Tensor polarizability and dispersive quantum measurement of multilevel atoms

Optimally extracting information from measurements performed on a physical system requires an accurate model of the measurement interaction. Continuously probing the collective spin of an Alkali atom cloud via its interaction with an off-resonant optical probe is an important example of such a measurement where realistic modeling at the quantum level is possible using standard techniques from atomic physics. Typically, however, tutorial descriptions of this technique have neglected the multilevel structure of realistic atoms for the sake of simplification. In this paper we account for the full multilevel structure of Alkali atoms and derive the irreducible form of the polarizability Hamiltonian describing a typical dispersive quantum measurement. For a specific set of parameters, we then show that semiclassical predictions of the theory are consistent with our experimental observations of polarization scattering by a polarized cloud of laser-cooled Cesium atoms. We also derive the signal-to-noise ratio under a single measurement trial and use this to predict the rate of spin-squeezing with multilevel Alkali atoms for arbitrary detuning of the probe beam.Comment: Significant corrections to theory and data. Full quality figures and other information available from http://minty.caltech.edu/papers.ph

Targeted JAM-C deletion in germ cells by Spo11-controlled Cre recombinase

Meiosis is a crucial process for the production of functional gametes. However, the biological significance of many genes expressed during the meiotic phase remains poorly understood, mainly because of the lethal phenotypes of the knockout mice. Functional analysis of such genes using the conditional knockout approach is hindered by the lack of suitable Cre transgenic lines. We describe here the generation of transgenic mice expressing Cre recombinase under the control of the meiotic Spo11 gene. Using LacZ-R26(loxP) and EYFP-R26(loxP) reporter mice, we show the specific expression and activity of Cre during meiosis in males and females. Spo11(Cre) mice were then crossed with floxed Nbs1 and JAM-C mice to produce conditional knockouts. A strong reduction of Nbs1 and JAM-C protein levels was found in the testis. Although Nbs1-deleted mice developed minor gonadal abnormalities, JAM-C-knockout mice showed a spermiogenetic arrest, as previously described for the null mice. These results provide strong evidence that Spo11(Cre) transgenic mice represent a powerful tool for deleting genes of interest specifically in meiotic and/or in postmeiotic germ cells

Pharmacokinetics and Pharmacodynamics of Therapeutic Doses of Basal Insulins NPH, Glargine, and Detemir After 1 Week of Daily Administration at Bedtime in Type 2 Diabetic Subjects: A randomized cross-over study

OBJECTIVE-To compare the pharmacokinetics and pharmacodynamics of NPH, glargine, and detemir insulins in type 2 diabetic subjects. RESEARCH DESIGN AND METHODS-This study used a single-blind, three-way, cross-over design. A total of 18 type 2 diabetic subjects underwent a euglycemic clamp for 32 h after a subcutaneous injection of 0.4 units/kg at 2200 h of either NPH, glargine, or detemir after 1 week of bedtime treatment with each insulin. RESULTS-The glucose infusion rate area under the curve(0-32 h) was greater for glargine than for detemir and NPH (1,538 +/- 688; 1,081 +/- 785; and 1,170 +/- 703 mg/kg, respectively; P 150 mg/dL. CONCLUSIONS-Compared with NPH and detemir, glargine provided greater metabolic activity and superior glucose control for up to 32 h.Lucidi, P.; Porcellati, F.; Rossetti ., P.; Candeloro, P.; Cioli, P.; Marzotti, S.; Andreoli, AM.... (2011). Pharmacokinetics and pharmacodynamics of therapeutic doses of basal insulins NPH, glargine, and detemir after 1 week of daily administration at bedtime in type 2 diabetic subjects: a randomized cross-over study. Diabetes Care. 34(6):1312-1314. doi:10.2337/dc10-1911S1312131434

The effectiveness of the anti-CD11d treatment is reduced in rat models of spinal cord injury that produce significant levels of intraspinal hemorrhage

We have previously reported that administration of a CD11d monoclonal antibody (mAb) improves recovery in a clip-compression model of SCI. In this model the CD11d mAb reduces the infiltration of activated leukocytes into the injured spinal cord (as indicated by reduced intraspinal MPO). However not all anti-inflammatory strategies have reported beneficial results, suggesting that success of the CD11d mAb treatment may depend on the type or severity of the injury. We therefore tested the CD11d mAb treatment in a rat hemi-contusion model of cervical SCI. In contrast to its effects in the clip-compression model, the CD11d mAb treatment did not improve forelimb function nor did it significantly reduce MPO levels in the hemi-contused cord. To determine if the disparate results using the CD11d mAb were due to the biomechanical nature of the cord injury (compression SCI versus contusion SCI) or to the spinal level of the injury (12th thoracic level versus cervical) we further evaluated the CD11d mAb treatment after a T12 contusion SCI. In contrast to the T12 clip compression SCI, the CD11d mAb treatment did not improve locomotor recovery or significantly reduce MPO levels after T12 contusion SCI. Lesion analyses revealed increased levels of hemorrhage after contusion SCI compared to clip-compression SCI. SCI that is accompanied by increased intraspinal hemorrhage would be predicted to be refractory to the CD11d mAb therapy as this approach targets leukocyte diapedesis through the intact vasculature. These results suggest that the disparate results of the anti-CD11d treatment in contusion and clip-compression models of SCI are due to the different pathophysiological mechanisms that dominate these two types of spinal cord injuries

