Bifactorial Analysis Research Articles

Acculturation Scale to Russia for Chinese Students: Development and Psychometric Verification

The topic on diagnosing intercultural adaptation and psychological acculturation to a new socio-cultural environment is relevant in connection with the processes of globalization and, in particular, with the growth of academic mobility in education. Research on this problem are especially relevant for Russian science due to the lack of acculturation scales, which are widely represented in Western and international psychology. In 2019, a research team led by Professor A. Ardila developed the Russian-language Acculturation Scale for Russia (ASR), which was validated on a sample of international university students from 71 countries of the world. The aim of the present study was to adapt the ASR for the Chinese students studying in Russian universities. Chinese students are the largest group of international students from far abroad studying at Russian universities, while many of them experience significant difficulties in adapting to a new socio-cultural environment, as well as in learning the Russian language. In total, the study involved 213 Chinese students (59% - female) studying at Russian universities, of which 93 students (58% - female) completed the Russian-language version of the ASR, and 118 students (61% - female) completed the Chinese version of the ASR, which was designed using the back translation. Both ASR versions were psychometrically tested using Cronbachs and MacDonalds coefficients, as well as bifactorial analysis. The methods of descriptive statistics and the Wilcoxon W-test were used to compare the Russian-language and Chinese versions of the ASR. The normalization was carried out by means of non-linear percentile normalization (stanines). As a result, a high consistency of the Russian-language and Chinese versions of the ASR and their equivalence with each other were shown. Both versions can be used to assess the level of acculturation of Chinese students to Russia, while the Chinese version is recommended for the Chinese students who have been living in Russia for less than 1-1.5 years and/or have a poor Russian proficiency.

Psychometry and estimation of cutoff points of Jefferson Scale of empathy in dental students.

The objective of this study was to determine the psychometric properties of the 3-dimensional latent model of empathy on the Jefferson Scale of Physician Empathy instrument (version S), and to verify the existence of cutoff points capable of differentiating empathy measures classified as: "high," "medium," and "low" using data collected from observations of students from 11 dental faculties of 5 Central American and Caribbean countries (n = 3082) between 2015 and 2019. This is an exploratory, "a posteriori," and non-experimental study. Factor structure and factor invariance by country and gender were analyzed. Hierarchical cluster analysis and bifactorial analysis were applied, and the data were normalized by cluster and by percentiles within them. Confirmatory factor analysis showed that the original model was replicable and fit the data, while multigroup analysis allowed assuming an invariant factor structure by country and by gender. There is reliability in the measurement made by the scale and its dimensions. The instrument has adequate psychometric properties, and cutoff values obtained allow people with lower or higher levels of empathy and its components to be classified. Therefore, these results solve the problem of comparing the scores and observed levels of empathy between dental schools within and between countries and between genders. Such comparisons were only possible since the original data of each study were made available for traditional statistical methods.

Evaluation of a workshop on social skills for professional practices in students of psychology and human communication therapy in the FPyTCH of the UJED

Objective: To present the result obtained from the evaluation of a workshop on social skills for professional practices in students of Psychology and Human Communication Therapy within the Community Services Center at the Faculty of Psychology and Human Communication Therapy belonging to the Juárez University of the State of Durango. Methodology: Mixed in a sequential explanatory design (DEXPLIS), through the statistical analysis of a constant sample from the results obtained in the social skills scale tests (Gismero), EMES-C and EMES-M in three different moments using the IBM SPSS®, applying the bifactorial analysis of variance by ranges or Friedman's test. Contribution: Achieve a correct interpretation of the results from the established hypothesis, paying attention to the particularities of the professional work, seeking that the student of Psychology and Human Communication Therapy near to graduate has a repertoire of competent social skills, that contribute to efficient professional performance and personal fulfillment, as well as the development of positive attitudes and the reduction of emotional exhaustion.

Research on the Quality of Fiber-Reinforced Composites

The paper aims an experimental study of the quality of composite materials based on the coefficient of uniformity, an indicator that appreciates the influence of different factors on their mechanical behavior. For the experiment, composite plates having an epoxy resin matrix and various types of reinforcement were made. Each plate is made up of five layers of fabric. These plates take into account two factors of influence, the number of layers with discontinuities and the size of the discontinuity. Then a bifactorial dispersion analysis is made that can differentiate the influences of the two factors.

