Evolution equation for short surface waves on water of finite depth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Short and long period optimization of drug doses in the treatment of AIDS

Técnicas de otimização numérica são úteis na solução de problemas de determinação da melhor entrada para sistemas descritos por modelos matemáticos e cujos objetivos podem ser expressos de uma maneira quantitativa. Este trabalho aborda o problema de otimizar as dosagens dos medicamentos no tratamento da AIDS em termos de um balanço entre a resposta terapêutica e os efeitos colaterais. Um modelo matemático para descrever a dinâmica do vírus HIV e células CD4 é utilizado para calcular a dosagem ótima do medicamento no tratamento a curto prazo de pacientes com AIDS por um método de otimização direta utilizando uma função custo do tipo Bolza. Os parâmetros do modelo foram ajustados com dados reais obtidos da literatura. Com o objetivo de simplificar os procedimentos numéricos, a lei de controle foi expressa em termos de uma expansão em séries que, após truncamento, permite obter controles sub-ótimos. Quando os pacientes atingem um estado clínico satisfatório, a técnica do Regulador Linear Quadrático (RLQ) é utilizada para determinar a dosagem permanente de longo período para os medicamentos. As dosagens calculadas utilizando a técnica RLQ , tendem a ser menores do que a equivalente terapia de dose constante em termos do expressivo aumento na contagem das células T+ CD4 e da redução da densidade de vírus livre durante um intervalo fixo de tempo.

THE B-FORM TO Z-FORM TRANSITION OF POLY(DG-M(5)DC) IS SENSITIVE TO NEUTRAL SOLUTES THROUGH AN OSMOTIC-STRESS

Several neutral solutes, ranging in size from methanol to a tetrasaccharide, stachyose, are shown to stabilize the left-handed Z form of the methylated polynucleotide poly(dG-m(5)dC). The action of these solutes is consistent with an osmotic stress, that is, with their effect on water chemical potentials coupled to a difference in the number of-associated water molecules between the B and Z conformations. The apparent difference in hydration between the two forms is, however, dependent on the particular solute used to probe the reaction. The effect of solutes is not consistent either with a direct binding of solute or with an indirect effect on electrostatics or ion binding through changes in the solution dielectric constant. The interplay of NaCl and neutral solute in modulating the B-Z transition suggests that salt also could be stabilizing the Z form through an osmotic stress.

A human retrieval study of plasma-sprayed hydroxyapatite-coated plateau root form implants after 2 months to 13 years in function

Calcium phosphate-based bioactive ceramics in various physical and chemical formulations have been extensively utilized as biomaterials for bone regeneration/conduction. However, the determination of their in vivo temporal behavior from the short to long term in humans has been a challenge due to the lack of physical reference for morphologic and morphometric evaluation. The present study evaluated bone morphology and morphometry (bone-to-implant contact [BIC]) around plasma-sprayed hydroxyapatite (PSHA)-coated endosseous implants that were retrieved due to prosthetic reasons while successfully in function at the posterior region of the jaws from as early as 2 months to ~13 years after a 6-month healing period after placement. Bone morphology was evaluated by light microscopy, and BIC was determined using computer software. Irrespective of the time in vivo, lamellar bone was observed in close contact with the implant PSHA-coated surface and between plateaus. BIC ranged from ~35-95%, was highly directional, and Haversian-like osteonic morphology between plateaus was observed for most implants. The PSHA coating was present with little variation in thickness between the samples retrieved regardless of time in vivo. © 2010 by Begell House, Inc.

Intrinsic magnetic properties of BixCo2-xMnO 4 spinels obtained by short-time etching

We report the structural and magnetic properties of Co2MnO 4, partially substituted by Bi at the octahedral site. Bismuth enhances ferromagnetism due to a decrease of the Co2+-Co2+ antiferromagnetic interactions and an increase of the Mn3+-Mn 4+ exchanges. Spurious phases (magnetic and/or nonmagnetic oxides) can easily form because of the large differences between the ionic radii of Bi3+ and Co3+, hiding or altering the intrinsic physical properties of the main BixCo2-xMnO4 phase. An easy way to eliminate the secondary phases is using acid reagents. Short-time etching of Bi0.1Co1.9MnO4 using nitric acid was successfully used, keeping most of the properties of the initial compound, with no alteration of the crystallographic structure. Final stoichiometry was respected (∼Bi0.08Co1.82MnO4), meaning that the material after etching definitely contains bismuth elements in its structure and the observed properties are intrinsic to the oxide spinel. Additional experiments were performed as a function of the synthesis conditions, showing that an optimal pH value of 7 allowed the best magnetic response of the non-doped material. © 2013 Elsevier B.V. All rights reserved.

