<i>States of Matter</i>

Goodstein, David L.; Stanley, H. Eugene

doi:10.1063/1.3023520

Cited by 68 publications

(87 citation statements)

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“…5, the relative magnetic susceptibility change is plotted versus the maximum signal intensity drop in each experiment. The magnetic susceptibility change induced by a paramagnetic agent depends on the square of the magnetic moment (8).…”

Section: Resultsmentioning

confidence: 99%

Dynamic imaging with lanthanide chelates in normal brain: Contrast due to magnetic susceptibility effects

Villringer

Rosen

Belliveau

et al. 1988

Magnetic Resonance in Med

643

318

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Using a one-dimensional rapid imaging technique, we have found that injection of lanthanide chelates such as Gd(DTPA)2- leads to a significant decrease (50%) in rat brain signal intensity at 1.45 T using T2-weighted pulse sequences; however, no effect of comparable size is observed with T1-weighted pulse sequences. The transient effect and its kinetics were followed with a temporal resolution of between 1 and 8 s. Experiments with different lanthanide chelates show that the observed decrease in signal intensity correlates with the magnetic moment of each agent but not with their longitudinal relaxivity. Three-dimensional chemical-shift resolved experiments demonstrate significant line broadening in brain during infusion with Dy(DTPA)2-. Our results show that the cause of this effect is the difference in susceptibility between the capillaries, containing the contrast agent, and the surrounding tissue. As a result of these susceptibility differences, field gradients are produced in the tissue and diffusion of water through these gradients leads to a loss of spin phase coherence and thus a decrease in signal intensity. We propose this as a new type of contrast agent mechanism in NMR. The effect and its kinetics are likely to be related to important physiological parameters such as cerebral blood volume and cerebral blood flow, and do not depend on a breakdown of the blood-brain barrier as do conventional contrast agent techniques.

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Section: Resultsmentioning

confidence: 99%

Dynamic imaging with lanthanide chelates in normal brain: Contrast due to magnetic susceptibility effects

Villringer

Rosen

Belliveau

et al. 1988

Magnetic Resonance in Med

643

318

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“…We will assume that α = β for this calculation. 8 Given this assumption, the true heat capacity is C = (δH + α)τ 1 /∆T .…”

Section: Maintaining the Balance Revisitedmentioning

confidence: 99%

Experiments on the Self-Organized Critical State of 4He

Chatto

Lee

Duncan³

et al. 2007

J Low Temp Phys

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AcknowledgementsThere are a number of people I would like to thank for their contributions to this thesis. My advisor David Goodstein was insightful, encouraging, and patient throughout the many challenges of performing a low-temperature experiment. Our conversations were always helpful because David has an extraordinary ability to make complicated concepts seem simple and intuitive. I had two mentors in the lab, Peter Day and Richard Lee, who taught me everything I know about performing experiments in low-temperature physics. My first lab experience was working with Peter. He provided me with the cryostat I used throughout my graduate career, answered hundreds of questions, and patiently showed me the techniques I needed. Richard returned to Caltech as my thesis experiment was taking shape. He was also an excellent resource for the tricks and techniques of low-temperature physics. (Plus, he made B.O.B.2, the electrical filtering system on this cryostat). However, what helped me most was that he patiently asked hundreds of questions, which forced me to think through all the details of my experiment. It is with his help that I avoided many pitfalls.There are a number of other physicists who made significant contributions to this work. Particularly helpful were the members of the DYNAMX team from the University of New Mexico (Rob Duncan, Dimitri Sergatskov, Alex Babkin, and Steve Boyd). They provided material help with the cryo-valve system and the construction of the experimental cell. In addition, they provided a lot of expertise on performing experiments on the SOC state of 4 He. In particular, I would like to thank Rob Duncan, who served as a secondary thesis advisor during a critical time in the experiment as David Goodstein recovered from an injury. Also helpful were discussions with two theorists, Peter Weichman and Rudolf Haussmann, who helped give meaning to my results.I would like to thank my parents for many many years of encouragement and support, and not asking me too often when I was going to get my degree.I would also like to thank my wife Avital, who provided an enormous amount of support and, through an intricate dance of prodding and patience, helped guide me through this endeavor. Lastly, I thank my son Jacob, whose arrival helped destroy the illusion that maybe, just maybe, I could be a graduate student forever. We report the first results of the heat capacity of the SOC state, C ∇T , for heat fluxes 60nW/cm 2 < Q < 13 µW/cm 2 and corresponding temperatures 9 nK > T SOC − T λ > −1.1 µK. We find that C ∇T tracks the static (i.e., zero heat flux) unrounded (i.e., in zero gravity) heat capacity C 0 with two exceptions. The first is that within 250 nK of T λ , C ∇T is depressed relative to C 0 and the maximum in C ∇T is shifted to 50 nK below T λ . The second difference is that at high heat flux, C ∇T is again depressed relative to C 0 with the departure starting at about 650 nK below T λ .We present the most extensive measurements of the speed and attenuation of the SOC wave to date. We report wav...

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“…However, since we calculate properties over a much longer number of MCS than is required for structural relaxation, we continue to call the calculated energy fluctuation term the specific heat and denote it as C v for convenience. At the phase transition, C v shows a peak as fluctuations in energy 39 become large. The U p value at which we observe a peak in C v on cooling from the melt state is termed the crystallization U p , in tune with experimental ͑calorimetry͒ convention, even though crystallization takes place over a range of U p .…”

Section: Model and Simulation Techniquementioning

confidence: 99%

Polymer crystallization in the presence of “sticky” additives

Dasmahapatra

Nanavati

Kumaraswamy

2009

The Journal of Chemical Physics

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The effect of "sticky" additives ͑viz., those that have attractive interactions with the polymer͒ on polymer crystallization, has been investigated by dynamic Monte Carlo ͑DMC͒ simulations. Additive-polymer attractive interactions result in a slowing down of the polymer chain diffusivity in the melt state. Our results show that with increasing additive stickiness, polymer crystallinity decreases monotonically, and thinner crystallites form, viz., crystallization is inhibited by the presence of sticky additives. Unusually, the observed "specific heat" peak at the phase transition shows nonmonotonic behavior with additive stickiness, and exhibits a maximum for intermediate values of additive stickiness. While the origins of this unexpected behavior are not clear, we show that it correlates with a large interchange between crystalline and amorphous states of the monomers, in the vicinity of the additives. At this intermediate additive stickiness, we also find that crystallization follows a qualitatively different route-crystallinity shows a non-Avrami-like evolution, unlike the case at low or high additive stickiness.

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States of Matter

Cited by 68 publications

References 0 publications

Dynamic imaging with lanthanide chelates in normal brain: Contrast due to magnetic susceptibility effects

Dynamic imaging with lanthanide chelates in normal brain: Contrast due to magnetic susceptibility effects

Experiments on the Self-Organized Critical State of 4He

Polymer crystallization in the presence of “sticky” additives

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