2,079 research outputs found
Bosonic molecules in a lattice: unusual fluid phase from multichannel interactions
We show that multichannel interactions significantly alter the phase diagram
of ultracold bosonic molecules in an optical lattice. Most prominently, an
unusual fluid region intervenes between the conventional superfluid and the
Mott insulator. In it, number fluctuations remain but phase coherence is
suppressed by a significant factor. This factor can be made arbitrarily large,
at least in a two-site configuration. We calculate the phase diagram using
complementary methods, including Gutzwiller mean-field and density matrix
renormalization group (DMRG) calculations. Although we focus on bosonic
molecules without dipolar interactions, we expect multichannel interactions to
remain important for dipolar interacting and fermionic molecules.Comment: 6 pages incl. refs, 4 figure
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The social consequences of minor innovations in construction
Innovation studies in construction focus on a desire to increase economics and efficiency at a large scale. This has resulted in a skewed perspective that sees only major corporations with substantial R&D resources, complex projects, or national interests at the heart of innovation. By adopting anthropological methods, it becomes possible to examine the two aims of this paper: to demonstrate that an accumulation of minor innovations can have significant consequences; and to show that these are inherently social rather than purely economic. Results come from fieldwork studying the improvisatory house-building practices of the Kelabit people of rural Borneo, tracing changes to the technologies used for roofing and foundations, and describes how these are mutually entangled with new social structures. The conclusion is that we should think more broadly about the forms and effects of innovation in construction, and recognise the significance of improvisation at the level of the individual or small group
Spectral line shape of resonant four-wave mixing induced by broad-bandwidth lasers
We present a theoretical and experimental study of the line shape of resonant four-wave mixing induced by broad-bandwidth laser radiation that revises the theory of Meacher, Smith, Ewart, and Cooper (MSEC) [Phys. Rev. A 46, 2718 (1992)]. We adopt the same method as MSEC but correct for an invalid integral used to average over the distribution of atomic velocities. The revised theory predicts a Voigt line shape composed of a homogeneous, Lorentzian component, defined by the collisional rate Ξ, and an inhomogeneous, Doppler component, which is a squared Gaussian. The width of the inhomogeneous component is reduced by a factor of β2 compared to the simple Doppler width predicted by MSEC. In the limit of dominant Doppler broadening, the width of the homogeneous component is predicted to be 4Ξ, whereas in the limit of dominant homogeneous broadening, the predicted width is 2Ξ. An experimental measurement is reported of the line shape of the four-wave-mixing signal using a broad-bandwidth, "modeless", laser resonant with the Q1 (6) line of the A2 Ξ£ - X2 Ξ (0,0) system of the hydroxyl radical. The measured widths of the Voigt components were found to be consistent with the predictions of the revised theory
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Sustainable construction: exploring the capabilities of Nigerian construction firms
As the built environment accounts for much of the world's emissions, resource consumption and waste, concerns remain as to how sustainable the sector is. Understanding how such concerns can be better managed is complex, with a range of competing agendas and institutional forces at play. This is especially the case in Nigeria where there are often differing priorities, weak regulations and institutions to deal with this challenge. Construction firms are in competition with each other in a market that is growing in size and sophistication yearly. The business case for sustainability has been argued severally in literature. However, the capability of construction firms with respect to sustainability in Nigeria has not been studied. This paper presents the preliminary findings of an exploratory multi-case study carried out to understand the firm's views on sustainability as a source of competitive advantage. A international firm and a lower medium-sized indigenous firm were selected for this purpose. Qualitative interviews were conducted with top-level management of both firms, with key themes from the sustainable construction and dynamic capabilities literature informing the case study protocol. The interviews were transcribed and analysed with the use of NVivo software. The findings suggest that the multinational firm is better grounded in sustainability knowledge. Although the level of awareness and demand for sustainable construction is generally very poor, few international clients are beginning to stimulate interest in sustainable buildings. This has triggered both firms to build their capabilities in that regard, albeit in an unhurried manner. Both firms agree on the potentials of market-driven sustainability in the long term. Nonetheless, more drastic actions are required to accelerate the sustainable construction agenda in Nigeria
Steel-concrete connections for floating wave energy converters
In order to make wave power technologies competitive within the overall energy market, there needs to be significant reductions in the levelised cost of energy (LCoE). One area for potential cost reduction is the use of cheaper materials that are suitable for use in the harsh marine environment, such as reinforced concrete, which gives good corrosion and fatigue properties while providing excellent strength and stiffness at low unit cost. Concrete has the potential to be used for a wide range of wave energy device configurations, however in general use has been limited to nearshore fixed bottom wave energy converters. To date, no dynamic floating wave energy devices have successfully utilised reinforced concrete as structural material, mainly due to the uncertainty surrounding the behaviour of critical dynamic connections between concrete sections and other materials. This paper explores the main issues surrounding steel-concrete connections for floating wave energy converters, providing a review of available design options and standards and assessing the applicability of these to WECs. A methodology is proposed for the evaluation of connection options, and a case study of the Squid 12S floating WEC (developed by Albatern) is presented.This work has been carried out as part of the IDCORE programme, funded by the Energy Technology Institute and RCUK Energy programme (grant no. EP/J500847/1
Requirement for sphingosine kinase 1 in mediating phase 1 of the hypotensive response to anandamide in the anaesthetised mouse
In the isolated rat carotid artery, the endocannabinoid anandamide induces endothelium-dependent relaxation via activation of the enzyme sphingosine kinase (SK). This generates sphingosine-1-phosphate (S1P) which can be released from the cell and activates S1P receptors on the endothelium. In anaesthetised mice, anandamide has a well-characterised triphasic effect on blood pressure but the contribution of SK and S1P receptors in mediating changes in blood pressure has never been studied. Therefore, we assessed this in the current study.
