735 research outputs found
Dynamical Instability of a Doubly Quantized Vortex in a Bose-Einstein condensate
Doubly quantized vortices were topologically imprinted in Na
condensates, and their time evolution was observed using a tomographic imaging
technique. The decay into two singly quantized vortices was characterized and
attributed to dynamical instability. The time scale of the splitting process
was found to be longer at higher atom density.Comment: 5 pages, 4 figure
Psychological Safety and Norm Clarity in Software Engineering Teams
In the software engineering industry today, companies primarily conduct their
work in teams. To increase organizational productivity, it is thus crucial to
know the factors that affect team effectiveness. Two team-related concepts that
have gained prominence lately are psychological safety and team norms. Still,
few studies exist that explore these in a software engineering context.
Therefore, with the aim of extending the knowledge of these concepts, we
examined if psychological safety and team norm clarity associate positively
with software developers' self-assessed team performance and job satisfaction,
two important elements of effectiveness.
We collected industry survey data from practitioners (N = 217) in 38
development teams working for five different organizations. The result of
multiple linear regression analyses indicates that both psychological safety
and team norm clarity predict team members' self-assessed performance and job
satisfaction. The findings also suggest that clarity of norms is a stronger
(30\% and 71\% stronger, respectively) predictor than psychological safety.
This research highlights the need to examine, in more detail, the
relationship between social norms and software development. The findings of
this study could serve as an empirical baseline for such, future work.Comment: Submitted to CHASE'201
Recommended from our members
The Observations Of The X-Ray Source Hz Herculis-Hercules X-1
NASAESASRCAstronom
Velocity Dispersion of Dissolving OB Associations Affected by External Pressure of Formation Environment
This paper presents a possible way to understand dissolution of OB
associations (or groups). Assuming rapid escape of parental cloud gas from
associations, we show that the shadow of the formation environment for
associations can be partially imprinted on the velocity dispersion at their
dissolution. This conclusion is not surprising as long as associations are
formed in a multiphase interstellar medium, because the external pressure
should suppress expansion caused by the internal motion of the parental clouds.
Our model predicts a few km s as the internal velocity dispersion.
Observationally, the internal velocity dispersion is km s which
is smaller than our prediction. This suggests that the dissipation of internal
energy happens before the formation of OB associations.Comment: 6 pages. AJ accepte
Fifty Years of IMF Variation: The Intermediate-Mass Stars
I track the history of star count estimates of the Milky Way field star and
open cluster IMFs, concentrating on the neglected mass range from 1 to 15
M. The prevalent belief in a universal IMF appears to be without
basis for this mass range. Two recent estimates of the field star IMF using
different methods and samples give values of the average logarithmic slope
between -1.7 and -2.1 in the mass range 1.1 to 4 M. Two
older estimates between 2 and 15 M disagree severely; the field IMF
in this range is essentially unknown from star counts. Variations in
among open cluster IMFs in this mass range have not decreased despite numerous
detailed studies, even for studies using homogeneous data and reduction
procedures and including only clusters with a significant mass range. These
cluster variations \textit{might} be due to the combined effects of sampling,
systematic errors, stellar evolution uncertainties, dynamical evolution, and
unresolved binaries. If so, then the cluster data are consistent with a
universal IMF, but are also consistent with sizeable variations. The cluster
data do not allow an estimate of an average IMF or because the average
depends on the choice of weighting procedure and other effects. If the spread
in cluster IMFs is in excess of the effects listed above, real IMF variations
must occur that do not depend much on physical conditions explored so far. The
complexity of the star formation process seen in observations and simulations
suggests that large realization-to-realization differences might be expected,
in which case an individual cluster IMF would be in part the product of
evolutionary contingency in star formation, and the function of interest is the
probability distribution of IMF parameters.Comment: 18 pages, including 4 figures: invited talk presented at the
conference on "IMF@50: The Stellar Initial Mass Function Fifty Years Later"
held at Abbazia di Spineto, Siena, Italy, May 2004; to be published by Kluwer
Academic Publishers, edited by E. Corbelli, F. Palla, and H. Zinnecke
Evidence for Superfluidity of Ultracold Fermions in an Optical Lattice
The study of superfluid fermion pairs in a periodic potential has important
ramifications for understanding superconductivity in crystalline materials.
Using cold atomic gases, various condensed matter models can be studied in a
highly controllable environment. Weakly repulsive fermions in an optical
lattice could undergo d-wave pairing at low temperatures, a possible mechanism
for high temperature superconductivity in the cuprates. The lattice potential
could also strongly increase the critical temperature for s-wave superfluidity.
Recent experimental advances in the bulk include the observation of fermion
pair condensates and high-temperature superfluidity. Experiments with fermions
and bosonic bound pairs in optical lattices have been reported, but have not
yet addressed superfluid behavior. Here we show that when a condensate of
fermionic atom pairs was released from an optical lattice, distinct
interference peaks appear, implying long range order, a property of a
superfluid. Conceptually, this implies that strong s-wave pairing and
superfluidity have now been established in a lattice potential, where the
transport of atoms occurs by quantum mechanical tunneling and not by simple
propagation. These observations were made for unitarity limited interactions on
both sides of a Feshbach resonance. For larger lattice depths, the coherence
was lost in a reversible manner, possibly due to a superfluid to insulator
transition. Such strongly interacting fermions in an optical lattice can be
used to study a new class of Hamiltonians with interband and atom-molecule
couplings.Comment: accepted for publication in Natur
Measurement of the Electric Form Factor of the Neutron at Q^2 = 0.3-0.8 (GeV/c)^2
The electric form factor of the neutron, G_En, has been measured at the Mainz
Microtron by recoil polarimetry in the quasielastic D(e_pol,e'n_pol)p reaction.
Three data points have been extracted at squared four-momentum transfers Q^2 =
0.3, 0.6 and 0.8 (GeV/c)^2. Corrections for nuclear binding effects have been
applied.Comment: 9 pages, 7 figures, 2 tables. Accepted for publication in EPJ
Block of NMDA receptor channels by endogenous neurosteroids: implications for the agonist induced conformational states of the channel vestibule
N-methyl-D-aspartate receptors (NMDARs) mediate synaptic plasticity, and their dysfunction is implicated in multiple brain disorders. NMDARs can be allosterically modulated by numerous compounds, including endogenous neurosteroid pregnanolone sulfate. Here, we identify the molecular basis of the use-dependent and voltage-independent inhibitory effect of neurosteroids on NMDAR responses. The site of action is located at the extracellular vestibule of the receptor's ion channel pore and is accessible after receptor activation. Mutations in the extracellular vestibule in the SYTANLAAF motif disrupt the inhibitory effect of negatively charged steroids. In contrast, positively charged steroids inhibit mutated NMDAR responses in a voltage-dependent manner. These results, in combination with molecular modeling, characterize structure details of the open configuration of the NMDAR channel. Our results provide a unique opportunity for the development of new therapeutic neurosteroid-based ligands to treat diseases associated with dysfunction of the glutamate system
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