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The early developing embryo is initially composed of three tissue layers, the ectoderm, endoderm, and mesoderm, that are generated from the epiblast layer of the embryo during week 3 by a process called gastrulation. The ectoderm, the most dorsal layer, gives rise to the skin, whilst the neuroectoderm, which is induced within the ectoderm at the midline, rolls up to form the neural tube and contains the progenitors of the brain and spinal cord (Figure 3.1A). The endoderm, the most ventral layer, gives rise to the epithelial cells of the lungs, prostate gland, the gastrointestinal tract and its associated organs. Sandwiched between these layers is the mesoderm, which is subdivided. The paraxial mesoderm contributes to the musculoskeletal system and dermis in the trunk, the intermediate mesoderm contributes to the urogenital system and internal reproductive organs, the somatic portion of the lateral plate mesoderm forms the skeleton and connective tissue of the limbs together with the body wall, whilst the splanchnic mesoderm portion of the lateral plate mesoderm forms the smooth muscle layers of the endodermal organs. The cardiogenic mesoderm (not shown) contributes to the heart whilst the notochord (or axial mesoderm) gives rise to the nucleus pulposus of the intervertebral disks (Figure 3.1A). In addition, a fourth tissue layer, the neural crest, arises at the interface of the ectoderm and neuroectoderm (Figure 3.1A). Neural crest cells form by an epithelial-mesenchymal transformation and are multipotent and migratory. In the trunk, the neural crest cells contribute to the peripheral nervous system, whereas in the head, neural crest cell derivatives include odontoblasts, together with the skeletal system and dermis of the face. Additionally, cranial neural crest cells contribute to the outflow tract and cushions of the heart. For further details of embryonic development, the reader is referred to Larsen’s Human Embryology .
This article studies a classical problem in statistical decision theory: a hypothesis test of a sharp null in the presence of a nuisance parameter. The main contribution of this article is a characterization of two finite-sample properties often deemed reasonable in this environment: admissibility and similarity. Admissibility means that a test cannot be improved uniformly over the parameter space. Similarity requires the null rejection probability to be unaffected by the nuisance parameter.
The characterization result has two parts. The first part—established by Chernozhukov, Hansen, and Jansson (2009, Econometric Theory 25, 806–818)—states that maximizing weighted average power (WAP) subject to a similarity constraint suffices to generate admissible, similar tests. The second part—hereby established—states that constrained WAP maximization is (essentially) a necessary condition for a test to be admissible and similar. The characterization result shows that choosing an admissible, similar test is tantamount to selecting a particular weight function to report weighted average power. This result applies to full vector inference with a nuisance parameter, not to subvector inference.
The article also revisits the theory of testing in the instrumental variables model. Specifically—and in light of the relevance of the weighted average power criterion in the main theoretical result—the article suggests a weight function for the structural parameters of the homoskedastic instrumental variables model, based on the priors proposed by Chamberlain (2007). The corresponding test is, by construction, admissible and similar. In addition, the test is shown to have finite- and large-sample properties comparable to those of the conditional likelihood ratio test.
Mental health professionals form an important component of the response teams currently working in the Democratic Republic of the Congo to treat what is historically the second-largest Ebola outbreak. They provide psychological treatment to patients under extraordinary conditions, helping them cope with anxiety and the daily death of other patients.
This study analyses the extent to which cheating occurs in a real selection setting. A two-stage, unproctored and proctored, test administration was considered. Test score inconsistencies were concluded by applying a verification test (Guo and Drasgow Z-test). An initial simulation study showed that the Z-test has adequate Type I error and power rates in the specific selection settings explored. A second study applied the Z-test statistic verification procedure to a sample of 954 employment candidates. Additional external evidence based on item time response to the verification items was gathered. The results revealed a good performance of the Z-test statistic and a relatively low, but non-negligible, number of suspected cheaters that showed higher distorted ability estimates. The study with real data provided additional information on the presence of suspected cheating in unproctored applications and the viability of using item response times as an additional evidence of cheating. In the verification test, suspected cheaters spent 5.78 seconds per item more than expected considering the item difficulty and their assumed ability in the unproctored stage. We found that the percentage of suspected cheaters in the empirical study could be estimated at 13.84%. In summary, the study provides evidence of the usefulness of the Z-test in the detection of cheating in a specific setting, in which a computerized adaptive test for assessing English grammar knowledge was used for personnel selection.
