, there was a 12.8% reduction in leaf area after harvest, and a 9.8% decrease in leaf volume after harvest in the plots under study

Internal Friction On Aisi 304 Stainless Steels With Low Tensile Deformations At Temperatures Between - 50 And 20 °c

Austenitic stainless steels specimens were deformed by tension in temperatures in the range of - 50 °C to 20 °C and 0.03 to 0.12 true strain, in order to obtain different volumetric fractions of ε (hexagonal close packed) and α′ (body centered cubic) strain induced martensites. The morphology, distribution and volumetric fractions of the martensites were characterized by metallography and dilatometry analysis and quantified by ferrite detector measurements. The damping behavior of specimens with different volumetric fractions of martensites was studied in an inverted torsion pendulum in the 40 °C to 400 °C range. The ε- and α′-martensites reversion was observed in the temperature range of 50 °C 200 °C and 500 °C 800 °C, respectively, by dilatometry. Internal friction curves in function of temperature of the deformed samples presented internal friction peaks. The first internal friction peak is related to sum of the amount of ε- and α′-martensites. For low deformations it aligns around 130 °C and it is related only to the ε → γ reverse transformation. The peak situated around 350 °C increases with the specimen degree of deformation and is, probably, related to the presence of α′/γ interfaces, and deformed austenite. Copyright © 2010 T. F. A. Santos and M. S. Andrade.2010Padilha, A.F., Rios, P.R., Decomposition of austenite in austenitic stainless steels (2002) ISIJ International, 42 (4), pp. 325-337Blanc, C., Lacombe, P., Baroux, B., Beranger, G., Mcanismes de dformation des aciers inoxydables austnitiques (1990) Les Aciers Inoxydables, pp. 611-617. , Courtaboeuf, France ditions de PhysiqueGuy, K., Butler, E.P., West, D.R.F., Epsilon and alpha prime martensite formation and reversion in austenitic stainless steels (1982) Journal de Physique, 43 (4), pp. 575-580Fischer, G.J., MacIag, R.J., Peckner, D., Bernstein, I.M., The wrought stainless steels (1977) Handbook of Stainless Steels, 1, pp. 11-19. , New York, NY, USA McGraw-HillMartins, L.F.M., Plaut, R.L., Padilha, A.F., Effect of carbon on the cold-worked state and annealing behavior of two 18wtCr-8wtNi Austenitic stainless steels (1998) ISIJ International, 38 (6), pp. 572-579Mangonon, L., Thomas, G., Martensite phases in 304 stainless steel (1970) Metallurgical and Materials Transactions, 1 (6), pp. 1577-1586Baker, L.J., Parker, J.D., Daniel, S.R., The use of internal friction techniques as a quality control tool in the mild steel industry (2003) Journal of Materials Processing Technology, 143-144 (1), pp. 442-447Andrade, M.S., Gomes, O.A., Vilela, J.M.C., Serrano, A.T.L., Moraes, J.M.D., Formability evaluation of two austenitic stainless steels (2004) Journal of the Brazilian Society of Mechanical Sciences and Engineering, 26 (1), pp. 47-50Taylan, V., Wagoner, R.H., Lee, J.K., Formability of stainless steel (2006) Metallurgical and Materials Transactions A, 37, pp. 1875-1880De, A.K., Murdock, D.C., Mataya, M.C., Speer, J.G., Matlock, D.K., Quantitative measurement of deformation-induced martensite in 304 stainless steel by X-ray diffraction (2004) Scripta Materialia, 50 (12), pp. 1445-1449Petit, B., Gey, N., Cherkaoui, M., Bolle, B., Humbert, M., Deformation behavior and microstructure/texture evolution of an annealed 304 AISI stainless steel sheet. Experimental and