48 research outputs found
Temporary inhibition of Moloney-murine sarcoma virus (M-MSV) induced-tumours by adoptive transfer of ricin-treated T-lymphocytes.
The potential use of tumour-specific T-lymphocytes loaded with ricin in cell targeting experiments was investigated. Moloney-murine sarcoma virus (M-MSV)-specific T-lymphocytes, obtained in mass mixed leucocyte-tumour cell culture (MLTC) and a M-MSV-specific cytotoxic T-lymphocyte (CTL) clone, were incubated with 125I-labelled ricin in order to evaluate toxin uptake and release. The internalized ricin (4.5 X 10(-17) mol and 6.5 X 10(-17) mol per 10(2) MLTC and CTL clone cells, respectively) was released rapidly during the first 30 min following treatment, and at a constant but slower rate over the next few hours. The cytotoxic activity of ricin-treated cells evaluated against antigen-related target cells, in a short term incubation 51Cr release assay, was unaffected during the first 30 min after treatment but decreased with time over the next few hours. However, the growth of antigen related as well as of unrelated tumour cells was strongly inhibited by the addition of ricin-treated cells to the culture system, thus indicating that released ricin is toxic for untreated target cells. The in vivo localization pattern of ricin-treated radiolabelled MLTC cells was found to be comparable with that of untreated cells 1 h after i.v. injection into syngeneic sublethally irradiated mice. After 6 h, however, more radiolabel was recovered from the liver of mice receiving ricin-treated MLTC cells. Ricin-treated M-MSV-specific T-lymphocytes were injected i.v. into tumour bearing sublethally irradiated mice. A temporary tumour growth inhibition (up to 6 days) was achieved following transfer of low doses of ricin-treated MLTC or CTL clone cells (1 X 10(6) and 0.5 X 10(6), respectively). In contrast, in M-MSV injected control mice, receiving only free toxin (from 5 to 20 ng) or untreated tumour-specific effector cell tumours grew progressively. The therapeutic effect was apparently specific since the injection of ricin-treated alloreactive T-lymphocytes did not influence tumour growth. These results suggest that M-MSV-specific T-lymphocytes loaded with ricin can deliver toxin to the target tumour mass and have a transient therapeutic effect
Static Charge Density Wave Order in the Superconducting State of La2-xBaxCuO4
Charge density wave (CDW) correlations feature prominently in the phase
diagram of the cuprates, motivating competing theories of whether fluctuating
CDW correlations aid superconductivity or whether static CDW order coexists
with superconductivity in inhomogeneous or spatially modulated states. Here we
report Cu -edge resonant x-ray photon correlation spectroscopy (XPCS)
measurements of CDW correlations in superconducting LaBaCuO
. Static CDW order is shown to exist in the superconducting state at
low temperatures and to persist up to at least 85\% of the CDW transition
temperature. We discuss the implications of our observations for how
\emph{nominally} competing order parameters can coexist in the cuprates.Comment: 6 pages, 5 figures, Accepted in Phys. Rev. B Rapid Communication
Doping Dependence of Collective Spin and Orbital Excitations in Spin 1 Quantum Antiferromagnet LaSrNiO Observed by X-rays
We report the first empirical demonstration that resonant inelastic x-ray
scattering (RIXS) is sensitive to \emph{collective} magnetic excitations in
systems by probing the Ni -edge of LaSrNiO (). The magnetic excitation peak is asymmetric, indicating the
presence of single and multi spin-flip excitations. As the hole doping level is
increased, the zone boundary magnon energy is suppressed at a much larger rate
than that in hole doped cuprates. Based on the analysis of the orbital and
charge excitations observed by RIXS, we argue that this difference is related
to the orbital character of the doped holes in these two families. This work
establishes RIXS as a probe of fundamental magnetic interactions in nickelates
opening the way towards studies of heterostructures and ultra-fast pump-probe
experiments.Comment: 8 pages, 4 figures, see ancillary files for the supplemental materia
Pressure-induced collapsed-tetragonal phase in SrCo2As2
We present high-energy x-ray diffraction data under applied pressures up to p
= 29 GPa, neutron diffraction measurements up to p = 1.1 GPa, and electrical
resistance measurements up to p = 5.9 GPa, on SrCo2As2. Our x-ray diffraction
data demonstrate that there is a first-order transition between the tetragonal
(T) and collapsed-tetragonal (cT) phases, with an onset above approximately 6
GPa at T = 7 K. The pressure for the onset of the cT phase and the range of
coexistence between the T and cT phases appears to be nearly temperature
independent. The compressibility along the a-axis is the same for the T and cT
phases whereas, along the c-axis, the cT phase is significantly stiffer, which
may be due to the formation of an As-As bond in the cT phase. Our resistivity
measurements found no evidence of superconductivity in SrCo2As2 for p <= 5.9
GPa and T >= 1.8 K. The resistivity data also show signatures consistent with a
pressure-induced phase transition for p >= 5.5 GPa. Single-crystal neutron
diffraction measurements performed up to 1.1 GPa in the T phase found no
evidence of stripe-type or A-type antiferromagnetic ordering down to 10 K.
