Hypershifted spin spectroscopy with dynamic nuclear polarization at 1.4 K.

Dynamic nuclear polarization (DNP) enhances nuclear magnetic resonance (NMR) sensitivity by transferring polarization from unpaired electrons to nuclei, but nearby nuclear spins are difficult to detect or "hidden" due to strong electron-nuclear couplings that hypershift their NMR resonances. Here, we detect these hypershifted spins in a frozen glycerol-water mixture doped with TEMPOL at ~1.4 K using spin diffusion enhanced saturation transfer (SPIDEST), which indirectly reveals their spectrum.

Quantitative analysis of cross-talk in partly deuterated samples of nuclear spins hyperpolarized by dynamic nuclear polarization (DNP) in the thermal mixing regime.

Dynamical nuclear polarization (DNP) is a powerful method that allows one to polarize virtually any spin-bearing nucleus by transferring electron polarization by microwave irradiation of the electron Zeeman transitions. Under certain conditions, the DNP process can be described in thermodynamical terms using the thermal mixing (TM) model. Different nuclear species can exchange energy indirectly through their interactions with the electron spins and reach a common spin temperature.

Spin relaxation: is there anything new under the Sun?

Spin relaxation has been at the core of many studies since the early days of nuclear magnetic resonance (NMR) and the underlying theory worked out by its founding fathers. This Bloch-Redfield-Abraham relaxation theory has been recently reinvestigated () in the perspective of Lindblad theory of quantum Markovian master equations in order to account for situations where the widely used semi-classical relaxation theory breaks down. In this article, we review the conventional approach of quantum mechanical theory of NMR relaxation and show that, under the usual assumptions, it is equivalent to the Lindblad formulation.

Constant-adiabaticity pulse schemes for manipulating singlet order in 3-spin systems with weak magnetic non-equivalence.

Parahydrogen-induced polarization (PHIP) is a source of nuclear spin hyperpolarization, and this technique allows for the preparation of biomolecules for in vivo metabolic imaging. PHIP delivers hyperpolarization in the form of proton singlet order to a molecule, but most applications require that a heteronuclear (e.g.

Constant-adiabaticity ultralow magnetic field manipulations of parahydrogen-induced polarization: application to an AA'X spin system.

The field of magnetic resonance imaging with hyperpolarized contrast agents is rapidly expanding, and parahydrogen-induced polarization (PHIP) is emerging as an inexpensive and easy-to-implement method for generating the required hyperpolarized biomolecules. Hydrogenative PHIP delivers hyperpolarized proton spin order to a substrate via chemical addition of H in the spin-singlet state, but it is typically necessary to transfer the proton polarization to a heteronucleus (usually C) which has a longer spin lifetime. Adiabatic ultralow magnetic field manipulations can be used to induce the polarization transfer, but this is necessarily a slow process, which is undesirable since the spins continually relax back to thermal equilibrium.

Representation of population exchange at level anti-crossings.

A theoretical framework is proposed to describe the spin dynamics driven by coherent spin mixing at level anti-crossings (LACs). We briefly introduce the LAC concept and propose to describe the spin dynamics using a vector of populations of the diabatic eigenstates. In this description, each LAC gives rise to a pairwise redistribution of eigenstate populations, allowing one to construct the total evolution operator of the spin system.

Algorithmic cooling of nuclear spins using long-lived singlet order.

Algorithmic cooling methods manipulate an open quantum system in order to lower its temperature below that of the environment. We achieve significant cooling of an ensemble of nuclear spin-pair systems by exploiting the long-lived nuclear singlet state, which is an antisymmetric quantum superposition of the "up" and "down" Zeeman states. The effect is demonstrated by nuclear magnetic resonance experiments on a molecular system containing a coupled pair of near-equivalent C nuclei.

Author Correction: Generating and sustaining long-lived spin states in N,N'-azobenzene.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Generating and sustaining long-lived spin states in N,N'-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-N,N'-azobenzene.

Fast destruction of singlet order in NMR experiments.

Some nuclear spin systems support long-lived states, which display greatly extended relaxation times relative to the relaxation time of nuclear spin magnetization. In spin-1/2 pairs, such a long-lived state is given by singlet order, representing the difference of the population of the nuclear singlet state and the mean population of the three triplets. In many cases, the experiments with long-lived singlet order are very time-consuming because of the need to wait for singlet order decay before the experiment can be repeated; otherwise, spin order remaining from a previous measurement may lead to experimental artifacts.

Transport of hyperpolarized samples in dissolution-DNP experiments.

Dissolution dynamic nuclear polarization (D-DNP) experiments rely on the transfer of a sample between two high-field magnets. During this transfer, samples might experience passage through regions where the stray fields of the magnets are very weak, can approach zero, and even change their sign. This can lead to unexpected spectral features in spin systems that undergo transitions from weak- to strong-coupling regimes and vice versa, much like in field cycling nuclear magnetic resonance experiments.

Constant-adiabaticity radiofrequency pulses for generating long-lived singlet spin states in NMR.

A method is implemented to perform "fast" adiabatic variation of the spin Hamiltonian by imposing the constant adiabaticity condition. The method is applied to improve the performance of singlet-state Nuclear Magnetic Resonance (NMR) experiments, specifically, for efficient generation and readout of the singlet spin order in coupled spin pairs by applying adiabatically ramped RF-fields. Test experiments have been performed on a specially designed molecule having two strongly coupled C spins and on selectively isotopically labelled glycerol having two pairs of coupled protons.

