1,166 research outputs found
Hamiltonians separable in cartesian coordinates and third-order integrals of motion
We present in this article all Hamiltonian systems in E(2) that are separable
in cartesian coordinates and that admit a third-order integral, both in quantum
and in classical mechanics. Many of these superintegrable systems are new, and
it is seen that there exists a relation between quantum superintegrable
potentials, invariant solutions of the Korteweg-De Vries equation and the
Painlev\'e transcendents.Comment: 19 pages, Will be published in J. Math. Phy
Brain serotonin synthesis capacity in obsessive-compulsive disorder: effects of cognitive behavioral therapy and sertraline.
Cognitive behavioral therapy (CBT) and selective serotonin reuptake inhibitors (SSRIs) are both effective treatments for some patients with obsessive-compulsive disorder (OCD), yet little is known about the neurochemical changes related to these treatment modalities. Here, we used positron emission tomography and the α-[11C]methyl-L-tryptophan tracer to examine the changes in brain regional serotonin synthesis capacity in OCD patients following treatment with CBT or SSRI treatment. Sixteen medication-free OCD patients were randomly assigned to 12 weeks of either CBT or sertraline treatment. Pre-to-post treatment changes in the α-[11C]methyl-L-tryptophan brain trapping constant, K* (ml/g/min), were assessed as a function of symptom response, and correlations with symptom improvement were examined. Responders/partial responders to treatment did not show significant changes in relative regional tracer uptake; rather, in responders/partial responders, 12 weeks of treatment led to serotonin synthesis capacity increases that were brain-wide. Irrespective of treatment modality, baseline serotonin synthesis capacity in the raphe nuclei correlated positively with clinical improvement. These observations suggest that, for some patients, successful remediation of OCD symptoms might be associated with greater serotonergic tone
More than Mechanisms: Shifting Ideologies for Asset-Based Learning in Engineering Education
Learning spaces, the practices in which people engage, and the representations they use are ideological. Ideologies are coherent constellations of values, beliefs, and practices that impose order on how disciplines like engineering operate. Historically, engineering spaces have been dominated by a relatively technocratic, rationalistic, and exclusionary ideology, but more recent attention to asset-based approaches to engineering education offers transformative promise. Asset-based ideologies can reshape images of legitimized engineering practice, recasting engineering education to disrupt dominant exclusionary ideologies. This paper describes an assets-based learning space, SETC, that recaptures the imagination of engineering for technological and social change. Drawing from extensive ethnographic observational data, interviews, and artifacts produced in SETC, we describe aspects of this learning space, including the use of representations and practices that specifically support expansive forms of engineering practiced by youth of color. We also explore how SETC’s commitment to antiracist and liberatory practices, including shifting relationships to technology and engineering design in service of enhancing life, manifests in its transformative mission to design programs and activities for youth that disrupt dominant ideologies. SETC centers making and tinkering as legitimate expressions of engineering, and we present a case of a youth participant to illustrate the rich engineering learning that the space makes possible. The case features Naeem engineering a gear-based project that expresses his interpretation of Black Lives Matter. Situated in his long history in the learning space, we explore how youth’s interactions with conventionalized representations—which serve to maintain dominant ideologies—are enhanced by asset-based commitments. This paper contributes specific recommendations for designing spaces for new ideologies, making engineering education more equitable for youth of color while also expanding notions of what engineering is and the forms that it can take
Process outgrowth in oligodendrocytes is mediated by CNP, a novel microtubule assembly myelin protein
Oligodendrocytes (OLs) extend arborized processes that are supported by microtubules (MTs) and microfilaments. Little is known about proteins that modulate and interact with the cytoskeleton during myelination. Several lines of evidence suggest a role for 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNP) in mediating process formation in OLs. In this study, we report that tubulin is a major CNP-interacting protein. In vitro, CNP binds preferentially to tubulin heterodimers compared with MTs and induces MT assembly by copolymerizing with tubulin. CNP overexpression induces dramatic morphology changes in both glial and nonglial cells, resulting in MT and F-actin reorganization and formation of branched processes. These morphological effects are attributed to CNP MT assembly activity; branched process formation is either substantially reduced or abolished with the expression of loss-of-function mutants. Accordingly, cultured OLs from CNP-deficient mice extend smaller outgrowths with less arborized processes. We propose that CNP is an important component of the cytoskeletal machinery that directs process outgrowth in OLs
Fundamental limitations on "warp drive" spacetimes
"Warp drive" spacetimes are useful as "gedanken-experiments" that force us to
confront the foundations of general relativity, and among other things, to
precisely formulate the notion of "superluminal" communication. We verify the
non-perturbative violation of the classical energy conditions of the Alcubierre
and Natario warp drive spacetimes and apply linearized gravity to the
weak-field warp drive, testing the energy conditions to first and second order
of the non-relativistic warp-bubble velocity. We are primarily interested in a
secondary feature of the warp drive that has not previously been remarked upon,
if it could be built, the warp drive would be an example of a "reaction-less
drive". For both the Alcubierre and Natario warp drives we find that the
occurrence of significant energy condition violations is not just a high-speed
effect, but that the violations persist even at arbitrarily low speeds.
