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Search Results: 1 - 10 of 341651 matches for " Fernandes Jr. E. G. "
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Twenty years of research on cholesteric lyotropic liquid crystals at the Chemistry Institute of the University of S?o Paulo
Alcantara, M. R.;Fernandes Jr., E. G.;
Brazilian Journal of Physics , 2002, DOI: 10.1590/S0103-97332002000300009
Abstract: in this paper we present a review of twenty years of research on cholesteric liquid crystals at the chemistry institute of the university of s?o paulo. the results on the interaction forces, responsible for the maintenance of the helical structure, are a function of the chemical variability obtained in these systems. the last results obtained using rheological techniques are presented, and research in this field was undertaken in order to understand the cholesterization process when different systems and inductors are involved.
Twenty years of research on cholesteric lyotropic liquid crystals at the Chemistry Institute of the University of S o Paulo
Alcantara M. R.,Fernandes Jr. E. G.
Brazilian Journal of Physics , 2002,
Abstract: In this paper we present a review of twenty years of research on cholesteric liquid crystals at the Chemistry Institute of the University of S o Paulo. The results on the interaction forces, responsible for the maintenance of the helical structure, are a function of the chemical variability obtained in these systems. The last results obtained using rheological techniques are presented, and research in this field was undertaken in order to understand the cholesterization process when different systems and inductors are involved.
Collapse of the Cooper pair phase coherence length at a superconductor to insulator transition
S. M. Hollen,G. E. Fernandes,J. M. Xu,J. M. Valles Jr
Physics , 2013, DOI: 10.1103/PhysRevB.87.054512
Abstract: We present investigations of the superconductor to insulator transition (SIT) of uniform a-Bi films using a technique sensitive to Cooper pair phase coherence. The films are perforated with a nanohoneycomb array of holes to form a multiply connected geometry and subjected to a perpendicular magnetic field. Film magnetoresistances on the superconducting side of the SIT oscillate with a period dictated by the superconducting flux quantum and the areal hole density. The oscillations disappear close to the SIT critical point to leave a monotonically rising magnetoresistance that persists in the insulating phase. These observations indicate that the Cooper pair phase coherence length, which is infinite in the superconducting phase, collapses to a value less than the interhole spacing at this SIT. This behavior is inconsistent with the gradual reduction of the phase coherence length expected for a bosonic, phase fluctuation driven SIT. This result starkly contrasts with previous observations of oscillations persisting in the insulating phase of other films implying that there must be at least two distinct classes of disorder tuned SITs.
Caracteriza??o de solos altimontanos em dois transectos no Parque Estadual do Ibitipoca (MG)
Dias, H. C. T.;Schaefer, C. E. G. R.;Fernandes Filho, E. I.;Oliveira, A. P.;Michel, R. F. M.;Lemos Jr., J. B.;
Revista Brasileira de Ciência do Solo , 2003, DOI: 10.1590/S0100-06832003000300009
Abstract: little is known about the soil diversity of brazilian highland regions, despite their recent upgrading in view of the ecotouristic potential of some areas. chemical, mineralogical and micromorphological attributes of ten soil profiles along two transects in the quartzitic domains of the ibitipoca state park, minas gerais state, brazil, were studied in relation to their pedogenesis. at local level, soil formation is more closely associated with litho-structural elements (lithology, faults and fractures), than with topographical variations. the soils are al-saturated (> 60% at the surface), negatively charged, and markedly dystrophic. the existing cec is almost entirely attributable to the organic matter contribution, in view of the very low clay fraction activity. results revealed the marked presence of low crystallinity fe-forms, commonly found in high altitude vegetation, where organic matter accumulation inhibits fe and al oxide crystallization. all soils are kaolinitic, even the ferrocarbic spodosol, and some contain 2:1 clays such as illite and hydroxy-interlayered vermiculite, indicating their resistance to weathering under the present pedoenvironmental conditions. micromorphological analyses of the spodosol presented typical features of a podzolization process: predominant quartz grain interbedded between polymorphic organic matter aggregates at the surface, single grain structure and presence of "ortstein" in the spodic horizon (bs), formed by organic-mineral and mineral materials, monomorphic and fractured, with co-precipitated amorphous al, si and fe. the micropedological features of the spodic bs are similar to those of the "placic" horizon, with two depositional ferruginous covers; one reddish-brown (ferridrite and hematite) and the other yellowish (goethite). the intergranular plasma of the spodic horizon comprises two different plasmic zones: one of kaolinitic composition with a higher aluminium content, and a ferruginous one, richer in silica, suggesti
Efeitos dos excessos de alumínio, cloro e manganês em dois cultivares de soja (Glycine max (L.) Merrill)
Malavolta, E.;Freitas Jr., E. de;Andreola, F.;Cavalcante, F.S.;Solis, F.A.M.;Fernandes, J.M.;Santos, G.A,;Bertoloti, G.;Cabrini, H.M.;Carvalho Fo, H.C.;Rochelle, H.J.;Vieira, I.M.S.;Machado, I.S.;Eimori, I.E.;Andrioli, I.;Ribeiro, I.S.;Kaminski, J.;Jorge, J.A.;Carvalho, J.E.R.;
Anais da Escola Superior de Agricultura Luiz de Queiroz , 1980, DOI: 10.1590/S0071-12761980000100022
Abstract: two soybean cultivars, santa rosa and fv-1, were grown in nutrient solution in the presence of high concentrations of al (24 ppm), ci (1750 ppm) and mn (25 ppm). observations, measurements and chemical analyses allowed for the following conclusions to be drawn: (1) symptoms of toxicity are in agreement with those described in the literatura; (2) the detrimental effect obeyed the decreasing order - mn al ci; (3) dry matter production by the variety ufv - 1 was relatively more affected by the treatments; (4) leaf analyses do not provide a reliable indication of the sensitivity of the two varieties to the high levels of the three elements in the substrate; (5) ca/al ratio in the roots keeps a good relationship with the relative tolerance of the two cultivas to excess al in the medium.
