122 research outputs found
Magnetization steps in a diluted Heisenberg antiferromagnetic chain: Theory and experiments on TMMC:Cd
A theory for the equilibrium low-temperature magnetization M of a diluted
Heisenberg antiferromagnetic chain is presented. The magnetization curve, M
versus B, is calculated using the exact contributions of finite chains with 1
to 5 spins, and the "rise and ramp approximation" for longer chains. Some
non-equilibrium effects that occur in a rapidly changing B, are also
considered. Specific non-equilibrium models based on earlier treatments of the
phonon bottleneck, and of spin flips associated with cross relaxation and with
level crossings, are discussed. Magnetization data on powders of TMMC diluted
with cadmium [i.e., (CH_3)_4NMn_xCd_(1-x)Cl_3, with 0.16<=x<=0.50 were measured
at 0.55 K in 18 T superconducting magnets. The field B_1 at the first MST from
pairs is used to determine the NN exchange constant, J, which changes from -5.9
K to -6.5 K as x increases from 0.16 to 0.50. The magnetization curves obtained
in the superconducting magnets are compared with simulations based on the
equilibrium theory. Data for the differential susceptibility, dM/dB, were taken
in pulsed magnetic fields (7.4 ms duration) up to 50 T, with the powder samples
in a 1.5 K liquid-helium bath. Non-equilibrium effects, which became more
severe as x decreased, were observed. The non-equilibrium effects are
tentatively interpreted using the "Inadequate Heat Flow Scenario," or to
cross-relaxation, and crossings of energy levels, including those of excited
states.Comment: 16 pages, 14 figure
Spectral sensitive phonon wipeout due to a fluctuating spin state in a Fe2+ coordination polymer
Raman scattering in the spin-crossover system [Fe(pmd)(H2O){Au(CN)2}2]*H2O
reveals a complex three-phase spin-state transition in contrast to earlier
observations in magnetization measurements. We observe different spin state
phases as function of temperature and electromagnetic radiation in the visible
spectral range. There exists a fluctuating spin state phase with an unexpected
wipeout of the low frequency phonon scattering intensity. Furthermore we
observe one phase with reduced symmetry that is attributed to a cooperative
Jahn-Teller effect. Pronounced electron-phonon interaction manifests itself as
a strong Fano-resonance of phonons related to {FeN6} and {FeN4O2} coordination
octahedra. Density functional theory supports this interpretation.Comment: 9 pages, 9 figures, 3 table
Woodrow Wilson’s diplomatic agenda and strategic military interventions: how they affected the Russian Civil War 1918-1920
This thesis aims to understand the factors that affected Woodrow Wilson’s foreign and military policy actions, which subsequently led to decisions that dictated United States’ intervention into the Russian Civil War, 1918-1920. The background information discussed demonstrates the importance of the Russian Civil War. This chaotic time in history surrounding World War I caused much of Woodrow Wilson’s dilemma and consequentially changed future of Soviet-American relations. It details how it would take numerous foreign policy shifts to convince Mr. Wilson to send U.S. troops to intervene into North Russia and Siberia. Lenin’s opposing perspective will encompass what is contained in much of the supporting information surrounding this thesis. In conjunction with military operations there, the allies attempted to broker peace with Lenin and the Bolsheviks in the form of the Prinkipo Proposal, the Bullitt Mission, and the Hoover-Nansen Proposal. The concluding question that frames the argument of this research will answer what happened because Wilson intervened on Russian soil and how it affected the Communist world revolution. What positive results, if any, can be discovered? (Author abstract)Rinehart, R.A. (2017) Woodrow Wilson’s diplomatic agenda and strategic military interventions: how they affected the Russian Civil War 1918-1920. Retrieved from http://academicarchive.snhu.eduMaster ArtsHistoryCollege of Online and Continuing Educatio
Exome sequencing in suspected monogenic dyslipidemias
Exome sequencing is a promising tool for gene mapping in Mendelian disorders. We used this technique in an attempt to identify novel genes underlying monogenic dyslipidemias
An Organic Spin Crossover Material in Water from a Covalently Linked Radical Dyad
A covalently linked viologen radical cation dyad acts as a reversible thermomagnetic switch in water. Cycling between diamagnetic and paramagnetic forms by heating and cooling is accompanied by changes in optical and magnetic properties with high radical fidelity. Thermomagnetic switches in water may eventually find use as novel biological thermometers and in temperature-responsive organic materials where the changes in properties originate from a change in electronic spin configuration rather than a change in structure
Posttranscriptional Regulation of the Human LDL Receptor by the U2-Spliceosome
Background: The low-density lipoprotein receptor (LDLR) in the liver is the major determinant of LDL-cholesterol levels in human plasma. The discovery of genes that regulate the activity of LDLR helps to identify pathomechanisms of hypercholesterolemia and novel therapeutic targets against atherosclerotic cardiovascular disease.Methods: We performed a genome-wide RNA interference screen for genes limiting the uptake of fluorescent LDL into Huh-7 hepatocarcinoma cells. Top hit genes were validated by in vitro experiments as well as analyses of datasets on gene expression and variants in human populations.Results: The knockdown of 54 genes significantly inhibited LDL uptake. Fifteen of them encode for components or interactors of the U2-spliceosome. Knocking down any one of 11 out of 15 genes resulted in the selective retention of intron 3 of LDLR. The translated LDLR fragment lacks 88% of the full length LDLR and is detectable neither in non-transfected cells nor in human plasma. The hepatic expression of the intron 3 retention transcript is increased in non-alcoholic fatty liver disease as well as after bariatric surgery. Its expression in blood cells correlates with LDL-cholesterol and age. Single nucleotide polymorphisms and three rare variants of one spliceosome gene, RBM25, are associated with LDL-cholesterol in the population and familial hypercholesterolemia, respectively. Compared to overexpression of wild type RBM25, overexpression of the three rare RBM25 mutants in Huh-7 cells led to lower LDL uptake.Conclusions: We identified a novel mechanism of post-transcriptional regulation of LDLR activity in humans and associations of genetic variants of RBM25 with LDL-cholesterol levels.</p
Pressure, temperature and light influence on spin transition solids
Present paper is an overview of our efforts during the past few years to understand complicated corelations of physical phenomena related to pressure in Fe(I1) solid state spin transition systems. Some principal results concerning p, T, λ-experiments are extracted. In the context of correlation of the crystallographic phase transition with simultaneous HS → LS relaxation and LS → HS photopopulation, we show the latest results: Brillouin and magnetic measurements on the crystal [Fe(pt6](BF6)2
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