Nets: Network estimation for time series

This work proposes novel network analysis techniques for multivariate time series.We define the network of a multivariate time series as a graph where verticesdenote the components of the process and edges denote non zero long run partialcorrelations. We then introduce a two step LASSO procedure, called NETS, toestimate high dimensional sparse Long Run Partial Correlation networks. This approachis based on a VAR approximation of the process and allows to decomposethe long run linkages into the contribution of the dynamic and contemporaneousdependence relations of the system. The large sample properties of the estimatorare analysed and we establish conditions for consistent selection and estimation ofthe non zero long run partial correlations. The methodology is illustrated with anapplication to a panel of U.S. bluechips.

La resiliència

El present treball és un aprofundiment teòric sobre la resiliència, un concepte transgressor en les ciències socials que invita a tenir una nova visió de les situacions concretes, a un canvi de perspectiva que ens guia a refermar maneres d’intervenció diferents. Precisament, perquè ens porta a canviar la nostra mirada vers les persones i sobre la vida. Aquest projecte s’emmarca en els orígens del concepte, en quin moment es troba avui dia, aquelles teories explicatives i una aportació sobre la seva visió pràctica; tenint present en tot moment tant la dimensió individual com la dimensió comunitària del mateix. La resiliència, reconeix el valor de la imperfecció de l’espècia humana. No és una resposta immediata a l’adversitat sinó un procés que està en constant construcció, canvi i/o evolució en el transcurs del temps. No és un concepte absolut ni total, sinó que està lligat als conceptes dinàmics i complexos de desenvolupament i creixement humà i va més enllà de l’actitud passiva de resistir qualsevol cop; implica l’actitud proactiva d’aprendre/reapendre a viure i construir/reconstruir la vida.

Learning-induced plasticity in auditory spatial representations revealed by electrical neuroimaging.

Auditory spatial representations are likely encoded at a population level within human auditory cortices. We investigated learning-induced plasticity of spatial discrimination in healthy subjects using auditory-evoked potentials (AEPs) and electrical neuroimaging analyses. Stimuli were 100 ms white-noise bursts lateralized with varying interaural time differences. In three experiments, plasticity was induced with 40 min of discrimination training. During training, accuracy significantly improved from near-chance levels to approximately 75%. Before and after training, AEPs were recorded to stimuli presented passively with a more medial sound lateralization outnumbering a more lateral one (7:1). In experiment 1, the same lateralizations were used for training and AEP sessions. Significant AEP modulations to the different lateralizations were evident only after training, indicative of a learning-induced mismatch negativity (MMN). More precisely, this MMN at 195-250 ms after stimulus onset followed from differences in the AEP topography to each stimulus position, indicative of changes in the underlying brain network. In experiment 2, mirror-symmetric locations were used for training and AEP sessions; no training-related AEP modulations or MMN were observed. In experiment 3, the discrimination of trained plus equidistant untrained separations was tested psychophysically before and 0, 6, 24, and 48 h after training. Learning-induced plasticity lasted <6 h, did not generalize to untrained lateralizations, and was not the simple result of strengthening the representation of the trained lateralizations. Thus, learning-induced plasticity of auditory spatial discrimination relies on spatial comparisons, rather than a spatial anchor or a general comparator. Furthermore, cortical auditory representations of space are dynamic and subject to rapid reorganization.

Carbon content in Amazonian Oxisols after forest conversion to pasture

Soil plays an important role in the C cycle, and substitution of tropical forest by cultivated land affects C dynamic and stock. This study was developed in an area of expansion of human settlement in the Eastern Amazon, in Itupiranga, State of Pará, to evaluate the effects of native forest conversion to Brachiaria brizantha pasture on C contents of a dystrophic Oxisol. Soil samples were collected in areas of native forest (NF), of 8 to 10 year old secondary forest (SF), 1 to 2 year old SF (P1-2), 5 to 7 year old SF (P5-7), and of 10 to 12 year old SF (P10-12), and from under pastures, in the layers 0-2, 2-5 and 5-10 cm, to evaluate C levels and stocks and carry out separation of OM based on particle size. After deforestation, soil density increased to a depth of 5 cm, with greater increase in older pastures. Variation in C levels was greatest in the top soil layer; C contents increased with increasing pasture age. In the layers 2-5 and 5-10 cm, C content proved to be stable for the types of plant cover evaluated. Highest C concentrations were found in the silt fraction; however, C contents were highest in the clay fraction, independent of the plant cover. An increase in C associated with the sand fraction in the form of little decomposed organic residues was observed in pastures, confirming greater sensitivity of this fraction to change in soil use.