An interesting feature of this construction is that it is now meaningful to
place a finite mass spaceship at the center of the warp bubble, and compare the
warp field energy with the mass-energy of the spaceship. There is no hope of
doing this in Alcubierre's original version of the warp-field, since by
definition the point in the center of the warp bubble moves on a geodesic and
is "massless". That is, in Alcubierre's original formalism and in the Natario
formalism the spaceship is always treated as a test particle, while in the
linearized theory we can treat the spaceship as a finite mass object. For both
the Alcubierre and Natario warp drives we find that even at low speeds the net
(negative) energy stored in the warp fields must be a significant fraction of
the mass of the spaceship.Comment: 18 pages, Revtex4. V2: one reference added, some clarifying comments
and discussion, no physics changes, accepted for publication in Classical and
Quantum Gravit
A doubly responsive probe for the detection of Cys4-tagged proteins
International audienceRecombinant proteins bearing a tag are crucial tools for assessing protein location or function. Small tags such as Cys4 tag (tetracysteine; Cys–Cys–X–X–Cys–Cys) are less likely disrupt protein function in the living cell than green fluorescent protein. Herein we report the first example of the design and synthesis of a dual fluorescence and hyperpolarized 129Xe NMR-based sensor of Cys4-tagged proteins. This sensor becomes fluorescent when bound to such Cys4-tagged peptides, and the 129Xe NMR spectrum exhibits a specific signal, characteristic of the biosensor-peptide association
Hospitalist involvement in family medicine residency training: A CERA study
BACKGROUND AND OBJECTIVES: Little is known about the impact of hospitalists on family medicine residencies. We surveyed family medicine residency directors to assess attitudes about hospitalists and their involvement in residency teaching.
METHODS: Questions were included in the 2012 Council of Academic Family Medicine Educational Research Alliance (CERA) survey of family medicine residency directors. Univariate statistics were used to describe programs, directors, and our questions on the use of hospitalists. Bivariate statistics were used to examine relationships between the use of hospitalists to teach and program characteristics.
RESULTS: Forty-one percent (n=175) of residency directors completed the hospitalist section of the CERA survey. Sixty-six percent of residency programs were community based/university affiliated. The majority of directors who have, or are planning to develop, a hospitalist service currently use an internal medicine service (92.5%), followed by family medicine (39.1%), pediatrics (35.4%), OB/laborists (18.0%), and combined services (8.7%). The majority of programs with a hospitalist training track (or plans to develop one) indicated that this was for a family medicine service. Sixty percent of programs that have a hospitalist service involve hospitalists in teaching. Twenty percent of directors reported that hospitalists serve as family medicine faculty, and 63% viewed them as good educators. However, 85% reported no reduction in inpatient teaching by family medicine faculty despite using hospitalist teaching services.
CONCLUSIONS: Hospitalists have a significant educational role in family medicine resident training. Further research is needed to explore how hospitalists and family medicine faculty can collaborate to promote enhanced efficiency and effectiveness as residency teachers
A Novel Inhibitory Mechanism of Mitochondrion-Dependent Apoptosis by a Herpesviral Protein
Upon viral infection, cells undergo apoptosis as a defense against viral replication. Viruses, in turn, have evolved elaborate mechanisms to subvert apoptotic processes. Here, we report that a novel viral mitochondrial anti-apoptotic protein (vMAP) of murine Îł-herpesvirus 68 (ÎłHV-68) interacts with Bcl-2 and voltage-dependent anion channel 1 (VDAC1) in a genetically separable manner. The N-terminal region of vMAP interacted with Bcl-2, and this interaction markedly increased not only Bcl-2 recruitment to mitochondria but also its avidity for BH3-only pro-apoptotic proteins, thereby suppressing Bax mitochondrial translocation and activation. In addition, the central and C-terminal hydrophobic regions of vMAP interacted with VDAC1. Consequently, these interactions resulted in the effective inhibition of cytochrome c release, leading to the comprehensive inhibition of mitochondrion-mediated apoptosis. Finally, vMAP gene was required for efficient ÎłHV-68 lytic replication in normal cells, but not in mitochondrial apoptosis-deficient cells. These results demonstrate that ÎłHV-68 vMAP independently targets two important regulators of mitochondrial apoptosis-mediated intracellular innate immunity, allowing efficient viral lytic replication
Superintegrability with third order invariants in quantum and classical mechanics
We consider here the coexistence of first- and third-order integrals of
motion in two dimensional classical and quantum mechanics. We find explicitly
all potentials that admit such integrals, and all their integrals. Quantum
superintegrable systems are found that have no classical analog, i.e. the
potentials are proportional to \hbar^2, so their classical limit is free
motion.Comment: 15 page
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