Short-term effect of alginate-biochar microbeads in corn germination

Biochar is the solid by-product of biomass pyrolysis. It is a promising soil conditioner and can be a material with high aggregate economic value, since its performance can improve plant’s nutrient utilization and reduce the usage of conventional fertilizers. Biochar can be used in the formulation of new types of fertilizers as polymeric microbeads. These microbeads can be enriched with biochar and nutrients in its matrix to form fertilizers of slow release of nutrients. Thus, as a promising agricultural material, it is important to assess the environmental hazards caused by the implementation of these microbeads. In this context, seeds were sown in a soil-less Petri dish with microbeads produced with biochar from sugarcane enriched with or without phosphate. The seeds germination and its vitality were evaluated by the first germination count (FGC) and the germination speed index (GSI). The short-term effects showed that the microbeads, in general, assessed by the means of FGC, GSI and mass gain showed the best performance, suggesting that the environment created by these materials provided the best chemical and physical interaction with the embryonic axes.

A study of the errors of the averaged models in the restricted three-body problem in a short time scale

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Assessment of physical activity by accelerometer and IPAQ-short version in patients with chronic kidney disease undergoing hemodialysis

To compare the short version of International Physical Activity Questionnaire (IPAQ) and the accelerometer measurement of physical activity (PA) in patients undergoing hemodialysis. Sample consisted of 40 patients (19 men) aged 45 ± 16 years. Patients reported their PA using the IPAQ during a face-to-face interview, and wore an Actigraph GT3-X accelerometer for 1 week to obtain minutes per day of light PA, moderate-to-vigorous PA (MVPA) and total PA as well as raw counts per day (vector magnitude). All PA-related variables were significantly correlated among instruments (r = 0.34-0.47) when analyzed as a group. However, when analyzed separately by gender, the relationships were present for women only (r = 0.46-0.62). IPAQ significantly underestimated light PA (IPAQ vs. accelerometer: 180.0 vs. 251.1 min/day, p = 0.019), but no differences were found between methods for MVPA and total PA. Modest correlations were found between self-reported PA time by IPAQ (short version) and accelerometer, but only in women. However, the IPAQ may underestimate light PA, which is the main form of PA in this population.

Entwicklung einer Fokalebenen-Driftkammer für niederenergetische Pionen und experimentelle Bestimmung einer inversen Transfermatrix für das Short-Orbit-Spektrometer

Die Drei-Spektrometer-Anlage am Mainzer Institut für Kernphysik wurde um ein zusätzliches Spektrometer ergänzt, welches sich durch seine kurze Baulänge auszeichnet und deshalb Short-Orbit-Spektrometer (SOS) genannt wird. Beim nominellen Abstand des SOS vom Target (66 cm) legen die nachzuweisenden Teilchen zwischen Reaktionsort und Detektor eine mittlere Bahnlänge von 165 cm zurück. Für die schwellennahe Pionproduktion erhöht sich dadurch im Vergleich zu den großen Spektrometern die Überlebenswahrscheinlichkeit geladener Pionen mit Impuls 100 MeV/c von 15% auf 73%. Demzufolge verringert sich der systematische Fehler ("Myon-Kontamination"), etwa bei der geplanten Messung der schwachen Formfaktoren G_A(Q²) und G_P(Q²), signifikant. Den Schwerpunkt der vorliegenden Arbeit bildet die Driftkammer des SOS. Ihre niedrige Massenbelegung (0,03% X_0) zur Reduzierung der Kleinwinkelstreuung ist auf den Nachweis niederenergetischer Pionen hin optimiert. Aufgrund der neuartigen Geometrie des Detektors musste eine eigene Software zur Spurrekonstruktion, Effizienzbestimmung etc. entwickelt werden. Eine komfortable Möglichkeit zur Eichung der Driftweg-Driftzeit-Relation, die durch kubische Splines dargestellt wird, wurde implementiert. Das Auflösungsvermögen des Spurdetektors liegt in der dispersiven Ebene bei 76 µm für die Orts- und 0,23° für die Winkelkoordinate (wahrscheinlichster Fehler) sowie entsprechend in der nicht-dispersiven Ebene bei 110 µm bzw. 0,29°. Zur Rückrechnung der Detektorkoordinaten auf den Reaktionsort wurde die inverse Transfermatrix des Spektrometers bestimmt. Hierzu wurden an Protonen im ¹²C-Kern quasielastisch gestreute Elektronen verwendet, deren Startwinkel durch einen Lochkollimator definiert wurden. Daraus ergeben sich experimentelle Werte für die mittlere Winkelauflösung am Target von sigma_phi = 1,3 mrad bzw. sigma_theta = 10,6 mrad. Da die Impulseichung des SOS nur mittels quasielastischer Streuung (Zweiarmexperiment) durchgeführt werden kann, muss man den Beitrag des Protonarms zur Breite des Piks der fehlenden Masse in einer Monte-Carlo-Simulation abschätzen und herausfalten. Zunächst lässt sich nur abschätzen, dass die Impulsauflösung sicher besser als 1% ist.