Fluctuations in Saffman-Taylor fingers with quenched disorder

We make an experimental characterization of the effect that static disorder has on the shape of a normal Saffman-Taylor finger. We find that static noise induces a small amplitude and long wavelength instability on the sides of the finger. Fluctuations on the finger sides have a dominant wavelength, indicating that the system acts as a selective amplifier of static noise. The dominant wavelength does not seem to be very sensitive to the intensity of static noise present in the system. On the other hand, at a given flow rate, rms fluctuations of the finger width, decrease with decreasing intensity of static noise. This might explain why the sides of the fingers are flat for typical Saffman-Taylor experiments. Comparison with previous numerical studies of the effect that temporal noise has on the Saffman-Taylor finger, leads to conclude that the effect of temporal noise and static noise are similar. The behavior of fluctuations of the finger width found in our experiments, is qualitatively similar to one recently reported, in the sense that, the magnitude of the width fluctuations decays as a power law of the capillary number, at low flow rates, and increases with capillary number for larger flow rates.

FERTILIZER RECOMMENDATION SYSTEM FOR MELON BASED ON NUTRITIONAL BALANCE

Melon is one of the most demanding cucurbits regarding fertilization, requiring knowledge of soils, crop nutritional requirements, time of application, and nutrient use efficiency for proper fertilization. Developing support systems for decision-making for fertilization that considers these variables in nutrient requirement and supply is necessary. The objective of this study was parameterization of a fertilizer recommendation system for melon (Ferticalc-melon) based on nutritional balance. To estimate fertilizer recommendation, the system considers the requirement subsystem (REQ), which includes the demand for nutrients by the plant, and the supply subsystem (SUP), which corresponds to the supply of nutrients through the soil and irrigation water. After determining the REQtotal and SUPtotal, the system calculates the nutrient balances for N, P, K, Ca, Mg, and S, recommending fertilizer application if the balance is negative (SUP < REQ), but not if the balance is positive or zero (SUP ≥ REQ). Simulations were made for different melon types (Yellow, Cantaloupe, Galia and Piel-de-sapo), with expected yield of 45 t ha-1. The system estimated that Galia type was the least demanding in P, while Piel-de-sapo was the most demanding. Cantaloupe was the least demanding for N and Ca, while the Yellow type required less K, Mg, and S. As compared to other fertilizer recommendation methods adopted in Brazil, the Ferticalc system was more dynamic and flexible. Although the system has shown satisfactory results, it needs to be evaluated under field conditions to improve its recommendations.

Evaluation of Dense Bridge Floor Concrete Using High Range Water Reducer, May 1983

The objectives of this research project are: (1) To determine the feasibility of proportioning, mixing, placing and finishing a dense portland cement concrete in a bridge floor using conventional mixing, placing and finishing equipment. (2) To determine the economics, longevity, maintenance performance and protective qualities of a dense portland cement concrete bridge floor when using a high rangewater reducing admixture. The purpose of a high range water reducing admixture is to produce a dense, high quality concrete at a low water-cement ratio witj adequate workability. A low water-cement ratio contributes greatly to increased strength. The normal 7 day strength of untreated concrete would be expected i n 3 days using a superplasticizer. A dense concrete also has the desirable properties of excellent durability and reduced permeability. It is felt that a higher quality, denser, higher strength portland cement concrete can be produced and placed, using conventional equipment, by the addition of a high range water reducing admixture. Such a dense concrete, w i t h a water/cement ratio of approximately 0.30 to 0.35, would be expected to be much less permeable and thus retard the intrusion of chloride. With care and attention given to obtaining the design cover over steel (2% inches clear), it i s hoped that protection for the design life of the structure will be obtained. Evaluation of this experimental concrete bridge floor included chloride content and delamination testing of the concrete floor five years after construction. A comparitive evaluation o f a control section o f concrete without the water reducing admixture was conducted. Other items o f comparison include workability during construction, strength, density, water-cement ratio and chloride penetration.

