scholarly journals Radiative Detection of Single-pulse and Spin-echo Nuclear Magnetic Resonance

1977 ◽  
Vol 30 (4) ◽  
pp. 461 ◽  
Author(s):  
GVH Wilson ◽  
DH Chaplin ◽  
P Cooke ◽  
HR Foster ◽  
P Lynam
Keyword(s):  
Thermal Conductivity ◽  
Spin Echo ◽  
Single Pulse ◽  
Dielectric Materials ◽  
Rf Heating ◽  
Rf Coil ◽  
Ferromagnetic Metals ◽  
New Information ◽  
Host Materials ◽  
Radiative Detection

The radiative detection of n.m.r. in thermally oriented radioactive nuclei by observing the effects of a resonant RF field on the anisotropic angular distribution of the ')I-ray radiations was first suggested by Bloembergen and Temmer (1953). The main advantage of radiative detection over conventional n.m.r. techniques, which detect the EMF induced in an RF coil by the precessing nuclei, would be that far fewer nuclei are required. Furthermore, such experiments should lead to new information on the fundamentals of the influence of resonant fields on the emission of radiations by nuclei (Shirley 1968). Thus, following the suggestion of Bloembergen and Temmer, several unpublished attempts were made to detect n.m.r. in nuclei that were oriented in paramagnetic dielectric materials at low temperatures. These attempts failed, probably because of the combination of nonresonant RF heating and the low thermal conductivity of the host materials. More recently, it has been realized that ferromagnetic metals offer significant advantages as host materials, e.g. large hyperfine magnetic fields generally act on the nuclei, the thermal conductivity is relatively high and, relative to the applied RF fields, there is a large ferromagnetic enhancement (Portis and Gossard 1960) of the RF fields which act on the nuclei.

Thermal conductivity study of porous low-k dielectric materials

2000 ◽  
Vol 77 (1) ◽  
pp. 145-147 ◽  
Author(s):  
Chuan Hu ◽  
Michael Morgen ◽  
Paul S. Ho ◽  
Anurag Jain ◽  
William N. Gill ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Materials ◽  
Low K

Thermal conductivity study of porous low K dielectric materials

1999 ◽  
Vol 565 ◽  
Author(s):  
Chuan Hu ◽  
Michael Morgen ◽  
Paul S. Ho ◽  
Anurag Jain ◽  
William. N. Gill ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Dielectric Materials ◽  
Porous Films ◽  
Low Dielectric ◽  
Omega Method ◽  
3 Omega ◽  
Low Dielectric Constant Materials ◽  
Low K ◽  
Method Analysis

AbstractA quantitative characterization of the thermal properties is required to assess the thermal performance of low dielectric constant materials. Recently we have developed a technique based on the 3-omega method for measuring the thermal conductivity of porous dielectric thin films. In this paper we present the results on the measurements of thermal conductivity of thin porous films using this method. A finite element method analysis is used to evaluate the approximations used in the measurement. Two porosity-weighted thermal resistor models are proposed to interpret the results. By studying the dependence of the thermal conductivity on porosity, we are able to discuss the scaling rule of thermal conductivity. Additionally, a steady state layered heater model is used for evaluating the significance of introducing porous ILDs into an interconnect structure.

High-resolution 1H-NMR spectroscopy of blood plasma for metabolic studies

1994 ◽  
Vol 40 (7) ◽  
pp. 1245-1250 ◽  
Author(s):  
R A Wevers ◽  
U Engelke ◽  
A Heerschap
Keyword(s):  
Nmr Spectroscopy ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Spin Echo ◽  
Single Pulse ◽  
Plasma Samples ◽  
Inborn Errors ◽  
Glutathione Biosynthesis ◽  
Health And Disease ◽  
Quantitative Analyses

Abstract Although spin-echo techniques are often used to obtain 1H-NMR spectra of serum or plasma samples, they do not provide reliable quantitative analyses of metabolites. We present a standardized procedure, optimized for sensitivity, for using single-pulse 1H-NMR spectroscopy to analyze deproteinized plasma. The detection limit for various metabolites ranges between 2 and 40 mumol/L. The method allows quantitative analysis of many compounds of interest in studies of inborn errors of metabolism, including betaine and dimethylglycine, which cannot be measured easily with other techniques. For lactate, tyrosine, threonine, and alanine, we obtained results that correlated well with those obtained by established techniques. We also present a library containing resonance positions of 38 compounds occurring in plasma samples in health and disease, including 14 as-yet-unidentified resonances. As an example of the diagnostic power of the technique we show a spectrum of a plasma sample from a patient with 5-oxoprolinuria (pyroglutamic aciduria; McKusick 266130), an enzymatic defect in glutathione biosynthesis.

High Resolution NMR Spectroscopy on Whole-Body Imagers:Optimized Single-and Multi-Pulse Experiments in Vitro

1995 ◽  
Vol 50 (10) ◽  
pp. 942-948
Author(s):  
Fritz Schick
Keyword(s):  
Aqueous Solutions ◽  
Spin Echo ◽  
Single Pulse ◽  
Spin Systems ◽  
The Body ◽  
Coupling Constants ◽  
Whole Body ◽  
Receiver Coil

Abstract From 100 ml spherical glass bottles filled with aqueous solutions and suspended in a homogeneous magnetic field, NMR spectra with linewidths of about 0.7 Hz were achieved in single-pulse and multi-pulse spectra. A relatively wide receiver coil as the body coil or the standard head coil of the manufacturer were employed to acquire spectra after different non-localized pulse sequences. Examples of single-pulse spectra and double spin-echo spectra of aqueous solutions with lactate, citrate, or glucose are demonstrated and discussed. The fact that all experiments can be performed using well-defined pulse angles acting on the entire sample at the field strenght of the whole-body unit allows to determine the characteristics (e.g. chemical shift differences, coupling constants) of spin systems of biologically important molecules precisely, without need for additional spectrometers. Constant flip angles are advantageous for adequate theoretical analysis of spectra from coupled spin systems. The effects of a defined "misadjustment" of the transmitter on the spectra can be measured directly, whereas localized methods always yield a superposition of signals due to the distribution of flip angles inside the selected volume. In some cases, optimized sequence parameters for localized examinations in vivo can be derived numerically from the analyzed coupling data.

