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  • 1
    Electronic Resource
    Electronic Resource
    Direct measurements of magnetostrictive process in amorphous wires using a scanning tunneling microscope (abstract) : The 6th joint magnetism and magnetic materials (MMM)-intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7030-7030 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a new and versatile method to measure, on a nanometric scale directly, the magnetostrictive properties during the magnetization process to saturation, using a modified scanning tunneling microscope (STM). Both positive and negative magnetostrictive amorphous as-quenched wires have been studied. The studied samples are single pieces of amorphous wires typically 125 μm in diameter and 10–15 mm long. The magnetostriction data are then correlated with the longitudinal magnetization process, measured by a conventional induction technique and by SQUID magnetometry. The longitudinal magnetization process measurements have been performed in the same wires used in the STM studies. The field dependence of the magnetostriction helps to discern the operative magnetization process in the wires. In a 12-mm-long Co-based amorphous wire we observe a continuous rotation of the magnetization from zero field to saturation. The field dependence of the magnetization is a linear process reaching a value of about 5100 G at 8 Oe applied field. The magnetostrictive process for the same wire measured with a STM shows a continuous shrinking of the samples as a function of the applied field, reaching a value of −280 A(ring) for 8 Oe applied field. The obtained δl/l||sat, −2.3×10−6, agrees well with reported values of the saturation magnetostriction constant for this wire. In a 15-mm-long Fe-based amorphous wire we observe a more complicated field dependence of both the magnetization and the magnetostriction processes from zero-field to saturation.The longitudinal magnetization saturates at about 14000 G for 60 Oe applied field. The magnetostrictive process for the same wire measured with STM shows an elongation onset at about 1 Oe, pointing unambiguously to a 180° domain wall movement as the operative magnetization process below this field value. The field dependence of the magnetostriction saturates at about +5000 A(ring) for 60 Oe applied field. The obtained δl/l||sat, about +3.3×10−5, is again consistent with reported values of the saturation magnetostriction constant. Thus the STM approach to determine λ, on an A(ring) length scale, gives us a distinct great advantage in studying the magnetization process towards saturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358077
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  • 2
    Electronic Resource
    Electronic Resource
    Giant magnetoresistive sensors for rotational speed control (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5459-5461 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article demonstrates spin valve (sv) sensor applications as rotational speed control devices, in a Wheatstone bridge configuration. The sensor architecture uses two active self-biased sv elements (dimensions 400×6 μm2) in a CoZrNb flux guide. The other two spin valves are inactivated for external fields inferior to 150 Oe. Inactivation is achieved by increasing the ferromagnetic coupling of the inactive spin valves above 200 Oe, by roughening the surface of the underlying oxide layer (12 Å average roughness). When excited by a magnetized wheel with 60 N-S poles rotating at 360 rpm, the sensor yields a 400 mV pp square wave output with rise/fall times corresponding to an angular resolution of 0.17°. Amplitude is independent of speed (0–3000 rpm), and of sensor to wheel separation (0.5≤d(mm)≤2.0). Bridge output decreases 26% when temperature is increased to 150 °C. Bridge offset of 350 mV is caused by the resistance differences between the active and inactive sv elements. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369975
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetostrictive influence on the bistability of amorphous wires (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1164-1168 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effect of tension and external field on the magnetization process in amorphous positive magnetostrictive Fe-Si-B wires. The radial stress created during the in-rotating water quenching technique of producing these wires causes a radial anisotropy. Using a simple phenomenological model which assumes a continuous distribution for the values of these radial stresses, we fit the observed values of the remanence as a function of the applied longitudinal stress and obtain information about the stress distribution. We also explain in a consistent manner the dependence of the magnetization process on the applied longitudinal stress. On doing so, a value of the saturation magnetostriction constant λs=28×10−6 is obtained for a Fe77.5Si7.5B15 amorphous wire. In the stress dependence of the nucleation field for the Barkhausen jump we observe a minimum. A quantitative explanation for this minimum is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346712
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  • 4
    Electronic Resource
    Electronic Resource
    Tunneling measurements of the energy gap in Tl- and Bi-based oxide superconductors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5026-5028 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss the behavior found in tunneling measurements obtained by us on two high-Tc superconductors—a ceramic sample of Tl2Ca2Ba2Cu3O10+δ and a Bi4Ca3Sr3Cu4O16+δ single crystal—using a scanning tunneling microscope. We compare some of the experimental curves with simple model calculations, assuming different tunnel-barrier shapes (i.e., different barrier heights, degree of asymmetry, thickness, etc.), and also different quasiparticle density-of-states profiles and tunnel-junction configurations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344712
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  • 5
    Electronic Resource
    Electronic Resource
    Direct measurements of magnetostrictive process in amorphous wires using scanning tunneling microscopy (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3374-3376 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a versatile capability to measure directly the magnetostrictive properties through the magnetization process on a nanometric scale using a modified scanning tunneling microscope. Single 10 mm long, 125 μm diam amorphous wires of both positive and negative magnetostriction have been studied and the data are compared with the hysteretic loops determined by both ac and SQUID magnetic measurements. This improved technique promises interesting possibilities, from both fundamental and applications points of view, in a number of scientific disciplines especially of interest in life and environmental sciences. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113762
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  • 6
    Electronic Resource
    Electronic Resource
