974 resultados para rocket motors
Resumo:
Vivimos rodeados de tecnología. La irrupción de ordenadores, tablets y smartphones en la sociedad ha hecho que ésta cambie y ha conseguido que sean posibles nuevos métodos de enseñanza mediante el empleo de estos dispo sitivos. Entre los nuevos métodos de enseñanza aparece el uso de los videojuegos como medio de aprendizaje. Son videojuegos, que a diferencia de los videojuegos tradicionales, no buscan el entretenimiento del jugador sino formarle dejando la diversión en un segundo plano. Estos juegos no están destinados exclusivamente al campo de la educación. Instituciones como el ejército también hacen uso de ellos para preparar a sus tropas, e incluso los hospitales los utilizan como métodos de rehabilitación. El desarrollo de videojuegos puede realizarse con un mínimo de conocimiento en programación tanto a nivel individual o como en grupos reducidos. Esto es posible gracias a las facilidades que ofrecen los motores gráficos de hoy en día. Con este proyecto se quiso realizar un tutorial que facilite el diseño y desarrollo de videojuegos sobre una plataforma móvil, como es Android , de cara a su uso posterior en la creación de juegos serios. Para el desarrollo del tutorial se elaboró un videojuego de plataformas en avance 2D. ABSTRACT: We are surounded by technologies. As computers, tablets and smartphones have arisen, our society has chaned, making use of these new technological devices in teaching area. Videogames use arises as a new way of learning, so it complements the traditional methods of teaching. The main aim of serious videogames, in contrast to videogames which people usually buy in any store, is training instead of entertaining. Recreation is on a secondary plane. Serious games aren’t only designed for education but also for other institutions such as the army (to train the troops) and hospitals (as a rehabilitation method). Videogames development can be done by an individual on group of people if they have a bascis knowledge of programming. This is posible due to graphic motors have a lot of aids in the present. This project tries to make a tutorial that makes the design and development of serious games easier. A platform videogame in advance 2D has been made for the development of this tutorial.
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A trajetória de vida do publicitário, jornalista, contista, novelista, romancista e ensaísta Orígenes Lessa é rica em experiência profissional e conhecimento intelectual na propaganda e na literatura. O objetivo central deste trabalho foi o de resgatar seu itinerário na propaganda, seus valores, as técnicas de publicidade por ele utilizadas, bem como suas contribuições para a evolução da propaganda brasileira. O publicitário, detentor também de ampla produção literária, foi o primeiro presidente da APP Associação dos Profissionais de Propaganda. Trabalhou em uma das primeiras agências de publicidade do Brasil, a Eclética. Começou a atuar em 1928 na multinacional General Motors, depois em agências estrangeiras, como a J.W. Thompson, e em meios de comunicação nacionais, consolidando uma carreira de 57 anos dedicados à publicidade. Adotamos o método de pesquisa histórica buscando os vínculos entre a trajetória pessoal e profissional de Orígenes Lessa e o desenvolvimento da publicidade. Privilegiamos o período das décadas de 20 e 30, época de ativa militância do publicitário na área. Destacamos sua percepção do trabalho do redator publicitário, seus valores, principais trabalhos e as repercussões dos mesmos na sociedade brasileira.(AU)
Resumo:
A trajetória de vida do publicitário, jornalista, contista, novelista, romancista e ensaísta Orígenes Lessa é rica em experiência profissional e conhecimento intelectual na propaganda e na literatura. O objetivo central deste trabalho foi o de resgatar seu itinerário na propaganda, seus valores, as técnicas de publicidade por ele utilizadas, bem como suas contribuições para a evolução da propaganda brasileira. O publicitário, detentor também de ampla produção literária, foi o primeiro presidente da APP Associação dos Profissionais de Propaganda. Trabalhou em uma das primeiras agências de publicidade do Brasil, a Eclética. Começou a atuar em 1928 na multinacional General Motors, depois em agências estrangeiras, como a J.W. Thompson, e em meios de comunicação nacionais, consolidando uma carreira de 57 anos dedicados à publicidade. Adotamos o método de pesquisa histórica buscando os vínculos entre a trajetória pessoal e profissional de Orígenes Lessa e o desenvolvimento da publicidade. Privilegiamos o período das décadas de 20 e 30, época de ativa militância do publicitário na área. Destacamos sua percepção do trabalho do redator publicitário, seus valores, principais trabalhos e as repercussões dos mesmos na sociedade brasileira.(AU)
Resumo:
