Looking for the Logarithms in Four-Dimensional Nambu-Jona-Lasinio Models

We study the problem of triviality in the four dimensional Nambu-Jona-Lasinio model with discrete chiral symmetry using both large-N expansions and lattice simulations. We find that logarithmic corrections to scaling appear in the equation of state as predicted by the large-N expansion. The data from $16^4$ lattice simulations is sufficiently accurate to distinguish logarithmically trivial scaling from power law scaling. Simulations on different lattice sizes reveal an interesting interplay of finite size effects and triviality. We argue that such effects are qualitatively different for theories based on fundamental scalar rather than fermion fields. Several lessons learned here can be applied to simulations and analyses of more challenging field theories.Comment: 25 pages, 14 ps figure

Fate of the Josephson effect in thin-film superconductors

The dc Josephson effect refers to the dissipationless electrical current -- the supercurrent -- that can be sustained across a weak link connecting two bulk superconductors. This effect is a probe of the fundamental nature of the superconducting state. Here, we analyze the case of two superconducting thin films connected by a point contact. Remarkably, the Josephson effect is absent at nonzero temperature, and the resistance across the contact is nonzero. Moreover, the point contact resistance is found to vary with temperature in a nearly activated fashion, with a UNIVERSAL energy barrier determined only by the superfluid stiffness characterizing the films, an angle characterizing the geometry, and whether or not the Coulomb interaction between Cooper pairs is screened. This behavior reflects the subtle nature of the superconductivity in two-dimensional thin films, and should be testable in detail by future experiments.Comment: 16 + 8 pages. 1 figure, 1 tabl

The effective potential of N-vector models: a field-theoretic study to O(\epsilon^3)

We study the effective potential of three-dimensional O($N$) models. In statistical physics the effective potential represents the free-energy density as a function of the order parameter (Helmholtz free energy), and, therefore, it is related to the equation of state. In particular, we consider its small-field expansion in the symmetric (high-temperature) phase, whose coefficients are related to the zero-momentum $2j$-point renormalized coupling constants $g_{2j}$. For generic values of $N$, we calculate $g_{2j}$ to three loops in the field-theoretic approach based on the $\epsilon$-expansion. The estimates of $g_{2j}$, or equivalently of $r_{2j}\equiv g_{2j}/g_4^{j-1}$, are obtained by a constrained analysis of the series that takes into account the exact results in one and zero dimensions.Comment: 22 pages, RevTex, Nucl. Phys. B, in pres

Magnetic Nanoparticle Sensors

Many types of biosensors employ magnetic nanoparticles (diameter = 5–300 nm) or magnetic particles (diameter = 300–5,000 nm) which have been surface functionalized to recognize specific molecular targets. Here we cover three types of biosensors that employ different biosensing principles, magnetic materials, and instrumentation. The first type consists of magnetic relaxation switch assay-sensors, which are based on the effects magnetic particles exert on water proton relaxation rates. The second type consists of magnetic particle relaxation sensors, which determine the relaxation of the magnetic moment within the magnetic particle. The third type is magnetoresistive sensors, which detect the presence of magnetic particles on the surface of electronic devices that are sensitive to changes in magnetic fields on their surface. Recent improvements in the design of magnetic nanoparticles (and magnetic particles), together with improvements in instrumentation, suggest that magnetic material-based biosensors may become widely used in the future

Labeling Efficacy of Superparamagnetic Iron Oxide Nanoparticles to Human Neural Stem Cells: Comparison of Ferumoxides, Monocrystalline Iron Oxide, Cross-linked Iron Oxide (CLIO)-NH2 and tat-CLIO