Distances to common production and marketing supply chain destinations may vary, and this has economic and animal health implications for small-scale food animal operations. Proximity to these destinations can affect the economic viability and marketing decisions of small-scale operations and may represent significant barriers to sustainability. Data were collected using a cross-sectional survey conducted by the US Department of Agriculture's (USDA) National Animal Health Monitoring System in 2011 using a stratified systematic sample of 16,000 small-scale (gross annual farm sales between US$10,000 and 499,999) operations from all 50 states. A total of 7925 food-animal operations were asked about the farthest one-way distance (in miles) to slaughter facilities, destinations where they sold animals or products, and feed sources. Across all small-scale operations, 95% of operations reported the farthest distance animals or products were transported for sale was 241 km (150 miles) or less. For distance to slaughter facilities, 95% of operations reported the farthest distance was 145 km (90 miles) or less. For feed shipped by a supplier, 95% of operations reported the farthest distance was 322 km (200 miles) or less. The 95th percentile for distance increased as farm sales increased, indicating larger operations were more likely to travel long distances. The results of this study are an important benchmark for understanding the economic and animal health implications of long transportation distances for operations that are small and/or focused on direct marketing.
Test security can be a major problem in computerized adaptive testing, as examinees can share information about the items they receive. Of the different item selection rules proposed to alleviate this risk, stratified methods are among those that have received most attention. In these methods, only low discriminative items can be presented at the beginning of the test and the mean information of the items increases as the test goes on. To do so, the item bank must be divided into several strata according to the information of the items. To date, there is no clear guidance about the optimal number of strata into which the item bank should be split. In this study, we will simulate conditions with different numbers of strata, from 1 (no stratification) to a number of strata equal to test length (maximum level of stratification) while manipulating the maximum exposure rate that no item should surpass (rmax) in its whole domain. In this way, we can plot the relation between test security and accuracy, making it possible to determine the number of strata that leads to better security while holding constant measurement accuracy. Our data indicates that the best option is to stratify into as many strata as possible.
Dietary habits vary widely among regions and cultural groups, and FFQ need to be designed for specific populations. The objectives of the present study were to develop and test the repeatability and relative validity of a medium-length semi-quantitative FFQ for measuring the energy and macronutrient intakes of a specific population and to contribute a methodological framework for this procedure.
Palestinian families in the Hebron area.
After a preliminary survey of a subgroup of homemakers using 3 d diet recall, stepwise multiple regression analysis was used for selected nutrients to choose foods for inclusion in the FFQ.
The FFQ was administered to a study population of 169 women representing the same number of families.
The Wilcoxon test and Bland–Altman plots were used to compare the FFQ results with the mean 3 d diet recall results. A high level of concordance was found, validating the FFQ. In this population, the mean consumption of SFA was above recommendations and the intakes of vitamin D, folic acid, Ca, Fe and K were deficient.
The availability of diet assessment instruments designed for specific populations and cultures is of immense value to researchers and policy makers. The study describes a simple and effective method to develop and validate an FFQ for a given population of interest.
In this study we analyze the electrical behavior of a junction formed by an ultraheavily Ti implanted Si layer processed by a Pulsed Laser Melting (PLM) and the non implanted Si substrate. This electrical behavior exhibits an electrical decoupling effect in this bilayer that we have associated to an Intermediate Band (IB) formation in the Ti supersaturated Si layer. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements show a Ti depth profile with concentrations well above the theoretical limit required to the IB formation. Sheet resistance and Hall mobility measurements in the van der Pauw configuration of these bilayers exhibit a clear dependence with the different measurement currents introduced (1µA-1mA). We find that the electrical transport properties measured present an electrical decoupling effect in the bilayer as function of the temperature. The dependence of this effect with the injected current could be explained in terms of an additional current flow in the junction from the substrate to the IB layer and in terms of the voltage dependence in the junction with the measurement current.
To propose and apply an instrument to assess the breakfast quality of children and adolescents in the Mediterranean area.