Polymer surfaces on small length- and short time-scales

The behaviour of a polymer depends strongly on the length- and time scale as well as on the temperature rnat which it is probed. In this work, I describe investigations of polymer surfaces using scanning probe rnmicroscopy with heatable probes. With these probes, surfaces can be heated within seconds down to rnmicroseconds. I introduce experiments for the local and fast determination of glass transition and melting rntemperatures. I developed a method which allows the determination of glass transition and melting rntemperatures on films with thicknesses below 100 nm: A background measurement on the substrate was rnperformed. The resulting curve was subtracted from the measurement on the polymer film. The rndifferential measurement on polystyrene films with thicknesses between 35 nm and 160 nm showed rncharacteristic signals at 95 ± 1 °C, in accordance with the glass transition of polystyrene. Pressing heated rnprobes into polymer films causes plastic deformation. Nanometer sized deformations are currently rninvestigated in novel concepts for high density data storage. A suitable medium for such a storage system rnhas to be easily indentable on one hand, but on the other hand it also has to be very stable towards rnsurface induced wear. For developing such a medium I investigated a new approach: A comparably soft rnmaterial, namely polystyrene, was protected with a thin but very hard layer made of plasma polymerized rnnorbornene. The resulting bilayered media were tested for surface stability and deformability. I showed rnthat the bilayered material combines the deformability of polystyrene with the surface stability of the rnplasma polymer, and that the material therefore is a very good storage medium. In addition we rninvestigated the glass transition temperature of polystyrene at timescales of 10 µs and found it to be rnapprox. 220 °C. The increase of this characteristic temperature of the polymer results from the short time rnat which the polymer was probed and reflects the well-known time-temperature superposition principle. rnHeatable probes were also used for the characterization of silverazide filled nanocapsules. The use of rnheatable probes allowed determining the decomposition temperature of the capsules from few rnnanograms of material. The measured decomposition temperatures ranged from 180 °C to 225 °C, in rnaccordance with literature values. The investigation of small amounts of sample was necessary due to the rnlimited availability of the material. Furthermore, investigating larger amounts of the capsules using rnconventional thermal gravimetric analysis could lead to contamination or even damage of the instrument. rnBesides the analysis of material parameters I used the heatable probes for the local thermal rndecomposition of pentacene precursor material in order to form nanoscale conductive structures. Here, rnthe thickness of the precursor layer was important for complete thermal decomposition. rnAnother aspect of my work was the investigation of redox active polymers - Poly-10-(4-vinylbenzyl)-10H-rnphenothiazine (PVBPT)- for data storage. Data is stored by changing the local conductivity of the material rnby applying a voltage between tip and surface. The generated structures were stable for more than 16 h. It rnwas shown that the presence of water is essential for succesfull patterning.

Interactions between short-term and long-term plasticity: shooting for a moving target

Far from being static transmission units, synapses are highly dynamical elements that change over multiple time scales depending on the history of the neural activity of both the pre- and postsynaptic neuron. Moreover, synaptic changes on different time scales interact: long-term plasticity (LTP) can modify the properties of short-term plasticity (STP) in the same synapse. Most existing theories of synaptic plasticity focus on only one of these time scales (either STP or LTP or late-LTP) and the theoretical principles underlying their interactions are thus largely unknown. Here we develop a normative model of synaptic plasticity that combines both STP and LTP and predicts specific patterns for their interactions. Recently, it has been proposed that STP arranges for the local postsynaptic membrane potential at a synapse to behave as an optimal estimator of the presynaptic membrane potential based on the incoming spikes. Here we generalize this approach by considering an optimal estimator of a non-linear function of the membrane potential and the long-term synaptic efficacy—which itself may be subject to change on a slower time scale. We find that an increase in the long-term synaptic efficacy necessitates changes in the dynamics of STP. More precisely, for a realistic non-linear function to be estimated, our model predicts that after the induction of LTP, causing long-term synaptic efficacy to increase, a depressing synapse should become even more depressing. That is, in a protocol using trains of presynaptic stimuli, as the initial EPSP becomes stronger due to LTP, subsequent EPSPs should become weakened and this weakening should be more pronounced with LTP. This form of redistribution of synaptic efficacies agrees well with electrophysiological data on synapses connecting layer 5 pyramidal neurons.