Neural networks as mechanisms to regulate division of labor.

Abstract In social insects, workers perform a multitude of tasks, such as foraging, nest construction, and brood rearing, without central control of how work is allocated among individuals. It has been suggested that workers choose a task by responding to stimuli gathered from the environment. Response-threshold models assume that individuals in a colony vary in the stimulus intensity (response threshold) at which they begin to perform the corresponding task. Here we highlight the limitations of these models with respect to colony performance in task allocation. First, we show with analysis and quantitative simulations that the deterministic response-threshold model constrains the workers' behavioral flexibility under some stimulus conditions. Next, we show that the probabilistic response-threshold model fails to explain precise colony responses to varying stimuli. Both of these limitations would be detrimental to colony performance when dynamic and precise task allocation is needed. To address these problems, we propose extensions of the response-threshold model by adding variables that weigh stimuli. We test the extended response-threshold model in a foraging scenario and show in simulations that it results in an efficient task allocation. Finally, we show that response-threshold models can be formulated as artificial neural networks, which consequently provide a comprehensive framework for modeling task allocation in social insects.

An Evaluation of Concrete Bridge Deck Surfacing in Iowa (with corrections), MLR-75-1, 1975

Iowa has been using low slump concrete for repair and surfacing of deteriorated bridge decks on a routine basis since the mid 1960'2. More than 150 bridges have been resurfaced by this method with good results. A study was initiated in 1973 to evaluate 15 bridges resurfaced with low slump concrete, and one bridge resurfaced with latex modified concrete. The evaluation includes an assessment of concrete physical properties, chloride penetration rates, concrete consolidation, and riding qualities of the finished bridge deck. Results indicate that the overall properties of these two types of concrete are quite similar and have resulted in a contractor option concerning which system shall be used on bridge deck repair/resurfacing projects.

Construction of a Bridge Floor Using High Range Water Reducer, Construction Report, HR-192, 1978

The use of a high range water reducer in bridge floors was initiated by an Iowa Highway Research Board project (HR-192) in 1977 for two basic reasons. One was to determine the feasibility of using a high range water reducer (HRWR) in bridge floor concrete using conventional concrete proportioning, transporting and finishing equipment. The second was to determine the performance and protective qualities against chloride intrusion of a dense concrete bridge floor by de-icing agents used on Iowa's highways during winter months. This project was basically intended to overcome some problems that developed in the original research project. The problems alluded to are the time limits from batching to finishing; use of a different type of finishing machine; need for supplemental vibration on the surface of the concrete during the screeding operation and difficulty of texturing. The use of a double oscillating screed finishing machine worked well and supplemental vibration on one of the screeds was not needed. The limit of 45 minutes from batching the concrete to placement on the deck was verified. This is a maximum when the HRWR is introduced at the batch plant. The problem of texturing was not solved completely but is similar to our problems on the dense "Iowa System" overlay used on bridge deck repair projects. This project reinforced some earlier doubts about using truck transit mixers for mixing and transporting concrete containing HRWR when introduced at the batch plant.

Formation of virus-like clusters is an intrinsic property of the tumor necrosis factor family member BAFF (B cell activating factor).