The internal mechanism of cilia is among the most ancient biological motors on an evolutionary scale. It produces beat patterns that consist of two phases: during the effective stroke, the cilium moves approximately as a straight rod, and during the recovery stroke, it rolls close to the surface in a tangential motion. It is commonly agreed that these two phases are designed for efficient functioning: the effective stroke encounters strong viscous resistance and generates thrust, whereas the recovery stroke returns the cilium to starting position while avoiding viscous resistance. Metachronal coordination between cilia, which occurs when many of them beat close to each other, is believed to be an autonomous result of the hydrodynamical interactions in the system. Qualitatively, metachronism is perceived as a way for reducing the energy expenditure required for beating. This paper presents a quantitative study of the energy expenditure of beating cilia, and of the energetic significance of metachronism. We develop a method for computing the work done by model cilia that beat in a viscous fluid. We demonstrate that for a single cilium, beating in water, the mechanical work done during the effective stroke is approximately five times the amount of work done during the recovery stroke. Investigation of multicilia configurations shows that having neighboring cilia beat metachronally is energetically advantageous and perhaps even crucial for multiciliary functioning. Finally, the model is used to approximate the number of dynein arm attachments that are likely to occur during the effective and recovery strokes of a beat cycle, predicting that almost all of the available dynein arms should participate in generating the motion.
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KIF (kinesin superfamily) proteins are microtubule-dependent molecular motors that play important roles in intracellular transport and cell division. The extent to which KIFs are involved in various transporting phenomena, as well as their regulation mechanism, are unknown. The identification of 16 new KIFs in this report doubles the existing number of KIFs known in the mouse. Conserved nucleotide sequences in the motor domain were amplified by PCR using cDNAs of mouse nervous tissue, kidney, and small intestine as templates. The new KIFs were studied with respect to their expression patterns in different tissues, chromosomal location, and molecular evolution. Our results suggest that (i) there is no apparent tendency among related subclasses of KIFs of cosegregation in chromosomal mapping, and (ii) according to their tissue distribution patterns, KIFs can be divided into two classes–i.e., ubiquitous and specific tissue-dominant. Further characterization of KIFs may elucidate unknown fundamental phenomena underlying intracellular transport. Finally, we propose a straightforward nomenclature system for the members of the mouse kinesin superfamily.
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Neuritic outgrowth is a striking example of directed motility, powered through the actions of molecular motors. Members of the myosin superfamily of actin-associated motors have been implicated in this complex process. Although conventional myosin II is known to be present in neurons, where it is localized at the leading edge of growth cones and in the cell cortex close to the plasma membrane, its functional involvement in growth cone motility has remained unproven. Here, we show that antisense oligodeoxyribonucleotides, complementary to a specific isoform of conventional myosin (myosin IIB), attenuate filopodial extension whereas sense and scrambled control oligodeoxyribonucleotides have no effect. Attenuation is shown to be reversible, neurite outgrowth being restored after cessation of the antisense regimen. Myosin IIB mRNA was present during active neurite extension, but levels were minimal in phenotypically rounded cells before neurite outgrowth and message levels decreased during antisense treatment. By contrast, the myosin IIA isoform is shown to be expressed constitutively both before and during neurite outgrowth and throughout exposure to myosin IIB antisense oligodeoxyribonucleotides. These results provide direct evidence that a conventional two-headed myosin is required for growth cone motility and is responsible, at least in part, for driving neuritic process outgrowth.
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Although microtubules (MTs) are generally thought to originate at the centrosome, a number of cell types have significant populations of MTs with no apparent centrosomal connection. The origin of these noncentrosomal MTs has been unclear. We applied kinetic analysis of MT formation in vivo to establish their mode of origin. Time-lapse fluorescence microscopy demonstrated that noncentrosomal MTs in cultured epithelial cells arise primarily by constitutive nucleation at, and release from, the centrosome. After release, MTs moved away from the centrosome and tended to depolymerize. Laser-marking experiments demonstrated that released MTs moved individually with their plus ends leading, suggesting that they were transported by minus end-directed motors. Released MTs were dynamic. The laser marking experiments demonstrated that plus ends of released MTs grew, paused, or shortened while the minus ends were stable or shortened. Microtubule release may serve two kinds of cellular function. Release and transport could generate the noncentrosomal MT arrays observed in epithelial cells, neurons, and other asymmetric, differentiated cells. Release would also contribute to polymer turnover by exposing MT minus ends, thereby providing additional sites for loss of subunits. The noncentrosomal population of MTs may reflect a steady-state of centrosomal nucleation, release, and dynamics.