Spin-polarized total-energy calculations demonstrate that the cT phase is the
stable phase at high pressure with a c/a ratio of 2.54. Furthermore, these
calculations indicate that the cT phase of SrCo2As2 should manifest either
A-type antiferromagnetic or ferromagnetic order.Comment: 6 pages, 5 figure
Electronic character of charge order in square planar low valence nickelates
Charge order is a central feature of the physics of cuprate superconductors
and is known to arise from a modulation of holes with primarily oxygen
character. Low-valence nickelate superconductors also host charge order, but
the electronic character of this symmetry breaking is unsettled. Here, using
resonant inelastic x-ray scattering at the Ni -edge, we identify
intertwined involvements of Ni , , and O
orbitals in the formation of diagonal charge order in an
overdoped low-valence nickelate LaNiO. The Ni
orbitals, strongly hybridized with planar O , largely shape the
spatial charge distribution and lead to Ni site-centered charge order. The
orbitals play a small, but non-negligible role in the charge
order as they hybridize with the rare-earth orbitals. Our results reveal
that the low-energy physics and ground-state character of these nickelates are
more complex than those in cuprates.Comment: Accepted in Physical Review X; 7 pages plus references and
supplementary material
Resonant inelastic x-ray scattering data for Ruddlesden-Popper and reduced Ruddlesden-Popper nickelates
Ruddlesden-Popper and reduced Ruddlesden-Popper nickelates are intriguing
candidates for mimicking the properties of high-temperature superconducting
cuprates. The degree of similarity between these nickelates and cuprates has
been the subject of considerable debate. Resonant inelastic x-ray scattering
(RIXS) has played an important role in exploring their electronic and magnetic
excitations, but these efforts have been stymied by inconsistencies between
different samples and the lack of publicly available data for detailed
comparison. To address this issue, we present open RIXS data on La4Ni3O10 and
La4Ni3O8.Comment: Data descriptor article; accepted in Scientific Data; 8 pages; 6
figure
Charge density wave memory in a cuprate superconductor
Although CDW correlations are a ubiquitous feature of the superconducting cuprates, their disparate properties suggest a crucial role for pinning the CDW to the lattice. Here, we report coherent resonant X-ray speckle correlation analysis, which directly determines the reproducibility of CDW domain patterns in La1.875Ba0.125CuO4 (LBCO 1/8) with thermal cycling. While CDW order is only observed below 54 K, where a structural phase transition creates inequivalent Cu-O bonds, we discover remarkably reproducible CDW domain memory upon repeated cycling to far higher temperatures. That memory is only lost on cycling to 240(3) K, which recovers the four-fold symmetry of the CuO2 planes. We infer that the structural features that develop below 240 K determine the CDW pinning landscape below 54 K. This opens a view into the complex coupling between charge and lattice degrees of freedom in superconducting cuprates