Effect of citric acid leaching on the demineralization and thermal degradation behavior of sugarcane trash and bagasse

The effect of leaching with citric acid on the ash fraction removed and the resulting changes in thermal degradation behavior of sugarcane trash (SCT) and sugarcane bagasse (SCB), was studied. A comparison between citric acid and well-known leaching agents including H2SO4, HCl and water, was made considering their effects on chemical, structural and thermal properties of the leached SCT and SCB. Demineralization and potential biomass hydrolysis was evaluated based on proximate and elemental analyses, Fourier transform infrared spectroscopy (FTIR-ATR) and thermogravimetric analysis (TGA). For citric acid and the reference leaching solutions, the mass fraction of ash removed was in a narrow range (between 38.9 and 54.1%) regardless of biomass type and leaching conditions (temperature and time) tested. The nonparametric bifactorial analysis of results revealed that the nature of leaching solution and its interaction with contact time are of major significance when demineralizing both SCT and SCB. Interestingly, no significance of temperature and its interaction with contact time was found. In acid-treated samples, the 1730 cm−1 IR-band was sharpened while the signal at 1600 cm−1 was largely attenuated, which could be attributed to the modification of the xylan fraction and to the substitution of C=O by OH groups. These mild structural changes, caused by hydrolysis, demonstrated to be very important for subsequent thermal degradation. The later was confirmed by the disappearance of the hemicellulose decomposition peak in the derivative thermogravimetric (DTG) curve.

MYOCARDIAL REACTION TO ENERGY DRINKS IN A GUINE A PIG: STRUCTURAL CHANGES

The aim of this study was to evaluate myocardial changes in a short-haired guinea pig (Cavia porcellus L) after everyday use of energy drinks for 60 days. The experiments were carried out on 11 male gui- nea pigs, age of 2 months, with a mean weight of 220±0.2 g. The guinea pigs were randomly grouped into a control group of 5 guinea pigs and experimen- tal group of 6. Experimental group guinea pigs were orally administered energy drinks 4 ml per day as a single oral dose. After the 60 days experiment, the quantitatively evaluated structures of myocardial in- terstitial collagen in the left ventricle using automa- ted image analysis system, which was connected to Olympus BXx51 microscope. Assessment was per- formed with Image-Pro Plus 5.1 analysis system. We calculated volume and perimeter of the interstitial fibrillar collagen in the left ventricular myocardium, the number of separate fibers in the field of view were counted. In total, there was evaluated 100 fields of view in the control group and 120 fields of view in the experimental group. Statistical analysis was per- formed using statistical package SPSS Statistics 20 and Microsoft Excel. We used bifactorial analysis of variance (ANOVA) to compare histomorphometric parameters between the two groups. We assessed that the difference between parameters was up to 1% and the individual specific effect was counting for 50% (p < 0.05). Variation of the featu- res was much larger within the experimental group, when compared to the control group. Maximum ave- rage values of the fibrillar collagen volume, perimeter and the number of separate fibers in the field of view were 1.2 times larger in the experimental group than in the control group. Repeated energy drink consumption acts as external factor stimulating adaptive remodeling processes. Quantative structural changes of fibrillar collagen in left ventricle of experimental group animals are reaction to a stress factor. Unbalanced changes of fi- brillar collagen may determine inadequate remodeling and become a reason for pathogenesis.

In Vitro and In Vivo Feedstuff Digestibility for Snook, Centropomus undecimalis, Juveniles

AbstractThe degree of hydrolysis (DH) of the ingredients was evaluated for Centropomus undecimalis juveniles. The in vitro experiment included wheat gluten (WG), corn gluten (CG), soybean meal (SBM) and pretreated phytase (SBM + phytase), soy protein concentrate (SPC), canola meal (CAN) and pretreated phytase (CAN + phytase), poultry byproduct meal (PBPM), chicken meal (CHKM), dried whey (DW), Pota meal (PM: mix of giant squid, fish soluble protein concentrate, crustacean meal, and fish oil), and Protiblend (PTB: aquatic and render mix). The highest acidic DH occurred with PTB (0.38 ± 0.06), CHKM (0.33 ± 0.3), and PBPM (0.25 ± 0.03). In the alkaline condition, PTB (1.6 ± 0.17 and 0.98 ± 0.05 for pyloric caeca and intestine, respectively) and CG (1.04 ± 0.4 and 0.75 ± 0.2 for caeca and intestine, respectively) provided the highest DH values. In vitro digestibility demonstrated that PTB was the highest (85.3%) followed by PBPM (51.4%), CAN + phytase (47.6%), CG (45.1%), and CHKM (46.5%). The in vivo experiment concerned the WG, CHKM, PBPM, PM, and PTB diets plus a reference diet with fishmeal (Ref diet). The total %DH was different (P < 0.05) with the lowest values for the WG diet (0.34 ± 0.09%) and Ref diet (0.34 ± 0.15). Free amino acid released during digestion was displayed for these diets and a bifactorial analysis produced no difference (P > 0.05). The apparent digestive coefficients ranged from 89.8 to 92.9% for protein and from 68 to 71.4% for energy.

