18,114 research outputs found
Negative Differential Resistivity and Positive Temperature Coefficient of Resistivity effect in the diffusion limited current of ferroelectric thin film capacitors
We present a model for the leakage current in ferroelectric thin- film
capacitors which explains two of the observed phenomena that have escaped
satisfactory explanation, i.e. the occurrence of either a plateau or negative
differential resistivity at low voltages, and the observation of a Positive
Temperature Coefficient of Resistivity (PTCR) effect in certain samples in the
high-voltage regime. The leakage current is modelled by considering a
diffusion-limited current process, which in the high-voltage regime recovers
the diffusion-limited Schottky relationship of Simmons already shown to be
applicable in these systems
Extreme tunability of interactions in a Li Bose-Einstein condensate
We use a Feshbach resonance to tune the scattering length a of a
Bose-Einstein condensate of 7Li in the |F = 1, m_F = 1> state. Using the
spatial extent of the trapped condensate we extract a over a range spanning 7
decades from small attractive interactions to extremely strong repulsive
interactions. The shallow zero-crossing in the wing of the Feshbach resonance
enables the determination of a as small as 0.01 Bohr radii. In this regime,
evidence of the weak anisotropic magnetic dipole interaction is obtained by
comparison with different trap geometries
Molecular ion trap-depletion spectroscopy of BaCl
We demonstrate a simple technique for molecular ion spectroscopy. BaCl
molecular ions are trapped in a linear Paul trap in the presence of a
room-temperature He buffer gas and photodissociated by driving an electronic
transition from the ground X state to the repulsive wall of the
A state. The photodissociation spectrum is recorded by monitoring the
induced trap loss of BaCl ions as a function of excitation wavelength.
Accurate molecular potentials and spectroscopic constants are determined.
Comparison of the theoretical photodissociation cross-sections with the
measurement shows excellent agreement. This study represents the first
spectroscopic data for BaCl and an important step towards the production of
ultracold ground-state molecular ions.Comment: 5 pages, 5 figure
Graph Convolutional Network-based Feature Selection for High-dimensional and Low-sample Size Data
Feature selection is a powerful dimension reduction technique which selects a
subset of relevant features for model construction. Numerous feature selection
methods have been proposed, but most of them fail under the high-dimensional
and low-sample size (HDLSS) setting due to the challenge of overfitting. In
this paper, we present a deep learning-based method - GRAph Convolutional
nEtwork feature Selector (GRACES) - to select important features for HDLSS
data. We demonstrate empirical evidence that GRACES outperforms other feature
selection methods on both synthetic and real-world datasets.Comment: 24 pages, 4 figures, 4 table
Design of Peptide Inhibitors That Bind the bZIP Domain of Epstein–Barr Virus Protein BZLF1
Designing proteins or peptides that bind native protein targets can aid the development of novel reagents and/or therapeutics. Rational design also tests our understanding of the principles underlying protein recognition. This article describes several strategies used to design peptides that bind to the basic region leucine zipper (bZIP) domain of the viral transcription factor BZLF1, which is encoded by the Epstein–Barr virus. BZLF1 regulates the transition of the Epstein–Barr virus from a latent state to a lytic state. It shares some properties in common with the more studied human bZIP transcription factors, but also includes novel structural elements that pose interesting challenges to inhibitor design. In designing peptides that bind to BZLF1 by forming a coiled-coil structure, we considered both affinity for BZLF1 and undesired self-association, which can weaken the effectiveness of an inhibitor. Several designed peptides exhibited different degrees of target-binding affinity and self-association. Rationally engineered molecules were more potent inhibitors of DNA binding than a control peptide corresponding to the native BZLF1 dimerization region itself. The most potent inhibitors included both positive and negative design elements and exploited interaction with the coiled-coil and basic DNA-binding regions of BZLF1.David H. Koch Institute for Integrative Cancer Research at MIT (Graduate Fellowship)National Institutes of Health (U.S.) (Award GM067681)National Science Foundation (U.S.) (Award 0821391
- …