2,889 research outputs found
On the reliability of negative heat capacity measurements
A global protocol for the thermostatistical analysis of hot nuclear sources
is discussed. Within our method of minimization of variances we show that the
abnormal kinetic energy fluctuation signal recently reported in different
experimental data (M.D'Agostino et al.-Phys. Lett. B 473 (2000) 219, N. Le
Neindre et al.- contr. to the XXXVIII Bormio Winter Meeting on Nucl. Phys.
(2001) 404) is a genuine signal of a first order phase transition in a finite
system.Comment: 15 Postscript figures, submitted to NUCL. Phys. A on 24-apr-200
The ground state of the Lithium atom in strong magnetic fields
The ground and some excited states of the Li atom in external uniform
magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for
field strengths ranging from zero up to 2.35 10^8 T. With increasing field
strength the ground state undergoes two transitions involving three different
electronic configurations: for weak fields the ground state configuration
arises from the field-free 1s^22s configuration, for intermediate fields from
the 1s^22p_{-1} configuration and in high fields the 1s2p_{-1}3d_{-2}
electronic configuration is responsible for the properties of the atom. The
transition field strengths are determined. Calculations on the ground state of
the Li+ ion allow us to describe the field-dependent ionization energy of the
Li atom. Some general arguments on the ground states of multi-electron atoms in
strong magnetic fields are provided.Comment: 11 pages, 6 figures, submitted to Physical Review
The ground state of the carbon atom in strong magnetic fields
The ground and a few excited states of the carbon atom in external uniform
magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for
field strengths ranging from zero up to 2.35 10^9 T. With increasing field
strength the ground state undergoes six transitions involving seven different
electronic configurations which belong to three groups with different spin
projections S_z=-1,-2,-3. For weak fields the ground state configuration arises
from the field-free 1s^2 2s^2 2p_0 2p_{-1}, S_z=-1 configuration. With
increasing field strength the ground state involves the four S_z=-2
configurations 1s^22s2p_0 2p_{-1}2p_{+1}, 1s^22s2p_0 2p_{-1}3d_{-2}, 1s^22p_0
2p_{-1}3d_{-2}4f_{-3} and 1s^22p_{-1}3d_{-2}4f_{-3}5g_{-4}, followed by the two
fully spin polarized S_z=-3 configurations 1s2p_02p_{-1}3d_{-2}4f_{-3}5g_{-4}
and 1s2p_{-1}3d_{-2}4f_{-3}5g_{-4}6h_{-5}. The last configuration forms the
ground state of the carbon atom in the high field regime \gamma>18.664. The
above series of ground state configurations is extracted from the results of
numerical calculations for more than twenty electronic configurations selected
due to some general energetical arguments.Comment: 6 figures,acc. Phys.Rev.
Spin oscillations in transient diffusion of a spin pulse in n-type semiconductor quantum wells
By studying the time and spatial evolution of a pulse of the spin
polarization in -type semiconductor quantum wells, we highlight the
importance of the off-diagonal spin coherence in spin diffusion and transport.
Spin oscillations and spin polarization reverse along the the direction of spin
diffusion in the absence of the applied magnetic field are predicted from our
investigation.Comment: 5 pages, 4 figures, accepted for publication in PR
Boundary line analysis of the effect of water-filled pore space on nitrous oxide emission from cores of arable soil
The boundary line has been proposed as a model of the effects of a variable on a biological response, when this variable might limit the response in only some of a set of observations. It is proposed that the upper boundary (in some circumstances the lower boundary) represents the response function of interest. Boundary-line analysis is a method for estimating this response function from data. The approach has been used to model the emission of N2O from soil in response to various soil properties. However, the methods that have been used to identify the boundary are based on somewhat ad hoc partitions of the data. A statistical model that we have presented previously has not been applied to this problem in soil science, and we do so here to represent how the water-filled pore space (WFPS) of the soil affects the rate of N2O emission. We derive a boundary-line response that can be shown to be a better model for the data than an unbounded alternative by statistical criteria. Furthermore, the fitted boundary-response model is consistent with past empirical observations and modelling studies with respect to both the WFPS at which the potential emission rate is largest and the measurement error for the emission rates themselves. We show how the fitted model might be used to interpret data on soil volumetric water content with respect to seasonal changes in potential emissions, and to compare potential emissions between soil series that have contrasting physical properties
Betibeglogene Autotemcel Gene Therapy for Non-β⁰/β⁰ Genotype β-Thalassemia