Using optimal control methods with constraints to generate singlet states in NMR.

A method is proposed for optimizing the performance of the APSOC (Adiabatic-Passage Spin Order Conversion) technique, which can be exploited in NMR experiments with singlet spin states. In this technique magnetization-to-singlet conversion (and singlet-to-magnetization conversion) is performed by using adiabatically ramped RF-fields. Optimization utilizes the GRAPE (Gradient Ascent Pulse Engineering) approach, in which for a fixed search area we assume monotonicity to the envelope of the RF-field.

Salud Tiene Sabor: a model for healthier restaurants in a Latino community.

Background: The prevalence of overweight and obesity in children has risen nationally in recent decades, and is exceptionally high in low-income communities of color such as South Los Angeles CA. Independently owned restaurants participating in the Salud Tiene Sabor program at ethnic foods marketplace Mercado La Paloma in South Los Angeles are responding to the childhood obesity crisis by posting calories for menu items and providing nutrition information to patrons.

Purpose: To evaluate whether menu labeling and nutrition information at point of purchase have an influence on availability of healthy food options, patron awareness of calorie information, and restaurant owners' support of the program.

PPO and HMO performance factors: insurance company evaluation criteria.

A venture into managed care should be done only following the proper amount of due diligence. The goal should be to select the most effective managed care organization with the flexibility to meet long-term needs and the mission to work on an ongoing basis to improve service and managed care performance. Unfortunately, all too often purchasers do not demand critical information from managed care service providers.

Thin-fiber cutaneous innervation and its intraepidermal contribution studied by labeling methods and neurotoxin treatment in rats.

Sensory nerves innervating rat distal limb skin were labeled by axonal transport of an enzyme-lectin conjugate injected into lumbar dorsal root ganglia (DRG), with emphasis on tracing the course of the thin axons. Selective neonatal neurotoxin destruction of most unmyelinated sensory or sympathetic axons was achieved by treatment with capsaicin (CAP) and 6-hydroxydopamine (6-OHDA), respectively. The relationship of substance P-immunoreactive (SPI) axons to the patterns of axonal transport-labeled thin axons was compared in normal and neurotoxin-treated animals.

Deafferentation in animals as a model for the study of pain: an alternative hypothesis.

The notion that post-deafferentation autonomy is a pain response is unsupported by the results of studies with neurotoxins. The selective massive destruction of a fiber system considered essential to normal nociception--unmyelinated primary afferent axons--prior to deafferenting nerve lesions did not stop or even significantly impede post-denervation DI despite massive evidence from humans and animals that pain following nerve lesions originates in the periphery and is generated by abnormal discharges in the injured nerve. In addition, when a reduction in abnormal impulse discharges of both large and small injured sensory axons could be inferred following neonatal sympathectomy, DI was not reduced in incidence or severity.

Absence of intraspinal sprouting in dorsal root axons caudal to a partial spinal hemisection: a horseradish peroxidase transport study.

Primary afferent sprouting in the spinal cord was evaluated by comparing the central projection of horseradish peroxidase (HRP)-labeled sciatic nerve afferent axons in nonlesioned control rats, and in rats subjected to acute or chronic partial spinal hemisections as adults. The lesions were performed at various levels from T10 to L3, and removed supraspinal and varying amounts of descending propriospinal afferents to lumbar segments receiving the maximal sciatic projection. The hemisections typically involved all but the dorsal column, although in some cases a portion of the dorsal column, including the corticospinal tract, was also transected.

An examination of intraspinal sprouting in dorsal root axons with the tracer horseradish peroxidase.

Postdeafferentation reorganization in the central terminal fields of spared dorsal root axons was evaluated by examining the intraspinal distribution of horseradish peroxidase-labeled sciatic nerve afferent fibers at various intervals following the removal of several lumbar dorsal root ganglia. The sciatic projection to the spinal cord, as determined by the pattern and density of intraspinal reaction product, was remarkably stable following the ganglionectomies. For as long as 3 months later, there was no evidence that sciatic afferent fibers had formed anomalous connections either with new spinal segments or in denervated areas within normal segments of entry.

The influence of housing condition on autotomy following dorsal rhizotomy in rats.

Forty-four rats were subjected to unilateral intradural section of dorsal roots T13-L6. Of these, 10 were housed alone and 34 were housed with female rats. Each of the 10 animals housed alone-self-mutilated to an extreme degree, with 7 cannibalizing the denervated limb.

Chromosomal isolabelling caused by three rounds of synthesis in late replicating regions.

Isolabelling only occurs in CHO cells that have been allowed to replicate for more than 2 but less than 3 cell divisions in the presence of BrdU. The isolabelling is confined to late replicating regions of the chromosomes. The staining patterns obtained indicate that BrdU was incorporated three times in these regions and that the isolabelling did not come from the segregation of label in polynemic chromosomes.

Saccharin-induced sister chromatid exchanges in Chinese hamster and human cells.

Since the induction of sister chromatid exchanges in cultured cells has been shown to be the most sensitive mammalian system to detect the effects of mutagenic carcinogens, Chinese hamster ovary cells and human lymphocytes were exposed to the sodium saccharin found to induce bladder cancer in rats. Both that saccharin and a highly purified extract of it increased the yield of sister chromatid exchanges in both types of cells. The results, which were repeatable and statistically highly significant, indicated that the weak carcinogen, saccharin, is also mutagenic in the sense that it induces cytogenetic changes.