5,213 research outputs found
Relaxation of the field-cooled magnetization of an Ising spin glass
The time and temperature dependence of the field-cooled magnetization of a
three dimensional Ising spin glass, Fe_{0.5}Mn_{0.5}TiO_{3}, has been
investigated. The temperature and cooling rate dependence is found to exhibit
memory phenomena that can be related to the memory behavior of the low
frequency ac-susceptibility. The results add some further understanding on how
to model the three dimensional Ising spin glass in real space.Comment: 8 pages RevTEX, 5 figure
Non-equilibrium dynamics in an interacting nanoparticle system
Non-equilibrium dynamics in an interacting Fe-C nanoparticle sample,
exhibiting a low temperature spin glass like phase, has been studied by low
frequency ac-susceptibility and magnetic relaxation experiments. The
non-equilibrium behavior shows characteristic spin glass features, but some
qualitative differences exist. The nature of these differences is discussed.Comment: 7 pages, 11 figure
Memory and superposition in a spin glass
Non-equilibrium dynamics in a Ag(Mn) spin glass are investigated by
measurements of the temperature dependence of the remanent magnetisation. Using
specific cooling protocols before recording the thermo- or isothermal remanent
magnetisations on re-heating, it is found that the measured curves effectively
disclose non-equilibrium spin glass characteristics such as ageing and memory
phenomena as well as an extended validity of the superposition principle for
the relaxation. The usefulness of this "simple" dc-method is discussed, as well
as its applicability to other disordered magnetic systems.Comment: REVTeX style; 8 pages, 4 figure
Protein crystals in adenovirus type 5-infected cells: requirements for intranuclear crystallogenesis, structural and functional analysis
Intranuclear crystalline inclusions have been observed in the nucleus of epithelial cells infected with Adenovirus serotype 5 (Ad5) at late steps of the virus life cycle. Using immuno-electron microscopy and confocal microscopy of cells infected with various Ad5 recombinants modified in their penton base or fiber domains, we found that these inclusions represented crystals of penton capsomers, the heteromeric capsid protein formed of penton base and fiber subunits. The occurrence of protein crystals within the nucleus of infected cells required the integrity of the fiber knob and part of the shaft domain. In the knob domain, the region overlapping residues 489–492 in the FG loop was found to be essential for crystal formation. In the shaft, a large deletion of repeats 4 to 16 had no detrimental effect on crystal inclusions, whereas deletion of repeats 8 to 21 abolished crystal formation without altering the level of fiber protein expression. This suggested a crucial role of the five penultimate repeats in the crystallisation process. Chimeric pentons made of Ad5 penton base and fiber domains from different serotypes were analyzed with respect to crystal formation. No crystal was found when fiber consisted of shaft (S) from Ad5 and knob (K) from Ad3 (heterotypic S5-K3 fiber), but occurred with homotypic S3K3 fiber. However, less regular crystals were observed with homotypic S35-K35 fiber. TB5, a monoclonal antibody directed against the Ad5 fiber knob was found by immunofluorescence microscopy to react with high efficiency with the intranuclear protein crystals in situ. Data obtained with Ad fiber mutants indicated that the absence of crystalline inclusions correlated with a lower infectivity and/or lower yields of virus progeny, suggesting that the protein crystals might be involved in virion assembly. Thus, we propose that TB5 staining of Ad-infected 293 cells can be used as a prognostic assay for the viability and productivity of fiber-modified Ad5 vectors
Evidence-Based Professional Development of Science Teachers in Two Countries
The focus of this collaborative research project of King?s College London, and the Weizmann Institute, Israel. project is on investigating the ways in which teachers can demonstrate accomplished teaching in a specific domain of science and on the teacher learning that is generated through continuing professional development programs (CPD) that lead towards such practice. The interest lies in what processes and inputs are required to help secondary school science teachers develop expertise in a specific aspect of science teaching. `It focuses on the design of the CPD programmes and examines the importance of an evidence-based approach through portfolioconstruction in which professional dialogue pathes the way for teacher learning. The set of papers highlight the need to set professional challenge while tailoring CPD to teachers? needs to create the environment in which teachers can advance and transform their practice. The cross-culture perspective added to the richness of the development and enabled the researchers to examine which aspects were fundamental to the design by considering similarities and differences between the domains
Optical properties of carbon nanofiber photonic crystals
Carbon nanofibers (CNF) are used as components of planar photonic crystals.
Square and rectangular lattices and random patterns of vertically aligned CNF
were fabricated and their properties studied using ellipsometry. We show that
detailed information such as symmetry directions and the band structure of
these novel materials can be extracted from considerations of the polarization
state in the specular beam. The refractive index of the individual nanofibers
was found to be n_CNF = 4.1.Comment: 10 pages, 4 figure
Short range ferromagnetism and spin glass state in
Dynamic magnetic properties of are
reported. The system appears to attain local ferromagnetic order at
K. Below this temperature the low field
magnetization becomes history dependent, i.e. the zero field cooled (ZFC) and
field cooled (FC) magnetization deviate from each other and closely logarithmic
relaxation appears at our experimental time scales (0.3- sec). The zero
field cooled magnetization has a maximum at K,
whereas the field cooled magnetization continues to increase, although less
sharply, also below this temperature. Surprisingly, the dynamics of the system
shows non-equilibrium spin glass (SG) features not only below the maximum in
the ZFC magnetization, but also in the temperature region between this maximum
and . The aging and temperature cycling experiments show only
quantitative differences in the dynamic behavior above and below the maximum in
the ZFC-magnetization; similarly, memory effects are observed in both
temperature regions. We attribute the high temperature behavior to the
existence of clusters of short range ferromagnetic order below
; the configuration evolves into a conventional spin glass
state at temperatures below .Comment: REVTeX style; 8 pages, 8 figure
Fatal myocardial infarction after lung resection in a patient with prophylactic preoperative coronary stenting†
In this report we present the case of a 77-yr-old man who underwent resection of the upper lobe of the left lung for a carcinoma, six weeks after percutaneous transluminal coronary angioplasty (PTCA) with stenting of the left anterior descending (LAD) and circumflex coronary arteries. Antiplatelet therapy with clopidogrel was interrupted two weeks before surgery to allow for epidural catheter placement and to minimize haemorrhage. The surgical procedure was uneventful. In the immediate postoperative period, however, the patient suffered severe myocardial ischaemia. Emergency coronary angiography showed complete thrombotic occlusion of the LAD stent. In spite of successful recanalization, reinfarction occurred and the patient died in cardiogenic shock. Prophylactic preoperative coronary stenting may put the patient at risk of stent thrombosis if surgery cannot be postponed for three months. In such cases, other strategies such as perioperative β-blockade for preoperative cardiac management should be considered. Br J Anaesth 2004; 92: 743-
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