Electric-field-induced strain mechanisms in lead-free 94%(Bi1/2Na1/2)TiO3-6%BaTiO3

High resolution neutron diffraction has been used to investigate the structural origin of the large electric-field-induced remanent strain in 94(Bi1/2Na1/2)TiO3-6BaTiO(3) ceramics. The virgin material was found to be a mixture of near-cubic phases with slight tetragonal and rhombohedral distortions of a(0)a(0)c(+) and a(-)a(-)a(-) octahedral tilt type, respectively. Application of an electric field of 4.57 kV/mm transformed the sample to a predominantly rhombohedral a(-)a(-)a(-) modification with a significantly higher degree of structural distortion and a pronounced preferred orientation of the c-axis along the field direction. These electric field-induced structural effects contribute significantly to the macroscopic strain and polarization of this system.open40

Identification, validation and clinical implementation of cancer biomarkers: Translational strategies of the EORTC PathoBiology Group

AbstractThe increasing demand for personalized cancer therapy requires a strong, intense, and continuous collaboration between pre-clinical and clinical investigators. As a part of the EORTC Translational Research Divison, the EORTC PathoBiology Group (EORTC PBG), focuses on discovery and validation of cancer biomarkers, providing both scientific evidence as well as quality assurance. The clinically relevant target-identification and validation studies carried out in the last decades within the EORTC PBG represent a paradigm for EORTC studies in which laboratory investigations on human biologic material are used to support the development of drugs directed to defined target molecules. The experience acquired within the EORTC PBG with respect to standardization of cancer biomarker test kits and reagents, quality assessment/assurance of cancer biomarker determinations, development of standard operating procedures for assessment of these markers as well as instruction of methodologies and teaching of ethical issues represent a valuable contribution of the EORTC PBG to the onco-translational strategies of the EORTC

Abortive Lytic Reactivation of KSHV in CBF1/CSL Deficient Human B Cell Lines

Since Kaposi's sarcoma associated herpesvirus (KSHV) establishes a persistent infection in human B cells, B cells are a critical compartment for viral pathogenesis. RTA, the replication and transcription activator of KSHV, can either directly bind to DNA or use cellular DNA binding factors including CBF1/CSL as DNA adaptors. In addition, the viral factors LANA1 and vIRF4 are known to bind to CBF1/CSL and modulate RTA activity. To analyze the contribution of CBF1/CSL to reactivation in human B cells, we have successfully infected DG75 and DG75 CBF1/CSL knock-out cell lines with recombinant KSHV.219 and selected for viral maintenance by selective medium. Both lines maintained the virus irrespective of their CBF1/CSL status. Viral reactivation could be initiated in both B cell lines but viral genome replication was attenuated in CBF1/CSL deficient lines, which also failed to produce detectable levels of infectious virus. Induction of immediate early, early and late viral genes was impaired in CBF1/CSL deficient cells at multiple stages of the reactivation process but could be restored to wild-type levels by reintroduction of CBF1/CSL. To identify additional viral RTA target genes, which are directly controlled by CBF1/CSL, we analyzed promoters of a selected subset of viral genes. We show that the induction of the late viral genes ORF29a and ORF65 by RTA is strongly enhanced by CBF1/CSL. Orthologs of ORF29a in other herpesviruses are part of the terminase complex required for viral packaging. ORF65 encodes the small capsid protein essential for capsid shell assembly. Our study demonstrates for the first time that in human B cells viral replication can be initiated in the absence of CBF1/CSL but the reactivation process is severely attenuated at all stages and does not lead to virion production. Thus, CBF1/CSL acts as a global hub which is used by the virus to coordinate the lytic cascade

Relaxor Characteristics of Morphotropic Phase Boundary (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3 Modified with Bi(Zn1/2Ti1/2)O3

Morphotropic phase boundary (Bi1/2Na1/2)TiO3(Bi1/2K1/2)TiO3 (BNTBKT), was modified with increasing additions of Bi(Zn1/2Ti1/2)O3 (BZT). Microstructure, electric-field-induced strain and polarization, dielectric permittivity, and temperature-dependent piezoelectric coefficient were investigated and compared with crystal structure measured in situ as a function of applied electric field. Furthermore, permittivity and piezoelectric coefficient were characterized as a function of electric field. For small additions of BZT, an applied electric field leads to an irreversible phase transition into a ferroelectric phase with remanent polarization and a reduced relative permittivity. Increasing the content of BZT increased the threshold field for the transition. For additions of more than 2 mol% BZT, the piezoelectric coefficient dropped, permittivity remained almost constant, and a high normalized strain of up to 500 pm/V was observed. However, no field-dependent structural change was evidenced by the in situ X-ray experiment.close373