    Variation in bilateral asymmetry of the Lusitanian toadfish along the Portuguese coast (2005)
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 21 (2005), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Three types of bilateral asymmetry [antisymmetry (AS), directional asymmetry (DA) and fluctuating asymmetry (FA)] have long been recognized in the literature. It is often assumed that DA and AS have a larger genetic basis than FA, which therefore provides a measure of developmental stability. To examine changes in bilateral asymmetry of the Lusitanian toadfish, Halobatrachus didactylus (Bloch & Schneider, 1801), collected in 10 localities along the Portuguese coast, the distribution of left–right values of three external and two internal morphometric variables and one meristic variable were evaluated for normality and deviations of the mean to 0; kurtosis and skewness were also determined. AS was found for the majority of variables in all locations, although DA was also very frequent. FA was observed in only four locations for three variables. A general pattern of negative and low Spearman correlations between asymmetry levels and concentrations of heavy metals and pollutants and mean heterozygosity was found. However, exceptions to this pattern indicate that different asymmetry types can occur across the distribution range in a single trait and that the three types of asymmetry are dynamically interrelated, the shifts from FA to the other two types possibly being due to environmental stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0426.2005.00627.x
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  • 7
    Electronic Resource
    Electronic Resource
    Metazoan parasites as biological indicators of population structure of Halobatrachus didactylus on the Portuguese coast (2005)
    Berlin, Germany : Blackwell Verlag GmbH
    Journal of applied ichthyology 21 (2005), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A total of 366 Halobatrachus didactylus (Bloch & Schneider 1801) individuals were obtained between September and November 2000 from commercial fishing vessels at eight localities along the Portuguese coast and analysed for metazoan parasite infections. Three species of parasites were found: Hysterothylacium aduncum Rudolphi 1802; Progrillotia dasyatidis Beveridge et al. 2004, which constitutes a new host record for the Lusitanian toadfish; and Nerocila orbignyi Guérin-Méneville 1829. Prevalence and mean abundance were determined for the total fish population in each sample. Significant differences in the number of parasitized fish among the samples analysed indicate differences in the H. didactylus populations along the Portuguese coast. The cluster analysis performed to prevalence data pointed out two major clusters: one composed of mainly estuarine samples and one that grouped samples from coastal areas; this is in agreement with the results obtained by morphological and genetic analysis performed for the same samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0426.2005.00655.x
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  • 8
    Electronic Resource
    Electronic Resource
    On the food of the European eel, Anguilla anguilla (L.), in the upper zone of the Tagus estuary, Portugal (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 41 (1992), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The estuarine food habits of the European eel, Anguilla anguilla (L.), in the upper zone of the Tagus estuary have been studied through the analysis of 210 specimens collected during 1988. Eels, measuring from 136 to 627 mm in total length, fed on prey organisms ranging from 2.0 to 76.0 mm in length. Amphipods and the shore crab, Carcinus maenas (L.), were the most important food items found. In more saline muddy bottom areas polychaetes, bivalves and shrimp increased their importance as prey, replacing the amphipods as preferential food. Fish were always a secondary, although significant, prey item. The occurrence of seasonal variations in eels' diet could be attributed to fluctuations in prey densities. There was evidence of a close relationship between the quantity of prey organisms in the benthos and the composition of eels' stomach contents, but a certain degree of food selection based on size, concealment capacity and motility of prey, was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1992.tb02712.x
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  • 9
    Electronic Resource
    Electronic Resource
    Age determination in Pomatoschistus mi nut us (Pallas) and Pomatoschistus microps (Kreyer) (Pisces: Gobiidae) from the upper Tagus estuary, Portugal (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 39 (1991), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The use of scale inspection as a means of age-determination in Pomatoschistus microps and Pomatoschistus minutus in the Tagus estuary is confirmed, but annulus formation pattern is different from that described for P. microps in the area of the British Isles (Miller, 1975). In Britain, two annuli are laid down on the scales each year, but in the Tagus, only one annulus is formed. One possible reason for this difference is the fact that in the Tagus the peak breeding season and the lowest water temperatures coincide. Therefore, the two causes of annulus formation coexist at the same time of year.Population structure in both species is dominated by the 0-group, which appears earlier (April/May) than reported for other areas. Maximum age seems not to exceed 26 months in P. microps and 32 months in P. minutus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1991.tb04374.x
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  • 10
    Electronic Resource
    Electronic Resource
    The feeding strategies of Liza ramada (Risso, 1826) in fresh and brackish water in the River Tagus, Portugal (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 42 (1993), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The stomach contents of samples of the mugilid Liza ramada (Risso, 1826), captured at Alcochete (brackish water zone of the Tagus Estuary) differed from those from Vala Nova (freshwater zone of the same estuary).In the freshwater zone of the estuary the mullet ingested preferentially planktonic micro-algae, while in the brackish water they ate benthic micro-algae.The stomach contents from Vala Nova showed a higher diversity of food items, compared with those from Alcochete. At Alcochete the Naviculales (numerical frequency, 82%) was the most representative order, while at Vala Nova it was the Coscinodiscales (61%) and the Chlorococcales (16%).In fresh water, the stomach contents contained about 25–4% organic matter, while at Alcochete only 8.7% was found.In the brackish water zone the ingestion rhythm was related to the tidal cycle, attaining a maximum during the high tide and a minimum at low tide.At Vala Nova the mullet ate regularly throughout the day. showing a slight increase at dawn and dusk. Apparently, the fish remained inactive by night, at both locations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1993.tb00308.x
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