721 research outputs found
Multiple slope sweep generator Patent
Transistorized circuit for producing multiple slope voltage swee
Pulse generator using transistors and silicon controlled rectifiers produces high current pulses with fast rise and fall times
Electrical pulse generator uses power transistors and silicon controlled rectifiers for producing a high current pulse having fast rise and fall times. At quiescent conditions, the standby power consumption of the circuit is equal to zero
Pulse modulator providing fast rise and fall times Patent
Electric circuit for producing high current pulse having fast rise and fall tim
Linear sawtooth voltage-wave generator employing transistor timing circuit having capacitor-zener diode combination feedback Patent
Linear sawtooth voltage wave generator with transistor timing circuit having capacitor and zener diode feedback loop
Impact of ultrafast electronic damage in single particle x-ray imaging experiments
In single particle coherent x-ray diffraction imaging experiments, performed
at x-ray free-electron lasers (XFELs), samples are exposed to intense x-ray
pulses to obtain single-shot diffraction patterns. The high intensity induces
electronic dynamics on the femtosecond time scale in the system, which can
reduce the contrast of the obtained diffraction patterns and adds an isotropic
background. We quantify the degradation of the diffraction pattern from
ultrafast electronic damage by performing simulations on a biological sample
exposed to x-ray pulses with different parameters. We find that the contrast is
substantially reduced and the background is considerably strong only if almost
all electrons are removed from their parent atoms. This happens at fluences of
at least one order of magnitude larger than provided at currently available
XFEL sources.Comment: 15 pages, 3 figures submitted to PR
Beyond icosahedral symmetry in packings of proteins in spherical shells
The formation of quasi-spherical cages from protein building blocks is a
remarkable self-assembly process in many natural systems, where a small number
of elementary building blocks are assembled to build a highly symmetric
icosahedral cage. In turn, this has inspired synthetic biologists to design de
novo protein cages. We use simple models, on multiple scales, to investigate
the self-assembly of a spherical cage, focusing on the regularity of the
packing of protein-like objects on the surface. Using building blocks, which
are able to pack with icosahedral symmetry, we examine how stable these highly
symmetric structures are to perturbations that may arise from the interplay
between flexibility of the interacting blocks and entropic effects. We find
that, in the presence of those perturbations, icosahedral packing is not the
most stable arrangement for a wide range of parameters; rather disordered
structures are found to be the most stable. Our results suggest that (i) many
designed, or even natural, protein cages may not be regular in the presence of
those perturbations, and (ii) that optimizing those flexibilities can be a
possible design strategy to obtain regular synthetic cages with full control
over their surface properties.Comment: 8 pages, 5 figure
Assessing cellular response to functionalized α-helical peptide hydrogels
α-Helical peptide hydrogels are decorated with a cell-binding peptide motif (RGDS), which is shown to promote adhesion, proliferation, and differentiation of PC12 cells. Gel structure and integrity are maintained after functionalization. This opens possibilities for the bottom-up design and engineering of complex functional scaffolds for 2D and 3D cell cultures.</p
Interpretation of heart rate variability via detrended fluctuation analysis and alpha-beta filter
Detrended fluctuation analysis (DFA), suitable for the analysis of
nonstationary time series, has confirmed the existence of persistent long-range
correlations in healthy heart rate variability data. In this paper, we present
the incorporation of the alpha-beta filter to DFA to determine patterns in the
power-law behaviour that can be found in these correlations. Well-known
simulated scenarios and real data involving normal and pathological
circumstances were used to evaluate this process. The results presented here
suggest the existence of evolving patterns, not always following a uniform
power-law behaviour, that cannot be described by scaling exponents estimated
using a linear procedure over two predefined ranges. Instead, the power law is
observed to have a continuous variation with segment length. We also show that
the study of these patterns, avoiding initial assumptions about the nature of
the data, may confer advantages to DFA by revealing more clearly abnormal
physiological conditions detected in congestive heart failure patients related
to the existence of dominant characteristic scales.Comment: 18 pages, 14 figure
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