1,101 research outputs found
Non-thermal nuclear magnetic resonance quantum computing using hyperpolarized Xenon
Current experiments in liquid-state nuclear magnetic resonance quantum
computing are limited by low initial polarization. To address this problem, we
have investigated the use of optical pumping techniques to enhance the
polarization of a 2-qubit NMR quantum computer (13C and 1H in 13CHCl3). To
efficiently use the increased polarization, we have generalized the procedure
for effective pure state preparation. With this new, more flexible scheme, an
effective pure state was prepared with polarization-enhancement of a factor of
10 compared to the thermal state. An implementation of Grover's quantum search
algorithm was demonstrated using this new technique.Comment: 4 pages, 3 figures. Submitted for publicatio
Generating and sustaining long-lived spin states in 15N,15N′-azobenzene
Long-Lived spin States (LLSs) hold a great promise for sustaining non-thermal spin order and investigating various slow processes by Nuclear Magnetic Resonance (NMR) spectroscopy. Of special interest for such application are molecules containing nearly equivalent magnetic nuclei, which possess LLSs even at high magnetic fields. In this work, we report an LLS in trans-15N,15N′-azobenzene. The singlet state of the 15N spin pair exhibits a long-lived character. We solve the challenging problem of generating and detecting this LLS and further increase the LLS population by converting the much higher magnetization of protons into the 15N singlet spin order. As far as the longevity of this spin order is concerned, various schemes have been tested for sustaining the LLS. Lifetimes of 17 minutes have been achieved at 16.4 T, a value about 250 times longer than the longitudinal relaxation time of 15N in this magnetic field. We believe that such extended relaxation times, along with the photochromic properties of azobenzene, which changes conformation upon light irradiation and can be hyperpolarized by using parahydrogen, are promising for designing new experiments with photo-switchable long-lived hyperpolarization
Splicing factor ESRP1 controls ER-positive breast cancer by altering metabolic pathways
The epithelial splicing regulatory proteins 1 and 2 (ESRP1 and ESRP2) control the epithelial-to-mesenchymal transition (EMT) splicing program in cancer. However, their role in breast cancer recurrence is unclear. In this study, we report that high levels of ESRP1, but not ESRP2, are associated with poor prognosis in estrogen receptor positive (ER+) breast tumors. Knockdown of ESRP1 in endocrine-resistant breast cancer models decreases growth significantly and alters the EMT splicing signature, which we confirm using TCGA SpliceSeq data of ER+ BRCA tumors. However, these changes are not accompanied by the development of a mesenchymal phenotype or a change in key EMT-transcription factors. In tamoxifen-resistant cells, knockdown of ESRP1 affects lipid metabolism and oxidoreductase processes, resulting in the decreased expression of fatty acid synthase (FASN), stearoyl-CoA desaturase 1 (SCD1), and phosphoglycerate dehydrogenase (PHGDH) at both the mRNA and protein levels. Furthermore, ESRP1 knockdown increases the basal respiration and spare respiration capacity. This study reports a novel role for ESRP1 that could form the basis for the prevention of tamoxifen resistance in ER+ breast cancer
Anaerobic biodegradation of light hydrocarbons in crude oil: A comparison of laboratory experiments and field data
Transfer of Parahydrogen Induced Polarization in Scalar Coupled Systems at Variable Magnetic Field
Para-Hydrogen Induced Polarization (PHIP) experiments were performed in
coupled multispin systems at variable magnetic fields. We studied the magnetic
field dependence of PHIP in styrene, which is the product of hydrogenation of
phenylacetylene. At low magnetic fields where the spins are coupled strongly
by scalar interaction efficient polarization transfer among the interacting
protons takes place. The experimentally observed spectra are in good agreement
with the simulation, which takes into account eight coupled spins. We also
demonstrate effects of nuclear spin level anti-crossings on the PHIP pattern.
