Controlling the nature of a charged impurity in a bath of Feshbach dimers

We theoretically study the dynamics of a trapped ion that is immersed in an ultracold gas of weakly bound atomic dimers created by a Feshbach resonance. Using quasi-classical simulations, we find a crossover from dimer dissociation to molecular ion formation depending on the binding energy of the dimers. The location of the crossover strongly depends on the collision energy and the time-dependent fields of the Paul trap. Deeply bound dimers lead to fast molecular ion formation, with rates approaching the Langevin collision rate $\Gamma'_\text{L}\approx4.8\times10^{-9}\,$cm$^3$s$^{-1}$. The kinetic energies of the created molecular ions have a median below $1\,$mK, such that they will stay confined in the ion trap. We conclude that interacting ions and Feshbach molecules may provide a novel approach towards the creation of ultracold molecular ions with applications in precision spectroscopy and quantum chemistry.Comment: 9 pages and 12 figures including appendice

Probing the Interface of a Phase-Separated State in a Repulsive Bose-Fermi Mixture

We probe the interface between a phase-separated Bose-Fermi mixture consisting of a small BEC of $^{41}$K residing in a large Fermi sea of $^6$Li. We quantify the residual spatial overlap between the two components by measuring three-body recombination losses for variable strength of the interspecies repulsion. A comparison with a numerical mean-field model highlights the importance of the kinetic energy term for the condensed bosons in maintaining the thin interface far into the phase-separated regime. Our results demonstrate a corresponding smoothing of the phase transition in a system of finite size.Comment: The Supplemental Materials are located in the Ancillary file

Is Scrum fit for global software engineering?

Distributed software engineering and agility are strongly pushing on today's software industry. Due to inherent incompatibilities, for years, studying Scrum and its application in distributed setups has been subject to theoretical and applied research, and an increasing body of knowledge reports insights into this combination. Through a systematic literature review, this paper contributes a collection of experiences on the application of Scrum to global software engineering (GSE). In total, we identified 40 challenges in 19 categories practitioners face when using Scrum in GSE. Among the challenges, scaling Scrum to GSE and adopting practices accordingly are the most frequently named. Our findings also show that most solution proposals aim at modifying elements of the Scrum core processes. We thus conclude that, even though Scrum allows for extensive modification, Scrum itself represents a barrier for global software engineering, and development teams have to customize Scrum properly to benefit from agile software development in GSE

Predictors of weight loss in young adults who are over-weight or obese and have psychosocial problems:a post hoc analysis

BACKGROUND: The aim of this study is in a general practice trial setting to identify predictive factors for weight loss after 1 year among young adults who are over-weight or obese and who have several psychosocial problems. METHODS: Twenty-eight general practitioners recruited 495 patients aged 20–45 years with psychosocial problems for a randomized general preventive study to increase self-efficacy to achieve a self-prioritised goal for a better life by discussions of resources and barriers for reaching the goal. The present study is a post hoc analysis of possible predictors of weight loss among all 218 patients who have over-weight or obesity. A 23-pages questionnaire was completed before and 1 year after randomization. 111 patients had a one-hour preventive health consultation with their general practitioners focused on life coaching and a follow-up consultation within 3 months, and 107 patients had no preventive consultation. RESULTS: Twenty-two patients stated during the preventive consultation that weight loss was a prioritised goal. They had a mean weight loss of 4.7 kgs compared with 1.6 kgs in the group without this goal and 1.6 kgs in the group without preventive consultation. In a logistic regression model, predictors of weight loss or no weight loss were a) pre-interventional consideration of weight loss within 30 days, b) having weight loss as a prioritised goal for improved quality of life, c) being female, d) being in the oldest half of participants, and e) having many psychosocial problems. In a linear regression model, the predictors together explained about 11 % of the weight loss. Important predictors were: obesity (explained 4 %), pre-interventional consideration of weight loss within 30 days (3 %), and having a preventive health consultation with weight loss as a prioritised goal (2 %). CONCLUSIONS: Pre-interventional consideration of weight loss within 30 days and having weight loss as a prioritised goal during the health consultation were two important predictors for weight loss. By structured interventions focussing on the patients’ priorities, self-chosen goals, their resources and barriers for reaching the goals, changes may be obtained; especially in participants with many problems who often do not accept participation in procedures on risks. CLINICALTRIALS GOV REGISTRATION: NCT 01231256, Aug. 22. 2010

Observation of a Strong Atom-Dimer Attraction in a Mass-Imbalanced Fermi-Fermi Mixture

We investigate a mixture of ultracold fermionic $^{40}$K atoms and weakly bound $^{6}$Li$^{40}$K dimers on the repulsive side of a heteronuclear atomic Feshbach resonance. By radio-frequency spectroscopy we demonstrate that the normally repulsive atom-dimer interaction is turned into a strong attraction. The phenomenon can be understood as a three-body effect in which two heavy $^{40}$K fermions exchange the light $^{6}$Li atom, leading to attraction in odd partial-wave channels (mainly p-wave). Our observations show that mass imbalance in a fermionic system can profoundly change the character of interactions as compared to the well-established mass-balanced case

From Scrum to Agile: A Journey to Tackle the Challenges of Distributed Development in an Agile Team

Background: Agile and distributed software development are two trends that continue to increase rapidly in today's software industry. Even though the benefits achievable by combining them are potentially many, the intrinsic challenges of such marriage often lead to severe complications that can jeopardize the successful completion of software projects. Method: To investigate empirically how these two trends can coexist without compromising on the agile core values and principles, we conducted an exploratory holistic case study. Focusing on the development team of a Danish SME having both distributed offices as well as teleworking arrangements, we showcase (the evolution of) their practices. Results: The case is an example of the effective application of the agile reflective culture that allowed the company to evolve to a level in which the collocation restrictions of agile software development are overcome by a continuously evolving software process geared towards reducing waste to achieve speed and simplicity. Conclusions: Even though results need to be considered carefully due to the single nature of the reported case, we highlight five elements that have been fundamental in such journey: agile servant-leader, agile team, trust, virtual work environment, inspect & adapt, and reduce waste. Extensive information is provided to frame the context and to allow meaningful future comparisons

Ultrafast many-body interferometry of impurities coupled to a Fermi sea

The fastest possible collective response of a quantum many-body system is related to its excitations at the highest possible energy. In condensed-matter systems, the corresponding timescale is typically set by the Fermi energy. Taking advantage of fast and precise control of interactions between ultracold atoms, we report on the observation of ultrafast dynamics of impurities coupled to an atomic Fermi sea. Our interferometric measurements track the non-perturbative quantum evolution of a fermionic many-body system, revealing in real time the formation dynamics of quasiparticles and the quantum interference between attractive and repulsive states throughout the full depth of the Fermi sea. Ultrafast time-domain methods to manipulate and investigate strongly interacting quantum gases open up new windows on the dynamics of quantum matter under extreme non-equilibrium conditions.Comment: 21 pages, 14 figure