Large blocking force in Bi 1/2Na 1/2TiO 3-based lead-free piezoceramics

Blocking stress (sigma(b)) and free strain (S-f) are the most important parameters for piezoelectric actuators, both having a decisive impact on the electromechanical performance. Here, we report on the blocking stress of lead-free piezoceramics, using 0.94Bi(1/2) Na1/2TiO3-0.06BaTiO(3) (6BT) and 0.98(0.94Bi(1/2)Na(1/2)TiO(3)-0.06BaTiO(3))-0.02K(0.5)Na(0.5)NbO3 (2KNN) as prototypical compositions. While 6BT delivers high sigma(b) = 102 MPa at 125 degrees C, the addition of 2 mol.% K0.5Na0.5NbO3 results in a large sigma(b) = 124 MPa at room temperature. Therefore, both lead-free materials outperform lead zirconate titanate at their respective peak temperatures.close111

Electric-field-induced polarization and strain in 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO(3) under uniaxial stress

The strain and polarization hystereses of lead-free 0.94Bi(1/2)Na(1/2)TiO(3)-0.06BaTiO(3) during unipolar electric field loading are obtained from room temperature to 150 degrees C under uniaxial compressive stress up to 446 MPa. At intermediate temperatures a stress-dependent peak evolves in both the maximum strain and polarization. At 125 degrees C a large strain with a large-signal piezoelectric coefficient d(33)* of 884 pm V-1 is observed, which decays upon the application of stress. This behavior is rationalized with a change in the primary strain mechanism from domain switching at low temperatures to a reversible electric field-induced transition from an ergodic relaxor state to a long-range order at high temperatures. Moreover, the energy terms w (the output mechanical work) and e(P) (the charged electrical energy density) that are related to the deformation and the polarization, respectively, are analyzed and used to define a large-signal efficiency eta* = w(w + e(P))(-1). It is found that eta* saturates at similar to 150 MPa but decreases with increasing temperature and electric field. It is furthermore observed that notable strains are achieved at stress levels even far beyond the quasi-statically determined blocking force. Therefore, it is proposed that the presented testing procedure is suited to assess the dynamic actuatoric performance of a piezoceramic.close12

Optimal working regime of lead-zirconate-titanate for actuation applications

The large-signal unipolar behavior of PZT is characterized under combined electrical, thermal, and mechanical loading. Maximum strain S-max and polarization P-max feature a pronounced sensitivity on stress with a field-dependent peak evolving at around -50 MPa that is associated with enhanced non-180 degrees domain switching. As notable strains are achieved in excess of the quasi-statically measured blocking stress, it is suggested that the testing procedure presented within this work is suited to supplement blocking force measurements in order to comprehensively evaluate the electromechanical performance of a piezoceramic. With the suppression of non-180 degrees domain switching at high stress levels, S-max(sigma) decreases at a faster rate than P-max(sigma). Accordingly, the electrostrictive coefficient Q(11) is shown to be stress-dependent. This observation is rationalized with the stress-dependent change of domain processes. It is furthermore found that Q(11) features a notable dependence on temperature, increasing from 0.018 m(4) C-2 at 25 degrees C to 0.028 m(4) C-2 at 150 degrees C under zero-stress. To assess the actuatoric efficiency, a novel figure of merit eta* is defined to quantify the fraction of input energy utilized for mechanical work.close7

Giant electric-field-induced strains in lead-free ceramics for actuator applications - status and perspective

In response to the current environmental regulations against the use of lead in daily electronic devices, a number of investigations have been performed worldwide in search for alternative piezoelectric ceramics that can replace the market-dominating lead-based ones, representatively Pb(Zr (x) Ti1-x )O-3 (PZT)-based solid solutions. Selected systems of potential importance such as chemically modified and/or crystallographically textured (K, Na)NbO3 and (Bi1/2Na1/2)TiO3-based solid solutions have been developed. Nevertheless, only few achievements have so far been introduced to the marketplace. A recent discovery has greatly extended our tool box for material design by furnishing (Bi1/2Na1/2)TiO3-based ceramics with a reversible phase transition between an ergodic relaxor state and a ferroelectric with the application of electric field. This paired the piezoelectric effect with a strain-generating phase transition and extended opportunities for actuator applications in a completely new manner. In this contribution, we will present the status and perspectives of this new class of actuator ceramics, aiming at covering a wide spectrum of topics, i.e., from fundamentals to practice.close776

A High-Temperature-Capacitor Dielectric Based on K0.5Na0.5NbO3-Modified Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3

A high-temperature dielectric, (1x)(0.6Bi(1/2)Na(1/2)TiO(3)0.4Bi(1/2)K(1/2)TiO(3))xK(0.5)Na(0.5)NbO(3), off the morphotropic phase boundary of the parent matrix 0.8Bi(1/2)Na(1/2)TiO(3)0.2Bi(1/2)K(1/2)TiO(3), has been developed for application as a high-temperature capacitor. In addition to temperature-dependent permittivity and dielectric loss, DC conductivity and field-dependent permittivity are reported. These properties are correlated with temperature-dependent structure data measured at different length scales using Raman spectroscopy and neutron diffraction. It is suggested that all materials investigated are ergodic relaxors with two types of polar nanoregions providing different relaxation mechanisms. The most attractive properties for application as high-temperature dielectrics are obtained in a material with x,=,0.15 at less than 10% variation of relative permittivity of about 2100 between 54 degrees C and 400 degrees C.close191