Randomized, cross-sectional survey of breakfast consumption using a validated semi-quantitative FFQ administered at school by trained dietitians between Tuesday and Friday. A Breakfast Quality Index (BQI) score was developed, assigning a positive value to the consumption of cereals, fruit, vegetables, dairy products, MUFA, Ca and compliance with energy recommendations, and to the absence of SFA and trans-rich fats. Data were analysed by Student's t test and ANOVA.
Schools in Granada and Balearic Islands (Spain).
All schoolchildren (n 4332) aged 8–17 years at randomly selected and representative schools between 2006 and 2008, stratified by age and sex.
Breakfast was not consumed by 6·5 % of participants. BQI score was highest for children aged 7–9 years and decreased with age (P = 0·001). Females scored higher in all age groups. The lowest score was in males aged 14–17 years and the highest in females aged 7–9 years (P = 0·006).
The proposed BQI appears useful to estimate the breakfast quality of schoolchildren and to form a basis for nutrition education.
This paper describes several simulation studies that examine the effects of capitalization on chance in the selection of items and the ability estimation in CAT, employing the 3-parameter logistic model. In order to generate different estimation errors for the item parameters, the calibration sample size was manipulated (N = 500, 1000 and 2000 subjects) as was the ratio of item bank size to test length (banks of 197 and 788 items, test lengths of 20 and 40 items), both in a CAT and in a random test. Results show that capitalization on chance is particularly serious in CAT, as revealed by the large positive bias found in the small sample calibration conditions. For broad ranges of θ, the overestimation of the precision (asymptotic Se) reaches levels of 40%, something that does not occur with the RMSE (θ). The problem is greater as the item bank size to test length ratio increases. Potential solutions were tested in a second study, where two exposure control methods were incorporated into the item selection algorithm. Some alternative solutions are discussed.
Zirconia nanopowders doped with different concentrations of Eu were prepared by the solgel method followed by a thermal treatment at 500°C. Morphological and crystallographic characteristics were studied by scanning electron microscopy, X-Ray diffraction and UV spectroscopoy. Results showed a modification of the size of nanopowder particles when the concentration of Eu is increased from 0.0 to 4.0 wt%. Also, at lower concentration of Eu the tetragonal ZrO2 is the most abundant phase while high concentrations of Eu lead to the formation of the monoclinic phase. The UV spectroscopy of ZrO2 samples shows two main absorption peaks at 228 and 214 nm. The novel characteristics of the ZrO2 nanopowders doped with Eu allow us to propose them for use as solar UV radiation detectors.
This paper reports the synthesis and characterization of the ZrO2:Co nanosystem, by incorporation of Co nanoparticles (CoNP) into tetragonal and monoclinic zirconia. ZrO2 was synthesized by a sol-gel process, while cobalt nanoparticles were obtained through a colloidal method by chemical reduction of a metal precursor. CoNP were incorporated by two different approaches: during the synthesis of the ZrO2 and by classical impregnation of CoNP on zirconium oxide. The size of Cobalt nanoparticles was controlled through the concentration of reducing agent (NaBH4) and passivanting agent (1-dodecanethiol). According to SEM and TEM analysis, the diameter of the zirconium oxide particles depends on the CoNP concentration added; the particle size for pure zirconia treated at 500°C is 200 nm and 180 nm for ZrO2:Co. X-Ray diffraction showed presence of the tetragonal and monoclinic zirconia, but the abundance of each one depends on the Co nanoparticles and thermally treatment.
In computerized adaptive testing, the most commonly used valuating function is the Fisher information function. When the goal is to keep item bank security at a maximum, the valuating function that seems most convenient is the matching criterion, valuating the distance between the estimated trait level and the point where the maximum of the information function is located. Recently, it has been proposed not to keep the same valuating function constant for all the items in the test. In this study we expand the idea of combining the matching criterion with the Fisher information function. We also manipulate the number of strata into which the bank is divided. We find that the manipulation of the number of items administered with each function makes it possible to move from the pole of high accuracy and low security to the opposite pole. It is possible to greatly improve item bank security with much fewer losses in accuracy by selecting several items with the matching criterion. In general, it seems more appropriate not to stratify the bank.