Distribution of empathetic orientation among dentistry students of Cartagena, Colombia

Objective To describe the level of empathy of dental students at the University of Cartagena. Methods A descriptive, quantitative study on a sample of 360 students from 1st to 5th year of Dentistry at the University of Cartagena (Colombia) during the second academic period of 2012. The Spanish version for students (S version) of the Jefferson Scale of Physician Empathy (JSPE) was administered to them. The analysis consisted of calculating descriptive statistics, the arithmetic mean, and standard deviation of all the factors and their corresponding levels. The comparison of means was performed through bifactorial analysis of variance model III, with first-order interaction and application of the Duncan multiple comparison test. Results Statistically significant differences were found for the "year" variables (p<0.005) and gender (p <0.001). Lower empathic orientation values were found for 1st year students and higher value were found for women. No significance was found in the interaction between these two factors (p>0.05). Conclusions Empathic orientation values in the dental students assessed were different depending on the level or year of study and the student's gender. This may influence the comprehensive training promoted by higher education institutions as part of their educational projects. It also provides an imperative for the promotion of interpersonal skills interpersonal skills among students starting in the first years of their training to help improve the quality of health care provided.

Seasonality of Ichthyofauna Bycatch in Shrimp Trawls from Different Depth Strata in the Southern Brazilian Coast

Rodrigues-Filho, J.L.; Branco, J.O.; Monteiro, H.S.; Verani, J.R., and Barreiros, J.P., 2015. Seasonality of ichthyofauna bycatch in shrimp trawls from different depth strata in the southern Brazilian coast.Changes in the species composition and ecological descriptors of fish assemblages in terms of abiotic factors such as depth, temperature, salinity, and granulometry were analyzed. Monthly trawls, from October 2003 to September 2004 (30 minutes each) were analyzed in two areas covering an important shrimp fishing site of the Brazilian coast. Results using bifactorial analysis of variance revealed a seasonal variation of environmental variables (p < 0.05), and granulometry analyses showed that the composition of the fishing grounds was similar—mostly sand. A total of 12,613 fish were collected: 7880 in area I and 4733 in area II. The highest values of capture in numerical abundance (catch per unit effort) occurred during winter. Fifty taxa were caught in area I, and 53 taxa were caught in area II. Both values are considered high when compared to previous studies conducted in nearby areas. Sciaenidae was the most speciose family in all samples and in both areas were dominant in number of species (37 species in area I and 42 species in area II). Cynoscion striatus was the most abundant and dominant species in both areas. Estimates of ecological descriptors, such as richness, diversity, and evenness, showed that the ichthyofauna structure was strongly influenced by climatic factors, and all values were more pronounced during fall and winter. The permutational multivariate analysis of variance demonstrated that ichthyofauna species composition differs among seasons. The Student's t test applied a posteriori showed that the community composition differed (significantly) in the following comparisons: spring vs. fall (p < 0.05) and winter vs. summer (p < 0.05). According to similarity percentage analysis, changes in the community structure were mainly correlated with species classified as abundant, which occurred unevenly during the different periods. Our results show that the fish community is influenced by seasonal variations such as salinity and temperature but not by depth or sand grain sizes.As alterações na composição específica e nos descritores ecológicos das assembleias de peixes em função dos fatores abióticos, tais como profundidade, temperatura, salinidade e granulometria, foram analisadas no presente trabalho. Arrastos mensais de trinta minutos de duração foram realizados em duas áreas com diferentes profundidades em um importante ponto de pesca camaroeira do litoral sul brasileiro. Paralelamente, registrou—se os valores de temperatura e salinidade da água, bem como foi amostrado o tipo de substrato dos fundos de pesca. A aplicação do teste t de Student demonstrou variação sazonal dessas variáveis ambientais no estudo (p < 0,05) e a análise granulométrica demonstrou que a composição dos fundos de pesca foi bastante similar, sendo composta principalmente por areia. No total foram capturados 12.613 exemplares, sendo 7.880 na área I e 4.733 na área II. Os maiores valores de captura (CPUE) ocorreram no inverno. Foram capturados 50 táxons na área I e 53 na área II, um alto valor quando comparado com estudos pretéritos em localidades próximas. A família dos sciaenideos foi a mais representativa nas coletas, predominando em ambas as áreas espécies incidentais (37 na área I e 42 na área II). Cynoscion striatus foi a espécie mais abundante e predominante em ambas as áreas. As estimativas dos descritores ecológicos, tais como a riqueza, a diversidade e equitabilidade, evidenciaram que a estrutura da ictiofauna foi fortemente influenciada pelo fator tempo e que os valores mais acentuados ocorreram no outono e inverno. A aplicação da PERMANOVA demonstrou que a composição especifica da ictiofauna diferiu entre as estações. O teste t de Student a posteriori demonstrou que a composição da comunidade na primavera diferiu do outono e in

