Univariate versus multivariate modeling of panel data

Panel data can be arranged into a matrix in two ways, called 'long' and 'wide' formats (LFand WF). The two formats suggest two alternative model approaches for analyzing paneldata: (i) univariate regression with varying intercept; and (ii) multivariate regression withlatent variables (a particular case of structural equation model, SEM). The present papercompares the two approaches showing in which circumstances they yield equivalent?insome cases, even numerically equal?results. We show that the univariate approach givesresults equivalent to the multivariate approach when restrictions of time invariance (inthe paper, the TI assumption) are imposed on the parameters of the multivariate model.It is shown that the restrictions implicit in the univariate approach can be assessed bychi-square difference testing of two nested multivariate models. In addition, commontests encountered in the econometric analysis of panel data, such as the Hausman test, areshown to have an equivalent representation as chi-square difference tests. Commonalitiesand differences between the univariate and multivariate approaches are illustrated usingan empirical panel data set of firms' profitability as well as a simulated panel data.

Développement et validation d'une méthode de calcul indépendant des unités moniteur basée sur les simulations Monte Carlo pour la vérification des traitements IMRT

Résumé : La radiothérapie par modulation d'intensité (IMRT) est une technique de traitement qui utilise des faisceaux dont la fluence de rayonnement est modulée. L'IMRT, largement utilisée dans les pays industrialisés, permet d'atteindre une meilleure homogénéité de la dose à l'intérieur du volume cible et de réduire la dose aux organes à risque. Une méthode usuelle pour réaliser pratiquement la modulation des faisceaux est de sommer de petits faisceaux (segments) qui ont la même incidence. Cette technique est appelée IMRT step-and-shoot. Dans le contexte clinique, il est nécessaire de vérifier les plans de traitement des patients avant la première irradiation. Cette question n'est toujours pas résolue de manière satisfaisante. En effet, un calcul indépendant des unités moniteur (représentatif de la pondération des chaque segment) ne peut pas être réalisé pour les traitements IMRT step-and-shoot, car les poids des segments ne sont pas connus à priori, mais calculés au moment de la planification inverse. Par ailleurs, la vérification des plans de traitement par comparaison avec des mesures prend du temps et ne restitue pas la géométrie exacte du traitement. Dans ce travail, une méthode indépendante de calcul des plans de traitement IMRT step-and-shoot est décrite. Cette méthode est basée sur le code Monte Carlo EGSnrc/BEAMnrc, dont la modélisation de la tête de l'accélérateur linéaire a été validée dans une large gamme de situations. Les segments d'un plan de traitement IMRT sont simulés individuellement dans la géométrie exacte du traitement. Ensuite, les distributions de dose sont converties en dose absorbée dans l'eau par unité moniteur. La dose totale du traitement dans chaque élément de volume du patient (voxel) peut être exprimée comme une équation matricielle linéaire des unités moniteur et de la dose par unité moniteur de chacun des faisceaux. La résolution de cette équation est effectuée par l'inversion d'une matrice à l'aide de l'algorithme dit Non-Negative Least Square fit (NNLS). L'ensemble des voxels contenus dans le volume patient ne pouvant être utilisés dans le calcul pour des raisons de limitations informatiques, plusieurs possibilités de sélection ont été testées. Le meilleur choix consiste à utiliser les voxels contenus dans le Volume Cible de Planification (PTV). La méthode proposée dans ce travail a été testée avec huit cas cliniques représentatifs des traitements habituels de radiothérapie. Les unités moniteur obtenues conduisent à des distributions de dose globale cliniquement équivalentes à celles issues du logiciel de planification des traitements. Ainsi, cette méthode indépendante de calcul des unités moniteur pour l'IMRT step-andshootest validée pour une utilisation clinique. Par analogie, il serait possible d'envisager d'appliquer une méthode similaire pour d'autres modalités de traitement comme par exemple la tomothérapie. Abstract : Intensity Modulated RadioTherapy (IMRT) is a treatment technique that uses modulated beam fluence. IMRT is now widespread in more advanced countries, due to its improvement of dose conformation around target volume, and its ability to lower doses to organs at risk in complex clinical cases. One way to carry out beam modulation is to sum smaller beams (beamlets) with the same incidence. This technique is called step-and-shoot IMRT. In a clinical context, it is necessary to verify treatment plans before the first irradiation. IMRT Plan verification is still an issue for this technique. Independent monitor unit calculation (representative of the weight of each beamlet) can indeed not be performed for IMRT step-and-shoot, because beamlet weights are not known a priori, but calculated by inverse planning. Besides, treatment plan verification by comparison with measured data is time consuming and performed in a simple geometry, usually in a cubic water phantom with all machine angles set to zero. In this work, an independent method for monitor unit calculation for step-and-shoot IMRT is described. This method is based on the Monte Carlo code EGSnrc/BEAMnrc. The Monte Carlo model of the head of the linear accelerator is validated by comparison of simulated and measured dose distributions in a large range of situations. The beamlets of an IMRT treatment plan are calculated individually by Monte Carlo, in the exact geometry of the treatment. Then, the dose distributions of the beamlets are converted in absorbed dose to water per monitor unit. The dose of the whole treatment in each volume element (voxel) can be expressed through a linear matrix equation of the monitor units and dose per monitor unit of every beamlets. This equation is solved by a Non-Negative Least Sqvare fif algorithm (NNLS). However, not every voxels inside the patient volume can be used in order to solve this equation, because of computer limitations. Several ways of voxel selection have been tested and the best choice consists in using voxels inside the Planning Target Volume (PTV). The method presented in this work was tested with eight clinical cases, which were representative of usual radiotherapy treatments. The monitor units obtained lead to clinically equivalent global dose distributions. Thus, this independent monitor unit calculation method for step-and-shoot IMRT is validated and can therefore be used in a clinical routine. It would be possible to consider applying a similar method for other treatment modalities, such as for instance tomotherapy or volumetric modulated arc therapy.