A Geological Itinerary Through the Southern Apennine Thrust-Belt (Basilicata—Southern Italy)

Open access via Springer Compact AgreementPeer reviewedPublisher PD

Assessment of soil fungal diversity in different alpine tundra habitats by means of pyrosequencing

Abstract Studying fungal diversity is vital if we want to shed light on terrestrial ecosystem functioning. However, there is still poor understanding of fungal diversity and variation given that Fungi are highly diversified and that most of fungal species remain uncultured. In this study we explored diversity with 454 FLX sequencing technology by using the Internal Transcribed Spacer 1 (ITS1) as the fungal barcode marker in order to evaluate the effect of 11 environmental conditions on alpine soil fungal diversity, as well as the consistency of those results by taking into account rare or unidentified Molecular Operational Taxonomic Units (MOTUs). In total we obtained 205131 ITS1 reads corresponding to an estimated fungal gamma diversity of between 5100 and 12 000 MOTUs at a 98% similarity threshold when considering respectively only identified fungal and all MOTUs. Fungal beta-diversity patterns were significantly explained by the environmental conditions, and were very consistent for abundant/rare and fungal/unidentified MOTUs confirming the ecological significance of rare/unidentified MOTUs, and therefore the existence of a fungal rare biosphere. This study shows that a beta-diversity estimation based on pyrosequencing is robust enough to support ecological studies. Additionally, our results suggest that rare MOTUs harbour ecological Guillaume Lentendu and Lucie Zinger equally contributed to this paper. Electronic supplementary material The online version of this articl

Characterizing the entanglement of symmetric many-particle spin-1/2 systems

Analyzing the properties of entanglement in many-particle spin-1/2 systems is generally difficult because the system's Hilbert space grows exponentially with the number of constituent particles, $N$. Fortunately, it is still possible to investigate many-particle entanglement when the state of the system possesses sufficient symmetry. In this paper, we present a practical method for efficiently computing various bipartite entanglement measures for states in the symmetric subspace and perform these calculations for $N\sim 10^3$. By considering all possible bipartite splits, we construct a picture of the multiscale entanglement in large symmetric systems. In particular, we characterize dynamically generated spin-squeezed states by comparing them to known reference states (e.g., GHZ and Dicke states) and new families of states with near-maximal bipartite entropy. We quantify the trade-off between the degree of entanglement and its robustness to particle loss, emphasizing that substantial entanglement need not be fragile.Comment: Updated version reflects changes made in January 200

Optimal estimation of qubit states with continuous time measurements

We propose an adaptive, two steps strategy, for the estimation of mixed qubit states. We show that the strategy is optimal in a local minimax sense for the trace norm distance as well as other locally quadratic figures of merit. Local minimax optimality means that given $n$ identical qubits, there exists no estimator which can perform better than the proposed estimator on a neighborhood of size $n^{-1/2}$ of an arbitrary state. In particular, it is asymptotically Bayesian optimal for a large class of prior distributions. We present a physical implementation of the optimal estimation strategy based on continuous time measurements in a field that couples with the qubits. The crucial ingredient of the result is the concept of local asymptotic normality (or LAN) for qubits. This means that, for large $n$, the statistical model described by $n$ identically prepared qubits is locally equivalent to a model with only a classical Gaussian distribution and a Gaussian state of a quantum harmonic oscillator. The term `local' refers to a shrinking neighborhood around a fixed state $\rho_{0}$. An essential result is that the neighborhood radius can be chosen arbitrarily close to $n^{-1/4}$. This allows us to use a two steps procedure by which we first localize the state within a smaller neighborhood of radius $n^{-1/2+\epsilon}$, and then use LAN to perform optimal estimation.Comment: 32 pages, 3 figures, to appear in Commun. Math. Phy

Optical Magnetometry

Some of the most sensitive methods of measuring magnetic fields utilize interactions of resonant light with atomic vapor. Recent developments in this vibrant field are improving magnetometers in many traditional areas such as measurement of geomagnetic anomalies and magnetic fields in space, and are opening the door to new ones, including, dynamical measurements of bio-magnetic fields, detection of nuclear magnetic resonance (NMR), magnetic-resonance imaging (MRI), inertial-rotation sensing, magnetic microscopy with cold atoms, and tests of fundamental symmetries of Nature.Comment: 11 pages; 4 figures; submitted to Nature Physic