micromechanical modeling (2007) International Journal of Plasticity, 23 (2), pp. 323-341De, A.K., Speer, J.G., Matlock, D.K., Murdock, D.C., Mataya, M.C., Comstock, Jr.R.J., Deformation-induced phase transformation and strain hardening in type 304 austenitic stainless steel (2006) Metallurgical and Materials Transactions, 37 (6), pp. 1875-1886Ritchie, I.G., Mathew, P.M., Pan, Z.I., Osborne, C., Prikryl, J.K., Mechanical relaxation spectroscopy in steel wire research (1989) Wire Journal International, pp. 201-218Nowick, A.S., Berry, B.S., (1972) Anelastic Relaxation in Crystalline Solids, , New York, NY, USA Academic PressReed-Hill, R.E., (1992) Physical Metallurgy Principles, , Boston, Mass, USA PWS-KentShewmon, P., (1989) Diffusion in Solids, Minerals, , Philadelphia, Pa, USA Metals Materials SocietyYu, N., Koval, G.S., Firstov, J.V., Van Humbeeck, J., Delaey, L., Jang, W.Y., B 2 intermetallic compounds of Zr. new class of the shape memory alloys (1995) Journal of Physics, 5 (8), p. 1103Zenati, R., Bernard, C., Calmet, C., Guillemet, S., Fantozzi, G., Durand, B., Internal friction investigation of phase transformation in nearly stoichiometric LaMnO3+ (2005) Journal of the European Ceramic Society, 25 (6), pp. 914-935Perkins, J., (1975) Shape Memory Effects in Alloys, , San Diego, Calif, USA Metallurgical Society of AIMEBaraz, V.R., Grachev, S.V., Rol'Shchikov, L.D., Internal friction in non-stable austenitic steels (1972) Steel in the USSR, 2, pp. 670-672Talonen, J., Hnninen, H., Damping properties of austenitic stainless steels containing strain-induced martensite (2004) Metallurgical and Materials Transactions A, 35 (8), pp. 2401-2406Pinto, T.B., Gomes, O.A., Vilela, J.M.C., Andrade, M.S., Serrano, A.L., De Moraes, J.M.D., Relationship between internal friction and strain induced martensite amount in an AISI 304 stainless steel Proceedings of the 58th Annual International Congress of the Brazilian Association of Metallurgy and Materials July 2003 Rio de Janeiro, Brazil, pp. 3137-3144ASTM Standard E-646, 1993Vilela, J.M.C., Oliveira, N.J.L., Andrade, M.S., Gonzalez, B.M., Santos, C.E.R., De Moraes, J.M.D., Metallographic analysis of stainless steels after deformation at different temperatures Proceedings of the 56th Annual International Congress of the Brazilian Association of Metallurgy and Materials 2001 Belo Horizonte, Brazil, pp. 510-519Santos, T.F.A., Andrade, M.S., Dilatometric evaluation of strain-induced martensite reversion in AISI 304 austenitic stainless steel (2008) Matria, 13 (4), pp. 587-596Das, A., Tarafder, S., Experimental investigation on martensitic transformation and fracture morphologies of austenitic stainless steel (2009) International Journal of Plasticity, 25 (11), pp. 2222-2247Lo, K.H., Shek, C.H., Lai, J.K.L., Recent developments in stainless steels (2009) Materials Science and Engineering R, 65, pp. 39-104Gey, N., Petit, B., Humbert, M., Electron backscattered diffraction study of / ' martensitic variants induced by plastic deformation in 304 stainless steel (2005) Metallurgical and Materials Transactions A, 36 (12), pp. 3291-3299Humbert, M., Petit, B., Bolle, B., Gey, N., Analysis of the - ′ variant selection induced by 10 plastic deformation in 304 stainless steel at -60C (2007) Materials Science and Engineering A, 454-455, pp. 508-517Santos, T.F.A., Andrade, M.S., Castro, A.L.R., Influence of heating rate on the reversion of strain-induced martensite in AISI 304 austenitic stainless steel (2009) Revista Escola de Minas, 62 (1), pp. 53-5