Experimental and Numerical Analysis of Different Volutes in a Centrifugal Compressor

In a centrifugal compressor the flow around the diffuser is collected and led to the pipe system by a spiral-shaped volute. In this study a single-stage centrifugal compressor with three different volutes is investigated. The compressorwas first equipped with the original volute, the cross-section of which was a combination of a rectangle and semi-circle. Next a new volute with a fully circular cross-section was designed and manufactured. Finally, the circular volute wasmodified by rounding the tongue and smoothing the tongue area. The overall performance of the compressor as well as the static pressure distribution after the impeller and on the volute surface were measured. The flow entering the volute was measured using a three-hole Cobra-probe, and flow visualisations were carriedout in the exit cone of the volute. In addition, the radial force acting on theimpeller was measured using magnetic bearings. The complete compressor with thecircular volute (inlet pipe, full impeller, diffuser, volute and outlet pipe) was also modelled using computational fluid dynamics (CFD). A fully 3-D viscous flow was solved using a Navier-Stokes solver, Finflo, developed at Helsinki University of Technology. Chien's k-e model was used to take account of the turbulence. The differences observed in the performance of the different volutes were quite small. The biggest differences were at low speeds and high volume flows,i.e. when the flow entered the volute most radially. In this operating regime the efficiency of the compressor with the modified circular volute was about two percentage points higher than with the other volutes. Also, according to the Cobra-probe measurements and flow visualisations, the modified circular volute performed better than the other volutes in this operating area. The circumferential static pressure distribution in the volute showed increases at low flow, constant distribution at the design flow and decrease at high flow. The non-uniform static pressure distribution of the volute was transmitted backwards across the vaneless diffuser and observed at the impeller exit. At low volume flow a strong two-wave pattern developed into the static pressure distribution at the impeller exit due to the response of the impeller to the non-uniformity of pressure. The radial force of the impeller was the greatest at the choke limit, the smallest atthe design flow, and moderate at low flow. At low flow the force increase was quite mild, whereas the increase at high flow was rapid. Thus, the non-uniformityof pressure and the force related to it are strong especially at high flow. Theforce caused by the modified circular volute was weaker at choke and more symmetric as a function of the volume flow than the force caused by the other volutes.