The peak hypotensive response to 1 and 10 mg/kg anandamide was measured in control C57BL/6 mice and in mice pretreated with selective inhibitors of SK1 (BML-258, also known as SK1-I) or SK2 ((R)-FTY720 methylether (ROMe), a dual SK1/2 inhibitor (SKi) or an S1P1 receptor antagonist (W146). Vasodilator responses to S1P were also studied in isolated mouse aortic rings.
The hypotensive response to anandamide was significantly attenuated by BML-258 but not by ROMe. Antagonising S1P1 receptors with W146 completely blocked the fall in systolic but not diastolic blood pressure in response to anandamide. S1P induced vasodilation in denuded aortic rings was blocked by W146 but caused no vasodilation in endothelium-intact rings.
This study provides evidence that the SK1/S1P regulatory-axis is necessary for the rapid hypotension induced by anandamide. Generation of S1P in response to anandamide likely activates S1P1 to reduce total peripheral resistance and lower mean arterial pressure. These findings have important implications in our understanding of the hypotensive and cardiovascular actions of cannabinoids
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IL-36Ξ± Exerts Pro-Inflammatory Effects in the Lungs of Mice
Interleukin (IL-) 36 cytokines (previously designated as novel IL-1 family member cytokines; IL-1F5β IL-1F10) constitute a novel cluster of cytokines structurally and functionally similar to members of the IL-1 cytokine cluster. The effects of IL-36 cytokines in inflammatory lung disorders remains poorly understood. The current study sought to investigate the effects of IL-36Ξ± (IL-1F6) and test the hypothesis that IL-36Ξ± acts as a pro-inflammatory cytokine in the lung in vivo. Intratracheal instillation of recombinant mouse IL-36Ξ± induced neutrophil influx in the lungs of wild-type C57BL/6 mice and IL-1Ξ±Ξ²β/β mice in vivo. IL-36Ξ± induced neutrophil influx was also associated with increased mRNA expression of neutrophil-specific chemokines CXCL1 and CXCL2 in the lungs of C57BL/6 and IL-1Ξ±Ξ²β/β mice in vivo. In addition, intratracheal instillation of IL-36Ξ± enhanced mRNA expression of its receptor IL-36R in the lungs of C57BL/6 as well as IL-1Ξ±Ξ²β/β mice in vivo. Furthermore, in vitro incubation of CD11c+ cells with IL-36Ξ± resulted in the generation of neutrophil-specific chemokines CXCL1, CXCL2 as well as TNFΞ±. IL-36Ξ± increased the expression of the co-stimulatory molecule CD40 and enhanced the ability of CD11c+ cells to induce CD4+ T cell proliferation in vitro. Furthermore, stimulation with IL-36Ξ± activated NF-ΞΊB in a mouse macrophage cell line. These results demonstrate that IL-36Ξ± acts as a pro-inflammatory cytokine in the lung without the contribution of IL-1Ξ± and IL-1Ξ². The current study describes the pro-inflammatory effects of IL-36Ξ± in the lung, demonstrates the functional redundancy of IL-36Ξ± with other agonist cytokines in the IL-1 and IL-36 cytokine cluster, and suggests that therapeutic targeting of IL-36 cytokines could be beneficial in inflammatory lung diseases
Phase-space entropy cascade and irreversibility of stochastic heating in nearly collisionless plasma turbulence
We consider a nearly collisionless plasma consisting of a species of `test
particles' in 1D-1V, stirred by an externally imposed stochastic electric
field. The mean effect on the particle distribution function is stochastic
heating. Accompanying this heating is the generation of fine-scale structure in
the distribution function, which we characterize with the collisionless
(Casimir) invariant . We find
that is transferred from large scales to small scales in both position
and velocity space via a phase-space cascade enabled by both particle streaming
and nonlinear interactions between particles and the stochastic electric field.
We compute the steady-state fluxes and spectrum of in Fourier space, with
and denoting spatial and velocity wavenumbers, respectively. Whereas
even the linear phase mixing alone would lead to a constant flux of to
high (towards the collisional dissipation range) at every , the
nonlinearity accelerates this cascade by intertwining velocity and position
space so that the flux of is to both high and high
simultaneously. Integrating over velocity (spatial) wavenumbers, the -space
(-space) flux of is constant down to a dissipation length (velocity)
scale that tends to zero as the collision frequency does, even though the rate
of collisional dissipation remains finite. The resulting spectrum in the
inertial range is a self-similar function in the plane, with power-law
asymptotics at large and . We argue that stochastic heating is made
irreversible by this entropy cascade and that, while collisional dissipation
accessed via phase mixing occurs only at small spatial scales rather than at
every scale as it would in a linear system, the cascade makes phase mixing even
more effective overall in the nonlinear regime than in the linear one.Comment: 26 pages, 6 figure
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