OBJECTIVE: We wanted to compare the human neural stem cell (hNSC) labeling efficacy of different superparamagnetic iron oxide nanoparticles (SPIONs), namely, ferumoxides, monocrystalline iron oxide (MION), cross-linked iron oxide (CLIO)-NH(2) and tat-CLIO. MATERIALS AND METHODS: The hNSCs (5 x 10(5) HB1F3 cells/ml) were incubated for 24 hr in cell culture media that contained 25 microg/ml of ferumoxides, MION or CLIO-NH(2), and with or without poly-L-lysine (PLL) and tat-CLIO. The cellular iron uptake was analyzed qualitatively with using a light microscope and this was quantified via atomic absorption spectrophotometry. The visibility of the labeled cells was assessed with MR imaging. RESULTS: The incorporation of SPIONs into the hNSCs did not affect the cellular proliferations and viabilities. The hNSCs labeled with tat-CLIO showed the longest retention, up to 72 hr, and they contained 2.15+/-0.3 pg iron/cell, which are 59 fold, 430 fold and six fold more incorporated iron than that of the hNSCs labeled with ferumoxides, MION or CLIO-NH(2), respectively. However, when PLL was added, the incorporation of ferumoxides, MION or CLIO-NH(2) into the hNSCs was comparable to that of tat-CLIO. CONCLUSION: For MR imaging, hNSCs can be efficiently labeled with tat-CLIO alone or with a combination of ferumoxides, MION, CLIO-NH(2) and the transfection agent PLL.This research was supported by the Korean Health 21 R & D Project, Ministry of Health & Welfare (Project No. A040004), by the National R&D Program for Cancer Control, Ministry of Health & Welfare, Republic of Korea (Grant no. 0420080-1), and by the National R & D Program of the Korean Ministry of Science and Technology (Project No. SC-3111

In Vivo MR Imaging of Magnetically Labeled Mesenchymal Stem Cells in a Rat Model of Renal Ischemia

Objective: This study was designed to evaluate in vivo MR imaging for the depiction of intraarterially injected superparamagnetic iron oxide (SPIO)-labeled mesenchymal stem cells (MSCs) in an experimental rat model of renal ischemia. Materials and Methods: Left renal ischemia was induced in 12 male Sprague-Dawley rats by use of the catheter lodging method. In vivo MR signal intensity variations depicted on T2*-weighted sequences were evaluated in both the left and right kidneys prior to injection (n = 2), two hours (n = 4), 15 hours (n = 2), 30 hours (n = 2) and 72 hours (n = 2) after injection of SPIO-labeled MSCs in both kidneys. Signal intensity variations were correlated with the number of Prussian blue stain-positive cells as visualized in histological specimens. Results: In an in vivo study, it was determined that there was a significant difference in signal intensity variation for both the left and right cortex (40.8 +/- 4.12 and 26.4 +/- 7.92, respectively) and for both the left and right medulla (23.2 +/- 3.32 and 15.2 +/- 3.31, respectively) until two hours after injection (p < 0.05). In addition, signal intensity variation in the left renal cortex was well correlated with the number of Prussian blue stain-positive cells per high power field (r = 0.98, p < 0.05). Conclusion: Intraarterial injected SPIO-labeled MSCs in an experimental rat model of renal ischemia can be detected with the use of in vivo MR imaging immediately after injection.This study was partly supported by a grant from the Seoul Research and Business Development Program 10548 and by a grant (A062260) from the Innovative Research Institute for Cell Therapy, Republic of Korea.Ittrich H, 2007, J MAGN RESON IMAGING, V25, P1179, DOI 10.1002/jmri.20925Hauger O, 2006, RADIOLOGY, V238, P200, DOI 10.1148/radiol.2381041668Togel F, 2005, AM J PHYSIOL-RENAL, V289, pF31, DOI 10.1152/ajprenal.00007.2005Bos C, 2004, RADIOLOGY, V233, P781, DOI 10.1148/radiol.2333031714Bulte JWM, 2004, NMR BIOMED, V17, P484, DOI 10.1002/nbm.924Grove JE, 2004, STEM CELLS, V22, P487Herzog EL, 2003, BLOOD, V102, P3483, DOI 10.1182/blood-2003-05-1664Kalish H, 2003, MAGNET RESON MED, V50, P275, DOI 10.1002/mrm.10556Frank JA, 2003, RADIOLOGY, V228, P480, DOI 10.1148/radiol.2281020638Jo SK, 2003, KIDNEY INT, V64, P43Kale S, 2003, J CLIN INVEST, V112, P42, DOI 10.1172/JCI200317856Bulte JWM, 2003, MAGNET RESON MED, V50, P201, DOI 10.1002/mrm.10511Kraitchman DL, 2003, CIRCULATION, V107, P2290, DOI 10.1161/01.CIR.0000070931.62772.4EGupta S, 2002, KIDNEY INT, V62, P1285Krause DS, 2002, GENE THER, V9, P754Bulte JWM, 2001, NAT BIOTECHNOL, V19, P1141Lewin M, 2000, NAT BIOTECHNOL, V18, P410Kelly KJ, 2000, SEMIN NEPHROL, V20, P4Firbank MJ, 1999, PHYS MED BIOL, V44, pN261, DOI 10.1088/0031-9155/44/12/403Josephson L, 1999, BIOCONJUGATE CHEM, V10, P186Sutton TA, 1998, SEMIN NEPHROL, V18, P490Thadhani R, 1996, NEW ENGL J MED, V334, P1448SHANLEY PF, 1986, AM J PATHOL, V122, P462