Fabrication of nanoparticles by short-distance sputter deposition

During the past decades, tremendous research interests have been attracted to investigate nanoparticles due to their promising catalytic, magnetic, and optical properties. In this thesis, two novel methods of nanoparticle fabrication were introduced and the basic formation mechanisms were studied. Metal nanoparticles and polyurethane nanoparticles were separately fabricated by a short-distance sputter deposition technique and a reactive ion etching process. First, a sputter deposition method with a very short target-substrate distance is found to be able to generate metal nanoparticles on the glass substrate inside a RIE chamber. The distribution and morphology of nanoparticles are affected by the distance, the ion concentration and the process time. Densely-distributed nanoparticles of various compositions are deposited on the substrate surface when the target-substrate distance is smaller than 130mm. It is much less than the atoms’ mean free path, which is the threshold in previous research for nanoparticles’ formation. Island structures are formed when the distance is increased to 510mm, indicating the tendency to form continuous thin film. The trend is different from previously-reported sputtering method for nanoparticle fabrication, where longer distance between the target and the substrate facilitates the formation of nanoparticle. A mechanism based on the seeding effect of the substrate is proposed to interpret the experimental results. Secondly, in polyurethane nanoparticles’ fabrication, a mechanism is put forward based on the microphase separation phenomenon in block copolymer thin film. The synthesized polymers have formed dispersed and continuous phases because of the different properties between segments. With harder mechanical property, the dispersed phase is remained after RIE process while the continuous phase is etched away, leading to the formation of nanoparticles on the substrate. The nanoparticles distribution is found to be affected by the heating effect, the process time and the plasma power. Superhydrophilic property is found on samples with these two types of nanoparticles. The relationship between the nanostructure and the hydrophilicity is studied for further potential applications.

Viable neutrophils release mitochondrial DNA to form neutrophil extracellular traps

Neutrophil extracellular traps (NETs) represent extracellular structures able to bind and kill microorganisms. It is believed that they are generated by neutrophils undergoing cell death, allowing these dying or dead cells to kill microbes. We show that, following priming with granulocyte/macrophage colony-stimulating factor (GM-CSF) and subsequent short-term toll-like receptor 4 (TLR4) or complement factor 5a (C5a) receptor stimulation, viable neutrophils are able to generate NETs. Strikingly, NETs formed by living cells contain mitochondrial, but no nuclear, DNA. Pharmacological or genetic approaches to block reactive oxygen species (ROS) production suggested that NET formation is ROS dependent. Moreover, neutrophil populations stimulated with GM-CSF and C5a showed increased survival compared with resting neutrophils, which did not generate NETs. In conclusion, mitochondrial DNA release by neutrophils and NET formation do not require neutrophil death and do also not limit the lifespan of these cells.

Analytical form of the Probability Density Function of travel times in rectangular zone with Tchebyshev’s metric

Geometrical dependencies are being researched for analytical representation of the probability density function (pdf) for the travel time between a random, and a known or another random point in Tchebyshev’s metric. In the most popular case - a rectangular area of service - the pdf of this random variable depends directly on the position of the server. Two approaches have been introduced for the exact analytical calculation of the pdf: Ad-hoc approach – useful for a ‘manual’ solving of a specific case; by superposition – an algorithmic approach for the general case. The main concept of each approach is explained, and a short comparison is done to prove the faithfulness.

Health literacy among young adults: a short survey tool for public health and health promotion research

Health literacy (HL) is context-specific. In public health and health promotion, HL in the private realm refers to individuals' knowledge and skills to prevent disease and to promote health in everyday life. However, there is a scarcity of measurement tools explicitly geared to private realm contexts. Our aim was to develop and test a short survey tool that captures different dimensions of HL in the context of family and friends. We used cross-sectional data from the Swiss Federal Surveys of Adolescents from 2010 to 2011, comprising 7983 males and 366 females between 18 and 25 years. HL was assessed through a set of eight items (self-reports). We used principal component analysis to explore the underlying factor structure among these items in the male sample and confirmatory factor analysis to verify the factor structure in the female sample. The results showed that the tested item set represented dimensions of functional, interactive and critical HL. Two sub-dimensions, understanding versus finding health-relevant information, denoted functional HL. Interactive and critical HL were each represented with two items. A sum score based on all eight items (Cronbach's α: 0.64) showed expected positive associations with own and parental education among males and females (p < 0.05). The short item set appears to be a feasible measurement tool to assess HL in the private realm. Its broader application in survey studies may help to improve our understanding of how this form of HL is distributed in the general population.