It is shown that rapid passage through the level anti-crossing enables highly
efficient polarization transfer between specific spin orders. In addition, we
studied PHIP transfer to 13C and 19F hetero-nuclei. It is shown that hetero-
nuclei can be efficiently polarized in a wide field range; in particular, for
polarizing them it is not necessary to go to ultra-low fields, which provide
their strong coupling to protons. The resulting polarization is of the
multiplet type and gives strong enhancements of the individual NMR lines. In
general, variation of the magnetic field gives the opportunity for
manipulating PHIP patterns and transferring polarization to target spins of
choice
Randomized comparison of the effects of the vitamin D(3 )adequate intake versus 100 mcg (4000 IU) per day on biochemical responses and the wellbeing of patients
BACKGROUND: For adults, vitamin D intake of 100 mcg (4000 IU)/day is physiologic and safe. The adequate intake (AI) for older adults is 15 mcg (600 IU)/day, but there has been no report focusing on use of this dose. METHODS: We compared effects of these doses on biochemical responses and sense of wellbeing in a blinded, randomized trial. In Study 1, 64 outpatients (recruited if summer 2001 25(OH)D <61 nmol/L) were given 15 or 100 mcg/day vitamin D in December 2001. Biochemical responses were followed at subsequent visits that were part of clinical care; 37 patients completed a wellbeing questionnaire in December 2001 and February 2002. Subjects for Study 2 were recruited if their 25(OH)D was <51 nmol/L in summer 2001. 66 outpatients were given vitamin D; 51 completed a wellbeing questionnaire in both December 2002 and February 2003. RESULTS: In Study 1, basal summer 25-hydroxyvitamin D [25(OH)D] averaged 48 ± 9 (SD) nmol/L. Supplementation for more than 6 months produced mean 25(OH)D levels of 79 ± 30 nmol/L for the 15 mcg/day group, and 112 ± 41 nmol/L for the 100 mcg/day group. Both doses lowered plasma parathyroid hormone with no effect on plasma calcium. Between December and February, wellbeing score improved more for the 100-mcg/day group than for the lower-dosed group (1-tail Mann-Whitney p = 0.036). In Study 2, 25(OH)D averaged 39 ± 9 nmol/L, and winter wellbeing scores improved with both doses of vitamin D (two-tail p < 0.001). CONCLUSION: The highest AI for vitamin D brought summertime 25(OH)D to >40 nmol/L, lowered PTH, and its use was associated with improved wellbeing. The 100 mcg/day dose produced greater responses. Since it was ethically necessary to provide a meaningful dose of vitamin D to these insufficient patients, we cannot rule out a placebo wellbeing response, particularly for those on the lower dose. This work confirms the safety and efficacy of both 15 and 100 mcg/day vitamin D(3 )in patients who needed additional vitamin D
Exploiting adiabatically switched RF-field for manipulating spin hyperpolarization induced by parahydrogen
A method for precise manipulation of non-thermal nuclear spin polarization by
switching a RF-field is presented. The method harnesses adiabatic correlation
of spin states in the rotating frame. A detailed theory behind the technique
is outlined; examples of two-spin and three-spin systems prepared in a non-
equilibrium state by Para-Hydrogen Induced Polarization (PHIP) are considered.
We demonstrate that the method is suitable for converting the initial
multiplet polarization of spins into net polarization: compensation of
positive and negative lines in nuclear magnetic resonance spectra, which is
detrimental when the spectral resolution is low, is avoided. Such a conversion
is performed for real two-spin and three-spin systems polarized by means of
PHIP. Potential applications of the presented technique are discussed for
manipulating PHIP and its recent modification termed signal amplification by
reversible exchange as well as for preparing and observing long-lived spin
states
Manipulating spin hyper-polarization by means of adiabatic switching of a spin-locking RF-field
We propose a technique for transferring the multiplet spin polarization (CIDNP
or PHIP, or one created by any other method), which is the mutual entanglement
of spins, into net hyper-polarization with respect to the direction of a high
magnetic field by slowly (adiabatically) switching-off a strong external RF-
field with a specially selected frequency. The net hyper-polarized molecules
can then be used in NMR spectroscopy or imaging for strong signal enhancement
cis Versus trans-Azobenzene: Precise Determination of NMR Parameters and Analysis of Long-Lived States of 15N Spin Pairs
We provide a detailed evaluation of nuclear magnetic resonance (NMR)
parameters of the cis- and trans-isomers of azobenzene (AB). For determining
the NMR parameters, such as proton–proton and proton–nitrogen J-couplings and
chemical shifts, we compared NMR spectra of three different isotopomers of AB:
the doubly 15N labeled azobenzene, 15N,15N′-AB, and two partially deuterated
AB isotopomers with a single 15N atom. For the total lineshape analysis of NMR
spectra, we used the recently developed ANATOLIA software package. The
determined NMR parameters allowed us to optimize experiments for investigating
singlet long-lived spin states (LLSs) of 15N spin pairs and to measure LLS
lifetimes in cis-AB and trans-AB. Magnetization-to-singlet-to-magnetization
conversion has been performed using the SLIC and APSOC techniques, providing a
degree of conversion up to 17 and 24% of the initial magnetization,
respectively. Our approach is useful for optimizing the performance of
experiments with singlet LLSs; such LLSs can be exploited for preserving spin
hyperpolarization, for probing slow molecular dynamics, slow chemical
processes and also slow transport processes
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