Ferromagnetic semiconductors

The current status and prospects of research on ferromagnetism in semiconductors are reviewed. The question of the origin of ferromagnetism in europium chalcogenides, chromium spinels and, particularly, in diluted magnetic semiconductors is addressed. The nature of electronic states derived from 3d of magnetic impurities is discussed in some details. Results of a quantitative comparison between experimental and theoretical results, notably for Mn-based III-V and II-VI compounds, are presented. This comparison demonstrates that the current theory of the exchange interactions mediated by holes in the valence band describes correctly the values of Curie temperatures T_C magnetic anisotropy, domain structure, and magnetic circular dichroism. On this basis, chemical trends are examined and show to lead to the prediction of semiconductor systems with T_C that may exceed room temperature, an expectation that are being confirmed by recent findings. Results for materials containing magnetic ions other than Mn are also presented emphasizing that the double exchange involving hoping through d states may operate in those systems.Comment: 18 pages, 8 figures; special issue of Semicon. Sci. Technol. on semiconductor spintronic

EPR Studies for GdBa2Cu3 O 7−δ Added with Nanosized Ferrite ZnFe2 O 4 Before and After Irradiation by 3 MeV H+ Ions

(ZnFe2O4)xGdBa2Cu3O7−δ superconducting samples, 0 ≤ x ≤ 0.40 wt%, were synthesized using a conventional solid-state reaction technique. The prepared samples were investigated using electron paramagnetic resonance (EPR) measurements. EPR measurements were carried out, at different temperatures 100 K ≤ T ≤ 300 K, for the prepared samples before and after irradiation by 3 MeV protons. An isotropic symmetric EPR line with g factor ≈2 is detected for the samples before irradiation, corresponding to Gd3+ ions. A single strong and broad isotropic EPR line is observed for all samples after irradiation with g ≈2.65. The broadness is attributed to the superposition of signals resulting from the clustering of Gd3+ ions and the dipole interaction between these ions. The number of spins (N) participating in EPR resonance showed a decrease with increasing temperature, while the activation energy (Ea) experienced an increase with x up to 0.06 wt% followed by a further decrease. © 2016, Springer Science+Business Media New York

An informatics model for tissue banks – Lessons learned from the Cooperative Prostate Cancer Tissue Resource

BACKGROUND: Advances in molecular biology and growing requirements from biomarker validation studies have generated a need for tissue banks to provide quality-controlled tissue samples with standardized clinical annotation. The NCI Cooperative Prostate Cancer Tissue Resource (CPCTR) is a distributed tissue bank that comprises four academic centers and provides thousands of clinically annotated prostate cancer specimens to researchers. Here we describe the CPCTR information management system architecture, common data element (CDE) development, query interfaces, data curation, and quality control. METHODS: Data managers review the medical records to collect and continuously update information for the 145 clinical, pathological and inventorial CDEs that the Resource maintains for each case. An Access-based data entry tool provides de-identification and a standard communication mechanism between each group and a central CPCTR database. Standardized automated quality control audits have been implemented. Centrally, an Oracle database has web interfaces allowing multiple user-types, including the general public, to mine de-identified information from all of the sites with three levels of specificity and granularity as well as to request tissues through a formal letter of intent. RESULTS: Since July 2003, CPCTR has offered over 6,000 cases (38,000 blocks) of highly characterized prostate cancer biospecimens, including several tissue microarrays (TMA). The Resource developed a website with interfaces for the general public as well as researchers and internal members. These user groups have utilized the web-tools for public query of summary data on the cases that were available, to prepare requests, and to receive tissues. As of December 2005, the Resource received over 130 tissue requests, of which 45 have been reviewed, approved and filled. Additionally, the Resource implemented the TMA Data Exchange Specification in its TMA program and created a computer program for calculating PSA recurrence. CONCLUSION: Building a biorepository infrastructure that meets today's research needs involves time and input of many individuals from diverse disciplines. The CPCTR can provide large volumes of carefully annotated prostate tissue for research initiatives such as Specialized Programs of Research Excellence (SPOREs) and for biomarker validation studies and its experience can help development of collaborative, large scale, virtual tissue banks in other organ systems

Bridging consent: from toll bridges to lift bridges?

