196,336 research outputs found
Band structure of a two-dimensional ferromagnetic antidot lattice
No full textThe spin wave band structure of a two-dimensional square array of NiFe circular
antidots having diameter of 120 nm and periodicity of 800 nm has been investigated by
using Brillouin light scattering technique and micromagnetic calculations based on the
dynamical matrix method [1]. The external magnetic field was applied in the plane and
perpendicularly to the transferred wave vector. Extended and localized spin modes
having a propagative nature were found. Opening of bandgaps is interpreted in terms of
Bragg diffraction of spin waves from the antidot lattice and this effect is explained by
studying the behaviour of the internal field as shown in Fig.1. The mean internal field is
larger along the vertical rows of antidots and smaller between the antidots (see panel (a)
for extended modes and (c) for localized modes). By developing an analytical model
according to which the mean internal field is represented by means of a rectangular step
function characterized by a region 1 corresponding to vertical rows of antidots and a
region 2 between the antidots (see panels (b) and (d)), the relevant scattering potential
for Bragg reflection is not provided by the holes themselves, but by the concomitant
internal field inhomogeneity between holes [2]. This is in contrast to antidots in
photonics and electronics where the back-reflection is directly caused by the presence of
holes. The research leading to these results has received funding from the European
Community's Seventh Framework Programme (FP7/2007-2013) under Grant
Agreement n228673 (MAGNONICS).
[1] L. Giovannini, F. Montoncello, and F. Nizzoli, Phys. Rev. B 75, 024416 (2007).
[2] R. Zivieri, S. Tacchi, F. Montoncello, L. Giovannini, F. Nizzoli, M. Madami, G.
Gubbiotti, G. Carlotti, S. Neusser, G. Duerr, and D. Grundler, Phys. Rev. B 83, (2012)
Spin wave band structure of a two-dimensional ferromagnetic antidot array -- Presentazione orale by R. Zivieri - Conferenza internazionale
No full textThe spin wave band structure of a two-dimensional square array of NiFe circular antidots (ADs) has been investigated both experimentally and theoretically by using Brillouin light scattering (BLS) technique and micromagnetic calculations, carried out by means of the dynamical matrix method (DMM) with implemented periodic boundary conditions [1]. Sample consists of 22 nm NiFe film with etched circular having diameter of 120 nm and periodicity of 800 nm. As depicted in the inset to Fig.1, the external magnetic field is applied along y direction, while the transferred wave vector is along x direction. Both the experimental measurements and the calculated spin wave dispersion provide evidence for either extended or localized magnonic modes having a propagative nature. Extended modes spreading in the “horizontal” channels comprised between adjacent rows of ADs have a non-vanishing precession amplitude also along the horizontal rows of holes. These spin-wave modes are labelled as DEnBZ (black curves) where nBZ denotes a given Brillouin zone with n=1,2,.. Instead, the other kind of spin-wave modes, mainly localized along the horizontal rows of antidots, the so-called localized modes [2], are labelled as DElocnBZ (red curves). Both families of modes exhibit bandgaps at Brillouin zone boundaries predicted by the DMM calculations. Opening of bandgaps is interpreted in terms of Bragg diffraction of spin waves from the AD lattice and a quantitative explanation of this effect is given by studying the behavior of the mean internal field. The calculated mean internal field experienced by the two kind of modes is strongly inhomogeneous and is larger in correspondence of ADs. The DE2BZ mode exhibits its maximum precession amplitude where the internal field is larger (smaller) and has thus a larger (smaller) frequency. Band gaps are also calculated within the analytical model according to a perturbation approach. The eigenfunctions representing frequency modes at the BZs boundaries belonging to n-th and (n+1)-th band (sin (k π / a) x and cos (k π / a) x with k = 1,2,.., respectively) are interchanged with respect to those of electrons in electronic bands studied within the nearly-free electron model. This can be understood taking into account that the periodic mean internal field has its maxima in correspondence of ADs, while the periodic electronic potential is minimum close to the nuclei and vice versa. A comparison between the bandgap measured by BLS and the values calculated by means of the analytical model and by using the DMM is shown in Table 1. According to the analytical model, it is found that the relevant scattering potential for Bragg reflection is not provided by the holes themselves, but by the concomitant internal field inhomogeneity between holes [3]. This is in contrast to antidots in photonics and electronics where the back-reflection is directly caused by the presence of holes. The results of this study are important also for the potential applications of these patterned structures that can be used in magnonic devices. Indeed, AD behaves not only as waveguide for spin waves, but the presence of bandgaps permits to filter the frequency of travelling excitations. In this way, AD can be used also as a filter for spin waves.
The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement n228673 (MAGNONICS).
[1] L. Giovannini, F. Montoncello, and F. Nizzoli, Phys. Rev. B 75, 024416 (2007)
[2] S. Tacchi, M. Madami, G. Gubbiotti, G. Carlotti, A.O. Adeyeye, S. Neusser, B. Botters, and D. Grundler,
IEEE Trans. Magn. 46, 172 (2010)
[3] R. Zivieri, S. Tacchi, F. Montoncello, L. Giovannini, F. Nizzoli, M. Madami, G. Gubbiotti, G. Carlotti, S.
Neusser, G. Duerr, and D. Grundler, “Bragg diffraction of spin waves from a two dimensional antidot lattice
”, in press in Physical Review B --
Presentazione orale by R. Zivieri - Conferenza internazional
Impact of moisture buffering on indoor climate for mechanically ventilated offices.
No full textThe aim of this work is to demonstrate the reliability of a simplified model in predicting the RH variation inside a room, taking into account the indoor material buffering effect.
