19 research outputs found
Multiple-spin coherence transfer in linear Ising spin chains and beyond: numerically-optimized pulses and experiments
We study multiple-spin coherence transfers in linear Ising spin chains with
nearest neighbor couplings. These constitute a model for efficient information
transfers in future quantum computing devices and for many multi-dimensional
experiments for the assignment of complex spectra in nuclear magnetic resonance
spectroscopy. We complement prior analytic techniques for multiple-spin
coherence transfers with a systematic numerical study where we obtain strong
evidence that a certain analytically-motivated family of restricted controls is
sufficient for time-optimality. In the case of a linear three-spin system,
additional evidence suggests that prior analytic pulse sequences using this
family of restricted controls are time-optimal even for arbitrary local
controls. In addition, we compare the pulse sequences for linear Ising spin
chains to pulse sequences for more realistic spin systems with additional
long-range couplings between non-adjacent spins. We experimentally implement
the derived pulse sequences in three and four spin systems and demonstrate that
they are applicable in realistic settings under relaxation and experimental
imperfections-in particular-by deriving broadband pulse sequences which are
robust with respect to frequency offsets.Comment: 11 page
Ionic liquid-catalyzed green protocol for multi-component synthesis of dihydropyrano[2,3-c]pyrazoles as potential anticancer scaffolds
A series of 6-amino-4-substituted-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles 5a–j were synthesized via one-pot, four-component condensation reactions of aryl aldehydes 1a–j, propanedinitrile (2), hydrazine hydrate (3) and ethyl acetoacetate (4) under solvent-free conditions. We report herein the use of the Brønsted acid ionic liquid (BAIL) triethylammonium hydrogen sulphate [Et3NH][HSO4] as catalyst for this multi-component synthesis. Compared with the available reaction methodology, this new method has consistent advantages, including excellent yields, a short reaction time, mild reaction conditions and catalyst reusability. Selected synthesized derivatives were evaluated for in vitro anticancer activity against four human cancer cell lines viz. melanoma cancer cell line (SK-MEL-2), breast cancer cell line(MDA-MB-231), leukemia cancer cell line (K-562) and cervical cancer cell line (HeLa). Compounds 5b, 5d, 5g, 5h and 5j exhibited promising anticancer activity against all selected human cancer cell lines, except HeLa. Molecular docking studies also confirmed 5b and 5d as good lead molecules. An in silico ADMET study of the synthesized anticancer agents indicated good oral drug-like behavior and non-toxic nature.UDN is very much thankful to Babasaheb Ambedkar Research and Training Institute (BARTI, Pune, India) for financial supportS
The Fantastic Four: A plug 'n' play set of optimal control pulses for enhancing nmr spectroscopy
We present highly robust, optimal control-based shaped pulses designed to
replace all 90{\deg} and 180{\deg} hard pulses in a given pulse sequence for
improved performance. Special attention was devoted to ensuring that the pulses
can be simply substituted in a one-to-one fashion for the original hard pulses
without any additional modification of the existing sequence. The set of four
pulses for each nucleus therefore consists of 90{\deg} and 180{\deg}
point-to-point (PP) and universal rotation (UR) pulses of identical duration.
These 1 ms pulses provide uniform performance over resonance offsets of 20 kHz
(1H) and 35 kHz (13C) and tolerate reasonably large radio frequency (RF)
inhomogeneity/miscalibration of (+/-)15% (1H) and (+/-)10% (13C), making them
especially suitable for NMR of small-to-medium-sized molecules (for which
relaxation effects during the pulse are negligible) at an accessible and widely
utilized spectrometer field strength of 600 MHz. The experimental performance
of conventional hard-pulse sequences is shown to be greatly improved by
incorporating the new pulses, each set referred to as the Fantastic Four
(Fanta4).Comment: 28 pages, 19 figure
Broadband 180 degree universal rotation pulses for NMR spectroscopy designed by optimal control
Broadband inversion pulses that rotate all magnetization components 180
degrees about a given fixed axis are necessary for refocusing and mixing in
high-resolution NMR spectroscopy. The relative merits of various methodologies
for generating pulses suitable for broadband refocusing are considered. The de
novo design of 180 degree universal rotation pulses using optimal control can
provide improved performance compared to schemes which construct refocusing
pulses as composites of existing pulses. The advantages of broadband universal
rotation by optimized pulses (BURBOP) are most evident for pulse design that
includes tolerance to RF inhomogeneity or miscalibration. We present new
modifications of the optimal control algorithm that incorporate symmetry
principles and relax conservative limits on peak RF pulse amplitude for short
time periods that pose no threat to the probe. We apply them to generate a set
of pulses suitable for widespread use in Carbon-13 spectroscopy on the majority
of available probes
Data from: Sida pradeepiana sp. nov. (Malvaceae) from India
The new species Sida pradeepiana is described from the Idukki district of Kerala state, India. It resembles S. alnifolia and S. rhomboidea, but differs by its concolorous-rhomboid leaves, unarticulated pedicels, mericarp apex beaked with a single muticous process and stellate pubescent mericarps and hilum of the seeds