Evaluation of Joint Sleep and Idle Mode in IEEE 802.16e WIMAX
Fuad M. Abinader Jr.,Vicente A. De Sousa Jr.,Anderson B. Fernandes,Adaildo G. Dassuncao
International Journal of Computer Science Issues , 2012,
Abstract: As energy availability limits usage time for mobile devices, modern wireless systems implement Power Saving Mechanisms (PSMs). Determining optimal PSM parameters and switch points when applying all PSM mechanisms jointly in the same scenario is a trade-off between power savings and system performance degradation. This work presents an unpublished performance study of the joint operation of Sleep Mode and Idle Mode on an accurate 802.16e PSM NS-2 simulation implementation, with the MS experiencing two different classes of Internet traffic, namely HTTP Web Browsing and Always-On traffic. We first determine which set of PSM parameters influence the most on power savings and performance degradation (in terms of TCP retransmissions) via a 2k.r factorial analysis. Then, we explore those PSM parameters via full factorial analysis in order to determine optimal transition points between Sleep Mode and Idle Mode, such that we achieve power savings without high performance degradation. Results showed that although we managed to obtain good power saving results for a wide range of PSM parameters, performance degradation can be substantial if the Sleep Mode Inactivity Timer is such that PSM is activated within TCP RTT or the timers for Sleep Mode and Idle Mode are such that there is a € competition€ between which PSM mechanism should be activated. Under established conditions, we observe a significant power saving gains followed by a surprising system performance enhancement.
Optical Tractor Beam with Chiral Light
David E. Fernandes,Mário G. Silveirinha
Physics , 2015,
Abstract: We suggest a novel mechanism to induce the motion of a chiral material body towards an optical source. Our solution is based on the interference between a chiral light beam and its reflection on an opaque mirror. Surprisingly, it is theoretically shown that the electromagnetic response of the material may be tailored in such a way that independent of the specific body location with the respect to the mirror, it is always pushed upstream against the photon flow associated with the incoming wave. Moreover, it is proven that by controlling the handedness of the incoming light it may be possible to harness the sign of the optical force, switching from a pulling force to a pushing force.
Statistical behavior and symmetry tests
Mitchell, G. E.;Shriner, Jr, J. F.;
Brazilian Journal of Physics , 2004, DOI: 10.1590/S0103-97332004000500023
Abstract: symmetries and statistical properties in nuclei are closely related. the most striking example is the extremely large enhancement of parity violation in neutron resonances. statistical distributions can provide information about the underlying character of nuclear properties. level statistics and electromagnetic transition distributions have been used successfully to provide unique tests of predictions of random matrix theory.
Mineralogical Appraisal of Sediments of Duricrust Suites and Pans around Jwaneng Area, Botswana
JR Atlhopheng, G-I E Ekosse
Journal of Applied Sciences and Environmental Management , 2007,
Abstract: A mineralogical investigation of duricrust suites in Letlhakeng valley, and five pans around Jwaneng in Botswana was undertaken in order to know the mineral assemblages and infer on their landscape formation. In Letlhakeng, duricrusts comprised calcretes, silcretes and ferricretes. Calcretes were dominated by the minerals: calcite, quartz and to a lesser extent dolomite. Silcrete mineralogy was dominated by quartz, opal, and some occurrences of palygorskite, microcline and rutile. The intermediate forms of cal-silcretes yielded quartz, muscovite, and kaolinite. Ferricretes occurred on an area of the valley capping, with minerals dominated by goethite and haematite. The indurates are believed to have been formed through groundwater mechanisms. The general lowering of the valley, led to precipitation of the duricrusts. The pans were dominated by calcrete and silcrete only. The calcretes mineralogy was mainly calcite, dolomite and quartz. Illite-montmorillonite and sepiollite were also present. Samples of pan clay floor, other than being dominated by calcite, dolomite and quartz, also had sepiollite ferrian. Pans and valleys are accumulation sites, with polygenetic modes of genesis. The duricrusts have undergone several alterations throughout time.
Electronic band structure of polytypical nanowhiskers: a theoretical approach based on group theory and k$\cdot$p method
P. E. Faria Jr,G. M. Sipahi
Physics , 2012,
Abstract: Semiconductor nanowhiskers made of III-V compounds exhibit great potential for technological applications. Controlling the growth conditions, such as temperature and diameter, it is possible to alternate between zinc blend and wurtzite crystalline phases, giving origin to the so called polytypism. This effect has great influence in the electronic and optical properties of the system, generating new forms of confinement to the carriers. A theoretical model capable to accurately describe electronic and optical properties in these polytypical nanostructures can be used to study and develop new kinds of nanodevices. In this study, we present the development of a wurtzite/zincblend polytypical model to calculate the electronic band structure of nanowhiskers based on group theory concepts and the k$\cdot$p method. Although the interest is in polytypical superlattices, the proposed model was applied to a single quantum well of InP to extract the physics of the wurtzite/zincblend polytypism. By the analysis of our results, some trends can be predicted: spatial carriers' separation, predominance of perpendicular polarization (xy plane) in the luminescence spectra and interband transition blueshifts with strain. A possible range of values for the WZ InP spontaneous polarization was suggested.
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