Comparative Study of Substrate-Based and Commercial Formulations of Arbuscular Mycorrhizal Fungi in Romaine Lettuce Subjected to Salt Stress

To compare the effect of substrate-based and commercial arbuscular mycorrhizal fungi (AMF) in salt stress tolerance of Romaine lettuce a bifactorial analysis was carried out. Under non-saline conditions, only plants inoculated with formulation 1 stimulated shoot weight but not related with greater root AMF colonization. Phosphorus and potassium concentrations in leaves were improved by mycorrhizal association. Irrigation with 100 mM sodium chloride (NaCl) did not affect leaf relative water content and we observed no osmotic adjustment in leaves from non-mycorrhizal plants. However, root dry biomass and its starch content decreased, while leaf starch and root soluble sugar concentrations were enhanced. Lettuce inoculated with formulation 2 and substrate-based Glomus intraradices showed the highest root colonization percentages. Nevertheless, none of the mycorrhizal treatments induced a significant improvement on growth of lettuce subjected to salt stress. Romaine lettuce seems to be a moderately tolerant variety to salinity and therefore, the contribution of AMF was minimized.

Evaluación de los niveles de orientación empática en estudiantes de odontología de la Universidad Finis Terrae de Santiago, Chile

ObjetiveTo evaluate the empathetic orientation of the dentistry students of Finis Terrae University. Materials and MethodsThis investigation is a non experimental, descriptive, cross-sectional research. 309 out of 430 students participated. They belonged to the 1°, 2°, 3°, 4° and 5° grade of the Dentistry School of Finis Terrae University (Chile) in 2012. The Jefferson Scale of Physician Empathy was applied. Shapiro-Wilk normality test and Levene homoscedasticity test were performed for the analysis of the data obtained. Subsequently, descriptive statigraphs were considered in all the studied factors and finally average comparison was made through Bifactorial analysis of variance and a Duncan multiple comparison test. ResultsHigher scores in the JSPE with statistical significance were obtained in women when compared with men (p<0.05). No significant differences were found in the scores related to the grade. ConclusionsWomen had higher levels of empathetic orientation than men during their educational program. Both, women and men had shown changes in their scores as the curriculum develops. That effect is more pronounced in women than men.

Estudio epidemiológico de los casos de triquinelosis registrados en la provincia de Santa Fe, Argentina, 1998-2009

To characterize recorded trichinosis cases and outbreaks in Santa Fe Province, Argentina, from 1998 to 2009 from epidemiological, clinical, and laboratory viewpoints. An analysis was conducted of 1 519 epidemiological records of persons who had signs and symptoms compatible with trichinosis in Santa Fe Province in the period 1998-2009. A descriptive statistical analysis of information in epidemiological records and of clinical and laboratory results, as well as a bifactorial analysis of possible associations with epidemiological and environmental factors were also carried out. Trichinosis symptoms were found in 1 276 cases; 372 met the clinical case definition and 224 samples were positive by indirect immunofluorescence, independent of their clinical case classification. There were 27 outbreaks that involved 1 157 cases identified in eight departments, with greater frequency in the province's center and south. Annual distribution of epidemiologically associated cases was heterogeneous, with greater frequency in the period 2000-2003 and in the months of August to October. Probability of becoming sick was greater with consumption of products from informal sources (OR = 3.69; P = 0.014) and in rural areas (OR = 1.799; P = 0.011). Disease incubation period (median) was 12 days. The risk of becoming sick was 2.06 times greater in persons who ate meat or ate pork by-products than in those who did not. The greatest number of outbreaks occurred in departments that were more populous and where pork production was greater. Specific actions should be designed for prevention and control of the disease in those departments. Epidemiological risk analysis should be considered in evaluating, managing, and communicating trichinosis health risks.