A comparative study of silver amalgam and compomer as retrograde filling materials in periapical surgery

Objective: A comparative study is made of the histological effects of silver amalgam versus compomer (Dyract®) 90 days after placement as retrograde filling materials in experimental animals. Method: Six Beagle dogs were used, with total pulpectomy and orthograde material filling followed by periapical surgery of the 6 upper and 6 lower incisors (for a total of 72 teeth). Thirty-six teeth corresponded to the right side and were filled with the control material (silver amalgam), while the 36 teeth on the left side were filled with the compomer study material (Dyract®). After three months the animals were sacrificed and the histological study was carried out, with evaluation of bone formation, inflammation, and the tissue in contact with the filler material. The results obtained were subjected to a descriptive and comparative statistical analysis (chi-square test). Results: The samples retrogradely filled with compomer showed significantly greater percentage inflammation (76.19% versus 26.66% in the control group). On the other hand, a large proportion of samples with root cement growth were found in the compomer group. Filler material expulsion was also significantly more common when compomer was used. Conclusions: the comparative study of the histological findings showed greater inflammation but also greater root cement growth in the compomer group versus the controls

Ohjelmoinnin perusteet -kurssin opintosuoritusten analyysi

The purpose of this Bachelor’s thesis is to review Fundamentals of programming course over six-year time period (2001–2006). We try to find out if students have passed the course in years 2005 and 2006, after the change of a lecturer, relatively more often than before. We also analyze the problem areas of the course so that these kinds of problems could be avoided in future. The work includes building of the database, creating of the statistics and analysis of the results. The statistics tell many things about development of the course but the analysis phase gives even more accurate information. In analysis phase we look for significant statistical differences with chi-square test and try to find causes and solutions for those differences. In this study we found out that the biggest proportion of passed students was in year 2006. However year 2005 had very bad results which were caused by many different factors. That’s why the null hypothesis, that year 2005 and 2006 had better results than the earlier years, has to be rejected. Despite that the good results in year 2006 imply that the course has developed in right direction.

O ajuste de funções matemáticas a dados experimentais

The least square method is analyzed. The basic aspects of the method are discussed. Emphasis is given in procedures that allow a simple memorization of the basic equations associated with the linear and non linear least square method, polinomial regression and multilinear method.

Data mining and mall users profile

Marketing scholars have suggested a need for more empirical research on consumer response to malls, in order to have a better understanding of the variables that explain the behavior of the consumers. The segmentation methodology CHAID (Chi-square automatic interaction detection) was used in order to identify the profiles of consumers with regard to their activities at malls, on the basis of socio-demographic variables and behavioral variables (how and with whom they go to the malls). A sample of 790 subjects answered an online questionnaire. The CHAID analysis of the results was used to identify the profiles of consumers with regard to their activities at malls. In the set of variables analyzed the transport used in order to go shopping and the frequency of visits to centers are the main predictors of behavior in malls. The results provide guidelines for the development of effective strategies to attract consumers to malls and retain them there.

Supporting older people’s independent living at home through social and health care collaboration