<p>Abstract</p> <p>Background</p> <p>The ability to share human biological samples, associated data and results across disease-specific and population-based human research biobanks is becoming increasingly important for research into disease development and translation. Although informed consent often does not anticipate such cross-domain sharing, it is important to examine its plausibility. The purpose of this study was to explore the feasibility of bridging consent between disease-specific and population-based research. Comparative analyses of 1) current ethical and legal frameworks governing consent and 2) informed consent models found in disease-specific and population-based research were conducted.</p> <p>Discussion</p> <p>Ethical and legal frameworks governing consent dissuade cross-domain data sharing. Paradoxically, analysis of consent models for disease-specific and population-based research reveals such a high degree of similarity that bridging consent could be possible if additional information regarding bridging was incorporated into consent forms. We submit that bridging of consent could be supported if current trends endorsing a new interpretation of consent are adopted. To illustrate this we sketch potential bridging consent scenarios.</p> <p>Summary</p> <p>A bridging consent, respectful of the spirit of initial consent, is feasible and would require only small changes to the content of consents currently being used. Under a bridging consent approach, the initial data and samples collection can serve an identified research project as well as contribute to the creation of a resource for a range of other projects.</p

Realizing the promise of population biobanks: a new model for translation

The promise of science lies in expectations of its benefits to societies and is matched by expectations of the realisation of the significant public investment in that science. In this paper, we undertake a methodological analysis of the science of biobanking and a sociological analysis of translational research in relation to biobanking. Part of global and local endeavours to translate raw biomedical evidence into practice, biobanks aim to provide a platform for generating new scientific knowledge to inform development of new policies, systems and interventions to enhance the public’s health. Effectively translating scientific knowledge into routine practice, however, involves more than good science. Although biobanks undoubtedly provide a fundamental resource for both clinical and public health practice, their potentiating ontology—that their outputs are perpetually a promise of scientific knowledge generation—renders translation rather less straightforward than drug discovery and treatment implementation. Biobanking science, therefore, provides a perfect counterpoint against which to test the bounds of translational research. We argue that translational research is a contextual and cumulative process: one that is necessarily dynamic and interactive and involves multiple actors. We propose a new multidimensional model of translational research which enables us to imagine a new paradigm: one that takes us from bench to bedside to backyard and beyond, that is, attentive to the social and political context of translational science, and is cognisant of all the players in that process be they researchers, health professionals, policy makers, industry representatives, members of the public or research participants, amongst others

Superconducting properties of chromium Cr-YBCO grown by pulsed laser deposition

Thin superconducting films of type Chromium incorporated YBa 2Cu3CrxO6+δ have been grown by Pulsed Laser Deposition (PLD). The prepared films have been characterized using X-ray powder diffraction (XRD) and Energy Dispersive X-Ray (EDS) analysis. The superconducting transition temperature Tc determined from electrical resistivity measurements was found to slightly increase for low Cr-content (x) and decreases when x andgt; 0.05. Furthermore, the surface morphology of the Cr doped and the pure YBCO films were investigated by Scanning Probe Microscope (SPM). © 2008 IOP Publishing Ltd.Abou-Aly A. I., 2002, INT C RES TRENDS SCI, P91; Guth K, 2001, PHYS REV B, V64, DOI 10.1103-PhysRevB.64.140508; HAMMOND RH, 1996, ADV SUPERCONDUCTIVIT, V8, P1029; Koo JH, 2003, J PHYS-CONDENS MAT, V15, pL729, DOI 10.1088-0953-8984-15-46-L03; LINDEMER TB, 1991, PHYSICA C, V178, P93, DOI 10.1016-0921-4534(91)90163-S; MacManus-Driscoll JL, 1998, ANNU REV MATER SCI, V28, P421, DOI 10.1146-annurev.matsci.28.1.421; Weber A, 2003, APPL PHYS LETT, V82, P772, DOI 10.1063-1.1543640; Yao X, 2002, PHYSICA C, V378, P107, DOI 10.1016-S0921-4534(02)01392-811

Structure, thermal analysis and magnetism of the doubly bridged linear polymer [Ni(4-NH2-C6H4CO2)2(CH3OH)2] · CH3OH