Effect of air-temperature and diet composition on the drying process of pellets for japanese abalone (Haliotis discus hannai) feeding

The aim of this research was to study the effect of air-temperature and diet composition on the mass transfer kinetics during the drying process of pellets used for Japanese Abalone (Haliotis discus hannai) feeding. In the experimental design, three temperatures were used for convective drying, as well as three different diet compositions (Diets A, B and C), in which the amount of fishmeal, spirulin, algae, fish oil and cornstarch varied. The water diffusion coefficient of the pellets was determined using the equation of Fick's second law, which resulted in values between 0.84-1.94×10-10 m2/s. The drying kinetics was modeled using Page, Modified Page, Root of time, Exponential, Logarithmic, Two-Terms, Modified Henderson-Pabis and Weibull models. In addition, two new models, referred to as 'Proposed' models 1 and 2, were used to simulate this process. According to the statistical tests applied, the models that best fitted the experimental data were Modified Henderson-Pabis, Weibull and Proposed model 2, respectively. Bifactorial analysis of variance ANOVA showed that Diet A (fishmeal 44%, spirulin 9%, fish oil 1% and cornstarch 36%) presented the highest diffusion coefficient values, which were favored by the temperature increase in the drying process.

Efeitos da dieta suplementada com ômega-3 no músculo sóleo de ratos submetidos à natação: análise histológica e morfométrica

As lesões musculares têm sido observadas como as mais frequentes nos esportes. Considerando a produção de espécies reativas de oxigênio como um fator de risco para instalação de lesões e características antioxidantes e anti-inflamatórias do ômega-3, o objetivo deste trabalho foi verificar as alterações histológicas e morfométricas do músculo sóleo de ratos que realizaram natação, associado a uma dieta suplementada com ômega-3. Para sua realização foram utilizados 31 ratos Wistar divididos em quatro grupos, sendo os grupos A e C suplementados com azeite de oliva e B e D com 3g/dia de ômega-3 por quatro semanas. Os grupos C e D foram submetidos à natação cinco dias/semana por 28 dias, com acréscimo de 5% do peso corporal a partir da segunda semana, enquanto que os grupos A e B não realizaram treinamento. Após este período os animais foram sacrificados, o músculo sóleo retirado e corado com Hematoxilina-eosina para avaliação morfológica. Análise de variância bifatorial, com nível de significância de 5%, foi utilizada para análise dos valores do menor diâmetro das fibras musculares. Os grupos A e B (sedentários) apresentaram padrões histológicos de normalidade. O grupo C apresentou aumento do tecido endomisial e do número de núcleos, presença de fibras fagocitadas e de contornos poligonais não mantidos, enquanto que o grupo D apresentou poucas fibras fagocitadas e de contornos poligonais preservados. Com relação à medida do menor diâmetro das fibras musculares, as análises mostraram diferenças para o fator treinamento, mas não para o fator suplementação e a interação entre eles. As alterações histológicas induzidas pelo exercício foram atenuadas no grupo suplementado com ômega-3, sugerindo um efeito protetor da suplementação, contudo, o aumento do diâmetro das fibras para os grupos expostos ao exercício está relacionado ao efeito do treinamento e não à suplementação.

Loading of the G-Factor in Human Figure Drawing

This study reports the results of a bifactorial analysis of the criteria of the Human Figure Drawing Test, based on the original Goodenough system. This analysis was designed to assess the loading of the general factor of intelligence for that test. 541 children (52.9% boys, 47.1% girls; ages 5-10 years) attending preschool through Grade 4 in public and private schools were studied. Principal component analysis with oblimin rotation identified four components which were not highly correlated, making it possible to conduct a bifactorial analysis. The results were interpreted as showing the predominance of a single general factor, so the existence of a latent variable capable of explaining most of the variance (56.84%) between the items seems likely.

