63 research outputs found
Colloidal topological insulators
Topological insulators insulate in the bulk but exhibit robust conducting
edge states protected by the topology of the bulk material. Here, we design a
colloidal topological insulator and demonstrate experimentally the occurrence
of edge states in a classical particle system. Magnetic colloidal particles
travel along the edge of two distinct magnetic lattices. We drive the colloids
with a uniform external magnetic field that performs a topologically
non-trivial modulation loop. The loop induces closed orbits in the bulk of the
magnetic lattices. At the edge, where both lattices merge, the colloids perform
skipping orbits trajectories and hence edge-transport. We also observe
paramagnetic and diamagnetic colloids moving in opposite directions along the
edge between two inverted patterns; the analogue of a quantum spin Hall effect
in topological insulators. We present a new, robust, and versatile way of
transporting colloidal particles, enabling new pathways towards lab on a chip
applications
Buffer influence on magnetic dead layer, critical current and thermal stability in magnetic tunnel junctions with perpendicular magnetic anisotropy
We present a thorough research on Ta/Ru-based buffers and their influence on
features crucial from the point of view of applications of MTJs, such as
critical switching current and thermal stability. We investigate devices
consisting of buffer/FeCoB/MgO/FeCoB/Ta/Ru multilayers for three different
buffers: Ta 5 / Ru 10 / Ta 3, Ta 5 / Ru 10 / Ta 10 and Ta 5 / Ru 20 / Ta 5 (all
thicknesses in nm). In addition, we study systems with a single FeCoB layer
deposited above as well as below the MgO barrier. The crystallographic texture
and the roughness of the buffers are determined by means of XRD and atomic
force microscopy measurements. Furthermore, we examine the magnetic domain
pattern, the magnetic dead layer thickness and the perpendicular magnetic
anisotropy fields for each sample. Finally, we investigate the effect of the
current induced magnetization switching for nanopillar junctions with lateral
dimensions ranging from 1 {\mu}m down to 140 nm. Buffer Ta 5 / Ru 10 / Ta 3,
which has the thickest dead layer, exhibits a large increase in the thermal
stability factor while featuring a slightly lower critical current density
value when compared to the buffer with the thinnest dead layer Ta 5 / Ru 20 /
Ta 5
Mass spectrometry-based analysis of therapy-related changes in serum proteome patterns of patients with early-stage breast cancer
<p>Abstract</p> <p>Background</p> <p>The proteomics approach termed proteome pattern analysis has been shown previously to have potential in the detection and classification of breast cancer. Here we aimed to identify changes in serum proteome patterns related to therapy of breast cancer patients.</p> <p>Methods</p> <p>Blood samples were collected before the start of therapy, after the surgical resection of tumors and one year after the end of therapy in a group of 70 patients diagnosed at early stages of the disease. Patients were treated with surgery either independently (26) or in combination with neoadjuvant chemotherapy (5) or adjuvant radio/chemotherapy (39). The low-molecular-weight fraction of serum proteome was examined using MALDI-ToF mass spectrometry, and then changes in intensities of peptide ions registered in a mass range between 2,000 and 14,000 Da were identified and correlated with clinical data.</p> <p>Results</p> <p>We found that surgical resection of tumors did not have an immediate effect on the mass profiles of the serum proteome. On the other hand, significant long-term effects were observed in serum proteome patterns one year after the end of basic treatment (we found that about 20 peptides exhibited significant changes in their abundances). Moreover, the significant differences were found primarily in the subgroup of patients treated with adjuvant therapy, but not in the subgroup subjected only to surgery. This suggests that the observed changes reflect overall responses of the patients to the toxic effects of adjuvant radio/chemotherapy. In line with this hypothesis we detected two serum peptides (registered m/z values 2,184 and 5,403 Da) whose changes correlated significantly with the type of treatment employed (their abundances decreased after adjuvant therapy, but increased in patients treated only with surgery). On the other hand, no significant correlation was found between changes in the abundance of any spectral component or clinical features of patients, including staging and grading of tumors.</p> <p>Conclusions</p> <p>The study establishes a high potential of MALDI-ToF-based analyses for the detection of dynamic changes in the serum proteome related to therapy of breast cancer patients, which revealed the potential applicability of serum proteome patterns analyses in monitoring the toxicity of therapy.</p
Inductive determination of the optimum tunnel barrier thickness in magnetic tunnelling junction stacks for spin torque memory applications
We use pulsed inductive microwave magnetometry to study the precessional
magnetization dynamics of the free layer in CoFeB/MgO/CoFeB based magnetic
tunnelling junction stacks with varying MgO barrier thickness. From the field
dependence of the precession frequency we are able to derive the uniaxial
anisotropy energy and the exchange coupling between the free and the pinned
layer. Furthermore the field dependence of the effective damping parameter is
derived. Below a certain threshold barrier thickness we observe an increased
effective damping for antiparallel orientation of free and pinned layer which
would inhibit reversible low current density spin torque magnetization
reversal. Such inductive measurements, in combination with wafer probe station
based magneto transport experiments, allow a fast determination of the optimum
tunnel barrier thickness range for spin torque memory applications in a
lithography free process.Comment: 22 pages, 5 figure
Simultaneous polydirectional transport of colloidal bipeds
Detailed control over the motion of colloidal particles is relevant in many
applications in colloidal science such as lab-on-a-chip devices. Here, we use
an external magnetic field to assemble paramagnetic colloidal spheres into
colloidal rods of several lengths. The rods reside above a square magnetic
pattern and are transported via modulation of the direction of the external
magnetic field. The rods behave like bipeds walking above the pattern.
Depending on their length, the bipeds perform topologically distinct classes of
protected walks above the pattern. We demonstrate that it is possible to design
parallel polydirectional modulation loops of the external field that command up
to six classes of bipeds to walk on distinct predesigned paths. We use such
parallel polydirectional loops to induce the collision of reactant bipeds,
their polymerization addition reaction to larger bipeds, the separation of
product bipeds from the educts, the sorting of different product bipeds, and
also the parallel writing of a word consisting of several different letters
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