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Vaccinia uses actin-based motility for virion movement in host cells, but the specific protein components have yet to be defined. A cardinal feature of Listeria and Shigella actin-based motility is the involvement of vasodilator-stimulated phosphoprotein (VASP). This essential adapter recognizes and binds to actin-based motility 1 (ABM-1) consensus sequences [(D/E)FPPPPX(D/E), X = P or T] contained in Listeria ActA and in the p90 host-cell vinculin fragment generated by Shigella infection. VASP, in turn, provides the ABM-2 sequences [XPPPPP, X = G, P, L, S, A] for binding profilin, an actin-regulatory protein that stimulates actin filament assembly. Immunolocalization using rabbit anti-VASP antibody revealed that VASP concentrates behind motile virions in HeLa cells. Profilin was also present in these actin-rich rocket tails, and microinjection of 10 μM (intracellular) ABM-2 peptide (GPPPPP)3 blocked vaccinia actin-based motility. Vinculin did not colocalize with VASP on motile virions and remained in focal adhesion contacts; however, another ABM-1-containing host protein, zyxin, was concentrated at the rear of motile virions. We also examined time-dependent changes in the location of these cytoskeletal proteins during vaccinia infection. VASP and zyxin were redistributed dramatically several hours before the formation of actin rocket tails, concentrating in the viral factories of the perinuclear cytoplasm. Our findings underscore the universal involvement of ABM-1 and ABM-2 docking sites in actin-based motility of Listeria, Shigella, and now vaccinia.
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Chemosensation in the nervous system of the nematode Caenorhabditis elegans depends on sensory cilia, whose assembly and maintenance requires the transport of components such as axonemal proteins and signal transduction machinery to their site of incorporation into ciliary structures. Members of the heteromeric kinesin family of microtubule motors are prime candidates for playing key roles in these transport events. Here we describe the molecular characterization and partial purification of two heteromeric kinesin complexes from C. elegans, heterotrimeric CeKinesin-II and dimeric CeOsm-3. Transgenic worms expressing green fluorescent protein driven by endogenous heteromeric kinesin promoters reveal that both CeKinesin-II and CeOsm-3 are expressed in amphid, inner labial, and phasmid chemosensory neurons. Additionally, immunolocalization experiments on fixed worms show an intense concentration of CeKinesin-II and CeOsm-3 polypeptides in the ciliated endings of these chemosensory neurons and a punctate localization pattern in the corresponding cell bodies and dendrites. These results, together with the phenotypes of known mutants in the pathway of sensory ciliary assembly, suggest that CeKinesin-II and CeOsm-3 drive the transport of ciliary components required for sequential steps in the assembly of chemosensory cilia.
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Proteins of the kinesin superfamily define a class of microtubule-dependent motors that play crucial roles in cell division and intracellular transport. To study the molecular mechanism of axonal transport, a cDNA encoding a new kinesin-like protein called KIF3C was cloned from a mouse brain cDNA library. Sequence and secondary structure analysis revealed that KIF3C is a member of the KIF3 family. In contrast to KIF3A and KIF3B, Northern and Western analysis indicated that KIF3C expression is highly enriched in neural tissues such as brain, spinal cord, and retina. When anti-KIF3C antibodies were used to stain the cerebellum, the strongest signal came from the cell bodies and dendrites of Purkinje cells. In retina, anti-KIF3C mainly stains the ganglion cells. Immunolocalization showed that the KIF3C motor in spinal cord and sciatic nerve is mainly localized in cytoplasm. In spinal cord, the KIF3C staining was punctate; double labeling with anti-giantin and anti-KIF3C showed a clear concentration of the motor protein in the Golgi complex. Staining of ligated sciatic nerves demonstrated that the KIF3C motor accumulated at the proximal side of the ligated nerve, which suggests that KIF3C is an anterograde motor. Immunoprecipitation experiments revealed that KIF3C and KIF3A, but not KIF3B, were coprecipitated. These data, combined with previous data from other labs, indicate that KIF3C and KIF3B are “variable” subunits that associate with a common KIF3A subunit, but not with each other. Together these results suggest that KIF3 family members combinatorially associate to power anterograde axonal transport.