The title compound [Ni(4-NH2-C6H4CO2)2(CH3OH)2] · CH3OH (1) consists of Ni(II) atoms doubly bridged by p-aminobenzoate ligands (PAB) into 1D chains which are further connected into a 3D framework by methanol molecules through hydrogen bonding. Compound 1 is monoclinic P2(1)-n, a = 9.0903(5) Å, b = 10.9059(5) Å, c = 9.9994(5) Å, β = 106.6880(10)°, Z = 4. Intrachain π-π interactions are observed between the aromatic rings of doubly bridging PAB ligands. The aromatic rings are in an offset arrangement with 3.607 Å interplanar spacing. The magnetic data of compound 1 for the temperature range 300-3 K is indicative of ferromagnetically coupled nickel species. The best fitting parameters were obtained for J = 0.74 cm-1, D = -2.48 cm-1 and g = 2.35. Thermogravimetric analysis of 1 indicates a sharp weight loss of one PAB ligand centered at 387.42 °C (ΔH = 94.86 kJ-mol) and a loss of two coordinated methanol molecules at 489.20 °C with ΔH = 29.78 kJ-mol. The formation constant of Ni(II) with p-aminobenzoic acid has been evaluated at different temperatures using pH titration techniques in 50percent ethanol. The obtained values at 25 °C are log Kf1 = 3.24 and log Kf2 = 1.21. The thermodynamic parameters of complexation were also calculated and discussed. © 2006 Elsevier Ltd. All rights reserved.ABRAHAMS BF, 1994, NATURE, V369, P727, DOI 10.1038-369727a0; AMIRASLANOV IR, 1978, ZH STRUKT KHIM, V19, P1120; AMIRASLANOV IR, 1980, J STRUCT CHEM+, V21, P104, DOI 10.1007-BF00754176; AMIRASLANOV IR, 1978, ZH STRUKT KHIM, V19, P1129; AMIRASLANOV IR, 1980, ZH STRUKT KHIM, V21, P112; AMIRASLANOV IR, 1980, J STRUCT CHEM+, V21, P109, DOI 10.1007-BF00754177; AMIRASLANOV IR, 1979, ZH STRUKT KHIM, V20, P1075; AMIRASLANOV IR, 1980, J STRUCT CHEM+, V21, P363, DOI 10.1007-BF00746861; BATTAGLIA LP, 1991, J CHEM SOC FARADAY T, V87, P3863, DOI 10.1039-ft9918703863; Batten SR, 1999, J CHEM SOC DALTON, P2987, DOI 10.1039-a903487k; CARLUCCI L, 1995, J AM CHEM SOC, V117, P4562, DOI 10.1021-ja00121a014; CARLUCCI L, 1995, ANGEW CHEM INT EDIT, V34, P1895, DOI 10.1002-anie.199518951; CARLUCCI L, 1995, INORG CHEM, V34, P5698, DOI 10.1021-ic00126a048; Chui SSY, 1999, SCIENCE, V283, P1148, DOI 10.1126-science.283.5405.1148; Claessens CG, 1997, J PHYS ORG CHEM, V10, P254, DOI 10.1002-(SICI)1099-1395(199705)10:5254::AID-POC8753.0.CO;2-3; DANIEL EA, 1978, AUST J CHEM, V31, P723; DEACON GB, 1980, COORDIN CHEM REV, V33, P227, DOI 10.1016-S0010-8545(00)80455-5; DENEEF T, 1976, PHYS REV B, V13, P4141, DOI 10.1103-PhysRevB.13.4141; DENEEF T, 1975, THESIS EINDHOVEN NET; EDWARDS DA, 1968, CAN J CHEMISTRY, V46, P3443; El-Dessouky M.A., 1988, AFINIDAD, V416, P321; Escuer A, 1998, INORG CHIM ACTA, V269, P313, DOI 10.1016-S0020-1693(97)05801-5; Fan J, 2001, INORG CHEM COMMUN, V4, P501, DOI 10.1016-S1387-7003(01)00259-3; FUJITA M, 1994, J AM CHEM SOC, V116, P1151, DOI 10.1021-ja00082a055; GABLE RW, 1990, J CHEM SOC CHEM COMM, P1677, DOI 10.1039-c39900001677; Garden SJ, 2002, ACTA CRYSTALLOGR B, V58, P701, DOI 10.1107-S0108768102007978; Glidewell C, 2002, ACTA CRYSTALLOGR B, V58, P864, DOI 10.1107-S0108768102009941; Goher MAS, 2002, POLYHEDRON, V21, P1871, DOI 10.1016-S0277-5387(02)01061-6; Holman KT, 2005, POLYHEDRON, V24, P221, DOI 10.1016-j.poly.2004.11.017; Jager L, 2001, J MOL STRUCT, V570, P159, DOI 10.1016-S0022-2860(01)00491-4; Janiak C, 2000, J CHEM SOC DALTON, P3885, DOI 10.1039-b003010o; Jensen P, 1999, CHEM COMMUN, P177, DOI 10.1039-a808777f; Kabbani AT, 2004, J CHEM CRYSTALLOGR, V34, P749, DOI 10.1007-s10870-004-7650-3; KABBANI AT, 1981, J MAGN RESON, V43, P90, DOI 10.1016-0022-2364(81)90084-6; Karanovic L, 2002, ACTA CRYSTALLOGR C, V58, pm275, DOI 10.1107-S0108270102004341; KITAGAWA S, 1998, B CHEM SOC JPN, V71, P1; Kondo M, 1997, ANGEW CHEM INT EDIT, V36, P1725, DOI 10.1002-anie.199717251; Kutasi AM, 2002, AUST J CHEM, V55, P311, DOI 10.1074-CH02065; Maji TK, 2001, POLYHEDRON, V20, P651, DOI 10.1016-S0277-5387(01)00729-X; Manson JL, 1999, J MATER CHEM, V9, P979, DOI 10.1039-a808089e; Manson JL, 2001, J AM CHEM SOC, V123, P162, DOI 10.1021-ja0024791; Martell A.E., 1992, DETERMINATION USE ST; Masoud MS, 2002, THERMOCHIM ACTA, V381, P119, DOI 10.1016-S0040-6031(01)00691-8; Meyer F, 2001, INORG CHEM COMMUN, V4, P305, DOI 10.1016-S1387-7003(01)00188-5; Pan L, 2001, CHEM COMMUN, P105, DOI 10.1039-b007344j; PARVEEN S, 1981, P NATL ACAD SCI IN A, V51, P337; Riggio I, 2001, INORG CHIM ACTA, V313, P120, DOI 10.1016-S0020-1693(00)00374-1; Robson R., 1992, ACS SYM SER; SUBRAMANIAN S, 1995, ANGEW CHEM INT EDIT, V34, P2127, DOI 10.1002-anie.199521271; Sundholm D, 1998, J PHYS CHEM A, V102, P7137, DOI 10.1021-jp9813589; Tong ML, 2002, ACTA CRYSTALLOGR C, V58, pM232, DOI 10.1107-S0108270102002962; YAGHI OM, 1995, NATURE, V378, P703, DOI 10.1038-378703a0; Yan B, 1998, MATER RES BULL, V33, P1517, DOI 10.1016-S0025-5408(98)00133-0; ZAWOROTKO MJ, 1994, CHEM SOC REV, V23, P283, DOI 10.1039-cs9942300283; ZAWOROTOTKO MJ, 2006, J COORD CHEM, P6599

