Mathematical retroreflectors

Retroreflectors are optical devices that reverse the direction of incident beams of light. Here we present a collection of billiard type retroreflectors consisting of four objects; three of them are asymptotically perfect retroreflectors, and the fourth one is a retroreflector which is very close to perfect. Three objects of the collection have recently been discovered and published or submitted for publication. The fourth object - notched angle - is a new one; a proof of its retroreflectivity is given.Comment: 32 pages, 19 figure

Dinâmica da matéria orgânica sob sistemas de manejo no solo no município de Paragominas-PA.

Uma das características marcantes do plantio direto é o aumento do teor de matéria orgânica na camada superficial do solo com o decorrer do tempo de sua implantação. O presente trabalho teve como objetivo avaliar a dinâmica da matéria orgânica sob sistemas de manejo em Paragominas-PA. O estudo foi executado na fazenda Juparanã, com delineamento de blocos ao acaso com quatro tratamentos, o T1 (plantio direto: soja/milho em rotação), T2 (plantio direto: milho/soja, em rotação), T3 (plantio convencional: soja/milho) e T4 (plantio convencional: monocultivo de soja) com três repetições. Foram coletadas amostras deformadas, na camadas: 0-5, 5-10, 10-20, 20-30 e 30-50 cm. A MO, foi analisada no Laboratório de Solos da Embrapa Amazônia Oriental e as médias foram submetidas à análise de variância. Conclui-se que o plantio direto proporcionou ao longo do tempo aumento nos teores de matéria orgânica no solo, quando comparado ao de preparo convencional

Noether's Symmetry Theorem for Variational and Optimal Control Problems with Time Delay

We extend the DuBois-Reymond necessary optimality condition and Noether's symmetry theorem to the time delay variational setting. Both Lagrangian and Hamiltonian versions of Noether's theorem are proved, covering problems of the calculus of variations and optimal control with delays.Comment: This is a preprint of a paper whose final and definite form will appear in the international journal Numerical Algebra, Control and Optimization (NACO). Paper accepted for publication 15-March-201

Macrophage Targeting pH Responsive Polymersomes for Glucocorticoid Therapy

Glucocorticoid (GC) drugs are the cornerstone therapy used in the treatment of inflammatory diseases. Here, we report pH responsive poly(2-methacryloyloxyethyl phosphorylcholine)–poly(2-(diisopropylamino)ethyl methacrylate) (PMPC–PDPA) polymersomes as a suitable nanoscopic carrier to precisely and controllably deliver GCs within inflamed target cells. The in vitro cellular studies revealed that polymersomes ensure the stability, selectivity and bioavailability of the loaded drug within macrophages. At molecular level, we tested key inflammation-related markers, such as the nuclear factor-κB, tumour necrosis factor-α, interleukin-1β, and interleukin-6. With this, we demonstrated that pH responsive polymersomes are able to enhance the anti-inflammatory effect of loaded GC drug. Overall, we prove the potential of PMPC–PDPA polymersomes to efficiently promote the inflammation shutdown, while reducing the well-known therapeutic limitations in GC-based therapy

Atributos físicos e produção de soja sob sistemas de manejo em latossolo amarelo no município de Redenção-PA.

O presente trabalho teve como objetivo avaliar atributos físicos e produção de soja sob sistemas de manejo em Latossolo Amarelo no município de Redenção-Pa. O estudo foi desenvolvido na Fazenda Modelo, Redenção, nos anos 2001 a 2003. Utilizou-se o delineamento experimental em blocos casualizados, em área de cerrado, em Latossolo Vermelho Amarelo distrófico, em parcelas sub-divididas. As parcelas com área de 100m x 36,50m (3.650m2) corresponderam aos tratamentos: T1 (plantio direto) e T2 (preparo convencional), com três repetições. As subparcelas constaram de coletas de amostras de solo indeformadas nas profundidades: 0-10, 10-20, 20-30, 30-50cm. As análises foram determinadas no Laboratório de Física de Solo da Embrapa Amazônia Oriental. Os dados de foram submetidos a análise de variância. De acordo com os resultados o plantio direto empreendeu incremento na microporosidade e porosidade total; enquanto que o monocultivo apresentou maiores densidades aparentes e mesmo macroporosidade. Variações anuais foram assinaladas na densidade aparente, a exceção das camadas mais profundas e da microporosidade não superficial, havendo incremento destes indicadores ao longo dos anos. O plantio direto proporcionou maior produtividade de soja, comparativamente ao preparo convencional

Presence of Enterobacteriaceae and Clostridiaceae in thte soil according to the use of biofertilizers of feces from goats and sheep.

The use of biofertilizers appears as an alternative to the use of chemical fertilizers and use of residues generated by animal production. However, the presence of possible pathogens belonging to the families Enterobacteriaceae and Clostridiaceae in biofertilizers from feces can lead to sanitary and ecological problems

Effects of residues on the degradation of PHA produced from mixed microbial cultures and processed in extrusion

Thermal degradation upon melting is one of the major drawbacks reported for polyhydroxyalkanoates (PHA). However, the role of residues originating from the fermentation and the extraction steps on the thermal stability of this class of biopolymers still needs to be clarified. In the particular case of PHA produced from mixed microbial cultures (MMC), this topic is even less documented in the literature. Here, two polyhydroxy(butyrate-co-valerate) (PHBV) produced from MMC enriched in PHA accumulating organisms and fed with cheese whey were studied. A micro extrusion line is used to produce filaments and assess the processability and the degradation of processed PHBV. The prototype micro extrusion line allows for studying grams of materials. The two PHBV contain 18 mol% HV. PHBV was recovered with 11 wt% residues, and further submitted to a purification procedure resulting in a second biopolyester containing less than 2 wt% impurities. The thermorheological characterization of the two PHBV is first presented, together with their semicrystalline properties. Then the processing windows of the two biopolyesters are presented. Finally, the properties of extruded filaments are reported and the thermomechanical degradation of PHBV is extensively studied. The structure was assessed by wide angle X-ray diffraction, mechanical and rheological properties are reported, thermal properties are studied with differential scanning calorimetry and thermogravimetric analysis, whereas Fourier Transform Infrared spectroscopy was used to assess the impact of the extrusion on PHBV chemical structure. All results obtained with the two PHBV are compared to assess the effects of residues on both PHBV processability and degradation