New Strategies for Designing Robust Universal Rotation Pulses: Application to Broadband Refocusing at Low Power
Optimizing pulse performance often requires a compromise between maximizing signal amplitude and minimizing spectral phase errors. We consider methods for the de novo design of universal rotation pulses, applied specifically but not limited to refocusing pulses. Broadband inversion pulses that rotate all magnetization components 180 degrees about a given fixed axis are necessary for refocusing and mixing in high-resolution NMR spectroscopy. The relative merits of various methodologies for generating pulses suitable for broadband refocusing are considered. The de novo design of 180 degrees universal rotation pulses (180 degrees(UR)) using optimal control can provide improved performance compared to schemes which construct refocusing pulses as composites of existing pulses. The advantages of broadband universal rotation by optimized pulses (BURBOP) are most evident for pulse design that includes tolerance to RF inhomogeneity or miscalibration. Nearly ideal refocusing is possible over a resonance offset range of +/- 170% relative to the nominal pulse B-1 field, concurrent with tolerance to B-1 inhomogeneity/miscalibration of +/- 33%. We present new modifications of the optimal control algorithm that incorporate symmetry principles (S-BURBOP) and relax conservative limits on peak RF pulse amplitude for short time periods that pose no threat to the probe. We apply them to generate a set of low-power 180 degrees(BURBOP) pulses suitable for widespread use in C-13 spectroscopy on the majority of available probes. A quantitative measure for the B reduced spectral phase error provided by these symmetry principles is also derived. For pulses designed according to this symmetry, refocusing phase errors are virtually eliminated upon application of EXOR-CYCLE or an equivalent G-180 degrees(S-BURBOP)-G gradient sandwich, independent of resonance offset and RF inhomogeneity. The magnitude of the refocused component is not significantly compromised in achieving such ideal phase performance
Broadband 180 Degree Universal Rotation Pulses for NMR Spectroscopy Designed by Optimal Control
Broadband inversion pulses that rotate all magnetization components 180 degrees about a given fixed axis are necessary for refocusing and mixing in high-resolution NMR spectroscopy. The relative merits of various methodologies for generating pulses suitable for broadband refocusing are considered. The de novo design of 180 degree universal rotation pulses using optimal control can provide improved performance compared to schemes which construct refocusing pulses as composites of existing pulses. The advantages of broadband universal rotation by optimized pulses (BURBOP) are most evident for pulse design that includes tolerance to RF inhomogeneity or miscalibration. We present new modifications of the optimal control algorithm that incorporate symmetry principles and relax conservative limits on peak RF pulse amplitude for short time periods that pose no threat to the probe. We apply them to generate a set of pulses suitable for widespread use in Carbon-13 spectroscopy on the majority of available probes
Broadband 180 Degree Universal Rotation Pulses for NMR Spectroscopy Designed by Optimal Control
Broadband inversion pulses that rotate all magnetization components 180 degrees about a given fixed axis are necessary for refocusing and mixing in high-resolution NMR spectroscopy. The relative merits of various methodologies for generating pulses suitable for broadband refocusing are considered. The de novo design of 180 degree universal rotation pulses using optimal control can provide improved performance compared to schemes which construct refocusing pulses as composites of existing pulses. The advantages of broadband universal rotation by optimized pulses (BURBOP) are most evident for pulse design that includes tolerance to RF inhomogeneity or miscalibration. We present new modifications of the optimal control algorithm that incorporate symmetry principles and relax conservative limits on peak RF pulse amplitude for short time periods that pose no threat to the probe. We apply them to generate a set of pulses suitable for widespread use in Carbon-13 spectroscopy on the majority of available probes
Linear Phase Slope in Pulse Design: Application to Coherence Transfer
Using optimal control methods, robust broadband excitation pulses can be designed with a defined linear phase dispersion. Applications include increased bandwidth for a given pulse length compared to equivalent pulses requiring no phase correction, selective pulses, and pulses that mitigate the effects Of relaxation. This also makes it possible to create pulses that are equivalent to ideal hard pulses followed by an effective evolution period. For example, in applications, where the excitation pulse is followed by a constant delay, e.g. for the evolution of heteronuclear couplings, part of the pulse duration can be absorbed in existing delays, significantly reducing the time overhead of long, highly robust pulses., We refer to the class of such excitation pulses with a defined linear phase dispersion as ICEBERG pulses (inherent Coherence Evolution optimized Broadband Excitation Resulting in constant phase Gradients). A systematic study of the dependence of the excitation efficiency on the phase dispersion of the excitation pulses is presented, which reveals surprising opportunities for improved pulse sequence performance