Comparación de tres estrategias de tamizaje para la prevención de la infección perinatal por VIH en Colombia: análisis de decisiones

To apply decision analysis to compare the cost-effectiveness of three strategies for HIV screening of pregnant women and to recommend the one most appropriate for the health care system of Colombia. An economic study applying decision analysis to three types of HIV screening of expectant women: voluntary, universal, and optional. All the women in Colombia with unknown HIV status who were admitted for child birth were included. The study included all the direct medical costs incurred from the time of testing through the first year following delivery, according to the General System for Healthcare Social Security. Cost-effectiveness ratio and the savings of each of the strategies were compared. For every 10,000 women, the universal strategy detected five cases more than the voluntary strategy and seven cases more than the optional. The universal strategy carried a cost of approximately US$ 17 for each HIV-positive newborn; that is, less than half of that of the voluntary strategy (US$ 38) and less than the optional (US$ 24). According to the bifactorial analysis, the universal screening strategy was less costly than the voluntary and more effective than both of the others, regardless of prevalence, the false-positive rate of each method, and the rate of maternal compliance with screening. The screening strategy currently in use in Colombia is more costly (in both the medium- and long-term), less effective, and less capable of prevention, than the universal screening strategy. The recommendation to the national health authorities of Colombia is to begin screening all pregnant women for HIV infection using third-generation testing.

The influence of algal densities on the toxicity of chromium for Ceriodaphnia dubia Richard (Cladocera, Crustacea)

Food availability may affect metal toxicity for aquatic organisms. In the present study, the influence of high, medium and low densities of the algae Pseudokirchneriella subcapitata (10(6), 10(5) and 10(4) cells.mL(-1), respectively) on the chronic toxicity of chromium to the cladoceran Ceriodaphnia dubia was investigated. C. dubia was exposed to a range of chromium concentration from 2.71 to 34.04 microg.L(-1) and fed with algae at various densities. In another experiment, the green alga was exposed to chromium concentrations (94 to 774 microg.L(-1)) and supplied as food in different densities to zooplankton. The survival and reproduction of the cladoceran were measured in these toxicity tests. The IC50 for Cr to P. subcapitata and metal accumulated by algal cells were determined. The results of a bifactorial analysis (metal versus algal densities) showed that metal toxicity to zooplankton was dependent on algal densities. Significant toxic effects on the reproduction and survival of C. dubia were observed at 8.73, 18.22 and 34.04 microg.L(-1) Cr when the test organisms were fed with 10(6) cells.mL(-1) of P. subcapitata. Although the chlorophyta retain low chromium content, a decrease in the reproduction and survival of C. dubia occurred when they were fed with high algal density contaminated with 774 microg.L(-1) Cr. It was concluded that high algal density have an appreciable influence on chromium toxicity to daphnids.

Effects of shrimp trawling on the structure of macrobenthic communities of Paraná's inner shelf

The objective of present contribution was analyzes disturbances caused by shrimp trawling on macrobenthic communities of soft bottom on two areas: one located within a currently trawled area and the other impacted in the past by trawling activity, but where supposingdly there is no trawling in the present. Samples were taken using an iron core of 0.05 m² with a 500µm mesh attached to one of the core ends received the collected material by SCUBA diving. Bi-factorial analysis of variance (MANOVA) was performed to compare ecological descriptors for both areas. To analyze and compare the communities’ structure was performed a MDS and similarity analyses (ANOSIM). It is not found significant difference for anything ecological descriptor, nor to the total of polychaetes, bivalves and crustaceans between areas. However, significant differences were found among months, except to the total of bivalves and Shannon & Wiener diversity index, indicating that differences were more related to temporal variation than to area variation.

Effects of interactions between algal densities and cadmium concentrations on Ceriodaphnia dubia fecundity and survival

The influence of different densities of the algae Pseudokirchneriella subcapitata on the chronic toxicity of cadmium to Ceriodaphnia dubia was investigated. The importance of algal cells as a source of metal to zooplankton was studied by exposing P. subcapitata cells to free cadmium ions and supplying the algae as food to C. dubia. The results of a bifactorial analysis (metal versus food levels) showed that metal toxicity to zooplankton was dependent on food level. Significant toxic effects on the fecundity and survival of C. dubia were observed at low metal concentrations with high algal density. Algae contaminated with Cd 2+ were less toxic to cladoceran than was the Cd 2+ in solution. Green algae retained cadmium and released low metal concentration in the test medium. We concluded that algal cells are an important route of exposure to metal and a factor that has an appreciable influence on the expression of metal toxicity to daphnids.

Bi-factorial analysis for resolution of GPS equations

A great variety of causes are implied in the resolution of GPS equations systems for obtaining precise point positioning. Among them, the time interval between observations and the number of observations are relevant to know the influence in positioning unknowns ( X, Y, Z). In this paper, we perform a statistical study showing the possible influence of both factors in the obtained solution. From the results of this paper we conclude that the X and Y solution are independent of the above factors; however, Z shows a significant effect in the manner that time interval and the number of observations are chosen. The results provide insight into the most appropriate design for solving the equation systems of GPS observations.