An exhaustive study on the resulting impurity profile in Si samples implanted with Ti with high doses and subsequently Pulsed-Laser Melting (PLM) annealed is presented. Two different effects are shown to be present in the two different stages of the annealing. In the melting stage the box-shaped effect tends to increase the thickness of the implanted layer and to decrease the maximum peak concentration as the energy density of the annealing increases. On the contrary, in the solidifying stage, the snow-plow effect decreases the thickness of the layer and increases the maximum peak concentration as the energy density of the annealing increases. Moreover, as a direct consequence of the snow-plow effect, part of the impurities is expelled from the sample by the surface.
We have analyzed the degree of crystalline lattice recovery in samples implanted with Ti concentrations well above the Mott limit and subsequently Pulsed-Laser Melting (PLM) annealed by means of Raman spectroscopy and Rutherford Backscattering Spectroscopy (RBS). Since very recently, theoretical studies predicted Ti interstitial sites for the Intermediate Band (IB) formation, the knowledge of the Ti impurity lattice location after PLM annealing is an essential point that can be elucidated by means of RBS measurements. After PLM annealings, Raman and RBS measurements have shown a decrease in the lattice crystalline quality as implanted dose is increased, yielding a significantly improvement of the lattice quality at the highest energy density studied. The RBS channeling spectra show that after PLM annealings Ti impurities are mostly occupying interstitial lattice sites.
We have studied the Pulsed-Laser Melting (PLM) effects on Ti implanted GaP to form an Intermediate Band (IB). Structural analysis has been carried out by means of Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), Raman spectroscopy and Glancing Incidence X-Ray Diffraction (GIXRD). After the PLM annealing, Ti concentration is over the Mott limit. Nevertheless, the Raman spectra show a forbidden TO vibrational mode of GaP. This result suggests the formation of crystalline domains with a different orientation in the annealed region regarding to the GaP unannealed substrate. This conclusion has been corroborated by GIXRD measurements. As a result of the polycrystalline lattice, a drop of the mobility is produced.
The Egyptian vulture Neophron percnopterus is categorized as Endangered on the IUCN Red List, as well as on the European and Spanish Red Lists. Spain is home to the most important breeding population of Egyptian vultures in Europe but this population has differing trends at a regional scale. We present data for the Egyptian vulture population in the Cantabrian Mountains, north-west Spain, during the last 3 decades and assess the main threats to the species there. The Egyptian vulture population in the Cantabrian Mountains was estimated to be 175 breeding pairs in 2008, which comprised 13–14% of the Spanish population. This population has been stable, or increasing slightly, since 2000. During 2000–2008 4.3% of the Cantabrian Egyptian vulture population was affected by the use of illegal poison. During the same period the number of sheep and goats reared (which contributes to the maintenance of Egyptian vulture territories) was reduced by 27.4%, which could lead to food shortages for the vultures in the near future. Currently 32 breeding pairs (18.3% of the population) have wind turbines within their foraging areas, with an average of 59 wind turbines per territory (range 1–176). During the next few years this number will increase to 110 turbines per territory within 69 vulture territories (39.4% of the population). Nearly a third (32.6%) of breeding territories are located outside protected areas. Better coordination between administrative areas is needed to guarantee the conservation of the Cantabrian Mountains population of Egyptian vultures through effective surveillance and protection in the numerous existing protected areas.
The purpose of this study was to determine the magnitude and distribution of acute gastrointestinal illness (GI) in the Chilean population, describe its burden and presentation, identify risk factors associated with GI and assess the differences between a 7-day, 15-day and a 30-day recall period in the population-based burden of illness study design. Face-to-face surveys were conducted on 6047 randomly selected residents in the Metropolitan region, Chile (average response rate 75·8%) in 2008. The age-adjusted monthly prevalence of GI was 9·2%. The 7-day recall period provided annual incidence rate estimates about 2·2 times those of the 30-day recall period. Age, occupation, healthcare system, sewer system, antibiotic use and cat ownership were all found to be significant predictors for being a case. This study expands on the discussion of recall bias in retrospective population studies and reports the first population-based burden and distribution of GI estimates in Chile.