Tässä tutkimuksessa tarkasteltiin ikäihmisten kotona asumista sosiaali- ja terveydenhuollon yhteistyön näkökulmasta. Tutkimuksen tarkoituksena oli lisätä ymmärrystä iäkkäiden kotihoidon asiakkaiden voimavaroista arjesta selviytymisen näkökulmasta, ja tutkia miten asiakkaiden hoito sosiaali- ja terveydenhuollon yhteistyönä toteutuu. Tutkimus oli poikkileikkaustutkimus, jossa sovellettiin kuvailevaa ja vertailevaa tutkimusasetelmaa. Tutkimusaineisto kerättiin yhden länsisuomalaisen kunnan kotihoidon asiakkailta (≥65 v.) ja heitä hoitavilta ammattihenkilöiltä. Kotihoidon 21 iäkästä asiakasta kuvasivat omia voimavarojaan arjesta selviytymisen näkökulmasta sekä kokemuksiaan hoidon toteutumisesta ammattihenkilöiden yhteistyönä. Aineisto kerättiin avoimella haastattelulla ja analysoitiin sisällön analyysillä. Lisäksi 25 kotihoidon ammattihenkilöä: 13 kotipalvelun työntekijää, 11 kotisairaanhoitajaa ja lääkäri kuvasivat kokemuksiaan iäkkään asiakkaan hoidon toteutumisesta ammattihenkilöiden yhteistyönä. Aineisto kerättiin fokusryhmähaastattelulla ja analysoitiin sisällön analyysillä. Näiden tulosten sekä aikaisemman kirjallisuuden perusteella laadittiin strukturoitu kyselylomake, jolla analysoitiin ja vertailtiin asiakkaiden ja ammattihenkilöiden näkemyksiä siitä, miten asiakkaiden hoito sosiaali- ja terveydenhuollon yhteistyönä toteutui. Esitestausten jälkeen kyselylomake lähetettiin 200 kotihoidon asiakkaalle ja 570 heitä hoitavalle kotihoidon työntekijälle: 485 kotipalvelun työntekijälle, 81 kotisairaanhoitajalle ja 4 lääkärille. Kyselyyn vastasi 120 asiakasta (60 %) ja 370 ammattihenkilöä (65 %). Ryhmien välisten erojen tarkastelussa käytettiin ristiintaulukointia, Pearsonin khin neliötestiä ja Fisherin tarkan todennäköisyyden testiä. Iäkkäiden asiakkaiden kuvauksissa voimavarat muodostuivat elämänhallinnan tunteesta ja toimintatahdon säilymisestä. Asiakkaat ammensivat arkeen voimaa harrastuksista ja sosiaalisesta verkostosta, mutta ulkopuolisten asettamat elämisen ehdot, terveydentilan heikkeneminen sekä yksinäisyys asettivat ikäihmisen ja hänen voimavaransa suurten haasteiden eteen. Tulokset osoittivat, että ammattihenkilöiden toiminta oli osittain ristiriidassa ikäihmisten omien odotusten kanssa, eikä se kaikilta osin tukenut asiakkaiden omia voimavaroja. Ammattihenkilöt tekivät hoitoon liittyviä päätöksiä ja toimintoja asiakkaiden puolesta, vaikka asiakkaille itselleen oli tärkeää elämänhallinnan tunne ja toimintatahdon säilyminen. Asiakkaiden voimavarojen tukemista moniammatillisena yhteistyönä vaikeuttivat ammattihenkilöiden vaikeus tunnistaa asiakkaiden omia voimavaroja sekä niitä uhkaavia tekijöitä, tiedon kulun ongelmat, tavoitteeton ja epäyhtenäinen tapa toimia sekä ammattihenkilöiden vastakkain asettuvat näkemyserot ja toimintatavat. Asiakkaiden ja ammattihenkilöiden näkemykset toteutetusta hoidosta erosivat toisistaan tilastollisesti merkitsevästi (p<0.05). Asiakkaat arvioivat sekä itsenäiseen toimintaan tukemisen että fyysisen, psyykkisen ja sosiaalisen tuen toteutuneen työntekijöitä huonommin. Yhteistyön kehittämishaasteita kotihoidossa ovat asiakkaan oman elämänsä asiantuntijuuden vahvistaminen, toimintakulttuurin muuttaminen asiakaslähtöiseksi tavoitteelliseksi toiminnaksi, ammattihenkilöiden roolien ja vastuun selkiyttäminen sekä tiedon kulun menetelmien kehittäminen. Tutkimus vahvistaa gerontologisen hoitotieteen tietoperustaa ja tuottaa uutta tietoa, jota voidaan soveltaa sosiaali- ja terveysalan koulutuksessa ja johtamisessa

Moisture sorption isotherms and isosteric heat determination in Chilean papaya (Vasconcellea pubescens)

The moisture sorption isotherms of Chilean papaya were determined at 5, 20, and 45 ºC, over a relative humidity range of 10-95%. The GAB, BET, Oswin, Halsey, Henderson, Smith, Caurie and Iglesias-Chirife models were applied to the sorption experimental data. The goodness of fit of the mathematical models was statistically evaluated by means of the determination coefficient, mean relative percentage deviation, sum square error, root-mean-square error, and chi-square values. The GAB, Oswin and Halsey models were found to be the most suitable for the description of the sorption data. The sorption heats calculated using the Clausius-Clapeyron equation were 57.35 and 59.98 kJ·mol-1, for adsorption and desorption isotherms, respectively.