BACKGROUND: Betibeglogene autotemcel (beti-cel) gene therapy for transfusion-dependent β-thalassemia contains autologous CD34+ hematopoietic stem cells and progenitor cells transduced with the BB305 lentiviral vector encoding the β-globin (βA-T87Q) gene. METHODS: In this open-label, phase 3 study, we evaluated the efficacy and safety of beti-cel in adult and pediatric patients with transfusion-dependent β-thalassemia and a non-β0/β0 genotype. Patients underwent myeloablation with busulfan (with doses adjusted on the basis of pharmacokinetic analysis) and received beti-cel intravenously. The primary end point was transfusion independence (i.e., a weighted average hemoglobin level of ≥9 g per deciliter without red-cell transfusions for ≥12 months). RESULTS: A total of 23 patients were enrolled and received treatment, with a median follow-up of 29.5 months (range, 13.0 to 48.2). Transfusion independence occurred in 20 of 22 patients who could be evaluated (91%), including 6 of 7 patients (86%) who were younger than 12 years of age. The average hemoglobin level during transfusion independence was 11.7 g per deciliter (range, 9.5 to 12.8). Twelve months after beti-cel infusion, the median level of gene therapy-derived adult hemoglobin (HbA) with a T87Q amino acid substitution (HbAT87Q) was 8.7 g per deciliter (range, 5.2 to 10.6) in patients who had transfusion independence. The safety profile of beti-cel was consistent with that of busulfan-based myeloablation. Four patients had at least one adverse event that was considered by the investigators to be related or possibly related to beti-cel; all events were nonserious except for thrombocytopenia (in 1 patient). No cases of cancer were observed. CONCLUSIONS: Treatment with beti-cel resulted in a sustained HbAT87Q level and a total hemoglobin level that was high enough to enable transfusion independence in most patients with a non-β0/β0 genotype, including those younger than 12 years of age. (Funded by Bluebird Bio; HGB-207 ClinicalTrials.gov number, NCT02906202.)
Spin injection and spin accumulation in all-metal mesoscopic spin valves
We study the electrical injection and detection of spin accumulation in
lateral ferromagnetic metal-nonmagnetic metal-ferromagnetic metal (F/N/F) spin
valve devices with transparent interfaces. Different ferromagnetic metals,
permalloy (Py), cobalt (Co) and nickel (Ni), are used as electrical spin
injectors and detectors. For the nonmagnetic metal both aluminium (Al) and
copper (Cu) are used. Our multi-terminal geometry allows us to experimentally
separate the spin valve effect from other magneto resistance signals such as
the anomalous magneto resistance (AMR) and Hall effects. We find that the AMR
contribution of the ferromagnetic contacts can dominate the amplitude of the
spin valve effect, making it impossible to observe the spin valve effect in a
'conventional' measurement geometry. In a 'non local' spin valve measurement we
are able to completely isolate the spin valve signal and observe clear spin
accumulation signals at T=4.2 K as well as at room temperature (RT). For
aluminum we obtain spin relaxation lengths (lambda_{sf}) of 1.2 mu m and 600 nm
at T=4.2 K and RT respectively, whereas for copper we obtain 1.0 mu m and 350
nm. The spin relaxation times tau_{sf} in Al and Cu are compared with theory
and results obtained from giant magneto resistance (GMR), conduction electron
spin resonance (CESR), anti-weak localization and superconducting tunneling
experiments. The spin valve signals generated by the Py electrodes (alpha_F
lambda_F=0.5 [1.2] nm at RT [T=4.2 K]) are larger than the Co electrodes
(alpha_F lambda_F=0.3 [0.7] nm at RT [T=4.2 K]), whereas for Ni (alpha_F
lambda_F<0.3 nm at RT and T=4.2 K) no spin signal is observed. These values are
compared to the results obtained from GMR experiments.Comment: 16 pages, 12 figures, submitted to PR
Boundary line analysis of the effect of water-filled pore space on nitrous oxide emission from cores of arable soil
Quantum Magnetism of Spin-Ladder Compounds with Trapped-Ion Crystals
The quest for experimental platforms that allow for the exploration, and even
control, of the interplay of low dimensionality and frustration is a
fundamental challenge in several fields of quantum many-body physics, such as
quantum magnetism. Here, we propose the use of cold crystals of trapped ions to
study a variety of frustrated quantum spin ladders. By optimizing the trap
geometry, we show how to tailor the low dimensionality of the models by
changing the number of legs of the ladders. Combined with a method for
selectively hiding of ions provided by laser addressing, it becomes possible to
synthesize stripes of both triangular and Kagome lattices. Besides, the degree
of frustration of the phonon-mediated spin interactions can be controlled by
shaping the trap frequencies. We support our theoretical considerations by
initial experiments with planar ion crystals, where a high and tunable
anisotropy of the radial trap frequencies is demonstrated. We take into account
an extensive list of possible error sources under typical experimental
conditions, and describe explicit regimes that guarantee the validity of our
scheme
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