Starting from the characterization of the main hygroscopic properties of wood fiber an analysis of reliability of measured data for vapour permeability and sorption isotherm and their influence on numerical simulation is carried out. The determination of measured
Moisture Buffer Value for the wood fiber is carried out through the simulation of the MBV test for uncoated elements. The results are compared to those from literature.
The ventilation influence as room factor is taken into account for the whole room hygroscopic performance. More scenarios for different mechanical ventilation rates are foreseen considering a demand controlled and a fixed volume airflow. Simulations are carried out considering Turin weather data
Impatto del moisture buffering sul clima interno di uffici ventilati meccanicamente
No full textThe aim of this work is to demonstrate the reliability of measured hygroscopic properties of materials in predicting the RH variation inside a room taking into account the material’s buffering effect.
An analysis of reliability of the measured hygroscopic properties and their influence on numerical simulation is carried out.
The influence of an important room factor as ventilation on the moisture buffer is taken into account for different scenarios
Cryptic species in tropic sands--interactive 3D anatomy, molecular phylogeny and evolution of meiofaunal Pseudunelidae (Gastropoda, Acochlidia)
No full textTowards realistic estimations of the diversity of marine animals, tiny meiofaunal species usually are underrepresented. Since the biological species concept is hardly applicable on exotic and elusive animals, it is even more important to apply a morphospecies concept on the best level of information possible, using accurate and efficient methodology such as 3D modelling from histological sections. Molecular approaches such as sequence analyses may reveal further, cryptic species. This is the first case study on meiofaunal gastropods to test diversity estimations from traditional taxonomy against results from modern microanatomical methodology and molecular systematics
The evolutionary history of human chromosome 7
No full textWe report on a comparative molecular cytogenetic and in silico study on evolutionary changes in human chromosome 7 homologs in all major primate lineages. The ancestral mammalian homologs comprise two chromosomes (7a and 7b/16p) and are conserved in carnivores. The subchromosomal organization of the ancestral primate segment 7a shared by a lemur and higher Old World monkeys is the result of a paracentric inversion. The ancestral higher primate chromosome form was then derived by a fission of 7b/16p, followed by a centric fusion of 7a/7b as observed in the orangutan. In hominoids two further inversions with four distinct breakpoints were described in detail: the pericentric inversion in the human/African ape ancestor and the paracentric inversion in the common ancestor of human and chimpanzee. FISH analysis employing BAC probes confined the 7p22.1 breakpoint of the pericentric inversion to 6.8 Mb on the human reference sequence map and the 7q22.1 breakpoint to 97.1 Mb. For the paracentric inversion the breakpoints were found in 7q11.23 between 76.1 and 76.3 Mb and in 7q22.1 at 101.9 Mb. All four breakpoints were flanked by large segmental duplications. Hybridization patterns of breakpoint-flanking BACs and the distribution of duplicons suggest their presence before the origin of both inversions. We propose a scenario by which segmental duplications may have been the cause rather than the result of these chromosome rearrangement
Chromosome Evolution in New World Monkeys (Platyrrhini)
No full textDuring the last decades, New World monkey (NWM, Platyrrhini, Anthropoideae) comparative cytogenetics has shed light on many fundamental aspects of genome organisation and evolution in this fascinating, but also highly endangered group of neotropical primates. In this review, we first provide an overview about the evolutionary origin of the inferred ancestral NWM karyotype of 2n = 54 chromosomes and about the lineage-specific chromosome rearrangements resulting in the highly divergent karyotypes of extant NWM species, ranging from 2n = 16 in a titi monkey to 2n = 62 in a woolly monkey. Next, we discuss the available data on the chromosome phylogeny of NWM in the context of recent molecular phylogenetic analyses. In the last part, we highlight some recent research on the molecular mechanisms responsible for the large-scale evolutionary genomic changes in platyrrhine monkeys. Copyright (C) 2012 S. Karger AG, Base
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Figure 1 in Redescription and three-dimensional reconstruction of the limnic acochlidian gastropod Strubellia paradoxa (Strubell, 1892) (Gastropoda: Euthyneura) from Ambon, Indonesia
No full textFigure 1. Three-dimensional reconstruction of general anatomy, central nervous (CNS), circulatory, excretory, and anterior digestive systems of Strubellia paradoxa, paratype. (A) External morphology (contracted specimen, right view), arrowhead indicates position of diaphragm between head–foot and visceral sac; (B) overview of microanatomy showing internal organ systems; (C) CNS (posterior view, buccal ganglia omitted); (D) CNS, including buccal ganglia at left (right view); (E) excretory and circulatory systems (ventrolateral right view), asterisk indicates intersection between kidney and nephroduct; (F) buccal apparatus and anterior pedal gland, right view, asterisks indicate ciliated part of oesophagus. Abbreviations: ao, aorta; au, auricle; bc, bursa copulatrix; bg, buccal ganglion; bm, buccal mass; ccm, cerebral commissure; cg, cerebral ganglion; cns, central nervous system; dg, digestive gland; dkd, distal lumen of kidney; es, oesophagus; ey, eye; ft, foot; go, gonad; gog, gastro-oesophageal ganglion; gp, genital pore; ht, heart; kd, kidney; ln, labial tentacle nerve; nd, nephroduct; ndl, distal loop of nephroduct; np, position of nephroporus; oc, odontophore cavity; on, optic nerve; opt, opticalPublished as part of Brenzinger, B., Neusser, T.P., Glaubrecht, M., Haszprunar, G. & Schrödl, M., 2010, Redescription and three-dimensional reconstruction of the limnic acochlidian gastropod Strubellia paradoxa (Strubell, 1892) (Gastropoda: Euthyneura) from Ambon, Indonesia, pp. 183-209 in Journal of Natural History 45 (3-4) on page 186, DOI: 10.1080/00222933.2010.521862, http://zenodo.org/record/521243
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
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