Exploratory Biomarker Analysis In The Ph 3 Echelon‐1 Study: Worse Outcome With Abvd In Patients With Elevated Baseline Levels Of Scd30 And Tarc

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149507/1/hon99_2630.pd

Influence of pH on Ca2+ current and its control of electrical and Ca2+ signaling in ventricular myocytes

Modulation of L-type Ca2+ current (ICa,L) by H+ ions in cardiac myocytes is controversial, with widely discrepant responses reported. The pH sensitivity of ICa,L was investigated (whole cell voltage clamp) while measuring intracellular Ca2+ (Ca2+i) or pHi (epifluorescence microscopy) in rabbit and guinea pig ventricular myocytes. Selectively reducing extracellular or intracellular pH (pHo 6.5 and pHi 6.7) had opposite effects on ICa,L gating, shifting the steady-state activation and inactivation curves to the right and left, respectively, along the voltage axis. At low pHo, this decreased ICa,L, whereas at low pHi, it increased ICa,L at clamp potentials negative to 0 mV, although the current decreased at more positive potentials. When Ca2+i was buffered with BAPTA, the stimulatory effect of low pHi was even more marked, with essentially no inhibition. We conclude that extracellular H+ ions inhibit whereas intracellular H+ ions can stimulate ICa,L. Low pHi and pHo effects on ICa,L were additive, tending to cancel when appropriately combined. They persisted after inhibition of calmodulin kinase II (with KN-93). Effects are consistent with H+ ion screening of fixed negative charge at the sarcolemma, with additional channel block by H+o and Ca2+i. Action potential duration (APD) was also strongly H+ sensitive, being shortened by low pHo, but lengthened by low pHi, caused mainly by H+-induced changes in late Ca2+ entry through the L-type Ca2+ channel. Kinetic analyses of pH-sensitive channel gating, when combined with whole cell modeling, successfully predicted the APD changes, plus many of the accompanying changes in Ca2+ signaling. We conclude that the pHi-versus-pHo control of ICa,L will exert a major influence on electrical and Ca2+-dependent signaling during acid–base disturbances in the heart

Theory of Two-Dimensional Quantum Heisenberg Antiferromagnets with a Nearly Critical Ground State

We present the general theory of clean, two-dimensional, quantum Heisenberg antiferromagnets which are close to the zero-temperature quantum transition between ground states with and without long-range N\'{e}el order. For N\'{e}el-ordered states, `nearly-critical' means that the ground state spin-stiffness, $\rho_s$, satisfies $\rho_s \ll J$, where $J$ is the nearest-neighbor exchange constant, while `nearly-critical' quantum-disordered ground states have a energy-gap, $\Delta$, towards excitations with spin-1, which satisfies $\Delta \ll J$. Under these circumstances, we show that the wavevector/frequency-dependent uniform and staggered spin susceptibilities, and the specific heat, are completely universal functions of just three thermodynamic parameters. Explicit results for the universal scaling functions are obtained by a $1/N$ expansion on the $O(N)$ quantum non-linear sigma model, and by Monte Carlo simulations. These calculations lead to a variety of testable predictions for neutron scattering, NMR, and magnetization measurements. Our results are in good agreement with a number of numerical simulations and experiments on undoped and lightly-doped $La_{2-\delta} Sr_{\delta}Cu O_4$.Comment: 81 pages, REVTEX 3.0, smaller updated version, YCTP-xxx