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Bacterial flagellar motors rotate, obtaining power from the membrane gradient of protons or, in some species, sodium ions. Torque generation in the flagellar motor must involve interactions between components of the rotor and components of the stator. Sites of interaction between the rotor and stator have not been identified. Mutational studies of the rotor protein FliG and the stator protein MotA showed that both proteins contain charged residues essential for motor rotation. This suggests that functionally important electrostatic interactions might occur between the rotor and stator. To test this proposal, we examined double mutants with charged-residue substitutions in both the rotor protein FliG and the stator protein MotA. Several combinations of FliG mutations with MotA mutations exhibited strong synergism, whereas others showed strong suppression, in a pattern that indicates that the functionally important charged residues of FliG interact with those of MotA. These results identify a functionally important site of interaction between the rotor and stator and suggest a hypothesis for electrostatic interactions at the rotor–stator interface.
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By using elastic measurements on single DNA molecules, we show that stretching a negatively supercoiled DNA activates homologous pairing in physiological conditions. These experiments indicate that a stretched unwound DNA locally denatures to alleviate the force-driven increase in torsional stress. This is detected by hybridization with 1 kb of homologous single-stranded DNA probes. The stretching force involved (≈2 pN) is small compared with those typically developed by molecular motors, suggesting that this process may be relevant to DNA processing in vivo. We used this technique to monitor the progressive denaturation of DNA as it is unwound and found that distinct, stable denaturation bubbles formed, beginning in A+T-rich regions.
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Alpha herpesviruses infect the vertebrate nervous system resulting in either mild recurrent lesions in mucosal epithelia or fatal encephalitis. Movement of virions within the nervous system is a critical factor in the outcome of infection; however, the dynamics of individual virion transport have never been assessed. Here we visualized and tracked individual viral capsids as they moved in axons away from infected neuronal cell bodies in culture. The observed movement was compatible with fast axonal flow mediated by multiple microtubule motors. Capsids accumulated at axon terminals, suggesting that spread from infected neurons required cell contact.
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Efficient motility of the eukaryotic flagellum requires precise temporal and spatial control of its constituent dynein motors. The central pair and its associated structures have been implicated as important members of a signal transduction cascade that ultimately regulates dynein arm activity. To identify central pair components involved in this process, we characterized a Chlamydomonas motility mutant (pf6-2) obtained by insertional mutagenesis. pf6-2 flagella twitch ineffectively and lack the 1a projection on the C1 microtubule of the central pair. Transformation with constructs containing a full-length, wild-type copy of the PF6 gene rescues the functional, structural, and biochemical defects associated with the pf6 mutation. Sequence analysis indicates that the PF6 gene encodes a large polypeptide that contains numerous alanine-rich, proline-rich, and basic domains and has limited homology to an expressed sequence tag derived from a human testis cDNA library. Biochemical analysis of an epitope-tagged PF6 construct demonstrates that the PF6 polypeptide is an axonemal component that cosediments at 12.6S with several other polypeptides. The PF6 protein appears to be an essential component required for assembly of some of these polypeptides into the C1-1a projection.
Reciprocal electromechanical properties of rat prestin: The motor molecule from rat outer hair cells
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Cochlear outer hair cells (OHCs) are responsible for the exquisite sensitivity, dynamic range, and frequency-resolving capacity of the mammalian hearing organ. These unique cells respond to an electrical stimulus with a cycle-by-cycle change in cell length that is mediated by molecular motors in the cells' basolateral membrane. Recent work identified prestin, a protein with similarity to pendrin-related anion transporters, as the OHC motor molecule. Here we show that heterologously expressed prestin from rat OHCs (rprestin) exhibits reciprocal electromechanical properties as known for the OHC motor protein. Upon electrical stimulation in the microchamber configuration, rprestin generates mechanical force with constant amplitude and phase up to a stimulus frequency of at least 20 kHz. Mechanical stimulation of rprestin in excised outside-out patches shifts the voltage dependence of the nonlinear capacitance characterizing the electrical properties of the molecule. The results indicate that rprestin is a molecular motor that displays reciprocal electromechanical properties over the entire frequency range relevant for mammalian hearing.