811 research outputs found
Effect of strain on the phase separation and devitrification of the magnetic glass state in thin films of La<SUB>5/8-y</SUB>Pr<SUB>y</SUB>Ca<SUB>3/8</SUB>MnO<SUB>3</SUB> (y= 0.45)
We present our study of the effect of substrate induced strain on La5/8 - yPryCa3/8MnO3 (y = 0.45) thin films grown on LaAlO3, NdGaO3 and SrTiO3 substrates that show large scale phase separation. It is observed that unstrained films grown on NdGaO3 behave quite similarly to bulk material but the strained films grown on SrTiO3 show melting of the insulating phase to the metallic phase at low temperatures. However, the large scale phase separation and metastable glass-like state is observed in all the films despite differences in substrate induced strain. The measurements of resistivity as a function of temperature under a cooling and heating in unequal field (CHUF) protocol elucidate the presence of a glass-like metastable phase generated due to kinetic arrest of the first order transformation in all the films. Like structural glasses, these magnetic glass-like phases show evidence of devitrification of the arrested charge order antiferromagnetic insulator (CO-AFI) phase to the equilibrium ferromagnetic metallic (FMM) phase with isothermal increase of magnetic field and/or iso-field warming. These measurements also clearly show the equilibrium ground state of this system to be FMM and the metastable glass-like phase to be AFI phase
Combinatorial activities of SHORT VEGETATIVE PHASE and FLOWERING LOCUS C define distinct modes of flowering regulation in Arabidopsis.
BACKGROUND: The initiation of flowering is an important developmental transition as it marks the beginning of the reproductive phase in plants. The MADS-box transcription factors (TFs) FLOWERING LOCUS C (FLC) and SHORT VEGETATIVE PHASE (SVP) form a complex to repress the expression of genes that initiate flowering in Arabidopsis. Both TFs play a central role in the regulatory network by conferring seasonal patterns of flowering. However, their interdependence and biological relevance when acting as a complex have not been extensively studied. RESULTS: We characterized the effects of both TFs individually and as a complex on flowering initiation using transcriptome profiling and DNA-binding occupancy. We find four major clusters regulating transcriptional responses, and that DNA binding scenarios are highly affected by the presence of the cognate partner. Remarkably, we identify genes whose regulation depends exclusively on simultaneous action of both proteins, thus distinguishing between the specificity of the SVP:FLC complex and that of each TF acting individually. The downstream targets of the SVP:FLC complex include a higher proportion of genes regulating floral induction, whereas those bound by either TF independently are biased towards floral development. Many genes involved in gibberellin-related processes are bound by the SVP:FLC complex, suggesting that direct regulation of gibberellin metabolism by FLC and SVP contributes to their effects on flowering. CONCLUSIONS: The regulatory codes controlled by SVP and FLC were deciphered at the genome-wide level revealing substantial flexibility based on dependent and independent DNA binding that may contribute to variation and robustness in the regulation of flowering
Explicit MBR All-Symbol Locality Codes
Node failures are inevitable in distributed storage systems (DSS). To enable
efficient repair when faced with such failures, two main techniques are known:
Regenerating codes, i.e., codes that minimize the total repair bandwidth; and
codes with locality, which minimize the number of nodes participating in the
repair process. This paper focuses on regenerating codes with locality, using
pre-coding based on Gabidulin codes, and presents constructions that utilize
minimum bandwidth regenerating (MBR) local codes. The constructions achieve
maximum resilience (i.e., optimal minimum distance) and have maximum capacity
(i.e., maximum rate). Finally, the same pre-coding mechanism can be combined
with a subclass of fractional-repetition codes to enable maximum resilience and
repair-by-transfer simultaneously
Magnetic glass in Shape Memory Alloy : Ni45Co5Mn38Sn12
The first order martensitic transition in the ferromagnetic shape memory
alloy Ni45Co5Mn38Sn12 is also a magnetic transition and has a large field
induced effect. While cooling in the presence of field this first order
magnetic martensite transition is kinetically arrested. Depending on the
cooling field, a fraction of the arrested ferromagnetic austenite phase
persists down to the lowest temperature as a magnetic glassy state, similar to
the one observed in various intermetallic alloys and in half doped manganites.
A detailed investigation of this first order ferromagnetic austenite (FM-A) to
low magnetization martensite (LM-M) state transition as a function of
temperature and field has been carried out by magnetization measurements.
Extensive cooling and heating in unequal field (CHUF) measurements and a novel
field cooled protocol for isothermal MH measurements (FC-MH) are utilized to
investigate the glass like arrested states and show a reverse martensite
transition. Finally, we determine a field -temperature (HT) phase diagram of
Ni45Co5Mn38Sn12 from various magnetization measurements which brings out the
regions where thermodynamic and metastable states co-exist in the HT space
clearly depicting this system as a 'Magnetic Glass'.Comment: Magnetic field tunes kinetic arrest and CHUF shows devitrification
and melting of Magnetic glas
Magnetism, Upper critical field and Thermoelectric power of Magneto-Superconductor RuSr2Eu1.5Ce0.5Cu2O10
Magnetic susceptibility, M-H plot, magnetoresistance and thermoelectric power
of the RuSr2Eu1.5Ce0.5Cu2O10 superconductor are measured. Values of the
magnetic transition temperature Tmag, superconductivity transition temperature
Tc, upper critical field Hc2, chemical potential mu, and energy width for
electric conduction W(sigma) are obtained from these measurements. It has been
found that Tmag = 140 K, Tc = 25 K (33 K) from susceptibility
(magnetoresistance) measurements, Hc2 (0) > 32 T, mu = 8 meV, and W(sigma) =
58.5 meV. These values are compared with other ruthenate superconductors, and
resulting physical information is discussed.Comment: 18 pages of TEXT + FIGS. To appear in - J. PHYS. COND. MATT. (2006
Physical property characterization of Fe-tube encapsulated and vacuum annealed bulk MgB2
We report phase formation, and detailed study of magnetization and
resistivity under magnetic field of MgB2 polycrystalline bulk samples prepared
by Fe-tube encapsulated and vacuum (10-5 torr) annealed (750 0C) route.
Zero-field-cooled magnetic susceptibility (cZFC) measurements exhibited sharp
transition to superconducting state with a sizeable diamagnetic signal at 39 K
(Tc). The measured magnetization loops of the samples, despite the presence of
flux jumps, exhibited a stable current density (Jc) of around 2.4 x 105 A/cm2
in up to 2 T (Tesla) field and at temperatures (T) up to 10 K. The upper
critical field is estimated from resistivity measurements in various fields and
shows a typical value of 8 T at 21 K. Further, cFC measurements at an applied
field of 0.1 T reveal paramagnetic Meissner effect (PME) that is briefly
discussed.Comment: 13 pages text + figs. accepted: solid state commun. (2006
Electromagnetically induced transparency in cold 85Rb atoms trapped in the ground hyperfine F = 2 state
We report electromagnetically induced transparency (EIT) in cold 85Rb atoms,
trapped in the lower hyperfine level F = 2, of the ground state 5
(Tiwari V B \textit{et al} 2008 {\it Phys. Rev.} A {\bf 78} 063421). Two steady
state -type systems of hyperfine energy levels are investigated using
probe transitions into the levels F = 2 and F = 3 of the
excited state 5 in the presence of coupling transitions F = 3
F = 2 and F = 3 F = 3, respectively. The
effects of uncoupled magnetic sublevel transitions and coupling field's Rabi
frequency on the EIT signal from these systems are studied using a simple
theoretical model.Comment: 12 pages, 7 figure
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