Optimally squeezed spin states

We consider optimally spin-squeezed states that maximize the sensitivity of the Ramsey spectroscopy, and for which the signal to noise ratio scales as the number of particles $N$. Using the variational principle we prove that these states are eigensolutions of the Hamiltonian $H(\lambda)=\lambda S_z^2-S_x,$ and that, for large $N$, the states become equivalent to the quadrature squeezed states of the harmonic oscillator. We present numerical results that illustrate the validity of the equivalence

Sedimentology, stratigraphic context, and implications of Miocene intrashelf bottomset deposits, offshore New Jersey

Drilling of intrashelf Miocene clinothems onshore and offshore New Jersey has provided better understanding of their topset and foreset deposits, but the sedimentology and stratigraphy of their bottomset deposits have not been documented in detail. Three coreholes (Sites M27–M29), collected during Integrated Ocean Drilling Program (IODP) Expedition 313, intersect multiple bottomset deposits, and their analysis helps to refine sequence stratigraphic interpretations and process response models for intrashelf clinothems. At Site M29, the most downdip location, chronostratigraphically well-constrained bottomset deposits follow a repeated stratigraphic motif. Coarse-grained glauconitic quartz sand packages abruptly overlie deeply burrowed surfaces. Typically, these packages coarsen then fine upwards and pass upward into bioturbated siltstones. These coarse sand beds are amalgamated and poorly sorted and contain thin-walled shells, benthic foraminifera, and extrabasinal clasts, consistent with an interpretation of debrites. The sedimentology and mounded seismic character of these packages support interpretation as debrite-dominated lobe complexes. Farther updip, at Site M28, the same chronostratigraphic units are amalgamated, with the absence of bioturbated silts pointing to more erosion in proximal locations. Graded sandstones and dune-scale cross-bedding in the younger sequences in Site M28 indicate deposition from turbidity currents and channelization. The sharp base of each package is interpreted as a sequence boundary, with a period of erosion and sediment bypass evidenced by the burrowed surface, and the coarse-grained debritic and turbiditic deposits representing the lowstand systems tract. The overlying fine-grained deposits are interpreted as the combined transgressive and highstand systems tract deposits and contain the deepwater equivalent of the maximum flooding surface. The variety in thickness and grain-size trends in the coarse-grained bottomset packages point to an autogenic control, through compensational stacking of lobes and lobe complexes. However, the large-scale stratigraphic organization of the bottomset deposits and the coarse-grained immature extrabasinal and reworked glauconitic detritus point to external controls, likely a combination of relative sea-level fall and waxing-and-waning cycles of sediment supply. This study demonstrates that large amounts of sediment gravity-flow deposits can be generated in relatively shallow (~100–200 m deep) and low-gradient (~1°–4°) clinothems that prograded across a deep continental shelf. This physiography likely led to the dominance of debris flow deposits due to the short transport distance limiting transformation to low-concentration turbidity currents

Gaussian quantum operator representation for bosons

We introduce a Gaussian quantum operator representation, using the most general possible multimode Gaussian operator basis. The representation unifies and substantially extends existing phase-space representations of density matrices for Bose systems and also includes generalized squeezed-state and thermal bases. It enables first-principles dynamical or equilibrium calculations in quantum many-body systems, with quantum uncertainties appearing as dynamical objects. Any quadratic Liouville equation for the density operator results in a purely deterministic time evolution. Any cubic or quartic master equation can be treated using stochastic methods

Whirlin function in proprioceptive mechanotransduction.

Proprioceptive sensory feedback is critical for many aspects of motor control. This form of sensory feedback derives largely from specialized mechanoreceptors located within muscles: the muscle spindle (MS; responsive to changes in muscle length) and the Golgi tendon organ (GTO; responsive to changes in muscle tension) (1). Anatomical and physiological analysis has provided insight into the sensory transduction process in MS and GTO afferents and has demonstrated that the afferent stretch response is primarily carried by sodium currents (2). The stretch-evoked MS-afferent impulse frequency is significantly diminished by amiloride, implicating the Degenerin/ENaC family of sodium channels as components of the MS-afferent mechanotransduction channel (3). Glutamate, released from sensory terminals, tonically maintains afferent excitability, possibly by regulating membrane insertion of mechano-transduction channels (4). Despite these recent advances, the molecular mechanisms that underlie the transformation of proprioceptive mechanical stimuli into electrical impulses remain largely unknown. In a molecular screen for new proprioceptor specific molecules, we recently found that whirlin is selectively expressed in proprioceptive sensory neurons in dorsal root ganglia. Whirlin encodes a scaffold protein with important roles in hair cell and photoreceptor sensory transduction (5), raising the possibility that whirlin also functions in the proprioceptive mechanotransduction process. Using an in vitro muscle/nerve preparation, we find that the activation of spindle afferents by mechanical stretch is compromised in whirlin mutant mice when compared to heterozygous mice. Application of exogenous glutamate normalizes afferent stretch-sensitivity. These observations suggest that essential components of the proprioceptive transduction machinery are inefficiently ‘deployed’ in whirler mutant mice. Given that whirlin contains three PDZ-domains, and is known to recruit macromolecular complexes to specific subcellular locations, we speculate that whirlin may function to recruit and/or ensure the proper subcellular localization of a mechano-transduction complex in proprioceptive sensory terminals. Our current studies are aimed at testing this hypothesis. The identification of whirlin provides opportunities to identify additional components of the proprioceptive transduction machinery. The parallel expression of whirlin in proprioceptive muscle afferents, hair cells and photoreceptor cells raises the possibility of a central role for whirlin in diverse sensory transduction processes