The oligomeric state of BAFF (B cell activing factor), a tumor necrosis factor (TNF) family cytokine that plays a critical role in B cell development and survival, has been the subject of recent debate. Myc-tagged BAFF starting at residue Gln136 was previously reported to crystallize as trimers at pH 4.5, whereas a histidine-tagged construct of BAFF, starting at residue Ala134, formed a virus-like cluster containing 60 monomers when crystallized at pH 9.0. The formation of the BAFF 60-mer was pH dependent, requiring pH &gt;or= 7.0. More recently, 60-mer formation was suggested to be artificially induced by the histidine tag, and it was proposed that BAFF, like all other TNF family members, is trimeric. We report here that a construct of BAFF with no amino-terminal tag (Ala134-BAFF) can form a 60-mer in solution. Using size exclusion chromatography and static light scattering to monitor trimer to 60-mer ratios in BAFF preparations, we find that 60-mer formation is pH-dependent and requires histidine 218 within the DE loop of BAFF. Biacore measurements established that the affinity of Ala134-BAFF for the BAFF receptor BAFFR/BR3 is similar to that of myc-Gln136-BAFF, which is exclusively trimeric in solution. However, Ala134-BAFF is more efficacious than myc-Gln136-BAFF in inducing B cell proliferation in vitro. We additionally show that BAFF that is processed and secreted by 293T cells transfected with full-length BAFF, or by a histiocytic lymphoma cell line (U937) that expresses BAFF endogenously, forms a pH-dependent 60-mer in solution. Our results indicate that the formation of the 60-mer in solution by the BAFF extracellular domain is an intrinsic property of the protein, and therefore that this more active form of BAFF may be physiologically relevant.

Evaluation of Gap-Graded Asphalt Concrete Mixtures, Vol. 1. Physical Properties (Part I: Mechanical Properties), HR-157, Volume 1, 1972 (1973)

This report presents the results of a comparative laboratory study between well- and gap-graded aggregates used in asphalt concrete paving mixtures. A total of 424 batches of asphalt concrete mixtures and 3,960 Marshall and Hveem specimens were examined. There is strong evidence from this investigation that, with proper-combinations of aggregates and asphalts, both continuous- and gap-graded aggregates can produce mixtures of high density and of qualities meeting current design criteria. There is also reason to believe that the unqualified acceptance of some supposedly desirable, constant, mathematical relationship between adjacent particle sizes of the form such as Fuller's curve p = 100(d/D)^n is not justified. It is recommended that the aggregate grading limits be relaxed or eliminated and that the acceptance or rejection of an aggregate for use in asphalt pavement be based on individual mixture evaluation. Furthermore, because of the potential attractiveness of gap-graded asphalt concrete in cost, quality, and skid and wear resistance, selected gap-graded mixtures are recommended for further tests both in the laboratory and in the field, especially in regard to ease of compaction and skid and wear resistance.

Evaluation of Gap-Graded Asphalt Concrete Mixtures Vol. 3. Appendix, HR-157, Volume 3 (Part 3), 1972 (1973)

This report presents the results of a comparative laboratory study between well- and gap-graded aggregates used in asphalt concrete paving mixtures. A total of 424 batches of asphalt concrete mixtures and 3,960 Marshall and Hveem specimens were examined. There is strong evidence from this investigation that, with proper combinations of aggregates and asphalts, both continuous- and gap-graded aggregates can produce mixtures of high density and of qualities meeting current design criteria. There is also reason to believe that the unqualified acceptance of some supposedly desirable, constant, mathematical relationship between adjacent particle sizes of the form such as Fuller's curve p = 100 (d/D)n is not justified. It is recommended that. the aggregate grading limits be relaxed or eliminated and that the acceptance or rejection of an aggregate for use in asphalt pavement be based on individual mixture evaluation. Furthermore, because of the potential attractiveness of gap-graded asphalt concrete in cost, quality, and skid and wear resistance, selected gap-graded mixtures are recommended for further tests both in the laboratory and in the field, especially in regard to ease of compaction and skid and wear resistance.