Inheritance of resistance to powdery mildew in pea and pathogenesis-related aspects

The inheritance of resistance to powdery mildew in the pea cultivar MK-10 and some histological aspects of infection were assessed. For the inheritance study, F1, F2, backcrosses and F3 generations of MK-10 crossed with two susceptible populations were evaluated. Histological evaluations included percentage of germinated conidia, percentage of conidia that formed appresoria, percentage of conidia that established colonies, and number of haustoria per colony. Segregation ratios obtained in the resistance inheritance study were compared by Chi-square (ײ) test and the histological data were analyzed by Tukey's test at 5% probability. It was concluded that resistance of MK-10 to powdery mildew is due to a pair of recessive alleles since it is expressed in the pre-penetration stage and completed by post-penetration localized cellular death, characteristic of the presence of the pair of recessive alleles er1er1.

Mapping of QTLs related with wood quality and developmental characteristics in hybrids (Eucalyptus grandis x Eucalyptus urophylla)

The present work aimed to characterize and identify QTLs for wood quality and growth traits in E. grandis x E. urophylla hybrids. For this purpose a RAPD linkage map was developed for the hybrids (LOD=3 and r=0.40) containing 52 markers and 12 linkage groups. Traits related to wood quality and growth were evaluated in the QTL analyses. QTL analyses were performed using chi-square tests, single-marker, interval mapping and composite interval mapping analyses. All approaches led to the identification of similar QTLs associated with wood density, cellulose pulp yield and percentage of extractives, which were detected and confirmed by both the interval mapping and composite interval mapping methodologies. Some QTLs regions were confirmed only by the composite interval mapping methodology: percentage of soluble lignin, percentage of insoluble lignin, CBH and total height. Overlapping QTLs regions were detected, and these, can be the result of major genes involved in the regulation and control of the growth traits by epistatic interactions. In order to evaluate the effect of early selection using RAPD molecular data, molecular markers adjacent to QTLs were used genotype selection. The analysis of selection differential values suggests that for all the traits the phenotypic selection at seven years should generate larger genetic gains than early selection assisted by molecular markers and the combination of the strategies should elevate the selection efficiency.

Estudo randomizado para avaliação da dieta hipolipídica nos sintomas digestivos no pós-operatório imediato da colecistectomia por videolaparoscopia

OBJETIVO: Validar a necessidade da prescrição da dieta hipolipídica na prevenção ou redução dos sintomas dispépticos no período pós-operatório de pacientes submetidos à colecistectomia por videolaparoscopia. MÉTODOS: Foram selecionados 40 pacientes, distribuídos em dois grupos, isentos de doenças hepáticas, pancreáticas, litíase da via biliar, gastrite, úlcera, diabetes e dislipidemia. Foi realizado anamnese alimentar, identificação de dispepsias antes do aparecimento da colelitíase e orientações sobre a conduta alimentar no pós-operatório (normal ou hipolipídica). Foi utilizado o teste chi-square e a correlação de Pearson, considerando pd"0,05 como significância estatística. RESULTADOS: Comparando-se os dois grupos de pacientes sem dispepsias no pré-operatório, observou-se que no grupo I, sete pacientes (63,6%) permaneceram assintomáticos e no grupo II, quatro (66,7%). No grupo I, em quatro (36,4%) houve aparecimento de sintomas e no grupo II, em dois (33,3%), logo p=0,684. Correlacionando-se os dois grupos dispépticos no pré-operatório, observou-se que houve permanência, aparecimento ou desaparecimento dos sintomas no pós-operatório, sendo p=0,114. CONCLUSÃO: Não houve repercussão significativa da dieta hipolipídica na prevenção dos sintomas dispépticos, principalmente nos pacientes assintomáticos no pré-operatório. Sendo assim, não há necessidade em se orientar uma dieta hipolipídica. De modo que, cabe ao cirurgião avaliar cada paciente individualmente e ajustar a dieta às necessidades do paciente e às condições clínicas associadas.

