Application of the CINGEN program a thermal network data generator

The application of the CINGEN computer program and two of its supporting programs for the evaluation of structural and thermal performance of physical systems was described. The CINGEN program was written and implemented to avoid the duplication effort of performing a finite element approach for structural analysis and a finite differencing technique for thermal analysis, as well as the desire for a geometrical representation of the thermal model to reduce modeling errors. The program simplifies the thermal modeling process by performing all of the capacitance and conductance calculations normally done by the analyst. Each solid element is divided into five tetrahedrons, allowing the total volume to be calculated precisely. A sample problem was illustrated

On the relationship between sigma models and spin chains

We consider the two-dimensional $\rm O(3)$ non-linear sigma model with topological term using a lattice regularization introduced by Shankar and Read [Nucl.Phys. B336 (1990), 457], that is suitable for studying the strong coupling regime. When this lattice model is quantized, the coefficient $\theta$ of the topological term is quantized as $\theta=2\pi s$, with $s$ integer or half-integer. We study in detail the relationship between the low energy behaviour of this theory and the one-dimensional spin-$s$ Heisenberg model. We generalize the analysis to sigma models with other symmetries.Comment: To appear in Int. J. MOd. Phys.

Spin transition in Gd3_3N@C80_{80}, detected by low-temperature on-chip SQUID technique

We present a magnetic study of the Gd$_3$N@C$_{80}$ molecule, consisting of a Gd-trimer via a Nitrogen atom, encapsulated in a C$_{80}$ cage. This molecular system can be an efficient contrast agent for Magnetic Resonance Imaging (MRI) applications. We used a low-temperature technique able to detect small magnetic signals by placing the sample in the vicinity of an on-chip SQUID. The technique implemented at NHMFL has the particularity to operate in high magnetic fields of up to 7 T. The Gd$_3$N@C$_{80}$ shows a paramagnetic behavior and we find a spin transition of the Gd$_3$N structure at 1.2 K. We perform quantum mechanical simulations, which indicate that one of the Gd ions changes from a $^8S_{7/2}$ state ($L=0, S=7/2$) to a $^7F_{6}$ state ($L=S=3, J=6$), likely due to a charge transfer between the C$_{80}$ cage and the ion

Na(V)1.5 sodium channel window currents contribute to spontaneous firing in olfactory sensory neurons

Olfactory sensory neurons (OSNs) fire spontaneously as well as in response to odor; both forms of firing are physiologically important. We studied voltage-gated Na+ channels in OSNs to assess their role in spontaneous activity. Whole cell patch-clamp recordings from OSNs demonstrated both tetrodotoxin-sensitive and tetrodotoxin-resistant components of Na+ current. RT-PCR showed mRNAs for five of the nine different Na+ channel α-subunits in olfactory tissue; only one was tetrodotoxin resistant, the so-called cardiac subtype NaV1.5. Immunohistochemical analysis indicated that NaV1.5 is present in the apical knob of OSN dendrites but not in the axon. The NaV1.5 channels in OSNs exhibited two important features: 1) a half-inactivation potential near −100 mV, well below the resting potential, and 2) a window current centered near the resting potential. The negative half-inactivation potential renders most NaV1.5 channels in OSNs inactivated at the resting potential, while the window current indicates that the minor fraction of noninactivated NaV1.5 channels have a small probability of opening spontaneously at the resting potential. When the tetrodotoxin-sensitive Na+ channels were blocked by nanomolar tetrodotoxin at the resting potential, spontaneous firing was suppressed as expected. Furthermore, selectively blocking NaV1.5 channels with Zn2+ in the absence of tetrodotoxin also suppressed spontaneous firing, indicating that NaV1.5 channels are required for spontaneous activity despite resting inactivation. We propose that window currents produced by noninactivated NaV1.5 channels are one source of the generator potentials that trigger spontaneous firing, while the upstroke and propagation of action potentials in OSNs are borne by the tetrodotoxin-sensitive Na+ channel subtypes.This work was aided by support from Boston University, the Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD) P30 DC-04657; D. Restrepo, principal investigator], and NIDCD Grants DC-04863 to V. Dionne and DC-006070 to D. Restrepo and T. E. Finger. (Boston University; P30 DC-04657 - Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD)]; DC-04863 - Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD)]; DC-006070 - Rocky Mountain Taste and Smell Center Core for Cellular Visualization and Analysis [National Institute on Deafness and Other Communication Disorders (NIDCD)])https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4122723/Accepted manuscrip

Control of the cation occupancies of MnZn ferrite synthesized via reverse micelles

Variations in cation occupancy in mixed metal ferrite systems can affect their electronic and magnetic properties. It is known that different synthesis parameters can lead to various cation distributions and the ability to tune these distributions is of great interest. This study uses the extended x-ray-absorption fine structure–IR relationship to investigate the effect of various Fe2+/Fe3+ ratios in initial synthesis conditions on cation distribution for manganesezincferrite (MZFO). Differences in the precipitated material before firing could lead to differences in the final material if fired under similar conditions. This work uses several different ratios of Fe3+/Fe2+, which will affect the initial cell potential for the reaction, to synthesize nano MZFO. All samples were fired for 5h at 500°C under flowing nitrogen. Transmission electron microscopy micrographs reveal highly crystalline uniform nanoparticles of 16±2nm. The x-ray diffraction revealed single phase crystalline MZFO with an average crystallite size of around 14nm. The saturation magnetization ranged from 43to68emu∕g as measured by vibrating-sample magnetometry. The Fourier transform infrared (FTIR) analysis was used to determine the cation occupancies while changing the initial Fe3+/Fe2+ ratios from 10∕90 to90∕10. The FTIRspectra revealed a shift in the first absorption region in the far IR from 566.98to549.62cm−1 corresponding to the octahedral occupancies. This shift corresponds to a change in the percentage of octahedral sites occupied by manganese from roughly 25% to 12%. This change in manganese occupancy is also observed in the iron occupancies, which in turn help to explain the variation in saturation magnetization

Dexmedetomidine as Adjuvant Therapy for Acute Postoperative Neuropathic Pain Crisis

Background: Dexmedetomidine is a potent α2-adrenergic agonist U.S. Food and Drug Administration (FDA) approved for sedation. While its use as an analgesic has been described in the palliative medicine literature, its use for managing an acute neuropathic pain episode is less well known. Methods: Here we describe the use of adjuvant dexmedetomidine in a patient with metastatic sarcoma suffering from an acute postoperative neuropathic pain crisis. Conclusion: Among patients with acute neuropathic pain for whom additional opioids raises respiratory-related concerns, the use of dexmedetomidine should be considered as a viable treatment alternative.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140116/1/jpm.2013.0556.pd