Enzyme convertedstarch in pigment coating

Tämän diplomityön tavoitteena oli selvittää entsyymikonvertoinnin mahdollisuudet vaikuttaa sideainetärkkelyksen toiminnallisiin ominaisuuksiin. Tärkein tehtävä oli etsiä vastaukset kysymykseen, kuinka paljon entsyymikonvertointia optimoimalla voidaan maksimoida tärkkelyksen positiivisia vaikutuksia. Tavoitteena oli myös tutkia, voiko lisäaineita käyttämällä ja tärkkelystä plastisoimalla säilyttää tärkkelyksen vaikutus paperin jäykkyyteen ja saada tärkkelysfilmille joustavuutta. Kirjallisuusosassa tarkasteltiin tärkkelyksen entsyymikonvertointiin vaikuttavia tekijöitä, eri tärkkelysraaka-aineiden eroja, sekä konvertoinnissa käytettävien entsyymien ominaisuuksia. Kirjallisuusosassa tarkasteltiin myöstärkkelyksen käyttöä sideaineena pigmenttipäällystyksessä. Kokeellisessa osassakeskityttiin selvittämään entsyymikonvertoinnin olosuhteiden, käytettävän raakatärkkelyksen ja entsyymin vaikutusta konvertoidun tärkkelyksen ominaisuuksiin. Konvertoiduista tärkkelyksistä valmistettiin päällystyspastat, ja tutkittiin niinpastan kuin päällystetyn paperin ominaisuuksia. Myös erilaisten pehmentimien vaikutusta niin päällystyspastaan, kuin paperin pinnalle tutkittiin. Havaittiin, että konvertoimalla tärkkelysketjua entsymaattisesti, voidaan tärkkelysketjun pituutta säädellä. Tarkoituksena oli konvertoida tärkkelystä niin, että tärkkelyksen molekyyliketjujakaumat sisältävät lyhyitä, keskipitkiä sekäpitkiä molekyylejä. Päällystämisen havaittiin olevan vaikeaa Helicoaterilla varsinkin pitkäketjuista tärkkelystä suuren määrän sisältävillä pastoilla. Myös tärkkelys/lateksi-suhde vaihteli eri pastoilla. Päällystyspastojen reologisia ominaisuuksia testattaessa huomattiin, että tärkkelysketjun pituuden kasvaessa pastanviskositeetti lisääntyy ja vesiretentio vähenee. Havaittiin vain muutamia teknisiä paperiominaisuuksia, jotka korreloivat hyvin tärkkelysketjun pituuden kanssa. Näitä olivat kiilto, Gurley-Hill huokoisuus, taivutusvastus, taivutuspituus sekä IGT pintalujuus. Pehmentimien ei havaittu vaikuttavan moneenkaan paperin eri tekniseen ominaisuuteen. Suurimmat erot huomattiin paperin taivutuspituudessa ja taivutusvastuksessa.

Innovatiivisen tietopalvelun markkinointi "case Liikekirjuri"

Tutkielman tavoitteena oli kehittää SuomenKirjurituotteen tuottaman sähköisessä muodossa olevan Liikekirjuri-tietopalvelun markkinointia. Käyttäjät ovat taloushallinnon ammattilaisia, pääasiassa tilitoimistoja. Tavoitteeseen pyrittiin selvitämällä asiakasyrityksille tärkeimpiä tuotteen ominaisuuksia sekä niitä tekijöitä, jotka ovat vaikuttaneet nykyisten asiakkaiden hankintapäätökseen. Lisäksi pyrittiin selvittämään, miten tehokkaana asiakkaat ovat kokeneet markkinointiviestinnän. On myös haluttu selvittää,kuinka tyytyväisiä asiakkaat ovat palveluun ja sen ominaisuuksiin. Tutkielma koostuu teoria- ja empiriaosuuksista. Teoriaosassa esitellään innovaation diffuusiota, informaatiopalveluiden taloustiedettä sekä yritysmarkkinointia. Empiirisen osuuden muodostaa kvantitatiivinen tutkimus, joka suoritettiin kirjekyselynä. Tutkimuksen perusteella päädyttiin seuraaviin tuloksiin ja suosituksiin: Myyntityön tulisi olla aktiivisempaa. Markkinoinnissa on hyväkorostaa suhteelliseen hyötyyn lukeutuvia ominaisuuksia. Referenssien käyttöä tulisi tehostaa. Havaittiin myös, että nykyiset asiakkaat ovat olleet erittäin tyytyväisiä ohjelmistoon.