Does a previous surgical experience interfere on psychic stress in patients submitted to major surgery?

OBJECTIVE: to evaluate the impact of stress in patients undergoing major surgeries under general anesthesia, relating their physical and psychic reactions to the different stages of stress. METHODS: we studied 100 adult patients of both genders, who were divided into two groups: Group 1 - 22 patients without experience with surgery; Group 2 - 78 patients previously submitted to medium and major surgery. To investigate the stress, we used the Inventory of Stress Symptoms for Adults, developed by Lipp, the day before the procedure and two days and seven days after the operation. The comparison of groups with respect to gender, pain, and percentage of stress were performed using the Chi-square test, and for the age variable the Student's t test was used. Differences were considered significant at p<0.05. RESULTS: the groups were not homogeneous as for the overall percentage of stress on the three measurements. G1 had decreased postoperative stress, whilst in G2 it increased. Psychological symptoms of stress prevailed in both groups. CONCLUSION: previous surgery reduced preoperative stress but did not affect postoperative emotional disorders.

Comparative analysis between identified injuries of victims of fall from height and other mechanisms of closed trauma

OBJECTIVE: To analyze the lesions diagnosed in victims of falls, comparing them with those diagnosed in other mechanisms of blunt trauma.METHODS: We conducted a retrospective study of trauma protocol charts (prospectively collected) from 2008 to 2010, including victims of trauma over 13 years of age admitted to the emergency room. The severity of injuries was stratified by the Abbreviated Injury Scale (AIS) and Injury Severity Score (ISS). Variables were compared between the group of victims of falls from height (Group 1) and the other victims of blunt trauma (Group 2). We used the Student t, chi-square and Fisher tests for comparison between groups, considering the value of p <0.05 as significant.RESULTS: The series comprised 4,532 cases of blunt trauma, of which 555 (12.2%) were victims of falls from height. Severe lesions (AISe"3) were observed in the extremities (17.5%), in the cephalic segment (8.4%), chest (5.5%) and the abdomen (2.9%). Victims of Group 1 had significantly higher mean age, AIS in extremities / pelvis, AIS in the thoracic segment and ISS (p <0.05). The group 1 had significantly (p <0.05) higher incidence of tracheal intubation on admission, pneumothorax, hemothorax, rib fractures, chest drainage, spinal trauma, pelvic fractures, complex pelvic fractures and fractures to the upper limbs.CONCLUSION: Victims of fall from height had greater anatomic injury severity, greater frequency and severity of lesions in the thoracic segment and extremities.

Ultrasonografic changes in the axillary vein of patients with lymphedema after mastectomy

OBJECTIVE: To determine the prevalence of sonographic abnormalities (SA) in the axillary vein of patients with and without post-mastectomy lymphedema. METHODS: We studied a sample of 80 women, divided into two equal groups, with and without lymphedema, with B mode ultrasound, color and pulsed Doppler. The primary variable, SA, is defined as change in the venous diameter, parietal thickening, intraluminal images, compressibility, parietal collapse at inspiration and feature of the axillary venous flow on the operated side. Secondary variables were: stage of lymphedema, surgical technique, number of radio and chemotherapy sessions, limb volume, weight and age. The differences between the proportions in the groups were determined using the Chi-square test and / or Fisher's test. For continuous variables, we used the Mann-Whitney Test. To estimate the magnitude of the associations, we used the prevalence rate of SA in both groups as a measure of frequency, and as a measure of association, the prevalence ratio (PR) obtained as a function of relative risk (RR) and estimated by the test Mantel-Haenszel homogeneity test. We adopted the statistical significance level of 5% (p < 0.05). RESULTS: only the criterion "parietal thickening" was strongly associated with the lymphedema group (p = 0.001). The prevalence of SA was 55% in patients with lymphedema and 17.5% in the group without it, with difference in prevalence of 37.5%. CONCLUSION: the prevalence of SA was higher in patients undergoing mastectomy with lymphedema than in those without lymphedema.