Magnetic susceptibility study of Ce3+ in PbCeA (A=Te, Se, S)

The magnetic susceptibility of Pb(1-x)Ce(x)A (A=S, Se and Te) crystals with Ce3+ concentrations 0.006 &lt;= x &lt;= 0.036 was investigated in the temperature range from 2 K to 300 K. The magnetic susceptibility data was found to be consistent with a E-2(5/2) lowest manifold for Ce3+ ions with a crystal-field splitting Delta=E(Gamma(8))-E(Gamma(7)) of about 340 K, 440 K and 540 K for Pb1-xCexTe, Pb1-xCexSe, and Pb1-xCexS, respectively. For all the three compounds the doublet Gamma(7) lies below the Gamma(8) quadruplet which confirms the substitution of Pb2+ by Ce3+ ions in the host crystals. The observed values for the crystal-field splitting are in good agreement with the calculated ones based on the point-charge model. Moreover, the effective Lande factors were determined by X-band (similar to 9.5 GHz), electron paramagnetic measurements (EPR) to be g=1.333, 1.364, and 1.402 for Ce ions in PbA, A = S. Se and Te, respectively. The small difference with the predicted Lande factor g of 10/7 for the Gamma(7) (J=5/2) ground state was attributed to crystal-field admixture. (C) 2012 Elsevier B.V. All rights reserved.The work in Brazil was supported by FAPESP. The work at AUB\ud was supported by the University Research Board. The work in\ud Poland was supported by the EU. The authors are thankful for this\ud support