Single-pulse nuclear spin echo in magnets

1998 ◽  
Vol 57 (18) ◽  
pp. 11554-11564 ◽  
Author(s):  
I. G. Kiliptari ◽  
V. I. Tsifrinovich
Keyword(s):  
Nuclear Spin ◽  
Spin Echo ◽  
Single Pulse

scholarly journals High thermal conductivity in soft elastomers with elongated liquid metal inclusions

2017 ◽  
Vol 114 (9) ◽  
pp. 2143-2148 ◽  
Author(s):  
Michael D. Bartlett ◽  
Navid Kazem ◽  
Matthew J. Powell-Palm ◽  
Xiaonan Huang ◽  
Wenhuan Sun ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Liquid Metal ◽  
Heat Dissipation ◽  
Dielectric Materials ◽  
Phonon Transport ◽  
High Thermal Conductivity ◽  
Stretchable Electronics ◽  
Mechanical Stiffness ◽  
Mechanical Coupling ◽  
Thermally Conductive

Soft dielectric materials typically exhibit poor heat transfer properties due to the dynamics of phonon transport, which constrain thermal conductivity (k) to decrease monotonically with decreasing elastic modulus (E). This thermal−mechanical trade-off is limiting for wearable computing, soft robotics, and other emerging applications that require materials with both high thermal conductivity and low mechanical stiffness. Here, we overcome this constraint with an electrically insulating composite that exhibits an unprecedented combination of metal-like thermal conductivity, an elastic compliance similar to soft biological tissue (Young’s modulus < 100 kPa), and the capability to undergo extreme deformations (>600% strain). By incorporating liquid metal (LM) microdroplets into a soft elastomer, we achieve a ∼25× increase in thermal conductivity (4.7 ± 0.2 W⋅m−1⋅K−1) over the base polymer (0.20 ± 0.01 W⋅m−1·K−1) under stress-free conditions and a ∼50× increase (9.8 ± 0.8 W⋅m−1·K−1) when strained. This exceptional combination of thermal and mechanical properties is enabled by a unique thermal−mechanical coupling that exploits the deformability of the LM inclusions to create thermally conductive pathways in situ. Moreover, these materials offer possibilities for passive heat exchange in stretchable electronics and bioinspired robotics, which we demonstrate through the rapid heat dissipation of an elastomer-mounted extreme high-power LED lamp and a swimming soft robot.

Dual Pump Femtosecond Laser Induced Plasma

2008 ◽  
Author(s):  
Meg Mahat ◽  
Tae Y. Choi ◽  
Nasrasadani Seifolah ◽  
Arup Neogi
Keyword(s):  
Emission Intensity ◽  
Short Pulse ◽  
Single Pulse ◽  
Atomic Emission ◽  
Dielectric Materials ◽  
Pulse Excitation ◽  
Time Resolved ◽  
Breakdown Spectroscopy ◽  
Short Pulse Laser ◽  
Ultra Short Pulse

Laser-induced breakdown spectroscopy (LIBS) can provide a noncontact way of inspecting a specimen including distinct signature of atomic composition of the sample. Ultra-short pulse laser enables characterization of any materials by utilizing the multiphoton process, which is a dominant carrier generation mechanism for dielectric materials. Additionally, femtosecond LIBS yields low background and better defined atomic lines than the nanosecond LIBS. We have performed a time-resolved emission intensity measurement for an iron oxide (Fe3O4, magnetite). The emission intensity has the peak value at 100 ps time delay, signifying that the succeeding pump beam is interacting with the plasma generated in the vicinity of the sample by the preceding beam. The dual pulses significantly enhance the atomic emission as compared to single pulse excitation and enables ultrafast time-resolved spectroscopy.

scholarly journals The Problem of Metal Needles in Acupuncture-fMRI Studies

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Florian Beissner ◽  
Ulrike Nöth ◽  
Thomas Schockert
Keyword(s):  
Image Quality ◽  
Sensory Stimulation ◽  
Laser Acupuncture ◽  
Rf Heating ◽  
Rf Coil ◽  
Safe Alternative ◽  
Transmitter Coil ◽  
Acupuncture Research ◽  
Underlying Mechanisms ◽  
Metal Needle

Acupuncture is a therapy based on sensory stimulation of the human body by means of metal needles. The exact underlying mechanisms of acupuncture have not been clarified so far. Functional magnetic resonance imaging (fMRI) has become an important tool in acupuncture research. Standard acupuncture needles, which are made of ferromagnetic steel, however, are problematic in acupuncture-fMRI studies for several reasons, such as attraction by the scanner's magnetic field, significant image distortions and signal-dropouts, when positioned close to the head or even heating due to absorption of radio frequency (RF). The aim of this study was to compare two novel types of acupuncture needles with a standard needle for their effect on MRI image quality. The standard needle severely reduced image quality, when located inside the RF coil. The nonferromagnetic metal needle may pose a risk due to RF heating, while the plastic needle has a significantly larger diameter. In conclusion, our recommendations are: (1) standard needles should not be used in MRI; (2) Nonferromagnetic metal needles seem to be the best choice for acupoints outside of the transmitter coil; and (3) only plastic needles are suited for points inside the coil. Laser acupuncture may be a safe alternative, too.

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