Magnetic and pair correlations of the Hubbard model with next-nearest-neighbor hopping

A combination of analytical approaches and quantum Monte Carlo simulations is used to study both magnetic and pairing correlations for a version of the Hubbard model that includes second-neighbor hopping $t^{\prime }=-0.35t$ as a model for high-temperature superconductors. Magnetic properties are analyzed using the Two-Particle Self-Consistent approach. The maximum in magnetic susceptibility as a function of doping appears both at finite $$ and at $t^{\prime }=0$ but for two totally different physical reasons. When $t^{\prime }=0$, it is induced by antiferromagnetic correlations while at $t^{\prime }=-0.35t$ it is a band structure effect amplified by interactions. Finally, pairing fluctuations are compared with $$-matrix results to disentangle the effects of van Hove singularity and of nesting on superconducting correlations. The addition of antiferromagnetic fluctuations increases slightly the $d$-wave superconducting correlations despite the presence of a van Hove singularity which tends to decrease them in the repulsive model. Some aspects of the phase diagram and some subtleties of finite-size scaling in Monte Carlo simulations, such as inverted finite-size dependence, are also discussed.Comment: Revtex, 8 pages + 15 uuencoded postcript figure

Texture analysis of computed tomography images of acute ischemic stroke patients

Computed tomography (CT) images are routinely used to assess ischemic brain stroke in the acute phase. They can provide important clues about whether to treat the patient by thrombolysis with tissue plasminogen activator. However, in the acute phase, the lesions may be difficult to detect in the images using standard visual analysis. The objective of the present study was to determine if texture analysis techniques applied to CT images of stroke patients could differentiate between normal tissue and affected areas that usually go unperceived under visual analysis. We performed a pilot study in which texture analysis, based on the gray level co-occurrence matrix, was applied to the CT brain images of 5 patients and of 5 control subjects and the results were compared by discriminant analysis. Thirteen regions of interest, regarding areas that may be potentially affected by ischemic stroke, were selected for calculation of texture parameters. All regions of interest for all subjects were classified as lesional or non-lesional tissue by an expert neuroradiologist. Visual assessment of the discriminant analysis graphs showed differences in the values of texture parameters between patients and controls, and also between texture parameters for lesional and non-lesional tissue of the patients. This suggests that texture analysis can indeed be a useful tool to help neurologists in the early assessment of ischemic stroke and quantification of the extent of the affected areas.1076107

Ultra-high sensitive strain sensor based on post-processed optical fiber Bragg grating

An ultra-high sensitive strain sensor is proposed. The sensing head, based on the post-processing of a fiber Bragg grating, is used to perform passive and active strain measurements. Both wavelength and full width half maximum dependences with the applied strain are studied for the passive sensor, where maximum sensitivities of 104.1 pm/με and 61.6 pm/με are respectively obtained. When combining the high performance of this sensor with a ring laser cavity configuration, the Bragg grating will act as a filter and high resolution measurements can be performed. With the proposed sensor, a resolution of 700 nε is achieved

Insulin therapy modulates mitochondrial dynamics and biogenesis, autophagy and tau protein phosphorylation in the brain of type 1 diabetic rats

AbstractThe main purpose of this study was to examine whether streptozotocin (STZ)-induced type 1 diabetes (T1D) and insulin (INS) treatment affect mitochondrial function, fission/fusion and biogenesis, autophagy and tau protein phosphorylation in cerebral cortex from diabetic rats treated or not with INS. No significant alterations were observed in mitochondrial function as well as pyruvate levels, despite the significant increase in glucose levels observed in INS-treated diabetic rats. A significant increase in DRP1 protein phosphorylated at Ser616 residue was observed in the brain cortex of STZ rats. Also an increase in NRF2 protein levels and in the number of copies of mtDNA were observed in STZ diabetic rats, these alterations being normalized by INS. A slight decrease in LC3-II levels was observed in INS-treated rats when compared to STZ diabetic animals. An increase in tau protein phosphorylation at Ser396 residue was observed in STZ diabetic rats while INS treatment partially reversed that effect. Accordingly, a modest reduction in the activation of GSK3β and a significant increase in the activity of phosphatase 2A were found in INS-treated rats when compared to STZ diabetic animals. No significant alterations were observed in caspases 9 and 3 activity and synaptophysin and PSD95 levels. Altogether our results show that mitochondrial alterations induced by T1D seem to involve compensation mechanisms since no significant changes in mitochondrial function and synaptic integrity were observed in diabetic animals. In addition, INS treatment is able to normalize the alterations induced by T1D supporting the importance of INS signaling in the brain

Produtividade Da Crotalaria Juncea Sob Podas E Densidades De Semeadura Nos Tabuleiros Costeiros Do Piauí

The northern region of Piauí state is an important center of irrigated organic fruit farming, wherein sandy soils with low organic matter content are predominant, besides climate with high temperatures, long periods of water deficit and constant wind. Given this situation, it becomes necessary to investigate alternative management options able to meet the challenges of agricultural productivity. In this context, green manuring becomes an important practice, mainly when using fast-growing species and with great potential for biomass production. Thus, a study was carried out at Embrapa Meio-Norte to measure Crotalaria juncea biomass yield after thinning and at various sowing densities. The evaluated parameters were plant height, stem diameter, number of branches per plant, fresh and dry weight of shoots and roots. The results showed that sowing density had no influence on plant height; however, unthinned plants reached greater heights, which might have been due to reduced competition for light. Thinning had no effect on diameters of plant stem base; on the other hand, lower planting densities promoted larger diameters also due to less competition. Likewise, the number of branches per plant was not affected by thinning, being greater at lower planting densities on account of less competition. Thinned plants achieved higher averages of fresh shoot weight. Nevertheless, shoot dry biomass was greater at higher planting densities. Furthermore, both fresh and dry weight of roots were not influenced by any of the adopted treatments. © 2016, Universidade Federal Rural do Semi-Arid. All rights reserved.29487888

Antibiotic resistance genes detected in the marine sponge <i>Petromica citrina</i> from Brazilian coast

Although antibiotic-resistant pathogens pose a significant threat to human health, the environmental reservoirs of the resistance determinants are still poorly understood. This study reports the detection of resistance genes (ermB, mecA, mupA, qnrA, qnrB and tetL) to antibiotics among certain culturable and unculturable bacteria associated with the marine sponge Petromica citrina. The antimicrobial activities elicited by P. citrina and its associated bacteria are also described. The results indicate that the marine environment could play an important role in the development of antibiotic resistance and the dissemination of resistance genes among bacteria